SnO2/Au nanosheets prepared via the Joule–Lenz self-heating method were developed as Surface Enhanced Raman Scattering (SERS) substrates for trace detection. The effects of current intensity and processing time on morphology and Raman enhancement were systematically investigated. Structural and morphological characteristics were analyzed by SEM, XRD, and Raman spectroscopy. Finite element simulations using COMSOL Multiphysics were conducted to elucidate the electromagnetic enhancement mechanism and identify regions of high local field intensity. The results show that the SnO2/Au nanosheet substrate enables detection of Methylene Blue at concentrations as low as 10-11 M and thiram down to 10-8 M. These findings demonstrate a practical strategy for developing scalable and low-cost SnO2-based SERS substrates through morphology-controlled nanostructure engineering for trace-level detection applications.
This paper presents the theoretical basis and computational analysis for selecting a Tunnel Boring Machine (TBM) suitable for the underground section of Hanoi Urban Railway Line 2 (Nam Thang Long–Tran Hung Dao). Based on the geological and hydrogeological assessment together with particle size distribution (PSD) analysis of Metro Line 2, the study identifies the Earth Pressure Balance Shield TBM (EPB) as the most suitable tunnelling solution for the prevailing geological conditions, comprising water-saturated soft soils, mixed-face ground conditions, and a high groundwater table. Subsequently, operational data obtained from the geologically comparable Hanoi Metro Line 3 (Nhon–Hanoi Station) were used to constrain the feasible range of the empirical torque coefficient (α) within the range recommended by JSCE (10–25) for preliminary cutterhead torque estimation. The selected design parameters include a shield diameter of approximately 6.73 m, a shield length of approximately 9.8 m, determined in accordance with JSCE recommendations and practical engineering experience, together with a design cutterhead torque of approximately 5,500 kN·m. Accordingly, the torque coefficient (α = 18) was selected from operational monitoring data obtained from the S9–S10 section of Hanoi Metro Line 3 under geological conditions comparable to those of Metro Line 2, providing a basis for preliminary TBM design. The proposed procedure provides a practical and quantitative framework for preliminary EPB TBM selection and cutterhead torque estimation for metro projects developed under geological conditions comparable to those of Hanoi Metro Line 2.
In this work, we report the effect of fuel content on the green upconversion emission of Er/Yb/Li tri-doped hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) composite phosphor prepared by the solution combustion method using urea as the fuel. X-ray diffraction confirms the formation of mixed phases, including the main HA phase with a hexagonal structure and the secondary β-TCP phase; their percentage composition depends on the fuel content. Scanning electron microscopy indicates spherical particles with average sizes ranging from 118.7 nm to 306.6 nm. Under 975 nm excitation, the phosphors exhibit intense green upconversion (UC) emission (560 nm), which reaches its maximum at the optimal fuel content of 30 mol%. This phenomenon is due to the high fuel content, which enhances crystallinity and contributes to the improved emission-intensity of the phosphors. In summary, the phosphor exhibits intense green UC emission with a uniform particle size, making it suitable for biomedical applications.
In this study, In2O3 nanostructures were synthesized by the hydrothermal method through a two-step process, including hydrothermal treatment followed by heat treatment. The hydrothermal conditions, namely temperature and time, were varied to obtain different morphological characteristics of the In2O3 nanostructures. The hydrothermal time and temperature were investigated at three different temperature points and three different time points to determine the optimal conditions at which the In2O3 nanosheets exhibit the most well-defined morphology for gas sensing applications. The hydrothermal condition of 180 °C for 12 h was selected for further investigation of the structural and electrical properties. The morphological and structural characteristics were analyzed using techniques such as field-emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The results reveal that the nanostructures exhibit diverse morphologies, depending on the hydrothermal conditions, particularly temperature and time. In addition, the gas sensing capabilities of the In2O3 nanosheets toward ammonia were also investigated.
Although a-Fe2O3 is a promising photocatalyst for Advanced Oxidation Processes in dye-polluted wastewater treatment, its practical efficiency is limited by inherent drawbacks including rapid electron-hole recombination and poor electron mobility. This study proposes a TiO2/a-Fe2O3 nanocomposite system to enhance dye removal efficiency of a-Fe2O3, specifically Methylene Blue (MB), in which hierarchical porous, coral-like a-Fe2O3 was prepared via a thermal phase transition process from g-Fe2O3. X-ray diffraction analysis and peak deconvolution were used to confirm that the phase transition to a-Fe2O3 completed after 3 hours of annealing at 800 °C. With the combination of TiO2 and a-Fe2O3, the dye degradation efficiency increased significantly, demonstrating superior photocatalytic performance under visible light compared to the conventional photo-Fenton process observed for pure a-Fe2O3. In detail, this nanocomposite system achieved nearly 100% degradation of 20 ppm MB within 2 hours, reaching the degradation rate constant of 1.5595 h-1 which was considerably higher than that of a-Fe2O3 (k = 0.4563 h-1). Furthermore, TiO2/a-Fe2O3 proved to be durable, maintaining over 90% efficiency after five reuse cycles with MB concentration of 40 ppm with negligible structural degradation. This enhanced performance is proposed due to the synergistic photocatalytic effect, including photo-Fenton and photocatalytic pathways, which comes from the favorable band alignment of TiO2 and a-Fe2O3. These findings contributed that the TiO2/a-Fe2O3 is promising catalyst with great potential for practical applications in solar-driven treatment of dye-polluted wastewater.
