Magnetic chitosan nanocomposites have been synthesized on the basis of amine-functionalized magnetite nanoparticles. These nanocomposites can be removed conveniently from water with the help of an external magnet because of their exceptional properties. The nanocomposites were applied to remove heavy metal ions from water because chitosan that is inactive on the surface of the magnetic nanoparticles is coordinated with them. The interaction between chitosan and heavy metal ions is reversible, which means that those ions can be removed from chitosan in weak acidic deionized water with the assistance of ultrasound radiation. On the basis of the reasons referred to above, synthesized magnetic chitosan nanocomposites were used as a useful recyclable tool for heavy metal ion removal. This work provides a potential platform for developing a unique route for heavy metal ion removal from wastewater.
Carboxyl-enriched monodisperse porous Fe3O4 nanoparticles with diameters of about 85-nm have been synthesized via a simple hydrothermal method. The porous structure of the product is confirmed further by transmission electron microscopy (TEM) observation and nitrogen sorption measurement with a Brunauer-Emmett-Teller (BET) surface area about 36.61 m2/g. An IR spectrum of the sample identifies that abundant carboxylate groups are formed on the surface of the nanoparticles as well as the pore surface. Because of the confined effect of the nanochannels in the nanoparticles and carboxyl-functionalized Fe3O4 nanoparticles, and the strong interaction between ibuprofen and COO-, as-prepared porous nanoparticles show a more extraordinary sustained-release property than that of hollow silica nanoparticles in vitro. This result suggests that as-prepared porous nanoparticles can also be used for the targeted delivery of other aromatic acid drugs.
Luminescent nanoparticles with dual-mode long-lived luminescence are of great importance for their attractive applications in biosensing, bioimaging, and data encoding. Herein, we report the realization of up-and downconversion emission of Mn 2+ dopants in multilayer nanoparticles of NaGdF 4 :Yb/Tm@NaGdF 4 :Ce/Mn@NaYF 4 upon excitation at 980 and 254 nm, respectively. The dual-mode emission of the Mn 2+ dopants at 531 nm have a long-lived lifetime up to ∼30 ms as a result of the spin-forbidden optical transition of Mn 2+ within the 3d 5 configuration. After ceasing steady excitation at the two wavelengths, the long-lived feature of Mn 2+ luminescence allows a longer persistent time than lanthanide emissions, thereby enabling the ease of data decoding by a cell phone camera under a burst mode. The long-lived green upconversion emission also permits the generation of a long green tail emission upon dynamic excitation at 980 nm. These attributes make the as-prepared Mn 2+ -doped multilayer nanoparticles particularly attractive for multilevel anticounterfeiting.
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