Acquisition of a Scanning ESCA Spectrometer: Probing the Interfaces of Bio-, Geo- and Nanomaterials

这笔拨款支持莱斯大学获得用于生物、地球和纳米材料界面表征的扫描电子能谱化学分析（ESCA）仪器。ESCA，也被称为x射线光电发射光谱（XPS），是一种强大而通用的评估复杂材料表面的方法。材料界面表征是许多材料研究中的一项重要活动；对于生物材料、地质材料和纳米材料来说，开发新材料和了解它们的性质是必不可少的。它本质上是一种表面技术，只对样品的顶部几个埃敏感，但在适当的条件下，可以用于探测深度达20纳米的深度。一些项目需要对表面的原子浓度进行深度剖析，而另一些项目则需要了解界面上化学键的性质。还有一些人对几十微米级界面的化学映射感兴趣。几乎所有的参与者都必须能够测量表面的原子组成，而快速一致地分析多个样品的能力具有特殊的价值。ESCA可以测量表面碳和氮的相对含量，并可以确定碳是石墨还是与氮结合。ESCA的工作原理是用受控的x射线源轰击表面，并解析光电子的动能；然后利用这些能量来识别表面原子及其化学状态。从XPS数据可以推断出表面原子种类的相对数量，以及它们的化学环境。虽然样品是在真空条件下评估的，但该技术是灵活的-导电和非导电粉末和薄膜都用该方法进行了分析。特殊的系统有一个聚焦的，强烈的x射线源，导致小光斑尺寸（10微米）和高x射线通量。该功能加快了数据收集速度，其大型样本平台允许快速分析多个样本。扫描能力还可以实现更广泛的表面化学实验，例如表面附近原子组成的深度剖面和数十微米长度尺度的化学制图。获得一台扫描ESCA对于学生的训练和发展、本科生和研究生的专门课程以及讲习班将特别重要。超过30名研究生、数十名博士后和本科生将能够使用这个系统来了解表面化学如何在他们的研究中发挥作用。扫描ESCA的存在将使我们能够实施一套程序，不仅教学生如何使用仪器，而且还强调界面化学在生物和纳米工程等领域的重要性。

This grant supports the acquisition of a scanning electron spectroscopy for chemical analysis (ESCA) instrument for interface characterization of bio- , geo- and nanomaterials at Rice University. ESCA, also known as x-ray photoemission spectroscopy (XPS), is a powerful and versatile method for evaluating the surfaces of complex materials. The characterization of material interfaces is an important activity in much of materials research; for bio-, geo- and nanomaterials it is essential for developing new materials and understanding their properties. It is intrinsically a surface technique sensitive only to the top several angstroms of a sample, but with the appropriate conditions can be used to probe depths up to 20 nanometers. Several projects require depth profiling of atomic concentrations at surfaces while others need information about the nature of chemical bonding at interfaces. Still others are interested in chemical mapping of interfaces at the tens of micron level. Nearly all participants must be able to measure the atomic composition of surfaces, and the ability to analyze multiple samples quickly and consistently is of particular value. ESCA can measure the relative amounts of carbon and nitrogen at a surface and can determine whether the carbon is graphitic or bound to nitrogen. ESCA works by bombarding surfaces with a controlled X-ray source and resolving the kinetic energy of the photoemitted electrons; these energies are then used to identify surface atoms and their chemical state. Both the relative amounts of atomic species at surfaces, as well as their chemical environment can be deduced from XPS data. Though samples are evaluated under vacuum conditions, the technique is flexible- conductive and non-conductive powders and thin films have been analyzed with this method. The specific system has a focused, intense x-ray source, leading to small spot sizes (10 microns and high x-ray flux. This feature speeds data collection and its large sample platforms allow for rapid analysis of multiple samples. The scanning capability also enables a wider range of surface chemical experiments, such as depth profiles of atomic composition near surfaces and chemical mapping at the tens of micron length scale. The acquisition of a scanning ESCA will be especially significant to student training and development, specialized courses for undergraduates and graduates, and workshops. Over thirty graduate students, and tens of post-docs and undergraduates will be able to use this system to understand how surface chemistry plays a role in their research. The existence of a scanning ESCA will allow us to implement a set of programs that not only teaches students how to use the instrument, but also highlights the importance of interface chemistry in areas such as bio- and nanoengineering.