The systematic investigation of the dependence of the orientation and capillary interaction of hydrophobized polystyrene microcubes at the liquid/air interface on the surface tension of the aqueous subphase is reported. By decreasing the subphase surface tension, the preferential orientation of the cubes was observed to change independent of the surfactant type from the vertex up to the edge up and finally to the face up. Concomitantly, the structure of the aggregates obtained by cube assembly was observed to change from a close-packed hexagonal to tilted linear and finally to flat plate. In particular, the preferential orientation of the cubes was virtually independent of the surfactant charge at a constant surface tension. In addition, reconfigurable microcube assemblies at the liquid/air interface, which respond to the surface tension of the subphase, were observed for the first time. The dynamic reconfigurability of preformed microcube aggregates induced by adding surfactant to the subphase may open new pathways to dynamic assemblies at liquid/air interfaces, which may be interesting, e.g., for sensing applications.
Graphene, a single layer of two-dimensional carbon material, has attracted much attention due to its excellent comprehensive properties including high mechanical strength, antibacterial property, excellent thermal and electrical conductivities, high specific surface area, impermeability, etc. In this study, 3-epoxypropyl-5,5-dimethylhydantoin (GH), as a precursor of [Formula: see text]-halamine, was synthesized and attached onto graphene oxide (GO) for enhanced antibacterial activity. The synthesized GO–GH was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and X-ray photoelectron spectroscopy (XPS). After chlorination treatment by household bleach solution, the chlorinated graphene oxide-3-epoxypropyl-5,5-dimethylhydantoin (GO–GH–Cl) possessed great antibacterial efficacy. The synthesized GO–GH–Cl was added to chitosan (CS) solution to produce GO–GH–Cl/CS hybrid films via a solution casting method. The as-prepared antimicrobial hybrid films showed excellent antibacterial activity and could kill 100% of S. aureus and 100% of E. coli O157:H7 within 10[Formula: see text]min and 30[Formula: see text]min of contact time, respectively.
The impact of the particle size and wettability on the orientation and order of assemblies obtained by self-organization of functionalized microscale polystyrene cubes at the water/air interface is reported. An increase in the hydrophobicity of 10-and 5-μm-sized self-assembled monolayer-functionalized polystyrene cubes, as assessed by independent water contact angle measurements, led to a change of the preferred orientation of the assembled cubes at the water/air interface from face-up to edge-up and further to vertex-up, irrespective of microcube size. This tendency is consistent with our previous studies with 30-μmsized cubes. However, the transitions among these orientations and the capillary force-induced structures, which change from flat plate to tilted linear and further to close-packed hexagonal arrangements, were observed to shift to larger contact angles for smaller cube size. Likewise, the order of the formed aggregates decreased significantly with decreasing cube size, which is tentatively attributed to the small ratio of inertial force to capillary force for smaller cubes in disordered aggregates, which results in more difficulties to reorient in the stirring process. Experiments with small fractions of larger cubes added to the water/air interface increased the order of smaller homo-aggregates to values similar to neat 30 μm cube assemblies. Hence, collisions of larger cubes or aggregates are shown to play a decisive role in breaking metastable structures to approach a global energy minimum assembly.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.