Controllable Preparation Of Novel Fluorescent Carbon Dots And Their Application In Bioactive Molecule Sensin

In the development modern agriculture,the widespread application of pesticides has not only increased crop yield,but also caused serious environmental pollution and ecological imbalance.Pesticide residues can directly threaten water and soil safety.They can also reach and accumulate in human body through the food chain and endangering life and health.Moreover,harmful metabolites and molecules produced upon stimulation of the pesticides in surrounding environment can hurt the organisms.Therefore,it is crucial to develop a universal and convenient method to accurately monitor either pesticide residues or pesticide-induced oxidative damage in living organisms.Application of visual monitoring to track pesticide residues and associated damage in organisms is an efficient and intuitive strategy.It can quickly identifies the presence of pesticide residues as well as help to reveal their impact on organisms,which is crucial for environmental protection and public health.However,currently there are very limited tools to achieve visual monitoring of pesticide residues or associated damage in living organisms.Therefore it is urgent to develop new methods and related imaging probes.Organic functional materials have been widely used in environmental fields,including photocatalytic degradation of organic pollutants and gas separation,due to their excellent optical properties,easy processing,and high customization.In response to the serious lack of relevant methods for visualizing the monitoring of pesticides and associated damage in living organisms,this thesis developed two types of fluorescent probes,HBTR and HBTM-HP,which can sensitively and intuitively monitor pesticides（Thiram）and associated damage（H₂O₂）in living organisms.The main work and results are summarized as follows:（1）Construction of Cu²⁺-based fluorescent probes for imaging and monitoring ofThiram in soil,plant and zebrafish samples.Tetramethylthiuram disulfide,commonly know as Thiram,is an organic sulfur compound that is extensively employed as a fungicide in agriculture.This widespread use leads to a higher probability of exposure to Thiram in occupational environments,as well as through the consumption of contaminated food.Consequently,it is crucial to monitor the presence of Thiram in biological organisms.In this work,We focused on creating a series of multicolor probes,known as the HBTR series（including HBTH,HBTB,HBTP,HBTS）,utilizing 2-（2-hydroxyphenyl）benzothiazole（HBT）as the foundational fluorescent molecule.These probes possess adjustable emission wavelengths,spanning from 550 nm to 680 nm,enabling flexible and efficient detection and live imaging of Thiram.The HBTR probes can rapidly respond to Cu²⁺within 2 s by forming a fluorescence-quenching HBTR-Cu²⁺complex.This phenomenon is primarily due to the coordination of Cu²⁺with the hydroxyl and adjacent benzothiazole nitrogen atoms in HBT,which inhibits the excited-state intramolecular proton transfer（ESIPT）effect of the probe to quench the fluorescence.When Thiram is added to the system,Cu²⁺can form a more stable complex with Thiram to release the previously coordinated HBTR probe,so that the intramolecular ESIPT effect is restored to recover the fluorescence.Among them,the near-infrared probe HBTP has a Stokes shift greater than 240 nm,and the detection limit of Cu²⁺can reach 1.6 nmol/L.The fluorescence intensity of HBTP-Cu²⁺at 650 nm was positively correlated with Thiram concentration,and the low detection of 42 nmol/L and excellent selectivity for Thiram were exhibited.Taking advantage of this characteristic,the HBTP probe has been successfully applied to the detection and analysis of Thiram in samples from different environments（water,soil,plants）,and to realize the imaging and monitoring of Thiram in live zebrafish,which provides a means for assessing ecological and health risks and toxicological studies.（2）Constructed a H₂O₂-specific fluorescent probe for evaluating oxidative stress in pesticides-treated cells,rice roots and zebrafish.This section of work primarily revolves the development of universal visual probes to monitor the biological damage caused by environmental pollutants,including pesticides.A common feature of organismal damage induced by environmental pollutants is oxidative stress.Hydrogen peroxide（H₂O₂）,the most stable and widely existing reactive oxygen species（ROS）,intuitively and reliably reflects the redox homeostasis and its disorder in organisms.Hence,this work has chosen H₂O₂ as the indicator and developed a new H₂O₂-responsive fluorescent probe,HBTM-HP based on HBT for assessing the oxidative damage to cells,rice roots,and zebrafish caused by pesticides.By employing a phenylboronic acid ester as the responsive group,a highly special recognition of H₂O₂ was achieved.By the action of H₂O₂,the probe transitions from HBTM-HP to HBTM,leading to the restoration of the excited-state intramolecular proton transfer（ESIPT）process with a significant fluorescence enhancement at 600 nm(?_fl>0.7),which is advantageous for reducing the interference of autofluorescence from tissue background.Experimental results show that endogenous H₂O₂ in mammalian cells,rice root systems and living zebrafish can be monitored effectively by HBTM-HP,which,has been successfully used to monitor H₂O₂ levels in organisms exposed to environmental pesticides.Reserch finds that the gradually increasing levels of H₂O₂ associated with the concentration of pesticides and the duration of its exposure.Additionally,HBTM-HP can also be used to evaluate oxidative stress caused by 4 different types of systemic pesticides and distinguish the degree of that.Through mechanistic proof,the abnormal produce of H₂O₂ is related to various enzyme activities（SOD,CAT,GPx）,pointing out a consistency between the oxidative stress caused by pesticides and the H₂O₂-related effects.Therefore,this work has successfully constructed an universal fluorescent probe to evaluate the states of oxidative stress in various organisms,providing a new tool for future analysis of pesticide-induced oxidative stress and mechanisms in biological toxicity.（3）Construction of visible light-driven hydrogen-bonded organic framework materials for photocatalytic antimicrobialAs environmental pollution worsens,the spread of antibiotic-resistant bacteria has become a severe threat to human health,urgently necessitating the development of novel and environmentally friendly antimicrobial materials to prevent the dissemination and antibiotic resistance of bacterial.Against this backdrop,photocatalytic antibacterial technology offers an innovative solution by utilizing photo-functional materials（i.e.,photocatalysts）in antimicrobial.The core of this technology lies in developing visible light-driven photosensitive materials achieve efficient and biocompatible characteristics.Thus,exploring and developing new photo-functional materials has become a key approach to address the issue of antibiotic resistance and promote the advancment in photocatalytic antibacterial technology.This section of work concentrates on developing efficient,environmentally friendly,and visible light-responsive antibacterial nanomaterials.The selected organic photo-functional material is porous crystalline hydrogen-bonded organic framework PCF-1,which can be synthesized via a simple solvent-assisted crystallization method.This material is formed by the H₄TBAPy,a molecule possesses photosensitive properties that can interacte with surrounding molecules through hydrogen bonds to form a stable structure due to two-dimensional layer.Experimental results show that PCF-1 nanoparticles are highly crystallined with a uniform three-dimensional rod-like nanostructures which exhibit outsdanding stability and biocompatibility.Under the action of visible light,various ROS are effectively produced,including hydroxyl radicals（·OH）and singlet oxygen（¹O₂）.Photocatalytic antibacterial experiments prove that PCF-1 displays over 92%antibacterial efficiency against both Gram-negative bacteria Escherichia coli（E.coli）and Gram-positive bacteria Staphylococcus aureus（S.aureus）under visible light irradiation.It is demonstrated that PCF-1 kill bacteria by destroying cell membrane as its antibacterial mechanism.This work explores the application of PCF-1 in antibacterial activity,providing a new insight into the development of efficient,environmentally friendly and visible light-responsive antibacterial nanomaterials.In summary,In summary,this paper focuses on the application of organic optical functional materials in environmental monitoring and governance,and comprehensively uses a variety of technical means to carry out in-depth exploration and research work based on imaging platforms.In order to solve the problem of visual monitoring of pesticides and their damage indicators,two new fluorescent probes HBTR and HBTM-HP were developed in this paper,which successfully realized the imaging of pesticide residues and their induced oxidative damage in living organisms.Additionally,in order to solve the problem of antibiotic resistance,a visible light-responsive nanomaterial PCF-1 was successfully prepared,and its antibacterial application was explored.This thesis provides new ideas and potential solutions for pesticide residue monitoring,in vivo imaging,and antibacterial fields.It also expands the application of visual imaging research in environmental monitoring and health indicator surveillance.