High aspect ratio Ca 6 Si 6 O 17 (OH) 2 nanowires: Green hydrothermal synthesis, formation mechanism, optical and photoluminescence properties

Abstract Calcium silicate 1D nanostructures have aroused widespread concern and become widely available for drug delivery, and photoluminescence host, etc. , which however have traditionally been synthesized via high temperature based molten salt synthesis or solution-based techniques, in the presence of organic template or solvents. Herein, a facile controllable green hydrothermal route (200 °C, 12.0 h) to uniform high aspect ratio high purity Ca 6 Si 6 O 17 (OH) 2 nanowires (diameter: 20.0–120.0 nm, aspect ratio: 60.0–350.0) has been developed for the first time by using abundant CaCl 2 ·2H 2 O and Na 2 SiO 3 ·9H 2 O as raw materials, in the absence of any organic stabilizer, template, or directing agent. Effects of process parameters such as molar ratio of reactants, reaction time, temperature, reactant concentration, and dropping rate on the hydrothermal products were investigated in detail, and an intrinsic highly anisotropic structure induced hydrothermal formation mechanism of the high aspect ratio Ca 6 Si 6 O 17 (OH) 2 nanowires was proposed. The Ca 6 Si 6 O 17 (OH) 2 nanowires exhibited a transparent characteristic from the ultraviolet to visible range, and the Ca 6 Si 6 O 17 (OH) 2 :1.2%Tb 3+ nanophosphors demonstrated the strongest photoluminescence emission intensity. With the doping molar percentage of Tb 3+ changing from 0.5% to 1.5%, the quantum yields (QYs) varied within the range of 43%–72%, definitely suggesting the Ca 6 Si 6 O 17 (OH) 2 nanowires as a great promising host candidate for green-emitting luminescent materials in light display systems, and optoelectronic devices, etc.