Selective detection of Co2+ by L-CyS/AA CQDs and Construction of PASS 0 gate

Since the accidental discovery of carbon quantum dots (CQDs) in 2004, they have been widely used in the field of fluorescence sensing by combining their good optical and physicochemical properties with a wide source of raw materials and a simple synthesis process. In this work, we have synthesised sulphur-doped carbon quantum dots L-CyS/AA CQDs by a one-step microwave method using L-cysteine (L-CyS) and ascorbic acid (AA) as carbon and sulphur sources. It was also analysed by fluorescence spectroscopy, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The prepared L-CyS/AA CQDs showed good dispersion under TEM with a spherical shape and an average particle size of 7.3 nm. L-CyS/AA CQDs were observed to be bright blue-green fluorescent with strong fluorescence (>3.5*10³ a.u.) under UV light irradiation. PASS 0 logic gate operation can be achieved by controlling different fluorescent input and output. L-CyS/AA CQDs were able to achieve selective detection of Co²⁺ with a LOD of 63.2 μM, which provides a new method for Co²⁺ detection that can be used for the detection of Co²⁺ in real water samples.