A facile method is proposed to synthesize carbon quantum dots (C-dots) from citric acid using concentrated sulfuric acid as carbonization reagents with temperature below 100 °C during the whole process. The prepared C-dots has a Gaussian distribution in its lateral size with the average value around 6.37 nm. High quality of the C-dots is revealed through the optical performances such as sharp band-edge absorption, typical absorption peak and nearly excitation-independent blue emissions. Further, the pH condition is found to have correlation on the strong and stable photoluminescence property.
Highly sensitive detection of CTLA‑4‑positive T‑cell subgroups based on nanobody and fluorescent carbon quantum dots