Kuldeep S. Rathore

Energy Band Gap Studies of CdS Nanomaterials

The CdS nanoparticles of different sizes are synthesized by a simple chemical method. Here, CdS nanoparticles are grown through the reaction of solution of different concentration of CdCl2 with H2S. X-ray diffraction pattern confirms nano nature of CdS and has been used to determine the size of particle. Optical absorption spectroscopy is used to measure the energy band gap of these nanomaterials by using Tauc relation. Energy band gap ranging between 3.12 eV to 2.47 eV have been obtained for the samples containing the nanoparticles in the range of 2.3 to 6.0 nm size. A correlation between the band gap and size of the nanoparticles is also established.

Amidic C–N bond cleavage of isatin: chemoselective synthesis of pyrrolo[2,3,4-kl]acridin-1-ones using Ag NPs decorated rGO composite as an efficient and recoverable catalyst under microwave irradiation

We have developed a facile approach for the synthesis of Ag NPs decorated reduced graphene oxide (Ag NPs/rGO) composite via a novel chemical route. This synthetic protocol involves protection, reduction and functionalization of graphene oxide in one step. The as prepared Ag NPs/rGO composite has been characterized by TEM, XRD, SEM, XPS, EDX, UV-Vis, CV, Raman and FT-IR spectra. The results showed that plenty of Ag NPs (∼28 nm) are homogeneously distributed onto the surface of rGO. Further, catalytic application of this fascinating nanomaterial has been utilized for the chemoselective synthesis of pyrrolo[2,3,4-kl]acridin-1-ones via ring-opening or amidic C–N bond cleavage of isatin. The Ag NPs/rGO composite possesses assets of both Ag NPs and reduced graphene oxide, thus, providing enhanced surface acidity with good dispersion ability that is usually missing in Ag NPs alone. After completion of the catalytic reaction, the Ag NPs/rGO composite could be easily recovered by simple filtration and recycled for 7 times without significant loss in its catalytic activity. The recycling and hot-filtration experiments proved the high stability and absence of leaching of the synthesized nanomaterial during the catalytic process. Furthermore, the proposed protocol showed excellent results in terms of green parameters confirming its effectiveness and profound appeal.

Determination of glass-forming ability of Ge1-xSnxSe2.5 (0≤x≤0.5) alloys using differential scanning calorimetry

The glass-forming ability of Ge1− x Sn x Se2.5 (0 ≤ x ≤ 0.5) alloys was studied using differential scanning calorimetry. Samples were scanned at different heating rates under non-isothermal conditions. Various simple quantitative methods were employed to assess the stability of the glassy materials in the above-mentioned system. All of these methods are based on characteristic temperatures, such as the glass-transition temperature, T g, the onset-of-crystallization temperature, T c, and the peak crystallization temperature, T p. A crystallization rate factor, K, has also been used as a measure of the thermal stability of the glasses. It was found that Ge0.7Sn0.3Se2.5 was the least stable among all the samples.

Cadmium Sulphide Nanocrystallites: Synthesis, Optical and Electrical Studies

CdS nanocrystals with sizes between 3 and 4 nm were synthesized via a competitive reaction chemistry method, where the thio‐glycerol is used to restrict the crystal growth as a capping agent. The structural and morphological characterization of the samples have been done using X‐ray diffraction (XRD) and Transmission Electron Microscope (TEM) while compositional analysis has been carried out using Energy Dispersive Analysis of X‐rays (EDAX) measurements. The particle size of the nanocrystal calculated from TEM has been found to be in the range of 3 to 4 nm. Absorption spectrum have been obtained using UV‐Vis spectrophotometer to find the optical band gap and it has been found to be 3.2 eV. The emission spectrum of the CdS nanocrystals shows peak centered at 535 nm, which is attributed to the presence of cadmium vacancies in the lattice. The conductivity of CdS nanocrystals has been determined by I–V measurement using the electrometer over the temperature range from room to 373 K. It is observed that the c...

Determination of optical and electrical properties of ZnSe thin films

A thin film of zinc selenide (ZnSe) was deposited onto a clean glass substrate using a vacuum evaporation technique. This thin film was characterized through X-ray diffraction, which indicated that the film was polycrystalline in nature. Absorption and transmission spectra of this thin film were recorded using a spectrophotometer. The energy band gap, refractive index and extinction coefficient were determined using these spectra. It was found that the energy band gap of ZnSe film was 2.55 eV. It was also observed that the refractive index and extinction coefficient of the film decreased with the increase of wavelength. The conductivity of this thin film was determined by current–voltage measurement using an electrometer over the temperature range from room temperature to 413 K. It was observed that conductivity increased with increase in temperature. This is explained on the basis of structural changes occurring due to the change in grain size and the increase in carrier density.

Microwave-assisted nanocatalysis: A CuO NPs/rGO composite as an efficient and recyclable catalyst for the Petasis-borono–Mannich reaction

A CuO NP decorated reduced graphene oxide (CuO NPs/rGO) composite was synthesized and characterized using various analytical techniques viz. XRD, TEM, SEM, UV-Vis, FT-IR, EDX, XPS and CV. The activity of the catalyst was probed for the Petasis-Borono–Mannich (PBM) reaction of boronic acids, salicylaldehydes, and amines under microwave irradiation (MW). The CuO NPs/rGO composite works as a catalyst as well as a susceptor and augments the overall ability of the reaction mixture to absorb MW. The synergistic effect of MW and CuO NPs/rGO resulted in an excellent outcome of the reaction as indicated by the high TOF value (3.64 × 10−3 mol g−1 min−1). The catalytic activity of the CuO NPs/rGO composite was about 12-fold higher under MW compared to the conventional method. The catalyst was recovered by simple filtration and recycled 8 times without significant loss in activity. This atom-economical protocol includes a much milder procedure, and a catalyst benign in nature, does not involve any tedious work-up for purification, and avoids hazardous reagents/byproducts and the target molecules were obtained in good to excellent yields.

Study of the electrical and optical properties of Ge27Se58Pb15 chalcogenide glass

ABSTRACT The present article reports electrical and optical properties of Ge27Se58Pb15 chalcogenide glass prepared through melt quenching technique. The dc electrical conductivity has been studied as a function of temperature and activation energy of conduction has been computed. The electrical study suggest that conduction in the glassy sample takes place via variable range hopping and thermally assisted tunneling of charge carriers. Thermally activated conduction is observed in high temperature range (348–423 K) while in lower temperature range (298–348 K), conduction follows Mott’s VRH model. Besides this, optical constants, i.e. energy band gap, refractive index, etc. were also computed for thin film of Ge27Se58Pb15 glass and band gap value suggest that sample is a semiconductor.

Synthesis and characterization of oxime-modified phenylimido vanadium(V) isopropoxide and their hydrolytic study

Heteroleptic complexes of the type [V(NPh)(OiPr)3-n{(ONC)(CH3)(C4H3O-2)}n] {where n = 1 (1), 2 (2) and 3 (3)} were synthesized by the reactions of [V(NPh)(OiPr)3] (A) with 2-acetylfuryl oxime in different molar ratios in anhydrous benzene. All these new derivatives have been characterized by elemental analyses, Fourier transform infrared spectroscopy, nuclear magnetic resonance (1H, 13C {1H}), 51V) and fast atom bombardment mass spectral studies. Spectral studies appear to be indicating mono-dentate and bi-dentate mode of attachment of the oximato moieties in the solution and solid state, respectively. Fast atom bombardment mass study of one of the representative derivative, [V(NPh){(ONC)(CH3)(C4H3O-2)}3] (3) suggests the monomeric nature of all these complexes. Thermogravimetric curve of [V(NPh){(ONC)(CH3)(C4H3O-2)}3] (3) shows large thermal events. Hydrolysis of [V(NPh)(OiPr)3] (A) and [V(NPh){(ONC)(CH3)(C4H3O-2)}3] (3) in moist propan-2-ol medium yielded vanadia, (a) and (b), respectively. However, hydrolysis of [V(NPh)(OiPr)3] (A) in n-hexane medium using calculated amount of water yielded hybrid material, (vn).The presence of (V = NPh) group in (vn) is confirmed by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectral studies as well as by the thermogravimetric study. The X-ray diffraction patterns of vanadia, (a) and (b) indicate formation of orthorhombic phase and the scanning electron microscope images of (a) and (b) show rod like morphology of the crystallites. Absorption spectra of vanadia, (a) and (b) indicate energy band gaps of 2.62 and 2.43 eV, respectively.Graphical AbstractHeteroleptic complexes of the type [V(NPh)(OiPr)3-n{(ONC)(CH3)(C4H3O-2)}n] {where n = 1, 2 and 3} were synthesized by the reactions of [V(NPh)(OiPr)3] with 2-acetylfuryl oxime. Hydrolysis of [V(NPh)(OiPr)3] and [V(NPh){(ONC)(CH3)(C4H3O-2)}3] in moist propan-2-ol medium yielded vanadia in orthorhombic phase, whereas, hydrolysis of [V(NPh)(OiPr)3] in n-hexane medium yielded hybrid material containing (V = NPh) linkages.

Facile Synthesis of Iron Oxide NPs as Magnetically Recyclable Catalysts for Chemoselective Synthesis of Pyrazolo[3,4-b]pyridine-5-carbonitiles in Aqueous Medium under Ultrasonic Irradiation.

The employed catalyst can be easily recovered by a magnetic field and reused five times without any loss of its high catalytic activity.