Sajad Hussain

Multifunctional g-C3N4 nanofibers: A template-free fabrication and enhanced optical, electrochemical, and photocatalyst properties

We have developed a facile, scale up, and efficient method for the preparation of graphitic-C3N4 nanofibers (GCNNFs) as electrodes for supercapacitors and photocatalysts. The as-synthesized GCNNFs have 1D structure with higher concentration of nitrogen that is favorable for higher conductivity and electrochemical performance. Secondly, the high surface area of GCNNF provides a large electrode-electrolyte contact area, sufficient light harvesting and mass transfer, as well as increased redox potential. Thus, the GCNNF supercapacitor electrode shows high capacitance of 263.75 F g(-1) and excellent cyclic stability in 0.1 M Na2SO4 aqueous electrolyte with the capacitance retention of 93.6% after 2000 cycles at 1 A g(-1) current density. GCNNFs exhibit high capacitance of 208 F g(-1) even at 10 A g(-1), with the appreciable capacitance retention of 89.5%, which proves its better rate capability. Moreover, the GCNNF shows enhanced photocatalytic activity in the photodegradation of RhB in comparison to the bulk graphitic-C3N4 (GCN). The degradation rate constant of GCNNF photocatalyst is almost 4 times higher than GCN. The enhanced photocatalytic activity of GCNNF is mainly due to the higher surface area, appropriate bandgap, and fewer defects in GCNNF as compared to GCN. As an economical precursor (melamine) and harmless, facile, and template-free synthesis method with excellent performance both in supercapacitors and in photodegradation, GCNNF is a strong candidate for energy storage and environment protection applications.

Synthesis, photoluminescence and field emission properties of well aligned/well patterned conical shape GaN nanorods

Vertically well aligned, well patterned and high density conical shaped GaN nanorods have been synthesized on a Si substrate by pre-treating the GaN powder with aqueous NH3via a facile chemical vapor deposition method without any catalyst. The nanorods obtained have been characterized by XRD, EDX, TEM, HRTEM and SAED. The observed diameter of the nanorods is 80–100 nm whereas their sharp tip angle measured is 55°. The calculated number of sharp nanorod tips in 1 mm2 is approximately 1.56 × 108, indicating high growth density of nanorods which is crucial for field emission properties. The GaN nanorods have exhibited impressive field emission properties and high stability with a lower turn-on field of 3.35 V μm−1 (0.01 mA cm−2) at room temperature which is sufficient for electron emission devices, field emission displays and vacuum nano-electronic devices. Moreover, uniform, well-aligned, well-patterned and high-density growth of GaN nanorods also make them promising candidates for nano-device design and integration in the future. The room-temperature PL emission with a strong peak at 370 nm (3.35 eV) indicates that GaN nanorods have potential application in light-emitting nano-devices. A vapor–solid growth mechanism for GaN nanorods has also been discussed briefly.

First-principle electronic, elastic, and optical study of cubic gallium nitride.

The ab initio pseudopotential (PP) method within the generalized gradient approximation (GGA) has been used to investigate the electronic, elastic constants, and optical properties of zinc-blende GaN. An underestimated band gap along with higher DOS and squeezed energy bands around the fermi level is obtained. The d-band effect is briefly discussed for electronic band structure calculations. With the help of elastic constants, acoustic wave speeds are calculated in [100], [110], and [111] planes. The dielectric constant, refractive index, and its pressure coefficient are well illustrated. The effect of hydrostatic pressure is explicated for all these properties. The results of the present study are evaluated with the existing experimental and first-principle calculations.

Structural, elastic constant, and vibrational properties of wurtzite gallium nitride: a first-principles approach.

Perdew-Wang proposed generalized gradient approximation (GGA) is used in conjunction with ultrasoft pseudopotential to investigate the structural, elastic constant, and vibrational properties of wurtzite GaN. The equilibrium lattice parameters, axial ratio, internal parameter, bulk modulus, and its pressure derivative are calculated. The effect of pressure on equilibrium lattice parameters, axial ratio, internal parameter (u), relative volume, and bond lengths parallel and perpendicular to the c-axis are discussed. At 52 GPa, the relative volume change is observed to be 17.8%, with an abrupt change in bond length. The calculated elastic constants are used to calculate the shear wave speeds in the [100] and [001] planes. The finite displacement method is employed to calculate phonon frequencies and the phonon density of states. The first- and second-order pressure derivative and volume dependent Gruneisen parameter (γ(j)) of zone-center phonon frequencies are discussed. These phonon calculations calculated at theoretical lattice constants agree well with existing literature.

VLS and VS effect on ferromagnetic behaviour of SnO2 nanobelts

Fabrication of SnO2 nanobelts has been carried out by employing vapour liquid solid (VLS) and vapour solid (VS) mechanism. Nanobelts obtained by VLS mechanism were fabricated at relatively low temperature using Fe powders as a catalyst by means of chemical vapour deposition (CVD) technique. Direct thermal evaporation of SnO2 nanobelts was carried out at 1350°C in the atmosphere of Argon gas via VS mechanism. In both cases, ramp rate was adjusted to 10°C/min. The structural, compositional and morphological characterisations of synthesised SnO2 nanobelts were conducted by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X‑ray spectroscopy (EDS). Magnetic behaviour of the nanobelts was studied by vibrating sample magnetometer (VSM). Cathodoluminescence (CL) spectra were studied using Renishaw Raman spectroscopy system. The growth of nanobelts is found to be homogeneous and dense. The nanobelts formed by VLS mechanism show ferromagnetic behaviour along with some other exciting results whereas the nanobelts formed by VS mechanism show a diamagnetic behaviour. The observed room temperature ferromagnetism in SnO2 nanobelts is superior to other oxides.

Effect of soya-milk based extender on the physico-morphological parameters of Murrah bull semen during cryopreservation

Present investigation was undertaken on three buffalo bulls (Murrah) to study the effect of cryopreservation using Soya-milk extender. A total of 18 collections from three bulls (six collections per bull) were utilized for the study. After initial evaluation, each semen sample was diluted in two different extenders viz. Tris egg yolk extender which acted as control and Soya-milk extender as experimental. Various sperm parameters were studied at equilibration and post-thaw stages. There was no significant difference for percent head abnormalities, percent midpiece abnormalities and acrosome integrity of spermatozoa among extenders at different stages of freezing. The progressive motility and live sperm percentage was significantly higher for Tris egg yolk extender at dilution, equilibration and postthaw stages, but the values for Soya-Milk were also within acceptable limits at all stages of freezing as compared to Tris egg yolk extender. Furthermore the percent tail abnormalities and total sperm abnormalities were significantly higher for soya-milk extender at post thaw. In conclusion the experimental extender could be used as an alternate plant based extender in the cryopreservation of bubaline semen.