Metal nanomaterials have attracted extensive attention in biological labeling and imaging due to their controllable physical and chemical properties. Recently, a lot of effort has been devoted to preparing various ultrasmall and functional copper nanoclusters (CuNCs) with different emissions from blue to red, soluble both in organic and aqueous phases. Herein, a novel one-step synthetic method is proposed for the preparation of stable water-soluble glutathione-capped (GSH-capped) CuNCs. The resulting nanoclusters have a good dispersibility and stability in aqueous media. The stability was examined by several test experiments. The mass detection in ESI-HRMS mode allowed ionization of several doubly charged species with formula Cu5L6, Cu6L6, Cu7L6, Cu8L6, and Cu9L6 (L = C10H16N3O6S). The use of advanced separation techniques including liquid chromatography (HPLC), gel electrophoresis (PAGE), and capillary electrophoresis (CE) allowed the separation of several clusters, some of which are larger than Au-25(GS)(18), as shown by PAGE. To the best of our knowledge, this is the first report on successful size-separation of CuNCs. Moreover, the synthesized CuNCs show a dose-dependent antimicrobial effect. At lower cluster concentration the growth of bacteria is partially reduced. However, at higher concentrations, the bacterial growth is completely restricted.

The transfer of chirality from one set of molecules to another is fundamental for applications in chiral technology and has likely played a crucial role for establishing homochirality on earth. Here we show that an intrinsically chiral gold cluster can transfer its handedness to an achiral molecule adsorbed on its surface. Solutions of chiral Au38(2-PET)24 (2-PET=2-phenylethylthiolate) cluster enantiomers show strong vibrational circular dichroism (VCD) signals in vibrations of the achiral adsorbate. Density functional theory (DFT) calculations reveal that 2-PET molecules adopt a chiral conformation. Chirality transfer from the cluster to the achiral adsorbate is responsible for the preference of one of the two mirror images. Intermolecular interactions between the adsorbed molecules on the crowded cluster surface seem to play a dominant role for the phenomena. Such chirality transfer from metals to adsorbates likely plays an important role in heterogeneous enantioselective catalysis.

The location of the Pd atoms in Pd2Au36(SC2H4Ph)24, is studied both experimentally and theoretically. X-ray photoelectron spectroscopy (XPS) indicates oxidized Pd atoms. Palladium K-edge extended X-ray absorption fine-structure (EXAFS) data clearly show Pd-S bonds, which is supported by far infrared spectroscopy and by comparing theoretical EXAFS spectra in R space and circular dichroism spectra of the staple, surface and core doped structures with experimental spectra.

The far infrared spectra of a series of well-defined gold clusters covered with 2-phenylethanethiolate were studied. The spectra of the clusters are different but the differences are subtle. The Au-S stretching vibrations give rise to bands around 300 cm(-1) and below. The relative intensity of these bands changes but they shift only slightly for different clusters. A low-frequency band was identified, which is sensitive to the conformation (trans/gauche) of the 2-phenylethanethiolate ligand.

The two enantiomers of the Au40(2-PET)24 cluster were collected using HPLC and analyzed by MALDI-TOF mass spectrometry, UV-vis- and CD-spectroscopy. The flexibility of the cluster surface allows racemization of the intrinsically chiral cluster at elevated temperatures (80-130 °C) which was monitored following the optical activity. The determined activation energy (25 kcal mol(-1)) lies in the range of previously reported values for Au38 nanoclusters whereas the activation entropy deviates significantly from the one in Au38. The latter may indicate that the racemization can take place via different mechanisms.

In an approach to design selectives olid catalysts we start fromt he knowledge,atthe molecularlevel,ofthe reactiontobecatalyzed.Thenhypothesisa re made on then atureo ft he actives itesr equired.A tt hisp oint we are readytosynthesizesolid materials, in where therequiredactivesitesare introduced as well definedentities.On topofthatthe adsorption propertiesof thesolid are taylored to optimizethe interactions between reactants, catalyst andproducts.Following this methodologyw ill presents olid catalysts in where thea ctive sitescorrespondtowelldefinedtransitionmetal complexesand organocatalysts thata re either graftedo rs tructurally builded into solids.In this case, ther oleo ft he solid can go beyond as imple support, since it is designed to interveneinthe reactioneither by stabilizing transitionstatesorbyintroducingadditionalactivesites.Well definedsingleormultiple activesitescan also be introduced into crystallinen anoporous materialsw ith controlleda dsorptionp roperties, andt his allows to perform newacidand redox,one step or multistepreactions.Finallyw ill show that by depositingm etal nanoparticles( Au, Pd,P t) on proactivesupports(CeO 2 ,Fe 2 O 3 , MgO,hydrotalcites,etc.) we can open new catalytic reactionroutesf or C-Cbond formation, oxidations andreductions.These catalytic system allowt he design of multifunctionals olid catalysts, that are able to carryo ut multistepp rocess through cascadet yper eactions that were not possiblebefore.

Bestowing chirality to metals is central in fields such as heterogeneous catalysis and modern optics. Although the bulk phase of metals is symmetric, their surfaces can become chiral through adsorption of molecules. Interestingly, even achiral molecules can lead to locally chiral, though globally racemic, surfaces. A similar situation can be obtained for metal particles or clusters. Here we report the first separation of the enantiomers of a gold cluster protected by achiral thiolates, Au(38)(SCH(2)CH(2)Ph)(24), achieved by chiral high-performance liquid chromatography. The chirality of the nanocluster arises from the chiral arrangement of the thiolates on its surface, forming 'staple motifs'. The enantiomers show mirror-image circular dichroism responses and large anisotropy factors of up to 4×10(-3). Comparison with reported circular dichroism spectra of other Au(38) clusters reveals that the influence of the ligand on the chiroptical properties is minor.

Chirality unveiled: Thiolate-protected Au40(SR)24 clusters were enantioenriched using an HPLC approach. CD spectra show strong mirror-image responses, indicating the intrinsic chirality of a cluster of unknown structure protected with achiral ligands.

Thiolate-protected gold nanoparticles and clusters combine size-dependent physical properties with the ability to introduce (bio)chemical functionality within their ligand shell. The engineering of the latter with molecular precision is an important prerequisite for future applications. A key question in this respect concerns the flexibility of the gold-sulfur interface. Here we report the first study on racemization of an intrinsically chiral gold nanocluster, Au38(SCH2CH2Ph)24, which goes along with a drastic rearrangement of its surface involving place exchange of several thiolates. This racemization takes place at modest temperatures (40-80 °C) without significant decomposition. The experimentally determined activation energy for the inversion reaction is ca. 28 kcal/mol, which is surprisingly low considering the large rearrangement. The activation parameters furthermore indicate that the process occurs without complete Au-S bond breaking.

Chiralität enthüllt: Thiolatstabilisierte Au40(SR)24-Cluster wurden mittels HPLC enantiomerenangereichert. CD-Spektroskopie ergab nahezu perfekt spiegelbildliche Spektren, was auf intrinische Chiralität des Clusters unbekannter Struktur hinweist, da achirale Liganden verwendet wurden. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

A simple method to create self-organized patterns of microparticles in polymer films is demonstrated. Dye-loaded zeolite crystals are used as model microparticles, allowing convenient imaging of the patterns by fluorescence microscopy. The pattern formation can be interpreted within the general framework of the model of local self-activation and lateral inhibition. Two starting parameters, namely the polymer concentration and the wet film thickness, control the size and shape of the particle aggregates in the patterns, as well as their spacing. The size of the aggregates ranges from 50 to 340μm.

We discuss artificial photonic antenna systems that are built by incorporating chromophores into one-dimensional nanochannel materials and by organizing the latter in specific ways. Zeolite L (ZL) is an excellent host for the supramolecular organization of different kinds of molecules and complexes. The range of possibilities for filling its one-dimensional channels with suitable guests has been shown to be much larger than one might expect. Geometrical constraints imposed by the host structure lead to supramolecular organization of the guests in the channels. The arrangement of dyes inside the ZL channels is what we call the first stage of organization. It allows light harvesting within the volume of a dye-loaded ZL crystal and also the radiationless transport of energy to either the channel ends or center. One-dimensional FRET transport can be realized in these guest-host materials. The second stage of organization is realized by coupling either an external acceptor or donor stopcock fluorophore at the ends of the ZL channels, which can then trap or inject electronic excitation energy. The third stage of organization is obtained by interfacing the material to an external device via a stopcock intermediate. A possibility to achieve higher levels of organization is by controlled assembly of the host into ordered structures and preparation of monodirectional materials. The usually strong light scattering of ZL can be suppressed by refractive-index matching and avoidance of microphase separation in hybrid polymer/dye-ZL materials. The concepts are illustrated and discussed in detail on a bidirectional dye antenna system. Experimental results of two materials with a donor-to-acceptor ratio of 33:1 and 52:1, respectively, and a three-dye system illustrate the validity and challenges of this approach for synthesizing dye-nanochannel hybrid materials for light harvesting, transport, and trapping.

The photocatalytic degradation of l-asparagine and l-glutamic acid over Au/TiO2 and TiO2 catalysts was investigated in situ by attenuated total reflection infrared (ATR-IR) in combination with modulation excitation spectroscopy. Oxalate was detected on the catalyst surface, which has not been reported before for degradation of amino acids by studies focusing on intermediates in solution. The ATR-IR spectra provide valuable information on the fate of the nitrogen. Ammonium was detected, in agreement with previous studies. Most importantly, strong signals of cyanide were observed, and this assignment has been corroborated by 15N labeling experiments. Cyanide was not reported before, to the best of our knowledge, for the photocatalytic degradation of amino acids. Cyanide was formed in the presence and the absence of gold particles on the TiO2 surface. The cyanide leads to leaching of gold via Au(CN)2− species that were detected in solution by mass spectrometry.

Size exclusion chromatography (SEC) on a semipreparative scale (10 mg and more) was used to size-select ultrasmall gold nanoclusters (<2 nm) from polydisperse mixtures. In particular, the ubiquitous byproducts of the etching process toward Au(38)(SR)(24) (SR, thiolate) clusters were separated and gained in high monodispersity (based on mass spectrometry). The isolated fractions were characterized by UV-vis spectroscopy, MALDI mass spectrometry, HPLC, and electron microscopy. Most notably, the separation of Au(38)(SR)(24) and Au(40)(SR)(24) clusters is demonstrated.

We present a method to evaluate the parameters defining the efficiency of luminescent solar concentrators (LSCs). The light harvesting and self-absorption properties of thin film LSCs on glass substrates are determined by optical spectroscopy and the resulting optical efficiency is consistent with the directly measured photon flux gain.

The synthesis of stopcocks based on zinc phthalocyanine for selective adsorption at the channel entrances of zeolite L is reported. The introduction of either an inert SiMe₃ moiety, an imidazolium cation or a reactive isothiocyanate (NCS) group allows attachment to the channel entrances of zeolite L through van der Waals interactions, electrostatic interactions, or covalent binding, respectively. Stopcocks that rely on van-der-Waals-driven adsorption require careful selection of the solvent used for the deposition onto the zeolite surface to avoid a nonspecific distribution of the molecules. Regarding the design of photonic antenna systems, a stopcock with a cationic tail was found to be the most convenient, based on the observation that efficient energy transfer from molecules located in the zeolite nanochannels is more readily obtained than in the other cases.

The defined pore networks of silicate-based molecular sieves are attractive for the development of highly organized inorganic/organic hybrid materials. Efficient energy transfer systems are obtained upon inclusion of dye molecules into the one-dimensional channels of zeolite L. The resulting host-guest materials form the basis for an advanced luminescent solar concentrator. The selective functionalization of the channel entrances with zinc phthalocyanine offers further possibilities in terms of employing the dye–zeolite composites for the sensitization of organic solar cells. Having larger pore sizes than zeolites as well as highly modifiable channel walls, mesoporous silicas have recently emerged as versatile starting materials for the synthesis of drug delivery devices. One of the most challenging aspects in this context is the control and the analysis of the functional group distribution. This topic is discussed on the basis of our recent work on the reaction of aminopropylalkoxysilanes with mesoporous silica MCM-41.

A combination of in situ attenuated total reflection infrared (ATR-IR) spectroscopy, UV−vis spectroscopy and transmission electron microscopy was used to study the adsorption of thiol-protected gold nanoparticles on TiO2 films and the behavior of the resulting composite films upon UV irradiation. The gold nanoparticles were covered by charged thiols N-acetyl-l-cysteine and l-glutathione and had a mean core diameter of about 1 nm. The TiO2 film was prepared by deposition of a slurry of TiO2 nanoparticles with a particles size of 21 nm. The combination of the two spectroscopic techniques showed that the adsorption of the gold nanoparticles onto the TiO2 films is significantly limited by intrafilm diffusion. Upon illumination the IR spectra revealed the removal of the adsorbed thiolates and the appearance of sulfates. These species were also observed when N-acetyl-l-cysteine adsorbed on TiO2 was illuminated, i.e., in the absence of gold. In the latter case oxalate was observed in large quantity on the TiO2 surface, in contrast to the illumination of the N-acetyl-l-cysteine-protected gold particles. This indicates a different pathway for the decomposition of the adsorbed thiol when adsorbed on the gold or directly on the TiO2 surface. In situ UV−vis spectroscopy also shows the formation of larger particles upon illumination, which is confirmed by transmission electron microscopy.

Attenuated total reflection infrared (ATR-IR) spectroscopy in a flow-through cell was used to study the photocatalytic mineralization of malonic acid and succinic acid over P25 TiO2 in situ. The experiments were performed in water at concentrations of 1.5×10−4mol/L and pH 3.5 at room temperature. Changes on the catalyst surface were observed within a few minutes. The first step in the mineralization of malonic acid is a photo-Kolbe reaction of adsorbed malonate. Part of the resulting C2 species is converted into oxalate and finally into carbon dioxide, and part desorbs from the surface. The branching ratio for the two pathways is 50:50. The mineralization reaction was also observed in the absence of dissolved oxygen, but at a slower rate. In the presence of dissolved 18O2, labeled oxygen was incorporated into the adsorbed oxalate. A dominant pathway in the mineralization of succinic acid involves the transformation to oxalate via malonate. Thus, it is proposed that a favored pathway for dicarboxylic acid mineralization is a photo-Kolbe reaction, followed by oxidation of the carbon-centered radical to a carboxylate, which corresponds to the overall formal shortening of the alkyl chain by one CH2 unit.