共查询到20条相似文献,搜索用时 31 毫秒
1.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(42):13058-13062
This paper describes the introduction of a thin titanium dioxide interlayer that serves as passivation layer and dopant source for hematite (α‐Fe2O3) nanoarray photoanodes. This interlayer is demonstrated to boost the photocurrent by suppressing the substrate/hematite interfacial charge recombination, and to increase the electrical conductivity by enabling Ti4+ incorporation. The dendritic nanostructure of this photoanode with an increased solid–liquid junction area further improves the surface charge collection efficiency, generating a photocurrent of about 2.5 mA cm−2 at 1.23 V versus the reversible hydrogen electrode (vs. RHE) under air mass 1.5G illumination. A photocurrent of approximately 3.1 mA cm−2 at 1.23 V vs. RHE could be achieved by addition of an iron oxide hydroxide cocatalyst. 相似文献
2.
Dichroic Nd3+:Au–antimony glass (K2O–B2O3–Sb2O3) nanocomposites (NCs) have been synthesized by single-step melt-quench thermochemical reduction process. The UV–Vis–NIR spectra show surface plasmon resonance (SPR) band of Au0 nanoparticles (NPs) and absorption peaks of Nd3+ ions. XRD and SAED results indicate growth of Au0 NPs along (200) plane. TEM image reveals elliptical Au0 NPs having sizes 12–21 nm (aspect ratio ~1.2) responsible for the dichroic behavior. Photoluminescent upconversion under excitation at 805 nm exhibit two emission bands of Nd3+ ions at 540 (green) and 650 (red) nm due to 4G7/2 → 4I9/2 and 4G7/2 → 4I13/2 transitions respectively. Both bands undergo maximum 8 and 11 fold intensity enhancements respectively at 0.03 wt% Au0 (4.1 × 1018 atoms/cm3). Local field enhancement (LFE) induced by Au0 SPR and energy transfer (ET) from Au0 → Nd3+ is found to be responsible for enhancement while ET from Nd3+ → Au0 and optical re-absorption due to Au0 SPR for quenching. 相似文献
3.
Binding energy (BE) behavior and signal intensity as function of V conc. and ligands L were critically examined in Vn/SiO2 species (where n = +5, +4, and +3) and securing of optimized products and ESCA samples is described. The results moreover demonstrate conditions and approaches whereby ESCA can provide reliable information on highly diluted surface compound systems. From aquous media 1.0–1.2 wt. % VV and 0.4–1.2 wt. % VIII proved to be preferred ranges whereas in non aqueous (metalorganic) preparates the surprisingly low concentration of 0.4–0.15 wt. % VIII gave usable spectra and even 0.4 wt. % VV could be measured. ESCA data with the peroxo complex (?Si? O)3V? (O2) (I) confirmed these trends. Superiorly subdivided surface compounds (reflected in the quality of spectra) are obtainable from V[N(SiMe3)2]3 impregnations where 0.4–0.5 wt. % VIII (or VV) are maximum/optimum conc. limits. Evidence for formulating Vn/SiO2 as three legged surface compounds is summarized and diagnostic/predictive uses of the additivity principle for surface electron states illustrated. In the (?Si? O)3V? L series, where L = none, ?O, and ? (O2) positive ΔBE shifts for ?Si? O? V (0.7 eV); V?O (0.6 eV); and V? (O2) (0.4 eV) were estimated. Tentative BE contributions of some donor ligands (and ? Cl) are also suggested. In (I) ESCA indicated a formal oxidation state of approx. +4. Certain limits (precautions) with ESCA are noted and extensions of the additivity relationship discussed. 相似文献
4.
Lee-Jene Lai Yaw-Wen Yang Yao-Kwang Lin Li-Ling Huang Yi-Heui Hsieh 《Colloids and surfaces. B, Biointerfaces》2009,68(2):130-135
This investigation describes the surface characterization of rabbit immunoglobulin G (IgG) conjugated with gold nanoparticles. Goat anti-rabbit immunoglobulin G tagged with 5 nm gold nanoparticles was applied to detect the IgG. Then, the autocatalyzed deposition of Au3+ onto the surface of anti-IgGAu increased the surface area per gold nanoparticle. The immobilization chemistries and the atomic concentrations of Au4f, P2p, S2p, C1s, N1s and O1s of the resulting antibody-modified Au electrodes were determined by X-ray photoelectron spectroscopy (XPS). The sulfur that is involved in the cysteamine binding and the enlargement of the gold nanoparticles are identified using cyclic voltammetry. The results reveal that the surface area per gold particle, following the autocatalyzed deposition Au3+ on the surface of anti-IgGAu, was approximately seven times higher than that before deposition. 相似文献
5.
Glenna So Ming Tong Dr. Steven Chi Fai Kui Dr. Hsiu‐Yi Chao Dr. Nianyong Zhu Dr. Chi‐Ming Che Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(41):10777-10789
The complexes [Au3(dcmp)2][X]3 {dcmp=bis(dicyclohexylphosphinomethyl)cyclohexylphosphine; X=Cl? ( 1 ), ClO4? ( 2 ), OTf? ( 3 ), PF6? ( 4 ), SCN?( 5 )}, [Ag3(dcmp)2][ClO4]3 ( 6 ), and [Ag3(dcmp)2Cl2][ClO4] ( 7 ) were prepared and their structures were determined by X‐ray crystallography. Complexes 2 – 4 display a high‐energy emission band with λmax at 442–452 nm, whereas 1 and 5 display a low‐energy emission with λmax at 558–634 nm in both solid state and in dichloromethane at 298 K. The former is assigned to the 3[5dσ*6pσ] excited state of [Au3(dcmp)2]3+, whereas the latter is attributed to an exciplex formed between the 3[5dσ*6pσ] excited state of [Au3(dcmp)2]3+ and the counterions. In solid state, complex [Ag3(dcmp)2][ClO4]3 ( 6 ) displays an intense emission band at 375 nm with a Stokes shift of ≈7200 cm?1 from the 1[4dσ*→5pσ] absorption band at 295 nm. The 375 nm emission band is assigned to the emission directly from the 3[4dσ*5pσ] excited state of 6 . Density functional theory (DFT) calculations revealed that the absorption and emission energies are inversely proportional to the number of metal ions (n) in polynuclear AuI and AgI linear chain complexes without close metal???anion contacts. The emission energies are extrapolated to be 715 and 446 nm for the infinite linear AuI and AgI chains, respectively, at metal???metal distances of about 2.93–3.02 Å. A QM/MM calculation on the model [Au3(dcmp)2Cl2]+ system, with Au???Cl contacts of 2.90–3.10 Å, gave optimized Au???Au distances of 2.99–3.11 Å in its lowest triplet excited state and the emission energies were calculated to be at approximately 600–690 nm, which are assigned to a three‐coordinate AuI site with its spectroscopic properties affected by AuI???AuI interactions. 相似文献
6.
Dr. Mahdi Hesari Prof. Dr. Zhifeng Ding 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(60):14821-14825
Bright, near-infrared electrochemiluminescence (NIR–ECL) of Au18 nanoclusters is reported herein. Spooling ECL and photoluminescence spectroscopy were used to track and link NIR emissions at 832 and 848 nm to three emissive species, Au180*, Au181+* and Au182+*, with a considerably high ECL efficiency of 5.5 relative to that of the gold standard Ru(bpy)32+/TPrA (with 5–6 % reported ECL efficiency). The unprecedentedly high efficiency is due to the overlapped oxidation potentials of Au180 and tri-n-propylamine as co-reactant, the exposed facets of Au180 gold core, and electrocatalytic loops. These discoveries will add a new member to the efficient NIR-ECL gold nanoclusters family and bring more potential applications. 相似文献
7.
Tirtha Som Basudeb Karmakar 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(2):640-646
Dichroic Sm3+: Au-antimony glass nanocomposites are synthesized in a new reducing glass (dielectric) matrix (mol%) K2O–B2O3–Sb2O3 (KBS) by a single-step melt-quench technique involving selective thermochemical reduction. X-ray diffraction (XRD) and selected area electron diffraction (SAED) results indicate that Au0 nanoparticles are grown along the (2 0 0) plane direction. The transmission electron microscopic (TEM) image reveals the elliptical Au0 nanoparticles having major axis range 12–17 nm. Dichroic behavior is due to elliptical shape of Au0 nanoparticles of aspect ratio ~1.2. Au0 NPs of concentration of 0.03 wt% (4.1 × 1018 atoms/cm3) drastically enhances the intensity (~7-folds) of electric dipole 4G5/2 → 6H9/2 red transition (636 nm) of Sm3+ ions and then attenuates with further increase in Au0 concentration. The magnetic dipole 4G5/2 → 6H5/2 green (566 nm) and 4G5/2 → 6H7/2 orange (602 nm) transitions remain almost unaffected by presence of nano Au0. Local field enhancement (LFE) induced by Au0 SPR and energy transfer (ET) from fluorescent Au0 → Sm3+ ions are found to be responsible for the enhancement while reverse ET from Sm3+ → Au0 and optical re-absorption due to Au0 SPR for attenuation. 相似文献
8.
The geometrical structure and electronic properties of a series of Au N (N = 1–8) clusters supported on a Mg2+, Al3+-containing layered double hydroxides (MgAl–LDH) are investigated using density functional theory. The Au clusters are supported on two typical crystal faces of the LDH platelet, the basal {0001} and the lateral $ \{ 10\,\bar{1}\,0\} $ crystal face, respectively, corresponding to the top and edge site of monolayer MgAl–LDH lamella for the sake of simplicity. It is revealed that an increase in the charge transfer from the LDH lamella to the Au N clusters at the edge site rather than clusters on the top surface, demonstrating a preferential adsorption for Au N clusters at the edge of LDH lamella. Moreover, the calculated adsorption energy of the Au N clusters on the LDH lamella increases with the cluster size, irrespective of the adsorption site. The investigation on the interaction between O2 and Au N clusters on the LDH lamella is further carried out for understanding the catalytic oxidation properties of the LDH-supported Au catalyst. The formation of reactive O2 ? species, a necessary prerequisite in catalytic oxidation of CO, by O2 bridging two Au atoms of Au N clusters indicates that the LDH-supported Au catalyst has the required characteristics of a chemically active gold catalyst in CO oxidation. 相似文献
9.
《Electrochemistry communications》2000,2(7):503-507
The initial stage of gold oxide layer formation on the gold electrode surface was investigated in 0.5 M H2SO4. X-ray photoelectron spectroscopy (XPS) spectra of pure gold and the anodically polarized gold electrode surface were compared quantitatively. It was found that gold anodic polarization in the E range from ∼1.3 to 2.1 V causes increase in intensity of the XPS spectra at an electron binding energy εb=85.9 eV for gold and at εb=530 eV for oxygen. These εb values correspond to Au3+ and O2− oxidation states in hydrous or anhydrous gold oxide. The larger the amount of the anodically formed surface substance the higher is the intensity of the spectrum at the εb values mentioned above. It was concluded that gold anodic oxidation, yielding most likely an Au(III) hydroxide surface layer, takes place in the E range of the anodic current wave beginning at E≈1.3 V. At EB=1.7 V (the potential of the Burshtein minimum) the stationary surface layer consists of 2.5 to 3 molecular layers of Au(OH)3. The theoretical amount of charge required for the reduction of one molecular layer of Au(OH)3 is ∼0.15 mC cm−2, since the Au(OH)3 molecule is planar and occupies about four atomic sites on the electrode surface. 相似文献
10.
Qiongke Wang Yanfeng Chen Jiajie Xu Yue Situ Hong Huang 《Research on Chemical Intermediates》2018,44(4):2365-2378
Few reports have been published on the optimization of nanostructures while doping with the Ti (Ti3+/Ti4+) elemental. Here, Ti-doped α-Fe2O3 nanorod arrays prepared via the hydrothermal method with the addition of TiCl3 as the Ti source and urea as the morphological regulator were used as photoanodes in photoelectrochemical cells. In the process of a hydrothermal reaction, Ti elemental was incorporated into α-Fe2O3 photoanodes using TiCl3 as precursor and urea was used as the morphological regulator to assist α-Fe2O3 to form nanorod arrays. The photoelectrochemical performance of the as-prepared Ti-doped α-Fe2O3 nanorod array (TF1) photoanodes exhibited a remarkable photocurrent of 0.22 mA cm?2 (275 times higher than that of the undoped α-Fe2O3 nanorod arrays) at 1.23 V (vs. RHE) and a 150-mV cathodic shift of photocurrent onset potential. The enhanced photoelectrochemical performance was ascribed to the synergistic effect of the one-dimensional nanoarray structure and the Ti elemental doping, which increased donor density and reduced photogenerated electron–hole recombination. 相似文献
11.
采用沉积沉淀法制备了 CO 低温氧化催化剂 Au/α-Fe2O3, 通过 X 射线衍射、X 射线光电子能谱、N2 吸附-脱附、傅里叶变换红外光谱、H2 程序升温还原和 CO2 程序升温脱附等手段对催化剂进行了表征, 探讨了在室温大气气氛下光线照射以及表面吸附等环境因素所导致的催化剂存贮失活及其作用机理. 结果表明, 经 110 oC 干燥的 Au/α-Fe2O3催化剂表面同时存在 Au3+和 Auδ+ (0 ≤ δ ≤ 1) 物种, 且前者催化 CO 氧化的活性更高; 在室温大气气氛下, 紫外线照射会引起 Au3+的还原和 Au 颗粒的生长, 导致催化剂的不可逆失活. 此外, 空气中的 H2O 和 CO2 可同时吸附在 α-Fe2O3的表面, 形成表面碳酸盐物种, 会引起催化剂的可逆失活. 相似文献
12.
Y. Keriti A. Keffous K. Dib S. Djellab M. Trari 《Research on Chemical Intermediates》2018,44(3):1537-1550
The effect of Er3+ doping (1%) on the structural, optical and photocatalytic properties of In2O3 thin films deposited on quartz substrates by spin coating was investigated. The In2O3:1% Er3+ films, annealed in the temperature range 800–1000 °C, were characterized by X-ray diffraction, scanning electron microscopy (SEM), atomic force microscopy, UV–Vis spectroscopy, ellipsometry and photoluminescence (PL). The films are polycrystalline with a cubic structure and the lattice parameter increases with the incorporation of Er3+ owing to its larger radius. The SEM images of the film show a granular morphology with large grains (~ 200 nm). The doped In2O3 film exhibits less transparency than In2O3 in the UV–visible region with band gaps of 3.42 and 3.60 eV, respectively. PL shows strong lines at 548 and 567 nm, assigned to Er3+ under direct excitation at 532 nm. The energy diagram of the junction In2O3:1% Er3+/Na2SO4 (0.1 M) solution plotted from physical and photoelectrochemical characterizations shows the feasibility of the films for Rhodamine B (RhB) degradation under solar light. The conduction band at 2.22 V deriving from the In3+:5s orbital is suitably positioned with respect to the O2/O 2 · level (~ 1.40 VSCE), leading to oxidation of 32% of 10 ppm RhB within 40 min of solar irradiation. 相似文献
13.
V. V. Smirnov S. A. Nikolaev G. P. Murav’eva L. A. Tyurina A. Yu. Vasil’kov 《Kinetics and Catalysis》2007,48(2):265-270
Nanosized gold particles immobilized on γ-Al2O3 exhibited catalytic activity in the allylic isomerization reaction of allylbenzene. As the size of gold nanoparticles was decreased from 40 to 2 nm, their specific activity per surface gold atom nonmonotonically increased from 0.5 to 110 (mol products) (mol Ausurface)?1 h?1. The particles greater than 40 nm were practically inactive. 相似文献
14.
The growth and reduction of compact (α-) and overlying hydrous (β-) oxide films on polycrystalline Au electrodes in aqueous 0.1 M H2SO4 solutions have been investigated using potentiostatic, cyclic voltammetry, ellipsometric and quartz crystal microbalance (QCMB) techniques. All α-oxide films, formed with time at constant potentials up to 2.6 V, or by multicycling of the potential, are non-hydrated in nature, even when covered by a thick β-oxide film. The α-oxide film composition is suggested to be AuO below 1.5 V, and a mixture of AuO+Au2O3 at potentials above this, becoming predominantly Au2O3 at very high potentials. Up to three monolayers of Au2O3 can be formed. When formed at constant potential, the β-oxide film becomes increasingly hydrated as it thickens with time of growth, with a mass to charge ratio and refractive index consistent with Au2O3·H2O and later with Au2O3·2H2O. In contrast, the β-oxide film formed by multicycling has a higher mass overall, and becomes less hydrated as it thickens with time, with a mass and refractive index consistent with Au2O3·10H2O at short times, ranging to Au2O3·2H2O as the film thickens. 相似文献
15.
Using Fe3O4 nano-particles as seeds, a new type of Fe3O4/Au composite particles with core/shell structure and diameter of about 170 nm was prepared by reduction of Au3+ with hydroxylamine in an aqueous solution. Particle size analyzer and transmission electron microscope were used to analyze
the size distribution and microstructure of the particles in different conditions. The result showed that the magnetically
responsive property and suspension stability of Fe3O4 seeds as well as reduction conditions of Au3+to Au0are the main factors which are crucial for obtaining a colloid of the Fe3O4/Au composite particles with uniform particle dispersion, excellent stability, homogeneity in particle sizes, and effective
response to an external magnet in aqueous suspension solutions. UV-Vis analysis revealed that there is a characteristic peak
of Fe3O4/Au fluid. For particles with d(0.5)=168 nm, the λmax is 625 nm. 相似文献
16.
Hsin‐Tsung Chen Jee‐Gong Chang Shin‐Pon Ju Hui‐Lung Chen 《Journal of computational chemistry》2010,31(2):258-265
We have elucidated the mechanism of CO oxidation catalyzed by gold nanoparticles through first‐principle density‐functional theory (DFT) calculations. Calculations on selected model show that the low‐coordinated Au atoms of the Au29 nanoparticle carry slightly negative charges, which enhance the O2 binding energy compared with the corresponding bulk surfaces. Two reaction pathways of the CO oxidation were considered: the Eley–Rideal (ER) and Langmuir–Hinshelwood (LH). The overall LH reaction O2(ads) + CO(gas) → O2(ads) + CO(ads) → OOCO(ads) → O(ads) + CO2(gas) is calculated to be exothermic by 3.72 eV; the potential energies of the two transition states ( TSLH1 and TSLH2 ) are smaller than the reactants, indicating that no net activation energy is required for this process. The CO oxidation via ER reaction Au29 + O2(gas) + CO(gas) → Au29–O2(ads) + CO(gas) → Au29–CO3(ads) → Au29–O(ads) + CO2(gas) requires an overall activation barrier of 0.19 eV, and the formation of Au29–CO3(ads) intermediate possesses high exothermicity of 4.33 eV, indicating that this process may compete with the LH mechanism. Thereafter, a second CO molecule can react with the remaining O atom via the ER mechanism with a very small barrier (0.03 eV). Our calculations suggest that the CO oxidation catalyzed by the Au29 nanoparticle is likely to occur at or even below room temperature. To gain insights into high‐catalytic activity of the gold nanoparticles, the interaction nature between adsorbate and substrate is also analyzed by the detailed electronic analysis. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010 相似文献
17.
Glasses of the composition XNa2O · 4Al2O3 (96-X) B2O3 (mole%) where X = 10, 20, 30 to which 0.03 g V2O5 per 100 g glass was added, were prepared by normal melting. Their absorption characteristics together with the corresponding V-free base glasses were determined before and after gamma irradiation. The characteristic spectra of the unirradiated glasses show absorption bands at 315, 470, 560–580, 610–650, 700–870, and 860–1000 nm, indicating the presence of vanadium ions in more than one oxidation state, viz, V5+, V4+, and V3+. Gamma irradation of V-containing glasses causes the formation of color centers in the glass matrices, with absorption bands at 330, 500, and 610 nm, and photoreduced [V3+] and [V2+] ions with absorption bands at 350–355 and 530–570 and 520 nm, respectively. Photoreduced [V4+] may also be formed, giving rise to absorptions at 690–700 and 750–800 nm. The induced vanadium ions are found to absorb at shorter wavelengths than the intrinsic ones. An explanation based on the difference in the field energy of the two states is given. 相似文献
18.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(15):4214-4219
Nanotubular Fe2O3 is a promising photoanode material, and producing morphologies that withstand high‐temperature calcination (HTC) is urgently needed to enhance the photoelectrochemical (PEC) performance. This work describes the design and fabrication of Fe2O3 nanotube arrays that survive HTC for the first time. By introducing a ZrO2 shell on hydrothermal FeOOH nanorods by atomic layer deposition, subsequent high‐temperature solid‐state reaction converts FeOOH‐ZrO2 nanorods to ZrO2‐induced Fe2O3 nanotubes (Zr‐Fe2O3 NTs). The structural evolution of the hematite nanotubes is systematically explored. As a result of the nanostructuring and shortened charge collection distance, the nanotube photoanode shows a greatly improved PEC water oxidation activity, exhibiting a photocurrent density of 1.5 mA cm−2 at 1.23 V (vs. reversible hydrogen electrode, RHE), which is the highest among hematite nanotube photoanodes without co‐catalysts. Furthermore, a Co‐Pi decorated Zr‐Fe2O3 NT photoanode reveals an enhanced onset potential of 0.65 V (vs. RHE) and a photocurrent of 1.87 mA cm−2 (at 1.23 V vs. RHE). 相似文献
19.
Yuxiong Wang Guang Hong Yaoyu Zhang Prof. Yue Liu Dr. Wanglai Cen Prof. Lianzhou Wang Prof. Zhongbiao Wu 《Angewandte Chemie (International ed. in English)》2023,62(42):e202310525
C−H dissociation and C−C coupling are two key steps in converting CH4 into multi-carbon compounds. Here we report a synergy of Au and Ag to greatly promote C2H6 formation over Au1Ag single-atom alloy nanoparticles (Au1Ag NPs)-modified ZnO catalyst via photocatalytic oxidative coupling of methane (POCM) with O2 and H2O. Atomically dispersed Au in Au1Ag NPs effectively promotes the dissociation of O2 and H2O into *OOH, promoting C−H activation of CH4 on the photogenerated O− to form *CH3. Electron-deficient Au single atoms, as hopping ladders, also facilitate the migration of electron donor *CH3 from ZnO to Au1Ag NPs. Finally, *CH3 coupling can readily occur on Ag atoms of Au1Ag NPs. An excellent C2H6 yield of 14.0 mmol g−1 h−1 with a selectivity of 79 % and an apparent quantum yield of 14.6 % at 350 nm is obtained via POCM with O2 and H2O, which is at least two times that of the photocatalytic system. The bimetallic synergistic strategy offers guidance for future catalyst design for POCM with O2 and H2O. 相似文献