Optical Properties of Semiconductor Nanocrystals
... particles with the number of atoms ranging from a few atoms to several hundreds of thousands atoms. The evolution of the properties of matter from atom
to crystal can be described in terms of the two steps: from atom to cluster and
from cluster to crystal.
The main distinctive feature of clusters is ...
Structural and Functional Characterization of Luminescent Silver
... energies of clusters containing a greater number of atoms (N >
20) show some deviation from the jellium model due to the
distortion of potential well used to describe the electronic
transitions in these metal NCs.17 The electronic transition in
these Ag NCs leading to luminescence is attributed to t ...
J. Jhaveri, S. Avasthi, G. Man, W. McClain, K. Nagamatsu, J. Schwartz, A. Kahn, J.C. Sturm, "Hole-blocking Crystalline Silicon/Titanium-Oxide Heterojunction with Very Low Interface Recombination Velocity", Proc. IEEE Photovoltaic Spec. Conf. (PVSC), Paper 912, Tampa, FL (JUN 2013).
Parametric down-conversion devices: The coverage of the
... 50 MHz to 1 GHz). These devices are called Synchronously
Pumped OPO (SPOPO), Fig. 1c. It should be emphasized that in all
down-conversion devices operating with ultrashort (i.e. picosecond or femtosecond) pulses, the NLC length must be short enough
so that group velocity mismatch (GVM) does not se ...
... The most common forms of SiC include powders,
fibers, whiskers, coatings and single crystals. There are
several methods to produce SiC depending on the product form desired and its application. Purity of the product
imposes certain restrictions on the selection of the
method of production.
SiC powde ...
J. Phys. Chem. 1993,97, 2618
... Excited-state intramolecular proton transfer (ESIPT) has
received considerable attention both experimentally and theoretically.14 The ESIPT process generally involves transfer of a
hydroxyl (or amino) proton to an acceptor such as a carbonyl
oxygen or a nitrogen atom in the excited state, resulting ...
Thermal conductivity of individual silicon nanowires
... reduced. This clearly indicates that enhanced boundary scattering has a strong effect on phonon transport in Si nanowires. 共ii兲 For the 37, 56, and 115 nm diam wires, thermal
conductivities reach their peak values around 210, 160, and
130 K, respectively. This is in sharp contrast to the peak of
Characterization of Quinine and Its Determination
... chemical quenching. Concentration quenching results from excessive absorption of either
primary or fluorescent radiation by the solution. Collisional quenching may be caused by
nonradiative loss of energy from the excited molecules, and the quenching agent (such as
oxygen) may facilitate conversion ...
... (ii)Dissolution of both Sodium hydroxide pellets and concentrated sulphuric
(VI) acid is an exothermic process because final (T2) temperature is higher
than the initial temperature (T1) thus causes a rise in temperature.
The above reactions show heat loss to and heat gain from the surrounding as
Ferroelectric materials for solar energy conversion
... represents the maximum voltage which can be generated by the
cell. Voc is limited (in a standard semiconductor junction) by the
band gap of the absorber layer, with additional recombination
losses (at open circuit, all photo-generated charges recombine).
Jsc is the photo-current extracted when the v ...
Analysis of thermal diffusivity in aluminum (particle)
... and 40 mm, was pre-dried for 1 h in a vacuum chamber at
393 K before incorporation into the PMMA matrix. Then
aluminum powder was added to the solution, stirred and
mixed well. The solution was cast in a mold of dimensions
larger than the ®nal ones required for the samples. The
specimen was put into ...
... The degree to which a dipole,P, is induced by the electric field, E, is described
by the molecular polarizability,
is related to how readily the electrons will move under the influence of an
electric field with respect to the nuclei of the molecule.
If the molecule undergoes some internal ...
Thermophotovoltaic (TPV) energy conversion is a direct conversion process from heat to electricity via photons. A basic thermophotovoltaic system consists of a thermal emitter and a photovoltaic diode cell.The temperature of the thermal emitter varies between different systems from about 900 °C to about 1300 °C, although in principle TPV devices can extract energy from any emitter with temperature elevated above that of the photovoltaic device (forming an optical heat engine). The emitter can be a piece of solid material or a specially engineered structure.Thermal emission is the spontaneous emission of photons due to thermal motion of charges in the material. For normal TPV temperatures, this radiation is mostly at near infrared and infrared frequencies. The photovoltaic diodes can absorb some of these radiated photons and convert them into free charge carriers, that is electricity.Thermophotovoltaic systems have few, if any, moving parts and are therefore very quiet and require low maintenance. These properties make thermophotovoltaic systems suitable for remote-site and portable electricity-generating applications. Their efficiency-cost properties, however, are often rather poor compared to other electricity-generating technologies. Current research in the area aims at increasing the system efficiencies while keeping the system cost low. In the design of a TPV system, it is usually desired to match the optical properties of thermal emission (wavelength, polarization, direction) with the most efficient conversion characteristics of the photovoltaic cell, since unconverted thermal emission is a major source of inefficiency. Most groups focus on gallium antimonide (GaSb) cells. Germanium (Ge) is also suitable. Much research and development in TPVs therefore concerns methods for controlling the emitter's properties.TPV cells have often been proposed as auxiliary power conversion devices for regeneration of lost heat in other power generation systems, such as steam turbine systems or solar cells. A prototype TPV hybrid car was even built. The ""Viking 29"" (TPV) powered automobile, designed and built by the Vehicle Research Institute (VRI) at Western Washington University.TPV research is a very active area. Among others, the University of Houston TPV Radioisotope Power Conversion Technology development effort is aiming at combining thermophotovoltaic cell concurrently with thermocouples to provide a 3 to 4-fold improvement in system efficiency over current radioisotope thermoelectric generators.