200 GHz single chip dynamic nuclear polarization microsystems

The single chip integration of the sensitivity relevant part of nuclear magnetic resonance (NMR) [1-17], electron spin resonance (ESR) [18-26], and dynamic nuclear polarization (DNP) enhanced NMR detectors [27] is a promising approach to improve the limit of detection, especially for nanoliter and subnanoliter samples. Recently, the single chip integration of a DNP microsystem operating at 11 GHz (ESR)/16 MHz (NMR) has been demonstrated [27]. Here, we report on single chip DNP microsystems operating at 200 GHz (ESR)/300 MHz (NMR). The single chip integrated microsystems consist of a single or an array of microwave oscillators operating at about 200 GHz for ESR excitation/detection and of a radio frequency receiver operating at about 300 MHz with frequency downconversion for NMR detection. The proposed microsystems, integrated into a single chip of about 1 mm^2, eliminate the need of a high power microwave generator (e.g., a gyrotron) and high quality microwave waveguides. The NMR excitation is performed with a non-integrated coil. To exemplify its possible applications, 1H DNP enhanced NMR experiments on solid samples of volumes from 100 pL to 4 nL are performed at temperatures from 15 to 300 K. DNP enhancements as large as 50 are achieved with 2% α,γ-bisdiphenylene-β-phenylallyl in polystyrene (2% BDPA:PS) at 15 K. This work demonstrates the possibility of extending the single chip approach to the realization of probes for DNP studies of nanoliter and subnanoliter samples at high frequency, high field, and low temperature.