Pranati Nayak

Green approach for the large-scale synthesis of metal/metal oxide nanoparticle decorated multiwalled carbon nanotubes

Herein we report a green approach for the synthesis of metal/metal oxide nanoparticle decorated multiwalled carbon nanotubes using focused solar radiation. The synthesis method demonstrates a large scale, cost effective and spontaneous production of carbon nanotube supported metal/metal oxide nanoparticles for energy and biological applications.

Synthesis of Au-MWCNT–Graphene hybrid composite for the rapid detection of H2O2 and glucose

We report the fabrication of a novel amperometric biosensor based on narrow sized Au nanoparticles (∼4 nm) decorated multiwalled carbon nanotube-solar exfoliated graphene (MWCNTs–sG) hybrid composite as an enzyme immobilizer and sensing matrix for hydrogen peroxide (H2O2) and glucose. Au nanoparticles decorated MWCNTs–sG hybrid composite was synthesized by a green technique using focused solar radiation and was then characterized. The fabricated biosensor displays good catalytic response toward H2O2 redox reaction with wide linearity ranging from 1 mM to 62 mM and with fast amperometric response at a response time of <1 s. The limit of detection is calculated to be 13 μM (S/N = 3). When employed for enzymatic glucose detection, the sensor shows excellent fast response with a response time of ∼0.1 s toward glucose over a concentration range from 50 μM to 20 mM with a detection limit of 2.48 μM. Using Michaelis–Menton enzyme kinetics, the apparent Michaelis–Menton constant (Km) is estimated to be 1.07 mM which depicts high affinity of the enzyme biosensor toward substrate. This is because of the synergistic combination of small sized Au nanoparticles on graphene layers in the presence of MWCNTs as conducting spacer which in turn enhances the electrochemically active surface area. This favors better enzyme immobilization on the hybrid material and promotes direct electron transfer mechanism. In addition, the biosensor shows satisfactory selectivity over coexisting interference species, such as UA, AA, DA, and good reproducibility. On the basis of easy large-scale green synthesis technique of the sensor material, its ultrafast response, wide range of linearity and low detection limit, the present biosensor promises potential applications in electrochemical biosensing.

Influence of localized surface plasmons on Pauli blocking and optical limiting in graphene under femtosecond pumping

The Pauli blocking limit and optical limiting threshold have been found to be modified following silver-nanoparticle decoration of functionalized hydrogen induced exfoliated graphene. Femtosecond Z-scan experiments have been used to measure the Pauli blocking range, optical limiting threshold, and the third order nonlinear susceptibility (χ(3)) values. The observed results have been explained by modified band structure of graphene in the presence of silver nanoparticles and their localized surface plasmon resonances.