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Photonic materials for high-temperature applications: Synthesis and characterization by X-ray ptychographic tomography
摘要： Photonic materials for high-temperature applications need to withstand temperatures usually higher than 1000 ?C, whilst keeping their function. When exposed to high temperatures, such nanostructured materials are prone to detrimental morphological changes, however the structure evolution pathway of photonic materials and its correlation with the loss of material’s function is not yet fully understood. Here we use high-resolution ptychographic X-ray computed tomography (PXCT) and scanning electron microscopy (SEM) to investigate the structural changes in mullite inverse opal photonic crystals produced by a very-low-temperature (95 ?C) atomic layer deposition (ALD) super-cycle process. The 3D structural changes caused by the high-temperature exposure were quantified and associated with the distinct structural features of the ceramic photonic crystals. Other than observed in photonic crystals produced via powder colloidal suspensions or sol-gel infiltration, at high temperatures of 1400 ?C we detected a mass transport direction from the nano pores to the shells. We relate these different structure evolution pathways to the presence of hollow vertexes in our ALD-based inverse opal photonic crystals. Although the periodically ordered structure is distorted after sintering, the mullite inverse opal photonic crystal presents a photonic stopgap even after heat treatment at 1400 ?C for 100 h.
关键词： Ptychography X-ray computed tomography,High-temperature applications,3D image analysis,Photonic materials,Low-temperature atomic layer deposition
更新于2025-09-23 15:21:01
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Carbon and graphene quantum dots: a review on syntheses, characterization, biological and sensing applications for neurotransmitter determination
摘要： Neuro-transmitters have been considered to be essential biochemical molecules, which monitor physiological and behavioral function in the peripheral and central nervous systems. Thus, it is of high pharmaceutical and biological significance to analyze neuro-transmitters in the biological samples. So far, researchers have devised a lot of techniques for assaying these samples. It has been found that electro-chemical sensors possess features of robustness, selectivity, and sensitivity as well as real-time measurement. Graphene quantum dots (GQDs) and carbon QDs (CQDs) are considered some of the most promising carbon-based nanomaterials at the forefront of this research area. This is due to their characteristics including lower toxicity, higher solubility in various solvents, great electronic features, inertness, high specific surface areas, plenty of edge sites for functionalization, and strong chemical versatility, in addition to their ability to be modified via absorbent surface chemicals and the addition of modifiers or nano-materials. Hence in the present review, the synthesis methods of GQDs and CQDs has been summarized and their characterization methods also been analyzed. The applications of carbon-based QDs (GQDs and CQDs) in biological and sensing areas, such as biological imaging, drug/gene delivery, antibacterial and antioxidant activity, photoluminescence sensors, electrochemiluminescence sensors and electrochemical sensors, have also been discussed. This study then covers sensing features of key neurotransmitters, including dopamine, tyrosine, epinephrine, norepinephrine, serotonin and acetylcholine. Hence, issues and challenges of the GQDs and CQDs were analyzed for their further development.
关键词： Carbon quantum dots,Graphene quantum dots,Neurotransmitters,Biological applications,Sensing applications,Electrochemical sensors
更新于2025-09-23 15:19:57
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Discovery of Novel Two-Dimensional Photovoltaic Materials Accelerated by Machine Learning
摘要： Searching for novel, high-performance, two-dimensional photovoltaic (2DPV) materials is an important pursuit for solar cell applications. In this work, an efficient method based on the machine learning algorithm combined with high-throughput screening is developed. Twenty-six 2DPV candidates are successfully ruled out from 187093 experimentally identified inorganic crystal structures, whose conversion efficiencies are predicted by density functional theory calculations. Our results indicate that Sb2Se2Te, Sb2Te3, and Bi2Se3 exhibit conversion efficiencies that are much higher than those of others, which make them promising 2DPV candidates for further applications. The superior photovoltaic performance is then analyzed, and the hidden structure-related relationships with photovoltaic properties are established, thus providing important information for the further examination of 2DPV materials. Given the rapid development of the database of materials, this approach not only provides an efficient way of searching for novel 2DPV materials but also can be applied to exploration of a broad range of functional materials.
关键词： high-throughput screening,machine learning,solar cell applications,density functional theory,two-dimensional photovoltaic materials
更新于2025-09-23 15:19:57
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Six novel carbon and silicon allotropes with their potential application in photovoltaic field
摘要： By stacking up five novel cagelike structures, three novel three-dimensional (3D) sp3 bonding networks, named hP24, hP30 and hP36, were predicted in this work for the first time. These three newly discovered structures have trigonal unit cell with the space groups of P-3m1, P-3m1 and P3m1, respectively. Using first-principle calculations, the physical properties, including structural, mechanical, electronic and optical properties of C and Si in hP24, hP30 and hP36 phases were systematically studied. All these newly discovered carbon and silicon allotropes were proven to be thermodynamically and mechanically stable. The wide indirect bandgap value in range of 3.89 ~ 4.03 eV suggests that C in hP24, hP30 and hP36 phases have the potential to applied in high frequency and high power electronic devices. The direct bandgap value in range of 0.60 ~ 1.16 eV, the smaller electron and hole effective mass than diamond-Si, and the significantly better photon absorption characteristics than diamond-Si suggest that hP24-Si, hP30-Si and hP36-Si are likely to have better performance in photovoltaic applications than diamond-Si. hP24-Si also have the potential to be applied in infrared detectors.
关键词： carbon and silicon allotropes,effective mass,direct bandgap,photovoltaic applications,stability
更新于2025-09-23 15:19:57
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Wavelength-Conversion Material-Mediated Semiconductor Bonding for Photovoltaic Applications
摘要： Wavelength-conversion material-mediated semiconductor wafer bonding has been demonstrated, by utilizing an adhesive and viscous organic matrix embedding fluorescent particles. The wavelength-converting heterointerface can practically lead the spectral light incidence suitable for each photovoltaic material. This bonding and interfacial scheme is expected to enhance solar cell efficiency and structure flexibility by photon management and current matching among subcells. Moreover, our novel scheme provides the bonding formation and the interfacial function generation simultaneously, and therefore potentially realizes low-cost and high-throughput production processes.
关键词： fluorescent particles,wavelength-conversion,solar cell efficiency,photovoltaic applications,semiconductor bonding
更新于2025-09-23 15:19:57
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Magnetic bipolar transistor based on ZnO/NiO/Si heterostructure using pulsed laser deposition
摘要： Oxide semiconductors are promising candidates for next generation electronics. In this work, magnetic bipolar transistor was fabricated by growing thin films of p-NiO and n-ZnO on n-type silicon wafer by pulsed laser deposition technique with an in-situ annealing at 670○ C in the presence of oxygen. The structural characterization of these films was done by X-ray diffraction and Raman spectroscopy and magnetic properties were studied by vibrating sample magnetometer (VSM). I-V characteristic of fabricated transistor was tested in common emitter configuration with DC biasing. Junction parameters such as ideality factor, series resistance, and transistor parameters like q-point were determined by using conventional transistor output characteristics. The diode and transistor showed an increase in current with the externally applied magnetic field due to the presence of Nickel or Oxygen vacancies in NiO attributing to spin polarized bipolar transport. Therefore the current amplification in these devices can be controlled by spin; making it attractive for spintronic applications.
关键词： oxide semiconductors,pulsed laser deposition,spintronic applications,magnetic bipolar transistor
更新于2025-09-23 15:19:57
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Organic Photodetectors: Materials, Structures, and Challenges
摘要： Owing to the advantages of solution processing, light weight, low cost and mechanical flexibility, organic photodetectors (OPDs) have attracted great interests and become a new member in the photodetector family. Nowadays, OPDs have made considerable progress and can be compared with traditional photodetectors in some aspects. They present potential applications in portable and wearable devices. However, there are still some issues that need to be overcome and there is great room for new development. In this essay, the significant advances of OPDs are summarized and discussed, and the future for OPDs is prospected from the aspects of materials, structures and applications. We believe that this essay can inspire new ideas for developing innovative high-performance OPDs and exploring their practical applications.
关键词： materials,organic photodetectors,structures,applications
更新于2025-09-23 15:19:57
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[IEEE 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Xiamen, China (2019.12.17-2019.12.20)] 2019 Photonics & Electromagnetics Research Symposium - Fall (PIERS - Fall) - Stealth Design of the Quantum Radar Scattering Based on the Two Typical 2D Targets
摘要： We have developed a robust sensor for mounting on bridges over rivers and streams. These bridge-mounted river stage sensors (BMRSS) make periodic measurements of the distance from the sensor to the water level below. Properly interpreted, these measurements provide river-stage information, data of great importance to society and crucial to effective ?ood forecasting. The traditional approach to river stage measurement is the installation of pipes in rivers, digging stilling wells, and the construction of attendant brick-and-mortar infrastructure. The cost of this approach limits the deployment to larger rivers. In most instances, river-stage data from smaller tributaries are few, even though such data can greatly enhance the quality of ?ood-forecasting models’ outputs. In contrast, BMRSS units are an order of magnitude less expensive and allow for widespread deployment. BMRSS units incorporate an ultrasonic distance-measuring module, a solar panel/battery/charge controller, and a GPS receiver. In recent years, the Internet access through commercial cellular networks has become ubiquitous, even in most rural areas. BMRSS units incorporate cell modems and transmit data through the Internet to servers at the Iowa Flood Center. Here, the data are ingested into relational databases and made available to ?ood forecasting models and information systems. We have deployed and operated more than 220 BMRSS units across Iowa, many for several years continuously.
关键词： hazards,cellular networks,Sensor systems and applications,instrumentation and measurement
更新于2025-09-23 15:19:57
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Radiation effects on the performance of flexible perovskite solar cells for space applications
摘要： Solar cells for space applications are required to be tolerant to harsh environmental conditions. Especially, tolerance against radiation and charged particles is mandatory. Here we study the effect of low-energy (<< 1 MeV) proton radiation to evaluate the radiation tolerance of flexible perovskite solar cells (PSCs). Low-energy protons are more likely to be stopped in the shallower regions of solar cells, thereby causing greater performance degradation than high-energy protons. Flexible PSCs with layer sequence PET/ITO/PEDOT:PSS/perovskite/PCBM/BCP/metal were fabricated and were irradiated with 100 keV protons (fluence from ~ 3 × 1010 to ~ 3 × 1012 protons/cm2, equating several years in space). Flexible PSCs exhibited a good radiation tolerance and did not show color center formation, revealing their outstanding resistance against low-energy proton radiation. This can be credited to the combined effect of intrinsically large carrier diffusion length exceeding the thin absorber film thickness and the defect tolerance of perovskite crystals.
关键词： defect tolerance,space applications,radiation tolerance,low-energy proton radiation,flexible perovskite solar cells
更新于2025-09-23 15:19:57
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Survey and technological analysis of laser and its defense applications
摘要： The laser technology has made remarkable progress over the past couple of decades. It is being widely employed in diverse domains, such as holography, space sciences, spectroscopy, medical sciences, micro and power electronics, industrial engineering, and most distinctively, as directed energy military weapons. Owing to their active transmissions, laser systems are similar to microwave radars to some extent; however, unlike conventional radars, the laser operates at very high frequencies thus making it a potent enabler of narrow-beam and high energy aerial deployments, both in offensive and defensive roles. In modern avionics systems, laser target indicators and beam riders are the most common devices that are used to direct the Laser Guided Weapons (LGW) accurately to the ground targets. Additionally, compact size and outstanding angular resolution of laser-based systems motivate their use for drones and unmanned aerial applications. Moreover, the narrow-beam divergence of laser emissions offers a low probability of intercept, making it a suitable contender for secure transmissions and safety-critical operations. Furthermore, the developments in space sciences and laser technology have given synergistic potential outcomes to use laser systems in space operations. This paper comprehensively reviews laser applications and projects for strategic defense actions on the ground or in space. Additionally, a detailed analysis has been done on recent advancements of the laser technology for target indicators and range-finders. It also reviews the advancements in the field of laser communications for surveillance, its earlier state of the art, and ongoing scientific research and advancements in the domain of high energy directed laser weapons that have revolutionized the evolving military battlefield. Besides offering a comprehensive taxonomy, the paper also critically analyzes some of the recent contributions in the associated domains.
关键词： Survey,Non-lethal Weapons,Taxonomy,Laser Military Projects,Laser Military Applications,Directed Energy Weapons,Laser Systems
更新于2025-09-23 15:19:57