Periodically arranged benzene-linker molecules on boron-doped single-crystalline diamond films for DNA sensing

Electrochemical surface modification via reduction of 4-nitrobenzene diazonium tetrafluoroborate in acetonitrile solution has been performed on highly boron-doped homoepitaxial single-crystalline CVD diamond films to build up surface functionalization for DNA hybridization. Due to significantly improved voltammetric resolution and regularly oriented arrangements, covalently bonded 4-nitrophenyl groups on single-crystalline diamond are characterized to have two successive reversible one-electron transfer reactions interacting with stable radical anion and dianion species. This is new and has not been detected on other electrode materials. Their surface density is in the range of 7.9 × 1013 molecules/cm2 or 1.3 × 10−10 mol/cm2 as detected by cyclic voltammetric measurements. The aminophenyl-modified diamond surface was further modified by cross linker molecules and thiol-modified DNA oligonucleotides. The resulting DNA immobilization on diamond surface is confirmed by DNA hybridization reaction, using fluorescein-labeled complementary/non-complementary target DNA oligonucleotides. We characterize the DNA film using AFM experiments which reveal a closed and dense film with a height of about 90 Å. Finally, we compare the attachment efficiency on initially H-terminated and oxidized diamond surfaces.