Tunable dendrimer-like porous silica nanospheres: Effects of structures and stacking manners on surface wettability

Similar to raspberry-like particles with dual-size roughness, dendrimer-like porous silica nanospheres (DPSNs) have great potentials to fabricate superhydrophobic nano-coatings due to facile and controllable synthesis, center-radial large pores and interconnected wrinkles on particle surface. However, there are very limited reports about the effects of structures and stacking manners of DPSNs on wettability up to date. In this work, various nano-coatings with different particle stacking manner (i.e., micro- and/or nano-roughness) are successfully constructed by using a series of DPSNs with tunable particle sizes and surface pore sizes as building blocks, based on paint- and dip-coating methods. For relatively flat surface and compact sphere stacking manner obtained by paint-coating, compared with solid silica nanospheres (SSNs)-coated glass slides, DPSNs-coated glass slides possess more nano-roughness to allow air pockets to exist center-radial porous channels, thus enhancing the hydrophobicity. Moreover, dip-coating makes higher surface submicro- and nano-roughness than paint-coating due to loose and locally aggregated stacking manner, thus achieving superhydrophobicity for both small and large DPSNs. In addition, owing to lower light scattering, small DPSNs are more suitable to prepare the coated slide glass with superhydrophobicity and enhanced transmittance. These interesting findings are significant to guide the design and synthesis of functional nano-coatings.