Colloidal Quantum Dot Chains:Self-assembly Mechanism And Fluorescent Sensing For As(?)

Arsenic is a common pollutant in water samples.There are four main kinds of oxidation states:-3,0,3,5.The specific forms are usually affected by environmental pH or redox potential.It is highly toxic to organisms and can easily lead to skin changes,respiration,cardiovascular,gastrointestinal,genotoxicity,gene mutation,carcinogenic effects and other harmful lesions.The World Health Organization have recommended arsenic levels should not exceed 10 ppb in water.Therefore,the research and development of arsenic detection technology is one of the most important work of chemist.Available methods for arsenic detection include spectroscopic method,electrochemical analysis.surface-enhanced Raman spectroscopy,colorimetry and so on.However,those methods are either complex,expensive,difficult to operate,or low sensitive.So,on the one hand,we have designed and synthesized a high sensitivity and selectivity As(?)detection probe;on the other hand,we have designed and developed a ratio fluorescence probe based on the above probe and a color-multiplexing-based fluorescent test paper,which could be extended to the visual detection of a wide range of analytes in the environment by the construction of highly efficient ratiometric nanoprobes.The main contents of the study are as follows:(1)The first part is the summarized of arsenic,including the morphology and influencing factor,the harmful to human,and the common methods for arsenic detection.(2)The synthetic of colloidal quantum dot chain and its influencing factors have been discussed in this paper.A self-assembled colloidal quantum dot chain with surface mercapto functionalized was designed.It was formed by a red luminescent quantum dot with carboxyl functionalized and in the presence of the intermediate trithiocyanuric acid(TTCA).In the experiment,TTCA could replace the carboxyl on the surface of cadmium telluride quantum dot and self-assemble aggregation.Because of the steric resistance,the third sulfhydryl group could not take part in the substitution reaction,thus forming a chain of colloidal quantum dots.(3)Based on the red emission quantum dots and blue emitting carbon dots,a pink emission ratio fluorescence probe was designed and synthesized in this part,to achieve an ultra-sensitive,visual detection probe for As(III)ion in environmental water samples.In the detection process,due to the formation of As-S bond,quantum dot chain aggregated,and resulted in the fluorescence quenching.However,no reaction between As(?)and carbon dots,thus the blue emission remains unchanged.As a result,a very wide/consecutive "from pink to green" response to the presence of amount of arsenic ions.The detection limit is as low as 1 ppb.Finally,a ratio fluorescence test paper for arsenic detection was constructed,provides a simple visual detection method for ultra-sensitive detection of arsenic ions.