Preparation And Application Of Sensors Based On Metal Nanoclusters In Environmental Detection

In this paper,the gold nanoclusters（AuNCs@CAZ）,silver nanoclusters（Ag NCs@CAZ）and copper nanoclusters（CuNCs@CAZ）coated with ceftazidime（CAZ）were synthesized,respectively.A ratiometric fluorescent probe was construted by combining CuNCs@CAZ with Eosin Y（EY）,the acetaminophen（APAP）-capped gold nanoclusters（AuNCs@APAP）and silver nanoclusters（Ag NCs@APAP）were prepared,respectively.The effects of storage time,salt ion tolerance strength,p H,and exposure time on the stability of fluorescent probes were explored.A series of characterizations of instruments,such as UV-vis absorptions spectra（UV-vis）,photoluminescence spectra（PL）,high resolution transmission electron microscopy（HRTEM）,fourier transforms infrared spectrometer（FTIR）,X-ray diffractometer（XRD）,X-ray photoelectron spectroscopy（XPS）,steady-state/transient fluorescence spectrophotometer（FLS980）and Zetasizer Nano particle size potentiometer,were used to reveal the synthesis mechanism and existing surface states of fluorescent probes.In this paper,the as-prepared fluorescence probes exhibited excellent properties,such as good photostability,low toxicity,good biocompatibility,wate-solubility and mild synthesis conditions,and have been successfully applied to detect mercury,2,4-dinitrophenol（2,4-DNP）,4-nitrophenol（4-NP）and cetylpyridinium chloride（CPC）in environmental water samples.The specific research content is as follows:CAZ templated water-soluble AuNCs@CAZ,Ag NCs@CAZ,and CuNCs@CAZ were synthesized via one-pot method,respectively.The optical properties and morphology of the three were systematically characterized by UV-vis,PL,HRTEM,FTIR,XRD,XPS and other instruments.Owing to the better fluorescence performance and economics of CuNCs@CAZ,a method for determination of2,4-DNP was established based on the internal filtering effect（IFE）between CuNCs@CAZ and 2,4-DNP,which caused fluorescence quenching of CuNCs@CAZ.The relative fluorescence intensity F₀/F of CuNCs@CAZ was linearly ralated to the 2,4-DNP concentration over the range from 0.5 to 20μg/m L with good linear correlation（R²=0.9931）,and the limit of detection（LOD）was 93.1 ng/m L.The as-synthesized AuNCs@CAZ and Ag NCs@CAZ could be applied in sensitive detection of 2,4-DNP,the LOD was 50.0 ng/m L and 39.8 ng/m L with a good linear range from 0.05 to 15μg/m L（R²=0.9982）,and0.6 to 15μg/m L（R²=0.9979）,respectively.This method has been successfully used for the detection of2,4-DNP in real water samples.A ratiometric fluorescent probe EY-CuNCs@CAZ was constructed by combining CuNCs@CAZ and EY based on the F（?）rster resonance energy transfer（FRET）mechanism.The carboxyl groups of EY were activated by adding N-（3-Dimethylaminopropyl）-Nˊ-ethylcarbodiimide hydrochloride（EDC）and N-hydroxysuccinimide（NHS）,and then form amido link between the activated carboxyl groups and amine groups of CuNCs@CAZ to prepare ratiometric fluorescence probe EY-CuNCs@CAZ,while the quantum yield（QY）was increased from 3.15%（CuNCs@CAZ）to 4.40%.The ionic association was conformed between CPC and EY,which resulted in quenching fluorescence intensity of the EY in EY-CuNCs@CAZ,a ratiometric fluorescence sensitive detection of CPC in water samples has been constructed with a wide linear range(0.05-1.75×10^-5 mol/L),and the LOD is 0.37μM.This method was applied to the detection of CPC content in environmental water samples with satisfactory recoveries in the range of 101.52-107.74%.APAP templated water-soluble,emitting yellow AuNCs@APAP was prepared.AuNCs@APAP mixed with imidazoles,such as imidazole（Im）,1-methylimidazole（1-MIm）,2-methylimidazole（2-MIm）,4-methylimidazole（4-MIm）,2,4-dimethylimidazole（1,2-MIm）and 1-vinylimidazole（1-VIm）,which could lead to varying degrees of fluorescence intensity enhancement,the enhancement effect was as follows:1,2-MIm>2-MIm>4-MIm>1-MIm>Im>1-VIm.The mechanism of AuNCs@APAP fluorescence enhancement was mainly attributed to its p H-dependent and solvent-dependent effects.2,4-DNP and4-nitrophenol（4-NP）could cause fluorescence quenching of AuNCs@APAP,the methods for detection2,4-DNP and 4-NP were established,respectively,and the quenching mechanism was explored by characterizations of instruments.The LOD of 2,4-DNP and 4-NP was calculated as 0.301μg/m L and 0.246μg/m L,respectively,within a broad linear range from 0.375 to 12.5μg/m L for 2,4-DNP,and from 0.375 to25μg/m L for 4-NP,it was practical to determine 2,4-DNP and 4-NP in actual water.The water-soluble silver nanoclusters（Ag NCs@APAP）were prepared by using APAP as a protecant and a reducant in the dark at 55°C.The thiol groups on the surface of thiocyanic acid（TTA）was deprotonated under alkaline conditions,and strong complexation casued fluorescence quenching of Ag NCs@APAP.Based on the complexation reaction between Hg²⁺and TTA,the fluorescence intensity of Ag NCs@APAP-TTA was restored with the addition of Hg²⁺,then a method for measuring Hg²⁺was established.The fluorescence recovery degree F/F₀ and the concentration of Hg²⁺showed a good linear relationship with the range from 0.1 to 100μM.The regression equation was:F/F₀=0.0276C_Hg²⁺+0.9696（R²=0.9982）,and the LOD of Hg²⁺,determined by 12 repetitive measurements of 100μM Hg²⁺,was 28n M,the relative standard deviation（RSD）was 4.12%.This method possessed great selectivity toward Hg²⁺relative to other metal ions and could be used to detect Hg²⁺in drinking water samples.