Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 347
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Inorg Chem ; 58(20): 14075-14084, 2019 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-31573800

RESUMO

As well-known functional groups with excellent electro/photochromic and ion-exchange properties, bipyridinium motifs have been used in functionalized metal-organic coordination polymers, but they are still rarely applied to construct actinide coordination polymers. In this work, we utilized a bipyridinium-based carboxylic acid, 1,1'-bis(4-carboxyphenyl)-4,4'-bipyridinium bis(chloride) ([H2bcbp]Cl2), as the organic ligand to assemble with uranyl cations. By the introduction of different kinds of auxiliary ligands and adjustment of the pH, five novel uranyl coordination compounds, 1-5, have been synthesized through hydrothermal reactions. Starting from uranyl ions and terephthalic acid (H2TP) and H2bcbp ligands, [(UO2)2(bcbp)(TP)2]·3H2O (1) has a wave-shaped two-dimensional (2D) structure consisting of dinuclear units connected by terephthalate linkers and further supported by the longer H2bcbp ligands. [(UO2)2(bcbp)(PA)2]·4H2O (2) has a zigzag chain of dimeric uranium units, and [(UO2)2(bcbp)(bpdc)2]·5H2O (3) forms a one-dimensional ribbonlike structure. The 2D structures of [(UO2)(bcbp)(OH)(H2O)]·Cl (4) and [(UO2)(bcbp)Cl]·Cl (5) are similar, both of which are constructed from dinuclear uranyl units and bcbp2- ligands. Furthermore, the performance for perrhenate removal of compound 4 with a cationic framework is assessed, and we found that compound 4 can efficiently remove ReO4- from an aqueous solution in a wide range of pH values. This work extends the library of viologen derivative-based uranyl coordination polymers, provides to some extent broader insights into actinide coordination chemistry of functionalized ligands, and may facilitate the ion-exchange applications of related coordination polymers.

2.
Chemistry ; 2019 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-31633825

RESUMO

Scintillator is a unique class of luminescent materials with specific applications towards radiation detection. The emitters within state-of-the-art scintillators are mostly limited to bismuth, cerium, europium, thallium, lead, tungsten etc. Shared feature in these elements is relative high atomic number responsible for high radiation stopping power and radiation-induced luminescence. Searching for new scintillating materials is an essential target aiming at specific applications. In this Concept article, we will discuss our recent works on the topic of "uranyl-bearing scintillators". As a vergin territory in this field, uranyl-bearing scintillator shows intrinsic merits for designing new materials with X-ray detection capability, i.e. the large photoelectric cross-section, high X-ray attenuation efficiency, and high crystal density. In addition, we also present the challenge in the further development on the uranyl-bearing scintillators.

3.
Chem Commun (Camb) ; 55(78): 11715-11718, 2019 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-31509115

RESUMO

When exposed to UV (365 nm, 2 mW) radiation, the bulk crystals of a two-dimensional metal-organic framework [Hphen]2[(UO2)2(ox)3] (1,phen = 1,10-phenanthroline, ox = oxalate) are exfoliated into thin sheets (2 µm) and its photoluminescence can be quenched in an incredibly sensitive manner, setting 1 as a superior UV-detection material. When upgrading the UV source into a 300 W xenon light source, the crystals of 1 can be further exfoliated into monolayer nanosheets (0.92 nm).

4.
Environ Sci Technol ; 53(18): 10917-10925, 2019 Sep 17.
Artigo em Inglês | MEDLINE | ID: mdl-31432660

RESUMO

The pertechnetate anion (99TcO4-) is a long-lived radioactive species that is soluble in aqueous solution, in contrast to sparingly soluble 99TcO2. Results are reported for photocatalytic reduction and removal of perrhenate (ReO4-), a nonradioactive surrogate for 99TcO4-, using a TiO2 (P25) nanoparticle suspension in formic acid under UV-visible irradiation. Re(VII) removal up to 98% was achieved at pH = 3 under air or N2. The proposed mechanism is Re(VII)/Re(IV) reduction mediated by reducing radicals (·CO2-) from oxidation of formic acid, not direct reduction by photogenerated electrons of TiO2. Recycling results indicate that photocatalytic reduction of ReO4- exhibits excellent regeneration and high activity with >95% removal even after five cycles. 99Tc(VII) is more easily reduced than Re(VII) in the presence of NO3- with very slow redissolution of reduced 99Tc. This study presents a novel method for the removal of ReO4-/99TcO4- from aqueous solution, with potential application for deep geological disposal.

5.
Chemistry ; 25(54): 12567-12575, 2019 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-31376188

RESUMO

Designability is an attractive feature for metal-organic frameworks (MOFs) and essential for reticular chemistry, and many ideas are significantly useful in the carboxylate system. Bi-, tri-, and tetra-topic phosphonate ligands are used to achieve framework structures. However, an efficient method for designing phosphonate MOFs is still on the way, especially for uranyl phosphonates, owing to the complicated coordination modes of the phosphonate group. Uranyl phosphonates prefer layer or pillar-layered structures as the topology extension for uranyl units occurs in the plane perpendicular to the linear uranium-oxo bonds and phosphonate ligands favor the formation of compact structures. Therefore, an approach that can construct three-dimensional (3D) uranyl phosphonate MOFs is desired. In this paper, a sterically hindered phosphonate ligand method (SHPL) is described and is successfully used to achieve 3D framework structures of uranyl phosphonates. Four MOF compounds ([AMIM]2 (UO2 )(TppmH4 )⋅H2 O (UPF-101), [BMMIM]2 (UO2 )3 (TppmH4 )2 ⋅H2 O (UPF-102), [Py14]2 (UO2 )3 (TppmH4 )2 ⋅3 H2 O (UPF-103), and [BMIM](UO2 )3 (TppmH3 )F2 ⋅2 H2 O (UPF-104); [AMIM]=1-allyl-3-methylimidazolium, [BMMIM]=1-butyl-2,3-dimethylimidazolium, [Py14]=N-butyl-N-methylpyrrolidinium, and [BMIM]=1-butyl-3-methylimidazolium) are obtained by ionothermal synthesis, with zero-dimensional nodes of uranyl phosphonates linked by steric tetra-topic ligands, namely tetrakis[4-(dihyroxyphosphoryl)phenyl]methane (TppmH8 ), to give 3D framework structures. Characterization by PXRD, UV/Vis, IR, Raman spectroscopy, and thermogravimetry (TG) were also performed.

6.
Life Sci Space Res (Amst) ; 22: 1-7, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31421843

RESUMO

After successfully launching two space laboratories, namely, Tiangong-1 and Tiangong-2, China has announced her next plan of constructing the Chinese Space Station (CSS) in 2022. The CSS will provide not only platforms for Chinese scientists to carry out experimental studies in outer space but also opportunities for open international cooperation. In this article, we review the development of China's manned space exploration missions and the preliminary plan for CSS. Additionally, China has initiated space radiation research decades ago with both ground-based simulation research platform and space vehicles and has made noticeable progresses in several aspects. These include studies on human health risk assessment using mammalian cell cultures and animals as models. Furthermore, there have been numerous studies on assessing the space environment in plant breeding.

7.
Inorg Chem ; 58(15): 10047-10056, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31287677

RESUMO

Separation of trivalent actinides An(III) from lanthanides Ln(III) is a worldwide challenge owing to their very similar chemical behaviors. It is highly desirable to understand the nature of selectivity for the An(III)/Ln(III) separation with various ligands through theoretical calculations because of their radiotoxicity and experimental difficulties. In this work, we have investigated three dithioamide-based ligands and their extraction behaviors with Am(III) and Eu(III) ions using the scalar-relativistic density functional theory. The results show that the dithioamide-based ligands have stronger electron donating ability than do the corresponding diamide-based ones. All analyses including geometry, Mulliken population, QTAIM (quantum theory of atoms in molecules), and NBO (natural bond orbital) suggest that the Am-S/N bonds possess more covalency compared to the Eu-S/N bonds, and the M-S bonds have more covalent character than the M-N bonds. Thermodynamic results reveal that N2,N9-diethyl-N2,N9-di-p-tolyl-1,10-phenanthroline-2,9-bis(carbothioamide) (L1) has a stronger complexing ability with metal ions owing to its rigid structure and that N6,N6'-diethyl-N6,N6'-di-p-tolyl-[2,2'-bipyridine]-6,6'-bis(carbothioamide) (L2) shows a higher selectivity for the Am(III)/Eu(III) separation. In addition, these dithioamide-based ligands possess Am(III)/Eu(III) selectivity higher than those of the corresponding diamide-based ones, although the former have weaker complexing ability with metal ions, probably due to the greater covalency of the M-S bonds. This theoretical evaluation provides valuable insights into the nature of the selectivity for the Am(III)/Eu(III) separation and information on designing of efficient An(III)/Ln(III) separation with dithioamide-based ligands.

8.
Inorg Chem ; 58(15): 10239-10247, 2019 Aug 05.
Artigo em Inglês | MEDLINE | ID: mdl-31318539

RESUMO

Tetradentate 1,10-phenanthroline-2,9-dicarboxamide (PDAM) derivatives have been well documented as effective binding ligands toward MA(III) and Ln(III), while the structural analysis and species determination of the complexes are still limited. Herein, we report a combined study on the coordination of Eu(III) with PDAM derivatives using electrospray ionization mass spectrometry (ESI-MS), time-resolved laser-induced fluorescence (TRLIF), and density functional theory (DFT) calculations. PDAM derivatives here involve N,N'-diethyl-N,N'-diethyl-2,9-diamide-1,10-phenanthroline (Et-Et-DAPhen), N,N'-dibutyl-N,N'-dibutyl-2,9-diamide-1,10-phenanthroline (But-But-DAPhen), and N,N'-dihexyl-N,N'-dihexyl-2,9-diamide-1,10-phenanthroline (Hex-Hex-DAPhen). The collision-induced dissociation (CID) test shows that these alkyl-DAPhen ligands coordinate strongly with Eu(III), given that the coordination moieties remain intact during CID. The 1/2 EuIII-L species was found to be the dominant component for all three ligands, as evidenced by ESI-MS and fluorescence titration. The fluorescence decay results indicate that the hydration numbers of Eu(III) are reduced from 9 to 1 upon complexation, in agreement with the fact that the 1/2 EuIII-L species are formed, and eight water molecules are exactly replaced by eight donor atoms of two alkyl-DAPhen ligands. In addition, the DFT calculations suggest that the 1:2 EuIII-L species is more stable than the 1/1 EuIII-L species and the Eu-oxygen/nitrogen (Eu-O/N) bonds have a dominant ionic character, with the O atoms having stronger electron-donating abilities toward Eu(III) in comparison to the N atoms.

9.
Phys Chem Chem Phys ; 21(29): 16017-16031, 2019 Jul 24.
Artigo em Inglês | MEDLINE | ID: mdl-31304940

RESUMO

Enterobactin (Ent) is a typical siderophore with strong iron affinity. Its dynamics in its intact form and holo state remains to be studied to understand its role in the in vivo behavior of metal ions and to facilitate its potential application in drug design and environmental remediation. Here, we report molecular dynamics simulations of both Ent enantiomers and their complexes with key actinides (Am3+, Cm3+, Th4+, U4+, Np4+ and Pu4+) to study the folding equilibria of Ent enantiomers and their binding affinity with actinides. For comparison, the ferric cation was also considered. In their neutral state, both enantiomers may exist in their folded and extended states in the aqueous phase with the former more stable owing to the favorable cation-π, π-π, and H-bond interactions. A helicity preference was observed in the folded states of Ent enantiomers, which was solidified when binding with Fe3+ while disrupted when binding with actinides. Upon binding with metal ions, the dynamics of Ent enantiomers exhibited dependence on the metal ions, and appeared to be more flexible in An3+/4+-Ent complexes than in Fe3+-Ent complexes. The conformational analysis and the energy decomposition of M3+/4+-Ent complexes indicated that their distinct conformational variations and dynamic fluxionality are enthalpy driven behaviors and dependent on the nature of the loaded metal ions. The Fe3+-Ent complexes had a more compact conformation, while the relatively loosely bound An3+/4+-Ent complexes allowed solvent water molecules to access the first coordination shell of An3+/4+ and weaken the interaction between An3+/4+ and Ent. This work is expected to enrich our knowledge of the folding equilibria of Ent enantiomers and their An3+/4+-Ent complexes, and contribute to communities that concern the in vivo and in vitro behaviors of Ent enantiomers and actinides.


Assuntos
Elementos da Série Actinoide/química , Enterobactina/química , Modelos Moleculares , Conformação Molecular , Simulação de Dinâmica Molecular , Estereoisomerismo , Termodinâmica
10.
ACS Nano ; 13(8): 9198-9205, 2019 Aug 27.
Artigo em Inglês | MEDLINE | ID: mdl-31330102

RESUMO

A Ti3(AlxCu1-x)C2 phase with Cu atoms with a degree of ordering in the A plane is synthesized through the A site replacement reaction in CuCl2 molten salt. The weakly bonded single-atom-thick Cu layers in a Ti3(AlxCu1-x)C2 MAX phase provide actives sites for catalysis chemistry. As-synthesized Ti3(AlxCu1-x)C2 presents unusual peroxidase-like catalytic activity similar to that of natural enzymes. A fabricated Ti3(AlxCu1-x)C2/chitosan/glassy carbon electrode biosensor prototype also exhibits a low detection limit in the electrochemical sensing of H2O2. These results have broad implications for property tailoring in a nanolaminated MAX phase by replacing the A site with late transition elements.

11.
Nat Commun ; 10(1): 2570, 2019 06 25.
Artigo em Inglês | MEDLINE | ID: mdl-31239437

RESUMO

Searching for actinide decorporation agents with advantages of high decorporation efficiency, minimal biological toxicity, and high oral efficiency is crucial for nuclear safety and the sustainable development of nuclear energy. Removing actinides deposited in bones after intake is one of the most significant challenges remaining in this field because of the instantaneous formation of highly stable actinide phosphate complexes upon contact with hydroxyapatite. Here we report a hydroxypyridinone-based ligand (5LIO-1-Cm-3,2-HOPO) exhibiting stronger affinity for U(VI) compared with the reported tetradentate hydroxypyridinone ligands. This is further revealed by the first principles calculation analysis on bonding between the ligand and uranium. Both in vitro uranium removal assay and in vivo decorporation experiments with mice show that 5LIO-1-Cm-3,2-HOPO can remove uranium from kidneys and bones with high efficiencies, while the decorporation efficiency is nearly independent of the treatment time. Moreover, this ligand shows a high oral decorporation efficiency, making it attractive for practical applications.


Assuntos
Osso e Ossos/química , Quelantes/administração & dosagem , Piridonas/administração & dosagem , Lesões por Radiação/terapia , Urânio/toxicidade , Adsorção , Animais , Osso e Ossos/metabolismo , Quelantes/química , Feminino , Humanos , Rim/química , Rim/metabolismo , Ligantes , Camundongos , Piridonas/química , Lesões por Radiação/induzido quimicamente , Lesões por Radiação/metabolismo , Urânio/química , Urânio/metabolismo
12.
Chemistry ; 25(44): 10309-10313, 2019 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-31169335

RESUMO

As a less explored avenue, actinide-based metal-organic frameworks (MOFs) are worth studying for the particularity of actinide nodes in coordination behaviour and assembly modes. In this work, an azobenzenetetracarboxylate-based anionic MOF supported by uranyl-carboxyl helical chain units was synthesized, incorporating linear uranyl as the metal centre. This kind of helical chain-type building unit is reported for the first time in uranyl-based MOFs. Structural analysis reveals that the formation of helical chain secondary units can be attributed to restricted equatorial coordination of rigid flat azobenzene ligand to uranyl centres. Meanwhile, this newly-synthesized anionic material has been used to remove Eu3+ ions, as a non-radioactive surrogate of Am3+ ion, through an ion-exchange process with [(CH3 )2 NH2 ]+ ions in its open channels, as evidenced by a combination of 1 H NMR spectroscopy, EDS and PXRD.

13.
Metallomics ; 11(7): 1200-1206, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31241124

RESUMO

Environmental factors may play a critical role in the etiology and pathogenesis of Parkinson's disease (PD). However, the association of PD with specific chemical species remains largely unknown. Here we prepared three kinds of iron oxide nanoparticles and examined their cytotoxicity in a cellular model of PD. We found that lysosome-targeted nanoparticles showed significant cytotoxicity in SH-SY5Y cells. Inhibition of AMPK could aggravate the neurotoxicity of lysosome-targeted nanoparticles as well as mitochondrion-targeted nanoparticles. Alteration of mitochondrial membrane potentials was found to be in agreement with the neurotoxicity of iron nanoparticles. These results suggested an important role of AMPK in regulating iron nanoparticle-associated neurotoxicity.

15.
Nano Lett ; 19(6): 3671-3675, 2019 06 12.
Artigo em Inglês | MEDLINE | ID: mdl-31062980

RESUMO

Nanocarriers-derived anticancer therapeutics typically suffers from poor tumor penetration and suboptimal antitumor efficacy. Although PEGylation improves the stability of nanoparticles and prolongs drug circulation, it further increases the size of nanoparticles and adversely affects the tumor penetration. Here, we developed a light-triggered PEGylation/dePEGylation strategy, whereby near-infrared (NIR)-/pH- dual responsive dePEGylation activates iRGD for tumor targeting. The embedded up-conversion nanoparticles (UCNPs) could efficiently convert NIR to UV-vis which cleaved the linker to remove PEG. NIR-induced dePEGylation remarkably improved vascular extravasation of drugs and deep tumor penetration. Therefore, the stimuli-responsive nanocarriers facilitated the tumor-targeted delivery of drugs through blood circulation and enhanced the antitumor effects.

16.
J Phys Chem A ; 2019 May 23.
Artigo em Inglês | MEDLINE | ID: mdl-31120248

RESUMO

Recently, the carbon nanobelt (CNB) comprising a closed loop of fully fused edge-sharing benzene rings has been reported in experiment. To explore its potential molecular properties and applications, we performed scalar relativistic density functional theory investigations on the interaction mechanisms of the CNB with a series of actinides atoms (An= Th-Am). Computations indicate that doping of actinide (An) atoms onto the surface of the CNB can result to the formation of stable actinide endohedral An@CNB compounds, along with the formation of C-An-C rings as well as a drastic structural transformation of the CNB. Compared to transuranium actinides, Th, Pa and U exhibit stronger adsorption affinity to the CNB in terms of the calculated binding energies. The AdNDP analysis shows that there form five 3c-2e bonds and two 5c-2e bonds in An@CNB for An = Th, Pa and U, with fewer multicenter bonds for An = Np, Pu and Am. These theoretical results provide a new strategy for chemical modification and functionalization of the CNB by actinides doping in the future.

17.
Inorg Chem ; 58(10): 6934-6945, 2019 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-31038934

RESUMO

Bipyridine organic bases are beneficial to the synthesis of novel uranyl-organic hybrid materials, but the relationship between their molecular structures and specific roles as structure-directing agents, especially for the semirigid dicarboxylate systems, is still unclear. Here we demonstrate how the bipyridine ligands direct the coordination assembly of uranyl-organic compounds with a semirigid dicarboxylate linker, 4,4'-dicarboxybiphenyl sulfone (H2dbsf), by utilizing a series of bipyridine ligands, 1,10-phenanthroline (phen), 2,2'-bipyridine (2,2'-bpy), 5,5'-dimethylbipyridine (5,5'-dmbpy), 4,4'-bipyridine (4,4'-bpy), or 1,3-di(4-pyridyl)propane (bpp). Under hydrothermal conditions, eight uranyl-organic coordination polymers (UCPs), four of which [[UO2(dbsf)(phen)] (1), [UO2(dbsf)(phen)]·H2O (1'), [U4O10(dbsf)3]2[H2bpp]2 (6), and [U4O10(dbsf)3]2[H2bpp] (6')] were reported previously, were synthesized and divided into two types based on the chelate or template effect of these bipyridine ligands. 1, 1', [UO2(dbsf)(2,2'-bpy)] (2), and [(UO2)2(dbsf)2(5,5'-dmbpy)2] (3) are springlike triple helices with bipyridine ligands (phen, 2,2'-bpy, or 5,5'-dmbpy) as chelate ligands, while [U4O10(dbsf)3][H2(4,4'-bpy)] (4), [U4O10(dbsf)3]2[H(4,4'-bpy)]2[Ni(H2O)6] (5), 6, and 6' are tetranuclear uranyl-mediated 2-fold-interpenetrating networks with 4,4'-bpy or bpp as template ligands and charge-balancing agents. The participation or not in uranyl coordination of different bipyridine ligands promotes not only diversity in uranyl speciation and final topological structures among different classes of organic bases but also consistency for the same types of bipyridine ligands, which thus endows the possibility of the rational design of UCPs based on semirigid dicarboxylate ligands with the aid of cautiously selected bipyridine ligands.

18.
J Am Chem Soc ; 2019 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-31064178

RESUMO

Semiconductive metal-organic frameworks (MOFs) have attracted extraordinary research interest in recent years; however, electronic applications based on these emerging materials are still in their infancy. Herein, we show that a lanthanide-based semiconductive MOF (SCU-12) can effectively convert X-ray photons to electrical current signals under continuous hard X-ray radiation. The semiconductive MOF-based polycrystalline detection device presents a promising X-ray sensitivity with the value of 23.8 µC Gyair-1 cm-2 under 80 kVp X-ray exposure, competitive with the commercially available amorphous selenium ( α-Se) detector. The lowest detectable X-ray dose rate is 0.705 µGy s-1, representing the record value among all X-ray detectors fabricated by polycrystalline materials. This work discloses the first demonstration of hard radiation detection by semiconductive MOFs, providing a horizon that can guide the synthesis of a new generation of radiation detection materials by taking the advantages of structural designability and property tunability in the MOF system.

19.
Environ Sci Technol ; 53(9): 5102-5110, 2019 05 07.
Artigo em Inglês | MEDLINE | ID: mdl-30945863

RESUMO

Molecular dynamics (MD) simulations were performed to investigate the influence of curvature and backbone rigidity of an oxygenated surface, here graphene oxide (GO), on its adsorption of uranyl in collaboration with humic acid (HA). The planar curvature of GO was found to be beneficial in impeding the folding of HA. This, together with its rigidity that helps stabilize the extended conformation of HA, offered rich binding sites to interact with uranyl with only marginal loss of binding strength. According to our simulations, the interaction between uranyl and GO was mainly driven by electrostatic interactions. The presence of HA not only provided multiple sites to compete/cooperate with GO for adsorption of free uranyl but also interacted with GO acting as a "bridge" to connect uranyl and GO. The potential of mean force (PMF) profiles implied that HA significantly enhanced the interaction strength between uranyl and GO and stabilized the uranyl-GO complex. Meanwhile, GO could reduce the diffusion coefficients of uranyl and HA and retard their migrations in aqueous solution. This work provides theoretical hints on the GO-based remediation strategies for the sites contaminated by uranium or other heavy metal ions and oxygenated organic pollutants.


Assuntos
Grafite , Substâncias Húmicas , Adsorção , Simulação de Dinâmica Molecular , Óxidos
20.
ACS Appl Mater Interfaces ; 11(18): 16905-16913, 2019 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-30993970

RESUMO

The physiochemical properties of nanoparticles (NPs), including surface charge, will affect their uptake, transformation, translocation, and final fate in the environment. In this study, we compared the phytoxoxicity and transport behaviors of nano CeO2 (nCeO2) functionalized with positively charged (Cs-nCeO2) and negatively charged (PAA-nCeO2) coatings. Cucumber seedlings were hydroponically exposed to 0-1000 mg/L of Cs-nCeO2 and PAA-nCeO2 for 14 days and the contents, distribution, translocation, and transformation of Ce in plants were analyzed using inductively coupled plasma mass spectrometry, micro X-ray fluorescence (µ-XRF), and X-ray absorption near-edge spectroscopy (XANES), respectively. Results showed that the seedling growth and Ce contents in plant tissues were functions of exposure concentrations and surface charge. Cs-nCeO2 was adsorbed strongly on a negatively charged root surface, which led to significantly higher Ce contents in the roots and lower translocation factors of Ce from the roots to shoots in Cs-nCeO2 group than in PAA-nCeO2 group. The results of µ-XRF showed that Ce elements were mainly accumulated at the root tips and lateral roots, as well as in the veins and at the edge of leaves. XANES results revealed that the proportion of Ce(III) was comparable in the plant tissues of the two groups. We speculated that Cs-nCeO2 and PAA-nCeO2 were partially dissolved under the effect of root exudates, releasing Ce3+ ions as a result. Then, the Ce3+ ions were transported upward in the form of Ce(III) complexes along the vascular bundles and eventually accumulated in the veins. The other portion of Cs-nCeO2 and PAA-nCeO2 entered the roots through the gap of a Casparian strip at root tips/lateral roots and was transported upward as intact NPs and finally accumulated at the edge of the blade. This study will greatly advance our information on how the properties of NPs influence their phytotoxicity, uptake, and subsequent trophic transfer in terrestrial food webs.


Assuntos
Cério/química , Cucumis sativus/efeitos dos fármacos , Nanopartículas/química , Plântula/efeitos dos fármacos , Transporte Biológico/efeitos dos fármacos , Cério/farmacologia , Cério/toxicidade , Cucumis sativus/crescimento & desenvolvimento , Cucumis sativus/ultraestrutura , Espectrometria de Massas , Nanopartículas/toxicidade , Folhas de Planta/efeitos dos fármacos , Raízes de Plantas/química , Raízes de Plantas/efeitos dos fármacos , Plântula/crescimento & desenvolvimento , Plântula/ultraestrutura , Espectroscopia por Absorção de Raios X
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA