Interfaces at the Ultimate Limit

Addressing the Problem

Fundamental studies on interfaces have led to breakthrough advances in electronics, computer, mechanical, aerospace, energy and health care sectors. Most, if not all, earlier studies have focused on interfaces between materials with thicknesses ranging from several tens of nanometers to hundreds of microns and larger.

The objective of this effort is to initiate fundamental studies on understanding interfaces between materials which approach their ultimate thickness limit. The ultimate (smallest) thickness limit for solid substrates is a single-atom and single-atom thick materials such as graphene, boron nitride, etc. have recently been synthesized. In this research, we will consider interfaces between single-atom thick graphene and a single-layer of water.

Even though water has been studied extensively in the literature, bulk properties of water—let alone interfacial properties—remain enigmatic. By taking advantage of the computing facilities at Illinois, combined with novel experimental approaches to probe single-layer water, this research effort will provide unprecedented physical insights into graphene-water interfaces, opening up opportunities for next generation of scientific breakthroughs.

Impact of the Work on Society

A number of driving technologies of central importance to our society necessitate fundamental studies on graphene-water interfaces. First, because of the growing emphasis on water purification, due to the water storage problem, development of novel and energy efficient membranes for salt separations is currently an area of immense interest. Ultra-thin graphene membranes open up opportunities for low-energy desalination of water.

Second, separating hydrogen from hydrogen/nitrogen or hydrogen/hydrocarbon mixtures, or separating pairs of gases such as N2/O2, CO2/CH4, etc. can lead to rapid advances in environmental and energy-related processes. A novel approach to separate gases is to exploit the solubility of gas in water. By considering gas-water mixtures, gases can separate efficiently based on their solubility in water. Even though polymer membranes are widely investigated for gas-gas and gas-water separations, the efficiency of the separations can be significantly improved by considering ultra-thin membranes such as graphene.

Third, graphene sheets deposited on solid-state substrates are widely investigated to design next generation electronic devices. Understanding graphene interfaces is central to control the electronic properties of graphene composites.

Research Goals

The goals of our project include:

  • Perform Quantum Monte Carlo (QMC) calculations to determine the interaction energy between graphene and water molecules;
  • Perform STM experiments to visualize water structure and other properties of water on graphene;
  • Perform atomistic and multi-scale calculations, using the force-fields obtained from QMC, to compute water structure, dynamics and transport;
  • Develop fundamental insights by comparing computations to experiment and explore various applications.