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Noble metal nanoclusters allow for the atomically‐precise control of their composition. However, to create nanoclusters with pre‐defined optical properties, comprehensive description of their structure‐property relation is required. Here, we report the gold atom doping impact on one‐photon and two‐photon absorption (TPA) and luminescence properties of ligated silver nanoclusters via combined experimental studies and time‐dependent density functional theory simulations (TD‐DFT). We synthesized a series of Ag25−xAux(DMBT)18 nanoclusters where x=0, 1 and 5–10. For Ag24Au1(DMBT)18 we demonstrate that the presence of the central Au dopant strongly influences linear and non‐linear optical properties, increasing photoluminescence quantum yield and two‐photon brightness, with respect to undoped silver nanoclusters. With improved TPA and luminescence, atomically‐precise AuAg alloys presented in our work can serve as robust luminescent probes e.g. for bioimaging in the second biological window. [ABSTRACT FROM AUTHOR]

In this study, polyelectrolyte (PE) layers are deposited on substrates made by glass covered with an array of gold nanoparticles (GNPs). In particular, the samples studied have 0 PE layers (GGPE 0 ), 3 PE layers (GGPE 3 ), 11 PE layers (GGPE 11 ), and 21 PE layers (GGPE 21 ). All samples have been studied by micro-Raman spectroscopy. An acetic acid solution (10% v/v) has been used as a standard solution in order to investigate the SERS effect induced by different numbers of PE layers in each sample. The Surface Enhancement Raman Spectroscopy (SERS) effect correlating to the number of PE layers deposited on the samples has been shown. This effect is explained in terms of an increase in the interaction between the photon of the laser source and the plasmonic band of the GNPs due to a change of the permittivity of the surrounding medium around the GNPs. The trends of the ratios of the intensities of the Raman bands of the acetic acid solution (acetic acid and water molecules) on the band at 1098 cm − 1 ascribed to the substrates increase, and the number of PE layers increases. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate that the plasmonic heat delivered by a single layer of homogeneously distributed gold nanoparticles (AuNPs), immobilized on a glass substrate, can be optically tuned by taking advantage of the properties of an organic layer based on azobenzene and nematic liquid crystal (NLC) molecules. The effect, which exploits the dependence of the NLC refractive index value on the molecular director orientation, is realized using the polarization-dependent, light-induced molecular reorientation of a thin film of photo-aligning material that the NLC is in contact with. The reversibility of the optically induced molecular director reorientation of the NLC enables an active modulation of the plasmonic photo-induced heat. [ABSTRACT FROM AUTHOR]

Herein we report the transformation of [Au25(SR)18]0 into Au28(SR)21 induced by ligand exchange reaction. In contrast to other reported cluster transformations, which proceed at elevated temperature and large excess of incoming ligands, the transformation reported here occurs under mild conditions (room temperature, very low thiol excess) with a chiral ligand. A difference of one methyl group between incoming and leaving thiol is sufficient to induce the transformation. To the best of our knowledge the Au28(SR)21 cluster has not been isolated before. [ABSTRACT FROM AUTHOR]

The photo-induced heating from a layer of uniformly distributed gold nanoparticles has been characterized to investigate the impact of a direct interaction of the metallic nanostructures with a drop of E7 nematic liquid crystal. A double effect is obtained: an increase of the photo-induced heating due to a change in the refractive index of the medium surrounding the nanoparticles (from air to E7) and a new way of exploiting this heating to induce a phase transition of the E7 NLC (from anisotropic to isotropic phase), with a significant decrease of the necessary energy density in the case of an impinging green radiation. [ABSTRACT FROM AUTHOR]

We have carried out an experiment on a flexible polymeric substrate, coated with a monolayer of gold nanoparticles, which demonstrates how the combined effect of nanoparticle growth and stretching influences the average normalized gap between particles, thus modifying the extinction spectra of the sample. The study paves the way for the realization of a plasmonic strain sensor based on the plasmonic coupling of gold nanoparticles deposited onto elastomeric films: application of a mechanical stretching induces a change of colour of the device and a fine control of the applied strain allows a continuous tuning of the colour. [ABSTRACT FROM PUBLISHER]

[Display omitted] • CO adsorption on Au/TiO 2 was monitored in a system free of Ni-contamination. • IR bands around 2070 cm−1 were assigned to negatively charge Au following reduction. • Two positively charged Au species were identified in the presence of O 2. The presence of negatively charged gold species on Au surfaces or supported Au nanoparticles has widely been reported based on the appearance of IR bands of adsorbed CO located below 2090 cm−1. However, others have proposed that these bands may be solely due to the presence of Ni-CO species contaminating the sample surfaces. CO adsorption was monitored here using a CO supply, DRIFTS reaction cell and lines in which contamination by nickel could be excluded. Our data show that a band at 2067 cm−1 appeared without the involvement of Ni carbonyls, the observed band being assigned to CO adsorbed on negatively charged Au. [ABSTRACT FROM AUTHOR]

Abstract: TiO2 coated Au nanoparticles were synthesized and characterized by TEM, XPS and XRD. It was found that the Au nanoparticles were coated with TiO2 thus forming a core–shell structure. Electron transfer, adsorption and photodegradation of malonic acid on the catalyst were investigated by in situ attenuated total reflection infrared (ATR-IR) spectroscopy. Malonic acid adsorbed and underwent photodegradation efficiently in air and nitrogen atmosphere under UV light illumination on the prepared catalyst. As intermediate species oxalate was observed on the catalyst surface during the photodegradation of malonic acid. The Au nanoparticles accelerate the degradation of malonic acid by capturing the conduction band electrons of TiO2. The ATR spectra also reveal interface electron transfer from Au nanoparticles to TiO2 under visible light illumination and from TiO2 to Au nanoparticles under UV illumination. [Copyright &y& Elsevier]

[Display omitted] Langmuir-Blodgett (LB) technique allows the deposition of gold nanoparticles and nanoclusters (atomically precise nanoparticles below 2 nm in diameter) onto solid substrates with an unprecedented degree of control and high transfer ratios. Nanoclusters are expected to follow the crinkle folding mechanism, which promotes the formation of trilayers of nanoparticles but kinetically disfavors the formation of the fourth layer. LB films of Au 38 (SC 2 H 4 Ph) 24 nanocluster were prepared at a range of surface pressures in the bilayer/trilayer regime and their internal structure was analyzed with X-ray Reflectivity (XRR) and Grazing-Incidence Wide-Angle X-ray Scattering (GIWAXS). Bimodal atomic force microscopy (AFM) imaging was used to quantify the elastic modulus, which can be correlated with the topography at the same point on the surface. Nanocluster bilayers and trilayers exhibited the elastic moduli of ca. 1.2 GPa and 0.9 GPa respectively. Films transferred in the 20–25 mN/m surface pressure regime displayed a particular propensity to form highly vertically organized trilayers. Further compression resulted in disorganization of the layers. Crucially, the use of two cantilevers of contrasting stiffness for bimodal AFM measurements has demonstrated a new approach to quantify the mechanical properties of ultrathin films without the use of deconvolution algorithms to remove the substrate contribution. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]