nanosa15 - abstracts of talks

Marcus Adama, Talha Erdemb, Gordon M. Stachowskia, Zeliha Soran-Erdemb, Hilmi Volkan Demirb,c, Nikolai Gaponika, Alexander Eychmüllera
a Physical Chemistry, TU Dresden, Bergstr. 66b, 01062 Dresden, Germany
b Department of Physics, Department of Electrical and Electronics Engineering and UNAM-Institute of Materials Science and Nanotechnology, Bilkent University, TR-06800, Ankara, Turkey
c School of Electrical and Electronic Engineering and School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 639798, Singapore

While fluorescent lamps and OLEDs raise concerns due to different drawbacks, solid state lighting (SSL) technologies based on color conversion, white light emitting diodes (w-LEDs)
are highly promising candidates. Essentially initiated by the development of the first blue light-emitting diodes (LEDs) and recently awarded with a Nobel Prize in physics, SSL-based 
luminaires became commercially available within two decades. Unfortunately, today's state-of-the-art devices mainly suffer from bad color rendering and a cold white hue due to their 
rare earth based conversion layers with a lack of intensity in the red spectral region. One solution for this issue are color conversion layers based on semiconductor quantum dots 
(QDs) with their spectral tunability and color purity.1,2 Although devices with QD-based conversion layers have been shown, they often suffer from photooxidation. Embedding 
high quality CdSe/ZnS QDs with an alloyed gradient shell into disodium tetraborate (borax) yields QD-salt mixed crystals with excellent optical properties and high stability.3
The QDs and mixed crystals were synthesized according to a spectral modeling, ensuring their suitability to produce excellent luminaires. Based on this approach, a final w-LED with 
a color rendering index of 91, luminous efficiency of radiation of 341 lm/Wopt. and a correlated color temperature of 2720 K was manufactured.
[1] Nano Lett. 2012, 12, 5348
[2] Adv. Funct. Mater. 2015, 25, 2638
[3] Chem. Mater. 2014, 26, 3231.

Structural order in organic solar cells is paramount: it reduces energetic disorder, boosts charge and exciton mobilities, and assists exciton splitting. Owing to spatial
localization of electronic states, microscopic descriptions of photovoltaic processes tend to overlook the influence of structural features at the mesoscale. Long-range electrostatic 
interactions nevertheless probe this ordering, making local properties depend on the mesoscopic order. Using a technique developed to address spatially aperiodic excitations in thin films 
and in bulk, we show how inclusion of mesoscale order resolves the controversy between experimental and theoretical results for the energy-level profile and alignment in a variety of
photovoltaic systems, with direct experimental validation. Optimal use of long-range ordering also rationalizes the acceptor-donor-acceptor paradigm for molecular design of donor dyes. We
predict open-circuit voltages of planar heterojunction solar cells in excellent agreement with experimental data, based only on crystal structures and interfacial orientation.

Nature Materials (2014) doi:10.1038/nmat4167

Recently discovered 2D flat colloidal nanocrystals composed of AIIBVI semiconductors has gained considerable attention due to their unique electronic and optical properties that
were shown to surpass properties of nanocrystals of other dimensionalities. In nearly a decade a great deal of progress has been made in the synthesis of nanoplatelets and heterostructures on
their basis with various size and composition. However surface chemistry and its alteration gained considerably less attention.
Recently it was shown that upon the addition of non-solvent to the colloidal suspension of NPLs the latter ones tend to assemble in a face-to-face fashion into giant micrometer-sized "needles"
exhibiting polarized emission. In our work we use another approach which does not require non-solvent addition. Instead, we employ nanoscopic forces that are mainly governed by the ligands on
the nanocrystal surface. Self-assembly process was studied by Dynamic Light Scattering technique and TEM-measurements. In contrast to non-solvent approach our method allows to prepare nanometer-
sized aggregates consisting of tens of nanocrystals and size of these stacks could be controlled by the nature and concentration of ligands. We have also demonstrated that conventional synthetic
procedures lead to the nanoplatelets aggregation that could be reversed by additional post-synthetic treatment. Results of this work are considered to allow directional alignment of 2D
nanocrystals that in turn is of great importance for the implementation of nanocrystals in various practical applications.

One of the major strengths of colloidal synthesis is the possibility to synthesize a huge amount of nanoparticles at the same time with sub-nanometer precision. As a result, 
colloidal nanocrystal synthesis has been highly developed in the last three decades, so that to date, there are a large variety of materials, material compositions, shapes and sizes available. 
Concerning possible applications, however, colloidal solutions can be disadvantageous, namely if the nanoparticles need to be separated from their solution, which can result in a loss of the 
advantageous nanoscopic properties. Therefore, appropriate assembly techniques need to be developed with the aim to control interparticle interactions and conserve the nanoscopic properties. 
Our group mainly focuses on the development of novel types of macroscopic hydrogels and aerogels by employing tailored colloidal nanocrystals as building blocks. Such gels are self-supported 
assemblies of colloidal nanocrystals exhibiting high specific surfaces and extremely low densities.[1,2] We will therefore present recent developments in the synthesis of gel-like monoliths 
built from semiconductor and noble metal nanoparticles.[3,4] The necessary fabrication steps will be explained starting from examples for nanocrystal synthesis,[5] surface functionalization 
and controlled destabilization to yield hydrogels, and their subsequent transformation to xerogels and aerogels.[3,4] In-depth characterization of these materials will be shown with a special
focus on optical spectroscopy and fluorescence lifetimes. In the case of fluorescent gel-type assemblies, by determination of the quantum yield of each processing step, optimizations in the
synthesis can be achieved, and insights in the importance of each processing step can be derived. 
Certain aerogel systems exhibit physical properties which do not equal those of their building blocks in solution. For example, on a CdSe/CdS quantum rod system, we observed ultralong 
fluorescence lifetimes in combination with high quantum yields, which we assign to a delocalization of electrons and a resulting charge carrier separation in the nanoparticle networks, in 
combination with a reduced fluorescence quenching, the latter being a result of a reduced mobility of the ligands.[4]

References
[1]	I. U. Arachchige, S. L. Brock, Accounts of Chemical Research, 2007, 40, 801
[2]	A. Eychmuller, Angewandte Chemie Int. Ed., 2005, 44, 4839.
[3]	N. C. Bigall, et al., Angewandte Chemie Int. Ed., 2009, 48, 9731.
[4]	S. Sánchez-Paradinas, D. Dorfs, S. Friebe, A. Freytag, A. Wolf, N. C. Bigall, submitted
[5]	S. Naskar, A. Schlosser, J. F. Miethe, F. Steinbach, A. Feldhoff, N. C. Bigall,  Chemistry of Materials, 2015, 27, 3159. 

ZnO is currently attracting significant interest as a candidate for hybrid photovoltaic and light-emitting devices. We studied - in an all-ultrahigh vacuum approach - the 
interfacing of ZnO with various conjugated organic molecules, including perylene derivatives, oligo(phenylenes) as well as ladder-type oligo(phenylenes) whose fundamental optical excitation 
is resonant to the ZnO band gap. The talk will summarize our recent efforts to tune the morphology and the electronic structure of the hybrid interface. By appropriate interfacial design, we are 
able to control electron-hole separation at the ZnO/organic interface and, alternatively, to achieve excitonic energy transfer with efficiencies of up to 80 %.  

Effective exploitation of nanoparticles for applications in energy conversion (e.g., photovoltaics) and heterogenous catalytic processes requires the ability to assemble a variety 
of dissimilar components into a single architecture, and to do so in a way that enables facile interparticle communication as well as access to the individual components. Sol-gel methodologies 
represent a powerful approach for the assembly of nanoparticles into a variety of desirable architectures, from 2-D thin films to aerogels with 3-D interconnected matter-pore networks.  Although 
sol-gel methodologies have traditionally been applied to oxides, we have pioneered work showing that metal chalcogenides can also be assembled into single-component thin films and aerogels by a 
process of oxidative chalcogenide linking, and very recently, this method has been applied to phosphides. In this presentation, current efforts focused on understanding the parameters that 
effect chalcognide gelation rates (identity of chalcogen and binding ligand) to enable programmable assembly of multicomponent networks with varying degrees of heterogeneity will be discussed in 
light of their potential applications in photovoltaics.  This work will be juxtaposed against parallel work in the Brock lab exploring the incorporation of metal phosphide nanoparticles into 
oxide aerogels for generation of hydrodesulfurization catalysts that resist sintering.  Insights gained into the key factors that enable bonding between chemically dissimilar units will be 
shared.

Nanoscale transmission of quantum excitations in quantum information technologies must preserve the quantum character of the information. One proposed realization for nanoscale 
quantum information transfer uses hybrid systems of metallic nanoparticles (MNP) and semiconductor quantum dots (QD), with plasmons in MNPs moving qubits from QD to QD. Ultimately, a quantum 
description of the entire system, treating the MNPs and QDs on an equal footing, is needed to fully account for size quantization, quantized plasmons, coherent coupling, interparticle tunneling 
and nonlocal and nonlinear response. To achieve this, a quantum description of the MNPs is needed.

To this end, we use real-space time-dependent density functional theory (TDDFT) for a quantum description of MNPs. The MNPs are Au jellium nanospheres. We consider the limit of small MNPs where 
size quantization plays a key role. So far, it has proven difficult to clearly distinguish MNP excitations as single-particle transition or plasmonic modes, because the excitations have hybrid 
character. Previously, we showed that individual, small MNPs support "quantum core plasmons", charge oscillations primarily localized near the MNP core, and "classical surface plasmons", charge 
oscillations more at the MNP surface. Both of these are collective oscillations. We discuss more detailed analysis of the time dependence of driven systems to characterize more fully these 
excitations. Both types of modes have a "sloshing" character with charge oscillating between filled energy shells just below the Fermi level and empty shells just above the Fermi level. At the 
same time, both types have "inversion" character with charge continuously emptying from levels far below the Fermi level and filling shells far above the Fermi level. The sloshing character is 
dominant in classical surface plasmon modes. The inversion character is more single-particle like and is dominant for core plasmons. 

While TDDFT yields information about the nature of the excitations in MNPs, DFT can't address the quantum character of these excitations, ie whether the excitations are harmonic-like, bosonic, 
fermionic. Such information is necessary for building good models for quantized plasmons in MNPs. To begin to address these issues, we have explored simple models for interacting electrons on a 
linear chain. For short chains, the eigenmodes of the interacting electrons in the system are found exactly. As expected, the ground state shows a Mott transition as the hopping along the chain 
is varied. For the hopping regime where the interacting ground state of the system is metallic, we discuss initial results that analyze the character of the excitations. We use the results to 
identify which excitations are fermionic/bosonic, which are collective, which are harmonic oscillator-like, when nonlinear effects appear. Implications for plasmon quantization in small systems 
are discussed.   

[1] E. Townsend and G. W. Bryant, Nano Lett. 12, 429 (2012)

We present quantum dynamical studies of ultrafast photoinduced exciton migration and dissociation in functional organic materials, in view of understanding the key microscopic 
factors that lead to efficient charge generation in photovoltaics applications. As highlighted by recent experiments, these processes can be guided by quantum coherence, despite the presence of 
static and dynamic disorder. Our approach combines parametrized Hamiltonians, based on TDDFT and/or high-level electronic structure calculations, with accurate quantum dynamics simulations using 
the Multi-Configuration Time-Dependent Hartree (MCTDH) method [1] as well as non-Markovian reduced dynamics techniques [2]. This talk will specifically address (i) the dynamics of exciton 
migration in oligo-(p-phenylene vinylene) and oligothiophene assemblies [3], and (ii) exciton dissociation in donor-acceptor materials, including models for P3HT-PCBM heterojunctions [4,5] as 
well as highly ordered thiophene-perylene diimide assemblies [6]. In line with experiment, our simulations show that the primary exciton breakup is an ultrafast and coherent process. 
Furthermore, efficient free carrier generation is shown to be feasible on ultrafast time scales, despite the Coulomb barrier that typically far exceeds thermally available energy. This is due to 
several factors that can be shown to work together [5]: First, the effective lowering of the Coulomb barrier due to charge delocalization, second, the vibronically hot nature of the primary 
excitonic and charge transfer states, and third, the effect of initial exciton delocalization. From these studies, design principles can be extracted for optimal donor-acceptor combinations, 
especially in regioregular assemblies.

[1] M. H. Beck, A. Jäckle, G. A. Worth, and H.-D. Meyer, Phys. Rep. 324, 1 (2000). 
[2] K. H. Hughes, B. Cahier, R. Martinazzo, H. Tamura, and I. Burghardt, Chem. Phys. 442, 111 (2014). 
[3] A. N. Panda, F. Plasser, A. J. A. Aquino, I. Burghardt, and H. Lischka, J. Phys. Chem. A, 117, 2181 (2013), R. Binder, J. Wahl, S. Römer, and I. Burghardt, Faraday Disc., 163, 
205 (2013), R. Binder, S. Römer, J. Wahl, and I. Burghardt, J. Chem. Phys., 141, 014101 (2014).
[4] H. Tamura, I. Burghardt, and M. Tsukada, J. Phys. Chem. C 115, 9237 (2011), H. Tamura, R. Martinazzo, M. Ruckenbauer, and I. Burghardt, J. Chem. Phys., 137, 22A540 (2012),H. Tamura and 
I. Burghardt, J. Phys. Chem. C, 117, 15020 (2013).
[5] H. Tamura and I. Burghardt, J. Am. Chem. Soc. (Communication) 135, 16364 (2013), M. Huix-Rotllant, H. Tamura, and I. Burghardt, J. Phys. Chem. Lett., DOI: 10.1021/acs.jpclett.5b00336 (2015). 
[6] T. Roland et al., Phys. Chem. Chem. Phys. 14, 273 (2012), J. Wenzel, A. Dreuw, and I. Burghardt, Phys. Chem. Chem. Phys. 15, 11704 (2013).

Solution-processed semiconductor nanocrystals have attracted great interest in photonics including color conversion and enrichment in quality lighting and display backlighting [1]. 
In this talk, we will present architectures of colloidal nanocrystals obtained by tailoring and controlling the dimensionality, size, and composition of these nanostructures in an effort to 
realize high performance in light generation and lasing [2]. These cover types of colloidal quantum dots, quantum rods and quantum wells. Based on the rational design and control of excitonic 
processes in these nanocrystals, we successfully demonstrated highly efficient light-emitting diodes [3] and lasers [4,5]. To this end, we systematically studied and showed that electronic-type 
tuning in colloidal quantum heterostructures allows for fine tunability [6]. Here ultra-low threshold stimulated emission was achieved using engineered core/shell architectures enabling 
substantially suppressed Auger recombination, enabling the first liquid laser of nanocrystals [4]. Also, we developed an all-colloidal solid laser using these nanocrystals as the optical gain 
media for the first time in a fully colloidal resonator [5]. As an extreme case of solution-processed highly-confined quasi-2D colloids, we showed that the atomically flat heteronanoplatelets 
uniquely combine ultra-low threshold stimulated emission and record high optical gain coefficients and the controlled stacking of these nanoplatelets further tune their excitonic properties [7].
The recent progress in the colloidal optoelectronics suggest that solution-processed quantum materials hold great promise to challenge epitaxial counterparts in the near future.

References:

[1] T. Erdem and H. V. Demir, Nature Photonics 5, 126 (2011); H. V. Demir et al., Nano Today 6, 632 (2011)
[2] B. Guzelturk et al., Laser & Photonics Reviews 8, 73 (2014); and J. Phys. Chem. Lett. 5, 2214 (2014).
[3] X. Yang et al., Advanced Materials 24, 4180 (2012); Advanced Functional Materials 24, 5977 (2014); ACS Nano 8, 8224 (2014); and Small 10, 246 (2014).
[4] Y. Wang et al., Advanced Materials 27, 169 (2015).
[5] B. Guzelturk et al., Advanced Materials in press (2015). DOI: 10.1002/adma.201500418 
[6] A. F. Cihan et al. ACS Nano 7, 4799 (2013); and J. Phys. Chem. Lett. 4, 4146 (2013).
[7] B. Guzelturk et al. ACS Nano 8, 6599 (2014); and ACS Nano 8, 12524 (2014). 

Symmetry aspects of ZnO clusters: from nested shells to tetrapods

A. Dmytruk1*, I. Dmitruk2, I. Blonskyi1, R. Belosludov3, A. Kasuya3
 
1 Institute of Physics, National Academy of Sciences of Ukraine, 
prosp. Nauky, 46, Kyiv, Ukraine
2 Faculty of Physics, Taras Shevchenko National University of Kyiv, 
prosp. Glushkova, 2, Kyiv, Ukraine
3 Institute for Materials Research, Tohoku University, 
Sendai 980-8577, Japan
*Corresponding author: admytruk@gmail.com

Discovery of ZnO magic clusters [1] in mass spectra of laser ablation of zinc peroxide bulk powder [2] initiated discussion on their structure [3] and properties [4]. We suggest a nested shell 
model of the clusters, which perfectly explains the observed magic numbers in the mass spectra. To validate the model, we performed a stress-test for the clusters: a small random displacement of 
all the atoms, and the following geometry optimization of so distorted clusters. Multiple such calculations have been run to ensure statistical reasonableness of the results. To reduce the 
elapsed time, we performed calculations at the semiempirical theory level AM1, which has been shown acceptable for ZnO cluster energy evaluation [5]. Firefly 8.1.0 software [6] was used for the 
cluster geometry optimization. A small code on C has been written to perform the stress-test. The important option of the calculations was the possibility to keep a desired symmetry of a cluster 
during both the distortion and the geometry optimization. In such a way we have studied the total energy of the clusters on step-by-step reduced symmetry. It was found, that reduction of the 
symmetry for some clusters lowers their total energy, that can be explained by Jahn-Teller effect [7]. Such clusters are symmetrically appropriate seeds for growth of ZnO tetrapods.

1. A. Dmytruk, I. Dmitruk, I. Blonskyy, R. Belosludov, Y. Kawazoe, A. Kasuya. Microelectron. J 2009, 40, 218.
2. A. Dmytruk, I. Dmitruk, A. Kasuya. Mat.-wiss. u. Werkstofftech. 2009, 40, 265.
3. B. Wang, X. Wang, J. Zhao. J. Phys. Chem. C 2010, 114, 5741.
4. C. Caddeo, G. Malloci, F. De Angelis, L. Colombo, A. Mattoni. Phys. Chem. Chem. Phys., 2012, 14, 14293.
5. A. Dmytruk. Advanced Materials Research 2015, 1117, 26.
6. A. Granovsky. http://classic.chem.msu.su/gran/firefly/index.html
7. H. Jahn, E. Teller. Proc. Roy. Soc. London A 1937, 161, 220.

Localized surface plasmon resonances (LSPRs) do not only exist in metallic nanoobjects/nanoparticles. One of the major necessities for an LSPR to occur is a sufficiently high 
density of free charge carriers. Consequently, degenerately doped semiconductor nanoparticles are candidates for the occurrence of LSPRs.
In contrary to metal nanoparticles, the charge carrier density in degenerately doped nanoparticles is tunable by adjusting the degree of doping which results in an easily tunable resonance 
frequency of the LSPR over a broad range of the NIR.(1)
We will discuss the plasmonic properties of degenerately self-doped Cu2-xSe nanoparticles. We will show results on the influence of the doping degree on the LSPR as well as recent
results of various other chemical approaches to influence the plasmonic behavior of this type of nanoparticles (e.g. shell growth, ion exchange etc.).(1-3)

(1)    Dorfs, D.; Hartling, T.; Miszta, K.; et al. J. Am. Chem. Soc. 2011, 133, 11175.
(2)    Dilena, E.; Dorfs, D.; George, C.; et al. J. Mater. Chem. 2012, 22, 13023.
(3)    Scotognella, F.; Della Valle, G.; Kandada, A. R. S.; Dorfs, D.; et al. Nano Lett. 2011, 11, 4711.

The high flexibility of chemical routes for tailoring the properties of colloidal nanocrystals (NCs) and NC-based composites stimulates ever-growing activities on synthesis, 
investigation, and application. Heterogeneous NCs of alloy, core-shell, side-by-side and other types of NCs were developed. Revealing the internal structure of such heterogeneous NCs and 
bringing them into accord with model expectations is much more challenging than for their homogeneous counterparts. Along with varying the NC size and composition, changing the ligand on NC 
surface is additional powerful way of tuning NC properties. Even though numerous NC-ligand systems have been studied and show promising application outlooks, many aspects of NC-ligand 
interaction are to be clarified yet. 
Different sets of spectroscopic techniques have been used for getting understanding about the structure of the NCs and its relation with their apparent physical and chemical properties. X-ray 
photoemission spectroscopy (XPS) and vibrational Raman spectroscopy are both sensitive to chemical bonds in matter, herewith providing a complimentary information about them. When applied to 
colloidal NCs, XPS delivers information about the chemical composition of NC, stabilizing ligands, and chemical interaction between both. From Raman scattering spectrum of NCs one can derive 
information on atomic vibrations (phonons), lattice constant, degree of surface disorder, strength of electron phonon coupling. 
Here, we applied the combination of Raman scattering and Photoemission spectroscopies to several challenging NC systems, aiming at the establishing the internal NC structure and ligand effect on
the structure of their surface. In particular, a comparison of CuInS2 NCs either alloyed with Zn atoms or covered with a ZnS shell was performed. Owing to the possibility of selective 
probing  the CuInS2 and ZnS phases using different laser wavelengths, the two ways of Zn incorporation can be revealed in the Raman spectra. By analyzing the variation of the 
elemental composition, e.g. Cu/Zn ratio, from XPS data, the evolution of the ZnS shell thickness or Zn content in the CuInS2 lattice upon Zn-carrying reagent in the solution is established. 
Another kind of NCs studied were ultrasmall (< 2 nm) CdSe and In2S3 NCs. They show phonon Raman spectra distinct from their massive counterparts, and we consider the 
high surface-to-volume ratio as well as non-stoichiometry, as the possible reasons defining the characteristic lattice vibrations. The role of stabilizing molecules on the surface structure of 
ultrasmall NCs was also investigated. A separate XPS/Raman investigation was performed on the effect of initial ligand substitution for iodide or chloride on the surface of CdSe and PbSe NCs. 
The exchange for halide ligands was previously shown to improve electrical properties of the NCs, but other possible effects still need to be investigated. Here we investigated this exchange for 
different NC cation (Cd or Pb) and halide ion (I or Cl) and found different effect on both XPS and Raman spectra of NCs. These results obtained are discussed in terms of the efficiency of the 
ligand exchange and resistance of the NC surface towards oxidation. 

Surprisingly, after more than 20 years of research the mechanism of radiative recombination of the ground exciton state in colloidal CdSe nanocrystals (NCs), which is known to 
be an optically passive (dark) exciton state, is still under discussion. The experimentally observed radiative recombination from the dark exciton state should be caused by the admixture with 
optically active (bright) exciton states via phonons or some external or internal magnetic field. The energy splitting between the dark exciton and the lowest bright exciton state depends 
strongly on the size and shape of the NC and might be of the order of 20 meV in CdSe NCs with 2.3 nm diameter.
In this work we study theoretically the effect of the spins of the surface dangling bonds on the PL of CdSe NCs.[1] We show that spins of dangling bonds open new recombination channels for the 
dark exciton recombination which is connected with flip-flip and flip-flop spin-assisted recombination of the dark exciton.  Calculations show that at low temperatures the interaction between 
dangling bonds and NC excitons leads to the dynamical polarization of the dangling bond spins along the anisotropic axis following by the formation of a dangling bond magnetic polaron.  An 
increase of the temperature, or of the external magnetic field perpendicular to the anisotropic axis, destroys the polaron state. This results in a shift of the transition energy and an increase 
of its recombination rate. Thus thermal depolarization  of the polaron state may explain the small activation energies observed in the  temperature dependences of the exciton lifetimes in CdSe 
NCs. The exchange interaction of the electron spin with spins of the surface dangling bonds explains also radiative recombination of the dark excitons in nanowires, nanorods and nanoplatelets.

[1] A. Rodina and Al. L. Efros to be published

Owing to f electrons, rare-earth elements present unique magnetic and optical properties that are potentially useful for imaging of malignant tumors. Towards such applications, 
herein we present our recent results on magnetic resonance (MR) and upconversion luminescence imaging of tumors by using rare-earth nanoparticles such as NaGdF4 and NaGdF4:Yb/Er. To tailor the 
properties of the rare-earth nanoparticles, core-shell NaGdF4:Yb/Er@NaGdF4 structures were prepared and successfully used in detecting micrometastasis of gastric cancer. Doping rare-earth 
nanocrystals with different lanthanides or transition metal ions has been demonstrated to be effective for tailoring the optical properties of the rare-earth nanoparticles. However, an unusual 
superlattice structure with aligned crystalline orientations was observed from polydispersed NaYF4:Yb,Er,Mn nanocrystals with dispersity up to α~20%. The underlying mechanism will be discussed.

We will review recent advances in the control and understanding of plasmons in systems that have atomic dimensions along one or more directions. In particular, we will discuss 
plasmons in graphene, carbon nanotubes, and fullerenes, as well as thin metal layers and molecules such as polycyclic aromatic hydrocarbons. A simple, powerful, analytical eigenmode expansion 
formalism will be reviewed in the electrostatic limit, along with tutorial examples of application to the understanding of plasmons in these systems, including the derivation of approximate 
expressions for the plasmon frequencies and wave functions. Intrinsic advantages of plasmons in atomic-scale systems will be also discussed, and in particular, theie large electrical tunability,
their strong nonlinear response, and the possibility of reaching quantum strong coupling.

The talk will describe optical and electronic properties of nanostructures assembled from interacting plasmonic, excitonic and bimolecular elements. The combination of crystalline 
nanocrystals having superior optical responses (which are much stronger than the molecular ones) and bio-molecular building blocks (DNAs, proteins, polymers) is a very intriguing opportunity. 
New physical effects in these nanostructures may come from Coulomb, electromagnetic and tunnel interactions.  The talk will include a few examples: 
(1)	When constructing our structures we were certainly inspired by nature. Helical plasmonic nanostructures, made from gold nanoparticles and DNA-origami, have the geometry of α-helix protein.  
Such plasmonic bio-assemblies exhibit an unprecedented strength of optical activity (circular dichroism) in the visible wavelength interval [1,2].  
(2)	Nano-assemblies from semiconductor nanocrystals demonstrate ultra-fast Förster energy transfer [3] and resemble natural photosynthetic systems.  
(3)	Metal nanocrystals exhibit strong collective resonances, so-called plasmon excitations. The wave functions of plasmons are complex and we treat such wave functions using the Kinetic DFT 
recently developed by us [4].  In the next step, we apply the Kinetic DFT to the problem of generation of high-energy electrons in nanocrystals with hot spots [5,6]. 
(4)	Many-body interactions between excitons, plasmons and phonons in nano-assemblies should be treated using theoretical methods of quantum optics and give rise to quantum interference effects 
observed as Fano transparency windows [7,8].  

[1] A. Kuzyk, R. Schreiber, Z. Fan, G. Pardatscher, E.-M. Roller, A. Högele, F. C. Simmel, A. O. Govorov, T. Liedl, Nature 483, 311 (2012). 
[2] A.Kuzyk, R. Schreiber, H. Zhang, A.O. Govorov, T. Liedl, Na Liu, Nature Materials 13, 862 (2014).
[3]  C. E. Rowland, I. Fedin, H. Zhang, S.K. Gray, A.O. Govorov, D.V. Talapin, and R.D.Schaller, Nature Materials 14, 484  (2015). 
[4] A.O. Govorov, H. Zhang, V. Demir, and Y.K. Gun'ko, Nano Today 9, 85 (2014);  A.O. Govorov and H. Zhang, J. Phys. Chem. C, 119, 6181 (2015). 
[5]  H. Harutyunyan, A. B. F. Martinson, D. Rosenmann, L.K. Khorashad, A.O.Govorov, and G.P. Wiederrecht, Nature Nanotechnology, online (2015). 
[6] W. Li, Z. J. Coppens, L. Vázquez, W. Wang, A. O. Govorov,   J. Valentine, Nature Communications, accepted. 
[7] W. Zhang, G. W. Bryant, A. O. Govorov, Phys. Rev. Lett. 97, 146804 (2006).   
[8] M. L. Kerfoot, A.O. Govorov, D. Lu, R. J. O. Babaoye, Y. N. Gad, C. Czarnocki, M. Tsukamoto, A. S. Bracker, D. Gammon, and M. Scheibner, Nature Communications 5, 3299 (2014).   

Quantum dynamics calculations are carried out on model systems corresponding to two, three and four quantum dots interacting with a dissipative, plasmonic structure.  We show how 
ultrafast laser pulses can be used to create significant entanglement among the dots from an initially cold system.  We also show how a repeating laser pulse pattern can be used to prepare the 
system in an entangled state for an arbitrary length of time.

In order to explore the possibility for designing and fabricating nanostructures based on non-directional bonding, we have recently investigated a Fullerene-metal coordinated system
and produced magic number hybrid C60-Au clusters on the Au(111) surface. One of such magic number clusters, (C60)7-Au19, consists of a hexagonal 19-Au atom island wrapped
around by seven C60 molecules. One of the molecules sits directly above the gold island, the remaining six molecules sit next to the edges of the gold hexagon. A (C60)12-Au49 cluster is
also observed. In this case, there are three molecules sitting on top of a 49-atom Au island and nine sitting next to the step edges. Take the (C60)7-Au19 cluster for example, the 
moleculemolecule vdW bonding is optimized by maintaining a C60-C60 distance very close to the distance in bulk C60. Molecule-Au bonding is also optimized by connecting each of the
surrounding six molecules to a step edge. The higher charge density at the step edges favours the charge transfer from Au to C60. The lateral distance between the molecule sitting on top of
the Au island and the surrounding six molecules is very close to the C60-C60 distance in bulk C60, allowing an effective interaction among all seven molecules. The result is that this hybrid
(C60)7-Au19 cluster has a remarkable stability. The 19-Au island on its own is not stable beyond 200 K, a (C60)7 cluster on its own is not stable beyond 240 K. The hybrid cluster,
however, is stable up to 400 K, demonstrating a clear property-structure relationship and the potential of nano-scale assembly in creating new materials. The hybrid clusters are held
together by neither directional H-bonding nor covalently bonding. Instead, the collective interaction among all the constituents within the cluster is responsible for the stability of the
cluster. We call this type of interaction "globally optimized metal-organic coordination". This global interaction arises from charge transfer between the metal and the molecule as well as
the vdW bonding between the molecules.

Single particle spectroscopy is a powerful tool for studying nanomaterials. It is capable of revealing information about how differences in size, shape and environment affect 
properties - which is often hidden in ensemble measurements. This talk will concentrate on recent results from my laboratory where ultrafast transient absorption microscopy has been used to 
study energy relaxation in single metal nanostuctures. These measurements provide detailed information about the damping of the breathing vibrational modes of the nano structures, and the motion 
of propagating surface plasmon polaritons (SPPs) in metal nanowires. For the breathing mode measurements, the main topic of interest is how the damping is affected by viscous liquids, especially 
the role of visco-elasticity. For the SPPs our experiments provide unique information about propagation length, and how the SPPs couple between different nano structures. 

We present theory of light-matter interaction in multi-functional graphene quantum dots. By engineering size, shape, edge, sublattice symmetry, number of layers and carier density 
one can generate semiconductor, metallic and magnetic nanoparticles out of graphene. We will describe how metallic gate and light can control magnetic properties of graphene quantum dots with 
broken sublattice symmetry and how semiconductor graphene quantum dots can generate entangled photon pairs via  bi-exciton-exciton cascade. 

Resonant coupling between distinct excitons in organic supramolecular assemblies and inorganic semiconductors is supposed to offer a new approach to design novel opto-electronic 
devices. Here, we report on colloidal nanohybrids, which consist of supramolecular tubular J-aggregates decorated with semiconducting quantum dots (QDs) via an electrostatic self-assembly 
process. The role of the QD in the energy transfer process can be switched from donor to acceptor by tuning its size and thereby the band gap while keeping the chemistry unaltered. The tubular 
structure of the J-aggregates remains unaltered and the particles are located within a close distance to the aggregate surface of less than 4 nm. The close proximity of J aggregates and QDs 
results in strong excitation energy transfer coupling, which is close to 100% for the case of energy transfer from the QD donor to the J-aggregate acceptor and approx. 20% for the reverse case. 
This system demonstrates a model for an organic-inorganic light harvesting complex using methods of self-assembly in aqueous solution and highlights a possible route towards hierarchical 
synthesis of structurally well-defined supramolecular objects for advanced functionality.

We discuss the quantum light emission of many two level emitters coupled to a metal- nanoparticle for two specific cases:
a) We develope an exact density matrix approach to the full, nonperturbative quantum statistics and light matter correlations for a single plasmon mode under the condition of external pumping 
and dissipation. Since the numerical effort scales with the third power in the number of emitters, hundreds of identical emitters can be treated exactly. Notably the solution requires none of 
the common approximations such as good/bad cavity limit. 
b) We apply a number state basis to explain time resolved luminescence 
of semiconductor quantum dots coupled to a metal - nanoparticle as a function of nanoparticle diameter and spacer between the metal and the emitters. 
A comparison to experiments (H.Lange et al, Hamburg) is given.

reference:
Numerically exact solution of the many emitter-cavity laser problem: Application to the fully quantized spaser emission,
Marten Richter, Michael Gegg, T. Sverre Theuerholz, and Andreas Knorr
Phys. Rev. B 91, 035306 (2015).

Controlling the energy level alignment at hybrid inorganic/organic semiconductor interfaces is required to enable a desired functionality of that heterostructure. For instance, a 
type-II alignment may facilitate charge separation while a type-I alignment would allow for energy transfer and radiative recombination. For the inorganic semiconductor ZnO, two types of 
molecular interlayers can be employed to tune the energy level alignment with respect to an organic semiconductor deposited on top. These are (i) covalently bonded self-assembled monolayers with 
dipoles and (ii) strong molecular acceptors and donors. The underlying, fundamentally different, mechanisms giving rise to the level tuning with both interlayer types are discussed, and the 
impact of different level alignment on hybrid heterostructure function (energy and charge transfer) is demonstrated.

Semiconductor nanocrystals attract scientific attention because of their size and shape dependent properties, making them interesting candidates for application in solar energy 
conversion, lighting, display technology, or biolabelling. However, many of the best studied nanocrystalline materials contain toxic heavy metals; this seriously limits their potential for 
widespread application. Possible less toxic alternatives to cadmium- or lead-containing semiconductors can be found among copper sulfide-based semiconductors, such as copper indium sulfide, 
copper indium selenide, copper indium zinc sulfide, copper tin zinc sulfide, or copper tin sulfide. However, the synthesis of these ternary and quaternary materials requires the adjustment 
of the reactivities of two or three cationic precursors, which makes finding optimum reaction conditions more challenging compared to the synthesis of binary compounds. Frequently, during the 
growth process of such ternary and quaternary semiconductors the formation of copper sulfide  seeds and/or copper sulfide-containing hybrid nanostructures can be observed. Copper sulfide, which 
is a solid state superionic conductor, can play the role of the catalyst in such reactions and influence the shape of the resulting ternary and quaternary materials. Here, our recent results in 
the synthesis of ternary and quaternary copper sulfide-based semiconductor nanocrystals will be presented and the role of the copper sulfide seeds, as well as the ligand molecules and solvents 
in the shape control of the resulting materials will be discussed. 

During the last decade cation exchange (CE) reactions have emerged as a new strategy for fabrication of nanomaterials via post-synthetic chemical modification. On the nanoscale CE 
reactions were applied and studied mostly on semiconductor II-VI, III-V and IV-VI compounds. In this method cations of a pre-synthesized parent nanocrystal (NC) can be partially or completely 
replaced by new guest cations with retention of its size, shape, and, in some cases, even crystal structure. A main prerequisite for such selective transformation is the preservation of the 
anion sublattice of NCs owing to a much larger size of anions, relative to cations, and thus their lower mobility in a crystal lattice. Therefore, pre-formed NCs serve as templates for a design 
of novel nanostructures. In this respect especially interesting is partial CE as a toolkit for fabrication of complex alloyed and heterostructures. 

In our work we address these two types of structures starting from binary copper sulfide and selenide NCs. Thus, we propose a straightforward and reproducible approach to prepare multinary 
alloyed NCs. Our strategy includes two main steps: 1) synthesis of binary copper chalcogenide nanoparticles [1] with 2) subsequent partial in-situ CE (i.e. partial replacement of host Cu+ ions 
by guest cations, such as Zn2+, In3+ or Sn4+) with preservation of anionic framework, and thus without major altering of the size and shape of parent NCs [2, 3]. 
In this way, our synthesis scheme combines a facile NC morphology control with its compositional tunability by simply adjusting the initial feed ratio of guest cation-precursors to copper 
chalcogenide particles in the reaction mixture.

On the other hand, we show that by applying partial CE it is also possible to obtain heterostructures starting from copper selenide particles. This has been achieved by exchanging Cu+
ions by Zn2+ or Cd2+ ions which formed phases (ZnSe, CdSe) that are in principle immiscible with Cu2-xSe. In both cases, partial CE led essentially to Janus-like 
NC heterostructures represented by a ZnSe (or CdSe) domain sharing a close-to-flat interface with the remaining Cu2-xSe portion. We also found that the exchange is generally faster 
and more effective in Cu2-xSe NCs presenting a higher density of Cu vacancies, which supports vacancy diffusion as one of the main drivers of CE.

[1] Saldanha P. L. et al. Generalized One-Pot Synthesis of Copper Sulfide, Selenide-Sulfide, and Telluride-Sulfide Nanoparticles. Chem. Mater. 2014, 26, 1442-1449.
[2] Lesnyak V. et al. Alloyed Copper Chalcogenide Nanoplatelets via Partial Cation Exchange Reactions. ACS Nano 2014, 8, 8407-8418.
[3] Akkerman Q. A. et al. From Binary Cu2S to Ternary Cu-In-S and Quaternary Cu-In-Zn-S Nanocrystals with Tunable Composition via Partial Cation Exchange. ACS Nano 2015, 9, 521-531.

Monolithic nanoporous metals and carbides are technologically important for a wide range of applications, from catalysts and catalyst supports to energetic materials. A convenient 
way of preparation starts with co-gelation of interpenetrating networks of carbonizable polymeric and oxide nanoparticles. Heating at high temperatures (e.g., 800 deg C) under argon yields 
carbon and oxide nanoparticles in intimate contact, whereas they react carbothermally yielding self-supporting monolithic nanoporous 3D dispersions of metallic (case of Fe, Co, Ni, Cu, Sn) or 
carbide (case of Cr, Ti, Hf) nanoparticles. Contact and mixing of reacting nanoparticles can be improved by nanoencapsulation of the entire polymer-oxide network under a thin meltable conformal 
polymer coating, reducing the temperature of the carbothermal reduction by as much as 400 deg C. Advantageously, carbonizable polymers have been selected from the family of phenolic resins, 
e.g., resorcinol-formaldehyde or polybenzoxazines, whereas the acidity of the oxide gelling system catalyzes the gelation of the polymer. Polybenzoxazines in particular are highly crosslinked 
and sturdy mechanically, operating as sacrificial (consumable) templates holding the developing nanostructure together longer for partial annealing to take effect, yielding larger, defect-free 
monoliths. The porosity and particle size of nanoporous iron obtained from interpenetrating polybenzoxazine-iron oxide networks can be fine-tuned further by varying the processing temperature. 
Ignition of 800-deg C processed, 91% porous Fe monoliths filled with LiClO4 yields explosive behavior by rapid expansion of the pore-filling gas. Processing at higher temperatures (>1,000 deg C) 
reduces porosity to <72%, pore walls get thicker and ignition of LiClO4-filled samples results in thermite behavior. 

Surface plasmon resonance in metal nanostructures has been used to enhance the efficiency of semiconductors and/or molecular chromophore based solar energy conversion devices by 
increasing the absorption or energy transfer rate through the enhanced local field strength. In more recent years, it has been shown that excitation of plasmons in metal nanostructures can lead 
to the injection of hot electrons into semiconductors and enhanced photochemistry. This novel mechanism suggests that plasmonic nanostructures can potentially function as a new class of widely 
tunable and robust light harvesting materials for photo-detection or solar energy conversion. However, plasmon-induced hot electron injections from metal to semiconductor or molecules are still 
inefficient because of the competing ultrafast hot electron relaxation (via ultrafast electron-electron and electron-phonon scattering) processes within the metallic domain. 

In this paper we discuss a recent study on the plasmon-exciton interaction mechanisms in colloidal quantum-confined semiconductor-gold nanorod heterostructures. In CdSe NRs with Au tips, the 
distinct plasmon band of the Au nanoparticles was completely damped due to strong interaction with the CdSe domain. Using transient absorption spectroscopy, we show that optical excitation of 
plasmons in the Au tip leads to efficient hot electron injection into the semiconductor nanorod. In the presence of sacrificial electron donors, this plasmon induced hot electron transfer 
process can be utilized to drive photoreduction reactions under continuous illumination. Ongoing studies are examining the mechanism of this surprisingly efficient plasmon induced hot electron 
transfer process and explore possible approaches for  improving its efficiency through controlling the size and shape of the plasmonic and excitonic domains.

Semiconductor nanocrystals with sufficiently large dimensions can host electron-hole excitons whose confinement is governed by the Coulomb interaction. Such nanocrystals may thus 
connect the regime of strong exciton confinement occurring in very small nanocrystals to that of purely electrostatically bound, bulk-type excitons in macroscopically large crystals. Here, we 
present an optical characterization of excitons and bi-excitons in CdTe nanocrystals with a diameter of 7 to 23 nm, surface-passivated with a CdSe shell with a thickness of 1.5 nm. We report the 
results of micro-photoluminescence spectroscopy of individual CdTe nanocrystals at cryogenic temperature under varying excitation powers and magnetic field strength.  We determine the bi - 
exciton binding energy, diamagnetic shift constant and Landé g-factor, observing that they are approaching their bulk limit values with increase of nanocrystal size. Our results indicate that 
individual colloidal nanocrystals of sufficiently large size are useful model systems to neatly characterize exciton states that already have a strong bulk character.

Metal nanomaterials are one major class of enablers for clean technology. For example, they play vital roles as electrocatalysts-the core part in fuel cells. Despite large
efforts in academia and industry, the world-wide commercialization of fuel cells is still blocked by critical issues including high cost, insufficient activity, and low durability. 
These issues are all closely related to the electrocatalysts. Therefore, it is of great interests to develop simple synthetic methods and generate metallic electrocatalysts of 
both high catalytic activity and high durability. 
Here we will present facile spontaneous methods to fabricate a series of metallic aerogels (such as Pd, Pt, PtPd, PtAg, etc.) with high electrocatalytic performances in fuel cell 
reactions. The porous metallic aerogels have nanowire/nanotube-like network nanostructures with very high surface area and large porosity.1-3 Electrochemical tests show that these 
metallic aerogels have very high electrocatalytic activities combined with good durability toward oxygen reduction reaction (ORR) or ethanol/formic acid oxidation reactions. For 
instance, the beta-cyclodextrin modified Pd aerogel show 2.3 times mass activity toward ethanol electrooxidation compared to the commercial Pd/C;1 and the Pt80Pd20 aerogel show 5 
times mass activity enhancement toward ORR compared to the commercial Pt/C catalyst.2,3
Our results show that metallic areogels are a new class of promising electrocatalysts.

Soon to Come

Plasmonic excitations in a nanocavity possess a unique ability to create highly confined and intense local field with a broad energy distribution. It has been demonstrated in our 
several recent studies that the color of electroluminescence from single molecules can be effectively tuned once it is placed within a nanocavity constructed by a scanning tunneling 
microscopy[1a]. The same plasmon generated under the excitation of a weak continuum light can result in stimulated Raman spectral images with unprecedented spatial resolution, below one 
nanometer[1b], which enable to observe the inner structure and surface configuration of a single molecule by optical means. Moreover, the inelastic electron scattering process can even become 
nonlinear under such plasmonic excitations[1c]. By combining the density matrix approach and first principles calculations, the experimentally observed peculiar light emission spectral profiles 
of the single molecules have been fully reproduced. It is revealed that the nanocavity plasmon (NCP) could act like a tunable, strong and ultra-fast electromagnetic source that can alter the 
color of the emission through nonlinear processes[2a,2b]. In the conventional theory for light-matter interaction, it is generally assumed that the electromagnetic field is a classic field that 
uniformly interacts with the molecule. However, the spatial distribution of the NCP field needs to be comparable with the size of the molecule to achieve sub-nm resolution Raman images and the 
uniform plan wave approximation is no longer appropriate. We have developed a general theory to fully take into account the locality of the NCP. It is found that the optical transition matrix of 
the molecule becomes dependent on the position and distribution of the plasmonic field, which is responsible for the spatially resolved Raman image of a molecule. It is also shown that the 
resonant Raman image reflects the electronic transition density of the electronic transition. In combination with the first principles calculations, the simulated Raman images of a porphyrin 
derivative adsorbed on the silver surface nicely reproduce their experimental counterparts. 

1.	(a) Z.C. Dong, et al. Nature Photonics, 4 (2010) 50; (b) R. Zhang, et al. Nature, 498 (2013) 82; (c) C.K. Xu et al. Nature Physics, 10 (2014) 753
2.	(a) G.J. Tian, PRL, 106 (2011) 177401; (b) G.J. Tian and Y. Luo, ACIE, 52 (2013) 4814; (c) S. Duan, et al., to be published.

Colloidal inorganic nanocrystals (NCs) are among the most exploited nanomaterials to date due to their extreme versatility [1]. Research on NCs went through much advancement in the 
last fifteen years, for example in the synthesis, which opened up the possibility to control their size, shape and topology in chemical composition. An additional step forward was the creation 
of a wide range of superstructures from the assembly of such NCs. This, coupled with the possibility to replace the native ligands on the surface of the NCs with shorter molecules, has conferred 
unique electrical features to films of NCs that make them attractive for low cost alternatives to many technologies. Progress also came from the study of chemical transformations in 
nanostructures, most notably via cation exchange, which involves replacement of the sublattice of cations in a crystal with a new sublattice of different cations, while the sublattice of anions 
remains in place. Also, a new field of study has emerged recently, aiming at investigating the transformations in colloidal synthesized nanomaterials under conditions like thermal annealing and/
or irradiation. In part this research is boosted by the recent availability of microscopy tools by which one can follow the transformations on individual NCs in-situ, i.e. when such 
perturbations are actually applied to the sample. Finally, new fascinating perspectives are opened by new classes of plasmonic NCs that are not based on noble metals [2]. The present talk will 
highlight the recent progress from our group on the synthesis of NCs with various functionalities (with emphasis on plasmonic and semiconducting materials), on the study of their chemical and 
structural transformations, and on their assembly.   
 
[1] M. Kovalenko, L. Manna, et al., ACS Nano  (2015), doi: 10.1021/nn506223h.
[2] A. Comin and L. Manna, Chem. Soc. Rev. (2014), 43, 3957-3975.

We introduce our recent work on multi-gram scale syntheses of semiconductor nanocrystals (Cd3P2,[1] Cd3As2, Zn3P2/ZnO,[2] SnO2,[3] ect.[4]) and their composites (Cd3P2/CdSe, Cd3P2/CdS,
Cd3As2/Cd3P2, SnO2/C,[3] Cd3P2/PS,[5] MoS2/CNTs[6]) via the hot-bubbling technique.[7] The synthesized nanocrystals have been employed as sensitized solar cells, lithium ions battery and bio-labeling probes.
It was found that the II-V group semiconductor quantum dots (QDs) exhibit prominent size-effects by control of the synthetic parameters such as reaction temperature, growth time, types of 
capping ligands and Cd:P ratio in the initial precursors. The band-emission of Cd3P2 originates from the recombination of a fast decay of the bright state and a slow component resulting 
from the transition associated with a low-lying "dark" state in Cd6P7 QDs. The band alignment at the hetero-interfaces in Cd3P2/CdSe core/shell QDs (CS-QDs) undergoes a change from a Type-I
to a Type II structure when the CdSe shell thickness increases. The energetic positions of the conduction and valence bands for the different-sized Cd3P2 QDs were determination using cyclic
voltammetry.[8] The electrochemical band gap energy (ΔEEl) was correlated to the optical band gap energy (ΔEOp), and the energy level offsets of Cd3P2 together with TiO2, CdSe and CdS were determined.
The synthesized QDs were assembled onto an optically transparent conductive substrate (F-doped tin oxide) and a Cd3P2 QDs sensitized solar cell (QDSSC) was prepared.[9] The incident photon to current
efficiency (IPCE) spectra of core Cd3P2 and CS-QDs on a TiO2 (P25) electrode measured in I3-/I- electrolyte resembles the corresponding absorbance, which demonstrates the Cd3P2 QDs to be photo-active
from the NIR to UV-vis spectral region. Results show that the QDSSC derived from Cd6P7/CdSe (4 MLs) CS-QDs gives the highest solar energy conversion efficiency of 3.2% under standard air mass
1.5 illumination (100 mW·cm-2, AM1.5). The short-circuit photocurrent density is 11.8 mA·cm-2, the open-circuit photovoltage is 0.48 V and the fill factor is 0.57. 
References
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A. Eychmüller, J. Am. Chem. Soc. 2010, 132, 5613-5616.
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117, 7026-7038; c) S. He, M. Huang, W. Ye, D. Chen, S. He, L. Ding, Y. Yao, L. Wan, J. Xu, S. Miao, J. Phys. Chem. B 2014, 118, 12207-12214.
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cX. Mao, S. Zhang, Q. Ma, L. Wan, H. Niu, S. Qin, S. Miao, J. Xu, J. Sol-Gel Sci. Technol. 2015, 1-9.

Molecular recognition is involved in nearly each process in biological systems. Chiral biomolecules discriminate their targets from all other molecules using the principle of 
complementarity. The recognition occurs, only if a receptor molecule fits energetically and structurally to a target molecule as lock fits to key. Here we report the investigation of the chiral 
recognition process between biomolecules and the surface of chiral nanocrystals, i.e. at nano/bio interface. Using the enantioselective phase transfer technique [1], we have shown that chiral 
CdSe quantum dots attach left-handed (L) and right-handed (D) enantiomers of chiral biomolecules with different efficiency. The formation of heteropairs (DL or LD) of the nanocrystals and 
biomolecules has been found up to 50 times more preferable comprising to the formation of homopairs (LL or DD). The preferential adsorption of L- or D-biomolecules requires the difference in the 
binding energies for heteropairs and homopairs, which has been determined by us from density functional theory (DFT) calculations as equal to 0.2 eV. We believe that this research will influence 
existing views and approaches in pharmaceutical industry and, in particular, in drug delivery systems.

Progress in nanomedicine will be driven by the ability to detect and manipulate the living matter at the molecular scale in order to cure cancers or fix genetic anomalies. One of 
the most promising way is the use of confined optical source in the ultra-violet wavelengths to image by self fluorescence, to analyse by enhanced Raman spectroscopy and to repair the wrong 
molecular sequences by inducing local chemical reaction.  Metallic nanoparticles are widely recognized as local sources of energy that resolve the above issues thanks to their optical properties 
based to the plasmon resonance. To achieve UV plasmonics, aluminum appears as the best candidate cite{gerard2015}. This metal has a negative dielectric constant combined with a low loss 
coefficient at UV wavelengths down to 100 nm, matching all the criteria to obtain high energy Localized Surface Plasmon Resonances (LSPR) [martin2014]. 
UV Localized Surface Plasmon Resonances (LSPRs) are very attracting because their energy matches with most of the electronic transition energies of molecules or solids. In this scope, the 
development of efficient and low-cost techniques for the synthesis of reproducible Al nano-structures with very good crystalline quality and optical properties has to be investigated [martin2013, martin2015].
 
In this presentation, we describe various methods for the growth of crystalline Al-NPs. The nanoparticles are made using very reproducible synthesis routes. The first approach is based on the 
reduction of aluminum ions. The second approach relies on the use of sono-chemistry of aluminum foils. Particles as small as 2nm have been synthesized and characterized with a transmission 
electron microscope, extinction spectroscopy and other methods. 
By playing on various the medium of synthesis and the temperature of reaction, it appears to be possible to tune under control the size of the nanoparticles. We completed the characterizations 
by investigating the optical properties of the synthesized Al NPs. Extinction measurements were performed on different solutions containing Al NPs using a UV-visible spectrometer.
	
Sharp extinction peaks appear unveiling LSPR excitations of Al NPs. The relatively low FHWM of the LSPR peak indicates a good homogeneity of the NPs size as it has been verified by the TEM 
characterizations. Furthermore, it appears that the alumina shell is tremendously photoluminescent, thus paving the way for numerous applications as nano markers . . .
To summarize, we described in this presentation various chemical method for the growth of aluminum nanoparticle. AL-NPs present a very good homogeneity and reproducibility. They exhibit sharp 
localized surface plasmon resonances (LSPRs) in the UV region as it has been showed by extinction spectroscopy characterization.

The authors acknowledge the Région Champagne-Ardennes, the Conseil général de l'Aube, and the FEDER funds through their support of the regional platform Nanomat. JM 
acknowledges support from the DRRT (project PlasmUV). JP thanks the ANR projects TWINS and NATO for the financial support.

[gerard2015] Gerard, Davy and Gray, Stephen K, "Aluminium plasmonics," Journal of Physics D: Applied Physics, Vol.48, No.18, 184001, 2015.
[martin2014] Martin, Jérôme and Kociak, Mathieu and Mahfoud, Zackaria and Proust, Julien and Gerard, Davy and Plain, Jérôme, "High-Resolution Imaging and Spectroscopy of
Multipolar Plasmonic Resonances in Aluminum Nanoantennas,"  Nano Letters, Vol.14, No.10, 5517-5523, 2014.
[martin2013] Martin, Jérôme and Proust, Julien and Gerard, Davy and Plain, Jérôme, "Localized surface plasmon resonances in the ultraviolet from large scale nanostructured
aluminum films," Optical Materials Express, Vol.3, No.7, 954, 2013.
[martin2015] Martin, Jérôme and Plain, Jérôme, "Fabrication of aluminium nanostructures for plasmonics," Journal of Physics D: Applied Physics, Vol.48, No.18, 184002, 2015.

Photovoltaic and photo-catalytic processes are initiated by a light-driven charge separation at an interface of two complementary materials. The separation competes with electron-
vibrational energy losses, energy transfer, charge recombination and other processes. Our group has developed [1-9] and implemented [10,11] a suite of theoretical and simulation approaches, 
aimed at modeling these events in the time domain and at the atomistic level of detail, as they occur in experiment. The approaches combine time-dependent density functional theory with non-
adiabatic molecular dynamics [1]. They treat electrons quantum-mechanically and nuclei semi-classically.

We show how the asymmetry of electron and hole transfer at a polymer/nanotube interface can be used to optimize solar cell performance [12]; that the mechanism of electron injection from a CdSe 
nanoparticle into nanoscale TiO2 depends on the dimensionality of the latter [13]; that plasmon-driven charge separation on TiO2 sensitized with plasmonic nanoparticles has a 50% chance to occur 
already during light absorption [14]; that optically dark states govern the rates and yields of singlet fission and charge transfer at a pentacene/C60 interface [15]; that nanoscale materials 
exhibit a new, Auger-assisted type of electron transfer [16]; that the low efficiency of photo-catalytic water splitting by GaN is due to unfavorable competition of charge relaxation and 
transfer [17]; that atomic defects can be both detrimental and beneficial for the charge separation [18]; how a long, insulating bridge can accelerate charge separation [19]; why graphene, a 
metal, can be used as a TiO2 sensitizer [20]; and how excited electrons can be extracted from quantum dots prior to relaxation [21]; how electron relaxation in quantum dots is influenced by 
Auger processes [22]; that energy losses dynamics in nanoscale materials are determined by dark, optically inaccessible states [23].

The software [10,11] is available free of charge at http://gdriv.es/pyxaid.

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3. S. R. Fischer, B. F. Habenicht, A. B. Madrid, W. R. Duncan, O. V. Prezhdo, "Regarding the validity of the time-dependent Kohn-Sham approach for electron-nuclear dynamics via trajectory 
surface hopping", J. Chem. Phys., 134, 024102 (2011).
4. H. M. Jaeger, S. Fisher, O. V. Prezhdo, "Decoherence induced surface hopping", J. Chem. Phys., 137, 22A545 (2012).
5. A. V. Akimov, O. V. Prezhdo "Second quantized surface hopping", Phys. Rev. Lett., 113, 153003 (2014).
6. L. Wang, D. Trivedi, O. V. Prezhdo "Global flux surface hopping", J. Theor. Comp. Chem., 10, 3598-3605 (2014).
7. A. V. Akimov, R. Long, O. V. Prezhdo, "Coherence penalty functional: A simple method for adding decoherence in Ehrenfest dynamics", J. Chem. Phys., 140, 194107 (2014).
8. L.-J. Wang, O. V. Prezhdo, "A simple solution to the trivial crossing problem in surface hopping", J. Phys. Chem. Lett., 5, 713 (2014).
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12. R. Long, O. V. Prezhdo "Asymmetry in the Electron and Hole Transfer at a Polymer-Carbon Nanotube Heterojunction", Nano Lett. 14, 3335 (2014).
13. D. N. Tafen, R. Long, O. V. Prezhdo "Dimensionality of nanoscale TiO2 determines the mechanism of photoinduced electron injection from a CdSe nanoparticle", Nano Lett., 14, 1790 (2014).R. Long, 
O. V. Prezhdo, J. Am. Chem. Soc., 136, 4343 (2014).
14. R. Long, O. V. Prezhdo "Instantaneous generation of charge-separated state on TiO2 surface sensitized with plasmonic nanoparticles", J. Am. Chem. Soc., 136, 4343 (2014).
15. A. V. Akimov, O. V. Prezhdo "Non-adiabatic dynamics of charge transfer and singlet fission at the pentacene/C60 interface", J. Am. Chem. Soc., 136, 1599 (2014).
16. H. Zhu, Y. Yang, K. Hyeon-Deuk, M. Califano, N. Song, Y. Wang, W. Zhang, O. V. Prezhdo, T. Lian "Auger-assisted electron transfer from photoexcited semiconductor quantum dots", Nano Lett., 14, 1263 (2014).
17. A. V. Akimov, J. T. Muckerman, O. V. Prezhdo "Nonadiabatic dynamics of positive charge during photocatalytic water splitting on GaN(10-10) surface: Charge localization governs splitting 
efficiency", J. Am. Chem. Soc., 135, 8682 (2013).
18. R. Long, N. J. English, O. V. Prezhdo "Defects are needed for fast photo-induced electron transfer from a nanocrystal to a molecule: Time-domain ab initio analysis", J. Am. Chem. Soc., 135, 18892 (2013).
19. V. V. Chaban, V. V. Prezhdo, O. V. Prezhdo "Covalent linking greatly enhances photoinduced electron transfer in fullerene-quantum dot nano-composites: Time-domain ab initio study", J. Chem. Phys. Lett., 4, 1 (2013).
20. R. Long, N. English, O. V. Prezhdo "Photo-induced charge separation across the graphene-TiO2 interface is faster than energy losses: a time-domain ab initio analysis", J. Am. Chem. Soc., 134, 14238 (2012)
21. R. Long, O. V. Prezhdo "Ab initio nonadiabatic molecular dynamics of the ultrafast electron injection from a PbSe quantum dot into the TiO2 surface", J. Am. Chem. Soc., 133, 19240 (2011).
22. D. J. Trivedi, L. J. Wang, O. V. Prezhdo, "Auger-mediated electron relaxation is robust to deep hole traps: time-domain ab initio study of CdSe quantum dots", Nano Lett., 15, 2086-2091 (2015).
23. O. Postupna, H. M. Jaeger, O. V. Prezhdo "Photoinduced dynamics in carbon nanotube aggregates steered by dark excitons", J. Phys. Chem. Lett., 5, 3872-3877 (2014).

Advances in the prediction and manipulation of thermal energy have been hampered by a lack of control and sensitivity needed to measure thermal behavior at the meso and nanoscales. 
Understanding heat transfer at the nanoscale is essential to design new technologies in many fields of current research.  For example, in the semiconductor industry, as device dimensions 
continue to be reduced and number densities increase, heat dissipation becomes an increasingly serious problem.  This problem is exacerbated by the fact that certain pathways for heat 
dissipation may become less efficient at the nanoscale because the size of the nanostructure is close in scale to the phonon mean-free path and, in this size regime, the classical heat diffusion 
law breaks down with current models not fully describing experimental observations. Currently, photothermal heating of noble metal nanostructures is an active area of research, whose 
applications have been demonstrated in many different areas including remote release of encapsulated material, melting of strands of DNA, thermal therapy for destruction of tumors, and 
controlled manipulation of phase transitions of phospholipid membranes. In addition to the traditional research interests in photothermal cancer therapy, a new area of research has been 
initiated where localized heating of metal nanoparticles is used to activate chemical reactions.  The significant surface heating enables molecules in the vicinity of the nanoheater to overcome 
high potential energy barriers in chemical reactions. These general areas of research will be greatly enhanced by a method that can measure the absolute local temperatures around optically 
excited nanostructures with the spatial resolution on the size of the nanostructures.  
In this talk I will introduce a new optical probe technique using a laser trapped erbium oxide nanoparticle (~ 100 nm) that measures absolute temperature below the diffraction limit.  Scanning 
and measuring the photoluminescence spectrum of an emitting laser trapped erbium oxide nanoparticle over a gold nanostructure immersed in water generates a temperature image.  The scanning 
optical probe thermometer (SOPT) measures the absolute temperature by collecting erbium emission intensities from the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions. These transitions are 
thermalized and the absolute temperature is calculated from the relative ratio of the emission intensities between the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions using Boltzmann statistics.  
When the optical thermal sensor size is reduced below the diffraction limited size, then the resolution of temperature measurement is now no longer limited by the point-spread function of the 
microscope, but is limited by the size of the nanosensor. We used this technique to collect a thermal image of a cluster of optical excited nanowires. A convolution analysis of the thermal 
profile shows that the point-spread function of our measurement is a Gaussian with a FWHM of 165 nm.  We attribute the width of this function to clustering of Er2O3 nanoparticles in solution.  
The scanning optical probe thermometer is used to measure the temperature where vapor nucleation occurs in degassed water (555 K), confirming that a nanoscale object heated in water will 
superheat the surrounding water to the spinodal decomposition temperature. Subsequently, the temperature inside the vapor bubble rises to the melting point of the gold nanostructure (~1300 K) 
where a temperature plateau is observed.  The rise in temperature is attributed to inhibition of thermal transfer to the surrounding liquid by the thermal insulating vapor cocoon.

We report on systematic theoretical and  experimental study of the energy transfer in ensemble of closely packed CdTe nanocrystals. We identify the responsible mechanism as the
Förster resonant energy transfer (FRET). We prove that at low temperatures mainly the ground dark exciton states in the initially excited small size (donor) nanocrystals participate in 
the dipole-dipole FRET leading to the additional excitation of the larger size (acceptor) nanocrystals. Such process becomes possible due to the weak admixture of the bright exciton states to
the dark states. The admixture takes place even in zero magnetic field  and  allows the radiative recombination of the dark excitons. External magnetic field considerably enhances this 
admixture thus increasing  the energy transfer rate from the dark excitons as well as the radiative rates of dark excitons in both donor and acceptor nanocrystals. Theoretical modeling allowed 
us to determine the spectral dependence of the energy transfer probability, to evaluate energy transfer rates and their  dependencies on the magnetic field, to describe the spectral shift of 
the photoluminescence maximum due to the energy transfer and to reproduce experimentally observed  spectral  dependence of the photoluminescence recombination dynamics in external magnetic 
field.

Controlling the self-organization of nanoparticle building-blocks at different length scales is one of the major challenges of nanomaterials research. This is especially important 
for nanoparticles displaying localized surface plasmon resonances since their controlled self-assembly, especially if hierarchical, can grant access to the investigation of interesting optical 
changes derived from the interaction of the individual components. This talk will provide an overview on hierarchical assemblies recently developed in our group, and comprising different types 
of plasmonic building-blocks, such as noble metal- and vacancy-doped semiconductor nanoparticles.[1-3] It will be shown how various self-assembly approaches can be used to produce hierarchical 
assemblies based on such plasmonic building-blocks at different length scales and how this enables the investigation of interesting optical effects.[4, 5] 
  
REFERENCES
1.	Kriegel, I., C. Jiang, J. Rodríguez-Fernández, R. D. Schaller, D. V. Talapin, E. da Como and J. Feldmann, J. Am. Chem. Soc. 2012, 134, 1583-1590.
2.	Kriegel, I., J. Rodríguez-Fernández, A. Wisnet, H. Zhang, C. Waurisch, A. Eychmüller, A. Dubavik, A. Govorov and J. Feldmann, ACS Nano 2013, 7, 4367-4377.
3.	Kriegel, I., A. Wisnet, A.R. Srimath Kandada, F. Scotognella, F. Tassone, C. Scheu, H. Zhang, A.O. Govorov, J. Rodríguez-Fernández and J. Feldmann, J. Mater. Chem. C 2014, 2, 3189-3198. 
4.	Neyshtadt, S., I. Kriegel, J. Rodríguez-Fernández, S. Hug, B. Lotsch and E. Da Como, Nanoscale 2015, 7, 6675-6682.
5.	Muhammed, M. A. H., M. Döblinger and J. Rodríguez-Fernández, 2015.

One-dimensional semiconductor nanorods are a very promising class of materials for applications in modern optoelectronic devices, such as light-emitting diodes, solar cells, novel 
displays, and lasers. Their ability to emit linearly polarized light is considered to simplify device structures and improve the overall efficiencies. To ensure macroscopic polarization in such 
devices, the biggest challenge is the long-range alignment of nanorods by controllable means. We propose a technique that combines the photo-induced alignment with nanorod's self-assembly. With 
this approach, we are able to actively control the alignment directions of highly emissive semiconductor nanorods in both microscopic and macroscopic scale with the order parameter as high as 
0.87. As a result, polarized emission has been achieved with the degree of polarization of 0.62. Furthermore, patterned alignment of nanorods with spatially varying local orientations has been 
realized to demonstrate the great flexibility of this approach. Besides new opportunities for applications, our method of alignment offers new insights into host-guest interactions governing 
self-assembly of colloidal nanocrystals within the host molecular matrix.

The life cycle of plants and photosynthetic bacteria is based on the efficient harvesting of solar energy. These organisms are spectacular examples of nature's engineering 
capabilities. They absorb photons in intricate protein-pigment molecular aggregates known as light-harvesting complexes (LHCs). Then, the energy is transferred in the form of molecular 
excitations down to reaction centers, where charge separation enables fundamental biochemical reactions. Optimal efficiency of light absorption and excitation transfer within the LHCs are 
crucial characteristics in the competition of these organisms for energy resources. Thus, understanding excitation dynamics in LHCs at the microscopic level can provide us with new principles 
for the design of artificial sun-powered systems. 

In this talk I will describe how specially designed nanostructures can be used to probe and modify energy transfer in LHCs of photosynthetic bacteria. In the beginning I will overview the 
general concepts and challenges of excitation dynamics in natural LHCs by using green sulfur bacteria as a model system. I will then discuss examples, where optical cavities and plasmonic 
nanostructures accentuate response signals from LHCs, and will explain how these can be used to modify the energy transfer paths in living organisms. 

Silver and gold nanoparticles have unique optical properties that are associated with the excitation of collective excitations of the conduction electrons known as plasmon 
resonances.  The resonance frequencies are sensitive to particle shape and size, which means that the color of the nanoparticles can be tuned over a wide range of wavelengths, and they are also 
sensitive to the arrangement of the nanoparticles into aggregates and arrays.  This talk will emphasize recent theory and experiments which have probed the effect of arrays of these particles in 
1D, 2D and 3D on optical response.  The arrays in 1D and 2D can be made using standard lithography tools, but much of the talk will emphasize bottom-up assembly of 3D arrays that is possible 
using DNA-functionalized nanoparticles and self-assembly of nanoparticle superlattices driven by DNA hybridization.  We show that the array structures lead to new kinds of hybrid optical modes 
in which localized surface plasmon resonances in the nanoparticles are coupled with photonic modes of the lattices, including Bragg modes, Fabry-Perot modes and other modes.  These hybrid modes
are often much narrower than the isolated particle plasmons, and films composed of these superlattices have unusual metamaterials properties. We also show that for 2D lattices it possible to 
generate a new class of sub-wavelength laser in which excitons in laser dyes are coupled with the hybrid lattice modes to produce enhanced stimulated emission. 

Electrocatalysis plays a major role in electrochemical energy conversion and storage devices, specifically in polymer electrolyte fuel cells and water electrolyzers. The role of the 
electrocatalyst is not only to provide an energetically favorable reaction pathway in order to reach the highest possible reaction kinetics, it also needs to favor the desired product 
selectivity. In addition, electrocatalysts need to withstands often device operation times over several thousands of hours without showing degradation. In electrochemical energy conversion 
devices, mostly nanoparticulate catalyst systems are employed in the quest for maximizing specific surface area and active surface sites. 
In this contribution, some examples for nanoparticulate catalyst systems and their specific applications to important, energy conversion relevant reactions will be shown. This will contain 
supported as well as unsupported catalyst systems for the oxygen reduction and evolution reaction as well as for the electrochemical reduction of CO2 to for synthetic hydrocarbons. 

Photoluminescent nanomaterials have attracted much attention. Graphene as a perfect π-conjugated single sheet is not photoluminescent for a lack of electronic bandgaps. Therefore, 
the creation of energy bandgaps has been a popular strategy to impart photoluminescence emissions, such as cutting graphene sheets into small pieces or manipulating the π electronic network to 
form quantum-confined sp2 "islands", which apparently involve the formation or exploitation of structural defects. In fact, defects in graphene materials not only play a critical role in the 
creation of bandgaps for emissive electronic transitions, but also contribute directly to the emissions. As similar defect-derived photoluminescence has been found in carbon nanotubes and small 
carbon nanoparticles, dubbed carbon "quantum" dots or "carbon dots", here results from a closer examination on the emissions in these different yet related carbon nanomaterials toward a global 
view on the shared and/or distinctive mechanistic origins are discussed.

Nanoparticles of different functional materials can self-assemble from colloidal solutions into long range ordered periodic structures (superlattices). Through a series of 
systematic studies of self-assembly phenomena in single- and multicomponent nanoparticle assemblies we demonstrate that self-assembly of nanoscale objects is guided by an intricate interplay of 
entropy-driven crystallization an interparticle interactions, such as van der Waals forces. The surface ligands also play an important and sometimes counterintuitive role. For example, organic 
ligands with long hydrocarbon chains introduce many-body interactions involving multiple nanoparticles and stabilizing low density structures. Finally, on the example of tetrahedral CdSe 
nanocrystals, we will show that non spherical shape introduces rotational entropy as an important additional term to the free energy balance. 

Epitaxial heterostructures play a key role in electronics and optoelectronics. In a close analogy, performance of nanocrystal based devices depends on the perfection of interfaces formed between 
nanocrystal layers. We systematically studied the epitaxial growth of nanocrystal superlattices and revealed an exceptional strain tolerance of nanocrystal epitaxy reveals. It follows a 
universal island size scaling behavior and shows a strain-driven transition from layer-by-layer to Stranski-Krastanov growth regime with non-trivial island height statistics. Kinetic bottlenecks 
play an important role in nanocrystal epitaxy, especially in the transition from sub-monolayer to multilayer coverage and the epitaxy of nanocrystals with anisotropic shape. 

This talk explores our work on the modelling of charge injection and recombination at the interface between TiO2 and organic dyes. The investigated processes are of fundamental 
importance in the operation of dye senstitized solar cells and are also important in a variety of photocatalytic system. We initially present our partitioning techniqe enabling the study of 
charge injection in systems that differ for the anchoring group, the exposed surface and the dye. We then discuss what are the limitation of theoretical modelling in predicting the charge 
recombiation rate. On the basis of these models we propose new molecular design of dyes with low charge recombination. Finally we explore the possibility of achieving high quality prediction by 
statistical analysis of combined large sets of experimental and computational data. 

(1) Ip Chung M, Eleuteri A, Troisi A, Phys. Chem. Chem. Phys. 16, 19106-19110, 2014  
(2) Maggio E, Solomon GC, Troisi A, ACS Nano 8, 409–418, 2014
(3) Maggio E, Martsinovich N, Troisi A, Angew. Chem. Int. Ed. Eng.,  52, 973-975, 2013
(4) Ambrosio F, Martsinovich N, Troisi A, J. Phys. Chem. Lett., 1531-1531, 2012
(5) Martsinovich N, Troisi A, Energy. Environ. Sci. 4, 4473-4495, 2011 

The interest in 2-dimensional systems with a honeycomb lattice and related Dirac-type electronic bands has exceeded the prototype graphene. Currently, 2-dimensional atomic and 
nanoscale systems are extensively investigated in the search for materials with novel electronic properties that can be tailored by geometry. I will show how atomically coherent honeycomb 
superlattices of rocksalt (PbSe, PbTe) and zincblende (CdSe, CdTe) semiconductors can be obtained by nanocrystal self-assembly, covalent attachment, and subsequent cation exchange. Atomistic 
theory and analytical predict that these artificial graphene systems combine Dirac-type electronic bands with the beneficial properties of a semiconductor, such as the presence of a band gap and 
strong spin-orbit coupling, leading to the quantum spin Hall effect. I will present the first experimental results on the opto-electrical characterisation of PbSe and CdSe honeycomb 
semiconductors. 

Magnetostatic (dipolar) interactions between nanoparticles promise to open new ways to design nanocrystalline magnetic materials and devices if the collective magnetic properties 
can be controlled at the nanoparticle level. Magnetic dipolar interactions are sufficiently strong to sustain magnetic order at ambient temperature in assemblies of closely-spaced nanoparticles 
with magnetic moments of ≥ 100 µB. The use of Lorenz microscopy  and electron holography with sub-particle resolution allow us to reveal the correlation between particle arrangement and magnetic 
order in self-assembled 1D and quasi-2D arrangements of ferromagnetic nanoparticles. In the initial states, dipolar ferromagnetism is observed, antiferromagnetism and local flux closure, 
depending on the particle arrangement. Surprisingly, after magnetic saturation, measurements and numerical simulations show that overall ferromagnetic order exists in the present nanoparticle 
assemblies even when their arrangement is completely disordered. Furthermore, unusual domain structures arise in these systems as the result of dipolar interactions and shape anisotropy, in the
absence of inter-particle exchange coupling. Such direct quantification of the correlation between topological and magnetic order is essential for the technological exploitation of magnetic 
quasi-2D nanoparticle assemblies. 

Self-assembly of only one functionalized porphyrin dye molecule with one CdSe/ZnS quantum dot (QD) not only modifies the photoluminescence quantum yield but also creates a few 
energetically clearly distinguishable electronic states, opening additional effective relaxation pathways. The related energy modifications show a pronounced sensitivity to the specific nature 
of the respective dye. We assign the emerging energies to surface states. Time-resolved PL spectroscopy in combination with spectral deconvolution reveals that surface properties of QDs are a 
complex interplay of the nature of the dye molecule and the topography of the ligand layer across a temperature range from 77 to 290 K. This includes a kind of phase transition of 
trioctylphosphine oxide ligands, switching the nature and quantum yield of surface states observed below and above the phase transition temperature. Most importantly, our findings can be closely 
related to recent calculations of ligand-induced modifications of surface states of QDs. The identification of the optical properties emerged from a combination of spectroscopy on single QDs and 
QDs in an ensemble. We present a general concept of formation principles for self assembly of dye molecules onto the surface of colloidal QDs in competition to ligand dynamics.

Future nanophotonic architectures will require nanostructures with specific roles that work together cooperatively, such as structures for nanoscale optical switching and others for 
guiding and propagating energy. Optical switching at the nanoscale can be targeted with plasmonic structures that can confine and enhance optical near-fields so as to induce, for example, strong 
nonlinear or ultrafast hot electron responses that modulate extinction. The free electrons responsible for plasmonic responses also respond to light on an ultrafast time-scale, making them ideal
for fast switching opportunities. For propagation of energy in nanophotonic structures, nanostructured materials inspired by natural photosynthetic membranes represent an opportunity for 
efficient and directional energy transport. In natural photosystems, light harvesting complexes can transport excitons to the reaction center core with near unity conversion of absorbed photons 
to separated charge. A key to this process is the high rate of exciton hopping and the directionality of exciton flow due to an energy level waterfall effect of excitons in complexes as the 
reaction center core is approached. Efforts to induce similar behavior in biomimetically inspired nanostructures are described.

Eduard I. Zenkevich1, Evgenii I. Sagun2, Alexander P. Stupak2, Valery N. Knyukshto2, Thomas Blaudeck3, Christian von Borczyskowski3

1)National Technical University of Belarus, Nezavisimosti Ave., 65, 220013 Minsk, Belarus. 
2)B.I. Stepanov Institute of Physics, National Academy of Science of Belarus, Nezavisimosti Ave., 70, 220072 Minsk, Belarus. 
3)Center for Nanostructural Materials and Analytics, Institute of Physics, University of Technology Chemnitz, Reichenhainer Str. 70, 09107 Chemnitz, Germany. 

The presented material covers the basics of nanotechnology, focusing on hybrid organic-inorganic nanoassemblies based on self-assembly principles. Here, we are willing to discuss the formation 
principles and mechanisms of excitation energy relaxation being studied for nanoassemblies based on core/shell CdSe(ZnS) colloidal semiconductor quantum dots (QD) exhibiting size-dependent 
photophysical properties and surfacely activated by pyridyl-substituted porphyrins, H2P (bulk solutions) in  liquid solvents at  295 K (steady-state, picosecond time-resolved luminescence 
spectroscopy and single molecule spectroscopy). We have shown that the formation process of nanoassemblies is in competition with ligand dynamics. At least two time scales are found for the 
formation of "QD-H2P" nanoassemblies: (i) one faster than 60 s by saturation of empty attachment sites and (ii) one slower than 600 s, which is attributed to a reorganisation of the tri-n-octyl 
phosphine oxide (TOPO) ligand shell. Finally, this process results in a nearly complete exchange of the shell by porphyrin dye molecules.
Upon formation of "QD-H2P" nanoassemblies the QD photoluminescence (PL) is quenched as can be detected both via single particle detection and ensemble experiments in solution. PL quenching has 
been quantitatively assigned to FRET QD→H2P (10-14%) and NON-FRET (86-90%) processes. With respect to NON-FRET process, it was shown for the first time that the related QD PL quenching rate 
(caused by attached porphyrin molecule) scales inversely with the QD diameter and can be understood in terms of a tunnelling of the electron (of the excited electron-hole pair) followed by a 
(self-) localization of the electron or formation of trap states. 
In addition, using near-IR photoluminescence measurements, we performed a quantitative comparative studying the efficiencies of the singlet oxygen generation by alone QDs and "QD-H2P" 
nanoassemblies upon variation of the laser pulse energy. It was found that for "QD-H2P" nanoassemblies the experimental efficiencies of singlet oxygen generation are essentially higher with 
respect to those obtained for alone QDs. In the case of "QD-H2P" nanoassemblies, it was proven also that the non-linear dependence of the efficiency of singlet oxygen generation on the laser 
pulse energy is caused by non-radiative intraband Auger processes, realized in QD counterpart. These results may be considered as a direct proof of the realization of namely FRET QD→porphyrin 
process followed by the singlet oxygen generation via porphyrin triplet states. Finally, it has been found that values of FRET QD→H2P efficiencies  obtained via direct measurements of IR-
emission of singlet oxygen at low laser excitation (ΦIR = 0.12 ± 0.03) are in a good agreement with the corresponding FRET efficiencies found from the direct sensitization data for porphyrin 
fluorescence (ΦFRET = 0.14 ± 0.02) in nanoassemblies. Such quantitative analysis was done for the first time and shows that namely FRET process QD→H2P is a main reason of singlet oxygen 
generation by QD→H2P nanoassemblies. 
Concluding, our findings highlight that single functionalized organic molecules (pyridyl-substituted porphyrins in our case) may be considered as one of the probes for the complex interface 
physics and dynamics of colloidal semiconductor QD. These observations are in line also with the microscopic understanding of blinking phenomena of single QD.

Many different aerogel materials are known to be accessible via the controlled destabilization of the respective nanoparticle solutions. Especially for applications in heterogeneous 
catalysis materials with high specific surface areas are highly desirable. Here we present a simple method to obtain a mixed ZnPd/ZnO aerogel via a reductive treatment of a pre-formed Pd/ZnO 
aerogel. Different morphologies of the Pd/ZnO aerogels could be achieved by controlling the destabilization of the ZnO sol. All aerogels show a high CO2-selectivity of up to 96 % and a very good 
activity in methanol steam reforming. The method presented can be used for many different transition metal/metal oxide systems and hence opens a path to a huge variety of possible materials.