Radhaballabh Bhar

Luminescent S-doped carbon dots: an emergent architecture for multimodal applications

A facile route has been developed to synthesise and isolate sulphur doped fluorescent carbon dots for the first time. Such carbogenic quantum dots exhibit a wide band gap of 4.43 eV with a high open circuit voltage (VOC) of 617 mV along with a fill factor (FF) as high as 37%, using phenyl-C60-butyric acid methyl ester (PCBM) as the electron transporting layer. Besides the wide band gap, which is useful in the fabrication of solar cells, sulphur modified carbon dots also exhibit a high fluorescence quantum yield of 11.8% without any additional surface passivation, producing a unique fluorescent probe for further applications. In addition, the particles have a strong tendency to interact with the surface of gold nanoparticles and produce a thin fluorescent layer over their surfaces. Moreover, as they are completely biocompatible in nature, the highly fluorescent S-doped carbon dots have a strong potential for use in bioimaging applications. Interestingly, owing to the presence of oxygen and sulphur functionality, the highly negatively charged particles can easily bind with positively charged DNA-PEI complexes, simply by mixing them, and after interaction with DNA, bright blue fluorescence has been observed under an excitation wavelength of 405 nm .

An efficient electrode for simultaneous determination of guanine and adenine using nano-sized lead telluride with graphene

Herein, lead telluride (PbTe) nanocrystals were chemically synthesized at room temperature via reduction of homogeneous mixtures of tartrate complexes of Pb2+ and Te4+ with sodium borohydride. Graphene (GR) was synthesized through thermal reduction of graphene oxide (GO) in the presence of Zn dust. The structure, phase, and morphology of the synthesized PbTe and GR were characterized by XRD, FESEM, and EDX. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used to study the electro-oxidation behaviors of guanine and adenine molecules on the surface of the composite of lead telluride and graphene-modified graphite paste electrode (PbTe/GRGP). The voltammetric responses revealed that the electrocatalytic properties of these biomolecules (GU and AD) were significantly improved after incorporation of both PbTe nanoparticles and graphene into graphite powder in comparison with those of bare graphite (bare GP) and the graphene graphite paste electrode (GR/GP). CV studies indicate well defined and distinct irreversible oxidation peaks for both biomolecules upon treatment of the PbTe/GRGP electrode with a solution of biomolecules in phosphate buffer (pH 5). DPV measurements illustrated the appearance of two well defined oxidation peaks of GU and AD with a peak potential separation of 289 mV. Under optimized experimental conditions, the modified electrode exhibited wider linear ranges of 4–140 μM and 3–50 μM with the detection limits of 80 nM (S/N = 3) and 70 nM for GU and AD, respectively. Furthermore, the modified electrode was successfully used in spiked human urine and serum samples to determine the GU and AD contents for real time applications.

A simple fast microwave-assisted synthesis of thermoelectric bismuth telluride nanoparticles from homogeneous reaction-mixture

AbstractA new simple chemical method for synthesis of nanocrystalline bismuth telluride (Bi2Te3) has been developed by microwave assisted reduction of homogeneous tartrate complexes of bismuth and tellurium metal ions with hydrazine. The reaction is performed at pH 10. The nano-crystallites have rhombohedral phase identified by XRD. The size distribution of nanoparticle is narrow and it ranges between 50 to 70xa0nm. FESEM shows that the fine powders are composed of small crystallites. The TEM micrographs show mostly deformed spherical particles and the lattice fringes are found to be 0.137xa0nm. Energy dispersive X-ray spectroscopy (EDX) analysis shows the atomic composition ratio between bismuth and tellurium is 2:3. Thermoelectric properties of the materials are studied after sintering by spark plasma sintering method (SPS). The grain size of the material after sintering is in the nanometer range. The material shows enhanced Seebeck coefficient and electrical conductivity value at 300xa0K. The figure of merit is found to be 1.18 at 300xa0K.n Graphical Abstractᅟ

Sildenafil citrate (Viagra) reduces surface roughness of human erythrocytes: Atomic-force-microscopic study

Sildenafil citrate (Viagra) is used to treat erectile dysfunction and pulmonary arterial hypertension. The objective of this study was to analyze the action of sildenafil citrate on normal human erythrocytes in vitro at a concentration (2.5 mg/mL) higher than the prescribed for clinical conditions. Imaging of drug-treated erythrocytes was done using an atomic-force microscope in contact mode in air. Data analysis was performed using the scanning probe-microscopy software WSxM. The study revealed that the drug causes hemolysis of erythrocytes at high concentration in vitro at room temperature. The ghosts (membranes) of erythrocytes with reduced cell size and deformed shape were observed using atomic force-microscope imaging at low magnification. In addition, the high-magnification images revealed alterations in the nanostructural features of the erythrocyte membrane. There was a complete loss of characteristic membrane-architecture pattern. The root-mean-square surface roughness of the cell membrane after drug treatment was measured and found to be significantly less than that of erythrocytes in the native state. Sildenafil citrate causes hemolysis of erythrocytes in vitro at high concentration with significant alterations in morphometric properties, like change in cell shape, reduction in cell dimension, and disruption of membrane cytoarchitecture, along with a severe drop in membrane root-mean-square surface roughness.

Ultrastructure and Chemical Composition of Elephant Hair in the Context of Chemical Signals in the Asian Elephant Elephas maximus

Basic knowledge of chemical signalling in Asian elephants (Elephas maximus) involves identification of the female-emitted-male-received sex pheromone (Z)-7-dodecenyl acetate and a series of malodorous compounds together with frontalin from the temporal gland secretion of adult males. We describe the ultrastructure and lipid chemistry of the tail hair of the Asian elephant which may have special significance in relation to the scent flagging behaviour of receptive females of the species. Scanning electron micrographs of both the surface and cross sections of the elephant hairs show a marked deviation from those observed in the hair of other mammalian species. Chemical analysis of tail and head hair reveals the presence of C8–C24 fatty acids that included straight-chain saturated, unsaturated and some branched-chain compounds. The significance of these fatty acids in relation to flagging behaviour is discussed.