1Shanghai Synchrotron Radiation Facility, Zhangjiang Laboratory (SSRF, ZJLab), Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201204 2Shanghai Applied Radiation Institute and State Key Lab Advanced Special Steel, Shanghai University, Shanghai 200444 3Guangxi Key Lab of Multisource Information Mining & Security, Guangxi Normal University, Guilin 541004 4Division of Interfacial Water, CAS Key Laboratory of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800 5School of Science, East China University of Science and Technology, Shanghai 200237
Abstract：Recently, there are great efforts that have been taken to suppressing/controlling the coffee ring effect, but it is of challenge to achieve inexpensive and efficient control with less disturbance, suitable for scalable production and highly enhancing the printing/dyeing color fastness. By only adding trace amounts of salt into the suspensions, here we experimentally achieve the facile and highly efficient control of the coffee ring effect of suspended matter on substrates of graphene, natural graphite, and polyethylene terephthalate surfaces. Notably, friction force measurements show that ion-controlled uniform patterns also greatly enhance color fastness. Molecular dynamics simulations reveal that, due to strong hydrated cation-$\pi$ interactions between hydrated cations and aromatic rings in the substrate surface, the suspended matters are adsorbed on the surfaces mediated by cations so that the suspended matters are uniformly distributed. These findings will open new avenues for fabricating functional patterns on graphene substrates and will benefit practical applications including printing, coating, and dyeing.
2020, Vol. 37 
