共查询到20条相似文献,搜索用时 312 毫秒
1.
Vacancy‐rich layered materials with good electron‐transfer property are of great interest. Herein, a full‐spectrum responsive vacancy‐rich monolayer BiO 2?x has been synthesized. The increased density of states at the conduction band (CB) minimum in the monolayer BiO 2?x is responsible for the enhanced photon response and photo‐absorption, which were confirmed by UV/Vis‐NIR diffuse reflectance spectra (DRS) and photocurrent measurements. Compared to bulk BiO 2?x, monolayer BiO 2?x has exhibited enhanced photocatalytic performance for rhodamine B and phenol removal under UV, visible, and near‐infrared light (NIR) irradiation, which can be attributed to the vacancy V Bi‐O′′′ as confirmed by the positron annihilation spectra. The presence of V Bi‐O′′′ defects in monolayer BiO 2?x promoted the separation of electrons and holes. This finding provides an atomic level understanding for developing highly efficient UV, visible, and NIR light responsive photocatalysts. 相似文献
2.
We report an oxygen vacancy (V o)-rich metallic MoO 2−x nano-sea-urchin with partially occupied band, which exhibits super CO 2 (even directly from the air) photoreduction performance under UV, visible and near-infrared (NIR) light illumination. The V o-rich MoO 2−x nano-sea-urchin displays a CH 4 evolution rate of 12.2 and 5.8 μmol g catalyst−1 h −1 under full spectrum and NIR light illumination in concentrated CO 2, which is ca. 7- and 10-fold higher than the V o-poor MoO 2−x, respectively. More interestingly, the as-developed V o-rich MoO 2−x nano-sea-urchin can even reduce CO 2 directly from the air with a CO evolution rate of 6.5 μmol g catalyst−1 h −1 under NIR light illumination. Experiments together with theoretical calculations demonstrate that the oxygen vacancy in MoO 2−x can facilitate CO 2 adsorption/activation to generate *COOH as well as the subsequent protonation of *CO towards the formation of CH 4 because of the formation of a highly stable Mo−C−O−Mo intermediate. 相似文献
3.
A straightforward aqueous synthesis of MoO 3?x nanoparticles at room temperature was developed by using (NH 4) 6Mo 7O 24?4 H 2O and MoCl 5 as precursors in the absence of reductants, inert gas, and organic solvents. SEM and TEM images indicate the as‐prepared products are nanoparticles with diameters of 90–180 nm. The diffuse reflectance UV‐visible‐near‐IR spectra of the samples indicate localized surface plasmon resonance (LSPR) properties generated by the introduction of oxygen vacancies. Owing to its strong plasmonic absorption in the visible‐light and near‐infrared region, such nanostructures exhibit an enhancement of activity toward visible‐light catalytic hydrogen generation. MoO 3?x nanoparticles synthesized with a molar ratio of Mo VI/Mo V 1:1 show the highest yield of H 2 evolution. The cycling catalytic performance has been investigated to indicate the structural and chemical stability of the as‐prepared plasmonic MoO 3?x nanoparticles, which reveals its potential application in visible‐light catalytic hydrogen production. 相似文献
4.
A low‐temperature topochemical reduction strategy is used herein to prepare unconventional phosphors with luminescence covering the biological and/or telecommunications optical windows. This approach is demonstrated by using Bi III‐doped Y 2O 3 (Y 2?xBi xO 3) as a model system. Experimental results suggest that topochemical treatment of Y 2?xBi xO 3 using CaH 2 creates randomly distributed oxygen vacancies in the matrix, resulting in the change of the oxidation states of Bi to lower oxidation states. The change of the Bi coordination environments from the [BiO 6] octahedra in Y 2?xBi xO 3 to the oxygen‐deficient [BiO 6?z] polyhedra in reduced phases leads to a shift of the emission maximum from the visible to the near‐infrared region. The generality of this approach was further demonstrated with other phosphors. Our findings suggest that this strategy can be used to explore Bi‐doped or other classes of luminescent systems, thus opening up new avenues to develop novel optical materials. 相似文献
5.
Visible‐light‐responsive reversible color‐switching systems are attractive to many applications because visible light has superior penetration and causes far less damage to organic molecules than UV. Herein, we report that self‐doping of SnO 2−x nanocrystals with Sn 2+ red‐shifts their absorption to the visible region and simultaneously produces oxygen vacancies, which can effectively scavenge photogenerated holes and thus enable the color switching of redox dyes using visible light. Wavelength‐selective switching can also be achieved by coupling the photocatalytic activity of the SnO 2−x NCs with the color‐switching kinetics of different redox dyes. The fast light response enables the further fabrication of a solid film that can be repeatedly written on using a visible laser pen or projection printing through a photomask. This discovery represents a big step forward towards practical applications, especially in areas in which safety issues and photodamage by UV light are of concern. 相似文献
6.
The electrochemical, UV/Vis–NIR absorption, and emission‐spectroscopic features of (TBA +)( 1 −) and the corresponding neutral complex 1 were investigated (TBA +=tetrabutylammonium; 1 −=[Au III(Pyr,H‐edt) 2] −; Pyr,H‐edt 2−=pyren‐1‐yl‐ethylene‐1,2‐dithiolato). The intense electrochromic NIR absorption ( λmax=1432 nm; ε=13000 M −1 cm −1 in CH 2Cl 2) and the potential‐controlled visible emission in the range 400–500 nm, the energy of which depends on the charge of the complex, were interpreted on the grounds of time‐dependent DFT calculations carried out on the cis and trans isomers of 1 , 1 −, and 1 2−. In addition, to evaluate the nonlinear optical properties of 1 x− ( x=0, 1), first static hyperpolarizability values βtot were calculated ( βtot=78×10 −30 and 212×10 −30 esu for the cis isomer of 1 − and 1 , respectively) and compared to those of differently substituted [Au(Ar,H‐edt) 2] x− gold dithiolenes [Ar=naphth‐2‐yl ( 2 ), phenyl ( 3 ); x=0, 1]. 相似文献
7.
Ce 1‐xNd xO 2‐δ ( x = 0.05–0.55) solid solutions prepared by sol‐gel route were crystallized in a cubic fluorite structure. The solid limit was determined to be as high as x = 0.45. Raman spectra of the solid solutions with lower composition exhibited only one band, which was assigned to F2g mode. Increasing composition produced broad and asymmetric F2g mode with an appearance of low frequency tail. The new broad peak observed at higher frequency side of the F2g mode associated with the oxygen vacancy in the lattice. The impedance spectra of the solid solutions showed definitely ionic conduction, and Ce 0.80Nd 0.20O 2‐δ solid solution possessed a maximum conductivity. At 500 °C, the conductivity and activation energy were 2.65 × 10 ?3S/cm and 0.82 eV, respectively. 相似文献
8.
In this study, we explored the feasibility of using electrochemically generated γ‐Li xV 2O 5 as an insertion‐type anode in the lithium‐ion capacitor (LIC) with activated carbon (AC) as a cathode. Along with the native form of V 2O 5, their carbon composites are also used as the electrode material which is prepared by high‐energy ball milling. The electrochemical pre‐lithiation strategy is used to generate the desired γ‐phase of V 2O 5 (γ‐Li xV 2O 5). Under the optimized mass loading conditions, the LICs are assembled with γ‐Li xV 2O 5 as anode and AC as a cathode in the organic medium. Among the different LICs fabricated, AC/γ‐Li xV 2O 5‐BM50 configuration delivered an energy density of 33.91 Wh kg ?1 @ 0.22 kW kg ?1 with excellent capacity retention characteristics. However, a dramatic increase in energy density (43.98 Wh kg ?1@0.28 kW kg ?1) is noted after the electrolyte modification with fluoroethylene carbonate. The high temperature performance of the assembled LIC is also studied and found that γ‐Li xV 2O 5 phase can be used as a potential battery‐type component to construct high‐performance hybrid charge storage devices. 相似文献
9.
In this work, a series of flower-like Bi/BiOClxBr(1−x) heterojunction photocatalysts have been developed. Bi nanoparticles were grown on the BiOClxBr(1−x) nanosheets via an in situ chemical reduction with the assistance of cetyltrimethylammonium chloride and cetyltrimethylammonium bromide aqueous solution. The in situ growth of Bi nanoparticles on the BiOClxBr(1−x) nanosheets could not only give rise to the optical absorption in the visible region, but also promote the photocatalytic performance of BiOClxBr(1−x). Bi/BiOCl0.8Br0.2 exhibited the highest photocatalytic performance, which could completely degrade RhB in 12 min under the UV light irradiation and 6 min under visible light irradiation, respectively. Moreover, holes and superoxide radicals were verified to be the primarily active species in the photocatalytic process. 相似文献
10.
Near‐monodisperse Bi‐doped anatase TiO 2 nanospheres with almost uniform diameters in the range of 117 to 87 nm were prepared simply by introducing different amounts of bismuth nitrate pentahydrate into the reaction system and subsequent calcinations. X‐ray diffraction, UV‐visible diffuse reflectance spectra, and X‐ray photoelectron spectroscopy confirm that the doped ions substitute some of the lattice titanium atoms, and furthermore, Bi 3+ and Bi 4+ ions coexist. All the Bi‐doped TiO 2 samples show much better photocatalytic activity than pure TiO 2 in the degradation of rhodamine B (RhB) under the irradiation of visible light ( λ>420 nm), and, interestingly, it was found that the degradation mechanism is different from the conventional one, which has already been reported elsewhere. The detailed mechanism is discussed in this article. 相似文献
11.
In this study, the characterization and photocatalytic activity of Bi 2WO 6/Bi 2O 3 under visible‐light irradiation was investigated in detail. The results suggested that Bi 2WO 6/Bi 2O 3 can be synthesized by a facile one‐pot hydrothermal route using a super big 200 mL Teflon‐lined autoclave with optimal sodium oleate/Bi molar ratio of 1.25. Through the characterization of Bi 2WO 6/Bi 2O 3 by X‐ray diffraction, scanning electron microscopy, X‐ray photoelectron spectroscopy, Fourier transform infrared, UV‐vis diffuse reflectance spectra and Photoluminescence spectra, it was found that the as‐prepared composite possessed smaller crystallite size and higher visible‐light responsive than the pure Bi 2WO 6. Moreover, it was expected that the as‐prepared composites exhibited enhanced photocatalytic activity for the degradation of Rhodamine B under visible‐light irradiation, which could be ascribed to their improved light absorption property and the reduced recombination of the photogenerated electrons and holes during the photocatalytic reaction. In general, this study could provide a principle method to synthesize Bi 2WO 6/Bi 2O 3 with enhanced photocatalytic activity by one‐step hydrothermal synthesis route for environmental purification. 相似文献
12.
The determination of the crystal structure of the M phase, (Mn xZn 1–x) 2V 2O 7 (0.75 < x < 0.913), in the pseudobinary Mn 2V 2O 7–Zn 2V 2O 7 system for x ≃ 0.8 shows that the previously published triclinic unit‐cell parameters for this thortveitite‐related phase do not describe a true lattice for this phase. Instead, single‐crystal X‐ray data and Rietveld refinement of synchrotron X‐ray powder data show that the M phase has a different triclinic structure in the space group P with Z = 2. As prior work has suggested, the crystal structure can be described as a distorted version of the thortveitite crystal structure of β‐Mn 2V 2O 7. A twofold superstructure in diffraction patterns of crystals of the M phase used for single‐crystal X‐ray diffraction work arises from twinning by reticular pseudomerohedry. This superstructure can be described as a commensurate modulation of a pseudo‐monoclinic basis structure closely related to the crystal structure of β‐Mn 2V 2O 7. In comparison with the distortions introduced when β‐Mn 2V 2O 7 transforms at low temperature to α‐Mn 2V 2O 7, the distortions which give rise to the M phase from the β‐Mn 2V 2O 7 prototype are noticeably less pronounced. 相似文献
13.
Five mixed‐metal mixed‐valence Mo/V polyoxoanions, templated by the pyramidal SeO 32? heteroanion have been isolated: K 10[Mo VI12V V10O 58(SeO 3) 8]?18 H 2O ( 1 ), K 7[Mo VI11V V5V IV2O 52(SeO 3)]?31 H 2O ( 2 ), (NH 4) 7K 3[Mo VI11V V5V IV2O 52(SeO 3)(Mo V6V V‐ O 22)]?40 H 2O ( 3 ), (NH 4) 19K 3[Mo VI20V V12V IV4O 99(SeO 3) 10]?36 H 2O ( 4 ) and [Na 3(H 2O) 5{Mo 18?xV xO 52(SeO 3)} {Mo 9?yV yO 24(SeO 3) 4}] ( 5 ). All five compounds were characterised by single‐crystal X‐ray structure analysis, TGA, UV/Vis and FT‐IR spectroscopy, redox titrations, and elemental and flame atomic absorption spectroscopy (FAAS) analysis. X‐ray studies revealed two novel coordination modes for the selenite anion in compounds 1 and 4 showing η,μ and μ,μ coordination motifs. Compounds 1 and 2 were characterised in solution by using high‐resolution ESI‐MS. The ESI‐MS spectra of these compounds revealed characteristic patterns showing distribution envelopes corresponding to 2? and 3? anionic charge states. Also, the isolation of these compounds shows that it may be possible to direct the self‐assembly process of the mixed‐metal systems by controlling the interplay between the cation “shrink‐wrapping” effect, the non‐conventional geometry of the selenite anion and fine adjustment of the experimental variables. Also a detailed IR spectroscopic analysis unveiled a simple way to identify the type of coordination mode of the selenite anions present in POM‐based architectures. 相似文献
14.
It is shown that U VO 2+ ions can reside at U VIO 22+ lattice sites during mild reduction and crystallization process under solvothermal conditions, yielding a complicated and rare mixed‐valent uranium phosphonate compound that simultaneously contains U IV, U V, and U VI. The presence of uranium with three oxidation states was confirmed by various characterization techniques, including X‐ray crystallography, X‐ray photoelectron, electron paramagnetic resonance, FTIR, UV/Vis‐NIR absorption, and synchrotron radiation X‐ray absorption spectroscopy, and magnetism measurements. 相似文献
15.
Titanium‐oxide‐based materials are considered attractive and safe alternatives to carbonaceous anodes in Li‐ion batteries. In particular, the ramsdellite form TiO 2(R) is known for its superior lithium‐storage ability as the bulk material when compared with other titanates. In this work, we prepared V‐doped lithium titanate ramsdellites with the formula Li 0.5Ti 1?xV xO 2 (0≤ x≤0.5) by a conventional solid‐state reaction. The lithium‐free Ti 1?xV xO 2 compounds, in which the ramsdellite framework remains virtually unaltered, are easily obtained by a simple aqueous oxidation/ion‐extraction process. Neutron powder diffraction is used to locate the Li channel site in Li 0.5Ti 1?xV xO 2 compounds and to follow the lithium extraction by difference‐Fourier maps. Previously delithiated Ti 1?xV xO 2 ramsdellites are able to insert up to 0.8 Li + per transition‐metal atom. The initial gravimetric capacities of 270 mAh g ?1 with good cycle stability under constant current discharge conditions are among the highest reported for bulk TiO 2‐related intercalation compounds for the threshold of one e ? per formula unit. 相似文献
16.
Vanadium tellurites display a rich structural chemistry with interesting physical properties, such as second harmonic generation (SHG). Tellurites, i.e. Te 4+O x, are often observed in unusual structures and form various structural motifs, including isolated clusters, chains, layers, and three‐dimensional networks. Similarly, vanadates, i.e. V 5+O x, show rich structural features, such as VO 4 tetrahedra, VO 5 square pyramids or trigonal bipyramids, and VO 6 octahedra. Strontium vanadium tellurite, Sr 7V 4Te 12O 41, was obtained from the melt of the solid‐state reaction of SrTeO 4 and VO 2 in a sealed quartz tube as it cooled from 973 K. The crystal structure exhibits a one‐dimensional latticework along the a axis comprised of paired Sr 3Te 3O x units, namely Sr 6Te 6O 2x+1, with corner‐shared TeO 4 polyhedra – and specifically the Te lone‐pair electrons – facing outward in the bc plane. The Sr 6Te 6O 2x+1 latticework is helical and is layered in the b‐axis direction against sheets of corner‐shared VO 4 tetrahedra, and is linked in the c‐axis direction via individual corner‐shared SrO 8 square prisms. 相似文献
17.
Despite its electron deficiency, boron is versatile in forming multiple bonds. Transition‐metal–boron double bonding is known, but boron–metal triple bonds have been elusive. Two bismuth boron cluster anions, BiB 2O − and Bi 2B −, containing triple and double B−Bi bonds are presented. The BiB 2O − and Bi 2B − clusters are produced by laser vaporization of a mixed B/Bi target and characterized by photoelectron spectroscopy and ab initio calculations. Well‐resolved photoelectron spectra are obtained and interpreted with the help of ab initio calculations, which show that both species are linear. Chemical bonding analyses reveal that Bi forms triple and double bonds with boron in BiB 2O − ([Bi≡B−B≡O] −) and Bi 2B − ([Bi=B=Bi] −), respectively. The Bi−B double and triple bond strengths are calculated to be 3.21 and 4.70 eV, respectively. This is the first experimental observation of Bi−B double and triple bonds, opening the door to design main‐group metal–boron complexes with multiple bonding. 相似文献
18.
A family of nonlinear optical materials that contain the halide, oxide, and oxyhalide polar units simultaneously in a single structure, namely ABi 2(IO 3) 2F 5 (A=K ( 1 ), Rb ( 2 ), and Cs ( 3 )), have been designed and synthesized. They crystallize in the same polar space group ( P 2 1) with a two‐dimensional double‐layered framework constructed by [BiF 5] 2− and [BiO 2F 4] 5− units connected to each other by four F atoms, in which two [IO 3] − groups are linked to [BiO 2F 4] 5− unit on the same side. A hanging Bi−F bond of [BiF 5] 2− unit is located on the other side via ionic interaction with the layer‐inserted alkali metal ions to form three‐dimensional structure. The well‐ordered alignments of these polar units lead to a very strong second‐harmonic generation response of 12 ( 1 ), 9.5 ( 2 ), and 7.5 ( 3 ) times larger than that of potassium dihydrogen phosphate under 1064 nm laser radiation. All of them exhibited a wide energy bandgap over 3.75 eV, suggesting that they will have a high laser damage threshold. 相似文献
19.
A new linear bismuth(III) coordination polymer, catena‐poly[[chloridobismuth(III)]‐μ 3‐1,10‐phenanthroline‐2,9‐dicarboxylato‐κ 6O2: O2, N1, N10, O9: O9], [Bi(C 14H 6N 2O 4)Cl] n, has been obtained by an ionothermal method and characterized by elemental analysis, energy‐dispersive X‐ray spectroscopy, IR spectroscopy, thermal stability studies and single‐crystal X‐ray diffraction. The structure is constructed by Bi(C 14H 6N 2O 4)Cl fragments in which each Bi III centre is seven‐coordinated by one Cl atom, four O atoms and two N atoms. The coordination geometry of the Bi III cation is distorted pentagonal–bipyramidal (BiO 4N 2Cl), with one bridging carboxylate O atom and one Cl atom located in the axial positions. The Bi(C 14H 6N 2O 4)Cl fragments are further extended into a one‐dimensional linear polymeric structure via subsequent but different centres of symmetry (bridging carboxylate O atoms). Neighbouring linear chains are assembled via weak C—H...O and C—H...Cl hydrogen bonds, forming a three‐dimensional supramolecular architecture. Intermolecular π–π stacking interactions are observed, with centroid‐to‐centroid distances of 3.678 (4) Å, which further stabilize the structure. In addition, the solid‐state fluorescence properties of the title coordination polymer were investigated. 相似文献
20.
A family of nonlinear optical materials that contain the halide, oxide, and oxyhalide polar units simultaneously in a single structure, namely ABi 2(IO 3) 2F 5 (A=K ( 1 ), Rb ( 2 ), and Cs ( 3 )), have been designed and synthesized. They crystallize in the same polar space group ( P 2 1) with a two‐dimensional double‐layered framework constructed by [BiF 5] 2− and [BiO 2F 4] 5− units connected to each other by four F atoms, in which two [IO 3] − groups are linked to [BiO 2F 4] 5− unit on the same side. A hanging Bi−F bond of [BiF 5] 2− unit is located on the other side via ionic interaction with the layer‐inserted alkali metal ions to form three‐dimensional structure. The well‐ordered alignments of these polar units lead to a very strong second‐harmonic generation response of 12 ( 1 ), 9.5 ( 2 ), and 7.5 ( 3 ) times larger than that of potassium dihydrogen phosphate under 1064 nm laser radiation. All of them exhibited a wide energy bandgap over 3.75 eV, suggesting that they will have a high laser damage threshold. 相似文献
|