Preparation and characterization of self-assembled alkanephosphate monolayers on glass substrate coated with nano-TiO2 thin film

Self-assembled alkanephosphate monolayers on glass substrate coated with sol-gel TiO2 thin film were prepared by means of molecular self-assembly process. The wetting behavior and structure of the alkanephosphate monolayers were characterized by means of contact angle measurement and X-ray photoelectron spectroscopic analysis. The friction behavior of the glass substrate coated with TiO2 thin film and the alkanephosphate SAMs in sliding against an Si3N4 ball was examined on a one-way reciprocating friction tester. As a result, water contact angle on alkanephosphate SAMs is at 90-104 degrees. The SAMs of alkanephosphate are bonded to the TiO2 covering layer on the glass substrate by way of monodentate and bidentate coordination. In n-monoalkanephosphate SAMs, the monodentate and bidentate of adjacent phosphate headgroups are linked by intermolecular hydrogen bonding. The SAMs of long chain n-monoalkanephosphate show considerably decreased friction coefficient in sliding against the Si3N4 ball under low load, compared with the TiO2 covering layer on the glass substrate. (C) 2001 Elsevier Science Ltd. All rights reserved.