Multiwavelength Light-Emitting Diode-Array-Embedded Nuclear Magnetic Resonance System: A Noninvasive In Situ Platform...

The integration of in situ photonic excitation with nuclear magnetic resonance (NMR) spectroscopy offers a powerful approach for investigating photochemical intermediates and elucidating reaction mechanisms. However, existing illumination strategies commonly rely on lasers or high-power LEDs coupled through optical fibers, quartz light guides, or custom light sleeves inserted into the NMR sample volume. These invasive configurations suffer from poor illumination homogeneity, limited control flexibility, contamination risks, and distortion of magnetic field homogeneity─factors that can lead to inconsistent reaction conditions, sample degradation, and compromised spectral quality. To overcome these limitations, we introduce a noninvasive embedded multiwavelength optical NMR (NIEMO-NMR) system. Utilizing flexible printed circuit technology and submillimeter-scale micro-LEDs, NIEMO-NMR integrates a cylindrically curved LED array into the interior of the NMR probe with minimal electromagnetic interference, preserving all standard probe functionalities. This architecture enables uniform and controllable circumferential illumination of the sample. Light pulses are precisely synchronized with radiofrequency pulses via programmable sequences, supporting multiwavelength selectivity, tunable excitation intensity, noninvasive operation, and high spatial uniformity. We validated the system through a series of in situ Photo-NMR experiments, including 1D and 2D ¹H/¹⁹F photochemically induced dynamic nuclear polarization studies of biomolecules under spinning and static conditions, as well as wavelength-selective photochemical isomerization kinetics of molecular photo switches. The results demonstrate that NIEMO-NMR enables noninvasive, spectrally selective illumination with minimal magnetic interference and high spatiotemporal resolution, offering a precise, accessible, and efficient platform for integrated Photo-NMR studies.