In this study, a novel CeO 2 -TiO 2 nanocomposite denoted as CeO 2 -3TiO 2 was successfully synthesized via a facile one pot hydro-thermal method without alkali. It exhibits high photocatalytic reduction reactivity toward Cr(VI) under visible light. The photocatalytic reactivity of CeO 2 -3TiO 2 is 18 times higher than that of pure CeO 2 , 28 times higher than pure TiO 2 , 15 times higher than the sample of simply mixed CeO 2 and TiO 2 . The solution with Cr(VI) initial concentration of 2780 ppb can be fast photoreduced by CeO 2 -3TiO 2 in 60 min under visible light to meet the criterion of U.S. Environmental protection Agency. Characterization results indicate CeO 2 -3TiO 2 has the good crystal form of heterojunction structure, narrow pore size distribution , narrow energy gap and high photogenerated electron-hole separation efficiency. Based on the experimental results, a speculated photocatalytic mechanism was proposed.
The generation of high levels of ammonia in industries, agricultural sectors, and water treatment plants has triggered the necessity to detect high ammonia concentrations in a flexible way to ensure proactive measures for protecting humans and the environment. Therefore, it is essential to develop highly sensitive multifunctional sensors that have long-term stability, high durability, and a large stretch range. In our work, a novel approach was developed for fabricating flexible sensors consisting of polyurethane (PU) yarn and the loaded Ti 3 C 2 T x /CeO 2 /TiO 2 (abbreviated as MTCe) nanocomposites. The structures and morphology of the yarn-shaped sensors were analysed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and other characterisation methods. In addition, gas and strain responses were recorded and analysed using an AES-4SD flexible electronic device. The response of the yarn-shaped sensors to 100 ppm NH 3 was 42.9 % at room temperature (25 °C), indicating its excellent gas sensitivity. In addition, the sensors exhibited some key advantages, such as a large stretch range (60 %), high sensitivity (up to 385.285), and good durability (200 stretches/releases at 20 % stretch), which may be considered a remarkable achievement in the field of flexible sensor manufacturing for multiple applications.
A single-pot surfactant-free sol-gel method is reported for the facile and bulk synthesis of ultrafine-nanospherical CeO 2 /TiO 2 composites with different CeO 2 loadings and their photocatalytic-activity for the degradation and mineralization of tetracycline (TC) under visible-light irradiation is investigated for the first time. The incorporation of CeO 2 favored the controlled crystalline growth of TiO 2 in its anatase phase, and their crystallinity and particle size were significantly decreased. The textural and optical properties of TiO 2 were also improved with the incremental addition of CeO 2 by increasing their specific surface-area and visible-light absorption respectively. The optical band gap of TiO 2 decreased to 2.24 eV with the incorporation of 1% CeO 2 and it further decreased to 2.21 eV with the incremental amount of CeO 2 . Due to the formation of heterojunction in the composite, the recombination rate of electron-hole pairs was significantly decreased. A highest TC removal efficiency of ~99% was observed for 4% CeO 2 /TiO 2 composite for a period of 80 min of visible-light irradiation. Moreover, 88.2% TC mineralization efficiency was achieved for a period of 240 min of visible light irradiation. The enhanced catalytic-activity could be attributed to the synergy of high degree of adsorption followed by an enhanced photocatalysis at the heterointerface formed by the adjacent contact between TiO 2 and CeO 2 . The synergistic effects of low-particle size, high surface-area, enhanced visible-light absorption, reduced band-gap, and increased life-time of the photogenerated charge-carriers through the formation of heterointerface contributed to its high photocatalytic activity. The hydroxyl and superoxide-anion radicals played a superior role in the photocatalytic process. Moreover, the composites retained its efficiency for seven-cycles of reaction without any significant-loss in its activity and structural and textural stability.
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