The water-solubleglutathione-protected [Au-25(GSH)(18)](-1) nanocluster was investigatedby integratingseveral methodologies such as molecular dynamics simulations, essentialdynamics analysis, and state-of-the-art time-dependent density functionaltheory calculations. Fundamental aspects such as conformational, weakinteractions and solvent effects, especially hydrogen-bonds, wereincluded and found to play a fundamental role in assessing the opticalresponse of this system. Our analysis demonstrated not only that theelectronic circular dichroism is extremely sensitive to the solventpresence but also that the solvent itself plays an active role inthe optical activity of such system, forming a chiral solvation shellaround the cluster. Our work demonstrates a successful strategy toinvestigate in detail chiral interfaces between metal nanoclustersand their environments, applicable, e.g., to chiral electronic interactionsbetween clusters and biomolecules.

Spent sulfite liquor, a side-stream from the pulp and paper industry, is an abundantly available carbon source for bio-based platform chemicals. The biotechnological valorization of side streams in biorefineries is hampered by the inability of many microorganisms to metabolize and deal with aldonic acids. Based on the principles of Green Chemistry, the electrochemical reduction of aldonic acids into the corresponding biomass sugars appears as a prospective process for the conversion of these acids into fermentable carbohydrates. In our paper, the investigation of electrochemical reduction of gluconic and xylonic acids into glucose and xylose, respectively, is presented. The proposed mechanism on a gold-coated silver electrode was determined via ReaxFF molecular dynamics simulations and quantum chemistry calculations. Model solutions with an aldonic acid concentration of 2.5 wt % were used for the experiments. Compared to a two-electrode compartment cell, the amounts of glucose and xylose produced in the undivided cell were more than 4 and 5.5 times higher, respectively. The electrode surface was analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. Despite the relatively low conversion rate, our results show that electrochemical reduction of aldonic acids into their corresponding aldoses in model solutions is possible, which represents an important step toward side-stream valorization.

The conductivity of substrate-supported metallic nanowires can be adjusted, e.g., by strain or adsorbates. In this article, the effect of atomic hydrogen and toluene-3,4- dithiol (TDT) adsorption on the quasi-1D structures of the Si(553)-(5 2)-Au reconstruction is investigated. Reflectance anisotropy spectroscopy (RAS) and infrared ellipsometry reveal optical signatures of the surface. Spectral modifications related to the adsorbate exposure suggest the activation of adsorption-induced interband transitions. Density functional theory (DFT) calculations reproduce the spectral modifications and explain their origin. Preferential adsorption on sites located at the step edges of the structure occurs independent of the type of adsorbate and induces a charge transfer between electronic states related to the step edges and the Au dimer rows. This charge redistribution modifies the electronic structure close to the Fermi level, enhances the dimerization of the Au chains, and strongly influences the low-energy region of the RAS spectra. While previous studies employed atomic H as a chief adsorbate, it is shown here that even molecular H deeply modifies the Si(553)-Au optical response. Structural modification of Au-Si(553) by H and TDT adsorbates as suggested from recent ab initio calculations are verified.

Quantification of oxidative stress is a challenging task that can help in monitoring chronic inflammatory respiratory airway diseases. Different studies can be found in the literature regarding the development of electrochemical sensors for H2O2 in cell culture medium to quantify oxidative stress. However, there are very limited data regarding the impact of the cell culture medium on the electrochemical quantification of H2O2. In this work, we studied the effect of different media (RPMI, MEM, DMEM, Ham's F12 and BEGM/DMEM) on the electrochemical quantification of H2O2. The used electrode is based on reduced graphene oxide (rGO) and gold nanoparticles (AuNPs) and was obtained by co-electrodeposition. To reduce the electrode fouling by the medium, the effect of dilution was investigated using diluted (50% v/v in PBS) and undiluted media. With the same aim, two electrochemical techniques were employed, chronoamperometry (CH) and linear scan voltammetry (LSV). The influence of different interfering species and the effect of the operating temperature of 37 degrees C were also studied in order to simulate the operation of the sensor in the culture plate. The LSV technique made the sensor adaptable to undiluted media because the test time is short, compared with the CH technique, reducing the electrode fouling. The long-term stability of the sensors was also evaluated by testing different storage conditions. By storing the electrode at 4 degrees C, the sensor performance was not reduced for up to 21 days. The sensors were validated measuring H2O2 released by two different human bronchial epithelial cell lines (A549, 16HBE) and human primary bronchial epithelial cells (PBEC) grown in RPMI, MEM and BEGM/DMEM media. To confirm the results obtained with the sensor, the release of reactive oxygen species was also evaluated with a standard flow cytometry technique. The results obtained with the two techniques were very similar. Thus, the LSV technique permits using the proposed sensor for an effective oxidative stress quantification in different culture media and without dilution.

Optical properties of metal nanostructures are the basis of several scientific and technological applications. When the nanostructure characteristic size is of the order of few nm or less, it is generally accepted that only a description that explicitly describes electrons by quantum mechanics can reproduce faithfully its optical response. For example, the plasmon resonance shift upon shrinking the nanostructure size (red-shift for simple metals, blue-shift for d-metals such as gold and silver) is universally accepted to originate from the quantum nature of the system. Here we show instead that an atomistic approach based on classical physics, omega FQF mu (frequency dependent fluctuating charges and fluctuating dipoles), is able to reproduce all the typical "quantum " size effects, such as the sign and the magnitude of the plasmon shift, the progressive loss of the plasmon resonance for gold, the atomistically detailed features in the induced electron density, and the non local effects in the nanoparticle response. To support our findings, we compare the omega FQF mu results for Ag and Au with literature time-dependent DFT simulations, showing the capability of fully classical physics to reproduce these TDDFT results. Only electron tunneling between nanostructures emerges as a genuine quantum mechanical effect, that we had to include in the model by an ad hoc term.

A copper-containing metal organic framework was prepared using the new organic linker 5-(2-{[(prop-2-yn-1-yloxy)carbonyl]-amino} ethoxy)isophthalic acid [1,3-H2YBDC (where Y = alkYne and BDC = Benzene DiCarboxylate)] and functionalized with gold particles by reaction with HAuCl4 under thermal treatment in methanol. The resulting system was investigated by complementary techniques to obtain information on its structure and morphology. In the present work, x-ray photoelectron spectroscopy (XPS) was employed to analyze the chemical composition of a representative specimen. Besides wide scan spectra, data obtained by the analysis of the C 1s, O 1s, N 1s, Cu 2p, and Au 4f signals are presented and critically discussed. The results highlight the reduction of Au(III) to mostly Au(I) species. Overall, the data presented herein may act as useful guidelines for the eventual tailoring of material properties and their possible implementation toward functional applications in heterogeneous catalysis.

Multiphoton photoreduction of photosensitive metallic precursors via direct laser writing (DLW) is a promising technique for the synthesis of metallic structures onto solid substrates at the sub-micron scale. DLW triggered by a two photon absorption process is done using a femtosecond NIR laser (? = 780 nm), tetrachloroauric acid (HAuCl4) as a gold precursor, and isinglass as a natural hydrogel matrix. The presence of a polymeric, transparent matrix avoids unwanted diffusive processes acting as a network for the metallic nanoparticles. After the writing process, a bath in deion-ized water removes the gold precursor ions and eliminates the polymer matrix. Different aspects underlying the growth of the gold nanostructures (AuNSs) are here investigated to achieve full control on the size and density of the AuNSs. Writing parameters (laser power, exposure time, and scanning speed) are optimized to control the patterns and the AuNSs size. The influence of a second bath containing Au to further control the size and density of the AuNSs is also investigated, ob-serving that these AuNSs are composed of individual gold nanoparticles (AuNPs) that grow indi-vidually. A fine-tuning of these parameters leads to an important improvement of the created struc-tures' quality, with a fine control on size and density of AuNSs.

An approach for the preparation of noble metal nanoparticles supported on nanostructured metal oxides is described herein. The approach is based on the sequential generation of the noble metal nanoparticles and of a metal oxide phase inside a cross-linked polymer colloid (microgel). By tuning the properties of the employed microgel, the nature and amount of both the noble metal nanoparticles and the metal oxide phase can be independently varied. The resulting composite colloids are colloidally stable and, upon isolation by precipitation and subsequent calcination, produce noble metal nanoparticles dispersed on a crystalline, nanostructured oxide phase. Preliminary catalytic tests provide information on the accessibility of the noble metal nanoparticles and, particularly in the case of gold, result in promising catalytic performances in the aerobic oxidation of alcohols.

Cyclic trinuclear complexes (CTCs) of d10 metal frames, obtained through the reaction between angular ditopic anionic bridging ligands and 11th group elements M(I) complexes, have aroused considerable attention due to their potential application in optoelectronics and molecular recognition. Experimental evidences show that the reaction of gold(I) CTCs, featuring imidazolate bridging ligands, with different substrates (CH3I and I2) result to the formation of carbene, bis-carbene or square planar complexes depending on the nature of both the reactants depending on and of the substituent at the imidazolyl ring. Herein, we report the results of a detailed computational investigation of the reactivity by considering two different substituents at the ring ligand: methyl or benzyl groups. All the electronic and steric factors ruling the reactivity have been pointed out and, in particular, the not innocent behaviour of the imidazolyl rings in the activation of C-I bonding. Experimentally, the X-ray crystal structure demonstrates that the reaction between the gold(I) CTC - having 1-methyl-imidazolate as bridging ligand- with MeI provides the formation of a square planar gold complex with the formation of new Au-I and Au-CH3 linkages. In Figure 1 is reported the optimized structure obtained by computational calculations within Gaussian 16 package. Such a reactivity, beyond to the classic addition of iodine traditionally classified as "oxidative addition", has been explained accordingly to the newly introduced Inverted Ligand Field concept. A reasonable explanation has been also provided for the role of the different substituents at the imidazolyl ring in the reactivity.

Heterostructures of single- and few-layer black phosphorus (2D bP) functionalized with gold nanoparticles (Au NPs) have been recently reported in the literature, exploiting their intriguing properties and biocompatibility for catalytic, therapeutical and diagnostic applications. However, a deeper insight on the structural and electronic properties at the interface of the 2D bP/Au NP heterostructure is still lacking. In this work, 2D bP is functionalized with Au nanoparticles (NPs) through in situ deposition-precipitation heterogeneous reaction. The smallest realized Au NPs have a diameter around 10 nm as revealed by atomic-force and scanning electron microscopy, and are partially positively charged as revealed by X-ray Photoelectron Spectroscopy (XPS). XPS, UV-vis and Raman spectroscopy, supported by density functional theory (DFT) calculations, confirmed that while the structural and electronic properties of 2D bP are overall preserved, a soft-pairing between P atoms at the surface of 2D bP and Au atoms at the surface of Au NPs occurs, leading to a partial charge transfer at the 2D bP/Au interface, with a positive charge being localized on the Au atoms directly bonded to 2D bP. DFT calculations also predicted a band gap lowering, by 0.8 eV, for phosphorene functionalized with a tetranuclear Au cluster. Larger effects are expected as the Au cluster nuclearity (and coverage) increases.

Three-dimensional chemical mapping was adopted to investigate an ancient fire-gilded buckle found in Rome. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) were used to detect and locate degradation products aiming to identify the alteration processes. Inorganic and organic compounds present in the outermost part of such a class of cultural heritage objects can be considered the result of long-term interaction with the burial environment. ToF-SIMS depth profiling experiments can provide chemical information at the molecular level and high resolved spatial information (about 1 ?m laterally, and 1 nm in depth). In this work, the attention was focused on the identification and localization of the ionic and molecular species involved in the degradation process. Results showed the presence of copper oxides, chlorides, and sulfides as common corrosion products but also the presence of species related to copper and bronze corrosion process, such as atacamite and its polymorphs. 3D maps for all the relevant molecular species allowed to visualize at the same time the eruption of copper chlorides throughout the micro/nanochannels present on the gold surface, the recrystallization of compounds of minor elements from the substrate, a pathway followed by silico-aluminates from the surface toward the internal corrosion layers, but mostly the evidence of biological activity of Sulfur Reducing Bacteria (SRB) living in anaerobic conditions.

We show nanoscale spectroscopy and mapping of plasmon-excition coupling in Au/ZnO nanostructure by STEM-EELS and STEM-CL. Interestingly, the Au plasmon resonance is localized at Au/vacuum interface, while the ZnO signal is localized inside Au nanoparticle.

The application of a new hydrometallurgical process for gold extraction by thiosulphate leaching from Romanian mining wastes, coming from Balan and Deva deposits, was studied. Another objective of this work was to develop an integrated flow-sheet including the recycling of process solution and of the activated coconut carbon used for gold purification. There was obtained 85% of Au extraction after leaching; moreover, an integrated flow-sheet, including recycling of process solution and carbon, was outlined, based on results obtained at a laboratory scale, using a schematic chemical circuit of treatment. Global recovery of the process (leaching-adsorption-desorption-electrodeposition) of about 75-80% of Au was achieved. The developed integrated flowsheet, allows to recycle the reagents during the process, with a loss of only 5-10%, in particular thiosulphate and alcohol, for each complete circuit of treatment.

Magneto-plasmonic nanoparticles constituted of gold and iron oxide were obtained in an aqueous environment by laser ablation of iron and gold targets in two successive steps. Gold nanoparticles are embedded in a mucilaginous matrix of iron oxide, which was identified as magnetite by both microscopic and spectroscopic analyses. The plasmonic properties of the obtained colloids, as well as their adsorption capability, were tested by surface-enhanced Raman scattering (SERS) spectroscopy using 2,2 '-bipyridine as a probe molecule. DFT calculations allowed for obtaining information on the adsorption of the ligand molecules that strongly interact with positively charged surface active sites of the gold nanoparticles, thus providing efficient SERS enhancement. The presence of iron oxide gives the bimetallic colloid new possibilities of adsorption in addition to those inherent to gold nanoparticles, especially regarding organic pollutants and heavy metals, allowing to remove them from the aqueous environment by applying a magnetic field. Moreover, these nanoparticles, thanks to their low toxicity, are potentially useful not only in the field of sensors, but also for biomedical applications.

Gap plasmon-based optical metasurfaces have been extensively used for demonstration of flat optical elements with various functionalities efficiently operating at near-infrared and telecom wavelengths. Extending their operation to the visible is however impeded by the progressively increased plasmon absorption for shorter wavelengths. We investigate the possibility to improve the performance of gap plasmon-based metasurfaces in the visible by employing monocrystalline gold flakes as substrates instead of evaporated polycrystalline gold films, while using the electron-beam lithography patterning of the evaporated thin gold films for fabrication of top gold nanobricks, which define gap-plasmon resonator elements of the metasurfaces. We demonstrate that the efficiency can be improved by modest but noticeable amount of ?5% if all other configuration parameters are preserved.

In this work new energy storage components were prepared depositing films made of polyaniline (PANI) modified with gold/magnetite nanoparticles on flexible graphite foils. Three types of composite materials termed PANI/FeO, PANI/Au/FeO and PANI/Au/FeO@Yne (where @Yne is a propynylcarbamate group) were obtained by electrosynthesis. Galvanostatic charge-discharge (CD) and impedance tests (EIS) were performed to verify their efficiency in charge storage properties: for the gold-containing electrodes PANI/Au/FeO and PANI/Au/FeO@Yne areal capacities values of 45.6 and 46.5 mAh cm were found in 0.5 M HSO + 0.1 M LiClO electrolyte solution at a current density of 0.5 mA cm. These values are twofold higher than those found for PANI/FeO electrodes and fourfold greater than those for PANI alone (11.0 mAh cm). In turn PANI/Au/FeO and PANI/Au/FeO@Yne were employed to assemble gel-state symmetric devices. CD, EIS and longtime resistance tests were made on the new devices that displayed an areal capacities of 100.0 mAh cm for PANI/Au/FeO and 73.6 mAh cm PANI/Au/FeO@Yne respectively. To our knowledge this is the first time that AuNP-modified magnetite nanoparticles are used in energy storage devices preparation.

Plasmonic nanosystems built by metal/semiconductor hybrid nanoparticles had shown promising applications enabling an efficient solar light harvesting and enhancing the photocatalytic activity. Core-shell systems as Au-TiO2nanoparticles are ideal candidates due to the dynamic synergy established at the interface able to improve the e-/h+pairs separation and stability. Recently, anisotropic AuNPs gain increasing interests thanks to their tunable localized surface plasmon resonance band (LSPR) in the visible range.1However, reliable protocols to synthesize anisotropic AuNPs covered with TiO2by direct wet chemistry approaches is still challenging.2Herein, we report a novel synthetic protocol for the preparation of star-shaped AuNPs (AuNS) functionalized with nanostructured thin TiO2layers, by exploiting a designed bench-top microfluidic reactor.3This one-pot seedless procedure is based on the accurate mixture of gold and titania precursors that allows the direct and continuous production of AuNS@TiO2without adding any stabilizer agent. The hybrid composites exhibit a stable red-shift LSPR band and a good dispersibility in water and alcohols. Au/TiO2nanosystems show under simulated solar light a catalytic photoactivity toward the Rhodamine-B degradation. Before the photocatalytic tests, any eventual residual ligand on the NP surface has been cleaned-off by treating NPs with H2O2, affording purified hybrid nanosystems highly active and water dispersible.AuNS@TiO2were fully characterized by UV/vis, ICP-OES, HRTEM, STEM, EELS map to disclose the Ti distribution. This innovative procedure is reproducible and scalable, allowing the production of a high amount of shape-controlled AuNS@TiO2hybrid nanoparticles, dispersed in solution and easy to concentrate in small volumes.1. N. Li, P. Zhao, D. Astruc Angew. Chemie, Int. Ed.2014, 53, 1756.2. B. Wu, D. Liu, S. Mubeen, T. T. Chuong, M. Moskovits, G. D. Stucky JACS2016, 138(4) 1114.3. A. Silvestri, L. Lay, R. Psaro, L. Polito, C. Evangelisti Chem. Eur. J.2017, 23, 9732.

The availability of raw materials (RMs) from marginal resources as industrial wastes is fundamental for the European and non-European countries for economic and environmental reasons, and of strategic importance for industrial production, due to their high concentration on valuable metals. It is therefore important the development of innovative environmentally friendly processes, to achieve RMs and critical raw materials (CRMs) of economic interest, by exploitation of the secondary RMs. Hydrometallurgical gold extraction by thiosulphate leaching represents an example of the application of these new processes: Au extraction of 85% was experimentally obtained after leaching; moreover, the overall process achieved about 80% Au recovery, this being in line with the conventional cyanidation process. These results are very encouraging, considering that this is a commercially innovative process. The optimization of process parameters and operating conditions should permit the best results in terms of process yields to be achieved.

This work is focused on the synthesis, characterization, and preliminary biological evaluation of bio-conjugated Au-III and Cu-II complexes with the aim of overcoming the well-known side effects of chemotherapy by improving the selective accumulation of an anticancer metal payload in malignant cells. For this purpose, carbohydrates were chosen as targeting agents, exploiting the Warburg effect that accounts for the overexpression of glucose-transporter proteins (in particular GLUTs) in the phospholipid bilayer of most neoplastic cells. We linked the dithiocarbamato moiety to the C1 position of three different monosaccharides: d-glucose, d-galactose, and d-mannose. Altogether, six complexes with a 1:2 metal-to-ligand stoichiometry were synthesized and in vitro tested as anticancer agents. One of them showed high cytotoxic activity toward the HCT116 colorectal human carcinoma cell line, paving the way to future in vivo studies aimed at evaluating the role of carbohydrates in the selective delivery of whole molecules into cancerous cells.