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

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Prospects of Colloidal Nanocrystals for Electronic and Optoelectronic Applications

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Principles Of Fluorescence Spectroscopy

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.

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

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

Diversity of life

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

Environmental applications of graphene-based nanomaterials.

This paper gives a brief description of activities of the Microelectronics Centre of IIT, Kharagpur in technology development over the past few years. Standard facilities for wafer processing and mask making by an optical pattern generator have been established and IC test structures of diffused resistors, I2L cells and ring oscillators have been fabricated and tested. Design and fabrication of a low capacity “telecard” chip, an I2L gate array and a VCO chip for pressure sensors are in progress. Work has also been undertaken on some VLSI unit processes: (i) Tungsten Disilicide has been grown and characterised. Annealing in forming gas at 1000°C for one hour following the e-beam evaporation of high purity tungsten on silicon has been found to be adequate for complete silicidation giving resistivities in the range of 30–50 μΩ-cm. (ii) Application of microwave plasma for dry processing in VLSI has been investigated. A rapid growth of SiO2 has been observed at a rate of 300 A per minute (typical) in dense oxy...

Microelectronics Technology Development at IIT Kharagpur

CdSe nanowires were prepared by a simple DC electrochemical process using porous anodic alumina templates FESEM micrographs demonstrated the growth of CdSe nanowires of diameter 200-300 nm by filling up the nano-pores in alumina X-ray diffraction patterns revealed the growth of CdSe with hexagonal phase The absorption spectrum showed a band gap value nearer to bulk CdSe Room temperature photoluminescence measurement showed the defect related emission from the nanowires

Template assisted growth of aligned CdSe nanowires by DC electrochemical process

An electrical ly-pumped terahertz (THz) frequency radiation source (or detector), including an optical gain (or absorption) material with two electrodes electrically coupled to the optical gain material. The optical gain (or absorption) material is formed substantially of at least one group IV element and doped with at least one dopant, which has an intracenter transition frequency in a range of about 0.3THz to 30THz. Also, a method of manufacturing electrical ly-pumped THz frequency radiation sources (or detectors).

Terahertz frequency radiation sources and detectors

Near infrared light emission in the range of 1.5-1.8 μm, sustaining upto 110 K temperature has been obtained from direct band gap transition in Ge1-xSnx nanostructures grown by molecular beam epitaxy on P-Si(100) substrates.

Photoluminescence Characteristics Of Ge1-xSnx Nanostructures Grown On Si Substrates Using Molecular Beam Epitaxy

This study deals with the fabrication of germanium (Ge) micropillars (MPs) followed by their development into novel Ge-MPs/Cu2ZnSnS4 (CZTS) heterojunction-based photodetectors. Vertically oriented and uniform Ge MPs templates were fabricated using facile and cost-effective wet-chemical etching techniques at the wafer scale. The CZTS thin films were deposited by pulsed laser deposition technique on MPs to obtain Ge MPs/CZTS heterostructures. Scanning electron microscopy and atomic force microscopy have been carried out to study the morphologies of the as-grown conical-shaped Ge MPs and their heterostructure with CZTS. The fabricated Ge MPs/CZTS heterostructure was then developed into a self-powered photodetector exhibiting broadband photodetection characteristics covering a wavelength range from visible-near infrared to short wave infrared (Vis-NIR-SWIR) region.

Samit K. Ray

Papers

Microelectronics Technology Development at IIT Kharagpur

Template assisted growth of aligned CdSe nanowires by DC electrochemical process

Terahertz frequency radiation sources and detectors

Photoluminescence Characteristics Of Ge1-xSnx Nanostructures Grown On Si Substrates Using Molecular Beam Epitaxy

Self-Powered, Broadband (400–1800 Nm), Highly Responsive Photodetectors Based on Germanium Micropillars/Cu2-ZnSnS4 Heterojunctions