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1.
Cancer Immunol Immunother ; 73(6): 101, 2024 Apr 17.
Artigo em Inglês | MEDLINE | ID: mdl-38630265

RESUMO

BACKGROUND: Adoptive transfer of in vitro expanded tumor-infiltrating lymphocytes (TILs) has been effective in regressing several types of malignant tumors. This study assessed the yield and factors influencing the successful expansion of tumor-infiltrating lymphocytes (TILs) from head and neck squamous cell carcinoma (HNSCC), along with their immune phenotypes. METHODS: TILs were expanded from 47 surgically resected HNSCC specimens and their metastasized lymph nodes. The cancer tissues were cut into small pieces (1-2 mm) and underwent initial expansion for 2 weeks. Tumor location, smoking history, stromal TIL percentage, human papillomavirus infection, and programmed death-ligand 1 score were examined for their impact on successful expansion of TILs. Expanded TILs were evaluated by flow cytometry using fluorescence-activated cell sorting. A second round of TIL expansion following the rapid expansion protocol was performed on a subset of samples with successful TIL expansion. RESULTS: TILs were successfully expanded from 36.2% samples. Failure was due to contamination (27.6%) or insufficient expansion (36.2%). Only the stromal TIL percentage was significantly associated with successful TIL expansion (p = 0.032). The stromal TIL percentage also displayed a correlation with the expanded TILs per fragment (r = 0.341, p = 0.048). On flow cytometry analysis using 13 samples with successful TIL expansion, CD4 + T cell dominancy was seen in 69.2% of cases. Effector memory T cells were the major phenotype of expanded CD4 + and CD8 + T cells in all cases. CONCLUSION: We could expand TILs from approximately one-third of HNSCC samples. TIL expansion could be applicable in HNSCC samples with diverse clinicopathological characteristics.


Assuntos
Neoplasias de Cabeça e Pescoço , Imunoterapia Adotiva , Humanos , Linfócitos do Interstício Tumoral , Carcinoma de Células Escamosas de Cabeça e Pescoço/terapia , Transferência Adotiva , Neoplasias de Cabeça e Pescoço/terapia
3.
Small ; 20(9): e2306468, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-37857588

RESUMO

Organic semiconductors have great potential to revolutionize electronics by enabling flexible and eco-friendly manufacturing of electronic devices on plastic film substrates. Recent research and development led to the creation of printed displays, radio-frequency identification tags, smart labels, and sensors based on organic electronics. Over the last 3 decades, significant progress has been made in realizing electronic devices with unprecedented features, such as wearable sensors, disposable electronics, and foldable displays, through the exploitation of desirable characteristics in organic electronics. Neverthless, the down-scalability of organic electronic devices remains a crucial consideration. To address this, efforts are extensively explored. It is of utmost importance to further develop these alternative patterning methods to overcome the downscaling challenge. This review comprehensively discusses the efforts and strategies aimed at overcoming the limitations of downscaling in organic semiconductors, with a particular focus on four main areas: 1) lithography-compatible organic semiconductors, 2) fine patterning of printing methods, 3) organic material deposition on pre-fabricated devices, and 4) vertical-channeled organic electronics. By discussing these areas, the full potential of organic semiconductors can be unlocked, and the field of flexible and sustainable electronics can be advanced.

4.
Sci Total Environ ; 912: 169204, 2024 Feb 20.
Artigo em Inglês | MEDLINE | ID: mdl-38104814

RESUMO

Accurate estimation of emissions from industrial point sources is crucial in understanding the effectiveness of reduction efforts and establishing reliable emission inventories. In this study, we employ an airborne Chemical Ionization Mass Spectrometry (CIMS) instrument to quantify sulfur dioxide (SO2) emissions from prominent industrial facilities in South Korea, including power plants, a steel mill, and a petrochemical facility. Our analysis utilizes the box mass balance technique to derive SO2 emissions and associated uncertainty. We evaluate the interpolation methods between 2D kriging and 3D radial basis function. The results demonstrate that the total uncertainty of the box mass balance technique ranges from 5 % to 28 %, with an average of 20 %. Mixing ratio ground extrapolation from the lowest altitude of the airborne sampling to the ground emerges as the dominant source of uncertainty, followed by the determination of the boundary layer height. Adequate sampling at multiple altitudes is found to be essential in reducing the overall uncertainty by capturing the full extent of the plume. Furthermore, we assess the uncertainty of the single-height transect mass balance method commonly employed in previous studies. Our findings reveal an average precision of 47 % for this method, with the potential for overestimating emissions by up to 206 %. Samplings at fewer altitudes or with larger altitude gaps increase the risk of under-sampling and elevate method uncertainties. Therefore, this study provides a quantitative basis to evaluate previously airborne observational emission constraints.

5.
Epidemiol Health ; 45: e2023095, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37905312

RESUMO

OBJECTIVES: Inhalation exposure to humidifier disinfectants has resulted to various types of health damages in Korea. To determine the epidemiological correlation necessary for presuming the legal causation, we aimed to develop a method to synthesize the entire evidence. METHODS: Epidemiological and toxicological studies are systematically reviewed. Target health problems are selected by criteria such as frequent complaints of claimants. Relevant epidemiologic studies are reviewed and the risk of bias and confidence level of the total evidence are evaluated. Toxicological literature reviews are conducted on three lines of evidence including hazard information, animal studies, and mechanistic studies, considering the source-to-exposure-to-outcome continuum. The confidence level of the body of evidence is then translated into the toxicological evidence levels for the causality between humidifier disinfectant exposure and health effects. Finally, the levels of epidemiological and toxicological evidence are synthesized. RESULTS: Under the Special Act revised in 2020, if the history of exposure and the disease occurred/worsened after exposure were approved, and the epidemiological correlation between the exposure and disease was verified, the legal causation is presumed unless the company proves the evidence against it. The epidemiological correlation can be verified through epidemiological investigations, health monitoring, cohort investigations and/or toxicological studies. It is not simply as statistical association as understood in judicial precedents, but a general causation established by the evidence as a whole, i.e., through weight-of-the-evidence approach. CONCLUSIONS: The weight-of-the-evidence approach differs from the conclusive single study approach and this systematic evidence integration can be used in presumption of causation.


Assuntos
Desinfetantes , Umidificadores , Animais , Humanos , Desinfetantes/toxicidade , Exposição por Inalação/efeitos adversos , Causalidade
6.
Biomed Res Int ; 2022: 2534350, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36506913

RESUMO

Multilevel lumbar fusion with posterior pedicle screw fixation is a widely performed surgical procedure for the management of adult spinal deformity. However, there has not been a comprehensive biomechanical study on the different types of fusion levels in terms of stability and possible complications. We aimed to investigate the biomechanical properties of multilevel lumbar fusion according to different types of upper and lower fusion levels. Six different types of fusions were performed using three-dimensional finite element models. Type A and B referred to the group of which upper fusion level was L1 and T10, respectively. Subtype 1, 2, and 3 referred to the group of which lower fusion level was L5, S1, and ilium, respectively (A1, L1-L5; A2, L1-S1; A3, L1-ilium; B1, T10-L5; B2, T10-S1; B3, T10-ilium). Flexion, extension, axial rotation, and lateral bending moments were applied, and the risk of screw loosening and failure and adjacent segment degeneration (ASD) was analyzed. Stress at the bone-screw interface of type B3 was lowest in overall motions. The risk of screw failure showed increasing pattern as the upper and lower levels extended in all motions. Proximal range of motion (ROM) increased as the lower fusion level changed from L5 to S1 and the ilium. For axial rotation, type B3 showed higher proximal ROM (16.2°) than type A3 (11.8°). In multilevel lumbar fusion surgery for adult spinal deformity, adding iliac screws and increasing the fusion level to T10-ilium may lower the risk of screw loosening. In terms of screw failure and proximal ASD, however, T10-ilium fusion has a higher potential risk compared with other fusion types. These results will contribute for surgeons to provide adequate patient education regarding screw failure and proximal ASD, when performing multilevel lumbar fusion.


Assuntos
Parafusos Pediculares , Fusão Vertebral , Adulto , Humanos , Análise de Elementos Finitos , Fusão Vertebral/métodos , Vértebras Lombares/cirurgia , Fenômenos Biomecânicos , Amplitude de Movimento Articular , Rotação
7.
Micromachines (Basel) ; 13(11)2022 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-36422382

RESUMO

Polymethylmethacrylate (PMMA) is commonly applied to microfluidic devices due to its excellent biocompatibility, high optical transparency, and suitability for mass production. Recently, various surface treatment methods have been reported to improve the wettability of polymers, which is directly related to adhesion. In this research, the effect of a UV irradiation technique and an IPA rinsing technique as surface treatments for PMMA is investigated regarding the water contact angle of the PMMA surface. PMMA sheets that were 1.62 mm thick and commercially available were exposed to UV light with four different exposure times. Significant decreases in the water contact angle were observed after exposure to UV light, and the lowered contact angles due to the UV irradiation increased over time. According to the measurement, the water contact angle is a function of UV exposure dose as well as storage time after UV exposure. We examined the effect of a IPA rinsing process after UV irradiation and observed an increase in the water contact angle.

8.
Polymers (Basel) ; 14(14)2022 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-35890650

RESUMO

Electrophysiological signals are collected to characterize human health and applied in various fields, such as medicine, engineering, and pharmaceuticals. Studies of electrophysiological signals have focused on accurate signal acquisition, real-time monitoring, and signal interpretation. Furthermore, the development of electronic devices consisting of biodegradable and biocompatible materials has been attracting attention over the last decade. In this regard, this review presents a timely overview of electrophysiological signals collected with biodegradable polymer electrodes. Candidate polymers that can constitute biodegradable polymer electrodes are systemically classified by their essential properties for collecting electrophysiological signals. Moreover, electrophysiological signals, such as electrocardiograms, electromyograms, and electroencephalograms subdivided with human organs, are discussed. In addition, the evaluation of the biodegradability of various electrodes with an electrophysiology signal collection purpose is comprehensively revisited.

9.
Biochem Biophys Res Commun ; 615: 63-69, 2022 07 30.
Artigo em Inglês | MEDLINE | ID: mdl-35605407

RESUMO

HucR is a MarR family protein of Deinococcus radiodurans, which binds tightly to the intergenic region of HucR and the uricase gene to inhibit their expression. Urate (or uric acid) antagonizes the repressor function of HucR by binding to HucR to impede its association with the cognate DNA. The previously reported crystal structure of HucR was without the bound urate showing significant structural homology to other MarR structures. In this paper, we report the crystal structure of HucR determined with the urate bound. However, despite the fact that the urate is found at a site well-known to harbor ligands in other MarR family proteins, the overall HucR structure indicates that no significant change in structure takes place with the urate bound. Structure analysis further suggests that the urate interaction in HucR is mediated by histidine/glutamate side chains and ordered water molecules stabilized by various residues. Such interaction is quite unique compared to other known structural interactions between urate and its binding proteins. Furthermore, structural comparison of the apo- and the urate bound forms allows us to hypothesize that the Trp20-mediated water network in the apo-form stabilizes the proper HucR fold for cognate DNA binding, and that urate binding, also via Trp20, and the consequent reorganization of water molecules in the binding pocket, likely disrupts the DNA binding configuration to result in the attenuated DNA binding.


Assuntos
Deinococcus , Proteínas de Bactérias/metabolismo , Cristalografia por Raios X , DNA/química , Deinococcus/química , Ligação Proteica , Ácido Úrico/metabolismo , Água/metabolismo
10.
ACS Omega ; 6(50): 34752-34762, 2021 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-34963958

RESUMO

It is necessary to apply a nonenzymatic glucose fuel cell using a proton exchange membrane for an implantable biomedical device that operates at low power. The permeability of glucose with high viscosity and a large molecular weight in the porous medium of the diffusion layer was investigated for use in fuel cells. Carbon paper was prepared as an anode diffusion layer, and it was analyzed with a diffusion layer treated with polytetrafluoroethylene (PTFE) and a microporous layer (MPL). When untreated carbon paper was applied, the peak power density (PPD) and open-circuit voltage (OCV) increased as the glucose concentration and flow rate increased. On this occasion, the highest PPD of 17.81 µW cm-2 was achieved at 3 mM and a 2.0 mL min-1 glucose aqueous solution (at atmospheric pressure and 36.5 °C). The diffusion layer, which became more hydrophobic through PTFE treatment, adversely affected glucose permeability. In addition, the addition of an MPL decreased OCV and PPD with increasing glucose concentrations and flow rates. Compared with untreated carbon paper, the PPD was six times lower approximately. Consequently, it was confirmed that the properties of carbon paper, such as low hydrophobicity, high porosity, and thin thickness, would be advantageous for nonenzymatic glucose fuel cells.

11.
Molecules ; 26(18)2021 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-34576916

RESUMO

Perovskite is attracting considerable interest because of its excellent semiconducting properties and optoelectronic performance. In particular, lead perovskites have been used extensively in photovoltaic, photodetectors, thin-film transistors, and various electronic applications. On the other hand, the elimination of lead is essential because of its strong toxicity. This paper reports the synthesis of lead-free calcium titanate perovskite (CaTiO3) using a solution-processed combustion method. The chemical and morphological properties of CaTiO3 were examined as a function of its thickness by scanning electron microscopy, X-ray diffraction (XRD), atomic force microscopy, X-ray photoelectron spectroscopy, and ultraviolet-visible spectrophotometry. The analysis showed that thicker films formed by a cumulative coating result in larger grains and more oxygen vacancies. Furthermore, thickness-dependent hysteresis behaviors were examined by fabricating a metal-CaTiO3-metal structure. The electrical hysteresis could be controlled over an extremely low voltage operation, as low as 100 mV, by varying the grain size and oxygen vacancies.

12.
Microsyst Nanoeng ; 7: 69, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34567781

RESUMO

Chip-to-chip and world-to-chip fluidic interconnections are paramount to enable the passage of liquids between component chips and to/from microfluidic systems. Unfortunately, most interconnect designs add additional physical constraints to chips with each additional interconnect leading to over-constrained microfluidic systems. The competing constraints provided by multiple interconnects induce strain in the chips, creating indeterminate dead volumes and misalignment between chips that comprise the microfluidic system. A novel, gasketless superhydrophobic fluidic interconnect (GSFI) that uses capillary forces to form a liquid bridge suspended between concentric through-holes and acting as a fluid passage was investigated. The GSFI decouples the alignment between component chips from the interconnect function and the attachment of the meniscus of the liquid bridge to the edges of the holes produces negligible dead volume. This passive seal was created by patterning parallel superhydrophobic surfaces (water contact angle ≥ 150°) around concentric microfluidic ports separated by a gap. The relative position of the two polymer chips was determined by passive kinematic constraints, three spherical ball bearings seated in v-grooves. A leakage pressure model derived from the Young-Laplace equation was used to estimate the leakage pressure at failure for the liquid bridge. Injection-molded, Cyclic Olefin Copolymer (COC) chip assemblies with assembly gaps from 3 to 240 µm were used to experimentally validate the model. The maximum leakage pressure measured for the GSFI was 21.4 kPa (3.1 psig), which corresponded to a measured mean assembly gap of 3 µm, and decreased to 0.5 kPa (0.073 psig) at a mean assembly gap of 240 µm. The effect of radial misalignment on the efficacy of the gasketless seals was tested and no significant effect was observed. This may be a function of how the liquid bridges are formed during the priming of the chip, but additional research is required to test that hypothesis.

13.
Small ; 17(28): e2100695, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34114327

RESUMO

Power outages caused by the aging of high-voltage power facilities can cause significant economic and social damage. To prevent such problems, it is necessary to implement a widespread and sustainable monitoring system. Partial discharge (PD) is a preliminary symptom of power equipment aging accompanying the light, typically in the UV range. UVC (200-280 nm) is more useful than UVA and UVB because of low interference from the environment owing to its solar-blindness by the stratosphere. Therefore, to realize a wide-range and durable diagnosis system, it is necessary to develop sensors that can selectively detect UVC, while enabling mass production at low-cost and low power consumption. Here, a solution-processable photodiode sensor that is inexpensive, mass-producible, and self-powered with selective UVC detection is developed. The optoelectronic characteristics of photodiode consisting of organic p-polymer and inorganic n-ZnO nanoparticles are systematically studied to determine the optimum p-type polymer and its thickness. The device shows high-performance: fast response time (rise/fall time: 36.6/37.0 ms) and high spectral response in the UVC region (maximum responsivity of 20 mA W-1 ) under self-powered operation. Furthermore, the practical application of the device to detect PD signals with a visual alarm system under UVC release conditions is demonstrated.


Assuntos
Nanopartículas , Alta do Paciente , Humanos , Polímeros , Luz Solar
14.
Nanomaterials (Basel) ; 11(6)2021 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-34071164

RESUMO

An AlGaN/GaN heterostructure based hydrogen sensor was fabricated using a dual catalyst layer with ZnO-nanoparticles (NPs) atop of Pd catalyst film. The ZnO-NPs were synthesized to have an average diameter of ~10 nm and spin coated on the Pd catalyst layer. Unlike the conventional catalytic reaction, the fabricated sensors exhibited room temperature operation without heating owing to the photocatalytic reaction of the ZnO-NPs with ultraviolet illumination at 280 nm. A sensing response of 25% was achieved for a hydrogen concentration of 4% at room temperature with fast response and recovery times; a response time of 8 s and a recovery time of 11 s.

15.
Environ Pollut ; 286: 117195, 2021 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-33975218

RESUMO

The characteristics of primary gas/aerosol and secondary aerosol emissions were identified for small passenger vehicles using typical fuel types in South Korea (gasoline, liquefied petroleum gas (LPG), and diesel). The generation of secondary organic aerosol (SOA) was explored using the potential aerosol mass (PAM) oxidation flow reactor. The primary emissions did not vary significantly between fuel types, combustion technologies, or aftertreatment systems, while the amount of NH3 was higher in gasoline and LPG vehicle emissions than that in diesel vehicle emissions. The SOA emission factor was 11.7-66 mg kg-fuel-1 for gasoline vehicles, 2.4-50 mg kg-fuel-1 for non-diesel particulate filter (non-DPF) diesel vehicles (EURO 2-3), 0.4-40 mg kg-fuel-1 for DPF diesel vehicles (EURO 4-6), and 3-11 mg kg-fuel-1 for LPG vehicles (lowest). The carbonaceous aerosols (equivalent black carbon (eBC) + primary organic aerosol + SOA) of diesel vehicles in EURO 4-6 were reduced by up to 95% compared to those in EURO 2-3. The expected SOA yield increased through the hot-condition combustion section of a vehicle, over the SOA range of 0.2-155 µg m-3. These results provide the necessary data to analyze all types of SOA generated by the gas-phase oxidation in vehicle emissions in metropolitan areas.


Assuntos
Poluentes Atmosféricos , Petróleo , Aerossóis/análise , Poluentes Atmosféricos/análise , Gasolina/análise , Veículos Automotores , Tecnologia , Emissões de Veículos/análise
16.
ACS Appl Mater Interfaces ; 13(11): 13372-13382, 2021 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-33709683

RESUMO

Calcium stannate (CaSnO3) is an inorganic perovskite material with an ultrawide bandgap (4.2-4.4 eV) that is associated with its unique structural characteristics. Owing to its remarkable optical and electric properties and high physical and chemical stability, it has recently drawn significant interest for various applications such as photocatalysts for the degradation of organic compounds and hydrogen production under UV radiation, gas sensors, and thermally stable capacitors. In this study, we demonstrate a self-powered deep-UV (DUV) p-i-n photodetector consisting of CaSnO3 thin film as an efficient DUV absorber via a low-temperature solution process. The physical, optical, and electrical properties of the as-synthesized CaSnO3 are characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, high-resolution transmission electron microscopy, ultraviolet-visible spectroscopy, photoluminescence spectroscopy, space charge limited current, and four-point probe measurements. As a key component in a p-i-n DUV photodetector, the thickness of the CaSnO3 absorber layer and operating bias are optimized to enhance charge carrier transport, light absorption, and signal-to-noise ratio. As a result, the optimized device shows a high performance at zero bias under 254 nm UV illumination: with a specific detectivity of 1.56 × 1010 Jones, fast rise/fall time of 80/70 ms, and high 254:365 nm photocurrent rejection ratio of 5.5 along with a stable photoresponse during 100 continuous cycles initially as well as after 1 month of storage. Accordingly, this study suggests that a novel CaSnO3-based photodiode prepared via a solution process can be employed for many practical DUV-detection applications.

17.
Clin Biomech (Bristol, Avon) ; 76: 105021, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32416405

RESUMO

BACKGROUND: Comparative studies of the biomechanical effects of plates of varying lengths and different screw insertion angles on allograft spacers are lacking. METHODS: Finite element model analysis of a previously validated, three-dimensional, intact cervical spinal segment model of C3-6 was conducted in the present study. On the C5-6 segment, anterior discectomy and fusion were performed using allograft spacers and different combinations of anterior plates and screws. The biomechanical characteristics of combinations of short, medium, and maximal length plates with screw insertion angles of 0°, 8°, 16°, and 32° were analyzed. FINDINGS: In flexion and extension, the risk of allograft spacer subsidence decreased as screw angles increased. Short plates with a screw insertion angle of 32° posed the lowest subsidence risk, similar to medium length plates with a screw insertion angle of 16°, in all motion conditions. The risk of bone yielding increased as plate length increased, but decreased as the screw insertion angle increased. INTERPRETATION: Short plates with a large screw insertion angle (32°) showed the highest mechanical stability and load sharing of allograft spacers and the lowest risk of screw loosening. Accordingly, we recommend the use of a short plate and large screw insertion angle for anterior cervical discectomy and fusion.


Assuntos
Placas Ósseas , Parafusos Ósseos , Vértebras Cervicais/cirurgia , Análise de Elementos Finitos , Aloenxertos/cirurgia , Fenômenos Biomecânicos , Humanos , Transplante Homólogo
18.
Opt Express ; 28(7): 10145-10152, 2020 Mar 30.
Artigo em Inglês | MEDLINE | ID: mdl-32225606

RESUMO

Wavelength-division multiplexed optical communication systems used in 5G networks require tunable wavelength filters with narrow bandwidth for 100 GHz channel spacing, wide wavelength range to cover 16 channels, and a side mode suppression ratio (SMSR) exceeding 30 dB. To fabricate wavelength filters satisfying these specifications, tunable Bragg grating filters based on polymeric optical waveguides are proposed. The combination of mode-sorting waveguide and tilted Bragg grating enables the extraction of Bragg reflected signals to another path, without using an external circulator. Moreover, the double reflection by the two-stage cascaded structure produces narrower reflection bandwidth, improved SMSR characteristics, and reduced adjacent-channel crosstalk through the suppression of undesired mode coupling. The proposed device exhibits a 20 dB bandwidth of 1.0 nm and SMSR of 35 dB, over the entire wavelength-tuning range.

19.
Opt Express ; 28(3): 3768-3778, 2020 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-32122038

RESUMO

Solid-state light detection and ranging, capable of performing beam scanning without using any mechanical moving parts, requires a phase-modulator array. Polymers facilitate the fabrication of efficient phase modulators with low drive power, owing to their high thermo-optic (TO) effect and low thermal conductivity. We designed and fabricated a polymeric phase-modulator array and analyzed the temporal response of the TO phase modulator. The frequency response of the phase modulator was measured for a Mach-Zehnder interferometer (MZI), and the transfer function was modeled in terms of multiple poles and zeros. The frequency response of a fabricated beam-scanning device incorporating the TO phase modulator was also measured. The temporal response of the beam scanner was confirmed to coincide well with that of the MZI modulator. The device exhibited a fast rise time of 12 ms, accompanied by slight power variations appearing for a long period (over hundreds of seconds), which originated from the inherent viscoelastic effect of the polymer materials.

20.
Nanomaterials (Basel) ; 10(2)2020 Feb 24.
Artigo em Inglês | MEDLINE | ID: mdl-32102300

RESUMO

A hybrid film consisting of zinc oxide nanoparticles (ZnO NPs) and carbon nanotubes (CNTs) is formed on a glass substrate using a simple and swift spin coating process for the use in ultraviolet photodetectors (UV PDs). The incorporation of various types of CNTs into ZnO NPs (ZnO@CNT) enhances the performance of UV PDs with respect to sensitivity, photoresponse, and long-term operation stability when compared with pristine ZnO NP films. In particular, the introduction of single-walled CNTs (SWNTs) exhibits a superior performance when compared with the multiwalled CNTs (MWNTs) because SWNTs can not only facilitate the stability of free electrons generated by the O2 desorption on ZnO under UV irradiation owing to the built-in potential between ZnO and SWNT heterojunctions, but also allow facile and efficient transport pathways for electrons through SWNTs with high aspect ratio and low defect density. Furthermore, among the various SWNTs (arc-discharged (A-SWNT), Hipco (H-SWNT), and CoMoCat (C-SWNT) SWNTs), we demonstrate the ZnO@A-SWNT hybrid film exhibits the best performance because of higher conductivity and aspect ratio in A-SWNTs when compared with those of other types of SWNTs. At the optimized conditions for the ZnO@A-SWNT film (ratio of A-SWNTs and ZnO NPs and electrode distance), ZnO@A-SWNT displays a sensitivity of 4.9 × 103 % with an on/off current ratio of ~104 at the bias of 2 V under the UV wavelength of 365 nm (0.47 mW/cm2). In addition, the stability in long-term operation and photoresponse time are significantly improved by the introduction of A-SWNTs into the ZnO NP film when compared with the bare ZnO NPs film.

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