Removal of contaminants in wastewater, such as heavy metals, has become a severe problem in the world. Numerous technologies have been developed to deal with this problem. As an emerging technology, nanotechnology has been gaining increasing interest and many nanomaterials have been developed to remove heavy metals from polluted water, due to their excellent features resulting from the nanometer effect. In this work, novel nanomaterials, including carbon-based nanomaterials, zero-valent metal, metal-oxide based nanomaterials, and nanocomposites, and their applications for the removal of heavy metal ions from wastewater were systematically reviewed. Their efficiency, limitations, and advantages were compared and discussed. Furthermore, the promising perspective of nanomaterials in environmental applications was also discussed and potential directions for future work were suggested.
We report in this communication the design and fabrication of solutionprocessed white light-emitting diodes (LEDs) containing a bilayer of heavy metal-free colloidal quantum dots (QDs) and polymer in the device active region. White electroluminescence was obtained in the LEDs by mixing the red emission of ZnCuInS/ZnS core/shell QDs and the blue-green emission of poly(N,N 0 -bis(4-butylphenyl)-N,N 0bis(phenyl)benzidine). A high color rendering index of 92 was achieved as compared to a 5310 K blackbody reference by virtue of broadband emission of the QDs. The Commission Internationale de l'Eclairage chromaticity coordinates of the white LED output exhibit a distinctive bias dependence. Finally, aging of the white LEDs was studied, revealing the difference between the photochemical stabilities of the QDs and polymer molecules and the consequent effect on the color evolution of the LEDs.
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