Boron Nitride Nanosheets Improve Sensitivity and Reusability of Surface Enhanced Raman Spectroscopy

Surface enhanced Raman spectroscopy (SERS) is a useful multidisciplinary analytic technique. However, it is still a challenge to produce SERS substrates that are highly sensitive, reproducible, stable, reusable, and scalable. Here, we demonstrate that atomically thin boron nitride (BN) nanosheets have many unique and desirable properties to help solve this challenge. The synergic effect of the atomic thickness, high flexibility, stronger surface adsorption capability, electrical insulation, impermeability, high thermal and chemical stability of BN nanosheets can increase the Raman sensitivity by up to two orders, and in the meantime attain long-term stability and extraordinary reusability not achievable by other materials. These advances will greatly facilitate the wider use of SERS in many fields

Gas protection of two-dimensional nanomaterials from high-energy impacts

Two-dimensional (2D) materials can be produced using ball milling with the help of liquid surfactants or solid exfoliation agents, as ball milling of bulk precursor materials usually produces nanosized particles because of high-energy impacts. Post-milling treatment is thus needed to purify the nanosheets. We show here that nanosheets of graphene, BN, and MoS2 can be produced by ball milling of their bulk crystals in the presence of ammonia or a hydrocarbon ethylene gas and the obtained nanosheets remain flat and maintain their single-crystalline structure with low defects density even after a long period of time; post-milling treatment is not needed. This study does not just demonstrate production of nanosheets using ball milling, but reveals surprising indestructible behaviour of 2D nanomaterials in ammonia or hydrocarbon gas under the high-energy impacts; in other milling atmospheres such as air, nitrogen or argon the same milling treatment produces nanosized particles. A systematic study reveals chemisorption of ammonia and hydrocarbon gases and chemical reactions occurring at defect sites, which heal the defects by saturating the dangling bonds. Density functional theory was used to understand the mechanism of mechanochemical reactions. Ball milling in ammonia or hydrocarbon is promising for mass-production of pure nanosheets

Synthesis and applications of two-dimensional nanomaterials

&nbsp;A new method has been invented to produce two-dimensional (2D) materials in large quantities. In addition to that, the biocompatibility of boron nitride (BN) nanosheets was investigated. Furthermore, for the first time, we have successfully produced thermally isotropic bulk BN from BN nanosheets using a spark plasma sintering (SPS) technique.<br /

Superb storage and energy saving separation of hydrocarbon gases in boron nitride nanosheets via a mechanochemical process

Light hydrocarbon olefin and paraffin gas mixtures are produced during natural gas or petrochemical processing. The petrochemical industry separates hydrocarbon gas mixtures by using an energy-intensive cryogenic distillation process, which accounts for 15% of global energy consumption [1]. The development of a new energy-saving separation process is needed to reduce the energy consumption. In this research, we develop a green and low energy mechanochemical separation process in which boron nitride (BN) powders were ball milled at room temperature in the atmosphere of an alkyne or olefin and paraffin mixture gas. BN selectively adsorbs a much greater quantity of alkyne and olefin gas over paraffin gases, and thus the paraffin gas is purified after the ball milling process. The adsorbed olefin gas can be recovered from the BN via a low-temperature heating process. The mechanochemical process produces extremely high uptake capacities of alkyne and olefin gases in the BN (708 cm3/g for acetylene (C2H2) and 1048 cm3/g for ethylene (C2H4)) respectively. To the best of our knowledge, assisted by ball milling, BN nanosheets have achieved the highest uptake capacities for alkyne/olefin gases, which are superior to all other materials reported so far. Chemical analysis reveals that large amounts of olefin gases were quasi-chemically adsorbed on the in-situ formed BN nanosheets via C–N bond formation, whereas small amount of paraffin gases was physically adsorbed on BN nanoparticles. This scalable mechanochemical process has great potential as an industrial separation method and can realize substantial energy savings.</p

In situ prepared V2O5/graphene hybrid as a superior cathode material for lithium-ion batteries

Developing synthetic methods for graphene based cathode materials, with low cost and in an environmentally friendly way, is necessary for industrial production. Although the precursor of graphene is abundant on the earth, the most common precursor of graphene is graphene oxide (GO), and it needs many steps and reagents for transformation to graphite. The traditional approach for the synthesis of GO needs many chemicals, thus leading to a high cost for production and potentially great amounts of damage to the environment. In this study, we develop a simple wet ball-milling method to construct a V2O5/graphene hybrid structure in which nanometre-sized V2O5 particles/aggregates are well embedded and uniformly dispersed into the crumpled and flexible graphene sheets generated by in situ conversion of bulk graphite. The combination of V2O5 nanoparticles/aggregates and in situ graphene leads the hybrid to exhibit a markedly enhanced discharge capacity, excellent rate capability, and good cycling stability. This study suggests that nanostructured metal oxide electrodes integrated with graphene can address the poor cycling issues of electrode materials that suffer from low electronic and ionic conductivities. This simple wet ball-milling method can potentially be used to prepare various graphene based hybrid electrodes for large scale energy storage applications