Preparation of superhydrophobic and oleophobic diamond nanograss array

The paper reports on the fabrication of superhydrophobic boron-doped diamond nanograss surfaces. The boron-doped diamond nanograss array (BDD NG) was prepared simply by reactive ion etching (RIE) with oxygen plasma of highly boron-doped (the boron doping level is 8 × 1019 B cm−3) polycrystalline diamond electrodes. Depending on the RIE conditions, substrates with different nanograss densities can be prepared. Chemical functionalization of the NG array surface with octadecyltrichlorosilane (OTS) or 1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFTS) led to the formation of superhydrophobic surfaces. Under optimized conditions, BDD NG surfaces with contact angles as high as 160° and quasi null hysteresis (< 2°) can be reached. A water droplet deposited on the surface tends to roll off when the NG surface was tilted by a few degrees. Furthermore, the BDD NG array chemically modified with PFTS displays oleophobic properties. A contact angle of 94° was measured for hexadecane. The resulting surfaces were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, and contact angle (CA) measurements.