A full-wavelength coverage colorimetric sensor depending on polymer-carbon nanodots from blue to red for visual detection of nitrite via smartphone

A key challenge for preparing colorimetric sensor is to achieve full-wavelength color change under visible light. Herein, a full-wavelength coverage visible light-stimulated colorimetric sensor for specific detection of NO₂⁻ is constructed with polymer-carbon nanodots (PCNDs). The developed sensor is based on the principle that the fluorescence of PCNDs can be excited by visible light and visualized with a black background owning to the front and back light being absorbed. The as-achieved sensor exhibits high sensitivity and selectivity for visualization detection of NO₂⁻ in blue (from blue to orange) and red channel (from red to orange), respectively. Furthermore, a ColorAssist with a smartphone is used to obtain ΔRGB values for quantitative analysis of NO₂⁻ based on color intensity. Importantly, the proposed sensor can be applied for on-site NO₂⁻ detection in meat products with satisfied results. The developed strategy is not only portable and accessible for in situ analysis, but also has dual output color signal and full-wavelength coverage. As far as we know, this is the first full-wavelength coverage visible light-stimulated dual-channel colorimetric sensor for visual detection of NO₂⁻. Therefore, we believe that these studies will broaden the application of colorimetric sensor in on-site environmental monitoring and diseases diagnostic.