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TiO2 powder has been prepared by simple and low cost sol–gel procedure. The structural and morphological properties of prepared TiO2 powder were studied using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The XRD pattern clearly shows (1 1 1) maximum intensive plane of TiO2 material with other less intensive peaks, in absence of any other impurities. The dye degradation properties of TiO2 powder were characterized using UV–Visible absorption spectroscopic technique. The photocatalytic dye degradation properties for methylene blue (MB) dye were studied. The photocatalytic dye degradation results show fast degradation of methylene blue (MB) dye in presence of TiO2 powder in solution. Above results show TiO2 material is useful for photocatalytic dye degradation application.

A simple, efficient and economically viable method for the Heck reaction has been accomplished in the absence of phosphine ligand. The Heck reaction was performed using nanostructured Ni-Co/ZnO material as a heterogeneous catalyst in a DMF/H2O solvent system and in the presence of K2CO3, at 120 °C. The Ni-Co/ZnO nanostructures were prepared by the facile reduction-impregnation method. The structural and morphological properties of Ni-Co/ZnO nanostructure were investigated using various physico-chemical characterization techniques. Structural studies displayed the formation of hexagonal (wurtzite) ZnO. Electron microscopy imaging showed the presence of agglomerated clusters of Ni-Co nanoparticles over the surfaces of elliptical, flower bud-like and irregularly shaped sub-micron sized particle bundles of ZnO. The elemental composition analysis (EDX) confirmed the loading of Ni and Co nanoparticles over the nanocrystalline ZnO. The surface chemical state analysis of Ni-Co/ZnO material validated that Ni nanostructure exists in Ni2+ and Ni3+ species, whereas, Co nanostructure exists in Co2+ and Co3+ species. UV–Vis diffuse reflectance spectroscopy displays red shift in the light absorption edge of Ni-Co/ZnO catalyst compared to pure ZnO. The as-prepared Ni-Co bimetallic supported ZnO nanostructure showed better catalytic activity and stability for the Heck reactions under phosphine ligand-free conditions. Ni-Co/ZnO catalyzed Heck reactions afforded the corresponding cross-coupled products with moderate to good yields (up to 92%). Ni-Co/ZnO catalyst could be reused for five successive runs without significant loss of catalytic activity.

Herein, we report nitrogen-doped TiO2 (N-TiO2) solid-acid nanocatalysts with heterogeneous structure employed for the solvent-free synthesis of α-aminophosphonates through Kabachnik–Fields reaction. N-TiO2 were synthesized by direct amination using triethylamine as a source of nitrogen at low temperature and optimized by varying the volume ratios of TiCl4, methanol, water, and triethylamine, under identical conditions. An X-ray diffraction (XRD) study showed the formation of a rutile phase and the crystalline size is 10 nm. The nanostructural features of N-TiO2 were examined by HR-TEM analysis, which showed they had rod-like morphology with a diameter of ∼7 to 10 nm. Diffuse reflectance spectra show the extended absorbance in the visible region with a narrowing in the band gap of 2.85 eV, and the high resolution XPS spectrum of the N 1s region confirmed successful doping of N in the TiO2 lattice. More significantly, we found that as-synthesized N-TiO2 showed significantly higher catalytic activity than commercially available TiO2 for the synthesis of a novel series of α-amino phosphonates via Kabachnik–Fields reaction under microwave irradiation conditions. The improved catalytic activity is due to the presence of strong and Bronsted acid sites on a porous nanorod surface. This work signifies N-TiO2 is an efficient stable catalyst for the synthesis of α-aminophosphonate derivatives.

NiCo2O4 nanostructures were synthesized via a chemical bath deposition method on stainless steel substrate by employing nickel chloride, cobalt chloride and urea as the starting reactants, at 343 K to 373 K for 5 h without the assistance of any additives. The influence of deposition temperature on the morphology (particle size and shape) of NiCo2O4 nanoflowers was examined. Also the shape‐dependent electrochemical properties of the nanoflowers electrodes were investigated. The mature nanoflowers structure and its improved electron conductivity is beneficial for supercapacitor application, the NiCo2O4 nanoflower thin films deposited at 363 K temperature onto stainless steel substrate exhibits 610 F/g at 1 mA/cm2, good rate capability with superior cycling performance up to 5000th cycles. Our findings demonstrate the importance of shape-controlled synthesis of NiCo2O4 nanoflowers on stainless steel substrate in development of high-performance energy-storage systems. Keywords: Mature nanoflower, Nickel cobalt oxide, Supercapacitor, Chemical bath deposition method

We have explored nanocrystalline ZnO and Cu-ZnO catalyst for the preparation of 3-styrylchromones with trans selectivity derived from 3-formylchromones. Synthesis of ZnO and Cu-ZnO nano flakes (NFs) was carried by precipitation technique. The analytical techniques such as UV-Visible spectroscopy, X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), field emission scanning electron microscopy (FESEM) and energy-dispersive analysis X-ray spectroscopy (EDAX) were used to characterize the catalysts. The XRD pattern showed highly pure wurtzite ZnO and Cu-ZnO. The FESEM images showed nano flakes such as sunflower seed morphology in the range width of 9–34 nm and length 90–180 nm. Doping of copper in ZnO was employed to study the selectivity of Knoevenagel and Knoevenagel-Doebner reactions. Knoevenagel condensation was catalyzed efficiently by pure ZnO nano flakes, whereas the Cu-ZnO nano flakes facilitate the Knoevenagel-Doebner reaction. Present synthetic protocols are novel, very clean and high yielding for synthesis of 3-styrylchromones. Almost same yield was observed to the recycled catalyst up to four runs. Keywords: Heterogeneous catalysis, ZnO nano flakes, Knoevenagel condensation, Knoevenagel-Doebner reaction, 3-Styrylchromone

For synthesis of flavoring agent E-ethyl cinnamate in an economic way using Wittig reaction, MnO2 doped MgO nanocomposites were prepared by alkali leached hydrothermal method. The resultant nanocomposites were characterized by XRD, UV-DRS, FT-IR, FESEM, EDAX, XPS and Hammett indicator method. This surface modified MnO2 doped MgO can be used as green solid base for Wittig reaction between benzaldehyde and phosponium salt for synthesis of E-ethyl cinnamate under solvent free approach. Nanocomposite of MgO with MnO2 in combination with green mechanochemical approach seems to be more economic in comparison to pure nanosized MgO under conventional solvent stirring. Both efforts are complementary for promoting surface basic activity of MgO for high-yield synthesis of E-ethyl cinnamate using Wittig reaction. The product ethyl cinnamate has been characterized by HR-MS, IR, 1H NMR.

One-pot green synthesis of propargylamines using ZnCl2 loaded TiO2 nanomaterial under solvent-free conditions has been effectively accomplished. The aromatic aldehydes, amines, and phenylacetylene were reacted at 100 °C in the presence of the resultant catalyst to form propargylamines. The nanocrystalline TiO2 was initially synthesized by a sol–gel method from titanium(IV) isopropoxide (TTIP) and further subjected to ZnCl2 loading by a wet impregnation method. X-ray diffraction (XRD) patterns revealed the formation of crystalline anatase phase TiO2. Field emission scanning electron microscopy (FESEM) showed the formation of agglomerated spheroid shaped particles having a size in the range of 25–45 nm. Transmission electron microscopy (TEM) validates cubical faceted and nanospheroid-like morphological features with clear faceted edges for the pure TiO2 sample. Surface loading of ZnCl2 on spheroid TiO2 nanoparticles is evident in the case of the ZnCl2 loaded TiO2 sample. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Ti4+ and Zn2+ species in the ZnCl2 loaded TiO2 catalyst. Energy-dispersive X-ray (EDS) spectroscopy also confirmed the existence of Ti, O, Zn and Cl elements in the nanostructured catalyst. 15% ZnCl2 loaded TiO2 afforded the highest 97% yield for 3-(1-morpholino-3-phenylprop-2-ynyl)phenol, 2-(1-morpholino-3-phenylprop-2-ynyl)phenol and 4-(1,3-diphenylprop-2-ynyl)morpholine under solvent-free and aerobic conditions. The proposed nanostructure-based heterogeneous catalytic reaction protocol is sustainable, environment-friendly and offers economic viability in terms of recyclability of the catalyst.

The syntheses of Cu, Fe and Mn doped nanocrystalline MgO was carried out using alkali leached hydrothermal technique. The synergistic effect of transition metals (Cu, Fe and Mn) doping, particle size and nano-scale morphology on surface basicity enhancement was established in one pot Wittig reaction. The doped and undoped nanocrystalline MgO catalysts are characterized by XRD, UV-DRS, FT-IR, FESEM, EDS and XPS techniques. XRD study revealed formation of pure cubic phase of undoped and up to 1 wt% Cu, Fe and Mn doped MgO. The FESEM photographs of transition metal doped MgO indicated the formation of prismatic hexagonal nano plates and nanosheets with thickness in the range 20–70 nm. The catalytic activity of synthesized catalysts was investigated in one pot Wittig reaction of benzaldehyde, triphenylphosphine and ethyl bromoacetate at room temperature in DMF solvent. The Mn doped nanocrystalline MgO catalyst shows 98% yield under optimized reaction conditions. Enhancement of surface basicity due to doping of Mn in MgO was ascertained by UV-DRS and XPS study. The characterization of Wittig product ethyl cinnamate was carried out using HR-MS, 1H NMR, 13C NMR. The 1H NMR evaluates 95:5% E/Z ratio of ethyl cinnmate. Reported methodology is eco-friendly and easy to scale up.

Flower-like nanostructures of molybdenum disulphide (MoS2) have been effectively synthesised by the hydrothermal method and further doped with nitrogen using varying concentrations of urea. The formed hierarchical nanostructures are characterised by spectroscopy as well as electrochemical techniques. The structural analysis confirms the formation of a hexagonal MoS2 crystal structure. The existence of MoO2/MoO3/MoS2 composites is also observed after heating MoS2 with a lower urea concentration. Surface morphological analysis of all the prepared compositions shows the appearance of flower-like nanostructures formed by the stacking of 20–80 nanosheets to create individual flower petals. Nitrogen doping shows enhancement in the specific capacitance of MoS2 due to an increase in the electronic conductivity. Furthermore, the specific capacitance is enhanced due to the formation of an MoO2/MoO3/MoS2 composite. The highest specific capacitance calculated from the charge–discharge curve for nitrogen-doped MoS2 prepared using 1 : 1 (MoS2 : urea) weight ratio is observed at around 129 (F g−1) at 2 (A g−1) specific current. The nitrogen-doped MoS2 demonstrates almost four-fold enhancement in specific capacitance than pristine nano-shaped MoS2.

A set of hierarchical Cd x Zn1−x O nanoflakes (x = 0, 0.01 and 0.03) was prepared by the co-precipitation method using methanol as solvent. The prepared samples were characterized by UV–visible, X-ray diffraction, field emission scanning electron microscopy and energy-dispersive X-ray analysis techniques. The slight red shift in the Cd-doped ZnO confirms the doping of Cd2+ ions into ZnO lattices. The average crystallite size of Cd-doped ZnO nanoflakes was found to be in the range of 10–28 nm. The catalytic activity of Cd-ZnO nanoflakes in conjunction with microwave irradiation was investigated for reactions between o-phenylenediamine with aldehydes. It was found that the presence of Cd content in ZnO promotes rapid and selective synthesis of 2-substituted benzimidazoles under solvent-free conditions. The improvement of the catalytic activity by Cd doping is discussed in the light of the Brunauer–Emmet–Teller method. The catalyst could be reused up to five cycles without any significant loss of catalytic activity.

Pd loaded ZnO nanoparticles have been explored as an efficient catalyst for Suzuki-Miyaura cross-coupling reactions under ambient and ligand-free conditions. For this purpose, the low temperature synthesis of ZnO nanoparticle was accomplished by the solution based approach using stoichiometric amount of zinc acetate and urea. The Pd/ZnO nanocrystalline catalyst was prepared by loading 3% PdCl2 on ZnO nanoparticles by simple wet impregnation technique. This catalyst efficiently performed Suzuki-Miyaura reactions with various ring substituted aryl bromides and boronic acids. The resultant Pd/ZnO nanocrystalline material conferred 97% yield under optimized reaction conditions. The nanostructured Pd loaded ZnO catalyst was characterized by XRD, FESEM, EDS, FETEM, STEM-BF-DF, XPS and BET techniques. XRD pattern of Pd/ZnO sample hints the presence of Pd as minor phase loaded on ZnO nanocrystalline material, while overall XPS analysis discloses effective loading of Pd (0) on ZnO surface. FESEM/TEM–EDS also revealed reasonable Pd loading on ZnO nanoparticles. The FETEM examination of unloaded ZnO and Pd loaded ZnO disclosed particle size in the range 25–40 nm. The nanocrystalline Pd/ZnO catalyst was reused without significant loss of catalytic activity. The present methodology is cost effective, environmentally friendly, easy to scale up and can become an alternative to homogeneous catalysis.

An environmental friendly nanocrystalline Ni x TiO 2 ( x = 5 and 7%) was synthesized by hydrothermal method. The requisite quantity of commercial TiO 2 and Ni(NO 3 ) 2 ·6H 2 O was leached in alkaline medium using hydrothermal reactor at 120 °C. The anatase nanocrystalline undoped and Ni-doped TiO 2 was obtained for the first time for the functional catalysis. The reported method is effective for the synthesis of visible light driven photocatalyst and easy to scale-up. XRD results showed that the nickel was doped in the form of NiO. SEM picture shows spherical morphology to Ni-doped TiO 2 and nanofibered particle to hydrothermally treated TiO 2 samples. FESEM pictures of hydrothermally alkali treated undoped and Ni-doped TiO 2 powders afforded the particles size in the range of 50–85 nm. The DRS analysis confers visible absorption edge to Ni-doped TiO 2 at 550 nm. Ni-doped TiO 2 catalysts showed 63% more efficiency than the commercial TiO 2 to degradation of methylene blue dye under visible light irradiation.

We report the solvothermal synthesis of nanostructured ZnO hexagons by hydrothermal method via intermediate zinc adipate. The intermediate zinc adipate was obtained using precursors zinc acetate and adipic acid in aqueous and organic medium. Detailed XRD analysis of the zinc adipate was studied for the first time. Thermal study of intermediate showed the formation of ZnO at 400 °C. XRD study demonstrated the existence of wrutzite ZnO of high degree of crystallinity with crystallite size in the range of 20–25 nm. Scanning Electron Microscopy (SEM) showed distinguished morphology in different medium. Transmission Electron Microscopy (TEM) demonstrated nanostructured ZnO hexagons with average size 25–50 nm. The band gap for aqueous and organic mediated ZnO was found to be 3.24 and 3.26 eV, respectively. The band gap obtained is higher than the bulk ZnO, which implies nanocrystalline nature of the material.

Electrical and gas sensing properties of nanocrystalline ZnO:Cu, having Cu X wt% (X = 0.0, 0.5, 1.0, and 1.5) in ZnO, in the form of pellet were investigated. Copper chloride and zinc acetate were used as precursors along with oxalic acid as a precipitating reagent in methanol. Material characterization was done by X-ray diffraction (XRD), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM) and inductive coupled plasma with optical emission spectrometry (ICP-OES). FE-SEM showed the self-aligned Cu-doped ZnO nano-clusters with particles in the range of 40-45 nm. The doping of 0.5% of copper changes the electrical conductivity by an order of magnitude whereas the temperature coefficient of resistance (TCR) reduces with increase in copper wt% in ZnO. The material has shown an excellent sensitivity for the H{sub 2}, LPG and CO gases with limited temperature selectivity through the optimized operating temperature of 130, 190 and 220 deg. C for H{sub 2}, LPG and CO gases, respectively at 625 ppm gas concentration. The %SF was observed to be 1460 for H{sub 2} at 1% Cu doping whereas the 0.5% Cu doping offered %SF of 950 and 520 for CO and LPG, respectively. The response and recovery time was foundmore » to be 6 to 8 s and 16 s, respectively.« less

Rose-red color Nb 2 Zr 6 O 17 - x N x oxynitride photocatalyst was synthesized by thermal ammonolysis of Nb 2 Zr 6 O 17 at 1073 K. TEM image of Nb 2 Zr 6 O 17 - x N x sample showed prismatic pseudo orthorhombic shaped particles with clear edges and an average particle size in the range of 80–90 nm. The photocatalytic activities of the oxynitride samples were studied for hydrogen production by H 2 S splitting under visible light irradiation. The oxynitride Nb 2 Zr 6 O 17 - x N x gave the quantum yield of 13.5% in the production of hydrogen from decomposition of hydrogen sulfide under visible light irradiation.

We report here the synthesis of self-assembled aligned hexagonal prismatic Cu doped ZnO nanoparticles in aqueous and organic medium. The average particle size was found to be in the range of 40–85 nm. Structural study revealed the existence of ZnO phase with wurtzite structure. The copper was present as oxide, situated at the core of prismatic form of wurtzite ZnO nanoparticle with clear edges and faces. The maximum hydrogen production rate achieved was 1932 μmol h −1 over the as synthesized Cu doped ZnO suggesting as an active photocatalyst for hydrogen sulfide decomposition under visible light irradiation. The effect of copper concentration as a dopant on the photocatalytic activity of Cu-ZnO was studied. The photocatalytic activity of Cu-ZnO synthesized in organic media was observed to be higher as compared to aqueous medium.

We offer sui-generis strategy for synthesis of nanosized chalcogenide semiconductors in polymer matrix by a novel polymer-inorganic solid-state reaction. In our previous report, the rationale of this strategy has been successfully established by the solid-state reaction between CdI2 and an intentionally chosen engineering thermoplastic, namely, polyphenylene sulphide (PPS). In the pursuit of this work, we explored the possibility of using other cadmium salts viz cadmium nitrate, cadmium chloride and cadmium acetate in place of cadmium iodide for the envisaged solidstate reaction with PPS. All the reactions were carried out at the melting temperature of PPS (285oC) in 1:1 and 10:1 molar ratios of polymer to cadmium salt. The resultant products were characterised by XRD, TEM-SAED and DRS. It is observed that only cadmium nitrate yielded CdS nanocrystallites (average size of 15nm) entrapped in modified polymer matrix in a competing behaviour with cadmium iodide when reacted in 10:1 molar ratio while (i) cadmium acetate leads to the formation of only cadmium oxide and (ii) cadmium chloride exhibits grossly incomplete solid state reaction yielding understated quantity of CdS when reacted with PPS.

We have explored the possibility of using environmentally stable nano-CdS embedded in thermally stable polymer matrix as an efficient photocatalyst for the hydrogen generation by photodecomposition of hydrogen sulphide under visible light irradiation. Initially, we restricted our attempt to the usage of nano-CdS synthesized by novel polymer-inorganic solid-state reaction between cadmium iodide and polyphenylene sulphide (PPS). The structural study revealed the formation of nanocrystallites of CdS with the particle size ranging from 6 to 28 nm entrapped in modified (cyclized) PPS matrix. A quantum yield of 19.7% for the H 2 generation was accomplished with CdS–PPS nanocomposite in pristine state, which appears to be superior in comparison to that of the conventional Pt loaded CdS. We believe that this straightforward approach can be extended to synthesise other nano-metal sulphides in polymer network for photocatalytic and allied applications.

The effect of the solvents on particle size and morphology of ZnO is investigated. The optical properties of nano ZnO were studied extensively. During this study, zinc oxalate was prepared in aqueous and organic solvents using zinc acetate and oxalic acid as precursors. The thermo-gravimetric analysis (TGA/DTA) showed formation of ZnO at 400 °C. Nano-size zinc oxide was obtained by thermal decomposition of aqueous and organic mediated zinc oxalate at 450 °C. The phase purity was confirmed by XRD and crystal size determined from transmission electron microscopy (TEM) was found to be 22–25 nm for the aqueous and 14 –17 nm in organic mediated ZnO. Scanning electron microscope (SEM) also revealed different nature of surfaces and microstructures for zinc oxide obtained in aqueous and organic solvents. The UV absorption spectra showed sharp absorption peaks with a blue shift for organic mediated ZnO, due to monodispersity and lower particle size. Sharp peaks and absence of any impurity peaks in photoluminescence spectra (PLS) complement the above observations.

We offer a novel polymer-inorganic solid-state reaction route for the in situ generation of nanochalcogenide semiconductor in the network of polymer which itself acts as a chalcogen source. We have exemplified feasibility of this route by reacting CdI 2 with engineering thermoplastic polyphenylene sulphide (PPS). These two reactants in 1:1 and 10:1 molar ratios were simply heated at the crystalline melting temperature of PPS. The resultant products were characterized by X-ray diffractometry, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM, with selected area electron diffraction). The prima facie observations revealed the formation of cubic nanocrystallites of CdS with the particle size ranging from 6 to 20 nm entrapped in modified (cyclized) PPS matrix when the reactants were taken in 10:1 molar ratio. A tentative mechanism has been suggested for such hitherto unattempted solid-state reaction.

TiO2/Cu2O heterojunction solar cells have been successfully synthesized by an electrochemical route. The structural, morphological and optical properties of TiO2/Cu2O heterojunction solar cells were studied using x-ray diffraction, scanning electron microscopy and UV–vis spectroscopic techniques. The change in morphology is observed due to the effect of the annealing atmosphere on TiO2/Cu2O heterojunction. The surface morphological study shows truncated triangular and nanostar-like Cu2O material using air and nitrogen annealing. The oxidation state of TiO2 and Cu2O materials was studied by x-ray photoelectron spectroscopy. The J–V characteristics curve shows maximum 0.31% photoconversion efficiency of nitrogen-annealed TiO2/Cu2O heterojunction solar cells.

In view of this, we investigated new visible light nanostructured semiconductor photocatalyst especially in the field of composite metal oxide photocatalyst for solar hydrogen production from H 2 S. For this purpose, two methodologies using a quantum mechanical material design and the microscopic surface analysis on a nanometer scale are adopted. The catalysts are synthesized by our proprietary soft chemical approaches. Also, a demonstrative reaction system for the effective solar hydrogen production is presented.