Scandium detection of carbon dot based on bottom-up hydrothermal synthesis

Scandium is a rare earth element that is relatively scarce on Earth. The need for its rapid qualitative detection has increased dramatically owing to its extensive use in various high-tech sectors and potential environmental concerns. This work aims to develop a portable, simple, low-cost specific detection sensor for on-site qualitative detection of Sc 3+ ions. Multiple carbon dots were synthesized via the “bottom-up” hydrothermal method and characterized by morphology, structure, and optical properties. The characteristic structure of “salicylic acid” was determined as the core of the Sc 3+ selective detection function through precursor molecular engineering design. Further investigation was conducted into the impact of various factors on the Sc 3+ specific fluorescence detection performance of related derived carbon dots, including the electronic and spatial effects of various substituents on the aromatic skeleton of precursor molecules and the size of aromatic conjugated systems. The detection performance of carbon dots derived from different precursor sources was compared, and the optimal carbon dots derived from 2-hydroxy-3-naphthoic acid were selected, with a lower detection limit (4.38 ppb) and a significant blue shift (from green visible light to blue visible light range). On this basis, a portable device capable of detecting Sc 3+ ions, the 2-3-CDs PVA membrane, was developed. Our work presents the first discovery of carbon dots as Sc 3+ ion fluorescence sensors, providing new insights and beneficial results for subsequent rare earth element detection.