| The environmental pollution problems have been the focus of the whole society.Water resources contaminated with heavy metal ions have brought terrible hazards to public health.Metalloid arsenic contaminated water has become one of the greatest threats to the health and existence of mankind.The reliable assay and monitoring of arsenic in water have always been one of the hot spots of heavy metal analysis.Conventional methods for arsenic detection are based on instrumental analytical methods like atomic spectroscopy and mass spectrometry.These techniques have achieved some progress including accurately and sensitively quantitative analysis,however,they show some obvious defects including complicated sample pretreatment,vast sample volume,high instrument price,high maintenance cost,only laboratory analysis due to bulky instruments,long testing time,etc.Therefore,it's of high necessity and significance to develop facile,relible,sensitive and on-site analytical methods for detection of arsenic in environmental samples.In this dissertation,due to specific recognition interaction of DN A probe and peculiar properties of various nanomaterials,we have designed several kinds of spectro-/electro-chemical sensing platforms,whose analytical mechanism and performance have been investigated in detail.These methods have been also applied to detect arsenic in real samples.The main content of this thesis is as follows:1.Introduction.This chapter gives a brief review about arsenic origin,pollution and threats.It summarizes the research situation of the analytical methods of inorganic arsenic and the advances of novel sensing techniques based on various nanomaterials for arsenic detection.This part elaborates the paper selected topic basis and the major research contents.2.Electrochemical determination of arsenite by exploiting arsenite-induced conformational change of ss DNA and Methylene Blue.An electrochemical sensor was designed based on As???-specific binding probe ss DNA?SBP DNA,a single-stranded DNA?and the electrochemical indicator Methylene Blue?MB?,achieving highly sensitive and selective detection of As???by d ifferential pulse voltammetry?DPV?.The linear range of this electrochemical sensor was from 0.1 to150 ppb,with a limintion of detection?LOD?of 0.075 ppb.It practicability was demonstrated by different water samples.The proposed electrochemical method possessed label-free way,high sensitity and good selectivity,which may have great potential for reliable detection of As???in complex environmental samples.3.Electrochemical sensor for arsenite detection using graphene oxide assisted generation of prussian blue particles as nanolabels.An electrochemical sensor was fabricated for arsenite detection using?-?stacking between graphene oxide?GO?and?GT?-rich ssDNA,the specific binding interaction between As???and?GT?-rich ssDNA and GO-assisted generation of prussian blue nanoparticles?PB NPs?as enhanced electrochemical label.This sensor can be used for sensitive detection of arsenite with a linear range from 0.2 to 500 ppb and a LOD down to 0.058 ppb.With the help of EDTA,the sensor exhibited high specificity against other interfering ions and was successfully used to detect As???in real water samples.This biosensor showed the advantages of low cost,free label and high sensitivity and great potential for trace arsenite detection in complicated environment.4.Multimodal assay of arsenite in environmental samples with improved sensitivity by using multi-ligands modified silver nanoparticles.Based on the localized surface plasmon resonance?LSPR?and highly electro-chemical activity of multiligands functionalized silver nanoparticles?Ag NPs?probe,multimodal assay of colorimetric/spectrophotometric and electrochemical methods was developed for As???detection.Multiligands?asparagine,Asn;glutathione,GSH;and dithiothreitol,DTT?functionalized Ag NPs probe?denoted as GSH/DTT/Asn-Ag NPs?were prepared through reduction method.As???can induce the aggregation of Ag NPs probe via As-O and As-S linkages,causing dramatic changes of absorption bands of Ag NPs along with the color change of solutions.This colorimetric/spectrophotometric assay showed convenient and rapid way for As???assay from0.4 to 200 ppb,with a LOD as 0.36 ppb.The As???-induced aggregation of Ag NPs probe on the Au electrode surface can be used as the electrochemical sensor for detection of As???by DPV.The electrochemical sensor showed markedly improved sensitivity and the LOD down to 5.2 ppt.The strategy featured high sensitivity,low cost and short analytical time.The plasmonic metal nanoparticles-based multimodal sensing method had successfully been applied for arsenic detection in real samples.5.QDs@Tb-nucleotide nanocomposite as ratiometric fluorescent probe for visual detection of arsenate via the inhibition of acid phosphatase bioactivity.QDs@Tb-GMP displayed single-excitation and dual-emission fluorescence around652 nm from QDs and 547 nm from Tb-GMP polymers.The fluorescence of Tb-GMP can be quenched effectively due to the disintegration of Tb-GMP structure via hydrolysis of GMP by ACP,whereas the fluorescence of QDs was inert to ACP as internal reference.The presence of arsenate can effectively inhibit the bioactivity of ACP by competitive binding interaction,and thus the hydrolysis of GMP was prevented by As?V?.So QDs@Tb-GMP can be used as a fluorescent signal-on probe for selective and sensitive detection of arsenate ranging from 0.5 to 200 ppb.QDs@Tb-GMP has great advantages like facile preparation process,good solubility,and environmentally friendly properties.This method showed an improved LOD with 0.39 ppb and can be used for visual assay of As?V?.In addition,the nanocomposite can be used to detect total inorganic arsenic level in real samples.6.Colorimetric and electroche mical bimodal detection of arsenate based on cobalt oxyhydroxide with peroxidase-like activity towards arsenate absorption.A colorimetric sensor was developed based o n cobalt oxyhydroxide?CoOOH?nanoflakes with intrinsic peroxidase-like activity and its specitic absorption with As?V?via electrostatic attraction and As-O bonds.The colored oxidation products would be decreased due to As?V?-inhibited peroxidase-like activity of CoOOH,realizing spectral assay for As?V?assay from 4 to 500 ppb,with a LOD as 3.72 ppb.When As?V?was absorbed on the surface of CoOOH modified electrode,the oxidation products ABTSox can be decreased,leading to the decrease of reduction currents.Thus a electrochemical sensor was developed for more sensitive detection of As?V?from 0.1 to 150 ppb,with a LOD as 0.052 ppb.This bimodal methods can be used to detect the total inorganic arsenic after oxidation of arsenic in real samples. |
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