Vijay Bhooshan Kumar

Recent Advancement in Functional Core-Shell Nanoparticles of Polymers: Synthesis, Physical Properties, and Applications in Medical Biotechnology

This paper covers the core-shell nanomaterials, mainly, polymer-core polymer shell, polymer-core metal shell, and polymer-core nonmetal shells. Herein, various synthesis techniques, properties, and applications of these materials have been discussed. The detailed discussion of the properties with experimental parameters has been carried out. The various characterization techniques for the core-shell nanostructure have also been discussed. Their physical and chemical properties have been addressed. The future aspects of such core-shell nanostructures for biomedical and various other applications have been discussed with a special emphasis on their properties.

Manifestation of the Gouy phase in vector-vortex beams

Experimental measurements of the twirl and changes in the anisotropy of the constant intensity ellipse, and the rotation of the polarization singular lemon pattern a generalized vector-vortex beam experiences around the two foci due to the converging and diverging conical waves and in between, are presented and interpreted as being due to the universal form of the Gouy phase, φ(G)=mπ/2.

Ultrasonic cavitation of molten gallium: Formation of micro- and nano-spheres

Pure gallium has a low melting point (29.8°C) and can be melted in warm water or organic liquids, thus forming two immiscible liquid phases. Irradiation of this system with ultrasonic energy causes cavitation and dispersion of the molten gallium as microscopic spheres. The resultant spheres were found to have radii range of 0.2-5 μm and they do not coalesce upon cessation of irradiation, although the ambient temperature is well above the m.p. of gallium. It was found that the spheres formed in water are covered with crystallites of GaO(OH), whereas those formed in organic liquids (hexane and n-dodecane) are smooth, lacking such crystallites. However, Raman spectroscopy revealed that the spheres formed in organic liquids are coated with a carbon film. The latter may be the factor preventing their coalescence at temperatures above the m.p. of gallium.

Ultrasonic cavitation of molten gallium in water: entrapment of organic molecules in gallium microspheres

Simultaneous formation of gallium microspheres and entrapment of organic materials within them can be accomplished by applying ultrasonic energy to a heated solution of the organic substance that contains the molten metal. This method was used with aqueous solutions (5–10 mM) of four organic compounds (phenanthroline, Congo Red, crystal violet and rhodamine 6G) at 55 °C, a temperature at which the gallium is molten. Irradiation with ultrasonic energy for ca. 3 min dispersed the molten gallium into microscopic spheres, which were found to contain various amounts of these organic compounds. Immersion of the isolated spheres in pure water results in slow leaching of some of the above compounds.

Sonochemical synthesis, structural, magnetic and grain size dependent electrical properties of NdVO4 nanoparticles

NdVO4 nanoparticles are successfully synthesized by efficient sonochemical method using two different structural directing agents like CTAB and P123. The phase formation and functional group analysis are carried out using X-ray diffraction (XRD) and fourier transform infra red (FT-IR) spectra, respectively. Using Scherrer equation the calculated grain sizes are 27 nm, 24 nm and 20 nm corresponding to NdVO4 synthesized by without surfactant, with CTAB and P123, respectively. The TEM images revealed that the shape of NdVO4 particles is rice-like and rod shaped particles while using CTAB and P123 as surfactants. The growth mechanism of NdVO4 nanoparticles is elucidated with the aid of TEM analysis. From electrical analysis, the conductivity of NdVO4 nanoparticles synthesized without surfactant showed a higher conductivity of 5.5703 × 10(-6) S cm(-1). The conductivity of the material depends on grain size and increased with increase in grain size due to the grain size effect. The magnetic measurements indicated the paramagnetic behavior of NdVO4 nanoparticles.

Facile one-step sonochemical synthesis of ultrafine and stable fluorescent C-dots

This work describes a one-step synthesis of carbon dots (C-dots), which is carried out by sonication of polyethylene glycol (PEG-400) for 0.5-3h. The effect of the various experimental parameters, such as sonication time, amplitude and temperature on the size and the fluorescence of the C-dots was studied. It was found that the average diameter of the C-dots is between 2 and 9 nm, depending on the preparation conditions. The highest quantum yield of emission was ∼ 16%. These high fluorescence properties of the C-dots could be used for bioimaging and for solar cell applications.

The sonochemical synthesis of Ga@C-dots particles

This research article is focused on a one-step sonochemical fabrication of carbon dots (C-dots) doped with Ga atom (Ga@C-dots). The synthesis is carried out by sonicating in molten Ga, polyethylene glycol (PEG-400) as the reaction medium for 30–120 min. The produced Ga@C-dots is present in the PEG supernatant and has an average diameter of 5 ± 2 nm. Herein, fluorescence is used to probe the emission of Ga@C-dots and to examine if it differs from that of pristine C-dots. The new product was also characterized by fluorimetric, surface charge potential, and XPS (X-ray photoelectron spectroscopy) measurements. It was revealed that the physical properties of the Ga@C-dots are different from pristine C-dots. We attribute the fluorescence spectrum to energy transfer from the C-dots to the Ga particles. Ga@C-dots show high photosensitization with respect to pristine C-dots.

A hydrothermal reaction of an aqueous solution of BSA yields highly fluorescent N doped C-dots used for imaging of live mammalian cells

In the current study, we present a new and facile synthesis of N doped C-dots (N@C-dots) by hydrothermally reacting an aqueous solution of Bovine Serum Albumin (BSA). The as-prepared quantum dots (QDs) exhibited high quantum yield (44%), high photostability, colloidal stability, and high functionalization efficiency. In addition to their low cost, the N@C-dots have demonstrated a non-toxic and long-lasting effect when applied for imaging human cells (human osteosarcoma U2OS cells). Importantly, with high physiological stability, excellent biocompatibility, and homogenous distribution, the N@C-dot suspension was exploited for high quality cell imaging and to model the biological effects at the nuclear level. Moreover, the water-soluble N@C-dots are nontoxic to the selected cell line in our preliminary evaluation.

Topological structures in vector-vortex beam fields

Optical singularities of index Iu=±1/2 associated with lemon, monstar, and star topological structures in π-symmetric fields and singularities of index Ic=±1 associated with radial, circulation (elliptic), spiral, node, and saddle structures in 2π-symmetric vector fields are studied in detail here. The topological structures in the polarization ellipse orientation field, the Stokes field, and the Poynting vector field are derived from the same vector-vortex beam fields, and their interdependencies are explored using a designed experimental setup. We find that the inherently stable topological approach is much more informative for a deeper understanding of complex vector-vortex beam fields.

Chiral imprinting in molten gallium

Chiral imprinting in molten gallium can be attained by ultrasonic irradiation of molten Ga overlayed by an aqueous solution of D- or L-tryptophan. The products are micro/nanoparticles of Ga encapsulating molecules of one of the enantiomers. After leaching of the enantiomer in pure water, molecular templates are left on the surface of the gallium particles, enabling the entrapment of the specific enantiomer from a solution of the racemate and yielding an enantiomeric excess of 6–12%. The extent of the enantiomeric excess was determined using polarimetry, Chiral HPLC and circular dichroism measurements.