Department of Chemistry, Virginia Commonwealth University , 1001 West Main Street, Richmond, Virginia 23284-2006, United States.
Department of Chemistry, Kansas State University , 1212 Mid-Campus Drive North, Manhattan, Kansas 66506-0401, United States.
Langmuir. 2017 Dec 5;33(48):13719-13732. doi: 10.1021/acs.langmuir.7b02259. Epub 2017 Aug 29.
Chemical gradients play an important role in nature, driving many different phenomena critical to life, including the transport of chemical species across membranes and the transport, attachment, and assembly of cells. Taking a cue from these natural processes, scientists and engineers are now working to develop synthetic chemical gradients for use in a broad range of applications, such as in high-throughput investigations of surface properties, as means to guide the motions and/or assembly of liquid droplets, vesicles, nanoparticles, and cells and as new media for stationary-phase-gradient chemical separations. Our groups have been working to develop new methods for preparing chemical gradients from organoalkoxysilane and organochlorosilane precursors and to obtain a better understanding of their properties on macroscopic to microscopic length scales. This review highlights our recent work on the development of controlled-rate infusion and infusion-withdrawal dip-coating methods for the preparation of gradients on planar glass and silicon substrates, on thin-layer chromatography plates, and in capillaries and monoliths for liquid chromatography. We also cover the new knowledge gained from the characterization of our gradients using sessile drop and Wilhelmy plate dynamic water contact angle measurements, X-ray photoelectron spectroscopy mapping, and single-molecule tracking and spectroscopy. Our studies reveal important evidence of phase separation and cooperative interactions occurring along multicomponent gradients. Emerging concepts and new directions in the preparation and characterization of organosilane-based chemical gradients are also discussed.
化学梯度在自然界中起着重要的作用，驱动着许多对生命至关重要的不同现象，包括跨膜的化学物质运输以及细胞的运输、附着和组装。受这些自然过程的启发，科学家和工程师们现在正在努力开发用于广泛应用的合成化学梯度，例如用于高通量表面性质研究，作为引导液滴、囊泡、纳米粒子和细胞运动和/或组装的手段，以及作为固定相梯度化学分离的新介质。我们的团队一直在努力开发从有机烷氧基硅烷和有机氯硅烷前体制备化学梯度的新方法，并更好地了解它们在宏观到微观长度尺度上的性质。这篇综述重点介绍了我们最近在平面玻璃和硅基底、薄层色谱板以及用于液相色谱的毛细管和整体柱上制备梯度的恒速输注和输注-提取浸涂方法的开发工作。我们还介绍了使用固着液滴和威廉米平板动态水接触角测量、X 射线光电子能谱映射以及单分子跟踪和光谱学对我们的梯度进行表征所获得的新知识。我们的研究揭示了沿多组分梯度发生相分离和协同相互作用的重要证据。还讨论了基于有机硅的化学梯度的制备和表征方面的新兴概念和新方向。
