11-巯基十一烷酸包裹的金纳米颗粒薄膜的二次电子发射

Enhanced secondary electron emission from 11-mercaptoundecanoic acid-stabilized Au nanoparticle film

采用改进的Peterk合成法合成11-巯基十一烷酸(Mercaptoundecanoic Acid,MUA)包覆的金纳米颗粒。通过调控MUA与氯金酸质量比,得到分布均匀且稳定性较好的不同粒径(<3 nm)的纳米金颗粒前驱体溶液,进而滴加该溶液形成薄膜。扫描电子显微镜(Scanning Electron Microscope,SEM)观测到薄膜中具有大量微米级的块状集团。同步辐射掠入射X射线衍射(Grazing Incidence X-ray Diffraction,GIXRD)揭示其具有面外长程有序的超晶格结构;X射线光电子谱(X-ray Photoelectron Spectroscopy,XPS)证实薄膜中Au-S键的形成。通过紫外光电子能谱(Ultraviolet Photoelectron Spectroscopy,UPS)进一步发现常温下1.5 nm粒径的薄膜具有比单晶金样品强10倍的优异二次电子发射能力,且发射峰半高宽是单晶金样品的1/4。本研究表明,MUA包覆的金纳米薄膜在电子发射源以及光电探测上具有应用前景。

Background： Functionalized gold nanoparticles with unique localized surface plasmon resonance （LSPR） effects can be used as building blocks for constructing 3D structures towards novel nanoscale electronic or electro-optic devices. Purpose： In this work, we aim to study the structure and photoemission property relationship of the film of 11-mercaptoundecanoic acid-stabilized Au nanoparticles with a diameter less than 3 rim. Methods： Au nanoparticles stabilized by l l-mercaptoundecanoic acid （MUA） with a diameter less than 3 nm are preparedfollowing a modified Peterk＇s method which is deposited on Cu substrate to prepare thin film. The as-prepared films are characterized by X-ray photoelectron spectroscopy （XPS）, ultraviolet photoemission spectroscopy （UPS）, transmission electron microscopy （TEM）, and grazing incidence X-ray diffraction （GIXRD）. Results： As shown by the scanning electron microscope （SEM） images, the obtained films of Au nanoparticle with a diameter of 1.8 nm are consisted of micron size blocks. Fourier transform infrared spectroscopy （FT-IR） and XPS indicate that Au-S bonds are successfully formed. Moreover, GIXRD studies show that superlattice structure with strong preferred out-of-plane orientation is formed in the obtained 1.8-nm Au nanoparticle film. While the secondary electron peaks observed in UPS spectrum of all these Au nanopartides films （with a diameter less than 3 rim） are much stronger than that of Au（111） reference sample, the peak of the 1.5-nm nanoparticle film is the strongest, and is about 10 times of that of Au（111） reference sample. Conclusion： In this study, the film of 1.5-nm MUA-stabilized Au nanoparticles exhibited most enhanced photoemission intensity and had the potential applications in electron sources and photo detectors.