Liquid nitrogen-assisted synthesis of fluorescent carbon dots from Blueberry and their performance in Fe3+ detection

•Fluorescent carbon dots (C-dots) are synthesized by a facile method.•The as-prepared C-dots have strong fluorescence between 350 and 550 nm.•In a wide pH and temperature range, the C-dots are stable and show fluorescence property.•The C-dots can be used to detect Fe+3 as a fluorescence sensor. Fluorescent carbon dots (C-dots) were synthesized by a facile method containing liquid N2 treatment and centrifuge processes. The photophysical properties of the C-dots in an aqueous solution were examined at various conditions such as concentration, temperature, pH and excitation wavelength by using UV–vis absorption, fluorescence and time-resolved fluorescence spectroscopies. The C-dots emitted a broad fluorescence between approximately 350–550nm and their fluorescence was tuned by changing excitation wavelength. The as-prepared C-dots were applied to Fe3+ detection from aqueous solution. Spectroscopic data revealed that the as-prepared C-dots were used to detect Fe3+ in the range of 12.5μM to 100μM as a fluorescence sensor.