Department of Chemical Engineering, Texas Tech University, Lubbock, TX, 79409, USA.
Department of Chemical Engineering, Texas A&M University, College Station, TX, 77843, USA.
Small. 2015 Jun 10;11(22):2661-8. doi: 10.1002/smll.201403466. Epub 2015 Jan 29.
For the first time, pristine graphene can be controllably crumpled and unfolded. The mechanism for graphene is radically different than that observed for graphene oxide; a multifaced crumpled, dimpled particle morphology is seen for pristine graphene in contrast to the wrinkled, compressed surface of graphene oxide particles, showing that surface chemistry dictates nanosheet interactions during the crumpling process. The process demonstrated here utilizes a spray-drying technique to produce droplets of aqueous graphene dispersions and induce crumpling through rapid droplet evaporation. For the first time, the gradual dimensional transition of 2D graphene nanosheets to a 3D crumpled morphology in droplets is directly observed; this is imaged by a novel sample collection device inside the spray dryer itself. The degree of folding can be tailored by altering the capillary forces on the dispersed sheets during evaporation. It is also shown that the morphology of redispersed crumpled graphene powder can be controlled by solvent selection. This process is scalable, with the ability to rapidly process graphene dispersions into powders suitable for a variety of engineering applications.
首次实现了对原始石墨烯的可控褶皱和展开。与氧化石墨烯观察到的机制截然不同，原始石墨烯呈现出多面褶皱、凹陷的颗粒形态，而氧化石墨烯颗粒则呈现出褶皱、压缩的表面，这表明表面化学在褶皱过程中决定了纳米片的相互作用。这里展示的过程利用喷雾干燥技术来生产水基石墨烯分散体的液滴，并通过快速液滴蒸发来诱导褶皱。首次直接观察到 2D 石墨烯纳米片逐渐向 3D 褶皱形态的尺寸转变；这是通过喷雾干燥器内部的新型样品收集装置进行成像的。通过改变蒸发过程中分散片上的毛细作用力，可以调整折叠程度。还表明，通过选择溶剂可以控制再分散褶皱石墨烯粉末的形态。该过程具有可扩展性，能够快速将石墨烯分散体加工成适用于各种工程应用的粉末。
