Study On Femtosecond Laser Preparation And Properties Of Functionalized Gold Nanoparticle Microsensor

During the development of electronic devices,miniaturization and higher integration have always been the mainstream and the research frontier.In the field of gas sensors,chemiresistor whose resistance changes when exposing to the analyte is highly suitable for practical usage owing to its simple structure and instrumentation.Miniaturization of gas sensors carries added benefits of better portability,lower costs,and allowing for multianalyte detection by integrating various sensors in one device.In addition,the miniaturization of sensors can integrate different sensors in a limited space,which is of great significance for building electronic nose systems with identification and quantification functions.Miniaturization also helps to integrate different types of sensors,such as gas sensors,humidity sensors,photodetectors,to build a multi-functional sensing platform.This multi-functional microdevice might gain widespread application in the on-chip integration,multivariablemicrosensor arrays,and multifunctional micro sensing system.In our paper,laser writing technology is proposed to fabricate a micro gas sensor based on 11-mercaptoundecanoic acid functionalized gold nanoparticles,which are assembled and deposited over the spacing between two electrodes.The particle-to-particle electron transport is interpreted as hopping mechanism.The experiment of microsensor was conducted on organic vapor and relative humidity.When nanoparticles are exposed to analytes,the adsorption of VOCs on the sensor surface cause the change of physical parameters,such as the dielectric constant of the dielectric intervening space and the core-to-core distance.In our experiment,gold nanoparticles functionalized with 11-mercaptoundecanoic acid were synthesized by a one-step one-phase reduction of AuPPh₃Cl.The average particle size of the gold nanoparticles was2.78±0.44 nm.In our study,laser writing technology is introduced to fabricate a planarized microsensor.By this method,the microsensor has been fabricated with a size of 48.9?m×5.8?m×0.26?m.With the exposure to ortho-xylene,the response value increased linearly from 0.011 to 0.412 corresponding to a concentration of 100-5000ppm.The microsensor has a fast response and recovery speed whose response and recovery time are within 80s.The microsensor has shown the maximum response value to ortho-xylene among seven target gases?ortho-xylene,toluene,ethanol,benzene,methanol,acetone,chloroform?.The comparison between the microsensor and the drop-cast film was made.In 5000 ppm ortho-xylene,the response value of the microsensor is 0.412,obviously higher than 0.044 of drop-cast film.The respond time is 57 s shorter than 127 s.The microsensor showed improved response value from minimum 1.8 to maximum 6.7 times for seven species of VOCs compared with the drop-cast film,and the response time to most gases is only 1/3 of the drop-cast film.We attribute shorter response time and more sensitive response to the larger surface-volume ratio brought by the rough surface and the miniaturization of device.The microsensor exhibited excellent properties with higher response and shorter response time for seven analytes compared with drop-cast film.The laser direct writing technology could be applied to the miniaturization and integration of sensor devices,and might gain widespread application in the on-chip integration,multivariable microsensor arrays,and multifunctional micro sensing system.