Abstract
Semi-permeable membranes are important elements in water purification and energy generation applications, for which the atomic thickness and strength of graphene can enhance efficiency and permeation rate while maintaining good selectivity. Here, we show that an osmotic pressure difference forms across a suspended graphene membrane as a response to a sucrose concentration difference, providing evidence for its semi-permeability. This osmotic pressure difference is detected via the deflection of the graphene membrane that is measured by atomic force microscopy. Using this technique, the time dependence of this deflection allows us to measure the water permeation rate of a single 3.4 µm diameter graphene membrane. Its value is close to the expected value of a single nanopore in graphene. The method thus allows one to experimentally study the semi-permeability of graphene membranes at the microscale when the leakage rate is minuscule. It can therefore find use in the development of graphene membranes for filtration, and can enable sensors that measure the concentration and composition of solutions.
Highlights
Semi-permeable membranes are of essential for filtration and separation in the chemical, food and pharmaceutical industry [1]
Any further distribution of this work must difference forms across a suspended graphene membrane as a response to a sucrose concentration maintain attribution to difference, providing evidence for its semi-permeability. This osmotic pressure difference is the author(s) and the title of the work, journal detected via the deflection of the graphene membrane that is measured by atomic force citation and DOI
A sheet of singlelayer graphene grown by chemical vapor deposition (CVD) is transferred on top of the chip and suspended over the cavities using water dissolvable polyvinyl alcohol transfer polymer (figure 1(c))
Summary
Semi-permeable membranes are of essential for filtration and separation in the chemical, food and pharmaceutical industry [1]. The chemical stability [9] and mechanical strength of graphene [10,11,12] are advantageous. These properties have attracted considerable attention for studies into graphene-based water purification [13,14,15,16,17,18,19,20,21,22,23], gas separation [24,25,26,27,28] and gas sensing [29,30,31]. To further understand water permeability of graphene at the single pore level, it is of interest to develop experimental techniques to measure the permeability on a microscopic level
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