Covalent biofunctionalization of silicon nitride surfaces.

Covalently attached organic monolayers on etched silicon nitride (SixN4; x ≥ 3) surfaces were prepared by reaction of SixN4-coated wafers with neat or solutions of 1-alkenes and 1-alkynes in refluxing mesitylene. The surface modification was monitored by measurement of the static water contact angle, XPS, IRRAS, AFM, and ToF-SIMS, and evidence for the formation of Si−C bonds is presented. The etching can be achieved by dilute HF solutions and yields both Si−H and N−H moieties. The resulting etched SixN4 surfaces are functionalized by terminal carboxylic acid groups in either of two ways:  (a) via attachment of a 10-undecenoic acid 2,2,2-trifluoroethyl ester (trifluoro ethanol ester) and subsequent thermal acid hydrolysis; (b) through attachment of a photocleavable ester, and subsequent photochemical cleavage, as this would allow photopatterned functionalized SixN4. The carboxylic acids are successfully used for the attachment of oligopeptides (aspartame) and complete proteins using EDC/NHS chemistry. Fina...