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Advanced Materials for Energy-Water Systems Center

Research Thrust Area 1: Tailoring Interfacial Interactions

Thrust Leader: Jeff Elam
Thrust Deputy Leader: Andrei Tokmakoff
Principal Investigators: Wei Chen, Chong Liu, George Schatz, Matthew Tirrell   

Thrust 1 is motivated by two Research Questions:

1. How do electrostatics, hydrogen bonding, surface chemistry, and microstructure influence interfacial affinity and the organization of the solution’s boundary layers?

The interaction between an aqueous adsorbate and a binding site is dictated not just by the strength of a single, isolated bond, but also by numerous steric interactions, the electrical properties of the surface and solution, and the organization of water’s hydrogen-bond network at the interface and around the host-adsorbate complex. These properties also govern the organization and dynamics of solutes and ions in the interfacial boundary layers of the solution. In order to selectively control water/solid interfaces, we must understand how these effects collectively influence adsorption.

2. What principles govern selective, rapid, and reversible adsorption of ions and molecules on complex polymer structures in aqueous solutions?

Nature’s enzymes, receptors, and ion channels have evolved extraordinary capabilities to bind a specific target with incredible selectivity and high affinity, while maintaining reversibility and rapid turnover. For instance, ion channels typically contain a selectivity filter specific to a certain ion. In the case of the KcsA potassium ion channel, a four-site selectivity filter formed by protein backbone amide carbonyls passes K+ at rates >108 ions s-1 while retaining a 1000:1 discrimination over Na+. We know that such systems have optimally sized and flexible/dynamic binding sites, tailored electrostatic and hydrogen bonding interactions, and unusually small desolvation penalties, but we do not have the predictive understanding of how these principles work in concert to achieve remarkable selectivity. To develop versatile adsorption and sensing technologies, we must describe these cooperative effects systematically in the context of high surface-to-volume polymeric materials functionalized with novel binding moieties.

Equipment/ Tools

Array of bubblers” containing chemical precursors used in atomic layer deposition 

  • Atomic layer deposition (ALD) is a highly controlled method for depositing precise thin films to a desired thickness onto a substrate.
  • ALD enables the growth” of differing multilayer structures. 

Atomic layer deposition reactor (Beneq model TFS 500

  • Enables users to deposit simple binary oxides, metals, and complex nanocomposites in a well-controlled manner.
  • Capable of depositing large 300mm wafers/objects.

Drop shape analyzer – DSA25

  • Designed for determining the wettability of solids my means of the contact angle as well as the surface tension of liquids.
  • Quick and versatile dosing for surface-free energy and surface tension.
  • High-resolution camera and high-quality zoom lens for accurate display of the drop with optimum size lead to a precisely measured contact angle or surface tension.

SRS QCM200 quartz crystal microbalance

  • Quartz crystal microbalance with dissipative monitoring combines real-time adsorption and desorption measurements in a liquid-phase environment. The QCM is sensitive to sub-monolayer mass changes and can measure viscosity and mechanical properties of adsorbed materials.
  • The technique is used by AMEWS researchers to monitor both the synthesis and adsorption-desorption characteristics of model surfaces. The technique yields chemisorption rates of functional molecules and corresponding activation energies, which are then used in comparison with simulations and theory.

2D IR spectrometer

  • Ultrafast 2D IR spectrometer designed for use in transmission for bulk systems and attenuated total internal reflection.
  • Allows measurements of solvation dynamics, orientational diffusion of molecules in solution, and vibrational coupling and anharmonicity.    
  • Specifically designed to allow measurement of difficult, highly scattering samples and solid-liquid interfaces.