| Mercury is one of the most toxic heavy metals.It is easy for accumulating in biont,and then enters into the food chain and results in some irreversible damages for human beings.It will cause some dysfunctions,such as lapse of memory,gingivitis,digestive functional disturbance,and neuropathy when human uptake the excess mercury.Because of its high toxicity,our country has stipulate that the concentration of mercury is respectively not higher than 0.001 mg/L and 0.05 mg/L in drinking water and industrial waste water.Therefore,it is very important for detection and control of Hg2+ in real time.Fluorescence and adsorption method is respectively has many merits in detection and removal of Hg2+ than other methods,such as rapid,sensitive and efficient etc.At present,many fluorescence probe and adsorbents have been developed for Hg2+ determination and adsorption.However,some shortcomings are existed in the developing of fluorescence probe,like the complex preparation process,specific apparatus requirement,time consuming,low fluorescence quantum yield and poor selectivity etc.Also the developed adsorbents often have poor adsorption capacity.Based on these existing problems,it is a straightforward way to improve the efficiency comprehensive utilization of resources by using simple and facile method to prepare new fluorescence probe with high fluorescence quantum yield and selectivity.This research design and synthesis two different fluorescence probes for Hg(II)highly selective detection based on the one-step rapid reaction between dopamine(DA)and resorcinol(RS)for generating high quantum yield fluorescence molecule.And prepare two polydopamine(PDA)-base adsorbents for efficient removal of Hg2+ based on the property of DA oxidation of self-polymerization.1.The research found that DA and RS could rapidly react and generate azamonardine with high fluorescence quantum yield(72.6%)in alkali solution.By using this reaction,RS was straightly used as a probe for highly selective and sensitive determination DA concentrations within 5 min through fluorescence “off-on”.This method could detect DA concentration in a linear range of 10 n M-20 mM and low of detection(LOD)of 1.8 n M,and it was succeeded for determination of DA in human urine.2.Based on the mechanism of reaction between DA and RS,a novel water soluble fluorescence probe(C-DA)was synthesized from the reaction between natural phenols which were DA and RS structure based catechine.The fluorescence of C-DA was selectively quenching to both Cu(II)and Hg(II).Na BH4 and phytic acid could respectively mask the interference of Hg(II)and Cu(II).The detection linear range of C-DA for Cu(II)and Hg(II)were 0-10 mM and 0-8 mM,respectively,and the calculated LOD were 3.0 n M and 102.7 n M,respectively.For detection mechanism,Cu(II)oxidized the catechol to quinone and itself was reduced to Cu(I),then Cu(I)combined with catechu quinone in a molar ratio of 1:1.Nevertheless,Hg(II)straightly combined with catechol in a molar ratio of 1:1.3.Based on the mechanism of reaction between DA and RS,the aminothiazole group was firstly introduced on the framework of RS struture,and then reacted with DA to synthesize a novel acid-alkali dual response fluorescence and colorimetric probe(S3)for Hg2+ selective detection.Also,S3 can sensitively distinguish the acid and alkali solution through its changeable color.S3 with a high quantum yield of 26.12% in acid solution,and strong absorption at 425 nm in alkaline solution.Therefore,S3 could realize the Hg2+ detection by fluorescence and colorimetric method in acid(p H =5.0)and alkaline(p H = 7.5)solution with the linear detection range of 0-35 mM and 0-12 mM,LOD of 146.3 n M and 149.2 n M,respectively.Hg2+ was combined with S3 in the ratio of 1:2 and 1:1 in acidic and basic solution,respectively.The probable detection mechanism of S3 for Hg2+ was proposed through various characterizations.According to the double response of S3 in acid and basic solution for Hg2+ determination,it is promising for S3 analysis Hg2+ concentration in complex industrial waste water.4.By utilization the oxidation of self-polymerization and reducibility properties of DA,the composite of RGO@PDA was fabricated through one-pot method from GO and DA.The dynamics and thermodynamics of Hg2+ adsorbed on RGO@PDA were studies.And the maximum adsorption capacity of RGO@PDA to Hg2+ was 1339 mg/g.On this basis,polydopamine nanospheres(PDA NSs)with uniform size were prepared for Hg2+ removal.The adsorption of Hg2+ on PDA NSs was a spontaneous and endothermic pseudo second-order process.It fitted to Langmuir isothermal adsorption.The maximum adsorption capacity of PDA nanospheres was 2076.81 mg/g.Furthermore,a 100%desorption capacity of PDA nanospheres could be obtained in 0.1 M HCl solution.After five times adsorption-desorption recycle,there were no drop of the adsorption capacity and considerable changes of structure for adsorbent.It is hopeful for using PDA NSs in removal of Hg2+ in unqualified waste water. |
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