A combination of experimental and computational methods was used to study the Cu²⁺ ions recognition by 9-hydroxyphenal-1-one carbon quantum dots (HPHN-CQDs). HPHN-CQDs were proved to be an efficient fluorescent probe that can detect Cu²⁺ ions with high selectivity and sensitivity, and the detection limit was 4.8 nM. We performed a detailed analysis of the fluorescence quenching mechanism of HPHN-CQDs by means of density functional theory (DFT) and time-dependent density functional theory (TDDFT). The orbital interaction diagram indicated that the presence of Cu²⁺ can affect the luminescence behavior of HPHN by changing its orbital distribution. In addition, the electron was transferred from the excited HPHN to the 3d orbital of Cu²⁺, which would hinder the recombination of electron-hole pairs and promote the fluorescence quenching of HPHN-CQDs. The photophysical process revealed that the fluorescence rate constant of HPHN-Cu²⁺ was substantially decreased compared with that of HPHN, which is consistent with the experimental results.

实验和计算方法的组合用于研究9-羟基苯-1-基碳量子点（HPHN-CQDs）对Cu ²⁺离子的识别。事实证明，HPHN-CQD是一种高效的荧光探针，可以高选择性和高灵敏度地检测Cu ²⁺离子，检测限为4.8 nM。我们通过密度泛函理论（DFT）和时变密度泛函理论（TDDFT）对HPHN-CQD的荧光猝灭机理进行了详细分析。轨道相互作用图表明，Cu ²⁺的存在可以通过改变HPHN的轨道分布来影响其发光行为。此外，电子从激发的HPHN转移到Cu ²⁺的3d轨道，这将阻碍电子-空穴对的重组并促进HPHN-CQDs的荧光猝灭。光物理过程表明，与HPHN相比，HPHN-Cu ²⁺的荧光速率常数大大降低，这与实验结果相符。