3 research outputs found
Single chip dynamic nuclear polarization microsystem
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. In particular, we report 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/HO 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
High sensitivity field asymmetric ion mobility spectrometer
A high sensitivity field asymmetric ion mobility spectrometer (FAIMS) was designed, fabricated, and tested. The main components of the system are a 10.6 eV UV photoionization source, an ion filter driven by a high voltage/high frequency n-MOS inverter circuit, and a low noise ion detector. The ion filter electronics are capable to generate square waveforms with peak-to-peak voltages up to 1000 V at frequencies up to 1 MHz with adjustable duty cycles. The ion detector current amplifier has a gain up to 1012 V/A with an effective equivalent input noise level down to about 1 fA/Hz1/2 during operation with the ion filter at the maximum voltage and frequency. The FAIMS system was characterized by detecting different standard chemical compounds. Additionally, we investigated the use of a synchronous modulation/demodulation technique to improve the signal-to-noise ratio in FAIMS measurements. In particular, we implemented the modulation of the compensation voltage with the synchronous demodulation of the ion current. The analysis of the measurements at low concentration levels led to an extrapolated limit of detection for acetone of 10 ppt with an averaging time of 1 s
Single-chip electron spin resonance detectors operating at 50 GHz, 92 GHz, and 146 GHz
We report on the design and characterization of single-chip electron spin resonance (ESR) detectors operating at 50 GHz, 92 GHz, and 146 GHz. The core of the single-chip ESR detectors is an integrated LC-oscillator, formed by a single turn aluminum planar coil, a metal-oxide-metal capacitor, and two metal-oxide semiconductor field effect transistors used as negative resistance network. On the same chip, a second, nominally identical, LC-oscillator together with a mixer and an output buffer are also integrated. Thanks to the slightly asymmetric capacitance of the mixer inputs, a signal at a few hundreds of MHz is obtained at the output of the mixer. The mixer is used for frequency down-conversion, with the aim to obtain an output signal at a frequency easily manageable off-chip. The coil diameters are 120 μm, 70 μm, and 45 μm for the U-band, W-band, and the D-band oscillators, respectively. The experimental frequency noises at 100 kHz offset from the carrier are 90 Hz/Hz1/2, 300 Hz/Hz1/2, and 700 Hz/Hz1/2 at 300 K, respectively. The ESR spectra are obtained by measuring the frequency variations of the single-chip oscillators as a function of the applied magnetic field. The experimental spin sensitivities, as measured with a sample of α,γ-bisdiphenylene-β-phenylallyl (BDPA)/benzene complex, are 1 × 108 spins/Hz1/2, 4 × 107 spins/Hz1/2, 2 × 107 spins/Hz1/2 at 300 K, respectively. We also show the possibility to perform experiments up to 360 GHz by means of the higher harmonics in the microwave field produced by the integrated single-chip LC-oscillators