The Preparation Of Novel Copper Nanoparticles And Their Applications In Environmental Analysis

With the continuous development of social economy,a great number of toxic and harmful pollutants appear in the environment,such as heavy metals,persistent organic pollutants,and so on.Therefore,analyzing and monitoring the composition,content,and chemical forms of environment pollutants has become more and more important.The traditional detection techniques for environmental analysis were reported,such as chromatography,atomic absorption spectrometry,inductively coupled plasma mass spectrometry,biochip technology,electrochemical method and immunological methods,etc.But these traditional methods were tedious,time-consuming,and costly,it is difficult to achieve effective and efficient analysis of detection.In addition,the objects of environmental analysis and monitoring are often trace substances.Thus,the demand of analytical method is higher and higher in this field.Compared with traditional methods,the fluorescence analytical method has some remarkable characteristics,such as high sensitivity,simpleness,and convenience.So fluorescence analytical method has been developed rapidly in the field of environmental analysis.In this thesis,fluorescence analysis method is used to set up several new fluorescent platforms based on copper nanoparticles?Cu NPs?,which are applied to Hg²⁺,Fe³⁺ and picric acid?PA?analysis.This paper mainly contains the content of three following respects:Part 1: D-penicillamine-templated copper nanoparticles via ascorbic acid reduction as a mercury ion sensor.The experiments were carried in dark conditions,and the as-prepared DPA-Cu NPs were aggregated with red fluorescence emission.The emission from the aggregates could be attributed to ligand-to-metal charge transfer from the thiolate ligands in the DPA to the Cu atoms.We also surmised that when Hg²⁺ was added to the DPA-Cu NPs solution,it can easily bind to the surface of DPA-Cu NPs through the high-affinity metallophilic Hg²⁺-Cu interactions to form a complex.The interaction energy between Hg²⁺ and Cu is so high among two neutral units that the binding force of thiolate ligands in the DPA to the Cu atoms was broken,so the DPA-Cu NPs aggregates were disrupted,leading to the fluorescence quenching of DPA-Cu NPs.Based on the above phenomenon,an Hg²⁺ detection method was successfully established.At the same time,a series of experimental parameters were performed,including the concentration ratios of each component,synthesis time and the p H value.Under the optimal conditions,the system displayed a detection limit as low as 32 n M toward Hg²⁺ and a good selectivity over other metal ions.The method has been successfully applied to detect Hg²⁺ in real samples with satisfied recovery and accuracy.Part 2: L-Histidine-protected copper nanoparticles as a fluorescent probe for sensing ferric ions.In this chapter,a simple and one-pot method was developed to innovatively synthesize fluorescent L-His-Cu NPs using L-Histidine as stabilizing agent and ascorbic acid as reducing agent under ambient temperature?25 °C?without stirring.As a paramagnetic transition metal ion with empty d shells,Fe³⁺ has the propensity to quench the fluorescence of the neighboring fluorophore by energy or electron transfer.Besides,Fe³⁺ has a higher thermodynamic affinity and could chelate with nitrogen atom of amine group very fast.Due to the binding force of Fe³⁺ to the nitrogen atom,the neighboring L-His-Cu NPs could be pulled closely.So the good dispersivity-L-His-Cu NPs were aggregated,leading to the fluorescence quenching of L-His-Cu NPs.Based on the above phenomenon,a Fe³⁺ detection method was successfully established.In addition,we found that after adding strong chelater EDTA to the L-His-Cu NPs/Fe³⁺ system,the fluorescence “turn off-on” phenomenon was observed.Thus,we inferred that the interaction between Fe³⁺ and the L-His-Cu NPs was relatively weak,so EDTA could break the bonds of Fe³⁺ to the nitrogen atom of amine group in L-Histidine molecule by competing with Fe³⁺.In addition,the experimental system of synthesis ratio,reaction time and p H value and other related parameters were optimized.Furthermore,a series of experimental parameters were performed,including the concentration ratios of each component,synthesis time and the p H value.Under the optimal conditions,the system displayed a detection limit as low as 82 n M toward Fe³⁺ and a good selectivity over other metal ions.The method has been successfully applied to detect Fe³⁺ in real samples with satisfied recovery and accuracy.Part 3: Synthesis of Fluorescent Copper Nanoparticles with p H Dependence via Etching Process for Picric Acid Detection.In this work,the water-soluble fluorescent Cu NPs with blue fluorescence emission were innovatively synthesized via the process of etching from non-luminescent nanocrystals,where trisodium citrate served as a template and sodium borohydride as a reducing agent.The preparation process includes two steps,one is the synthesis of larger-size Cu nanocrystals and the other is subsequent etching into fluorescent Cu NPs by using L-glutathione?GSH?.Importantly,the as-prepared Cu NPs showed satisfactory stability in an aqueous medium and exhibited an especially wide range of p H responsiveness.The fluorescence intensity of the as-prepared Cu NPs would be markedly enhanced with increasing p H.Moreover,the fluorescence intensity of Cu NPs can be quenched by PA easily,but other compounds and ions only quenched the negligible fluorescence of Cu NPs.Thus,the fluorescent Cu NPs were applied to selectively and sensitively detecting PA in aqueous solution,and the detection limit was 65 n M.The probable fluorescence quenching mechanism was the inner filter effect.Furthermore,the developed sensor was successfully applied to detect PA in real samples with satisfied recovery and accuracy.