Abstract
This articles reports a simple and green method for preparing uniform silver nanoparticles (AgNPs), for which self-polymerized 3,4-dihydroxy-l-phenylalanine (polyDOPA) is used as the reducing and stabilizing agent in aqueous media. The AgNPs functionalized by polyDOPA were analyzed by UV–Vis spectroscopy, high-resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), Raman spectrophotometry, and X-ray diffraction (XRD) techniques. The results revealed that the polyDOPA-AgNPs with diameters of 25 nm were well dispersed due to the polyDOPA. It was noted that the polyDOPA-AgNPs showed selectivity for Pb2+ and Cu2+ detection with the detection limits for the two ions as low as 9.4 × 10−5 and 8.1 × 10−5 μM, respectively. Therefore, the polyDOPA-AgNPs can be applied to both Pb2+ and Cu2+ detection in real water samples. The proposed method will be useful for colorimetric detection of heavy metal ions in aqueous media.
Highlights
Heavy metal pollution in air, soil and water is a serious problem and it is a growing threat to humanity and the environment
This study reported a simple and green approach for the synthesis of AgNPs in an aqueous medium using polyDOPA as a reducing agent and stabilizer
The size of the synthesized spherical AgNPs was about 20 nm, and they were surrounded by polyDOPA with a thickness of about 5 nm
Summary
Heavy metal pollution in air, soil and water is a serious problem and it is a growing threat to humanity and the environment. Certain metals, including lead, copper, mercury and cadmium ions, show toxicity at trace amounts [2,3]. FFiigguurree 33AA sshhoowwss tthhee ccoolloorr cchhaannggeess iinn tthhee ppoollyyDDOOPPAA--AAggNNPPss ssoolluuttiioonn aafftteerr tthhee aaddddiittiioonn ooff vvaarriioouuss mmeettaall iioonnss. After the addition of Cu2+ ions, the color of the polyDOPA-AgNPs solution was changed from yellow to bInrto.InJw.t.MJn.o,Ml.aoSnlc. TThis rreessuulltt wwaass cclleeaarrllyy ccoommppaarreedd wwiitthh ppoollyyDDOOPPAA--AAggNNPPssiinn tthhee aabbsseennccee ooffPPbb222+++ and Cu22+++ioionnss(F(Figiguurree11))..AAlslsoo, ,ththeeaaggggrreeggaattioionnooffppoolylyDDOOPPAA--AAggNNPPssddiiddnnoottooccccuurr iinn tthhee pprreesseennce ooff aannyy other metal ion, such as tthhee CCdd22+++ iioonn((FFiigguurree55CC))..TThheerreeffoorree,,iitt wwaass ccoonnffiirrmmeedd tthhaatt thee change in the solutioonnccoololorranadndthethoebsoerbvseedrviendteninsitteynrsaityio irnatFioiguinre F3Ciguwreere3cClosweleyreasscolocsiaetleydawssitohcitahteeadggwreitghattihone abgeghraevgioatrionf thbeehpaovlyioDrOoPfAt-hAegNpoPlsy.DPOarPtAic-uAlagrNlyP, tsh. TTEEMM iimmaaggeess ooff ppoollyyDDOOPPAA--AAggNNPPss iinn tthheepprreesseenncceeooff(A(A))CCuu2+22++;; ((BB))PPbb22+2++;; aanndd ((CC)) CCdd222+++ iioonnss ((00..11 μμMM)). Zeta potentials of polyDOPA-AgNPs interacted with metal ions. FFrroomm tthhee aabboovvee rreessuullttss,, aa ppoossssiibbllee mmeecchhaanniissmm ffoorr tthhee iinntteerraaccttiioonn ooff ppoollyyDDOOPPAA--AAggNNPPss wwiitthh ssppeecciifificc hheeaavvyy metal ions wwaass pprrooppoosseedd,, aassddepepicitcetdedininFiFgiugruere7.7A.
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