<i>De Novo</i> Proteins Template the Formation of Semiconductor Quantum Dots

Here, we present the first instance of utilizing <i>de novo</i> proteins to regulate the size of cadmium sulfide (CdS) quantum dots. Four proteins were found to bind to CdS and cap the growth of CdS quantum dots, leading to precise size control, as evidenced by absorbance and fluorescence spectra. Increasing the concentration of CdS does not change the absorbance and emission peaks, thereby indicating that the proteins effectively constrain the size of the quantum dots. Employing different proteins also yielded quantum dots with distinct optical and physical properties, including the appearance of biomediated nanorods when SynI3 was utilized. Moreover, the <i>de novo</i> proteins effectively maintained the stability of the quantum dots for up to 7 days, surpassing the stability of quantum dots capped by the small molecule, l-cysteine. The ability to cap CdS likely stems from their affinities for Cd²⁺, yet there does not seem to be a direct correlation between the affinity for Cd²⁺ and the size of resulting quantum dots.