Tito Viswanathan

Structural and optoelectronic properties of P3HT-graphene composites prepared by in situ oxidative polymerization

Poly(3-hexylthiophene) (P3HT)-graphene nanocomposites were synthesized via in situ oxidative polymerization of 3-hexylthiophene monomer in the presence of graphene. The main thrust was to investigate the structural and optoelectronic properties of P3HT-graphene nanocomposites with various graphene concentrations. NMR spectroscopy was used to determine the regioregularity of the polymer composites, whereas Fourier transform infrared spectroscopy and differential scanning calorimetry were used to study their structural and thermal properties. Moreover, cyclic voltammetry was employed to evaluate the HOMO levels of the nanocomposites, while optical spectrophotometry (UV-Vis-NIR) was utilized to determine the optical bandgap of the composites. The information from the aforementioned techniques was used to estimate the HOMO-LUMO energy levels. The results revealed changes in the optical bandgap of P3HT with increasing graphene content. Furthermore, an extensive study aiming at the effect of graphene content on...

Expression of adiponectin in choroidal tissue and inhibition of laser induced choroidal neovascularization by adiponectin

The aim of this study was to investigate the role of adiponectin (APN) in a mouse model of laser induced choroidal neovascularization (CNV). We have shown by immunohistochemistry that the expression of APN, adiponectin receptor 1, adiponectin receptor 2 and T cadherin gradually increased from day 1 to day 7 post‐laser in laser treated mice compared to controls. Recombinant APN (rAPN) was injected intraperitoneally (i.p., 25 μg/mouse) or intravitreally (2 μg/eye) in lasered mice. Another set of lasered mice received APN peptide via i.p. (75 μg/mouse) or intravitreal (30 μg/eye) route. Control mice received a similar treatment with PBS, control protein or control peptide after laser treatment. We found that in the i.p. and intravitreal injection of rAPN resulted in 78% and 68% inhibition respectively in the size of CNV complex compared to control mice. Similar results were observed when APN peptide was injected intravitreally or i.p. Treatment with rAPN or the peptide resulted in decreased levels of vascular endothelial growth factor. Thus, APN inhibited choroidal angiogenesis and may have therapeutic implications in the treatment of wet age related macular degeneration.

Microwave assisted synthesis and characterization of silicon and phosphorous co-doped carbon as an electrocatalyst for oxygen reduction reaction

Doped carbon materials have gained a lot of attention recently due to their wide array of applications. These doped carbon materials have a tremendous potential to replace expensive metal based electrocatalysts in fuel cells. A recently established microwave assisted technique, which does not make use of any inert or reducing gases, has been used to synthesize novel silicon (Si), phosphorous (P) co-doped carbon (SiPDC), as yet not reported in the literature. The method is simple, rapid and economical. Tannin, a renewable resource material is chosen as the carbon source, polyphosphoric acid is utilized as the dehydrating agent/P source and silicone oil is chosen as the Si source. Brunauer–Emmett–Teller analysis reveals the surface area of SiPDC to be 641.51 m2 g−1 and X-ray photoelectron spectroscopy confirms the doping of Si and P at 8.80% and 4.20% respectively. The doped carbon material is utilized for oxygen reduction reaction (ORR) in 0.1 M KOH. The mechanism of ORR is found to be a four electron reduction process based on rotating disk electrode studies. Electrochemical stability studies are performed to evaluate the effectiveness of the catalyst for practical applications.

A Comprehensive Review of Phosphorus Removal Technologies and Processes

Phosphorus removal from polluted water is a global concern considering the detrimental environmental effects that excess phosphorus has. Phosphorus can lead to poor water quality and aquatic life loss due to eutrophication when found in excess in aquatic systems. Industry and agriculture are two of the main sources that lead to the accumulation of phosphorus in wastewater. In an attempt to prevent harmful environmental effects of excess phosphorus, several techniques have been designed to remove phosphorus from wastewater. These techniques range from adsorption and precipitation to enhanced biological phosphorus removal and constructed wetlands. Adsorption and precipitation predominantly require the use of different metals in the phosphorus removal process. This article reviews the results found in the last nine years pertaining to phosphorus removal through the use of adsorption and precipitation using different metal-containing compounds. Advances concerning the parameters of enhanced biological phosphorus removal have also been studied and communicated in this article.

Photovoltaic devices based on high density boron-doped single-walled carbon nanotube/n-Si heterojunctions

A simple and easily processible photovoltaic device has been developed based on boron-doped single-walled carbon nanotubes (B-SWNTs) and n-type silicon (n-Si) heterojunctions. The SWNTs were substitutionally doped with boron atoms by thermal annealing, in the presence of B2O3. The samples used for these studies were characterized by Raman spectroscopy, thermal gravimetric analysis, transmission electron microscopy, and x-ray photoelectron spectroscopy. The fully functional solar cell devices were fabricated by airbrush deposition that generated uniform B-SWNT films on top of the n-Si substrates. The carbon nanotube films acted as exciton-generation sites, charge collection, and transportation while the heterojunctions formed between B-SWNTs and n-Si acted as charge dissociation centers. The current-voltage characteristics in the absence of light and under illumination, as well as optical transmittance spectrum are reported here. It should be noted that the device fabrication process can be made amenable t...

Ammonia Gas Sensing Behavior of Tanninsulfonic Acid Doped Polyaniline-TiO2 Composite

A highly active tannin doped polyaniline-TiO2 composite ammonia gas sensor was developed and the mechanism behind the gas sensing activity was reported for the first time. A tanninsulfonic acid doped polyaniline (TANIPANI)-titanium dioxide nanocomposite was synthesized by an in situ polymerization of aniline in the presence of tanninsulfonic acid and titanium dioxide nanoparticles. X-ray diffraction and thermogravimetric analysis were utilized to determine the incorporation of TiO2 in TANIPANI matrix. UV-Visible and infrared spectroscopy studies provided information about the electronic interactions among tannin, polyaniline, and TiO2. Scanning electron microscopy (SEM) along with energy dispersive X-ray spectroscopy (EDS) and atomic force microscopy (AFM) surface analysis techniques were used to investigate the metal oxide dispersions inside polyaniline matrix. Gas sensors were prepared by spin coating solutions of TANIPANI-TiO2 and TANIPANI composites onto glass slides. Sensors were tested at three different concentrations (20 ppm, 40 ppm, and 60 ppm) of ammonia gas at ambient temperature conditions by measuring the changes in surface resistivity of the films with respect to time. Ammonia gas sensing plots are presented showing the response values, response times and recovery times. The TANIPANI-TiO2 composite exhibited better response and shorter recovery times when compared to TANIPANI control and other polyaniline composites that have been reported in the literature. For the first time a proposed mechanism of gas sensing basing on the polaron band localization and its effects on the gas sensing behavior of polyaniline are reported.

Inhibition of new vessel growth in mouse model of laser-induced choroidal neovascularization by adiponectin peptide II

We have investigated the effect of adiponectin (APN) peptide II on new vessel growth in mouse model of choroidal neovascularization (CNV) or wet type age‐related macular degeneration (AMD). Mice were injected intraperitoneally with APN peptide II, control peptide, or PBS on day 1–7 or day 5–14. APN, AdipoR1, PCNA, and VEGF localization was investigated using confocal microscopy, immunohistochemistry, and RT‐PCR. APN peptide II decreased the relative area of FITC‐dextran perfused vessels by 4‐fold, PCNA expression by 3‐fold, and the number of PCNA stained HUVEC and MAVEC cells by 38 and 46%, respectively. We concluded that APN peptide II inhibits CNV size on days 7 and 14 by inhibiting the proliferation of endothelial cells in vivo and in vitro. APN peptide II may have therapeutic potential to inhibit CNV or wet AMD.

Cleavage of in vitro and in vivo formed lens protein cross-links by a novel cross-link breaker

The purpose of this study was to investigate the effect of N-phenacyl-4,5-dimethylthiazolium bromide (DMPTB), an advanced glycation end product (AGE) cross-link breaker, on lens protein cross-links formed in vitro and in vivo. DMPTB was synthesized and its structure confirmed by its NMR spectrum. To show whether DMPTB can inhibit AGE cross-linking, recombinant human αA-crystallin was glycated with glucose-6-phosphate (G6P) in the presence and absence of DMPTB. Reversal of the already formed cross-links was studied by treating pre-glycated αA-crystallin with DMPTB. The ability of DMPTB to cleave in vivo formed cross-links was ascertained by treating water-insoluble protein fractions from diabetic human lenses with this compound. Glycation of αA-crystallin with G6P showed several high molecular weight (HMW) protein bands on the SDS-PAGE gel; DMPTB inhibited the formation of these HMW proteins. Molecular sieve HPLC confirmed the inhibition of formation of larger aggregates not separated by SDS-PAGE. Treatment of pre-glycated αA-crystallin with DMPTB gave evidence for the degradation of the already formed cross--linked HMW aggregates. Both molecular sieve HPLC and reverse-phase HPLC of the water-insoluble protein fractions from two diabetic human lenses showed that DMPTB could degrade a major portion of the cross-linked HMW aggregates to lower molecular weight proteins. This suggests that the cross-linked proteins in human lenses are formed predominantly by the advanced glycation process and cross-link breakers like DMPTB may have application for the intervention of protein cross-linking in the eye lens.

Evaluation of a Renewable Resource-based Carbon-Iron Oxide Nanocomposite for Removal of Arsenic from Contaminated Water

High arsenic concentration in groundwater is found in many countries, including Bangladesh, India, Vietnam, Thailand and United States. In these countries, the arsenic concentrations have reached dangerous levels for human consumption, especially where the main source of drinking water is from groundwater. Many techniques have been developed for arsenic removal, one being the use of iron oxide or magnetite nanoparticles for heavy metal removal. In this study, a novel tannin-based carbon-iron oxide composite has been developed by us for arsenic removal and results show that a concentration of 100 ppb As in water could be brought down to <10 ppb with the maximum capacity of the arsenic removal calculated to be 1.5 mg As/g Fe in the nanocomposite. The characterization of the nanocomposite and the advantages of using this renewable resource-based nanocomposite are also discussed.

Lignosulfonic Acid-Doped Polyaniline (Ligno-PaniTM) — A Versatile Conducting Polymer

The use of renewable natural resources to develop or improve existing technologies is an important area of research to the scientific community. The availability and functionality of these resources very often make it possible to reduce the cost and improve the properties of existing products. One such natural resource that has received a great deal of attention over the years is lignin.