Actively Tunable "Single Peak/Broadband" Absorbent, Highly Sensitive Terahertz Smart Device Based on VO2.

In recent years, the development of terahertz (THz) technology has attracted significant attention. Various tunable devices for THz waves (0.1 THz-10 THz) have been proposed, including devices that modulate the amplitude, polarization, phase, and absorption. Traditional metal materials are often faced with the problem of non-adjustment, so the designed terahertz devices play a single role and do not have multiple uses, which greatly limits their development. As an excellent phase change material, VO2's properties can be transformed by external temperature stimulation, which provides new inspiration for the development of terahertz devices. To address these issues, this study innovatively combines metamaterials with phase change materials, leveraging their design flexibility and temperature-induced phase transition characteristics. We have designed a THz intelligent absorber that not only enables flexible switching between multiple functionalities but also achieves precise performance tuning through temperature stimulation. Furthermore, we have taken into consideration factors such as the polarization mode, environmental temperature, structural parameters, and incident angle, ensuring the device's process tolerance and environmental adaptability. Additionally, by exploiting the principle of localized surface plasmon resonance (LSPR) accompanied by local field enhancement, we have monitored and analyzed the resonant process through electric field characterization. In summary, the innovative approach and superior performance of this structure provide broader insights and methods for THz device design, contributing to its theoretical research value. Moreover, the proposed absorber holds potential for practical applications in electromagnetic invisibility, shielding, modulation, and detection scenarios.

Auto-encoder design based on the 1D-VD-CNN model for the detection of honeysuckle from unknown origin.

The disadvantages of the traditional one-dimensional convolution neural network (1D-CNN) model based on honeysuckle near-infrared spectral data (NIRS) include high parameter quantity, low efficiency, and inability to identify unknown categories effectively. In this paper, we propose a one-dimensional very deep convolution neural network (1D-VD-CNN) and design an auto-encoder mechanism for detecting honeysuckle from unexplored habitats. First, the 1D-VD-CNN model uses the efficient very deep (VD) structure to replace the hidden layer structure in the traditional 1D-CNN model. The model can be directly applied to analyze one-dimensional near-infrared spectral data (NIRS). Second, combining the reconstruction error of the auto-encoder, a honeysuckle identification method considering an unknown origin is designed, which can solve the problem of high confidence in convolution neural networks by using an auto-encoder and reconstruction errors of the samples to be tested. Whether the sample is an unknown variety can be determined by comparing the corrected confidence level with the preset threshold value. The results show that the accuracy of the 1D-VD-CNN training set and test set is 100%, and the loss value converges to 0.001. Compared with the traditional 1D-CNN model, the parameters and FLOPs are reduced by nearly 71% and 8%, respectively. At the same time, compared with the NIRS analysis and the PLS-DA method, the 1D-VD-CNN model has higher efficiency and better recognition performance for honeysuckle near-infrared spectral classification. Meanwhile, the accuracy rate of the auto-encoder for the category detection mechanism of honeysuckle from an unknown origin is 98%. The model can quickly and efficiently classify honeysuckle from different habitats and detect honeysuckle from unexplored habitats.

Deciphering the roles of ammonium doping for lead-free (NH4)xCs3-xCu2I5 perovskites to regulate the photoelectronic properties.

Inorganic ammonium (NH4+) is the simplest amine cation with perfect symmetry, the smallest radius and many H atoms, allowing itself to be used as a potential dopant in achieving high-quality perovskite materials. As a composition-modulation strategy, NH4+-doped (NH4)xCs3-xCu2I5 (0 < x < 1.5) lead-free perovskites were successfully synthesized via the eco-friendly ball milling method in this work. As the ammonium content increases, the lattice constants of (NH4)xCs3-xCu2I5 shrink and the grain sizes increase. The doping of NH4+ effectively passivates the lattice defects, suppresses the non-radiative recombination and tunes the energy band structure, resulting in better fluorescence properties. UV-pumped deep-blue LEDs based on (NH4)xCs3-xCu2I5 phosphors were fabricated, which showed improved performance and tunable emission. These results demonstrate the potential of the NH4+-doping strategy for improving the performance of lead-free perovskite optoelectronics.

Correction: Tunable deep-blue luminescence from ball-milled chlorine-rich Csx(NH4)1-xPbCl2Br nanocrystals by ammonium modulation.

Correction for 'Tunable deep-blue luminescence from ball-milled chlorine-rich Csx(NH4)1-xPbCl2Br nanocrystals by ammonium modulation' by Hongfei Xiao et al., Chem. Commun., 2022, 58, 3827-3830, DOI: 10.1039/D1CC07125D.

Tunable deep-blue luminescence from ball-milled chlorine-rich Csx(NH4)1-xPbCl2Br nanocrystals by ammonium modulation.

For the first time, a novel class of deep-blue (DB)-emitting Csx(NH4)1-xPbCl2Br (0.3 ≤ x ≤ 1) perovskite nanocrystals (PNCs) were prepared by a facile ligand-assisted one-step ball milling method. The resulted PNCs are characterized by high chlorine content (66.7%) and excellent color purity. Their photoluminescence position can be finely modulated from 434 nm to 447 nm, which extends notably beyond the current Rec. 2020 color standard, by the NH4+ content. Among them, Cs0.3(NH4)0.7PbCl2Br shows the highest quantum yield close to 40%. The PNCs exhibit high phase and optical stability under ambient conditions and UV light according to the NH4+ content. This work offers a new avenue to produce DB perovskites for future full-color displays and optoelectronics.

Tantalum-Doped TiO2 Prepared by Atomic Layer Deposition and Its Application in Perovskite Solar Cells.

Tantalum (Ta)-doped titanium oxide (TiO2) thin films are grown by plasma enhanced atomic layer deposition (PEALD), and used as both an electron transport layer and hole blocking compact layer of perovskite solar cells. The metal precursors of tantalum ethoxide and titanium isopropoxide are simultaneously injected into the deposition chamber. The Ta content is controlled by the temperature of the metal precursors. The experimental results show that the Ta incorporation introduces oxygen vacancies defects, accompanied by the reduced crystallinity and optical band gap. The PEALD Ta-doped films show a resistivity three orders of magnitude lower than undoped TiO2, even at a low Ta content (0.8-0.95 at.%). The ultraviolet photoelectron spectroscopy spectra reveal that Ta incorporation leads to a down shift of valance band and conduction positions, and this is helpful for the applications involving band alignment engineering. Finally, the perovskite solar cell with Ta-doped TiO2 electron transport layer demonstrates significantly improved fill factor and conversion efficiency as compared to that with the undoped TiO2 layer.

Design of C3 N4 -Based Hybrid Heterojunctions for Enhanced Photocatalytic Hydrogen Production Activity.

Semiconductors and metals can form an Ohmic contact with an electric field pointing to the metal, or a Schottky contact with an electric field pointing to the semiconductor. If these two types of heterojunctions are constructed on a single nanoparticle, the two electric fields may cause a synergistic effect and increase the separation rate of the photogenerated electrons and holes. Metal Ni and Ag nanoparticles were successively loaded on the graphitic carbon nitride (g-C3 N4 ) surface by precipitation and photoreduction in the hope of forming hybrid heterojunctions on single nanoparticles. TEM/high-resolution TEM images showed that Ag and Ni were loaded on different locations on C3 N4 , which indicated that during the photoreduction reaction Ag+ obtained electrons from C3 N4 in the reduction reaction, whereas oxidation reactions proceeded on Ni nanoparticles. Photocatalytic hydrogen production experiments showed that C3 N4 -based hybrid heterojunctions can greatly improve the photocatalytic activity of materials. The possible reason is that two heterojunctions could form a long-range electric field similar to the p-i-n structure in semiconductors. Most of the photogenerated carriers were generated and then separated in this electric field, thereby increasing the separation rate of electrons and holes. This further improved the photocatalytic activity of C3 N4 .

A Loop All-Fiber Current Sensor Based on Single-Polarization Single-Mode Couplers.

Low current sensitivity and insufficient system stability are two key problems in all-fiber current sensor (AFCS) studies. In order to solve the two problems, a novel AFCS combining single-polarization single-mode (SPSM) couplers and a loop structure is presented in this paper with a design that incorporates the advantages of both SPSM couplers and a loop structure. SPSM couplers are shown to simplify the AFCS system and reduce the risk of interference, and the loop structure can enhance the current sensitivity. Both theory and experiment prove that the new AFCS can simultaneously overcome two prevalent obstacles of low current sensitivity and low stability.

Internet Hospitals in China: Cross-Sectional Survey.

BACKGROUND: The Internet hospital, an innovative approach to providing health care, is rapidly developing in China because it has the potential to provide widely accessible outpatient service delivery via Internet technologies. To date, China's Internet hospitals have not been systematically investigated. OBJECTIVE: The aim of this study was to describe the characteristics of China's Internet hospitals, and to assess their health service capacity. METHODS: We searched Baidu, the popular Chinese search engine, to identify Internet hospitals, using search terms such as "Internet hospital," "web hospital," or "cloud hospital." All Internet hospitals in mainland China were eligible for inclusion if they were officially registered. Our search was carried out until March 31, 2017. RESULTS: We identified 68 Internet hospitals, of which 43 have been put into use and 25 were under construction. Of the 43 established Internet hospitals, 13 (30%) were in the hospital informatization stage, 24 (56%) were in the Web ward stage, and 6 (14%) were in full Internet hospital stage. Patients accessed outpatient service delivery via website (74%, 32/43), app (42%, 18/43), or offline medical consultation facility (37%, 16/43) from the Internet hospital. Furthermore, 25 (58%) of the Internet hospitals asked doctors to deliver health services at a specific Web clinic, whereas 18 (42%) did not. The consulting methods included video chat (60%, 26/43), telephone (19%, 8/43), and graphic message (28%, 12/43); 13 (30%) Internet hospitals cannot be consulted online any more. Only 6 Internet hospitals were included in the coverage of health insurance. The median number of doctors available online was zero (interquartile range [IQR] 0 to 5; max 16,492). The median consultation fee per time was ¥20 (approximately US $2.90, IQR ¥0 to ¥200). CONCLUSIONS: Internet hospitals provide convenient outpatient service delivery. However, many of the Internet hospitals are not yet mature and are faced with various issues such as online doctor scarcity and the unavailability of health insurance coverage. China's Internet hospitals are heading in the right direction to improve provision of health services, but much more remains to be done.