Wang Kai, Geng Cuihuan, Wang Fang, Zhao Yajun, Ru Zongling
School of Chemical and Environmental Engineering, Anyang Institute of Technology Anyang 455000 China
Teaching and Research Office of Neihuang Country Anyang 456300 China.
RSC Adv. 2021 Aug 13;11(44):27645-27652. doi: 10.1039/d1ra04558j. eCollection 2021 Aug 9.
A facile and green strategy for the fabrication of fluorescent urea-doped carbon dots (N-CDs) has been explored. Significantly, the fluorescent N-CDs could recognize iodide ions (I) with high selectivity, and their photoluminescence could be efficiently quenched by the addition of I. The sensitivity analysis for I indicated a linear relationship in the range from 12.5 to 587 μM with the detection limit as low as 0.47 μM. Furthermore, the I induced fluorescence (FL) quenching mechanism was investigated employing a combination of techniques, including UV-vis/fluorescence spectroscopy, Density Functional Theory (DFT) calculation, TEM and time-resolved fluorescence decay measurements. The DFT calculation results demonstrated that the amino- and amide groups of N-CDs play a significant role in iodide recognition through the formation of multiple N-H⋯I, C-H⋯I and C([double bond, length as m-dash]O)N-H⋯I interactions with I. The TEM experiment confirmed the aggregation process when I was added to the N-CDs solution. Moreover, the radiative decay rate of N-CDs, which was first measured and reported the kinetic behaviors of the FL-quenching process, decreased from 3.30 × 10 s to 1.95 × 10 s after the coordination with I ions. The reduced lifetime demonstrated that the excited energy dissipation led to a dynamic quenching process. Therefore, such carbon materials can function as effective fluorescent switches for the selective detection of I ions.
探索了一种简便绿色的制备荧光尿素掺杂碳点（N-CDs）的策略。值得注意的是，荧光N-CDs能够高选择性地识别碘离子（I⁻），并且加入I⁻后其光致发光能够被有效猝灭。对I⁻的灵敏度分析表明，在12.5至587 μM范围内呈线性关系，检测限低至0.47 μM。此外，采用紫外可见/荧光光谱、密度泛函理论（DFT）计算、透射电子显微镜（TEM）和时间分辨荧光衰减测量等多种技术相结合的方法，研究了I⁻诱导的荧光（FL）猝灭机制。DFT计算结果表明，N-CDs的氨基和酰胺基团通过与I⁻形成多个N-H⋯I、C-H⋯I和C（=O）N-H⋯I相互作用，在碘离子识别中起重要作用。TEM实验证实了向N-CDs溶液中加入I⁻时的聚集过程。此外，首次测量并报道了FL猝灭过程动力学行为的N-CDs的辐射衰减率，在与I⁻离子配位后从3.30×10⁶ s⁻¹降至1.95×10⁶ s⁻¹。寿命缩短表明激发能量耗散导致了动态猝灭过程。因此，这种碳材料可作为有效荧光开关用于选择性检测I⁻离子。
