Ashutosh Kumar Shukla

Metallic nanoparticles: green synthesis and spectroscopic characterization

Metallic nanoparticles are finding new applications in medical, pharmaceutical, food and agriculture sectors. Applications include drug delivery, targeted cancer remedies, biomarker mapping, gene delivery and molecular imaging. This article reviews green strategies for the preparation of metallic nanoparticles, using enzymes, vitamins, monosaccharides, polysaccharides and biodegradable polymers. Microwave-assisted synthesis is detailed. Then, we review nanoparticle characterization using UV–visible spectroscopy and Fourier transform infrared spectroscopy. We also present applications for water purification.

ESR and optical study of Mn2+ doped ammonium selenate single crystals

ESR and optical absorption studies of manganese doped ammonium selenate single crystals are performed at X-band and room temperature to ascertain the site symmetry and location of impurity ions in the lattice. Manganese ions are expected to enter the lattice interstitially. Various spin Hamiltonian parameters are determined. Optical absorption study is also done and associated distortion in the crystal lattice is estimated.

Electron Magnetic Resonance (EMR) Technique and Nanoparticle Characterization

This chapter summarizes the applications of Electron Magnetic Resonance (EMR) spectroscopy for characterization of nanoparticle systems. It covers review of reported recent research on EMR characterization of metallic nanoparticles and metal oxyhydroxide/metal oxide nanoparticles which are important for technological as well as biomedical applications. Photo generated charge carriers in nanocrystalline materials as studied by EMR are also included in this review. Efforts have been made to highlight open problems that need further investigations.

Electron Paramagnetic Resonance and Optical Absorption of VO2+ Doped Ammonium Selenate Single Crystals

An electron paramagnetic resonance study of vanadyl ions doped in ammonium selenate single crystals is carried out at room temperature. It is found that the VO2+ ion takes up an interstitial site. The spin Hamiltonian parameters obtained from the crystal rotations are g||=1.9576 ± 0.0002, g⊥=1.9889 ± 0.0002, A||=203 ± 2 G, A⊥=78 ± 2 G. An optical absorption study is also carried out to evaluate various bonding parameters. On the basis of these parameters the nature of bonding in the complex is discussed.

EPR AND OPTICAL ABSORPTION STUDIES OF VO2+ DOPED DIAMMONIUM HEXAAQUA MAGNESIUM(?) SULFATE

ABSTRACT Electron paramagnetic resonance (EPR) studies of VO2+ impurity ion in single crystals of diammonium hexaaqua magnesium(II) sulfate are carried out at 9.5 GHz (X-band) at room temperature. Different spin-Hamiltonian parameters are determined. VO2+ is expected to enter the lattice substitutionally. Superhyperfine splitting is also observed. An EPR study of a powder sample is done that supports the data obtained from single crystal studies. Optical absorption studies are also performed at room temperature. The crystal field parameter (Dq), tetragonal parameters (Ds and Dt), and various bonding parameters are evaluated to estimate the covalency and nature of bonding of VO2+ with its different ligands.

Absorption spectrum of Mn2+ ions doped in diammonium hexaaquamagnesium(II) sulfate

Optical absorption is a tool to investigate the site symmetry of metal ion and associated distortion in doped single crystals. It provides the energy of different orbital levels of metal ion and separation among them. Mn2+ ions in various single crystals and glasses have been the subject of recent investigations [1–3]. We have studied optical absorption spectra of Mn2+ doped diammonium hexaaquamagnesium(II) sulfate in order to obtain the energy level ordering using matrices of Tanabe and Sugano [4] and to discuss the associated distortion.

EPR Studies of Mn2+-Doped Diammonium Hexaaqua Magnesium(II) Sulfate

Electron paramagnetic resonance (EPR) studies of Mn2+ impurity in single crystals of diammonium hexaaqua magnesium(II) sulfate have been carried out at 9.3 GHz (X-band) at room temperature. The EPR spectra exhibit a group of five fine structure transitions. The spin-Hamiltonian parameters were determined. Mn2+ enters the lattice interstitially. The EPR spectrum of a powder sample supports the data obtained by single crystal studies. - PACS number: 76.30

Green Synthesis and Spectroscopic Characterization of Nanoparticles

Nanoparticles have many applications in different fields including food and agriculture. Synthesis and characterization of nanoparticles have therefore attracted interest of scientific community. Here we review green methods of synthesis of metal and metal oxide nanoparticles. We describe synthesis using enzymes, monosaccharides, polysaccharides and biodegradable polymers. We explain the role of vitamins as reducing and capping agents in green synthesis of nanoparticles. Microwave assisted synthesis and biobased methods have also been illustrated with examples. We then discuss nanoparticle characterization using UV-Visible spectroscopy and Fourier-transform infrared spectroscopy. Applications in diverse fields including water purification are then highlighted.

EPR Studies of Cerium Dioxide Nanoparticles

This chapter intends to provide a review of EPR spectroscopic characterization of ceria nanoparticles. It covers recent EPR applications to investigate the synthesis, local structure, and distortion of ceria nanoparticles. Room temperature ferromagnetism, toxicological screening, free radical scavenging properties, catalytic effects, and some other properties of ceria nanoparticles as studied by EPR are also included in this chapter.

Role of structural distortion on thermoelectric aspects of heavily Sr2+ doped GdMnO3

Manganites had been proposed as one of the potential n-type oxide materials to develop thermoelectric power generators. In the present investigation, we studied the structural and thermoelectric properties of Gd1-xSrxMnO3 (GSMO) (0.5 ≤ x  ≤ 0.8) polycrystalline ceramics synthesized by a conventional solid-state route. Rietveld refinement of XRD patterns revealed the distorted orthorhombic Pbnm crystal structure in all the compositions. The decrease in J-T distortions, present on the Gd-rich side of GSMO (x  ≤  0.6), due to favored formation of Mn4+ was calculated. Thermoelectric properties such as Seebeck coefficient (S) and electrical conductivity (σ) of these ceramics were measured in the temperature range from room temperature to 900 °C. The negative values of the Seebeck coefficient throughout the temperature range confirm the n-type semiconducting nature in all the compositions. The conduction mechanism (below metal-semiconductor transition) of these materials was analyzed using the small polaron hopping conduction model.Manganites had been proposed as one of the potential n-type oxide materials to develop thermoelectric power generators. In the present investigation, we studied the structural and thermoelectric properties of Gd1-xSrxMnO3 (GSMO) (0.5 ≤ x  ≤ 0.8) polycrystalline ceramics synthesized by a conventional solid-state route. Rietveld refinement of XRD patterns revealed the distorted orthorhombic Pbnm crystal structure in all the compositions. The decrease in J-T distortions, present on the Gd-rich side of GSMO (x  ≤  0.6), due to favored formation of Mn4+ was calculated. Thermoelectric properties such as Seebeck coefficient (S) and electrical conductivity (σ) of these ceramics were measured in the temperature range from room temperature to 900 °C. The negative values of the Seebeck coefficient throughout the temperature range confirm the n-type semiconducting nature in all the compositions. The conduction mechanism (below metal-semiconductor transition) of these materials was analyzed using the small polaro...