Revealing luminescence quenching mechanism of quantum dots under harsh conditions for designing highly robust anti-counterfeiting surface

Quenching mechanisms of AIZS and AIZS@SiO 2 core–shell nanoparticles were investigated. • Thermal quenching was mainly caused by the decomposition of organic ligands. • Chemical quenching was mainly resulted from the destruction of crystal structure. • Fluorescent quenching of hierarchical porous micro-nano surfaces was obviously improved. • Micro-nano hierarchical porous surfaces showed an application in information encryption field. Luminescence quenching is a common but undesirable phenomenon to quantum dots (QDs). However, systematic studies of quenching mechanism under harsh conditions are lacking. Herein, firstly, temperature-dependent PL intensity of Ag-In-Zn-S (AIZS) and their monodispersed silica-coated core–shell nanoparticles (AIZS@SiO 2 ) was conducted through thermal cycling experiments. PL intensity of AIZS QDs sharply decreased at 150 °C ( T q ), meanwhile a broad peak at 2932 cm −1 ascribed to C–H unit was detected. With continuously increasing temperature to 300 °C, this vibration band became stronger correspondingly, and PL intensity became weaker and weaker, providing direct support that thermal quenching was caused by decomposition of organic ligands. As expected, T q of AIZS@SiO 2 nanoparticles was increased to 250 °C owing to the thermal shielding of silica. Different from heating treatment, corrosive liquid seriously damaged crystal structure of AIZS QDs. XRDs pattern of AIZS@SiO 2 nanoparticles also became irregular after a longer treatment time, alkaline molecules still contacted core through mesoporous. Based on these findings, micro-nano hierarchical porous surfaces were constructed to trap air pockets for isolating luminescent component from harsh environments. With the helpful of thermal insulting property of air and silver mirror reaction, PL intensity was nearly unchanged even the functional surfaces were kept at 300 °C for 2 h and immersed into the strong alkaline solution for 24 h. The highly stable hierarchical porous surfaces showed good potential application in anti-counterfeiting and information encryption fields. Overall, this work provided theoretical insights in quenching mechanism of QDs and design guidance for QD with excellent robustness. Download: Download high-res image (128KB) Download: Download full-size image