Regulating properties of quantum dots: effect of methyl side groups of mercapto acids

Abstract

A series of mercapto acids with and without methyl side groups, namely 3-mercaptopropanoic acid (MPA), 4-mercaptobutyric acid (MBA), 5-mercaptovaleric acid (MVA), 3-mercaptobutyric acid (3MBA), 3-mercaptoisobutyric acid (MIBA), 3-mercapto-2-methylbutyric acid (MMBA) and 3-mercapto-2,2-dimethylpropanoic acid (MDMPA), were synthesized and used as capping agents to prepare CdTe quantum dots (QDs) by a modified hydrothermal method with Na₂TeO₃ as Te source. By comparing the growth rate, size distribution, fluorescence and solution stability of QDs capped with these mercapto acids, the effect of the position and amount of the methyl side groups of mercapto acids in the aqueous synthesis of CdTe QDs was revealed. The use of branched mercapto acids with one methyl side group (3MBA and MIBA) was superior to obtain QDs with narrow size distribution, strong fluorescence and good long-term solution stability than the use of linear mercapto acids (MPA, MBA and MVA) whereas the use of branched mercapto acids with two methyl side groups (MMBA and MDMPA) was not equally successful. Among these mercapto acids, 3MBA-QDs had the strongest fluorescence and MIBA-QDs had the narrowest size distribution. Our results are helpful for synthesizing QDs with good properties by selecting and designing appropriate capping agents.