There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Large-Scale Fabrication of Boron Nitride Nanosheets and Their Utilization in Polymeric Composites with Improved Thermal and Mechanical Properties

Increasing concerns about the atmospheric CO2 concentration and its impact on the environment are motivating researchers to discover new materials and technologies for efficient CO2 capture and conversion. Here, we report a study of the adsorption of CO2, CH4, and H2 on boron nitride (BN) nanosheets and nanotubes (NTs) with different charge states. The results show that the process of CO2 capture/release can be simply controlled by switching on/off the charges carried by BN nanomaterials. CO2 molecules form weak interactions with uncharged BN nanomaterials and are weakly adsorbed. When extra electrons are introduced to these nanomaterials (i.e., when they are negatively charged), CO2 molecules become tightly bound and strongly adsorbed. Once the electrons are removed, CO2 molecules spontaneously desorb from BN absorbents. In addition, these negatively charged BN nanosorbents show high selectivity for separating CO2 from its mixtures with CH4 and/or H2. Our study demonstrates that BN nanomaterials are excellent absorbents for controllable, highly selective, and reversible capture and release of CO2. In addition, the charge density applied in this study is of the order of 1013 cm–2 of BN nanomaterials and can be easily realized experimentally.

Charge-controlled switchable CO2 capture on boron nitride nanomaterials

Reduced graphene oxide (RGO) has proved to be a promising candidate in high-performance gas sensing in ambient conditions. However, trace detection of different kinds of gases with simultaneously high sensitivity and selectivity is challenging. Here, a chemiresistor-type sensor based on 3D sulfonated RGO hydrogel (S-RGOH) is reported, which can detect a variety of important gases with high sensitivity, boosted selectivity, fast response, and good reversibility. The NaHSO3 functionalized RGOH displays remarkable 118.6 and 58.9 times higher responses to NO2 and NH3, respectively, compared with its unmodified RGOH counterpart. In addition, the S-RGOH sensor is highly responsive to volatile organic compounds. More importantly, the characteristic patterns on the linearly fitted response-temperature curves are employed to distinguish various gases for the first time. The temperature of the sensor is elevated rapidly by an imbedded microheater with little power consumption. The 3D S-RGOH is characterized and the sensing mechanisms are proposed. This work gains new insights into boosting the sensitivity of detecting various gases by combining chemical modification and 3D structural engineering of RGO, and improving the selectivity of gas sensing by employing temperature dependent response characteristics of RGO for different gases.

A 3D Chemically Modified Graphene Hydrogel for Fast, Highly Sensitive, and Selective Gas Sensor

We uncover the constitutive relation of graphene and probe the physics of its optical phonons by studying its Raman spectrum as a function of uniaxial strain. We find that the doubly degenerate E(2g) optical mode splits in two components: one polarized along the strain and the other perpendicular. This splits the G peak into two bands, which we call G(+) and G(-), by analogy with the effect of curvature on the nanotube G peak. Both peaks redshift with increasing strain and their splitting increases, in excellent agreement with first-principles calculations. Their relative intensities are found to depend on light polarization, which provides a useful tool to probe the graphene crystallographic orientation with respect to the strain. The 2D and 2D(') bands also redshift but do not split for small strains. We study the Gruneisen parameters for the phonons responsible for the G, D, and D(') peaks. These can be used to measure the amount of uniaxial or biaxial strain, providing a fundamental tool for nanoelectronics, where strain monitoring is of paramount importance.

Uniaxial strain in graphene by Raman spectroscopy: G peak splitting, Grüneisen parameters, and sample orientation

Investigation of hexagonal boron nitride nanosheet (BNNS)/plasmonic nanoparticle (NP) composites is of crucial importance for developing plasmaron-based nanodevices. In this study, a simple and effective way for depicting the fabrication of BNNS/Au NP nanocomposites is reported. Diblock copolymer-based NP arrays exhibiting high hexagonal ordering and offering easy control of particle size are utilized to produce Au NP arrays by directly bonding them to BNNSs on a large scale, allowing to investigate the underlying physics of the metal/BNNS interface. The coupling between BNNSs and plasmonic Au NP arrays, work function, charge transfer and surface-enhanced Raman scattering (SERS) of BNNS phonon modes are explored. It is revealed that local surface plasmon resonance (LSPR) of Au NPs induces an electromagnetic mechanism responsible for enhanced Raman results of BNNSs when placing them below Au NPs. In contrast, essential contribution of chemical enhancement from charge transfer induced by energy realignment at the metal/BNNS interface is manifested in hybrid systems of Au NPs and encapsulated BNNS. This work is the first demonstration on evolution of plasmon resonance and charge-based interactions dependent on metal/BNNS interface, thus providing straightforward implications to further develop BNNS-based plasmonics, optoelectronics, and electronics.

Self-assembly based plasmonic nanoparticle array coupling with hexagonal boron nitride nanosheets.

The capability of hexagonal boron nitride (h-BN) to adsorb gas atoms may stimulate various promising applications in environment remediation and energy storage, while the interactivity with gas molecules yet remains challenging due to its inherent chemical inertness. In this article, we report a feasible and effective route for the scalable synthesis of vertically aligned h-BN nanowalls assisted by reduced graphene oxide (rGO) without metallic catalysts. The average thickness of the fine h-BN nanowalls is few-atomic layers about 3.7 nm, that grow on the large substrate-like flakes transformed from the pristine rGO. The hierarchical h-BN nanowalls exhibit an enhanced gas adsorption performance, not only through physisorption owing to the synergistic combination of different porous geometries, but also through chemisorption via the open edge groups. Moreover, it demonstrates a significantly enhanced adsorption of CO2 over CH4 as compared to the h-BN nanosheets with similar sizes. Density functional theory calculations reveal that the -OH edge groups can effectively increase the adsorption capability towards CO2, accompanied by a shortened adsorption distance when the gas molecule is energetically stabilized. The wetting characteristics of h-BN nanowalls was further examined by contact angle goniometry.

Graphene-facilitated synthesized vertically aligned hexagonal boron nitride nanowalls and their gas adsorption properties.

The excellent physical and chemical properties of cubic boron nitride (c-BN) film make it a promising candidate for various industry applications. However, the c-BN film thickness restricts its practical applications in many cases. Thus, it is indispensable to develop an economic, simple and environment-friend way to synthesize high-quality thick, stable c-BN films. High-cubic-content BN films are prepared on silicon (100) substrates by radio frequency (RF) magnetron sputtering from an h-BN target at low substrate temperature. Adhesions of the c-BN films are greatly improved by adding hydrogen to the argon/nitrogen gas mixture, allowing the deposition of a film up to 5-μm thick. The compositions and the microstructure morphologies of the c-BN films grown at different substrate temperatures are systematically investigated with respect to the ratio of H2 gas content to total working gas. In addition, a primary mechanism for the deposition of thick c-BN film is proposed.

https://iopscience.iop.org/article/10.1088/1674-1056/25/10/106801/pdf

Thick c-BN films deposited by radio frequency magnetron sputtering in argon/nitrogen gas mixture with additional hydrogen gas

The invention provides a gas sensitive element based on a hexagonal boron nitride nano sheet/iron oxide nano particle composite material and a preparation method and application thereof, belonging to the technical field of semiconductor materials. According to the invention, the hexagonal boron nitride nano sheet/iron oxide nano particle composite material is used as a gas sensing material, the properties of high thermal conductivity, low thermal expansion coefficient, low dielectric constant, high chemical stability and high specific surface area of hexagonal boron nitride nano sheets are utilized, and the gas sensing performance of the gas sensing element can be improved by combining the high sensitivity of iron oxide nano particles to n-butanol gas. Example results show that when the gas sensitive element based on the hexagonal boron nitride nano sheet/iron oxide nano particle composite material is used for n-butanol gas detection, the response time is 12.6 s, the recovery time is 27 s, and the optimal working temperature is 375 DEG C.

Gas sensitive element based on hexagonal boron nitride nano sheet/iron oxide nano particle composite material and preparation method and application thereof

The invention relates to the field of thin film materials and semiconductor materials, and provides a hexagonal boron nitride thick film based on ion beam sputtering deposition, a preparation method and application. According to the preparation method, the large-area high-quality hexagonal boron nitride thick film is prepared on the surface of a substrate through adopting a method of combining double-ion-beam sputtering deposition with ion beam cleaning, so that the defect that a toxic and flammable precursor is generally used when the hexagonal boron nitride film is prepared through a chemical vapor deposition method is overcome, the problem that the top end of the thick film is cracked, and the adhesion to the substrate is not good due to the fact that the stress is too large when the hexagonal boron nitride thick film is prepared in the prior art is solved, a substrate transition layer and a nitride buffer layer such as catalytic metal/alloy are not used, and parameters of ion beamsputtering deposition are controlled, so that the prepared hexagonal boron nitride thick film has the characteristics that the stability is obviously improved, the structure is more ordered, the impurity content is extremely low, the insulativity is good, and the film thickness can reach 1 um; and the prepared hexagonal boron nitride thick film can be applied to insulating layers, protective layers, dielectric layers, heat dissipation layers and the like in electronic and optoelectronic devices.

Hexagonal boron nitride thick film based on ion beam sputtering deposition, preparation method and application

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