Synergistic functionalization of aligned silicon nanowires by Ag nanoparticles&PPy wrapping for improving gas-sensing response at high humidity level

Abstract

Abstract In the field of disease diagnosis, there are few applications of gas sensors. But, gas sensors can specifically identify certain diseases. So, there is a great need for gas sensors capable of responding to trace amounts of special biomarker gases in high ambient humidity. The dual-modulated composite array of Ag NPs-modified PPy@SiNWs core-shell structures (Ag-PPy@SiNWs) are developed for sensitive response to a rarefied biomarker of NH3 at high ambient humidity. A repeated metal-assisted chemical etching (MACE) was first performed to fabricate a loose array of pristine SiNWs. Then Ag-PPy@SiNWs array one-step prepared via vapor phase polymerization (VPP) of Py on SiNWs with AgNO3 as oxidant. In the process, surface modification by Ag NPs is achieved in parallel to the PPy-shell formation during Py polymerization. PPy hetero-shell and Ag NPs contribute to NH3-sensing performance under high ambient humidity. Ag-PPy @ SiNWs can detect rare NH3 as low as 200 ppb at room temperature and 80% RH. Finally, the paper analyzes the sensing mechanism of Ag-PPy@SiNWs for NH3 under high humidity, especially the contribution induced by Ag NPs.