Kenji Ogino

Poly(9,9-di-n-octylfluorene) (PFO) applications are limited by green emission defects and imbalanced charge transport. To overcome this, novel branched polystyrene-graft-polyfluorene (PSt-g-PFO) copolymers with varying grafting densities were synthesized. The highly branched architecture induces intense steric hindrance, acting as a physical shield to isolate PFO emissive cores. This successfully suppresses detrimental interchain π–π stacking, mitigating the ~530 nm green emission. Furthermore, the moderately grafted PSt-g-PFO2 promotes locally ordered crystalline packing, achieving a maximum electron mobility of 6.16 × 10⁻⁶ cm²/(V·s), an order of magnitude higher than linear PFO. This structural design effectively decouples deleterious aggregation from charge transport.

To mitigate health hazards from pathogenic bacteria (Escherichia coli, Staphylococcus aureus) and fungi (Aspergillus niger) as well as the coating mildew issue in high-humidity indoor environments, and to overcome the challenges of particle agglomeration and non-uniform distribution in conventional benzalkonium chloride (BAC)-clay composites, this study proposes a wet chemical strategy to prepare BAC-hectorite antimicrobial composites using synthetic hectorite as a high-performance carrier, which is superior to natural clays such as montmorillonite and kaolin in structural uniformity, ion-exchange efficiency, and dispersion stability. Characterization using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analysis confirmed the successful intercalation of BAC cations into the hectorite interlayers through ion exchange. This resulted in a significant expansion of the interlayer spacing from 1.0–1.2 nm to 1.5–1.8 nm, a marked alleviation of particle agglomeration, and an optimized pore structure. A clear structure–activity relationship between preparation conditions, microstructure regulation, and antimicrobial performance is systematically established. Antibacterial tests revealed superior efficacy against Gram-positive bacteria; the composite exhibited an inhibition zone of 13.31 mm and a minimum inhibitory concentration (MIC) of 4 μg/mL against S. aureus, compared to 11.62 mm and 32 μg/mL against E. coli. Practical application tests demonstrated that at an ultralow addition level of 0.4%, incorporating this composite into latex paint achieved an antibacterial rate exceeding 99.9% against both pathogens. When added to putty powder, it yielded Grade 0 mold resistance with no observable growth. Furthermore, compounding with polypropylene (PP) increased the elongation at break to approximately 600%, simultaneously realizing antibacterial, antifungal, and toughening functions, thereby not only conferring antibacterial functionality but also significantly enhancing toughness—resolving the typical polymer embrittlement caused by traditional inorganic antibacterial fillers. Short-term evaluations confirm that this composite offers a stable structure, high-efficiency antimicrobial properties, and improved substrate mechanics at low loading levels. These findings provide technical support and experimental guidance for the functional upgrading of indoor decorative coatings, putties, and polymer materials used in high-humidity scenarios such as kitchens and bathrooms.

Coal gangue accumulation causes land occupation and environmental risks in mining areas, but its use as a planting substrate offers a pathway for ecological restoration. This study optimized a coal gangue-based planting substrate by integrating phosphogypsum, spent mushroom substrate, biochar, and a water retention agent. Using a three-factor, four-level orthogonal design with a fixed value of 10% phosphogypsum, the study assessed the effects of the coal gangue-to-spent mushroom substrate ratio, biochar, and water retention agent on substrate properties, nutrient availability, plant growth, and Pb leaching. The results showed that the tested formulations maintained substrate pH within a near-neutral range across treatments. The coal gangue-to-spent mushroom substrate ratio was the dominant factor controlling substrate structure, water-holding capacity, nutrient status, and ryegrass growth. Increasing the spent mushroom substrate proportion reduced bulk density and improved field water capacity, pore structure, and nutrient availability. Biochar most effectively reduced Pb leaching, although excessive application inhibited growth, whereas the water retention agent mainly enhanced water retention and plant growth. The optimal formulation was 80% coal gangue, 20% spent mushroom substrate, 1% biochar, 1.5 g kg⁻¹ water retention agent and 10% phosphogypsum, providing a theoretical and practical optimization basis for coal gangue reutilization and ecological restoration in mining areas.

Poly(9,9-di-n-octylfluorene) (PFO) suffers from interchain aggregation, which degrades its blue spectral stability and charge transport. To address this, a series of rod-coil diblock copolymers (PFO-b-PMMAs) with varying poly(methyl methacrylate) (PMMA) chain lengths were synthesized via Steglich coupling. The non-conjugated PMMA blocks act as bulky steric spacers in the solid state, effectively suppressing detrimental PFO aggregation and enhancing pure blue emission stability. Furthermore, moderate PMMA blocks (PFO-b-PMMA1 and PFO-b-PMMA2) promote favorable β-phase formation and ordered crystalline packing. This microstructural optimization yields a maximum electron mobility of 1.98 × 10⁻⁶ cm²/(V·s) for PFO-b-PMMA2, markedly higher than the PFO-2 homopolymer (4.13 × 10⁻⁷ cm²/(V·s)). However, an overlong PMMA block (PFO-b-PMMA3) introduces excessive steric hindrance (T_g = 66 °C) that disrupts crystallization, acting as an insulating barrier that reduces mobility. Thus, precisely tuning the non-conjugated block length effectively maximizes both the blue spectral stability and electron transport capabilities of PFO-based materials.

This study reports the preparation of benzalkonium chloride-modified montmorillonite (MMT-1227) via a wet chemical method and systematically investigates its structural characteristics and antimicrobial/antifungal properties. The modified montmorillonite was comprehensively characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Brunauer–Emmett–Teller (BET) surface area analysis. The results confirmed the successful intercalation of benzalkonium chloride into montmorillonite layers, leading to altered surface morphology, increased interlayer spacing, and enhanced hydrophobicity. Antimicrobial assays demonstrated that MMT-1227 exhibits potent activity against both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus, with inhibition zone diameters of 15.6 ± 0.2 mm and 17.7 ± 0.2 mm, respectively, and minimum inhibitory concentrations (MIC) of 1 mg/mL and 0.5 mg/mL. When incorporated into latex paint at a mass fraction of 0.3%, MMT-1227 achieved a 99.9% antibacterial rate against both strains after 24 h. Additionally, fungal resistance testing in accordance with GB/T 1741-2020 revealed that the modified paint films completely inhibited the growth of eight common mold strains (e.g., Aspergillus niger, Trichoderma viride), achieving a resistance grade of 0. These findings validate that benzalkonium chloride modification endows montmorillonite with excellent antimicrobial and antifungal properties, highlighting its potential as a high-performance additive for functional coatings and related antimicrobial materials.

To optimize the performance of low-molecular-weight poly{[N,N’-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5’-(2,2’-bithiophene)} [P(NDI2OD-T2)] as an electron-transporting layer material, the electron-transporting behavior of P(NDI2OD-T2) in blends with polystyrene (PSt) was investigated. The results demonstrated that blends of P(NDI2OD-T2) with 10 wt% PSt after annealing exhibited significantly higher electron-transporting performance compared to unblended P(NDI2OD-T2). The electron mobility of the annealed blends reached 3.26 × 10-4 cm2/V·s, approximately 30 times higher than that of annealed unblended P(NDI2OD-T2) (1.08 × 10-5 cm2/V·s) and about 100 times higher than that of unannealed unblended P(NDI2OD-T2) (2.95 × 10-6 cm2/V·s). This enhanced performance is attributed to changes in the aggregate state and phase separation, particularly influenced by the unique properties of low-molecular-weight P(NDI2OD-T2) in facilitating uniform film formation and phase stability.

As global CO₂ emissions continue to rise, addressing their environmental impact is critical in combating climate change. Photocatalytic CO₂ reduction, which mimics natural photosynthesis by converting CO₂ into valuable fuels and chemicals using solar energy, represents a promising approach for both reducing emissions and storing energy sustainably. However, the development of efficient photocatalysts, particularly those capable of absorbing visible light, remains a challenge. Graphitic carbon nitride (g-C₃N₄) has gained attention for its visible light absorption and chemical stability, though its performance is hindered by rapid electron–hole recombination. Similarly, bismuth tungstate (Bi₂WO₆) is a visible-light-active photocatalyst with promising properties, but also suffers from limited efficiency due to charge recombination. To overcome these limitations, this study focuses on the design and synthesis of a g-C₃N₄/Bi₂WO₆ composite photocatalyst, leveraging the complementary properties of both materials. The composite benefits from enhanced charge separation through the formation of a heterojunction, reducing recombination rates and improving overall photocatalytic performance. The optimized g-C₃N₄/Bi₂WO₆ composite exhibited significant improvements in the production rates of both CH4 and CO, achieving 18.90 and 17.78 μmol/g/h, respectively, which are 2.6 times and 1.6 times higher than those of pure B_i2WO₆. The study explores how optimizing the g-C₃N₄/Bi₂WO₆ interface, increasing surface area, and adjusting material ratios can further enhance the efficiency of CO₂ reduction. Our findings demonstrate the potential of this composite for solar-driven CO₂ conversion, offering new insights into photocatalyst design and paving the way for future advancements in CO₂ mitigation technologies.

To enhance the charge transport performance of poly(9,9-di-n-octylfluorene) (PFO) in polymer light-emitting diodes (PLEDs), the electron transport behaviors of PFO blended with polystyrene (PSt) were investigated. Electron-only (EO) devices were fabricated using a solution process to assess electron transport performance. The results demonstrated that blending PFO with a minority of PSt induced β-phase formation and phase separation upon annealing, contributing to improved electron transport properties. EO measurements revealed that the electron mobility of PFO/PSt blends (PSt: 30wt%, 40%) after annealing was higher than that of pure PFO in both states.

We synthesized n-type polymers poly{[N,N′-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5′-(2,2′-bithiophene)} [P(NDI2OD-T2)] and poly{[N,N′-bis(3-(4-cardanol)propyl)-naphthalene-1,4,5,8-tetracarboxylic diimide]-alt-[5,5′-bis(2-thienyl)-2,2′-bithiophene]} [P(NDICL-T2)] with cardanol-based side chains via Stille coupling to enhance electron mobility. Replacing the 2-octyldodecyl side chain with cardanol in P(NDICL-T2) improved electron mobility due to increased chain flexibility and ordered packing. Lower glass transition temperature (t_g), red-shifted UV-vis absorption, results from crystalline structure analysis, indicating tighter lamellar spacing and enhanced molecular ordering, and smoother surface morphology confirmed the enhanced intermolecular interactions and uniform film formation.