المؤلفون: Fong, C. F., Yamashita, D., Fang, N., Fujii, S., Chang, Y. -R., Taniguchi, T., Watanabe, K., Kato, Y. K.

مصطلحات موضوعية: Physics - Optics, Physics - Applied Physics

الوصف: Two-dimensional (2D) van der Waals layered materials with intriguing properties are increasingly being adopted in hybrid photonics. The 2D materials are often integrated with photonic structures including cavities to enhance light-matter coupling, providing additional control and functionality. The 2D materials, however, needs to be precisely placed on the photonic cavities. Furthermore, the transfer of 2D materials onto the cavities could degrade the cavity quality $(Q)$ factor. Instead of using prefabricated PhC nanocavities, we demonstrate a novel approach to form a hybrid nanocavity by partially covering a PhC waveguide post-fabrication with a suitably-sized 2D material flake. We successfully fabricated such hybrid nanocavity devices with hBN, WSe$_2$ and MoTe$_2$ flakes on silicon PhC waveguides, obtaining $Q$ factors as high as $4.0\times10^5$. Remarkably, even mono- and few-layer flakes can provide sufficient local refractive index modulation to induce nanocavity formation. Since the 2D material is spatially self-aligned to the nanocavity, we have also managed to observe cavity PL enhancement in a MoTe$_2$ hybrid cavity device, with a cavity Purcell enhancement factor of about 15. Our results highlights the prospect of using such 2D materials-induced PhC nanocavity to realize a wide range of photonic components for hybrid devices and integrated photonic circuits.
Comment: 9 pages, 4 figures

الوصول الحر: http://arxiv.org/abs/2308.10566Test

المؤلفون: Fang, N., Chang, Y. R., Fujii, S., Yamashita, D., Maruyama, M., Gao, Y., Fong, C. F., Kozawa, D., Otsuka, K., Nagashio, K., Okada, S., Kato, Y. K.

المصدر: Nat. Commun. 15, 2871 (2024)

مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics

الوصف: The development of van der Waals heterostructures has introduced unconventional phenomena that emerge at atomically precise interfaces. For example, interlayer excitons in two-dimensional transition metal dichalcogenides show intriguing optical properties at low temperatures. Here we report on room-temperature observation of interface excitons in mixed-dimensional heterostructures consisting of two-dimensional tungsten diselenide and one-dimensional carbon nanotubes. Bright emission peaks originating from the interface are identified, spanning a broad energy range within the telecommunication wavelengths. The effect of band alignment is investigated by systematically varying the nanotube bandgap, and we assign the new peaks to interface excitons as they only appear in type-II heterostructures. Room-temperature localization of low-energy interface excitons is indicated by extended lifetimes as well as small excitation saturation powers, and photon correlation measurements confirm single-photon emission. With mixed-dimensional van der Waals heterostructures where band alignment can be engineered, new opportunities for quantum photonics are envisioned.
Comment: 8 pages, 4 figures

الوصول الحر: http://arxiv.org/abs/2307.15399Test

المؤلفون: Fang, N., Yamashita, D., Fujii, S., Maruyama, M., Gao, Y., Chang, Y. R., Fong, C. F., Otsuka, K., Nagashio, K., Okada, S., Kato, Y. K.

المصدر: Nat. Commun. 14, 8152 (2023)

مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics

الوصف: Nanomaterials exhibit unique optical phenomena, in particular excitonic quantum processes occurring at room temperature. The low dimensionality, however, imposes strict requirements for conventional optical excitation, and an approach for bypassing such restrictions is desirable. Here we report on exciton transfer in carbon-nanotube/tungsten-diselenide heterostructures, where band alignment can be systematically varied. The mixed-dimensional heterostructures display a pronounced exciton reservoir effect where the longer-lifetime excitons within the two-dimensional semiconductor are funneled into carbon nanotubes through diffusion. This new excitation pathway presents several advantages, including larger absorption areas, broadband spectral response, and polarization-independent efficiency. When band alignment is resonant, we observe substantially more efficient excitation via tungsten diselenide compared to direct excitation of the nanotube. We further demonstrate simultaneous bright emission from an array of carbon nanotubes with varied chiralities and orientations. Our findings show the potential of mixed-dimensional heterostructures and band alignment engineering for energy harvesting and quantum applications through exciton manipulation.
Comment: 9 pages, 4 figures

الوصول الحر: http://arxiv.org/abs/2307.07124Test

المؤلفون: Fang, N., Yamashita, D., Fujii, S., Otsuka, K., Taniguchi, T., Watanabe, K., Nagashio, K., Kato, Y. K.

المصدر: Adv. Opt. Mater. 10, 2200538 (2022)

مصطلحات موضوعية: Physics - Optics, Condensed Matter - Materials Science

الوصف: The unique optical properties of two-dimensional layered materials are attractive for achieving increased functionality in integrated photonics. Owing to the van der Waals nature, these materials are ideal for integrating with nanoscale photonic structures. Here we report on carefully designed air-mode silicon photonic crystal nanobeam cavities for efficient control through two-dimensional materials. By systematically investigating various types and thickness of two-dimensional materials, we are able to show that enhanced responsivity allows for giant shifts of the resonant wavelength. With atomically precise thickness over a macroscopic area, few-layer flakes give rise to quantization of the mode shifts. We extract the dielectric constant of the flakes and find that it is independent of the layer number down to a monolayer. Flexible reconfiguration of a cavity is demonstrated by stacking and removing ultrathin flakes. With an unconventional cavity design, our results open up new possibilities for photonic devices integrated with two-dimensional materials.
Comment: 8 pages, 5 figures

الوصول الحر: http://arxiv.org/abs/2201.06684Test

المؤلفون: Krushynska, A. O., Janbaz, S., Oh, J. H., Wegener, M., Fang, N. X.

المصدر: Applied Physics Letters, 123 (24), Art.-Nr.: 240401 ; ISSN: 0003-6951, 1077-3118

مصطلحات موضوعية: ddc:530, Physics, info:eu-repo/classification/ddc/530

العلاقة: info:eu-repo/semantics/altIdentifier/wos/001123966200001; info:eu-repo/semantics/altIdentifier/issn/0003-6951; info:eu-repo/semantics/altIdentifier/issn/1077-3118; https://publikationen.bibliothek.kit.edu/1000168482Test

الإتاحة: https://doi.org/10.1063/5.0189043Test
https://publikationen.bibliothek.kit.edu/1000168482Test

المؤلفون: Otsuka, K., Fang, N., Yamashita, D., Taniguchi, T., Watanabe, K., Kato, Y. K.

المصدر: Nat. Commun. 12, 3138 (2021)

مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics

الوصف: When continued device scaling reaches the ultimate limit imposed by atoms, technology based on atomically precise structures is expected to emerge. Device fabrication will then require building blocks with identified atomic arrangements and assembly of the components without contamination. Here we report on a versatile dry transfer technique for deterministic placement of optical-quality carbon nanotubes. Single-crystalline anthracene is used as a medium which readily sublimes by mild heating, leaving behind clean nanotubes and thus enabling bright photoluminescence. We are able to position nanotubes of a desired chirality with a sub-micron accuracy under in-situ optical monitoring, thereby demonstrating deterministic coupling of a nanotube to a photonic crystal nanobeam cavity. A cross junction structure is also designed and constructed by repeating the nanotube transfer, where intertube exciton transfer is observed. Our results represent an important step towards development of devices consisting of atomically precise components and interfaces.
Comment: 9 pages, 5 figures

الوصول الحر: http://arxiv.org/abs/2012.01741Test

المؤلفون: Fang, N., Toyoda, S., Taniguchi, T., Watanabe, K., Nagashio, K.

المصدر: Adv. Func. Mater. 2019, 29, 1904465

مصطلحات موضوعية: Physics - Applied Physics, Condensed Matter - Materials Science

الوصف: Two-dimensional (2D) layered materials are promising for replacing Si to overcome the scaling limit of recent ~5 nm-length metal-oxide-semiconductor field-effect transistors (MOSFETs). However, the insulator/2D channel interface severely degrades the performance of 2D-based MOSFETs, and the origin of the degradation remains largely unexplored. Here, we present the full energy spectra of the interface state densities (Dit) for both n- and p- MoS2 FETs, based on the comprehensive and systematic studies, i.e., thickness range from monolayer to bulk and various gate stack structures including 2D heterostructure with h-BN as well as typical high-k top-gate structure. For n-MoS2, Dit around the mid gap is drastically reduced to 5*10^11 cm-2eV-1 for the heterostructure FET with h-BN from 5*10^12 cm-2eV-1 for the high-k top-gate MoS2 FET. On the other hand, Dit remains high, ~10^13 cm-2eV-1, even for the heterostructure FET for p-MoS2. The systematic study elucidates that the strain induced externally through the substrate surface roughness and high-k deposition process is the origin for the interface degradation on the conduction band side, while sulfur-vacancy-induced defect-states dominate the interface degradation on the valance band side. The present understanding on the interface properties provides the key to further improving the performance of 2D FETs.

الوصول الحر: http://arxiv.org/abs/2006.10440Test

المؤلفون: Fang, N., Otsuka, K., Ishii, A., Taniguchi, T., Watanabe, K., Nagashio, K., Kato, Y. K.

المصدر: ACS Photonics 7, 1773 (2020)

مصطلحات موضوعية: Condensed Matter - Mesoscale and Nanoscale Physics

الوصف: Hexagonal boron nitride is widely used as a substrate for two-dimensional materials in both electronic and photonic devices. Here, we demonstrate that two-dimensional hexagonal boron nitride is also an ideal substrate for one-dimensional single-walled carbon nanotubes. Nanotubes directly attached to hexagonal boron nitride show bright photoluminescence with narrow linewidth at room temperature, comparable to air-suspended nanotubes. Using photoluminescence excitation spectroscopy, we unambiguously assign the chiralities of nanotubes on boron nitride by tracking individual tubes before and after contact with boron nitride. Although hexagonal boron nitride has a low dielectric constant and is attached to only one side of the nanotubes, we observe that optical transition energies are redshifted as much as ~50 meV from the air-suspended nanotubes. We also perform statistical measurements on more than 400 tubes, and the redshifts are found to be dependent on tube diameter. This work opens up new possibilities for all-solid-state carbon nanotube photonic devices by utilizing hexagonal boron nitride substrates.
Comment: 7 pages, 5 figures

الوصول الحر: http://arxiv.org/abs/2003.03054Test

المؤلفون: Hu L, Xu J, Zhang W, Wang J, Fang N, Luo Y, Xu L, Liu J, Zhang Y, Ran H, Guo D, Zhou J

المصدر: International Journal of Nanomedicine, Vol Volume 17, Pp 5229-5246 (2022)

مصطلحات موضوعية: low-intensity focused ultrasound, thrombolysis, pfh, rtpa, phase transition, Medicine (General), R5-920

الوصف: Liu Hu1,2 *, Jie Xu1 *, Wenli Zhang,1,2 Junrui Wang,1,2 Ni Fang,1,2 Ying Luo,1,2 Lian Xu,1,2 Jia Liu,1 Yu Zhang,1 Haitao Ran,3 Dajing Guo,1 Jun Zhou1 1Department of Radiology, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, People’s Republic of China; 2Chongqing Key Laboratory of Ultrasound Molecular Imaging & Department of Ultrasound, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, People’s Republic of China; 3Department of Ultrasound, Institute of Ultrasound Imaging, The Second Affiliated Hospital of Chongqing Medical University, Chongqing, People’s Republic of China*These authors contributed equally to this workCorrespondence: Jun Zhou, Tel +86 23 6288 7295, Email zhoujun@hospital.cqmu.edu.cnBackground and Objective: Thrombosis is a common disease that poses a great threat to life and health. Most thrombolytic effects of traditional treatments or nanomedicine are not efficient or safe enough. Therefore, we designed a nanoparticle (NP) with a combination of a phase transition material and thrombolytic drugs for efficient and safe thrombolysis.Methods: A thrombus fibrin-targeted and phase transition NP was designed and contained perfluorohexane (PFH) and the thrombolytic drug rtPA core, with CREKA polypeptides attached to the shell of the PLGA NPs. Characterization of the phase transition and ultrasound imaging of the NPs was carried out under low-intensity focused ultrasound (LIFU). LIFU-responsive drug release in vitro was also explored. Under the synergistic effect of PFH and rtPA, the efficient thrombolysis ability of the NPs was studied in vitro and in vivo. In vivo monitoring of thrombosis and biosafety were also verified.Results: The PPrC NPs had good ultrasound imaging ability under LIFU irradiation and were related to the phase transition characteristics of the NPs. CREKA polypeptides can effectively increase the aggregation of the NPs on thrombi. Under static and dynamic conditions in vitro, the “liquid to gas” transformation effect of PFH can perform the destruction function of the excavator at the thrombus site and promote the specific release of rtPA, and the subsequent rtPA drug thrombolysis can further fully dissolve the thrombus. In vivo experiments showed that the NPs can monitor the formation of thrombi and have good thrombolytic effects, with significantly reduced bleeding side effects. The biochemical indexes of the rats were within normal limits after treatment.Conclusion: PPrC NPs loaded with PFH and rtPA combining a mechanical way of blasting with thrombolytic drugs may be a promising new and reliable approach for thrombus monitoring and treatment.Keywords: low-intensity focused ultrasound, thrombolysis, PFH, rtPA, phase transition

وصف الملف: electronic resource

العلاقة: https://www.dovepress.com/a-synergistic-and-efficient-thrombolytic-nanoplatform-a-mechanical-met-peer-reviewed-fulltext-article-IJNTest; https://doaj.org/toc/1178-2013Test

الوصول الحر: https://doaj.org/article/e899e321c9d24a3c99678054c592f50aTest

المؤلفون: Fang N, Liu J, Hou J, Zhong Y, Luo Y, Hu L, Zhang W, Wang J, Xu J, Zhou J, Zhang Y, Ran H, Guo D

المصدر: International Journal of Nanomedicine, Vol Volume 17, Pp 2019-2039 (2022)

مصطلحات موضوعية: bionic system, low-intensity focused ultrasound, thrombus, magnetic navigation, macrophage, Medicine (General), R5-920

الوصف: Ni Fang,1,2,* Jia Liu,1,* Jingxin Hou,1,2 Yixin Zhong,1,2 Ying Luo,1,2 Liu Hu,1,2 Wenli Zhang,1,2 Junrui Wang,1,2 Jie Xu,1 Jun Zhou,1 Yu Zhang,1 Haitao Ran,2 Dajing Guo1 1Department of Radiology, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010, People’s Republic of China; 2Chongqing Key Laboratory of Ultrasound Molecular Imaging & Department of Ultrasound, Second Affiliated Hospital of Chongqing Medical University, Chongqing, 400010, People’s Republic of China*These authors contributed equally to this workCorrespondence: Dajing Guo, Email guodaj@163.comBackground: Arterial thrombosis is a serious threat to human health. Recently, many thrombus-targeted nanoparticles (NPs) have been constructed for detecting thrombi or monitoring thrombolysis, but their thrombus-targeting performance is limited. Considering this drawback, we designed a specific bionic system with enhanced thrombus-targeting ability.Materials and Methods: In the bionic system, gelatin was chosen as a carrier, and Fe3O4 served as a magnetic navigation medium and a magnetic resonance (MR) imaging agent. The CREKA peptide, which targets fibrin, was conjugated to the surface of gelatin to prepare targeted NPs (TNPs), which were then engulfed by macrophages to construct the bionic system. At the targeted site, the bionic system released its interior TNPs under low-intensity focused ultrasound (LIFU) irradiation. Moreover, the targeting performance was further improved by the conjugated CREKA peptide.Results: In this study, we successfully constructed a bionic system and demonstrated its targeting ability in vitro and in vivo. The results indicated that most TNPs were released from macrophages under LIFU irradiation at 2 W/cm2 for 10 min in vitro. Additionally, the enhanced thrombus-targeting ability, based on the natural tropism of macrophages toward inflammatory thrombi, magnetic navigation and the CREKA peptide, was verified ex vivo and in vivo. Moreover, compared with the bionic system group, the group treated with TNPs had significantly decreased liver and spleen signals in MR images and significantly enhanced liver and spleen signals in fluorescence images, indicating that the bionic system is less likely to be cleared by the reticuloendothelial system (RES) than TNPs, which may promote the accumulation of the bionic system at the site of the thrombus.Conclusion: These results suggest that the magnet-guided bionic system with LIFU responsiveness is an excellent candidate for targeting thrombi and holds promise as an innovative drug delivery system for thrombolytic therapy.Keywords: bionic system, low-intensity focused ultrasound, thrombus, magnetic navigation, macrophage

وصف الملف: electronic resource

العلاقة: https://www.dovepress.com/magnet-guided-bionic-system-with-lifu-responsiveness-and-natural-throm-peer-reviewed-fulltext-article-IJNTest; https://doaj.org/toc/1178-2013Test

الوصول الحر: https://doaj.org/article/d2a64f6021d64e11abb4c0e53a9129c0Test