Study On The Colorimetric And Fluorescent Dual Probe For Environmental Analysis

Nowadays, environment problem has attracted more and more public concerns. However, due to the complexity of environment samples, extremely low concentrations of some pollutants and high requirement for instrumentation; it is difficult for us to realize the on-the-spot environmental detection. Thus, the development of a fast, direct, simple method for environment analysis is of great importance. Optical probes with dual channels are good candidate for realizing this goal, because they not only enable the visualization of the target simply by the naked eye, but also validate further quantitative analysis in a sensitive feature. Moreover, double channels as self-control could cancel out the environmental fluctuations, which is more adaptive for practical application. However, so far, the dual signal method are mainly relied on the complex synthesis of organic probes which are time-consuming, and the low yield of which substantially necessitate colorimetric and fluorescent dual probe based on novel material with simplicity both in principle and in operation.In this article, we focus on developing novel nanomaterial such as infinite coordination polymer (ICP) nanoparticles, MnO2 nanosheets, graphene quantum dots (GQDs), for the detection of pollutant molecules, such as hypochlorite (ClO-), alkaline phosphatase (ALP), acetylcholinesterase (AChE), with dual signal response. The developed method are successfully applied on the direct hypochlorite sensing in tap water, dynamic monitoring periodical alkaline phosphatase activity (APA) variation in eutrophication process, the risk assessment of parathion poisoning and management in rat brain. These studies offer a new strategy and great promise for the on-site detection of pollutant molecules with dual response, which is of great importance in protecting environmental safety, maintaining public health. This article was divided into four chapters as follows:Chapter 1. OverviewThis part gave a comprehensive overview for the development of environmental analysis and environmental applications of colorimetric and fluorescent dual probe. We introduced several optical nanomaterials such as ICP nanoparticles, quantum dots, noble-metal nanoclusters, which are promising in visible environmental analysis. Finally, we expounded the significance and main contents of our article.Chapter 2. Valence-tautomeric Infinite Coordination Polymer Nanoparticles for Its Potential Application for Colorimetric and Fluorescence Dual Mode Sensing of HypochloriteIn this work, we for the first time developed a visual and fluorescent dual probe for hypochlorite (ClO-) based on stimuli-responsive valence-tautomeric infinite coordination polymer (ICP) nanoparticles encapsulated with a fluorescent dye, i.e., rhodamine B (RhB). In the absence of ClO-, the as-formed RhB@{Co(3,5-dbsq)(3,5-dbcat)(bix)} ICP nanoparticles are well dispersed and quite stable in aqueous solution. However, the addition of ClO- into the dispersion of RhB@{Co(3,5-dbsq)(3,5-dbcat)(bix)} destroys the {Co(3,5-dbsq)(3,5-dbcat)(bix)} network structure, resulting in the release of RhB from ICP nanoparticles into the solvent. As a consequence, the color of the dispersion changed from purple to orange-red and, in the meantime, the fluorescence of RhB turns on, which constitutes a new mechanism for colorimetric and fluorescence dual-model sensing of ClO-. With the method demonstrated here, the ClO- in tap water can be easily visualized by the naked eye and detected quantitatively through double channels. This study not only offers a new method for on-the-spot visible detection of ClO- in environmental samples, but also provides a strategy for designing dual mode sensing mechanisms based on the stimulus response of ICP nanomaterials.Chapter 3. Stimulus Response of Au-NPs@GMP-Tb Core-Shell Nanoparticles: Toward Dual-Mode Sensing of Alkaline Phosphatase Activity in Algal Blooms of a Freshwater LakeIn this study, we demonstrate a colorimetric and fluorescent dual-mode method for alkaline phosphatase activity (APA) sensing in freshwater lake with stimuli-responsive gold nanoparticles@terbium-guanosine monophosphate (Au-NPs@GMP-Tb) core-shell nanoparticles. Initially, the core-shell nanoparticles were fabricated based on Au-NPs decorated with a fluorescent GMP-Tb shell. Upon being excited at 290 nm, the as-formed Au-NPs@GMP-Tb core-shell nanoparticles emit green fluorescence, and the decorated GMP-Tb shell causes the aggregation of Au-NPs. However, the addition of ALP destroys GMP-Tb shell, resulting in the release of Au-NPs from the shell into the solvent. As a consequence, the aggregated Au-NPs solubilizes with the changes in the UV-vis spectrum of the dispersion, and in the meantime, the fluorescence of GMP-Tb shell turns off, which constitutes a new mechanism for colorimetric and fluorescent dual-mode sensing of APA. With the method developed here, we could monitor the dynamic change of APA during an algal bloom of a freshwater lake, both by the naked eye and further confirmed by fluorometric determination. This study not only offers a new method for on-site visible detection of APA but also provides a strategy for dual-mode sensing mechanisms by the rational design of the excellent optical properties of Au-NPs and the adaptive inclusion properties of the luminescent infinite coordination polymers.Chapter 4. Highly Sensitive MnO2-Nanosheet-Based Assay with Turn on Fluorescence for Cerebrospinal Acetylcholinesterase Activity:A Biomarker of Exposure to Organophosphorus PesticidesIn this work, we demonstrated a MnO2-nanosheet-based assay with turn on fluorescence and colorimetric change realized cerebrospinal AChE activity determination as a biomarker for OPs exposure of rat directly. The MnO2 nanosheets served as a nanoquencher towards luminescent graphene quantum dots (GQDs) to form MnO2/GQDs architecture with very weak emission; With presence of the AChE, the AChE-catalyzed hydrolysis of acetylthiocholine (ATCh) to produce the enzymatic product thiocholine with reducibility, and thereby leading to the redox reaction which convert MnO2 nanosheets into Mn2+ and the release of luminescent GQDs into solution. This process eventually results in the increase of the fluorescence emitted from luminescent GQDs, and in the meantime, the color of the dispersion changed from dark brown to colorless, which provides a straightforward basis for the sensing of AChE with dual mode. With the method demonstrated here, the AChE in rat can be easily visualized by the naked eye and detected quantitatively through instruments. This study not only offers a new method for monitoring of AChE as a biomarker for detecting the exposure to OPs, but also provides a strategy for dual-mode sensing mechanisms by the rational design of the excellent nanoquencher and the adaptive luminescent material.