The pH value plays a vital role in many biological and chemical reactions. In this work, the fiber-optic chemical pH sensors were fabricated based on carboxyl ZnCdSe/ZnS quantum dots (QDs) and tapered optical fiber . The photoluminescence (PL) intensity of QDs is pH-dependence because protonation and deprotonation can affect the process of electron-hole recombination. The evanescent wave of tapered optical fiber was used as excitation source in the process of PL. To obtain higher sensitivity, the end faces of fiber were optimized for cone region. By lengthening the cone region and shrinking the end diameter of optical fiber, evanescent wave was enhanced and the excitation times of QDs were increased, which improved the PL intensity and the sensitivity of the sensor. The sensitivity of sensor can reach as high as 0.139/pH in the range of pH 6.00–9.01. The surface functional modification was adopted to prepare sensing films. The carboxyl groups on the QDs ligands are chemically bonded to the fiber surface, which is good for response time (40 s) and stability (decreased 0.9 % for 5 min). These results demonstrated that ZnCdSe/ZnS QDs-based fiber-optic chemical pH sensors are promising approach in rapid and precise pH detection.
Yahui He,Yao Zhu,Siyuan Wang,Haixiang Wang,Aijin Ma,Jing Wang,Baoguo Sun
This study used the phase inversion method to prepare a novel ZnCdSe/ZnS quantum dot molecularly imprinted (ZnCdSe/ZnS@MIPs) polyethersulfone (PES) fluorescent composite (ZnCdSe/ZnS@MIPs@PES) membrane for the rapid detection of pyrraline (PRL). This membrane addressed the challenges presented by quantum dots molecularly imprinted polymers (QDs@MIPs) particles in liquids and required no pre-treatments during the analysis for accurate content determination at a low LOD. When the samples passed through the membrane via an automatic circulating filtration device, the PRL was specifically adsorbed due to the imprinted recognition sites on the ZnCdSe/ZnS@MIPs particles, causing membrane fluorescence quenching. Matrix-interfering components were removed for the porous structure of the membrane. Compared with the ZnCdSe/ZnS@MIPs solution method, the detection limit and accuracy of the ZnCdSe/ZnS@MIPs@PES membrane technique was significantly more successful in enhancing enrichment and purification functionality, reducing the analysis duration from 3 to 4 d to 45 min, while the operational procedure was decreased from 16 steps to two. When applied for PRL analysis in milk with 15% PES content and 6 mg ZnCdSe/ZnS@MIPs addition, the PRL was quantitatively detected in a broad concentration range (30–1000 μg/L) with R 2 =0.99. The LOD of ZnCdSe/ZnS@MIPs@PES membrane decreased at a higher sample injection volume, reaching a minimum of 18.1476 μg/L at 14 mL injection.
危险品化学品经营许可证（带存储）