Organosilane self-assembled monolayers directly linked to the diamond surfaces

Abstract

An amino-terminated self-assembled monolayer (SAM) was prepared from p-aminophenyltrimethoxysilane (H2N(CH)6Si(OCH3)3,APhS) on diamond substrates irradiated by vacuum ultraviolet (VUV) light (wavelength: 172nm) through chemical vapor deposition. Furthermore, the APhS-SAM was irradiated by VUV light in air. After the VUV irradiation, only one layer of siloxane (SiOx) was left as a result of the selective decomposition of organic compounds. APhS-SAM was reprepared on the SiOx surface. The evidence as to the respective processes was clearly obtained by x-ray photoelectron spectroscopy (XPS) and water contact angle measurements. Based on the chemical bonding states analysis, APhS-SAMs were confirmed to be directly linked to the diamond substrates and SiOx layers with bonding types of Si–O–C and Si–O–Si, respectively. The compositions obtained by XPS measurement indicate that the thickness of the SiOx layer was increased gradually by repeating the APhS-SAM formations and VUV irradiations in this order. Finally, we are successful in controlling the nano-scale thickness of the SiOx layer, which is the interface between APhS-SAMs and diamond substrates.

Photochemical Functionalization of Hydrogen-Terminated Diamond Surfaces: A Structural and Mechanistic Study

“…By using reactions which are prevalent in synthetic organic chemistry as well as those used for modifying silicon surfaces, many different methods for diamond functionalization have been developed. These include reactions involving radical initiators such as organic peroxides, , halogenation of diamond surfaces with subsequent organic functionalization, − electrochemical reduction of diazonium salts, and photochemical terminations at varying energies (172 nm, 7.2 eV) (254 nm, 4.9 eV). , By terminating the surface with molecules which have reactive groups at the exposed interface, further modifications such as DNA or protein attachment for use in sensing applications can be achieved. ,,,, …”

Electrical Bias Dependent Photochemical Functionalization of Diamond Surfaces

“…The high stability of diamond makes it a difficult material to functionalize. Previous approaches to functionalizing diamond surfaces with molecular species have included electrochemical, thermal, − radical, , and photochemical − activation methods. We previously reported molecules bearing an alkene (CC) group will link to the surface of hydrogen-terminated diamond when illuminated with ultraviolet light at 254 nm, forming a well-defined monolayer film. , These monolayers are chemically robust and can be used as a starting point for linking biomolecules such as DNA and proteins 3 to the surface and/or conferring properties such as resistance to protein binding. , While this functionalization procedure is clearly very effective, the ability to functionalize diamond with alkenes using 254 nm light is surprising because diamond and most organic alkenes are essentially transparent at this wavelength.…”

Diamond surface engineering for molecular sensing with nitrogen—vacancy centers

“…Finally, hydroxl groups can be used to attach molecules of interest by esterification 307–310 and thermal alkylation. 311 Moreover, hydroxl groups may serve as anchoring points for phosphonic acid headgroups, 312 for silanization, 313–315 or for precursor molecules in growth of capping films via atomic layer deposition (see Section 4.2.3). Starting with oxygen-annealed diamond substrates, Grotz et al used silanization to covalently bind the 4-maleimido-TEMPO spin label.…”