CdSe/TiO2 core-shell nanoparticles produced in AOT reverse micelles: applications in pollutant photodegradation using visible light

CdSe quantum dots with a prominent band-edge photoluminescence were obtained by a soft AOT water-in-oil (w/o) microemulsion templating method with an estimated size of 2.7 nm. The CdSe particles were covered with a TiO2 layer using an intermediate SiO2 coupling reagent by a sol-gel process. The resulting CdSe/TiO2 core/shell nanoparticles showed appreciable photocatalytic activity at λ = 405 nm which can only originate because of electron injection from the conduction band of CdSe to that of TiO2

CdSe quantum dots using polyselenide precursor in soft chemical conditions

CdSe quantum dots were prepared by a simple microemulsion templating technique at low temperature and using common inorganic precursors. Size control was obtained by small variations in reactant concentrations. The chalcogenide source was a polyselenide solution. Narrow (30-40nm fwhm) band gap photoluminescence low defect level and high quantum yield were obtained.FCT and FEDER for financial support to the Research Centre, CFUM [PEst-C/FIS/UI0607/2011 (F-COMP-01-0124-FEDER-022711)] and to the research project PTDC/FIS/113199/200

Photocatalytic properties of BaSnO3 perovskite nanoparticles conjugated with CdTe@CdS quantum dots in water-splitting

In this work, we report the photoactivity of BaSnO3 in the photoreduction of methylviologen and the effect of quantum dot sensitization by covalently linking CdTe/CdS core/shell quantum dots in the surface of BaSnO3.FCT - CFUM Strategic Project PEst-C/FIS/UI0607/2013 (F-COMP-01-0124-FEDER-022711)

Synthesis of new benzo[a]phenoxazinium probes possessing carboxylic ester, hydroxyl and amino functional groups: photophysical studies in dry ethanol and conjugation with CdTe quantum dots

A new series of benzo[a]phenoxazinium chlorides possessing hydroxyl, ethyl ester and amino functional groups as terminal substituents at the 9- and 5-positions of the tetracyclic aromatic system in different combinations, was synthesised. A photophysical study was carried out in anhydrous ethanol and water, as a function of solution pH. Acid dissociation constants were estimated and found to depend on the nature of the terminal groups. Experimental evidence for an additional molecular form is presented and is compatible with J-aggregates of the deprotonated form of some of the earlier studied the benzo[a]phenoxazinium chlorides. The benzo[a]phenoxazinium chloride possessing the amino terminal group was reacted with the carboxylic acid of CdTe quantum dots (QDs) to obtain a conjugate of the dye and QD. Initial photophysical characterisation indicates both photoinduced electron and energy transfer between the QD and the attached benzo[a]phenoxazinium chloride.Fundação para a Ciência e a Tecnologia (FCT

Energy Transfer via Exciton Transport in Quantum Dot Based Self-Assembled Fractal Structures

Semiconductor quantum dot (QD) assemblies are promising systems for light harvesting and energy conversion and transfer, as they have a superior photostability compared to classical dyes and their absorption and emission properties can be tuned during synthesis. Here, we investigate excitonic energy transfer in self-assembled dentrite-type fractal structures consisting of QDs by microscopically mapping their fluorescence spectra and lifetimes. The behaviors of CdSe/ZnS and CdTe QD assemblies are compared; in particular, the energy transfer probability is found to be stronger in CdTe-based structures, scaling with their radiation quantum yield. Our results indicate Förster-type energy transfer in both systems, although with a higher efficiency in CdTe. The energy transfer is caused by near-field (nonradiative) dipole–dipole coupling between the individual QDs within a dendrite, with the excitation migrating from the edges to the center of the structure. The experimental findings are supported by theoretical modeling results obtained by using master equations for exciton migration/decay kinetics in diffusion-limited fractal aggregates composed of identical particles

Energy transfer via exciton transport in quantum dot based self-assembled fractal structures

Semiconductor quantum dot (QD) assemblies are promising systems for light harvesting and energy conversion and transfer, as they have a superior photostability compared to classical dyes and their absorption and emission properties can be tuned during synthesis. Here, we investigate excitonic energy transfer in self-assembled dentrite-type fractal structures consisting of QDs by microscopically mapping their fluorescence spectra and lifetimes. The behaviors of CdSe/ZnS and CdTe QD assemblies are compared; in particular, the energy transfer probability is found to be stronger in CdTebased structures, scaling with their radiation quantum yield. Our results indicate Förster-type energy transfer in both systems, although with a higher efficiency in CdTe. The energy transfer is caused by near-field (nonradiative) dipole−dipole coupling between the individual QDs within a dendrite, with the excitation migrating from the edges to the center of the structure. The experimental findings are supported by theoretical modeling results obtained by using master equations for exciton migration/decay kinetics in diffusion-limited fractal aggregates composed of identical particles.Fundação para a Ciência e a Tecnologia (FCT) PTDCFIS- 113199-2009, PEst-C/FIS/UI0607/201