Investigation of Au SAMs Photoclick Derivatization by PM-IRRAS

Abstract

In this work we present a clean one-step process for modifying headgroups of selfassembled monolayers (SAMs) on gold using photo-enabled click chemistry. A thiolated, cyclopropenonecaged strained alkyne precursor was first functionalized onto a flat gold substrate through self-assembly. Exposure of the cyclopropenone SAM to UV-A light initiated the efficient photochemical decarbonylation of the cyclopropenone moiety, revealing the strained alkyne capable of undergoing the interfacial strainpromoted alkyne-azide cycloaddition (SPAAC). Irradiated SAMs were derivatized with a series of model azides with varied hydrophobicity to demonstrate the generality of this chemical system for the modification and fine-tuning of the surface chemistry on gold substrates. SAMs were characterized at each step with polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) to confirm successful functionalization and reactivity. Furthermore, to showcase the compatibility of this approach with biochemical applications, cyclopropenone SAMs were irradiated and modified with azide-bearing cell adhesion peptides to promote human fibroblast cell adhesion, then imaged by live cell fluorescence microscopy. Thus, the "photoclick" methodology reported here represents an improved, versatile, catalyst-free protocol that allows for a high degree of control over the modification of material surfaces, with applicability in materials science as well as biochemistry.

Amide-Assisted Polymerization of 1,3-Butadiyne Containing Thiolate Ligands on Small Gold Nanoparticles

“…UV irradiation of self-assembled monolayers of alkyl thiolates on 2D gold surfaces and AuNPs is known to cause cleavage of the Au–S bond through photooxidation of the thiolate and other mechanisms. − Degradation mechanisms and rates strongly depend on conditions, such as wavelength and intensity of the light source, type of solvent, structure of the alkylthiolate ligand, and presence of oxygen. , A systematic study on the photodegradation of small AuNPs in chloroform solutions during irradiation with a nanopulsed laser and in a Luzchem photoreactor at different wavelengths (UV-A and -C) was conducted by Pocoví-Martínez et al UV-C irradiation led to aggregation and fusion of the nanoparticle cores within minutes, whereas UV-A irradiation led to aggregation and precipitation when a laser was used and no change when conducted in the photoreactor. It is also noted that Workentin and co-workers successfully used small alkylthiolate-protected AuNPs as substrates for photochemical reactions at an excitation wavelength of 350 nm. − The high stability of the gold cores in these cases may be explained by the filtering effect of the used photoreactive groups.…”

Light‐Triggered Nickel‐Catalyzed Azide−Alkyne Cycloaddition for the Preparation of 1,5‐Disubstituted 1,2,3‐Triazoles

“…Light‐induced SPAAC induced by light relies on the unmasking of the click‐active dibenzocyclooctynes by irradiation at 350 nm of cyclopropenone precursors (Scheme 1). Such metal‐free process is of particular interest for cellular or RNA labelling, [2a,b] but also to derivatize/pattern materials [2c–g] . Since the first report of König and coworkers in 2006, numerous light‐triggered CuAAC have been developed (Scheme 1).…”

Light-Triggered Click Chemistry

“…The utility of this transformation was demonstrated through successful glycan labeling as well as surface immobilization. In these studies, the biotin-containing cyclopropenone 142 was used for cell labeling experiments, while the amino-terminated linker appended cyclopropenone 143 was used for immobilization on brush polymers (Scheme c). ,− The cyclopropenone-based photoinduced click chemistry was also applied to surface functionalization, hydrogel derivatization, functionalization of nanoparticles, and synthesis of heterobivalent agents. − …”