Plasmon Mediated Electron Transfer and Temperature Dependent Electron-Phonon Scattering in Gold Nanoparticles Embedded in Dielectric Films.

Excitation of localized surface plasmon resonance in metal nanoparticles (NPs) embedded in a glassy matrix generates hot electrons, which can be extracted for different optoelectronic applications. The insights of plasmon relaxation dynamics with varying surrounding dielectric environments and temperature dependence electron-phonon scattering process in gold (Au) NPs are still not very clear. Here, we have employed ultrafast transient absorption (TA) spectroscopy to explore the hot plasmon mediated electron transfer (PMET) and electron-phonon dynamics of photo-excited Au NPs in glassy film matrix with variable SiO2 /TiO2 compositions at cryogenic (5 K) to room temperature (300 K). Herein, we have chosen two pump excitation wavelengths (400 and 700 nm). The 400 nm excitation (d→sp) generates hot electron and the 700 nm excitation (sp→sp) provide information of direct plasmon relaxation. Drastic reduction of the transient signal of Au NPs in the high TiO2 content film as compared to pure SiO2 confirm hot electron transfer (HET) from Au plasmon to TiO2 . Electron-phonon scattering time constant (τe-ph ) of Au NPs in the glassy film is found to be faster in presence of TiO2 due to facile electron transfer/injection. Temperature dependent TA studies suggest that electron-phonon scattering time decreases with temperature. These findings would assist to develop more advanced photo-voltaic, opto-electronic and quantum optic-based devices using the plasmonic metal NPs.

Ultrafast Charge Delocalization Dynamics of Ambient Stable CsPbBr3 Nanocrystals Encapsulated in Polystyrene Fiber.

CsPbBr3 nanocrystals (NCs) encapsulated in a transparent polystyrene (PS) fiber matrix (CsPbBr3 @PS) have been synthesized to protect the NCs. The ultrafast charge delocalization dynamics of the embedded NCs have been demonstrated, and the results are compared with the pristine CsPbBr3 in toluene. The electrospinning method was employed for the preparation of CsPbBr3 @PS fibers by using a polystyrene solution doped with pre-synthesized CsPbBr3 and characterized by XRD, HRTEM, and X-ray photoelectron spectroscopy (XPS). Energy level diagrams of CsPbBr3 and PS suggest that CsPbBr3 @PS fibers make a type I core-shell structure. The carrier cooling for CsPbBr3 @PS fibers is found to be much slower than pure CsPbBr3 NCs. This observation suggests that photoexcited electrons from CsPbBr3 NCs get delocalized from the conduction band of the perovskite to lowest unoccupied molecular orbital (LUMO) of the PS fiber matrix. The CsPbBr3 @PS fibers possess remarkable stability under ambient conditions as well as in water over months. The clear understanding of charge carrier relaxation dynamics of CsPbBr3 confined in PS fibers could help to design robust optoelectronic devices.

Nanoparticle Induced Morphology Modulation in Spin Coated PS/PMMA Blend Thin Films.

The influence of adding nanoparticles on the ascast morphology of spin coated immiscible polystyrene/poly(methyl methacrylate) (PS/PMMA) thin films of different thickness (hE) and composition (RB, volume ratio of PS to PMMA) has been explored in this article. To understand the precise effect of nanoparticle addition, the morphology of PS/PMMA thin blend films spin cast from toluene on a native oxide covered silicon wafer substrate was first investigated. It is seen that in particle free films, the generic morphology of the films remains nearly unaltered with increase in hE, for RB = 3:1 and 1:3. In contrast, strong hE dependent morphology transformation is observed in films with RB = 1:1. Subsequently, thiol-capped gold nanoparticles (AuNP) containing films with different particle concentrations (CNP) were cast from the same solvent along with the polymer mixture. We observe that addition of AuNPs barely alters the generic morphology of the films with RB = 3:1. In contrast, the presence of the particles significantly influences the morphology of the films with RB = 1:1 and 1:3, particularly at higher CNP (≈10.0%). X-ray photoelectron spectroscopy and X-ray reflectivity of some samples reveal that the AuNPs tend to migrate to the free surface through the PS phase, thereby stabilizing this layer partially or fully (depending on CNP) against dewetting over a surface of adsorbed PMMA layer and influencing the ascast morphology as a function of CNP. The work is fundamentally important in understanding largely overlooked implications of nanoparticle addition on the morphology of PS/PMMA blend thin films which forms the fundamental basis for future interesting studies involving dynamics of nanoparticles within the blend thin films.

Development of nano-porous hydroxyapatite coated e-glass for potential bone-tissue engineering application: An in vitro approach.

To reconstruct the defects caused by craniectomies autologous, bone grafting was usually used, but they failed most commonly due to bone resorption, infections and donor-site morbidity. In the present investigation, an effort has been made for the first time to check the feasibility and advantage of using hydroxyapatite (HAp) coated e-glass as component of bone implants. Sol-gel synthesized coatings were found to be purely hydroxyapatite from XRD with graded and interconnected pores all over the surface observable in TEM. The interconnected porous nature of ceramics are found to increase bioactivity by acting to up-regulate the process of osseointegration through enhanced nutrient transfer and induction of angiogenesis. From TEM studies and nano indentation studies, we have shown that pores were considered to be appropriate for nutrient supply without compromising the strength of sample while in contact with physiological fluid. After SBF immersion test, porous surface was found to be useful for nucleation of apatite crystals, hence increasing the feasibility and bioactivity of sample. However, our quasi-dynamic study showed less crystallization but had significant formation of apatite layer. Overall, the in vitro analyses show that HAp coated e-glass leads to significant improvement of implant properties in terms of biocompatibility, cell viability and proliferation, osteoinductivity and osteoconductivity. HAp coating of e-glass can potentially be utilized in fabricating durable and strong bioactive non-metallic implants and tissue engineering scaffolds.

In Situ Synthesis of Mesoporous TiO2 Nanofibers Surface-Decorated with AuAg Alloy Nanoparticles Anchored by Heterojunction Exhibiting Enhanced Solar Active Photocatalysis.

We designed an electrospinning synthesis protocol to obtain in situ, the mesoporous TiO2 nanofibers, which are surface-decorated with plasmonic AuAg nanoparticles (AuAg-mTNF-H). Such alloy nanoparticles are found to be partially exposed on the surface of the nanofibers. Characterization by HRTEM and EDS confirmed the formation of 1:1 AuAg alloy nanoparticles on the surface of TiO2 nanofibers with heterojunction at the interfaces. On the basis of electron microscopic characterization, we proposed that, during the formation of the nanofibers, the incorporated metal ions with surface capping of negative charges migrated toward the outer surface of the nascent fibers under the influence of high positive voltage required for electrospinning. As a result, after the subsequent thermal treatment, the crystallization of TiO2 nanofibers and the formation of alloy nanoparticles took place, leading to the formation of a deep heterojunction through partial embedment of the nanoparticles. The formation of AuAg alloy also restricted the oxidation of Ag, thus making the nanoparticles highly stable in ambient condition. Accordingly, such unique AuAg-mTNF-H photocatalyst shows strong light absorption property covering the entire range of visible wavelengths with stability. The solar light harvesting property of AuAg-mTNF-H was verified by monitoring solar light induced H2 evolution via water splitting and photodecomposition of MB. In both the cases AuAg-mTNF-H showed excellent H2 evolution and photodecomposition of dye.

Electrospun ZrO2 nanofibers: precursor controlled mesopore ordering and evolution of garland-like nanocrystal arrays.

We observed that the hydrolysis-condensation reaction of precursors makes a significant difference in constructing ordered mesopores in electrospun ZrO2 nanofibers. Transmission-SAXS studies confirm the generation of uniform clusters of size ∼1.44 nm in the ZrOCl2·8H2O (inorganic salt) derived sol due to its relatively slow hydrolysis-condensation process. These initial -Zr-O-Zr- clusters acted as building blocks to form uniform 3D ordered cubic (Pm3[combining macron]m) mesopores in the presence of Pluronic F127 surfactant. In contrast, the commonly used Zr-alkoxide (zirconium n-propoxide) precursor, which is highly hydrolysable even after the use of a controlling agent, generates larger clusters with broad size distributions due to the uncontrolled hydrolysis-condensation of alkoxy groups. Accordingly, in the presence of F127, the alkoxide derived sol yielded disordered mesopores in the resultant fibers. XRD under dynamic heating conditions (up to 900 °C) and the corresponding TEM studies of the ZrOCl2·8H2O derived nanofibers confirmed the retention of mesopores even in the extremely thin nanofibers (diameter ∼15-25 nm) after the amorphous to crystal phase transformation (cubic/tetragonal). An interesting morphological transformation has been observed in the nanofibers at 900 °C where the fibers have been uniformly segmented by distinct single nanocrystals (width ∼15-65 nm) with mesopores. Further heat-treatment at 1100 °C made these segmented nanofibers nonporous, and a garland-like appearance with monoclinic nanocrystal arrays was formed.

Understanding the Effect of Single Cysteine Mutations on Gold Nanoclusters as Studied by Spectroscopy and Density Functional Theory Modeling.

Fluorescent metal nanoclusters have generated considerable excitement in nanobiotechnology, particularly in the applications of biolabeling, targeted delivery, and biological sensing. The present work is an experimental and computational study that aims to understand the effects of protein environment on the synthesis and electronic properties of gold nanoclusters. MPT63, a drug target of Mycobacterium tuberculosis, was used as the template protein to synthesize, for the first time, gold nanoclusters at a low micromolar concentration of the protein. Two single cysteine mutants of MPT63, namely, MPT63Gly20Cys (mutant I) and MPT63Gly40Cys (mutant II) were employed for this study. The experimental results show that cysteine residues positioned in two different regions of the protein induce varying electronic states of the nanoclusters depending on the surrounding amino acids. A mixture of five-atom and eight-atom clusters was generated for each mutant, and the former was found to be predominant in both cases. Computational studies, including density functional theory (DFT), frontier molecular orbital (FMO), and natural bond orbital (NBO) calculations, validated the experimental observations. The as-prepared protein-stabilized nanoclusters were found to have applications in the imaging of live cells.

Ni nanoparticles on RGO as reusable heterogeneous catalyst: effect of Ni particle size and intermediate composite structures in C-S cross-coupling reaction.

The present work demonstrates the C-S cross-coupling reaction between aryl halides and thiols using nickel nanoparticles (Ni NPs) supported on reduced graphene oxide (Ni/RGO) as a heterogeneous catalyst. It is observed that the uniformly dispersed Ni NPs supported on RGO could exhibit excellent catalytic activity in C-S cross-coupling reactions and the catalytic application is generalized with diverse coupling partners. Although the electron-rich planar RGO surface helps in stabilizing the agglomeration-free Ni NPs, the catalytic process is found to occur involving Ni(II) species and the recovered catalyst containing both Ni(0)/Ni(II) species is equally efficient in recycle runs. A correlation of loading of Ni species, size of NPs and the intermediate Ni-related heterostructures formed during the catalytic process has been established for the first time, and found to be best in the C-S cross-coupling reaction for Ni(0) and Ni(II) NPs of the average sizes 11-12 nm and 4 nm, respectively.

In Situ Mg/MgO-Embedded Mesoporous Carbon Derived from Magnesium 1,4-Benzenedicarboxylate Metal Organic Framework as Sustainable Li-S Battery Cathode Support.

Development of advanced carbon cathode support with the ability to accommodate high sulfur (S) content as well as effective confinement of the sulfur species during charge-discharge is of great importance for sustenance of Li-S battery. A facile poly(vinylpyrrolidone)-assisted solvothermal method is reported here to prepare Mg-1,4-benzenedicarboxylate metal organic framework (MOF) from which mesoporous carbon is derived by thermal treatment, where the hexagonal sheetlike morphology of the parent MOF is retained. Existence of abundant pores of size 4 and 9 nm extended in three dimensions with zigzag mazelike channels helps trapping of S in the carbon matrix through capillary effect, resulting in high S loading. When tested as a cathode for lithium-sulfur battery, a reversible specific capacity of 1184 mAh g-1 could be achieved at 0.02 C. As evidenced by X-ray photoelectron spectroscopy, in situ generated Mg in the carbon structure enhances the conductivity, whereas MgO provides support to S immobilization through chemical interactions between Mg and sulfur species for surface polarity compensation, restricting the dissolution of polysulfide into the electrolyte, the main cause for the "shuttle phenomenon" and consequent capacity fading. The developed cathode shows good electrochemical stability with reversible capacities of 602 and 328 mAh g-1 at 0.5 and 1.0 C, respectively, with retentions of 64 and 67% after 200 cycles. The simple MOF-derived strategy adopted here would help design new carbon materials for Li-S cathode support.

Selective Cu4Pd alloy nanoparticles anchoring on amine functionalized graphite nanosheets and their use as reusable catalysts for a C-C coupling reaction with the sacrificial role of Cu for Pd-regeneration.

A facile method for the synthesis of phase selective alloy nanoparticles (NPs), Cu4Pd and their in situ anchoring on the surface of amine functionalized graphite nanosheets (AFGNS) by solvothermal process has been demonstrated. It has been seen that upon adding CuCl2·H2O and PdCl2 into the reaction medium containing AFGNS, the -NH2 group initially helps to immobilize Cu(2+) ions from CuCl2·H2O. During the solvothermal reaction in presence of N,N-dimethylformamide (DMF; solvent cum reducing agent) Pd(2+) gets reduced first due to its higher reduction potential. These Pd NPs in turn help in the reduction of Cu(2+) to Cu in an epitaxial manner. Finally at high temperature and long reaction time Cu and Pd combine to form the Cu4Pd alloy NPs along with a small fraction of Cu NPs. The conditions to obtain Cu4Pd NPs have been optimized through controlled reactions. The as prepared Cu4Pd@AFGNS composite has been successfully used for Suzuki-Miyuara C-C coupling reaction with sufficiently high yield and reusability of up to five cycles. The progress of the reaction was monitored using a fluorimeter. Interestingly, it has been observed that the small fraction of the Cu NPs present in the system played a sacrificial role in regenerating metallic Pd NPs in the first and second reaction cycles, followed by Cu from the Cu4Pd alloy itself from the third cycle onwards which played the sacrificial role to regenerate Pd(0). A probable reaction mechanism of the catalytic reaction with Cu4Pd@AFGNS has been suggested.

Porous SiO2 nanofiber grafted novel bioactive glass-ceramic coating: A structural scaffold for uniform apatite precipitation and oriented cell proliferation on inert implant.

A composite bioactive glass-ceramic coating grafted with porous silica nanofibers was fabricated on inert glass to provide a structural scaffold favoring uniform apatite precipitation and oriented cell proliferation. The coating surfaces were investigated thoroughly before and after immersion in simulated body fluid. In addition, the proliferation behavior of fibroblast cells on the surface was observed for several culture times. The nanofibrous exterior of this composite bioactive coating facilitated homogeneous growth of flake-like carbonated hydroxyapatite layer within a short period of immersion. Moreover, the embedded porous silica nanofibers enhanced hydrophilicity which is required for proper cell adhesion on the surface. The cells proliferated well following a particular orientation on the entire coating by the assistance of nanofibrous scaffold-like structural matrix. This newly engineered composite coating was effective in creating a biological structural matrix favorable for homogeneous precipitation of calcium phosphate, and organized cell growth on the inert glass surface.

Functionalized C@TiO2 hollow spherical architecture for multifunctional applications.

Hierarchical anatase titania (TiO2) with a hollow spherical architecture decorated with functionalized carbon dots (C(F)@THS) was synthesized by a solvothermal decomposition of titanium(IV) isopropoxide (TTIP) in the presence of a solution mixture containing thiourea and citric acid. Interestingly, the concomitant presence of thiourea and citric acid has been found to be essential to obtain such hierarchical hollow architecture because individual constituents produced non-hollow spheres when hydrothermally treated with TTIP. The co-existence of these two constituents also accelerates the growth of hollow spheres. BET surface area study of C(F)@THS revealed the existence of a slit like mesoporosity with a surface area value of 81 m(2) g(-1). Time dependent FESEM and TEM studies confirmed the formation of nanoflake like structures in the intermediate stages followed by the growth of a hollow spherical architecture. We proposed that these nanoflakes get accumulated on the bubble surface to form such hollow spherical morphology. The PL spectral study and Raman shift of the as prepared C(F)@THS confirmed the presence of functionalized graphitic C dots on the surface. A thorough XPS analysis was conducted to explore the nature and relative atomic concentration of the functional groups (-COOH, -CONH2, -NH2). This C(F)@THS sample showed very fast and selective dye (methylene blue and methyl violet) adsorption ability (even from a mixture of two different dye solutions) due to these δ-site containing functional groups on the surface. As C(F)@THS showed only two times reusability for adsorption, the dye adsorbed C(F)@THS was calcined at 450 °C in air to yield organic free anatase TiO2 hollow spheres (THS) with a retention of the original structure. THS was recycled as an efficient and a reusable photocatalyst (k = 9.36 × 10(-2) min(-1)) as well as a photoanode in dye sensitized solar cells (DSSCs) having Jsc value of 19.58 mA cm(-2) with overall efficiency of 6.48%.

Electrochemical energy storage in montmorillonite K10 clay based composite as supercapacitor using ionic liquid electrolyte.

Exploring new electrode materials is the key to realize high performance energy storage devices for effective utilization of renewable energy. Natural clays with layered structure and high surface area are prospective materials for electrical double layer capacitors (EDLC). In this work, a novel hybrid composite based on acid-leached montmorillonite (K10), multi-walled carbon nanotube (MWCNT) and manganese dioxide (MnO2) was prepared and its electrochemical properties were investigated by fabricating two-electrode asymmetric supercapacitor cells against activated carbon (AC) using 1.0M tetraethylammonium tetrafluroborate (Et4NBF4) in acetonitrile (AN) as electrolyte. The asymmetric supercapacitors, capable of operating in a wide potential window of 0.0-2.7V, showed a high energy density of 171Whkg(-1) at a power density of ∼1.98kWkg(-1). Such high EDLC performance could possibly be linked to the acid-base interaction of K10 through its surface hydroxyl groups with the tetraethylammonium cation [(C2H5)4N(+) or TEA(+)] of the ionic liquid electrolyte. Even at a very high power density of 96.4kWkg(-1), the cells could still deliver an energy density of 91.1Whkg(-1) exhibiting an outstanding rate capability. The present study demonstrates for the first time, the excellent potential of clay-based composites for high power energy storage device applications.

Zirconia based superhydrophobic coatings on cotton fabrics exhibiting excellent durability for versatile use.

A fluorinated silyl functionalized zirconia was synthesized by the sol-gel method to fabricate an extremely durable superhydrophobic coating on cotton fabrics by simple immersion technique. The fabric surfaces firmly attached with the coating material through covalent bonding, possessed superhydrophobicity with high water contact angle ≈163 ± 1°, low hysteresis ≈3.5° and superoleophilicity. The coated fabrics were effective to separate oil/water mixture with a considerably high separation efficiency of 98.8 wt% through ordinary filtering. Presence of highly stable (chemically and mechanically) superhydrophobic zirconia bonded with cellulose makes such excellent water repelling ability of the fabrics durable under harsh environment conditions like high temperature, strong acidic or alkaline solutions, different organic solvents and mechanical forces including extensive washings. Moreover, these coated fabrics retained self-cleanable superhydrophobic property as well as high water separation efficiency even after several cycles, launderings and abrasions. Therefore, such robust superhydrophobic ZrO2 coated fabrics have strong potential for various industrial productions and uses.

Cu2O Nanoparticles Anchored on Amine-Functionalized Graphite Nanosheet: A Potential Reusable Catalyst.

Synthesis of Cu2O-amine-functionalized graphite nanosheet (AFGNS) composite has been accomplished at room temperature. In the first step, AFGNS is synthesized by wet chemical functionalization where the -NH2 groups formed on nanosheet surface help to anchor the Cu(2+) ions homogeneously through coordinate bonds. Reduction of Cu(2+) (3.4 × 10(-2) mmol) in the presence of NaBH4 (1.8 mmol) can be restricted to Cu(1+) on AFGNS surface at room temperature. This leads to the formation of uniform Cu2O nanoparticles (NP) on AFGNS. The role played by the -NH2 groups in anchoring Cu(2+) ions and followed by stabilizing the Cu2O NP on AFGNS was understood by controlled reactions in the absence of -NH2 groups and without any graphitic support, respectively. The prepared Cu2O-AFGNS composite shows excellent catalytic activity toward degradation of an azo dye, methyl orange, which is an environmental pollutant. The dye degradation proceeds with high rate constant value, and the composite shows high stability and excellent reuse capability.

Attenuation of the early events of α-synuclein aggregation: a fluorescence correlation spectroscopy and laser scanning microscopy study in the presence of surface-coated Fe3O4 nanoparticles.

The aggregation of α-synuclein (A-syn) has been implicated in the pathogenesis of Parkinson's disease (PD). Although the early events of aggregation and not the matured amyloid fibrils are believed to be responsible for the toxicity, it has been difficult to probe the formation of early oligomers experimentally. We studied the effect of Fe3O4 nanoparticle (NP) in the early stage of aggregation of A-syn using fluorescence correlation spectroscopy (FCS) and laser scanning microscopy. The binding between the monomeric protein and NPs was also studied using FCS at single-molecule resolution. Our data showed that the addition of bare Fe3O4 NPs accelerated the rate of early aggregation, and it did not bind the monomeric A-syn. In contrast, L-lysine (Lys)-coated Fe3O4 NPs showed strong binding with the monomeric A-syn, inhibiting the early events of aggregation. Lys-coated Fe3O4 NPs showed significantly less cell toxicity compared with bare Fe3O4 NPs and can be explored as a possible strategy to develop therapeutic application against PD. To the best of our knowledge, this report is the first example of using a small molecule to attenuate the early (and arguably the most relevant in terms of PD pathogenesis) events of A-syn aggregation.

Mesoporous alumina films: effect of oligomer formation toward mesostructural ordering.

Alumina films with Im3̅m, Ia3d, and onion-like mesopores have been synthesized using a single sol composition derived from an modified alumina precursor (MAP), partial acetylacetone (acac) chelated aluminum secondary butoxide (ASB/acac = 1:0.5). We observed that MAP undergoes oligomerization with aging time and the differently aged MAP generates different micellar structures in the presence of P123 in alumina sols, and forms differently ordered mesostructured coatings. The time-dependent changes in the chemical nature of the MAP have been studied through ATR-FTIR spectroscopy. The nature of micellar transformations in the sols have been studied by transmission SAXS investigations. It has been observed that the size of the micelles gradually increases with time. On aging, MAP contains more bridging alkoxide groups with lesser hydrophilic characteristics; this reduces its interaction with the hydrophilic groups in the P123 micelle. Therefore, a mesostructure with low curvature is gradually formed in the sol due to the rigid nature of cross-linked MAP. Low angle XRD and TEM studies of the coatings obtained from the above sols have confirmed the generation of three distinctly different types of ordered mesoporous arrangements after heat treatments. The time-induced mesophase transformation mechanism has been proposed based upon the experimental results. The study reveals transformation of a modified Al alkoxide solution with respect to time and its successful use to obtain mesoporous alumina films of different ordered structures on glass.

Controlled synthesis and characterization of the elusive thiolated Ag55 cluster.

A stable, Ag55 cluster protected with 4-(tert-butyl)benzyl mercaptan (BBSH) was synthesized which exhibits two prominent absorption bands with maxima at 2.25 and 2.81 eV. A molecular ion peak at m/z 11 500 ± 20 in matrix assisted laser desorption ionization mass spectrum (MALDI MS), assigned to Ag55(BBS)31 was observed. Electrospray ionization (ESI MS) shows a prominent trication along with higher charged species. An analogous Ag55(PET)31 (PET = 2-phenylethanethiol, in the thiolate form) was also synthesized under optimized conditions which proves the amenability of this cluster and the synthetic methodology to other ligands.

Pd-Ni alloy nanoparticle doped mesoporous SiO2 film: the sacrificial role of Ni to resist Pd-oxidation in the C-C coupling reaction.

A Pd-Ni alloy nanoparticle (NP) doped mesoporous SiO2 film was synthesized using a one pot inorganic-organic sol-gel process in the presence of structure director P123. Pure Pd and Ni NP containing films were also synthesized as controls. Overall a composition of 10 mol% metal (in the case of Pd-Ni, 5 mol% of each metal) and 90 equivalent mol% SiO2 was maintained in the heat-treated films. Grazing incidence X-ray diffraction and transmission electron microscopy studies of the final heat-treated Pd-Ni doped films revealed the (111) oriented growth of the Pd-Ni alloy NPs, with an average size of 5.3 nm, residing inside the mesopores of the SiO2 film. We performed the C-C coupling reaction employing the film-catalysts and the progress of the reaction was monitored using a fluorimeter. Overall, only the Pd-Ni alloy NP doped film showed good catalytic activity with excellent recyclability. It has been determined that the higher oxidising ability of metallic Ni restricted the oxidation of Pd in the Pd-Ni alloy catalyst under the reaction conditions, leading to the maintained reusability in consecutive cycles.

Stable Ni nanoparticle-reduced graphene oxide composites for the reduction of highly toxic aqueous Cr(VI) at room temperature.

Inherent properties of graphene can be experienced by integrating it with different nanomaterials to form unique composite materials. Decorating the surface of graphene sheets with nanoparticles (NPs) is one of the recent approaches taken up by scientists all over the world. This article describes a simple synthesis route to preparing stable Ni NP-reduced graphene oxide (Ni-RGO) composite material. The otherwise unstable bare Ni NPs are stabilized when embedded in the RGO sheets. This synthesized composite material has a potential application in the formic acid-induced reduction of highly toxic aqueous Cr(VI) at room temperature (25 °C). The reduction of dichromate using formic acid as a reducing agent is a well-known redox reaction. However, the rate of the reaction is very slow at room temperature, which can be enhanced very significantly in the presence of Ni-RGO by introducing an intermediate redox step with formic acid. The Ni-RGO composite material is an easy to prepare, cheap, stable, reusable material that has the potential to replace costly Pd NPs used in this context. Ni-RGO is also found to be very active in enhancing the rate of reduction of other metal ions in the presence of formic acid at room temperature.