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Worldwide efforts have been focused to introduce greener chemical and energetic processes that drive the society away from the dependency on fossil fuels, looking to reduce the environmental footprint of modern societies. Catalysis for instance, has been for decades the winning technology which helps to improve the efficiency of processes in petrochemical, pharmaceutical, and biomedical industries to mention a few. Efficiency of catalysts come mostly from its structure and composition which proportionate high activity and selectivity. However, the use of expensive noble metals as catalyst materials remains a key issue for industrial applications. Thus, developing materials that reduce and mitigate carbon dioxide emissions as well as decrease of waste of the materials using during these processes remain a tremendous challenge to overcome. Nanotechnology for instance, is a growing technology with great impact in the industrial,pharmaceutical and energetical sectors. In fact, nanomaterials provide a better economical option, less waste and still with superior performance than their bulk counterparts which is explained from their reduce size, shape and larger surface areas which leads to overall higher catalytic performance. Nanocatalysis modify the rate of a chemical reaction by speeding up or accelerating the reaction rate without being consumed, making the process more energetically favored. Nanocatalyst have significant impact in different industrial processes as chemical reactions to produce fine chemicals, or for renewable energy and among others. As it was mentioned previously, the high performance of nanocatalyst is associated with the atoms at the surface of the nanostructure which are known as the active sites for catalysis. Moreover, it is well known that surface atoms placed at the corner or edges of the nanocatalyst are more active than those surface atoms at planes, and it the same manner with surface-to-volume ratio, their number will increase with decrease of particle size. In addition to nanoparticle size, crystallographic facets lead to different shapes or morphologies which are also contributing to the number of atoms at the surface, edges and corners. All of these contributing together to the efficiently performance of nanocatalyst for the target reactions . In this thesis is presented nanocatalyst materials development, and studies about their synergetic effect of the different components for heterogeneous catalytic applications.First, benzaldehyde byproduct is an intermediate in the production of fine chemicals and additives. Tuning selectivity to benzaldehyde is therefore critical in alcohol oxidation reactions at the industrial level where the typical methods employ toxic oxidant chemicals for its production. Herein, we report a simple but innovative method for the synthesis of palladium hydride and nickel palladium hydride nanodendrites with controllable morphology, high stability, and excellent catalytic activity. The synthesized dendrites can maintain the palladium hydride phase even after their use in the chosen catalytic reaction. Remarkably, the high surface area morphology and unique interaction between nickel-rich surface and palladium hydride (β-phase) of these nanodendrites are translated in an enhanced catalytic activity for benzyl alcohol oxidation reaction. Our Ni/PdH0.43 nanodendrites demonstrated a high selectivity towards benzaldehyde of about 92.0% with a conversion rate of 95.4%, showing higher catalytic selectivity than their PdH0.43 counterparts and commercial Pd/C. The present study opens the door for further exploration of metal/metal-hydride nanostructures as next-generation catalytic materials.Second, palladium hydride system (PdHx) has been of great interest primarily due to the high solubility of hydrogen on the palladium fcc (Pd-face centered cubic) lattice which make them suitable candidates as environmental friendly materials for applications in terms of storage and use of energy, having specific relevance in hydrogen storage, fuel cell, batteries, kinetics reversibility studies, and more. Palladium hydride properties do not only include adsorption and desorption of hydrogen, but they are also effective for electrocatalytic applications. Overall, palladium hydride and its alloys properties are strongly correlated with their electronic and crystal structure changes. Thus, a deep understanding and methodology for their production is crucial for their use in the mentioned applications. Despite of the studies found in literature, there is still a lack of studies for direct but simple synthesis of palladium hydride with practical applications. For instance, palladium hydride literature studies are mostly based on in-situ studies where a limitation of sample, stability and reproducibility are some of the major problems associated with them which also leads to a lack of studies related to their properties and how to tune them. Herein, we reported a simple yet well designed method for the synthesis of stable β palladium hydride with different morphologies and decoration of its surface with organic ligands which lead to different effects in terms of nanocrystal sizes and the ability of tune of its properties. Upon the use of different capping agents during the synthesis, diverse magnetic properties have arisen, as well as an increase in their hydrogen storage capacity. These properties are found to be different from their counterpart of pure palladium and palladium hydride material without coating agents.Third, developing non-platinum materials with enhance performance for electrocatalytic reactions has been gaining attention in recently years. Palladium and Palladium-based materials are the most suitable candidates to substitute platinum catalysts in anodic and cathodic reactions. Here we developed a facile path to synthesize PdCu nanowires having alloy and intermetallic phases within their structures. To the best of our knowledge, the catalytic properties of *PdCu intermetallic nanowires for hydrogen evolution reaction and formic acid oxidation reaction are higher than their PdCu alloy counterpart and those previously reported for 0D and 1D bimetallic nanostructures. Tafel slopes and overpotential presented here during hydrogen evolution reaction of *PdCu NWs in both acidic and basic conditions are superior than PdCu alloy nanowires, Pd nanowires and comparable to commercial Pt. In terms of formic acid oxidation reaction, *PdCu NWs also exhibits the highest mass activity, followed by PdCu alloy NWs, and being both superior than commercial Pd. In addition, PdCu nanowires also exhibit superior stability for both reactions: hydrogen evolution reaction in acid and basic conditions, and formic acid oxidation reaction as well as good resistance against CO poisoning. Density functional theory (DFT) calculations demonstrate that the improved HER performance at acidic condition is due to the decrease in the hydrogen binding energy of the compressed PdCu-B2 phase, and the improved HER performance at alkaline condition is due to the reduced water dissociation barriers at alkaline condition of *PdCu intermetallic phase.

Hydrogen is the most preferred choice as an energy source to replace the nonrenewable energy resources such as fossil fuels due to its beneficial features of abundance, ecofriendly, and outstanding gravimetric energy density. Splitting water through a proton exchange membrane (PEM) electrolyzer is a well‐known method of hydrogen production. But the major impediment is the sluggish kinetics of oxygen evolution reaction (OER). Currently, scientists are struggling to build out an acid‐stable electrocatalyst for OER with low overpotential and excellent stability. In this review, the reaction mechanism and characterization parameters of OER are introduced, and then the improvement method of metal nanocatalysts (noble metal catalysts and noble metal‐free catalysts) in acidic media is discussed. Particularly, the application of single‐atom catalysts in acidic OER is summarized, which is current researching focus. At the same time, we also briefly introduced the cluster phenomenon, which is easy to occur in the preparation of single‐atom catalysts. More importantly, we summarized the in situ characterization methods such as in situ X‐ray absorption spectroscopy, in situ X‐ray photoelectron spectroscopy, and so forth, which are conducive to further understanding of OER reaction intermediates and active sites. Finally, we put forward some opinions on the development of acidic OER.

3-Alkenylindoles are biologically and medicinally very important compounds, and their syntheses have received considerable attention. Herein, we report the synthesis of 3-alkenylindoles via a regioselective alkenylation of indoles, catalysed by a ruthenium nanocatalyst (RuNC). The reaction tolerates several electron-withdrawing and electron-donating groups on the indole moiety. Additionally, a “robustness screen” has also been employed to demonstrate the tolerance of several functional groups relevant to medicinal chemistry. With respect to the Ru nanocatalyst, it has been demonstrated that it is recoverable and recyclable up to four cycles. Also, the catalyst acts through a heterogeneous mechanism, which has been proven by various techniques, such as ICPMS and three-phase tests. The nature of the Ru nanocatalyst surface has also been thoroughly examined by various techniques, and it has been found that the oxides on the surface are responsible for the high catalytic efficiency of the Ru nanocatalyst.

The development of materials science and engineering in the past decades has been closely related to the emerging challenges associated with industrial and socio-economical requirements. Catalysis research has always been in a very central position in many different industry sectors. Learning from nature, materials research community has been long understood that the isolated catalytic components are no longer sufficient to meet new technological challenges. With more strict requirements of higher conversion and higher selectivity towards specific product(s), and lower energy demands during reactions, it is often very little room for singular catalyst material to play an efficient role. Instead, considerable attention has been placed in composite catalyst research. Rich knowledge in such regard has been obtained in plenty of catalysis research disciplines, like artificial photosynthesis, electrochemical energy conversion, tandem catalysis, as well as new types of conventional nanocatalysts with tentative compositions. Still, large gap in regard of nanocomposite catalyst materials is still difficult to be filled in near future. For instance, materials selection is an open field with uncountable possibilities, opportunities as well as problems. Synergetic effect is the utmost goal while its implementation is still questionable in most systems. Tandem catalysis represents revolutionary catalytic design philosophy, but its application in real life industry reactions is rare so far. This dissertation depicts mainly the nanocomposite catalyst materials, and studies the synergetic effect between each component in different systems. It is divided into three fields. Firstly, in Part I, 2D material support in catalysis is studied and the influence of supporting material in catalytic activity and selectivity is discussed. It includes Chapter 3, in which graphene-hemin nanocomposite system was developed and explored through a simple wet synthesis route. It is applied in toluene oxidation reaction to examine the effect in primary C-H bond activation reaction. Also, the effect of graphene as support is investigated in detail. Secondly, in Part II, alloy nanocatalysts are designed and the synergetic effect between different components are studied. It includes Chapter 4 and 5. In Chapter 4, nanoporous palladium (Pd) catalyst is synthesized. It is then alloyed with gold (Au) component to form Au-Pd alloy catalyst, with maintained nanoporous morphology. Its superior oxidative catalytic efficiency is assessed in benzyl alcohol oxidation reaction and methanol electro-oxidation reaction. The alloy formation and the synergetic effect between Au and Pd components are studied. In Chapter 5, a nano-star shaped Au-Cu alloy catalyst is synthesized and used in CO2 reduction application. The high hydrocarbon yield is related to the alloy composition and rough surface morphology. Lastly, nanocomposite is widely used in photocatalysis, therefore the contribution of metallic and semiconductor components, and their integration effect is studied. It includes Chapter 6. In Chapter 6, tandem catalyst composed of TiO2 and Au/Pd nanowheel is fabricated. After annealing in inert environment, the nanocomposite is tested in benzimidazole synthesis reaction. It features a highly green reaction route with photocatalytic nature, and of remarkable yield in target molecule product. The role of each component and the synergetic effect is compared.

Immobilized enzyme-based catalytic constructs could greatly improve various industrial processes due to their extraordinary catalytic activity and reaction specificity. In recent decades, nano-enzymes, defined as enzyme immobilized on nanomaterials, gained popularity for the enzymes' improved stability, reusability, and ease of separation from the biocatalytic process. Thus, enzymes can be strategically incorporated into nanostructured materials to engineer nano-enzymes, such as nanoporous particles, nanofibers, nanoflowers, nanogels, nanomembranes, metal-organic frameworks, multi-walled or single-walled carbon nanotubes, and nanoparticles with tuned shape and size. Surface-area-to-volume ratio, pore-volume, chemical compositions, electrical charge or conductivity of nanomaterials, protein charge, hydrophobicity, and amino acid composition on protein surface play fundamental roles in the nano-enzyme preparation and catalytic properties. With proper understanding, the optimization of the above-mentioned factors will lead to favorable micro-environments for biocatalysts of industrial relevance. Thus, the application of nano-enzymes promise to further strengthen the advances in catalysis, biotransformation, biosensing, and biomarker discovery. Herein, this review article spotlights recent progress in nano-enzyme development and their possible implementation in different areas, including biomedicine, biosensors, bioremediation of industrial pollutants, biofuel production, textile, leather, detergent, food industries and antifouling.

The oxygen adsorption and its catalytic reaction with hydrogen on Pt–Rh single crystals were studied at the nanoscale by Field Emission Microscopy (FEM) and Field Ion Microscopy (FIM) techniques at 700 K. Both FEM and FIM use samples prepared as sharp tips, apexes of which mimic a single nanoparticle of catalyst considering their similar size and morphology. Oxygen adsorption on Pt-17.4 at.%Rh samples leads to the formation of subsurface oxygen, which is manifested in the field emission (FE) patterns: for O2 exposure of ~3 Langmuir (L), {113} planes appear bright in the emission pattern, while for higher oxygen doses, i.e. 84 L, the bright regions correspond to the high index planes between the {012} and {011} planes. Formation of subsurface oxygen is probably accompanied by a surface reconstruction of the nanocrystal. The subsurface oxygen can be effectively reacted off by subsequent exposure of the sample to hydrogen gas at 700 K. The hydrogenation reaction was observed as a sudden, eruptive change of the brightness seen on the FE pattern. This reaction resulted in the recovery of the initial field emission pattern characteristic of a clean tip, with {012} facets being the most visible. It was shown that the oxygen accumulation-reduction process is completely reversible. The obtained results indicate that the presence of subsurface species must be considered in the description of reactive processes on Pt–Rh catalysts., info:eu-repo/semantics/published

Graphical abstract, Highlights • Inorganic nanoparticles are widely used for reduction of Cr(VI) to Cr(III). • Role of nanoparticles in reduction of Cr(VI) depends upon nature of inorganic nanomaterial. • Synthesis, characterization and stabilization of nanoparticles used in Cr(VI) reduction is described. • Reduction of Cr(VI) by different reductants in the presence of inorganic nanocatalysts is discussed. • Mechanism and factors affecting the rate of catalytic reduction of Cr(VI) have been discussed., Hexavalent Chromium [Cr(VI)] is a highly carcinogenic and toxic material. It is one of the major environmental contaminants in aquatic system. Its removal from aqueous medium is a subject of current research. Various technologies like adsorption, membrane filtration, solvent extraction, coagulation, biological treatment, ion exchange and chemical reduction for removal of Cr(VI) from waste water have been developed. But chemical reduction of Cr(VI) to Cr(III) has attracted a lot of interest in the past few years because, the reduction product [Cr(III)] is one of the essential nutrients for organisms. Various nanoparticles based systems have been designed for conversion of Cr(VI) into Cr(III) which have not been critically reviewed in literature. This review present recent research progress of classification, designing and characterization of various inorganic nanoparticles reported as catalysts/reductants for rapid conversion of Cr(VI) into Cr(III) in aqueous medium. Kinetics and mechanism of nanoparticles enhanced/catalyzed reduction of Cr(VI) and factors affecting the reduction process have been discussed critically. Personal future insights have been also predicted for further development in this area.

Palladium in the form of G-Pd nanocomposite possesses multiple enzyme mimicking activity. It catalyzes the oxidation of dopamine, glutamate, H2O2 and NADH through dopamine oxidase, glutamate oxidase, peroxidase and NADH oxidoreductase biomimetic activity. Kinetic studies were performed to calculate the catalytic parameters of G-Pd nanocomposite towards the substrates for a potential heterogeneous catalyst. Among them, glutamate oxidase activity was coupled with peroxidase activity of G-Pd for the detection of glutamate, in the form of a paper based sensor. Analytical performance of G-Pd nanocomposite catalyzed glutamate detection was characterized, and found to be linear in the range 0–400 μM and 400–8000 μM with limit of detection and quantification of 49.4 μM and 117.9 μM respectively. Results from the present study provides substantial progress in the practical application of nanomaterials as heterogeneous catalysts with multi enzyme mimicking property. G-Pd nanocomposite overcomes the complexity of enzyme based biosensors due to less number of reagents, better stability due to the absence of enzymes with mild storage conditions. Multi-mimetic catalytic activity of Pd will find applications in the field of analytical chemistry, biosensors, energy, environment and food safety.

The exploitation of nanocatalysts, at the boundary between homogeneous and heterogeneous catalysis, is tracking new efficient ways to produce renewable biofuels in environmentally friendly conditions. Their solid state makes them recyclable, and their nanomateric particle size enables high activities approaching those offered by homogeneous catalysts, as well as novel and unique catalytic behaviors not accessible to solids above the nanometer range. Furthermore, the use of magnetically active materials has led to the development of nanocatalysts easily recoverable through the application of magnetic fields. In this mini-review, latest achievements in the production of advanced biofuels using stable, highly active, cheap and reusable nanocatalysts are described. Specifically, biodiesel and high density fuels have been chosen as major topics of research for the design of catalytic nanomaterials.

Aihui Liang,1,2,* Chongning Li,1,2,* Dan Li,1,2,* Yanghe Luo,1–3 Guiqing Wen,1,2 Zhiliang Jiang1,2 1Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection, Guangxi Normal University, Ministry of Education, 2Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin University of Technology, Guilin, 3School of Food and Bioengineering, Hezhou University, Hezhou, China *These authors contributed equally to this work Abstract: The nanogold reaction between HAuCl4 and citrate is very slow, and the catalyst graphene oxide nanoribbon (GONR) enhanced the nanoreaction greatly to produce gold nanoparticles (AuNPs) that exhibited strong surface plasmon resonance (SPR) absorption (Abs) at 550nm and resonance Rayleigh scattering (RRS) at 550nm. Upon addition of the peptide of human chorionic gonadotropin (hCG), the peptide could adsorb on the GONR surface, which inhibited the catalysis. When hCG was added, peptides were separated from the GONR surface due to the formation of stable peptide–hCG complex, which led to the activation of GONR catalytic effect. With the increase in hCG concentration, the RRS and Abs signal enhanced linearly. The enhanced RRS value showed a good linear relationship with hCG concentration in the range of 0.2–20ng/mL, with a detection limit of 70pg/mL. Accordingly, two new GONR catalytic RRS/Abs methods were established for detecting hCG in serum samples. Keywords: nanocatalysis, graphene oxide nanoribbon, peptide regulation, hCG, RRS

The 1,3-dipolar cycloadditions of azomethine-ylides and -imines, nitrones, nitrilimines, and azides catalysed by inorganic nanoparticles are described. Emphasis is given to the nanometric catalysts involved, their structure, characterisation, and recyclability and, when remarkable, their preparation. Whenever possible, the improvements with respect to cycloadditions performed with the usual (non-nano) catalysts are discussed.

Para-, or 4-nitrophenol, and related nitroaromatics are broadly used compounds in industrial processes and as a result are among the most common anthropogenic pollutants in aqueous industrial effluent, this requires development of practical remediation strategies. Their catalytic reduction to the less toxic and synthetically desirable aminophenols is one strategy. However, to date, the majority of work focuses on catalysts based on precisely tailored, and often noble metal-based nanoparticles. The cost of such systems hampers practical, larger scale application. We report a facile route to bulk cobalt oxide-based materials, via a combined mechanochemical and calcination approach. Vibratory ball milling of CoCl2(H2O)6 with KOH, and subsequent calcination afforded three cobalt oxide-based materials with different combinations of CoO(OH), Co(OH)2, and Co3O4 with different crystallite domains/sizes and surface areas, Co@100, Co@350 and Co@600 (Co@###, = calcination temp). All three prove active for the catalytic reduction of 4-nitrophenol and related aminonitrophenols. In the case of 4-nitrophenol, Co@350 proved to be the most active catalyst, therein its retention of activity over prolonged exposure to air, moisture, and reducing environments, and applicability in flow processes is demonstrated.

Acid functionalization of a carbon support allows to enhance the electrocatalytic activity of Pd to hydrogenate benzaldehyde to benzyl alcohol proportional to the concentration of Brønsted‐acid sites. In contrast, the hydrogenation rate is not affected when H2 is used as a reduction equivalent. The different responses to the catalyst properties are shown to be caused by differences in the hydrogenation mechanism between the electrochemical and the H2‐induced hydrogenation pathways. The enhancement of electrocatalytic reduction is realized by the participation of support‐generated hydronium ions in the proximity of the metal particles., Pooled forces: A series of Pd/C catalysts with modified carbon supports were used for the electrochemical hydrogenation of benzaldehyde. The presence of acid groups at the metal–support interface enhances the catalytic activity of Pd due to the participation of Brønsted‐acid sites in the hydrogenation mechanism.

A catalytic system based on monolayer-functionalized gold nanoparticles (Au NPs) that can be electrochemically modulated and reversibly activated is reported. The catalytic activity relies on the presence of metal ions (Cd(2+) and Cu(2+) ), which can be complexed by the nanoparticle-bound monolayer. This activates the system towards the catalytic cleavage of 2-hydroxypropyl-p-nitrophenyl phosphate (HPNPP), which can be monitored by UV/Vis spectroscopy. It is shown that Cu(2+) metal ions can be delivered to the system by applying an oxidative potential to an electrode on which Cu(0) was deposited. By exploiting the different affinity of Cd(2+) and Cu(2+) ions for the monolayer, it was also possible to upregulate the catalytic activity after releasing Cu(2+) from an electrode into a solution containing Cd(2+) . Finally, it is shown that the activity of this supramolecular nanosystem can be reversibly switched on or off by oxidizing/reducing Cu/Cu(2+) ions under controlled conditions.

International audience; SynopsisMicrowave-assisted reductive amination with aqueous ammonia: sustainable pathway using a recyclable magnetic nickel based nanocatalyst.AbstractThe development of sustainable protocols for the reductive amination is a highly desirable pursuit in the domain of green synthesis. Magnetic nanocatalysts have found a unique niche in chemical synthesis in recent years as the recovery of expensive and/or toxic catalysts after their use are some of the salient features of these greener processes. Herein, we report the application of a recyclable nickel silica eggshell iron-based magnetic nanoparticles (Fe3O4@SiO2-Ni) for the expeditious microwave-assisted reductive amination of aryl aldehydes and ketones in aqueous ammonia; several desired primary amines were produced in good-to-excellent conversions. Extensive characterization of both, fresh and recycled Fe3O4@SiO2-Ni catalysts, showed that the Ni nanoparticles are highly dispersed on the silica shell and that the metal active phase is highly stable as the core–shell morphology is maintained after reaction, indeed the catalyst is recyclable up to six runs without deactivating. A synergic effect between the Ni nanoparticles and the silica support has been hypothesized wherein the Fe3O4@SiO2-Ni system worked as a bifunctional catalyst; support facilitates the activation of the substrate, and the metal nanoparticles promote the subsequent imine hydrogenation.

The catalytic activity of snowman‐like and core‐shell Fe3O4/Au nanoparticles (NPs), obtained through a “wet chemistry” approach which directly restitutes nanocatalysts stable and highly active in the reaction medium, was tested towards N‐alkylation reactions. The nanocatalysts were tested for the synthesis of secondary amines. The core‐shell NPs, thanks to the surface properties, homogeneous dispersion and intimate connection with reagents in the catalyst medium, exhibited an excellent catalytic activity (e. g. >99 % yield and conversion of aniline in very short time and mild conditions). Owing to the magnetic part, the nanoparticles can be easily separated and reused, showing an almost stable activity after 10 cycles.

Guiqing Wen,1,2,* Qi Jing,1,2,* Aihui Liang,1,2 Zhiliang Jiang1,2 1Key Laboratory of Ecology of Rare and Endangered Species and Environmental Protection (Guangxi Normal University), Ministry of Education, Guangxi Key Laboratory of Environmental Pollution Control Theory and Technology, Guilin, China; 2Department of Environment Science, College of Environment and Resources, Guangxi Normal University, Guilin, China *These authors contributed equally tothiswork Background: Microalbuminuria (mAlb) detection is essential for the diagnosis and prognosis of nephrotic patients and hypoproteinemia. In this article, we develop a new surface-enhanced Raman scattering (SERS) quantitative analysis method to detect mAlb in urine.Methods: Combined the mAlb immunoreaction with gold nanoreaction of graphene oxide nanoribbons (GONR)-HAuCl4-H2O2, and used Victoria blue B (VBB) as molecular probe with a SERS peak at 1,615 cm-1, a new SERS strategy for quantitative analysis of trace mAlb in urine was established.Results: The linear range of SERS quantitative analysis method is from 0.065 to 2.62 ng/mL, with a detection limit of 0.02 ng/mL. The SERS method was applied to analysis of mAlb in urine with good accuracy and reliability, the relative standard deviation is 0.49%–2.28% and the recovery is 96.9%–109.8%.Conclusion: This study demonstrated that the new SERS quantitative analysis method is of high sensitivity, good selectivity and simplicity. It has been applied to analysis of mAlb in urine, with satisfactory results. Keywords: graphene oxide nanoribbon, nanocatalysis, microalbumin immunoreaction, gold nanoreaction, SERS

The combination of metal nanoparticles (Pd or Pt NPs) with NAD-dependent thermostable alcohol dehydrogenase (TADH) resulted in the one-flask catalytic double reduction of 3-methyl-2-cyclohexenone to 3-(1S,3S)-methylcyclohexanol. In this article, some assumptions about the interactions between a chemocatalyst and a biocatalyst have been proposed. It was demonstrated that the size of the NPs was the critical parameter for the mutual inhibition: the bigger the NPs, the more harmful for the enzyme they were, even if the NPs themselves were only moderately inactivated. Conversely, the smaller the NPs, the more minimal the TADH denaturation, although they were dramatically inhibited. Resuming, the chemocatalysts were very sensitive to deactivation, which was not related to the amount of enzyme used, while the inhibition of the biocatalyst can be strongly reduced by minimizing the NPs/TADH ratio used to catalyze the reaction. Among some methods to avoid direct binding of NPs with TADH, we found that using large Pd NPs and protecting their surfaces with a silica shell, the overall yield of 3-(1S,3S)-methylcyclohexanol was maximized (36%).

Small core-shell Fe3O4@Pd superparamagnetic nanoparticles (MNPs) were obtained with good control in size and shape distribution by metal-complex thermal decomposition in organic media. The role of the stabilizer in the synthesis of MNPs was studied, employing oleylamine (OA), triphenylphosphine (TPP) and triphenylamine (TPA). The results revealed that, among the stabilizer investigated, the presence of oleylamine in the reaction media is crucial in order to obtain an uniform shell of Pd(0) in Fe3O4@Pd MNPs of 7 ± 1 nm. The synthesized core-shell MNPs were tested in Pd-catalyzed Heck-Mizoroki and Suzuki-Miyaura coupling reactions and p-chloronitrobenzene hydrogenation. High conversion, good reaction yields, and good TOF values were achieved in the three reaction systems with this nanocatalyst. The core-shell nanoparticle was easily recovered by a simple magnetic separation using a neodymium commercial magnet, which allowed performing up to four cycles of reuse. Fil: Biglione, Catalina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; Argentina Fil: Cappelletti, Ariel Leonardo. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; Argentina Fil: Strumia, Miriam Cristina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; Argentina. Universidad Nacional de Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto Multidisciplinario de Biología Vegetal. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Instituto Multidisciplinario de Biología Vegetal; Argentina Fil: Martín, Sandra Elizabeth. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina Fil: Uberman, Paula Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones en Físico-química de Córdoba. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Instituto de Investigaciones en Físico-química de Córdoba; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; Argentina

Nanosized ZSM-5 zeolite hexagonal cubic micro-blocks with different Si/Al ratios were successfully synthesized by using TPAOH in the presence of nonionic surfactant (Triton X-100) by a hydrothermal method. The samples prepared with the surfactant were characterized by XRD, XRF, FT-IR, N2 adsorption, HR-TEM, HR-SEM and NH3-TPD analysis to evaluate the particle structure, size and acid strength. Pure crystalline phase of ZSM-5 is confirmed by powder X-ray diffraction. FT-IR analysis further showed that nanosized zeolite has double five rings of the MFI-type of typical absorption at about 550cm-1. The SEM images clearly show that all ZSM-5 zeolite samples possess the similar hexagonal spheres morphology with particle size of about 320-360nm. The influence of Triton X-100 in the structural, textural, morphological and catalytic properties of ZSM-5 is compared with conventional ZSM-5. The catalytic activity of ZSM-5 zeolites with different Si/Al ratios (ZSM-5-WS(x) and ZSM-5-WOS(x)) is evaluated in the selective oxidation of benzyl alcohol (BzOH) using tert-butyl hydroperoxide (TBHP) as an oxidant and water as a solvent. The Triton X-100-assisted preparation yielded a zeolite exhibiting a higher conversion than the one prepared in the absence of Triton X-100. Among the catalysts, ZSM-5-WS(28) (Si/Al=28) catalyst exhibited significantly higher conversion at optimum conditions. This catalyst can be retrieved and reprocessed for five times without a significant loss in its activity and selectivity. � 2015.Published by Elsevier B.V.

A comparison between Au, TiO2 and self‐catalysed growth of SnO2 nanostructures using chemical vapour deposition is reported. TiO2 enables growth of a nanonetwork of SnO2, whereas self‐catalysed growth results in nanoclusters. Using Au catalyst, single‐crystalline SnO2 nanowire trees can be grown in a one‐step process. Two types of trees are identified that differ in size, presence of a catalytic tip, and degree of branching. The growth mechanism of these nanotrees is based on branch‐splitting and self‐seeding by the catalytic tip, facilitating at least three levels of branching, namely trunk, branch and leaf.

Angewandte Chemie / International edition 57(39), 12721-12726 (2018). doi:10.1002/anie.201806638, Published by Wiley-VCH, Weinheim

This is the peer reviewed version of the following article: Aygün, M., Chamberlain, T., Gimenez-Lopez, M., & Khlobystov, A. (2018). Magnetically Recyclable Catalytic Carbon Nanoreactors. Advanced Functional Materials, 28(34), 1802869, which has been published in final form at https://doi.org/10.1002/adfm.201802869 Multifunctional nanoreactors are assembled using hollow graphitized carbon nanofibers (GNFs) combined with nanocatalysts (Pd or Pt) and magnetic nanoparticles. The latter are introduced in the form of carbon‐coated cobalt nanomagnets (Co@Cn) adsorbed on GNF, or formed directly on GNF from ferrocene yielding carbon‐coated iron nanomagnets (Fe@Cn). High‐resolution transmission electron microscopy demonstrates that Co@Cn and Fe@Cn are attached effectively to the GNFs, and the loading of nanomagnets required for separation of the nanoreactors from the solution with an external magnetic field is determined using UV–vis spectroscopy. Magnetically functionalized GNFs combined with palladium or platinum nanoparticles result in catalytically active magnetically separable nanoreactors. Applied to the reduction of nitrobenzene the multifunctional nanoreactors demonstrate high activity and excellent durability, while their magnetic recovery enables significant improvement in the reuse of the nanocatalyst over five reaction cycles (catalyst loss < 0.5 wt%) as compared to the catalyst recovery by filtration (catalyst loss

Different types of biomass are being examined for their optimum hydrogen production potentials and actual hydrogen yields in different experimental set-ups and through different chemical synthetic routes. In this review, the observations emanating from research findings on the assessment of hydrogen synthesis kinetics during fermentation and gasification of different types of biomass substrates have been concisely surveyed from selected publications. This review revisits the recent progress reported in biomass-based hydrogen synthesis in the associated disciplines of microbial cell immobilization, bioreactor design and analysis, ultrasound-assisted, microwave-assisted and ionic liquid-assisted biomass pretreatments, development of new microbial strains, integrated production schemes, applications of nanocatalysis, subcritical and supercritical water processing, use of algae-based substrates and lastly inhibitor detoxification. The main observations from this review are that cell immobilization assists in optimizing the biomass fermentation performance by enhancing bead size, providing for adequate cell loading and improving mass transfer; there are novel and more potent bacterial and fungal strains which improve the fermentation process and impact on hydrogen yields positively; application of microwave irradiation and sonication and the use of ionic liquids in biomass pretreatment bring about enhanced delignification, and that supercritical water biomass processing and dosing with metal-based nanoparticles also assist in enhancing the kinetics of hydrogen synthesis. The research areas discussed in this work and their respective impacts on hydrogen synthesis from biomass are arguably standalone. Thence, further work is still required to explore the possibilities and techno-economic implications of combining these areas for developing robust and integrated biomass-to-hydrogen synthetic schemes.

Mercury (Hg) is a heavy metal pollutant, there is an urgent need to develop simple and sensitive methods for Hg(II) in water. In this article, a simple and sensitive resonance Rayleigh scattering (RRS) method was developed for determination of 0.008–1.33 µmol/L Hg, with a detection limit of 0.003 μmol/L, based on the Hg(II) regulation of gold nanoenzyme catalysis on the HAuCl4-H2O2 to form gold nanoparticles (AuNPs) with an RRS peak at 370 nm. Upon addition of molecular probes of Victoria blue B (VBB), the surface-enhanced Raman scattering (SERS) peak linearly decreased at 1612 cm−1 with the Hg(II) concentration increasing in the range of 0.013–0.5 μmol/L. With its good selectivity and good accuracy, the RRS method is expected to be a promising candidate for determining mercury ions in water samples.

Surface engineering of various nanoparticles (NPs) is of growing interest and an important step to induce/control optical and/or catalytic activities. Although a wide variety of biomedical applications of magnetic Fe3O4 NPs in diagnostics as well as therapeutics are well documented, the optical properties of the NPs still remain less well studied. Here we report a top-down fabrication methodology to modify a model ferrofluid with parent NPs sizes similar to 23 nm, using tartrate as a functionalizing ligand as well as solubilizing agent. The surface engineering involves ligand exchange and simultaneous phase transfer of Fe3O4 NPs (size similar to 23 nm) from chloroform to water along with subsequent core etching, resulting in a reduction of particle diameter to similar to 5 nm. We demonstrate that tartrate-functionalized Fe3O4 NPs (T-Fe3O4) exhibit ligand to metal charge transfer transition in the UV spectral region, excellent blue luminescence, and efficient reusable photocatalytic activities which are completely absent in the parent NPs. We have used the functionalized NPs for the photodegradation of biomedically important jaundice marker bilirubin in aqueous solution. The surface adsorption of Mn ions on the surface of the T-Fe3O4 NPs enables to control the degradation under UV light illumination. While the Mn-adsorbed T-Fe3O4 NPs can efficiently degrade bilirubin in dark condition, the activity is significantly reduced under UV light. Finally, the detailed photocatalytic mechanism associated with ultrafast charge and energy transfer process has been discussed. We believe that bilirubin degradation rate can be controlled under UV light by varying Mn ion concentration on the NPs surface which can be a significant advancement for bilirubin degradation study. Overall, the results represent a promising route for the fabrication of Fe3O4 NPs adaptable to diverse applications. Refereed/Peer-reviewed

Oxide-on-oxide systems are becoming increasingly important in nanocatalysis and surface engineering, because of the creation of hybridized interfaces holding high reactivity and selectivity toward oxidation reactions. Here we report on the results of a multitechnique surface science study conducted on an oxide/oxide model system. By depositing increasing amounts of vanadium oxide (VOx) on a titanium dioxide-rutile(110) substrate, we were able to follow the morphology and oxidation state of the overlayer. Three growth modes were detected: nanoclusters at low coverage (0.3 and 0.5 monolayer), one-dimensional strands aligned along the substrate [001] direction at monolayer coverage, and three-dimensional nanoislands at higher coverage (2.0 and 5.0 monolayers). All these structures share the same oxidation state (V2O3). We studied the reactivity and selectivity of these model catalysts toward partial oxidation of ethanol, finding that both of them depend on the VOx thickness. Nanoclusters can yield acetaldehyde through low-temperature oxidative dehydrogenation but show a scarce selectivity in the investigated temperature range. The monolayer coverage is the most reactive toward ethanol dehydration to ethylene, showing also good selectivity. Similar results are found at high coverage, although the overall reactivity of the systems toward alcohol oxidation decreases.

Palladium nanoparticles stabilized by PdC(binaphthyl) covalent bonds have been designed and synthesized. This new class of Pd nanoparticles was efficiently used as reusable catalysts for CC bond forming Heck, Suzuki-Miyaura and Sonogashira cross coupling reactions with high turnover. Even after the several catalytic cycles the Pd NPs had the same reactivity and particle size without any apparent agglomerization. � 2013 Elsevier B.V.

Nanosized Mg-doped ceria powders were obtained by self-propagating room temperature reaction without using surfactants or templates. X-ray diffraction analysis and field emission scanning microscopy results showed that the doped samples are solid solutions with fluorite-type structure and spherical morphology. Raman spectra revealed an increase in the amount of oxygen vacancies with the increase of Mg concentration. This increasing results in a narrowing of the bandgap of CeO2. The photocatalytic performances of the Mg-doped ceria solid solutions were evaluated by decomposing an organic dye, crystal violet under UV irradiation. The Mg-doped ceria solid solutions exhibit significantly better photocatalytic activity than the pure CeO2 and commercial TiO2. The higher first rate constant of the Mg-doped samples demonstrated that they are much more efficient than TiO2 and CeO2 under UV light. Mg2+ dopant ions and oxygen vacancies play a significant role in the enhancement of photocatalytic performances of the Mg-doped ceria.

International audience; A detailed knowledge of surface chemistry is necessary to bridge the gap between nanocrystal synthesis and applications. Although it has been proposed that carboxylic acids bind to metal oxides in a dissociative NC(X)2 binding motif, this surface chemistry was inferred from indirect evidence on HfO2 nanocrystals (NCs). Here, a more detailed picture of the coordination mode of carboxylate ligands on HfO2 and ZrO2 NC surfaces is shown by direct observation through solid-state NMR techniques. Surface-adsorbed protons are clearly distinguished and two coordination modes of the carboxylic acid are noted: chelating and bridging. It is also found that secondary ligands penetrate the ligand shell and have the same orientation with respect to the surface as the primary ligands, indicating that the ionic or hydrogen-bonding interactions with the surface are more important than the van der Waals interactions with neighboring ligands. During ligand exchange with amines, the chelating carboxylate is removed preferentially. Finally, it is shown that the HfO2 and ZrO2 NCs catalyze imine formation from acetone and oleylamine. Together with the previously reported catalytic activity of HfO2, these results put colloidal metal oxide nanocrystals squarely in the focus of catalysis research.

The hydrogenation of phenylacetone to cyclohexylacetone, in which the aromatic ring is selectively reduced in preference to the carbonyl group, has been achieved with chemoselectivities exceeding 90%. The catalyst (precatalyst) used to achieve this transformation comprises PVP-stabilized Rh nanoparticles dispersed in water with some phosphine ligand additives. Phosphine ligands with different steric and electronic properties and polarities were investigated for this purpose, and several clear trends were observed, showing the potential of well-defined phosphine ligands as modifiers in nanocatalysis.

It is demonstrated that the support effects play a crucial role in the gold nanocatalysis. Two types of support are considered—the “inert” support of hexagonal boron nitride (h-BN) with the N and B vacancy defects and the “active” support of rutile TiO2(110). It is demonstrated that Au and Au2 can be trapped effectively by the vacancy defects in h-BN. In that case, the strong adsorption on the surface defects is accompanied by the charge transfer to/from the adsorbate. The excess of the positive or negative charge on the supported gold clusters can considerably promote their catalytic activity. Therefore gold clusters supported on the defected h-BN surface can not be considered as pseudo-free clusters. We also demonstrate that the rutile TiO2(110) support energetically promotes H2 dissociation on gold clusters. We show that the formation of the OH group near the supported gold cluster is an important condition for H2 dissociation. We demonstrate that the active sites towards H2 dissociation on the supported Aun are located at corners and edges of the gold cluster in the vicinity of the low coordinated oxygen atoms on TiO2(110). Thus catalytic activity of a gold nanoparticle supported on the rutile TiO2(110) surface is proportional to the length of the perimeter interface between the nanoparticle and the support.