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Dopant-Free Squaraine-Based Polymeric Hole-Transporting Materials with Comprehensive Passivation Effects for Efficient All-Inorganic Perovskite Solar Cells
摘要： Quantum-dot (QD) white light-emitting diodes (LEDs) are promising for illumination and display applications due to their excellent color quality. Although they have a high quantum yield close to unity, the reabsorption of QD light leads to high conversion loss, significantly reducing the luminous efficacy and stability of QD white LEDs. In this report, SBA-15 mesoporous particles (MPs) with two-dimensional hexagonal pore structures (2D-HPS) are utilized to largely enhance the luminous efficacy and color-conversion efficiency of QD white LEDs in excess of 50%. The reduction in conversion loss also helps QD white LEDs to achieve a lifetime 1.9 times longer than that of LEDs using QD-only composites at harsh aging conditions. Simulation and testing results suggest that the waveguide effect of 2D-HPS helps in reducing the reabsorption loss by constraining the QD light inside the wall of 2D-HPS, decreasing the probability of being captured by QDs inside the hole of 2D-HPS. As such, materials and mechanisms like SBA-15 MPs with 2D-HPS could provide a new path to improve the photon management of QD light, comprehensively enhancing the performances of QD white LEDs.
关键词： stability,two-dimensional hexagonal pore structure,reabsorption,luminous efficacy,SBA-15 mesoporous particle,quantum-dot white light-emitting diode
更新于2025-09-11 14:15:04
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Reaction-probe infrared investigation on drastic change in reactivity of mesoporous silica for acetalization of cyclohexanone with methanol; pore-size dependence
摘要： Small-pored (< 2.5 nm) mesoporous silica showed remarkably higher catalytic activity for cyclohexanone acetalization with methanol than large-pored ones (≥2.5 nm). For the clari?cation of the pore-size e?ect of mesoporous silicas (MCM-41 and SBA-15) on the reactivity, the reaction probe infrared (IR) method was applied. No evident di?erences were observed by conventional IR characterization methods using CO, pyridine and acetonitrile adsorption. IR spectra of methanol, one of the reactants, on small-pored (MCM-41) and large-pored (SBA-15) samples appeared the same. On the other hand, adsorption of cyclohexanone resulted in di?erent IR spectra: a C]O stretching band appeared at lower frequency side on MCM-41 at a small amount of adsorption in addition to that observed on SBA-15. This result indicates the presence of the stronger interaction of cyclohexanone with MCM-41 than that with SBA-15. When the time course of the reaction was observed by in-situ IR observation, the consumption of activated carbonyl groups and the generation of 1,1-dimethoxycyclohexane, the reaction product, were con?rmed. The presence of the activated cyclohexanone was most probably due to the adsorption on two (or more) OH groups in vicinity, while a non-activated species occupied a single OH group. The reaction probe IR method is thus, a direct and e?ective approach to extract the small di?erences in catalysis.
关键词： Pore-size dependence,Acetalization,Infrared spectroscopy,Reaction-probe,Mesoporous silica
更新于2025-09-10 09:29:36
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Non-monotonous wetting of graphene-mica and MoS2-mica interfaces with a molecular layer of water
摘要： Hydration of interfaces with a layer of water is a ubiquitous phenomenon, which has important implications for numerous natural and technologically important processes. Nevertheless, at the nanoscale the understanding of the wetting process is still limited, since it is experimentally difficult to follow. Here, graphene and monolayers of MoS2 deposited on dry mica are used to investigate wetting of the 2D material-mica interfaces with a molecularly thin layer of water employing scanning force microscopy in different modes. Wetting occurs non-monotonously in time and space for both types of interfaces. It starts at relative humidities (RH) of 10-17 % for graphenes and 8-9 % for MoS2, and it concludes with a homogeneous layer at 25-30 % and 15-20 %, respectively. Investigation of the process at the graphene-mica interface indicates that up to about 25 % RH, initially a highly compliant and unstable layer of water spreads, which subsequently stabilizes by developing labyrinthine nanostructures. Moreover, these nanostructures exhibit distinct mechanical deformability and dissipation, which is ascribed to different densities of the confined water layer. The laterally structured morphology is explained by the interplay of counteracting long-range dipole-dipole repulsion and short-range line tension, with the latter caused at least in part by the mechanical deformation of the 2D material. The proposed origins of the interactions are common for thin layers of polar molecules at interfaces, implying that the lateral structuring of thin wetting layers at sub-monolayer concentrations may also be a quite general phenomenon.
关键词： confinement,energy dissipation,hydration,slit pore,nanostructures,mechanical compliance,2D material
更新于2025-09-10 09:29:36
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Flow through polydisperse pores in an anodic alumina membrane: A new method to measure the mean pore diameter
摘要： We describe a novel technique for the characterization of the mean pore radius of self-ordered porous anodic alumina membranes. We have studied the flow of liquids through cylindrical membrane pores under conditions of very low Reynolds number (Re ? 1). We find that the flow data are well-described by Poiseuille’s law. Characterization is achieved through the application of the H?gen-Poiseuille equation on flow measurements conducted in a simple and compact experimental setup. This setup allows for the monitoring of flow as a result of the pressure difference between the two sides of the membrane without the use of sophisticated and costly laboratory equipment. The proposed method has been tested by flow experiments using liquids of various viscosities. Good agreement is found between the results obtained from the flow data and the pore radii measured by scanning electron microscopy. Consistent results for the mean pore radius for the same membrane have been obtained in all cases.
关键词： Poiseuille’s law,scanning electron microscopy,anodic alumina membrane,mean pore diameter,flow measurement
更新于2025-09-10 09:29:36
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Pore forming channels as a drug delivery system for photodynamic therapy in cancer associated with nanoscintillators
摘要： According to the World Health Organization (WHO), cancer is one of main causes of death worldwide, with 8.2 million people dying from this disease in 2012. Because of this, new forms of treatments or improvement of current treatments are crucial. In this regard, Photodynamic therapy (PDT) has been used to successfully treat cancers that can be easily accessed externally or by fibre-optic endoscopes, such as skin, bladder and esophagus cancers. In addition, this therapy can used alongside radiotherapy and chemotherapy in order to kill cancer cells. The main problem in implementing PDT is penetration of visible light deeper than 10 mm in tissues, due to scattering and absorption by tissue chromophores. Unfortunately, this excludes several internal organs affected by cancer. Another issue in this regard is the use of a selective cancer cell-photosensitizing compound. Nevertheless, several groups have recently developed scintillation nanoparticles, which can be stimulated by X-rays, thereby making this a possible solution for light production in deeper tissues. Alternative approaches have also been developed, such as photosensitizer structure modifications and cell membrane permeabilizing agents. In this context, certain channels lead to transitory plasma membrane permeability changes, such as pannexin, connexin hemmichannels, TRPV1-4 and P2X7, which allow for the non-selective passage of molecules up to 1,000 Da. Herein, we discuss the particular case of the P2X7 receptor-associated pore as a drug delivery system for hydrophilic substances to be applied in PDT, which could also be carried out with other channels. Methylene blue (MB) is a low cost dye used as a prototype photosensitizer, approved for clinical use in several other clinical conditions, as well as photodynamic therapy for fungi infections.
关键词： PDT,pore forming channels,nanoscintillators,drug delivery,cancer
更新于2025-09-09 09:28:46
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Effect of CsI(Tl) micro-conical-frustums on the performance of the pixelated CsI(Tl) scintillation screen in X-ray imaging
摘要： The pixelated CsI(Tl) scintillation screen based on oxidized silicon micro-pore array template with CsI(Tl) micro-conical-frustums (CMCF) was proposed. The effect of the CMCF on the performance of the pixelated CsI(Tl) scintillation screen in X-ray imaging was studied by using Geant4 Monte Carlo simulation code. The variations of the light output (LO), modulation transfer function (MTF) and detective quantum efficiency (DQE) for the screen with the cone angle β of the CMCF in X-ray imaging were revealed. The results show that the LO of the pixelated scintillation screen with CMCF is superior to that of the screens with CsI(Tl) micro-cylinders (CMC) or with reversed CsI(Tl) micro-conical-frustums (RCMCF), but the spatial resolution of the X-ray imaging system by using the pixelated scintillation screen with RCMCF is better than that by using the screens with CMCF or with CMC. At low frequency, the cone angle β corresponding to DQEs from good to bad are 2.40°, 0.00° and -2.40°. But at high frequency, the cone angle β corresponding to DQEs from good to bad change to 2.40°, -2.40° and 0.00°. The reason is that, for a pixelated scintillation screen, the DQE for the screen not only depends on the efficiency of X-ray absorption, but also depends on the number of scintillation photons exiting the bottom the screen per interacting X-ray photon and its Poisson excess, and MTF. The simulated results of DQEs show that the comprehensive performance of the pixelated CsI(Tl) screen with CMCF in X-ray imaging is better than that of the screens with CMC or with CRMCF.
关键词： Shape of CsI(Tl) micro-conical-frustum,Performance in X-ray imaging,Oxidized silicon micro-pore array template,Pixelated CsI(Tl) scintillation screen
更新于2025-09-09 09:28:46
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Ni and Co Substituted Zinc Ferri-chromite: A Study of their Influence in Photocatalytic Performance
摘要： Enhanced photocatalytic activity was demonstrated in the present study for two systems i.e., Zn1-xNixFeCrO4 and Zn1-xCoxFeCrO4 (0.0 ≤ x ≤ 1.0) in photo degradation of methyl orange, methyl red and congo red dyes. The basic aim of this study is to find a suitable compound of doped zinc ferrichromite as photocatalyst for degradation of organic dyes. A sol-gel process used for synthesis of crystalline nanopowders gave better photocatalytic activity under the UV light radiations. The result showed that, dyes undergo fast degradation with UV light in presence of doped compounds. The rate of degradation of dyes was estimated spectro-photometrically from residual concentration in dyes.
关键词： Surface area,synthesis,Pore volume,Photocatalytic activity,Sol-gel
更新于2025-09-09 09:28:46
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Tomography-based determination of Nusselt number correlation for the porous volumetric solar receiver with different geometrical parameters
摘要： Pore-scale numerical models of the porous volumetric solar receiver are established in this paper. By using the X-ray computed tomography and the imaging processing techniques, models of porous media with different geometrical parameters are reconstructed. The conjugate heat transfer process in the porous volumetric solar receiver is solved based on the direct pore-scale numerical simulation. The turbulent effect of fluid flow inside porous geometry is considered by the Shear-Stress Transport k-ω model and the absorbed solar energy is simulated by following the Beer’s law. The results present that the inlet velocity and the geometrical parameters influence the thermal performance of the porous volumetric solar receiver. Larger inlet velocity tends to enhance the convective heat transfer between fluid and solid phases meanwhile decreases noticeably the overall temperature. Receiver with larger porosity is preferred because it limits the reflection losses. The Nusselt number increases as the porosity becomes larger. As a result, the general correlation of Nusselt number for the porous volumetric solar receiver is derived as a function of porosity and Reynolds number. This correlation is applicable with the porosity ranging from 0.74 to 0.89 and the pore Reynolds number ranging from 3 to 233.
关键词： Solar energy,Pore-scale numerical simulation,Convective heat transfer,Volumetric solar receiver,Nusselt number correlation,Porous media
更新于2025-09-09 09:28:46
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Monolithic silicon carbide with interconnected and hierarchical pores fabricated by reaction‐induced phase separation
摘要： Hierarchically porous silicon carbide (SiC) monoliths were fabricated based on polycarbosilane (PCS), divinyl benzene (DVB), and decalin, by a sequence of procedures including catalyst-free hydrosilylation reaction-induced phase separation, ambient-pressure drying, calcination, and HF etching. The influences of ratios of each component on the phase separation were systematically studied. It was found that isotactic polypropylene added as a nonreactive additive could effectively tailor the microstructure and improve the mechanical properties of SiC monoliths. The resultant SiC monoliths mainly consisted of β-SiC nanocrystals, and possessed low bulk density (0.7 g/cm3), high porosity (78%), large specific area (100.6 m2/g), high compressive strength (13.5 ± 1.6 MPa), and hierarchical pores (macropores around 350 nm, mesopores around 4 nm and 20 nm). These properties make SiC monoliths promising materials for catalyst/catalyst support, gas separator, and the reinforcement of high-temperature composites.
关键词： nanocrystal,reaction induced phase separation,hierarchical pore,ambient pressure drying,SiC monolith
更新于2025-09-09 09:28:46
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Theoretical analysis of experimental densification kinetics in final sintering stage of nano-sized zirconia
摘要： The experimental densi?cation kinetics of 7.8 mol% Y2O3-stabilized zirconia was analyzed theoretically during isothermal sintering in the ?nal stage. By taking concurrent grain growth into account, a possible value of the grain-size exponent n was examined. The Coble’s corner-pore model recognized widely was found not to be applicable for explaining the densi?cation kinetics. The corner-pore model of n = 4 shows a signi?cant divergence in the kinetics at di?erent temperatures. Microstructural observation shows that most pores are not located at grain corners and have a size comparable to the surrounding grains. The observed pore structure is similar to the di?usive model where single pore is surrounded by dense body. The di?usive model combined with theoretical sintering stress predicts n = 1 or n = 2, which shows a good consistence to the measured densi?cation kinetics. During sintering of nano-sized powder, it is found that the densi?cation kinetics can be explained distinctively by the di?usive single-pore model.
关键词： Pore structure,Sintering,Grain-growth,Kinetics,Densi?cation
更新于2025-09-04 15:30:14