Exploration of accessibility of internal pore surface by using rigid nanoparticles as a probe for constructing the integrated nanocomposites

Many mesoporous materials with different morphologies, dimensions, pore sizes and structures have been fabricated and served as carriers to load a wide range of guest species. The high accessibility of pore interiors should be of very significance for efficient loading in the nanocarriers and resultant performance of the formed nanocomposites. In this work, by electrostatic self-assembly, the rigid nanoparticles (NPs) were used as probes to detect the accessibility of internal surface of different pore channels of two typical porous materials, i.e., conventional mesoporous silica nanospheres (MSNs) with uniform hexagonal ordered mesopores and recently created dendritic porous silica NPs (DPSNs) with center-radial porous structure. Interestingly, even 1.6 +/- 0.4 nm of ultrafine Au NPs have an uneven and low density distribution on the internal pore surface of MSNs owing to small tubular pores with only two openings. On the contrary, the rigid NPs with different particle sizes from 1.6 +/- 0.4 nm to 7.8 +/- 1.9 nm can enter DPSNs through open center-radial large pores with 360 degrees diffusion direction, and achieve a high density and well-dispersed loading on the surface of internal pore channels. Besides, based on the size effect, the integrated DPSNs-NH2@Au@Pt nanocomposite with hierarchical spatial distributions of large Au NPs on particle surface and small Pt NPs on both internal pore surface and particle surface were successfully constructed. These results provide an important insight into the accessibility of internal pore surface toward rigid NPs and the smart construction of multifunctional nanocomposites. (C) 2019 Elsevier B.V. All rights reserved