Stabilization of (CdSe)ZnS quantum dots with polypyrrole formed by UV/VIS irradiation initiated polymerization

Polypyrrole formation initiated by UV/VIS irradiation and stabilization of (CdSe)ZnS quantum dots is reported. Presented results demonstrate that UV/VIS irradiation is slowly destructing Q-dots that decreases quantum yield and shifts peak of photoluminescence (PL) spectra to short wavelength range. The same Q-dot solution under UV/VIS light irradiation in the presence of pyrrole is more stable, there is no PL band shifts only PL intensity of Q-dot decrease. UV/VIS induced Ppy formation process in the presence/absence of Q-dots dissolved in toluene and phosphate buffer saline (PBS) not containing Q-dots was investigated. The increase in the optical absorbance in the range of 400 nm-600 nm was exploited for the monitoring of polypyrrole formation process. Results obtained proved that in the presence of UV/VIS formed polypyrrole destruction of Q-dots is much slower if compared with bare Q-dots destruction under similar conditions. However, formed polypyrrole showed no positive effect on quantum yield of Q-dot, just the opposite-polypyrrole quenched Q-dot photoluminescence. Results presented and observation by other authors on pyrrole polymerization allow to predict that by UV/VIS induced polymerization formed polypyrrole is assembling polymeric layer on heterogeneous phase between Q-dot and toluene or water (in PBS solution). Established pi-pi conjugated chain of formed polypyrrole quenches photoluminescence of Q-dot because this polymer was formed in close proximity to Q-dot surface.