C. Gopalakrishnan

Optical, bactericidal and water repellent properties of electrospun nano-composite membranes of cellulose acetate and ZnO.

In this report, ZnO nanoparticles embedded cellulose acetate (CA) fibrous membrane with multifunctional properties have been prepared through electrospinning method. The morphology of the electrospun composite membrane was analyzed by scanning electron microscope (SEM). It was found that the polymer concentration in the solution has a significant effect on the morphology of the fibers. The optical property of the sample was tested using photo luminescence (PL) spectra. There is no significant change in the emission features of cellulose acetate with the addition of ZnO. The anti-bacterial property of the sample was studied using disk diffusion method. The wettability of the pure and composite fibrous membrane was also studied by measuring the contact angle of water on the membrane. It was observed that the embedded ZnO in the CA was responsible for the hydrophobic nature of the surface.

Ultrafine dispersed CuO nanoparticles and their antibacterial activity

Copper oxide nanoparticles with a particle size ranging from 80 to 160 nm were prepared by a wet chemical procedure. Copper carbonate hydroxide and sodium hydroxide were used as raw materials. Copper hydroxide was generated as a precursor which was thermally decomposed to CuO nanoparticles. The nanoparticles were characterised using atomic force microscopy, X-ray diffraction and UV-visible spectrometry. The nanoparticles were tested for antibacterial activity against Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella paratyphi and Shigella strains.

A Combinatorial effect of carboxymethyl cellulose based scaffold and microRNA-15b on osteoblast differentiation

The present study was aimed to synthesize and characterize a bio-composite scaffold containing carboxymethyl cellulose (CMC), zinc doped nano-hydroxyapatite (Zn-nHAp) and ascorbic acid (AC) for bone tissue engineering applications. The fabricated bio-composite scaffold was characterized by SEM, FT-IR and XRD analyses. The ability of scaffold along with a bioactive molecule, microRNA-15b (miR-15b) for osteo-differentiation at cellular and molecular levels was determined using mouse mesenchymal stem cells (mMSCs). miR-15b acts as posttranscriptional gene regulator and regulates osteoblast differentiation. The scaffold and miR-15b were able to promote osteoblast differentiation; when these treatments were combined together on mMSCs, there was an additive effect on promotion of osteoblast differentiation. Thus, it appears that the combination of CMC/Zn-nHAp/AC scaffold with miR-15b would provide more efficient strategy for treating bone related defects and bone regeneration.

Study of magnetization reversal of uniaxial Ni nanodots by magnetic force microscopy and vibrating sample magnetometer

In this work we report on the study of magnetization reversal in zero dimensional nickel nanodots patterned using a novel polymer based soft lithography technique. The nanodots, having their easy axis of magnetization normal to the plane of the sample, were characterized by in situ MFM observations, performed under varying magnetic fields to understand the magnetization reversal process. The average demagnetization curve of the sample was obtained from the MFM images. The results compare well with the demagnetization curve obtained from vibrating sample magnetometer (VSM) measurements. Further, the angular dependence of in-plane magnetization reversal process was investigated by studying the magnetization data obtained from the VSM performed at different angles of field orientation with respect to the sample.

Influence Of Plasma Pretreatment In The Formation Of Diamond-Like Carbon Thin Films

Plasma-enhanced chemical vapor deposition has been used to synthesize diamond-like carbon (DLC) thin films. High purity argon and methane gases were used as precursors for the fabrication of the DLC films. The influence of plasma pretreatment on the growth of the DLC films has been studied by subjecting one of the substrates to plasma pretreatment prior to deposition of the DLC films, while maintaining the other substrate as the control. The structural properties of the DLC films have been characterized using atomic force microscopy and Raman spectroscopy. The film grown on the pretreated substrate shows a more uniform coating as compared to the film grown on non-pretreated silicon substrate. The results are discussed based on diffusivity of carbon on silicon and the effect of the plasma pretreatment.

Biocompatibility studies on lanthanum oxide nanoparticles

Lanthanum oxide nanoparticles (LONP), a rare earth metal oxide, have unique properties that make them a suitable candidate for several biomedical applications. We investigated certain key in vitro and in vivo biocompatibility endpoints on LONP. LONP were cytotoxic in in vitro assays and predominantly exerted their action via release of reactive oxygen species. These nanoparticles were neither irritants nor sensitizers in a rabbit model. LONP extracts did not exert any acute systemic toxicity effects in mice. On the other hand LONP exerted toxicity to the liver following oral administration, suggesting that these particles are absorbed from the gastrointestinal (GI) tract and deposited in the hepatobiliary system. LONP did not induce any mutation in the Ames test both in the presence or absence of S-9. These observations provide a base line biocompatibility and toxicity data on LONP. The current findings will also be useful in defining standards for nanoparticle containing devices.

Effects of argon ion bombardment on the structure and magnetic properties of ultrathin Fe filmsa)

Modifications of structural, compositional, and magnetic properties of ultrathin Fe/Si bilayer films induced by Ar+ ion bombardment have been studied. The films were grown at room temperature using an electron beam evaporation system. After evaporation, the samples were bombarded with 3 keV Ar+ ions at fluences around 4×1015 ions/cm2. The self-organization of the Fe nanostructures and the subsequent change in morphology due to the Ar+ bombardment were studied using atomic force microscopy. The structural changes were investigated using grazing incidence x-ray diffractometer. Furthermore, the changes in magnetization and magnetic orientation were studied using vibrating sample magnetometer. It is seen that the Ar+ ion bombardment tends to rotate the easy axis of magnetization of the Fe/Si bilayer film. The results also indicate significant change in structural characteristics, indicating that ion bombardment can be used as an efficient technique of tuning the magnetic properties of ultrathin magnetic films.

Effect of template engineering on morphology and magnetic properties of Ni nanodots fabricated using polysulfone templated lithography

The fabrication of magnetic nanodots using polysulfone templated lithography has been recently explored as a potential technique for bit patterned media fabrication. This work describes the efforts made to identify the ideal template engineering technique so as to develop a standard media fabrication technique. Nanoporous polysulfone membranes were fabricated using a phase inversion process. Nickel nanodots were then evaporated onto silicon substrates using the polysulfone membrane as a mask. The work maps the changes in the structural and magnetic properties of the nanodots fabricated using one of the three different template engineering techniques identified. The samples were studied using atomic force microscopy and a vibrating sample magnetometer. The results indicated that the fabrication of the mask on the substrate itself gave the best feature size, consistent shape and structure and the least deviation in magnetization due to thermal agitation. The dynamics of the growth process has also been postulated based on the results.

Magnetic properties of carbon nanosheets

Two-dimensional carbon nanosheets have been fabricated using inductively coupled radio frequency plasma-enhanced chemical vapour deposition. The structural properties of the nanosheets have been characterised using atomic force microscopy, scanning electron microscopy and X-ray diffractometer. The magnetisation of the samples was studied using vibrating sample magnetometer. The magnetisation of the nanosheets was found to be diamagnetic for fast synthesis processes (30 and 60 min). On the other hand, the nanosheets exhibited a weak ferromagnetic response for the slow (120 min) synthesis process. Energy dispersive spectrometry and atomic absorption spectroscopy confirmed that the magnetisation exhibited by the carbon nanosheets was an intrinsic property and that it was not due to contamination from the substrate. Raman spectroscopy studies revealed that the ferromagnetic carbon nanosheets have a higher ratio (1.20) of graphite peak (I G) to disordered peak (I D) than normally expected (0.75–0.90). Available data indicated that the magnetisation was due to the presence of structural disorders.

SYNTHESIS OF CARBON NANOSHEETS AND CARBON NANOPARTICLES BY RF-PLASMA ENHANCED CHEMICAL VAPOR DEPOSITION

In this study, thin sheets like carbon nanostructures and carbon nanoparticles have been effectively synthesized with CH4 and Ar as precursors at low temperature (< 400°C) by inductively coupled radio frequency plasma enhanced chemical vapor deposition on silicon and glass substrates. The surface morphology and chemical composition were studied by atomic force microscopy (AFM), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) analysis. AFM studies show that the nanoparticles roughly about 70 to 80 nm in diameter surrounded by nanosheets. Nanosheets are about 100 nm in thickness, which attain approximately 1.75 μm lengths. EDS results revealed that the atomic percentage of carbon in the particle like structure is more than that in the nanosheet like structures.