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Nayak B.B.,CSIR - Institute of Minerals And Materials Technology
Applied Physics A: Materials Science and Processing | Year: 2012

Defect-free and long SiC/C nanocables have been produced by heating SiC powder at 3000°C by employing dc arc plasma (Ar) in a specially designed configuration of graphite arc. Microstructural characterizations of the heat-treated powder carried out by TEM, HRTEM, SAED, EDS, and micro Raman spectroscopy showed the nanocables to consist of a SiC shell/sheath stuffed with wire type solid C core. A possible mechanism is discussed to explain the cable-type growth. © 2011 Springer-Verlag.

Pradhan G.K.,CSIR - Institute of Minerals And Materials Technology | Parida K.M.,CSIR - Institute of Minerals And Materials Technology
ACS Applied Materials and Interfaces | Year: 2011

This work reports the facile synthesis of α-Fe 2O 3 nanorods and nanohexagons and its application as sunlight-driven photocatalysis. The obtained products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), scanning electron microscopy (SEM), diffused reflectance spectroscopy (DRUV-vis), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The phase and crystallinity were confirmed from the XRD study. Electron microscopy study clearly indicates the formation of different morphologies of nanocrystals. These hematite nanostructures were used as a model system for studying the shape-dependent photocatalytic degradation of phenol, methylene blue, and congo red. Amongst all the nanostructured semiconductors, Pt-doped hematite nanorod showed 55% efficiency towards the decolonization of methylene blue and 63% toward congo red under sun light illumination. The difference in photocatalytic activity is discussed in terms of their crystallize size and morphological ordering. © 2011 American Chemical Society.

Parida K.,CSIR - Institute of Minerals And Materials Technology | Mohapatra L.,CSIR - Institute of Minerals And Materials Technology
Dalton Transactions | Year: 2012

A series of novel photocatalysts Zn/Cr LDH with different Zn/Cr molar ratios (2:1, 3:1, 4:1 and 2:1-CO 3) were fabricated by a co-precipitation method and evaluated for photodecomposition of water using visible light irradiation. Various characterization methods were employed to investigate the structures, morphologies and photocatalytic properties. In comparison to Zn/Cr (2:1) LDH, Zn/Cr-CO 3 (2:1) LDH extends the absorption edges to the visible region and exhibits good photocatalytic activity, even without the assistance of co-catalysts. The visible light photocatalytic activity is ascribed to the charge transfer spectra of octahedral Cr ions in LDH. Zn/Cr-CO 3 LDH shows enhanced photocatalytic activities compared to Zn/Cr LDH as carbonate ions oxidise by holes to form carbonate radicals, inhibit the rapid recombination of e - and h + charge carriers and thereby suppress the backward reaction to some extent. This work provides a detailed understanding of the semiconductor properties of LDHs for photocatalytical hydrogen evolution. © 2012 The Royal Society of Chemistry.

Bag B.,CSIR - Institute of Minerals And Materials Technology | Pal A.,CSIR - Institute of Minerals And Materials Technology
Organic and Biomolecular Chemistry | Year: 2011

The new signaling probes 2-6, rhodamine-B derivatives of various receptors which contain different donor atoms for effective metal ion coordination, were synthesized and their absorption as well as fluorescence spectral responses were evaluated in the presence of various metal ions. All these probes along with the reference probe 1 have exhibited optimal metal ion-induced absorption and fluorescence enhancement with Hg(ii) ion in the longer wavelength region (>500 nm) in MeCN, exploiting the spectral characteristics of metal ion-induced structural transformation of rhodamine. The selectivity and sensitivity towards Hg(ii) ion were better pronounced in MeCN-H 2O (1:1 v/v) medium, implying the role of the solvent molecules, water in particular, in the preferential Hg(ii) coordination environment. Complexation of Hg(ii) to 1-6 not only enhanced the absorption at ∼560 nm, which turned the colourless solution into pink to facilitate a naked eye detection, but also amplified the fluorescence intensity simultaneously to offer high sensitivity of detection at lower concentration. The Hg(ii)-induced photo-physical spectral responses of 1-6 in presence of other competitive metal ions rendered their high selectivity towards Hg(ii). Further, their reversible dual channel signaling pattern under the action of counter anions, exploiting coordination tendency of anions towards Hg(ii), which compete with probe-metal interaction, implied the reversibility in their Hg(ii) coordination. The selectivity, sensitivity and reversibility, in principle, establishes the potential of these probes as chemosensors for Hg(ii) ion detection. © 2011 The Royal Society of Chemistry.

Pradhan A.C.,CSIR - Institute of Minerals And Materials Technology | Parida K.M.,CSIR - Institute of Minerals And Materials Technology
Journal of Materials Chemistry | Year: 2012

In situ incorporation of mesoporous Al 2O 3 (meso-Al 2O 3) into the MCM-41 extraframework without blocking the pores generates an ordered, long range and high surface area mesoporous support Al 2O 3-MCM-41 (AM). The mesoporous support surprisingly shows high surface area as compared to pristine MCM-41. The incorporation of meso-Al 2O 3 into the extraframework of MCM-41 through the silanol group is evidenced by FTIR, 27Al MAS NMR and 29Si MAS NMR spectroscopy. The result shows that Si/Al ratio 10 (AM 10) possesses improved textural properties as compared to AM 50 and AM 90. Iron is incorporated onto the surface of AM 10 in order to modify the surface property of AM 10, forming composite Fe/Al 2O 3-MCM-41 (Fe/AM 10). Characterization by small angle X-ray diffraction (SXRD), transmission electron microscopy (TEM), and N 2 adsorption-desorption measurements reveals that the mesoporous support and iron incorporated support possess large BET surface area (207-1244 m 2 g -1), narrow pore size (2.4-2.7 nm) and high pore volume (0.370-2.37 cm 3 g -1). Among them, AM 10 shows highest surface area (1244 m 2 g -1), narrow pore size (2.7 nm) and pore volume (2.37 cm 3 g -1). The incorporation effect of both meso-Al 2O 3 and iron in the formation of Fe/AM 10 has been well established by 27Al MAS NMR spectroscopy. X-Ray photoelectron spectroscopy study confirms the 2+ state of iron in Fe/AM 10 and also establishes the incorporation of meso-Al 2O 3 and iron. Among the prepared mesoporous supports and different wt% of iron incorporated supports, it is seen that 5 Fe/AM 10 ('5' denotes the wt% of iron) has high adsorption as well as photo-Fenton degradation activity for MB. Moreover, 5 Fe/AM 10 is not merely a good adsorbent but also an efficient catalyst in the adsorption and photo-Fenton degradation (100%) of MB in 15 and 5 minutes, respectively. Furthermore, in the case of mixed cationic and anionic dyes (uniform mixture of methylene blue and methyl orange), MO adsorption and degradation (by photo-Fenton process) occur appreciably on the surface of MB through cationic-anionic interaction of MB and MO. © 2012 The Royal Society of Chemistry.

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