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N‐Heterocyclic carbenes (NHCs) have drawn considerable interest in the field of nanomaterials chemistry as highly stabilizing ligands enabling the formation of strong and covalent carbon–metal bonds. Applied to gold nanoparticles synthesis, the most common strategy consists of the reduction of a preformed NHC‐AuI complex with a large excess of a reducing agent that makes the particle size difficult to control. In this paper, we report the straightforward synthesis of NHC‐coated gold nanoparticles (NHC‐AuNPs) by treating a commercially available gold(I) precursor with an easy‐to‐synthesize NHC‐BH3 reagent. The latter acts as both the reducing agent and the source of surface ligands operating under mild conditions. Mechanistic studies including NMR spectroscopy and mass spectrometry demonstrate that the reduction of gold(I) generates NHC‐BH2Cl as a by‐product. This strategy gives efficient control over the nucleation and growth of gold particles by varying the NHC‐borane/gold(I) ratio, allowing unparalleled particle size variation over the range of 4.9±0.9 to 10.0±2.7 nm. Our strategy also allows an unprecedented precise and controlled seeded growth of gold nanoparticles. In addition, the as‐prepared NHC‐AuNPs exhibit narrow size distributions without the need for extensive purification or size‐selectivity techniques, and are stable over months. [ABSTRACT FROM AUTHOR]

In this paper, the run of the decorating process of the active support, like CeO2, by the gold nanoparticles via deposition‐precipitation method has been studied. Two types of the Au/CeO2 systems with different mean particle size (but the same morphology) of the support have been investigated. It was noted that the decoration process proceeds easily only for large crystals with average size about 67 nm. Three hypotheses were tested in order to explain unsuccessful initial Au nanoparticles decoration of the cube‐like CeO2 crystals with average size about 14 nm as a support. The tests have shown that the ratio of the molar content of the chloroauric acid to the total surface area of the support (MAu/SCeO2) has a significant impact on the decorating process of CeO2 by nano‐Au. If the above ratio is too small, the thin layer of gold instead of the Au nanoparticles is formed on the support surface. In this paper, the calculations of the real surface area (from TEM/HRTEM data) were used to adjust the optimum the MAu/SCeO2 to obtain the Au/CeO2 system with the desired properties. [ABSTRACT FROM AUTHOR]

Biomass constitutes a renewable source for new chemical platforms. Among other processes the catalytic ones represent a green alternative when active and selective catalysts can be developed. In this paper, applications of gold and gold‐based catalysts have been reviewed in the field of the selective oxidations. Indeed, from the discovery of the peculiarity of gold as catalytic material, the liquid phase oxidations have been differently viewed. Three important biomass‐derived molecules, namely glucose, hydroxymethyl furfural (HMF) and glycerol have been considered as precursors for products of industrial interest where gold catalysts have played an important role. This review starts from the research on monometallic gold catalysts which have been explored initially and then look at gold as modifier of other metal catalyst. This latter field is still in evolution and probably needs to be look at in the future. Golden path: Applications of gold and gold‐based catalysts for selective liquid‐phase oxidation of biomass‐derived products have been reviewed. Three important molecules, namely glucose, hydroxymethyl furfural (HMF) and glycerol have been considered as precursors for products of industrial interest. [ABSTRACT FROM AUTHOR]

In this paper, we aimed at investigating the effect of the presence of small TiO2 crystallites over the transfer of hot electrons from Au nanoparticles (NPs) mediated by the surface plasmon resonance (SPR) excitation and its subsequent photocatalytic activities. To this end, we employed TiO2 colloidal spheres composed of TiO2 crystallites of 8.5 nm in size decorated with Au NPs (TiO2–Au) of 17 nm in size over the TiO2 surface as model materials. Moreover, the photocatalytic degradation of methylene blue (MB) under visible light excitation was employed as a target plasmonic transformation. We found that the plasmonic photocatalytic activity was significantly higher for the TiO2–Au hybrid relative to its individual Au NPs or TiO2 counterparts under excitation at 633 nm. These results could be explained based on the transfer of hot electrons generated upon the SPR excitation from Au NPs to the TiO2 conduction band in the TiO2–Au material, which will be recombined on the surface of TiO2 crystallites or at the interface between TiO2 crystallites, decreasing electrons density in Au NPs that lead to the formation of hydroxyl radicals that contribute and improve the photocatalytic degradation of MB. This mechanism was supported by the fact that the presence of TiO2 leads to a decrease in the p‐aminothiophenol to p,p′‐dimercaptoazobenzene SPR‐mediated oxidation in the TiO2–Au relative to Au NPs. We believe that the results reported herein suggest that TiO2–Au materials may represent attractive systems for designing plasmonic photocatalysts with improved performances towards a variety of transformations using solar/visible light as the energy input. TiO2–Au material presented improved plasmonic photocatalytic activity under visible light. TiO2 formed by small crystallites enhances plasmonic photocatalytic performance. This mechanism involving the transfer of SPR‐excited hot electrons from Au to TiO2 was further supported by probing the SPR‐mediated catalytic oxidation of p‐aminothiophenol (PATP) to p,p′‐dimercaptoazobenzene (DMAB). [ABSTRACT FROM AUTHOR]

The influence of the size and oxidation state of Au nanoparticles (AuNPs) as electrocatalysts for the electro-oxidation of cellulose was studied. Carbon paper electrodes modified with AuNPs were used as the electrocatalysts for the electro-oxidation of cellulose dissolved in 1.3 m NaOH. The size and oxidation state of the AuNPs were determined by using SEM, TEM, and X-ray photoelectron spectroscopy. Both the size and the oxidation state of the AuNPs were found to influence the electrocatalytic properties of the electrode, as studied by using cyclic voltammetry, square wave voltammetry, and electrochemical impedance spectroscopy. The carbon paper electrodes decorated with AuNPs (less than 25 nm) that consist of metallic Au gave rise to a significantly higher electrocatalytic activity than a bare polycrystalline Au electrode. [ABSTRACT FROM AUTHOR]

Abstract: Mg(OH)2‐ and Mg(OH)2‐containing materials can provide excellent performance as supports for AuPd nanoparticles for the oxidation of glycerol in the absence of base, which is considered to be a result of additional basic sites on the surface of the support. However, its influence on the reaction solution is not generally discussed. In this paper, we examine the relationship between the basic Mg(OH)2 support and AuPd nanoparticles in detail using four types of catalyst. For these reactions, the physical interaction between Mg(OH)2 and AuPd was adjusted. It was found that the activity of the AuPd nanoparticles increased with the amount of Mg(OH)2 added under base‐free conditions, regardless of its interaction with the noble metals. In order to investigate how Mg(OH)2 affected the glycerol oxidation, detailed information about the performance of AuPd/Mg(OH)2, physically mixed (AuPd/C+Mg(OH)2) and (AuPd/C+NaHCO3) was obtained and compared. Furthermore, NaOH and Mg(OH)2 were added during the reaction using AuPd/C. All these results indicate that the distinctive and outstanding performance of Mg(OH)2 supported catalysts in base‐free condition is in fact directly related to its ability to affect the pH during the reaction and as such, assists with the initial activation of the primary alcohol, which is considered to be the rate determining step in the reaction. [ABSTRACT FROM AUTHOR]

Understanding how the spatial ordering of liquid crystalline nanoparticles can be controlled by different factors is of great importance in the further development of their photonic applications. In this paper, we report a new key parameter to control the mesogenic behavior of gold nanoparticles modified by rodlike thiols. An efficient method to control the spatial arrangement of hybrid nanoparticles in a condensed state is developed by changing the composition of the mesogenic grafting layer on the surface of the nanoparticles. The composition can be tuned by different conditions of the ligand exchange reaction. The thermal and optical behavior of the mesogenic and promesogenic ligands were investigated by using differential scanning calorimetry (DSC) and hot-stage polarized optical microscopy. The chemical structure of the synthesized hybrid nanoparticles was characterized by 1H NMR spectroscopy, thermogravimetric analysis (TGA), XPS, and elemental analysis, whereas the superstructures were examined by small-angle X-ray diffraction (SAXSRD) analysis. Structural studies showed that the organic sublayer made of mesogenic ligands is denser with an increasing the average ligand number, thereby separating the nanoparticles in the liquid crystalline phases, which changes the parameters of these phases. [ABSTRACT FROM AUTHOR]

So far, almost all electrochemistry theories are based on an assumption that the size of an electroactive molecule is negligible. However, this assumption will not be true if the size of an electroactive molecule is comparable to or smaller than the size of an electrode being used to study the electroactive molecule. In this paper, the electrochemical behaviors of ferrocenated gold nanoparticles have been studied using an electrode with a radius that is smaller than the radius of the particle. This allows for the observation of phenomena which cannot be explained by conventional electrochemical theories. Also, stochastic collision current, which cannot be observed on a macro- or microelectrode, can be directly observed. [ABSTRACT FROM AUTHOR]

Purpose: Noble metal nanoparticles have found several medical applications in the areas of radiation detection; x-ray contrast agents and cancer radiation therapy. Based on computational methods, many papers have reported the nanoparticle effect on the dose deposition in the surrounding medium. Here the authors report experimental results on how silver and gold nanoparticles affect the dose deposition in alanine dosimeters containing several concentrations of silver and gold nanoparticles, for five different beam energies, using electron spin resonance spectroscopy (ESR). Methods: The authors produced alanine dosimeters containing several mass percentage of silver and gold nanoparticles. Nanoparticle sizes were measured by dynamic light scattering and by transmission electron microscopy. The authors determined the dose enhancement factor (DEF) theoretically, using a widely accepted method, and experimentally, using ESR spectroscopy. Results: The DEF is governed by nanoparticle concentration, size, and position in the alanine matrix. Samples containing gold nanoparticles afford a DEF higher than 1.0, because gold nanoparticle size is homogeneous for all gold concentrations utilized. For samples containing silver particles, the silver mass percentage governs the nanoparticles size, which, in turns, modifies nanoparticle position in the alanine dosimeters. In this sense, DEF decreases for dosimeters containing large and segregated particles. The influence of nanoparticle size-position is more noticeable for dosimeters irradiated with higher beam energies, and dosimeters containing large and segregated particles become less sensitive than pure alanine (DEF < 1). Conclusions: ESR dosimetry gives the DEF in a medium containing metal nanoparticles, although particle concentration, size, and position are closely related in the system. Because this is also the case as in many real systems of materials containing inorganic nanoparticles, ESR is a valuable tool for investigating DEF. Moreover, these results alert to the importance of controlling the sizeposition of nanoparticles to enhance DEF. [ABSTRACT FROM AUTHOR]

Purpose: This paper reports a technique that enables the quantitative determination of the concentration of gold nanoparticles (GNPs) through the accurate detection of their fluorescence radiation in the diagnostic x-ray spectrum. Methods: Experimentally, x-ray fluorescence spectra of 1.9 and 15 nm GNP solutions are measured using an x-ray spectrometer, individually and within chicken breast tissue samples. An optimal combination of excitation and emission filters is determined to segregate the fluorescence spectra at 66.99 and 68.80 keV from the background scattering. A roadmap method is developed that subtracts the scattered radiation (acquired before the insertion of GNP solutions) from the signal radiation acquired after the GNP solutions are inserted. Results: The methods effectively minimize the background scattering in the spectrum measurements, showing linear relationships between GNP solutions from 0.1% to 10% weight concentration and from 0.1% to 1.0% weight concentration inside a chicken breast tissue sample. Conclusions: The investigation demonstrated the potential of imaging gold nanoparticles quantitatively in vivo for in-tissue studies, but future studies will be needed to investigate the ability to apply this method to clinical applications. [ABSTRACT FROM AUTHOR]

Adipic acid (AA) is one of the highest volume chemicals in world use with a wide range of commercial applications. This paper demonstrates the possibility of producing significant proportions of AA by the selective oxidation of cyclohexane (CH) in one step using various supported gold-nanoparticle (AuNP) catalysts. The catalysts were characterized by ICP, BET, XRD, X-ray photoelectron microscopy, and TEM. The catalytic activity tests were carried out in the liquid phase using autoclaves in the temperature range of 100-170 °C at 10 bar. A CH conversion of over 25 %, with 26% selectivity of AA and 70% selectivity of KA oil (cyclohexanone+cyclohexanol), was achieved over a nano-gold/TiO2 (anatase) catalyst. The superior performance of this catalyst is attributed to the smaller size of AuNPs, which has an average particle size of 2 nm. Good correlation between activity and Au particle size could be achieved. Overall, the particle size of the AuNPs showed a strong influence on catalytic performance. [ABSTRACT FROM AUTHOR]

This paper describes a surface-enhanced Raman scattering (SERS) systematic investigation regarding the functionalization of gold (Au) and silver (Ag) nanoparticles with diphenyl dichalcogenides, i.e. diphenyl disulfide, diphenyl diselenide, and diphenyl ditelluride. Our results showed that, in all cases, functionalization took place with the cleavage of the chalcogen-chalcogen bond on the surface of the metal. According to our density functional theory calculations, the molecules assumed a tilted orientation with respect to the metal surface for both Au and Ag, in which the angle of the phenyl ring relative to the metallic surface decreased as the mass of the chalcogen atom increased. The detected differences in the ordinary Raman and SERS spectra were assigned to the distinct stretching frequencies of the carbon-chalcogen bond and its relative contribution to the ring vibrational modes. In addition, the SERS spectra showed that there was no significant interaction between the phenyl ring and the surface, in agreement with the tilted orientation observed from our density functional theory calculations. The results described herein indicate that diphenyl dichalcogenides can be successfully employed as starting materials for the functionalization of Au nanoparticles with organosulfur, organoselenium, and organotellurium compounds. On the other hand, diphenyl disulfide and diphenyl diselenide could be employed for the functionalization of Ag nanoparticles, while the partial oxidation of the organotellurium unit could be detected on the Ag surface. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The image illustrates the operation mechanism of the photothermal activation of Ru/Au nanoparticles deposited on Siralox. Upon absorption of light by Au nanoparticles, the photon energy is thermalized, leading to the heating of smaller Ru nanoparticles located on the Au surface. This local heating serves to promote the selective methanation of CO2 by H2. For more information, see the Full Paper by H. García et al. on page 18436 ff. [ABSTRACT FROM AUTHOR]

The calculated Au38 cluster is represented in the middle of the cover picture, coated by the N ‐ heterocyclic carbenes (NHCs) presented in the paper. The falling binary code “01” illustrates that the Au38 clusters are issued from DFT calculations. Molecular bis(NHC) gold complexes obtained from the functionalization of the particles are represented around the cluster. An experimental 1H NMR solid ‐ state spectrum is shown in the lower part of the cover to remind the reader that the study combines experimental and computational approaches. More information can be found in the Full Paper by F. Tielens, F. Remacle, S. Richeter et al. on page 10446 ff. [ABSTRACT FROM AUTHOR]

The cover picture shows puffball‐shaped, flavin‐functionalized, monolayer‐protected gold nanoparticles that efficiently catalyze aerobic transformations. In their Full Paper, Y. Imada, T. Naota and co‐workers describe the synthesis of PPh3‐protected gold clusters functionalized with cationic and neutral flavins, and their catalytic activities for the aerobic oxidation of sulfides and reduction of alkenes. Both the oxidation and reduction reactions proceed with high efficiency under atmospheric pressure in O2 or air and mild conditions. The advantages of the nanoparticle catalysts over conventional methods are discussed from synthetic and mechanistic viewpoints. The article highlighted by this cover can be found on p. 99 ff. of Issue 1, 2015. [ABSTRACT FROM AUTHOR]

The Cover shows an industrial landscape, where Au nanoparticles are used as catalysts for oxidation reactions.In their Full Paper, L. M. D. R. de Sousa Martins et al. demonstrate an efficient single‐pot oxidative functionalization of cyclohexane and benzyl and methylbenzyl alcohols under mild conditions with high selectivity, catalyzed by reusable Au nanoparticles on Al2O3, Fe2O3, ZnO, and TiO2. Au nanoparticles on Fe2O3 led to an unusual almost exclusive formation of cyclohexanol by control of reaction time, but Au nanoparticles on TiO2 had a remarkable catalytic effect on acetophenone yield. [ABSTRACT FROM AUTHOR]

The cover picture shows the growth mechanism of Cu2O/noble‐metal nanocomposites and the application of these nanocomposites as surface‐enhanced Raman scattering (SERS) substrates, as reported by Z. Wang and co‐workers in their Full Paper on page 684 ff. They aim to synthesize SERS substrates with high sensitivity and good reproducibility for the detection of food contaminants. [ABSTRACT FROM AUTHOR]

Brown and gold The cover picture illustrates the concept of using gold nanoparticle‐decorated carbon nanotubes to directly electrochemically oxidize alginate—the principle, difficult‐to‐degrade component of brown macroalgae (as shown in the background of the cover picture). In their Full Paper on p. 135 ff., L. Q. Hoa, E. Tamiya et al. present analyses that suggest a reaction pathway similar to the chemical oxidation process by strong oxidants that results in oxidized alginate usable for cell and tissue engineering. This straightforward approach, in contrast to currently employed alginate‐metabolizing microbial approaches, can enhance the energy extraction efficiency of the whole biomass‐to‐energy conversion process through a fuel cell system without requiring any external energy, while simultaneously producing high‐value chemicals, paving the way for the future production of energy and feedstock materials from inedible biomass. [ABSTRACT FROM AUTHOR]

New water ‐ soluble gold nanoparticles stabilized by a nitrogen ‐ rich poly(ethylene glycol) (PEG) ‐ tagged substrate, which displayed excellent activity as recyclable catalyst for the mild and selective reduction of nitroarenes in water, have been prepared and characterized. Moreover, their potential ability as refractive index sensors has been demonstrated. More information can be found in the Full Paper on page 2437 by Roser Pleixats et   al. (DOI: 10.1002/asia.201500290). [ABSTRACT FROM AUTHOR]

The cover picture shows the TEM pictures of new gold nanoparticles confined in the ORMOSIL matrix of SiliaCat Au catalyst as background, with superimposed reaction scheme for the model oxidation of 1‐phenylethanol with hydrogen peroxide. In their Full Paper, L. M. Ilharco, M. Pagliaro and co‐workers explain why and how this new catalyst series is ideally suited for the practical utilization of sol‐gel encapsulated gold nanoparticles in a number of different reactions. The catalyst has a huge surface area and has been extensively characterized. The article highlighted by this cover can be found on p. 254 ff. of Issue 2, 2015. [ABSTRACT FROM AUTHOR]

Surface ‐ passivated SBA ‐ 15 ‐ supported gold nanoparticles that were nearly superhydrophobic, with a contact angle of 144°, were prepared by surface passivation based on a modified impregnation method, as reported by Jinsuo Gao et   al. in their Full paper on page   934   ff. In their study, which is featured on the Inside Cover, the authors found that the catalytic activity of these nanoparticles regarding the reduction of nitrobenzene was significantly increased (>14 times) when compared with non ‐ passivated SBA ‐ 15. Interestingly, the catalyst exhibited almost no catalytic activity for the more hydrophilic substrate 4 ‐ nitrophenol. Accordingly, such surface ‐ passivated catalysts may find use in the selective catalysis of hydrophobic substrates. [ABSTRACT FROM AUTHOR]

Selective oxidation The inside cover picture shows a mystique of TiO2‐supported Au nanoparticles as a photocatalyst for partial oxidations of organic substrates under sunlight irradiation and a CO2 atmosphere. In their Full Paper on p. 766 ff., Y. Ide et al. describe how the photocatalytic oxidation of aqueous phenol to hydroquinone on the catalyst under sunlight is modified to give a higher yield and selectivity if the reaction is conducted under a CO2 atmosphere. Au loading causes neither the visible light response nor the improved UV light‐induced charge separation efficiency of TiO2. A unique role of Au loading in the photocatalysis is proposed; Au nanoparticle loading drastically decreases the amount of the surface titanol, promoting the desorption of the product hydroquinone from the catalyst surface, especially if CO2 is present in the system. [ABSTRACT FROM AUTHOR]

Bimetallic Au–Pd nanoparticles were prepared in the functionalized ionic liquid [C2OHmim][NTf2] by the thermal decomposition of Pd(OAc)2 and Au(OAc)3. The Au atoms are mostly located in the NP core, leaving the Pd atoms ENriched at the surface. Moreover, the Pd atoms are electropositive, which leads to high activity in catalytic dehalogENation reactions. The activity of the heteronuclear nanoparticles may be attributed to charge transfer from Pd to Au and consequENtly to more efficiENt reductive elimination. For more details, see the Full Paper by N. Yan et   al. on page   1227   ff. [ABSTRACT FROM AUTHOR]