REG: Acquisition of an Atomic Force Microscope for the Study of Adsorbed Layers on Solids

Somasundaran， P. Columbia U.固体的表面改性在许多传统和新兴工业过程中起着至关重要的作用，这些过程依赖于粘附、润湿、润滑、电沉积、催化和聚集/分散等界面现象。吸附化学改性为控制胶体系统的界面行为提供了一种极好的方法。过去关于表面活性剂和聚合物在固体矿物上吸附的研究表明，这些物质之间的相互作用导致聚集，对界面行为有显著的影响。采用多管齐下的方法，将传统的吸附、润湿性和润滑技术与先进的荧光、电子自旋共振和共振拉曼光谱技术相结合，我们提出了离子表面活性剂在低浓度下可以单独吸附，在高浓度下可以成簇吸附（半胶束、半胶束、固体）2,3。重要的是，被吸附物质的重定向已经被提出在高浓度下发生。这种重定向和重构象可以产生剧烈的影响，例如，在润湿性和附着力方面，无机物被引入系统。而荧光和电子。当添加剂（表面活性剂、聚合物和自旋共振技术）产生了诸如极性、粘度和固体团簇聚集数等微观性质的信息时，重构也可能发生，但在分子尺度上，在表面团簇进化的浓度范围内进行的直接研究尚未完成。过去进行的研究是在高于临界胶束浓度的较高浓度范围内进行的4,5。扫描探针显微镜（SPM）的发展是一项有希望的创新。SPM是一个通用名称，目前包括扫描隧道显微镜和原子力显微镜。其他正在开发的SPM技术有扫描离子、磁力、光子扫描和热剖面显微镜6。在真空、空气或液体环境中，SPM技术在极高分辨率（原子尺度）下的三维地形测绘能力是无与伦比的。胶体体系中相互作用力的测量具有重要的理论意义和实际意义。SPM尖端与样品之间的相互作用力可以获得迄今为止尚未获得的分散系统的信息。所提出的原子力显微镜的采集将使我们能够直接在原位探测吸附层及其由于化学和流体动力因素而引起的结构变化。这将显著提高我们的研究能力，因为原子力显微镜与其他技术的同时使用将使我们能够在纳米尺度上理解界面过程。这样的信息也导致工程能力来操纵和控制表面的改性，通过吸附达到最佳效果。

ABSTRACT CTS-9809053 Somasundaran, P. Columbia U. Surface modification of solids plays a vital role in many traditional and emerging industrial processes dependent upon interfacial phenomena such as adhesion, wetting, lubrication, electrodeposition, catalysis and aggregation/dispersion. Chemical modification by adsorption offers an excellent means to control interfacial behavior of colloidal systems. Past work on adsorption of surfactants and polymers on solid minerals has shown that interactions among these species leading to aggregation can have marked effects on interfacial behavior1. Using a multipronged approach combining traditional techniques of adsorption, wettability and lubrication with advanced spectroscopic techniques of fluorescence, electron spin resonance and resonance Raman, we have proposed ionic surfactants to adsorb individually at low concentrations and in clusters at high concentrations (hemimicelles, admicelles, solloids)2,3. Importantly, reorientation of adsorbed species has been proposed to occur under high concentrations. Such reorientation and reconformation can have drastic effects, for example, in wettability and adhesion inorganics) are introduced into the system. While fluorescence and electron. Reconformation can also occur when additives (surfactants, polymers and spin resonance techniques have yielded information on such microproperties as polarity, viscosity and aggregation number of the clusters on solids, direct investigation on a molecular scale in the concentration range where surface aggregates evolve has not yet been done. Studies conducted in the past have been carried out in the higher concentration ranges above critical micelle concentration4,5. A promising innovation allowing such investigation is the development of scanning probe microscopy (SPM). SPM is a generic name and at present it includes scanning tunneling microscopy and atomic force microscopy. Other SPM techniques under development are scanning ion, magnetic f orce, photon scanning and thermal profiler microscopy6. The three dimensional topography-mapping capabilities of SPM techniques at extremely high resolution (atomic scale) in vacuum, air, or liquid environments are unparalleled. The interaction force measurements in colloidal systems are important both from a theoretical and practical point of view. The interaction force between the SPM tip and the sample can yield information which so far has not been obtainable for dispersed systems. The proposed acquisition of the atomic force microscope will enable us to directly probe the adsorbed layer in-situ and changes in its structure due to chemical and hydrodynamic factors. This will markedly increase our investigative capability since the use of atomic force microscope concurrently with other techniques will enable us to develop an understanding of interfacial processes on a nanoscale. Such information also leads to engineering capability to manipulate and control modification of surfaces by adsorption for optimum effect.