Spencer Julie A, Barclay Michael, Gallagher Miranda J, Winkler Robert, Unlu Ilyas, Wu Yung-Chien, Plank Harald, McElwee-White Lisa, Fairbrother D Howard
Department of Chemistry, Johns Hopkins University, Baltimore, MD, 21218, USA.
Graz Centre for Electron Microscopy, Steyrergasse 17, 8010 Graz, Austria.
Beilstein J Nanotechnol. 2017 Nov 15;8:2410-2424. doi: 10.3762/bjnano.8.240. eCollection 2017.
The ability of electrons and atomic hydrogen (AH) to remove residual chlorine from PtCl deposits created from -Pt(CO)Cl by focused electron beam induced deposition (FEBID) is evaluated. Auger electron spectroscopy (AES) and energy-dispersive X-ray spectroscopy (EDS) measurements as well as thermodynamics calculations support the idea that electrons can remove chlorine from PtCl structures via an electron-stimulated desorption (ESD) process. It was found that the effectiveness of electrons to purify deposits greater than a few nanometers in height is compromised by the limited escape depth of the chloride ions generated in the purification step. In contrast, chlorine atoms can be efficiently and completely removed from PtCl deposits using AH, regardless of the thickness of the deposit. Although AH was found to be extremely effective at chemically purifying PtCl deposits, its viability as a FEBID purification strategy is compromised by the mobility of transient Pt-H species formed during the purification process. Scanning electron microscopy data show that this results in the formation of porous structures and can even cause the deposit to lose structural integrity. However, this phenomenon suggests that the use of AH may be a useful strategy to create high surface area Pt catalysts and may reverse the effects of sintering. In marked contrast to the effect observed with AH, densification of the structure was observed during the postdeposition purification of PtC deposits created from MeCpPtMe using atomic oxygen (AO), although the limited penetration depth of AO restricts its effectiveness as a purification strategy to relatively small nanostructures.
评估了电子和原子氢（AH）从通过聚焦电子束诱导沉积（FEBID）由-Pt(CO)Cl形成的PtCl沉积物中去除残留氯的能力。俄歇电子能谱（AES）、能量色散X射线能谱（EDS）测量以及热力学计算支持了电子可以通过电子激发脱附（ESD）过程从PtCl结构中去除氯的观点。研究发现，对于高度大于几纳米的沉积物，电子的净化效果会受到净化步骤中产生的氯离子有限逃逸深度的影响。相比之下，使用AH可以有效地将氯原子从PtCl沉积物中完全去除，而与沉积物的厚度无关。尽管发现AH在化学净化PtCl沉积物方面极其有效，但其作为FEBID净化策略的可行性受到净化过程中形成的瞬态Pt-H物种迁移性的影响。扫描电子显微镜数据表明，这会导致形成多孔结构，甚至可能使沉积物失去结构完整性。然而，这种现象表明使用AH可能是制备高比表面积Pt催化剂的一种有用策略，并且可能逆转烧结的影响。与使用AH观察到的效果形成鲜明对比的是，在使用原子氧（AO）对由MeCpPtMe形成的PtC沉积物进行沉积后净化过程中，观察到结构致密化，尽管AO的有限穿透深度将其作为净化策略的有效性限制在相对较小的纳米结构上。
