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Technical Note: Influence of entrance window deformation on reference dosimetry measurement in various beam modalities
摘要： Purpose: Phantoms for horizontal-beam geometry can avoid issues in vertical-beam geometry, such as change in chamber depth due to evaporation, and defining the origin at the water surface. However, their thin entrance-windows would deform when these phantoms are filled, which can change the chamber depth, as pointed out by IAEA TRS-398. Currently, few reports [Arib et al., J. Appl. Clin. Med. Phys. 7, 55–64 (2006), and Kinoshita et al., Rep. Pract. Oncol. Radiother. 23, 199–206 (2018)] are available with practical data on window deformation. Therefore, we investigated the influence of entrance-window deformation on chamber depths in water phantoms and the measurements in various beam modalities. Methods: To examine widely used phantoms and phantoms with different characteristics, three phantom types were investigated (the number of phantoms investigated appears in parentheses): PTW—type 41023 (2), Qualita—QWP-04 (2), and IBA—WP34 (2). Prior to the investigation, these phantoms were stored for acclimatization in a room for approximately 10 h under the following two conditions: (1) room temperature: 21 ± 2 °C; (2) room temperature: 27 ± 2 °C. Using a dial indicator, the centers of the windows were monitored every 30 min for 12 h immediately after the phantoms were filled, in a treatment room at the room-temperature of 21 ± 2 °C. Results: Immediately after the phantoms were filled, the window deformation ranged from ?0.07 (inward-deformation) to 0.3 mm (outward-deformation) among the six phantoms, in comparison with empty phantom windows. For 12 h after the phantoms were filled, the change in the deformation was up to 0.23 mm, but typically less than 0.15 mm. Conclusions: Reference dosimetry in photon, electron, and proton beams would not be influenced significantly by these window behaviors, whereas the window deformation has a slight impact on those in heavy-ion beams.
关键词： ion chamber depth,water phantom,entrance window deformation,horizontal beam geometry
更新于2025-09-04 15:30:14
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Novel microreactors of polyacrylamide (PAM) CdS microgels for admirable photocatalytic H2 production under visible light
摘要： Cadmium sul?de, with its narrow band gap, can be used as a photocatalyst in the visible light region for the splitting of water, but its limited number of active sites and tendency to agglomerate are problematic for producing high yields of hydrogen. Therefore, an inverse emulsion polymerization method was used to fabricate polyacrylamide (PAM) microgels as a substrate to immobilize CdS nanoparticles (PAM-CdS). The PAM microgels not only immobilized the CdS nanoparticles, but also prevented aggregation. NeCd bonds in the PAM-CdS microgels facilitated electron transfer from the PAM to the CdS resulting in more electrons participating in the H2 production process. The electrostatic interactions between the PAM and CdS also hindered the recombination of electron-hole pairs. These PAM-CdS microgels exhibit admirable photocatalytic H2 production performance with a H2 production rate of up to 5.21 mmol h?1 g?1.
关键词： Visible-light water splitting,PAM microgels,CdS,Photocatalytic H2 production
更新于2025-09-04 15:30:14
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CuO photoelectrodes synthesized by the sol–gel method for water splitting
摘要： CuO is an attractive photocatalytic material for water splitting due to its high earth abundance and low cost. In this paper, we report the deposition of CuO thin films by sol–gel dip-coating process. Sol deposition has attractive advantages including low-cost solution processing and uniform film formation over large areas with a fairly good control of the film stoichiometry and thickness. Pure CuO phase was obtained for calcination temperatures higher than 360 °C in air. The CuO photocurrents for hydrogen evolution depend on the crystallinity and the microstructure of the film. Values of ?0.94 mA cm?2 at pH = 8 and 0 V vs. RHE were achieved for CuO photoelectrodes annealed at 400 °C under air. More interestingly, the stability of the photoelectrode was enhanced upon the sol–gel deposition of a TiO2 protective layer. In this all sol–gel CuO/TiO2 photocathode, a photocurrent of ?0.5 mA cm?2 is achieved at pH = 7 and 0 V vs. RHE with a stability of ~100% over 600 s.
关键词： TiO2 protecting layer for CuO photoelectrode,Sol–gel,CuO photoelectrode,Water splitting
更新于2025-09-04 15:30:14
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The Role of the Effect of Shadowing of Some Wavy Regions by Other Wavy Regions in the Formation of an Image of Snell’s Window
摘要： The shadowing of some regions of a wavy water surface by other regions can significantly influence the backscattered signal not only in the problem of remote monitoring of a water reservoir at grazing angles (e.g., in radar), but also in the problems of underwater vision. In this work, we present the results of a theoretical study of this phenomenon with respect to the model of underwater imaging of the sky (Snell’s window) near the image boundary. The numerical-simulation method is used to develop the statistically mean image of Snell’s window, which allows for the shadowing effects, and the corrected formula of the estimate of a wave parameter, namely, the water-surface slope variance, is obtained using the value of blurring of the boundary of Snell’s window.
关键词： underwater vision,wavy water surface,shadowing,numerical simulation,Snell’s window
更新于2025-09-04 15:30:14
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Atomic layer deposited TiO <sub/>2</sub> -IrO <sub/>x</sub> alloys enable corrosion resistant water oxidation on silicon at high photovoltage.
摘要： We synthesized by atomic layer deposition (ALD) TiO2-IrOx alloys that enable high photovoltages and catalyze water oxidation on silicon metal-insulator-semiconductor (MIS) photoanodes. The ratio of TiO2 to IrOx was precisely controlled by varying the number of ALD cycles for each precursor. Silicon with a 2 nm surface SiO2 layer was coated with TiO2-IrOx alloys ranging in composition from 18-35% iridium relative to the sum of titanium and iridium concentrations. IrOx catalyzed oxygen evolution and imparted a high work function to the TiO2-IrOx alloys, enabling photovoltages during water oxidation that exceeded 600 mV. TiO2 imparted stability and inhibited corrosion of the underlying silicon light absorber. After annealing in forming gas (5% H2 / 95% N2), TiO2-IrOx alloys were stable for 12 hours of continuous water oxidation in 1 M H2SO4. Key properties of the MIS junction affecting electrochemical operation were also extracted by electrochemical impedance spectroscopy. This work demonstrates that alloying by ALD is a promising approach for designing corrosion resistant Schottky contacts with optimized electronic and materials properties for catalyzed, solar driven water oxidation.
关键词： photovoltage,water oxidation,TiO2-IrOx alloys,Atomic layer deposition,corrosion resistance,silicon photoanodes
更新于2025-09-04 15:30:14
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A highly efficient NiFe nanoparticles decorated Si photoanode for photoelectrochemical water oxidation
摘要： n-Si is a narrow band gap semiconductor that has been demonstrated as an excellent photo-absorber material for photoelectrochemical (PEC) water splitting. Depositing a thin layer of Ni film on n-Si can form a Schottky junction at the interface, which offers a simple and useful route toward light-driven water oxidation. However, the relatively low catalytic activity of the Ni layer and the presence of interface states limits the application of this structure. Herein, we prepared a high performance NiFe nanoparticles decorated Si photoanode for the efficient solar driven water oxidation to H2. NiFe nanoparticles were dispersed on a Si substrate surface homogeneously to form an inhomogeneous metal-insulator-semiconductor (MIS) junction, which increased the photovoltage of photoanode. In addition, the oxide/oxyhydroxide layer on the deposited NiFe layer formed during the evaporation deposition acted as a highly efficient electrocatalyst, which also contributed to the high PEC performance of the photoanode. The photoanode covered with 2 nm NiFe film exhibited the best PEC performance with a low onset potential of 1.09 V vs. RHE (the potential required to reach the photocurrent of 1 mA/cm2), a high photocurrent of 25.2 mA/cm2 at 1.23 V vs. RHE, and a stable output over 50 h under AM 1.5G illumination due to the high performance inhomogeneous MIS junction and a thick oxide/oxyhydroxide catalytic shell formed on NiFe nanoparticle via an aging process.
关键词： photoelectrochemical water oxidation,oxide/oxyhydroxide layer,Si photoanode,NiFe nanoparticles,MIS junction
更新于2025-09-04 15:30:14
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Carbonyl linked carbon nitride loading few layered MoS2 for boosting photocatalytic hydrogen generation
摘要： Pristine graphitic carbon nitride g-C3N4 materials, as a novel metal-free photocatalyst with moderate activity, have attracted intense interest. However, its fast photogenerated carriers recombination always induces a relative low performance. Herein, we for the first time report one new =C=O group linked g-C3N4 (CO-C3N4) through CO2-assisted thermal polymerization of urea. It is found that the edge =C=O groups work as the photogenerated electrons collection sites, and then promote the carriers separation. The visible-light phototatalytic hydrogen evolution performance of our synthesized samples shows 1.85 times higher than that of the reference g-C3N4. To get a considerable visible-light driven photocatalytic hydrogen generation, a new few layered MoS2 with a small size (ca. 20 nm) is prepared through a liquid exfoliation, and then is loaded onto the CO-C3N4. The optimal MoS2/CO-C3N4 sample gives the photocatalytic hydrogen evolution of 1990 and 1440μmol/(g*h) under the λ > 400 and λ > 420 illumination, higher than the reported values in literatures. The sample also shows a considerable excellent photocatalytic activity of 44.3 μmol/(g*h) under LED-600 condition.
关键词： water splitting,CO-C3N4,MoS2,photocatalysis,H2 generation
更新于2025-09-04 15:30:14
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Water-dispersible Copper Sulfide Nanocrystals via Ligand Exchange of 1-dodecanethiol
摘要： In colloidal Cu2-xS nanocrystal synthesis, thiols are often used as organic ligands and sulfur source, as they yield high-quality nanocrystals. However, thiol ligands on Cu2-xS nanocrystals are difficult to exchange, limiting the applications of these nanocrystals in photovoltaics, biomedical sensing and photocatalysis. Here, we present an effective and facile procedure to exchange native 1-dodecanethiol on Cu2-xS nanocrystals by 3-mercaptopropionic acid, 11-mercaptoundecanoic acid, and S2- in formamide under inert atmosphere. The product hydrophilic Cu2-xS nanocrystals have excellent colloidal stability in formamide. Furthermore, the size, shape and optical properties of the nanocrystals are not significantly affected by the ligand exchange. Water-dispersible Cu2-xS nanocrystals are easily obtained by precipitation of the nanocrystals capped by S2-, 3-mercaptopropionate or 11-mercaptoundecanoate from formamide, followed by redispersion in water. Interestingly, the ligand exchange rates for Cu2-xS nanocrystals capped with 1-dodecanethiol are observed to depend on the preparation method, being much slower for Cu2-xS nanocrystals prepared through heating-up than through hot-injection synthesis protocols. XPS studies reveal that the differences in the ligand exchange rates are due to the surface chemistry of the Cu2-xS nanocrystals, where the nanocrystals prepared via hot-injection synthesis have a less dense ligand layer due to the presence of trioctylphosphine oxide during synthesis. A model is proposed that explains the observed differences in the ligand exchange rates. The facile ligand exchange procedures reported here enable the use of high-quality colloidal Cu2-xS nanocrystals prepared in the presence of 1-dodecanethiol in various applications.
关键词： thiol ligands,surface chemistry,ligand exchange,colloidal Cu2-xS nanocrystals,water-dispersible
更新于2025-09-04 15:30:14
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Direct storage of holes in ultrathin Ni(OH) <sub/>2</sub> on Fe <sub/>2</sub> O <sub/>3</sub> photoelectrodes for integrated solar charging battery-type supercapacitors
摘要： Energy storage is a very significant issue for utilization of solar energy due to its discontinuous and unstable energy flux. Herein, for the first time, we propose a Fe2O3@Ni(OH)2 core–shell nanorod array as a photoelectrochemical battery-type supercapacitor for the direct storage of solar energy. Under light illumination, Fe2O3 absorbs solar energy and produces electron–hole pairs, while Ni(OH)2 stores the photo-generated holes, which can be released as electricity when the light is switched off. In addition, by controlling the valence band position of the semiconductor and the thickness of Ni(OH)2, the side reaction of water oxidation (electrolyte decomposition), which is harmful for the applications of a photoelectrochemical supercapacitor, can be completely suppressed. As a consequence, the specific capacitance of the Fe2O3@Ni(OH)2 photoelectrochemical supercapacitor is enhanced up to 20.6 mF cm?2 at a discharge current density of 0.1 mA cm?2, which is about 4.5 times that of BiVO4/PbOx reported in a previous study. This study offers a very promising device for the direct storage of solar energy and deepens our understanding on the interface charge transfer between a photoelectrode and a battery-type capacitive material.
关键词： water oxidation suppression,Fe2O3@Ni(OH)2,photoelectrochemical supercapacitor,core–shell nanorod array,solar energy storage
更新于2025-09-04 15:30:14
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Potential Application of Metal–organic frameworks for Photocatalytic Water Splitting
摘要： These days, the environmental pollution and energy shortage are the crucial global issues. Therefore, replacing the renewable source of energy with the fossil fuels is the most promising approach to solve the aforementioned problems. Hydrogen is an attractive source energy because of its high energy density and its combustion by-product is only water. Hydrogen production through photosplitting of water over a semiconductor based photocatalyst is a desirable approach to diminish the global energy and environmental problems. However, its low solar conversion efficiency and finding suitable photocatalyst still remain as the main challenge for this system. Recently metal–organic frameworks (MOFs) have received great attention for the photocatalytic hydrogen production due to their large surface to volume ratio, design flexibility, and well-defined porosity. In this short review, we focus on the previous studies on the various types of MOFs based photocatalyst in the solar hydrogen production system. The main intention of review is to highlight the importance of coupling molecular approaches of catalyst design with materials science strategies in the improvement of MOFs based photocatalysts, which will undoubtedly lead to a very bright future for photocatalytic water.
关键词： Solar Energy,Photocatalytic Water Splitting,Metal–organic frameworks,Hydrogen Production,Renewable Energy
更新于2025-09-04 15:30:14