Effects of carbon nanotubes on photoluminescence properties of quantum dots

The effects of carbon nanotubes (CNT) with different surface groups on the luminescence properties of mercaptoacetic acid-capped CdSe quantum dots (QD) are reported. Carboxyl-, hydroxyl-, and amine-modified CNTs are used to interact with water-soluble luminescent mercaptoacetic acid-capped CdSe QDs. TEM and zeta-potential analysis results show that CNT and QDs can be assembled into complex nanostructure by electrostatic interaction. The photoluminescence (PL) quenching of QDs caused by CNTs can be described by a Stern - Volmer-type equation as well as by a double-logarithmic equation. Significant differences in the values of binding constants K-SV and K-b were found in these experiments. The binding constant for amine-terminated CNT is much higher compared to that of carboxyl- and hydroxyl-terminated CNTs. Dynamic quenching and photoluminescence resonance energy transfer between QDs and CNTs should be responsible for the quenching of photoluminescence emissions of QDs caused by CNTs with different groups. The strategy shown in this paper may be useful for creating a novel methodology for investigating intermolecular interaction, and the quenching phenomena may be used as selective molecular probes and developed as fluorescence sensors.