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Restriction of Molecular Rotors in Ultrathin Two-Dimensional Covalent Organic Framework Nanosheets for Sensing Signal Amplification
摘要： Covalent organic frameworks (COFs) have emerged as promising crystalline porous materials with well-defined structures, high porosity, tunable topology and functionalities suitable for various applications. However, studies of few-layered ultrathin two-dimensional (2D) COF nanosheets, which may lead to unprecedented properties and applications, are still limited. Herein we report the targeted synthesis of three azine-linked and imine-linked 2D COFs named NUS 30-32 using monomers containing aggregation-induced emission (AIE) rotor-active tetraphenylethylene (TPE) moieties, affording micro- and meso- dual pores in NUS-30 and NUS-32, and triple pores in NUS-31. For the first time, we demonstrate that these isostructural bulk COF powders can be exfoliated into ultrathin 2D nanosheets (2 – 4 nm thickness) by temperature-swing gas exfoliation approach. Compared with TPE monomers and COF model compounds, the AIE characteristic of NUS 30-32 nanosheets is distinctly suppressed due to the covalent restriction of the AIE molecular rotors in the confined 2D frameworks. As a result, the enhancement of conjugated conformations of NUS 30-32 nanosheets with unusual structure relaxation show signal amplification effect in biomolecular recognition of amino acids and small pharmaceutical molecules (L-dopa), exhibiting much higher sensitivity than their stacked bulk powders, TPE monomer, and COF model compound. Moreover, the binding affinity of the COF nanosheets toward amino acids can be controlled by increasing the number of azine moieties in the structure. Density functional theory (DFT) calculations reveal that binding affinity control results from the crucial geometric roles and stronger host-guest binding between azine moieties and amino acids. In addition, we demonstrate that minimal loading of the NUS-30 nanosheets in composite membranes can afford excellent performance for biomolecule detection. Our findings pave a way for the development of functional ultrathin 2D COF nanosheets with precise control over the nature, density, and arrangement of the binding active sites involved in enhanced molecule recognition.
关键词： molecular rotors,Covalent organic frameworks,aggregation-induced emission,biomolecular recognition,signal amplification,two-dimensional nanosheets
更新于2025-09-04 15:30:14
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Dependences of the Thermophysical Parameters of Activated Thermal-Emission Cathodes on the Current in a Stable Arc Discharge
摘要： The influence of electrical current (in the range 20–150 A) on the thermophysical characteristics of activated thermal cathodes (W + 2% ThO2) in a freely glowing low-pressure argon arc is investigated. For the first time, the dependences of key cathode parameters, such as the heat flux at the electrode, the voltage equivalent of the heat, the specific erosion, and the distributions of the temperature and work function over the extension length of the cathode from the holder, are obtained. A nonmonotonic dependence of the specific erosion on the electrical current with a minimal level at 50–60 A is noted.
关键词： thermophysical parameters,work function,thermal-emission cathodes,arc discharge,specific erosion
更新于2025-09-04 15:30:14
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Preliminary results of optical emission spectroscopy by line ratio method in the RF negative ion source at ASIPP
摘要： Optical emission spectroscopy (OES) using the trace rare gases of Ar and Xe have been carried out in a radio frequency (RF) driven negative ion source at Institute of Plasma Physics, Chinese Academy of Science (ASIPP), in order to determine the electron temperature and density of the hydrogen plasma. The line-ratio methods based on population models are applied to describe the radiation process of the excited state particles and establish their relations with the plasma parameters. The spectral lines from the argon and xenon excited state atoms with the wavelength of 750.4 nm and 828.0 nm are used to calculate the electron temperature based on the corona model. The argon ions emission lines with the wavelength of 480 nm and 488 nm are selected to calculate the electron density based on the collisional radiative model. OES has given the preliminary results of the electron temperature and density by varying the discharge gas pressure and RF power. According to the experimental results, the typical plasma parameters is Te≈2?4 eV and ne≈1×1017?8×1017 m-3 in front of plasma grid.
关键词： RF negative ion source,optical emission spectroscopy,neutral beam injection
更新于2025-09-04 15:30:14
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Near-Field and Far-Field Thermal Emission of an Individual Patch Nanoantenna
摘要： The far-field spectral and near-field spatial responses of an individual metal-insulator-metal nanoantenna are reported, using thermal fluctuations as an internal source of the electromagnetic field. The far-field spectra, obtained by combining Fourier transform infrared spectroscopy with spatial modulation based on a light falloff effect in a confocal geometry, have revealed two distinct emission peaks attributed to the excitation of the fundamental mode of the nanoantenna at two distinct wavelengths. Superresolved near-field images of the thermally excited mode have been obtained by thermal radiation scanning tunneling microscopy. Experimental results are supported by numerical simulations showing that it is possible to excite the same mode at different wavelengths near a resonance of the insulating dielectric material forming the antenna.
关键词： near-field,nanoantenna,thermal emission,microscopy,spectroscopy,far-field
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 18th International Conference on Bioinformatics and Bioengineering (BIBE) - Taichung, Taiwan (2018.10.29-2018.10.31)] 2018 IEEE 18th International Conference on Bioinformatics and Bioengineering (BIBE) - SAR ADC with DAC and SC Low-Pass Filter for Positron Emission Tomography Application
摘要： For positron emission tomography (PET), successive approximation register (SAR) analog-to-digital converter (ADC) and switched-capacitor (SC) low-pass filter implemented in tsmc 0.18-um CMOS process is presented. To reduce DAC switching energy and layout size, a hybrid resistor-capacitor DAC is applied. To save energy, asynchronous control logic to drive the ADC is used. A pre-amplifier based comparator circuit is built to reduce the kickback noise from the dynamic latch. The proposed filter uses cascades of first-order and second-order biquad seting blocks. In order to reach the largest possible input dynamic range, the method of dynamic range scaling and minimum capacitor scaling is used.
关键词： SAR ADC,SC Low-Pass Filter,Positron Emission Tomography,DAC
更新于2025-09-04 15:30:14
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Research on Beam Emission Spectroscopy Combined HL-2A Tokamak Real Experimental Data With Spectra Simulation Code
摘要： A beam emission spectroscopy (BES) diagnostic system has been developed on HL-2A tokomak. Combined with motional Stark effect (MSE) diagnostics, the BES could assess the radial electric ?eld Er and the safety factor q, which play an important role in plasma control and impurity transport processes. A simulation of spectra (SOS) code has been developed for spectra simulations based on various tokamak devices’ real situations. It can be used for designing visible spectral diagnostics systems and predicting their performance. In this paper, based on the HL-2A real experimental running parameters, we used the SOS code to simulate BES and MSE spectra. These spectra were consistent with experimental data ?tting results. The SOS code was also able to get the safety factor q and other parameters. The results reveal that the SOS code could be used to design similar diagnostic systems for ITER in the future.
关键词： neutral beam injection (NBI) diagnostics,motional Stark effect (MSE),simulation of spectra (SOS),Beam emission spectroscopy (BES)
更新于2025-09-04 15:30:14
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PET imaging in adaptive radiotherapy of gastrointestinal tumors
摘要： radiotherapy is a cornerstone in the multimodality treatment of several gastrointestinal (gi) tumors. Positron-emission tomography (PeT) has an established role in the diagnosis, response assessment and (re-)staging of these tumors. Nevertheless, the value of PeT in adaptive radiotherapy remains unclear. This review focuses on the role of PeT in adaptive radiotherapy, i.e. during the treatment course and in the delineation process.
关键词： gastrointestinal tract,Positron-emission tomography,radiotherapy
更新于2025-09-04 15:30:14
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Comparative Measurements of Photoelectron Emission in Bulk Samples and Island Films of Silver
摘要： The photoelectron emission has been studied of silver island films excited by a laser pulse of 10-ns duration at three wavelengths: 355, 532, and 1064 nm. It has been shown that, for wavelengths of 355 and 532 nm, the photoemission of island films significantly differs from the photoemission of a bulk sample. For an island film, dependence on the pulse energy characteristic for single-photon emission has been observed at a 355-nm wavelength. It has also been shown that the surface plasmon resonance in nanoparticles significantly affects the photoemission and character of its dependence on the energy of the laser pulse.
关键词： laser pulse,photoelectron emission,nanoparticles,silver island films,surface plasmon resonance
更新于2025-09-04 15:30:14
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Photophysics of Przewalskinone-B and its Binding Behavior with β- Cyclodextrin
摘要： The photophysical properties of Przewalskinone-B, a plant extract which is reported widely for its medicinal values were studied in the absence and presence of a drug carrier, β-Cyclodextrin. The steady state absorption, fluorescence excitation and emission spectra of Przewalskinone-B were studied in an aqueous medium. The fluorescence emission of Przewalskinone-B was analysed in presence of varying concentrations of β-Cyclodextrin in an alcohol/water medium. An appreciable quenching was observed in the emission intensity of Przewalskinone-B. There was also a red shift observed in both absorption and emission spectra in presence of β-Cyclodextrin which designated a convinced interaction between the two species.
关键词： Emission,Przewalskinone-B,Binding,β-Cyclodextrin
更新于2025-09-04 15:30:14
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Heat Resisting Metallic Meta-Skin for Simultaneous Microwave Broadband Scattering and Infrared Invisibility Based on Catenary Optical Field
摘要： Metallic skins are widely used in practical engineering owing to their inherent advantages in mechanical and physical characteristics. In this paper, a metasurface skin composed of subwavelength metallic gratings with space-variant orientations has been proposed to realize exotic electromagnetic properties in microwave and infrared regimes. Equivalent circuit theory and transfer matrix method have been adopted to quantitatively describe the optical fields and dispersion with high accuracy in a catenary form. Based on these analyses, broadband and wide-angle radar cross-section (RCS) reduction for microwave has been simulated and experimentally demonstrated. Additional characteristics such as high temperature resistance and low infrared thermal emission are also verified. It is believed that these results may provide a new platform to achieve multifunctional electromagnetic devices and are promising for many applications.
关键词： scattering,catenary optics,metasurface,thermal emission,all-metal metasurfaces
更新于2025-09-04 15:30:14