Samit K. Ray

Bio: Samit K. Ray is an academic researcher from Indian Institute of Technology Kharagpur. The author has contributed to research in topics: Photoluminescence & Thin film. The author has an hindex of 44, co-authored 507 publications receiving 8085 citations. Previous affiliations of Samit K. Ray include University of Delaware & Indian Institute of Technology Kanpur.

Characteristics of Ge Nanocrystals Grown by RF Magnetron Sputtering

Abstract: We report the self-assembled growth of Ge islands of different shapes and sizes on p-Si (001) by r.f. magnetron sputtering by varying the r.f. power, growth temperature and postdeposition annealing condition. The well known Stranski-Krastanov growth mechanism due to lattice mismatch between Si & Ge leads to the formation of Ge islands, similar to a more sophisticated MBE growth, albeit at a much higher pressure in our study. Ge nanocrystals embedded in SiO2 matrix have also been grown. Optical properties of nanocrystals exhibiting visible luminescence at room temperature are presented.

Morphological variations in geographically isolated populations of Bryum coronatum Schwager (Bryaceae, Bryales)

Abstract: Four populations of Bryum coronatum Schwager (Bryaceae, Bryales), collected from widely separated geographic regions - Sambalpur, Odisha; Lataguri, West Bengal; Gangtok and Changu, Sikkim; were studied with regard to variation in taxonomically significant morphological features as well as their dimension of both gametophytic and sporophytic features. In this study special emphasis has been put on spore dimension and spore ornamentation pattern as revealed by Scanning Electron Microscopy (SEM). Dimension of taxonomically significant morphological parameters were measured for four populations and were subjected to analysis of variance (One way ANOVA) and Principal component analysis (PCA). ANNOVA results showed significant variation for all features except leaf length and upper leaf cell breadth. PCA results corroborated ANNOVA result only for upper leaf cell breadth. Spore ornamentation as revealed through SEM, is found to be bacculate in all the populations. CCA graph revealed that summer, winter temperature and monsoon rainfall influence leaf size, lamina cell size, capsule size, peristome size and spore size. With the help of above mentioned observations and statistical analysis the morphological variations, due to phenotypic plasticity have been quantified to reach at a meaningful conclusion. Taxonomic significance of spore dimension and wall ornamentation is also discussed.

In situ grown superconducting YBCO films on buffered silicon substrates for device applications

Abstract: Thin films of YBa2Cu3O7−δ (YBCO) have been grownin situ on silicon single-crystal (100) substrate by using SrTiO3 as a buffer layer. The deposition has been carried out by on-axis rf magnetron sputtering method. The deposition condition have been optimized by studying the plasma characteristics and correlating them with the superconducting performance of the film. Films deposited at substrate temperature in the range of 680–700°C from stoichiometric YBCO targets in an argon + oxygen mixture (3∶1) are superconducting and showc-axis epitaxy. Compositional confirmation has been carried out using Rutherford backscattering. Scanning tunneling microscopy of the films reveal formation of well-defined layered structure with some defects in the initial stages ofin situ growth of the films. Films grown on SrTiO3 substrates have excellent crystalline quality (XRD), transition temperatureTc0=81 K and the critical current densityJc>2×105 A/cm2 for unpatterned films at 77 K. On silicon substrates using buffer layers thein situ deposited YBCO films shows a higher transition width andTc0 is also slightly less (71 K).

Photon assisted ultra-selective Formaldehyde sensing by defect induced NiO nanostructured sensing layer

Abstract: Indoor air quality (IAQ) monitoring is quite essential to maintain healthy human life. Among different pollutants effecting IAQ, formaldehyde is one toxic VOC that needs to be monitored. In this work, hierarchical NiO nanostructured thin film devices are used as highly selective and sensitive formaldehyde sensor in presence of light. The response in presence of light was obtained as 291.7% at 190 ppm with a fast response time of ∼ 24 s and recovery time of ∼ 42 s (at 190 ppm of formaldehyde). The sensor was found to be highly specific towards formaldehyde compared to other VOCs. The optimum operating temperature was ∼ 300°C, much less than the conventional NiO based sensors (∼600°C). The sensing layer was made optically active by inducing defects which resulted in the dependence of the sensing response on light irradiation to a considerable amount (∼82.4% in dark and ∼291.7% in light for 190 ppm formaldehyde). Thus, the fabricated light assisted sensor shows potential to develop future commercial formaldehyde sensor.

Prospects of Colloidal Nanocrystals for Electronic and Optoelectronic Applications

Abstract: Nanocrystals (NCs) discussed in this Review are tiny crystals of metals, semiconductors, and magnetic material consisting of hundreds to a few thousand atoms each. Their size ranges from 2-3 to about 20 nm. What is special about this size regime that placed NCs among the hottest research topics of the last decades? The quantum mechanical coupling * To whom correspondence should be addressed. E-mail: dvtalapin@uchicago.edu. † The University of Chicago. ‡ Argonne National Lab. Chem. Rev. 2010, 110, 389–458 389

Principles Of Fluorescence Spectroscopy

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Nanoscale metal oxide-based heterojunctions for gas sensing: A review

Abstract: Metal oxide-based resistive-type gas sensors are solid-state devices which are widely used in a number of applications from health and safety to energy efficiency and emission control. Nanomaterials such as nanowires, nanorods, and nanoparticles have dominated the research focus in this field due to their large number of surface sites facilitating surface reactions. Previous studies have shown that incorporating two or more metal oxides to form a heterojunction interface can have drastic effects on gas sensor performance, especially the selectivity. Recently, these effects have been amplified by designing heterojunctions on the nano-scale. These designs have evolved from mixed commercial powders and bi-layer films to finely-tuned core–shell and hierarchical brush-like nanocomposites. This review details the various morphological classes currently available for nanostructured metal-oxide based heterojunctions and then presents the dominant electronic and chemical mechanisms that influence the performance of these materials as resistive-type gas sensors. Mechanisms explored include p–n and n–n potential barrier manipulation, n–p–n response type inversions, spill-over effects, synergistic catalytic behavior, and microstructure enhancement. Tables are presented summarizing these works specifically for SnO2, ZnO, TiO2, In2O3, Fe2O3, MoO3, Co3O4, and CdO-based nanocomposites. Recent developments are highlighted and likely future trends are explored.

Diversity of life

Abstract: It is clear that the above can lead to confusion when scientists of different countries are trying to communicate with each other. Another example is the burrowing rodent called a gopher found throughout the western United States. In the southeastern United States the term gopher refers to a burrowing turtle very similar to the desert tortoise found in the American southwest. One final example; two North American mammals known as the elk and the caribou are known in Europe as the reindeer and the elk. We never sing “Rudolph the Red-nosed elk”! Confused? This was the reason for creating an internationally recognized system of naming organisms. To avoid confusion, living organisms are assigned a scientific name based on Latin or Latinized words. The English sparrow is Passer domesticus or Passer domesticus (italics or underlining these two names is the official written representation of a scientific name). Using a uniform naming system allows scientists from all over the world to recognize exactly which life form a scientist is referring to. The naming process is called the binomial system of nomenclature. Passer is comparable to a surname and is called the genus, while domesticus is the specific or species name (like your given name) of the English sparrow. Now scientists can give all sparrow-like birds the genus Passer but the species name will vary. All similar genera (plural for genus) can be grouped into another, “higher” category (see below). Study the following for a more through understanding of taxonomy. Taxonomy Analogy Kingdom: Animalia Country

Environmental applications of graphene-based nanomaterials.

Abstract: Graphene-based materials are gaining heightened attention as novel materials for environmental applications The unique physicochemical properties of graphene, notably its exceptionally high surface area, electron mobility, thermal conductivity, and mechanical strength, can lead to novel or improved technologies to address the pressing global environmental challenges This critical review assesses the recent developments in the use of graphene-based materials as sorbent or photocatalytic materials for environmental decontamination, as building blocks for next generation water treatment and desalination membranes, and as electrode materials for contaminant monitoring or removal The most promising areas of research are highlighted, with a discussion of the main challenges that we need to overcome in order to fully realize the exceptional properties of graphene in environmental applications