Orientation in Methyl- and Hydroxyl-Terminated Self-Assembled Alkanephosphate Monolayers on Titanium Oxide Surfaces Investigated with Soft X-ray Absorption

Abstract

Titanium oxide surfaces were coated with methyl-and hydroxyl-terminated dodecyl phosphate monolayers by immersion of the substrates into aqueous solutions of the corresponding ammonium salts (DDPO4-(NH4)2 and OH-DDPO4(NH4)2). The samples were examined by contact-angle measurements and nearedge X-ray absorption fine structure spectroscopy. DDPO4 was found to form self-assembled films of comparable quality to those of the longer octadecyl phosphate prepared from an organic solvent and to those of a similar thiol/gold system. The hydroxyl-terminated adsorbates, however, established films with a much lower degree of orientation under the same preparation conditions and showed "high" water contact angle values (50-55°) for a hydrophilic surface. Mixed films of both species establish a degree of orientation between those of both pure films, which is also reflected by their wettability.

Organic corrosion inhibitors: where are we now? A review. Part III. Passivation and the role of the chemical structure of organophosphates

“…It seems quite reasonable to continue searching for more efficient corrosion inhibitors of this class, including those for other metals and alloys, in the near future. For example, S. Tosatti et al [44,45] studied the monolayers formed in 48 h in aqueous solutions of ammonium salts of DDP and hydroxy-dodecyl phosphate (HDDP) on smooth and rough surfaces of Ti and TiO 2 . They found that on smooth surfaces the monolayers of DDP were densely packed, which provided hydrophobization of the surface (contact angle  = 110°), but the surface remained hydrophilic ( = 10-50°) after HDDP adsorption.…”

Titanium modified with layer-by-layer sol–gel tantalum oxide and an organodiphosphonic acid: A coating for hydroxyapatite growth

“…So, modifying the implant surface through phosphonic groups appears to be a way to promote a strong adhesion between the implant surface and bone tissue. Improvement of corrosion resistance is additionally obtained by this type of organic modification [23,24].…”

Influence of chain ordering on frictional properties of self-assembled monolayers (SAMs) in nano-lubrication

“…Formation of very stable organophosphonic acid monolayer on aluminum alloys covered with an amorphous thin oxide film has been reported in many studies (e.g., [80,85,86] [96]. It has been shown that alkylphosphonate SAMs on TiO 2 surface had comparable packing densities to those of alkanethiols on gold, and similar inclinations of the alkyl chains as well [97]. Tambe and Bhushan characterized the nanotribological properties of alkylsilane and perfluoroalkylsilane SAMs on Si(100) and alkylphosphonate SAMs on Al and found that alkylphosphonate SAMs exhibited lower coefficients of friction but comparable adhesive forces compared to the alkylsilane SAMs with the same alkyl chain lengths [93].…”