Strongly‐Coupled Freestanding Hybrid Films of Graphene and Layered Titanate Nanosheets: An Effective Way to Tailor the Physicochemical and Antibacterial Properties of Graphene Film

Abstract

An effective way to tailor the physicochemical properties of graphene film is developed by combining colloidal suspensions of reduced graphene oxide (rG‐O) nanosheets and exfoliated layered titanate nanosheets for the fabrication of freestanding hybrid films comprised of stacked and overlapped nanosheets. A flow‐directed filtration of such mixed colloidal suspensions yields freestanding hybrid films comprised of strongly‐coupled rG‐O and titanate nanosheets with tunable chemical composition. This is the first example of highly flexible hybrid films composed of graphene and metal oxide nanosheets. The intimate incorporation of layered titanate nanosheets into the graphene film gives rise not only to an increase of mechanical strength but also to increased surface roughness, chemical stability, and hydrophilicity; thus, the physicochemical properties of the graphene film can be tuned by hybridization with inorganic nanosheets. These freestanding hybrid films of rG‐O‐layered titanate show unprecedentedly high antibacterial property, resulting in the complete sterilization of Escherichia coli O157:H7 (≈100%) in the very short time of 15 min. The antibacterial activity of the hybrid film is far superior to that of the pure graphene film, underscoring the beneficial effect of the layered metal oxide nanosheets in improving the functionality of the graphene film.

A Direct Hybridization between Isocharged Nanosheets of Layered Metal Oxide and Graphene through a Surface‐Modification Assembly Process

“…[17] Of prime importance is that the very low thickness of exfoliated 2D nanosheets makes a strong electronic coupling with hybridized graphene nanosheets possible. [18] Thus, exfoliated 2D nanosheets of inorganic solids are supposed to be the most suitable nanostructures for maximizing a coupling effect with graphene nanosheets. The hybridization of 3d transition-metal oxide nanosheets with rGO nanosheets can provide a powerful way to improve the intrinsically inferior electrochemical properties of the metal oxides, limitations that include poor rate characteristics and serious capacity fading.…”

Unique Advantages of Exfoliated 2D Nanosheets for Tailoring the Functionalities of Nanocomposites

“…The freestanding hybrid films of rG-O and 2D Ti 0.91 O 2 nanosheets are fabricated by vacuum-assisted filtration of homogeneously mixed suspensions of rG-O and 2D Ti 0.91 O 2 nanosheets with several C/Ti 0.91 O 2 ratios of 0.8, 2, and 4 (i.e., TG1, TG2, and TG3). 17 In the obtained hybrid freestanding films, the exfoliated 2D nanosheets of rG-O and 2D Ti 0.91 O 2 are homogeneously mixed and well-ordered in LbL fashion along the c-axis. However, as presented in the field emission scanning electron microscopy (FE-SEM) images of Figure 8A, the freestanding hybrid films have nanosized sharp edges (i.e., nanoblades) on their surfaces, whereas the pure rG-O and 2D Ti 0.91 O 2 freestanding films commonly show a flat and clean surface structure.…”

“…57,58 The hybridization with highly anisotropic 2D graphene nanosheets results in the formation of 2D sheet-like morphology and the crystallization of the layered structure. Taking into consideration the fact that layered metal oxide is normally obtained under harsh synthesis condition such as solid-state reaction or hydrothermal reaction, 10,11,17 the coupling with the rG-O 2D nanosheet can induce a phase transformation into the layered structure under mild conditions, which is attributable to the structural similarity between the rG-O template and resulting layered materials.…”

Non-monotonous dependence of the electrical conductivity and chemical stability of a graphene freestanding film on the degree of reduction

“…[1][2][3] The reduction of graphene oxide (G-O) precursor yields chemically-prepared graphene, i.e. 5,6 The facile preparation of freestanding graphene lms widens the application elds of the graphene materials. 4 Of prime importance is that the elastic graphene lms can be easily fabricated by a simple vacuumassisted ltration of the resulting rG-O colloids.…”