Colorimetric And Photothermal Sensing Based On Metallophilic Interaction Between Mercury Ions And Noble Metal Nanozymes

Mercury ions(Hg²⁺)as a highly toxic heavy metal ions,it can cause a series of irreversible diseases even at very low concentrations.Traditional instrument detection methods are often limited by large equipments,tedious operations and professionals,and fail to meet point of care testing（POCT）requirements of Hg²⁺.Therefore,the development of simple,portable,rapid,sensitive and specific POCT methods of Hg²⁺is a current research hotspot in this field.The detection methods based on nanozymes have been shown that possessed potential application in the fields of environmental detection and disease diagnosis,bringing new opportunities for the construction of heavy metal ions POCT methods.Based on this,taking the advantages of excellent catalytic performance and good biocompatibility of noble metal nanozymes,the metallophilic interaction between Hg²⁺and noble metal nanozymes was fully investigated,and then the modulation mechanism of nanozymes oxidases（OXD）activity by metal ions was also illustrated.Finally,a simple and rapid colorimetric/photothermal sensing method for Hg²⁺analysis was successfully developed.This paper is divided into the following four parts:Chapter 1:The hazard and detection necessary of Hg²⁺are firstly introduced.Then,the classification,enzyme activity and four Hg²⁺sensing mechanisms of noble metal nanozymes in Hg²⁺analysis are reviewed.Finally,the sensing application of noble metal nanozymes with different analytical signals in Hg²⁺analysis is summarized.Chapter 2:Gold@silver core-shell nanoparticles（Au@Ag NPs）were prepared at room temperature by using seed growth method.The enzyme-like activity of Au@Ag NPs was fully studied and found that significant metallophilic interaction between Hg²⁺and Au@Ag NPs could effectively enhance the oxidase-like activity of Au@Ag NPs nanozymes,finally significantly oxidizing the chromogenic substrate3,3’,5,5’-tetramethylbenzidine（TMB）to produce blue colored TMBox.Due to the good photothermal effect of TMBox in the near-infrared region,it could enable the system producing a sensitive temperature response.Based on this,a fast and simple detection method with colorimetric and temperature analytical signals for Hg²⁺was successfully constructed.The experimental results show that the detection limit（LOD）of Hg²⁺with colorimetric/photothermal sensing analysis is 0.335μM and 0.275μM（3δ/k）,respectively.It provides a new approach for the simple and rapid detection of Hg²⁺in environmental samples.Chapter 3:The noble metal nanozymes of chitosan-platinum nanoparticles（Ch-Pt NP s）were prepared by using a simple one-pot method.It was found that a good metallophilic interaction between Hg²⁺and Ch-Pt NPs may significantly suppress the oxidase-like activity of Ch-Pt NPs nanozymes,providing an opportunity for producing colorimetric and photothermal signal response through an enzyme catalytic product of TMBox.Based on this,point of care detection and analysis method for Hg²⁺with colorimetric/photothermal double signal was successfully constructed.The experimental results show that the LODs of Hg²⁺with colorimetric/photothermal sensing analysis is12.7 n M and 10.2 n M（3δ/k）respectively.It exhibits good sensitivity and can also be used for Hg²⁺in the Yellow River water samples.Chapter 4:Summarizing the advantages and disadvantages of noble metal nanozymes-based colorimetric and photothermal sensors of Hg²⁺,and the development prospects of the specificity and sensitivity improvement of such sensors are also summarized.