Vijai K. Rai

Decoration of GO with Fe spinel-Naf/DMAP: an electrochemical probe for sensing H2O2 reduction

We herein report the preparation of graphene oxide decorated with Fe spinel (Fe3O4)-Naf/DMAP for an unprecedented and highly selective non-enzymatic electrochemical sensing of hydrogen peroxide reduction. The linking of 3,7-bis (dimethylamino)-phenothiazin-5-ium chloride (DMAP) to the graphene oxide occurred via electrostatic interactions of the cationic organic compound with negatively charged oxygen-containing groups (–COO− and –O−) available on the edges of the graphene oxide. Fe3O4 (Fe2+, Fe3+) nanoparticles were adhered further on SO3− moieties of the Nafion coated over the DMAP-GO/GCE through electrostatic interactions. This green approach was used to prepare a derived graphene oxide hybrid nano-material. This material was characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), UV-visible spectroscopy, X-ray diffraction (XRD), and cyclic voltammetry (CV). The prepared material was utilized to detect H2O2 subjected to electrocatalytic reduction and to determine its concentration in the linear range of 5.5 μM to 2.4 mM. Nafion was employed as a dispersion medium, and an anchor for Fe3O4 to make the composite and to prevent interfering effects of other metabolites. The detection limit of this highly selective and highly reproducible film was estimated to be 0.6 μM with a sensitivity of 32.0 μA mM−1 cm−2.

A co-operative effect of visible light photo-catalysis and CoFe2O4 nanoparticles for green synthesis of furans in water

A novel approach to poly-functionalized furan synthesis is disclosed via oxidative decarboxylative [3+2] cycloaddition using co-operative catalysis by visible light and CoFe2O4 nanoparticles under ambient reaction conditions with water as a solvent. Although the reported method is efficient without catalyst in the presence of visible light (70% yield in 4 h at rt), the use of catalyst not only increases the yield (91%) but also accelerates the conversion rate (2 h at rt).

Bi(NO3)3.5H2O catalyzed phosphonylation of aldehydes: An efficient route to α-hydroxyphosphonates

GRAPHICAL ABSTRACT ABSTRACT The Bi(NO3)3.5H2O mediated synthesis of α-hydroxyphosphonates via phosphonylation of aldehydes is reported herein. Both conventional and microwave technology was efficiently applied to range of aromatic, heteroaromatic, α,β-unsaturated aldehydes under solvent-free conditions. The solvent free conditions, avoidance of toxic reagents and excellent yield are some of the remarkable features of this protocol to access the medicinally privileged structure, α-hydroxyphosphonates.

Facile construction of AuNP modulated SDS-wrapped G-TC-tailored electrode for sensitive detection of ascorbic acid

A rapid and sensitive tailor-made electrode based on a gold nanoparticle (AuNP)-modulated hydrophilic sodium dodecylsulfate (SDS)-wrapped graphene (G)-tolonium chloride (TC) (GSTG) nanocomposite was designed step-by-step in an easy and green way for the detection of ascorbic acid (AcA). At a GSTG/chitosan(CHIT)-modified glassy carbon electrode (GCE), the oxidation potential of ascorbic acid not only appeared at a lower overpotential +200 mV vs. Ag/AgCl, but also the anodic current was enhanced about 20.8 times as compared to a bare GCE. Under optimal conditions, a GSTG/CHIT-modified GCE-based electrochemical sensor was fabricated for electrocatalytic oxidation of ascorbic acid with a high sensitivity of 4017.0 μA mM−1 in a wide linear range of 3 × 10−4–1 × 10−2 mM. The limit of detection was calculated to be 0.07 μM and the sensor was also investigated for the determination of ascorbic acid in real samples (Vitamin C tablets) with satisfactory results.

Bio-inspired unprecedented synthesis of reduced graphene oxide: a catalytic probe for electro-/chemical reduction of nitro groups in an aqueous medium

The first green reduction of graphene oxide (GO) using cashew leaf extract as biorenewable reducing agents containing water soluble tannins and gallic acid is reported herein. The synthesized rGO has been well characterized by TEM, SEM, XRD, FTIR, Raman, UV-vis spectroscopy, and cyclic voltammetry. A catalytic probe for electro-/chemical reduction of a nitro group into an amino group in an aqueous medium was also performed successfully.

First graphene oxide promoted metal-free nitrene insertion into olefins in water: towards facile synthesis of activated aziridines

A facile metal-free graphene oxide (GO)-catalyzed synthesis of tosylaziridines using PhINTs as the nitrene source is reported. The reaction involves nitrene insertion into a variety of styrene/nitrostyrene derivatives in the presence of iodine at room temperature and in water. The envisaged process is highly green, operationally simple, it employs metal-free catalysis and it affords excellent yields (85–92%) and high diastereoselectivity (95–98%) of the Z-isomer of the product. The catalyst used could be recycled for further use in other reactions.

Visible-light driven regioselective synthesis of 1H-tetrazoles from aldehydes through isocyanide-based [3 + 2] cycloaddition

A novel and green Co@g-C3N4 catalyzed visible light driven direct regioselective synthesis of 1H-tetrazoles directly from various aldehydes and sodium azide is reported. Herein, NaN3 not only behaves as a three-nitrogen donor of the tetrazole ring but also it converts aldehyde into isocyanide as a one-nitrogen source. The regioselectivity of the product, operational simplicity, ambient reaction conditions, no use of column chromatography for purification, excellent yield of products (84–95%) and recyclability of the catalyst up to five times without any substantial change in the morphology and catalytic efficiency are the salient features of the envisaged protocol.