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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.