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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]

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]

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]

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]

The best activity of bimetallic AuPd nanoparticles for alcohol oxidation reaction is usually achieved by adjusting the Au/Pd molar ratio. Herein, alloy AuPd nanoparticles of ∼2.5–3.5 nm, ranging from Au‐rich to Pd‐rich compositions, were synthesized through a sol‐immobilization method. A calcination step under air conditions caused an increase in size up to 5.5 nm, but also driven the segregation of Pd to the surface, which generated an Au rich core with Pd on the shell. At high Pd content, the shell structure is formed by PdO. The catalytic activity of Pd‐rich samples (1 : 1, 1 : 2 and 1 : 4 Au : Pd) for benzyl alcohol oxidation increased ∼4‐fold after calcination. Upon reduction with H2, surface PdO motifs are reduced to Pd that did not dissolve back into the AuPd alloy core, maintaining the metallic Pd shell. The catalytic activity decreased. Therefore, restructuring alloyed AuPd nanoparticles into core‐shell like structures with PdO in the shell is beneficial to the catalytic activity, but reduction of PdO layer was detrimental. These results provide new insights on the optimization of AuPd catalysts, considering not only the Au/Pd molar ratio, but also the importance of PdO, which was not anticipated in the previous literature. [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]

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]

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]

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]

A correction to the article "Simultaneous Generation of Mesoxalic Acid and Electricity From Glycerol on a Gold Anode Catalyst in Anion-Exchange Membrane Fuel Cells," published in a previous issue of the journal is presented.

Gold catalysis has experienced a tremendous development over the past decades, and is nowadays widely used in organic synthesis to perform chemical transformations of π‐bond‐containing molecules. Catalyst development has been based mostly on ligand development and counter‐ion strategies. More recently, the encapsulation of gold catalysts in (supra)molecular cages was explored as a new way to control selectivity and reactivity of gold catalysts. In this review, we describe the cages that have been employed as hosts for gold complexes, along with their impact on the catalytic performance. Covalent and supramolecular approaches to encapsulate single metal complexes will be described and the impact on the catalytic performance will be discussed. Also, recent strategies to pre‐organize multiple metal centers will be discussed. C‐Au‐ght! Recent advances in gold catalysis in (supra)molecular cages allow control of the reactivity, selectivity and enhanced stability of gold complexes. Both covalent and supramolecular strategies are reviewed and special features of each systems are highlighted. [ABSTRACT FROM AUTHOR]

Abstract: Au and AuPd nanoparticles supported on MgO and Al2O3 were employed for the selective aqueous phase oxidation of glycerol under basic conditions. Catalysts were prepared by sol‐immobilization without the addition of a stabilizing agent such as polyvinyl alcohol (PVA), which is generally added to stabilize the noble metal sol prior to immobilization. The obtained materials prepared with and without stabilizing agent were active for glycerol oxidation and showed similar catalytic performances—implying that the stabilizing polymer is not required to obtain active materials. Depending on the support used, it was possible to tailor the selectivity towards the desired oxidation products by using catalysts prepared with or without stabilizing agent. PVA‐free Au/γ‐Al2O3 exhibited a remarkably high selectivity towards tartronic acid (40 % at 97 % conversion), which was not observed for Au/γ‐Al2O3 prepared with PVA (27 % at isoconversion). Selective glycerol oxidation performed under base‐free conditions over AuPd/MgO catalysts also corroborated the previous results that the presence of a stabilizing polymer is not required to prepare active catalysts by sol‐immobilization. Thus, a facile way to circumvent the inherent drawbacks encountered by the use of polymer stabilizers during catalyst preparation is presented herein. Experimental results suggest that the presence of the polymer stabilizers can affect the reaction pathways and control selectivity. [ABSTRACT FROM AUTHOR]

Abstract: The development of artificial nanocatalysts, especially those incorporating the highly active biocatalysts (enzymes) present in nature, is a rapidly developing field in nanocatalysis and nanomaterials science. Dehydrogenases are exceptionally attractive, as they catalyze the oxidation of various cheap/common substrates to more expensive and desired products. However, their use in sustainable catalysis and/or their incorporation in advanced nanomaterials with catalytic functions are limited owing to one immense problem that can be formulated as a question: how can the electrons received from the oxidized substrate be removed? Here, a solution to this problem is demonstrated: we designed a unique nanomaterial composed of two redox enzymes (nonspecific glucose dehydrogenase and oxygen‐reducing laccase) and gold nanoparticles. Both enzymes were wired through the gold nanoparticles (10 nm) and direct electrochemical “communication” was achieved, allowing electron transfer from the redox center of glucose dehydrogenase to a copper center of laccase. As a result, self‐sufficient nanocatalysts were synthesized and shown to oxidize various carbohydrates directly with molecular oxygen. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (AuNPs) can be obtained from HAuCl4 by using poly(ethyleneimine) (PEI) as both reductant and stabilizing agent. However, the known affinity of PEI for different materials has not been exploited to coat them and turn their surface catalytic. We demonstrate that the irradiation of a solution of HAuCl4 and branched PEI 1800 (bPEI2K) with microwave (MW) yields PEI-stabilized AuNPs (MW-PEI@AuNPs) with an average size of 7.6 nm that are catalytically active in the reduction with NaBH4 of different nitroarenes functionalized with a variety of functional groups. Moreover, the as-prepared MW-PE@-AuNPs show affinity for different materials such as polystyrene (standard spectrophotometry disposal cuvettes), polypropylene (Falcon-type tubes), and silica (Silica gel 60), turning their surface catalytic without any additional synthetic step. This feature was exploited to transform standard tubing (Tygon, poly(ether ether ketone), and stainless steel) into flow reactors by simple passage of a solution of MW-PEI@AuNPs. This straightforward functionalization is especially appealing in the case of the stainless-steel tubing, one of the materials more widely used in HPLC, which is of interest for flow nanocatalysis. [ABSTRACT FROM AUTHOR]

The efficient single-pot oxidative functionalisation of alkanes and alcohols under mild conditions was catalysed by Au nanoparticles supported on Al2O3, Fe2O3, ZnO and TiO2. The obtained materials were tested for cyclohexane oxidation under mild conditions (60 °C, atmospheric pressure) using an environmentally friendly oxidant (H2O2). The materials were also tested in the oxidation of benzyl alcohol and methylbenzyl alcohol in the presence of tert-butylhydroperoxide as the oxidant under microwave irradiation. With regard to cyclohexane oxidation, all materials were highly selective towards the formation of cyclohexanol and cyclohexanone. No traces of byproducts were detected under the optimised conditions. Au on Fe2O3 led to the best results (13.5 % yield). This system showed an interesting almost exclusive formation of cyclohexanol at 4 h reaction time. Catalyst recycling was tested in up to five cycles, and the catalyst maintained almost the original level of activity after three cycles with no significant leaching. With regard to oxidation of benzyl alcohol and methylbenzyl alcohol, all materials were highly selective towards the formation of benzaldehyde or acetophenone, respectively. No traces of byproducts were detected. Addition of Au increased alcohol conversion from 5 (TiO2) to 91 % (Au/TiO2). The recycling of Au/TiO2 was tested in up to 10 cycles, and the catalytic activity remained high in the first four cycles. [ABSTRACT FROM AUTHOR]

The cover page of the journal "ChemCatChem" is presented.

A de novo synthesis of gold-nanoparticle-embedded, nitrogen-doped nanoporous carbon nanoparticles (Au@NC) was investigated in this work. Chloroauroic acid was encapsulated inside zeolitic imidazolate framework-8 (ZIF-8) nanoparticles during the synthesis and later reduced into gold nanoparticles. The as-synthesized gold-nanoparticle-embedded ZIF-8 (Au@ZIF-8) was then carbonized into Au@NC to enhance the stability of the nanoporous support. The results show that Au@NC exhibits a porous structure containing 3 wt % of gold. 2-Methylimidazole provided an abundant amount of nitrogen (19 wt %) on the carbon matrix, which resulted in a hydrophilic and positively charged surface that is useful for the reduction of 4-nitrophenol. The results of the catalytic reaction indicate that synthesized Au@NC could act as an effective catalyst with a turnover frequency (TOF) of 1185 g−1 s−1, which is higher than that of conventional naked Au nanoparticles (TOF: 339 g−1 s−1) and that of Au nanoparticles on activated carbon (TOF: 89 g−1 s−1). We propose that the enhanced performance of Au@NC resulted from homogeneous distribution of Au nanoparticles along with the hydrophilic and positively charged nitrogen-doped carbon surface. [ABSTRACT FROM AUTHOR]

Gold nanoparticles supported on carbon nanotubes were investigated as catalysts in the aerobic oxidation of various substrates (phenols, hydroquinones, catechols, aminophenols, and thiols). The nanohybrid system compares favorably with other supported noble metal catalysts in terms of overall efficacy as it operates at room temperature, under air atmosphere (no external oxidant needed), and can readily be recycled. [ABSTRACT FROM AUTHOR]

Gold and copper nanoparticles supported on cerium(IV) oxide (CeO2) powder, which were prepared using a simple multistep photodeposition method, showed strong absorptions at around λ=620 nm attributed to the surface plasmon resonance of Cu-Au nanoparticles and exhibited a higher level of activity than that of Au/CeO2 in the mineralization of organic acids (formic acid and acetic acid) in aqueous suspensions under light irradiation ( λ=640 nm) from a red light-emitting diode. The action spectrum in the mineralization of formic acid indicates that this mineralization involved a photoinduced step by the SPR of Cu-Au supported on CeO2. The apparent quantum efficiency reached 7.5 % at λ=625 nm and 5.2 % even at λ=700 nm. [ABSTRACT FROM AUTHOR]