Layered double hydroxide and Merrifield resin supported nanopalladium(0) catalysts are prepared by an exchange of PdCl(4)(2-) followed by reduction and well characterized for the first time. The ligand-free heterogeneous layered double hydroxide supported nanopalladium (LDH-Pd(0)) catalyst using the basic LDH in place of basic ligands indeed exhibits higher activity and selectivity in the Heck olefination of electron-poor and electron-rich chloroarenes in nonaqueous ionic liquids (NAIL) over the homogeneous PdCl(2) system. Using microwave irradiation, the rate of the Heck olefination reaction is accelerated, manifold with the highest turnover frequency ever recorded in the case of both electron-poor and electron-rich chloroarenes. The basic LDH-Pd(0) shows a superior activity over a range of supported catalysts, from acidic to weakly basic Pd/C, Pd/SiO(2,) Pd/Al(2)O(3), and resin-PdCl(4)(2-) in the Heck olefination of deactivated electron-rich 4-chloroanisole. The use of LDH-Pd(0) is extended to the Suzuki-, Sonogashira-, and Stille-type coupling reactions of chloroarenes in an effort to understand the scope and utility of the reaction. The catalyst is quantitatively recovered from the reaction by a simple filtration and reused for a number of cycles with almost consistent activity in all the coupling reactions. The heterogeneity studies provide an insight into mechanistic aspects of the Heck olefination reaction and evidence that the reaction proceeds on the surface of the nanopalladium particles of the heterogeneous catalyst. TEM images of the fresh and used catalyst indeed show that the nanostructured palladium supported on LDH remains unchanged at the end of the reaction, while the XPS and evolved gas detection by TGA-MS of the used catalyst identify ArPdX species on the heterogeneous surface. Thus, the ligand-free nanopalladium supported on LDH, synthesized by the simple protocol, displays superior activity over the other heterogeneous catalysts inclusive of nanopalladium in the C-C coupling reactions of chloroarenes.

In this report, we have designed a simple and efficient green chemistry approach for the synthesis of colloidal silver nanoparticles (b-AgNPs) that is formed by the reduction of silver nitrate (AgNO3) solution using Olax scandens leaf extract. The colloidal b-AgNPs, characterized by various physico-chemical techniques exhibit multifunctional biological activities (4-in-1 system). Firstly, bio-synthesized silver nanoparticles (b-AgNPs) shows enhanced antibacterial activity compared to chemically synthesize silver nanoparticles (c-AgNPs). Secondly, b-AgNPs show anti-cancer activities to different cancer cells (A549: human lung cancer cell lines, B16: mouse melanoma cell line & MCF7: human breast cancer cells) (anti-cancer). Thirdly, these nanoparticles are biocompatible to rat cardiomyoblast normal cell line (H9C2), human umbilical vein endothelial cells (HUVEC) and Chinese hamster ovary cells (CHO) which indicates the future application of b-AgNPs as drug delivery vehicle. Finally, the bio-synthesized AgNPs show bright red fluorescence inside the cells that could be utilized to detect the localization of drug molecules inside the cancer cells (a diagnostic approach). All results together demonstrate the multifunctional biological activities of bio-synthesized AgNPs (4-in-1 system) that could be applied as (i) anti-bacterial & (ii) anti-cancer agent, (iii) drug delivery vehicle, and (iv) imaging facilitator. To the best of our knowledge, there is not a single report of biosynthesized AgNPs that demonstrates the versatile applications (4-in-1 system) towards various biomedical applications. Additionally, a plausible mechanistic approach has been explored for the synthesis of b-AgNPs and its anti-bacterial as well as anti-cancer activity. We strongly believe that bio-synthesized AgNPs will open a new direction towards various biomedical applications in near future.

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N-doped ZnO/g-C3N4 hybrid core-shell nanoplates have been successfully prepared via a facile, cost-effective and eco-friendly ultrasonic dispersion method for the first time. HRTEM studies confirm the formation of the N-doped ZnO/g-C3N4 hybrid core-shell nanoplates with an average diameter of 50 nm and the g-C3N4 shell thickness can be tuned by varying the content of loaded g-C3N4. The direct contact of the N-doped ZnO surface and g-C3N4 shell without any adhesive interlayer introduced a new carbon energy level in the N-doped ZnO band gap and thereby effectively lowered the band gap energy. Consequently, the as-prepared hybrid core-shell nanoplates showed a greatly enhanced visible-light photocatalysis for the degradation of Rhodamine B compare to that of pure N-doped ZnO surface and g-C3N4. Based on the experimental results, a proposed mechanism for the N-doped ZnO/g-C3N4 photocatalyst was discussed. Interestingly, the hybrid core-shell nanoplates possess high photostability. The improved photocatalytic performance is due to a synergistic effect at the interface of the N-doped ZnO and g-C3N4 including large surface-exposure area, energy band structure and enhanced charge-separation properties. Significantly, the enhanced performance also demonstrates the importance of evaluating new core-shell composite photocatalysts with g-C3N4 as shell material.

Cu-doped TiO2 with varying amounts of Cu (0.2, 0.3, 0.5, 1, 2, and 5) are prepared by impregnation method and calcined at 350 and 450 °C for 5 h. These catalysts are characterized by X-ray diffraction, diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy energy-dispersive X-ray spectroscopy (EDAX), and transmission electron microscopy (TEM). The DRS studies are clearly showing the expanded photo response of TiO2 into the visible region on impregnation of copper ions. TEM images are depicting the fine dispersion of Cu particles on TiO2 surface. XPS studies are showing change in the binding energy values of Ti 2p, O 1s, and Cu 2p, indicating that copper ions are in interaction with TiO2. XPS results are also confirming that the oxidation state of copper is +2 in samples calcined at 350 °C and +1 in samples calcined at 450 °C. EDAX analysis supports the presence of copper species on the surface layers of TiO2. Photocatalytic hydrogen production activity studies are conducted over CuO/TiO2 and Cu2O/TiO2 catalysts in pure water and glycerol:water mixtures under solar irradiation. Maximum hydrogen production of 265 and 290 μmol h−1 is observed over 2 wt % CuO/TiO2 and Cu2O/TiO2 catalysts in pure water. A significant improvement in hydrogen production is observed in glycerol:water mixtures and maximum hydrogen production of 16,500 and 20,060 μmol h−1 is obtained over 0.5 wt % CuO/TiO2 and Cu2O/TiO2 catalysts in 5% glycerol aqueous solutions. No hydrogen production activity is observed on reduced catalysts under solar irradiation. Furthermore, when these catalysts are studied under UV irradiation, 2−3 fold increase in activity is observed on calcined catalysts, and the same level of activity is observed on reduced catalysts, but under these conditions the activity is limited by the dissolution of Cu ions into the solution. However, under solar irradiation a continuous and stable activity is observed over Cu2O/TiO2 catalyst. On the basis of the characterization and hydrogen production activity results, finely dispersed Cu in +1 oxidation state that is in interaction with TiO2 is proposed as a promising visible sensitive photocatalyst for the continuous production of hydrogen from glycerol:water mixtures.