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Oxygen vacancies are one of the prominent types of defects in metal oxides. In addition to their role in modifying the electronic properties in solids, these sites have been shown to activate chemical bonds. As a result, the use of defect‐rich metal oxides in the organic transformations is promising. The article gives an overview of various chemical processes that are in use for the chemical reduction of aromatic nitro compounds to amines. Recently, application of oxygen vacancies in transition metal oxide for the selective reduction of aromatic nitro compounds to the corresponding amines has emerged as a new method of synthesis of amines. Oxygen vacancies in reducible oxide such as CuO have been shown to decompose hydrazine hydrate to H2 and in situ cause the reduction of nitro arenes to corresponding amines. This concept article discusses the literature pertaining to the synthesis of nitro reduction reaction, various strategies employed thus far and the place the defect‐mediated synthesis holds. The article also discusses the perspectives and challenges that remain to be addressed to gain more insights into the mechanistic understanding of the role of oxygen vacancies in nitro reduction and beyond. [ABSTRACT FROM AUTHOR]

The efficient hydrogenation of N-heterocycles with H2 under mild conditions remains a significant challenge. In this work, polyphosphazene (PZs) microspheres, novel organic–inorganic hybrid materials possessing unique –P=N– structural units and a diverse range of side groups, were used to serve as support for the design of a stable and efficient Pd nanocatalyst (Pd/PZs). The PZs microspheres were prepared by self-assembly induced by precipitation polymerization, and Pd nanoparticles were grown and loaded on the support by a chemical reduction process. Several characterization techniques, including XRD, FTIR, SEM, TEM, XPS, BET and TGA, were used to study the structural features of the nanocomposites. The results revealed that Pd nanoparticles were uniformly distributed on the PZs microspheres, with primary sizes ranging from 4 to 9 nm based on the abundance of functional P/N/O groups in PZs. Remarkably high catalytic activity and stability were observed for the hydrogenation of quinoline compounds using the Pd/PZs nanocatalyst under mild conditions. Rates of 98.9% quinoline conversion and 98.5% 1,2,3,4-tetrahydroquinoline selectivity could be achieved at a low H2 pressure (1.5 bar) and temperature (40 °C). A possible reaction mechanism for quinoline hydrogenation over Pd/PZs was proposed. This work presents an innovative approach utilizing a Pd-based nanocatalyst for highly efficient multifunctional hydrogenation. [ABSTRACT FROM AUTHOR]

Molybdenum‐ or tungsten‐dependent formate dehydrogenases have emerged as significant catalysts for the chemical reduction of CO2 to formate, with biotechnological applications envisaged in climate‐change mitigation. The role of Met405 in the active site of Desulfovibrio vulgaris formate dehydrogenase AB (DvFdhAB) has remained elusive. However, its proximity to the metal site and the conformational change that it undergoes between the resting and active forms suggests a functional role. In this work, the M405S variant was engineered, which allowed the active‐site geometry in the absence of methionine Sδ interactions with the metal site to be revealed and the role of Met405 in catalysis to be probed. This variant displayed reduced activity in both formate oxidation and CO2 reduction, together with an increased sensitivity to oxygen inactivation. [ABSTRACT FROM AUTHOR]

Glycerol (GL) represents a widespread agro‐industrial waste. Its valorization is pivotal for a sustainable society because GL is a renewable compound deriving from biomass, but it has a high oxygen to carbon ratio, compared with feedstock used in the energy and chemistry sectors. Oxygen‐poor derivatives are easily and immediately transferable to the industry, avoiding a deep and pressing modification of the plants. From this perspective, keeping the carbon content but with an oxygen content reduction, we could effectively obtain the enhancement of the recovery and the use of GL converting it into attractive industrial building‐blocks. In this Review, we present and discuss the up‐to‐date results about the chemical reduction of GL into products with 3 carbon and 0, 1, or 2 oxygen atoms. The focus is on the transition metal (TM) catalysts that have made the hydrogenation reactions of GL possible, partitioning the metals into early and late, based on their position in the periodic table. This discussion will contribute to select and develop new catalysts aimed at the improvement of the yield and of the selectivity in the hydrogenation reactions of GL. [ABSTRACT FROM AUTHOR]

We have developed a biological macromolecule stabilized method for the preparation of cobalt sulfide nanoparticles using carboxymethyl cellouse (CMC) as a stabilizing agent. We investigated the formation of cobalt sulfide nanoparticles as a function of different amounts of CMC. At 0.05% w/v amount of CMC, the high percentage of cube shaped cobalt sulfide nanoparticles is obtained. The samples obtained from 0.01% w/v and 0.1% w/v amounts of CMC shows random shaped cobalt sulfide nanoparticles and aggregated cobalt sulfide nanostructures, respectively. The obtained cobalt sulfide nanoparticles are stabilized through the interactions of hydroxyl (–OH) and carboxylate (–COO–) functional groups in CMC. The CMC encapsulated cobalt sulfide nanoparticles were shown to have good catalytic activity for chemical reduction of p-nitroaniline in the presence of sodium borohydride. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Photocatalytic CO2 reduction to fuels and chemicals has been considered as the promising avenue to realize carbon resource recycling. Covalent organic frameworks (COFs) with pre‐designed and tailorable structures are promising platforms for studying the influence of the microenvironment of catalysts on photocatalytic CO2 reduction. Herein, we report three isomorphic COFs (TPHH‐COF, TPPD‐COF and TPBD‐COF) as heterogeneous photocatalysts for CO2 reduction and investigate the different levels of conjugation and planarity of COFs effect on the catalytic activity. Photoelectrochemical measurements show that TPPD‐COF has a narrower band gap and faster photocurrent response compared to TPHH‐COF and TPBD‐COF, probably due to the moderate conjugation and planarity. As the photocatalyst, TPPD‐COF showed the most outstanding photocatalytic activity with the production rates of 951 and 157 μmol·g–1·h–1 for CO and H2, respectively. This study illustrates the close relation between microenvironment and photocatalytic activity and provides new insights for designing high‐performance photocatalysts. [ABSTRACT FROM AUTHOR]

Herein, we engineered a novel pH-responsive ratiometric assay by virtue of the composite system of Ce3+-enhanced glutathione-encapsulated copper nanoclusters (GSH-CuNCs-Ce3+) and N-doped carbon quantum dots (N-CQDs). The GSH-CuNCs-Ce3+ and N-CQDs were fabricated using one-pot chemical reduction and hydrothermal approaches, respectively, and their morphologies as well as physical and chemical properties were testified in detail by a series of characterization techniques. At 350 nm excitation wavelength, the GSH-CuNCs-Ce3+/N-CQDs system (GCC-NC) featured the 440/650 nm dual-emitting property. The ratios of fluorescence intensities (F 650 /F 440) demonstrated a strong pH-dependence from 3.0 to 5.0 with a coefficient of determination of 0.9982. Consequently, the GCC-NC system was feasible for constructing a pH-responsive dual-emitting fluoroprobe. Based on the catalytic effect of acetylcholinesterase on acetylcholine to yield acetic acid and further trigger varying solution pH, the as-constructed GCC-NC fluoroprobe was satisfactorily applied for detecting malathion. Under optimized conditions, the newly developed GCC-NC fluoroprobe supplied a wider linear range (0.25–200 μM), lower detection limit (0.075 μM), satisfactory recoveries (96.3–106.2%) and higher precision for malathion in several kinds of fruit juice samples. The fortified experiments by malathion's structural analogues and metal ions provided compelling evidence that this fluoroprobe had strong anti-interference capacity and high specificity for malathion. These findings render us to believe that the as-constructed pH-responsive dual-emitting fluoroprobe holds great promise in trace malathion assay in food matrices. • A novel pH-responsive ratiometric fluoroprobe based on GSH-CuNCs-Ce3+ and N-CQDs (GCC-NC) is developed. • Ce3+ can trigger aggregation-induced emission property of CuNCs. • The ratiometric fluorescence probe based on GCC-NC can be used to detect OPs. • The ratiometric fluorescence probe for the detection of malathion shows low LOD, wide LR and high precision. • The ratiometric fluorescence probe possesses wide application prospects for residual monitoring of OPs in food matrices. [ABSTRACT FROM AUTHOR]

In this paper, Au nanoparticles (AuNPs) loaded ZrO 2 /ZnSnO 3 nanocubes are prepared through hydrothermal route and chemical reduction method. The crystal structure, morphology, element distribution, chemical composition, specific surface area and pore size of ZrO 2 /ZnSnO 3 nanocubes are described with XRD, TEM, XPS and BET. Interestingly, the incorporation of Zr ions induces the fragmentation of the edge of ZnSnO 3 nanocubes, which enhance specific surface area of ZrO 2 /ZnSnO 3 nanocubes. The response of ZnSnO 3 materials for isopropanol is increased through doping ZrO 2 and modifying AuNPs. The 1.5 at% AuNPs-loaded 5 at% ZrO 2 /ZnSnO 3 nanocubes presents a higher response to 100 ppm isopropanol with a fast response/recovery time (3/4 s) at the operating temperature of 260℃. And the generation of ZnSnO 3 , ZrO 2 and AuNPs heterojunctions contributes to raise the isopropanol response. In addition, the catalysis of ZrO 2 and AuNPs also can increase their reaction speed between absorbed oxygen and isopropanol molecules. This research results provide a new scheme for the development of isopropanol sensor. • AuNPs-ZrO 2 /ZnSnO 3 nanocubes are prepared by one-step hydrothermal method and chemical reduction method. • The catalytic effect of AuNPs and ZrO 2 enhances the response and reduce the response/recovery time of the sensor. • The detection limit is up to 410 ppb. [ABSTRACT FROM AUTHOR]

[Display omitted] • Electrochemical ammonia synthesis. • Vibration structure of nitrogenase protein. • Outlook on ammonia economy. The 100th anniversary of a leading nitrogen fixation technology developer like CASALE SA is a reason to reflect over the 20th century successful solution of the problem of world food supply, and to look out for solutions for sustainable developments with respect to ammonia production. We review the role of nitrogen as essential chemical constituent in photosynthesis and biology, and component of ammonia as it is used as fertilizer for primary production by photosynthesis for farming and food supply and its future role as energy carrier. While novel synthesis methods and very advanced synchrotron based x-ray analytical techniques are being developed, we feel it is important to refer to the historical and economical context of nitrogen. The breaking of the N N triple bond remains a fundamental chemical and energetic problem in this context. We review the electrochemical ammonia synthesis as an energetically and environmentally benign method. Two relatively novel X-ray spectroscopy methods, which are relevant for the molecular understanding of the catalysts and biocatalysts, i.e. soft X-ray absorption spectroscopy and nuclear resonant vibration spectroscopy are presented. We illustrate the perceived reality in fertilizer usage on the field, and fertilizer production in the factory complex with photos and thus provide a contrast to the academic view of the molecular process of ammonia function and production. [ABSTRACT FROM AUTHOR]

The effective reduction of hazardous organic pollutants in wastewater is a pressing global concern, necessitating the development of advanced treatment technologies. Pollutants such as nitrophenols and dyes, which pose significant risks to both human and aquatic health, making their reduction particularly crucial. Despite the existence of various methods to eliminate these pollutants, they are not without limitations. The utilization of nanomaterials as catalysts for chemical reduction exhibits a promising alternative owing to their distinguished catalytic activity and substantial surface area. For catalytically reducing the pollutants NaBH 4 has been utilized as a useful source for it because it reduces the pollutants quiet efficiently and it also releases hydrogen gas as well which can be used as a source of energy. This paper provides a comprehensive review of recent research on different types of nanomaterials that function as catalysts to reduce organic pollutants and also generating hydrogen from NaBH 4 methanolysis while also evaluating the positive and negative aspects of nanocatalyst. Additionally, this paper examines the features effecting the process and the mechanism of catalysis. The comparison of different catalysts is based on size of catalyst, reaction time, rate of reaction, hydrogen generation rate, activation energy, and durability. The information obtained from this paper can be used to steer the development of new catalysts for reducing organic pollutants and generation hydrogen by NaBH 4 methanolysis. • Urgent Global Effort: Reduce Hazardous Pollutants in Wastewater-A pressing global concern severe immediate worldwide action. • Reduce Nitrophenols and Dyes-Vital for safeguarding human and aquatic health from potential harm posed by these pollutants. • Promising Catalysts-High activity & ample surface area, they offer efficient pollutant reduction through chemical reduction. • Sustainable Energy: Catalytic methanolysis of sodium borohydride for hydrogen production, emphasizing sustainable solutions. [ABSTRACT FROM AUTHOR]

Hydrogenation of 1,5,9-cyclododecatriene in the presence of nanostructured nickel catalysts in a flow-through reactor at atmospheric hydrogen pressure was studied. NaX zeolite was used as a support. Nickel nanoparticles on the support surface were prepared by chemical reduction of the precursor (NiCl2) with NaBH4 and NH2NH2. The influence exerted on the yield of hydrogenation products by the nominal residence time of the gas phase in the reaction zone and by the process temperature was considered, and the catalyst operation life was analyzed. The catalysts showed high activity and allowed preparation of cyclododecane in ~100% yield at a process temperature of up to 160°С. [ABSTRACT FROM AUTHOR]

The processes of hydrogenation of furan and its derivatives (2-methylfuran, furfuryl alcohol, and furfural) in plug-flow type reactor under atmospheric hydrogen pressure at 20–220°С in the presence of supported nickel nanoparticles prepared via chemical reduction have been investigated. It has been found that nickel nanoparticles supported on magnesium oxide surface are the most reactive and stable under the considered conditions. This catalyst allows the corresponding hydrogenation products with 100% yield and complete conversion of the substrate. [ABSTRACT FROM AUTHOR]

Mg-based materials are very promising candidates for hydrogen storage. In this paper, the graphene supported Ni was introduced to the Mg 90 Al 10 system by hydrogenation synthesis (HS) and mechanical milling (MM). The 80 wt%Ni@Gn catalyst was synthesized by a facile chemical reduction method. The microstructures of the catalyst and composite show that Ni nanoparticles are well supported on the surface of graphene and they are dispersed uniformly on the surface of MgH 2 particles. After heating to 450 °C and holding at 340 °C for 2 h subsequently under 2.0 MPa hydrogen pressure, all the samples are almost completely hydrogenated. According to the temperature programmed desorption test, the Mg 90 Al 10 -8(80 wt%Ni@Gn) composite could desorb 5.85 wt% H 2 which comes up to 96% of the theoretical hydrogen storage capacity. Moreover, it shows the optimal hydriding/dehydriding performance, absorbing 5.11 wt% hydrogen within 400 s at 523 K, and desorbing 5.81 wt% hydrogen within 1800 s at 573 K. • The addition of 80 wt%Ni@Ni catalyst results in an increase of hydrogen absorption/desorption capacity. • The Mg 90 Al 10 -8(80 wt%Ni@Ni) composite exhibits better hydriding/dehydriding performance compared to other samples. • The hydrogen storage properties are improved due to a synergistic catalysis of Al and graphene supported Ni. [ABSTRACT FROM AUTHOR]

The reaction of either toluene-3,4-dithiol or benzene dithiol with phosphorus(III) trihalides generates the corresponding benzo-fused 1,3,2-dithiaphospholes, RC6H3S2PX (R = Me (1), R = H (2); X = Cl, Br, I). The P-chloro-dithiaphospholes undergo: (a) halogen abstraction reactions with Lewis acids forming phosphenium cations; (b) substitution with LiHMDS base and; (c) reduction chemistry with sodium metal to generate the P--P σ-bonded dimer, (RC6H3S2P)2. Reduction catalysis of aldehydes with pinacolborane using dithiaphospholes is compared with their dioxaphosphole and diazaphosphole counterparts as precatalysts, revealing interesting differences in the reactivity of this series of compounds. [ABSTRACT FROM AUTHOR]

In this paper, silver nanoparticles/sulfonated polystyrene (Ag/SPS) composite microspheres were synthesized by using sulfonated polystyrene microspheres (SPS) as carriers and loaded with silver nanoparticles on its surface. The composite microspheres were characterized by scanning electron microscopy, infrared spectroscopy, XRD spectroscopy and thermogravimetry. The results showed that at 70 °C and reaction time of 8 h, the monodispersity of Ag/SPS composite microspheres prepared by chemical reduction method was good and the silver nanoparticles were uniformly coated. The results of catalytic reduction of methylene blue showed that in a certain range, the higher the silver content of the composite microspheres, the faster the catalytic rate. The results of reuse experiments showed that the composite microspheres had high reusability. [ABSTRACT FROM AUTHOR]

Co-Mo particles were loaded on three dimensional graphene oxide (3DGO) carrier via a chemical reduction method to get a composite catalyst, Co-Mo/3DGO, for hydrogen generation from NaBH 4 hydrolysis. Hydrolysis measurement shows that the ratio Co:Mo = 0.7:0.3 realizes a much higher hydrogen generation rate (HGR) of 7023.3 mL H 2 ⋅ min − 1 ⋅ g M − 1 , about 1.6 times of that for the Mo element undoped Co/3DGO (4394 m L H 2 . min − 1. g M − 1 ) catalyst. And the reaction activation energy is as low as 35.6 kJ mol − 1. The as prepared Co 0.7 Mo 0.3 /3DGO catalyst disperses on 3DGO surface as smaller particles than Co/3DGO, and presents a waxberry like structure with more active sites for catalysis reaction, which enables the catalyst a superior catalytic activity. Besides abundant active sites, MoO 3 supported active blend of Co and CoO is another reason for the higher activity. Image 1 • Co-Mo/3DGO, catalyst for NaBH 4 hydrolysis was prepared. • The Co-Mo/3DGO catalyst presented a waxberry like structure with more active sites. • The catalyst had a superior catalytic activity, and HGR was 7023.3 mL H 2 ⋅ min − 1 ⋅ g M − 1 [ABSTRACT FROM AUTHOR]

The mean reaction force is introduced as the negative derivative of the free energy along a predefined reaction path. In analogy to the reaction force, this descriptor allows detailed characterization of different processes of the reaction mechanism and the assignment of electronic and structural free energy contributions to activation barriers. Due to its free energy dependence, the mean reaction force represents a new tool to study the influence of the environment on the reaction mechanism. Moreover, it enables the separation of catalytic effects in structural and electronic components responsible for the free energy barrier reduction of a reaction. To validate the method, the intramolecular proton transfer in tryptophan was studied in the gas phase, in aqueous solution and at the vacuum-water interface employing molecular dynamics simulation in combination with ab initio calculations and the quantum molecular/molecular mechanics (QM/MM) methodology. The obtained results were compared to static vacuum and continuum calculations. The mean reaction force distinguishes structural rearrangements as the dominant free energy component to reach the transition state from the neutral form, whereas electronic reorganization predominates the activation of the zwitterion in aqueous solution. In addition, it identifies the origin of the reduction of the activation barrier for desolvated functional groups at the water-vacuum interface as the absence of hydrogen bonds which stabilize charge delocalized species. [ABSTRACT FROM AUTHOR]

Catalysis holds a very important and promising place in chemical industry. In a typical chemical transformation, the use of a catalyst reduces the reagent-based waste and enhances the reaction selectivity, thereby minimizing the chances of getting any side product. In the recent years, the introduction of nanotechnology in the field of catalysis has further revolutionized it. It is the extremely small size, shape and remarkably large surface-area-to-volume ratio which sets apart a nanocatalyst from its ordinary bulk form and imparts it unique catalytic properties. In the present work, we report the application of heterogeneous nickel nanoparticles in the synthesis of some biologically important heterocyclic compounds. In brief, we doped titania nanostructures with nitrogen and then used them as a support material for immobilizing nickel nanoparticles onto them. The nanoparticles of nickel were prepared by the chemical reduction of nickel acetate. The catalyst thus prepared, i.e., nickel nanoparticles loaded over nitrogen-doped titania (nickel NPs @N-doped TiO2), was then explored for its catalytic activity toward the synthesis of pyrano[2,3-d]pyrimidines and 1,8-dioxo-octahydroxanthenes. The surface and the elemental composition of the catalyst was studied by SEM–EDX analysis. TEM analysis was done to study the internal morphology and the size of the nanostructures formed. The other studies included TGA, FTIR and XPS which gave information regarding thermal stability, presence of nitrogen in the titania framework and oxidation state of the nickel nanoparticles, respectively. [ABSTRACT FROM AUTHOR]

Iron mediated catalytic reactions are of great interest in the field of organic synthesis because they are economic and naturally abundant. However, the use of iron catalyst in the field of free radical cyclization or reduction of alkyl halides remains limited. Here we describe the use of an unprecedented combination of iron and zinc in the reduction and 5‐exo‐trig radical cyclization of alkyl halides under mild condition in the absence of added ligands or additives. The method is distinguished by its wide scope, functional group tolerance and the use of 1,4‐cyclohexadiene as the source of hydrogen, which aids easy purification. [ABSTRACT FROM AUTHOR]

Here, the reduction chemistry of mono‐ and binuclear α‐diimine‐Re(CO)3 complexes with proton responsive ligands and their application in the electrochemically‐driven CO2 reduction catalysis are presented. The work was aimed to investigate the impact of 1) two metal ions in close proximity and 2) an internal proton source on catalysis. Therefore, three different Re complexes, a binuclear one with a central phenol unit, 3, and two mononuclear, one having a central phenol unit, 1, and one with a methoxy unit, 2, were utilised. All complexes are active in the CO2‐to‐CO conversion and CO is always the major product. The catalytic rate constant kcat for all three complexes is much higher and the overpotential is lower in DMF/water mixtures than in pure DMF (DMF=N,N‐dimethylformamide). Cyclic voltammetry (CV) studies in the absence of substrate revealed that this is due to an accelerated chloride ion loss after initial reduction in DMF/water mixtures in comparison to pure DMF. Chloride ion loss is necessary for subsequent CO2 binding and this step is around ten times faster in the presence of water [2: kCl(DMF)≈1.7 s−1; kCl(DMF/H2O)≈20 s−1]. The binuclear complex 3 with a proton responsive phenol unit is more active than the mononuclear complexes. In the presence of water, the observed rate constant kobs for 3 is four times higher than of 2, in the absence of water even ten times. Thus, the two metal centres are beneficial for catalysis. Lastly, the investigation showed that the phenol unit has no impact on the rate of the catalysis, it even slows down the CO2‐to‐CO conversion. This is due to an unproductive, competitive side reaction: After initial reduction, 1 and 3 loose either Cl− or undergo a reductive OH deprotonation forming a phenolate unit. The phenolate could bind to the metal centre blocking the sixth coordination site for CO2 activation. In DMF, O−H bond breaking and Cl− ion loss have similar rate constants [1: kCl(DMF)≈2 s−1, kOH≈1.5 s−1], in water/DMF Cl− loss is much faster. Thus, the effect on the catalytic rate is more pronounced in DMF. However, the acidic protons lower the overpotential of the catalysis by about 150 mV. Two is better than one! The impact of two metal centres and of a proton source in a α‐diimine Re(CO)3‐catalyst on the electrochemical CO2‐to‐CO conversion has been investigated. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Vacuum-assisted method was used to synthesize Au@MC. • The uniform Au NPs were restricted by mesopore channels. • Au@MC exhibited a high activity for 4-nitrophenol reduction. Abstract In this work, we report a vacuum-assisted approach to synthesize tiny Au nanopartciles (Au NPs) entrapped into mesoporous carbon matrix (denoted as Au@MC). The tiny Au NPs are stably entrapped within the mesoporous structure and possess a small particle size (∼2.64 nm). The composite also exhibits a high specific surface area (∼421 m2 g−1), which may provide convenient transportation and diffusion for substrate molecules. Thus, Au@MC exhibits superior catalytic activity and reusability for 4-nitropheno (4-NP) reduction. The vacuum-assisted synthesis with unique nanostructure is expected to be applied in the preparation of other catalysts. [ABSTRACT FROM AUTHOR]

Graphical abstract Abstract A series of small-sized (about 2.0 nm) gold nanoparticles (AuNPs) with apparent lattice fringes are synthesized by NaBH 4 reduction of HAuCl 4 in the presence of stabilizing linear or dendronized 1,2,3-triazolyl-containing ferrocenyl polymers. These AuNPs show high catalytic activity for biphasic 4-nitrophenol (4-NP) reduction to 4-aminophenol (4-AP) by NaBH 4. The lower generation G1 dendronized polymers (DPs) is a more efficient stabilizer for AuNP catalytic activity in the reduction of 4-NP than linear G0 polymers or bulky G2 DPs. The G1 DP-stabilized AuNPs are robust and easily recyclable, and the catalyst is recovered and reused at least twenty times with progressive smooth AuNP size increase along with some decrease of catalytic activity. [ABSTRACT FROM AUTHOR]

Single-electron reduction of a carbonyl to a ketyl enables access to a polarity-reversed platform of reactivity for this cornerstone functional group. However, the synthetic utility of the ketyl radical is hindered by the strong reductants necessary for its generation, which also limit its reactivity to net reductive mechanisms. We report a strategy for net redox-neutral generation and reaction of ketyl radicals. The in situ conversion of aldehydes to a-acetoxy iodides lowers their reduction potential by more than 1 volt, allowing for milder access to the corresponding ketyl radicals and an oxidative termination event. Upon subjecting these iodides to a dimanganese decacarbonyl precatalyst and visible light irradiation, an atom transfer radical addition (ATRA) mechanism affords a broad scope of vinyl iodide products with high Z-selectivity. [ABSTRACT FROM AUTHOR]

SO x poisoning has been a critical problem in the chemistry of selective catalytic reduction of NOx, and many fundamental issues surrounding the reactions remain unclear. In this paper, reactions taking place in the 13 C 2 H 5 OH NO-S 18 O 2 O 2 system on a platinum single crystal surface were studied. Oxidation of 13 C 2 H 5 OH by S 18 O 2 proceeds mainly through 18 O-H reaction, and oxidation of the backbone carbon atoms can occur at high S 18 O 2 exposures, e.g., 1.6 Ls of S 18 O 2 for 0.4 L of 13 C 2 H 5 OH. Thus, the presence of S 18 O 2 only slightly suppresses the catalytic reduction of NO by 13 C 2 H 5 OH. Co-adsorbed O 2 evidently exerts a suppressive effect. When oxygen is lean (relative to S 18 O 2 ), the S 18 O 2 O 2 reactions mainly give rise to surface sulphoxy species at temperatures between 400 and 500 K and thus, the NO- 13 C 2 H 5 OH reactions can still proceed. The NO reduction reaction is completely suppressed when oxygen is rich, a result of the Pt surface being passivated. This finding provides a valuable guide for optimizing the reaction atmosphere to improve the efficiency of the selective catalytic reduction of NO by hydrocarbons (or oxygen-containing fragments from oxidation of hydrocarbons in this case). [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis of bimetallic Au-Pd and monometallic Au and Pd nanoparticles (NPs) by successive reduction of the respective metal ions using phytochemicals in the form of plant extract under ambient conditions. Phytochemicals act both as reducing and shape directing agent for metal and alloy NPs. The synthesized nanostructures were characterized by different microscopic, spectroscopic and diffractometric techniques. Microscopic results confirmed that the shape and size of the alloy nanostructures can be tuned by varying the concentration ratio of metal ions in the reaction medium. Energy dispersive X-ray and X-ray photoelectron spectroscopic analysis confirmed the formation of bimetallic Au-Pd nanostructures. The purity and crystalline properties were studied by X-ray diffraction technique. UV–vis spectra were recorded to study the optical properties of the synthesized nanostructures. Further, we tested the catalytic activity of both the monometallic and bimetallic alloy nanostructures in borohydride reduction of hazardous organic dye molecules in aqueous medium. The bimetallic alloy NPs exhibit better catalytic activities compared to their respective monometallic nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract Hydrogen peroxide and lipid hydroperoxides are formed during aerobic metabolism and contribute to oxidative stress, a major factor in many diseases and degenerative conditions. Although the selenoenzyme glutathione peroxidase (GPx) affords antioxidant protection in vivo by catalytically reducing harmful peroxides with glutathione, certain conditions benefit from the administration of small-molecule GPx mimetics for additional protection. To date, ebselen has been the most widely studied such compound, but its catalytic mechanism is complex and highly variable with conditions. Progress in elucidating the mechanistic details of its antioxidant activity is described in this review. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

The development of efficient bifunctional catalysts for both oxygen reduction and oxygen evolution reactions is highly desirable but challenging in energy conversion and storage systems. Here, a simple yet cost-effective strategy is developed to produce heteroatom-doped carbon nanospheres using natural cuttlefish ink as the precursor. For the oxygen reduction reaction, the catalyst exhibits more positive onset-potential and larger diffusion limiting current density compared with benchmark platinum catalyst in alkaline medium. Moreover, the as synthesized catalyst shows low onset-potential for oxygen evolution reaction, indicating its outstanding catalytic activity. The catalyst shows a potential gap of 0.75 V between the oxygen evolution reaction potential at a current density of 10 mA cm −2 and the oxygen reduction reaction potential at the half-wave potential, outperforming most of other noble metal-free carbon catalysts in the current state of research. The remarkable catalytic performance can be assigned to heteroatoms doping, full exposure of the active sites, large surface area and enrichment of pores for sufficient contact and rapid transportation of the reactants. This study offers a new approach for the synthesis of metal-free carbon nanomaterials from natural resources, and broadens the design for the fabrication of bifunctional oxygen reduction and oxygen evolution catalysts. [ABSTRACT FROM AUTHOR]

The activation process of a cobalt catalyst promoted with cerium compounds was examined. The reduction of precursor was performed in a High Pressure Cell (HPC), being a part of an ultra-high vacuum (UHV) system, at 500 °C under hydrogen atmosphere. X-ray photoelectron spectroscopy (XPS) was subsequently used to investigate the evolution of surface composition. High resolution X-ray photoelectron analysis confirms total reduction of cobalt oxide into Co metallic form. After exposure to hydrogen, Ce 4+ ions prevail in the structure of cerium oxides identified on the surface. [ABSTRACT FROM AUTHOR]

Laccases (EC 1.10.3.2) catalyze oxidation of phenolic groups in lignin to phenoxyl radicals during reduction of O 2 to H 2 O. Here, we examine the influence on this radical formation of mediators which are presumed to act by shuttling electrons between the laccase and the subunits in lignin that the enzyme cannot approach directly. Treatments of three different lignins with laccase-mediator-systems (LMS) including laccases derived from Trametes versicolor and Myceliophthora thermophila , respectively, and four individual mediators, 1-hydroxybenzotriazole (HBT), N-hydroxyphthalimide (HPI), 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) were assessed by real time electron paramagnetic resonance measurements. Radical steady state concentrations and radical formation rates were quantified. LMS treatments with 500 μM N-OH type mediators (HPI or HBT) did not affect the lignin radical formation, but increased doses of those mediators (5 mM) surprisingly led to significantly decreased radical formation rates and lowered steady state radical concentrations. Laccase-TEMPO treatment at a 5 mM mediator dose was the only system that significantly increased steady state radical concentration and rate of radical formation in beech organosolv lignin. The data suggest that electron shuttling by mediators is not a significant general mechanism for enhancing laccase catalyzed oxidation of biorefinery lignin substrates, and the results thus provide a new view on laccase catalyzed lignin modification. [ABSTRACT FROM AUTHOR]

3D-macroporous chitosan-based scaffolds (cryogels) were produced via growth of metal-polymer coordinated complexes and electrostatic interactions between oppositely charged groups of chitosan and metal ions under subzero temperatures. A mechanism of reduction of noble metal complexes inside the cryogel walls by glutaraldehyde is proposed, which produces discrete and dispersed noble metal nanoparticles. 3D-macroporous scaffolds prepared under different conditions were characterised using TGA, FTIR, nitrogen adsorption, SEM, EDX and TEM, and the distribution of platinum nanoparticles (PtNPs) and palladium nanoparticles (PdNPs) in the material assessed. The catalytic activity of the in situ synthesised PdNPs, at 2.6, 12.5 and 21.0 μg total mass, respectively, was studied utilising a model system of 4-nitrophenol reduction. The kinetics of the reaction under different conditions (temperature, concentration of catalyst) were examined, and a decrease of catalytic activity was not observed over 17 treatment cycles. Increasing the temperature of the catalytic reaction from 10 to 22 and 35 °C by PdNPs supported within the cryogel increased the kinetic rate by 44 and 126%, respectively. Turnover number and turnover frequency of the PdNPs catalysts at room temperature were in the range 0.20–0.53 h −1 . The conversion degree of 4-nitrophenol at room temperature reached 98.9% (21.0 μg PdNPs). Significantly less mass of palladium nanoparticles (by 30–40 times) was needed compared to published data to obtain comparable rates of reduction of 4-nitrophenol. [ABSTRACT FROM AUTHOR]

This study reports that aquahydroxocobinamide [(H2O)(HO–)Cbi(III)], a nucleotide‐free analogue of cobalamin (vitamin B12; Cbl), is capable of catalyzing the reduction of the two‐electron oxidized form of vitamin C, dehydroascorbic acid (DHA), to ascorbic acid by glutathione (GSH), whereas catalytic quantities of aquacobalamin do not accelerate the reaction. This observation is explained by different reactions taking place with the CoIII‐species of these complexes and GSH: Cbl(III) forms a stable complex with GSH, but Cbi(III) is relatively rapidly reduced to Cbi(II). The reaction of Cbi(II) with DHA in the presence of GSH includes the coordination of GSH onto CoII, the reaction of GS––Cbi(II) with DHA produces GS––Cbi(III) and the ascorbyl radical, which rapidly disproportionates to a mixture of ascorbic and dehydroascorbic acids, and further regeneration of Cbi(II). [ABSTRACT FROM AUTHOR]

Recent developments in catalytic reduction with H2 of glycerol, which is a by-product of biodiesel manufacture, and the involved chemistry are summarized and reviewed. There are more than ten potential C3 products of glycerol reduction. Among them, 1,2-propanediol can be obtained in very high yield and the production from glycerol is now commercialized. Production of 1,3-propanediol, allyl alcohol and propylene are now possible in > 60%, > 90% and > 80% yield, respectively. Key reaction steps are metal-catalyzed dehydrogenation/hydrogenation, acid-catalyzed dehydration, carbonyl-induced dehydration, metal-catalyzed direct hydrogenolysis and deoxydehydration. The 2-Propanol and small-ring compounds (oxetane, propylene oxide) cannot be produced from glycerol by combinations of these key reaction steps, and no catalytic system is known at present, although the conversion reactions have minus ∆G°. [ABSTRACT FROM AUTHOR]

Congo red is highly toxic and carcinogenic anionic dye. Its removal from aqueous medium by chemical reduction method using sodium borohydride as reducing agent in the presence of various nano-catalytic systems has been widely reported in literature during last ten years. This review article focuses on recent research of designing of various metal nanoparticles catalysts reported for catalytic reduction of Congo red by sodium borohydride (NaBH 4 ). Different nano-catalytic systems used for reduction of Congo red and their division on the basis of nature of metal nanoparticles and composition of supporting materials has been described critically. Advantages and disadvantages of different nano-catalysts used for reduction of Congo red and their capability to reduce Congo red present in industrial wastewater has been elaborated. An overview of different analytical techniques used for characterization of nano-catalytic systems reported for reduction of Congo red dye has been provided. Mechanism of chemical reduction of Congo red in the presence of nano-catalysts has been described critically with the help of recent literature. [ABSTRACT FROM AUTHOR]

Preparing dispersed cores-shell structured Au@SiO2 nanocomposites with an active Au core size below 2 nm that exhibit excellent catalytic performance still remains a major challenge in catalytic synthesis. In this work, we report a novel preparation method for a one-pot system fabrication of an ultrafine core-shell structured Au@SiO2 intestine-shaped nanocomposite. The preparation is used to fabricate catalysts with an Au core size of about 1.4 nm and requires neither prefabricated Au cores nor special reducing agents. Upon extraction of cetyltrimethylammonium bromide, abundant pores with a size of around 1.9 nm are formed in the silica shell. During the catalytic reduction of 4-nitrophenol to 4-aminophenolate, the catalyst unambiguously exhibits superior catalytic activity. Despite having a low 1.7% Au content in catalyst, the nanocomposites achieve an activity of ʊ = 19.1 × 10−3 s−1 mg−1. This is due to the fact that the polyvinylpyrrolidone coating is transformed into discrete particles in an alkaline solution, which exposes large active areas on the Au. [ABSTRACT FROM AUTHOR]

Organic hydroperoxide resistance (Ohr) enzymes are highly efficient Cys-based peroxidases that play central roles in bacterial response to fatty acid hydroperoxides and peroxynitrite, two oxidants that are generated during host-pathogen interactions. In the active site of Ohr proteins, the conserved Arg (Arg19 in Ohr from Xylella fastidiosa) and Glu (Glu51 in Ohr from Xylella fastidiosa) residues, among other factors, are involved in the extremely high reactivity of the peroxidatic Cys (Cp) toward hydroperoxides. In the closed state, the thiolate of Cp is in close proximity to the guanidinium group of Arg19. Ohr enzymes can also assume an open state, where the loop containing the catalytic Arg is far away from Cp and Glu51. Here, we aimed to gain insights into the putative structural switches of the Ohr catalytic cycle. First, we describe the crystal structure of Ohr from Xylella fastidiosa (XfOhr) in the open state that, together with the previously described XfOhr structure in the closed state, may represent two snapshots along the coordinate of the enzyme-catalyzed reaction. These two structures were used for the experimental validation of molecular dynamics (MD) simulations. MD simulations employing distinct protonation states and in silico mutagenesis indicated that the polar interactions of Arg19 with Glu51 and Cp contributed to the stabilization of XfOhr in the closed state. Indeed, Cp oxidation to the disulfide state facilitated the switching of the Arg19 loop from the closed to the open state. In addition to the Arg19 loop, other portions of XfOhr displayed high mobility, such as a loop rich in Gly residues. In summary, we obtained a high correlation between crystallographic data, MD simulations and biochemical/enzymatic assays. The dynamics of the Ohr enzymes are unique among the Cys-based peroxidases, in which the active site Arg undergoes structural switches throughout the catalytic cycle, while Cp remains relatively static. [ABSTRACT FROM AUTHOR]

Abstract: Nanoparticles (NPs) are actively investigated for their efficient use in catalysis, but their means of synthesis is a key factor influencing their catalytic properties owing to surface coverage with byproducts. Here, neutral electron‐ and hydride‐rich late transition metal organometallics are compared for the synthesis of late transition metal NPs in the presence of poly(vinylpirolidone) (PVP). In particular, the effect of electron‐reservoir donors, hydride‐reservoir donors, and electron‐rich dimers yielding NPs electrostatically stabilized by cationic organometallics are compared in terms of NP size and catalytic efficiency. The catalytic reactions scrutinized with excellent results include 4‐nitrophenol reduction to 4‐aminophenol by NaBH4 for the AuNPs and PdNPs, and Suzuki–Miyaura reactions for the PdNPs. The nature of the reductant has more influence on the NP size in the case of AuNPs than PdNPs, and the best NP catalysts are obtained with hydride‐reservoir complexes as reductants. The less bulky hydride donors are superior, with the complex [CoCp(ŋ4‐C5H6)] (Cp=ŋ5‐C5H5) giving the NPs with the best catalyst efficiencies for both reactions. Protection of the NP cores by the organometallic sandwich salt is found to be the key to catalytic efficiency. [ABSTRACT FROM AUTHOR]

To realize the efficient and complete removal of organic pollutants in waste water, it is highly urgent for scalable synthesis of either self-supported bimetallic nanocatalysts or anchored on carbon-based materials. In this study, a simple one-pot coreduction method was developed for preparing well-dispersed AgPd alloyed nanoclusters uniformly dispersed on reduced graphene oxide (AgPd NCs/rGO) at room temperature by utilizing 5-azacytosine as the capping agent. The nanocomposites were characterized by a set of physical characterizations. The formation mechanism and catalytic mechanism were discussed in some details. Moreover, the prepared AgPd NCs/rGO exhibited dramatically increased catalytic properties towards the reduction of 4-nitrophenol (4-NP) in the presence of NaBH 4 when compared to commercial Pd/C (20  wt .%). [ABSTRACT FROM AUTHOR]

α-MnO 2 nanotubes and their supported Au-Pd alloy nanocatalysts were prepared using hydrothermal and polyvinyl alcohol-protected reduction methods, respectively. Their catalytic activity for the oxidation of toluene/ m -xylene, acetone/ethyl acetate, acetone/ m -xylene and ethyl acetate/ m -xylene mixtures was evaluated. It was found that the interaction between Au-Pd alloy nanoparticles and α-MnO 2 nanotubes significantly improved the reactivity of lattice oxygen, and the 0.91 wt.% Au 0.48 Pd/α-MnO 2 nanotube catalyst outperformed the α-MnO 2 nanotube catalyst in the oxidation of toluene, m -xylene, ethyl acetate and acetone. Over the 0.91 wt.% Au 0.48 Pd/α-MnO 2 nanotube catalyst, (i) toluene oxidation was greatly inhibited in the toluene/ m -xylene mixture, while m -xylene oxidation was not influenced; (ii) acetone and ethyl acetate oxidation suffered a minor impact in the acetone/ethyl acetate mixture; and (iii) m -xylene oxidation was enhanced whereas the oxidation of the oxygenated VOCs (volatile organic compounds) was suppressed in the acetone/ m -xylene or ethyl acetate/ m -xylene mixtures. The competitive adsorption of these typical VOCs on the catalyst surface induced an inhibitive effect on their oxidation, and increasing the temperature favored the oxidation of the VOCs. The mixed VOCs could be completely oxidized into CO 2 and H 2 O below 320°C at a space velocity of 40,000 mL/(g·hr). The 0.91 wt.% Au 0.48 Pd/α-MnO 2 nanotube catalyst exhibited high catalytic stability as well as good tolerance to water vapor and CO 2 in the oxidation of the VOC mixtures. Thus, the α-MnO 2 nanotube-supported noble metal alloy catalysts hold promise for the efficient elimination of VOC mixtures. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) - as environmentally friendly “green” solvents- have been progressively used in various reactions as reagents, solvents and co-solvents including lipase-catalysed reactions. In fact, lipase-catalysed reactions in ILs are considered as a “green”-reaction and are more advantageous than chemical methods owing to the easy recovery of the product and the mild conditions of the reactions. The use of lipase in ILs provides many technological advantages compared to conventionally used solvents, such as selectivity enhancement, enzyme stability improvement, higher conversion rate, and better recyclability and recovery system. Nevertheless, in some cases, especially in hydrophilic ILs, lipase exhibits activity reduction when compared with organic solvents. Currently, various attempts have been made to enhance the performance of lipases in ILs. The main objective of this review is to demonstrate recent developments in the technology of using ILs as reaction media for lipase. It is expected that this review might be an inspiration in ILs assisted lipase-catalysed reactions to produce value-added materials including biofuels as well as biodiesel. [ABSTRACT FROM AUTHOR]

Pt nanoparticle (NP) embedded polystyrene- b-poly(4-vinylpyridine) colloids (Pt@PS- b-PVP) are prepared through flash nanoprecipitation (FNP). Uniform Pt@PS- b-PVP nanocomposites with ~5 nm Pt NPs decorating the surface on PS- b-PVP nanospheres are easily prepared with tunable size and Pt arrangement. The catalytic chromium reduction property of Pt@PS- b-PVP is tested. The hybrid colloids exhibited excellent catalytic performance as well as tunable ability dependent on the fined-controlled nanostructure. Moreover, the reported nanocomposites are reused for four times without loss of catalytic activity. [ABSTRACT FROM AUTHOR]

For the improvement of the properties of cemented carbides, ultra-fine spherical cobalt powders as binder were prepared using calcium cobaltite. The effects of the ratio of CaO to CoO, the calcination temperature and the reduction temperature on particle size and morphology of cobalt powders were studied. The results show that the average particle size of cobalt powders decreases with increasing the weight ratio of CaO to CoO, but increases with the calcination temperature and reduction temperature. The spherical cobalt powders with the mean particle size of 84 nm are obtained when the weight ratio of CaO to CoO is 7:4 and the calcination temperature and reduction temperature are 1000 °C and 700 °C, respectively. In addition, CaO regarded as the blocking agent can refine cobalt powders during the hydrogen reduction process. [ABSTRACT FROM AUTHOR]

Herein we report that a small amount of graphite can unexpectedly act as the catalyst to greatly promote the microwave exfoliation and reduction of graphite oxide in ambient air. The reaction can be finished in a few seconds in contrast to more than ten minutes without catalyst. The catalytic microwave exfoliated graphite oxide (CMEGO) is of higher quality than the traditional microwave exfoliated graphite oxide, including a much higher exfoliation degree with thinner graphene sheets and higher specific surface area (886 m2 g−1 vs. 466 m2 g−1), a much larger C/O ratio (19.4 vs. 6.3) and a higher lattice crystallinity, as well as significantly improved electrical conductivity (53180 S m−1 vs. 5140 S m−1). The CMEGO is used as anode for lithium-ion battery (LIB) and sodium-ion battery (SIB), and delivers ultrahigh reversible capacities, remarkable rate capabilities, and superior cycling stabilities in both LIB and SIB. [ABSTRACT FROM AUTHOR]

An unprecedented approach toward synthesis of α -substituted ethylphosphonates based on CuH-catalyzed conjugate reduction of vinylphosphonates has been successfully developed. This protocol features mild conditions, broad substrate scope, good functional group compatibility, high overall efficiencies, and easy gram-scale synthesis. The Cu-catalyzed reduction takes place in a highly selective manner on the phosphono substituted C C bond in the case of the reaction of alkenylphosphonates bearing both phosphono and alkyl or aryl substituted alkene moieties. Furthermore, the result of competitive reaction indicates that the Cu-catalyzed conjugate reduction of vinylphosphonate is more challenging and reproducible than the corresponding acrylate’s reaction. [ABSTRACT FROM AUTHOR]

In this work, two shapes of mesoporous Co 3 O 4 nanoarrays (i.e., nanosheets, nanowires) were synthesized through a facile hydrothermal method on nickel foam (Ni foam) substrates and tested as the Li-O 2 cathodes. The comparison of these two shapes of Co 3 O 4 nanoarrays revealed that the single crystalline feature of Co 3 O 4 nanosheets with a predominant high reactivity {112} exposed crystal plane, favorable nanostructure and high specific area displayed better catalytic performance. Furthermore, a new binder/carbon-free Pd nanoparticles (PdNPs) decorated Co 3 O 4 nanosheets cathode was also fabricated through the chemical reduction method. The presence of PdNPs effectively promotes the uniform growth of a fluffy, porous discharge product Li 2 O 2 layer on the surface of Pd/Co 3 O 4 electrode. The Pd/Co 3 O 4 electrode catalyzed Li-O 2 battery exhibited a higher specific capacity (1551 mAh g −1 at 50 mA g −1 ), lower over-potential and longer cycle life over 72 cycles at 100 mA g −1 with the capacity limited at 300 mAh g −1 . The superior catalytic performance for Li-O 2 batteries is ascribed to the unique design in both component and architecture of Pd/Co 3 O 4 electrode. [ABSTRACT FROM AUTHOR]

The controlled electrochemical uptake and reduction of metal precursors, AuCl 4 − , PdCl 4 2− , and PtCl 4 2− in polyaniline (PANI) is used in the synthesis of variable metal content composites. The potential and current associated with the initial electrochemical deposition of each metal precursor into pristine PANI is unique when compared to subsequent reduction in the composite materials. Deposition into the polymer and at existing deposits is resolved in the voltammetry for the reduction of Au and Pd in PANI. In contrast, distinct processes for Pt reduction into the polymer and at existing metal deposits are not resolved. After the initial reduction of the Pt precursor, the peak current continues to shift to more positive potential and diminishes as a function of increasing metal content. The PANI/metal composites are characterized using FTIR spectroscopy, thermal gravimetric analysis, and conductivity measurements to evaluate the interactions between the metal and polymer, the total metal content, and the electronic properties of the composites. The Au, Pd, and Pt metals deposited in PANI are evaluated using surface specific electrochemical reactions including the formation/reduction of metal oxide and the catalytic oxidation of n-propanol in alkaline solutions (pH ≈ 14). Furthermore, the electrochemical studies demonstrate that the oxidation/reduction of the polymer directly influences the polarization and reactivity of the metal surface in the organic matrix. The results confirm that PANI/metal composite materials containing Au, Pt, and Pd remain conductive in alkaline environments thereby expanding their use outside traditional acid solutions. [ABSTRACT FROM AUTHOR]

ABSTRACT This article highlights the progress in the synthesis of gelatin-immobilized anisotropic gold (Au) nanoparticles and their catalytic activity in 4-nitrophenol (4-NP) reduction. The catalytic process is monitored by using the UV-visible spectrophotometer, and the effect of shape and aspect ratio on the Au nanoparticles on catalytic activity is investigated. The catalytic process follows a pseudo-first-order kinetics with the rate constant in the range of 1.1 × 10−3 s−1 to 4.5 × 10−3s−1. It is found that high aspect ratio Au/gelatin shows the best conversion (99.89%), which is comparable to the spherical seed (99.93%). After a certain catalytic reaction, the recovery of expensive catalysts and their reuse without losing their activity is an essential element in the sustainable process development. The immobilization of the catalyst into gelatin allows the high aspect ratio Au/gelatin nanocatalyst to be recovered and reused for a number of cycles. [ABSTRACT FROM AUTHOR]

Gold nanoparticles (GNPs) are forecasted to provide an attractive platform in biomedicine and catalysis with their potentials of combining a variety of biophysicochemical properties into an integrated nanodevice with great therapeutic and optical functions. There are several reports of crude plant extracts mediating the conversion of metal ions into nanoparticles. However, we aimed to investigate the capability of single bioactive compounds, namely ginsenosides compound K (C-K) and Rh2, to accommodate a synergistic chemical reduction of gold salts by one-pot green chemistry. Ginsenosides C-K and Rh2 are unique triterpenoid saponins present in Panax ginseng Meyer, a perennial plant traditionally used as an oriental medicinal herbal with long history. C-K and Rh2 have demonstrated diverse pharmacological properties such as anticancer, anti-inflammation, anti-aging, and neuroprotective properties. The reduction of gold ions by these ginsenosides led to the production of nontoxic GNPs as tested in mouse macrophage (J774A.1) and human kidney epithelial (HEK-293) in vitro. The kinetics of the bioreduction and the influence of pH were examined by an ultraviolet-visible (UV-Vis) spectrophotometer. GNPs were characterized by field emission transmission electron microscopy (FE-TEM), X-ray diffraction (XRD), dynamic light scattering (DLS), and Fourier transform infrared (FTIR) spectroscopy. Ginsenoside loading efficiency of C-K-GNPs and Rh2-GNPs was determined to be approximately 62.83% and 54.91%, respectively, by thermogravimetric analysis (TGA). These results suggest that one-pot synthesis by ginsenosides C-K and Rh2 may be useful for producing ginsenoside-loaded gold nanocarriers. [ABSTRACT FROM AUTHOR]

The activity of the water reduction catalyst [CoIII(L1)(pyr)2]PF6 ( 1), where (L1)2− is a bis-amido pyridine ligand and pyr is pyrrolidine, is investigated. Catalyst 1 has an overpotential of 0.54 V and a high observed TOF of 23 min−1, albeit for a relatively short time. Considering the significant activity of 1 and aiming to improve catalyst design, a detailed structural and electronic study is performed to understand the mechanisms of deactivation. Experimental and theoretical evidence support that the metal-reduced [CoI(L1)]− is in tautomeric equilibrium with the ligand-reduced [CoII(L1 .)]− species. While [CoI(L1)]− favors formation of a CoIII−H− relevant for catalysis, the [CoII(L1 .)]− species leads to ligand protonation, structural distortions, and, ultimatley, catalyst deactivation. [ABSTRACT FROM AUTHOR]

An efficient, sustainable organocatalyst, glycine betaine, was developed for the reductive functionalization of CO2 with amines and diphenylsilane. Methylamines and formamides were obtained in high yield by tuning the CO2 pressure and reaction temperature. Based on identification of the key intermediate, that is, the aminal, an alternative mechanism for methylation involving the C0 silyl acetal and aminal is proposed. Furthermore, reducing the CO2 amount afforded aminals with high yield and selectivity. Therefore, betaine catalysis affords products with a diversified energy content that is, formamides, aminals and methylamines, by hierarchical two-, four- and six-electron reduction, respectively, of CO2 coupled with C−N bond formation. [ABSTRACT FROM AUTHOR]

HCl in solution accepts electron density from Au NPs and partially reduces at room temperature, as occurs with other simple diatomic molecules, such as O2 and H2. The activation can be run catalytically in the presence of alkynes to give exclusively E-vinyl chlorides, after the regio- and stereoselective transfer of HCl. Based also on this method, vinyl chloride monomer (VCM) can be produced in a milder and greener way than current industrial processes. [ABSTRACT FROM AUTHOR]