Quantitative phase analysis and molecular structure of human gallstones using synchrotron radiation X-ray diffraction and FTIR spectroscopy.

Human gallstones are the most common disorder in the biliary system, affecting up to 20 % of the adult population. The formation of gallstones is primarily due to the supersaturating of cholesterol in bile. In order to comprehend gallstone disease in detail, it is necessary to have accurate information about phase identification and molecular structure. Different types of gallstone samples were collected from the Middle East area after surgical operations including; cholesterol, pigment, and mixed gallstones. To estimate the basic information about the stone formation and the pathophysiology of cholelithiasis as well as to classify the collected human gallstones, attenuated total reflection Fourier transform Infrared spectrometry (ATR-FTIR) was used to analyze the different gallstone structures in the wavenumber range from 400 to 4000 cm-1. Calcium bilirubinate was specified by the bands at 1662 cm-1, 1626 cm-1, and 1572 cm-1, while cholesterol rings were designated by the bands at 1464, 1438, 1055, and 1022 cm-1. It can be assumed that all samples consist of mixed gallstones based on the doublets at 1375 cm-1 and 1365 cm-1. The levels of calcium bilirubin and various minerals varied among the analyzed samples, indicating the heterogeneity in their composition and suggesting potential implications for gallstone formation. Based on the quantitative phase analysis using synchrotron radiation X-ray diffraction (SR-XRD), two phases of anhydrous cholesterol as a major content and one phase of monohydrate cholesterols as trace content represent the main components of most of the gallstones. Additional phases of calcium carbonate in the form of calcite, vaterite, aragonite, and bilirubinate were also quantified. According to the outcomes of the FTIR and the SR-XRD measurements, there exists a statistical correlation between the different types of chemical constituents of the gallstones.

Simultaneous Growth Strategy of High-Optical-Efficiency GaN NWs on a Wide Range of Substrates by Pulsed Laser Deposition.

Here, we explore a catalyst-free single-step growth strategy that results in high-quality self-assembled single-crystal vertical GaN nanowires (NWs) grown on a wide range of common and novel substrates (including GaN, Ga2O3, and monolayer two-dimensional (2D) transition-metal dichalcogenide (TMD)) within the same chamber and thus under identical conditions by pulsed laser deposition. High-resolution transmission electron microscopy and scanning transmission electron microscopy (HR-STEM) and grazing incidence X-ray diffraction measurements confirm the single-crystalline nature of the obtained NWs, whereas advanced optical and cathodoluminescence measurements provide evidence of their high optical quality. Further analyses reveal that the growth is initiated by an in situ polycrystalline layer formed between the NWs and substrates during growth, while as its thickness increases, the growth mode transforms into single-crystalline NW nucleation. HR-STEM and corresponding energy-dispersive X-ray compositional analyses indicate possible growth mechanisms. All samples exhibit strong band edge UV emission (with a negligible defect band) dominated by radiative recombination with a high optical efficiency (∼65%). As all NWs have similar structural and optical qualities irrespective of the substrate used, this strategy will open new horizons for developing III-nitride-based devices.

Manipulation of hot carrier cooling dynamics in two-dimensional Dion-Jacobson hybrid perovskites via Rashba band splitting.

Hot-carrier cooling processes of perovskite materials are typically described by a single parabolic band model that includes the effects of carrier-phonon scattering, hot phonon bottleneck, and Auger heating. However, little is known (if anything) about the cooling processes in which the spin-degenerate parabolic band splits into two spin-polarized bands, i.e., the Rashba band splitting effect. Here, we investigated the hot-carrier cooling processes for two slightly different compositions of two-dimensional Dion-Jacobson hybrid perovskites, namely, (3AMP)PbI4 and (4AMP)PbI4 (3AMP = 3-(aminomethyl)piperidinium; 4AMP = 4-(aminomethyl)piperidinium), using a combination of ultrafast transient absorption spectroscopy and first-principles calculations. In (4AMP)PbI4, upon Rashba band splitting, the spin-dependent scattering of hot electrons is responsible for accelerating hot-carrier cooling at longer delays. Importantly, the hot-carrier cooling of (4AMP)PbI4 can be extended by manipulating the spin state of the hot carriers. Our findings suggest a new approach for prolonging hot-carrier cooling in hybrid perovskites, which is conducive to further improving the performance of hot-carrier-based optoelectronic and spintronic devices.

Identifying Carrier Behavior in Ultrathin Indirect-Bandgap CsPbX3 Nanocrystal Films for Use in UV/Visible-Blind High-Energy Detectors.

High-energy radiation detectors such as X-ray detectors with low light photoresponse characteristics are used for several applications including, space, medical, and military devices. Here, an indirect bandgap inorganic perovskite-based X-ray detector is reported. The indirect bandgap nature of perovskite materials is revealed through optical characterizations, time-resolved photoluminescence (TRPL), and theoretical simulations, demonstrating that the differences in temperature-dependent carrier lifetime related to CsPbX3 (X = Br, I) perovskite composition are due to the changes in the bandgap structure. TRPL, theoretical analyses, and X-ray radiation measurements reveal that the high response of the UV/visible-blind yellow-phase CsPbI3 under high-energy X-ray exposure is attributed to the nature of the indirect bandgap structure of CsPbX3 . The yellow-phase CsPbI3 -based X-ray detector achieves a relatively high sensitivity of 83.6 µCGyair-1 cm-2 (under 1.7 mGyair s-1 at an electron field of 0.17 V µm-1 used for medical diagnostics) although the active layer is based solely on an ultrathin (≈6.6 µm) CsPbI3 nanocrystal film, exceeding the values obtained for commercial X-ray detectors, and further confirming good material quality. This CsPbX3 X-ray detector is sufficient for cost-effective device miniaturization based on a simple design.

Enhanced UV Emission of GaN Nanowires Functionalized by Wider Band Gap Solution-Processed p-MnO Quantum Dots.

GaN-based UV light-emitting devices suffer from low efficiency. To mitigate this issue, we hybridized GaN nanowires (NWs) grown on Si substrates by plasma-assisted molecular beam epitaxy with solution-processed p-type MnO quantum dots (QDs) characterized by a wider band gap (∼5 eV) than that of GaN. Further investigations reveal that the photoluminescence intensity of the GaN NWs increases up to ∼3.9-fold (∼290%) after functionalizing them with p-MnO QDs, while the internal quantum efficiency is improved by ∼1.7-fold. Electron energy loss spectroscopy (EELS) incorporated into transmission electron microscopy reveals an increase in the density of states in QD-decorated NWs compared to the bare ones. The advanced optical and EELS analyses indicate that the energy transfer from the wider band gap p-MnO QDs to n-GaN NW can lead to substantial emission enhancement and greater radiative recombination contribution because of the good band alignment between MnO QDs and GaN NWs. This work provides valuable insights into an environmentally friendly strategy for improving UV device performance.

Optimized performance III-nitride-perovskite-based heterojunction photodetector via asymmetric electrode configuration.

Organometal halide perovskite photodetectors have recently drawn significant attention due to their excellent potential to perform as broadband photodetectors. However, the photoresponse in the ultraviolet (UV) spectrum can be improved by introducing wide bandgap semiconductors. In this work, we report on a methylammonium lead iodide/p-type gallium nitride (MAPI/p-GaN) heterojunction photodetector. We demonstrate that the device is capable of detecting in the UV region by p-GaN being hybridized with MAPI. We further investigate different symmetric and asymmetric metal-electrode contacts to enhance the device performance including the response time. The asymmetric electrode configuration is found to be the most optimal configuration which results in high photoresponse (photo-responsivity is 55 mA W-1 and fall time < 80 ms). As the light illumination occurs through the GaN side, its presence ultimately reduces MAPI degradation due to efficient absorption of the UV photons by GaN film.

Solar-Blind Self-Powered Photodetector Using Solution-Processed Amorphous Core-Shell Gallium Oxide Nanoparticles.

Solution-processed deep ultraviolet (DUV) photodetectors based on wide band gap oxide semiconductors (WBGS) working in the <280 nm wavelength range are drawing increasing attention of the research community because of their cost-effective production and potential use in diverse applications. Here, we report on the synthesis of novel core-shell amorphous gallium oxide nanoparticles (NPs) (a-Ga2Ox/GaOx NPs) that have not been previously obtained. The amorphous gallium oxide NPs were synthesized from gallium nitride using the femtosecond laser ablation in liquid technique. Transmission electron microscopy and electron energy-loss spectroscopy measurements revealed the amorphous NP nature with a Ga-rich core and oxide-rich shell. Optical properties of these core-shell amorphous gallium oxide NPs were investigated by time-resolved spectroscopy and photoluminescence. As a proof of concept, the amorphous gallium oxide NPs were used as an active layer in a solar-blind DUV photodetector with high responsivity (778 mA/W) at 244 nm, which is the highest responsivity recorded to date for any solution-processed DUV photodetector. This work on a high-performance solution-processed device paves the way for large-scale industrial application of the WBGS.

Self-Patterned CsPbBr3 Nanocrystals for High-Performance Optoelectronics.

All-inorganic lead halide perovskites are promising materials for many optoelectronic applications. However, two issues that arise during device fabrication hinder their practical use, namely, inadequate continuity of coated inorganic perovskite films across large areas and inability to integrate these films with traditional photolithography due to poor adhesion to wafers. Herein, for the first time, to address these issues, we show a room-temperature synthesis process employed to produce CsPbBr3 perovskite nanocrystals with two-dimensional (2D) nanosheet features. Due to the unique properties of these 2D nanocrystals, including the "self-assembly" characteristic, the "double solvent evaporation inducing self-patterning" strategy is used to generate high-quality patterned thin films in selected areas automatically after drop-casting, enabling fabrication of high-performance devices without using complex and expensive fabrication processing techniques. The films are free from microcracks. In a proof-of-concept experiment, photodetector arrays are used to demonstrate the superior properties of such films. We provide evidence of both high responsivity (9.04 A/W) and high stability across large areas. The photodetectors fabricated on a flexible substrate exhibit outstanding photoresponse stability. Advanced optical and structural studies reveal the possible mechanism. Our simple and cost-effective method paves the way for the next-generation nanotechnology based on high-performance, cost-effective optoelectronic devices.