Dual-signal optical detection of Lead(II) ions (Pb2+) using galloyl group-functionalized polydiacetylene.

In this study, we developed a novel galloyl group-functionalized polydiacetylene (Galloyl-PDA) sensor for colorimetric and fluorescent detection of Pb2+. Among three types of Galloyl-PDA vesicles prepared by changing the ratio of newly synthesized galloyl group-conjugated 10,12-pentacosadiynoic acid (Galloyl-PCDA) and matrix 10,12-tricosadinoic acid (TCDA), the blue Galloyl-PDA vesicles with 1:9 molar ratio of Galloyl-PCDA:TCDA showed the most dramatic color transitions to red with colorimetric response (CR) value of 46.66 ± 1.373% within 5 min upon addition of 50 µM Pb2+. However, they didn't exhibit any color change upon interaction with other heavy metals. Since the terminal galloyl moieties of the Galloyl-PDA vesicles could form coordination bonds with Pb2+, the Galloyl-PDA vesicles were stressed and showed obvious blue-to-red chromatic transitions. Besides, because the Galloyl-PDA vesicles exhibited nonfluorescent-to-fluorescent transitions, a linear response in colorimetric and fluorescent signals was observed in the range of 0-10 µM and 0.025-1 µM, respectively. From the colorimetric and fluorescent results, the limit of detection (LOD) was determined to be 1.329 µM and 0.068 µM, which is 8-fold and 12-fold better sensitivity than those of previously reported methods, respectively. Furthermore, the capability of our PDA sensor for detection of Pb2+ in tap water, river water, and human serum was validated with excellent precision and recovery rates of 97.14-100.0%, 99.05-103.3%, and 100.7-106.7%, respectively. As our PDA dual-signal sensor for Pb2+ is rapid, sensitive, specific, and detectable by the naked eye, this approach holds great promise for application in point-of-care testing (POCT).

Development of freshness indicator for monitoring chicken breast quality and freshness during storage.

An indicator for freshness and quality measurement was utilized to perceive changes in freshness quality while storing chicken breasts. Visible color changes of the indicator shows spoilage and freshness of the packaged products. In addition, changes in pH, volatile basic nitrogen (VBN), and Pseudomonas spp. were monitored. The color change sensor (ΔE) reflected the headspace pH during the chicken breasts' packaging process. After storing chicken breast at 20 °C for 24 h, the color change (ΔE) of the indicator for freshness and quality measurement changed. The color change (ΔE) values were correlated with quality characteristics such as sensory, microbiological, and chemical properties that were popularly used to settle the freshness of chicken breast. In conclusion, the results showed that the indicator for freshness and quality measurement was useful in settling the shelf life of chicken breast products by physicochemical changes and monitoring microbial safety. Supplementary Information: The online version contains supplementary material available at 10.1007/s10068-022-01034-x.

Electron-blocking by the potential barrier originated from the asymmetrical local density of state in the oxide semiconductor.

Defect generation in oxide semiconductor thin-film transistors under high-voltage driving has not been studied in depth despite being a crucial bottleneck in the making of the integrated circuit utilized in an oxide semiconductor. Here we report on the origin of the asymmetrical transport characteristics caused by the degradation in the oxide semiconductor during integrated circuit driving. The variation of the current profiles based on test conditions is related to the generation of local defect states in the oxide material; this generation could be caused by the structural change of the material. The numerical calculations show that the flow of the electron is blocked by the "electrical pocket" formed by the electric-field distortion due to the local defect states near the edge of the electrode.