M. A. Jothi Rajan

Spectroscopic Studies on Pure and Histidine-Functionalized Multiwalled Carbon Nanotubes

ABSTRACT Electron paramagnetic resonance, Fourier transform infrared, and ultraviolet-visible studies were carried out for pure and histidine-functionalized multiwalled carbon nanotubes. Electron paramagnetic resonance absorption spectral data were found to be the best fit for the Gaussian lineshape. The g-values indicate the presence of magnetic impurities in the samples and the interaction between the localized electrons and delocalized electrons in the nanotubes trapped at defects or magnetic ion sites. The electron spin concentration decreases with increasing concentration of histidine, which implies that the unpaired electrons undergo a reduction process in the histidine-functionalized multiwalled carbon nanotubes. Fourier transform infrared study confirms the presence of functional groups in pure and histidine-functionalized multiwalled carbon nanotubes. Ultraviolet-visible study reveals the formation of a charge transfer complex in histidine-functionalized multiwalled carbon nanotubes.

Ionic Conductivity and Power Conversion Efficiency Study of KI Incorporated Glucosyl Carboxonium Ion-based Biopolymer Crust Electrolyte

The impedance of well-characterized KI-incorporated glucosyl carboxonium ion-based biopolymer crust electrolytes up to a maximum 2.7 wt% was measured using electrical impedance spectroscopy. Enhanced ionic conductivity of 2.3657 × 10−2 S cm−1 on the addition of 2.7 wt% of KI was observed in contrast to earlier reported value for pure GCI of 4.5278 × 10−4 S cm−1. This is attributed due to the increased concentration of KI in the system and is corroborated with increased ion density (n), mobility (µ), and diffusion coefficients (D). Dielectric and modulus study shows the capacitive nature of electrolyte. Fabricated dye-sensitized solar cell using pure glucosyl carboxonium ion crust and KI-incorporated glucosyl carboxonium ion crust shows the efficiency of 1.19% for pure and shows the efficiency of 2.14% for 2.6 wt% of KI in glucosyl carboxonium ion at 1 sun condition.

Effect of Prolonged Duration of Gelatinization in Starch and Incorporation with Potassium Iodide on the Enhancement of Ionic Conductivity

ABSTRACT Three systems of starch-based crust electrolytes were prepared using various gelatinization times, various weight percentages (wt%) of starch, and various wt% of starch incorporated into potassium iodide. All the samples were subjected to electrochemical impedance spectroscopy, X-ray diffraction spectroscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, and transference number measurements. Electrochemical impedance spectroscopy shows that 1.7 wt% of starch has maximized the room temperature conductivity of the electrolyte to 1.4587 × 10−4 S cm−1. The conductivity was enhanced to 4.5278 × 10−4 S cm−1 on the increment of starch’s wt% from 1.7 to 3.2. This conductivity was further enhanced to 3.4609 × 10−3 S cm−1 on the addition of 0.3 wt% of potassium iodide. The conductivity enhancement was found due to the formation of glucosyl carboxonium ions. The effect of longer heating time in gelatinization is attributed to the formation of glucosyl carboxonium ions. X-ray diffraction spectroscopy affirms the reduction in crystallinity of starch. Scanning electron microscopy analysis shows the porous morphology of starch electrolyte, and addition of potassium iodide shows the morphology of bean nuts like particles seated on the pores. Fourier transform infrared confirms the degradation of starch. Transference number measurements of the crust electrolyte shows that ions are the dominant conducting species. All the results are authenticating that the conductivity enhancement in starch-based crust electrolyte is due to starch and the addition of inorganic salts. GRAPHICAL ABSTRACT

Peptide assisted synthesis and functionalization of gold nanoparticles and their adsorption by chitosan particles in aqueous dispersion

We have reported a novel method of synthesis of gold nanoparticles (GNPs), using two different peptides, e.g. glutathione (GSH) and glycyl-glycine (GG), as reducing agents. The formation of GNPs was observed with the development of the surface plasmon resonance (SPR) peak in UV-visible spectrum. The nanoparticles phase has been investigated using powder x-ray diffraction (XRD) method and has been seen to be single phase. The as-synthesized GNPs were not fully covered by the used peptides as seen by the thermogravimetry analysis (TGA), and therefore, trisodium citrate (TSC) has been used further as a ‘filler’ agent for GNPs to become well dispersible in aqueous medium. The Fourier transform infrared (FTIR) spectroscopy method has confirmed the presence of peptides and TSC coatings on the nanoparticles’ surface. In comparison, the GNPs formed using GG have been observed to be more stable than those formed using GSH. The nanoparticle size was measured using XRD, dynamic light scattering (DLS) and transmission electron microscopy (TEM). These dispersions were further used to investigate the interaction between the GNPs and chitosan (CS) microparticles. The effects of this interaction were studied using UV-visible spectroscopy, DLS and FTIR. XRD and TEM showed that GNPs were uptaken by CS microparticles.

Sonochemical Synthesis of Poly (Methyl Acrylate)

Polymers are prepared by various methods. The method of preparation plays an important role in deciding many of the physical properties of polymers. In this work Poly (Methyl Acrylate), PMA, is synthesized by free radical addition polymerization in the presence a monomer, an initiator under the influence of ultrasound. Methyl Acrylate (E-Merck, India) of proper strength is mixed with aqueous sodium peroxodisulphate solution of known strength and the time of passage of ultrasound is varied in steps of 30 minutes and 10 samples of solid PMA are obtained for 10 different periods of passage of ultrasound. Solid PMA samples are purified and air-dried under clean environment. TGA, DTA measurements are done on all the 10 PMA samples. The thermal stability of PMA with the change in the time of passage of ultrasound is discussed quantitatively. The thermal stability of PMA, synthesized sonochemically shows better results over the thermal method of synthesis. However in this paper we report the measurements made on PMA samples synthesized at 30 and 300 minutes sonication periods respectively.

Reduced graphene oxide aerogel networks with soft interfacial template for applications in bone tissue regeneration

Reduced Graphene Oxide aerogels (A-RGO), functionalized with chitosan, were found to induce and/or accelerate the mineralization of hydroxyapatite. The functionalized chitosan acts as a soft interfacial template on the surface of A-RGO assisting the growth of hydroxyapatite particles. The mineralization on these soft aerogel networks was performed by soaking the aerogels in simulated body fluid, relative to time. Polymer-induced mineralization exhibited an ordered arrangement of hydroxyapatite particles on reduced graphene oxide aerogel networks with a higher crystalline index (IC) of 1.7, which mimics the natural bone formation indicating the importance of the polymeric interfacial template. These mineralized aerogels which mimic the structure and composition of natural bone exhibit relatively higher rate of cell proliferation, osteogenic differentiation and osteoid matrix formation proving it to be a potential scaffold for bone tissue regeneration.

Europium-Doped Hydroxyapatite Nanorods: Influence of Silver Doping

In this work, we report the influence of silver nanoparticles of different size on the optical behavior of the europium-doped hydroxyapatite nanorods. The presence of ionic, plasmonically visible a...

Spectroscopic studies on pure and histidine functionalized MWCNTs

Electron spin resonance (ESR), Fourier transform infrared (FTIR) and Ultraviolet-visible (UV-Vis) studies were carried out for pure and histidine functionalized MWCNTs (0.2, 0.4 and 0.6 M concentration of histidine). EPR absorption spectral data found to be best fit for the Gaussian lineshape. The g-values indicate the presence of magnetic impurities in the samples and the interaction between the localized electrons and delocalized electrons in the nanotubes trapped at defects or magnetic ions site. The electron spin concentration decreases with increasing concentration of histidine, which implies that the unpaired electron in the MWCNTs undergo a reduction process in the histidine functionalized MWCNTs. FTIR study confirms the presence of functional groups in pure and histidine functionalized MWCNTs. UV-Vis study reveals that the formation of histidine-MWCNTs charge transfer complex.