New insight into modulated up-conversion luminescent silica nanotubes as efficient adsorbents for colored effluents

We report a simple and easy method to fabricate silica nanotubes (SNTs) with multicolor up-conversion luminescence by single-nozzle electrospinning based on phase separation effect without any templates. Multicolor up-conversion nanoparticles (UCNPs) were first synthesized by a similar hydrothermal route. Then, the water solution containing NPs were added slowly into the electrospinning precursor solution in a dropwise manner. After electrospinning process and calcination at 600 degrees C, pure SNTs with uniformly dispersed NPs were obtained. The as-produced up-conversion (UC) luminescent SNTs were used as an adsorbent for the removal of colorful dye from aqueous solutions. Adsorption experiments indicated that the SNTs have good adsorption capacity and that the adsorption amount can be traced by two indicators: the decrease in UV adsorption of the solutions and changes in the UC intensity of the SNTs. More importantly, the UC-SNT adsorbents are piece-like and could be effectively and quickly separated via filtration or centrifugation. Furthermore, the SNTs can regenerate by calcination and retain almost the same absorption capability for recycling use. Considering cost, function and cyclic utilization, UCNPs decorated SNTs may create a new platform for the preconcentration and separation of colored pollutants from waste water.