Minimally Adhesive, Advanced Non-Toxic Coatings of Hydrogen Peroxide Catalysts in Sol-Gel Matrices
Abstract
An anti-fouling (AF) strategy that can be employed on submerged surfaces is to use naturally occurring reagents in seawater to create biocides in situ. Halide salts are slowly oxidized by H2O2 to give positive halogen species, which are known to have biocidal properties at greater than mM concentrations. In the open ocean, concentrations of H2O2 approach 0.2 ?M and can be much higher (up to 50 ?M) in coastal areas where concentrations in rain water and runoff are in the range of 16–526 ?M. Hydrogen peroxide is also formed on submerged surfaces by organisms in the biofilm. At these concentrations of H2O2 and in the presence of the 0.5 M chloride, 1 mM bromide and 1 ?M iodide found in seawater, the production of positive halogen species cannot compete with the decomposition or consumption rate of positive halogen species. We have demonstrated that compounds derived from organoselenides and tellurides are efficient catalysts for the activation of hydrogen peroxide, that these materials are better catalysts sequestered in xerogels than in solution, and that the presence of H2O2 and surface-sequestered catalyst give reduced settlement of fouling organisms on surfaces. However, in xerogel formulations with optimized surface properties for fouling-release (FR) characteristics, the organochalcogen catalysts used to demonstrate this concept negatively impacted the surface properties of the coating, which increased adhesion of the fouling organisms and, in some cases, increased settlement. After a decade of study, the use of organochalcogen catalysts, while a successful laboratory approach, will not give AF/FR with meaningful lifetimes in the field. In this extension, we propose to modify the silicon-based xerogel coatings that we have employed with catalytic quantities (1-10 mole-%) of metal alkoxides of titanium and vanadium in the inorganic matrix as catalysts for the activation of hydrogen peroxide to produce hypohalous acids on the coating surface. As part of the inorganic matrix, the Ti and V modifications will not impact the organization of the organic modifications to the xerogel on the surface, which impart the characteristics of surface energy, charge, and topography – all critical features in the settlement of fouling organisms. The suite of coatings will be evaluated by ONR collaborators running assays for settlement and adhesion in the presence or absence of hydrogen peroxide (Clare, Alred, Finlay; Stafslien; Wendt; Hadfield). Fiberglass panels coated with the most promising catalyst-xerogel combinations will be tested in the field [CalPoly (Wendt), FIT (Swain) sites] to correlate laboratory and field results with desirable surface/catalyst characteristics. Characteristics to give optimal AF/FR characteristics will be identified in order to produce a new generation of materials.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Aug 12, 2016
- Source ID
- N000141512400
Entities
People
- Michael Detty
Organizations
- Office of Naval Research
- Research Foundation for the State University of New York
- United States Navy