Toughening Graphene by Integrating Carbon Nanotubes.

Perfect graphene is believed to be one of the strongest materials, yet its resistance to fracture is much less impressive. The modest fracture toughness is thought to be related to the general brittle nature in the fracture process of graphene and its two-dimensional (2D) analogous. The brittleness also makes it extremely difficult to assess mechanical properties of 2D materials. The introduction of carbon nanotubes (CNTs) into bulk materials has proven to be a widely accepted method for toughening and strengthening materials. To date, such toughening effect of CNTs on 2D materials is largely unknown. A unique material, rebar graphene, has been synthesized that consists of CNTs embedded in graphene. In this study, by implementing a "dry" transfer technique, the freely suspended rebar graphene was systematically tested under uniaxial tension mode inside a scanning electron microscope. Our combined experiments and molecular dynamics simulations confirm that the embedded CNTs divert and bridge the propagating crack and provide a toughening mechanism for the material. Our work identifies a promising extrinsic toughening strategy for 2D materials and provides mechanistic insights into the fracture process of graphene hybrid material.

Bridged Rebar Graphene functionalized aptasensor for pathogenic E. coli O78:K80:H11 detection.

We report a novel fabrication method of functionalised Bridged Rebar Graphene (BRG) onto newly designed nanostructured aptasensor for label free impedimetric sensing of pathogenic bacteria E. coli O78:K80:H11. The chemical facilitated unscrolling of MWCNT and subsequent bridging with terephthalaldehyde (TPA) to form 3D-hierarchical BRG nanoconstruct exhibited synergistic effect by combining enhanced electrical properties and facile chemical functionality for stable bio-interface. The bacteria-DNA interactions were captured on BRG nanostructured electrode by using specific anti-E.coli DNA aptamer (Kd~ 14nM), screened by new in-situ developed SELEX method using phenylboronic acid on microtitre plate. The developed nanostructured aptasensor demonstrated a low detection limit and sensitivity of ~ 101cfu/mL towards E. coli O78:K80:H11 with a dynamic response range from 101 to 106cfu/mL in water, juice and milk samples.

Three-Dimensional Rebar Graphene.

Free-standing robust three-dimensional (3D) rebar graphene foams (GFs) were developed by a powder metallurgy template method with multiwalled carbon nanotubes (MWCNTs) as a reinforcing bar, sintered Ni skeletons as a template and catalyst, and sucrose as a solid carbon source. As a reinforcement and bridge between different graphene sheets and carbon shells, MWCNTs improved the thermostability, storage modulus (290.1 kPa) and conductivity (21.82 S cm-1) of 3D GF resulting in a high porosity and structurally stable 3D rebar GF. The 3D rebar GF can support >3150× the foam's weight with no irreversible height change, and shows only a ∼25% irreversible height change after loading >8500× the foam's weight. The 3D rebar GF also shows stable performance as a highly porous electrode in lithium ion capacitors (LICs) with an energy density of 32 Wh kg-1. After 500 cycles of testing at a high current density of 6.50 mA cm-2, the LIC shows 78% energy density retention. These properties indicate promising applications with 3D rebar GFs in devices requiring stable mechanical and electrochemical properties.

Rivet Graphene.

Large-area graphene has emerged as a promising material for use in flexible and transparent electronics due to its flexibility and optical and electronic properties. The anchoring of transition metal nanoparticles on large-area single-layer graphene is still a challenge. Here, we report an in situ preparation of carbon nano-onion-encapsulated Fe nanoparticles on rebar graphene, which we term rivet graphene. The hybrid film, which allows for polymer-free transfer and is strong enough to float on water with no added supports, exhibits high optical transparency, excellent electric conductivity, and good hole/electron mobility under certain tensile/compressive strains. The results of contact resistance and transfer length indicate that the current in the rivet graphene transistor does not just flow at the contact edge. Carbon nano-onions encapsulating Fe nanoparticles on the surface enhance the injection of charge between rivet graphene and the metal electrode. The anchoring of Fe nanoparticles encapsulated by carbon nano-onions on rebar graphene will provide additional avenues for applications of nanocarbon-based films in transparent and flexible electronics.

Rebar graphene from functionalized boron nitride nanotubes.

The synthesis of rebar graphene on Cu substrates is described using functionalized boron nitride nanotubes (BNNTs) that were annealed or subjected to chemical vapor deposition (CVD) growth of graphene. Characterization shows that the BNNTs partially unzip and form a reinforcing bar (rebar) network within the graphene layer that enhances the mechanical strength through covalent bonds. The rebar graphene is transferrable to other substrates without polymer assistance. The optical transmittance and conductivity of the hybrid rebar graphene film was tested, and a field effect transistor was fabricated to explore its electrical properties. This method of synthesizing 2D hybrid graphene/BN structures should enable the hybridization of various 1D nanotube and 2D layered structures with enhanced mechanical properties.

Biofunctionalized rebar graphene (f-RG) for label-free detection of cardiac marker troponin I.

One-step microwave-assisted unscrolling of carbon nanotubes to form functionalized rebar graphene (f-RG) is reported. The well-characterized f-RG on an interdigitated electrode biochip in a FET configuration showed enhanced electronic properties, as demonstrated with I-V characteristics. The developed device was biofunctionalized with specific anti-cTnI antibodies exhibiting a shift of threshold voltage from -2.15 V to -0.5 V and decrease in electron mobility from 3.609 × 10(4) to 8.877 × 10(3) cm(2) V(-1) s(-1). The new sensing strategy holds great promise for its applicability in diagnostics exhibiting high sensitivity (∼ 1 pg/mL) and specificity toward cardiac marker (cTnI).