Objectives To evaluate the caries-preventive effects of silver diamine fluoride (SDF) applied using different protocols on root dentin by assessing antibacterial activity and carious lesion prevention in nonirradiated (NR) and irradiated (IR) dentin. Materials and methods Two hundred and forty root dentin specimens were allocated into eight groups based on dentin substrate (NR or IR) and SDF application protocol: control, 10 s application (10s), 10 s application with light curing (10sLC), and 60 s application (60s). Silver and fluoride distribution from the surface to a depth of 500 μm was analysed using energy-dispersive X-ray spectroscopy (n = 10). A multispecies biofilm model was used to evaluate biofilm biovolume and bacterial viability after 24 hours (n = 10). Carious lesion depth was assessed after 10 days of biofilm challenge (n = 10). Three-way ANOVA was applied for elemental analysis, while two-way ANOVA was used for biofilm analysis and lesion depth. Results The 10sLC and 60s application groups demonstrated superior surface silver precipitation, with greater accumulation observed in IR dentin. All SDF-treated groups showed significant suppression of biofilm formation and reduced bacterial viability compared with controls. Lesion depth was greater in IR dentin than in NR dentin. The greatest lesion depth reduction occurred in NR10sLC (NR dentin) and in IR10sLC and IR60s groups (IR dentin). Conclusions SDF effectively prevented caries in both dentin substrates, while IR dentin was more susceptible to lesion formation. The 10sLC protocol reduced lesion depth more than 60s in NR dentin, with comparable efficacy in IR dentin.
In this study, CeO2 nanorods rich in oxygen vacancies were synthesized via a microwave-assisted hydrothermal (MW) method. Ni catalysts supported on these nanorods were subsequently synthesized and evaluated for CO2 methanation. The Ni/CeO2 nanorod catalyst synthesized at an optimal MW power of 400 W exhibited the highest activity, achieving 76% CO2 conversion with 100% CH4 selectivity at a low temperature of 225 degrees C, outperforming the catalysts synthesized by hydrothermal synthesis (XCO2 = 33%) and those based on the commercial CeO2 (XCO2 = 61%). Furthermore, a 1,000-hour durability test confirmed the excellent stability of the Ni/CeO2 nanorod MW catalyst, with negligible carbon deposition and Ni sintering. The superior performance is attributed to the high concentration of oxygen vacancies generated by rapid nanorod growth under MW conditions, which enhances metal-support interaction that suppresses Ni nanoparticle agglomeration and enhances Ni dispersion. The MW method enables the formation of CeO2 nanorods within 30 min, significantly shorter than the 24 h required for conventional hydrothermal synthesis. This work highlights microwave-assisted hydrothermal synthesis as an energy-efficient strategy for producing oxygen-vacancy-rich CeO2 nanorods for CO2 valorization.
This study investigates the chemical modification of commercial-grade (Hero) magnesium oxide (MgO) via an acid-assisted hydrothermal (HT) treatment to enhance the performance of a nickel-molybdenum (NiMo) catalyst for the co-production of syngas and carbon nanotubes (CNTs) from biogas reforming. Nanoplate-structured magnesium hydroxide (Mg(OH)2) was obtained through structural reconstruction and surface modification using an optimum nitric acid concentration of 3 M. The resulting NiMo/MgO (Hero) HT 3 M catalyst achieved high CO2 and CH4 conversions of 96.14 % and 74.51 %, respectively, at 800 degrees C and gas hourly space velocity (GHSV) of 48,000 mL/g & sdot;h. The products, comprising syngas and CNTs, reached high yields of 95.58 % and 26.14 %, respectively, over 3 h of time-on-stream (TOS), substantially outperforming the untreated MgO counterpart, which yielded 72.34 % syngas and 17.95 % CNTs. Characterization revealed that the modified nanoplates contained abundant -OH groups and structural defects, resulting in improved metal dispersion, enhanced reducibility and a higher density of basic sites. These findings highlight that this facile acid-assisted hydrothermal treatment is an effective approach to modifying low-cost MgO supports, thereby improving catalyst performance and offering a cost-effective strategy for efficient biogas utilization.
