Abstract:

¹H NMR spectral features of hydrogen molecules in the stacking interstices of silicon dioxide microspheres with different sizes are studied. The chemical shift of hydrogen molecules is found to gradually shift towards higher fields as the size of the stacking interstices decreases. Combined with experimental results of variable temperature hydrogen spectroscopy, self-diffusion coefficients measurement, and scanning electron microscopy, the observed phenomenon is attributed to two factors, namely, 1) the microsphere size dependent local magnetic field inhomogeneity in the stacking interstices caused by the diamagnetic silicon dioxide microspheres; and 2) the rapid exchange among hydrogen molecules experiencing different local fields within the microsphere interstices. The results of this study demonstrate the potential of hydrogen gas as a probe molecule for measuring micro- and nano-scale pore sizes.

Key words: hydrogen gas, silicon dioxide, stacking interstices, NMR, chemical shift