Rational construction of red-emissive carbon dots for integrated optical sensing and smartphone-based quantification of amaranth

Given the paramount importance of monitoring food pigments in safeguarding public health, the development of efficient fluorescent sensing strategies enabling their on-site detection has emerged as a significant area of scientific research. An innovative technique for producing red fluorescent carbon dots (R-CDs) derived from azure A has been established to precisely control their optical properties throughout the synthesis process. The luminescence efficiency is optimized through the incorporation of small molecule ligands into the carbon framework, resulting in enhanced emission at 684 nm. Notably, the proposed R-CDs demonstrate selective responsiveness to amaranth, as evidenced by a visually distinctive color transition from cyan to red. Fluorescence quenching of the R-CDs exhibits concentration-dependent correlation with amaranth, characterized by rapid response and high-sensitivity detection at 16.7 nM. Trace-level analysis demonstrates an effective recovery rate for amaranth, highlighting the considerable potential of the proposed sensor for precise recognition of amaranth in food products. Moreover, the engineered R-CDs are further leveraged to establish a smartphone-integrated colorimetric imaging platform, facilitating precise and portable detection of amaranth in real samples with commendable accuracy. The comprehensive results validate a novel strategy for engineering long-wavelength fluorescent carbon dots, culminating in an advanced platform for the precise and accurate quantification of amaranth in complex real samples.