Electrochemiluminescence Mechanistic Insights of CuInS2/ZnS Nanocrystals with Hydrazine Compounds as Co-reactants

Screening a novel electrochemiluminescence (ECL) system and reducing electrochemical interference by lowering the ECL potential are crucial to ECL evolution. Herein, an ECL system is explored with different hydrazine compounds as coreactants and ternary CuInS2/ZnS nanocrystals (CIS/ZnS NCs) as a luminophore, demonstrating that hydrazine compounds with varied structures would assuredly affect the ECL triggering potential and efficiency. Electro-oxidized hydrazine-based coreactants containing a symmetrical structure and −N–N single bonds with strong reducibility could produce an efficient electron transfer recombination path with electro-oxidized CIS/ZnS NCs, which eventually generate efficient and low-triggering-potential ECL performance; otherwise, the hydrazine compounds with a double bond, such as −C═N or −C═O, or strong electronegative atoms would reduce the ECL efficiency and increase the ECL triggering potential, which result from double bonds or strong electronegative atoms of hydrazine compounds hindering the protonation of coreactants and then delaying the electron–hole recombination process. The structure of hydrazine-based coreactants with a −C═S double bond would competitively bond with the Cu element within CIS/ZnS NCs, contributing to the blank ECL with CIS/ZnS NCs as the luminophore. Furthermore, CIS/ZnS NCs exhibit two additional low hole injected processes under alkaline conditions through exploration of the differential pulse voltammetry (DPV) nature from CIS/ZnS NCs. The ultralow-triggering-potential of CIS/ZnS NCs around 0.11 V could be achieved by adjusting the hole injection processes of NCs and selecting pasoniazide as the coreactant, which is extremely below any previously reported ECL system. This work contributes to a deeper understanding of the ECL mechanism.