A ratiometric fluorescence and colorimetric dual-mode sensing platform based on sulfur quantum dots and carbon quantum dots for selective detection of Cu2+

Portable ratiometric fluorescence detection of Cu2+ and thiram

“…The appearance of new absorption peaks upon the addition of Cu 2+ to the CDs/OPD probes suggests the creation of new complexes within the probe system due to the addition of analytes. Previous studies have shown that OPD can be oxidized by Cu 2+ to produce a new complex oxidized state OPD (ox-OPD) with an absorption peak at 418 nm [55]. The generation of the novel complex of ox-OPD is confirmed in figure S9 by combining the changes observed in UV-visible absorption spectra and nuclear magnetic resonance analysis (NMR) [56,57].…”

A dually emissive MPA-CdTe QDs@N, S-GQD nanosensor for sensitive and selective detection of 4-nitrophenol using two turn-off signals

“…Several studies have reported the occurrence of double-response behavior when employing two fluorescent units or dual-emissive CQDs as detection sensors. 31,37–40 Dong et al 38 reported a two-turn-on fluorescence-based sensor for H 2 O in D 2 O and noted that the slope of the signal ratio lacked significance, indicating no concentration-dependent relationship. Our results reveal that this low slope is attributed to nearly equal changes in the fluorescence peaks.…”

“…This independence can be attributed to the presence of a single emission site in the QDs and the uniform size distribution of the QDs. 14,31,32 Excitation-dependent uorescence is typically observed in carbon-based QDs. 17,33,34 This, therefore, limits the possibility of using them at different excitation wavelengths in uorescence-based sensors.…”

Synthesis of Fluorescent Sulfur Quantum Dots for Bioimaging and Biosensing

“…Although the reaction time was very long (125 h) and the fluorescence quantum yield (QY) of the prepared SQDs was low (3.8%), this work opens a door for the direct preparation of fluorescent SQDs from cheap and abundant elemental S ( Wang et al, 2020 ). To date, most reported SQDs were prepared based on the elemental S-NaOH reaction system ( Chen et al, 2022 ; Qiao et al, 2020 ; Rong et al, 2022 ; Zhang et al, 2022 ). Wang H. et al (2019) found that adding H 2 O 2 to etch the surface of SQDs could reduce their non-radiative transition and increase the fluorescence QY of SQDs to 23% ( Figure 1C ).…”