National Physical Laboratory, Hampton Road, Teddington, UK.
Nanotechnology. 2012 Jul 20;23(28):285706. doi: 10.1088/0957-4484/23/28/285706. Epub 2012 Jun 25.
Here we report a non-contact method for microwave surface impedance measurements of reduced graphene oxide samples using a high Q dielectric resonator perturbation technique, with the aim of studying the water content of graphene oxide flakes. Measurements are made before, during and after heating and cooling cycles. We have modelled plane wave propagation of microwaves perpendicular to the surface of graphene on quartz substrates, capacitively coupled to a dielectric resonator. Analytical solutions are derived for both changes in resonant frequency and microwave loss for a range of water layer thicknesses. In this way we have measured the presence of adsorbed water layers in reduced graphene oxide films. The water can be removed by low temperature annealing on both single and multilayer samples. The results indicate that water is intercalated between the layers in a multilayer sample, rather than only being adsorbed on the outer surfaces, and it can be released by applying a mild heating.
我们在此报告了一种非接触式微波表面阻抗测量方法，用于使用高 Q 值介质谐振器微扰技术测量还原氧化石墨烯样品，目的是研究氧化石墨烯薄片的含水量。测量在加热和冷却循环前后进行。我们对微波在垂直于石英衬底上石墨烯表面传播进行了建模，该表面通过介质谐振器进行电容耦合。针对一系列水层厚度，我们推导出了谐振频率和微波损耗变化的解析解。通过这种方式，我们测量了还原氧化石墨烯薄膜中吸附水层的存在。通过在单层和多层样品上进行低温退火，可以去除水。结果表明，在多层样品中，水层被插入层间，而不仅仅是吸附在外表面上，并且可以通过适度加热将其释放。
