L. Syam Sundar

Enhanced Thermal Conductivity and Viscosity of Nanodiamond-Nickel Nanocomposite Nanofluids

We report a new type of magnetic nanofluids, which is based on a hybrid composite of nanodiamond and nickel (ND-Ni) nanoparticles. We prepared the nanoparticles by an in-situ method involving the dispersion of caboxylated nanodiamond (c-ND) nanoparticles in ethylene glycol (EG) followed by mixing of nickel chloride and, at the reaction temperature of 140°C, the use of sodium borohydrate as the reducing agent to form the ND-Ni nanoparticles. We performed their detailed surface and magnetic characterization by X-ray diffraction, micro-Raman, high-resolution transmission electron microscopy, and vibrating sample magnetometer. We prepared stable magnetic nanofluids by dispersing ND-Ni nanoparticles in a mixture of water and EG; we conducted measurements to determine the thermal conductivity and viscosity of the nanofluid with different nanoparticles loadings. The nanofluid for a 3.03% wt. of ND-Ni nanoparticles dispersed in water and EG exhibits a maximum thermal conductivity enhancement of 21% and 13%, respectively. For the same particle loading of 3.03% wt., the viscosity enhancement is 2-fold and 1.5-fold for water and EG nanofluids. This particular magnetic nanofluid, beyond its obvious usage in heat transfer equipment, may find potential applications in such diverse fields as optics and magnetic resonance imaging.

Graphene oxide induces cytotoxicity and oxidative stress in bluegill sunfish cells: Graphene oxide cytotoxic to blue gill sunfish cells

Graphene oxide (GO) is considered a promising material for biological application due to its unique properties. However, the potential toxicity of GO to aquatic organism particularly bluegill sun fish cells (BF‐2) is unexplored or remains poorly understood. GO‐induced cytotoxicity and oxidative stress in BF‐2 cells were assessed using a battery of biomarkers. Two different biological assays (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide and neutral red uptake were used to evaluate the cytotoxicity of GO on BF‐2 cells. It was found that GO induced dose‐ and time‐dependent cytotoxicity on BF‐2 cells. BF‐2 cells exposed to lower concentration of GO (40 μg ml–1) for 24 induced morphological changes when compared to their respective controls. As evidence for oxidative stress lipid peroxidation, superoxide dismutase, catalase, reactive oxygen species and 8‐hydroxy‐2′‐deoxyguanosine levels were increased and glutathione levels were found to decline in BF‐2 cells after treatment with GO. Our findings demonstrate that GO when exposed to BF‐2 fish cells cause oxidative stress.