  The integration on a single chip of the sensitivity-relevant electronics of
nuclear magnetic resonance (NMR) and electron spin resonance (ESR)
spectrometers is a promising approach to improve the limit of detection,
especially for samples in the nanoliter and subnanoliter range. Here we
demonstrate the co-integration on a single silicon chip of the front-end
electronics of an NMR and an ESR detector. The excitation/detection planar
spiral microcoils of the NMR and ESR detectors are concentric and interrogate
the same sample volume. This combination of sensors allows to perform dynamic
nuclear polarization (DNP) experiments using a single-chip integrated
microsystem having an area of about 2 mm$^2$. In particular, we report $^1$H
DNP-enhanced NMR experiments on liquid samples having a volume of about 1 nL
performed at 10.7 GHz(ESR)/16 MHz(NMR). NMR enhancements as large as 50 are
achieved on TEMPOL/H$_{2}$O solutions at room temperature. The use of
state-of-the-art submicrometer integrated circuit technologies should allow the
future extension of the single-chip DNP microsystem approach proposed here up
the THz(ESR)/GHz(NMR) region, corresponding the strongest static magnetic
fields currently available. Particularly interesting is the possibility to
create arrays of such sensors for parallel DNP-enhanced NMR spectroscopy of
nanoliter and subnanoliter samples.
