Preparation Of Carbon-Based Fluorescent Sensors And Their Application In Environmental Detection

In recent years,heavy metals have been found to be present in drinking water at measurable levels.These heavy metals end up in aquatic systems,such as oceans,lakes,rivers,ponds and drinking water.It will lead to adverse health problems.Therefore,detection of such unseen contaminants in water bodies is very important and is a challenging issue concerning human health monitoring.Different techniques are available for the detection of such drugs,including triple helix molecular switches,electrochemical sensors,enzyme-linked immunoassays,high-performance liquid chromatography,mass spectrometry,gas chromatography,thin-layer chromatography,and nuclear magnetic resonance spectroscopy.However,most detection strategies involve expensive instruments,complex operating procedures,and require expert operators to handle the instruments.In response,there is an urgent need to develop inexpensive,compact and reliable sensors for various applications such as detection and tracking of heavy metals in environmental water sources for the safety of humans and the environment.Various types of fluorescent sensors have attracted a great deal of attention due to their remarkable high sensitivity and ability to identify changes with the naked eye.Temperature plays a crucial role in biological responses and functions.Among the various options available for nanothermometry,fluorescence-based systems are the most effective because of their high temporal and spatial resolution.They also offer the dual function of imaging and temperature sensing.Many promising fluorescent nanomaterials such as semiconductor quantum dots(QDs),metal nanoclusters(NCs),carbon nanomaterials and rare earth doped nanoparticles are available.In this paper the following studies were carried out on the preparation and properties of carbonized polymer dots and synthesized dual-emission nanocomposites as well as on heavy metal and temperature detection.In this study,firstly,we prepared nitrogen-phosphorus carbonized polymer dots with yellow fluorescence by one-step hydrothermal method using o-phenylenediamine as carbon source and ammonium dihydrogen phosphate as phosphorus source,which is simple to synthesize,easy to operate,less costly,has good reproducibility,has high sensitivity and specific detection for silver ions,and its detection limit can reach 0.12 μM,,and can apply the prepared nitrogen-phosphorus carbonized polymer dots to actual water samples.polymer dots were applied to the actual water sample detection,on this basis,we also prepared a rapid detection of silver ions test paper,according to its convenience,can broaden the detection of nitrogen and phosphorus carbonized polymer dots in biological,medical,environmental and other fields.In the second part,we prepared a dual-emission fluorescent nanocomposite,using chitosan as the carbon source to prepare carbonized polymer dots by a one-step hydrothermal method,and using polymethacrylic acid as the stabilizer to synthesize silver nanoclusters by UV light irradiation,and self-assembling carbonized polymer dots and silver nanoclusters by electrostatic force.A dual-emission fluorescent nanocomposite responsive to temperature change was prepared.A good linearity between 20℃and 80℃was achieved.For this purpose,we introduced the dual-emission fluorescent nanocomposite into the membrane system to broaden the application in rapid and convenient detection of temperature.