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ZnO nanoparticles have been studied for potential cell labeling applications over the past several years. However, little progress has been made because of the limited emission color and poor water stability of ZnO nanoparticles. In this work, ZnO nanoparticles with various emission colors, including blue, green, yellow, and orange, were synthesized through an ethanol-based precipitation method. The emission color of the ZnO nanoparticles could be tuned by adjusting the pH value of the precipitation solution. The as-prepared ZnO nanoparticles were then encapsulated with silica to form ZnO@silica core shell nanoparticles, to improve the water stability of the ZnO nanoparticles. The visible emissions of the ZnO nanoparticles were well retained after they had been coated with silica shells. The resultant ZnO@silica core shell nanoparticles exhibited low cytotoxity and were promising in cell labeling applications.

CuInS(2)-ZnS alloyed nanocubes with high luminescence were synthesized through a solution-based diffusion method.

In this study, MnFe(2)O(4) nanoparticle (MFNP)-decorated graphene oxide nanocomposites (MGONCs) are prepared through a simple mini-emulsion and solvent evaporation process. It is demonstrated that the loading of magnetic nanocrystals can be tuned by varying the ratio of graphene oxide/magnetic nanoparticles. On top of that, the hydrodynamic size range of the obtained nanocomposites can be optimized by varying the sonication time during the emulsion process. By fine-tuning the sonication time, MGONCs as small as 56.8 ± 1.1 nm, 55.0 ± 0.6 nm and 56.2 ± 0.4 nm loaded with 6 nm, 11 nm, and 14 nm MFNPs, respectively, are successfully fabricated. In order to improve the colloidal stability of MGONCs in physiological solutions (e.g., phosphate buffered saline or PBS solution), MGONCs are further conjugated with polyethylene glycol (PEG). Heating by exposing MGONCs samples to an alternating magnetic field (AMF) show that the obtained nanocomposites are efficient hyperthermia agents. At concentrations as low as 0.1 mg Fe mL(-1) and under an 59.99 kA m(-1) field, the highest specific absorption rate (SAR) recorded is 1588.83 W g(-1) for MGONCs loaded with 14 nm MFNPs. It is also demonstrated that MGONCs are promising as magnetic resonance imaging (MRI) T(2) contrast agents. A T(2) relaxivity value (r(2) ) as high as 256.2 (mM Fe)(-1) s(-1) could be achieved with MGONCs loaded with 14 nm MFNPs. The cytotoxicity results show that PEGylated MGONCs exhibit an excellent biocompatibility that is suitable for biomedical applications.

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