Peng Zhang

Nano-CeO2 Exhibits Adverse Effects at Environmental Relevant Concentrations

Ceria nanoparticles (nano-CeO(2)), due to their widespread applications, have attracted a lot of concern about their toxic effects on both human health and the environment. The present work aimed to evaluate the in vivo effects of nano-CeO(2) (8.5 nm) on Caenorhabditis elegans (C. elegans) at environmental relevant concentrations (molar concentrations ranging from 1 nM to 100 nM). The results indicate that nano-CeO(2) could induce ROS accumulation and oxidative damage in C. elegans, and finally lead to a decreased lifespan. The most surprising thing is that the mean lifespan of nematodes was significantly decreased by 12% even at the exposure level of 1 nM (p < 0.01). In vitro tests suggest that the ability of nano-CeO(2) to catalyze ROS generation was involved in the mechanism for its toxicity to C. elegans. To our best knowledge, this is the first case in which nanoparticles exhibit adverse effects on organisms at such low concentrations (1nM-100 nM). So, our findings indicate the importance of nanotoxicological investigations at environmentally relevant concentrations and will attract more attentions on the risks of NPs exposure.

Biotransformation of Ceria Nanoparticles in Cucumber Plants

Biotransformation is a critical factor that may modify the toxicity, behavior, and fate of engineered nanoparticles in the environment. CeO(2) nanoparticles (NPs) are generally recognized as stable under environmental and biological conditions. The present study aims to investigate the biotransformation of CeO(2) NPs in plant systems. Transmission electron microscopy (TEM) images show needlelike clusters on the epidermis and in the intercellular spaces of cucumber roots after a treatment with 2000 mg/L CeO(2) NPs for 21 days. By using a soft X-ray scanning transmission microscopy (STXM) technique, the needlelike clusters were verified to be CePO(4). Near edge X-ray absorption fine structure (XANES) spectra show that Ce presented in the roots as CeO(2) and CePO(4) while in the shoots as CeO(2) and cerium carboxylates. Simulated studies indicate that reducing substances (e.g., ascorbic acids) played a key role in the transformation process and organic acids (e.g., citric acids) can promote particle dissolution. We speculate that CeO(2) NPs were first absorbed on the root surfaces and partially dissolved with the assistance of the organic acids and reducing substances excreted by the roots. The released Ce(III) ions were precipitated on the root surfaces and in intercellular spaces with phosphate, or form complexes with carboxyl compounds during translocation to the shoots. To the best of our knowledge, this is the first report confirming the biotransformation and in-depth exploring the translocation process of CeO(2) NPs in plants.

Uptake and distribution of ceria nanoparticles in cucumber plants

The presence and release of nanoparticles (NPs) into the environment have important implications for human health and the environment. A critical aspect of the risk assessment of nanoparticles is to understand the interactions of manufactured nanoparticles with plants. In this study, the uptake and distribution characteristics of two types of ceria nanoparticles with sizes of ca. 7 nm and 25 nm in cucumber plants were investigated using a radiotracer method and other techniques. With increasing concentration of the nanoparticles, concentration dependent absorption by the plant roots was noticed, but the majority of the particles only loosely adhered to the root surface. The seedlings treated with 7 nm ceria particles showed significantly higher ceria contents in both roots and shoots than those exposed to 25 nm ceria particles at all test concentrations (2, 20, and 200 mg L(-1)). Only very limited amounts of ceria nanoparticles could be transferred from the roots to shoots because the entry of nanoparticles into the roots was difficult. However, the results of tissue distributions of ceria nanoparticles in the plants and two dimensional distributions of the particles in the leaves imply that once they have entered into the vascular cylinder, ceria nanoparticles could move smoothly to the end of the vascular bundle along with water flow. To the best of our knowledge, this is the first detailed study of uptake and distribution of metal oxide nanoparticles in plants.

Comparative toxicity of nanoparticulate/bulk Yb2O3 and YbCl3 to cucumber (Cucumis sativus)

With the increasing utilization of nanomaterials, there is a growing concern for the potential environmental and health effects of them. To assess the environmental risks of nanomaterials, better knowledge about their fate and toxicity in plants are required. In this work, we compared the phytotoxicity of nanoparticulate Yb(2)O(3), bulk Yb(2)O(3), and YbCl(3)·6H(2)O to cucumber plants. The distribution and biotransformation of the three materials in plant roots were investigated in situ by TEM, EDS, as well as synchrotron radiation based methods: STXM and NEXAFS. The decrease of biomass was evident at the lowest concentration (0.32 mg/L) when exposed to nano-Yb(2)O(3), while at the highest concentration, the most severe inhibition was from YbCl(3). The inhibition was dependent on the actual amount of toxic Yb uptake by the cucumber plants. In the intercellular regions of the roots, Yb(2)O(3) particles and YbCl(3) were all transformed to YbPO(4). We speculate that the dissolution of Yb(2)O(3) particles induced by the organic acids exuded from roots played an important role in the phytotoxicity. Only under the nano-Yb(2)O(3) treatment, YbPO(4) deposits were found in the cytoplasm of root cells, so the phytotoxicity might also be attributed to the Yb internalized into the cells.

Phytotoxicity and biotransformation of La2O3 nanoparticles in a terrestrial plant cucumber (Cucumis sativus)

Abstract With the increasing applications of metal-based nanoparticles in various commercial products, it is necessary to address their environmental fate and potential toxicity. In this work, we assessed the phytotoxicity of lanthanum oxide (La2O3) NPs to cucumber plants and determined its distribution and biotransformation in roots by TEM and EDS, as well as STXM and NEXAFS. LaCl3 was also studied as a reference toxicant. La2O3 NPs and LaCl3 were both transformed to needle-like LaPO4 nanoclusters in the intercellular regions of the cucumber roots. In vitro experiments demonstrated that the dissolution of La2O3 NPs was significantly enhanced by acetic acid. Accordingly, we proposed that the dissolution of NPs at the root surface induced by the organic acids extruded from root cells played an important role in the phytotoxicity of La2O3 NPs. The reactions of active NPs at the nano-bio interface should be taken into account when studying the toxicity of dissolvable metal-based nanoparticles.

β-Amyloid peptide increases levels of iron content and oxidative stress in human cell and Caenorhabditis elegans models of Alzheimer disease.

Recent studies indicate that the deposition of β-amyloid peptide (Aβ) is related to the pathogenesis of Alzheimer disease (AD); however, the underlying mechanism is still not clear. The abnormal interactions of Aβ with metal ions such as iron are implicated in the process of Aβ deposition and oxidative stress in AD brains. In this study, we observed that Aβ increased the levels of iron content and oxidative stress in SH-SY5Y cells overexpressing the Swedish mutant form of human β-amyloid precursor protein (APPsw) and in Caenorhabditis elegans Aβ-expressing strain CL2006. Intracellular iron and calcium levels and reactive oxygen species and nitric oxide generation significantly increased in APPsw cells compared to control cells. The activity of superoxide dismutase and the antioxidant levels of APPsw cells were significantly lower than those of control cells. Moreover, iron treatment decreased cell viability and mitochondrial membrane potential and aggravated oxidative stress damage as well as the release of Aβ1-40 from the APPsw cells. The iron homeostasis disruption in APPsw cells is very probably associated with elevated expression of the iron transporter divalent metal transporter 1, but not transferrin receptor. Furthermore, the C. elegans with Aβ-expression had increased iron accumulation. In aggregate, these results demonstrate that Aβ accumulation in neuronal cells correlated with neuronal iron homeostasis disruption and probably contributed to the pathogenesis of AD.

Preparation of Catalytic Materials Using Ionic Liquids as the Media and Functional Components

Ionic liquids (ILs) have attracted much attention due to their unique properties and wide application potential in a variety of fields. The unusual properties of ILs provide numerous opportunities to design and prepare arious advanced materials, including highly efficient catalysts. In recent years, synthesis of different kinds of catalytic materials and their applications in chemical reactions have been studied extensively and have become a very interesting area. Herein, we present a review on the synthesis of catalytic materials using ILs as the media and/or functional components; the important and widely investigated topics are discussed, including mainly metal nanocatalysts/IL, functional IL/support, metals or metal oxides/IL/support, polymeric ILs (PILs) catalysts, and the performances of catalytic systems are highlighted. An outlook for this interesting area is also given at the end of the article.

Acquired Superoxide‐Scavenging Ability of Ceria Nanoparticles

Ceria nanoparticles (nanoceria) are well known as a superoxide scavenger. However, inherent superoxide-scavenging ability has only been found in the nanoceria with sizes of less than 5 nm and with very limited shape diversity. Reported herein is a strategy to significantly improve the superoxide-scavenging activity of nanoceria sized at greater than 5 nm. The nanoceria with sizes of greater than 5 nm, with different shapes, and with a negligible Ce(3+)/Ce(4+) ratio can acquire remarkable superoxide-scavenging abilities through electron transfer. This method will make it possible to develop nanoceria-based superoxide-scavengers with long-acting activity and tailorable characteristics.

Synergistic Phase and Disorder Engineering in 1T‐MoSe2 Nanosheets for Enhanced Hydrogen‐Evolution Reaction

MoSe2 is a promising earth-abundant electrocatalyst for the hydrogen-evolution reaction (HER), even though it has received much less attention among the layered dichalcogenide (MX2 ) materials than MoS2 so far. Here, a novel hydrothermal-synthesis strategy is presented to achieve simultaneous and synergistic modulation of crystal phase and disorder in partially crystallized 1T-MoSe2 nanosheets to dramatically enhance their HER catalytic activity. Careful structural characterization and defect characterization using positron annihilation lifetime spectroscopy correlated with electrochemical measurements show that the formation of the 1T phase under a large excess of the NaBH4 reductant during synthesis can effectively improve the intrinsic activity and conductivity, and the disordered structure from a lower reaction temperature can provide abundant unsaturated defects as active sites. Such synergistic effects lead to superior HER catalytic activity with an overpotential of 152 mV versus reversible hydrogen electrode (RHE) for the electrocatalytic current density of j = -10 mA cm-2 , and a Tafel slope of 52 mV dec-1 . This work paves a new pathway for improving the catalytic activity of MoSe2 and generally MX2 -based electrocatalysts via a synergistic modulation strategy.

Species-specific toxicity of ceria nanoparticles to Lactuca plants

Abstract Species-specific differences in the toxicity of manufactured nanoparticles (MNPs) have been reported, but the underlying mechanisms are unknown. We previously found that CeO2 NPs inhibited root elongation of head lettuce, whereas no toxic effect was observed on other plants (such as wheat, cucumber and radish). In this study, interactions between Lactuca plants and three types of CeO2 NPs (lab-synthesized 7 and 25 nm CeO2 NPs, and a commercial CeO2 NPs) were investigated. It was found that CeO2 NPs were toxic to three kinds of Lactuca genus plants and different CeO2 NPs showed different degrees of toxicity. The results of X-ray absorption near edge fine structure indicate that small parts of CeO2 NPs were transformed from Ce(IV) to Ce(III) in roots of the plants that were treated with CeO2 NPs during the seed germination stage. But the high sensitivity of Lactuca plants to the released Ce3+ ions caused the species-specific phytotoxicity of CeO2 NPs. Differences in sizes and zeta potentials among three types of CeO2 NPs resulted in their different degrees of biotransformation which accounted for the discrepancy in the toxicity to Lactuca plants. This study is among the few, and may indeed the first, that addresses the relation between the physicochemical properties of nanoparticles and its species-specific phytotoxicity.