The synthesis of fascinating multifunctional carbon dots (CDs) attracted immense attention. Here, a facile solvothermal treatment of red pitaya peels in acetic acid produced CDs (designated as ACDs, excitation/emission wavelengths at 357/432 nm). ACDs with high sp²-hybridized carbon and carboxylic group contents can rapidly and selectively reduce Au³⁺ to Au⁰, and stabilize produced Au nanoparticles (AuNPs). The synergetic effect of electron transfer from ACDs to Au³⁺ and inner filter effect (IFE) from ACDs to AuNPs quenches the fluorescence within 30 s. Simultaneously, the resulting AuNPs have a purple color with a maximum absorption at 545 nm for visual detection. Therefore, for the first time, we reported a fluorometric and colorimetric dual-mode sensing system for real-time, highly sensitive and selective detection of Au³⁺. The fluorescence quenching ratio and absorbance change linearly with the increase of Au³⁺ concentration in the range of 0.3–8.0 μM and 3.3–60.0 μM with limits of detection (LODs) at 0.072 μM and 2.2 μM, respectively. The assay was applied for Au³⁺ determination in spiked real water samples with recoveries from 95.5 to 105.0%, and relative standard deviation (RSD) of less than 6.5%. Furthermore, ACDs with good photostability, low cytotoxicity, and excellent biocompatibility were successfully applied for intracellular Au³⁺ sensing and imaging. In addition, ACDs exhibited an extraordinarily high antioxidant activity, with an IC₅₀ value for DPPH radical scavenging (0.70 μg mL⁻¹) much lower than that of ascorbic acid (4.34 μg mL⁻¹). The proposed strategy demonstrates the outstanding properties of ACDs in chemical and biomedical analysis.

令人着迷的多功能碳点（CD）的合成引起了极大的关注。此处，在乙酸生产的CD中对红火龙果皮进行了轻松的溶剂热处理（指定为ACD，激发/发射波长为357/432 nm）。具有高sp ^2-杂化的碳和羧基含量的ACD可以快速选择性地将Au ³⁺还原为Au ⁰，并稳定产生的Au纳米颗粒（AuNPs）。电子从ACD转移到Au ³⁺的协同效应从ACDs到AuNPs的内部过滤效应（IFE）在30 s内淬灭了荧光。同时，所得AuNPs呈紫色，可见光在545 nm处具有最大吸收。因此，我们首次报道了用于实时，高灵敏度和选择性检测Au ³⁺的荧光和比色双模传感系统。荧光猝灭率和吸光度随Au ³⁺浓度的增加在0.3–8.0μM和3.3–60.0μM的范围内线性变化，检出限（LOD）分别为0.072μM和2.2μM。该测定适用于Au ³⁺在加标的真实水样中进行测定，回收率为95.5至105.0％，相对标准偏差（RSD）小于6.5％。此外，具有良好的光稳定性，低细胞毒性和优异的生物相容性的ACD已成功应用于细胞内Au ³⁺感测和成像。此外，表现出的ACD格外高的抗氧化活性，与IC ₅₀为DPPH自由基清除值（0.70微克毫升^-1）比抗坏血酸低得多（4.34微克毫升^-1）。所提出的策略证明了ACD在化学和生物医学分析中的出色性能。