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1.
Given the changes in environmental conditions in the world, photocatalytic conversion of greenhouse gases is of great interest today. Our aim was to increase the photocatalytic efficiency of BiFeO 3/ZnS (p-n heterojunction photocatalyst) by varying the molar ratio of ZnS to perovskite structure of BiFeO 3 using hydrothermal synthesis. The results of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), FT-IR spectroscopy showed the small crystal size and suitable distribution of ZnS particles on the BiFeO 3 structure. The results of UV-visible, and photoluminescence (PL) spectroscopy analyses showed the good behavior of p-n heterostructure in absorption of visible light and lowering electron-hole recombination. The best visible light photocatalytic efficiency of CO 2 reduction, 24.8%, was obtained by an equimolar ratio of BiFeO 3/ZnS. 相似文献
2.
BACKGROUND: This research investigated the effect of platinum (Pt) on the reactivity of tungsten oxide (WO 3) for the visible light photocatalytic oxidation of dyes. RESULTS: Nanocrystalline tungsten oxide (WO 3) photocatalysts were synthesised by a sol‐gel process and employed for the photocatalytic degradation of Methyl Orange under visible light. For comparison commercial bulk WO 3 materials were also studied for the same reaction. These materials were fully characterised using X‐ray diffraction (XRD), UV‐visible diffuse reflection spectroscopy and transmission electron microscopy (TEM). The photocatalytic oxidation of iso‐propanol was used as a model reaction to follow the concomitant reduction of molecular oxygen. No reactions occured in the absence of platinum, which is an essential co‐catalyst for the multi‐electron reduction of oxygen. The platinised WO 3 catalysts were stable for multiple oxidation–reduction cycles. The results from the catalytic activity measurements showed that platinised nanocrystalline WO 3 is a superior oxidation photocatalyst when compared with bulk WO 3. Methyl Orange was completely decolourised in 4 h. CONCLUSIONS: The enhanced performance of nanocrystalline Pt‐WO 3 is attributed to improved charge separation in the nanosized photocatalyst. Platinum is an essential co‐catalyst to reduce oxygen. This photocatalyst could be applied to the treatment of organic pollutants in wastewater, with the advantage of using visible light compared with the widely studied TiO 2, which requires UV light. Copyright © 2011 Society of Chemical Industry 相似文献
3.
The improved photocatalyst carbon-doped WO 3/TiO 2 mixed oxide was synthesized in this study using the sol–gel method. The catalyst was thoroughly characterized by X-ray diffraction (XRD), diffuse reflectance UV–vis spectroscopy, N 2 adsorption desorption analysis, scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDX), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The photocatalytic efficiency of the prepared materials was evaluated with respect to the degradation of sodium diclofenac (DCF) in a batch reactor irradiated under simulated solar light. The progress of the degradation process of the drug was evaluated by high-performance liquid chromatography (HPLC), whereas mineralization was monitored by total organic carbon analysis (TOC) and ion chromatography (IC). The results of the photocatalytic evaluation indicated that the modified catalyst with tungsten and carbon (TWC) exhibited higher photocatalytic activity than TiO 2 (T) and WO 3/TiO 2 (TW) in the degradation and mineralization of diclofenac (TWC>TW>T). Complete degradation of diclofenac occurred at 250 kJ m −2 of accumulated energy, whereas 82.4% mineralization at 400 kJ m −2 was achieved using the photocatalytic system WO 3/TiO 2-C. The improvement in the photocatalytic activity was attributed to the synergistic effect between carbon and WO 3 incorporated into the TiO 2 structure. 相似文献
4.
In this work, a series of titania-supported NiO and CdO materials were synthesized by a modified sol-gel process. The prepared photocatalysts were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), and transmission electron microscopy (TEM). The activities of titania-supported NiO and CdO photocatalysts for photocatalytic degradation of Remazole Red F3B (RR) dye, under simulated sunlight, were investigated. The photocatalytic mineralization of an RR dye solution over various NiO-x/TiO 2 and CdO-x/TiO 2 photocatalysts under simulated sunlight was investigated. It was worthy noticing that the photocatalytic activity of titania improved using the prepared catalysts. The prepared TiO 2, NiO-5/TiO 2, and CdO-2/TiO 2 photocatalysts exhibited higher photocatalytic activity under simulated sunlight than did commercial TiO 2. The prepared photocatalysts were stable after photocatalytic degradation of the dye. The observed photocatalytic mineralization of the dye was 51 and 71% over NiO-10/TiO 2 and CdO-2/TiO 2 after 180 min of irradiation, respectively. Juxtaposing a p-NiO-5/TiO 2 semiconductor provided a potential approach for decreasing charge recombination. The prepared photocatalystsNiO-5/TiO 2 and CdO-2/TiO 2 are promising composites for the solar detoxification of textile wastewater. 相似文献
5.
In this work, WO 3-reduced graphene oxide (RGO) nanocomposite was synthesized via a simple one-pot hydrothermal method. The synthesized nanocomposite was characterized by SEM, XRD, EDX, UV–vis spectroscopy, N 2 adsorption/desorption, photocurrent response, electrochemical impedance spectroscopy and Raman spectroscopy. The superior contact between WO 3 and RGO sheets in the nanocomposite facilitates the photocatalytic degradation of methylene blue and evolution of oxygen. The cause of the enhanced photocatalytic performance could ascribe to the highly facilitated electron transport by the synergistic effect between WO 3 and RGO sheets, as well as suppressing the electron hole pair recombination in the nanocomposite. 相似文献
6.
Over the past few years, semiconductor materials (especially bismuth tungstate) exhibiting unique environment purification and energy conversion capacities arouse huge attention as impacted by issues of environmental pollution and energy shortage, whereas its application is restricted by the problems of high carrier recombination rate and unsatisfactory degradation efficiency. In this study, Eu:Bi 2WO 6 nanostructures containing Eu ions of different concentrations were synthesized with a chemical solution method, and CdS was generated on the surface of Eu:Bi 2WO 6 nanostructures in situ epitaxial to synthesize the Eu:Bi 2WO 6/CdS composites. The effects of Eu doping concentration on the crystal structure, chemical composition, local structure, optical properties and visible-light photocatalytic properties exhibited by Eu:Bi 2WO 6/CdS nanostructures were studied more specifically, and the Eu doping behavior on the improvement mechanisms for optical and photocatalytic performance exhibited by Eu:Bi 2WO 6/CdS nanostructures was clarified. The robust PL emission peak at about 390 nm and weak emission peak at nearly 450 nm are attributed to the exciton emission and defect state of Bi 2WO 6/CdS nanostructure, respectively. As indicated from the mechanism insights, the reasonable introduction of Eu 3+ could alter the band gap of the photocatalyst, and the epitaxial CdS could decrease the recombination probability of electron and hole in the Bi 2WO 6/CdS, while improving the photocatalytic activity. This study supplies new occasions for rational excogitation and better comprehending of atomic-scale complicated structures for applications in numerous fields (e.g., energy and environmental protection). 相似文献
7.
To make better use of solar light, a new Bi 2WO 6/Cu 1.8Se photocatalyst active to visible and near‐infrared light has been synthesized by a facile hydrothermal method. The composites were characterized by X‐ray diffractometry (XRD), scanning electron microscopy (SEM), UV‐vis diffuse reflectance spectroscopy (DRS), and photoluminescene (PL). The photocatalytic activities of Bi 2WO 6/Cu 1.8Se are evaluated by degrading Congo red solution and hydrogen generation from water. It was found that the molar percentage of Cu 1.8Se had great effects on the morphology and photocatalytic property of the Bi 2WO 6/Cu 1.8Se heterojunctions, and the composite with suitable molar amount of Cu 1.8Se exhibits much enhanced photocatalytic activity for Congo red degradation under visible and near‐infrared light irradiation and for hydrogen generation under visible light compared to Bi 2WO 6. The significant improvement photocatalytic activity of the composite could be attributed to its good light absorption, suitable band gap structure, and effective separation of photogenerated electron‐hole pairs of Bi 2WO 6/Cu 1.8Se heterojunction. This work presents an efficient multifunction photocatalyst owning the activity both for water splitting under visible light and for organic contaminants decomposition under visible‐near‐infrared light. 相似文献
8.
In this paper, WO 3 nanorods (NRs)/g-C 3N 4 composite photocatalysts were constructed by assembling WO 3 NRs with sheet-like g-C 3N 4. The as-synthesized photocatalysts were characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectroscopy and photoluminescence. The photocatalytic activity of the photocatalysts was evaluated by degradation of Rhodamine B (RhB) under simulated sunlight irradiation. Compared to pristine WO 3 NRs and g-C 3N 4, WO 3 NRs/g-C 3N 4 composites exhibit greatly enhanced photocatalytic activities. The enhanced performance of WO 3 NRs/g-C 3N 4 composite photocatalysts was mainly ascribed to the synergistic effect between WO 3 NRs and g-C 3N 4, which improved the photogenerated carrier separation. A possible degradation mechanism of RhB over the WO 3 NRs/g-C 3N 4 composite photocatalysts was proposed. 相似文献
9.
Highly efficient Eu-TiO 2/graphene composites were synthesized by a two-step method such as sol-gel and hydrothermal process. The synthesized photocatalysts were characterized by XRD, TEM, XPS, UV–vis diffuse reflectance spectroscopy and photoluminescence (PL) spectroscopy. The results confirmed that anatase Eu-TiO 2 nanoparticles with average 10 nm sizes were successfully deposited on two-dimensional graphene sheets. The UV–visible spectroscopy showed a red shift in the absorption edge of TiO 2 due to Eu doping and graphene incorporation. Moreover, effective charge separation in Eu-TiO 2/graphene composites was confirmed by PL emission spectroscopy compared to TiO 2/graphene, Eu-TiO 2 and pure TiO 2. The photocatalytic activity for H 2 evolution over prepared composites was studied under visible light irradiation (λ ≥ 400 nm). The results demonstrate that photocatalytic performance of the photocatalysts for hydrogen production increases with increasing doping concentration of Eu upto 2 at%. However, further increase in doping content above this optimum level has decreased the performance of photocatalyst. The enhanced photocatalytic performance for H 2 evolution is attributed to extended visible light absorption, suppressed recombination of electron-hole pairs due to synergistic effects of Eu and graphene. 相似文献
10.
Photocatalytic degradation of harmful organic matter is a feasible and environmentally friendly method. Bi 2WO 6 has become a hotspot of photocatalysts because of its unique layered structure and visible light response. In the present study, Sn doping was adopted to modified Bi 2WO 6 by hydrothermal method. The Sn-doped Bi 2WO 6 photocatalysts were characterized by XRD, SEM, TEM, BET, XPS, PL, and DRS, respectively. The results show that Sn-doped Bi 2WO 6 shows three-dimensional (3D) flower-like morphology, which is composed of two-dimensional (2D) nanosheets. Sn 4+ ions enter into the Bi 2WO 6 lattice, producing a degree of Bi 2WO 6 lattice distortion, which is in favor of reducing the recombination of photogenerated electrons and holes. Moreover, the specific surface area of Bi 2WO 6 is significantly increased after doping, which is beneficial to providing more active sites. The photocatalytic results show that 2%Sn-Bi 2WO 6 exhibits the highest photocatalytic activity. After 60 min of irradiation, the photocatalytic degradation degree of methylene blue (MB) increases from 80.6% for pure Bi 2WO 6 to 92.0% for 2%Sn-Bi 2WO 6. The first-order reaction rate constant of 2%Sn-Bi 2WO 6 is 0.030 min −1, which is 1.7 times than that of pure Bi 2WO 6. 相似文献
11.
A series of novel ZnO/Ag/Ag 2WO 4/AgI nanocomposites have been successfully synthesized by a facile ultrasonic-irradiation method and their photocatalytic activities were explored under visible-light illumination using rhodamine B. The synthesized nanocomposites were characterized by various techniques to determine their structural, morphological, and electronical properties. Effect of the amount of AgI, as visible-light sensitizer, on the photocatalytic activity was studied and it was found that the nanocomposite with 30% of AgI displayed the highest photocatalytic activity. Activity of this photocatalyst was almost 150, 17.8, and 55.1 times greater than those of the ZnO, ZnO/Ag/Ag 2WO 4, and ZnO/AgI photocatalysts, respectively. Besides, the importance of active species during the degradation process was explored and it was shown that superoxide anion radical has major role in the photodegradation reaction. Moreover, the outstanding performance of the best nanocomposite in degradations of three more dye pollutants was confirmed. Finally, a cascade mechanism was proposed for the greatly enhanced activity of the nanocomposites in degradation reactions. 相似文献
12.
Photocatalytic degradation is an ambitious and cost effective technique used for decontamination and sanitization of the waste polluted water of environment. Hydrothermal method is used to synthesis the carbon coupled WO 3 nanoparticles with different concentrations of carbon (0.0, 0.2, 0.5, 1.0 and 2.0%) from precursor Na 2WO 4·2H 2O with glucose and nitric acid. Synthesized nanoparticles were characterized by SEM, EDX, XRD, UV–Vis, and PL to study morphology, and particle size, composition, structural and optical properties, respectively. SEM revealed that morphology of the carbon coupled WO 3 nanoparticles becomes spherical by increasing amount of coupled carbon atoms. The average grain size of the carbon doped nanoparticles is found to be 15–20 nm. Furthermore, size of nanoparticles affect the band gap of synthesized nanoparticles as well. It has also been observed that carbon coupled WO 3 nanoparticles effectively take part in photo degradation due to reduction of electron–hole recombination rate. 相似文献
13.
We fabricated novel ternary nanocomposites through integration of C-dots (carbon dots), BiOCl, and nanosheets of graphitic carbon nitride (g-C 3N 4 nanosheets) by a cost-effective route. The fabricated photocatalysts were subsequently characterized by XRD, EDX, TEM, HRTEM, XPS, FT-IR, UV-vis DRS, TGA, BET, and PL methods to gain their structure, purity, morphology, optical, textural, and thermal properties. In addition, the degradation intermediates were identified by gas chromatography-mass spectroscopy (GC-MS). Photocatalytic performance of the synthesized samples was studied by photodegradations of three cationic (RhB, MB, and fuchsine), one anionic (MO) dyes, one colorless (phenol) pollutant and removal of an inorganic pollutant (Cr(VI)) under visible light. It was revealed that the ternary nanocomposite with loading 20% of BiOCl illustrated superlative performances in the selected photocatalytic reactions compared with the corresponding bare and binary photocatalysts. Visible-light photocatalytic activity of the g-C 3N 4 nanosheets/CDs/BiOCl (20%) nanocomposite was 42.6, 27.8, 24.8, 20.2, and 15.9 times higher than the pure g-C 3N 4 for removal of RhB, MB, MO, fuchsine, and phenol, respectively. Likewise, the ternary photocatalyst showed enhanced activity of 15.3 times relative to the g-C 3N 4 in photoreduction of Cr(VI). Moreover, the ternary nanocomposite exhibited excellent chemical stability and recyclability after five cycles. Finally, the mechanism for improved photocatalytic performance was discussed based on the band potential positions. 相似文献
14.
In this paper, a novel g-C 3N 4/2 wt% SnS 2 nanocomposite was successfully synthesized using an in-situ growth of SnS 2 on g-C 3N 4. X-ray diffraction (XRD), atomic force microscopy (AFM), Brunauer-Emmett-Teller (BET) method, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), diffuse reflectance spectroscopy (DRS), and photoluminescence (PL) spectrometer were used to characterize the photocatalysts. Exploring adsorption behavior, as an importatnt stage during photocatalytic reactions, is of great importance. Hence, both adsorption and photocatalytic performance of the synthesized photocatalysts have been investigated in detail. The adsorption isotherm fittings exhibited that Freundlich and Langmuir-Freundlich models can be applied to the methylene blue (MB) adsorption on the photocatalysts, indicating surface heterogeneity should be considered. A pseudo-second-order model was fitted to explore the adsorption kinetics. According to the observed redshift in the Fourier transform infrared spectroscopy (FTIR) result of g-C 3N 4/SnS 2 nanocomposite, π-π interaction was dominant during MB adsorption. Also, a slight redshift and significant PL intensity reduction in g-C 3N 4/SnS 2 nanocomposite led to 96% photocatalytic efficiency after 180 min under visible light radiation. The kinetics of photodegradation over g-C 3N 4/SnS 2 was about 9 and 3 times higher than those of g-C 3N 4 and SnS 2 photocatalysts, respectively. The superoxide and hydroxyl radicals were the main reactive species in the photocatalytic degradation with a Z-scheme charge transfer mechanism. The g-C 3N 4/SnS 2 nanocomposite was found to be remarkably stable after three consecutive cycles of MB degradation. 相似文献
15.
Highly ordered TiO 2 and WO 3–TiO 2 nanotubes were prepared by one-step electrochemical anodizing method and cobalt has been successfully deposited on these nanotubes by photo-assisted deposition process. The morphology, crystal structure, elemental composition and light absorption capability of samples were characterized by field emission scanning electron microscope, X-ray diffraction, energy dispersive X-ray spectrometer and ultraviolet–visible spectroscopy methods. All cobalt loaded samples show an appearance of red shift relative to the unloaded samples. The degradation of methylene blue was used as a model reaction to evaluate the photocatalytic activity of these novel visible-light-responsive photocatalysts. Results showed that the photocatalytic activity of bare WO 3–TiO 2 samples is higher than that with undoped TiO 2 sample. Compared with unmodified TiO 2 and WO 3–TiO 2, the Co/TiO 2 and Co/WO 3–TiO 2 samples exhibited enhanced photocatalytic activity in the degradation of methylene blue. Kinetic research showed that the reaction rate constant of Co/WO 3–TiO 2 is approximately 2.26 times higher than the apparent reaction rate constant of bare WO 3–TiO 2. This work provides an insight into designing and synthesizing new TiO 2–WO 3 nanotubes-based hybrid materials for effective visible light-activated photocatalysis. The catalysts prepared in this study exhibit industrially relevant interests due to the low cost and high photocatalytic activity. 相似文献
16.
In this study, ZnO nanoparticles were successfully deposited on the surface of ZnMgAl–CO 3–LDHs microspheres to form ZnO/ZnMgAl–CO 3–LDHs heterojunction photocatalysts by coprecipitation process. The samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and UV–vis diffuse reflectance spectroscopy. The results show that ZnO nanoparticles with diameters about 10–80 nm are tightly grown on the nanosheets of the ZnMgAl–CO 3–LDHs microspheres. Compared with the pristine ZnMgAl–CO 3–LDHs microspheres and pure ZnO, the photocatalytic activity of the heterojunction ZnO/ZnMgAl–CO 3–LDHs photocatalyst is significantly enhanced towards the degradation of phenol under UV light irradiation. The enhancement of the photocatalytic activity of the heterojunction catalysts can be ascribed to their improved light absorption property and the lower recombination rate of the photoexcited electrons and holes during the photocatalytic reaction. The optimal molar ratio of ZnO/ZnMgAl–CO 3–LDHs for the photocatalysis is 3. The heterojunction photocatalyst ZnO/ZnMgAl–CO 3–LDHs may be a promising photocatalyst for future application in water treatment due to its excellent performance in degradation of phenol. 相似文献
17.
In this work, a holmium oxide (Ho 2O 3/CNT) photocatalysts were successfully synthesized through a MOF assisted route for the first time. The effects of the morphology and purity on the photocatalytic behavior of the products, were investigated by determining various physicochemical properties. The Ho 2O 3/CNT nanocomposite was systematically analyzed by powder X-ray diffraction (P-XRD), transmission electron microscopy (TEM), ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy studies. The Ho 2O 3 derived from a MOF assisted synthetic route using Ho(NO 3) 3·5H 2O and terephthalic acid with a 1:1 M ratio at a temperature of 750 °C for 3 h prove the most advantageous, 98% degradation of 20 mg/L aqueous tetracycline pollutant was observed within 60 min. The elevated photocatalytic activity was mainly attributable to the unique synthetic route, improved crystallinity, wide UV-light absorption rate and excellent adsorption capabilities of CNT, as well as enhanced oxygen deficiency. The photocatalytic results confirm that the Ho 2O 3/CNT nanocomposite is an efficient photocatalyst for the degradation of toxic tetracycline pollutant and is thus suitable for use in environmental remediation. 相似文献
18.
Ag 2WO 4/g-C 3N 4 composites with different Ag 2WO 4 concentration and calcination temperature were synthesized via a mixing and heating approach. Various techniques were used to investigate the characters of the as-prepared samples, such as thermogravimetric analysis, X-ray diffraction, Fourier transform infrared spectroscopy, UV–Vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy and photoluminescence spectroscopy. The degradation of rhodamine B (20 ppm) under visible light was performed to investigate the photocatalytic activity of Ag 2WO 4/g-C 3N 4 composites. Results indicate that the Ag 2WO 4/g-C 3N 4 is actually Ag/Ag 2WO 4/g-C 3N 4 ternary system. 7.5 wt% Ag 2WO 4/g-C 3N 4 prepared at 300 °C presented the best photocatalytic performance in rhodamine B degradation. The degradation rate reaches 0.0679 min ?1, which is 3.25 times higher than the value of pure g-C 3N 4. The enhanced activity is attributed to the synergetic effect of Ag 2WO 4, g-C 3N 4 and metal Ag. Additionally, cycling experiments also proved that the Ag 2WO 4/g-C 3N 4 photocatalyst has good stability. 相似文献
19.
The quest for cost-effective environmental remediation has motivated the research for highly efficient and stable photocatalysts capable of degrading pollutants under visible-light illumination. Ag-based visible-light-responsive photocatalysts demonstrate alluring properties and applications in the elimination of organic pollutants in wastewater, however they often suffer from inherent photo-corrosion under illumination. Herein, we report the facile solution-phase synthesis of silver carbonate (Ag 2CO 3) microcrystals with varied morphological features in different solvents. The size and morphology of Ag 2CO 3 materials can be tuned on the basis of varying types and ratios of solvents. The specific synthetic method allows the orientation controllable growth of Ag 2CO 3 microcrystals with variable length-to-diameter ratios, with the surface harvesting more solar energy, and the photocatalyst suppressing the electron-hole recombination. The enhancement in both the photocatalytic activity and photostability of Ag 2CO 3 catalysts is evident when AgNO 3 and NaHCO 3 are employed as stabilizers. Operating in the presence of 0.02 M stabilizer, the photocatalyst demonstrates highly efficient and robust degradation performance of higher than 95% in 5 successive times towards typical organic dye rhodamine B (RhB). Active holes and reactive oxygen-containing superhydroxyl radicals (·O 2−) are determined by trapping experiments to be the main species responsible for improved photocatalytic performance. This work provides new insights into the development of high-performance, recyclable Ag-based photocatalytic materials for energy and environmental applications. 相似文献
20.
To improve the photocatalytic activity of Bi2WO6, ZIF-8 was successfully introduced with the in-situ growth for the first time. The addition of ZIF-8 effectively inhibited the recombination of photogenerated electron–hole pairs with further improved electron utilization efficiency. The superoxide anion, .O2?, generated, greatly improved the photocatalytic activity. The performance of Bi2WO6/ZIF-8 in the photodegradation of tetracycline (TC) was studied under different conditions, including the proportions of ZIF-8, the dosage of catalyst, and the concentration of TC. The results indicated that 10 mg of B/Z/5/1 offered the best photocatalytic activity under UV light, achieving 97.8% degradation of TC (20 mg/L) within 80 min. The measured rate constant (k) for TC degradation was almost 3 times that of pure Bi2WO6. The effects of pH, HA, and inorganic anions on the degradation of TC were also studied for the simulated real water. Further, B/Z/5/1 could be reutilized up to five cycles without reduction of the catalysis performance. Therefore, the Bi2WO6/ZIF-8 heterojunction composite material can be utilized as an efficient photocatalyst for remediation of environmental pollution. 相似文献
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