Gopala Ram Bhadu

A novel amperometric biosensor for hydrogen peroxide and glucose based on cuprous sulfide nanoplates

A facile, greener and template free route has been developed to produce cuprous sulfide (Cu2S) nanoplates (NPs) with average diameters of 70-150 nm, via one step solvothermal decomposition of a single-source precursor (SSP) Cu(ACDC)2 [ACDC = 2-aminocyclopentene-1-dithiocarboxylate] in the presence of ethylenediamine (EN) and triethylenetetramine (TETA) as structure orienting agents. The precursor complex and nanomaterials were thoroughly characterized by several common techniques and measurements, which give the composition and characteristics of the materials. Amperometric biosensors for hydrogen peroxide (H2O2) and glucose have been constructed by immobilizing the synthesized Cu2S NPs in glutaraldehyde on a glassy carbon (GC) electrode using a direct drop-coating method. The proposed sensor has displayed faster response, high and reproducible sensitivity (64.27 μA mM-1) with linear range of 10 μM to 3.75 mM, towards the electrochemical biosensing of H2O2 at -0.35 V (vs. Ag/AgCl). The sensor also showed high and reproducible sensitivity (61.67 μA mM-1) towards glucose determination with linear range of 10 μM to 3.1 mM. The anti-inference ability of electroactive molecules and favorable stability are some of the advantages of the proposed sensor. Finally, using the sensor we have determined the glucose concentration in a human blood serum sample. The results strongly demonstrate the usefulness of Cu2S NPs for biosensor design and other biological applications.

Colorimetric detection of Cu2+ and Pb2+ ions using calix[4]arene functionalized gold nanoparticles

Abstract.Calixarene functionalized gold nanoparticles (CFAuNPs) have been prepared and characterized by spectroscopic and microscopic (TEM) techniques. To use this material as potential colorimetric sensor, the binding property of this new material has been investigated with a large number of metal ions. It exhibited sharp colour change from dark brown to green and blue, detectable by naked-eye, in the presence of Cu2+ and Pb2+ ions, respectively. It has also triggered substantial change in surface plasmon resonance (SPR) band of the functionalized gold nanoparticles, which in case of Pb(II) is due to the inter particle plasmon coupling arising from the metal-induced aggregation of the nanoparticles and for Cu(II), it is because of the formation of AuCu alloy due to anti-galvanic exchange. The size and aggregation of the nanoparticles are confirmed from HRTEM images, elemental analysis and the line profiling for both the metal ions have been done by STEM-EDX analysis. Graphical AbstractCalixarene functionalized gold nanoparticles have been prepared, which detect Cu2+ and Pb2+ ions with visible colour change. For Pb(II), the colour change is due to metal-induced aggregation of the nanoparticles and for Cu(II), it is due to formation of Au–Cu alloy.

Mesoporous TUD-1 supported indium oxide nanoparticles for epoxidation of styrene using molecular O2

Activation of molecular O2 by metal or metal oxide nanoparticles is an area of recent research interest. In this work, for the first time, we report that indium oxide nanoparticles of <3 nm size dispersed on mesoporous silica (TUD-1) can activate molecular O2 and produce styrene epoxide with a selectivity of 60% and styrene conversion around 25% under mild conditions. It is found that neither indium oxide nor TUD-1 themselves respond to the styrene epoxidation reaction. The computational studies provide evidence that an oxygen molecule is highly polarized when it is located near the interface of both surfaces. The kinetic study shows that the reaction is of pseudo-first order and that the activation energy for styrene conversion is 12.138 kJ mol−1. The catalysts are recyclable for up to four regeneration steps, with the styrene conversion and styrene epoxide selectivity almost unchanged.

Highly active spherical amorphous MoS2: facile synthesis and application in photocatalytic degradation of rose bengal dye and hydrogenation of nitroarenes

Herein, we developed a facile method to prepare amorphous spherical MoS2 via a simple solvothermal decomposition of a precursor complex MoO2(acda)2 (Hacda = 2-aminocyclopentene-1-dithiocarboxylic acid) in the presence of triethylenetetramine (TETA) as a solvent at 200 °C in an inert atmosphere. The as-obtained product was characterized by X-ray diffraction analysis (XRD), electron diffraction X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and UV-vis spectroscopic techniques. The transmission electron microscopic study ascertains the amorphous particles to be of spherical structure. The amorphous MoS2 has shown photocatalytic activity for the degradation of rose bengal (RB) dye under visible light illumination. The kinetics of the decomposition process was also investigated and found to show the pseudo-first-order reaction kinetics with rate constants of 5.0 × 10−2 min−1. Furthermore, amorphous MoS2 was found to be highly effective in catalyzing the reduction of a series of nitroarenes to the corresponding anilines by an eco-friendly protocol.

Fluorescence characteristics of carbon nanoemitters derived from sucrose by green hydrothermal and microwave methods.

In this work, fluorescent carbon nanoparticles (CNPs) were prepared through two green methods i.e. microwave and hydrothermal, using sucrose as carbon precursor. Both of these methods have offered fluorescent CNPs as characterized by TEM, FTIR, zeta potential, absorbance and emission techniques. Excitation dependent emission spectra were exhibited by aqueous dispersion of these CNPs when they were subjected to different excitation wavelengths. The luminous characteristics of CNPs obtained from both of these methods were studied and compared. Their fluorescence stability in water and buffer was monitored for about three months. Influence of pH and various metal ions on emission spectra were investigated.

Multifunctional amine enables formation of polyamide nanofilm composite ultrafiltration and nanofiltration membranes with modulated charge and performance

Conventional thin film composite (TFC) nanofiltration (NF) membranes are positively or negatively charged with an active layer thickness of several nanometers depending on the preparation conditions. Low molecular weight cutoff (MWCO) ultrafiltration (UF) membranes obtained by the phase inversion process show low permeate flux due to the formation of a several micrometre thick skin layer. We have developed an extremely simple route to produce novel TFC NF (MCO∼180 Da) and UF (MWCO∼1 and 10 kDa) types of membranes with an active layer thickness in the range of 12–36 nm via supported interfacial polymerization using polyethyleneimine (PEI) as a monomer. The membrane charge, solute rejection, active layer thickness, and MWCO have been modulated by simple adjustment of diffusion of PEI towards the interfacial zone. TFC UF type of membranes were formed at PEI concentrations in the range of 0.01–0.03% w/v while NF membranes were formed at PEI concentrations in the range of 0.05–0.3% w/v. Our TFC NF membranes exhibited a permeate water flux of 19–24 L m−2 h−1 bar−1 which is about 4–5 times higher than those of PEI-based membranes and 1.3–4 times higher than those of a few commercial NF membranes of similar MWCOs. The TFC UF membranes showed a permeate flux of ca. 48–69 L m−2 h−1 bar−1, about 2–5 times higher than those of some UF membranes reported here. The process is scalable, and the membranes are useful for the separation of charge and neutral solutes with high efficiency.

Fluorescent carbon nanoparticles obtained from charcoal via green methods and their application for sensing Fe3+ in an aqueous medium

Two green methods (microwave and hydrothermal) were employed for the preparation of water dispersible fluorescent carbon nanoparticles (CNPs) from activated charcoal. Microwave and hydrothermally synthesized carbon nanoparticles, (MW-CNPs) and (HT-CNPs), respectively were characterized by microscopic and spectroscopic techniques. A detailed study of their fluorescence characteristics was made. MW-CNPs and HT-CNPs were tested for metal ion selectivity in aqueous medium. MW-CNPs showed selectivity for Fe3+ among the tested metal ions and important studies such as for interference, linear range and limit of detection were carried out. The application of MW-CNPs for detection of Fe3+ in water was demonstrated.