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Background: In carbon ion radiotherapy, accurate measurement of the three‐dimensional (3D) absorbed dose distribution is critical for effectively targeting tumors. Although micellar gel dosimeters exhibit considerable potential for measuring 3D absorbed dose distributions, few studies have focused on radiotherapy using carbon ion beams. Purpose: This study investigated the applicability of the surfactant hydrogel dosimeter (SHD), a micellar gel dosimeter, to measuring a 3D dose absorbed through carbon ion beam irradiation. Methods: A cubic target region of 34 mm per side was established at a depth of 46 mm below the upper surface of an SHD specimen. Scanning irradiation was performed using a pencil beam of carbon ions at the Ion‐beam Radiation Oncology Center in Kanagawa ("i‐ROCK"), Japan, under irradiation conditions set by the treatment planning system ("Monaco for Carbon", Ver. 5.20, Elekta AB, Sweden) to create a spread‐out Bragg peak within the target. The physical dose was set to 10 Gy at the isocenter, situated at the center of the target. The SHD responsiveness was measured twice using optical computed tomography (CT) ("Vista 15", Modus Medical Devices, Canada) for three irradiated specimens, and six types of measured optical attenuation coefficient (OAC) were obtained. To assess whether the OAC represented the absorbed dose expected in the treatment plan, we compared the relative distribution of the OAC and that of the absorbed dose. Relative fraction (RF) was used to measure the difference between the relative value of the OAC and that of the absorbed dose. Moreover, the distribution of OH radical (•OH) concentration obtained by Monte Carlo simulation ("PHITS" ver. 3.24 JAEA, Japan) and that of the OAC were compared. Results: In the direction of beam travel, the relative distribution of the OAC was lower than that of the absorbed dose. This discrepancy could be attributed to a decrease in the concentration of •OH produced by irradiation owing to the recombination reaction, which does not accurately reflect the absorbed dose. By contrast, the distributions in the plane perpendicular to the beam travel were consistent. The RF increased from ± 3% to ± 13% along the beam travel direction. The small RF in the plane perpendicular to the beam travel could be attributed to the constant distribution of linear energy transfer, regardless of the irradiation position, and the generation of radicals proportionally to the absorbed dose. The increase in RF along the beam travel direction was ascribed to ring artifacts in the irradiated region. Conclusion: The measurement of the absorbed dose distribution in the beam travel direction should be improved. The observed discrepancy is attributed to the reduced reactivity of the SHD due to a high liner energy transfer near the Bragg peak. However, the absorbed dose distribution can be effectively evaluated in the plane perpendicular to the direction of beam travel. [ABSTRACT FROM AUTHOR]

The electrofluorochromism of Eu complexes based on the valence change between Eu3+ and Eu2+ is demonstrated in a two-electrode electrochemical device consisting of Prussian blue (PB) as the counter electrode. This study aims to improve the electrofluorochromic (EFC) performance of luminescence switching between Eu3+ and Eu2+ by enhancing the electrochemical reactivity of the EFC device. By introducing a PB film as a counter electrode in a two-electrode device, the redox reaction of Eu3+/2+ is promoted because of charge compensation by the counter PB film. The increase in the reaction charge enables faster changes in the photoluminescence from Eu3+ to Eu2+ and an increase in the blue luminescence intensity from the Eu2+ state. This approach achieves a lowered driving voltage, accelerates the electrochemical redox reaction of the Eu complex, and enhances the reversibility of the valence change of the Eu ion. [ABSTRACT FROM AUTHOR]

Silver nanoparticles associated with polyvinylpyrrolidone were synthesized using an electrochemical method. When the polyvinylpyrrolidone-adsorbed silver nanoparticles were immersed in solvents with hydroxyl groups, the polyvinylpyrrolidone interacted with the solvent by hydrogen bonding. Hence, the dielectric environment around silver nanoparticles changed, leading to dynamic coloration switching with high sensitivity, reversibility, and bistability owing to the localized surface plasmon resonance bands. This achievement can be expected to contribute to the solvatochromic devices for a kind of sensors or switches. [ABSTRACT FROM AUTHOR]

In this study, polyvinylpyrrolidone (PVP) was introduced into an Ag deposition-based electrochromic (EC) device as a capping agent for electrodeposited Ag nanoparticles (AgNPs) to improve the coloration characteristics of EC devices and to precisely control the size and shape of the AgNPs. Through the coordination of PVP molecules with Ag+ ions in the EC electrolyte, the critical voltage for the deposition of AgNPs decreased, resulting in a lower operating voltage of the EC device in comparison with the conventional one. Because particle growth and AgNP aggregation were suppressed by the capping effect of PVP, uniform electrodeposition of AgNPs was achieved. Aggregation suppression enabled vivid cyan, yellow, and red coloration using a simple driving procedure. The suppression of AgNP aggregation by PVP was demonstrated even in an electrochemical system. Furthermore, the capping effect of PVP also improved image retention. Better color retention properties were achieved even without the use of any counter-modified electrode cells. [ABSTRACT FROM AUTHOR]

In this review, we describe the investigation of a ruthenium [Ru(II)] complex-based, AC voltage-driven, electrochemiluminescent (ECL) device first. The ECL turn-on response time and intensity were dramatically improved by introducing the AC method. The turn-on response time was speeded up by increasing the applied frequency: 4 ms response time was achieved at 200 Hz, which was much faster than when using the DC method (1.5 s). We also introduced rutile-type titanium dioxide nanoparticles (TiO2 NPs) in a Ru(II) complex-based AC-ECL device. The ECL intensity and the lifetimes of the ECL device with TiO2 NPs were greatly improved compared to those of the device without nanoparticles. Then we tried to improve photoelectrochemical properties of the Ru(II) complex by combining it with DNA molecules. We fabricated a novel DNA/Ru(bpy)32+ hybrid film that could immobilize the ECL-active Ru(bpy)32+ onto the electrode surface through electrophoretic migration. The hybrid film contained unique micrometer-scale aggregates of Ru(bpy)32+ in the DNA matrix. Surprisingly, by using the DNA/Ru(bpy)32+ hybrid film for the ECL device, luminescence could be obtained at frequencies as high as 10kHz, which corresponds to a response time shorter than 100μs.