Novel metal-free g-C₃N₄ photocatalysts with light yellow colors were synthesized by heating melamine precursor at different temperatures. The products were characterized by X-ray diffraction (XRD), ...transmission electron microscopy (TEM) and UV–vis diffuse reflectance spectra (DRS). The effect of calcining temperatures on photocatalytic activities of g-C₃N₄ samples were investigated based on the decomposition of phenol under visible light irradiation. The DRS spectra revealed that the g-C₃N₄ had strong absorption in the visible light region. The photocatalytic results indicated that the highest phenol degradation of 92.5% was achieved on the samples heated at 520°C for 4h. This study may provide an approach to development of novel metal-free photocatalysts to degrade organic pollutants by using visible light.
Novel Pd/BiVO4 visible light driven composite photocatalysts were synthesized by the impregnation method. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron ...microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectra (DRS). The photocatalytic activities of the Pd/BiVO4 samples were determined by oxidative decomposition of methyl orange in aqueous solution under visible light irradiation. The results indicated that the Pd/BiVO4 photocatalysts were monoclinic phase and consisted of quatrefoil-like and sphere particles. The DRS spectra showed that the composite samples greatly improved the ability of visible light absorption, the absorption edge shifted to red light. XPS results revealed that the doped Pd species existed in the form of palladium oxide. The photocatalytic experiments exhibited enhanced photocatalytic activities for methyl orange degradation under visible light irradiation. The mechanism of enhanced photocatalytic activities of Pd/BiVO4 samples was discussed in this paper.
State-of-the-art methods using attention mechanism in Recurrent Neural Networks have shown exceptional performance targeting sequential predictions and classifications. We explore the attention ...mechanism in Long-Short-Term Memory (LSTM) network based stock price movement prediction. Our proposed model significantly enhances the LSTM prediction performance in the Hong Kong stock market. The attention LSTM (AttLSTM) model is compared with the LSTM model in Hong Kong stock movement prediction. Further parameter tuning results also demonstrate the effectiveness of the attention mechanism in LSTM-based prediction method.
Covalent organic frameworks (COFs) have received much attention in the biomedical area. However, little has been reported about stimuli-responsive COF for drug delivery. Herein, we synthesized a ...hypoxia-responsive azo bond-containing COF with nanoscale size and immobilized both photosensitizers chlorin e6 (Ce6) and hypoxia-activated drug tirapazamine (TPZ) into the COFs. When such a COF entered the hypoxic environment and tumor, the COF structure was ruptured and loaded drugs were released from the COF. Together, upon near-infrared (NIR) light irradiation, Ce6 consumed oxygen to produce cytotoxic reactive oxygen species, leading to elevated hypoxia. Such two-step hypoxia stimuli successively induced the deintegration of COF, drug release and activation of TPZ. This promoted the TPZ to generate massive biotoxic oxyradical. In vitro and in vivo evaluation indicated that this two-step hypoxia-activated COF drug delivery system could kill cancer cells and inhibit the growth of tumors effectively.
The development of oxygen evolution reaction (OER) electrocatalysts remains a major challenge that requires significant advances in both mechanistic understanding and material design. Recent studies ...show that oxygen from the perovskite oxide lattice could participate in the OER via a lattice oxygen-mediated mechanism, providing possibilities for the development of alternative electrocatalysts that could overcome the scaling relations-induced limitations found in conventional catalysts utilizing the adsorbate evolution mechanism. Here we distinguish the extent to which the participation of lattice oxygen can contribute to the OER through the rational design of a model system of silicon-incorporated strontium cobaltite perovskite electrocatalysts with similar surface transition metal properties yet different oxygen diffusion rates. The as-derived silicon-incorporated perovskite exhibits a 12.8-fold increase in oxygen diffusivity, which matches well with the 10-fold improvement of intrinsic OER activity, suggesting that the observed activity increase is dominantly a result of the enhanced lattice oxygen participation.
Protonic ceramic fuel cells (PCFCs) or proton-conducting solid oxide fuel cells (SOFCs) are a class of electrochemical devices with high proton conductivity at the intermediate, even low operating ...temperatures (450–750 °C), which directly convert the chemical energy of hydrogen or hydrogen-containing fuels into electricity in a clean and efficient manner. In comparison to oxygen-ion conducting SOFCs, the operation at lower operating temperature overcomes the incompatibility and cathode delamination issues in high-temperature operated SOFCs. More attractively, the fuel is not diluted owing to the production of water at the cathode side. However, lowing working temperature weakens the electrode reaction kinetics and the ion migration, therefore the rational design of high-performance cathode materials is highly desired for PCFCs. Herein, we provide a review on the design criteria and state-of-art materials of PCFC composite cathodes including proton-conducting composite, proton-blocking composite and other types of composite cathodes, and discuss the underlying rationales and mechanisms. In particular, we discuss the feasibility of self-assembled composite cathodes used in PCFCs, and point out the future development directions of composite cathodes.
For variable and flexible objects, there is no appropriate intelligent method to quantitatively characterize the three-dimensional (3D) form, especially for garment development. To address the ...problem, we proposed a novel approach to mapping 3D flexible objects with the coded graphic as a medium. Two-dimensional mapping patterns were used to characterize the 3D form and extract metric information. The proposed graphic code is small in size and it is easy to demonstrate position. With different fabrication techniques, various coding materials are available. With only a monocular image, the method shows high accuracy and low cost without the need for camera calibration in advance. Specifically, the processes of the method, including the algorithm of feature extraction, decoding, mapping position calculation, and pattern generation, are discussed. Two tests were implemented, and the results showed that the method was accurate and simplified the process of made-to-measure garment development. The proposed method has great application potential in the manufacturing of labor-intensive and experience-dependent flexible industries, such as apparel, home decoration, shoes, and other related areas. It also sets the stage for further artificial intelligence research of flexible objects.
A new low-profile magneto-electric dipole antenna composed of a horizontal planar dipole and a vertically oriented folded shorted patch antenna is presented. The antenna is simply excited by a ...coaxial feed without the need of an additional balun. A rectangular cavity-shaped reflector is introduced for enhancing the stability in radiation pattern over the operating frequencies. A parametric study is performed for providing practical design guidelines. A prototype with a thickness of 0.173λ was designed, fabricated and measured. Results show that an impedance bandwidth of 54.8% for SWR ≤ 1.5 from 1.88 to 3.3 GHz was achieved. Stable radiation pattern with low cross polarization, low back radiation and an antenna gain of 8.6 ± 0.8 dBi was found over the operating frequencies. In addition, the antenna is d.c. grounded, which satisfies the requirement of many outdoor antennas.
Molybdenum disulfide (MoS2) and graphitic carbon nitride (g-C3N4) composite photocatalysts were prepared via a facile impregnation method. The physical and photophysical properties of the MoS2–g-C3N4 ...composite photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microcopy (HRTEM), ultraviolet–visible diffuse reflection spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) spectroscopy. The photoelectrochemical (PEC) measurements were tested via several on–off cycles under visible light irradiation. The photocatalytic hydrogen evolution experiments indicate that the MoS2 co-catalysts can efficiently promote the separation of photogenerated charge carriers in g-C3N4, and consequently enhance the H2 evolution activity. The 0.5wt% MoS2–g-C3N4 sample shows the highest catalytic activity, and the corresponding H2 evolution rate is 23.10 μmolh−1, which is enhanced by 11.3 times compared to the unmodified g-C3N4. A possible photocatalytic mechanism of MoS2 co-catalysts on the improvement of visible light photocatalytic performance of g-C3N4 is proposed and supported by PL and PEC results.
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•MoS2–g-C3N4 composite photocatalyst was synthesized for the first time.•The MoS2–g-C3N4 showed remarkably enhanced hydrogen evolution activity.•The HRTEM revealed intimate interfaces between g-C3N4 and MoS2.•The intimate interfaces promote the charge transfer and separation.•The mechanism was proposed and confirmed by PL and PEC results.
Don't be a dope: be a double dope! Graphene was doped with both boron and nitrogen at well‐defined doping sites to induce a synergistic effect that boosts its catalytic activity for oxygen reduction ...(see structure). The excellent catalytic performance of the new metal‐free catalyst is comparable to that of commercial Pt/C.
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