Construction Of Optical Nano Sensor For Detection Of As(?) In Water

As we all know,arsenic is one of the common pollutants in sewage.It exists in various forms and is affected by the surrounding environment.It mainly exists in the form of As3-,As0,As3+,and As5+.Among these forms of arsenic,trivalent arsenic is the most toxic.When taken in excess,it can lead to cancer in humans and,in severe cases,death.Concentrations of trivalent arsenic in water are prohibited from exceeding 10 parts per billion,as required by the WHO and EPA.Therefore,it is particularly important to develop the detection method with high sensitivity and good stability when it meets the low concentration standard.From the current development situation,atomic absorption spectroscopy(AAS),inductively coupled plasma mass spectrometer(ICP-MS),atomic fluorescence spectrometry(AFS)and other large instrument detection methods have been developed maturely.However,large equipment is not portable,expensive to maintain and requires professionals to operate,so it is not suitable for real-time in-situ detecting.Hence,the development of portable and rapid on-site detection of arsenic pollution has become a new research direction.We have carried out in-depth research and exploration on the development of colorimetry and fluorescence detection of toxic pollutants in water in recent years.In this paper,based on the colorimetric method to detect As(?)in water firstly,we further extended to the colorimetric/fluorescent dual mode method to detect As(?).A dual-mode detection method is provided for As(?)detection,which can largely meet the requirements of real-time in-situ detection in outdoor work.Specific research contents are as follows:(1)The forms of arsenic in the environment and its hazards are summarized,as well as the current common means of detecting As(?).(2)We constructed the TMT functionalized gold nanoparticles(TMT-Au NPs)for detection of As(?)in water.Using Au atoms in Au NPs can cantact with -SH to form Au—S bonds with strong binding force as the theoretical support,so as to functionally modify TMT on the surface of gold nanoparticles.The specific recognition group—SH exposed on the surface of Au NPs was combined with As(?)in water,cause gold nanoparticles to aggregate.Based on the local surface plasmon resonance effect(LSPR effect),the UV-vis absorption peak of TMT-Au NPs was changed,along with the color change of solution,so as to achieve the purpose of visual colorimetric detection.(3)We developed a system of colorimetric/fluorescent dual-mode optical nanosensors for the detection of As(?)in water.Firstly,amino-functionalized carbon dots(NCDs)was synthesized,and then TMT-Au NPs was mixed with NCDs to form a probe solution.After mixed,the fluorescence of NCDs is quenched to a great extent based on the internal filtration effect(IFE effect).When As(?)was added to the system solution,coordination occured between As(?)and—SH on the surface of TMT-Au NPs,resulting in the aggregation of TMT-Au NPs.Based on the local surface plasmonic resonance effect(LSPR effect),the UV-vis absorption peak of Au NPs was red-shifted,and the system solution had a visible color change.At the same time,the fluorescence of NCDs gradually recovered.Thus,the colorimetric/fluorescence dual mode detection could be achieved.In our work,the detection limits of colorimetry and fluorescence reached 0.67 ppb and 0.87 ppb,respectively.This method can realize super-sensitive and real-time in-situ dual-mode As(?)detection,which opens a new direction for the detection of As(?)in Water.