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Heavy metal ions have attracted considerable concern for their high toxicity and potential malign effects on the water environment, and adsorption has been regarded as one of the most versatile and effective techniques towards water treatment. In view of this, hierarchical porous carnation-like Ca4B10O19·7H2O microspheres self-assembled by two-dimensional (2D) quasi-hexagonal nanoplates are successfully synthesized for the first time as far as we know, by a facile and surfactant ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) assisted hydrothermal approach using CaCl2·2H2O, NaOH and H3BO3 as the raw materials. The as-obtained carnation-like Ca4B10O19·7H2O microspheres exhibit a uniform morphology, ca. 89% of which have a diameter within the range of 8.0–11.0 μm. A probable EDTA-2Na assisted self-assembly formation mechanism has also been proposed based on systematic control experiments. Meanwhile, the carnation-like Ca4B10O19·7H2O microspheres demonstrate a transparent characteristic from the ultraviolet to the visible region, a hierarchical porous structure (specific surface area: 32.79 m2 g−1, pore volume: 0.151 cm3 g−1, average pore diameter: 3.704 nm) and satisfactory thermal stability. In addition, the carnation-like microspheres are confirmed as great satisfactory adsorbents for heavy metal ion (Pb2+) removal with an adsorption capacity qm of 256.4 mg g−1, which may also be employed as excellent adsorbent candidates for other heavy metal or organic dye removal in water treatment as well as catalyst carriers in heterogeneous catalysis. [ABSTRACT FROM AUTHOR]

One-dimensional (1D) nanostructured metal borates have drawn considerable attention owing to their versatile applications in a multitude of fields, but it is still a great challenge to achieve a high aspect ratio in these materials via a facile and feasible route. Herein, ultralong Ca2B2O5·H2O nanowires with a length of 110–230 μm and ultrahigh aspect ratio of 240–750 are successfully synthesized for the first time via a facile water-bath pretreated eco-friendly hydrothermal technique in the absence of any additives, using low cost CaCl2, H3BO3 and NaOH as the raw materials. The formation mechanism of the ultralong nanowires is studied in detail by varying the process parameters (water-bath and hydrothermal temperature, duration time, etc.). The water-bath treatment plays a key role in the formation of thin hexagonal Ca(OH)2 nanoplates, favoring subsequent conversion to ultralong nanowires with a high aspect ratio. The as-obtained Ca2B2O5·H2O:5.0%RE3+ (rare earth, RE = Eu, Tb) nanophosphors exhibit strong photoluminescence emission and excitation performance, with corresponding Commission Internationale de l'Eclairage (CIE) values determined as (0.635, 0.364) and (0.320, 0.597) within the red and green regions, respectively. This not only suggests that the ultralong Ca2B2O5·H2O nanowires are promising structure- and function-integrated photoluminescent host candidates, but also provides a novel and facile route for the formation of high aspect ratio 1D nanostructures of other metal borates. [ABSTRACT FROM AUTHOR]

Three-dimensional hierarchical nanoarchitectures of metal borates self-assembled by one-dimensional or two-dimensional nanostructures have been paid extensive attention for their versatile compositions and excellent performance in various fields. Hilgardite-like metal borates have been widely employed as nonlinear optical materials and ideal hosts for various luminescent ions. In this contribution, we reported for the first time a mild surfactant-assisted hydrothermal process for the synthesis of uniform Ba2(B5O9)Cl·(H2O)0.5 microspheres at 160 °C for 6.0 h, by using BaCl2·2H2O, H3BO3, and NaOH as raw materials and ethylenediaminetetraacetic acid disodium salt (EDTA-2Na) as the surfactant. The effects of process parameters and the EDTA-2Na assisted formation mechanism were investigated in detail. The as-obtained microspheres exhibited a transparent characteristic from the ultraviolet to visible range. Within the experimental doping molar percentage of 0–10% in Ba2+, the as-prepared Ba2(B5O9)Cl·(H2O)0.5:6%Tb3+ phosphors demonstrated the strongest PL intensity, revealing the as-obtained Ba2(B5O9)Cl·(H2O)0.5 microspheres as a great promising host candidate for emitting luminescent materials in light display systems or optoelectronic devices. [ABSTRACT FROM AUTHOR]