Carbon dots based multicolor fluorescence sensor for ratiometric and colorimetric dual-model detection of Cu2+

Recent development in carbon dot-based gas sensors

“…If no change in fluorescence lifetime is observed during FL quenching, then IFE is the involved FL quenching mechanism. 6,14,17,38,41,46,47,53,81,89 The dynamic quenching kinetics follows the Stern–Volmer relation ofwhere ‘ F ’ and ‘ F 0 ’ are the FL intensity of CDs in the presence and absence of a quencher, k q is the quench rate, τ 0 is the FL lifetime and [C] is the quencher concentration. 38,47 The higher the electron donating ability of a gas molecule and the lower the steric hindrance, the higher the extent of FL quenching in the CD sensors.…”

“…the emission wavelength of one of the fluorophores is in the vicinity of the excitation wavelength of other fluorophores. 41,46,74,77 He et al 77 developed a blue luminescent CD (B-CD) and red luminescent CD (R-CD) co-doped mesoporous alumina (MA) that exhibited ratiometric fluorescence in the presence of oxygen. Its mechanism is similar to FRET and the energy transfer efficiency can be calculated usingwhere τ B-CD and τ B-CD/R-CD are the decay lifetime of B-CD single doped and B-CD/R-CD/MA, respectively.…”

“…A fluorescence sensor uses variation in the fluorescence intensity/quenching of CDs on absorption and desorption of analytes while colorimetric sensors use the shift in fluorescence peak of CDs as sensing signal. Optical sensors are attractive as they are simple, cost effective and provide rapid qualitative information as their results for various chemical species can be observed on-site with naked eye [43,46]. Unlike fluorescence and colorimetric sensors, which depend on the visual signals, the variation in the resistance or impedance of CDs deposited on glass carbon electrodes is used to detect analytes in electrochemical sensors.…”

“…A sensor is a kind of transducer which converts chemical information on concentration of a particular molecule into electrical or optical signals. Carbon dots have been used to detect several metal ions such as Sensors & Diagnostics Critical review Fe 3+ , 13,14,24,[36][37][38][39][40][41][42][43] Hg 2+ , 13,16,24,38,40,41,44 Cu 2+ , 13,16,24,[38][39][40][41]43,45,46 Ag + , 13,39,40,43 Pb 2+ , 14,[38][39][40]43 Cr 6+ (ref. 13, 16, 24, 41 and 47) and so on, relative humidity, 13,[48][49][50] temperature, 37 molecules in the liquid phase, 13,23,51,52 gas molecules, etc.…”

“…13, 16, 24, 41 and 47) and so on, relative humidity, 13,[48][49][50] temperature, 37 molecules in the liquid phase, 13,23,51,52 gas molecules, etc. Fluorescence sensors, 42,47,53,54 electrochemical sensors [54][55][56][57][58] and colorimetric sensors 43,46,54,59 are some of the widely explored CD-based sensor types. A fluorescence sensor uses variation in the fluorescence intensity/quenching of CDs on absorption and desorption of analytes, while colorimetric sensors use the shift in fluorescence peak of CDs as a sensing signal.…”