摘要 : The polycrystalline Yb 23 Cu 7 Mg 4 -type {Gd, Tb} 23 Ni 7 In 4 compounds (space group P 6 3 / mmc, N 194, hP 68) were prepared by arc melting with following annealing. They exhibit ferromagnetic ordering below Curie temperature T C = 142 K for Gd 23 Ni 7 In 4 and T C = 112 K for Tb 23 Ni 7 In 4, respectively. A field-sensitive antiferromagnetic transformation takes place around 90 K in Gd 23 Ni 7 In 4 and 106 K in Tb 26 Ni 7 In 4, respectively. Down to 10 K, they are soft ferromagnets with magnetizations of 4.7 μ B /Gd for Gd 23 Ni 7 In 4 and 5.7 μ B /Tb for Tb 23 Ni 7 In 4 in 90 kOe. In a field change of 50 kOe around T C, Gd 23 Ni 7 In 4 shows magnetic entropy change of −4.7 J/kg⋅K at 133–143 K, while Tb 23 Ni 7 In 4 shows magnetic entropy change of −5.4 J/kg⋅K at 109 K.

摘要 : The research of high-speed photodetector and high-speed optical receiver garners significant attention due to their indispensable properties in many fields including high-temperature event monitoring, security, and ad hoc network wireless communication. Inorganic perovskite oxides LaCoO 3 films showcase an extensive prospect in this area owing to their remarkable photoconductive effect. Up to present, however, LaCoO 3 films are mostly grown on rigid instead of flexible substrates, greatly limiting their applications to wearable optoelectronic sensors. In this work, we fabricated some flexible LaCoO 3 thin films to study their photoresponse. By inserting SrTiO 3 and BaTiO 3 as buffer layers, we find that LaCoO 3 thin films could epitaxially grow on the fluorphlogopite surface and show a stable photoresponse to visible-light. Nevertheless, we also found that the epitaxial strain and the content of surface-adsorbed oxygen could impact the photoconductivity. The mechanical strain generated by bending the fluorphlogopite substrate has been confirmed to has a tunable effect on the photoresponse. Moreover, with the fatigue tests of 10 5 bending cycles, the flexible LaCoO 3 thin films maintain a good photoresponse without any essentially weakening, proving a superior mechanical durability and stability. This work not only indicates the feasibility of the LaCoO 3 films applied for flexible photodetectors but also opens a path for other perovskite films applications for flexible substrate.

摘要 : Squaraines (SQs) are a significant family of near-infrared dyes with applications in fluorescence bioimaging, photodynamic therapy, etc. Most efforts have been devoted to modulating their nonlinear absorption while their nonlinear refraction has been neglected. Here, near-infrared broadband nonlinear absorption and refraction in two squaraine derivatives ( SQ-640 and SQ-670 ) are investigated with Z-scan (720–1300 nm) and time-resolved pump-probe method. With essentially similar conjugation and planarity in the two molecules, the effect of alkyl cyclization on the nonlinear optical response is discussed. A larger transition dipole moment is reached via alkyl cyclization and results in a wider range of nonlinear optical responses for SQ-670 . In addition to conventional transient absorption measurement, transient nonlinear refraction based on phase contrast pump-probe method are used for the study of ultrafast dynamics. Kinetic details from both measurements are compared and analyzed for further details of ultrafast photophysical mechanisms in these molecules. Besides, an intensity-dependent transition from saturable absorption to reverse saturable absorption in SQ-670 is observed at 720 nm which is mainly due to the combined contributions of one-photon absorption and TPA. Both samples display good nonlinear absorption (NLA) at the near-infrared region (750–1300 nm) which originates from two-photon absorption (TPA) and TPA induced excited state absorption. Bound electron response and negative excited state refraction dominate the nonlinear refraction of both molecules. Our work gains a deeper understanding of the NLO properties of squaraine derivatives from an alternative perspective and enriches the experimental research on squaraine derivatives. It may provide a useful reference for the future design of organic materials with excellent nonlinear optical responses.

摘要 : Organic Rankine cycle (ORC) and supercritical CO 2 (sCO 2 ) Brayton cycle are two key and competition technology routes as the power cycle of Lead–Bismuth micro-reactor (LBMR). However, few studies focus on the comparison of thermodynamic and economic performance between ORCs and sCO 2 cycles in nuclear micro-reactor. The objectives in this study are to perform parameters analysis and techno-economic comparison in ORCs and sCO 2 cycles with various configurations as the power cycle of LBMR, so as to provide the technical support for the selection of power cycle and its operating conditions in different scenarios. Several high/low-temperature working fluids are screened for ORCs in view to achieve high net efficiency ( η th ) and low electricity production cost ( EPC ). Multi-objective optimization is performed to solve the trade-off between η th and EPC, and then to compare the comprehensive performance of various cycles from thermodynamic, compact and economic aspects. Results show that, the η th and EPC of ORCs are comparable or superior to that in sCO 2 cycles when the two cycles have similar structures (simple/regenerative). Among the ORCs, the cascade ORC with two-side regeneration using N -Dodecane/Pentane as working fluid pair has the best performance. In all cycles, recompression sCO 2 cycle performs best, but only when the heat source temperature is higher than 460 °C, the performance of the recompression sCO 2 cycle are overall better than the cascade ORC.

摘要 : Electrolyzing water is an effective and feasible technology to achieve a large-scale hydrogen production in industry. However, it is still challenging to develop an efficient approach to fabricate a superior and stable hydrogen evolution reaction (HER) electrodes with low cost and outstanding catalytic efficiency. This work presents an innovative surface modification technique of plasma electrolytic oxidation (PEO) to fabricate superior MoN based coating electrodes. By simply introducing Na 2 MoO 4 and NiAc 2 into the electrolyte, a novel MoTiN and NiMoTiN coatings were successfully achieved on the surface of a titanium substrate by PEO and annealing treatments, which exhibits excellent mechanical adhesion and platinum-like catalytic properties. Importantly, it has been demonstrated that the newly formed MoTiN solid solution combined by active Mo 2 N and conductive TiN can contribute the superior catalytic activity and the subsequent Ni doping can effectively stabilize the structure and activity of MoTiN. Under the alkaline environment of 1 M KOH, the MoTiN and NiMoTiN coated electrodes require only 126 and 121 mV overpotential, respectively, to achieve a current density of 10 mA cm −2 . Additionally, under the same test conditions, NiMoTiN can operate stably for over 24 h, demonstrating excellent HER catalytic activity and stability. This work provides new insights into the preparation of HER electrodes with superior mechanical properties and excellent catalytic performance towards industrial hydrogen production.

摘要 : The incorporation of graphene quantum dots (GQDs) with efficient charge carrier transport capability into a tin oxide (SnO2) solution and the utilization of their distinct mass properties for effective self-stratification are proposed as a method for enhancing the efficiency and stability of perovskite solar cells. By employing an antisolvent spin-coating technique, an SnO2 electron transport layer (ETL) with a gradient energy band structure is prepared. Devices based on this gradient energy band ETL exhibit an efficiency of 22.3%, whereas the efficiency of devices with a single SnO2 ETL, used as a reference, is only 19.8%. Moreover, for unencapsulated devices, an efficiency of 86% is retained after continuous testing for 1000 h at 40 °C by an AM 1.5 G lamp. Further investigation reveals that the introduction of GQDs not only forms a gradient energy band structure but also effectively passivates the defects in the SnO2 layer itself, thus ameliorating the issues of charge carrier separation and recombination during the transport process. This work presents an approach to SnO2 ETL design, not only applicable to perovskite solar cells but also offering inspiration for other optoelectronic devices.

摘要 : The zero-bandgap properties of graphene (Gr) limit its various applications. Fluorination is an alternative strategy to open the bandgap to broaden its applications. However, traditional fluorination methods are detrimental to human health and contribute extensively to environmental pollution. Here, we develop a simple and safe process of weak fluorination that introduces fluorine atoms into Gr, breaking its zero-bandgap structure. This strategy is more environmentally friendly, risk-free, and harmless to humans, making it suitable for large-scale production. Through this highly controllable weak fluorination process, micro-area selective fluorination is achieved and induces excellent photoluminescence characteristics but maintains a high mobility, compared to the pristine Gr with zero bandgap. The degree of fluorination determines the photoelectric and transport properties of Gr. This work provides an experimental foundation for developing materials based on fluorinated graphene and designing high-performance functional devices.

摘要 : MXene is an emerging two-dimensional (2D) nanomaterial composed of several atomic layers of transition metal carbide/nitride/carbonitride. Due to its metal-analogous conductivity and rich surface functional groups, the facile surface modification of MXene is promising for extending its functionality into semiconductors. However, the application of surface-modulated MXene in robust memristor devices remains rarely reported. Here, the organic dye of celestine blue with conjugated skeleton and ionic interaction is employed to modify MXene, which succeeds to serve as the switching element in memristor device with synergetic ionotronic (ionic–electronic) property. Moreover, the device affords highly-robust performance through rational 2D sandwich heterojunction design. The underlying mechanism is elaborately clarified by theoretical charge transport modelling and experimental scanning electron microscopy analysis. This study sheds light on the prospect of high-performance MXene-based memristors through ionotronic modification strategy and provides efficient guidelines for broadening the application of novel 2D nanomaterials in non-volatile memory.

摘要 : Pyrophosphoric acid (PPi) is a crucial indicator for monitoring adenosine triphosphate hydrolysis processes, and abnormal PPi levels in the human body seriously threaten human health. Thus the efficient detection of the concentration of PPi in the aqueous solution is important and urgent. This paper described the successful synthesis of a tetraphenylethylene (TPE) derivative, named as TPE-4B, which contained four chelate pyridinium groups exhibiting aggregation-induced emission characteristics. TPE-4B was explicitly developed for the selective and sensitive fluorescence detection of PPi in aqueous solutions, showing a fluorescence "turn-on" response, and the detection limit was 65 nM. The four chelate pyridinium moieties of TPE-4B exhibited robust electrostatic interactions and binding capacity towards PPi, leading to the formation of aggregations, which was confirmed by zeta potential, dynamic light scattering, and scanning electron microscopy. Compared with free TPE-4B in the aqueous solution, the zeta potential of aggregations decreased from 20.7 to 4.2 mV, the average diameter increased from 155 to 403 nm, and the morphology transformed from porous nanostructures into a block-like format. Leveraging these properties, TPE-4B is a promising candidate for a "turn-on" fluorescence sensor designed to detect PPi in the aqueous solution.

摘要 : A water contact angle measurement method based on the improved Faster RCNN is proposed to address the issues of low accuracy and poor reproducibility caused by manual intervention in traditional water contact angle measurement processes. First, the Faster RCNN backbone network VGG16 was replaced with ResNet101, and the attention mechanism model convolutional block attention module (CBAM) was added at the end of its residual block to enhance the network's ability to extract features. Second, the feature pyramid network (FPN) was incorporated to fully extract feature information at different scales, and the Focal loss function was introduced to solve the problem of imbalanced positive and negative class samples. Finally, edge detection and corner extraction were performed on the located water droplets, and then the iterative reweighted least squares (IRLS) method was used to fit the elliptical contour to calculate the contact angle angle. The experimental results show that the improved Faster RCNN object detection algorithm improves mean average precision by 10.794% and speed by 11 frame/s over the original algorithm. The average standard deviation of contact angle angle measurements is 0.109°.