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Laser-induced synthesis and photocatalytic properties of hybrid organic–inorganic composite layers
摘要： A laser-based method was developed for the synthesis and simultaneous deposition of multicomponent hybrid thin layers consisting of nanoentities, graphene oxide (GO) platelets, transition metal oxide nanoparticles, urea, and graphitic carbon nitride (g-C3N4) for environmental applications. The photocatalytic properties of the layers were tested through the degradation of methyl orange organic dye probing molecule. It was further demonstrated that the synthesized hybrid compounds are suitable for the photodegradation of chloramphenicol, a widely used broad-spectrum antibiotic, active against Gram-positive and Gram-negative bacteria. However, released in aquatic media represents a serious environmental hazard, especially owing to the formation of antibiotic-resistant bacteria. The obtained results revealed that organic, urea molecules can become an alternative to noble metals co-catalysts, promoting the separation and transfer of photoinduced charge carriers in catalytic composite systems. Laser radiation induces the reduction of GO platelets and the formation of graphene-like material. During the same synthesis process, g-C3N4 was produced, by laser pyrolysis of urea molecules, without any additional heat treatment. The layers exhibit high photocatalytic activity, being a promising material for photodegradation of organic pollutants in wastewater.
关键词： transition metal oxide nanoparticles,urea,photocatalytic properties,hybrid organic–inorganic composite layers,graphene oxide,graphitic carbon nitride,methyl orange,laser-based synthesis,chloramphenicol
更新于2025-11-14 17:04:02
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Ultrafast Transition of Non-Uniform Graphene to High-Quality Uniform Monolayer Film on Liquid Cu
摘要： It is essentially important to synthesize uniform graphene films with controlled number of layers since their properties strongly depend on the number of layers. Although chemical vapor deposition (CVD) on Cu has been widely used to synthesize large-area graphene films, the growth on solid and liquid Cu suffers from poor thickness uniformity with a great number of adlayers and difficulty in forming continuous film even after a long growth time of hours, respectively. Here, we found that non-uniform graphene film initially grown on solid Cu foil can rapidly transform into continuously uniform monolayer graphene film on liquid Cu within 3 min. Moreover, the films obtained show larger grain size, higher quality, better optical and electrical properties and better performance in organic light-emitting diode (OLED) applications than the original films grown on solid Cu foil. By using carbon isotope labeling, we revealed that the multilayer-to-monolayer transition of graphene on liquid Cu experiences etching-‘self-aligning’-coalescence processes. This two-step CVD method not only opens up a new way for the rapid growth of uniform monolayer graphene films, but also provides helpful information for the controlled growth of uniform monolayers of other 2D materials such as monolayer h-BN.
关键词： film,2D material,chemical vapor deposition,number of layers,graphene
更新于2025-11-14 17:03:37
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High Efficiency Non‐Doped White Organic Light Emitting Diodes Based on a Bilayer Interface‐Exciplex Structure
摘要： High efficiency non-doped blue and white organic light emitting diodes (OLEDs) are realized by using a bilayer interface-exciplex (i-Exc) structure. Since the neutral exciplex are formed at the interface, the interface charge accumulation is reduced, thereby suppressing exciton quenching in the device. With the i-Exc structure, a maximum external quantum efficiency (EQE) of 23.1% is achieved in the non-doped blue phosphorescent OLED. Moreover, the white emission can be obtained by inserting an ultrathin orange-red phosphorescent emitter into the blue devices. The charge trapping in the orange-red emitter can be suppressed by adjusting the position of the ultrathin orange-red emitting layer in the device, contributing to superior spectral stability. The WOLED achieves an EQE of 20.0% and exhibits a stable warm white emission. The Commission Internationale de l’Eclairage (CIE) coordinates of WOLED are (0.41, 0.40) at 5 V and slightly change to (0.40, 0.41) at 9 V.
关键词： interface-exciplex,PHOLED,WOLED,bilayer structure,ultrathin non-doped emitting layers
更新于2025-11-14 15:26:12
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Charge extraction via graded doping of hole transport layers gives highly luminescent and stable metal halide perovskite devices
摘要： One source of instability in perovskite solar cells (PSCs) is interfacial defects, particularly those that exist between the perovskite and the hole transport layer (HTL). We demonstrate that thermally evaporated dopant-free tetracene (120 nm) on top of the perovskite layer, capped with a lithium-doped Spiro-OMeTAD layer (200 nm) and top gold electrode, offers an excellent hole-extracting stack with minimal interfacial defect levels. For a perovskite layer interfaced between these graded HTLs and a mesoporous TiO2 electron-extracting layer, its photoluminescence yield reaches 15% compared to 5% for the perovskite layer interfaced between TiO2 and Spiro-OMeTAD alone. For PSCs with graded HTL structure, we demonstrate efficiency of up to 21.6% and an extended power output of over 550 hours of continuous illumination at AM1.5G, retaining more than 90% of the initial performance and thus validating our approach. Our findings represent a breakthrough in the construction of stable PSCs with minimized nonradiative losses.
关键词： perovskite solar cells,stability,charge extraction,photoluminescence,hole transport layers,graded doping
更新于2025-11-14 15:25:21
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Design of an intermediate Bragg reflector within triple-junction solar cells for spectrum splitting applications
摘要： We investigate the use of distributed Bragg reflectors (DBRs) within triple-junction solar cells (TJSC) for spectrum splitting photovoltaics. An optical model of a lattice-matched (LM) GaInP/GaInAs/Ge TJSC with intermediate DBR is developed, in good agreement with measured reflectance. By modifying the DBR layer number, composition and thickness to broaden the reflectance band, we show that a DBR can provide suitable 900–1050 nm reflectance for spectrum splitting from the LM TJSC to a Si cell, resulting in a more efficient 4-junction receiver. For better practicality and cost effectiveness, we propose that the buffer layers in metamorphic (MM) TJSCs could additionally function as a DBR for spectrum splitting applications. We propose several DBR designs to achieve a suitable spectrum-splitting reflectance band from MM TJSCs to a Si cell, again resulting in a more efficient 4-junction receiver. Finally, we show that our intermediate DBR approach to spectrum splitting has the advantage of a greatly reduced angle-of-incidence dependence compared to a discrete dielectric filter.
关键词： Triple-junction solar cell,Spectrum splitting,Buffer layers,Distributed Bragg reflector
更新于2025-10-22 19:40:53
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[IEEE 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Waikoloa Village, HI (2018.6.10-2018.6.15)] 2018 IEEE 7th World Conference on Photovoltaic Energy Conversion (WCPEC) (A Joint Conference of 45th IEEE PVSC, 28th PVSEC & 34th EU PVSEC) - Design of Bragg Reflector in GaInP/GaInAs/Ge Triple-junction Solar Cells for Spectrum Splitting Applications
摘要： The use of intermediate distributed Bragg reflectors (DBRs) is investigated. Optical models for both commercial lattice-matched (LM) and metamorphic (MM) GaInP/GaInAs/Ge triple-junction solar cells (TJSCs) are developed, in good agreement with measured reflectance. Integrating a suitable DBR structure into a TJSC has the potential to provide the required IR reflectance for spectrum splitting from the LM and MM TJSC to a Si cell. We show that the intermediate DBR approach to spectrum splitting has the advantage of a greatly reduced angle-of-incidence dependence compared to a discrete dielectric filter.
关键词： Spectrum splitting,Buffer layers,Distributed Bragg reflector,Triple junction solar cell
更新于2025-10-22 19:40:53
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Impact of segmentation density on spectral domain optical coherence tomography assessment in Stargardt disease
摘要： Purpose Automated spectral domain optical coherence tomography (SD-OCT) segmentation algorithms currently do not perform well in segmenting individual intraretinal layers in eyes with Stargardt disease (STGD). We compared selective B-scan segmentation strategies for generating mean retinal layer thickness and preserved area data from SD-OCT scans in patients with STGD1. Methods Forty-five eyes from 40 Stargardt patients were randomly selected from the ongoing Natural History of the Progression of Atrophy Secondary to Stargardt Disease (ProgStar) study. All eyes underwent SD-OCT using a standard macular volume consisting of 1024 × 49 equally spaced B-scans within a 20 × 20 degree field centered on the fovea. All 49 B-scans were segmented manually to quantify total retina, outer nuclear layer (ONL), photoreceptor inner segments, photoreceptor outer segments (OS), and retinal pigment epithelial layer (RPE). Mean thickness and total area were generated using all 49 B-scans (spaced 122 μm apart), 25 B-scans (every other B-scan, spaced 240 μm apart), 17 B-scans (every third scan, 353 μm apart), and 13 B-scans (every fourth scan, 462 μm apart), as well as by using an Badaptive^ method where a subset (minimum 25 B-scans) of B-scans that the grader deemed as significantly different from adjacent B-scans were utilized. Mean absolute and percentage errors were calculated for macular thickness and area of different retinal layers for the different B-scan subset selection strategies relative to using all 49 B-scans, which was considered the reference or ground truth. Results Mean thickness and area measurements were significantly different for any regularly spaced reduction in B-scan density relative to the ground truth. When an adaptive approach was applied using a minimum of half the scans, the differences relative to ground truth were no longer significantly different. The mean percent differences for the area and thicknesses of the various layers ranged from 0.02 to 33.66 (p < 0.05 for all comparisons) and 0.44 to 7.24 (p > 0.05) respectively. Conclusion Manual segmentation of a subset of B-scans using an adaptive strategy can yield thickness and area measurements of retinal sublayers comparable to the reference ground truth derived from using all B-scans in the volume. These results may have implications for increasing the efficiency of SD-OCT grading strategies in clinical trials for STGD and other related macular degenerative disorders.
关键词： Stargardt,Segmentation density,Spectral domain optical coherence tomography,Retinal layers
更新于2025-09-23 15:23:52
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A Reflectionless Discrete Perfectly Matched Layer
摘要： Perfectly Matched Layer (PML) is a widely adopted non-re?ecting boundary treatment for wave simulations. Reducing numerical re?ections from a discretized PML has been a long lasting challenge. This paper presents a new discrete PML for the multi-dimensional scalar wave equation which produces no numerical re?ection at all. The re?ectionless discrete PML is discovered through a straightforward derivation using Discrete Complex Analysis. The resulting PML takes an easily-implementable ?nite di?erence form with compact stencil. In practice, the discrete waves are damped exponentially in the PML, and the error due to domain truncation is maintained at machine zero by a moderately thick PML. The numerical stability of the proposed PML is also demonstrated.
关键词： Perfectly matched layers,absorbing boundary,scalar wave equation,discrete complex analysis
更新于2025-09-23 15:23:52
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Novel Green Synthesis of Graphene Layers using Zante Currants and Graphene Oxide
摘要： The present work shows a facile route for the preparation of graphene layers and for the first time Zante currants extract used for the effective deoxygenation of graphene oxide has been reported. Zante currants (ZC) extract reduce effectively GO into few layered structures of graphene (FLG). The morphology of few layers graphene and graphene oxide (GO) were investigated by SEM and TEM. Reduction effect on graphene oxide confirm by other technique like Raman, FTIR, XRD and UV spectrophotometry. This procedure keep away the use of hazardous chemicals, thus providing a new hope for large scale production of chemically reduced graphene.
关键词： Graphene oxide (GO),Few layers graphene (FLG),Zante currants (ZC),Green synthesis
更新于2025-09-23 15:23:52
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Domino Reaction for the Sustainable Functionalization of Few-Layer Graphene
摘要： The mechanism for the functionalization of graphene layers with pyrrole compounds was investigated. Liquid 1,2,5-trimethylpyrrole (TMP) was heated in air in the presence of a high surface area nanosized graphite (HSAG), at temperatures between 80 °C and 180 °C. After the thermal treatments solid and liquid samples, separated by centrifugation, were analysed by means of Raman, Fourier Transform Infrared (FT-IR) spectroscopy, X-Rays Photoelectron Spectroscopy (XPS) and 1H-Nuclear Magnetic Resonance (1H NMR) spectroscopy and High Resolution Transmission Electron Microscopy (HRTEM). FT-IR spectra were interpreted with the support of Density Functional Theory (DFT) quantum chemical modelling. Raman findings suggested that the bulk structure of HSAG remained substantially unaltered, without intercalation products. FT-IR and XPS spectra showed the presence of oxidized TMP derivatives on the solid adducts, in a much larger amount than in the liquid. For thermal treatments at T ≥ 150 °C, IR spectral features revealed not only the presence of oxidized products but also the reaction of intra-annular double bond of TMP with HSAG. XPS spectroscopy showed the increase of the ratio between C(sp2)N bonds involved in the aromatic system and C(sp3)N bonds, resulting from reaction of the pyrrole moiety, observed while increasing the temperature from 130 °C to 180 °C. All these findings, supported by modeling, led to hypothesize a cascade reaction involving a carbocatalyzed oxidation of the pyrrole compound followed by Diels-Alder cycloaddition. Graphene layers play a twofold role: at the early stages of the reaction, they behave as a catalyst for the oxidation of TMP and then they become the substrate for the cycloaddition reaction. Such sustainable functionalization, which does not produce by-products, allows us to use the pyrrole compounds for decorating sp2 carbon allotropes without altering their bulk structure and smooths the path for their wider application.
关键词： infrared spectroscopy,Density Functional Theory,pyrrole compounds,quantum chemical modelling,graphene layers,Functional Groups
更新于2025-09-23 15:23:52