Construction Of PH And Hydrogen Peroxide Near Infrared Fluorescence Probes And Their Application In Food Detection

pH is an important factor affecting food quality.Research has shown that changes in pH value in food are closely related to the freshness,quality,safety,appearance,and taste of the food.For example,the early spoilage process of food often causes slight changes in its pH value.Therefore,development of a new intelligent tool to on-site detect slight pH changes in food samples in real-time is of great significance for evaluating the freshness,quality,and safety of food.Hydrogen peroxide（H₂O₂）is an important reactive oxygen species（ROS）.Due to its inherent bactericidal and bleaching properties,H₂O₂ has been widely used in food.However,excessive residual H₂O₂ in food samples not only has an adverse effect on the nutritional value of food,but also poses a huge threat to consumer health.Therefore,it is necessary to develop a reliable analytical method for on-site quantitative detection of H₂O₂ content in food samples.Fluorescent probes have the characteristics of high sensitivity,good selectivity,and strong quantitative ability,and their signal output can be easily obtained by the naked eye without relying on expensive equipment and tedious operations.Therefore,fluorescent probes are very suitable for real-time on-site detection of various analytes in food samples.In this thesis,a fluorescence probe for real-time on-site detection of slight pH changes in food and a fluorescence probe for real-time on-site detection of H₂O₂ content in food will be constructed.The specific research content is as follows:1.Design,synthesis,and application research of colorimetric and near-infrared fluorescence probes for tracking slight pH changes in food samples.In this study,a novel colorimetric and near-infrared fluorescence probe was rationally designed and synthesized.The probe exhibits a fluorescence response to pH in the near-infrared fluorescence wavelength region,which is beneficial for detecting pH changes in deep tissues of food samples and effectively avoiding interference from background fluorescence in food samples.Moreover,based on the unique conversion between ring-open and ring-close forms,the probe exhibits highly sensitive fluorescence response to slight pH changes near neutral pH values（0.1-0.2 pH units）.In addition,the probe produces obvious visual colorimetric changes with variations of pH value,which is conducive to real-time on-site visual detection.Practical application research has shown that the probe can be used to accurately detect the pH value in freshly squeezed juice.Moreover,by preparing test strips,this probe can serve as a simple and intelligent tool for real-time on-site detection of slight pH changes in packaged pork during the spoilage process,making it suitable for real-time monitoring of the freshness and quality of packaged pork.In addition,through fluorescence imaging,the probe successfully monitored slight pH changes in potato tissue infected with silver scurf disease,making it possible to further evaluate potato tissue infected with silver scurf disease.2.Smartphone-assisted colorimetric and near-infrared ratiometric fluorescent sensor for on-spot detection of H₂O₂ in food samples.In this study,a novel organic small molecule fluorescence probe was designed and synthesized to detect H₂O₂ in various food samples.The probe itself displays fluorescence in the near-infrared region.Therefore,it can effectively avoid interference from background fluorescence in food samples.After treating with H₂O₂,the probe exhibits a ratiometric near-infrared fluorescence response to H₂O₂,which is conducive to the quantitative detection of H₂O₂ content in various food samples.In addition,the probe exhibits a significant colorimetric response to H₂O₂,therefore,the probe can display a dual signal response of colorimetric and fluorescence to H₂O₂,improving the reliability of detecting H₂O₂ in food samples.Through fluorescence imaging,the probe has been successfully applied to detect exogenous and endogenous H₂O₂ in living cells,indicating that the probe can resist interference from various substances in the biological system when detecting H₂O₂.Moreover,the probe was used for real-time detecting H₂O₂ concentration in potato tissues infected with late blight.In order to achieve on-site quantitative detection of H₂O₂ concentration in food samples,a new portable and field deployable detection device has been further developed.The probe together with a self-made portable detection device and a smartphone were employed for on-site quantitative detection of H₂O₂ concentration in chicken wings and milk.