Laser-driven rapid functionalization of carbon surfaces and its application to the fabrication of fluorinated adsorbers†
The use of laser sources can expand the range of applications of photochemical surface functionalization strategies, increasing reaction rate and sample throughput. However, high irradiances can result in thermal effects and/or changes in the mechanism of photoinduced reactions. In this work we report on the use of a pulsed UV laser source for the modification of carbon surfaces using fluorinated terminal alkenes. A perfluorinated alkene, 1H,1H,2H-perfluoro-dec-1-ene (PFD), was used to modify amorphous carbon surfaces using a pulsed excimer laser (248 nm). The rate and yield of photoinduced PFD chemisorption was measured using Infrared Reflectance Absorption Spectroscopy (IRRAS) and compared to that obtained using a continuous lamp source. Quartz Crystal Microbalance (QCM) measurements were also used to obtain quantitative estimates of surface coverage and quantum yields. We found that, under the experimental conditions investigated, PFD chemisorption rates at bare carbon are proportional to the rate of incident photons. Simulations indicated that thermal effects of laser irradiation are expected to be minor, thus supporting the conclusion that the pulsed source can be used to accelerate the reaction rate without leading to changes in reaction mechanism. However, we observed that the limiting chemisorption yield was ∼30% higher for the laser source. We propose that this difference is due to photochemical formation of multilayers, a reaction that is slower than chemisorption at bare carbon, but that becomes evident when very high total fluence is applied via pulsed sources. Finally, we investigated the influence of reaction conditions on the ability of fluorinated carbon surfaces obtained via laser- and lamp-driven reactions to adsorb and capture fluorinated ligands via non-covalent fluorous–fluorous interactions.