The increasing production of waste polyethylene terephthalate (PET) is a growing problem worldwide. Environmentally benign conversion of waste PET to valuable materials remains a substantial challenge. In this paper, we developed a green route to reuse waste PET for low-cost synthesis of fluorescent carbon dots (CDs) via air oxidation followed by hydrothermal treatment in aqueous H₂O₂ solution. No expensive, corrosive, or toxic reagents, or severe conditions were required in the synthetic process. The resultant CDs possessed abundant oxygenous groups and unique photoluminescence (PL) properties, which showed a highly selective and sensitive detection of ferric ion (Fe³⁺) through a PL quenching effect (on-off). The fluorescence of CDs quenched by Fe³⁺ could be restored specifically with pyrophosphate anion (PPi), rendering the CDs/Fe³⁺ sensor promising for PPi detection (off-on). The linear ranges for Fe³⁺ and PPi detections were 0.5–400 and 2–600 μM, and the limit of detections (LODs) were 0.21 and 0.86 μM, respectively. The sensing system applied for Fe³⁺ and PPi assays in real water samples and human urine achieved good results. After detailed investigations, a possible electron transfer process was proposed for explaining the “on-off-on” sensing mechanism.

废弃的聚对苯二甲酸乙二酯（PET）的产量不断增加是世界范围内日益严重的问题。将废PET转化为有价值的材料对环境无害，这仍然是一个巨大的挑战。在本文中，我们开发了一种绿色路线重用废PET荧光碳点（CDS）的低成本的合成通过在水h空氧化然后通过水热处理₂ ö ₂溶液。合成过程中不需要昂贵，腐蚀性或有毒的试剂，也不需要苛刻的条件。生成的CD具有丰富的含氧基团和独特的光致发光（PL）特性，显示出对铁离子（Fe ³⁺）通过PL淬灭效果（开-关）。Fe ³⁺淬灭的CD的荧光可以通过焦磷酸盐阴离子（PPi）专门恢复，这使得CDs / Fe ³⁺传感器有望用于PPi检测（关闭）。Fe ³⁺和PPi检测的线性范围为0.5–400和2–600μM，检测限（LOD）分别为0.21和0.86μM。用于实际水样和人尿中Fe ³⁺和PPi分析的传感系统取得了良好的结果。经过详细的研究，提出了一种可能的电子转移过程来解释“开-关-开”感应机制。