Research Of Triangular Silver Nanoplates Applied In The Detection Of Several Trace Ions

Silver nanoplates?TAg-NPs? have captivated strongly attention because of their strong shape-dependent optical, physical, and chemical properties. Thus, many researchers have synthesized trangle silver nanoplates?TAg-NPs? succesfully with efficient and highly reproducible process and controllable-edge length and thickness as well as desired surface plasmon resonance bands for many applications in different fields. Recently, TAg-NPs have been extensively utilized as chromogenic reagents in colorimetric sensing systems. Then apply it to the early detection of biological living and disease diagnosis. In this work, without any surface modification agent, we only made use of the blue TAg-NPs interaction with analytes(such as Bovine serum albumin?BSA?, Pb²⁺, Cu²⁺) directly or indirectly. As a result, the morphology, color, and maximum absorbency of TAg-NPs changed, and the change of the maxium absorption wavelength is red-shifed to detection of traces of different substances(BSA, Pb²⁺,Cu²⁺).?1? According to the interaction of TAg-NPs and BSA in the presence of Britton-Robison buffer solution?BR? coupled with UV-visible spectrophotometric detection. Particularly, the wavelength of maximum absorbance??max? of TAg-NPs is red shifted in the presence of both BR?pH, 2.56? and BSA, and the color of the TAg-NPs/BSA/BR mixed solution changed from blue to light blue. Because BSA molecules combined with the surface of TAg-NPs through hydrogen bonds,hydrophobic effects, electrostatic forces and van der Waals forces at pH 2.56 and leading TAg-NPs and TAg-NPs aggregation, The color and corresponding maximum absorption wavelength of TAg-NPs were altered relying on the concentration of BSA.Furthermore, we found that the shift value of maximum absorption wavelength? Dl?between the TAg-NPs/BSA/BR mixture and the TAg-NPs/BR mixture were proportionate to the concentration of BSA in the range of 1.0 ng m L-1to 100.0 ng m L-1. The detection limit?3s/k? for BSA was found to be as low as 0.5 ng m L-1. and the correlation coefficient of r=0.9969. Thus, a simple and highly sensitive method for BSA detection by UV-visible spectrophotometry has been established.?2? The {111} surface energies of TAg-NP is lower than the{110} surface of TAg-NPs, It is means that the Ag atoms at the corners and on the {110} surface could be readily etched by the oxgen of atmosphere in the presence of BR?pH= 2.56?, which leading to the TAg-NPs corrode into hexagonal Ag nanoplates or a Nano disc and the wavelength of maximum absorbance??max? of TAg-NPs was blue shifted. However,when there was a small amount of lead ions in the solution, the reaction of PO43-and Pb²⁺ generated Pb3?PO4?2, which was then absorbed onto the TAg-NPs surfaces and leading to TAg-NPs aggregation, then prohibittng further corrosion of the TAg-NPs.Moreover, PO43- has three binding sites, two PO43- ions could reaction with three Pb²⁺ions to form big complex, which leading the morphology, and the maximum absorption wavelength of TAg-NPs varied distinctly with increasing the concentrations of Pb²⁺ in the presence of BR?pH=2.56?, The color of TAg-NPs becoming weak gradually, the change of maximum absorption wavelength? D l? of TAg-NPs/Pb²⁺/BR and TAg-NPs/BR solutions were proportional to the concentration of Pb²⁺. Thus, a simplely method for the determination of Pb²⁺ has been developed with spectrophotometric detection.?3? The development of the system is primarily counted on the principle of the TAg-NPs with high chemical activity and surface energy, the silver atom of vertices were oxidized to Ag2 O easily, when the solution involves high levels of NH₄ SCN,Ag2O react with SCN- to form Ag?SCN?2-, Ag?SCN?32-, Ag?SCN?43- complex. NH₄ SCN could corrode the corners of the TAg-NPs, which leaded the TAg-NPs transform them from TAg-NPs to Nano disc, and the color of blue TAg-NPs turned to yellow by the corrosive effect of NH₄ SCN. As a result, the maximum absorption peak of the TAg-NPs blue-shift. However, extremely low concentration of Cu²⁺ ions could reduced into Cu+ions by ascorbic acid(Vc and the Cu+ions could produce disproportionation reaction generated copper deposited on the{220} surface of TAg-NPs and vertices, the plasmon absorption of TAg-NPs showed a significant red-shift, and prevented the TAg-Nps were etched by NH₄ SCN. When the concentration of NH₄ SCN was constant,it is confirmed that the color was turned from yellow to blue, the morphology transformed by nanodisc gradually into trangles, and the plasmon absorption of TAg-NPs altered with the change of the concentration of Cu²⁺ ions, and the change values of the plasmon absorption of TAg-NPs were proportional to the concentrations of Cu²⁺ in the range of 6.0×10-8¹.0×10-6 mol/L. According to these phenomena, we demonstrated a novel assay to detect Cu²⁺ion by either UV-visible spectrophotometric detection or naked-eye successfully.