Coffee waste-derived carbon dots (C-CDs) that emit blue light were synthesized via hydrothermal process. The synthesized C-CDs have a round shape with average diameter of ∼3.7 nm. The C-CDs show PL emission centered at 450 nm with excitation wavelength at 360 nm. The C-CDs show promising applications as Fe³⁺ sensors in aqueous solutions by fluorescence quenching. The C-CDs exhibited strong turn-off fluorescence when trace Fe³⁺ was added to the solution. Furthermore, the C-CDs-Fe³⁺ can also be used as a turn-on sensor for the detection of ascorbic acid (AA). AA reduces Fe³⁺ to Fe²⁺, resulting in the recovery of fluorescence intensity of the quenched C-CDs. Thus, the C-CDs can be used as a rapid and effective dual mode “off-on” fluorescence sensor for Fe³⁺ and AA. The fluorescence response exhibits a good linear relationship with the concentration of Fe⁺³ and AA in the range of 0–100 and 0–1 µM, with a limit of detection (LOD) around 4.314 and 0.162 µM, respectively.

通过水热法合成了发出蓝光的咖啡废料衍生碳点 (C-CD)。合成的 C-CD 呈圆形，平均直径约为 3.7 nm。C-CD 显示 PL 发射以 450 nm 为中心，激发波长为 360 nm。通过荧光猝灭，C-CDs在水溶液中作为 Fe ^{3+传感器显示出有前景的应用。}当向溶液中添加痕量 Fe ³⁺时，C-CDs 表现出强烈的关闭荧光。此外，C-CDs-Fe ³⁺还可用作检测抗坏血酸（AA）的开启传感器。AA 将 Fe ³⁺还原为 Fe ²⁺，导致淬灭的 C-CD 的荧光强度恢复。因此，C-CDs 可以作为一种快速有效的双模式“关-开”荧光传感器用于 Fe ³⁺和 AA。^{荧光响应在 0-100 和 0-1 µM 范围内与 Fe +3}和 AA的浓度呈良好的线性关系，检测限 (LOD) 分别约为 4.314 和 0.162 µM。