Arvind Agarwal

Dumbbell shaped nickel nanocrystals synthesized by a laser induced fragmentation method

Dumbbell shaped nickel nanoparticles have been synthesized for the first time by laser induced fragmentation of bulk nickel powder in aqueous sodium dodecyl sulfate. The focused output of the third harmonic from a nanosecond pulsed Nd:YAG laser operating at 35 mJ/pulse energy was used for the photo-fragmentation of micron size particles suspended in 50 mM aqueous medium. Nickel anisotropic nanocrystals have been grown by recrystallisation of nickel particles due to laser plasma generated in sodium dodecyl sulfate solution. The Vibrating Sample Magnetometer measurements of dumbbell shaped nickel nanostructure show their good ferromagnetic nature. The mechanism of the synthesis of nanostructure through melting and fragmentation has been also discussed.

Opacity and plasmonic properties of Ag embedded glass based metamaterials

Plasmon resonance in noble metals at the nanoscale is technologically important for various applications in plasmonic devices. The synthesis and optoelectronic properties of silver based plasmonic metamaterials by the ion-exchange (Ag+–Na+) method in a soda-lime glass matrix have been investigated. The effects of annealing temperatures on plasmonic resonance of silver nanoclusters are discussed. During annealing the Ag+ is reduced to Ag0 and subsequently forms silver nanoparticles in the oxidizing atmosphere. The particle sizes calculated from Mie theory are in excellent agreement with the size measured from FEGTEM. The prepared materials were characterized by XRD, UV-vis, RBS, XPS and Raman spectra.

Effect of Mn doping on structural, optical and magnetic properties of SnO2 nanoparticles

The Mn doped SnO2 nanoparticles synthesized by cost effective chemical co-precipitation method has been investigated in the present work. The main focus of the work is to explore the structural, optical and magnetic properties of the SnO2 nanostructures. The crystallite size decreases with increase in Mn doping to SnO2 matrix. The optical band gap of doped SnO2 nanoparticles continuously decreases with increasing Mn ion doping concentration. All the doped SnO2 nanoparticles show paramagnetic behavior at room temperature. SnO2 exhibits ferromagnetic behavior in the range of low external applied magnetic field due to the presence of oxygen vacancies (Vo+) and defects. The undoped SnO2 nanoparticles are spherical in shape while Mn doped SnO2 nanoparticles show the segregation of the spherically shaped nanoparticles. Mn ions only enhance the paramagnetic ordering and degrade the ferromagnetism already present in the SnO2 nanoparticle.

Facile deposition and plasmonic resonance of Ag–Au nanoparticles in titania thin film

Plasmon resonance in noble metals at the nanoscale is technologically important for various applications as it is an important fundamental building block of plasmonic devices. Silver embedded in a glass matrix followed by the deposition of gold embedded in a titania matrix were synthesized in three to four steps by a simple and inexpensive thermal spray pyrolysis technique. The effects of annealing temperature on the plasmonic response and optical activity of silver and gold nanoclusters in soda-lime glass and titanium dioxide matrices have been investigated using UV-visible absorption spectroscopy and photoluminescence spectroscopy. The surface plasmon resonance (SPR) at a hybrid metal–dielectric interface for silver and gold was shown to be influenced by the presence of Ag+ ions and the increased particle size of gold nanoparticles as a function of post annealing temperature. This study reveals that the SPR and the luminescence properties are strongly dependent on the glass matrix, which cannot be achieved in all types of glass slides. Field emission scanning electron micrographs confirming the presence of randomly shaped nanoparticles whose size increases with annealing temperature were inconsistent with the particle size calculated from Mie theory.