研究目的
To enhance both sensitivity and resolution in PHIP experiments for very diluted samples by combining OPSY and PhD-PHIP pulse sequences.
研究成果
The combination of OPSY and PhD-PHIP pulse sequences effectively enhances both sensitivity and resolution in PHIP experiments for very diluted samples by filtering out thermal signals and acquiring high-resolution partial J-spectra. This method allows for higher receiver gain without saturation and provides clean spectra with narrow linewidths (e.g., 0.3 Hz), making it suitable for low-concentration applications and inhomogeneous magnetic fields.
研究不足
The method may have reduced performance in non-weak coupled spin systems due to lower hyperpolarization levels. The presence of devices or sensors near the coil could perturb B0 homogeneity, affecting results. The experiments are conducted under specific conditions (e.g., single scan, specific echo time) which may not generalize to all setups.
1：Experimental Design and Method Selection:
The study combines OPSY (Only Parahydrogen Spectroscopy) as a filter for thermally polarized signals and PhD-PHIP (Parahydrogen Discriminated-PHIP) as an acquisition block for high-resolution partial J-spectra. OPSY-d variant is used with specific gradient scheme (+g, -2g) for optimal filtering. PhD-PHIP uses a train of refocusing pulses with a digital filter to separate signals and improve resolution.
2：Sample Selection and Data Sources:
Samples consist of a solution of acetone-d6, 1-hexyne, and a rhodium complex catalyst, prepared under controlled nitrogen atmosphere. Parahydrogen is enriched and delivered to the sample.
3：List of Experimental Equipment and Materials:
Bruker Avance II console, imaging probe with 10 mm birdcage coil, 3D gradient coils (max gradient
4：5 T/m), r.f. pulses (π/2 and π pulses with durations 5 μs and 29 μs, respectively), magnetic field gradients (strength 50 mT/m, duration 1 ms), digital filter (width 500 Hz), echo time tE = 8 ms, 2048 refocusing pulses. Chemicals from Sigma Aldrich:
acetone-d6, 1-hexyne, rhodium complex (CAS 79255-71-3).
5：3).
Experimental Procedures and Operational Workflow:
4. Experimental Procedures and Operational Workflow: Samples are hydrogenated with parahydrogen for 15 s, followed by a 5 s wait. NMR experiments are conducted at 7 T magnetic field. OPSY-d sequence is applied with gradients and r.f. pulses to filter thermal signals, followed by PhD-PHIP acquisition with echo train and digital filtering. All experiments are single-scan.
6：Data Analysis Methods:
Data is analyzed to observe signal-to-noise ratio, resolution (linewidth), and comparison of spectra from different pulse sequences. Partial J-spectra are generated with the digital filter.
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