V.M. Abdul Mujeeb

Applications of chitosan powder with in situ synthesized nano ZnO particles as an antimicrobial agent.

ZnO nanoparticles are immobilized on the chitosan matrix by an in situ sol-gel conversion of precursor molecules in a single step. Three different composites are prepared by varying the concentration of sodium hydroxide with same quantity of chitosan and zinc acetate dihydrate. The composites were characterized by FTIR, UV-visible spectra, and XRD. The observed decrease in the band width corresponding to OH and NH2 group in the composites is ascribed to the reduction of hydrogen bond due to the presence of ZnO nanoparticles. The direct evidence of the immobilization of nano ZnO particles in the matrix was identified by SEM. The average particle size values obtained for the nanoparticles, using Debye-Scherrer equation from XRD, is in the range 10-18nm. Optical studies proved that all the three composites studied have the same band gap energy (3.28eV) in agreement with the reported values. We observed that the composites possess excellent antimicrobial activity against Gram negative bacteria Escherichia coli (E. coli) and Gram positive bacteria Staphylococcus aureus (S. aureus) than chitosan. Based on the above studies, the biocompatible, eco-friendly and low-cost composite powder could be applied in various fields as an antimicrobial agent.

Flexible chitosan-nano ZnO antimicrobial pouches as a new material for extending the shelf life of raw meat

As a breakthrough to open up the industrial use of novel environmentally benign packaging material, we propose the first report on portable chitosan-ZnO nano-composite pouches that will serve as elite entrants in smart packaging. A facile, one pot procedure was adopted for the preparation of the C-ZnC films. In order to tune the property of C-ZnC films, four different composite films were prepared by varying the concentration of ZnO. The prepared films were found to be much superior when compared to bare chitosan and other conventional films. Two bacterial strains that commonly contaminate in packed meat were selected as target microbes to elucidate the antimicrobial activity of the prepared C-ZnO film. Detailed investigations revealed that the antimicrobial efficiency is linearly related to the amount of ZnO nano-particles in the composite. The C-2 films exhibited excellent antimicrobial activity and was fabricated into packaging pouches for raw meat. The prepared pouches showed significant action against the microbes in raw meat owing to its complete inhibition of microbial growth on the sixth day of storage at 4°C. The C-2 pouches stand as a top-notch material when compared to polyethylene bag in extending the shelf life of raw meat.

Effect of Divalent ion Dopants on the Kinetics of Thermal Decomposition of Potassium Bromate

Isothermal decomposition of KBrO3 has been studied as a function of concentration of the dopants, SO42- and Ba2+ by isothermal thermogravimetry in the temperature range 668 - 683 K. The rate law and the activation energies remained unaltered by doping. The results suggest a diffusion-controlled mechanism, the diffusing species being both K+ and BrO3-.

Green synthesis of pure and doped semiconductor nanoparticles of ZnS and CdS

Abstract Nanoparticles of pure and Cu/Ag-doped CdS and ZnS have been synthesized via chemical bath deposition without using any capping or toxic reagents. The synthesis was carried out through a simple and less expensive green method. The XRD result shows that both pure CdS and ZnS and their doped derivatives are of high crystalline with hexagonal packing structure. The average crystalline size of all nanoparticles was calculated using Debye–Scherrer formula. The crystalline size of nanoparticles of pure samples varied with that of the doped sample. The average crystalline sizes of all nanoparticles are found to be in the range of 5.5–2.2 nm for CdS (from pure to doped) and 4.3–3.4 nm for ZnS, respectively. The band gap values obtained from UV-visible spectra are in the range of 3.5–2.1 eV for CdS and 3.3–2.7 eV for ZnS derivatives, respectively. The FTIR spectral data give characteristic peaks for Cd—S, Cu—S, Ag—S and Zn—S bonds and confirm the formation of respective nanoparticles. The peaks corresponding to the microstructural formation are also observed. The FE-SEM images show the granular morphological structure for all the samples. The agglomeration size of the samples in the range of 10–50 nm for CdS:Cu and 50–100 nm for ZnS:Cu is observed.

A DFT based analysis of adsorption of Hg2+ ion on chitosan monomer and its citralidene and salicylidene derivatives: Prior to the removal of Hg toxicity

A Density functional theory based study of adsorption of the toxic metal Hg (II) ion by chitosan monomer and two of its derivatives; citralidene and salicylidene chitosan, has been performed. The effect of structural features on the stability of studied complexes has been analyzed by using Gaussian03 software package. All the possible conformations of these adsorbents were studied using the global minimum geometries. All the adsorbing sites were studied by placing the metal ion on the centroid of the atoms and the stable conformer of the adsorbent-metal ion complex was identified. Interaction between Hg (II) and the adsorbents is found to be electrostatic. Metal ion binding with nitrogen atom is stronger than that with oxygen atoms in all the cases as the charge density of nitrogen is enhanced on Schiff base formation. The advantage of derivatives over chitosan monomer is their stability in acidic media. ΔE value of the complexes are in the order SC-Hg (II)>chitosan-Hg (II)>CC-Hg (II) which indicates that the stability of complexes increases with increase in energy gap. The study reveals that aromatic Schiff base derivatives of chitosan is better for Hg(II) intake than aliphatic derivatives.

A comparative study on the druggability of Schiff bases and dithiocarbamate derivatives of chitosan

The druggability of the Schiff bases and dithiocarbamate derivatives of chitosan was examined; the oral bioavailability and bioactivity of all these molecules against selected drug targets were investigated, as well as ADME/Tox studies were conducted. It was observed that the Lipinski’s rule of five was satisfied by all the molecules. The Schiff bases and dithiocarbamate derivatives of chitosan also show good bioactivity score for protease and enzyme inhibition. The ADME/Tox studies conducted show that almost all the derivatives are free from toxicity risks, except citral- and sulfur-containing derivatives. Substitution of the –SH group by –NH2 gives better positive results in toxicology studies. From this study, it has been observed that these molecules exhibit fairly good drug score and are orally viable molecules. The mechanism driving their bioactivity might be chelation of chitosan and its derivatives with essential metal ions. Chitosan and the derivatives studied can serve as good lead molecules for further research.

Density functional theory studies of Pb (II) interaction with chitosan and its derivatives.

Density functional theory (DFT) studies of Pb (II) ions interaction with biopolymer chitosan and its derivatives are presented. Schiff bases and N-alkylated/arylated derivatives of chitosan were characterized as adsorbents of lead ions and are studied at monomer level. Natural bond orbital (NBO) analysis was carried out for chitosan and derivatives to understand the donor-acceptor interactions. Molecular electrostatic potential (MEP) maps of the adsorbents were plotted with color code. Global reactivity parameters of adsorbents were calculated on the basis of frontier molecular orbital (FMO) energies. Structure of complexes formed between chitosan and derivatives with Pb (II) ion were examined at B3LYP/LanL2DZ level of DFT. The stability of the complexes are discussed based on the values of Eads. We observed that the N-reduced pyridine carboxaldehyde derivative of chitosan (RPC) forms more stable complex with Pb (II) ions than with other derivatves.

Effect of Particle Size on Non-Isothermal Decomposition of Potassium Titanium Oxalate

Abstract The effect of particle size on the thermal decomposition of potassium titanium oxalate (PTO) has been studied using TG-DTA-DTG techniques in nitrogen atmosphere at different heating rates. The thermal decomposition of PTO undergoes through five stages, finally forming the stable potassium titanate. The theoretical mass loss data agree very well with experimental data for all stages of the thermal decomposition of PTO. The third thermal decomposition stage of PTO, the combined elimination of carbon monoxide and carbon dioxide, were subjected to kinetic analyses by a model free method, which is based on the isoconversional principle. We observed that both the onset and peak temperatures in DTA and DTG and the apparent activation energy are independent of particle size. The kinetic results indicate that the third thermal decomposition stage of PTO, the combined elimination of carbon monoxide and carbon dioxide, undergoes through a single step.

Chitosan–green tea extract powder composite pouches for extending the shelf life of raw meat

In this study, Chitosan–green tea extract composite film was synthesized by a simple one-pot procedure and was ably characterized using XRD, FTIR, SEM, etc. The influence of noted factors such as water content, water solubility, water vapour transmission rate, contact angle and thermal stability was investigated in detail. The antimicrobial and antioxidant potentials of all the synthesized films were determined. Finally, an optimized composite film was crafted into a pouch-like bag for packing raw chicken meat. The efficiency of this smart pouch to extend shelf life of raw meat was compared with the common synthetic packaging material of low-density polyethylene.

Theoretical insights on flavanones as antioxidants and UV filters: A TDDFT and NLMO study

UV radiations can cause several irritations to the skin like sunburn, photo aging and even skin cancer. Sunscreens are widely used to protect the skin against these harmful radiations. One of the ingredients present in these sunscreens are organic molecules capable of absorbing these harmful radiations. Recently, the search is on for antioxidant molecules which can act as UV filters as they can facilitate photo protection. In this study, a computational investigation based on density functional theory (DFT) is attempted on flavanones namely pinocembrin, pinostrobin and alpinetin found in Boesenbergia pandurata. Several quantum chemical descriptors are computed to understand the antioxidant potentiality of these molecules. Quantum chemical descriptors of these flavanone molecules are found to be comparable to that of well-known anti-oxidant quercetin. UV response of these molecules are studied using time dependent density functional theory (TD-DFT) formalism and by means of natural bond orbital (NBO) theory. It could be seen that these molecules exhibit a broad absorption in the UV region 270-390nm. This falls exactly in the region of harmful UVB and UVA radiation. Thus, these molecules have the potential to absorb the harmful UV radiation. From NLMO cluster studies, the orbital contribution to absorption is explained. In flavanones, unlike other classes of flavonoids, there is a discontinuity in the electron conjugation due to the absence of C2C3 double bond. This might be the key structural feature that leads to the absorption of these molecules to be centered around the UV region. These molecules can thus be treated as promising candidates for antioxidant UV filters in sunscreens.