Illumination of Nanoliter-NMR Spectroscopy Chips for Real-Time Photochemical Reaction Monitoring.

We report the use of a small-volume nuclear-magnetic-resonance (NMR)-spectroscopy device with integrated fiber-optics for the real-time detection of UV-vis-light-assisted chemical reactions. An optical fiber is used to guide the light from LEDs or a laser diode positioned safely outside the magnet toward the 25 nL detection volume and placed right above the microfluidic channel, irradiating the transparent back of the NMR chip. The setup presented here overcomes the limitations of conventional NMR systems for in situ UV-vis illumination, with the microchannel permitting efficient light penetration even in highly concentrated solutions, requiring lower-power light intensities, and enabling high photon flux. The efficacy of the setup is illustrated with two model reactions activated at different wavelengths.