The development of nanocomposite photocatalysts with high photocatalytic activity, cost-effectiveness, a simple preparation process, and scalability for practical applications is of great interest. In this study, nanocomposites of TiO₂ Degussa P25 nanoparticles/activated carbon (TiO₂/AC) were prepared at various mass ratios of (4:1), (3:2), (2:3), and (1:4) by a facile process involving manual mechanical pounding, ultrasonic-assisted mixing in an ethanol solution, paper filtration, and mild thermal annealing. The characterization methods included XRD, SEM-EDS, Raman, FTIR, XPS, and UV-Vis spectroscopies. The effects of TiO₂/AC mass ratios on the structural, morphological, and photocatalytic properties were systematically studied in comparison with bare TiO₂ and bare AC. TiO₂ nanoparticles exhibited dominant anatase and minor rutile phases and a crystallite size of approximately 21 nm, while AC had XRD peaks of graphite and carbon and a crystallite size of 49 nm. The composites exhibited tight decoration of TiO₂ nanoparticles on micron-/submicron AC particles, and uniform TiO₂/AC composites were obtained, as evidenced by the uniform distribution of Ti, O, and C in an EDS mapping. Moreover, Raman spectra show the typical vibration modes of anatase TiO₂ (e.g., E_1g⁽¹⁾, B_1g⁽¹⁾, E_g⁽³⁾) and carbon materials with D and G bands. The TiO₂/AC with (4:1), (3:2), and (2:3) possessed higher reaction rate constants (k) in photocatalytic degradation of methylene blue (MB) than that of either TiO₂ or AC. Among the investigated materials, TiO₂/AC = 4:1 achieved the highest photocatalytic activity with a high k of 55.2 × 10⁻³ min⁻¹ and an MB removal efficiency of 96.6% after 30 min of treatment under UV-Vis irradiation (120 mW/cm²). The enhanced photocatalytic activity for TiO₂/AC is due to the synergistic effect of the high adsorption capability of AC and the high photocatalytic activity of TiO₂. Furthermore, TiO₂/AC promotes the separation of photoexcited electron/hole (e⁻/h⁺) pairs to reduce their recombination rate and thus enhance photocatalytic activity. The optimal TiO₂/AC composite with a mass ratio of 4/1 is suggested for treating industrial or household wastewater with organic pollutants.

In this study, TiO₂ nanowires on TiO₂ nanotubes arrays (TNWs/TNAs) and Au-decorated TNWs/TNAs nanostructures are designed and fabricated as a new type of photoanode for photoelectrochemical (PEC) water splitting. The TNWs/TNAs were fabricated on Ti folds by anodization using an aqueous NH₄F/ethylene glycol solution, while Au nanoparticles (NPs) and Au nanorods (NRs) were synthesized by Turkevich methods. We studied the crystal structure, morphology, and PEC activity of four types of nanomaterial photoanodes, including TNWs/TNAs, Au NPs- TNWs/TNAs, Au NRs-TNWs/TNAs, and Au NPs-NRs-TNWs/TNAs. The TiO₂ and Au-TiO₂ samples exhibited pure anatase phase of TiO₂ with (0 0 4), (1 0 1), and (1 0 5) preferred orientations, while Au-TiO₂ presented a tiny XRD peak of Au (111) due to a small Au decorated content of 0.7 ± 0.2 at.%. In addition, the samples obtained a well-defined and uniformed structure of TNAs/TNWs; Au NPs (size of 19.0 ± 1.9 nm) and Au NRs (width of 14.8 ± 1.3 nm and length of 99.8 ± 15.1 nm) were primarily deposited on TNWs top layer; sharp Au/TiO₂ interfaces were observed from HRTEM images. The photocurrent density (J) of the photoanode nanomaterials was in the range of 0.24–0.4 mA/cm². Specifically, Au NPs-NRs- decorated TNWs/TNAs attained the highest J value of 0.4 mA/cm² because the decoration of Au NPs and Au NRs mixture onto TNWs/TNAs improved the light harvesting capability and the light absorption in the visible-infrared region, enhanced photogenerated carriers’ density, and increased electrons’ injection efficiency via the localized surface plasmon resonance (LSPR) effect occurring at the Au nanostructures. Furthermore, amongst the investigated nanophotocatalysts, the Au NPs-NRs TNWs/TNAs exhibited the highest photocatalytic activity in the degradation of methylene blue with a high reaction rate constant of 0.7 ± 0.07 h⁻¹, which was 2.5 times higher than that of the pristine TNWs/TNAs.

In the present study, the structural, morphological, compositional, nanomechanical, and surface wetting properties of Bi₂Se₃ thin films prepared using a stoichiometric Bi₂Se₃ target and a Se-rich Bi₂Se₅ target are investigated. The Bi₂Se₃ films were grown on InP(111) substrates by using pulsed laser deposition. X-ray diffraction results revealed that all the as-grown thin films exhibited were highly c-axis-oriented Bi₂Se₃ phase with slight shift in diffraction angles, presumably due to slight stoichiometry changes. The energy dispersive X-ray spectroscopy analyses indicated that the Se-rich target gives rise to a nearly stoichiometric Bi₂Se₃ films, while the stoichiometric target only resulted in Se-deficient and Bi-rich films. Atomic force microscopy images showed that the films’ surfaces mainly consist of triangular pyramids with step-and-terrace structures with average roughness, R_a, being ~2.41 nm and ~1.65 nm for films grown with Bi₂Se₃ and Bi₂Se₅ targets, respectively. The hardness (Young’s modulus) of the Bi₂Se₃ thin films grown from the Bi₂Se₃ and Bi₂Se₅ targets were 5.4 GPa (110.2 GPa) and 10.3 GPa (186.5 GPa), respectively. The contact angle measurements of water droplets gave the results that the contact angle (surface energy) of the Bi₂Se₃ films obtained from the Bi₂Se₃ and Bi₂Se₅ targets were 80° (21.4 mJ/m²) and 110° (11.9 mJ/m²), respectively.

Đặt vấn đề: Công nghệ quang xúc tác vật liệu nano TiO2 dạng dây trên ống (TNWs/TNAs) mọc trực tiếp trên đế titan được cho là có hiệu suất cao trong quang phân hủy xanh methylene - tác nhân ảnh hưởng xấu gây ô nhiễm nguồn nước và sức khỏe con người. Mục tiêu nghiên cứu: 1) Chế tạo vật liệu nano TiO2 dạng dây trên ống bằng phương pháp anod hóa; 2) Khảo sát tính chất TNWs/TNAs trong quá trình quang xúc tác phân hủy xanh methylene (hình thái, thành phần hoá học, khả năng tái sử dụng của TNWs/TNAs trong quang xúc tác phân hủy xanh methylene). Đối tượng và phương pháp nghiên cứu: Chế tạo TNWs/TNAs bằng phương pháp anod hóa. Khảo sát tính chất vật liệu: dùng phổ nhiễu xạ tia X sử dụng bức xạ Cu Kα (λ = 1,5406 Å), công thức Scherrer, kính hiển vi điện tử quét (SEM, JEOL JSM-6500), phổ phân tán năng lượng tia X (EDS) được trang bị SEM. Đánh giá tính ổn định của vật liệu dựa trên TiO2 trong quang xúc tác phân hủy xanh methylene sau 5 chu kỳ sử dụng dựa trên quy luật động học Langmuir-Hinshelwood sau 2 giờ chiếu xạ UV. Kết quả: Tổng hợp thành công TNWs/TNAs pha anatase tinh khiết (kích thước tinh thể ~28,12 nm). Cấu trúc TNWs/TNAs (đường kính ~124,55 nm , độ dày màng ~4,8 µm) duy trì ổn định sau quá trình quang xúc tác. Hiệu suất phân hủy xanh methylene đạt ~59% sau 2 giờ chiếu xạ UV, và hằng số tốc độ phản ứng duy trì ~94,4% giá trị ban đầu sau 5 chu kỳ. Kết luận: TNWs/TNAs được tổng hợp sở hữu cấu trúc bền vững và thể hiện hiệu suất quang xúc tác ổn định trong phân hủy xanh methylene.

Nanocomposites of TiO₂ Degussa P25 nanoparticles/activated carbon (TiO₂/AC ) were prepared at various mass ratios of (4:1), (3:2), (2:3), and (1:4) by a facile process. The effects of TiO₂/AC mass ratios on the structural, morphological, and photocatalytic properties were systematically studied in comparison with bare TiO₂ and bare AC. TiO₂ nanoparticles exhibited dominant anatase and minor rutile phases, and a crystallite size of approximately 21 nm; while AC had XRD peaks of graphite and carbon, and a crystallite size of 49 nm. The composites exhibited tight decoration of TiO₂ nanoparticles on micron-/submicron AC particles, and uniform TiO₂/AC composites were obtained as evidenced by the uniform distribution of Ti, O, and C in an EDS mapping. Moreover, Raman spectra show the typical vibration modes of anatase TiO₂ (e.g., E_1g⁽¹⁾, B_1g⁽¹⁾, E_g⁽³⁾) and carbon materials with D and G bands. The TiO₂/AC with (4:1), (3:2), and (2:3) possessed higher reaction rate constants (k) in photocatalytic degradation of methylene blue (MB) than that of either TiO₂ or AC. Among the investigated materials, TiO₂/AC = 4:1 achieved the highest photocatalytic activity with a high k of 55.2×10^-3 min^-1 and an MB removal efficiency of 96.6% after 30 min treatment under UV-Vis irradiation (120 mW/cm²). The enhanced photocatalytic activity for TiO₂/AC is due to the synergistic effect of the high adsorption capability of AC and the high photocatalytic activity of TiO₂. Furthermore, TiO₂/AC promotes the separation of photoexcited electron/hole (e^-/h⁺) pairs to reduce their recombination rate and thus enhance photocatalytic activity. The optimal TiO₂/AC composite in this study can be used for treating industrial or household wastewater with organic pollutants.