Design And Application Of Nanosensor Based On MoS₂ And Quantum Dots

As is known to all,water is the basic substance on which human beings depend for survival.Furthermore,water is the restricting factor for the sustainable development of human society.With the rapid development of China’s economy,the demand for water resources is increasing.However,it is noted that the problem of water pollution is also becoming more and more severe.Water acidity and heavy metal ions have a profound impact on the pollution of water and the life safety for human andorganism.Because of the obvious disadvantages,such as expensive cost,complicated operation and large size,etc,the traditional detection methods cannot meet the needs of timely detection of water under different conditions.So the methods of quick research and simple detection of water acidity and heavy metal ions have become the focus of people’s attention.In recent years,due to the excellent properties of nanomaterials in the fields of optics,electrics and information science,nanomaterials and their derived systems have provided new methods and ideas for the convenient and quick detection of water pollution.In this paper,through the use of hydrothermal method and aqueous-phase synthesis,cadmium telluride quantum dots（CdTe QDs）and carbon quantum dots（CQDs）were synthesized,and characterized using UV-visible absorption spectrum（UV-vis）,fluorescence spectroscopy,transmission electron microscopy（TEM）techniques.It is shown that CdTe QDs and CQDs are characteristics of uniformparticle size,stableoptical properties and narrow fluorescence spectrum band.Since H⁺and OH^-have the specific binding interaction with the surface ligands of CdTe QDs,the pH of the solution can be detected by monitoring the change for the emission peak position of CdTe QDs using fluorescence spectrum technique.Along this line,the scope of pH values was determined as 4-11 in aqueous solution.At the same time,there are strong interaction of Hg²⁺with the hydroxyl and carboxy groups on the surface of CQDs.Consequently,CQDs will aggregate with the addition of Hg²⁺,resulting in the fluorescence quenching of CQDs.Based on these observations,herein we realized the sensitive detection of Hg²⁺in aqueous solution using the synthesized CQDs,and the detection limit was 26 n M.Moreover,this strategy showed the high specificity and sensitivity for the detection of Hg²⁺in the presence of other interfering metal ions.Finally,a nano-biosensor based on the synthesized molybdenum disulfide（MoS₂）nanosheet was constructed to detect Hg²⁺and Ag⁺in the mean time in aqueous solution by using fluorescence spectroscopy.The sensing principle for the fluorescence nano-biosensoris that the single-stranded DNA can form a stable double-stranded DNA with the formation of T-hg²⁺-Tor C-Ag⁺-C mismatch in the presence of Hg²⁺or Ag⁺.According to the different adsorption ability of single-stranded DNA and double-stranded DNA on MoS₂ nanosheets surfaces,a"turn-off"mode based nano-biosensorhas been developed in this work.With the use of this nano-biosensor,both of Hg²⁺and Ag⁺can be sensitively andselectively detected in water,and the detection limits of Hg²⁺and Ag⁺were estimated to be 6.8 n M and 8.9 n M,respectively.