P. Jeevanandam

Synthesis of self-assembled prismatic iron oxide nanoparticles by a novel thermal decomposition route

Magnetic nanostructured materials with novel morphologies are often required for interesting applications. In the present study, iron oxide nanoparticles with prismatic hexagonal morphology were synthesized using a novel low temperature thermal decomposition approach. The thermal decomposition of [Fe(CON2H4)6](NO3)3 in diphenyl ether at about 200 °C for 70 min leads to the formation of prismatic iron oxide nanoparticles. The prismatic particles were found to be made up of self-assembled iron oxide nanoparticles. The iron oxide nanoparticles were characterized using X-ray diffraction, thermal gravimetric analysis, elemental analysis, infrared spectroscopy, field emission-scanning electron microscopy coupled with energy dispersive X-ray analysis, and magnetic measurements. The mechanism of formation of prismatic iron oxide nanoparticles has also been investigated.

A novel thermal decomposition approach to synthesize hydroxyapatite–silver nanocomposites and their antibacterial action against GFP-expressing antibiotic resistant E. coli

A novel thermal decomposition approach to synthesize hydroxyapatite-silver (Hap-Ag) nanocomposites has been reported. The nanocomposites were characterized by X-ray diffraction, field emission scanning electron microscopy coupled with energy dispersive X-ray analysis, transmission electron microscopy and diffuse reflectance spectroscopy techniques. Antibacterial activity studies for the nanocomposites were explored using a new rapid access method employing recombinant green fluorescent protein (GFP) expressing antibiotic resistant Escherichia coli (E. coli). The antibacterial activity was studied by visual turbidity analysis, optical density analysis, fluorescence spectroscopy and microscopy. The mechanism of bactericidal action of the nanocomposites on E. coli was investigated using atomic force microscopy, and TEM analysis. Excellent bactericidal activity at low concentration of the nanocomposites was observed which may allow their use in the production of microbial contamination free prosthetics.

Sun-light-driven photocatalytic activity by ZnO/Ag heteronanostructures synthesized via a facile thermal decomposition approach

ZnO/Ag heteronanostructures with varying amounts of silver nanoparticles on ZnO nanorods were successfully synthesized via a novel and economical thermal decomposition approach. ZnO nanorods were first synthesized by a homogeneous precipitation method and silver nanoparticles were subsequently deposited on the surface of ZnO nanorods by the thermal decomposition of silver acetate in diphenyl ether at 220 °C. The amount of silver nanoparticles on the ZnO nanorods was controlled by varying the concentration of silver acetate during the thermal decomposition. The synthesized ZnO/Ag heteronanostructures were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDXA), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectroscopy. XRD results confirm the presence of silver nanoparticles (size = 24–31 nm) in the ZnO/Ag heteronanostructures. SEM and TEM images prove the presence of silver nanoparticles on the surface of ZnO nanorods. XPS results indicate the presence of metallic silver in ZnO/Ag. DRS results show characteristic surface plasmon resonance absorption due to silver nanoparticles and PL results indicate an effective separation of photogenerated electron–hole pairs in the ZnO/Ag heteronanostructures as compared to pristine ZnO nanorods. The synthesized ZnO/Ag heteronanostructures were explored as a catalyst towards the photodegradation of methylene blue in an aqueous solution and photostability of the ZnO/Ag heteronanostructures has also been demonstrated.

A facile synthetic approach for SiO2@Co3O4 core–shell nanorattles with enhanced peroxidase-like activity

SiO2@Co3O4 core–shell nanorattles with different Co3O4 shell thicknesses have been successfully synthesized by the calcination of SiO2@α-Co(OH)2 at 500 °C. The synthetic approach is facile, economical, and requires no surface modification. The synthesized materials were thoroughly characterized using powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) analysis, field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and diffuse reflectance spectroscopy (DRS). SEM analysis indicates a hierarchical core–shell morphology for SiO2@Co3O4 and the TEM results indicate the core–shell nanorattle morphology. Diffuse reflectance spectroscopy studies indicate that the SiO2@Co3O4 core–shell nanorattles show two absorption bands in the range 420–450 nm and 700–750 nm related to ligand to metal charge transfer transitions (O2− → Co2+ and O2− → Co3+). The SiO2@Co3O4 core–shell nanorattles act as an artificial peroxidase enzyme mimic with enhanced intrinsic peroxidase-like activity compared to pure Co3O4 nanoparticles and horseradish peroxidase (HRP), a natural enzyme. The SiO2@Co3O4 core–shell nanorattles show higher kcat and kcat/Km values compared to pure Co3O4 and HRP indicating their applicability as an artificial enzyme mimic in biomedicine and bio-sensing.

Effect of anions on the morphology of CdS nanoparticles prepared via thermal decomposition of different cadmium thiourea complexes in a solvent and in the solid state

Thermal decomposition of four different cadmium thiourea complexes as single source precursors in a solvent and in the solid state has been explored as an effective and convenient strategy for the controlled synthesis of CdS nanoparticles with unique morphologies for the first time. Thermal decomposition of four cadmium thiourea complexes with different anions (acetate, chloride, nitrate and sulfate) in diphenyl ether and solid state leads to CdS nanoparticles with different morphologies. The effect of anions on the structural, morphological and optical properties of CdS nanoparticles, prepared by both the methods, has been investigated. CdS nanoparticles derived from solid state thermal decomposition of the cadmium thiourea complexes with acetate, chloride, nitrate and sulfate ions exhibit spheres, nanotubes, nanoflowers and irregular morphologies, respectively. On the other hand, thermal decomposition of the cadmium thiourea complexes with acetate, chloride and nitrate ions in diphenyl ether results in CdS nanoparticles with microspheres, nanopyramids and a mixture of nanoparticles and nanorods morphologies, respectively. A detailed mechanism on the effect of anions on the morphology of CdS nanoparticles produced by both the methods has been proposed. The synthesized CdS nanoparticles with different morphologies have been explored as photocatalysts for the degradation of crystal violet in an aqueous solution under sunlight. The CdS nanoparticles prepared by thermal decomposition in the solid state possess higher photocatalytic efficiency than that prepared by thermal decomposition in the solvent.

Evolution of different morphologies of CdS nanoparticles by thermal decomposition of bis(thiourea)cadmium chloride in various solvents

Abstract CdS nanoparticles with different morphologies have been synthesized by thermal decomposition of bis(thiourea)cadmium chloride in different solvents without the use of any ligand/surfactant. CdS nanoparticles with pyramid, sponge-like and hexagonal disc-like morphologies were obtained in diphenyl ether (DPE), 1-octadecene (ODE) and ethylene glycol (EG), respectively. In addition, CdS nanoparticles with unique morphologies were obtained when the decomposition of the complex was carried out in mixed solvents (DPE–EG and ODE–EG). Extensive characterization of the CdS nanoparticles was carried out using powder X-ray diffraction, FT-IR spectroscopy, thermal analysis, field-emission scanning electron microscopy, diffuse reflectance spectroscopy and photoluminescence spectroscopy, and detailed mechanism of the formation of CdS nanoparticles with different morphologies in various solvents has been proposed.

Synthesis of Iron Oxide Nanoparticles by Thermal Decomposition Approach

An easy onepot reaction for the synthesis of iron oxide nanoparticles is reported. Thermal decomposition of iron acetyl acetonate (Fe(acac)3) in diphenyl ether, in the presence of oleic acid and oleyl amine followed by calcination, leads to the formation of iron oxide nanoparticles. Variation of concentration of the oleyl amine during the synthesis affects the morphology of the iron oxide nanoparticles produced.

Synthesis of gold-poly (dimethylsiloxane) nanocomposite through a polymer-mediated silver/gold galvanic replacement reaction

Silver-poly (dimethylsiloxane) nanocomposite films are prepared by an in-situ synthesis by incubating the polymer film in a silver nitrate aqueous solution and using the reducing properties of the polymer’s curing agent. Silver nanoparticles concentrated in the surface layer of the silver-poly (dimethylsiloxane) nanocomposite are further replaced by gold through a galvanic replacement reaction at the poly (dimethylsiloxane)/gold salt solution interface. It is demonstrated that, as a result of the galvanic replacement, the quasi-spherical silver nanoparticles uniformly distributed on the surface of the polymer are transformed into ribbon-like elongated gold aggregates. The formation of core-shell Ag-Au nanoparticles as an intermediate state of the low-temperature galvanic replacement is evidenced through microscopic and spectral methods. The collapse of this structure, in a later stage of the replacement, leads to the formation of elongated gold aggregates. The mechanism of the galvanic replacement under different conditions is investigated by closely following the evolution of the morphology, composition, and optical properties of the metal nanoparticles.

Comparison of galvanic displacement and electroless methods for deposition of gold nanoparticles on synthetic calcite

Gold nanoparticles have been deposited on synthetic calcite substrate by galvanic displacement reaction and electroless deposition methods. A comparative study has shown that electroless deposition is superior compared to galvanic displacement reaction for uniform deposition of gold nanoparticles on calcite. Characterization of the samples, prepared by two different deposition methods, was carried out by X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy (FE–SEM) and diffuse reflectance spectroscopy (DRS) measurements. FE–SEM studies prove that smaller nanoparticles of gold are deposited uniformly on calcite if electroless deposition method was employed and DRS measurements show the characteristic surface plasmon resonance of gold nanoparticles.

Synthesis of SnS2 Nanoparticles and Their Application as Photocatalysts for the Reduction of Cr(VI)

The present study reports the synthesis of SnS2 nanoparticles with different morphologies via a facile thermal decomposition approach. The SnS2 nanoparticles were synthesized using tin chloride and thiourea (or thioacetamide) in two different solvents (diphenyl ether and 1-octadecene). The SnS2 nanoparticles were extensively characterized using different analytical techniques. The crystallite size of SnS2 varies from 6.1 nm to 19.0 nm. Electron microscopy studies indicate that the SnS2 samples consist of flakes which assemble into different hierarchical structures such as ball dahlia, peony dahlia-like nanoflowers, nanoyarns and linear structures under different synthetic conditions. The SnS2 nanoparticles show interesting optical properties and the band gap varies from 2.31 eV to 2.94 eV. Detailed mechanism of formation of SnS2 nanoparticles with different morphologies has been proposed. The SnS2 nanoparticles were explored for photocatalytic reduction of Cr(VI) in an aqueous solution in the presence of sunlight and they act as visible light photocatalysts with good activity.