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[en] We have found that a photoactive metal selenide film, such as cdse, may be formed by cathodic eletrodeposition from a selenosulfite (Seso32-) solution without the need for a subsequent heat treating step which, it is hypothesized, was required by the simultaneous deposition of elemental selenium
[en] A simple method that combines an electrospray technique with directed assembly using an electrostatic field was used for decorating carbon nanotubes (CNTs) with nanocrystals. Colloidal CdSe and Au nanocrystals were electrosprayed and assembled onto random CNTs and vertically aligned CNTs in a controlled manner. The high level of electrical charge on the electrosprayed aerosol nanocrystals was responsible for the assembly. The technique can be used to assemble various compositions of nanomaterials onto different substrates and provides a versatile route for producing novel hybrid nanostructures.
[en] CdS nanocrystallites were prepared by sulphidation of cadmium arachidate LB multilayers. The composite multilayers were treated with aqueous CdCl2 and heat treated in the range of 100-250 deg C. PL studies show that annealing of CdCl2 treated multilayers results in strong enhancement of excitonic emission due to passivation of surface states. Atomic force microscopy studies indicate that up to 200 deg C, the CdA present in the multilayers assists in passivation of surface defects and restricts the growth of CdS nanocrystallites. (author)
[en] In the present work, spectroscopic features and sensitivity of poly[2-methoxy-5-(2′-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) and vanadyl 2,9,16,23-tetraphenoxy-29H,31H-phthalocyanine (VOPcPhO) based photodetector have been improved by employing cadmium selenide quantum dots (CdSe QDs). The incorporation of CdSe QDs has heightened the optical absorption, particularly in the range of 400–560 nm. The MEH-PPV:VOPcPhO:CdSe based hybrid photodetector (PD) has been investigated under the influence of illumination levels varying from 0–140 mW/cm2. The PD fabricated with CdSe QDs is found to be 3.2 times faster in response time and 2 times quicker in the recovery time as compared to the PD without CdSe QDs.
[en] Highlights: • Microscopic of CdSe/ZnS using anti-Stokes luminescence was confirmed. • Newly proposed photothermal deflection technique does not require multiple lasers. • Deflection of probe beam with respect to pump beam is an indicator of cooling. - Abstract: Photothermal deflection spectroscopy (PDS) is a highly sensitive and precise technique that is used to measure the optical absorption and thermal characteristics of a sample. While most applications of PDS utilize a heating beam, laser cooling of solids, or optical refrigeration as it is sometimes called, use this technique to determine if a laser is cooling or heating a sample. Current PDS methods for laser cooling require multiple laser wavelengths in both the Stokes and anti-Stokes region to ensure that cooling is occurring. This can cause problems if lasers must be changed or no lasers in the desired wavelength are available. Herein, we present a photothermal deflection technique that uses the deflection of the probe laser to determine if microcooling is occurring inside a sample.
[en] It was determined by experiments, that light with linear polarization was absorbed more intensively in CdSe nanocrystals, as compared to light with circular polarization. This testifies to discovery of linear-circular dichroism in CdSe nanocrystals
[en] The phase and energy relaxation of the localized electronic states has been studied in CdSxSe1-x mixed crystals with femtosecond pulses. Under resonant excitation, at 2K, the phase coherence of the localized excitons lasts several tens of picoseconds. Both phonon assisted interwell tunneling and interband radiative recombination are involved in this long decay. Before these processes, a coupling between localized excitons in a same well occurs, leading to the formation of biexcitons associated to a much faster decay time (∼700 fs). A detailed analysis of the dephasing mechanism due to one and two particle processes is performed via the observation of quantum beats between the localized excitonic and biexcitonic states. (orig.)