Photoluminescence, its temperature dependence, and photoluminescence excitation spectra of InAs quantum dots embedded in asymmetric InxGa1−xAs∕GaAs quantum wells [dots in a well (DWELL)] have been investigated as a function of the indium content x (x=0.10–0.25) in the capping InxGa1−xAs layer. The asymmetric DWELL structures were created with the aim to investigate the influence of different barrier values at the quantum dot (QD)/quantum well interface on the photoluminescence thermal quenching process. The set of rate equations for the two stage model for the capture and thermal escape of excitons in QDs are solved to analyze the nature of thermal activation energies for the QD photoluminescence quenching process. The two stage model for exciton thermal activation was confirmed experimentally in the investigated QD structures as well. The localization of nonradiative defects in InAs∕InGaAs DWELL structures is discussed on the base of comparison of theoretical and numerically calculated (fitting) results.

We report on optical enhancement of the 655 nm photoluminescence (PL) band intensity in the core-shell CdSe/ZnS nano-particles (quantum dots) under a laser illumination. Kinetic curves and 80 K-to-room temperature dependences of the PL intensity reveal two parallel processes: a reversible enhancement when the PL intensity is recovered after the laser illumination is turned off, and a non-reversible permanent increase of the PL output. Experimental data evidence that the PL enhancement is attributed to the light-activated increase of the energy barrier for photo-generated carriers to escape quantum dot levels. A trap recharging and/or photo-chemical bond restructure play a possible role in the luminescence photo-enhancement.

Core-shell CdSe/ZnS quantum dots are promising as bio-luminescent markers: being conjugated to bio molecules (proteins), they serve as luminescence tags in antigen-antibody biochemical reaction. This presents a possibility to detect, for example, the variation of the protein biomarkers to promote the early cancer diagnosis. We studied the effect of bio molecules conjugated to QDs using Raman scattering spectra, and found that in some cases the conjugation leads to noticeable variation of these spectra, so that the detection of bio molecules could be done more accurately. An explanation of the effect is proposed.

The authors performed scanning photoluminescence (PL) spectroscopy on CdSe∕ZnS core/shell quantum dots (QDs) bioconjugated to Interleukin 10 (IL10) antibody. The influence of IL10 on the QD photoluminescence spectra was explored on samples dried on solid substrates at various temperatures. A “blue” up to 15nm spectral shift of the PL maximum was observed on the bioconjugated QDs. The spectral shift is strongly increased after samples annealing above room temperature. A mechanism of the observed effect is attributed to changes in the QD electronic energy levels caused by local electric or stress field or chemical reactions which occurred on the QD surface.

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