Regulation Of Ag/Si-NPA Nanostructures By Current Annealing And Its Surface Enhanced Raman Scattering Effect

Silver nanoparticles because of its small size effect,surface effect,quantum size effect and macroscopic quantum tunneling effect,showing a unique electrical,magnetic and catalytic properties and excellent biocompatibility,optical sensing and etc.,which are widely used in our life.Silver nanoparticles are mainly physical,chemical and biological reduction method,which is more mature is the chemical reduction method,but due to the need to add in the preparation of dispersing agent or surfactant added,easy to cause pollution to the environment,and the increase of production cost reduction and porous structure through silicon nanoporous array itself has the silver ions from the aqueous solution of AgNO₃ reduction,the preparation method is simple and controllable,and without addition of reducing agent and dispersant,will not cause pollution to the samples.The main contents of the experiment are as follows:1.The silicon nanoporous pillar array（Si-NPA）was prepared by hydrothermal errosion method.The array has a composite system of nanometre and micron structure.The structure has three regular hierarchical distribution:regular array of silicon column on micron scale,silicon nanopore on silicon column and silicon nano single crystal particles that form pore wall.Si-NPA is a very ideal optoelectronic substrate,which can be used in the fields of LED,solar cell,sensing,SERS and so on.The Ag/Si-NPA composite system was prepared on the Si-NPA substrate by its surface activity and reducibility.2.The morphology of Ag/Si-NPA nanostructures before and after current annealing was observed,and the change rule of sample resistance during Ag/Si-NPA current annealing process was analyzed,and the mechanism of silver nanoparticle morphology evolution was analyzed.The three groups of experiments:（1）Ag/Si-NPA samples respectively on aging 24 hours Si-NPA immersion deposition for 3 min,（2）Ag/Si-NPA samples prepared by the impregnation deposition of freshly prepared Si-NPA wash over and immersion deposition 3min,（3）Ag/Si-NPA samples prepared freshly prepared Si-NPA prolong the cleaning time and then impregnation deposition 2min.Change the current and observe the changes of morphology of silver nanoparticles before and after current annealing.Through the experiment we can see:the size of silver nanoparticle at the top of the column and side small size decreased gradually after current annealing,with the current and electric field’s traiting to silver nanocrystals is finer and more uniform,covered on the surface of the silicon pillar,silver nanoparticles size from top to bottom column column increases gradually,in the pass after treated by electric column to the column bottom column decreases;in the larger current under the action of the Joule heating effect,between columns constitute a larger silver nanoparticles Bracelet like structure directly together,grain ripening,surface more smoothly.3.Use R6G for the detection of target molecules,the SERS performance test of the Ag/Si-NPA samples before and after the current annealing is tested.According to the experimental results:current annealing make the SERS performance of Ag/Si-NPA active substrate increased,this is because the enhancement of SERS is main caused by spherical silver nanoparticles at the top and side of the pillar,rather than micron and sub micron grade silver particles which depression between the pillars,in the power of treatment,because the size of silver nanoparticles on silicon pillar became smaller and more uniform distribution,so that the SERS performance of samples increased;and some processing in high current samples,because the current generate a lot of heat,and the experiment was carried out in the air,which resulting in nanocrystalline silver is oxidized,lead to the enhancement of SERS effect.