Structure of Liquid Surfaces

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This project focuses on synchrotron generated x-ray scattering using the National Synchrotron Light Source (NSLS) at Brookhaven National Laboratory and the Advanced Photon Light Source (APS) at Argonne National Laboratory to study the structural properties of thin liquid layers and related novel liquid surfaces. The structure and fluctuations of a thin liquid wetting layer that forms on various substrates will be characterized by x-ray specular reflectivity, off specular diffuse scattering and grazing incidence diffraction. A unique feature is that some of the wetting will involve the wetting of one liquid by a separate immiscible liquid. Solvation of selected nano-particles in these thin layers, accompanied by control of the thickness of the liquid, will make it possible to the study how 2-dimensional (2D) mesoscopic arrays form on deposition from solution. In addition, the interactions between thin wetting liquids and nano-scale structures on Si surfaces, and the manner in which alkane chains tethered to nano-particles order as the density of the nano-particles change will be investigated. A second benefit expected from this project, in addition to the expected scientific knowledge, is that new young researchers will be trained to carry out cutting edge research using these precious national synchrotron facilities. In addition, researchers participating in this grant will participate in the ongoing educational outreach activities at Harvard (see http://www.mrsec.harvard.edu/education.html) for example, the Research Experiences for Teachers program (RET) that makes it possible for teachers from local-area K-12 schools to participate in research.Understanding the structure and related physical properties of liquid surfaces and thin liquid films are important for a variety of processes that include lubrication, adhesion, catalysis, painting, and coatings. In addition, the experimental and theoretical study of wetting phenomena is contributing significantly to the current understanding of fundamental problems in statistical physics. For example, studying the wetting of substrates with nano-scale inhomogeneities is important for developing a technologically promising microprinting method for the production of nano-scale structures.