Functionalization is an important way to breed new properties and applications for a material. This review presents an overview of the progresses in functionalized hexagonal boron nitride (h-BN) nanomaterials. It begins with an introduction of h-BN structural features, physical and chemical properties, followed by an emphasis on the developments of BN functionalization strategies and its emerging properties/applications, and ends with the research perspectives. Different functionalization methods, including physical and chemical routes, are comprehensively described toward fabrication of various BN derivatives, hetero- and porous structures, etc. Novel properties of functionalized BN materials, such as high water solubility, excellent biocompatibility, tunable surface affinities, good processibility, adjustable band gaps, etc., have guaranteed wide applications in biomedical, electronic, composite, environmental and "green" energy-related fields.

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Functionalized hexagonal boron nitride nanomaterials: emerging properties and applications.

This article presents an overview of the up-to-date developments in boron nitride nanotubes (BNNTs), including theory, fabrication, structure, physical properties, chemical functionalization and applications. Soon after the discovery of carbon nanotubes, BNNTs were theoretically predicted, followed by their successful fabrication by arc-discharge in 1995. Subsequently, various methods were developed for the BNNT synthesis, although till now, the growth of highly pure single-walled BNNTs at large quantities remains a challenge. The physical property investigations reveal that BNNTs’ exhibit a stable wide band gap, superb mechanical strength, high thermal conductivity, ultra-violet light emission, etc. All these properties build up the solid basis for their future technological applications. Chemical modification is also a decent approach to adjust the BNNTs properties. In recent years the yield of multi-walled BNNTs has reached the grams level, that can allow their detailed chemical functionalization studies. So far, many kinds of functionalizations through different weak interactions and covalent bonding were developed. These treatments improved BNNT dispersions in solvents and extended their fields of applications. Moreover, some application-related studies on multi-walled BNNTs, such as composites fabrication, hydrogen storage, biocompatibility, and mechanical, and electrical breakdown tests have also been started in recent years.

Boron nitride nanotubes

Hexagonal boron nitride monolayers on metal supports: Versatile templates for atoms, molecules and nanostructures

Engineering of the optical, electronic, and magnetic properties of hexagonal boron nitride (h-BN) nanomaterials via oxygen doping and functionalization has been envisaged in theory However, it is still unclear as to what extent these properties can be altered using such methodology because of the lack of significant experimental progress and systematic theoretical investigations Therefore, here, comprehensive theoretical predictions verified by solid experimental confirmations are provided, which unambiguously answer this long-standing question Narrowing of the optical bandgap in h-BN nanosheets (from ≈55 eV down to 21 eV) and the appearance of paramagnetism and photoluminescence (of both Stokes and anti-Stokes types) in them after oxygen doping and functionalization are discussed These results are highly valuable for further advances in semiconducting nanoscale electronics, optoelectronics, and spintronics

Tuning of the Optical, Electronic, and Magnetic Properties of Boron Nitride Nanosheets with Oxygen Doping and Functionalization.

Tuning of band gap of hexagonal boron nitride (h-BN) has been a challenging problem due to its inherent chemical stability and inertness. In this work, we report the changes in band gaps in a few layers of chemical vapor deposition processed as-grown h-BN using a simple oxygen plasma treatment. Optical absorption spectra show a trend of band gap narrowing monotonically from 6 eV of pristine h-BN to 4.31 eV when exposed to oxygen plasma for 12 s. The narrowing of band gap causes the reduction in electrical resistance by ∼100 fold. The x-ray photoelectron spectroscopy results of plasma treated hexagonal boron nitride surface show the predominant doping of oxygen for the nitrogen vacancy. Energy sub-band formations inside the band gap of h-BN, due to the incorporation of oxygen dopants, cause a red shift in absorption edge corresponding to the band gap narrowing.

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Band gap effects of hexagonal boron nitride using oxygen plasma

Tuning the magnetic and transport properties of boron-nitride nanotubes via oxygen-doping

Magnetism in germanium-doped boron-nitride nanotubes

By considering the competition of thermal activation and effective pinning, a general description of temperature dependent resistivity under magnetic fields has been deduced in high temperature superconductors. The temperature dependent resistivity can be expressed as ρ = ρn(1−x)s, with the energy ratio x = Ueff(T,B)/kBT. This model is a consistent description of vortex glass theory. In the experiments of both single-phase Hg-1223 and Tl-2212 thin film superconductors, the temperature dependent resistivity under various magnetic fields can be scaled onto a straight line by plotting lnρ versus ln((T− Tg)/(Tc− Tg)) with the slope s. This scaling behaviour is striking evidence of the proposed model.

Scaling of the vortex-liquid resistivity in high temperature superconductors

Corrugation-induced metal-semiconductor transition in single-wall carbon nanotubes with a small radius

A bridge junction can be made by cutting a bulk ceramic superconductor into the right sizes. Using this sort of bridge, both dc and ac Josephson effects are confirmed in liquid nitrogen. We have observed microwave-induced steps at either nhf/2e or 2nhf/2e, where n is an integral, as well as the modulation of a critical supercurrent with the increase of microwave power or the externally applied magnetic field.

J. Wu

Papers

Tuning the magnetic and transport properties of boron-nitride nanotubes via oxygen-doping

Magnetism in germanium-doped boron-nitride nanotubes

Scaling of the vortex-liquid resistivity in high temperature superconductors

Corrugation-induced metal-semiconductor transition in single-wall carbon nanotubes with a small radius

The Josephson Effect in a Ceramic Bridge at Liquid Nitrogen Temperature