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.

Thin amorphous diamond-like nanocomposite (a-DLN) films are deposited on p-type crystalline silicon (c-Si) by plasma assisted chemical vapour deposition (PACVD) technique to use it as an ammonia (NH3) gas sensor operable at room temperature. The non-linear current–voltage (I–V) characteristic of a-DLN/c-Si heterojunction shows a very good rectifying property of the junction in air and quick sensitivity in NH3 gas at room temperature. The current output in reverse biased condition of the a-DLN/c-Si heterojunction is ~ 15 times higher in NH3 than in air. Sensor also shows a good recovery property to the original state, even at room temperature. Sensing material is characterized by using Field Emission Scanning Electron Microscope (FESEM), Fourier Transform Infrared Spectroscopy (FTIR) and UV–VIS Near-IR Spectroscopy, to understand the sensing behaviour.

A Novel Room Temperature Ammonia Gas Sensor Based on Diamond-Like Nanocomposite/c-Silicon Heterojunction

We have investigated the structural and electrical properties of metal-ferroelectric-insulator-semiconductor capacitors with 280-nm-thick SrBi2Ta2O9 (SBT) ferroelectric films grown on Si as well as on Si with buffer layer (HfO2). The SBT thin films and HfO2 buffer layer were fabricated using rf magnetron sputtering method. XRD patterns revealed the formation of well crystallized SBT perovskite thin film on the HfO2 buffer layer which is evident from sharp peaks in XRD spectra. The electrical properties of the metal-ferroelectric-insulator- semiconductor (MFIS) structure were characterized by varying thickness of the HfO2 layer. The width of memory window in the capacitance-voltage curves for the MFIS structure decreased with increasing thickness of HfO2 layer. Leakage current density decreased significantly after inserting HfO2 buffer layer. This shows that the proposed Al/SrBi2Ta2O9/HfO2/Si structure ideally suitable for high performance ferroelectric memories.

Characteristics of Al/SrBi 2 Ta 2 O 9 /HfO 2 /Si structure using HfO 2 as buffer layer for ferroelectric-gate field effect transistors

Study of Heterogeneous Interaction and Excess Thermo Dynamical Parameters in the Binary Mixtures of T-Butanol with Alkanes

An intense THz emission was observed from strained SiGe/Si quantum-well structures under strong pulsed electric field. The p-type structures were MBE-grown on n-type Si substrate and δ-doped with boron. Lines with wavelengths near 100 microns were observed in the emission spectrum. The modal structure in the spectrum gave evidence for the stimulated nature of the emission. The origin of the THz emission was attributed to intracenter optical transitions between resonant and localized boron levels.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Stimulated THz emission of acceptor-doped SiGe/Si

Carbon nanostructures technology has recently emerged as a key enabler for next-generation optoelectronic devices including deep UV detectors and light sources which is promising in health and environment monitoring Here, we report the fabrication of solution processed Carbon nano-dots (CNDs)/n-Si heterojunction showing broadband spectral response with a peak responsivity of ~ 125 A/W in UV (~300 nm) wavelength The surface topography and chemical information of synthesized CNDs via a facile synthesis route have been characterized showing the presence of surface chemical states resulting broad optical emission The CNDs/n-Si photo diodes exhibit very low dark current (~500 pA), excellent rectification ratio (~5*10^3), and very good photo-modulation in UV region Given the solution-processing capability of the devices and extraordinary optical properties of CNDs, the use of CNDs will open up unique opportunities for future high-performance, low-cost DUV photo detectors

Samit K. Ray

Papers

A Novel Room Temperature Ammonia Gas Sensor Based on Diamond-Like Nanocomposite/c-Silicon Heterojunction

Characteristics of Al/SrBi 2 Ta 2 O 9 /HfO 2 /Si structure using HfO 2 as buffer layer for ferroelectric-gate field effect transistors

Study of Heterogeneous Interaction and Excess Thermo Dynamical Parameters in the Binary Mixtures of T-Butanol with Alkanes

Stimulated THz emission of acceptor-doped SiGe/Si

Solution Processed CMOS compatible Carbon Nano-dots Based Heterojunction for Enhanced UV Detector