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.

Monolayers and a few layers of transition metal dichalcogenides (TMDs), organized as flakes or films, are notable for their electronic and optical properties, highlighting their interest for a variety of applications. Specifically, MoS 2 flakes and films show a direct bandgap in their 2D form, which opens to applications in energy storage, optoelectronic devices, and in biosensing applications. Interestingly, hybrid systems composed of MoS 2 flakes interfaced with metal nanoparticles, such as gold and silver, exploit the interplay between the interaction of plasmon of the metallic nanoparticle and the exciton of MoS 2 . Such plasmon− exciton interaction can be exploited to further improve the efficiency of TMD-based applications for sensing, catalysis, and photovoltaics. In this work, flakes of MoS 2 grown on SiO 2 /Si substrates were prepared by chemical vapor deposition (CVD) under ambient pressure and were subsequently decorated using gold nanoparticles of distinct sizes. Tip-enhanced Raman spectroscopy and tip-enhanced photoluminescence measurements as well as contact potential difference (CPD) were conducted to evaluate the plasmon−exciton coupling of MoS 2 flakes decorated with raspberry-like (∼100 nm) and seed-like (∼20 nm) gold nanoparticles.

Super-resolution fluorescence microscopy based on localization algorithms has tremendously impacted the field of imaging by improving the spatial resolution of optical measurements with specific blinking fluorophores and concomitant reduction of acquisition time. In vibrational spectroscopy and imaging, various methods have been developed to surpass the diffraction limit including near-field scattering methods, such as in tip-enhanced Raman and infrared spectroscopies. Although these scanning-probe techniques can provide exquisite spatial resolution, they often require long acquisition times and tedious fabrication of nano-scale scanning probes. Herein, stochastic optical reconstruction microscopy (STORM) protocol is applied on Raman measurements acquired using a wide-field home-built microscopy setup. We explore how the fluctuations of the Raman signal acquired over a series of time-lapse images at specific spectral ranges can be exploited with STORM processing, possibly revealing details with improved spatial resolution, under lower irradiance and with faster acquisition speed that cannot be achieved in point scanning mode over the same field of view. Samples studied here include patterned silicon, polystyrene microspheres on a silicon wafer, and graphene on a silicon/silicon dioxide substrate. The outcome presents an effective way to collect Raman images at selected spectral ranges with spatial resolutions of ∼200 nm over a large field of view under 532 nm excitation together with an acquisition speed improved by two orders of magnitude and under a significantly reduced irradiance compared to confocal laser scanning acquisition.