| In last decades, heavy metal pollution has becomes increasingly serious with the rapidly growing economy, which has threaten people’s life and health. Thus, there is an urgent need to develop a method with the advantage of fast and effective detection for trace heavy metal ions in solution, which is very important significance to monitor of the environment and human health. In this thesis, silicon nanowire arrays(SiNWs) have been fabricated by metal assisted chemical etching method are used as a template to prepare metal-SiNWs composite nanostructures. The effects of key fabrication parameters (AgNO3concentration, Fe(NO3)3concentration, and etching time) on the nanostructure SiNWs were carefully investigated by SEM, TEM, respectively. And the Raman spectra under different etching time was studied by Raman spectra characterization. Some meanningful results were achieved after fabricating and testing the Pb2+sensor. The main research contents and conclusions are as follows:(1) In the two-step metal assisted chemical etching process, silicon nanowire morphology and structure can be controlled by regulating the AgN03and Fe(NO3)3concentration, with the increase of concentration of AgNO3from0.002mol/L to0.1mol/L, morphological transition from solid nanowires to porous nanowires can be found. While the Fe(NO3)3concentration is between0.01mol/L-0.05mol/L, SiNWs length is increased from1.788μm to2.778μm with the Fe(NO3)3concentration increased, the chemical polish is observed when the concentration of Fe(NO3)3increases to0.5mol/L, SiNWs length is increased from1.923μm to4.613μm with the increasing etching time from30min to120min. SiNWs’ Raman peaks around520cm-1have a blue shift and the Raman peaks are broadened comparing with bulk silicon chip, and their line widths become larger with increasing SiNWs etching time from30min to120min.(2) The concentration of AgNO3and Fe(NO3)3play important roles to the lengths and arrangements of SiNWs arrays in one-step metal assisted chemical etching. The morphological transition of Si surfaces from solid nanowires to porous nanowires can be found with increasing AgNO3concentration and Fe(NO3)3concentration, which indicates that the re-dissolved Ag+would work as the main oxidative species for oxidizing the silicon substrate and forming SiNWs in the HF/AgNO3/Fe(NO3)3etching system. A novel mechanism is proposed to explain the formation of SiNWs in HF/AgNO3/Fe(NO3)3solution.(3) In the process of preparation of Au/SiNWs electrodes, the length of the silicon nanowires increased gradually with the increase of etching time, and the SEM and EDS results show that the content of gold deposit on the surface of the electrode gradually increased, as the etching time increased from20min to140min, and the content of gold deposition are4.17%,4.62%,4.78%,5.14%,15.17%,30.25%,33.22%, respectively. A Pb2+sensor has been fabricated using this Au/SiNWs composite structure. The peak current incresed with the increasing of etching time, the peak current is larger and the uniformity of silicon nanowires is best while the etching time is120min.(4) Silicon nanowires electrode of Au decorate was fabricated, using the method of chemical plating which decorate Au nanoparticles on SiNWs, and the SiNWs wasfabricated by metal assisted chemical etching method. The morphology of gold on the Au/SiNWs structures changes from granular surface gradually into flocculent as the etching time increased from20min to140min, and the content of gold deposition are15.31%,21.54%,24.91%,30.25%,31.07%,33.22%, respectively. A Pb2+sensor has been fabricated using this Au/SiNWs composite structure.The peak current increases with the increasing of gold deposition time.(5) On the conditions of optimal parameters, the results show that the anodic peak current increase with the increasing Pb2+concentration and their relationship is1=0.42866CPb2++96.85468(R2=0.98306) under the concentration range of50μg/L～200μg/L. The results show that this type of composite structure is very promising for the future development of sensors of Pb2+. |
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