Preparation And Sensing Application Of Single Metal Nanowire

Nanoelectrodes are electrodes smaller than 100 nm in at least one dimension,which have received great attention in basic electrochemical research and bioelectrical analysis research.Compared with electrodes of conventional size,nanoelectrodes have obvious advantages,such as smaller charging current and RC constant,higher current density,and faster mass transfer rate and electrochemical response.These advantages make it widely used in the study of electron transfer kinetics,biological analysis,highresolution imaging of scanning electrochemical microscopy(SECM),electrochemical sensing research,electrochemical catalysis and other fields.It is well known that precious metals(such as gold,silver,platinum)have excellent surface-enhanced Raman scattering(SERS)activity,electrocatalytic activity,and reactivity.The combination of nanowire electrodes and SERS has great advantages in electrochemical catalysis,electrochemical sensing,biomolecule detection,and single-cell imaging.Based on this,this paper aims to introduce the construction of nanowire electrode though laserassisted pulling technique and study its SERS performance at the single nanowire level and its application in the construction of biological sensor.The specific work is divided into the following three parts:1.single Ag nanowires(AgNWs)and single Au-coated AgNWs(Ag@AuNWs)were fabricated by the laser-assisted pulling method and the galvanic replacement reaction,respectively.The prepared single Ag@AuNWs show both high SERS activity and catalytic activity through in situ monitoring and assessing the plasmon-driven surface-catalytic reaction of 4-nitrothiophenol(4-NTP)dimerizing to 4,4’dimercaptoazobenzene(DMAB)and the reduction reaction of 4-NTP to paraaminothiophenol(PATP),respectively.The proposed bimetallic NWs exhibit good SERS activity and excellent catalytic performance and realize SERS performance research at the level of single NWs,which will be beneficial to expand the application of SERS in different fields,such as catalysis,sensing,and fundamental research at the single entity level.2.We developed a nanosensor based on a single gold nanowire(AuNW)using insitu SERS technology and used it for adenosine triphosphate(ATP)sensing detection.Single AuNWs was fabricated by laser-assisted pulling method and hydrofluoric acid(HF)etching process,and bonded to single strand HS-DNA by Au-S bond.Due to the complementary pairing between ATP aptamer and single stranded DNA,gold and silver bimetallic nanoparticles(Au/Ag NPs)containing thiol Raman dye and ATP aptamer were fixed on AuNW modified by DNA,and Au/Ag NPs of thiol Raman dye were attached to AuNW,thus showing strong SERS signal.In the presence of adenosine triphosphate(ATP),the Au/Ag NPs will be separated from the AuNW due to the strong specific affinity between the ATP aptamer and ATP molecular,resulting in the obvious decrease of the Raman signals,which can be used for ATP sensing with high sensitivity,selectivity and stability.This method establishes an ATP detection method with high sensitivity,good selectivity,good reproducibility and wide linear range,and the experimental results show that its linear range is 1 pM-100 nM,and the detection limit is 0.17 pM.This nanosensor can be used as an ideal platform for real applications,especially at some confined-space samples,such as trace detection,single cell and in vivo analysis.3.We developed a thrombin biosensor based on electrostatic adsorption using in situ surface-enhanced Raman spectroscopy(SERS).The method is mainly based on the electrostatic adsorption between the captured(thrombin aptamer)and probe(methyl violet,CV)molecules,that is,the specific interaction between thrombin and aptamer can weaken the electrostatic barrier effect generated by the diffusion of negatively charged aptamer and positively charged CV from the body solution to the conjugated AuNW-NPs surface.The more thrombin bound to the surface of the the conjugated AuNW-NPs surface,the more CV molecules were adsorbed and the stronger the Raman signal was observed.The biosensor showed high specificity,stability and selectivity.Experimental results showed that the detection results of thrombin in the range of 10 pM to 100 nM showed a linear distribution,with a detection limit of about 1.35 pM.Nanowires with the combination of nanoparticles used as SERS provides a large number of hot spots,to avoid the disadvantages of nanostructures on the weak signal,improves the detection signal strength,and its high sensitivity and selectivity to combine with small size effect AuNW-NPs in small molecule detection,living,and single cell with other sensors incomparable advantages in real-time monitoring.