A click-induced fluorescence-quenching sensor based on gold nanoparticles for detection of copper(II) ion and ascorbic acid

Gold nanoparticles (AuNPs), as one of the major tools of fluorescence-quenching sensors, have been widely used in biochemical analysis through fluorescence resonance energy transfer (FRET) effect. With the development of chemistry and biochemistry, reaction-based fluorescent sensors have attracted increasing attention because of their unique selectivity, high sensitivity and rapid detection. Here we report a click-induced fluorescencequenching sensor based on AuNPs for detection of copper ion (Cu2+) and ascorbic acid (AA). A fluorescent dye Rhodamine B-(CH2CH2O)4-azide (RB-PEG4-N3) is conjugated to the surface of AuNPs via Cu(I)-catalyzed azidealkyne cycloaddition (CuAAC) in the presence of Cu2+ and AA, leading to the fluorescence quenching of Rhodamine B. The sensor responds quickly (within less than 3 min). The fluorescent intensity linearly correlates with the concentration of Cu2+ in the range of 0-10(8) mu M. The limit of detection (LOD) for Cu2+ is 5.8 mu M. The concentration range for detection of AA is 0-3 mM. The LOD for AA is 0.13 mM. In addition, the application of the sensor is verified by performing detection in real samples such as fresh orange, juice, VC tablet, and lake water. This work expands the application of AuNPs-based fluorescence-quenching sensors for multi-component detection.