Ajay K. Mishra

Chitosan-based nanomaterials: A state-of-the-art review

This manuscript briefly reviews the extensive research as well as new developments on chitosan based nanomaterials for various applications. Chitosan is a biocompatible and biodegradable polymer having immense structural possibilities for chemical and mechanical modification to generate novel properties and functions in different fields especially in the biomedical field. Over the last era, research in functional biomaterials such as chitosan has led to the development of new drug delivery system and superior regenerative medicine, currently one of the most quickly growing fields in the area of health science. Chitosan is known as a biomaterial due to its biocompatibility, biodegradability, and non-toxic properties. These properties clearly point out that chitosan has greater potential for future development in different fields of science namely drug delivery, gene delivery, cell imaging, sensors and also in the treatment as well as diagnosis of some diseases like cancer. Chitosan based nanomaterials have superior physical and chemical properties such as high surface area, porosity, tensile strength, conductivity, photo-luminescent as well as increased mechanical properties as comparison to pure chitosan. This review highlights the recent research on different aspect of chitosan based nanomaterials, including their preparation and application.

Dendrimers, mesoporous silicas and chitosan-based nanosorbents for the removal of heavy-metal ions: A review

The application of nanomaterials as nanosorbents in solving environmental problems such as the removal of heavy metals from wastewater has received a lot of attention due to their unique physical and chemical properties. These properties make them more superior and useful in various fields than traditional adsorbents. The present mini-review focuses on the use of nanomaterials such as dendrimers, mesoporous silicas and chitosan nanosorbents in the treatment of wastewater contaminated with toxic heavy-metal ions. Recent advances in the fabrication of these nanoscale materials and processes for the removal of heavy-metal ions from drinking water and wastewater are highlighted, and in some cases their advantages and limitations are given. These next-generation adsorbents have been found to perform very well in environmental remediation and control of heavy-metal ions in wastewater. The main objective of this review is to provide up-to-date information on the research and development in this particular field and to give an account of the applications, advantages and limitations of these particular nanosorbents in the treatment of aqueous solutions contaminated with heavy-metal ions.

Synthesis and DNA binding studies of Ni(II), Co(II), Cu(II) and Zn(II) metal complexes of N1,N5-bis[pyridine-2-methylene]-thiocarbohydrazone Schiff-base ligand.

The thiocarbohydrazone Schiff-base ligand with a nitrogen and sulphur donor was synthesized through condensation of pyridine-2-carbaldehyde and thiocarbohydrazide. Schiff-base ligands have the ability to conjugate with metal salts. A series of metal complexes with a general formula [MCl2(H2L)]·nH2O (MNi, Co, Cu and Zn) were synthesized by forming complexes of the N1,N5-bis[pyridine-2-methylene]-thiocarbohydrazone (H2L) Schiff-base ligand. These metal complexes and ligand were characterized by using ultraviolet-visible (UV-Vis), Fourier Transform Infrared (FT-IR), 1H and 13C NMR spectroscopy and mass spectroscopy, physicochemical characterization, CHNS and conductivity. The biological activity of the synthesized ligand was investigated by using Escherichia coli DNA as target. The DNA interaction of the synthesized ligand and complexes on E. coli plasmid DNA was investigated in the aqueous medium by UV-Vis spectroscopy and the binding constant (Kb) was calculated. The DNA binding studies showed that the metal complexes had an improved interaction due to trans-geometrical isomers of the complexes than ligand isomers in cis-positions.

Spectral, thermal and in vitro antimicrobial studies of cyclohexylamine-N-dithiocarbamate transition metal complexes

Transition metal complexes of the type [M(L)(2)] and those containing monodentate phosphines of the type [M(L)(2)(PPh(3))] {M=Ni, Co, Cu and Zn; L=cyclohexylamine-N-dithiocarbamate; PPh(3)=triphenylphosphine} have been synthesized. The complexes were characterized using IR, UV-vis, NMR spectroscopy, and thermal analysis (TGA). The (1)H NMR, (13)C NMR and (31)P NMR showed the expected signals for the dithiocarbamate and triphenylphosphine moieties. The spectral studies in all compounds revealed that the coordination of metals occurs via the sulphur atom of the dithiocarbamate ligand in a bidentate fashion. Thermal behavior of the complexes showed that the complexes were more stable than their parent ligands. The ligand moiety is lost in the first step and the rest of the organic moiety decomposes in the subsequent steps. Furthermore, the ligand and their metal complexes were screened in vitro for their antibacterial activity against Escherichia coli, Staphylococcus aureus, Salmonella typhi, Enterococcus faecalis, Pseudomonas aeruginosa and Bacillus cereus and antifungal activities against Aspergillus flavus, Aspergillus carbonarius, Aspergillus niger and Aspergillus fumigatus. The metal complexes exhibited higher antimicrobial activity than the parent ligands. Generally, the zinc complexes were effective against the growth of bacteria with Zn(L)(2) displaying broad spectrum bacteriocidal activity at concentrations of 50microg/mL; and Ni(L)(2) was more effective against the growth of fungi at concentrations of 100-400microg/mL under laboratory conditions.

Biosorption potential of Gum ghatti-g-poly(acrylic acid) and susceptibility to biodegradation by B. subtilis

This article reports the biosorption potential of Gum ghatti (Gg)-grafted-acrylic acid (AA) polymer and its susceptibility to biodegradation by Bacillus subtilis (BS) in two different liquid media, i.e. phosphate buffered saline (PBS) and mineral salt medium (MSM). The progress of biodegradation was monitored after every 15 days using FT-IR and SEM techniques. The degradation of the polymer was further evidenced by a loss of weight of 23.2% and 27% in BS-MSM and BS-PBS, respectively, after 60 days. The AA-grafted polymer was then utilized for the removal of Pb(II) and Cu(II) from aqueous solution. The adsorption isotherm data were studied using Langmuir, Freundlich, Temkin, Flory-Huggins and Dubinin-Kaganer-Radushkevich isothermal models. High values of correlation coefficients confirmed the applicability of Langmuir isotherm model used to determine the adsorption capacity of the AA-grafted polymer. The maximum adsorption capacity was found to be 84.74 mg/g for Cu(II) and 310.55 mg/g for Pb(II). Kinetic data were evaluated using pseudo first order, pseudo second order, Elovich, intraparticle diffusion and liquid film diffusion models. The experimental kinetic data fitted well with the pseudo second order rate model.

Stabilisation of silver and copper nanoparticles in a chemically modified chitosan matrix

This work describes the stabilisation of silver and copper nanoparticles in chemically modified chitosan colloidal solution. Chitosan-N-2-methylidene-hydroxy-pyridine-6-methylidene hydroxy thiocarbohydrazide (CSPTH) was used as a stabilising and reducing agent for silver and copper nanoparticles. The modified chitosan derivatives and the synthesised nanoparticles were characterised by Fourier transform infrared (FT-IR) spectroscopy, Ultraviolet-visible (UV-Vis) spectroscopy and X-ray diffraction (XRD). Particle size, morphology and segregation of the nanoparticles were determined by transmission electron microscopy (TEM). The size of the nanoparticles was found to be less than 20 nm and 50 nm for silver and copper nanoparticles, respectively. These nanoparticles were stabilised in a chemically modified chitosan solution and their properties were studied using fluorescence spectroscopy, photoluminescence spectroscopy and surface-enhanced Raman scattering (SERS). The optical properties of silver nanoparticles in surface plasmon band (SPB) were enhanced at 407 nm compared to those of copper nanoparticles. Fluorescence (400 nm and 756 nm), photoluminescence (450 and 504 nm) and Raman scattering (1382 and 1581 cm(-1)) properties for the copper nanoparticles were superior to those of the silver nanoparticles.

Intelligent Nanomaterials: Processes, Properties, and Applications

The last three decades have seen extraordinary advances in the generation of new materials based on both fundamental elements and composites, driven by advances in synthetic chemistry and often drawing inspiration from nature. The concept of an intelligent material envisions additional functionality built into the molecular structure, such that a desirable response occurs under defined conditions.Divided into 4 parts: Inorganic Materials; Organic Materials; Composite Materials; and Biomaterials, the 22 chapters cover the latest research and developments in the processing, properties, and applications of intelligent nanomaterials. Included are molecular device materials, biomimetic materials, hybrid-type functionalized polymers-composite materials, information-and energy-transfer materials, as well as environmentally friendly materials.

Enhanced visible-light photocatalytic activity of multi-elements-doped ZrO2 for degradation of indigo carmine

Abstract In this study, C,N,S-doped ZrO 2 and a series of Eu doped C,N,S-ZrO 2 photocatalysts were synthesized by a coprecipitation method using thiourea as the source of C, N and S and Eu(NO 3 )·6H 2 O as source of Eu. The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), UV-visible diffuse reflectance spectroscopy, scanning electron microscopy (SEM)/energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). Indigo carmine (IC) was chosen as a model for organic pollutants and used to evaluate the photocatalytic performance of the photocatalysts under simulated solar light. Commercial ZrO 2 was used as a reference material. XRD and Raman results indicated the formation of both tetragonal and monoclinic phase ZrO 2 with particle size ranging from 8-30 nm. Multi-element doping had a great influence on the optical responses manifested as red shift in the absorption edge. The highest photocatalytic activity towards IC was observed for the Eu,C,N,S-doped ZrO 2 (0.6 mol.% Eu) sample ( k =1.09×10 −2 min −1 ). The commercial ZrO 2 showed the lowest photodegradation activity ( k =5.83×10 −4 min −1 ). The results showed that the control of Eu doping in the C,N,S-ZrO 2 was very important in reducing electron-hole recombination. The synergistic effect of Eu, C, N, and S in the ZrO 2 matrix led to enhanced utilization of simulated solar energy for the degradation of IC through narrowing of bandgaps.

Synthesis of γ-cyclodextrin/chitosan composites for the efficient removal of Cd(II) from aqueous solution

The synthesis of chitosan-graft-γ-cyclodextrin (Ch-g-γ-CD) using persulfate/ascorbic acid redox system was done and characterized by FTIR, XRD, TGA and SEM/EDX. The optimum yield of the copolymer was obtained using 16×10(-3) M γ-cyclodextrins (γ-CD), 2.8×10(-2) M ascorbic acid (AA), 1.8×10(-2) M K(2)S(2)O(8) and 0.1g chitosan in 25 mL of 2% aqueous formic acid at 45±0.2°C. The highest percent grafting samples were evaluated for cadmium metal ion (Cd(II)) removal from the aqueous solutions where the sorption capacities were found proportional to the grafting extent. The sorption was pH and concentration dependent where, pH=8.5 was found to be the optimum value. The adsorption data were modeled using Langmuir and Freundlich isotherms. The equilibrium data followed the Langmuir isotherm model with maximum sorption capacity of 833.33 mg/g. The influence of electrolytes, sodium chloride (NaCl) and sodium sulphate (Na(2)SO(4)) on Cd(II) uptake was also studied. Desorption of the cadmium loaded Ch-g-γ-CD was accomplished with 0.01 N H(2)SO(4). The adsorbent exhibited high reusability and could be successfully recycled for nine cycles where in the ninth cycle 27% adsorption was feasible.

Synthesis, characterization and photoluminescence properties of Ce3+-doped ZnO-nanophosphors

The present study involves the synthesis of Ce3+ doped ZnO nanophosphors by the zinc nitrate and cerium nitrate co-precipitation method. The synthesized nanophosphors were characterized with respect to their crystal structure, crystal morphology, particle size and photoluminescence (PL) properties using X-ray diffraction (XRD), scanning electron microscopy (SEM)/energy dispersive X-ray (EDX), transmission electron microscopy (TEM)/Energy-dispersive X-ray spectroscopy (EDS) and PL-spectroscopy respectively. XRD results revealed that ZnO nanophosphors are single phase and cubic type structures. Further, PL spectra of ZnO:Ce3+ nanophosphors showed green emission because of the charge transfer at single occupied oxygen vacancies with ZnO holes and red emission due to the cerium ion transitions. Intensity and fine structure of the Ce3+ luminescence and its temperature dependence are strongly influenced by the doping conditions. The formation of ZnO:Ce3+ nanophosphors was confirmed by Fourier transform infrared (FTIR) and XRD spectra.