Kusha Kumar Naik

Electrodeposition of spinel MnCo2O4 nanosheets for supercapacitor applications

Herein, we report a facile, low-cost and one-step electrodeposition approach for the synthesis MnCo2O4 (MCO) nanosheet arrays on indium doped tin oxide (ITO) coated glass substrates. The crystalline phase and morphology of the materials are studied by x-ray diffraction, energy dispersive x-ray analysis and field-emission scanning electron microscopy. The supercapacitor performance of the MCO nanosheets are studied in a three-electrode configuration in 2 M KOH electrolyte. The as-prepared binder-free electrode shows a high specific capacitance of 290 F g(-1) at 1 mV s(-1) with excellent cyclic stability even after 1000 charge/discharge cycles. The obtained energy density and power density of the MCO nanosheets are 10.04 Wh kg(-1) and 5.2 kW kg(-1) respectively. The superior electrochemical performances are mainly attributed to its nanosheet like structure which provides a large reaction surface area, and fast ion and electron transfer rate.

Field emission properties of ZnO nanosheet arrays

Electron emission properties of electrodeposited ZnO nanosheet arrays grown on Indium tin oxide coated glass substrates have been studied. Influence of oxygen vacancies on electronic structures and field emission properties of ZnO nanosheets are investigated using density functional theory. The oxygen vacancies produce unshared d electrons which form an impurity energy state; this causes shifting of Fermi level towards the vacuum, and so the barrier energy for electron extraction reduces. The ZnO nanosheet arrays exhibit a low turn-on field of 2.4 V/μm at 0.1 μA/cm2 and current density of 50.1 μA/cm2 at an applied field of 6.4 V/μm with field enhancement factor, β = 5812 and good field emission current stability. The nanosheet arrays grown by a facile electrodeposition process have great potential as robust high performance vertical structure electron emitters for future flat panel displays and vacuum electronic device applications.

Electrodeposited spinel NiCo2O4 nanosheet arrays for glucose sensing application

We report the growth of NiCo2O4 nanosheet arrays on a conducting substrate by a simple and highly reproducible electrodeposition method. Non-enzymatic glucose sensing properties of the as-prepared nanosheets are studied. NiCo2O4 nanosheets show a linear response with respect to the change in glucose concentration varying from 5 to 65 μM and exhibit a sensitivity value of 6.69 μA μM−1 cm−2 with a LOD value of 0.38 μM. It is proposed that nanosheets are advantageous for glucose sensing applications because of their large surface area with enormous active edges and superior electrochemical properties providing efficient transport pathways for both electrons and ions.

Electrodeposition of ZnCo2O4 nanoparticles for biosensing applications

We report the growth of ZnCo2O4 nanoparticles on indium tin oxide (ITO) coated glass substrates by a simple and highly reproducible electrodeposition method. The as-deposited ZnCo2O4 nanoparticles are characterized by various structural and microscopical tools for assessing their crystalline and morphological features. Electrochemical sensing properties of the as-prepared ZnCo2O4 nanoparticles towards glucose and dopamine are studied. ZnCo2O4 nanoparticles show linear response with respect to change in glucose concentration varying from 10 to 290 μM and possess an LOD value of 36.9 μM and a sensitivity of 0.92 μA μM−1 cm−2. In a similar way, ZnCo2O4 exhibits a linear response with respect to change in dopamine concentration varying from 5–100 μM with an LOD value of 15.4 μM and a sensitivity of 0.55 μA μM−1 cm−2 respectively.

Enhanced Nonenzymatic Glucose-Sensing Properties of Electrodeposited NiCo2O4–Pd Nanosheets: Experimental and DFT Investigations

Here, we report the facile synthesis of NiCo2O4 (NCO) and NiCo2O4-Pd (NCO-Pd) nanosheets by the electrodeposition method. We observed enhanced glucose-sensing performance of NCO-Pd nanosheets as compared to bare NCO nanosheets. The sensitivity of the pure NCO nanosheets is 27.5 μA μM-1 cm-2, whereas NCO-Pd nanosheets exhibit sensitivity of 40.03 μA μM-1 cm-2. Density functional theory simulations have been performed to qualitatively support our experimental observations by investigating the interactions and charge-transfer mechanism of glucose on NiCo2O4 and Pd-doped NiCo2O4 through demonstration of partial density of states and charge density distributions. The presence of occupied and unoccupied density of states near the Fermi level implies that both Ni and Co ions in NiCo2O4 can act as communicating media to transfer the charge from glucose by participating in the redox reactions. The higher binding energy of glucose and more charge transfer from glucose to Pd-doped NiCo2O4 compared with bare NiCo2O4 infer that Pd-doped NiCo2O4 possesses superior charge-transfer kinetics, which supports the higher glucose-sensing performance.

Enhanced electron field emission from NiCo2O4 nanosheet arrays

Electron emission properties of electrodeposited spinel NiCo2O4 nanosheet arrays grown on Ni foam have been studied. The work function of NiCo2O4 was calculated by density functional theory using the plane-wave basis set and used to estimate the field enhancement factor. The NiCo2O4 nanosheet arrays exhibited a low turn-on field of 1.86 V μm−1 at 1 μA cm−2 and current density of 686 μA cm−2 at 3.2 V μm−1, with field enhancement factor β = 1460 and good field emission current stability. The field emission properties of the NiCo2O4 nanosheet arrays showed enhanced performance compared to chemically prepared NiCo2O4 nanosheets. Hence, the nanosheet arrays have great potential as robust high performance vertical structure electron emitters for future flat panel displays and vacuum electronic device applications.

Glucose sensing and low-threshold field emission from MnCo2O4 nanosheets

Manganese cobalt oxide (MnCo2O4) nanosheets were grown on nickel (Ni) foam by a simple electrodeposition method. The as-synthesized nanosheets were characterized using X-ray diffraction and scanning electron microscopy. The Ni foam supports the growth of MnCo2O4 nanosheets without any aggregation, thereby increasing its catalytic and electronic properties. The electrochemical studies show that MnCo2O4 exhibits excellent electrocatalytic activity towards glucose sensing applications. The MnCo2O4 based glucose sensor shows a good sensitivity value of 8.2 μA μM−1 cm−2, with a response time of 19 s. In addition to this, field emission studies of as-synthesized MnCo2O4 reveal a low turn-on field value of 1.9 V μm−1 and good emission current stability, demonstrating MnCo2O4 nanosheets as a good field emitter material.