  We compare here the performances of two approaches to achieve such transfer:
PRESTO (Phase-shifted Recoupling Effects a Smooth Transfer of Order), which is
currently the method of choice to achieve the magnetization transfer from
protons to quadrupolar nuclei and which has been shown to supersede
Cross-Polarization under Magic-Angle Spinning (MAS) for quadrupolar nuclei and
D-RINEPT (Dipolar-mediated Refocused Insensitive Nuclei Enhanced by
Polarization Transfer) using symmetry-based SR4${}_1{}^2$ recoupling, which has
already been employed to transfer the magnetization in the reverse way from
half-integer quadrupolar spin to protons. We also test the PRESTO sequence with
R16${}_7{}^6$ recoupling using 270${}_0$90${}_180$ composite $\pi$-pulses as
inversion elements. This recoupling scheme has not so far been employed to
reintroduce dipolar couplings with protons. These various techniques to
transfer the magnetization from protons to quadrupolar nuclei are analyzed
using (i) an average Hamiltonian theory, (ii) numerical simulations of spin
dynamics, and (iii) experimental ${}^1$H $\rightarrow {}^{27}$Al and ${}^{1}$H
$\rightarrow {}^{17}$O transfers in as-synthesized AlPO4-14 and
${}^{17}$O-labelled fumed silica, respectively. The experiments and simulations
are done at two magnetic fields (9.4 and 18.8 T) and several spinning speeds
(15, 18-24 and 60 kHz). This analysis indicates that owing to its
$\gamma$-encoded character, PRESTO yields the highest transfer efficiency at
low magnetic fields and MAS frequencies, whereas owing to its higher robustness
to rf-field inhomogeneity and chemical shifts, D-RINEPT is more sensitive at
high fields and MAS frequencies, notably for protons exhibiting large offset or
CSA, such as those involved in hydrogen bonds.
