Jianxun Xu

Nanotips exhibit a low turn-on field and high emission current density, and are considered promising candidates in future cold-field emitters.

The scalable, efficient, and cost‐economic preparation method of graphene is the key to promoting the real applications of graphene. In recent years researchers have made intensive efforts to enhance the synthesis efficiency and reduce the production costs of the manufacturing processes, especially for the chemical vapor deposition methods. However, the efficiency and uniformity are difficult to further improve due to its complicated synthesis conditions. A high‐efficiency synthesis method to provide a large uniform production area suitable for graphene growth remains a great challenge until now. In this work, a facile and scalable ultrafast quenching method for growing graphene in air is developed by using scanning electromagnetic induction (SEMI) equipment. This method is successfully applied to grow a 400 mm × 400 mm graphene glass within 2 min in the air with a lab‐grade instrument. Thus‐produced multiple‐layered graphene glass is of a high uniformity, film adhesion, and full coverage, showing a surface resistance (Rs) below 500 Ω sq⁻¹. Outstanding electrothermal capabilities up to 1000 °C are demonstrated for their promising potential for transparent heating devices. The SEMI method, including the product size and growth rate, can be easily up‐scaled, which is believed to provide an effective route to grow graphene aiming at its real applications.

Currently, graphene films are expected to achieve real applications in various fields. However, the conventional synthesis methods still have intrinsic limitations, especially not being applicable on a surface with high curvature. Herein, an ultrafast synthesis method was developed for graphene and turbostratic graphite growth by a single subsecond pulse of microwaves generated by a household magnetron. We succeeded in growing high-quality around 10-layered turbostratic graphite in 0.16 s directly on the surface of an atomic force microscope probe and maintaining a tip curvature radius of less than 30 nm. The thus-produced probes showed high conductivity and tip durability. Moreover, turbostratic graphite film was also demonstrated to grow on the surface of dielectric Si flat substrates in a full coverage. Graphene can also grow on metallic Ni tips by this method. Our microwave ultrafast method can be used to grow high-quality graphene in a facile, efficient, and economical way.

Graphene has many excellent optical, electrical and mechanical properties due to its unique two-dimensional structure. High-efficiency preparation of large area graphene film is the key to achieve its industrial applications. In this paper, an ultrafast quenching method was firstly carried out to flow a single pulse current through the surface of a Si wafer with a size of 10 mm × 10 mm for growing fully covered graphene film. The wafer surface was firstly coated with a 5-nm-thick carbon layer and then a 25-nm-thick nickel layer by magnetron sputtering. The optimum quenching conditions are a pulse current of 10 A and a pulse width of 2 s. The thus-prepared few-layered graphene film was proved to cover the substrate fully, showing a high conductivity. Our method is simple and highly efficient and does not need any high-power equipment. It is not limited by the size of the heating facility due to its self-heating feature, providing the potential to scale up the size of the substrates easily. Furthermore, this method can be applied to a variety of dielectric substrates, such as glass and quartz.

Graphene functionalized nanotips are expected to possess promising potential for various applications based on the outstanding electrical and mechanical properties of graphene. However, current methods, usually requiring a high growth temperature and identical crystal surface to match graphene lattice, are suitable for graphene formation on a flat surface. It remains a big challenge to grow graphene on a nanosized convex surface and fabricate functionalized nanotips with high quality graphene at the apex. In this work, a novel ultrafast annealing method is developed for growing large area graphene on Ni nanotips within 1–2 s. Few layered or multiple layered graphene is presented on the apex or sidewall of the conical tip surface. Direct experimental evidences support that thus‐produced graphene is formed via the direct conversion of nickel carbide at the outer surface under the instantaneous high temperature, which is different from the conventional segregation mechanism. This newly developed ultrafast method provides a new route to produce graphene efficiently and economically, promising for both convex surfaces and flat substrates. Moreover, the graphene functionalized nanotips exhibit a great potential for nanoelectrical measurements and conductive scanning probe microscopy (SPM) applications.

Up to now, there have been many research studies that have revealed the unique phenomena of various materials encapsulated in a confined nano-sized space, such as in the interior of carbon nanotubes (CNTs). Confined in such a space several nanometers in size, these materials showed many different and interesting properties. However, the morphology and behaviors of these materials encapsulated in a comparatively bigger space, i.e., from tens of nanometers to microns, have been little investigated. In this work, carbon nanocones (CNCs), which are multilayered graphene-like nanomaterials with a hollow conical structure and an inner size varying continuously from several nanometers to micrometers, were used as the workhorse to investigate the nano-confinement effects on different scales. Gd acetate was adopted to be incorporated into the conical inner space of the CNCs. The corresponding Gd oxide, formed upon heating, showed a unique morphology and crystallization behavior in this sub-micron space. The confined Gd oxide was conical in shape, perfectly fitting the interior of the CNCs. Several crystallization orientations were often presented in the Gd oxide cone structure, and single crystallization was also observed located close to the apex of the CNCs. The crystal size of Gd oxide was over 100 nm, implying the effective scale of the confinement phenomenon between the CNCs and Gd oxide. Moreover, we further found that the Gd oxide cone retained its structure, instead of forming a spherical particle when it moved outward from the CNC driven by a high temperature, indicating the high stability of the conical Gd oxide nanocrystals.

Cardiac tissue engineering (CTE) has developed rapidly, but a great challenge remains in finding practical scaffold materials for the construction of engineered cardiac tissues. Carbon nanohorns (CNHs) may be a potential candidate due to their special structure and properties. The purpose of this study was to assess the effect of CNHs on the biological behavior of neonatal rat ventricular myocytes (NRVMs) for CTE applications. CNHs were incorporated into collagen to form growth substrates for NRVMs. Transmission electron microscopy (TEM) observations demonstrated that CNHs exhibited a good affinity to collagen. Moreover, it was found that CNH-embedded substrates enhanced adhesion and proliferation of NRVMs. Immunohistochemical staining, western blot analysis, and intracellular calcium transient measurements indicated that the addition of CNHs significantly increased the expression and maturation of electrical and mechanical proteins (connexin-43 and N-cadherin). Bromodeoxyuridine staining and a Cell Counting Kit-8 assay showed that CNHs have the ability to inhibit the proliferation of cardiac fibroblasts. These findings suggest that CNHs can have a valuable effect on the construction of engineered cardiac tissues and may be a promising scaffold for CTE.

We present a facile approach to sharpen dull carbon nanocone tip to make the materials more appropriate for AFM applications.