Browsing by Issue Date, starting with "2020-08-05"

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Plasmonic Manipulation of Sodium Chlorate Chiral Crystallization: Directed Chirality Transfer via Contact-Induced Polymorphic Transformation and Formation of Liquid Precursor
(2020-08-05)
Niinomi, Hiromasa
;
Sugiyama, Teruki
;
Tagawa, Miho
;
Ujihara, Toru
;
Omatsu, Takashige
The control of crystallization not only impacts the production of functional crystalline materials or pharmaceuticals but also provides profit to investigate the fundamental mechanism of crystallization. Recently, we have revealed that plasmonic optical tweezers (POT) can "manipulate" the crystallization of a pharmaceutical compound from its aqueous solution by optically trapping molecular clusters, offering a novel strategy to control crystallization. Here we report a variety of unique crystallization phenomena by applying POT to sodium chlorate (NaClO3) chiral crystallization from an aqueous microdroplet loaded on a plasmonic substrate. Plasmon excitation significantly promotes crystallization intermediated by an achiral metastable crystal as a precursor. Also, the direction of the creeping of the resulting chiral crystal can be controlled. By utilizing this phenomenon, we achieved the directed chirality transfer from the chiral crystal to the achiral crystal via a forced contact-induced polymorphic transformation by intentionally making creeping chiral crystal contact with an achiral crystal. Moreover, we captured, by in situ optical microscopic observation, a liquid precursor that intermediates the NaClO3 achiral crystallization for the first time. Our results highlight the plasmonic manipulation of crystallization opening a new door not only to control crystallization but also to investigate the unprecedented fundamental process of crystallization.
Perfect Absorption by an Atomically Thin Crystal
(2020-08-05)
Horng, Jason
;
Martin, Eric W.
;
Chou, Yu-Hsun
;
Courtade, Emmanuel
;
Chang, Tsu-chi
Optical absorption is one of the most fundamental processes in light-matter interactions. The ability to achieve and control high absorption is crucial for a broad range of modern photonic technologies. In nanomaterials of length scales much smaller than a wavelength, optical absorption is typically a weak perturbation. To achieve high absorption, exquisite techniques and structures have been developed, such as coherent interference of multiple laser beams and plasmonic metasurfaces. Here, we show that a robust critical-coupling condition exists to allow perfect absorption of light by a subnanometer-thick two-dimensional semiconductor, when the radiative-decay rate of the exciton resonance balances with its loss rate. We measure an absorption up to 99.6% in a monomolecular MoSe2 crystal placed in front of a flat mirror. We furthermore demonstrate control of the perfect absorption by tuning the exciton-phonon, exciton-exciton, and exciton-photon interactions with temperature, pulsed laser excitation, and a movable mirror, respectively. Our work suggests a mechanism to achieve and control critical coupling in two-dimensional excitonic systems, enabling photonic applications including ultrafast low-power light modulators and sensitive optical sensing.
Sequential Selective Solvent On-Film Annealing: Fabrication of Monolayers of Ordered Anisotropic Polymer Particles
(2020-08-05)
Tseng, Hsiao-Fan
;
Liang, Xiaobin
;
Liu, Chih-Ting
;
Chiu, Yu-Jing
;
Li, Jia-Wei
Although various strategies have been developed to prepare anisotropic polymeric particles, it remains challenging to fabricate monolayers of anisotropic polymeric particles, which can extend the applications of anisotropic particles. Here, we develop a novel and facile approach to fabricate monolayers of anisotropic polymeric particles. Monolayers of polystyrene (PS) microspheres with a mean diameter of 10 mu m are deposited on glass substrates coated with poly(methyl methacrylate) films, followed by sequential selective solvent on-film annealing processes. Monolayers of anisotropic polymeric particles, such as the snowman-like PS particles, are successfully fabricated. Such unique structures possess the long-range ordering of monolayers (the structure factor) and the anisotropic geometry of individual particles (the form factor). The nanomechanical properties of the PS particles are also characterized using atomic force microscopy force volume measurements, showing a decrease in the Young's moduli of the PS particles owing to the looser packing of the polymer chains. This work provides the most facile and versatile strategy by far to fabricate monolayers of ordered anisotropic polymeric particles, which arc inaccessible by other traditional means.
Alternative Strategy to Reduce Surface Recombination for InGaN/GaN Micro-light-Emitting Diodes-Thinning the Quantum Barriers to Manage the Current Spreading
(2020-08-06)
Chang, Le
;
Yeh, Yen-Wei
;
Hang, Sheng
;
Tian, Kangkai
;
Kou, Jianquan
Owing to high surface-to-volume ratio, InGaN-based micro-light-emitting diodes (mu LEDs) strongly suffer from surface recombination that is induced by sidewall defects. Moreover, as the chip size decreases, the current spreading will be correspondingly enhanced, which therefore further limits the carrier injection and the external quantum efficiency (EQE). In this work, we suggest reducing the nonradiative recombination rate at sidewall defects by managing the current spreading effect. For that purpose, we properly reduce the vertical resistivity by decreasing the quantum barrier thickness so that the current is less horizontally spreaded to sidewall defects. As a result, much fewer carriers are consumed in the way of surface nonradiative recombination. Our calculated results demonstrate that the suppressed surface nonradiative recombination can better favor the hole injection efficiency. We also fabricate the mu LEDs that are grown on Si substrates, and the measured results are consistent with the numerical calculations, such that the EQE for the proposed mu LEDs with properly thin quantum barriers can be enhanced, thanks to the less current spreading effect and the decreased surface nonradiative recombination.
Large Submillimeter Assembly of Microparticles with Necklace-like Patterns Formed by Laser Trapping at Solution Surface
(2020-08-06)
Lu, Jia-Syun
;
Wang, Hsuan-Yin
;
Kudo, Tetsuhiro
;
Masuhara, Hiroshi
;
交大名義發表
In colloidal solution, nanoparticles can be optically trapped by a tightly focused laser beam, and they are assembled in a focal spot whose diameter is typically about one micrometer. We herein report that a large submillimeter sized assembly of polystyrene microparticles with necklace-like patterns are prepared by laser trapping at a solution surface. The light propagation outside the focal spot is directly confirmed by 1064 nm backscattering images, and finite difference time domain simulation well supports the idea that an optical potential is expanded outside the focal spot based on light propagation through whispering gallery mode. This demonstration opens a new method for fabrication of a millimeter-order huge assembly by a single tightly focused laser beam.
Improved Constraints on Sterile Neutrino Mixing from Disappearance Searches in the MINOS, MINOS+, Daya Bay, and Bugey-3 Experiments
(2020-08-10)
Adamson, P.
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An, F. P.
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Anghel, I.
;
Aurisano, A.
;
Balantekin, A. B.
Searches for electron antineutrino, muon neutrino, and muon antineutrino disappearance driven by sterile neutrino mixing have been carried out by the Daya Bay and MINOS+ collaborations. This Letter presents the combined results of these searches, along with exclusion results from the Bugey-3 reactor experiment, framed in a minimally extended four-neutrino scenario. Significantly improved constraints on the theta(mu e) mixing angle are derived that constitute the most constraining limits to date over five orders of magnitude in the mass-squared splitting Delta m(41)(2), excluding the 90% C.L. sterile-neutrino parameter space allowed by the LSND and MiniBooNE observations at 90% CLs for Delta m(41)(2) < 13 eV(2). Furthermore, the LSND and MiniBooNE 99% C.L. allowed regions are excluded at 99% CLs for Delta m(41)(2) < 1.6 eV(2).
引導系統工程學生從「會發問」到產生學習熱忱的行動研究
(2020-08-10)
黃育綸
;
黃姿霓
;
交通大學電機系
Nanomolar Detection of H2S in an Aqueous Medium: Application in Endogenous and Exogenous Imaging of HeLa Cells and Zebrafish
(2020-08-11)
Naha, Sanay
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Thirumalaivasan, Natesan
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Garai, Somenath
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Wu, Shu-Pao
;
Velmathi, Sivan
The homeostasis of short-lived reactive species such as hydrogen sulfide/hypochlorous acid (H2S/HOCI) in biological systems is essential for maintaining intercellular balance. An unchecked increase in biological H2S concentrations impedes homeostasis. In this report, we present a molecular probe pyrenebased sulfonyl hydrazone derived from pyrene for the selective detection of H2S endogenously as well as exogenously through a "turn-off' response in water. The structure of the receptor is confirmed by Fourier-transform infrared spectroscopy, H-1 and C-13 nuclear magnetic resonance spectroscopy, electrospray ionization mass spectrometry, and single-crystal X-ray diffraction studies. The receptor shows excellent green emission in both the aqueous phase and solid state. Quenching of green emission of the receptor is observed only when H2S is present in water with a detection limit of 18 nM. Other competing anions and cations do not have any influence on the receptor's optical properties. The efficiency of H2S detection is not negatively impacted by other reactive sulfur species too. The sensing mechanism of H2S follows a chemodosimetric reductive elimination of sulfur dioxide, which is supported by product isolation. The receptor is found to be biocompatible, as evident by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and its utility is extended to endogenous and exogenous fluorescence imaging of HeLa cells and zebrafish.
Intrinsic Ultralow-Threshold Laser Action from Rationally Molecular Design of Metal-Organic Framework Materials
(2020-08-12)
Bera, Krishna Prasad
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Kamal, Saqib
;
Inamdar, Arif I.
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Sainbileg, Batjargal
;
Lin, Hung-, I
Metal-organic frameworks (MOFs) are superior for multiple applications including drug delivery, sensing, and gas storage because of their tunable physiochemical properties and fascinating architectures. Optoelectronic application of MOFs is difficult because of their porous geometry and conductivity issues. Recently, a few optoelectronic devices have been fabricated by a suitable design of integrating MOFs with other materials. However, demonstration of laser action arising from MOFs as intrinsic gain media still remains challenging, even though some studies endeavor on encapsulating luminescence organic laser dyes into the porous skeleton of MOFs to achieve laser action. Unfortunately, the aggregation of such unstable laser dyes causes photoluminescence quenching and energy loss, which limits their practical application. In this research, unprecedently, we demonstrated ultralow-threshold (similar to 13 nJ/cm(2)) MOF laser action by a judicious choice of metal nodes and organic linkers during synthesis of MOFs. Importantly, we also demonstrated that the white random lasing from the beautiful microflowers of organic linkers possesses a porous network, which is utilized to synthesize the MOFs. The highly luminescent broad-band organic linker 1,4-NDC, which itself exhibits a strong white random laser, is used not only to achieve the stimulated emission in MOFs but also to reduce the lasing threshold. Such white lasing has multiple applications from bioimaging to the recently developed versatile Li-Fi technology. In addition, we showed that the smooth facets of MOF microcrystals can show Fabry-Perot resonant cavities having a high quality factor of similar to 10(3) with excellent photostability. Our unique discovery of stable, nontoxic, high-performance MOF laser action will open up a new route for the development of new optoelectronic devices.
Light-Induced Nanowetting: Erasable and Rewritable Polymer Nanoarrays via Solid-to-Liquid Transitions
(2020-08-12)
Lin, Kuan-Ting
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Chen, Yu-Jia
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Huang, Meng-Ru
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Karapala, Vamsi Krishna
;
Ho, Jhih-Hao
Template wetting methods have been widely applied in the preparation of one-dimensional (1D) polymer nanomaterials. The pattern control using the template wetting methods, however, still remains a great challenge, mainly due to the nonselectivity of the polymers toward the environmental triggering. In this work, we present a facile light-induced nanowetting (LIN) method to fabricate patterned nanoarrays using anodic aluminum oxide (AAO) templates. Photoresponsive azobenzene-containing polymers (azopolymers) that exhibit light-induced reversible solidto-liquid transitions are used. Upon exposure to ultraviolet lights, the azopolymer chains can wet the nanopores of the AAO templates in a liquid state via capillary force. The azopolymer chains are then solidified by illuminating them with visible lights, resulting in the formation of azopolymer nanoarrays. Notably, using designed photomasks, the patterns of the nanoarrays can be ingeniously controlled with the characteristic of erasable and rewritable nanostructures.
New gravimetric-only and hybrid geoid models of Taiwan for height modernisation, cross-island datum connection and airborne LiDAR mapping
(2020-08-12)
Hwang, Cheinway
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Hsu, Hung-Jui
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Featherstone, W. E.
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Cheng, Ching-Chung
;
Yang, Ming
This paper combines gravity data collected from airborne, shipborne and terrestrial surveys and those derived from satellite altimetry to determine a high-resolution gravimetric and hybrid geoid model (on a 30" x 30 '' grid) in and around Taiwan. Some 6000 new land gravity values at a 0.03-mGal precision make a notable contribution to the geoid modeling. Shipborne gravity data in waters 20 km offshore Taiwan were collected to improve the coastal geoid precision. In a circular area of 50 km around each of the five major tide gauges in Taiwan, gravity data were measured to improve vertical datum connections between Taiwan and its four offshore islands. Height anomalies were computed first and then converted to geoid heights. At > 2000 benchmarks, we obtained measured geoid heights to assess the gravimetric-only geoid and to create a hybrid geoid. Our assessments and formal errors from least-squares collocation indicate few cm of standard deviations for both geoid models, but the gravimetric geoid has mean differences of up to 20 cm with the measured geoidal heights. The hybrid geoid is used in RTK-VBS orthometric heighting, achieving a 5-cm precision. The gravimetric geoid is used to determine the relative differences in the ocean's mean dynamic topography (MDT) between Taiwan and the four offshore islands, which are also compared with those from oceanic and altimetric methods for estimating MDT. Differences in MDT help to identify 41.7 cm and 54.1 cm offsets in the current vertical datums of Penghu and Lanyu islands. In a low-lying, flood-prone region of southern Taiwan, the hybrid geoid improves LiDAR mapping of sub-zero elevation zones by 20 cm, corresponding to 70 years of sea level rise at an assumed rate of 0.286 cm/yr.
Fano feature induced by a bound state in the continuum via resonant state expansion
(2020-08-13)
Pankin, Pavel S.
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Maksimov, Dmitrii N.
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Chen, Kuo-Ping
;
Timofeev, Ivan, V
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影像與生醫光電研究所
We consider light scattering by an anisotropic defect layer embedded into anisotropic photonic crystal in the spectral vicinity of an optical bound state in the continuum (BIC). Using a resonant state expansion method we derive an analytic solution for reflection and transmission amplitudes. The analytic solution is constructed via a perturbative approach with the BIC as the zeroth order approximation. The solution is found to describe the collapsing Fano feature in the spectral vicinity of the BIC. The findings are confirmed via comparison against direct numerical simulations with the Berreman transfer matrix method.
Attention and Functional Connectivity Among Patients With Early-Stage Subcortical Ischemic Vascular Disease and Alzheimer's Disease
(2020-08-13)
Tu, Min-Chien
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Hsu, Yen-Hsuan
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Yang, Jir-Jei
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Huang, Wen-Hui
;
Deng, Jie Fu
The current study compared attention profiles and functional connectivity of frontal regions in patients with early-stage subcortical ischemic vascular disease (SIVD) and Alzheimer's disease (AD). Twenty patients with SIVD, 32 patients with AD, and 23 subjects with normal cognition (NC) received cognition and resting-state functional MRI (rs-fMRI) evaluations. The Cognitive Abilities Screening Instrument (CASI) was used to assess global cognition, and simple attention, processing speed, divided attention, and vigilance/sustained attention were evaluated using the Digit Span Forward, Trail Making Test, Symbol Digit Modality Test, and Conners Continuous Performance Test, respectively. Voxel-based regional homogeneity (ReHo) derived from rs-fMRI data was analyzed to identify significant clusters, which were further correlated with attention profiles. Although the patients with SIVD and AD had comparable global cognitive ability, those with SIVD exhibited worse divided attention and vigilance/sustained attention than those with AD. Compared with the NC group, the patients with SIVD exhibited decreased ReHo within the right middle frontal gyrus (MFG) and left anterior cingulate gyrus (ACG), whereas the patients with AD exhibited increased ReHo within the right orbital part of frontal regions. Correlations between these three clusters with attention exhibited distinct patterns according to the dementia subtype, as did attention indices with significance in predicting global cognition. In summary, our study suggested that worse attention performance was associated with functional disconnection within the frontal regions among patients with SIVD than in those with AD. Frontal functional disconnection may underlie the pathogenesis responsible for defective divided attention, vigilance/sustained attention, and notable within-group variations identified in SIVD.
Giant photothermal nonlinearity in a single silicon nanostructure
(2020-08-14)
Duh, Yi-Shiou
;
Nagasaki, Yusuke
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Tang, Yu-Lung
;
Wu, Pang-Han
;
Cheng, Hao-Yu
Silicon photonics have attracted significant interest because of their potential in integrated photonics components and all-dielectric meta-optics elements. One major challenge is to achieve active control via strong photon-photon interactions, i.e. optical nonlinearity, which is intrinsically weak in silicon. To boost the nonlinear response, practical applications rely on resonant structures such as microring resonators or photonic crystals. Nevertheless, their typical footprints are larger than 10 mu m. Here, we show that 100nm silicon nano-resonators exhibit a giant photothermal nonlinearity, yielding 90% reversible and repeatable modulation from linear scattering response at low excitation intensities. The equivalent nonlinear index is five-orders larger compared with bulk, based on Mie resonance enhanced absorption and high-efficiency heating in thermally isolated nanostructures. Furthermore, the nanoscale thermal relaxation time reaches nanosecond. This large and fast nonlinearity leads to potential applications for GHz all-optical control at the nanoscale and super-resolution imaging of silicon.
Direct large-area growth of graphene on silicon for potential ultra-low-friction applications and silicon-based technologies
(2020-08-14)
Tseng, Wei-Shiuan
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Chen, Yen-Chun
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Hsu, Chen-Chih
;
Lu, Chen-Hsuan
;
Wu, Chih-, I
Deposition of layers of graphene on silicon has the potential for a wide range of optoelectronic and mechanical applications. However, direct growth of graphene on silicon has been difficult due to the inert, oxidized silicon surfaces. Transferring graphene from metallic growth substrates to silicon is not a good solution either, because most transfer methods involve multiple steps that often lead to polymer residues or degradation of sample quality. Here we report a single-step method for large-area direct growth of continuous horizontal graphene sheets and vertical graphene nano-walls on silicon substrates by plasma-enhanced chemical vapor deposition (PECVD) without active heating. Comprehensive studies utilizing Raman spectroscopy, x-ray/ultraviolet photoelectron spectroscopy (XPS/UPS), atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical transmission are carried out to characterize the quality and properties of these samples. Data gathered by the residual gas analyzer (RGA) during the growth process further provide information about the synthesis mechanism. Additionally, ultra-low friction (with a frictional coefficient similar to 0.015) on multilayer graphene-covered silicon surface is achieved, which is approaching the superlubricity limit (for frictional coefficients <0.01). Our growth method therefore opens up a new pathway towards scalable and direct integration of graphene into silicon technology for potential applications ranging from structural superlubricity to nanoelectronics, optoelectronics, and even the next-generation lithium-ion batteries.
Realizing a Cosolvent System for Stable Tin-Based Perovskite Solar Cells Using a Two-Step Deposition Approach
(2020-08-14)
Shahbazi, Saeed
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Li, Meng-Yu
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Fathi, Amir
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Diau, Eric Wei-Guang
;
交大名義發表
Applying a two-step procedure and solvent engineering, we fabricated a stable tin-based perovskite, formamidinium tin triiodide (FASnI(3)), solar cell for lead-free photovoltaic applications. The first step was deposition of a SnI2 layer with the solvent dimethyl sulfoxide; the second step was application of a cosolvent system containing hexafluoro-2-propanol (HFP), isopropyl alcohol (IPA), and chlorobenzene (CB) in a 5:5:2 ratio to deposit the FAI layer on the SnI2 layer. The traditional IPA solvent prevented the formation of a stable FASnI(3) layer such that a stable device could not be fabricated. HFP was hence used to form hydrogen bonds with IPA and FM to retard the crystal growth of FASnI(3); CB served as the antisolvent. Ethylenediammonium dihypophosphite in the first step was an effective reducing agent to increase the efficiency of power conversion from similar to 5% to similar to 7% with great reproducibility and stability over 4000 h.
【實驗場所職業安全衛生教育訓練】
(國立陽明大學, 2020-08-15)
陽明電子報編輯小組
為提昇校園實驗場所安全衛生觀念，降低災害風險，加強實驗場所.
【IRB教育訓練Ｉ】醫療器材法規與管理制度簡介
(國立陽明大學, 2020-08-15)
陽明電子報編輯小組
日期：8月31日（一）時間：18:00-21:00（IRB時數：3）
陽明輔具中心主辦，2020全球首發輔具長照大展
(國立陽明大學, 2020-08-15)
陽明電子報編輯小組
由陽明「ICF暨輔助科技研究中心」與展昭國際公司共同主辦的「2020臺灣長期照護大展」，7月30日至8月2日在台北南港展覽館盛大登場..
陽明深耕創客教育，「3D列印工程師」認證率全國最高
(國立陽明大學, 2020-08-15)
陽明電子報編輯小組
今年「經濟部3D列印工程師」第一次認證考試，全國共有613人報考、獲證率僅3成。陽明「3D列印工程師認證班」考生獲證率卻高達七成...