Dhaneswar Das

Synthesis and evaluation of antioxidant and antibacterial behavior of CuO nanoparticles

CuO nanoparticles were synthesized by thermal decomposition methods and characterized by UV-visible spectroscopy, XRD and TEM analysis. The resultant particles are nearly spherical and particle size is in the range of 15-30 nm. The antioxidant behavior of synthesized CuO nanoparticles was evaluated by scavenging free radicals of 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH). The free radical scavenging activity of CuO nanoparticles was monitored by UV-visible spectrophotometry. The antibacterial activity of CuO nanoparticles was tested against different bacterial strains. CuO nanoparticles showed efficient antioxidant activity and bactericidal effect against Eschericia coli and Pseudomonas aeruginosa.

Synthesis of ZnO nanoparticles and evaluation of antioxidant and cytotoxic activity.

ZnO nanoparticles were synthesized by thermal decomposition method and were characterized by UV-vis spectroscopy, XRD, SEM, EDX and TEM analysis. The resultant nanoparticles are nearly spherical and size is in the range of 40-50 nm. The antioxidant behavior of ZnO nanoparticles was assessed by scavenging free radicals of 2,2-diphenyl-1-picrylhydrazyl hydrate (DPPH) with varying nanoparticle concentration and time interval individually. The DPPH scavenging activity was monitored by UV-vis spectrophotometer. ZnO nanoparticles were also showing cytotoxic activity which was studied by hemolytic potentiality test.

An efficient quasi solid state dye sensitized solar cell based on polyethylene glycol/graphene nanosheet gel electrolytes

A poly(ethylene glycol)/graphene nanosheet quasi solid gel electrolyte was synthesized using an in situ polymerization technique for dye-sensitized solar cells (DSSCs). Fabrication of the DSSCs was carried out by sandwiching the poly(ethylene glycol)/graphene nanosheet (PEG/graphene nanosheet) gel electrolyte in between the dye sensitized TiO2 nanoflower photoanode and platinum based counter electrode using a spacer of thickness 25 μm. However, the graphene nanosheets form a network with PEG matrix channels in the gel electrolyte which enhances charge transportation. The PEG/graphene nanosheet gel electrolyte was characterized using Fourier transform infrared spectroscopy, cyclic voltammetry, scanning electron microscopy, transmission electron microscopy, thermal gravimetric analysis, atomic force microscopy and electrochemical impedance spectroscopy. Electrochemical impedance spectroscopy results demonstrate the reduction of charge transfer resistance (Rct) with the incorporation of graphene nanosheets which promotes charge transportation through the gel electrolyte. The reduction of (Rct) enhances the device efficiency which was observed in the current density vs. voltage (J–V) measurements and thereby the incident photon to converted electron (IPCE) curves. The maximum photovoltaic conversion efficiency of 5.16% was achieved.

Designing hierarchical NiO/PAni-MWCNT core–shell nanocomposites for high performance super capacitor electrodes

A novel type of nanocomposite material based on multi walled carbon nanotubes (MWCNT) and NiO nanoparticles coated with polyaniline (PAni) has been prepared by an in situ polymerization technique. Transmission electron microscopy confirms the core–shell structure of the composite. TG-analysis reveals that NiO/PAni-MWCNT nanocomposites exhibit better thermal stability than NiO-PAni. The synthesized nanocomposites have good conductivity and excellent electrochemical properties. The specific capacitance values of these composites were measured from their galvanostatic charge–discharge curves. The particles show a high value of specific capacitance and can find potential application as super capacitor electrodes.

Synthesis and characterization of SiO2/polyaniline/Ag core–shell particles and studies of their electrical and hemolytic properties: multifunctional core–shell particles

Three layers of conducting core–shell nanocomposite particles composed of SiO2/polyaniline (PAni)/Ag were prepared in the presence of silicon dioxide (SiO2) in an aqueous solution containing sodium dodecyl benzenesulfonate (SDBS) as a surfactant. SiO2 nanoparticles were coated by PAni, which results in the formation of core–shell nanocomposites. Silver nanoparticles were synthesized by a citrate reduction method. Ag nanoparticles could be electrostatically attracted onto the surface of SiO2/PAni nanocomposites, leading to the formation of SiO2/PAni/Ag nanocomposites with a core–shell structure. The products were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), current–voltage (I–V) analysis and cyclic voltammetry (CV). The resultant nanocomposites have good biological properties.

Designing Self-Healing Polymers by Atom Transfer Radical Polymerization and Click Chemistry

The development of smart self-healing polymeric materials and composites has been the subject of a tremendous amount of research over last few years. When self-healing materials are mechanically damaged, either internally (via crack formation) or externally (by scratching), they have the ability of restoring their original strength and recovering their inherent properties. For polymers to exhibit such a healing ability, they must contain some functionality which will either rebound among themselves or have the ability of coupling with other functionalities. Preparation of such multifunctional and well-defined macromolecules requires a smart selection of a controlled polymerization technique in combination with appropriate coupling reactions. Among all the polymerization techniques introduced so far, atom transfer radical polymerization (ATRP) is the most versatile owing to its exceptional properties like preparation of polymer with predetermined molecular weight, narrow polydispersity index, predetermined chain-end functionality, and tunable architecture. Click chemistry is an extremely powerful coupling approach which in combination with ATRP can be used for generation of polymers with almost all of the desired properties. In this chapter, an overview on the use of ATRP and click chemistry for polymerization of various “clickable” monomers using “clickable” ATRP initiators is provided along with other post-polymerization modification strategies that can be used to construct macromolecules with self-healing ability.