| Hierarchical three-dimensional(3D) nanoarchitectures have attracted much concern for their wide applications in energy storage, drug delivery, catalysis, sensors, water treatment, etc., owing to their outstanding properties such as unique porous structure, high specific surface area and good mechanical strength. Among multitudes of 3D hierarchical nanoarchitectures, metal borates have been paid extensive attention for their versatile compositions and excellent performance as anti-wear additives, photoluminescence host materials, micro-/nanoscale nonlinear photonic devices, catalyst support, adsorbents, and etc. Traditional high temperature based techniques, including molten salt synthesis and chemical vapor deposition, have demonstrated some distinct disadvantages such as high energy consumption, poor controllability and difficulty in mass production. Up to date, controllable synthesis of 3D hierarchical alkaline earth metal borates nanomaterials has been rarely reported. This thesis has thus focused on the facile controllable synthesis of 3D alkaline metal borates nanoarchitectures via a mild hydrothermal method, and also the potential applications in the fields of photoluminescence host materials and dye adsorption. The as-synthesized 3D alkaline metal borates nanoarchitectures can also be expected as catalyst support, fire-retardant materials, etc.Uniform hierarchical Ba2(B5O9)Cl·(H2O)0.5 microspheres have been achieved for the first time by a mild and surfactant-assisted hydrothermal process. The effects of process parameters on the hydrothermal products composition and morphology were investigated in detail, based on which the EDTA-2Na assisted formation mechanism of the Ba2(B5O9)Cl·(H2O)0.5 microspheres was put forward. Moreover, Ba2(B5O9)Cl·(H2O)0.5:xTb3+ phosphors were obtained via Tb3+ doping, and the results indicated that the Ba2(B5O9)Cl·(H2O)0.5:6%Tb3+ phosphors exhibited strong PL intensity within the experimental range. The as-obtained Ba2(B5O9)Cl·(H2O)0.5 microspheres were employed as the adsorbents for the removal of Pb2+ from the simulated waste water(50.0 mg L-1), with the removal efficiency up to 98% and the maximum adsorption capacities(qm) about 150 mg g-1. This revealed the Ba2(B5O9)Cl·(H2O)0.5 microspheres of satisfactory photoluminescence host and heavy metal ions adsorption materials.Hierarchical γ-Ba B2O4 hollow microspheres self-assembled by one-dimensional(1D) nanorods were successfully synthesized by a facile surfactant-assisted hydrothermal method. The plausible formation mechanism was proposed, which contained the EDTA-2Na assisted hydrothermal conversion, self- assembly, preferential growth and final Ostwald ripening. The γ-BaB2O4 hollow microspheres exhibited a large specific surface area as 46.25 m2 g-1, which demonstrated good adsorption performance when employed as the adsorbents for the removal of CR from the simulated waste water(50 mg L-1), with the removal efficiency up to 95% and the maximum adsorption capacities(qm) ca. 130 mg g-1. The subsequent mild thermal conversion(700 oC, 3.0 h) of the γ-Ba B2O4 hollow microspheres led to β-Ba B2O4 hollow microspheres, with well-preserved spherical morphology and high crystallinity. Furthermore, other barium borates with unique morphology have also been successfully synthesized, including urchin- like γ-BaB2O4 microspheres, γ-Ba B2O4 hollow polyhedrons and high aspect ratio γ-Ba B2O4 nanorods.Finally, carnation-like Ca4B10O19?7H2O microspheres self-assembled by nano-plates have been successfully synthesized via a hydrothermal method, and the corresponding thermal decomposition properties of the microspheres was preliminarily discussed. The microspheres exhibited good adsorption performance when utilized as the adsorbents for the removal of MB solution(100 mg L-1). The removal efficiency was up to 99.8%, and the maximum adsorption capacities(qm) was about 248 mg g-1, suggesting the attractive application prospect of the as-acquired carnation- like Ca4B10O19?7H2O microspheres in waste water treatment.
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