Shinya Yamanaka

Amorphous CaCO3 (ACC) has an intrinsically large specific surface area, rendering it a promising platform for developing various functional materials. However, its practical use is severely limited by an extremely short lifespan, which is typically only a few seconds, before its spontaneous recrystallization into vaterite or calcite. In this study, we investigate the use of citric acid to suppress the rapid crystallization of ACC in a mixed ethanol/ethylene glycol medium and to obtain reproducible high-surface-area ACC under controlled conditions. Experiments involving systematic variations in citric acid concentration (0.00–1.33% w/v) revealed that crystallization was completely inhibited at concentrations above 0.39% w/v, as confirmed by X-ray diffraction. Brunauer–Emmett–Teller analysis showed that ACC samples synthesized with 0.44–1.11% w/v citric acid achieved exceptionally high surface areas (600–700 m2/g). The observed suppression of crystallization is discussed in relation to previously reported interactions between citrate species and calcium carbonate phases, rather than being directly demonstrated at the molecular level. As a proof of concept, curcumin was loaded onto the prepared ACC samples, and enhanced dissolution behavior was observed, which plateaued above a specific surface area threshold. This finding highlights the importance of the surface-area-to-cargo ratio in future formulation strategies. The resulting stable high-surface-area ACC is a promising platform for the design of functional materials.

Magnetite (Fe3O4) nanoparticles are widely used as functional magnetic materials, characterized by their ferromagnetism, biocompatibility, and electrical conductivity. Because these properties strongly depend on particle size and morphology, controlling nucleation and growth is essential. The glycothermal method has emerged as a versatile route for synthesizing metal oxide nanoparticles with tunable shapes, and we previously demonstrated that morphology control can be achieved without additives simply by varying the solvent system. In this study, we investigated the influence of synthesis temperature and precursor concentration on the additive-free glycothermal formation of Fe3O4, interpreted through the framework of the LaMer model. Spherical secondary particles with diameters of 277–350 nm were formed, comprising primary nanoparticles whose sizes varied according to the reaction conditions. Electrical conductivity exhibited a strong negative correlation with specific surface area (r = −0.88). To elucidate this behavior, we compared crystalline size with the diameter derived from specific surface area, providing insights into the internal microstructure and packing density of the aggregates. Transmission electron microscopy analysis revealed that nanoscale roughness, correlation length, and Fourier components associated with different morphological length scales remained unchanged across all synthesis conditions. These results demonstrate that microstructural control in magnetite assemblies is crucial for tuning their electrical properties and highlight the potential of additive-free glycothermal synthesis for designing Fe3O4-based functional materials.

Carbon dioxide (CO2) is one of the greenhouse gasses that has various effects to the earth atmosphere. In recent years, carbon-based adsorbent used for CO2 adsorption. To increase the adsorption of CO2, the surface treatment should affect the adsorption sites. However, the mechanism of the ethanol surface treatment was lack of study. Hence in this study, we investigate the effects of ethanol treatment on candle soot surface and adsorption performance. Briefly, the raw soot (FS) was collected directly from the inner flame. The collected soot was treated with aqueous ethanol and labelled as washed soot (WS). Both FS and WS were studied for the significant effect on its physical, chemical properties and adsorption capacities. FS and WS showed the agglomeration of particles (mean diameter > 1). FS washed with ethanol significantly increased total pore volume (from 0.18 to 0.65 cm3/g) with almost the same surface area (from 111.01 to 113.54 m2/g). The CO2 adsorption capacity was revealed that the maximum adsorption capacity obtained by FS was 68 mg/g and slightly increased after the pre-treatment (69 mg/g). Meanwhile, Freundlich isotherm model fitted to the experimental data based on basis of the regression coefficient (R2) which are 0.979 (FS) and 0.993 (WS). Based on the isotherm, after ethanol treatment particles suggesting heterogeneous surface with large number of CO2 adsorption sites compared to non-treated soot.

The enhancement of carbon-supported components is a crucial factor in augmenting the interplay between carbon-supported and metal-active components in the utilization of catalysts for direct ethanol fuel cells (DEFCs). Here, we propose a strategy for designing a catalyst by modifying candle soot (CS) and loading nickel onto ordered carbon soot. The present study aimed to investigate the effect of the Ni nanoparticles content on the electrocatalytic performance of Ni–CS, ultimately leading to the identification of a maximum composition. The presence of an excessive quantity of nickel particles leads to a decrease in the number of active sites within the material, resulting in sluggishness of the electron transfer pathway. The electrocatalyst composed of nickel and carbon support, with a nickel content of 20 wt%, has demonstrated a noteworthy current activity of 18.43 mA/cm², which is three times that of the electrocatalyst with a higher nickel content of 25 wt%. For example, the 20 wt% Ni–CS electrocatalytic activity was found to be good, and it was approximately four times higher than that of 20 wt% Ni–CB (nickel–carbon black). Moreover, the chronoamperometry (CA) test demonstrated a reduction in current activity of merely 65.80% for a 20 wt% Ni–CS electrocatalyst, indicating electrochemical stability. In addition, this demonstrates the great potential of candle soot with Ni nanoparticles to be used as a catalyst in practical applications.

Alzheimer’s disease (AD) is thought to be caused by the deposition of amyloid-β (Aβ) in the brain. Aβ begins to aggregate approximately 20 years before the expression of its symptoms. Previously, we developed a microliter-scale high-throughput screening (MSHTS) system for inhibitors against Aβ aggregation using quantum dot nanoprobes. Using this system, we also found that plants in the Lamiaceae, particularly Perilla frutescens var. crispa, have high activity. The cultivation environment has the potential to enhance Aβ aggregation inhibitory activity in plants by changing their metabolism. Here, we report on cultivation factors that affected the activity of P. frutescens var. crispa cultivated in three fields under different cultivation conditions. The results revealed that the activity of P. frutescens var. crispa harvested just before flowering was highest. Interestingly, the activity of wind-shielded plants that were cultivated to prevent exposure to wind, was reduced to 1/5th of plants just before flowering. Furthermore, activity just before flowering increased following appropriate nitrogen fertilization and at least one week of drying from the day before harvest. In addition, we confirmed that the P. frutescens var. crispa leaf extracts suppressed Aβ-induced toxicity in nerve growth factor-differentiated PC12 cells. In this study, we demonstrated that flowering, wind, soil water content, and soil nitrogen content affected Aβ aggregation inhibitory activity, necessary to suppress Aβ neurotoxicity, in P. frutescens var. crispa extracts. This study provides practical cultivation methods for P. frutescens var. crispa with high Aβ aggregation inhibitory activity for the prevention of AD.