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1.
Nano Lett ; 24(26): 8171-8178, 2024 Jul 03.
Artigo em Inglês | MEDLINE | ID: mdl-38912705

RESUMO

Orientation engineering is a crucial aspect of thin film growth, and it is rather challenging to engineer film epitaxy beyond the substrate constraint. Guided by density functional theory calculations, we use SrRuO3 (SRO) as a buffer layer and successfully deposit [111]-oriented CoFe2O4 (CFO) on [001]-, [110]-, and [111]-oriented SrTiO3 (STO) substrates. This enables subsequent growth of [111]-oriented functional oxides, such as PbTiO3 (PTO), overcoming the constraint of the substrate. This strategy is quite general and applicable to lanthanum aluminate and yttria-stabilized zirconia substrates as well. X-ray Φ scans and atomic resolution aberration-corrected scanning transmission electron microscopy (AC-STEM) reveal detailed epitaxial relations in each of the cases, with four variants of [111]-CFO found on [001]-STO and two variants found on [110]-STO, formed to mitigate the large lattice misfit strain between the film and substrate. Our strategy thus provides a general pathway for orientation engineering of oxide epitaxy beyond substrate constraint.

2.
Nano Lett ; 24(21): 6337-6343, 2024 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-38742772

RESUMO

The bulk photovoltaic effect (BPVE) offers an interesting approach to generate a steady photocurrent in a single-phase material under homogeneous illumination, and it has been extensively investigated in ferroelectrics exhibiting spontaneous polarization that breaks inversion symmetry. Flexoelectricity breaks inversion symmetry via a strain gradient in the otherwise nonpolar materials, enabling manipulation of ferroelectric order without an electric field. Combining these two effects, we demonstrate active mechanical control of BPVE in suspended 2-dimensional CuInP2S6 (CIPS) that is ferroelectric yet sensitive to electric field, which enables practical photodetection with an order of magnitude enhancement in performance. The suspended CIPS exhibits a 20-fold increase in photocurrent, which can be continuously modulated by either mechanical force or light polarization. The flexoelectrically engineered photodetection device, activated by air pressure and without any optimization, possesses a responsivity of 2.45 × 10-2 A/W and a detectivity of 1.73 × 1011 jones, which are superior to those of ferroelectric-based photodetection and comparable to those of the commercial Si photodiode.

3.
Ann Surg Oncol ; 31(4): 2451-2460, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-38063990

RESUMO

BACKGROUND: We compare the application of intravenous indocyanine green (ICG) fluorescence imaging in lung cancer with near-infrared-I (NIR-I) and near-infrared-II (NIR-II) windows. METHODS: From March to December 2022, we enrolled patients who received an intravenous injection of ICG (5 mg/kg) 1 day before the planned lung cancer surgery. The lung cancer nodules were imaged by NIR-I/II fluorescence imaging systems, and the tumor-to-normal-tissue ratio (TNR) was calculated. In addition, the fluorescence intensity and signal-to-background ratio (SBR) of capillary glass tubes containing ICG covered with different thicknesses of lung tissue were measured by NIR-I/II fluorescence imaging systems. RESULTS: In this study, 102 patients were enrolled, and the mean age was 59.9 ± 9.2 years. A total of 96 (94.1%) and 98 (96.1%) lung nodules were successfully imaged with NIR-I and NIR-II fluorescence, and the TNR of NIR-II was significantly higher than that of NIR-I (3.9 ± 1.3 versus 2.4 ± 0.6, P < 0.001). In multiple linear regression, solid nodules (P < 0.001) and squamous cell carcinoma (P < 0.001) were independent predictors of a higher TNR of NIR-I/II. When capillary glass tubes were covered with lung tissue whose thickness was more than 2 mm, the fluorescence intensity and the SBR of NIR-II were significantly higher than those of NIR-I. CONCLUSIONS: We verified the feasibility of NIR-II fluorescence imaging in intravenous ICG lung cancer imaging for the first time. NIR-II fluorescence can improve the TNR and penetration depth of lung cancer with promising clinical prospects.


Assuntos
Verde de Indocianina , Neoplasias Pulmonares , Humanos , Pessoa de Meia-Idade , Idoso , Neoplasias Pulmonares/diagnóstico por imagem , Neoplasias Pulmonares/cirurgia , Imagem Óptica/métodos , Pulmão , Fluorescência
4.
Mol Pharm ; 2024 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-38686930

RESUMO

There has been an increase in the use of molecular probe diagnostic techniques for lung cancer, and magnetic resonance imaging (MRI) offers specific advantages for diagnosing pulmonary carcinoma. Furthermore, advancements in near-infrared II (NIR-II) fluorescence have provided a new method for precise intraoperative tumor resection. However, few probes combine preoperative diagnosis with intraoperative imaging. This study aims to fill this research void by employing a dual-modal probe that targets the epidermal growth factor receptor for MR and NIR-II imaging, enabling the preoperative diagnosis of lung cancer using MRI and precise intraoperative tumor localization using NIR-II with a single probe. The imaging effects and targeting ability of the probe were confirmed in cell lines, mouse models, and clinical samples. The MR signal decreased within 24 h in the patient-derived xenograft mouse model. The average signal-to-background ratio of NIR-II reached 3.98 ± 0.27. The clinical sample also showed a decrease in the T2 signal using MRI, and the NIR-II optical signal-to-background ratio was 3.29. It is expected that this probe can improve the diagnostic rate of lung cancer using MRI and enable precise intraoperative tumor resection using NIR-II.

5.
Environ Monit Assess ; 196(7): 656, 2024 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-38916777

RESUMO

Previous research on pesticides in green tea mainly focused on detection technology but lacked insights into pesticide use during cultivation. To address this gap, a survey was conducted among Rizhao green tea farmers. The survey results showed that most tea farmers were approximately 60 years old and managed small, scattered tea gardens (< 0.067 ha). Notably, tea farmers who had received agricultural training executed more standardized pesticide application practices. Matrine and thiazinone are the most used pesticides. A total of 16 types of pesticides were detected in the tested green tea samples, with 65% of the samples containing residues of at least one pesticide. Notably, higher levels of residues were observed for bifenthrin, cyfluthrin, and acetamiprid. The presence of pesticide residues varied significantly between seasons and regions. The risk assessment results indicated that the hazard quotient (HQ) values for all 16 pesticides detected in green tea were < 1, suggesting that these residue levels do not pose a significant public health concern.


Assuntos
Resíduos de Praguicidas , Praguicidas , Chá , Chá/química , Medição de Risco , Praguicidas/análise , Resíduos de Praguicidas/análise , Monitoramento Ambiental , Humanos , Fazendeiros , Agricultura , Camellia sinensis/química , Piretrinas/análise , China , Exposição Ocupacional/análise
6.
Bull Environ Contam Toxicol ; 112(4): 62, 2024 Apr 14.
Artigo em Inglês | MEDLINE | ID: mdl-38615308

RESUMO

Acetamiprid is a novel nicotinic pesticide widely used in modern agriculture because of its low toxicity and specific biological target properties. The objective of this study was to understand the photolysis pattern of acetamiprid in the water column and elucidate its degradation products and mechanism. It was observed that acetamiprid exhibited different photolysis rates under different light source conditions in pure water, with ultraviolet > fluorescence > sunlight; furthermore, its photolysis half-life ranged from 17.3 to 28.6 h. In addition, alkaline conditions (pH 9.0) accelerated its photolysis rate, which increased with pH. Using gas chromatography-mass spectrometry, five direct photolysis products generated during the exposure of acetamiprid to pure water were successfully separated and identified. The molecular structure of acetamiprid was further analyzed using density functional theory, and the active photodegradation sites of acetamiprid were predicted. The mechanism of the photolytic transformation of acetamiprid in water was mainly related to hydroxyl substitution and oxidation. Based on these findings, a comprehensive transformation pathway for acetamiprid was proposed.


Assuntos
Neonicotinoides , Praguicidas , Nicotina , Agricultura , Água
7.
Small ; 19(12): e2203201, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36593529

RESUMO

Nanocomposite films hold great promise for multifunctional devices by integrating different functionalities within a single film. The microstructure of the precipitate/secondary phase is an essential element in designing composites' properties. The interphase strain between the matrix and secondary phase is responsible for strain-mediated functionalities, such as magnetoelectric coupling and ferroelectricity. However, a quantitative microstructure-dependent interphase strain characterization has been scarcely studied. Here, it is demonstrated that the PbTiO3 (PTO)/PbO composite system can be prepared in nano-spherical and nanocolumnar configurations by tuning the misfit strain, confirmed by a three-dimensional reconstructive microscopy technique. With the atomic resolution quantitative microscopy with a depth resolution of a few nanometers, it is discovered that the strained region in PTO is much larger and more uniform in nanocolumnar compared to nano-spherical composites, resulting in much enhanced ferroelectric properties. The interphase strain between PbO and PTO in the nanocolumnar structure leads to a giant c/a ratio of 1.20 (bulk value of 1.06), accompanied by a Ti polarization displacement of 0.48 Å and an effective ferroelectric polarization of 241.7 µC cm-2 , three times compared to the bulk value. The quantitative atomic-scale strain and polarization analysis on the interphase strain provides an important guideline for designing ferroelectric nanocomposites.

8.
Eur J Nucl Med Mol Imaging ; 50(2): 494-507, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36207638

RESUMO

PURPOSE: During lung cancer surgery, it is very important to define tumor boundaries and determine the surgical margin distance. In previous research, systemically application of fluorescent probes can help medical professionals determine the boundaries of tumors and find small tumors and metastases, thereby improving the accuracy of surgical resection. However, there are very few safe and effective probes that can be applied to clinical trials up to now, which limits the clinical application of fluorescence imaging. Here we developed a new technology that can quickly identify the tumor area in the resected lung tissue during the operation and distinguish the tumor boundary and metastatic lymph nodes. EXPERIMENTAL DESIGN: For animal studies, a PDX model of lung cancer was established. The tumors, lungs, and peritumoral muscle tissues of tumor-bearing mice were surgically removed and incubated with a probe targeting epidermal growth factor receptor (EGFR) for 20 min, and then imaged by a closed-field near-infrared two-zone (NIR-II) fluorescence imaging system. For clinical samples, ten surgically removed lung tissues and 60 lymph nodes from 10 lung cancer patients undergoing radical resection were incubated with the targeting probe immediately after intraoperative resection and imaged to identify the tumor area and distinguish the tumor boundary and metastatic lymph nodes. The accuracy of fluorescence imaging was confirmed by HE staining and immunohistochemistry. RESULTS: The ex vivo animal imaging experiments showed a fluorescence enhancement of tumor tissue. For clinical samples, our results showed that this new technology yielded more than 85.7% sensitivity and 100% specificity in identifying the tumor area in the resected lung tissue. The average fluorescence tumor-to-background ratio was 2.5 ± 1.3. Furthermore, we also used this technique to image metastatic lymph nodes intraoperatively and showed that metastatic lymph nodes have brighter fluorescence than normal lymph nodes, as the average fluorescence tumor-to-background signal ratio was 2.7 ± 1.1. Calculations on the results of the fluorescence signal in relation to the number of metastatic lymph nodes yielded values of 77.8% for sensitivity and 92.1% for specificity. We expect this new technology to be a useful diagnostic tool for rapid intraoperative pathological detection and margin determination. CONCLUSIONS: By using fluorescently labeled anti-human EGFR recombinant antibody scFv fragment to incubate freshly isolated tissues during surgery, the probes can quickly accumulate in lung cancer tissues, which can be used to quickly identify tumor areas in the resected lung tissues and distinguish tumor boundaries and find metastases in lymph nodes. This technology is expected to be used for rapid intraoperative pathological detection and margin determination.


Assuntos
Neoplasias Pulmonares , Animais , Camundongos , Neoplasias Pulmonares/diagnóstico por imagem , Neoplasias Pulmonares/cirurgia , Neoplasias Pulmonares/patologia , Receptores ErbB/metabolismo , Imagem Óptica/métodos , Linfonodos/diagnóstico por imagem , Linfonodos/cirurgia , Corantes Fluorescentes , Anticorpos
9.
Nano Lett ; 22(24): 9900-9906, 2022 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-36524710

RESUMO

Double-perovskite oxides have attracted recent attention due to their attractive functionalities and application potential. In this paper, we demonstrate the effect of dual controls, i.e., the deposition pressure of oxygen (PO2) and lattice mismatch (ε), on tuning magnetic properties in epitaxial double-perovskite Sr2FeReO6 films. In a nearly lattice matched Sr2FeReO6/SrTiO3 film, the ferrimagnetic-to-paramagnetic phase transition occurs when PO2 is reduced to 30 mTorr, probably due to the formation of Re4+ ions that replace the stoichiometric Re5+ to cause disorders of B-site ions. On the other hand, a large compressive strain or tensile strain shifts this critical PO2 to below 1 mTorr or above 40 mTorr, respectively. The observations can be attributed to the modulation of B-site ordering by epitaxial strain through affecting elemental valence. Our results provide a feasible way to expand the functional tunability of magnetic double-perovskite oxides that hold great promise for spintronic devices.

10.
J Prosthet Dent ; 2023 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-37567843

RESUMO

Zygomatic implants (ZIs) can be a treatment option for patients with severe atrophy in the maxilla, but deviation during ZI placement could lead to serious complications. Surgical guides and dynamic navigation have been used to improve the accuracy of ZI placement, but both techniques are subject to human error. A 2-stage technique is described that enabled an autonomous dental robot to overcome mouth-opening restrictions for ZI placement. The technique enables the complete digitalization of ZI placement, further improving the accuracy of the drilling process.

11.
Acta Pharmacol Sin ; 43(3): 541-551, 2022 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-34035485

RESUMO

We previously showed that oral administration of exogenous glutathione (GSH) exerted a direct and/or indirect therapeutic effect on ischemic stroke rats, but the underlying mechanisms remain elusive. In the current study, we conducted a quantitative proteomic analysis to explore the pathways mediating the therapeutic effect of GSH in cerebral ischemia/reperfusion (I/R) model rats. Rats were subjected to middle cerebral artery occlusion (MCAO) for 2 h followed by reperfusion. The rats were treated with GSH (250 mg/kg, ig) or levodopa (L-dopa, 100 mg/kg, ig) plus carbidopa (10 mg/kg, ig). Neurologic deficits were assessed, and the rats were sacrificed at 24 h after cerebral I/R surgery to measure brain infarct sizes. We conducted a proteomic analysis of the lesion side striatum samples and found that tyrosine metabolism and dopaminergic synapse were involved in the occurrence of cerebral stroke and the therapeutic effect of GSH. Western blot assay revealed that tyrosine hydroxylase (TH) mediated the occurrence of I/R-induced ischemic stroke and the therapeutic effect of GSH. We analyzed the regulation of GSH on endogenous small molecule metabolites and showed that exogenous GSH had the most significant effect on intrastriatal dopamine (DA) in I/R model rats by promoting its synthesis and inhibiting its degradation. To further explore whether DA-related alterations were potential targets of GSH, we investigated the therapeutic effect of DA accumulation on ischemic brain injury. The combined administration of the precursor drugs of DA (L-dopa and carbidopa) significantly ameliorated neurological deficits, reduced infarct size, and oxidative stress, and decreased pro-inflammatory cytokines levels in the striatum of I/R injury rats. More interestingly, exogenous L-dopa/carbidopa could also greatly enhance the exposure of intracerebral GSH by upregulating GSH synthetases and enhancing homocysteine (HCY) levels in the striatum. Thus, administration of exogenous GSH exerts a therapeutic effect on ischemic stroke by increasing intrastriatal DA, and the accumulated DA can, in turn, enhance the exposure of GSH and its related substances, thus promoting the therapeutic effect of GSH.


Assuntos
Dopamina/metabolismo , Glutationa/farmacologia , AVC Isquêmico/patologia , Animais , Carbidopa/farmacologia , Citocinas/efeitos dos fármacos , Modelos Animais de Doenças , Homocistina/efeitos dos fármacos , Infarto da Artéria Cerebral Média/patologia , Levodopa/farmacologia , Masculino , Estresse Oxidativo/genética , Proteômica , Ratos , Ratos Wistar , Traumatismo por Reperfusão/patologia , Tirosina 3-Mono-Oxigenase/efeitos dos fármacos , Regulação para Cima
12.
J Nanobiotechnology ; 20(1): 142, 2022 Mar 18.
Artigo em Inglês | MEDLINE | ID: mdl-35303862

RESUMO

Hypoxia is a distinguished hallmark of the tumor microenvironment. Hypoxic signaling affects multiple gene expressions, resulting in tumor invasion and metastasis. Quantification of hypoxic status although challenging, can be useful for monitoring tumor development and aggressiveness. However, hypoxia-independent factors such as nonspecific binding and heterogenous probe delivery considerably influence the probe signal thereby disenabling reliable quantitative imaging in vivo. In this study, we designed a self-calibrated activatable nanoprobe Cy7-1/PG5-Cy5@LWHA that specifically detects nitroreductase activity upregulated in hypoxic tumor cells. Dual fluorescence emission of the nanoprobe enables ratiometric calibration and eliminates the target-independent interference. In orthotopic and metastatic breast cancer mouse models, Cy7-1/PG5-Cy5@LWHA demonstrated remarkable hypoxia sensing capability in vivo. Moreover, ratiometric processing provided quantitative hypoxia assessment at different tumor developmental stages and facilitated tumor burden assessment in the metastatic lymph nodes. Therefore, our study demonstrates that ratiometric imaging of Cy7-1/PG5-Cy5@LWHA can be a prospective noninvasive tool to quantitatively monitor tumor hypoxia, which would be beneficial for investigating the fundamental role of hypoxia in tumor progression and for evaluating response to novel anti-hypoxia therapeutics. Furthermore, successful detection of metastatic lymph nodes with the proposed imaging approach illustrates its potential clinical application in assessing lymph node status during surgery.


Assuntos
Corantes Fluorescentes , Hipóxia , Animais , Diagnóstico por Imagem , Camundongos , Estudos Prospectivos , Microambiente Tumoral
13.
J Nanobiotechnology ; 20(1): 143, 2022 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-35305654

RESUMO

Incomplete tumor resection is the direct cause of the tumor recurrence and metastasis after surgery. Intraoperative accurate detection and elimination of microscopic residual cancer improve surgery outcomes. In this study, a powerful D1-π-A-D2-R type phototheranostic based on aggregation-induced emission (AIE)-active the second near-infrared window (NIR-II) fluorophore is designed and constructed. The prepared theranostic agent, A1 nanoparticles (NPs), simultaneously shows high absolute quantum yield (1.23%), excellent photothermal conversion efficiency (55.3%), high molar absorption coefficient and moderate singlet oxygen generation performance. In vivo experiments indicate that NIR-II fluorescence imaging of A1 NPs precisely detect microscopic residual tumor (2 mm in diameter) in the tumor bed and metastatic lymph nodes. More notably, a novel integrated strategy that achieves complete tumor eradication (no local recurrence and metastasis after surgery) is proposed. In summary, A1 NPs possess superior imaging and treatment performance, and can detect and eliminate residual tumor lesions intraoperatively. This work provides a promising technique for future clinical applications achieving improved surgical outcomes.


Assuntos
Nanopartículas Multifuncionais , Nanopartículas , Humanos , Nanopartículas/uso terapêutico , Neoplasia Residual , Imagem Óptica , Nanomedicina Teranóstica/métodos
14.
Zhongguo Zhong Yao Za Zhi ; 47(10): 2759-2766, 2022 May.
Artigo em Chinês | MEDLINE | ID: mdl-35718496

RESUMO

Based on network pharmacology and molecular docking, the mechanism of danshensu and tetramethylpyrazine, the main active components of Shenxiong Glucose Injection(SGI), against myocardial ischemia-reperfusion injury(MIRI) was explored. Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform(TCMSP), GeneCards, and Online Mendelian Inheri-tance in Man(OMIM) were used to search the targets of the active components and the disease, and the common targets were screened. The "drug-component-disease-target" network was constructed by Cytoscape, and the protein-protein interaction network was established by STRING, followed by Gene Ontology(GO) term and Kyoto Encyclopedia of Genes and Genomes(KEGG) pathway enrichment by R software. AutoDock Vina was employed for the molecular docking between active components and core targets. A total of 15 potential targets of danshensu and tetramethylpyrazine against MIRI were screened out, involving the major GO terms of cyclooxyge-nase pathway, extracellular matrix binding, and antioxidant activity, and the main pathways of platelet activation and regulation of lipolysis in adipocytes. Danshensu and tetramethylpyrazine can form stable conformations with core targets prostaglandin G/H synthase 2(PTGS2), vascular endothelial growth factor A(VEGFA), and acetylcholinesterase(ACHE) with low binding energy. This study reflects the multi-component, multi-target, multi-pathway, and synergistic action characteristics of SGI, which provides a theoretical re-ference for further clarifying the anti-MIRI mechanism of SGI.


Assuntos
Medicamentos de Ervas Chinesas , Traumatismo por Reperfusão Miocárdica , Acetilcolinesterase , Medicamentos de Ervas Chinesas/farmacologia , Humanos , Medicina Tradicional Chinesa , Simulação de Acoplamento Molecular , Farmacologia em Rede , Fator A de Crescimento do Endotélio Vascular
15.
Angew Chem Int Ed Engl ; 61(16): e202201407, 2022 04 11.
Artigo em Inglês | MEDLINE | ID: mdl-35150037

RESUMO

The development of chemically recyclable polymers presents the most appealing solution to address the plastics' end-of-use problem. Despite the recent advancements, it is highly desirable to develop chemically recyclable polymers from commercially available monomers to avoid the costly and time-consuming commercialization. In this contribution, we achieve the controlled ring-opening polymerization (ROP) of bio-sourced δ-caprolactone (δCL) using strong base/urea binary catalysts. The obtained PδCL is capable of chemical recycling to δCL in an almost quantitative yield by thermolysis. Sequential ROP of δCL and l-lactide (l-LA) affords well-defined PLLA-b-PδCL-b-PLLA triblock copolymers, which behave as thermoplastic elastomers with excellent elastic recovery, tensile strength and ultimate elongation. The upcycling of PLLA-b-PδCL-b-PLLA to recover ethyl lactate and δCL with high yields is achieved by refluxing with ethanol and then distillation under reduced pressure.


Assuntos
Elastômeros , Poliésteres , Caproatos , Lactonas , Polimerização
16.
Small ; 17(12): e2006930, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33656259

RESUMO

Aliovalent doping is widely adopted to tune the electronic structure of transition-metal oxides for design of low-cost, active electrocatalysts. Here, using single-crystalline thin films as model electrocatalysts, the structure-activity relationship of Fe states doping in perovskite LaNiO3 for oxygen evolution reaction (OER) is studied. Fe4+ state is found to be crucial for enhancing the OER activity of LaNiO3 , dramatically increasing the activity by six times, while Fe3+ has negligible effect. Spectroscopic studies and DFT calculations indicate Fe4+ states enhance the degree of Ni/Fe 3d and O 2p hybridization, and meanwhile produce down-shift of the unoccupied density of states towards lower energies. Such electronic features reduce the energy barrier for interfacial electron transfer for water oxidization by 0.2 eV. Further theoretical calculations and H/D isotope experiments reveal the electronic states associated with Fe4+ -O2- -Ni3+ configuration accelerate the deprotonation of *OH to *O (rate-determining step), and thus facilitate fast OER kinetics.

17.
Crit Rev Food Sci Nutr ; 61(9): 1545-1555, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-32393047

RESUMO

With the development in international food trade, there has been emerging risks in the food chain. Food contamination can be caused by several factors in a complex food chain. This articles provides a comprehensive review of known chemical contaminants from the production of raw materials to the consumption of food products as well as prevention and control measures. Specifically, this review discusses the following topics, raw material contamination caused by environmental pollution, endogenous food contamination caused by processing methods, and cold chain system challenges in food e-commerce.


Assuntos
Contaminação de Alimentos , Manipulação de Alimentos , Poluição Ambiental , Alimentos , Contaminação de Alimentos/análise
18.
Nano Lett ; 20(3): 1890-1895, 2020 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-32004008

RESUMO

We report the control of the interplane magnetic exchange coupling in CaIrO3 perovskite thin films and superlattices with SrTiO3. By analyzing the anisotropic magneto-transport data, we demonstrate that a semimetallic paramagnetic CaIrO3 turns into a canted antiferromagnetic Mott insulator at reduced dimensions. The emergence of a biaxial magneto-crystalline anisotropy indicates the canted moment responding to the cubic symmetry. Extending to superlattices and probing oxygen octahedral rotation by half-integer X-ray Braggs diffraction, a more complete picture about the canted moment evolution with interplane coupling can be understood. Remarkably, a rotation of the canted moments' easy axes by 45° is also observed by a sign reversal of the in-plane strain. These results demonstrate the robustness of anisotropic magnetoresistance in revealing quasi two-dimensional canted antiferromagnets, as well as valuable insights about quadrupolar magnetoelastic coupling, relevant for designing future antiferromagnetic spintronic devices.

19.
Nano Lett ; 20(4): 2493-2499, 2020 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-32134679

RESUMO

Using interlayer interaction to control functional heterostructures with atomic-scale designs has become one of the most effective interface-engineering strategies nowadays. Here, we demonstrate the effect of a crystalline LaFeO3 buffer layer on amorphous and crystalline LaAlO3/SrTiO3 heterostructures. The LaFeO3 buffer layer acts as an energetically favored electron acceptor in both LaAlO3/SrTiO3 systems, resulting in modulation of interfacial carrier density and hence metal-to-insulator transition. For amorphous and crystalline LaAlO3/SrTiO3 heterostructures, the metal-to-insulator transition is found when the LaFeO3 layer thickness crosses 3 and 6 unit cells, respectively. Such different critical LaFeO3 thicknesses are explained in terms of distinct characteristic lengths of the redox-reaction-mediated and polar-catastrophe-dominated charge transfer, controlled by the interfacial atomic contact and Thomas-Fermi screening effect, respectively. Our results not only shed light on the complex interlayer charge transfer across oxide heterostructures but also provide a new route to precisely tailor the charge-transfer process at a functional interface.

20.
Small ; 16(50): e2004683, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33191619

RESUMO

Exploring exotic interface magnetism due to charge transfer and strong spin-orbit coupling has profound application in the future development of spintronic memory. Here, the emergence and tuning of topological Hall effect (THE) from a CaMnO3 /CaIrO3 /CaMnO3 trilayer structure are studied in detail, which suggests the presence of magnetic Skyrmion-like bubbles. First, by tilting the magnetic field direction, the evolution of the Hall signal suggests a transformation of Skyrmions into topologically-trivial stripe domains, consistent with behaviors predicted by micromagnetic simulations. Second, by varying the thickness of CaMnO3 , the optimal thicknesses for the THE signal emergence are found, which allow identification of the source of Dzyaloshinskii-Moriya interaction (DMI) and its competition with antiferromagnetic superexchange. Employing high-resolution transmission electron microscopy, randomly distributed stacking faults are identified only at the bottom interface and may avoid mutual cancellation of DMI. Last, a spin-transfer torque experiment also reveals a low threshold current density of ≈109 A m-2 for initiating the bubbles' motion. This discovery sheds light on a possible strategy for integrating Skyrmions with antiferromagnetic spintronics.

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