Annamraju Kasi Viswanath

Synthesis of YF3: Yb, Er upconverting nanofluorophores using chitosan and their cytotoxicity in MCF-7 cells

In this work, we described one pot hydrothermal synthesis of surface modified water soluble YF3: Yb, Er upconverting nanofluorophores (UCNFs) using natural biopolymer chitosan. The obtained nanocrystals have undergone X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM) and photoluminescence (PL) studies. The nanoparticles possess uniform particle size distribution with average size about 27 nm. The cytotoxicity results revealed that the chitosan capped nanoparticles exhibit excellent biocompatibility in human breast cancer cells. In conclusion, the water soluble chitosan capped YF3: Yb, Er nanoparticles could be used as a potential candidate in bio-imaging and therapeutic applications.

Synthesis and Characterization of Conducting Polyaniline Doped with Polymeric Acids

Conducting polyaniline doped with polymeric acids was synthesized by a in situ chemical polymerization method. The synthesized polymers were characterized by using UV‐Visible, FT‐IR spectroscopy and SEM analysis. Thermal stability of these polymers was evaluated by using TGA/DSC analysis. Among the three polymeric acids used for doping purpose, poly(vinyl sulphonic acid) doped polyaniline is found to be more conducting than those doped with other acids. From the temperature dependent conductivity measurements, an increase in conductivity with increase in temperature was observed.

Chitosan conjugation: A facile approach to enhance the cell viability of LaF3:Yb,Er upconverting nanotransducers in human breast cancer cells

In this study, chitosan functionalized LaF3:Yb,Er upconverting nanotransducers (UCNTs) with controlled size and shape have been successfully synthesized by a facile one pot precipitation method. The chitosan encapsulated UCNTs show bright upconversion fluorescence upon excitation with 974 nm NIR region. The average crystallite size of UCNTs about 7.6 nm was achieved using chitosan mediated synthesis. The FTIR result confirms the chitosan coating over the LaF3:Yb,Er nanoparticles. Due to the surface modification using natural biopolymer chitosan, the as-prepared nanocrystals show excellent biocompatibility even at high dose at 200 μg/ml. To the best of our knowledge the presented work is the first report on in vitro analysis of chitosan conjugated LaF3:Yb,Er upconverting nanocrystals in human breast (MCF-7) cancer cells. These nanotransducers can be used as luminescent probes for bioimaging and deep tissue cancer therapeutic applications.

Green synthesis of zinc oxysulfide quantum dots using aegle marmelos fruit extract and their cytotoxicity in HeLa cells

Zinc oxysulfide quantum dots have been attracting increasing research interest due to their tunable electronic, optical and magnetic properties. In this paper we report the green synthesis of zinc oxysulfide quantum dots in the range of a few nanometers using aegle marmelos fruit extract through a facile precipitation route. The zinc oxysulfide quantum dots (ZOS QDs) were characterized by X-ray diffraction, ultra violet-visible absorbance spectroscopy, photoluminescence spectroscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, and vibrating sample magnetometry. Energy dispersive X-ray spectroscopy of the synthesized samples indicates that 16% oxygen is incorporated into the zinc sulfide crystal lattice that results in an optical band-gap transformation from direct type for the zinc sulfide cubic phase to a decreased bandgap of 3.46 eV. The vibrating sample magnetometer analysis results showed the existence of room temperature ferromagnetism (RTF) in zinc oxysulfide quantum dots. The bandgap engineering approach adopted in this work to tailor the optical and electronic properties of zinc sulfide with the RTF magnetic properties of zinc oxide will have a significant impact on the development of ternary chalcogenides for magnetic and photonic applications. The prepared ZOS QDs exhibit good cell viability with HeLa cells and the toxicity results obtained from this research work provide a new direction for the development of nontoxic bandgap engineered ZOS based QDs for biological applications. To the best of our knowledge, this is the first report on the biocompatibility of novel ZOS QDs in HeLa cells.

Synthesis of α-Fe2−xAgxO3 nanocrystals and study of their optical, magnetic and antibacterial properties

To be an implicit disinfectant, inorganic nanoparticles have to show chemical stability, minimum cytotoxicity and effective bactericidal activity. Among metal oxide nanoparticles, iron oxide demonstrates a very high structural stability in corrosive biological environments and also has a relatively non-toxic profile in comparison with other metal nanoparticles such as ZnO. Iron oxide nanoparticles also exhibit bacterial growth inhibition properties on a wide spectrum of bacterial species mainly by generating reactive oxygen species (ROS) from water and oxygen. However, the efficiency of their antibacterial activity remains low. Probably, the main reason behind this is the aggregation and occurrence of large flocculates of nanoparticles in aqueous media due to their hydrophobic nature and hence their interaction with bacteria is limited. To overcome all these problems, in this study we incorporate silver ions into α-Fe2O3 to produce magnetic hybrid nanostructures with better colloidal stability and enhanced antibacterial activity due to their synergistic effect. The antibacterial activity of the prepared nanospheres was tested at 3 different concentrations (450, 600, 750 μg) against four bacterial strains – Bacillus subtilis, Staphylococcus aureus, Pseudomonas fluorescens and Escherichia coli using a disc diffusion method. The nanospheres showed a concentration dependent activity profile and remarkably, they were very effective against B. subtilis and P. fluorescens. Their antibacterial effect was found to be comparable to the standard antibiotic streptomycin used in this study. Furthermore, in this work structural, optical and magnetic properties of the prepared samples have been studied using different characterization tools.

Investigation of Spectroscopic and Thermal Properties of Poly(o‐toluidine) Doped with Polymeric Acids

Single step polymerization of poly(o‐toluidine) was carried out by using ammonium persulphate as an oxidizing agent. Formation of the conducting emeraldine salt phase of the polymer was confirmed by the UV‐visible and FT‐IR spectroscopic analysis. The elemental composition of the polymer was evaluated by using a CHNS analyzer. Thermal stability of these polymers was investigated by the thermogravimetric analysis. Among the three polymeric acids used for doping purposes, poly(acrylic acid) doped material was found to show less thermal stability compared to poly(styrene sulphonic acid) and poly(vinyl sulphonic acid) doped poly(o‐toluidine).

Synthesis and Characterization of Poly(o-anisidine) Doped with Polymeric Acids

ABSTRACT Conducting poly(o-anisidine) doped with polymeric acids [viz, poly(styrene sulphonic acid) (PSSA), poly(vinyl sulphonic acid) (PVSA) and poly(acrylic acid) (PAA)] was synthesized by in-situ chemical polymerization method using ammonium persulphate as an oxidizing agent. This is a single-step polymerization process for the direct synthesis of emeraldine salt phase of the polymer. The polymers were characterized by using UV-Vis., FT-IR spectroscopy, thermal analysis, and conductivity measurements. Formation of mixed phases of polymer together with conducting emeraldine salt phase are confirmed by spectroscopic techniques. Thermal analysis shows that PAA doped poly(o-anisidine) undergoes three stage decomposition pattern similar to unsubstituted polyaniline. While, in PSSA and PVSA, doped sample splitting up of the second weight loss stage is observed leading to a four-step decomposition pattern. Room temperature conductivity measurements show less conductivity in poly(o-anisidine) than in polyaniline, due to the cumulative steric as well as electronic effects of the bulky methoxy substituent present at ortho position on the benzene ring. Increase in conductivity with increase in temperature is observed by high temperature conductivity measurements, showing “thermally activated behavior.”

Antibacterial applications of α-Fe2O3/Co3O4 nanocomposites and study of their structural, optical, magnetic and cytotoxic characteristics

Owing to their multiple mechanisms of bactericidal activity, inorganic metal oxides and hybrid metal oxide nanocomposites may serve as a new class of effective disinfectants. Among metal oxide nanoparticles, iron oxide nanoparticles exhibit minimal or no cytotoxicity to human cells with very efficient bactericidal properties over a wide spectrum of bacteria. This paper presents the very first report on antibacterial properties of novel nanocomposites of iron oxide and cobalt oxide nanoparticles against pathogenic bacterial strains B. subtilis, S. aureus, E.coli and S. typhi. The enhanced bactericidal activity of the Fe/Co oxide nanocomposite was the result of synergistic effect of iron oxide and cobalt oxide nanoparticles. The nanocomposites were synthesized using co-precipitation route with increasing cobalt content in the sample and further characterized using XRD, TEM, Raman and VSM to investigate structural, optical and magnetic properties of the prepared nanocomposites, respectively. Also, the prepared nanocomposites were highly biocompatible and found non-toxic to human cell line MCF7.

Single Step Polymerization of Conducting Poly(O-Toluidine) Doped with Camphor Sulfphonic Acid: Synthesis and Characterization

Single step chemical polymerization of o-toluidine was carried out by using ammonium persulphate as an oxidizing agent. This is a direct process to synthesize the conducting emeraldine salt phase of the polymer using camphor sulphonic acid as a dopant. The polymer was characterized by UV-Vis. and FT-IR spectroscopy, scanning electron microscopy, TGA/DSC, elemental analysis and conductivity measurements. This method offers a polymer having very good physico-chemical properties with good electrical conductivity.

Understanding the effect of bound excitons on two photon absorption process in anatase TiO2 nanospheres using ultrafast pulses

Nanoparticles of Titanium dioxide (TiO2) with its unique optical and electronic characteristics is an important material for photochemical catalysis. The efficiency of catalytic activity of TiO2 anatase nanostructures is greatly influenced by the photo-generated bound excitons. It is found that the interaction of bound excitons generated in TiO2 enhances the cubic nonlinearity of the system due to strong oscillation of photo-generated bound excitons. The trapped electron hole pair concentration is directly proportional to the photocatalytic efficiency of the TiO2 anatase nanostructures. In our report, we show how these photo-generated bound excitons play a significant role in origin of third-order optical nonlinearities. In particular, we have measured large phase shift and seen two photon absorption process through closed and open aperture Z-scan, respectively, using femtosecond pulses at 532nm.