The structural and dynamical properties of LiBH 4 confined in porous carbon and ordered porous silica are studied using Li measurements show that Li + is also highly mobile. Therefore, we conclude that nanoconfinement of LiBH 4 strongly enhances diffusional mobility of borohydride anions and lithium in this material.

From the diffusional behavior of nanoparticles in heterogeneous hydrogels, quantitative information about submicron structural features of the polymer matrix can be derived. Pulsed-gradient spin-echo NMR is often the method of choice because it measures diffusion of the whole ensemble of nanoparticles. However, in (1)H diffusion-ordered spectroscopy (DOSY), low-intensity nanoparticle signals have to be separated from a highly protonated background. To circumvent this, we prepared (19)F labeled, PEGylated, water-soluble dendritic nanoparticles with a (19)F loading of ~7 wt % to enable background free (19)F DOSY experiments. (19)F nanoparticle diffusometry was benchmarked against (1)H diffusion-T2 correlation spectroscopy (DRCOSY), which has a stronger signal separation potential than the commonly used (1)H DOSY experiment. We used bootstrap data resampling to estimate confidence intervals and stabilize 2D-Laplace inversion of DRCOSY data with high noise levels and artifacts, allowing quantitative diffusometry even at low magnetic field strengths (30 MHz). The employed methods offer significant advantages in terms of sensitivity and selectivity.

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In our studies on particle mobility in polymer solutions, we have investigated and determined self-diffusion coefficients of nanoparticles in semidilute solutions of poly(ethylene glycol) (PEG, M w = 6, 20, 35, and 100 kDa). Specially designed PEGylated dendrimers with well-defined sizes (d h = 3.4−11.0 nm) and with internal 19 F moieties allow for background-free 19 F NMR diffusion measurements. This way, we were able to assess the self-diffusion coefficients as a function of particle diameter and length scales (correlation length, tube diameter, polymer radius of gyration) with high resolution. Scaling arguments allowed us to visualize a clear crossover between particles probing a lower apparent viscosity to near macroviscosity when the nanoparticle size is comparable to the PEG polymer coil size. The same arguments are shown to correctly predict particle diffusion coefficients as a function of polymer concentration when the particles are smaller than the polymer coils.

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