Based On Organic Small Molecular Silver Nanoparticles Visualization Research Of Metal Ions

The clusters of atoms in the size range of1~100nm were widelyconsidered as nanoparticles.Nobel metal nanoparticles attracted a lotof attention in the past few years because of their unique physical,chemical, biological properities.Silver nanoparticles (AgNPs) have alsocaused great interest of researchers for a long time due to theirexcellent antibacterial catalytic and optical properties as well as simplesynthesis methods and low cost. AgNPs show differentcolors in the stateof dispersion and aggregation depend on the surface plasmonresonance (SPR). Some functional molecules which were modified onAgNPs can not only protect the nanoparticles from aggre-gating butaslo react with the analyte by means of some actions. Based on this,AgNPs have been used to prepare colorimetric sensor to determinesome targets. In this paper, we discussed the synthesis of AgNPs, what’smore, we modified several different organic molecules onto AgNPs,then studied their response to some metal ions respectively. This methodhas a lot of advantages such as simple operation, low cost,reproducible and the most interesting is the result is visible comparedwith traditional methods.Ⅰ. Study of the synthesis of AgNPs and colorimetric analysis for Ni2+based on Cysteine-functionalized Ag nanoparticlesIn this study, we not only improved the synthesis of bare AgNPs butaslo selectively detected Ni2+based on Cysteine-functionalized Agnanoparticles (Cysteine-AgNPs). Ni2+ions lead to the aggregation ofthe AgNPs as a consequence of a chelation process between Ni2+ionand the two groups (–COOH,-NH2) in Cysteine on the AgNPs, then anew peak appeared at526nm, along with color changed. The resultswere characterized by transmit-ssion electron microscope(TEM), takingphotos and ultraviolet-visible spectr-oscopy(UV–vis). The synthesis of bare AgNPs modified made the whole procedure nearly one hour lessthan the traditional method due to we modified after ensuring thatNaBH4? was completely decomposed. The A526/A405shows a goodlinear relationship with Ni2+concentration (c) ranged from5.6μM to13.9μM, and the limit detected with naked eyes is low to4.9μM. Theseresults showed that except Co2+having a modest interference,modified AgNPs can selectively detect Ni2+in different metal ions, Thismethod is expected to be used for real sample analysis.Ⅱ. Direct naked-eye detection of Cr(VI) using ascorbicacid-capped silver nanoparticles as colorimetric probeWe described a very simple detection method for Cr(VI), Theascorbic acid-capped Ag nanoparticles(AA-AgNPs) were found toundergo aggregation accompany with color change and a significantred shift in the UV spectrum (500nm~600nm) in the presence of Cr(VI),however, the sensitivity of AA-AgNPs towards other22types of ions canbe negligible at the same condition. Also the effect of theconcentration of Cr(VI) to AA-AgNPs was investigated and Cr(VI) couldbe observed directly by naked eyes. The A548/A390shows a goodlinear relationship with Cr(VI) concentration (c) ranged from0μM to1.8μM, and the limit detected with naked eyes is low to1.24x10-7M.Theperformance of the colorimetric sensor was successfully evaluated theamount of Cr(VI) in lake water, indicating this simple and sensitivetechnique offers great promise for onsite monitoring of Cr(VI) inenvironment. Moreover, the mechanism of colorimetric sensor for thedetection of Cr (VI) was discussed.Ⅲ. Study of colorimetric sensor for alkaline earth based onThioglycollic acid-functionalized Ag nanoparticleThioglycollic acid(TGA) is a simplest sulfhydryl compound, which can form HSCH2COO-M2+-OOCCH2SH in the present of alkaline earthmetal ions, furthermore, the pKspof the hydroxide of the four ions aremuch more less than other’s. Based on this, we prepared a colorimetricsensor(TGA-AgNPs), and studied its response to alkaline earth metal ions,we found that this colorimetric shows strong response to alkaline earthmetal ions in a wide concentration range at pH12.20, furthermore, westudied the color change and the shifting of the SPR peak when addeddifferent concentrations of different alkaline earth metal ions, Thedetection limit of the four metal ions Mg2+，Ca2+，Sr2+，Ba2+are6.25μM,2.08μM,1.25μM,0.833μM with naked eye after staying for about5mins, respectively.Finally, it was applied to analyze the total amount ofCa and Mg of natural mineral water, and the detection result isconsistent with the report range. It provides some possibilities for thedetermination of hardness of tap water.Ⅵ. Rapid colorimetric detection for Pb2+based onTBA-functionalized Ag nanoparticlesA simple and highly selective thiobarbituric acid-modified Agnanoparticles (TBA-AgNPs) probe has been applied for the colorimetricdetection of lead ions (Pb2+),based on the fact that Pb2+ions lead tothe aggregation of the AgNPs as a consequence of a chelationprocess between Pb2+ion and TBA on the AgNPs. It was found that, atpH11, TBA-AgNPs show good selectivity to Pb2+ions, and other15kindsof metal ions did not interfere. The A540/A402shows a good linearrelationship with Pb2+concentration (c) ranged from3.97μM to27.8μM.The present method has the advantages of being simple, rapid, highlyselective and visible, and it offers the potential promise for rapiddetection of Pb2+in environmental samples.