ORMOSIL–ZrO2 hybrid nanocomposites and coatings on aluminium alloys for corrosion resistance; A sol-gel approach

Corrosion resistant coatings are prepared from a hybrid nanocomposite aerogel derived from tri-functional silanes, methyltrimethoxysilane (MTMS) and glycidyloxypropyl trimethoxysilane (GPTMS) and from a zirconium isopropoxide (ZIP) precursor which acts as an inorganic nano-dispersion in an organically modified silane (ORMOSIL) matrix. A series of hybrid compositions of MTMS and GPTMS are prepared in which the amount of ZIP is varied. The variations in the pH, viscosity and gelation time of the prepared compositions are monitored. The wet alcogels thus obtained are homogenized in a solvent using an ultrasonicator followed by coating the suspension on aluminium alloys and glass substrates using a dip coating unit. The prepared coatings are further dried and annealed at 400 °C for 1 h. The wet alcogels are also dried under ambient conditions for seven days resulting in hybrid nanocomposite aerogel monoliths and are calcined at 400 °C. The hybrid nanocomposites and coatings are further characterized using X-ray diffraction analysis, Fourier transform infrared spectroscopy, BET surface area analysis, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), UV-visible spectroscopy, potentiodynamic polarization and EIS measurements. The hybrid nanocomposite coated aluminium alloy shows enhanced corrosion protection when compared to the uncoated aluminium alloy. The anticorrosive feature of the ORMOSIL-ZrO2hybrid nanocomposite coatings makes them an important candidate in the field of protective environment resistant coatings

A COMPARATIVE STUDY OF THE PHYTOCHEMICALS, ANTIOXIDANT AND ANTIBACTERIAL POTENTIAL OF METHANOLIC EXTRACTS OF TRICHOSANTHES CUCUMERINA (L.) VAR. CUCUMERINA UNDER IN VITRO CULTURE AND NATURAL CONDITIONS

Objective: To compare the phytochemicals, antioxidative capacity and antibacterial profile of methanolic extracts of callus and naturally propagated plant species-Trichosanthes cucumerina (L.) var. cucumerina and to optimize an ideal protocol for in vitro callus and shoot induction.Methods: The sterilized seeds of Trichosanthes cucumerina (L.) var. cucumerina were inoculated in half Murashige and Skoog (MS) basal medium devoid of growth hormones to raise aseptic seedlings. Explants from aseptic seedlings used for callus induction in MS medium fortified with varying combinations of N6–Benzyl amino purine (BAP), 1-Naphthalene acetic acid (NAA) and 2,4–Dichlorophenoxy acetic acid (2,4-D). For in vitro soot induction, MS medium supplemented with different concentrations of 2,4-D, BAP and Kinetin-either alone or in combinations were employed. The callus harvested on 21st and 45th days were analyzed for a comparison of the influence of age of callus on the quantity of secondary metabolites. For a comparison with the naturally grown plant, all experiments were carried out with extracts from callus and wild plants. The antioxidant capacity of methanolic extracts was evaluated by 2,2-Diphenyl-1 Picryl Hydrazyl (DPPH) free radical scavenging assay and Ferric Reducing Antioxidant Power (FRAP) analysis. The antibacterial activity of were screened by the agar diffusion method using pathogenic bacteria such as Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus and documented through measurement of the diameter of growth inhibition zone (IZ). Results: The results on in vitro culture indicated that MS medium with BAP (0.5 mg/l) and 2,4-D (1 mg/l) was ideal for callus induction. For shoot induction, supplementation of MS medium with BAP-0.5 mg/l, 2,4,D-1.0 mg/l and Kinetin-0.5 mg/l was found to be most favourable. Direct root induction from the callus was found to occur in medium fortified with BAP-0.5 mg/l, 2,4, D-0.5 mg/l and NAA-1.0 mg/l. The phytoconstituents quantified were alkaloids, flavonoids, tannins, phenols and terpenoids and their levels were higher in wild plant in comparison to callus. Naturally grown plant possesses higher free radical scavenging ability and ferric reducing power than callus. Results of antibacterial activity indicated that the Gram-positive strain (Staphylococcus aureus) was more sensitive than the Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). The highest antibacterial activity recorded for naturally propagated plant extract against S. aureus (IZ = 13 mm) and was quite comparable with standard antibiotic cephatoxim (IZ = 20 mm) at 100mg concentration.Conclusion: Results concluded that this overexploited medicinal plant with lesser seed longevity could be successfully propagated by in vitro methods. The phytoconstituents with antioxidative and antibacterial potential were more abundant in naturally propagated plants than undifferentiated callus tissue. The extracts are potent antibacterial agents

Very low thermal conductivity in lanthanum phosphate-zirconia ceramic nanocomposites processed using a precipitation-peptization synthetic approach

A wet chemical synthetic approach involving precipitation-peptization mechanisms was successfully adopted for the development of LaPO4-ZrO2 nanocomposites with the ZrO2 content varying in the 5-20 wt% range. Stoichiometric lanthanum phosphate, formed as nanofibrils during the precipitation reaction with orthophosphoric acid, was subsequently transformed into nanorods of ~10 nm width and <100 nm length upon peptization at pH 2. Zirconia dispersions were homogeneously incorporated as ultrafine particulates through zirconium oxychloride hydrolysis using ammonia. The nanocomposite precursor thus obtained could be densified to >98% TD for the LaPO4-10 wt% ZrO2 composition upon sintering at 1600 °C. The addition of ZrO2 to LaPO4 impeded densification and grain growth inhibition of up to 50% was obtained for LaPO4-20 wt% ZrO2 nanocomposites. Furthermore, the nanocomposites indicated very low thermal conductivity values (1 W m-1 K-1) compared to single phase LaPO4. The non-reactivity of LaPO4 and ZrO2 at high temperatures and the low thermal conductivity values of LaPO4-ZrO2 render them effective for high temperature thermal insulation applications. © 2016 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique

A facile one pot synthetic approach for C3N4-ZnS composite interfaces as heterojunctions for sunlight-induced multifunctional photocatalytic applications

Herein, we report a facile one pot synthetic protocol for the creation of C3N4-ZnS composite interfaces by the co-pyrolysis of a precursor mix containing zinc nitrate, melamine, and thiourea at 550°C in air. The organic-inorganic semiconductor heterojunctions thus formed displayed increased absorbance in the longer wavelength region and facilitated broad absorption of visible light compared to pure ZnS, C3N4 and conventionally synthesized hybrid samples. The decreased emission intensity, increased photocurrent generation and decreased fluorescence lifetime revealed reduced exciton recombinations in the co-pyrolysed sample containing C3N4-ZnS heterostructures. The samples displayed sunlight driven photocatalytic reduction of nitrophenol as well as hydrogen generation (4 mmol g-1 h-1) by water splitting. © The Royal Society of Chemistry 2016

Reactive oxygen species (ROS) mediated enhanced anti-candidal activity of ZnS-ZnO nanocomposites with low inhibitory concentrations

Enhanced antifungal activity against the yeast species Candida albicans, Candida tropicalis and Saccharomyces cerevisiae was displayed by ZnS-ZnO nanocomposites prepared by a simple precipitation technique. The antifungal activity was significantly more in the presence of indoor light than under dark conditions and was a clear confirmation of the inhibitory role of reactive oxygen species (ROS) generated in situ by the photocatalytic nanocomposites. The generation of ROS was further evidenced by flow cytometry results and membrane permeabilisation studies. Time kill assay and growth curve analysis indicated diminished antifungal activity under dark conditions due primarily to Zn2+ efflux in solution. © 2015 The Royal Society of Chemistry

Melamine formaldehyde-metal organic gel interpenetrating polymer network derived intrinsic Fe-N-doped porous graphitic carbon electrocatalysts for oxygen reduction reaction

Fe, N doped porous graphitic carbon electrocatalyst (Fe-MOG-MF-C), obtained by pyrolysis of an Interpenetrating Polymer Network (IPN) comprised of melamine formaldehyde (MF as hard segment) and Metal-Organic Gel (MOG as soft segment), exhibited significant Oxygen Reduction Reaction (ORR) activity in alkaline medium. BET surface area analysis of Fe-MOG-MF-C showed high surface area (821 m2 g-1), while TEM, Raman and XPS results confirmed Fe and N co-doping. Furthermore, a modulated porous morphology with a higher degree of surface area (950 m2 g-1) has been accomplished for the system (Fe-MOG-MFN-C) when aided by a sublimable porogen, such as naphthalene. XPS results further demonstrated that these systems exhibited a better degree of distribution of graphitic N and an onset potential value of 0.91 V vs. RHE in 0.1 M KOH solution following an efficient four-electron ORR pathway. The electrocatalytic activity of Fe-MOG-MFN-C is superior to that of Fe-MOG-MF-C by virtue of its higher graphitic N content and surface area. Thus, the study presents a new class of IPN derived MF-MOG nanocomposites with the potential to generate extended versions of in situ Fe-N doped porous graphitic carbon structures with superior ORR activity

Bifunctional lanthanum phosphate substrates as novel adsorbents and biocatalyst supports for perchlorate removal

Porous lanthanum phosphate substrates, obtained by an environmentally benign colloidal forming process employing methyl cellulose, are reported here as excellent adsorbents of perchlorate with >98% efficiency and with 100% reusability. Additionally, the effectiveness of such substrates as biocatalyst supports that facilitate biofilm formation of perchlorate reducing microbes (Serratia marcescens NIIST 5) is also demonstrated for the first time. The adsorption of perchlorate ions is attributed to the pore structure of lanthanum phosphate substrate and the microbial attachment is primarily ascribed to its intrinsic hydrophobic property. Lanthanum phosphate thus emerges as a dual functional material that possesses an integrated adsorption/bioremediation property for the effective removal of ClO4- which is an increasingly important environmental contaminant. © 2014 Elsevier B.V

Catalytic Activity Studies of Modified Alumina in the Esterification of Benzyl Alcohol with Different Aliphatic Acids

244-252<span style="font-size:11.0pt;font-family: " times="" new="" roman";mso-fareast-font-family:"times="" roman";mso-bidi-font-family:="" mangal;mso-ansi-language:en-gb;mso-fareast-language:en-us;mso-bidi-language:="" hi"="" lang="EN-GB">A varied percentage of Fe, Co and Fe-Co mixtures were deposited on alumina support by dry impregnation method. The prepared materials were analyzed for their crystallinity, surface functional groups, morphology and elemental composition by P-XRD, FT-IR, and SEM-EDS techniques. Specific surface area of the catalytic materials was determined by BET technique using nitrogen as adsorbent. Further, surface acidity was estimated by TPD-NH3 and n- butylamine back titration method. The catalytic performances of these materials were checked in the esterification of benzyl alcohol with various aliphatic acids. The catalytic activity of Fe-Co/Al2O3 with 15% metal loading was found to be superior to other catalysts. The higher catalytic performance of the catalyst may be attributed to the higher surface acidity as well as synergetic effect of the metals. Further, the catalyst Fe-Co/Al2O3 (15%) was recyclable up to 5 times with negligible loss of its catalytic activity. A close relationship was noticed between surface acidity and catalytic performance of the materials.</span

Photoluminescent, self-cleaning titanium oxide nanocomposites with multifunctional properties

© The Royal Society of Chemistry 2014.Photoluminescent and self-cleaning properties of an Eu&lt;sup&gt;3+&lt;/sup&gt; doped titania-silica-lanthanum phosphate nanocomposite (Eu-TSL) prepared by an aqueous sol-gel process and films fabricated on glass substrates by dip coating are investigated in the present work. These nanocomposites containing Eu&lt;sup&gt;3+&lt;/sup&gt; as dopants exhibit red luminescence upon visible light excitation, after heat treatment at 400°C. For an excitation wavelength of 465 nm, the PL spectra of Eu-TSL show intense peaks at 613 nm (&lt;sup&gt;5&lt;/sup&gt;D&lt;inf&gt;0&lt;/inf&gt;-&lt;sup&gt;7&lt;/sup&gt;F&lt;inf&gt;2&lt;/inf&gt;), characteristic of Eu&lt;sup&gt;3+&lt;/sup&gt; ions. This red emission has a life time of ~0.5 ms. 1 mol% Eu added TSL shows ~96% methylene blue dye degradation after two hours UV light exposure which is attributed to the presence of anatase phase, optimum crystallite size (5.7 nm) and enhanced specific surface area (147 m&lt;sup&gt;2&lt;/sup&gt; g&lt;sup&gt;-1&lt;/sup&gt;). Eu-TSL was found to be five times more efficient in decolourization of methylene blue than Eu-TiO&lt;inf&gt;2&lt;/inf&gt; from the reported literature. Eu-TSL retains all the major properties including photoactivity, transparency (~97%) and low wettability (~80°). In addition, red emission could be integrated at very low europium doping levels (1 mol%). Even though europium doping on titania is reported widely, a multifunctional luminescent and self-cleaning composition based on Eu-TSL synthesized by an aqueous sol-gel route is reported for the first time