共查询到20条相似文献,搜索用时 15 毫秒
1.
One of the technologically most important requirements for the application of oxide-supported metal nanoparticles (NPs) in the fields of molecular electronics, plasmonics, and catalysis is the achievement of thermally stable systems. For this purpose, a thorough understanding of the different pathways underlying thermally-driven coarsening phenomena, and the effect of the nanoparticle synthesis method, support morphology, and degree of support reduction on NP sintering is needed. In this study, the sintering of supported metal NPs has been monitored via scanning tunneling microscopy combined with simulations following the Ostwald ripening and diffusion-coalescence models. Modifications were introduced to the diffusion-coalescence model to incorporate the correct temperature dependence and energetics. Such methods were applied to describe coarsening phenomena of physical-vapor deposited (PVD) and micellar Pt NPs supported on TiO2(110). The TiO2(110) substrates were exposed to different pre-treatments, leading to reduced, oxidized and polymer-modified TiO2 surfaces. Such pre-treatments were found to affect the coarsening behavior of the NPs.No coarsening was observed for the micellar Pt NPs, maintaining their as-prepared size of ~ 3 nm after annealing in UHV at 1060 °C. Regardless of the initial substrate pre-treatment, the average size of the PVD-grown NPs was found to increase after identical thermal cycles, namely, from 0.5 ± 0.2 nm to 1.0 ± 0.3 nm for pristine TiO2, and from 0.8 ± 0.3 nm to 1.3 ± 0.6 nm for polymer-coated TiO2 after identical thermal treatments. Although no direct real-time in situ microscopic evidence is available to determine the dominant coarsening mechanism of the PVD NPs unequivocally, our simulations following the diffusion-coalescence coarsening route were in significantly better agreement with the experimental data as compared to those based on the Ostwald-ripening model. The enhanced thermal stability of the micellar NPs as compared to the PVD clusters might be related to their initial larger NP size, narrower size distribution, and larger interparticle distances. 相似文献
2.
《Ultrasonics sonochemistry》2014,21(5):1624-1628
In this study, we applied sonodynamic therapy to cancer cells based on the delivery of titanium dioxide (TiO2) nanoparticles (NPs) modified with avidin protein, which preferentially discriminated cancerous cells from healthy cells. Subsequently, hydroxyl radicals were generated from the TiO2 NPs after activation by external ultrasound irradiation (TiO2/US treatment). Although 30% of the normal breast cells (human mammary epithelial cells) exhibited the uptake of avidin-modified TiO2 NPs, over 80% of the breast cancer cells (MCF-7) exhibited the uptake of avidin-TiO2 NPs. Next the effect of the TiO2/US treatment on MCF-7 cell growth was examined for up to 96 h after 1-MHz ultrasound was applied (0.1 W/cm2, 30 s) to cells that incorporated the TiO2 NPs. No apparent cell injury was observed until 24 h after the treatment, but the viable cell concentration declined to 68% compared with the control at 96 h. 相似文献
3.
Ihor Semkiv Hryhoriy Ilchuk Marek Pawlowski Viktor Kusnezh 《Opto-Electronics Review》2017,25(1):37-40
The Ag8SnSe6 argyrodite compound was synthesized by the direct melting of the elementary Ag, Sn and Se high purity grade stoichiometric mixture in a sealed silica ampoule. The prepared polycrystalline material was characterized by the X-ray diffraction (XRD), visible (VIS) and near-infrared (NIR) reflection and photoluminescence (PL) spectroscopy. XRD showed that the Ag8SnSe6 crystallizes in orthorhombic structure, Pmn21 space group with lattice parameters: а = 7.89052(6) Å, b = 7.78976(6) Å, c = 11.02717(8) Å. Photoluminescence spectra of the Ag8SnSe6 polycrystalline wafer show two bands at 1675 nm and 1460 nm. Absorption edge position estimated from optical reflectance spectra is located in the 1413–1540 nm wavelength range. 相似文献
4.
K. Gawlinska A. Iwan Z. Starowicz G. Kulesza-Matlak K. Stan-Glowinska M. Janusz M. Lipinski B. Boharewicz I. Tazbir A. Sikora 《Opto-Electronics Review》2017,25(4):274-284
In this work, two thermal- and air-stable, hole transporting materials (HTM) in perovskite solar cells are analyzed. Those obtained and investigated materials were two polyazomethines: the first one with three thiophene rings and 3,3′-dimethoxybenzidine moieties (S9) and the second one with three thiophene rings and fluorene moieties (S7). Furthermore, presented polyazomethines were characterized by Fourier transform infrared spectroscopy (FTIR), UV–vis spectroscopy, atomic force microscopy (AFM) and thermogravimetric analysis (TGA) experiments. Both polyazomethines (S7 and S9) possessed good thermal stability with a 5% weight loss at 406 and 377 °C, respectively. The conductivity of S7 was two orders of magnitude higher than for S9 polymer (2.7 × 10?8 S/cm, and 2.6 × 10?10 S/cm, respectively). Moreover, polyazomethine S9 exhibited 31 nm bathochromic shift of the absorption band maximum compared to S7.Obtained perovskite was investigated by UV–vis and XRD. Electrical parameters of perovskite solar cells (PSC) were investigated at Standard Test Conditions (STC). It was found that both polyazomethines protect perovskite which is confirmed by ageing test where Voc did not decrease significantly for solar cells with HTM in contrast to solar cell without hole conductor, where Voc decrease was substantial. The best photoconversion efficiency (PCE = 6.9%), among two investigated in this work polyazomethines, was obtained for device with the following architectures FTO/TiO2/TiO2 + perovskite/S7/Au. Stability test proved the procreative effects of polyazomethines on perovskite absorber. 相似文献
5.
《Photonics and Nanostructures》2014,12(2):205-211
A highly birefringent dispersion compensating hybrid photonic crystal fiber is presented. This fiber successfully compensates the chromatic dispersion of standard single mode fiber over E- to L-communication bands. Simulation results reveal that it is possible to obtain a large negative dispersion coefficient of about −1054.4 ps/(nm km) and a relative dispersion slope of 0.0036 nm−1 at the 1550 nm wavelength. The proposed fiber simultaneously provides a high birefringence of order 3.45 × 10−2 at the 1550 nm. Moreover, it is confirmed that the designed fiber successfully operates as a single mode in the entire band of interest. For practical conditions, the sensitivity of the fibers dispersion properties to a ±2% variation around the optimum values is carefully studied and the nonlinearity of the proposed fiber is also reported and discussed. Such fibers are essential for high speed transmission system as a dispersion compensator, sensing applications, fiber loop mirrors as well as maintaining single polarization, and many nonlinear applications such as four-wave mixing, etc. 相似文献
6.
《Ultrasonics sonochemistry》2014,21(1):289-294
The present study demonstrated the enhanced hydroxyl (OH) radical generation by combined use of dual-frequency (0.5 MHz and 1 MHz) ultrasound (US) and titanium dioxide (TiO2) nanoparticles (NPs) as sonocatalyst. The OH radical generation became the maximum, when 0.5 MHz US was irradiated at an intensity of 0.8 W/cm2 and 1 MHz US was irradiated at intensities at 0.4 W/cm2 in the presence of TiO2 NPs under the examined conditions. After incorporation of TiO2 NPs modified with targeting protein pre-S1/S2, HepG2 cancer cells were subjected to the dual-frequency US at optimum irradiation intensities (“targeted-TiO2/dual-US treatment”). Growth of the HepG2 cells was reduced by 46% compared with the control condition after irradiation of dual-frequency US for 60 s with TiO2 NPs incorporation. In contrast, HepG2 cell growth was almost the same as that in the control condition when cells were irradiated with either 0.5 MHz or 1 MHz ultrasound alone without TiO2 NP incorporation. 相似文献
7.
We have compared the adsorption properties of small Aun (n = 1–8) nanoparticles on the defect-free (stoichiometric) and defective (partially reduced) brookite TiO2(210) and anatase TiO2(101) surfaces using density functional theory calculations. The interaction between Au atoms and anatase TiO2(101) was determined to be quite weak and small Aun particles grown at defects (O vacancies) prefer extended 2D structures. By contrast, dispersion and 3D configurations appear to be favored at brookite TiO2(210) for Aun nanoparticles due to their strong interaction. Calculations of CO oxidation at Aun (n = 6–8) particles supported at defective brookite TiO2(210) show that occurrence of protruding low-coordinated Au atoms is essential for favorable CO adsorption and subsequent reaction with O2. In particular, the configuration of the Aun nanoparticles can determine the energetics in the formation of active Au atoms, and their mobility also affects the reaction between CO and O2 (or O). 相似文献
8.
John T. Yates 《Surface science》2009,603(10-12):1605-1612
Photochemistry from TiO2 surfaces is described for two cases: The UV-induced photodesorption of O2 from TiO2(1 1 0) – 1 × 1; and the hydrophilic effect caused by UV irradiation on TiO2. In both cases fundamental information about how these processes occur has been found. In the case of the O2 photodesorption kinetics, it has been found that the rate of the process is proportional to the square root of the UV flux, showing that second-order electron–hole pair recombination is dominant in governing the photodesorption rate. In addition these measurements provide an estimate of the concentration of hole traps in the TiO2 crystal. In other measurements of the UV-induced hydrophilicity, starting with the atomically-clean TiO2 surface, it has been shown that the effect occurs suddenly at a critical point during irradiation as a result of photooxidation of a monolayer of hydrocarbon (n-hexane) at equilibrium with ppm concentration of n-hexane in O2 at 1 atmosphere pressure. 相似文献
9.
V.M. Kalygina I.S. Egorova I.A. Prudaev O.P. Tolbanov V.V. Atuchin 《Chinese Journal of Physics (Taipei)》2017,55(1):59-63
The conduction model has been proposed for the metal-TiO2–Si (MIS) structures. Rutile films have been prepared on Si substrates by magnetron sputtering of TiO2 target and annealing in the air at temperatures T?=?800 and 1050 K. The current-voltage (CVC) and capacitance-voltage characteristics of the structures have been measured over the range of T?=?283–363 K. At positive potentials on the gate, the conductivity of the MIS structures is determined by the space charge-limited current in the dielectric layer. 相似文献
10.
《Ultrasonics sonochemistry》2014,21(1):317-323
We demonstrate a facile one-step method to synthesize Ni@Pt core–shell nanoparticles (NPs) with a control over the shape and the Pt-shell thickness of the NPs. By adjusting the relative reactivity of the Pt and Ni reagents in ultrasound-assisted polyol reactions, two Ni@Pt NP samples of the same composition (Ni/Pt = 1) and size (3–4 nm) but with different particle shape (octahedral vs. truncated octahedral) and different Pt-shell thicknesses (1–2 vs. 2–3 monolayer) are obtained. The control is achieved by using different Ni reagents, Ni(acac)2 (acac = acetylacetonate) and Ni(hfac)2 (hfac = hexafluoroacetylacetonate). A reaction mechanism that can explain all of the observations is proposed. The Ni@Pt NPs show up to threefold higher mass activity than pure Pt NPs in oxygen reduction reaction. Between the two Ni@Pt NP samples, the one composed of octahedral NPs with the thicker Pt-shell has higher activity than the other. 相似文献
11.
《Ultrasonics sonochemistry》2014,21(4):1284-1288
TiO2–WO3 heterostructures were synthesized at room temperature, ambient pressure, and short reaction time via a sonochemical approach. TEM and EDX images show that the prepared TiO2–WO3 heterostructures consist of globular agglomerates (∼250 nm in diameter) composed of very small (<5 nm) dense particles (WO3) dispersed inside the globules. The observed less intense monoclinic WO3 diffraction peak (around 2θ = 22° belonging to (0 0 1) plane) and the high intense hexagonal WO3 diffraction peak (around 2θ = 28° belonging to (2 0 0) plane) in XRD indicate that there may be phase transition occurring due to the formation of intimate bond between TiO2 and WO3. In addition, the formation of such new phase was also observed from Raman spectra with a new peak at 955 cm−1, which is due to the symmetric stretching of W = O terminal. The catalytic activity of TiO2–WO3 heterostructures was tested for the degradation of wastewater pollutant containing Tergitol (NP-9) by a process combined with ozonation and it showed two-fold degradation rate compared with ozone process alone. 相似文献
12.
W.A. Pisarski J. Pisarska R. Lisiecki W. Ryba-Romanowski 《Opto-Electronics Review》2017,25(3):238-241
Erbium-doped lead silicate glass has been investigated for near-infrared emission and up-conversion applications. Near-infrared emission due to 4I13/2 → 4I15/2 transition of Er3+ is relatively broad (70.5 nm) and long-lived (3.7 ms). Also, up-conversion luminescence spectra of Er3+ ions in lead silicate glass have been examined as a function of temperature. The relative intensities of luminescence bands corresponding to 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions of Er3+ were determined with temperature. The fluorescence intensity ratio and temperature sensitivity were calculated. The maximum sensitivity for Er3+ doped lead silicate glass is close to 26.4 × 10?4 K?1 at T = 590 K. 相似文献
13.
《Solid State Ionics》2006,177(3-4):237-244
Ongoing studies of the KHSeO4–KH2PO4 system aiming at developing novel proton conducting solids resulted in the new compound K2(HSeO4)1.5(H2PO4)0.5 (dipotassium hydrogenselenate dihydrogenphosphate). The crystals were prepared by a slow evaporation of an aqueous solution at room temperature. The structural properties of the crystals were characterized by single-crystal X-ray analysis: K2(HSeO4)1.5(H2PO4)0.5 (denoted KHSeP) crystallizes in the space group P 1¯ with the lattice parameters: a = 7.417(3) Å, b = 7.668(2) Å, c = 7.744(5) Å, α = 71.59(3)°, β = 87.71(4)° and γ = 86.04(6)°. This structure is characterized by HSeO4− and disordered (HxSe/P)O4− tetrahedra connected to dimers via hydrogen bridges. These dimers are linked and stabilized by additional hydrogen bonds (O–H–O) and hydrogen bridges (O–H…O) to build chains of dimers which are parallel to the [0, 1, 0] direction at the position x = 0.5.The differential scanning calorimetry diagram showed two anomalies at 493 and 563 K. These transitions were also characterized by optical birefringence, impedance and modulus spectroscopy techniques. The conductivity relaxation parameters of the proton conductors in this compound were determined in a wide temperature range. The transport properties in this material are assumed to be due to H+ protons hopping mechanism. 相似文献
14.
The super-hydrophobic and IR-reflectivity hollow glass microspheres (HGM) was synthesized by being coated with anatase TiO2 and a super-hydrophobic material. The super-hydrophobic self-cleaning property prolong the life time of the IR reflectivity. TBT and PFOTES were firstly applied and hydrolyzed on HGM and then underwent hydrothermal reaction to synthesis anatase TiO2 film. For comparison, the PFOTES/TiO2 mutual-coated HGM (MCHGM), PFOTES single-coated HGM (F-SCHGM) and TiO2 single-coated HGM (Ti-SCHGM) were synthesized as well. The MCHGM had bigger contact angle (153°) but smaller sliding angle (16°) than F-SCHGM (contact angle: 141.2°; sliding angle: 67°). Ti-SCHGM and MCHGM both showed similar IR reflectivity with ca. 5.8% increase compared with original HGM and F-SCHGM. For the thermal conductivity, coefficients of F-SCHGM (0.0479 W/(m K)) was basically equal to that of the original HGM (0.0475 W/(m K)). Negligible difference was found between the thermal conductivity coefficients of MCHGM-coated HGM (0.0543 W/(m K)) and Ti-SCHGM (0.0546 W/(m K)). 相似文献
15.
《Current Applied Physics》2010,10(5):1349-1353
Single crystals of semiorganic material calcium dibromide bis(glycine) tetrahydrate were grown from aqueous solution. The crystal belongs to monoclinic system, with a = 13.261(5) Å, b = 6.792(2) Å, c = 15.671(9) Å and β = 91.68(4)°. The presence of the elements in the title compound was confirmed by energy dispersive X-ray analysis. The solubility and metastable zone width were found. The grown crystals were tested by powder XRD, FTIR, Thermo Gravimetric and Differential Thermal Analysis, UV–vis–NIR analysis, dielectrical and mechanical studies. The transmittance of calcium dibromide bis(glycine) tetrahydrate crystal has been used to calculate the refractive index n, the extinction coefficient K and both the real ɛr and imaginary ɛi components of the dielectric constant as functions of wavelength. The optical band gap of calcium dibromide bis(glycine) tetrahydrate is 3.23 eV. 相似文献
16.
The Cr 2p and O 1s binding energy (BE) levels have been calculated by first principles methods for different models of hydroxylated (0001)-Cr2O3 surfaces. Several surface terminations have been considered. The calculations allow us to reproduce the O 1s shifts between O in oxide and OH groups. It is found that two main effects account for the OH binding energy shifts. On the one hand, the increased covalency of the O–H bond with respect to the Cr–O bond, lowers the electronic O (1s and 2p) energy, and in consequence the BE of the core levels (O 1s) are higher. On the other hand, the lower the OH coordination number, the higher the valence and core levels energy, and the lower the BE. Consequently, mono-coordinated hydroxyls have a binding energy near that of O2? in the oxide (ΔBEOH–O = ? 0.2–0.0 eV). Two-fold coordinated hydroxyls have a slightly higher BE (ΔBEOH–O = + 0.3 eV). Three-fold coordinated OH groups have a higher binding energy (ΔBEOH–O = + 0.6?0.7 eV), corresponding to that experimentally measured for OH groups. Finally, water adsorbed above OH groups exhibits a still higher BE (ΔBEHOH–O = + 0.9–1.0 eV). The ΔBE are slightly under-estimated under the initial state approximation, and overestimated under the final state (Z + 1) approximation. 相似文献
17.
Saadi Berri 《Chinese Journal of Physics (Taipei)》2017,55(1):195-202
The electronic structure and magnetic properties of the PtZrTiAl, PdZrTiAl and Pt0.5Pd0.5ZrTiAl Heusler alloys were investigated using the full-potential linearized augmented plane wave (FPLAPW) within the generalized gradient approximation (GGA). For the PtZrTiAl, and PdZrTiAl alloys, the results showed that these Heusler alloys were stable in the Type I structure. The (Pt, Pd)ZrTiAl Heusler alloys are found to exhibit half-metallic ferromagnetism for both the Type I and Type II structure. The total magnetic moments of the PtZrTiAl and PdZrTiAl alloys were obtained to be 3 μB per formula unit, which are in agreement with the Slater-Pauling rule mtot = (Nv ? 18). The half-metalliciy characteristic exists in the relatively wide ranges of 6.06–6.78 Å, and 6.13–6.73 Å for the PtZrTiAl and PdZrTiAl alloys, respectively. To complete the fundamental characteristics of these alloys, Pt0.5Pd0.5ZrTiAl is predicted to be a half-metallic ferromagnet with an energy gap of 0.90 eV in the minority spin and a complete spin polarization at the Fermi level. These new Heusler alloys may become ideal candidate material for future spintronic applications. 相似文献
18.
T.Y. Chen S.X. Huang Z. Tesanovic R.H. Liu X.H. Chen C.L. Chien 《Physica C: Superconductivity and its Applications》2009,469(9-12):521-528
The superconducting gap in FeAs-based superconductor SmFeAs(O1?xFx) (x = 0.15 and 0.30) and the temperature dependence of the sample with x = 0.15 have been measured by Andreev reflection spectroscopy. The intrinsic superconducting gap is independent of contacts while many other “gap-like” features vary appreciably for different contacts. The determined gap value of 2Δ = 13.34 ± 0.47 meV for SmFeAs(O0.85F0.15) gives 2Δ/kBTC = 3.68, close to the BCS prediction of 3.53. The superconducting gap decreases with temperature and vanishes at TC, in a manner similar to the BCS behavior but dramatically different from that of the nodal pseudogap behavior in cuprate superconductors. 相似文献
19.
《Current Applied Physics》2007,7(2):160-167
Color characteristics of the E- and O-modes in the fringe-field switching mode using the liquid crystal with negative dielectric anisotropy have been investigated. According to calculated and measured results for color shift up to 70° of polar angle in all directions, a cell with E-mode shows smaller color shift with varying viewing direction than a cell with O-mode in all grey levels, for instance, the color shift in a white state is much smaller in the E-mode (Δxy = 0.1819) than in the O-mode (Δxy = 0.0798). However, the color shift of the white state is strongly suppressed for both E-mode (Δxy = 0.0199) and O-mode (Δxy = 0.0093) with a dual domain structure. 相似文献
20.
M. Imaizumi T. Noji T. Adachi Y. Koike 《Physica C: Superconductivity and its Applications》2011,471(21-22):614-617
Annealing effects of FeSe1?xTex (0.6 ≦ x ≦ 1) single crystals have been investigated from measurements of the powder X-ray diffraction and specific heat. Through the annealing, several peaks of powder X-ray diffraction have become sharp and a clean jump of the specific-heat at the superconducting (SC) transition temperature, Tc, has been observed for x = 0.6–0.9, indicating bulk superconductivity. For annealed single-crystals of x = 0.6–0.8, the SC condensation energy, U0, and the SC gap, Δ0, at 0 K have been estimated as ~1.8 J/mol and 2.3–2.5 meV, respectively. The value of 2Δ0/kBTc is 3.9–4.5, indicating a little strong-coupling superconductivity. Both the electronic specific-heat coefficient in the normal state, γn, and the residual electronic specific-heat coefficient in the SC state, γ0, have been found to show significant x dependence. The values of γn are much larger than those estimated from the band calculation. 相似文献