Effect of Mercaptosuccinic Acid Stabilizer Agent on the Optical Properties of Colloidal CdTe Quantum Dots

In the present work, we report on the positive effect of mercaptosuccinic acid (MSA) stabilizer agent on the optical features of colloidal CdTe quantum dots (QDs). With this aim, we performed some spectroscopic measurements such as steady-state absorption and fluorescence, fluorescence quantum yield and time-resolved photoluminescence for five MSA-capped CdTe QD samples with different synthesis times. The first general aspect to highlight is that the QDs' average size increased with synthesis time (from 30 to 150 min) while the size dispersion decreased due to the Ostwald ripening mechanism. Second, comparing the optical properties of CdTe QDs obtained from the same synthesis route, we show that MSA stabilizer agent enhanced the optical properties of CdTe QDs as compared with other widely used stabilizer agents such as GSH and TGA. We ascribe this outcome to reduction of the number of surface defects of the CdTe QDs because the MSA stabilizer agent decreases the growth rate of nanocrystals, causing an improvement in their surface quality. In the light of Fermi's golden rule, we observed that for longer synthesis time the optical properties of CdTe QDs increases due to the enhancement of the direct radiative recombination rate of electrons and holes and decrease in the decay rate for core states. Finally, we investigated the pH-dependent fluorescence and demonstrated the similar behaviour in acidic range between MSA-capped CdTe and mercaptocarboxylates-capped CdTe.