A fluorescent sensor array based on carbon dots for the accurate determination of pH†

In this study, we present a sensor array for precise pH monitoring, based on carbon dots (CDs) synthesised from fructose and p-phenylenediamine through a one-step hydrothermal method. The CDs exhibited significant photostability and different fluorescence emissions in different pH conditions, making them suitable for real-time pH sensing across a wide pH range of 3 to 10. Our mechanistic studies revealed how surface functionalisation affects the pH response. For statistical analysis of our array data, we employed Gaussian process regression to create a predictive model for determining pH levels of test samples based on the array spectral data, and linear discriminant analysis for high-precision classification of pH values. This combined approach enabled a comprehensive analysis of the CDs' pH-sensitive fluorescence, demonstrating a significant methodological advancement in pH sensor technology. Our research advances the understanding of the fluorescence mechanisms of CDs in response to pH variations. Furthermore, our study demonstrates the power of integrating machine learning techniques to improve the performance and application scope of fluorescent nanomaterials. These findings have important implications for chemical sensing across a range of fields, including environmental monitoring and biomedical diagnostics.