Application On The Stability Of Nano-Welding "Hot Spots" In SERS And Its Ethanol Electrocatalysis

Nano-welding of nanomaterials has opened new applications in transparent electrodes,nano-level patterning,nano-catalysis,cancer treatment and thin-film solar cells.So far,different methods have been used for welding,such as light induction,thermal induction,capillary force,and chemical welding.These methods are mainly used for large-scale nano-networks.In view of the wide application of nano-welding,the following two research are mainly carried out:(1)Research on the stability of“hot spots”in plasma welding."Hot spots"play a key role in SERS.People have made great efforts to construct hot spots with various fine physical structures.However,it is still a huge challenge to prepare uniformly distributed hot spots to achieve the same enhancement of the spectrum of each“hot spots”;especially in quantitative detection,the poor spectral reproducibility greatly limits the wide application of SERS.Therefore,this paper systematically studies the influence of hot spots stability on SERS behavior.As far as we know,hot spots have not received widespread attention in previous studies.We systematically studied the stability thresholds of hot spots on excitation power,duration and wavelength.(2)The application of Au@Pd NPW welded by Joule heat in the electrocatalytic oxidation of ethanol.Direct ethanol fuel cells in alkaline media have high energy density,reasonable power density and environmental protection characteristics,so they have broad application prospects.Studies have shown that by designing and preparing electrocatalysts with large-area network structure with high conductivity and abundant high-activity sites as an effective electron transfer pathway,the activity of ethanol oxidation reaction can be further improved.The main research results are as follows:(1)The poor spectral reproducibility caused by the random distribution of“hot spots”and uneven enhancement greatly limits the practical application of surface-enhanced Raman scattering(SERS).Here,we report that“hot spots”show stability thresholds for excitation power,duration,and wavelength.Within the threshold range or after removing unstable“hot spots”,the SERS substrate shows a stable and reproducible SERS signal.These findings provide new insights into the spectral reproducibility of SERS,and greatly promote the design of reliable SERS detection and stable hot spots.(2)Palladium-coated gold(Au@Pd)bimetallic nanoparticles show high catalytic activity for the electrocatalytic oxidation of ethanol.The Joule heat welding strategy is used to adjust the electrocatalytic activity of Au@Pd NPW to effectively oxidize ethanol.We found that the Au@Pd NP film self-assembled through the interface can weld the Au@Pd NP film well through alternating current,forming a large-area network nano-membrane with improved conductivity and exposing the high crystal surface,thus having a better Catalytic activity.Among the two types of Au@Pd NP used to show the effect of welding on electrocatalytic activity,16+4.5 nm Au@Pd NPW showed higher electrocatalytic activity,reaching 10.89 m A cm^-2for 1M KOH+1 M C₂H₅OH solution compared with SCE,is 2.76 times that obtained on 16+4.5 nm Au@Pd NPs catalyst at-0.8-0.4 V.These results indicate that a simple welding strategy is helpful for the design and preparation of more effective and stable Pd-based electrocatalysts and other metal particulate catalysts,which are derived from separate counterparts.