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Controlled surface modification of poly(methyl methacrylate) film by fluoroalkyl end-capped vinyltrimethoxysilane oligomeric silica/hexagonal boron nitride nanocomposites
摘要： Fluoroalkyl end-capped vinyltrimethoxysilane oligomer [RF-(CH2CHSi(OMe)3)n-RF; n = 2, 3; RF = CF(CF3)OC3F7] undergoes sol–gel reactions in the presence of hexagonal boron nitride (h-BN) nanoparticles under alkaline or acidic conditions at room temperature to afford the corresponding fluorinated oligomeric silica/h-BN nanocomposites in good isolated yields (≥ 80%), respectively. The fluorinated oligomeric silica/h-BN nanocomposites thus obtained were found to exhibit a good dispersibility toward the traditional organic media including water. These two kinds of fluorinated nanocomposites were applied to the surface modification of poly(methyl methacrylate) (PMMA). The fluorinated nanocomposites prepared under alkaline conditions can give not only a good oleophobic characteristic imparted by longer fluoroalkyl groups in the composites but also the higher fluorescent emission related to the presence of h-BN on the only surface side of the modified PMMA film. In contrast, the fluorinated nanocomposites prepared under acidic conditions can provide a good oleophobic characteristic and a higher fluorescent emission on both the surface and even on the reverse side of the PMMA film. Such unique controlled surface modification ability will be discussed by 29Si solid-state NMR spectra of these two types of the nanocomposites.
关键词： Surface arrangement ability,Fluorescent ability,Oleophobicity,Hexagonal boron nitride,Surface modification,Fluorinated oligomeric nanocomposite,PMMA
更新于2025-09-16 10:30:52
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Probing Polaritons in 2D Materials with Synchrotron Infrared Nanospectroscopy
摘要： Polaritons, which are quasiparticles composed of a photon coupled to an electric or magnetic dipole, are a major focus in nanophotonic research of van der Waals (vdW) crystals and their derived 2D materials. For the variety of existing vdW materials, polaritons can be active in a broad range of the electromagnetic spectrum (meVs to eVs) and exhibit momenta much higher than the corresponding free-space radiation. Hence, the use of high momentum broadband sources or probes is imperative to excite those quasiparticles and measure the frequency-momentum dispersion relations, which provide insights into polariton dynamics. Synchrotron infrared nanospectroscopy (SINS) is a technique that combines the nanoscale spatial resolution of scattering-type scanning near-field optical microscopy with ultrabroadband synchrotron infrared radiation, making it highly suitable to probe and characterize a variety of vdW polaritons. Here, the advances enabled by SINS on the study of key photonic attributes of far- and mid-infrared plasmon- and phonon-polaritons in vdW and 2D crystals are reviewed. In that context the SINS technique is comprehensively described and it is demonstrated how fundamental polaritonic properties are retrieved for a range of atomically thin systems including hBN, MoS2, graphene and 2D heterostructures.
关键词： s-SNOM,hexagonal boron nitride,far-infrared SINS,2D materials,polaritons,infrared synchrotron nanospectroscopy,graphene
更新于2025-09-12 10:27:22
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Pt Nanoclusters Sandwiched between Hexagonal Boron Nitride and Nanographene as van der Waals Heterostructures for Optoelectronics
摘要： We report on the formation of nanoscopic heterostructures composed of the semimetal graphene, the metal platinum, and the insulator hexagonal boron nitride (h-BN). Both graphene and h-BN are chemically inert 2D materials with similar geometric but different electronic properties. Between these materials, a Pt nanoparticle array was encapsulated. Thereby, the h-BN/Rh(111) nanomesh served as a template for a well-ordered array of Pt nanoclusters, which were overgrown with graphene, forming single nano-heterostructures. We investigated this process in situ by high-resolution, synchrotron radiation-based XPS, and NEXFAS. The nanographene layers proofed tight against CO under the tested conditions. These nano-heterostructures could find a possible application in optoelectronics or as data storage material. At the same time, our approach represents a new route for the synthesis of nanographene.
关键词： nanoclusters,optoelectronics,hexagonal boron nitride,nanographene,data storage,graphene,platinum
更新于2025-09-12 10:27:22
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[IEEE 2019 IEEE 32nd International Conference on Micro Electro Mechanical Systems (MEMS) - Seoul, Korea (South) (2019.1.27-2019.1.31)] 2019 IEEE 32nd International Conference on Micro Electro Mechanical Systems (MEMS) - High-Frequency Hexagonal Boron Nitride (h-BN) Phononic Waveguides
摘要： This digest paper presents the first experimental demonstration of nanoscale phononic waveguides based on a two-dimensional (2D) layered crystalline material, namely hexagonal boron nitride (h-BN). Taking advantage of the planar geometry, the challenges in nanofabrication of 2D materials can be circumvented through a heterogeneous integration approach. Rich wave propagation characteristics of h-BN phononic waveguides are revealed in both finite element method (FEM) simulations and transmission measurements. Numerical analysis further indicates that the frequency response of the designed h-BN phononic waveguides can be finely tuned by varying the thickness or tension level of the h-BN crystals, across the high frequency (HF, 3?30 MHz) to very high frequency (VHF, 30?300 MHz) bands. Manipulation and guiding of high frequency mechanical waves on integratable 2D device platforms will open new opportunities in radio-frequency (RF) signal processing and on-chip quantum information technologies.
关键词： phononic waveguides,very high frequency (VHF),radio-frequency (RF) signal processing,quantum information technologies,high frequency (HF),hexagonal boron nitride (h-BN)
更新于2025-09-12 10:27:22
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Highly Efficient and Thermal-Stable QD-LEDs Based on Quantum Dots-SiO <sub/>2</sub> -BN Nanoplate Assemblies
摘要： Silica encapsulation effectively elevates the resistance of quantum dots (QDs) against water and oxygen. However, QDs-SiO2 composites present low thermal conductivity and strong thermal accumulation, leading to considerable fluorescent quenching of QDs in optoelectronic devices at high power. Here, a sandwich structural QDs-SiO2-BN nanoplate assembly material (QDs-SiO2-BNAs) is developed to reduce the thermal quenching and enhance the stability of QDs in LEDs. The QDs-SiO2-BNAs is fabricated by embedding QDs-SiO2 into the interlayer of layer-by-layer assembled BN nanoplates, and the BN nanoplates are pretreated by SiO2 encapsulation to strengthen the interaction with QDs-SiO2. This assembly structure endows the QDs with fast heat dissipation and double surface protection against air. The medium power QDs-converted LEDs (QD-LEDs) fabricated by directly on-chip packaging of the QDs-SiO2-BNAs gain 44.2 ℃ temperature reduction at 0.5 W in comparison with conventional QD-LEDs. After aging, the resulting QD-LEDs present degradation of only 1.2% under sustained driving for 250 hours. The QD-LEDs also pass the one-week reliability test at 85 ℃ / 85% RH with <±0.01 shift of the color coordinates, demonstrating the profound potential of the QDs-SiO2-BNAs in LED lighting and display applications.
关键词： stability,quantum dots,boron nitride,assembly,light-emitting diodes
更新于2025-09-12 10:27:22
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Dual growth mode of boron nitride nanotubes in high temperature pressure laser ablation
摘要： The morphological analysis of the end of boron nitride nanotubes (BNNTs) using high-resolution transmission electron microscopy (HR-TEM) can provide valuable insight into the growth mechanism in high temperature pressure (HTP) laser ablation where the best quality of BNNT materials can be obtained so far. Two growth modes of BNNT coexisting during the synthesis process have been proposed based on HR-TEM observation and length analysis. One is the root growth mode, in which boron nitride (BN) species formed via the surface interaction between surrounding N2 molecules and boron nanodroplets incorporate into the tubular structure. Another mode called open-end growth mode means the prolongation of tube growth from the exposed BN edge surrounding the surface of boron nanodroplets which is constructed by the heterogeneous nucleation of absorbed BN radicals from the gas plume. The statistical data, the proportions of end structures and the length of BNNTs, could be fitted to two growth modes, and the open-end growth mode is found to be especially effective in producing longer nanotubes with a higher growth rate. The scientific understanding of the growth mechanism is believed to provide the control for optimized production of BNNTs.
关键词： growth mechanism,high temperature pressure laser ablation,open-end growth mode,root growth mode,boron nitride nanotubes,HR-TEM
更新于2025-09-12 10:27:22
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Tunable reflected group delay from the graphene/hBN heterostructure at infrared frequencies
摘要： In this paper, we theoretically investigated the re?ected group delay from the graphene/hexagonal boron nitride (hBN) heterostructure in the infrared band. Since the signi?cant Lorentz resonance characteristic of the dielectric constant of hBN in the bands of near 7.28 μm and 12.72 μm, the new graphene/hBN heterostructure is used to realize ?exible switching of re?ected group delay by the Lorentz resonance mechanism. It is shown that the re?ected group delay can be e?ectively enhanced by tuning the Fermi energy or the number of graphene layers. Moreover, the re?ected group delay can be tuned positive or negative depending on the hBN thickness or incident angle. These results will be useful for design of graphene-based optical delay devices in the infrared band.
关键词： Graphene,Hexagonal boron nitride (hBN),Group delay,Infrared band
更新于2025-09-12 10:27:22
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Fabrication and characterization of quantum dot devices based on tetralayer graphene/hexagonal boron nitride heterostructures
摘要： We report on low temperature carrier transport property of quantum dot devices based on hexagonal boron nitride-encapsulated tetralayer graphene heterostructures. In the device with single dot geometry, we demonstrate a stochastic Coulomb blockade, suggesting formation of multiple dots coupled each other in series/parallel. Under a perpendicular magnetic field, the overlapping Coulomb diamonds are lifted at zero bias voltage and the charging energy is decreased. These imply the suppression of multiple dots behavior. Our results pave a way toward the investigation of interlayer correlation on single electron transport in few-layer graphene quantum dots.
关键词： magnetic field,hexagonal boron nitride,Coulomb blockade,tetralayer graphene,quantum dot
更新于2025-09-12 10:27:22
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pH-Controlled fluorescence switching in water-dispersed polymer brushes grafted to modified boron nitride nanotubes for cellular imaging
摘要： pH-Switchable, fluorescent, hybrid, water-dispersible nanomaterials based on boron nitride nanotubes (BNNTs) and grafted copolymer brushes (poly(acrylic acid-co-fluorescein acrylate) – P(AA-co-FA)) were successfully fabricated in a two-step process. The functionalization of BNNTs was confirmed by spectroscopic, gravimetric and imaging techniques. In contrast to “pure” BNNTs, P(AA-co-FA)-functionalized BNNTs demonstrate intense green fluorescence emission at 520 nm. Under neutral or alkaline pH values, P(AA-co-FA)-functionalized BNNTs are highly emissive in contrast to acidic pH conditions where the fluorescent intensity is absent or low. No increase in the absorption was observed when the suspension pH was increased from 7 to 10. The functionalized BNNTs are easily taken up by human normal prostate epithelium (PNT1A) and human prostate cancer cell lines (DU145) and are suitable for further evaluation in cellular imaging applications.
关键词： pH switching,surface modification,cellular imaging,fluorescence,boron nitride nanotubes,polymer brushes
更新于2025-09-12 10:27:22
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Synthesis of Perovskite CsPbBr <sub/>3</sub> Quantum Dots/Porous Boron Nitride Nanofiber Composites with Improved Stability and Their Reversible Optical Response to Ammonia
摘要： All-inorganic CsPbX3 (X = Cl, Br, I) perovskite quantum dots (QDs) have great potential for various applications due to their excellent photoluminescence properties. However, poor stability under long-term storage hinders their applications. Herein we report the utilization of porous boron nitride nanofibers (BNNFs) as a promising carrier for anchoring of CsPbBr3 QDs. Due to the good dispersion and immobilization of CsPbBr3 QDs, the resulting CsPbBr3/BNNF composites show excellent photostability and superior long-term storage stability in an air environment. Moreover, the CsPbBr3/BNNF composites exhibit an interesting ammonia-responsive behavior: i.e., a distinct decrease in photoluminescence intensity upon exposure to ammonia gas and the subsequent photoluminescence recovery after post-treatment in nitrogen gas. Even after treatment with ammonia gas for 3 h, the composites can still be recovered under nitrogen gas treatment. The fast response, reversibility, and stability of CsPbBr3/BNNF composites in the presence of ammonia gas could inspire a broader range of applications.
关键词： photostability,reversible optical response,perovskite quantum dots,boron nitride nanofibers,ammonia-responsive behavior
更新于2025-09-12 10:27:22