Controlled Formation of Thiol and Disulfide Interfaces

Abstract

The work reported herein describes the controlled creation of uniform thiol-functionalized siloxane-anchored self-assembled monolayers (SAMs) and their selective transformation into intramonolayer (bridging) disulfides. These disulfides provide for the efficient immobilization of (bio)molecules bearing pendant thiols or disulfides, with no need for added oxidant. The unambiguous development of this surface chemistry required analytical methods that distinguish thiol and disulfide moieties on a surface. Physical properties such as wetting and monolayer thickness do not suffice nor do routine spectroscopic techniques (e.g., XPS, IR). Therefore, a method for distinguishing and quantifying thiol and disulfide surface functionality on a monolayer array based on the reaction with 2,4-dinitrofluorobenzene (DNFB, Sanger's reagent) is reported. DNFB readily reacts with thiol-SAMs (but not with disulfides) to form stable derivatives with distinctive IR, UV, and XPS signatures. Finally, the thiol-disulfide chemistry is applied to thiol-functionalized hybrid silica nanoparticles. These high-surface-area nanoparticles provide solid supports heavily loaded with thiol groups whose chemistry is also reported herein.

Chemical and physical aspects of self-healing materials

“…Ionic interactions in polymers are primarily manifested by the formation of ionomers, [93] and selected polymers demonstrated self-healing attributes. For example, in poly(ethylene-co-methacrylic acid) (EMAA) shown in Figure 10 sheets can be surface modified to generate amine, [116] carboxylic acid, [117] hydroxyl, [118] UPy, [119] thiol, [120] furfuryl, [121] cinnamoyl, [122] anthracene, [123] or pyrenyl groups [124], which can react with their counterparts in the matrix. Thus, the nature of modifications will be determined by the polymer motif to form reversible bonds with a polymer matrix.…”

Two‐Dimensional Periodic Relief Gratings as a Versatile Platform for Label‐Free Specific DNA Detection

“…Figure shows a bulk plasmon band from a bare silicon substrate covered with native silicon oxide without apparent sulfur peak (S 2p). In the XPS spectra of the MPTES layer, the sulfur peak (S 2p) was detected at 163.7 eV, which indicated that all of the sulfur was present as thiol or disulfide . XPS was also used to study the composition of disulfide bridge after immobilization of DNA oligonucleotides.…”

Self-assembled monolayer assisted bonding of Si and InP

“…2, see appendix). Acetyl removal is monitored by infra-red spectroscopy based on the disappearance of the characteristic C = O double bond signal [30,31]. Subsequent processing depends on the specific substrates to be bonded and the two bonding paradigms that have been pursued.…”

“…The bonding of a thiol-SAM-modified silicon wafer to such a disulfide-bearing surface is based on a disulfide exchange reaction in which the intra-SAM S-S bonds of the disulfide surface are opened by reaction with a thiol-decorated monolayer to form new disulfide bonds across the interface (see Fig. 5(b)) [25,31]. Figure 5(c) shows a pair of silicon samples bonded using this process.…”

“…Conversion of thiol terminated SAMs into disulfide terminated SAMs [31]: The samples are placed in a solution of iodine (30 mg) in methanol (2 mL) for 15 minutes at room temperature, and subsequently cleaned as above.…”