Dense and vertically aligned ZnO nanowires ...
Another key feature of chemical vapor synthesis is thatit allows formation of doped or multi-component nanoparticles by use of multiple precursors. Schmechel et al. prepared nanocrystalline europium doped yttria(Y2O3:Eu3+)from organometallic yttrium and europiumprecursors. Senter et al. incorporated erbium intosilicon nanoparticles using disilane and an organometallicerbium compound as precursors. Srdic et al. prepared zirconia particles doped with alumina. Brehm et al. synthesized nanoparticles of indium oxide, tin oxide,and indium oxide doped with tin oxide (ITO) by chemicalvapor synthesis for the applications as transparent conductingoxides, catalysts and gas sensors. The powdersexhibit a narrow size distribution with an average size ofabout 5 nm.
ZnO nanoparticle-induced apoptosis in Jurkat T ..
In this review, different types of QD/drug nanoparticle formulations are described for their potential use in targeted delivery and therapy. Using the rich surface functionalization chemistry of QDs, targeting biomolecules and drug formulation can be integrated with QDs for traceable drug delivery and therapy and . Many studies have demonstrated that the incorporation of drug formulations with QDs did not compromise the drug efficacy. More importantly, the QD/drug nanoparticle formulations were able to serve as an excellent platform for development of a new generation of traceable drug delivery strategies for real time monitoring of the drug biodistribution and . Because of toxicity concerns, cadmium-based QDs might not be the best candidate for drug delivery and therapy. Thus, many research groups are currently synthesizing cadmium-free QDs for applications. For example, our group has demonstrated the synthesis of indium phosphide, silicon, and copper indium sulfide QDs for targeted tumor imaging and very low toxicity was observed from these formulations[-, ]. However, for -based drug studies, cadmium-based QDs will remain to be utilized, since toxicity is not a concern. Another potential concern for the use of QDs in delivery and therapy is the overall QD size. In general, it is preferable to minimize the overall size of QDs for applications to reduce their accumulation in the reticuloendothelial system. Recently, methods have been reported to reduce the size of the QDs by tailoring their surface coating. Finally, passivation of the QD surface with a long-lasting and robust polymer coating is essential to prevent the breakdown of QDs in the biological environment that gives rise to their toxicity. This is a definite concern for applications. Some reports have suggested that capping the QD core with a higher bandgap semiconductor or biomolecule can minimize the toxicity. But, it is worth noting that each additional step towards functionalizing the QDs will contribute to their final hydrodynamic size and could directly or indirectly affect their biodistribution. In the near future, we envision that the QD/drug nanoparticle formulations will gain wide interest in many healthcare-related research areas. For example, the developed formulations can be used for early cancer detection and therapy. Also, the formulations can be systematically tailored for personalized drug treatment. More importantly, additional modalities such as magnetic resonance imaging and positron emission tomography contrast agents can be integrated into the QD/drug formulations, thus allowing one to use two or more imaging modalities to verify the biodistribution and efficacy of the drug . We believe that in the next few years there will be a tremendous growth in developing QD/drug nanoparticle formulations for therapeutic and diagnostic applications.
In contrast, the toxicity values of Ag NPs varied greatly: 275-fold for mammalian cells in vitro and 500-fold for bacteria. Assumingly, the differential toxicity of nanosilver was due to different coatings that were often applied on the surface of Ag nanoparticles to stabilize them. Indeed, all used ZnO and CuO NPs were uncoated (Tables S5 and S7) but 60 % of Ag NPs used in studies with bacterial cells and 89 % of Ag NPs used in studies with mammalian cells were coated (Table S3). In case of mammalian cells, 55 % of studied Ag NPs had PVP coating, 24 % had peptide coating, and 11 % was uncoated. In case of bacterial cells PVP, mono- and disaccharides and biogenic coatings were reported. Interestingly, the uncoated Ag NPs were remarkably less inhibitory to bacteria than coated NPs. Specifically, to various bacterial strains 14 least inhibitory Ag NPs (MIC values >17 mg/L) were all uncoated. Within 32 Ag NPs that were inhibitory to bacteria at lower than 14 mg/L concentrations 28 were coated and only 4 uncoated, whereas the type of the coating seemed to play no role (Table S3). In case of mammalian cells in vitro we did not observe analogous effect of coating (Table S3).
ZnO Nanoparticles: Synthesis, ..
The toxicity of nanoparticulate ZnO to freshwater algae is due to soluble zinc from ZnO dissolution rather than any characteristic related to particle size.
Synthesis and Growth of ZnO Nanoparticles - The Journal …
(A) Low-magnification SEM image of the as-synthesizedZnO nanorings. (B) High magnification SEM image of a freestandingsingle-crystal ZnO nanoring, showing uniform and perfect geometricalshape. The ring diameter is 1 to 4 m, the thickness of the ring is 10to 30 nm, and the width of the ring shell is 0.2 to 1 m.
Synthesis and Growth of ZnO Nanoparticles
Nanoparticles (NPs) of copper oxide (CuO), zinc oxide (ZnO) and especially nanosilver are intentionally used to fight the undesirable growth of bacteria, fungi and algae. Release of these NPs from consumer and household products into waste streams and further into the environment may, however, pose threat to the ‘non-target’ organisms, such as natural microbes and aquatic organisms. This review summarizes the recent research on (eco)toxicity of silver (Ag), CuO and ZnO NPs. Organism-wise it focuses on key test species used for the analysis of ecotoxicological hazard. For comparison, the toxic effects of studied NPs toward mammalian cells in vitro were addressed. Altogether 317 L(E)C50 or minimal inhibitory concentrations (MIC) values were obtained for algae, crustaceans, fish, bacteria, yeast, nematodes, protozoa and mammalian cell lines. As a rule, crustaceans, algae and fish proved most sensitive to the studied NPs. The median L(E)C50 values of Ag NPs, CuO NPs and ZnO NPs (mg/L) were 0.01, 2.1 and 2.3 for crustaceans; 0.36, 2.8 and 0.08 for algae; and 1.36, 100 and 3.0 for fish, respectively. Surprisingly, the NPs were less toxic to bacteria than to aquatic organisms: the median MIC values for bacteria were 7.1, 200 and 500 mg/L for Ag, CuO and ZnO NPs, respectively. In comparison, the respective median L(E)C50 values for mammalian cells were 11.3, 25 and 43 mg/L. Thus, the toxic range of all the three metal-containing NPs to target- and non-target organisms overlaps, indicating that the leaching of biocidal NPs from consumer products should be addressed.
Synthesis, characterization and optical properties of zinc oxide ..
Metal oxide nanoparticles are finding increasing application in various commercial products, leading to concerns for their environmental fate and potential toxicity. It is generally assumed that nanoparticles will persist as small particles in aquatic systems and that their bioavailability could be significantly greater than that of larger particles. The current study using nanoparticulate ZnO (ca. 30 nm) has shown that this is not always so. Particle characterization using transmission electron microscopy and dynamic light scattering techniques showed that particle aggregation is significant in a freshwater system, resulting in flocs ranging from several hundred nanometers to several microns. Chemical investigations using equilibrium dialysis demonstrated rapid dissolution of ZnO nanoparticles in a freshwater medium (pH 7.6), with a saturation solubility in the milligram per liter range, similar to that of bulk ZnO. Toxicity experiments using the freshwater alga revealed comparable toxicity for nanoparticulate ZnO, bulk ZnO, and ZnCl2, with a 72-h IC50 value near 60 µg Zn/L, attributable solely to dissolved zinc. Care therefore needs to be taken in toxicity testing in ascribing toxicity to nanoparticles per se when the effects may be related, at least in part, to simple solubility.