Phosphorescent MoS2 quantum dots as a temperature sensor and security ink

Abstract

Currently, few phosphorescent materials (PMs) possess long phosphorescent lasting time and show their applications in chemical sensors. Herein, we disclose that the incorporation of few-layer molybdenum disulfide quantum dots (FL-MoS2 QDs) into poly(vinyl alcohol) (PVA) matrices emitted bright green phosphorescence with a long-lasting time of 3.0 s and a phosphorescence quantum yield of 20%. This enhanced phosphorescence originates from the formation of O−H•••S hydrogen bonding networks between rich sulfur sites of the FL-MoS2 QDs and hydroxyl groups of PVA molecules, which not only rigidifies the vibration modes of the FL-MoS2 QDs but also provides an oxygen-barrier. Further investigations reveal that the FL-MoS2 QD/PVA composites exhibited longer phosphorescent lasting time than N, S-doped carbon dots, few layer tungsten disulfide quantum dots, Rhodamine 6G, and Rhodamine B in PVA matrices. Since heat efficiently induced the removal of water moisture from PVA matrices, the FL-MoS2 QD/PVA composites were found to implemented for phosphorescence turn-on and naked-eye detection of temperature variations ranging from 30 to 70 °C. By contrast, the carbon dot/PVA composites were incapable of sensing environmental temperature due to their weak hydrogen bonding with hydroxyl groups of PVA matrices. Additionally, this study reveals the potential of the FL-MoS2 QDs/PVA composites as an advanced security ink for anti-counterfeiting and encryption applications. Given results could open a new direction for potential applications of two-dimensional quantum dots in phosphorescence-based sensors and security inks.