Yao Fan,Siying Che,Lei Zhang,Chunsong Zhou,Haiyan Fu,Yuanbin She
A novel dual-channel sensor array based on the “off” and “off–on” phenomenon of ZnCdSe quantum dots (QDs) - KMnO 4 system was established for the effective distinguish of 30 green teas with various species, grades and origins. Starting from optimization of QDs for the construction of the sensing system, their sensitivity and selectivity performances towards 10 representative green teas were tested first and the sensor systems based on ZnCdSe QDs were finally established. An obvious “off” response brought by the interactions between amino acids , quercetin, et al. and ZnCdSe QDs was obtained while an “off–on” phenomenon brought by the interactions between catechins and the ZnCdSe-KMnO 4 system had also been verified. Furthermore, based on the differential fluorescence “off–on” response of seven catechins, the qualitative and quantitative analyses of these catechins were successfully carried out with the linear range from 0.5 to 10 µg/mL. Most importantly, through adopting the dual-channel sensor, 30 green teas with different species, origins and grades can be accurately identified with the LDA model according to the spectral signals and the recognition accuracy could achieve 100 %.
As a new detection model, the reversible fluorescence “turn-off-on” sensor based on quantum dots (QDs) has already been successfully employed in the detections of many biochemical materials, especially in the researches on the interactions between anticancer drugs. The previous studies, however, mainly focused on simple-structured oligonucleotides and Calf thymus DNA . G-quadruplex, an important target for anti-cancer drug with special secondary structure , has been stimulating increasing research interests. In this paper, we report a new detection method based on the fluorescence “turn-off-on” model with water-soluble ZnCdSe QDs as the fluorescent probe , to analyze the interactions between anticancer drug (N-methyl-4-pyridyl) porphyrin (TMPyP) and nucleic acid , especially the G-quadruplex. The fluorescence of QDs can be quenched by TMPyP via photo-induced electron transfer and fluorescence resonance energy transfer , while on the other hand, the combination between TMPyP and G-quadruplex releases QDs from their quenchers and thus recovers the fluorescence. Most importantly, the fluorescence “turn-off-on” model has been employed, for the first time, to analyze the impacts of special factors on the interaction between TMPyP and G-quadruplex. The excellent selectivity of the system has been verified in the studies of the interactions between TMPyP and different DNAs (double-stranded DNA, single-stranded G-quadruplex, and different types of G-quadruplexes) in Na + or K + -containing buffer.
We report herein a “turn off-on” fluorescent sensor based on ZnCdSe quantum dots (ZnCdSe QDs) and self-assembled zinc porphyrin for sensitive and rapid detection of ochratoxin A (OTA). Using environmentally friendly dodecyl dimethyl betaine as “soft template”, zinc 5, 10, 15, 20-tetra(4-pyridyl)-21H-23H-porphine (ZnTPyP) was self-assembled into nanorods (SA-ZnTPyP) through a green process. The OTA detection process involves two steps: (1) the fluorescence of ZnCdSe QDs is significantly quenched by SA-ZnTPyP, and (2) the combination between SA-ZnTPyP and OTA releases ZnCdSe QDs from their quenchers such that the fluorescence is recovered. Under the optimized experimental conditions, the newly developed fluorescent sensor showed a linear response in concentration range 0.5–80 ng mL −1 , with a detection limit of 0.33 ng mL −1 . The excellent applicability of the system has been verified in milk and coffee samples, with relative recoveries between 98.33% and 103.70%. The proposed fluorescent sensor exhibits excellent selectivity and high sensitivity, and thus could be a promising tool for on-site determination of OTA in food safety control and environmental monitoring.
危险品化学品经营许可证（带存储）