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1.
Small ; : e2405279, 2024 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-39240017

RESUMO

This study introduces magnetized EGaIn@Fe, an innovative material synthesized by incorporating iron powder into the eutectic gallium-indium alloy (EGaIn). Unlike traditional methods requiring electrolyte environments for electrical control, EGaIn@Fe can be manipulated using external magnetic fields, expanding control from 2D to 3D spaces. The material exhibits both active and passive splitting capabilities under magnetic and electrical control, demonstrating exceptional deformability, precision, and flexibility. EGaIn@Fe shows significant promise in applications such as microfluidic channels, circuit repair, and soft robotics. Specifically, 5 wt.% EGaIn@Fe is optimal for microfluidic tasks and circuit repairs in confined spaces, while higher concentrations (10 and 15 wt.%) enhance 3D control and reduce material usage. Additionally, 20 wt.% EGaIn@Fe displays octopus-like movements for navigating impassable channels. EGaIn@Fe can enhance fluid manipulation in microfluidics, bridge gaps in circuit repairs, and enable flexible actuators in soft robotics, driving advancements in adaptive materials and technologies.

2.
Small ; 20(15): e2307284, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-37994259

RESUMO

High-entropy oxides (HEOs) are promising anode materials for lithium-ion batteries (LIBs), owing to their stable crystal structure, superionic conductivity, and high capacity. In this study, the (Cr, Mn, Fe, Co, and Ni)3O4 HEO via solid-state reaction is prepared. To improve the synthetic efficiency, it is necessary to understand the formation mechanism. Therefore, a high-resolution transmission electron microscopy (HRTEM) is used to record information during calcination at increasing temperature. The overall formation process included MnO2 and NiO aggregation at 500 °C, followed by (Mn, and Ni)3O4 combined with Co3O4 at 600 °C to form (Mn, Co, and Ni)3O4. At higher temperatures, Fe2O3 and Cr2O3 sequentially combined with (Mn, Co, and Ni)3O4 and formed the (Cr, Mn, Fe, Co, Ni)3O4 at 900 °C. In addition, the valence-state-changing mechanisms and ion arrangements of (Cr, Mn, Fe, Co, and Ni)3O4 are determined using electron energy loss spectroscopy (EELS) and extended X-ray absorption fine structure (EXAFS). This study successfully revealed the formation of HEO at atomic scale. The results provide valuable insights for improving the manufacturing process of (Cr, Mn, Fe, Co, and Ni)3O4 HEOs, which is expected to play a vital role in the development of anode materials for next-generation LIBs.

3.
Opt Lett ; 48(11): 2933-2936, 2023 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-37262247

RESUMO

This paper demonstrates an AlGaInP-based 620-nm red micro-light-emitting-diode (µ-LED) array and studies the enhancement effect of the surface treatments using (NH4)2Sx solutions by comparing the characteristics of µ-LED arrays with and without the (NH4)2Sx treatment. Furthermore, our µ-LED array demonstrates a measurement of the current efficiency (2.6 cd/A), which improves the light output uniformity. Also, we apply a setup for measuring the response time at the fast ns-level to analyze the effect of passivation in AlGaInP-based µ-LED arrays.

4.
Biomacromolecules ; 24(8): 3858-3871, 2023 08 14.
Artigo em Inglês | MEDLINE | ID: mdl-37523499

RESUMO

The investigation of the effects of electrical and mechanical stimulations on chondrogenesis in tissue engineering scaffolds is essential for realizing successful cartilage repair and regeneration. The aim of articular cartilage tissue engineering is to enhance the function of damaged or diseased articular cartilage, which has limited regenerative capacity. Studies have shown that electrical stimulation (ES) promotes mesenchymal stem cell (MSC) chondrogenesis, while mechanical stimulation (MS) enhances the chondrogenic differentiation capacity of MSCs. Therefore, understanding the impact of these stimuli on chondrogenesis is crucial for researchers to develop more effective tissue engineering strategies for cartilage repair and regeneration. This study focuses on the preparation of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) conductive polymer (CP) scaffolds using the freeze-drying method. The scaffolds were fabricated with varying concentrations (0, 1, 3, and 10 wt %) of (3-glycidyloxypropyl) trimethoxysilane (GOPS) as a crosslinker and an additive to tailor the scaffold properties. To gain a comprehensive understanding of the material characteristics and the phase aggregation phenomenon of PEDOT:PSS scaffolds, the researchers performed theoretical calculations of solubility parameters and surface energies of PSS, PSS-GOPS, and PEDOT polymers, as well as conducted material analyses. Additionally, the study investigated the potential of promoting chondrogenic differentiation of human adipose stem cells by applying external ES or MS on a PEDOT:PSS CP scaffold. Compared to the group without stimulation, the group that underwent stimulation exhibited significantly up-regulated expression levels of chondrogenic characteristic genes, such as SOX9 and COL2A1. Moreover, the immunofluorescence staining images exhibited a more vigorous fluorescence intensity of SOX9 and COL II proteins that was consistent with the trend of the gene expression results. In the MS experiment, the strain excitation exerted on the scaffold was simulated and transformed into stress. The simulated stress response showed that the peak gradually decreased with time and approached a constant value, with the negative value of stress representing the generation of tensile stress. This stress response quantification could aid researchers in determining specific MS conditions for various materials in tissue engineering, and the applied stress conditions could be further optimized. Overall, these findings are significant contributions to future research on cartilage repair and biophysical ES/MS in tissue engineering.


Assuntos
Condrogênese , Alicerces Teciduais , Humanos , Condrogênese/fisiologia , Engenharia Tecidual/métodos , Polímeros/farmacologia , Células-Tronco , Diferenciação Celular
5.
World J Surg Oncol ; 21(1): 331, 2023 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-37865772

RESUMO

BACKGROUND: This study aimed to conduct a case-control study of endoscopic and fluoroscopic metal stent placement combined with laparoscopic surgery versus conventional open Hartmann's procedure in treating acute left-sided colon cancer obstruction. Additionally, the study aims to discuss the application value of endoscopic and X-ray-guided metal stent placement combined with laparoscopic surgery in the treatment of acute left-sided colon cancer obstruction. METHODS: From June 2011 to December 2019, 23 patients with acute left-sided colon cancer obstruction who underwent metal stent implantation combined with laparoscopic surgery under endoscopy and X-ray fluoroscopy in Wenzhou Central Hospital were collected, and 20 patients with acute left-sided colon cancer obstruction who underwent traditional emergency open Hartmann's surgery during the same period were selected as a control group. All patients were diagnosed with left colon obstruction by plain abdominal film and/or CT before the operation and colon adenocarcinoma by colonoscopic biopsy and/or postoperative pathology. The operation time, intraoperative blood loss, postoperative anal exhaust time, the success rate of one-stage anastomosis, postoperative hospital stay, and postoperative complications were compared between the two groups. RESULTS: This study showed a significant difference in the therapeutic effect between the two groups. Compared with the traditional Hartmann's operation group, the success rate of one-stage anastomosis in endoscopic and X-ray-guided metal stent placement combined with the laparoscopic operation group was significantly higher than that in the Hartmann's operation group (P < 0.05). The overall incidence of postoperative complications and hospital stay were significantly lower in the observation group than in the Hartmann's group (P < 0.05). Further subgroup analysis of the overall postoperative complication rate of the two groups showed that the traditional Hartmann's operation group was more likely to have an incomplete intestinal obstruction (P < 0.05). This study also showed no significant differences between the two groups in operation time, intraoperative blood loss, number of harvested lymph nodes, and postoperative anal exhaust time (all P > 0.05). This study also found no significant differences between the two groups in overall survival rates or recurrence-free survival rates (all P > 0.05). CONCLUSIONS: The comparison of the therapeutic effects of the two groups verified the feasibility of endoscopy combined with X-ray fluoroscopy metal stent placement in combination with laparoscopic surgery in the treatment of acute left-sided colon cancer obstruction. Compared with the traditional emergency open Hartmann's procedure, metal stent implantation under endoscopy and X-ray fluoroscopy combined with laparoscopic surgery is more minimally invasive, safe, and effective. It avoids the traditional second or even third surgical trauma to effectively improve the quality of life of patients, so that patients can recover quickly after surgery.


Assuntos
Adenocarcinoma , Neoplasias do Colo , Obstrução Intestinal , Laparoscopia , Humanos , Neoplasias do Colo/cirurgia , Adenocarcinoma/cirurgia , Estudos de Casos e Controles , Qualidade de Vida , Raios X , Resultado do Tratamento , Estudos Retrospectivos , Laparoscopia/métodos , Colostomia/efeitos adversos , Obstrução Intestinal/etiologia , Obstrução Intestinal/cirurgia , Complicações Pós-Operatórias/epidemiologia , Anastomose Cirúrgica/métodos , Endoscópios/efeitos adversos , Fluoroscopia/efeitos adversos , Stents/efeitos adversos
6.
Nano Lett ; 22(19): 7944-7951, 2022 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-36129470

RESUMO

In this study, facile salt-assisted chemical vapor deposition (CVD) was used to synthesize ultrathin non-van der Waals chromium sulfide (Cr2S3) with a thickness of ∼1.9 nm. The structural transformation of as-grown Cr2S3 was studied using advanced in situ heating techniques combined with transmission electron microscopy (TEM). Two-dimensional (2D) and quasi-one-dimensional (1D) samples were fabricated to investigate the connection between specific planes and the dynamic behavior of the structural variation. The rearrangement of atoms during the phase transition was driven by the loss of sulfur atoms at elevated temperatures, resulting in increased free energy. A decrease in the ratio of the (001) plane led to an overall increase in surface energy, thus lowering the critical phase transition temperature. Our study provides detailed insight into the mechanism of structural transformation and the critical factors governing transition temperature, thus paving the way for future studies on intriguing Cr-S compounds.

7.
Pharmacogenet Genomics ; 32(1): 31-38, 2022 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-34380995

RESUMO

OBJECTIVES: Opioid dependence is currently one of the most serious problems affecting the social norms and public health system. Methadone maintenance therapy (MMT) is being widely used in treating heroin-dependent patients. The mechanism of methadone metabolism and disposition has been shown to involve cytochrome P450 (CYP450) and P-glycoprotein. The aim of this study was to explore the relationships among genetic polymorphisms, BMI and effective dose of methadone used in MMT within a northern Taiwan cohort. METHODS: One hundred heroin-dependent patients were enrolled in the study. The clinical data gathered included methadone dose, sex and BMI. DNA was collected from the oral swab of the participants to analyze the relevant alleles. RESULTS: An effective methadone dose correlated with sex, BMI and the presence of ABCB1 2677GG (rs2032582) and CYP2B6 516GG (rs374527). Furthermore, the CYP2B6 516GG homozygote was related to a higher average dose of methadone (GG: 68.50 ± 32.43; GT: 52.28 ± 25.75; TT: 44.44 ± 29.64; P < 0.02), whereas the ABCB1 2677GG homozygote was related to a lower dose (GG: 51.09 ± 20.83; GT: 69.65 ± 37.51; TT: 62.52 ± 30.44; P < 0.05). We examined the predictive effect of polymorphisms combined with sex and BMI on methadone dose by conducting multiple linear regressions. Our data predicted the average dose of methadone in approximately 30% of heroin-dependent patients. CONCLUSION: The interactions between genetic polymorphisms and clinical features proved useful in identifying the effective dose of MMT for heroin-dependent patients in Taiwan more precisely.


Assuntos
Dependência de Heroína , Preparações Farmacêuticas , Dependência de Heroína/tratamento farmacológico , Dependência de Heroína/genética , Humanos , Metadona , Testes Farmacogenômicos , Polimorfismo de Nucleotídeo Único/genética , Resultado do Tratamento
8.
Small ; 18(51): e2205306, 2022 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-36328712

RESUMO

Recently, perovskite (PV) oxides with ABO3 structures have attracted considerable interest from scientists owing to their functionality. In this study, CaFeOx is introduced to reveal the resistive switching properties and mechanism of oxygen vacancy transition in PV and brownmillerite (BM) structures. BM-CaFeO2.5 is grown on an Nb-STO conductive substrate epitaxially. CaFeOx exhibits excellent endurance and reliability. In addition, the CaFeOx also demonstrates an electroforming-free characteristic and multilevel resistance properties. To construct the switching mechanism, high-resolution transmission electron microscopy is used to observe the topotactic phase change in CaFeOx . In addition, scanning TEM and electron energy loss spectroscopy show the structural evolution and valence state variation of CaFeOx after the switching behavior. This study not only reveals the switching mechanism of CaFeOx , but also provides a PV oxide option for the dielectric material in resistive random-access memory (RRAM) devices.

9.
Opt Express ; 30(26): 46435-46449, 2022 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-36558597

RESUMO

Light extraction improvement is still an important issue for active-matrix organic light-emitting diode displays (AMOLEDs). In our previous work, a three-dimensional (3D) reflective pixel configuration embedding the OLED in the concave 3D reflector and patterned high-index filler had been proposed for significant enhancement of the pixel light extraction. In this work, influences of thin film encapsulation (TFE) on light extraction of such reflective 3D OLED pixels are considered as well by simulation studies. Unfortunately, the optical simulation reveals strong reduction of the light extraction efficiency induced by TFE layers. As such, an additional angle-selective optical film structure between the pixel and the encapsulation layers is introduced to control the angular distribution of the light coupled into the encapsulation layers and to solve TFE-induced optical losses. As a result, TFE-induced losses can be substantially reduced to retain much of light extraction efficiency. The results of this study are believed to provide useful insights and guides for developing even more efficient and power-saving AMOLEDs.

10.
Nano Lett ; 20(3): 1510-1516, 2020 Mar 11.
Artigo em Inglês | MEDLINE | ID: mdl-31725308

RESUMO

Crystalline Mo5O14 exhibits distinctive structural features such as tunnel structure and pseudolamellar arrangement according to the ideal model. However, the spatial resolution of the conventional technique of transmission electron microscopy (TEM) is insufficient to distinguish the actual positions of atoms. In this work, we aimed to systematically analyze and identify the Mo5O14 nanowires fabricated by the chemical vapor deposition (CVD) process. Utilizing high-angle annular dark-field (HAADF), annular bright-field (ABF), and enhanced annular bright-field (E-ABF) within the scanning transmission electron microscope (STEM) mode reveals the structural features at the atomic scale. In addition, the ultrahigh resolution images have confirmed the crystallographic insights in [001] growth direction for the Mo5O14 nanowires with a tunnel structure throughout the nanowire. The cross-sectional images show the unique close-packed plane and atomic arrangement with a network of MoO6 octahedra and MoO7 pentagonal bipyramids. These results are consistent with the theoretical atomic arrangement, supporting the realization of Mo5O14-type catalysts used in the selective oxidation process and battery applications.

11.
Small ; 16(3): e1905516, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31825564

RESUMO

Layered MoS2 is a prospective candidate for use in energy harvesting, valleytronics, and nanoelectronics. Its properties strongly related to its stacking configuration and the number of layers. Due to its atomically thin nature, understanding the atomic-level and structural modifications of 2D transition metal dichalcogenides is still underdeveloped, particularly the spatial control and selective precision. Therefore, the development of nanofabrication techniques is essential. Here, an atomic-scale approach used to sculpt 2D few-layer MoS2 into lateral heterojunctions via in situ scanning/transmission electron microscopy (STEM/TEM) is developed. The dynamic evolution is tracked using ultrafast and high-resolution filming equipment. The assembly behaviors inherent to few-layer 2D-materials are observed during the process and included the following: scrolling, folding, etching, and restructuring. Atomic resolution STEM is employed to identify the layer variation and stacking sequence for this new 2D-architecture. Subsequent energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy analyses are performed to corroborate the elemental distribution. This sculpting technique that is established allows for the formation of sub-10 nm features, produces diverse nanostructures, and preserves the crystallinity of the material. The lateral heterointerfaces created in this study also pave the way for the design of quantum-relevant geometries, flexible optoelectronics, and energy storage devices.

12.
Nanotechnology ; 31(36): 365702, 2020 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-32442986

RESUMO

With additional precursor soaking, a thin Al2O3 dielectric layer can be grown on mono-layer MoS2 by using atomic layer deposition (ALD). Similar optical characteristics are observed before and after ALD growth for the mono-layer MoS2, which indicates that minor damage to the thin 2D material film is introduced during the growth procedure. With the thin separation layer, luminescence enhancement and dual-color emission are observed by transferring MoS2 and WS2 mono-layer 2D materials to 5 nm Al2O3/mono-layer MoS2 samples, respectively. The results demonstrate that with careful treatment of the interfaces of 2D crystals with other materials, different stacked structures can be established.

13.
Sensors (Basel) ; 20(5)2020 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-32182926

RESUMO

This study presents a U-shaped optical fiber developed for a facile application of microRNA detection. It is fabricated by the lamping process and packaged in a quartz tube to eliminate human negligence. In addition, silanization and electrostatic self-assembly are employed to bind gold nanoparticles and miRNA-133a probe onto the silicon dioxide of the fiber surface. For Mahlavu of hepatocellular carcinoma (HCC), detection is determined by the wavelength shift and transmission loss of a U-shaped optical fiber biosensor. The spectral sensitivity of wavelength and their coefficient of determination are found at -218.319 nm/ ng/mL and 0.839, respectively. Concurrently, the sensitivity of transmission loss and their coefficient of determination are found at 162.394 dB/ ng/mL and 0.984, respectively. A method for estimating the limit of detection of Mahlavu is at 0.0133 ng/mL. The results show that the proposed U-shaped biosensor is highly specific to miRNA-133a and possesses good sensitivity to variations in specimen concentration. As such, it could be of substantial value in microRNA detection.


Assuntos
Técnicas Biossensoriais/instrumentação , MicroRNAs/análise , Fibras Ópticas , Técnicas Biossensoriais/métodos , Linhagem Celular Tumoral , Desenho de Equipamento , Ouro/química , Humanos , Limite de Detecção , Nanopartículas Metálicas/química , Silanos , Dióxido de Silício/química
14.
Molecules ; 25(19)2020 Oct 06.
Artigo em Inglês | MEDLINE | ID: mdl-33036279

RESUMO

Acne is a common skin condition observed in adolescents. Nutmeg (Myristica fragrans Houtt) (MF) is a well-known traditional Chinese medicine; its major toxic components, safrole and myristicin, are rich in essential oils. Essential oils of MF (MFO) were extracted by hydrodistillation; the residue was extracted using 50% methanol (MFE-M). The minimum inhibitory concentration (MIC) of MFE-M against Cutibacterium acnes and Staphylococcus aureus was 0.64 mg. Four compounds were obtained from MFE-M: myristicin (1), (+)-erythro-Δ8'-7S,8R- dihydroxy-3,3,5'-trimethoxy-8-O-4'-neolignan (2), (+)-erythro-Δ8'-7-hydroxy-3,4,3',5'-tetramethoxy 8-O-4-neolignan (3), and erythro-Δ8'-7-acetoxy-3,4,3',5'-tetramethoxy-8-O-4'-neolignan (4). Compound 2 exerted the strongest antimicrobial activity, with MICs of 6.25 and 3.12 µg/mL against C. acnes and S. aureus, respectively. Moreover, 2 inhibited NO, PGE2, iNOS, and COX-2 levels in RAW 264.7 cells induced by LPS or heat-killed C. acnes; NO production at 50% inhibitory concentrations (IC50) was 11.07 and 11.53 µg/mL, respectively. Myristicin and safrole content was higher in MFO than in MFE-M. MFO and MFE-M caused no skin irritation after a single topical application in Wistar rats. MFE-M, with low safrole and myristicin content, did not cause skin irritation and exhibited an anti-acne effect; moreover, 2 was identified as the active substance. Therefore, MFE-M could be employed to develop anti-acne compounds for use in cosmetics.


Assuntos
Anti-Inflamatórios/farmacologia , Lignanas/química , Myristica/química , Derivados de Alilbenzenos/farmacologia , Animais , Antibacterianos/química , Antibacterianos/farmacologia , Anti-Inflamatórios/química , Dioxolanos/farmacologia , Feminino , Propionibacteriaceae/efeitos dos fármacos , Ratos , Ratos Wistar , Safrol/farmacologia , Pele/efeitos dos fármacos , Staphylococcus aureus/efeitos dos fármacos
15.
Nano Lett ; 18(9): 6064-6070, 2018 09 12.
Artigo em Inglês | MEDLINE | ID: mdl-30130112

RESUMO

Transition metal oxide nanowires have attracted extensive attention because of their physical characteristics. Among them, ZnO nanowires have great potential. Due to the multifunctional properties of ZnO, devices built using ZnO-based heterostructures always perform well. In this study, interesting diffusion behavior between ZnO nanowires and Fe metal was observed by using in situ transmission electron microscopy. ZnO nanowires and Fe metal were annealed under ultrahigh vacuum (UHV) conditions at 800 K. By controlling the annealing time for the solid-state diffusion, porous Fe3O4 and unique ZnO/porous Fe3O4 nanowire heterostructures were formed. As-formed porous Fe3O4 nanowires with voids can be divided into two types by appearance: plate-like voids and zigzag-like hollow voids. From high-resolution transmission electron microscopy (HRTEM) images and fast Fourier transform (FFT) diffraction patterns, we found that plate-like voids formed along the {111} plane, which was the close-packed plane of Fe3O4, and that zigzag-like hollow voids formed along the {111}/{022} planes. Moreover, a transition region existed during diffusion, with a parallel relationship found between the Fe3O4 crystal with plate-like voids and the ZnO crystal. A sharp interface was determined to exist between the Fe3O4 crystal with zigzag-like hollow voids and ZnO. These oriented porous Fe3O4/ZnO axial nanowire heterostructures exhibited a unique appearance and interesting formation behavior. Furthermore, the structures had a high surface-area-to-volume ratio, which is promising for sensing applications.

16.
Nano Lett ; 18(2): 778-784, 2018 02 14.
Artigo em Inglês | MEDLINE | ID: mdl-29369633

RESUMO

The fabrication and placement of high purity nanometals, such as one-dimensional copper (Cu) nanowires, for interconnection in integrated devices have been among the most important technological developments in recent years. Structural stability and oxidation prevention have been the key issues, and the defect control in Cu nanowire growth has been found to be important. Here, we report the synthesis of defect-free single-crystalline Cu nanowires by controlling the surface-assisted heterogeneous nucleation of Cu atomic layering on the graphite-like loop of an amorphous carbon (a-C) lacey film surface. Without a metal-catalyst or induced defects, the high quality Cu nanowires formed with high aspect ratio and high growth rate of 578 nm/s. The dynamic study of the growth of heterogeneous nanowires was conducted in situ with a high-resolution transmission electron microscope. The study illuminates the new mechanism by heterogeneous nucleation control and laying the groundwork for better understanding of heterosurface-assisted nucleation of defect-free Cu nanowire on a-C lacey film.

17.
Small ; 14(6)2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29205879

RESUMO

Metal/metal oxides have attracted extensive research interest because of their combination of functional properties and compatibility with industry. Diffusion and thermal reliability have become essential issues that require detailed study to develop atomic-scaled functional devices. In this work, the diffusional reaction behavior that transforms piezoelectric ZnO into magnetic Fe3 O4 is investigated at the atomic scale. The growth kinetics of metal oxides are systematically studied through macro- and microanalyses. The growth rates are evaluated by morphology changes, which determine whether the growth behavior was a diffusion- or reaction-controlled process. Furthermore, atom attachment on the kink step is observed at the atomic scale, which has important implications for the thermodynamics of functional metal oxides. Faster growth planes simultaneously decrease, which result in the predominance of low surface energy planes. These results directly reveal the atomic formation process of metal oxide via solid-state diffusion. In addition, the nanofabricated method provides a novel approach to investigate metal oxide evolution and sheds light on diffusional reaction behavior. More importantly, the results and phenomena of this study provide considerable inspiration to enhance the material stability and reliability of metal/oxide-based devices.

18.
Small ; 14(6)2018 02.
Artigo em Inglês | MEDLINE | ID: mdl-29205791

RESUMO

The crossbar structure of resistive random access memory (RRAM) is the most promising technology for the development of ultrahigh-density devices for future nonvolatile memory. However, only a few studies have focused on the switching phenomenon of crossbar RRAM in detail. The main purpose of this study is to understand the formation and disruption of the conductive filament occurring at the crossbar center by real-time transmission electron microscope observation. Core-shell Ni/NiO nanowires are utilized to form a cross-structure, which restrict the position of the conductive filament to the crosscenter. A significant morphological change can be observed near the crossbar center, which results from the out-diffusion and backfill of oxygen ions. Energy dispersive spectroscopy and electron energy loss spectroscopy demonstrate that the movement of the oxygen ions leads to the evolution of the conductive filament, followed by redox reactions. Moreover, the distinct reliability of the crossbar device is measured via ex situ experiments. In this work, the switching mechanism of the crossbar core-shell nanowire structure is beneficial to overcome the problem of nanoscale minimization. The experimental method shows high potential to fabricate high-density RRAM devices, which can be applied to 3D stacked package technology and neuromorphic computing systems.

19.
Anal Chem ; 89(18): 9671-9675, 2017 09 19.
Artigo em Inglês | MEDLINE | ID: mdl-28805052

RESUMO

Transition metal oxides have attracted much interest owing to their ability to provide high power density in lithium batteries; therefore, it is important to understand the electrochemical behavior and mechanism of lithiation-delithiation processes. In this study, we successfully and directly observed the structural evolution of CNTs/MnO2 during the lithiation process using transmission electron microscopy (TEM). CNTs/MnO2 were selected due to their high surface area and capacitance effect, and the lithiation mechanism of the CNT wall expansion was systematically analyzed. Interestingly, the wall spacings of CNTs/MnO2 and CNTs were obviously expanded by 10.92% and 2.59%, respectively. The MnO2 layer caused structural defects on the CNTs surface that could allow penetration of Li+ and Mn4+ through the tube wall and hence improve the ionic transportation speed. This study provided direct evidence for understanding the role of CNTs/MnO2 in the lithiation process used in lithium ion batteries and also offers potential benefits for applications and development of supercapacitors.

20.
Small ; 13(15)2017 04.
Artigo em Inglês | MEDLINE | ID: mdl-28165195

RESUMO

The Forming phenomenon is observed via in situ transmission electron microscopy in the Ag/Ta2 O5 /Pt system. The device is switched to a low-resistance state as the dual filament is connected to the electrodes. The results of energy dispersive spectrometer and electron energy loss spectroscopy analyses demonstrate that the filament is composed by a stack of oxygen vacancies and Ag metal.

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