Nagesh Thakur’s research while affiliated with Himachal Pradesh University and other places

In this paper, we have reported the facile microwave-assisted synthesis of reduced graphene oxide- molybdenum disulphide (rGO-MoS2) nanocomposites and its utilization for the electrochemical detection of hydrazine. Nanocomposites were synthesized by using graphite oxide and MoS2 as starting material. The phase composition, morphology, structure and composition were analyzed by powdered X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy and transmission electron microscope. Well-defined morphology, crystallinity and two-dimensional flat structure of rGO-MoS2 nanocomposite have enhanced the detection limit and sensitivity of the sensor. The sensing studies have been conducted by utilizing cyclic voltammetry. The variation in the current with potential was studied by using modified gold electrode, which clearly indicate the enhancement in the peak current (22.0A to 33.9A) and reduction in the overpotential (0.27V to 0.12V) in case of rGO-MoS2 as compared to MoS2. The sensitivity and the detection limit obtained for rGO-MoS2 were found to be 89.89 A µM1 cm2 and 132 nM respectively, ascribed to the easy charge transfer, improved specific surface area and high conductivity of the nanocomposite.

In this study, a facile and scalable synthetic strategy has been developed to prepare 2D layered reduced graphene oxide-tungsten disulfide ([email protected]2) nanocomposite for the electrochemical detection of para nitrophenol (p-NP). The [email protected]2 nanocomposite was synthesized by using tungsten hexachloride (WCl6), thioacetamide (CH3CSNH2) and graphite oxide as starting material through a microwave-assisted route. The formation of the nanocomposite was confirmed by powder X-ray diffraction whereas the 2D structural morphology was established by using field emission scanning electron microscopy. The electrochemical measurement of the as-synthesized nanocomposite was done through cyclic voltammetry. The cyclic voltammetric study was carried out by using a modified glassy carbon electrode (GCE), which indicates the enhancement in the peak current (22.0μA to 33.9μA) in the case of rGO-WS2 as compared to WS2. To have a better understanding of the interaction mechanism, detection limit and sensitivity, differential pulse voltammetry was utilized. This reveals that the as-synthesized rGO-WS2 nanocomposite sensor exhibited good detection limit (2.88 μM), excellent sensitivity (0.589 µA µM-¹ cm-²) and broad linear range (0.50- 12.0 µM). Therefore, it is demonstrated that the [email protected]2 nanocomposite modified GCE provides superior electrochemical sensing application due to the synergistic effect of WS2 (high catalytic activity) and rGO nanosheets (high conductivity).

In this paper, MoS2 nanostructure was synthesized by using ammonium molybdate and thiourea as precursors through annealing in a tube furnace. The nanostructure was characterized for morphological, structural and elemental composition by using a field emission scanning electron microscope (FESEM), powder X-ray diffraction and energy-dispersive X-ray spectroscopy (EDS). The as-synthesized nanostructure was then immobilized on the gold electrode (working electrode) for the electrochemical detection of hydrazine. Cyclic voltammogram shows an intense peak at 22 µA, which proved the high electrocatalytic ability of the sensor. The strong electrocatalytic activity regarding the oxidation of hydrazine is ascribed to good electron transfer ability and high surface area of the nanoparticles. Further, the chronoamperometric study was conducted to estimate the sensitivity and the detection limit of the sensor. The sensor exhibited a detection limit and sensitivity of 196 nM and 5.71 µA/µM cm2 respectively. Promising results such as high electrical conductivity, lower detection limit and high sensitivity of the as-synthesized MoS2 nanostructure have proved its potential towards the electrochemical detection of hydrazine.

The exceptional properties of two-dimensional (2D) organic/inorganic layered materials makes them a promising candidate for use in electrochemical sensing application. In this work, the combination of two different layered materials as reduced graphene oxide (rGO) nanosheets and tungsten disulfide (WS2) separated by Fe3O4 nanoparticles, have been synthesized by microwave irradiation method for the detection of dopamine. Microwave-assisted synthesis of heterostructure rGO-WS2@Fe3O4 nanocomposite is a simple, cost-effective, high-yield and short-reaction time approach. The phase formation, surface morphology and structural properties of the nanocomposite show that the presence of Fe3O4 nanoparticles in between separated layered of rGO nanosheets and WS2 nanosheets prevent the agglomeration of nanoparticles as well as the restacking of the 2D layered materials. Due to well-defined morphologies and crystallinity, as-synthesized rGO-WS2@Fe3O4 nanocomposite was used as an efficient biosensor for the detection of dopamine, a neurotransmitter. The rGO-WS2@Fe3O4 nanocomposite was found to show a low limit of detection (LOD) i.e., 2.74 μM with the sensitivity of 3.18 μA μM⁻¹ cm⁻² for dopamine at a low potential of 0.2 V. Therefore, it is expected that the microwave-assisted cost-effective route can be developed for rGO combined with other inorganic layered materials to design electrochemical sensors for the determination of biological and pharmaceutical samples.

An epinephrine (also known as adrenaline) molecule plays an important role in neurotransmission. Human body is very sensitive to the change in its concentration and its alteration results, many neurological disorders including Parkinson's and Alzheimer's disease. Hence, the sensitivity and selectivity detection of epinephrine is a significant area of study for the diagnosis of diseases due to their abnormal level in body. The sensing of epinephrine has been carried out at biological pH. In the present work, reduced graphene oxide, reduced graphene oxide (rGO)-molybdenum disulphide (MoS2) and reduced graphene oxide (rGO)-molybdenum disulphide (MoS2) decorated Fe3O4 (rGO-MoS2@Fe3O4) nanocomposite was synthesized using microwave-assisted method for the electrochemical detection of epinephrine. The as-synthesized rGO-MoS2@Fe3O4 nanocomposite material was characterized to study the morphological and structural analysis by using X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and Raman spectroscopy techniques. In comparison to the bare glassy carbon electrode, rGO-MoS2@Fe3O4 nanocomposite exhibited superior electrocatalytic activity by decreasing the peak potential from 0.3 to 0.2 V and increasing the peak current from 26 μA to 42 μA (61% higher). Compared with reported literature, the rGO-MoS2@Fe3O4 nanocomposite was found to show a lower limit of detection of 1.37 μM and good sensitivity of 2.87 μAμM⁻¹cm⁻². Thus, from these results, it is concluded that the as-synthesized nanocomposite shows improved electrocatalytic properties.

Transition metal dichalcogenides especially molybdenum and tungsten disulfides have gained immense attention of the researchers worldwide, owning to their structure and properties similar to that of graphene. Versatile properties such as high surface area, resistivity, stability, good mechanical strength, easy charge transfer, feasibility in synthesis of these nanoparticles and tailorable band gap has made them widely applicable in different fields such as catalysis, sensing, adsorbent, lubricants, lithium-ion batteries, supercapacitor and solar light harvesting. This review has focused on synthesis and applications of different heterostructure based on MoS2 and WS2 in the area of chemical sensing. The main idea of this review is to motivate the designing of an efficient and economical nanomaterial based on MoS2 and WS2 for detection of different pollutants.

In this paper, silver-doped zinc oxide nanoparticles were synthesized by using a solution combustion technique, in which zinc nitrate is used as an oxidizer and tartaric acid as a fuel. The phase composition, morphology and structural properties of the as-synthesized zinc oxide and silver-doped zinc oxide were established by using powdered X-ray diffraction, field emission scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy studies. Due to well-defined morphologies and crystallinity, the pure zinc oxide and silver-doped zinc oxide nanostructures can be used as efficient chemical sensors for the detection of p-nitrophenol (PNP). ZnO was found to show a low value of the limit of detection (LOD), i.e., 2.175 µM/L, for p-nitrophenol sensing; moreover, a sharp decrease in the limit of detection was observed with an increase in the concentration of silver ions, and the LOD value decreased to 0.669 µM/L for 10 mol % silver-doped zinc oxide. It is therefore concluded that Ag-doped ZnO shows a lower limit of detection as compared to pure ZnO for p-nitrophenol sensing.