Self-assembling behaviour of Pt nanoparticles onto surface of TiO2 and their resulting photocatalytic activity

In the present study, self-assembling behaviour of guest nanoparticles (platinum) onto the surface of host support (titanium dioxide) during photodeposition process as a function of solution pH has been explored in detail by means of transmission electron microscope (TEM). The photocatalytic activity of the resulting bimetallic nanoassembly (Pt/TiO2) was evaluated by studying the degradation of two organic pollutants viz. triclopyr and methyl orange. Microscopic studies revealed that the deposition and/or distribution of Pt nanoparticles onto the surface of TiO2 were strongly guided by the ionization state of support which in turn was regulated by the solution pH of photodeposition process. A direct relationship between the solution pH of deposition process and the photocatalytic activity of resulting bimetallic catalyst has been observed. A mechanism based on the interparticle interaction between TiO2 and hydrolytic products of metal ions has been proposed for the differences in the photocatalytic activity of the resulting nanocomposite

Anisotropic silica mesostructures for DNA encapsulation

The encapsulation of biomolecules in inert meso or nanostructures is an important step towards controlling drug delivery agents. Mesoporous silica nanoparticles (MSN) are of immense importance owing to their high surface area, large pore size, uniform particle size and chemical inertness. Reverse micellar method with CTAB as the surfactant has been used to synthesize anisotropic mesoporous silica materials. We have used the anisotropic silica nanostructures for DNA encapsulation studies and observed a loading capacity of ~ 8 μ g mg−1 of the sample. On functionalizing the pores of silica with amine group, the amount of DNA loaded on the rods decreases which is due to a reduction in the pore size upon grafting of amine groups

Formation of calcium oxalate nanoparticles in leaves: significant role of water content and age of leaves

Calcium oxalate monohydrate (COM) was synthesized in the presence of leaves which act as a source of oxalate ions. Three different leaves, viz. Ficus religiosa (peepal in India), Heterophragma adenophyllum (Katsagon) and Spinacia oleracea Linn. (spinach) were used for the synthesis, which led to nanoparticles of COM of size 100–300 nm, 40–70 nm and 150–200 nm respectively. The particles are highly monodisperse, spherical and uniform in size as shown by TEM studies. The amount of COM formed varied significantly (35–80%) with the type of leaf used. The yield could be inversely correlated with the water content of the leaves; though water is essential for the formation of COM (dry leaves do not yield COM). Our studies show that the secretion of oxalate ions (to form COM) from the cells occurs even in leaves which have been removed from the living plants and the ability to secrete oxalate ions increases with the age of the leaf. The young leaves of F. religiosa do not show COM formation. In the presence of chelating agents (like citric acid) which can bind to Ca2+ ions, COM is absent, suggesting that the secretion of oxalate ions is prevented

Synthesis of nanocrystalline materials through reverse micelles: a versatile methodology for synthesis of complex metal oxides

We have been successful in obtaining monophasic nanosized oxides with varying chemical compositions using the reverse micellar method. Here we describe our methodology to obtain important metal oxides like ceria, zirconia and zinc oxide. The oxalate of cerium, zirconium and zinc were synthesized using the reverse micellar route. While nanorods of zinc oxalate with dimension, 120 nm in diameter and 600 nm in length, could be obtained, whereas spherical particles of size, 4-6 nm, were obtained for cerium oxalate. These precursors were heated to form their respective oxides. Mixture of nanorods and nanoparticles of cerium oxide was obtained. ZrO2 nanoparticles of 3-4 nm size were obtained by the thermal decomposition of zirconium oxalate precursor. ZnO nanoparticles (55 nm) were obtained by the decomposition of zinc oxalate nanorods. Photoluminescence (PL) studies at 20 K shows the presence of three peaks corresponding to free excitonic emission, free to bound and donor-acceptor transitions. We also synthesized nanoparticles corresponding to Ba1−x Pb x ZrO3 using the reverse micellar route. The dielectric constant and loss were stable with frequency and temperature for the solid solution

Graphene-based hybrid materials: synthetic approaches and properties

Carbon has a unique chemistry reflected in its wide presence in the inorganic and organic world - benzene, diamond, graphite, fullerene, carbon nanotubes and now graphene - carbon seems to be at the centre of action in the playground of scientific research. In this review, synthesis and unique properties of graphene and graphene-based composites have been discussed with particular emphasis on the environmentally benign (green) synthetic methods and their wide applications, especially in energy conversion, energy storage, electronics, biomedical and biosensing applications

Controlled Synthesis of Nanomaterials using Reverse Micelles

Monophasic nanosized oxides were synthesised mainly from metal oxalate nanorods obtainedusing the reverse micellar method. This paper focuses on the methodology to obtain importantmetal oxides like tin dioxide, cerium oxide (CeO2 ), zirconia, and zinc oxide. The effect of oxidationstate of the metal ion on the morphology of the oxalates was studied. Nanorods of zinc (II)oxalate (120 nm in dia and 600 nm in length) were obtained while spherical particles of size 4Œ6 nm were obtained for cerium (III) oxalate. The decomposition of these precursors at highertemperature led to the formation of their respective oxides. Mixture of nanorods and nanoparticles of CeO2 was obtained while 3Œ4 nm sized ZrO2 nanoparticles were obtained by thermaldecomposition of zirconium oxalate precursor. The dielectric constant and loss were highly stablewith frequency (at room temperature) for both ceria and zirconia nanoparticles.  ZnO nanoparticles(55 nm sized) were obtained by the decomposition of zinc oxalate nanorods. Three peaks corresponding to free excitonic emission, free-to-bound, and donor-acceptor transitions were observed in the photolumine scence studies at 20 K for ZnO nanoparticles.Defence Science Journal, 2008, 58(4), pp.531-544, DOI:http://dx.doi.org/10.14429/dsj.58.167

Facile charge transport in FeN_x/Mo₂N/CNT nanocomposites for efficient hydrogen evolution reactions

Molybdenum based materials are gaining importance as electrocatalysts for hydrogen evolution reaction because of their low cost and good electrocatalytic efficiency. Introducing iron nitride with molybdenum nitride as a composite results in efficient hydrogen evolution activity with current density of ∼120 mA/cm2 at −400 mV vs. RHE. The nanocomposites were characterized using powder XRD, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Electron Diffraction, Thermogravimetric Analysis and FTIR Spectroscopy. The electrochemical investigations suggest that the electrocatalytic activity of the composite increases with iron nitride content. The composite exhibits good electrochemical stability upto 42 hours in acidic medium. The hydrogen evolution reaction (HER) follows Volmer-Heyrovsky mechanism where Volmer reaction is the rate determing step

Nanoparticles of complex metal oxides synthesized using the reverse-micellar and polymeric precursor routes

Current interest in the properties of materials having grains in the nanometer regime has led to the investigation of the size-dependent properties of various dielectric and magnetic materials. We discuss two chemical methods, namely the reverse-micellar route and the polymeric citrate precursor route used to obtain homogeneous and monophasic nanoparticles of several dielectric oxides like BaTiO3, Ba2TiO4, SrTiO3, PbTiO3, PbZrO3 etc. In addition we also discuss the synthesis of some transition metal (Mn and Cu) oxalate nanorods using the reverse-micellar route. These nanorods on decomposition provide a facile route to the synthesis of transition metal oxide nanoparticles. We discuss the size dependence of the dielectric and magnetic properties in some of the above oxides