D. Duraibabu

Biogenic nanosilver incorporated reverse osmosis membrane for antibacterial and antifungal activities against selected pathogenic strains: An enhanced eco-friendly water disinfection approach

Reverse osmosis (RO) membranes have been used extensively in water desalination plants, waste water treatment in industries, agricultural farms and drinking water production applications. The objective of this work is to impart antibacterial and antifungal activities to commercially available RO membrane used in water purification systems by incorporating biogenic silver nanoparticles(AgNPs) synthesized using Rosa indica wichuriana hybrid leaf extract. The morphology and surface topography of uncoated and AgNPs-coated RO membrane were studied using Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Elemental composition of the AgNPs-coated RO membrane was analyzed by energy-dispersive X-ray spectroscopy (EDAX). The functional groups were identified by Fourier Transform Infrared spectroscopy (FT-IR). Hydrophilicity of the uncoated and AgNPs-coated RO membrane was analyzed using water contact angle measurements. The thermal properties were studied by thermogravimetric analysis (TGA). The AgNPs incorporated RO membrane exhibited good antibacterial and antifungal activities against pathogenic bacterial strains such as E. coli, S. aureus, M. luteus, K. pneumoniae, and P. aeruginosa and fungal strains such as Candida tropicalis, C. krusei, C. glabrata, and C. albicans.

Studies on mechanical, thermal and dynamic mechanical properties of functionalized nanoalumina reinforced sulphone ether linked tetraglycidyl epoxy nanocomposites

The objective of the present work is to synthesize 1,4′-bis (4-amine-phenoxy) sulphone benzene epoxy resin (TGBAPSB) via 1,4′-bis (4-amine-phenoxy) sulphone benzene (BAPSB) and epichlorohydrin in order to obtain tetra functional epoxy with improved properties. The molecular structure of TGBAPSB epoxy resin was confirmed from FTIR and NMR spectral data and molecular weight was determined by GPC and epoxy equivalent weight (EEW) by titration method. The amino functionalized nanoalumina (F-nAl) was synthesized via the sol–gel method using 3-aminopropyltriethoxysilane and has been confirmed by FT-IR. TGBAPSB epoxy resin was further reinforced with varying weight percentages (1–5 wt%) of F-nAl and cured with diaminodiphenylmethane (DDM). The thermal and thermo-mechanical behaviour of TGBAPSB epoxy matrix and nanocomposites were analysed by TGA, DMA and DSC. The surface morphology of the epoxy nanocomposites was examined using XRD, TEM, SEM and AFM studies. Data obtained from mechanical, thermal and thermo-mechanical, dielectric and water absorption studies indicate a significant improvement in properties of the resultant epoxy nanocomposites, which appear to be ideal material for advanced high performance applications when compared to those of neat epoxy matrices.

Highly responsive glutathione functionalized green AuNP probe for precise colorimetric detection of Cd2+ contamination in the environment

AuNPs phytosynthesized using the aqueous leaf extract of Rosa indica – wichuriana hybrid Francois guillot showed a well-defined surface plasmon band centered at around 520 nm which is the characteristic of gold nanoparticles. HRTEM micrographs showed that the sizes of the AuNPs were in the range of 5–13 nm. The AuNPs were functionalized using glutathione via the thiol group from the cysteine moiety to develop a highly responsive GSH-AuNP probe for precise colorimetric detection of Cd2+. The functionalization was confirmed by FT-IR. Atomic absorption spectroscopy was used to quantify the heavy metals present in the two water samples collected from the water bodies in Ranipet, a suburban town and industrial hub of Vellore city in the state of Tamil Nadu in southern India. The colorimetric selectivity of the GSH-AuNP probe to the quantified metal ions Mg2+, Ca2+, Ba2+, Ni2+, Mn2+, Cu2+, Hg2+, Co2+, Cd2+, Cr3+, Fe2+ was ascertained by UV-Vis spectroscopy. The observations demonstrate that only Cd2+ stimulated the GSH-AuNPs solution to turn from ruby red to purple and resulted in a substantial shift in the SP band to a longer wavelength of 594 nm owing to GSH-AuNPs aggregation. The minimum and maximum detection limit of Cd2+ by the GSH-AuNP probe was inferred to be 30–70 nM (3 × 10−8 M and 7 × 10−8 M) respectively. The feasibility of employing the probe practically in the environment to detect Cd2+ was demonstrated using two water samples. The aggregation-based change in color from ruby red to purple occurred in less than 10 min. This result could be considered a straight forward and instantaneous detection of Cd2+ devoid of any interference from other metal ions that were present in the water samples.

‘Green’ biocompatible organic–inorganic hybrid electrospun nanofibers for potential biomedical applications

Gold nanoparticles were prepared by green route using Couroupita guianensis leaves extract. The green synthesized gold nanoparticles exhibited maximum absorbance at 526 nm in the ultraviolet spectrum. By incorporating the green synthesized gold nanoparticles in poly(vinyl alcohol) matrix, unique green organic–inorganic hybrid nanofibers (poly (vinyl alcohol)–gold nanoparticles) were developed by electrospinning. Contact angle measurements showed that the prepared poly (vinyl alcohol)–gold nanoparticles were found to be highly hydrophilic. The crystallinity of gold nanoparticles was analyzed using XRD. The synthesized gold nanoparticles and poly (vinyl alcohol)–gold nanoparticles were characterized using high-resolution transmission electron microscope, Fourier transform-infrared spectroscopy and energy-dispersive analysis of X-ray. The ultimate aim of the present work is to achieve optimum antibacterial, antifungal, biocompatibility and antiproliferative activities at a very low loading of gold nanoparticles. Vero cell lines showed a maximum of 90% cell viability on incubation with the prepared poly (vinyl alcohol)–gold nanoparticles. MCF 7 and HeLa cell lines proliferated only to 8% and 9%, respectively, on incubation with the poly (vinyl alcohol)–gold nanoparticles, and also exhibited good antibacterial and antifungal activities against test pathogenic bacterial and fungal strains. Thus, the poly (vinyl alcohol)–gold nanoparticles could be used for dual applications such as antimicrobial, anticancer treatment besides being highly biocompatible.

Green Nanosilver as Reinforcing Eco-Friendly Additive to Epoxy Coating for Augmented Anticorrosive and Antimicrobial Behavior

Epoxy resin GY250 representing diglycidyl ethers of bisphenol-A (DGEBA) was reinforced with 1, 3 and 5wt % of surface functionalized silver nanoparticles (F-AgNPs) which were synthesized using Couroupita guianensis leaves extract with a view of augmenting the corrosion control property of the epoxy resin and also imparting antimicrobial activity to epoxy coatings on mild steel. Corrosion resistance of the coatings was evaluated by EIS, potentiodynamic polarization studies and cross scratch tests. AFM, SEM, HRTEM and EDX were utilized to investigate the surface topography, morphology and elemental composition of the coatings on MS specimens. Results showed that the corrosion resistance, hardness and Tg of the DGEBA/F-AgNPs coatings increased at 1wt % of F- AgNPs. The DGEBA/F-AgNPs coatings also offered manifold antimicrobial protection to the MS surfaces by inhibiting the growth of biofilm forming bacteria like P. aeruginosa, B. subtilis, the most common human pathogen E. coli and the most virulent human pathogenic yeast C. albicans.

Development and characterization of novel organic–inorganic hybrid sol–gel films

Organic–inorganic hybrid films were fabricated by reacting 3-glycidoxypropyltrimethoxysilane with 4,4′-diaminodiphenylether by hydrolysis and condensation reaction with acid catalysis. The chemical bonding between the organic and inorganic phases provides reinforcement to the films, and tetraethoxysilane was added in such a way that silica contents varied from 1 wt% to 3 wt% in the films. Structural characterization of the hybrid films was performed using Fourier transform infrared and nuclear magnetic resonance spectroscopic techniques. The thermal properties studied using thermogravimetric analysis, indicate an improved thermal stability for the films according to the percentage concentration of silica present in them. The water absorption was also found to be reduced for the films with increased silica content. The surface morphology was investigated by means of x-ray diffraction and scanning electron microscopic techniques. The films transparency and homogeneity seem to have been affected severely when the silica content kept on increasing and ultimately led to opaqueness in film.

Twin Applications of Tetra-Functional Epoxy Monomers for Anticorrosion and Antifouling Studies

This paper reports the development and characterization of nano-hybrid coatings using tetraglycidyl 2,2-bis(4-(4-amine phenoxy)phenyl)propane (TGBAPPP) and 3-aminopropyltriethoxysilane (APTES) functionalized ZnO as nano-reinforcement. The nano-hybrid coatings were cured by aromatic and aliphatic curing agents. The effect of the ZnO-APTES and curing agents on the corrosion and fouling resistant properties of these coatings was studied by electrochemical impedance, antifouling tests and toxicity test. It shows the tetraglycidyl epoxy nano-hybrid coatings have a better set of coating properties when compared to di-functional epoxy nano-hybrid coatings. The best results were obtained for ZnO-APTES loaded TGBAPPP with curing agent Aradur 140. These observations clearly indicate the synergistic effect of curing agent and nano-reinforcing effect of ZnO-APTES towards corrosion resistance.

Development and characterization of a novel skeletal modified tetraglycidyl epoxy toughened DGEBA epoxy matrices

The present work investigates the improvement in mechanical properties observed for commercially available diglycidyl ethers of bisphenol-A (DGEBA) with the incorporation of a new type of skeletal modified tetra glycidyl epoxy resin TGBAPB as modifier. Varying weight percentages of TGBAPB have been blended with DGEBA and cured with diaminodiphenylmethane (DDM). The chemical structure of TGBAPB was confirmed by FTIR, NMR, and molecular weight determination was carried out by ESI-MS spectroscopic techniques. The thermal properties were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and mechanical properties like tensile strength, flexural strength, impact strength were also studied by universal testing machine (UTM). Scanning electron microscopy (SEM) investigates the morphological behavior of the neat and blend epoxy resins. The results from different studies indicate that the blend epoxy resin system “B” comprising 75% DGEBA/25% TGBAPB has shown improvements in both toughness and stiffness, despite the fact that it is often found that the enhancement of these two properties together in a material cannot be simultaneously achieved. These aspects of this work are novel.

Development of Environmentally Acceptable Nano-Hybrid Coatings for Bio-Fouling Protection

Alternative coatings should be as effective as conventional paints but with lower toxicity. In the present study, a commercially available epoxy resin modified with non functionalized nanozinc oxide (nZnO) was examined to get information on its antifouling and anti-corrosive properties. Epoxy nanohybrid coating was synthesized using nZnO (in the amount of 0wt%, 1wt%, 3wt%, 5wt%, 7wt% and 10wt%) and diglycidyl ether of bisphenol A (DGEBA) type of epoxy resin. The curing behavior of these materials was ascertained from FT-IR spectral studies. The anti-corrosive properties of the nanohybrid were investigated using salt spray and electro chemical polarization studies. The surface morphology images were taken by SEM analysis. This study indicates that nZnO particles were dispersed homogenously through the polymer matrix. The nZnO incorporated coating was found to exhibit enhanced anticorrosive performance. Approximately 50% reduction in fouling attachment was achieved with coatings containing 3wt% of nZnO.

Development and characterization of tetraglycidyl epoxy reinforced inorganic hybrid nanomaterials for high performance applications

In the present work, tetraglycidyl 1,4′-bis (4-amine-phenoxy) benzene (TGBAPB) epoxy resin has been developed using 1,4′-bis (4-amine-phenoxy) benzene and epichlorohydrin. The amine-functionalized nanoalumina (F-nAl) was prepared using 3-aminopropyltriethoxysilane. TGBAPB epoxy resin was further reinforced with different weight percentages (1–5 wt%) of F-nAl and were cured with 4,4′-diaminodiphenylmethane. Thermal and thermomechanical behavior of TGBAPB epoxy matrix and nanocomposites were studied using thermogravimetric and differential scanning calorimetric analyses. The surface morphology of epoxy nanocomposites was examined using transmission electron microscopic, scanning electron microscopic, and atomic force microscopic studies respectively. Data obtained from mechanical and thermal studies/analysis indicate that these nanocomposites could be used as high-performance materials for varied advanced industrial and engineering applications.