共查询到20条相似文献,搜索用时 31 毫秒
1.
Incorporating plasmonic nanoparticles (NPs) in an organic solar cell (OSC) can improve device performance. In our simulation studies, at NP resonance, absorption in poly(3-hexythiophene)/phenyl-C61-butyric acid methyl ester (P3HT/PCBM) can be increased by encapsulating 50 nm Ag NPs with Al 2O 3, HfO 2, MoO 3, and SiO 2. At Ag NP resonance, when the oxide thickness is significant enough, oxides with high relative permittivity induces a higher electric field enhancement at the metal/dielectric interface. This is translated to improved absorption in the polymer layer. By integrating against AM1.5G, overall absorption in P3HT/PCBM is improved when incorporating Ag NPs encapsulated with a thin oxide shell into the polymer film. However, polymeric absorption loss is induced for oxide-encapsulated Ag NPs if MoO 3 and SiO 2 shells are more than 5 nm. For Al 2O 3 and HfO 2, Ag NPs should not be encapsulated with shells thicker than 10 nm. Modeling studies are also extended to absorption in a CH 3NH 3PbI 3 perovskite layer. It is revealed that both Al 2O 3 and HfO 2 have an optimal shell thickness of about 20 nm to ensure maximum absorption in CH 3NH 3PbI 3. The results can be utilized as a useful guideline when designing photovoltaics from an optical point of view. 相似文献
2.
Microbeam Radiation Therapy (MRT) exploits tumour selectivity and normal tissue sparing with spatially fractionated kilovoltage X-ray microbeams through the dose volume effect. Experimental measurements with Ta 2O 5 nanoparticles (NPs) in 9L gliosarcoma treated with MRT at the Australian Synchrotron, increased the treatment efficiency. Ta 2O 5 NPs were observed to form shells around cell nuclei which may be the reason for their efficiency in MRT. In this article, our experimental observation of NP shell formation is the basis of a Geant4 radiation transport study to characterise dose enhancement by Ta 2O 5 NPs in MRT. Our study showed that NP shells enhance the physical dose depending microbeam energy and their location relative to a single microbeam. For monochromatic microbeam energies below ∼70 keV, NP shells show highly localised dose enhancement due to the short range of associated secondary electrons. Low microbeam energies indicate better targeted treatment by allowing higher microbeam doses to be administered to tumours and better exploit the spatial fractionation related selectivity observed with MRT. For microbeam energies above ∼100 keV, NP shells extend the physical dose enhancement due to longer-range secondary electrons. Again, with NPs selectively internalised, the local effectiveness of MRT is expected to increase in the tumour. Dose enhancement produced by the shell aggregate varied more significantly in the cell population, depending on its location, when compared to a homogeneous NP distribution. These combined simulation and experimental data provide first evidence for optimising MRT through the incorporation of newly observed Ta 2O 5 NP distributions within 9L cancer cells. 相似文献
3.
Cymbopogon citratus-mediated pure aluminium oxide (Al 2O 3) and europium (Eu)-doped Al 2O 3 with different amounts of metal ion were prepared using a green synthesis method. Synthesised nanoparticles were characterised by ultraviolet (UV)-visible spectroscopy, photoluminescence (PL), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Synthesis of nanoparticles is confirmed by using UV-visible spectroscopy showing maximum absorption at 411 and 345 nm for Al 2O 3 and Eu-doped Al 2O 3, respectively. The antibacterial activity of prepared nanoparticles was evaluated against Pseudomonas aeruginosa, Streptococcus aureus, Escherichia coli and Klebsiella pneumoniae using a well-diffusion technique. The effect of pure Al 2O 3 and Eu-doped nanoparticles shows excellent results against P. aeruginosa, S. aureus, E. coli and K. pneumoniae. 相似文献
4.
The development of nanotechnologies has increased the amount of manufactured metal oxide nanoparticles in the environment. In the view of nanoparticle dispersion to the environment, assessment of their toxicity becomes very crucial. Aluminum oxide (Al 2O 3) nanoparticles have wide range of use in industry as well as personal care products. The aim of this study was to evaluate the dose dependent effects of 13-nm-sized Al 2O 3 nanoparticles on wheat correlating with the appearance of enzymatic and non-enzymatic antioxidant defense response. Wheat roots were exposed to different concentrations of Al 2O 3 nanoparticles (5, 25 and 50 mg mL ?1) for 96 h. The effects of Al 2O 3 nanoparticles were studied using different parameters such as H 2O 2 content, superoxide dismutase and catalase activity, lipid peroxidation, total proline, photosynthetic pigment and anthocyanin content. The results indicated that while Al 2O 3 nanoparticles caused a dose dependent increase in H 2O 2 content, superoxide dismutase activity, lipid peroxidation and proline contents, the catalase activity was decreased in compare the control. Moreover, total chlorophyll, chlorophyll a, carotenoids and anthocyanin contents reduced in the highest concentration 50 mg mL ?1. In conclusion, Al 2O 3 nanoparticles caused oxidative stress in wheat after 96 h. 相似文献
5.
This study provides the first proof of the novel application of bismuth oxide as a radiosensitiser. It was shown that on the highly radioresistant 9L gliosarcoma cell line, bismuth oxide nanoparticles sensitise to both kilovoltage (kVp) or megavoltage (MV) X-rays radiation. 9L cells were exposed to a concentration of 50 μg.mL −1 of nanoparticle before irradiation at 125 kVp and 10 MV. Sensitisation enhancement ratios of 1.48 and 1.25 for 125 kVp and 10 MV were obtained in vitro, respectively. The radiation enhancement of the nanoparticles is postulated to be a combination of the high Z nature of the bismuth ( Z = 83), and the surface chemistry. Monte Carlo simulations were performed to elucidate the physical interactions between the incident radiation and the nanoparticle. The results of this work show that Bi 2O 3 nanoparticles increase the radiosensitivity of 9L gliosarcoma tumour cells for both kVp and MV energies. Monte Carlo simulations demonstrate the advantage of a platelet morphology. 相似文献
6.
Metal-dielectric-graphene hybrid heterostructures based on oxides Al2O3, HfO2, and ZrO2 as well as on complementary metal–oxide–semiconductor compatible dielectric Si3N4 covering plasmonic metals Cu and Ag have been fabricated and studied. We show that the characteristics of these heterostructures are important for surface plasmon resonance biosensing (such as minimum reflectivity, sharp phase changes, resonance full width at half minimum and resonance sensitivity to refractive index unit (RIU) changes) can be significantly improved by adding dielectric/graphene layers. We demonstrate maximum plasmon resonance spectral sensitivity of more than 30,000 nm/RIU for Cu/Al2O3 (ZrO2, Si3N4), Ag/Si3N4 bilayers and Cu/dielectric/graphene three-layers for near-infrared wavelengths. The sensitivities of the fabricated heterostructures were?~?5–8 times higher than those of bare Cu or Ag thin films. We also found that the width of the plasmon resonance reflectivity curves can be reduced by adding dielectric/graphene layers. An unexpected blueshift of the plasmon resonance spectral position was observed after covering noble metals with high-index dielectric/graphene heterostructures. We suggest that the observed blueshift and a large enhancement of surface plasmon resonance sensitivity in metal-dielectric-graphene hybrid heterostructures are produced by stationary surface dipoles which generate a strong electric field concentrated at the very thin top dielectric/graphene layer. 相似文献
7.
Modern electronics and electrical systems demand efficient operation of dielectric polymer‐based capacitors at high electric fields and elevated temperatures. Here, polyimide (PI) dielectric composites prepared from in situ polymerization in the presence of inorganic nanofillers are reported. The systematic manipulation of the dielectric constant and bandgap of the inorganic fillers, including Al 2O 3, HfO 2, TiO 2, and boron nitride nanosheets, reveals the dominant role of the bandgap of the fillers in determining and improving the high‐temperature capacitive performance of the polymer composites, which is very different from the design principle of the dielectric polymer composites operating at ambient temperature. The Al 2O 3‐ and HfO 2‐based PI composites with concomitantly large bandgap and moderate dielectric constants exhibit substantial improvement in the breakdown strength, discharged energy density, and charge–discharge efficiency when compared to the state‐of‐the‐art dielectric polymers. The work provides a design paradigm for high‐performance dielectric polymer nanocomposites for electrical energy storage at elevated temperatures. 相似文献
8.
PurposeTitanium dioxide nanoparticles (TiO 2 NPs) have been investigated for their role as radiosensitisers for radiation therapy. The study aims to increase the efficiency of these NPs by synthesising them with samarium. MethodsSamarium-doped TiO 2 NPs (Ti(Sm)O 2 NPs) were synthesised using a solvothermal method. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and energy-dispersive X-ray spectroscopy (EDS) were performed for characterising of the Ti(Sm)O 2 NPs. The intracellular uptake and cytotoxicity were assessed in vitro using A549 and DU145 cancer cell lines. Furthermore, the effect of dose enhancement and generation of reactive oxygen species (ROS) in response to 6 MV X-rays was evaluated. Additionally, the image contrast properties were investigated using computed tomography (CT) images. ResultsThe synthesised Ti(Sm)O 2 NPs were about 13 nm in diameter as determined by TEM. The XRD pattern of Ti(Sm)O 2 NPs was consistent with that of anatase-type TiO 2. EDS confirmed the presence of samarium in the nanoparticles. At 200 μg/ml concentration, no differences in cellular uptake and cytotoxicity were observed between TiO 2 NPs and Ti(Sm)O 2 NPs in both A549 and DU145 cells. However, the combination of Ti(Sm)O 2 NPs and X-rays elicited higher cytotoxic effect and ROS generation in the cells than that with TiO 2 NPs and X-rays. The CT numbers of Ti(Sm)O 2 NPs were systematically higher than that of TiO 2 NPs. ConclusionsThe Ti(Sm)O 2 NPs increased the dose enhancement of MV X-ray beams than that elicited by TiO 2 NPs. Samarium improved the efficiency of TiO 2 NPs as potential radiosensitising agent. 相似文献
9.
One of the main mechanisms of nanoparticle toxicity is known to be the generation of reactive oxygen species (ROS) which primarily damage cell membranes. However, very limited data on membrane effects in anaerobic environments (where ROS could not be the cause of membrane damage) are available. In the following study, rumen anaerobe Ruminococcus flavefaciens 007C was used as a bacterial model to assess the potential effects of Al 2O 3 and TiO 2 nanoparticles on membranes in an anaerobic environment. Fatty acid profiles of cultures after exposure to Al 2O 3 or TiO 2 nanoparticles were analyzed and compared with the profiles of non-exposed cultures or cultures exposed to bulk materials. Analysis revealed dose–effect changes in membrane composition exclusively when cells were exposed to Al 2O 3 nanoparticles in a concentration range of 3–5 g/L, but were not present in cultures exposed to bulk material. On the other hand, the tested concentrations of nano-TiO 2 did not significantly affect the membrane profile of the exposed bacterium. The results suggest the possibility that Al 2O 3 induces changes in bacterial membranes by direct physical interaction, which was supported by TEM image analysis. 相似文献
10.
This article focuses on the effect of monovalent cation doping on the optical properties of rare earth (RE = Eu 3+, Tb 3+) co-doped Ca 14Zn 6Al 10O 35 which has been synthesized by a low temperature combustion method. Crystalline phase of the Ca 14Zn 6Al 10O 35 phosphor was examined and confirmed by X-ray diffraction measurement. Under near-ultraviolet light excitation Eu 3+-doped Ca 14Zn 6Al 10O 35 phosphor exhibit characterization of Eu 3+ emission bands that are located at a maximum wavelength ( λmax) of approximately 470 nm and other peaks centred at 593 nm and 615 nm, respectively. With Tb 3+-doped Ca 14Zn 6Al 10O 35 phosphor showing a green emission band centred at 544 nm under near-ultraviolet range. Furthermore, we studied the energy transfer process in Eu 3+/Tb 3+pair and enhancement in photoluminescence (PL) intensity with doping different charge compensation. Here we obtained the optimum PL emission intensity of the phosphor in broad and intense visible spectral range which may be significant for the fabrication of white light emitting diodes (WLEDs). 相似文献
11.
AimThis work is focused on the Monte Carlo microdosimetric calculations taking into account the influence of the AuNPs’ shape, size and mass concentration on the radiation dose enhancement for the high-energy 6 MV and 18 MV X-ray therapeutic beams from a medical linac. BackgroundDue to a high atomic number and the photoelectric effect, gold nanoparticles can significantly enhance doses of ionizing radiation. However, this enhancement depends upon several parameters, such as, inter alia, nanoparticles’ shape etc. MethodThe simulated system was composed of the therapeutic beam, a water phantom with the target volume (with and without AuNPs) located at the depth of the maximum dose, i.e. at 1.5 cm for the 6 MV beam and at 3.5 cm for the 18 MV one. In the study the GEANT4 code was used because it makes it possible to get a very short step of simulation which is required in case of simulating the radiation interactions with nanostructures. ResultsThe dependence between the dose increase and the mass concentration of gold was determined and described by a simple mathematical formula for three different shapes of gold nanoparticles — two nanorods of different sizes and a flat 2D structure. The dose increase with the saturation occurring with the increasing mass concentration of gold was observed. ConclusionsIt was found that relatively large cylindrical gold nanoparticles can limit the increase of the dose absorbed in the target volume much more than the large 2D gold nanostructure. 相似文献
12.
A clear understanding of physicochemical factors governing nanoparticle toxicity is still in its infancy. We used a systematic approach to delineate physicochemical properties of nanoparticles that govern cytotoxicity. The cytotoxicity of fourth period metal oxide nanoparticles (NPs): TiO 2, Cr 2O 3, Mn 2O 3, Fe 2O 3, NiO, CuO, and ZnO increases with the atomic number of the transition metal oxide. This trend was not cell-type specific, as observed in non-transformed human lung cells (BEAS-2B) and human bronchoalveolar carcinoma-derived cells (A549). Addition of NPs to the cell culture medium did not significantly alter pH. Physiochemical properties were assessed to discover the determinants of cytotoxicity: (1) point-of-zero charge (PZC) (i.e., isoelectric point) described the surface charge of NPs in cytosolic and lysosomal compartments; (2) relative number of available binding sites on the NP surface quantified by X-ray photoelectron spectroscopy was used to estimate the probability of biomolecular interactions on the particle surface; (3) band-gap energy measurements to predict electron abstraction from NPs which might lead to oxidative stress and subsequent cell death; and (4) ion dissolution. Our results indicate that cytotoxicity is a function of particle surface charge, the relative number of available surface binding sites, and metal ion dissolution from NPs. These findings provide a physicochemical basis for both risk assessment and the design of safer nanomaterials. 相似文献
13.
探明峡谷型喀斯特土壤矿物质的分布规律可以为喀斯特地区植被恢复和生态重建提供参考。基于动态监测样地(200 m×300 m)的网格取样,采用经典统计分析和地统计学方法分析土壤矿物质(SiO2、Fe2O3、CaO、MgO、Al2O3、MnO)的空间分布特征。结果表明,研究区土壤矿物质含量差异较大,但变异系数不大,SiO2和Al2O3占了土壤矿物质总量的85.99%;SiO2、Al2O3、MgO、MnO均服从正态分布,Fe2O3、CaO分别经过平方和倒数转换后也服从正态分布。土壤各矿物质半变异函数的最佳拟合模型均为指数模型,块金值与基台值比C0/(C0+C)均较小,具有中等或强烈的空间相关性,表明空间变异主要由结构性因素引起;Al2O3和MnO的变程较大,空间连续性较好,其它矿物质的变程较小且相近,空间依赖性较强;Kriging等值线图表明峡谷型喀斯特区土壤SiO2和MnO具有相似的空间分布,受坡位和人为干扰共同影响,基本呈现坡顶高、坡脚低的分布格局;Fe2O3、CaO和MgO的空间分布也相似,斑块较破碎,主要受地形的影响;Al2O3的空间格局呈单峰分布,沿海拔的升高而升高。因此,减少干扰、增加植被覆盖对土壤矿物质具有良好的保持和调控作用。 相似文献
14.
Recent improvements to SrAl 2O 4:Eu 2+, Dy 3+ phosphors have enabled the use of luminescent hosts with a stable crystal structure and high physical and chemical stability, thus overcoming the bottleneck in the applicability of ZnS:Cu phosphors. However, enhancement of afterglow lifetime and brightness in SrAl 2O 4:Eu 2+, Dy 3+ phosphors remains a challenging task. Here, we have improved the afterglow characteristics in terms of persistence time and brightness by a systematic investigation of the composition of Eu-doped alkaline earth aluminate SrAl 2O 4:Eu 2+, Dy 3+ crystals. We found that a Dy 3+/Eu 2+ ratio of ~2.4 and ~0.935 mol Eu 2+ (per mol of SrAl 2O 4) gave the brightest and longest emissions (11% and 9% increase for each). Doping with Si 4+ also resulted in a slight increase in brightness up to ~15%. Doping with alkali metal or alkaline earth metal significantly enhanced the phosphorescence intensity. In particular, doping with 0.005 mol Li + (per mol of SrAl 2O 4) alone boosted the phosphorescence intensity to 239% of the initial value, as compared to that observed for the non-doped crystal, while doping with 0.01 mol Mg 2+ and 0.005 mol Li + (per 1 mol SrAl 2O 4) boosted the phosphorescence intensity up to 313% of the initial value. The results of this investigation are expected to act as a guideline for the synthesis of bright and long persistent phosphors, and facilitate the development of persistent phosphors with afterglow characteristics superior to those of conventional phosphors. 相似文献
15.
Recognizing the severity of metal corrosion problems in animal buildings has prompted an attempt to finally determine the fundamental causes of corrosion. Based on a two-year field test, this paper investigated the corrosion mechanisms of various metal products exposed in three animal buildings by analyzing the composition of corrosion products, using advanced material surface analysis techniques, including energy dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) analyses. Data from these analyses showed that the corrosion products were mainly iron oxides (Fe 2O 3, Fe 3O 4, and FeO) on uncoated 1010 carbon steel and zinc oxides, sulfides, and carbonates on galvanized steel and galvalume (ZnO, ZnS, Zn(CO) 3, and Al 2O 3). Thus, it could be concluded that the fundamental mechanisms of metal corrosion in animal buildings are similar to the classic corrosion mechanisms and the high corrosion rates of metal products in animal buildings are due to the presence of high moisture levels. 相似文献
16.
A low-cost green and reproducible microbe ( Lactobacillus sp.)-mediated biosynthesis of Sb 2O 3 nanoparticles is reported. The synthesis was performed at around room temperature. X-ray and transmission electron microscopy analyses were performed to ascertain the formation of Sb 2O 3 nanoparticles. X-ray analysis indicated that Sb 2O 3 nanoparticles had a face-centered cubic unit cell structure. Individual nanoparticles as well as a few aggregates of 3–12 nm were found. A possible mechanism for the synthesis of nano Sb 2O 3 is proposed. 相似文献
17.
Glasses in the system xGd 2O 3·(100-x)[GeO 2·V 2O 5] with 0 ≤ × ≤ 20 mol% have been prepared from the melt quenching method. In this paper, we investigated changes in germanium
coordination number in gadolinium-vanadate-germanate glasses through molar volume analysis, measurements of densities, investigations
of FTIR and UV-VIS spectroscopy, calculations of density functional theory (DFT). Analyzing the structural changes resulted
from the IR spectra we found that the gadolinium ions have a pronounced affinity toward [VO 4] structural units which contain non-bridging oxygens necessary for the charge compensation. The introduction of the excess
of oxygen yields the formation of [VO 5] structural units. This attains maximum value at 5 mol% Gd 2O 3, in agreement with the density measurements. Further, the addition of the surplus of oxygen implies the transformation of
[VO 5] to [VO 4] structural units and the formation of VO 4−3 orthovanadate structural units. The UV-VIS spectra show a broad UV absorption band located in the 300–500 nm region. These
bands are assumed to originate from the combination of vanadium ions possibly present in the three states of valence. The
presence of Ge-Ge wrong bonds attains its maximum values in the samples with x = 5 and 15 mol% Gd 2O 3 (bands centered in the 250–300 nm range). DFT calculations show the massive vibrations of the [VO n] structural units coupled with each other via [GeO 6] and [GeO 4] structural units. This leads to the splitting of the bridge modes and a multiplication of the number of these bands. 相似文献
18.
A series of Mg 2Y 2Al 2Si 2O 12:Dy 3+,Eu 3+ was prepared using a solid-state method, and the phosphor emitted white light by tuning the ratio of Dy 3+/Eu 3+. The effects of La 3+/Lu 3+ on the structure and luminescence properties of Mg 2Y 2Al 2Si 2O 12:Dy 3+,Eu 3+ were explored. Under the influence of bond length and twist, the luminescence intensity of the materials increased first and then decreased under excitation with ultraviolet light. The lattice distortion of the trivalent cation La 3+-substituted Mg 2Y 2Al 2Si 2O 12:Dy 3+ and Eu 3+ phosphors was reduced, the symmetry of polyhedron occupied by the luminescence centre improved, and the thermal stability of the luminescence centre improved to a certain extent. White light emitting diodes (LEDs) were fabricated by combining a 370 nm LED chip and the Mg 2Y 2Al 2Si 2O 12:Dy 3+,Eu 3+,La 3+ (Mg 2Y 2Al 2Si 2O 12:Dy 3+,Eu 3+,Lu 3+) phosphor. The results showed that Mg 2Y 2Al 2Si 2O 12:Dy 3+,Eu 3+,La 3+/Lu 3+ may have potential application in the area of white LEDs. 相似文献
19.
Well-defined Pt monodispersed nanoparticles within the catalytically relevant 1–10 nm size regime were synthesized in solution phase by several synthetic methods which differed in the choice of reducing agent, surface stabilizer, reaction temperature and solvent. Three-dimensional model catalysts were fabricated by incorporating the metal nanoparticles into ordered channels of high surface area mesoporous oxides such as SiO 2, Al 2O 3 and Ta 2O 5 through either sonication or direct synthesis of the oxide support around the particles. Deposition of the same nanocrystals onto silica supports by means of the Langmuir–Schaeffer technique produced two-dimensional model catalysts. 相似文献
20.
The application of nanoparticles (NPs) in radiotherapy is an increasingly attractive technique to improve clinical outcomes. The internalisation of NPs within the tumour cells enables an increased radiation dose to critical cellular structures. The purpose of this study is to investigate, by means of Geant4 simulations, the dose enhancement within a cell population irradiated with a 150 kVp photon field in the presence of a varying concentration of tantalum pentoxide (Ta 2O 5) NP aggregates, experimentally observed to form shells within tumour cells. This scenario is compared to the more traditionally simulated homogeneous solution of NP material in water with the same weight fraction of Ta 2O 5, as well as to a cell population without NPs present. The production of secondary electrons is enhanced by increased photoelectric effect interactions within the high-Z material and this is examined in terms of their kinetic energy spectra and linear energy transfer (LET) with various NP distributions compared to water. Our results indicate that the shell formation scenario limits the dose enhancement at 150 kVp. The underlying mechanism for this limit is discussed. 相似文献
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