Surface Engineering of Quantum Dots for Self-Powered Ultraviolet Photodetection and Information Encryption

We demonstrate fabrication of photodetectors in the UVC and UVA regions, based on surface engineering of Mn2+-doped ZnS Qdot. Mn2+-doped ZnS Qdot exhibited UVC detection with a responsivity of 0.3 ± 0.02 A·W-1 and detectivity of 1.7 ± 0.2 1011 Jones. Following this, the Qdot was surface modified with 8-hydroxyquinoline 5-sulfonic acid ligand, which resulted in the formation of a bluish green zinc quinolate complex (Zn(QS)2) at the Qdot surface (defined as the quantum dot complex, QDC) exhibiting overall white photoluminescence. The detector developed with QDC as the photoactive material exhibited a responsivity of 0.2 ± 0.02 A·W-1 and detectivity of 1.2 ± 0.2 1011 Jones in the UVA band. This shift in the detection band from UVC in Qdot to UVA in QDC, through the surface complexation mechanism, is a new approach for tuning spectral detection featured in this work. Besides, the self-powered response of both the detectors exhibited attractive photoelectric characteristics. The detectors were incorporated in a portable prototype to show their potential application toward selective UVC and UVA spectral detection. Additionally, the dual-mode emission of the QDC was used for data encryption and decryption.