Fig. 1.

Typical transmission electron microscope image and schematic representation of Gd-DOTA-MSNs (66.3 ± 6.6 nm) prepared using (a) ‘Short delay’ co-condensation, where functionalities are internalised deeply in the structure (r₁ = 17.14 ± 0.49 mM⁻¹ s⁻¹), (b) ‘Long delay’ co-condensation, where functionalities are internalised nearer to the porous openings (r₁ = 33.57 ± 1.29 mM⁻¹ s⁻¹) and (c) post-grafting, where functionalities are loaded on external surfaces (r₁ = 10.77 ± 0.22 mM⁻¹ s⁻¹). (d) Post-grafted Gd-DOTA-non-porous silica nanoparticles (r₁ = 9.56 ± 0.47 mM⁻¹ s⁻¹). The chart displays r₁ relaxivities of corresponding nanoparticle samples, measured at 7 T.