Supplement of Magn. Reson., 2, 33–48, 2021
https://doi.org/10.5194/mr-2-33-2021-supplement© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Open Access

Supplement ofRoom-temperature hyperpolarization of polycrystalline samples
with optically polarized triplet electrons: pentacene
or nitrogen-vacancy center in diamond?
Koichiro Miyanishi et al.
Correspondence to: Koichiro Miyanishi (miyanishi@qi.mp.es.osaka-u.ac.jp), Takuya F. Segawa (segawat@ethz.ch),and Makoto Negoro (negoro@qiqb.otri.osaka-u.ac.jp)

The copyright of individual parts of the supplement might differ from the CC BY 4.0 License.

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510Estimation of the electron spin polarization of the NV− centers in microdiamonds

Using the EPR spectrum of the nanodiamonds with and without laser irradiation, we estimated the initial electron polarization
PeNV of the NV− centers between the mS = 0 and the mS = −1 states right after laser irradiation in the magnetic fieldsweep range. The obtained spectra are shown in Fig. S1. By comparing the signal intensity of the NV− with and withoutlaser irradiation within the shaded area, which is the optimized range used for the magnetic-field sweep, we obtained anenhancement of ca. 170. The estimated uncertainty, stemming from the noise in the thermal spectrum is ± 20 %. Having
a thermal polarization of 0.095 %, the electron spin polarization of the NV− right after laser irradiation is estimated to be
16 %. The thermally-polarized spectrum was averaged over 9 h, while the optically-polarized spectrum was recorded in 1 h.
Spectra were recorded using a field-swept ESE sequence (Fig. 3(a) in the main text) with an echo delay time of 2.1 µs at aMW frequency of 11.6 GHz. Please note that the sample orientation of the microdiamonds is different to that used in the DNP
measurements.

Figure S1. EPR powder spectrum of the microdiamond sample. The dashed line shows the EPR signal of the NV− centers just after laser
irradiation and the solid line shows the EPR signal without laser irradiation. The gray area corresponds to the magnetic field sweep range
used for the DNP experiments.

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NMR linewidth of 13 C in PBA with and without 1 H decoupling

Normarized Signal Intensity

The 13 C NMR of PBA with and without 1 H decoupling is shown in Fig. S2. Both signals are normalized by the maximum
signal intensity. The linewidth of the 13 C NMR signal with 1 H decoupling was 1.2 kHz and that without 1 H decoupling was
15 5.2 kHz. This signal broadening is due to the dipole–dipole interaction between 13 C spins and 1 H spins, the interaction, whichleads to the low spin diffusion coefficient in PBA.

Figure S2. NMR spectra of 13 C in PBA. The solid line shows the 13 C NMR signals with 1 H decoupling and the dashed line without 1 Hdecoupling.

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Polarization [%](c)

C Signal Intensity [a.u.]

(b)

13(a)

C Signal Intensity [a.u.]Hyperpolarized 13 C NMR is performed at a magnetic field of 0.46 T (corresponding to the ‘high-field’ horn of the EPR powder
spectrum of the microdiamonds in Fig. 3(d)) at a Larmor frequency of ω0,C = 4.95 MHz and a DNP-enhanced 13 C NMR
spectrum is shown in Fig. S3(a). Buildup curves of 13 C polarization with laser repetition frequency of R = 30, 50, 70 and
100 Hz are shown in Fig. S3(b).
The curve of longitudinal relaxation of the 13 C spins in microdiamonds are shown in Fig. S3(c) and the longitudinal relaxNVation time is T1,C
= 85 ± 5 s. In the longitudinal relaxation measurement, we change the delay time between the DNP process
and the NMR measurement.

1320C hyperpolarization in microdiamonds at the ‘high-field’ horn

Figure S3. Optical hyperpolarization in microdiamonds at a magnetic field of 0.46 T (corresponding to the ‘high-field’ horn of the EPR
MWpowder spectrum). (a) Signal intensity dependence on the microwave power ωrabi
at the high-field horn. The gray line shows the 13 C
Larmor frequency at high-field horn. (b) Buildup curves of 13 C polarization in microdiamonds. The blue, orange, green and red denote thelaser repetition frequency of 30 Hz, 50 Hz, 70 Hz and 100 Hz. (c) The relaxation curve for the 13 C NMR signal of microdiamonds.

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S4

Sample pictures

The pictures of the three samples in the glass tubes are shown in Fig. S4.
Fig. S5 shows the effect of oxidation in air on the color of the nanodiamond powders. Both samples are electron irradiatedand annealed (800◦ C in vacuum) nanodiamonds. Fig. S5(a) was taken before oxidation in air, while Fig. S5(b) was taken afteroxidation in air. The oxidation procedure removes sp2 carbon on the surface of the nanodiamonds, which was created during
the annealing step. The change in color from grey to white is a chemical key step to perform optical excitation of NV centersin nanodiamonds.

Figure S4. Pictures of the three samples (a) nanodiamonds, (b) microdiamonds and (c) pentacene doped benzoic acid.

Figure S5. Pictures of electron irradiated and annealed nanodiamonds (a) before oxidation in air (“dark”) and (b) after oxidation in air(“white”).

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