Anshu Singhal

Polyvinyl alcohol–In2O3 nanocomposite films: synthesis, characterization and gas sensing properties

Poly(vinyl alcohol) (PVA)–In2O3 (with 1 and 5 wt% In2O3 loading) nanocomposite films have been prepared by a solvent-casting technique. The In2O3 nanoparticles used in this work were prepared by nonhydrolytic alcoholysis ester elimination reaction of indium acetate in the presence of oleic acid and oleyl alcohol at 220 °C. X-Ray diffraction (XRD) patterns and transmission electron microscopy (TEM) studies indicate that the In2O3 nanocrystals obtained in this work are nearly monodisperse, highly crystalline with cubic bixbyite structure without the presence of any other impurity phase. The PVA–In2O3 nanocomposite films have been structurally characterized by XRD, Fourier transform infrared (FTIR) and Raman spectroscopy. The results confirm the incorporation of In2O3 nanocrystals in the PVA matrix and interactions between In2O3 nanocrystals and PVA molecules. The thermal properties of nanocomposite films have been investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The thermo-oxidative degradation temperature of PVA increases with the addition of In2O3 nanocrystals and the degree of crystallinity of the PVA matrix decreases in the presence of In2O3 nanocrystals in the nanocomposite films. The room temperature sensing characteristics of the naocomposite films have been studied for various gases, namely, H2S, NH3, CH3, CO, and NO. The PVA–In2O3 nanocomposite films show maximum sensitivity for H2S gas with fast response and reversibility. The response mechanism of the nanocomposite films to various gases is also proposed.

Organochalcogenido-bridged dimeric 2-methylallylpalladium complexes: synthesis, structure and their transformation into palladium chalcogenides

Organochalcogenido-bridged dimeric 2-methylallylpalladium complexes of the type [Pd2(μ-ER)2(η3-C4H7)2] (1) [ER = SBut (1a), SPh (1b), SC6F5 (1c), SePh (1d), TePh (1e)] have been prepared. The structure of the SBut bridged complex has been established by single crystal X-ray diffraction analysis. The four-membered Pd2S2 ring adopts a non-planar conformation with the two η3-2-MeC3H4 (η3-C4H7) in a syn configuration. The thermal behaviour of these complexes has been investigated by thermogravimetric analysis. These complexes yield Pd4E (E = S or Se) or Pd3Te2 at moderately low temperatures.

Synthesis and characterization of dimeric organochalcogenido-bridged methylpalladium and allylpalladium complexes

Abstract Dimeric organochalcogenido-bridged methylpalladium and allylpalladium complexes of the types [Pd 2 Me 2 (μ-SR′) 2 (PR 3 ) 2 ] and [Pd 2 (μ-ER′) 2 (ν 3 -allyl) 2 ] (E = S or Se; R = Et, i Pr, t Bu, Ph, C 6 H 4 CH 3 -4, C 6 H 4 Cl-4) have been synthesized and characterized by elemental analyses and nuclear magnetic resonance ( 1 H, 13 C and 31 P) spectroscopy. The methylpalladium complexes exist either as cis isomers or as a mixture of cis and trans forms, with the former predominating. The allylpalladium complexes exist in syn and anti forms. The dynamic behaviour in these complexes was studied by variable-temperature 1 H NMR spectroscopy. A few reactions of [Pd 2 (μ-Cl) 2 (ν 3 -allyl) 2 ] with free thiols were also investigated.

UV-shielding transparent PMMA/In2O3 nanocomposite films based on In2O3 nanoparticles

Self supporting poly(methyl methacrylate) (PMMA)/In2O3 with varying In2O3 content (1, 2, 5 and 10 wt% In2O3 loading) nanocomposite films have been prepared by solvent-casting and spin casting techniques. The nanocomposite films have been structurally characterized by X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectroscopy and the results confirm the incorporation of In2O3 nanoparticles in the PMMA matrix. The thermal properties of the nanocomposite films have been investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results show that the degradation of the polymer occurs at higher temperature in the presence of In2O3 nanoparticles and even a small amount of In2O3 nanoparticles (∼1 wt%) can greatly improve the thermal stability of PMMA. The UV-visible spectra of the nanocomposite films show that the films are UV-absorbing, and highly transparent in the visible region.

Tin oxide nanocrystals: controllable synthesis, characterization, optical properties and mechanistic insights into the formation process

A novel, surfactant-free, solution-phase method has been successfully developed for the synthesis of SnO2 nanocrystals using a solvothermal route. The nanocrystals having average diameters in the range 4–8 nm, have been synthesized by a non-aqueous sol–gel reaction using tin(IV) bis(acetylacetonate)dichloride, [(Sn(acac)2Cl2)] with benzyl alcohol as the reaction medium at 200 °C. The crystal structure, morphology, and sizes of the SnO2 nanocrystals have been determined by X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman studies. Raman peaks at 627, 768 cm−1 characteristic of the rutile phase of bulk SnO2 are observed along with broad surface vibration modes in the range 400–600 cm−1. Optical properties of the nanocrystals have been explored by optical absorption and photoluminescence (PL). A blue shift of the optical band gap of the nanocrystals is observed due to size effects. The estimated band gap of the SnO2 nanocrystals from optical absorption data is found to be 3.81 eV. The photoluminescence spectrum showed broad UV as well as visible emission. Based on the GC-MS and carbon-13 NMR analysis of the final reaction solution, a formation mechanism encompassing the ether elimination and solvolysis of acetylacetonate ligand is proposed.

Triazenido-bridged binuclear palladium(II) and platinum(II) complexes

Abstract Triazenido-bridged binuclear palladium(II) and platinum(II) complexes of the type [M 2 X 2 (μ-ArNNNAr) 2 (PR 3 2 (where M = Pd or Pt; X = Cl, Me, p -tol; Ar = Ph, p -tol or p-C 6 H 4 F; PR 3 = PEt 3 , PEt 3 , PBu 3 , PMe 2 Ph or PMePh 2 have been prepared by the reaction of [M 2 X 2 (μ-Cl) 2 (PR 3 ) 2 ] with free triazene in the presence of NaOH. These complexes were characterised by elemental analyses, IR and NMR ( 1 H, 31 P, 195 Pt) spectroscopy. Variable temperature NMR data reveal that the eight-membered metallocyclic ring has a rigid conformation. 195 Pt NMR data showed the existence of significant metal-metal interaction. A few reactions of these complexes have also been investigated by NMR spectroscopy.

SYNTHESIS AND CHARACTERIZATION OF BIS(DIPHENYLPHOSPHINO)ACETYLENE BRIDGED BINUCLEAR PLATINUM(II) COMPLEXES WITH TERMINAL ORGANOCHALCOGENIDE GROUPS. X-RAY CRYSTAL STRUCTURE OF [Pt2(SC6F5)4 (μ-Ph2PC≡CPPh2)2]

Abstract Binuclear platinum(II) complexes of the type [Pt2(ER)4(μ-Ph2PC≡CPPh2)2] (ER = SPr i , SBu t , SPh, SC6H4Cl-4, SC6F5, SePh) have been prepared and characterized by elemental analysis and NMR spectroscopy. A single-crystal X-ray structure determination of [Pt2(SC6 F5)4-(μ-Ph2PC≡CPPh2)2] has established the binuclear formulation with terminal thiolato groups. The platinum atoms lie in a distorted square planar environment with the sulfur and the phosphine ligands arranged in a cis fashion.

Corundum type indium oxide nanostructures: ambient pressure synthesis from InOOH, and optical and photocatalytic properties

A simple, cost effective, surfactant free and scalable synthesis of rhombohedral In2O3 (rh-In2O3) nanostructures with controllable size and shape has been developed under ambient pressure by thermal dehydration of InOOH nanostructures. The InOOH nanostructures have been prepared by solvothermal reaction between indium nitrate hydrate with tetramethylammonium hydroxide (TMAH) in anhydrous methanol at 140 °C without any surfactant. The structure and morphology of the nanostructures have been characterized in detail by X-ray powder diffraction (XRD), Raman spectroscopy, and high-resolution transmission electron microscopy (HRTEM). The studies reveal that highly crystalline nanostructures of InOOH and rh-In2O3 with rice-grain type morphology are formed. The optical properties of the InOOH and rh-In2O3 nanostructures have been explored by UV-visible diffuse reflectance spectroscopy (UV-DRS) and room-temperature photoluminescence (PL) studies. The direct band gap of as-synthesized InOOH and rh-In2O3 nanostructures was estimated to be 3.75 and 2.95 eV, respectively, from the diffuse reflectance absorbance spectra. Both InOOH and rh-In2O3 nanostructures show intense blue emission under UV excitation which is attributed to the presence of oxygen vacancies. The thermal stability of the rh-In2O3 phase has been studied by differential scanning calorimetry (DSC), differential thermal analysis (DTA) and dilatometry of the as prepared sample. The potential of InOOH and rh-In2O3 nanostructures as photocatalytic materials for hydrogen generation from water/methanol (2 : 1) mixtures under UV/vis irradiation has also been evaluated for the first time.

Synthesis and characterization of chloro/pyrazolato bridged binuclear organoplatinum(II) complexes: Single crystal structure of [Pt2 Ph2(μ-Cl)(μ-pz)(PMe2Ph)2]

Abstract Chloro/pyrazolato-bridged binuclear organoplatinum(II) complexes of the type [Pt 2 Ar 2 (μ-Cl)(μ-NN)(PR 3 ) 2 ] (Ar  Ph or C 6 H 4 OMe-4; NNH  pyrazole (pzH), 3,5-dimethylpyrazole (dmpzH) or 3,4,5-tri-methylpyrazole (tmpzH); PR 3  PBu 3 , PMe 2 Ph or PMePh 2 ) have been synthesized. These complexes exist exclusively in the cis form in which the phosphine ligands are trans to the bridging pyrazolate group. The crystal structure of [Pt 2 Ph 2 (μ-Cl)(μ-pz)(PMe 2 Ph) 2 ] is reported.

Trinuclear Complexes of Palladium(II) Containing Bridging Thiolate and Pyrazolate Ligands

Trinuclear palladium(II) complexes of the type [Pd3X2(µ-Y)2(µ-pz)2(PR3)2] [X=Cl or Ph; Y=Cl, SPh, SC6F5 or SC6H4C1-4; PR3=PPh3 or P(tol)3] are prepared and characterised by elemental analyses, NMR (1H and 31P-{1H}) and FAB mass spectral data.