The tunable synthesis of orange emissive carbon dots for sensitive and selective detection of Hg2+ via portable paper sensor

Creating a sensitive, accuracy and portable fluorescent probe to monitor Hg2+ with rapid visual convenient process is highly desirable but remains challenging. Herein, orange emissive carbon dots (O-CDs) were synthesized and optimized by solvothermal method using p-phenylenediamine (p-PDA) as precursor. The O-CDs emitted an orange emission at 594 nm excited at 480 nm, with QY of 23.25% and a long lifetime of 14.43 μs. The O-CDs exhibited sensitive quenching response towards Hg2+ based on dynamic quenching effect, which facilitated O-CDs utilizing as the fluorescent probe with the limit of detection at 37.6 nM. The O-CDs fulfilled sensing Hg2+ in environmental water with satisfactory recoveries (90.3%−107.8%) and relative standard deviation (RSD) of less than 3.81%, manifested their excellent environmental tolerance. Notably, the O-CDs based test paper was fabricated and served as a portable sensor with a smartphone assistant for detection of Hg2+, which greatly elevated the sensing performance of test paper. This work contributed an innovative approach for the synthesis of O-CDs, as well as a reliable sensitive sensor based on portable test paper for an intelligent readable recognizing system, which could be regarded as promising candidate for real detection of Hg2+.