Abstract: The possibility of occurrence of the excitonic quasimolecule formed of spatially separated electrons and holes in a nanosystem that consists of CuO quantum dots synthesized in a silicate glass matrix. It is shown that the major contribution to the excitonic quasimolecule binding energy is made by the energy of the exchange interaction of electrons with holes and this contribution is much more substantial than the contribution of the energy of Coulomb interaction between the electrons and holes.
Abstract: In this work, the development of room-temperature solution-processed hybrid solar cells based on carbon nanotubes (CNT) - CdSe quantum dot (QD) hybrid material incorporated into a layer of conjugated polymer poly [2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopenta [2,1-b;3,4-b′] dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)], PCPDTBT, has been demonstrated. Incorporation of multi walled CNTs helps to improve the long-term efficiency of the solar cells in respect of power conversion efficiency (PCE) and short-circuit current density (Jsc) compared to QD only based devices. For the formation of the hybrid material hexadecylamine (HDA)/ trioctylphosphine oxide (TOPO) capped CdSe QDs were attached to CNTs by engineering the interface between CNTs and CdSe QDs by introducing thiol functional groups to CNTs. Initial PCE values of about 1.9 % under AM1.5G illumination have been achieved for this hybrid CNT-CdSe photovoltaic device. Furthermore, the long term stability of the photovoltaic performance of the devices was investigated and found superior to CdSe QD only based devices. About 90 % of the original PCE remained after storage in a glove box for almost one year without any further encapsulation. It is assumed that the improvement is mainly due to the thiol-functionalization of the CNT interface leading to a strong binding of CdSe QDs and a resulting preservation of the nanomorphology of the hybrid film over time.
Abstract: Multifunctional Si-Fe nanocomposites with varying atom percent of Fe were prepared by the high energy ball milling technique. Presence of pristine Fe and Si as separate entities in the nanocomposites was confirmed through the analyses of their Mössbauer spectrum and, x-ray diffraction patterns. The average grain size of Si has been found to be 40nm and the superparamagnetic Fe particles in the nanocomposite systems has been found to increase with increase in milling time. Transmission electron microscopic images revealed discontinuous distribution of Fe in the Si matrix. The Si-Fe nanocomposites exhibit both magnetic and photoluminescence properties at room temperature. The photoluminescence intensity was found to decrease with increase in Fe content in the nanocomposite samples, however, saturation magnetization and retentivity increases. Thus it is imperative that by adjusting the composition of Si-Fe nanocomposites their properties can be tailored to suit the desired requirements for applications in electronic devices.
Abstract: Bismuth tungstate (Bi2WO6) nanoparticles were synthesized by microwave assisted method. The prepared nanoparticles were investigated by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), UV-visible spectroscopy and dielectric studies. The formation of Bi2WO6 nanoparticles was confirmed by X-ray diffraction (XRD). The morphology of Bi2WO6 nanoparticle was characterized using scanning electron microscopy SEM. The optical properties were studied by the UV-Visible absorption spectrum. The dielectric properties of Bi2WO6 nanoparticles were studied. The activation energy was calculated from AC conductivity studies.Key words: Bi2WO6 nanoparticles, XRD, SEM, TEM, UV analysis, Dielectric studies and AC conductivity studies
Abstract: This paper investigates the reliability and performance of a refrigeration system using nanolubricant with 1, 1, 1, 2-Tetrafluoroethane (HFC-134a) refrigerant. Mineral Oil (MO) is mixed with nanoparticles such as Titanium Dioxide (TiO2) and Aluminium Oxide (Al2O3). These mixtures were used as the lubricant instead of Polyolester (POE) oil in the HFC-134a refrigeration system as HFC-134a does not compatible with raw mineral oil. An investigation was done on compatibility of mineral oil and nanoparticles mixture at 0.1 and 0.2 grams / litre with HFC-134a refrigerant. To carry out this investigation, an experimental setup was designed and fabricated in the lab. The refrigeration system performance with the nanolubricant was investigated by using energy consumption test. The results indicate that HFC-134a and mineral oil with above mentioned nanoparticles works normally and safely in the refrigeration system. The refrigeration system performance was better than the HFC-134a and POE oil system. Thus nanolubricant (Mixture of Mineral Oil (MO) and nanoParticles) can be used in refrigeration system to considerably reduce energy consumption and better Coefficient of Performance (COP).