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.