Department of Chemical Engineering, National Taiwan University of Science and Technology, Daan Dist., Taipei City, 106, Taiwan; Department of Chemical Engineering, R&D Center for Membrane Technology, Chung Yuan Christian University, Chungli Dist., Taoyuan City, 320, Taiwan.
Department of Chemical Engineering, R&D Center for Membrane Technology, Chung Yuan Christian University, Chungli Dist., Taoyuan City, 320, Taiwan.
Environ Res. 2021 Jun;197:111008. doi: 10.1016/j.envres.2021.111008. Epub 2021 Mar 16.
In the present study, carbon-dots (CDs) were derived from the thermal oxidation of an agricultural waste, bitter tea residue, to obtain different sp/sp ratios and electronic structures for metal sensing. The CDs obtained from calcination at 700 °C exhibited the highest photoluminescence (PL) quantum yield (QY) of 11.8% among all the samples treated at different temperatures. These CDs had a high degree of graphitization, which resulted in a strong π-π* electron transition, and hence in a high QY. The strong photoluminescence of the CDs could be used to sense the metal ions Ag, Sr, Fe, Fe, Co, Ni, Cu, and Sn by monitoring their PL intensity at an excitation wavelength of 320 nm. The metals inhibited the PL intensity in the order Ag > Fe, Fe, Ni > Sr, Co, Cu, Sn, which demonstrated that the CDs exhibited high metal ion detection capability and selectivity. The detection of Fe using CDs was performed in the range of 10-100 ppm with a LOD (limit of detection) value of 0.380 ppm. Theoretical calculations demonstrated that Ag, Sr, and Sn induced charge transfer excitation and that Fe and Ni induced d-d transitions via complexation with the sp clusters. The charge transfer excitation and d-d transitions hindered the π-π* transition of the sp clusters, leading to a quenching effect. On the other hand, Li, Na, and K ions did not alter the π-π* transition of the sp clusters, resulting in a negligible quenching effect. In summary, the oxidation level and electronic structure of CDs derived from bitter tea residue could be tailored, and the CDs were shown to be a facile, sustainable, and eco-friendly material for metal sensing.
在本研究中，通过对农业废弃物——苦茶残渣进行热氧化，得到了具有不同 sp/sp 比和电子结构的碳点，用于金属传感。在不同温度下处理的所有样品中，经 700°C 煅烧得到的碳点具有最高的光致发光（PL）量子产率（QY），为 11.8%。这些碳点具有高度的石墨化程度，导致强烈的π-π电子跃迁，从而具有高的 QY。碳点的强荧光可用于通过监测在 320nm 激发波长下的 PL 强度来感应金属离子 Ag、Sr、Fe、Fe、Co、Ni、Cu 和 Sn。金属按 Ag>Fe、Fe、Ni>Sr、Co、Cu、Sn 的顺序抑制 PL 强度，这表明碳点表现出高的金属离子检测能力和选择性。使用碳点检测 Fe 的范围为 10-100ppm，检出限（LOD）值为 0.380ppm。理论计算表明，Ag、Sr 和 Sn 通过与 sp 簇络合诱导电荷转移激发，而 Fe 和 Ni 通过 d-d 跃迁诱导。电荷转移激发和 d-d 跃迁阻碍了 sp 簇的π-π跃迁，导致猝灭效应。另一方面，Li、Na 和 K 离子不会改变 sp 簇的π-π*跃迁，导致猝灭效应可忽略不计。总之，苦茶残渣衍生的碳点的氧化水平和电子结构可以进行调节，并且碳点是一种用于金属传感的简便、可持续和环保的材料。
