Edge enhancement in three-dimensional vortex imaging based on FINCH by Bessel-like spiral phase modulation.

Edge enhancement, as an important part of image processing, has played an essential role in amplitude-contrast and phase-contrast object imaging. The edge enhancement of three-dimensional (3D) vortex imaging has been successfully implemented by Fresnel incoherent correlation holography (FINCH), but the background noise and image contrast effects are still not satisfactory. To solve these issues, the edge enhancement of FINCH by employing Bessel-like spiral phase modulation is proposed and demonstrated. Compared with the conventional spiral phase modulated FINCH, the proposed technique can achieve high-quality edge enhancement 3D vortex imaging with lower background noise, higher contrast and resolution. The significantly improved imaging quality is mainly attributed to the effective sidelobes' suppression in the generated optical vortices with the Bessel-like modulation technique. Experimental results of the small circular aperture, resolution target, and the Drosophila melanogaster verify its excellent imaging performance. Moreover, we also proposed a new method for selective edge enhancement of 3D vortex imaging by breaking the symmetry of the spiral phase in the algorithmic model of isotropic edge enhancement. The reconstructed images of the circular aperture show that the proposed method is able to enhance the edges of the given objects selectively in any desired direction.

Colloidal Chiral Carbon Dots: An Emerging System for Chiroptical Applications.

Chiral CDots (c-CDots) not only inherit those merits from CDots but also exhibit chiral effects in optical, electric, and bio-properties. Therefore, c-CDots have received significant interest from a wide range of research communities including chemistry, physics, biology, and device engineers. They have already made decent progress in terms of synthesis, together with the exploration of their optical properties and applications. In this review, the chiroptical properties and chirality origin in extinction circular dichroism (ECD) and circularly polarized luminescence (CPL) of c-CDots is briefly discussed. Then, the synthetic strategies of c-CDots is summarized, including one-pot synthesis, post-functionalization of CDots with chiral ligands, and assembly of CDots into chiral architectures with soft chiral templates. Afterward, the chiral effects on the applications of c-CDots are elaborated. Research domains such as drug delivery, bio- or chemical sensing, regulation of enzyme-like catalysis, and others are covered. Finally, the perspective on the challenges associated with the synthetic strategies, understanding the origin of chirality, and potential applications is provided. This review not only discusses the latest developments of c-CDots but also helps toward a better understanding of the structure-property relationship along with their respective applications.

2D Ruddlesden-Popper Sn-Based Perovskite Weak Light Detector for Image Transmission and Reflection Imaging.

2D Ruddlesden-Popper Sn-based perovskite has excellent optoelectronic properties and weak halide ion migration characteristics, making it an ideal candidate for weak light detection, which has great potential in light communication, and medical applications. Although Sn-based perovskite photodetectors are developed, weak light detection is not demonstrated yet. Herein, a high-performance self-powered photodetector with the capability to detect ultra-weak light signals is designed based on vertical PEA2 SnI4 /Si nanowires heterojunction. Due to the low dark current and high light absorption efficiency, the devices present a remarkable responsivity of 42.4 mA W-1 , a high detectivity of 8 × 1011 Jones, and an ultralow noise current of 2.47 × 10-13 A Hz-1/2 . Especially, the device exhibits a high on-off current ratio of 18.6 at light signals as low as 4.60 nW cm-2 , revealing the capacity to detect ultra-weak light. The device is applied as a signal receiver and realized image transmission in light communication system. Moreover, high-resolution reflection imaging and multispectral imaging are obtained using the device as the sensor in the imaging system. These results reveal that 2D PEA2 SnI4 -based self-powered photodetectors with low-noise current possess enormous potential in future weak light detection.

A Multiscale Instance Segmentation Method Based on Cleaning Rubber Ball Images.

The identification of wear rubber balls in the rubber ball cleaning system in heat exchange equipment directly affects the descaling efficiency. For the problem that the rubber ball image contains impurities and bubbles and the segmentation is low in real time, a multi-scale feature fusion real-time instance segmentation model based on the attention mechanism is proposed for the object segmentation of the rubber ball images. First, we introduce the Pyramid Vision Transformer instead of the convolution module in the backbone network and use the spatial-reduction attention layer of the transformer to improve the feature extraction ability across scales and spatial reduction to reduce computational cost; Second, we improve the feature fusion module to fuse image features across scales, combined with an attention mechanism to enhance the output feature representation; Third, the prediction head separates the mask branches separately. Combined with dynamic convolution, it improves the accuracy of the mask coefficients and increases the number of upsampling layers. It also connects the penultimate layer with the second layer feature map to achieve detection of smaller images with larger feature maps to improve the accuracy. Through the validation of the produced rubber ball dataset, the Dice score, Jaccard coefficient, and mAP of the actual segmented region of this network with the rubber ball dataset are improved by 4.5%, 4.7%, and 7.73%, respectively, and our model achieves 33.6 fps segmentation speed and 79.3% segmentation accuracy. Meanwhile, the average precision of Box and Mask can also meet the requirements under different IOU thresholds. We compared the DeepMask, Mask R-CNN, BlendMask, SOLOv1 and SOLOv2 instance segmentation networks with this model in terms of training accuracy and segmentation speed and obtained good results. The proposed modules can work together to better handle object details and achieve better segmentation performance.

Histidine-Mediated Synthesis of Chiral Cobalt Oxide Nanoparticles for Enantiomeric Discrimination and Quantification.

Chiral transition metal oxide nanoparticles (CTMOs) are attracting a lot of attention due to their fascinating properties. Nevertheless, elucidating the chirality induction mechanism often remains a major challenge. Herein, the synthesis of chiral cobalt oxide nanoparticles mediated by histidine (Co3 O4 @L-His and Co3 O4 @D-His for nanoparticles synthesized in the presence of L- and D-histidine, respectively) is investigated. Interestingly, these CTMOs exhibit remarkable and tunable chiroptical properties. Their analysis by x-ray photoelectron, Fourier transform infrared, and ultraviolet-visible absorption spectroscopy indicates that the ratio of Co2+ /Co3+ and their interactions with the imidazole groups of histidine are behind their chiral properties. In addition, the use of chiral Co3 O4 nanoparticles for the development of sensitive, rapid, and enantioselective circular dichroism-based sensors is demonstrated, allowing direct molecular detection and discrimination between cysteine or penicillamine enantiomers. The circular dichroism response of the chiral Co3 O4 exhibits a limit of detection and discrimination of cysteine and penicillamine enantiomers as low as 10 µm. Theoretical calculations suggest that the ligand exchange and the coexistence of both species adsorbed on the oxide surface are responsible for the enantiomeric discrimination. This research will enrich the synthetic approaches to obtain CTMOs and enable the extension of the applications and the discovery of new chiroptical properties.

Multifunctional Organic-Inorganic Hybrid Perovskite Microcrystalline Engineering and Electromagnetic Response Switching Multi-Band Devices.

High-efficiency electromagnetic (EM) functional materials are the core building block of high-performance EM absorbers and devices, and they are indispensable in various fields ranging from industrial manufacture to daily life, or even from national defense security to space exploration. Searching for high-efficiency EM functional materials and realizing high-performance EM devices remain great challenges. Herein, a simple solution-process is developed to rapidly grow gram-scale organic-inorganic (MAPbX3 , X = Cl, Br, I) perovskite microcrystals. They exhibit excellent EM response in multi bands covering microwaves, visible light, and X-rays. Among them, outstanding microwave absorption performance with multiple absorption bands can be achieved, and their intrinsic EM properties can be tuned by adjusting polar group. An ultra-wideband bandpass filter with high suppression level of -71.8 dB in the stopband in the GHz band, self-powered photodetectors with tunable broadband or narrowband photoresponse in the visible-light band, and a self-powered X-ray detector with high sensitivity of 3560 µC Gyair -1  cm-2  in the X-ray band are designed and realized by precisely regulating the physical features of perovskite and designing a novel planar device structure. These findings open a door toward developing high-efficiency EM functional materials for realizing high-performance EM absorbers and devices.

Regulating interface Schottky barriers toward a high-performance self-powered imaging photodetector.

Two-dimensional (2D) layered organic-inorganic hybrid perovskites have attracted wide attention in high-performance optoelectronic applications due to their good stability and excellent optoelectronic properties. Here, a high-performance self-powered photodetector is realized based on an asymmetrical metal-semiconductor-metal (MSM) device structure (Pt-(PEA)2PbI4 SC-Ag), which introduces a strong built-in electric field by regulating interface Schottky barriers. Benefitting from excellent built-in electrical potential, the photodetector shows attractive photovoltaic properties without any power supply, including high photo-responsivity (114.07 mA W-1), fast response time (1.2 µs/582 µs) and high detectivity (4.56 × 1012 Jones). Furthermore, it exhibits high-fidelity imaging capability at zero bias voltage. In addition, the photodetectors show excellent stability by maintaining 99.4% of the initial responsivity in air after 84 days. This work enables a significant advance in perovskite SC photodetectors for developing stable and high-performance devices.

In Situ Fabrication of PdSe2/GaN Schottky Junction for Polarization-Sensitive Ultraviolet Photodetection with High Dichroic Ratio.

Polarization-sensitive ultraviolet (UV) photodetection is of great technological importance for both civilian and military applications. Two-dimensional (2D) group-10 transition-metal dichalcogenides (TMDs), especially palladium diselenide (PdSe2), are promising candidates for polarized photodetection due to their low-symmetric crystal structure. However, the lack of an efficient heterostructure severely restricts their applications in UV-polarized photodetection. Here, we develop a PdSe2/GaN Schottky junction by in situ van der Waals growth for highly polarization-sensitive UV photodetection. Owing to the high-quality junction, the device exhibits an appealing UV detection performance in terms of a large responsivity of 249.9 mA/W, a high specific detectivity, and a fast response speed. More importantly, thanks to the puckered structure of the PdSe2 layer, the device is highly sensitive to polarized UV light with a large dichroic ratio up to 4.5, which is among the highest for 2D TMD material-based UV polarization-sensitive photodetectors. These findings further enable the demonstration of the outstanding polarized UV imaging capability of the Schottky junction, as well as its utility as an optical receiver for secure UV optical communication. Our work offers a strategy to fabricate the PdSe2-based heterostructure for high-performance polarization-sensitive UV photodetection.

A defect-induced broadband photodetector based on WS2/pyramid Si 2D/3D mixed-dimensional heterojunction with a light confinement effect.

Broadband photodetection is of vital importance for both civil and technological applications. The widespread use of commercial photodiodes based on traditional semiconductors (e.g. GaN, Si, and InGaAs) is limited to the relatively narrow response range. In this work, we have demonstrated a self-driven and broadband photodetector based on WS2/pyramid Si 2D/3D mixed-dimensional van der Waals (vdW) heterojunction, which is assembled by directly transferring 2D WS2 film on 3D pyramid Si. Thanks to the enhanced light absorption with the pyramid Si structure, the defect-induced narrowed bandgap of the WS2 film, and high-quality vdW heterojunction, impressive device performances in terms of a large responsivity of 290 mA W-1, a high specific detectivity of up to 2.6 × 1014 Jones and an ultrabroad response spectrum ranging from 265 nm to 3.0 µm are achieved at zero bias. Importantly, the photodetector can function as an infrared imaging cell with a high spatial resolution. The totality of these excellent features confirms that the demonstrated WS2/pyramid Si 2D/3D mixed-dimensional vdW heterojunction device may hold great promise for applications in high-performance broadband infrared photodetection and imaging.

Reduced Red Mud as the Solar Absorber for Solar-Driven Water Evaporation and Vapor-Electricity Generation.

The emergent solar-driven water evaporation technology provides a reassuring scheme for red mud (RM) utilization in environment and materials science. With fewer restrictions on raw materials, wide availability of sheer quantity, and high complexity in chemical composition, the RM may be a promising candidate for solar absorbers. Here, we developed a novel solar absorber with reduced RM. It features favorable light absorption and photothermal conversion ability using biomass pyrolysis. When added to the polyvinyl alcohol and chitosan gel substrate, the light absorptance can reach 94.65%, while the corresponding evaporation rate is as high as 2.185 kg m-2 h-1 under an illumination density of 1 kW m-2. We further demonstrated its potential as an efficient solar absorber in the solar-driven water evaporation and the thermoelectric device to realize the stable and efficient coproduction of vapor and electricity.

Exploring the structural changes in nitrogen-fixing microorganisms of rhizosheath during the growth of Stipagrostis pennata in the desert.

PURPOSE: Rhizosheath is an adaptive feature for the survival of Stipagrostis pennata in desert systems. Although microorganisms play important ecological roles in promoting the nitrogen cycle of rhizosheath, the diversity and function of nitrogen-fixing microorganism communities have not been fully understood. MATERIALS AND METHODS: Therefore, the aim of the present study is to explore the nitrogen fixation ability of rhizosheaths and the changes in abundance of nitrogen-fixing microorganisms at different growth periods of S. pennata. We sequenced the nifH gene through sequencing to identify the structure and diversity of nitrogen-fixing microorganisms of S. pennata at different growth periods of rhizosheaths. RESULTS: A total of 1256 operational taxonomic units (OTUs) were identified by nifH sequence and distributed in different growth periods. There were five OTUs distributed in each sample at the same time, and the abundance and diversity of microorganisms in fruit period were much higher than those in other periods. Mainly four phyla were involved, among which Proteobacteria was the most abundant in all groups. CONCLUSIONS: In general, the present study investigated the abundance and characteristics of nitrogen-fixing microorganisms of rhizosheaths in different growth periods of S. pennata. It also may elucidate and indicate that the structure of nitrogen-fixing microorganisms of rhizosheaths in different growth periods of S. pennata had changed.

Self-Cleaning Integrative Aerogel for Stable Solar-Assisted Desalination.

The solar-assisted desalination generator (SADG) shows great potential for solving water scarcity problems. However, salt precipitation and accumulation is still a challenge for SADG, which slows down solar steam generation performance of evaporator during operation. Here, a facile integrative evaporator featuring stable and high evaporation performance breaks this bottleneck. By using a rational design in which amorphous carbon particles are evenly composited within the porous chitosan aerogel, the evaporator not only integrates excellent light absorption, heat management, and water transportation abilities but also endows a large vapor escape space. Upon desalination, salt concentration ingredients between carbon particles and chitosan membranes can be quickly balanced by water transport in interconnected chitosan chains, and thus salt precipiation on the evaporator surface would be avoided. Compared to other salt-rejection evaporators, the integrative evaporator can operate in 3.5 wt% brine for 60 days without salt precipiation and exhibits a stable evaporation rate (1.70 kg m-2 h-1), indicating its potential for practical applications in seawater desalination and the harvest of clean drinking water.

Strategy of All-Inorganic Cs3Cu2I5/Si-Core/Shell Nanowire Heterojunction for Stable and Ultraviolet-Enhanced Broadband Photodetectors with Imaging Capability.

In this study, for the first time, the integration of nontoxic ternary copper halide Cs3Cu2I5 with one-dimensional Si nanowires (NWs) was reported to achieve an ultraviolet (UV)-enhanced Si NW broadband photodetector. A compact and uniform coverage of Cs3Cu2I5 on the top and sidewall of Si NWs formed a core/shell heterostructure, in which Si NWs served as the growth template and the electron-transport layer, and Cs3Cu2I5 was employed as the UV photoactive material and the hole-transport layer. The as-fabricated Cs3Cu2I5/Si-core/shell NW photodetector demonstrates a multiband photodetection from the deep UV to near-infrared region, a fast response speed of 92.5/189.2 µs (265 nm), and a high photoresponsivity of 130 mA/W, nearly 600 times as much as the reference device constructed using Si NWs. More importantly, the proposed photodetector exhibits an excellent stability in air ambient. Typically, it could endure a high temperature of 60 °C for 11 h consecutive working; after storage in air ambient for two weeks, its photodetection ability can almost be retained. Additionally, high-resolution UV imaging applications were presented by employing the proposed photodetector as sensing pixels. These obtained results verify the effectiveness of the Cs3Cu2I5/Si-core/shell NW heterojunction strategy for UV-enhanced broadband photodetection, making such a device really possible for practical applications.

An Electrically Modulated Single-Color/Dual-Color Imaging Photodetector.

An electrically modulated single-/dual-color imaging photodetector with fast response speed is developed based on a small molecule (COi 8DFIC)/perovskite (CH3 NH3 PbBr3 ) hybrid film. Owing to the type-I heterojunction, the device can facilely transform dual-color images to single-color images by applying a small bias voltage. The photodetector exhibits two distinct cut-off wavelengths at ≈544 nm (visible region) and ≈920 nm (near-infrared region), respectively, without any power supply. Its two peak responsivities are 0.16 A W-1 at ≈525 nm and 0.041 A W-1 at ≈860 nm with a fast response speed (≈102 ns). Under 0.6 V bias, the photodetector can operate in a single-color mode with a peak responsivity of 0.09 A W-1 at ≈475 nm, showing a fast response speed (≈102 ns). A physical model based on band energy theory is developed to illustrate the origin of the tunable single-/dual-color photodetection. This work will stimulate new approaches for developing solution-processed multifunctional photodetectors for imaging photodetection in complex circumstances.

An ultrasensitive self-driven broadband photodetector based on a 2D-WS2/GaAs type-II Zener heterojunction.

High-performance broadband photodetectors have attracted extensive research interest because of their significance in optoelectronic applications. In this study, a highly sensitive room-temperature (RT) broadband photodetector composed of a WS2/GaAs type-II van der Waals heterojunction was demonstrated, which exhibited obvious photoresponse to broadband light illumination from 200 to 1550 nm beyond the limitation of the bandgaps. Impressive device performances were achieved in terms of a low noise current of ∼59.7 pA, a high responsivity up to 527 mA W-1, an ultrahigh Ilight/Idark ratio of 107, a large specific detectivity of 1.03 × 1014 Jones, a minimum detection light intensity of 17 nW cm-2 and an external quantum efficiency (EQE) up to 80%. Transient photoresponse measurements revealed that the present detector is capable of working at a high frequency with a 3 dB cutoff frequency up to 10 kHz and a corresponding rise/fall time of 21.8/49.6 µs. Notably, this heterojunction device demonstrated Zener tunneling behaviors with a threshold voltage of -4 V. The capacitance-voltage (C-V) properties of the heterojunction were investigated to understand the device performances. In addition, the as-fabricated device can function as an image sensor with an outstanding imaging capability. Considering the above superior features, the proposed WS2/GaAs type-II van der Waals heterojunction may find great potential in high-performance broadband photodetection applications.

Diamond based photodetectors for solar-blind communication.

High performance solar-blind photodetectors have been fabricated from diamond wafers. The peak responsivity is 13.0 A/W at 222 nm with a dark current of 0.93 nA under 60 V bias. The rise and decay times of the photodetector are about 1.3 µs and 203 µs, respectively. The responsivity and response time of the device are both among the best values ever reported for diamond-based photodetectors. A solar-blind optical communication system has been constructed by employing the diamond photodetector as a signal receiver for the first time. Benefiting from the high spectral selectivity of the diamond photodetector, the communication system has excellent anti-interference ability. The results reported in this paper may pave the way for the future application of diamond-based solar-blind photodetectors in confidential communications.

Highly Polarization-Sensitive, Broadband, Self-Powered Photodetector Based on Graphene/PdSe2/Germanium Heterojunction.

Polarization-sensitive photodetection in a broad spectrum range is highly desired due to the great significance in military and civilian applications. Palladium diselenide (PdSe2), a newly explored air-stable, group 10 two-dimensional (2D) noble metal dichalcogenide with a puckered pentagonal structure, holds promise for polarization-sensitive photodetection. Herein, we report a highly polarization-sensitive, broadband, self-powered photodetector based on graphene/PdSe2/germanium heterojunction. Owing to the enhanced light absorption of the mixed-dimensional van der Waals heterojunction and the effective carrier collection with graphene transparent electrode, the photodetector exhibits superior device performance in terms of a large photoresponsivity, a high specific detectivity, a fast response speed to follow nanosecond pulsed light signal, and a broadband photosensitivity ranging from deep ultraviolet (DUV) to mid-infrared (MIR). Significantly, highly polarization-sensitive broadband photodetection with an ultrahigh polarization sensitivity of 112.2 is achieved, which represents the best result for 2D layered material-based photodetectors. Further, we demonstrated the high-resolution polarization imaging based on the heterojunction device. This work reveals the great potential of 2D PdSe2 for high-performance, air-stable, and polarization-sensitive broadband photodetectors.

Relationship between microbial diversity and nitrogenase activity of Stipagrostis pennata rhizosheath.

Nitrogen is the key factor for plant survival and growth, especially in the desert. Stipagrostis pennata, a sand born drought-resistant plant, could colonize pioneerly in Gurbantunggut Desert during revegetation. One strategy for their environment adaptation was the rhizosheath formatted by root-hair, mucilaginous exudates, microbial components, and soil particles, for which not only provides a favorable living microenvironment but also supplies essential nutrients. To understand the relationship between microorganisms living in rhizosheaths and the nitrogen nutrition supply, the microbial diversity and nitrogenase activity was estimated during the growth of S. pennata. Five samples of the rhizosheath, which based on the development periods of the plant, regreen, flowering, filling, seed maturating, and withering period, were collected. The nitrogenase activity was estimated by acetylene reduction and the microbial diversity was analyzed by 16S rRNA high-throughput sequencing. The results showed that the nitrogenase activity was increased slowly during regreen to flowering, while reached a peak rapidly at filling sample and then decreased gradually. A total of 274 operational taxonomic units (OTUs) were identified and significant differences in community structure and composition at each growth period. Among them, the main phyla included Actinobacteria and Proteus, which were the most abundant phyla in all periods. In addition, the microbial diversity in the grain filling period was higher than other periods in view of the analysis of alpha diversity and beta diversity. Furthermore, principal component analysis (PCA) analysis showed that the microbial communities in the filling period was low in similarity with other periods. Most importantly, the OTUs associated with nitrogen fixation is the most during the filling period, involving Phagecidae and Fucoraceae. Overall, the study not only revealed the differences in nitrogenase activity among different developmental periods in S. pennata, but also explored the potential bridges between it and community structure and diversity of bacteria.

Simultaneous quantification of oxybutynin and its active metabolite N-desethyl oxybutynin in rat plasma by ultra-high-performance liquid chromatography-tandem mass spectrometry and its application in a pharmacokinetic study of oxybutynin transdermal patch.

A rapid, selective and sensitive ultra-high-performance liquid chromatography-tandem mass spectrometry method was developed to simultaneously determine oxybutynin and its active metabolite N-desethyl oxybutynin in rat plasma. A 0.1 mL sample of plasma was extracted with n-hexane. Chromatographic separation was performed on a UPLC BEH C18 column (2.1 × 100 mm i.d.,1.7 µm) with mobile phase of methanol-water (containing 2 mmol/L ammonium acetate and 0.1% formic acid; 90:10, v/v). The detection was performed in positive selected reaction monitoring mode. Each plasma sample was chromatographed within 3 min. The linear calibration curves were obtained in the concentration range of 0.0944-189 ng/mL (r ≥ 0.99) for oxybutynin and 0.226-18.0 ng/mL (r ≥ 0.99) for N-desethyl oxybutynin. The intra- and inter-day precision (relative standard deviation) values were not more than 14% and the accuracy (relative error) was within ±7.6%. The method described was superior to previous methods for the quantitation of oxybutynin with three product ions and was successfully applied to a pharmacokinetic study of oxybutynin and its active metabolite N-desethyl oxybutynin in rat plasma after transdermal administration.

Characterization of the focusing performance of axial line-focused spiral zone plates.

Axial line-focused spiral zone plates were developed for operation at optical wavelengths. The design, fabrication, and diffraction properties of the proposed element are presented. Numerical results showed that hollow beams could be generated, and that the element can be employed for a multi-wavelength operation. The hollow beam within the focal depth was demonstrated experimentally, using a charge-coupled device camera and sliding guide. The results were consistent with those obtained by the simulations. The proposed optical device exhibits significant potential for various applications including optical manipulation and lithography.