Space-Confined Growth for Thickness-Controlled Cs3Bi2I9 Perovskite Single Crystal Wafers for X-Ray Detectors.

The Cs3Bi2I9 single crystal, as an all-inorganic non-lead perovskite, offers advantages such as stability and environmental friendliness. Its superior photoelectric properties, attributed to the absence of grain boundary influence, make it an outstanding X-ray detection material compared to polycrystals. In addition to material properties, X-ray detector performance is affected by the thickness of the absorption layer. Addressing this, a space-confined method is proposed. The temperature field is determined through finite element simulation, effectively guiding the design of the space-confined method. Through this innovative method, a series of thickness-controlled perovskite single crystal wafers (PSCWs) are successfully prepared. Corresponding X-ray detectors are then prepared, and the impact of single crystal thickness on device performance is investigated. With an increase in single crystal thickness, a rise followed by a decline in device sensitivity is observed, reaching an optimal value at 0.7 mm thickness at 40V mm-1 with a device performance of 11313.6µC Gy-1 cm-2. This space-confined method enables the direct growth of high-quality perovskite single crystals with specified thickness, eliminating the need for slicing or etching.

SASEGAN-TCN: Speech enhancement algorithm based on self-attention generative adversarial network and temporal convolutional network.

Traditional unsupervised speech enhancement models often have problems such as non-aggregation of input feature information, which will introduce additional noise during training, thereby reducing the quality of the speech signal. In order to solve the above problems, this paper analyzed the impact of problems such as non-aggregation of input speech feature information on its performance. Moreover, this article introduced a temporal convolutional neural network and proposed a SASEGAN-TCN speech enhancement model, which captured local features information and aggregated global feature information to improve model effect and training stability. The simulation experiment results showed that the model can achieve 2.1636 and 92.78% in perceptual evaluation of speech quality (PESQ) score and short-time objective intelligibility (STOI) on the Valentini dataset, and can accordingly reach 1.8077 and 83.54% on the THCHS30 dataset. In addition, this article used the enhanced speech data for the acoustic model to verify the recognition accuracy. The speech recognition error rate was reduced by 17.4%, which was a significant improvement compared to the baseline model experimental results.

Fluorinated organic ammonium salt passivation for high-efficiency and stable inverted CsPbI2Br perovskite solar cells.

All-inorganic CsPbI2Br inverted perovskite solar cells (PSCs) have drawn increasing attention because of their outstanding thermal stability and compatible process with tandem cells. However, relatively low open circuit voltage (Voc) has lagged their progress far behind theoretical limits. Herein, we introduce phenylmethylammonium iodide and 4-trifluoromethyl phenylmethylammonium iodide (CFPMAI) on the surface of a CsPbI2Br perovskite film and investigate their passivation effects. It is found that CFPMAI with a -CF3 substituent significantly decreases the trap density of the perovskite film by forming interactions with the under-coordinated Pb2+ ions and effectively suppresses the non-radiative recombination in the resulting PSC. In addition, CFPMAI surface passivation facilitates the optimization of energy-level alignment at the CsPbI2Br perovskite/[6,6]-phenyl C61 butyric acid methyl ester interface, resulting in improved charge extraction from the perovskite to the charge transport layer. Consequently, the optimized inverted CsPbI2Br device exhibits a markedly improved champion efficiency of 14.43% with a Voc of 1.12 V, a Jsc of 16.31 mA/cm2, and a fill factor of 79.02%, compared to the 10.92% (Voc of 0.95 V) efficiency of the control device. This study confirms the importance of substituent groups on surface passivation molecules for effective passivation of defects and optimization of energy levels, particularly for Voc improvement.

Enhanced Efficiency and Stability of Inverted CsPbI2Br Perovskite Solar Cells via Fluorinated Organic Ammonium Salt Surface Passivation.

All-inorganic perovskite solar cells (PSCs) have recently received increasing attention due to their outstanding thermal stability. However, the performance of these devices, especially for the devices with a p-i-n structure, is still inferior to that of the typical organic-inorganic counterparts. In this study, we introduce phenylammonium iodides with different side groups on the surface of the CsPbI2Br perovskite film and investigate their passivation effects. Our studies indicate that the 4-trifluoromethyl phenylammonium iodide (CFPA) molecule with the -CF3 side group effectively decreases the trap density of the perovskite film by forming interactions with the undercoordinated Pb2+ ions and significantly inhibits the nonradiative recombination in the derived PSC, leading to an enhanced open-circuit voltage (Voc) from 0.96 to 1.10 V after passivation. Also, the CFPA post-treatment enables better energy-level alignment between the conduction band minimum of CsPbI2Br perovskite and [6,6]-phenyl C61 butyric acid methyl ester, thereby enhancing the charge extraction from the perovskite to the charge transport layer. These combined benefits result in a significant enhancement of the power conversion efficiency from 11.22 to 14.37% for inverted CsPbI2Br PSCs. The device without encapsulation exhibits a degradation of only ≈4% after 1992 h in a N2 glovebox.

A Tunable Terahertz Absorber Based on Double-Layer Patterned Graphene Metamaterials.

Graphene is widely used in tunable photonic devices due to its numerous exotic and exceptional properties that are not found in conventional materials, such as high electron mobility, ultra-thin width, ease of integration and good tunability. In this paper, we propose a terahertz metamaterial absorber that is based on patterned graphene, which consists of stacked graphene disk layers, open ring graphene pattern layers and metal bottom layers, all separated by insulating dielectric layers. Simulation results showed that the designed absorber achieved almost perfect broadband absorption at 0.53-1.50 THz and exhibited polarization-insensitive and angle-insensitive characteristics. In addition, the absorption characteristics of the absorber can be adjusted by changing the Fermi energy of graphene and the geometrical parameters of the structure. The above results indicate that the designed absorber can be applied to photodetectors, photosensors and optoelectronic devices.

Composition Engineering Growth of Cs3Bi2I9 Single Crystals with Low Defect Density for X-ray Detectors.

Cs3Bi2I9 (CBI) single crystal (SC) is a promising material for a higher-performance direct X-ray detector. However, the composition of CBI SC prepared by the solution method usually deviates from the ideal stoichiometric ratio, which limits the detector performance. In this paper, based on the finite element analysis method, the growth model of the top-seed solution method has been established, and then the influence of precursor ratio, temperature field, and other parameters on the composition of CBI SC has been simulated. The simulation results were used to guide the growth of the CBI SCs. Finally, a high-quality CBI SC with a stoichiometric ratio of Cs/Bi/I = 2.87:2:8.95 has been successfully grown, and the defect density is as low as 1.03 × 109 cm-3, the carrier lifetime is as high as 16.7 ns, and the resistivity is as high as 1.44 × 1012 Ω·cm. The X-ray detector based on this SC has a sensitivity of 29386.2 µC·Gyair-1 cm-2 at an electric field of 40 V·mm-1, and a low detection limit of 0.36 nGyair·s-1, creating a record for the all-inorganic perovskite materials.

Sr-Doping All-Inorganic CsPbBr3 Perovskite Thick Film for Self-Powered X-ray Detectors.

The all-inorganic perovskite cesium lead bromine (CsPbBr3) has attracted much attention in the field of X-ray detectors because of its high X-ray absorption coefficient, high carrier collection efficiency, and easy solution preparation. The low-cost anti-solvent method is the main method to prepare CsPbBr3; during this process, solvent volatilization will bring a large number of holes to the film, leading to the increase of defects. Based on the heteroatomic doping strategy, we propose that Pb2+ should be partially replaced by Sr2+ to prepare leadless all-inorganic perovskite. The introduction of Sr2+ promoted the ordered growth of CsPbBr3 in the vertical direction, increased the density and uniformity of the thick film, and achieved the goal of CsPbBr3 thick film repairing. In addition, the prepared CsPbBr3 and CsPbBr3:Sr X-ray detectors were self-powered without external bias, maintaining a stable response during on and off states at different X-ray dose rates. Furthermore, the detector base on 160 µm CsPbBr3:Sr had a sensitivity of 517.02 µC Gyair-1 cm-3 at zero bias under the dose rate of 0.955 µGy ms-1 and it obtained a fast response speed of 0.053-0.148 s. Our work provides a new opportunity to produce cost-effective and highly efficient self-powered perovskite X-ray detectors in a sustainable way.

Strategies for the preparation of high-performance inorganic mixed-halide perovskite solar cells.

Inorganic halide perovskites have attracted significant attention in the field of photovoltaics (PV) in recent years due to their superior intrinsic thermal stability and excellent theoretical power conversion efficiency (PCE). CsPbI3 with a bandgap of ∼1.7 eV is considered to be the most potential candidate for PV application. However, bulk CsPbI3 films exhibit poor phase stability. The substitution of some iodide ions with bromide/chloride in CsPbI3 results in the formation of mixed-halide CsPbX3 perovskites, which exhibit a good balance between phase stability and efficiency. The halogen-tunable mixed-halide inorganic perovskites have a bandgap matching the sunlight region and show great potential for application in multi-junction tandem and semitransparent solar cells. Herein, the progress of mixed-halide CsPbX3 PSCs is systematically reviewed, including CsPbI x Br y Cl3-x-y - and CsPbIBr2-based IPSCs. In the case of CsPbIBr2 IPSCs, we introduce the low-temperature deposition of CsPbIBr2 films, doping methods for the preparation of high-quality CsPbIBr2 films and strategies for improving the performance of solar cells. Furthermore, the mechanism of crystallization/interface engineering for the preparation of high-quality CsPbIBr2 films and efficient solar cells devices is emphasized. Finally, the development direction of further improving the PV performance and commercialization of mixed-halide IPSCs are summarized and prospected.

Enhancement of Electrochemical Performance of LiFePO4@C by Ga Coating.

LiFePO4 (LFP) is one of the cathode materials widely used in lithium ion batteries at present, but its electronic conductivity is still unsatisfactory, which will affect its electrochemical performance. Ga-coated LiFePO4@C (LFP@C) samples were prepared by a hydrothermal method and ultrasonic dispersion technology. Ga has good electrical conductivity and can rapidly conduct electrons within the LFP cathode material under the synergistic effect with C coating, thus improving the dynamic performance of the LFP cathode material. The experimental results show that LFP@C/Ga samples exhibit good electrochemical performance. Compared with the pristine LFP@C, the 1.0 wt % Ga-coated LFP@C cathode exhibits excellent discharge capacity and cycle stability. The former shows a discharge capacity of 152.6 mA h g-1 at 1 C after 100 cycles and a discharge capacity retention rate of 98.77%, while pristine LFP@C shows only a discharge capacity of 114.5 mA h g-1 and a capacity retention rate of 95.84% after 100 cycles at 1 C current density.

High Specific Capacitance of the Electrodeposited MnO2 on Porous Foam Nickel Soaked in Alcohol and its Dependence on Precursor Concentration.

In this work, we used the mixed solution of manganese acetate and sodium sulfate to deposit manganese dioxide on the three-dimensional porous nickel foam that was previously soaked in alcohol, and then the effects of solution concentrations on their capacitance properties were investigated. The surface morphology, microstructure, elemental valence and other information of the material were observed by scanning electron microscope (SEM), Transmission Electron Microscope (TEM), X-ray photoelectron spectroscopy (XPS), etc. The electrochemical properties of the material were tested by Galvanostatic charge-discharge (GCD), Cyclic Voltammetry (CV), Chronoamperometry (CA), Electrochemical impedance spectroscopy (EIS), etc. The MnO2 electrode prepared at lower concentrations can respectively reach a specific capacitance of 529.5 F g-1 and 237.3 F g-1 at the current density of 1 A g-1 and 10 A g-1, and after 2000 cycles, the capacity retention rate was still 79.8% of the initial capacitance, and the energy density can even reach 59.4 Wh Kg-1, while at the same time, it also has a lower electrochemical impedance (Rs = 1.18 Ω, Rct = 0.84 Ω).

Effects of electrodeposition time on a manganese dioxide supercapacitor.

As is well known that the specific capacitance of supercapacitors cannot be improved by increasing the mass of the deposited MnO2 films, which means an appropriate deposition duration is important. In this study, nanobelt-structured MnO2 films were prepared by the electrochemical deposition method under different deposition time to explore the effects of electrodeposition time change on the microstructure and electrochemical properties of this material. Benefiting from the microstructure of the MnO2 films, the transfer properties of the charged electrons and ions were promoted. Meanwhile, a 3D porous nickel foam was chosen as the deposition substrate, which rendered an enhancement of the MnO2 conductivity and the mass of the active material. The enhanced specific capacitance and specific surface area attributed to synergistic reactions. Subsequently, the electrochemical performances of the as-prepared materials were analyzed via cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS) tests. Results show that the optimum sample deposited for 50 s has a specific capacitance of 291.9 F g-1 at the current density of 1 A g-1 and lowest R ct. However, its electrochemical stability cannot come up to the level of the 300 s sample due to the microstructure change.

Correction: Effects of electrodeposition time on a manganese dioxide supercapacitor.

[This corrects the article DOI: 10.1039/D0RA01681K.].

Au@Pt nanodendrites enhanced multimodal enzyme-linked immunosorbent assay.

Single modal enzyme-linked immunosorbent assay (ELISA) covering colorimetric, fluorescence, and chemiluminescence techniques has been widely reported in recent years, whereas the combination of multiple signal channels in one immunosensing platform still faces huge challenges. Multimodal imaging will provide more comprehensive and precise diagnostic information by the combination of two or more imaging modalities. Inspired by this concept, we established a new kind of multimodal enzyme-linked immunosorbent assay (M-ELISA) based on the unique properties of Au@Pt nanodendrites. As a proof-of-concept demonstration, cardiac troponin I (cTnI) has been chosen as a model biomarker. Owing to the excellent photothermal effect and intrinsic peroxidase-like activity of Au@Pt nanodendrites, the concentration of cTnI can be quantificationally reflected by photothermal immunoassay, colorimetric immunoassay and ratiometric fluorescence immunoassay simultaneously. This developed M-ELISA demonstrated the good consistency with the chemiluminescence immunoassay method in clinical diagnosis for real serum samples.

Structural, optical and photoelectric properties of Mn-doped ZnO films used for ultraviolet detectors.

Mn-doped ZnO (MZO) films were prepared on glass substrates using sol-gel dip-coating technology. The microstructural, morphological, optical and photoelectric properties of MZO films were investigated at different withdrawal speeds (WS: 20, 40, 60 and 80 mm s-1). The X-ray diffraction (XRD) patterns showed that all the films obtained were polycrystalline with a hexagonal structure, and the highest crystallinity of MZO films was observed as films were deposited at 40 mm s-1. The UV-Vis spectra revealed that the average optical transmittance of all samples was over 60% and the energy band gap of films decreased from 3.616 to 3.254 eV with the increase in withdrawal speed. The formed Au/MZO/Au photodetectors (PDs) indicate that a device prepared at 40 mm s-1 shows superior properties both in response speed and detection capability, and the rise time is 1.871 s and fall time is 3.309 s at 365 nm for 3 V bias and the detectivity (D*) reaches ∼1.7 × 1010 Jones. Moreover, the responsivity of PDs is also affected by the distance between Au electrodes and external bias. This research provides a simple way to fabricate the UV PDs based on MZO films with faster response and higher detectivity.

Regulation of Substrate-Target Distance on the Microstructural, Optical and Electrical Properties of CdTe Films by Magnetron Sputtering.

Cadmium telluride (CdTe) films were deposited on glass substrates by direct current (DC) magnetron sputtering, and the effect of substrate-target distance (Dts) on properties of the CdTe films was investigated by observations of X-ray diffraction (XRD) patterns, atomic force microscopy (AFM), UV-VIS spectra, optical microscopy, and the Hall-effect measurement system. XRD analysis indicated that all samples exhibited a preferred orientation along the (111) plane, corresponding to the zinc blende structure, and films prepared using Dts of 4 cm demonstrated better crystallinity than the others. AFM studies revealed that surface morphologies of the CdTe films were strongly dependent on Dts, and revealed a large average grain size of 35.25 nm and a high root mean square (RMS) roughness value of 9.66 nm for films fabricated using Dts of 4 cm. UV-VIS spectra suggested the energy band gap (Eg) initially decreased from 1.5 to 1.45 eV, then increased to 1.68 eV as Dts increased from 3.5 to 5 cm. The Hall-effect measurement system revealed that CdTe films prepared with a Dts of 4 cm exhibited optimal electrical properties, and the resistivity, carrier mobility, and carrier concentration were determined to be 2.3 × 105 Ω∙cm, 6.41 cm²âˆ™V-1∙S-1, and 4.22 × 1012 cm-3, respectively.

Hierarchical manganese dioxide nanoflowers enable accurate ratiometric fluorescence enzyme-linked immunosorbent assay.

We first developed a green, mild and rapid method for the preparation of hierarchical manganese dioxide nanoflowers (MnO2 NFs) as nanozymes with intrinsic oxidase-like activity using citric acid for the reduction of potassium permanganate. The open structure of MnO2 NFs can lead to a larger specific surface area for improving the antibody loading amount and oxidase mimicking activity. In addition, carboxyl groups from the residual citric acid on the surface of MnO2 NFs afford a good affinity with the antibody through an amidation coupling reaction, which does not need complex surface modification anymore. Then, a reliable ratiometric fluorescence nanozyme-linked immunosorbent assay towards C-reactive protein (CRP) was designed successfully based on the MnO2 NFs. The high sensitivity and clinical feasibility of the presented methodology were demonstrated, which hold great promise in biomedical fields. Moreover, the mild and simple process for the synthesis of MnO2 NFs will make good contributions to many other applications.

Investigations on Structural, Optical and X-Radiation Responsive Properties of a-Se Thin Films Fabricated by Thermal Evaporation Method at Low Vacuum Degree.

Amorphous selenium (a-Se) thin films with a thickness of 1200 nm were successfully fabricated by thermal evaporation at a low vacuum degree of 10-2 Pa. The structural properties involving phase and morphology showed that a-Se thin films could be resistant to 60 °C in air. Also, a transformation to polycrystalline Selenium (p-Se) was shown as the annealing temperature rose to 62 °C and 65 °C, with obvious changes in color and surface morphology. Moreover, as the a-Se transformed to p-Se, the samples' transmittance decreased significantly, and the band gap declined dramatically from 2.15 eV to 1.92 eV. Finally, the X-radiation response of a-Se was investigated as an important property, revealing there is a remarkable response speed of photogeneration current both X-ray on and X-ray off, with a requirement of only a very small electrical field.

[Structural, morphological and optical properties of PbI2 thick films].

In the present paper, the structural, morphological and optical properties of PbI2 thick films prepared by close-spaced sublimation technique were investigated. It was found that the thickness of PbI2 films decreased from 1 000 µm to 220 µm with the increase in the sublimation source temperature. X-ray diffraction (XRD) pattern shows that the thick films are polycrystalline hexagonal structure with preferred growth orientation of (002) plane, and their grain size, dislocation density and growth stress are closely related to the source temperature. Images of scanning electron microscopy (SEM) reveal the accumulation of hexagonal plate-like particles which constitute the samples, and the particles with a diameter of 248 µm and a thickness of 32.7 µm, exhibit clearly layered structure. By spectrum fitting using Gauss function, the Raman spectra show a shift of about 147, 169, 217 and 210 cm(-1) respectively, the first three peaks correspond to the longitudinal optical vibrations (LO) mode in 4H-PbI2 crystal, while the last peak originate from a vibration pattern associated with SnO2 in substrate. Raman peak of 147 cm(-1) changes significantly with the increases in source temperature, and a dramatic decrease in peak intensity with broadening peak width occurred when the source temperature increased up to 225 degrees C or more. Under 340 nm excitation at room temperature, several weak photoluminescence peaks of PbI2 samples which associated with defects and exciton recombination near 2.25, 2.57 and 2.64 eV were observed. Given a comprehensive consideration of structural and spectral characterization results, PbI2 thick films with a thickness of about 659 µm deposited at a source temperature of 200 degrees C achieves the best crystalline quality.

Determination of diosgenin content in medicinal plants with enzyme-linked immunosorbent assay.

Many medicinal plants contain diosgenin, which has a significant medicinal value. However, there is currently no effective and rapid analytical method to determine the diosgenin content of plants or products. In the present work we have developed an indirect competitive enzyme-linked immunosorbent assay (ELISA) for the quantitative determination of diosgenin in herbal medicines. Diosgenin was conjugated with bovine serum albumin (BSA) for immunization. A polyclonal antibody developed in rabbits against a diosgenin-BSA conjugate was shown to be specific for diosgenin. The developed ELISA assay was highly sensitive, specific, and easy to perform. In addition, it gave more precise results with less variation than other methods that have been used in the past, including gravimetric and spectrophotometric assays, and correlated well with high-performance liquid chromatography. The diosgenin content determined by ELISA varied widely, with the highest and lowest values in rhizomes or tubers of Paris polyphylla and Dioscorea opposita Thunb. "Jiao-ban Yam", respectively, differing by more than 9000-fold. These results suggest that the ELISA method can be used as a rapid, simple, sensitive, and accurate tool for quantitative analysis of samples containing diosgenin, and may provide an important criterion for quality evaluation and a valuable tool for quality control of diosgenin-containing medicinal plants.

[Research on the polycrystalline CdS thin films prepared by close-spaced sublimation].

In the present paper, the factors of influence on the deposition rate of CdS films prepared by close-spaced sublimation (CSS) were first studied systematically, and it was found from the experiments that the deposition rate increased with the raised temperature of sublimation source, while decreased with the raised substrate temperature and the deposition pressure. The structure, morphology and light transmittance of the prepared samples were tested subsequently, and the results show: (1) The CdS films deposited under different oxygen partial pressure all present predominating growth lattice orientation (103), and further more the films will be strengthened after annealed under CdCl2 atmosphere. (2) The AFM images of CdS show that the films are compact and uniform in grain diameter, and the grain size becomes larger with the increased substrate temperature. Along with it, the film roughness was also augmented. (3) The transmittance in the shortwave region of visible light through the CdS films would be enhanced when its thickness is reduced, and that will help improve the shortwave spectral response of CdTe solar cells. Finally, the prepared CdS films were employed to fabricate CdTe solar cells, which have achieved a conversion efficiency of 10.29%, and thus the feasibility of CSS process in the manufacture of CdTe solar cells was validated primarily.