Effects of Derivatives of 3-Mercaptoisobutyric Acid on the Aqueous Synthesis of CdTe Quantum Dots

Mercapto acids can affect the obtaining CdTe quantum dots (QDs) with narrow size distribution and high fluorescent quantum yield (QY) that emit in the red to near-infrared region. To study their effects on CdTe QDs, three types of derivatives of 3-mercaptoisobutyric acid (MIBA) were designed and synthesized: hydrophilic side-chain derivative N-acetylcysteine (ACys), hydrophobic side-chain derivatives 3-mercapto-2-methylbutyric acid (MMBA) and 3-mercapto-2,2-dimethylpropanoic acid (MDMPA), and hydrophilic main-chain derivatives 3-mercaptoisobutoyl-3-aminopropanoic acid (MIBAPA), 3-mercaptoisobutoylglycine (MIBGly) and 3-mercaptoisobutoylaspartic acid (MIBAsp). To evaluate the effects of these MIBA derivatives on the properties of CdTe QDs, they were used as capping agents during hydrothermal synthesis of the QDs with sodium tellurite as the tellurium source. The effects of the mercapto acids were revealed by comparing the growth rate, and full width at half-maximum (FWHM) of the fluorescent peak of CdTe QDs capped with different mercapto acids. All three types of MIBA derivatives gave CdTe QDs with relatively narrow FWHM, similar to MIBA. The hydrophilic MIBA derivatives (ACys, MIBGly, MIBAPA, and MIBAsp) produced CdTe QDs with longer emission wavelength than those from hydrophobic derivatives. Hydrophilic side-chain MIBA, derivative ACys gave CdTe QDs with stronger fluorescence.