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Enhanced photocatalytic characteristics by Ag-sensitized TiO2 photocatalysts with mixed phases
摘要： The Ag-sensitized TiO2 photocatalysts with various contents of Ag were fabricated by a facile sol-gel method. The Ag nanoparticles with an average diameter of only a few nanometers distributed uniformly over the TiO2 surface. Their presence resulted in suppressed recombination and more effective utilization of the visible-light radiation through surface plasmon resonance. However, excess Ag nanoparticles led to higher recombination rates, reduced surface area, and thereby lower photocatalytic activity. Comparative study on the photocatalytic performance of the photocatalysts without and with various Ag loadings was systematically carried out. The moderate reduction of Ag nanoparticles by an appropriate surface treatment condition to increase the area for dye adsorption was favorable to photodegradation. By double calcinations, mixed phases of anatase and rutile were obtained, which exhibited better performance than single phase. The synergistic effect of Ag nanoparticles, mixed phase TiO2 and high surface area has qualified the Ag-sensitized TiO2 nanocomposites as highly promising photocatalysts.
关键词： Calcination,Photodegradation,Ag-sensitized,TiO2,Ag decoration,Mixed phases
更新于2025-09-04 15:30:14
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Kinetic spectrophotometric method for real-time monitoring of ultraviolet photoreactions: A mini-photoreactor
摘要： Photoreactors in research laboratories generally consist of UV-C or UV-A mercury lamps and vessels of volume ranging up to about 1.0 L of solutions (suspensions, solvents, reactants and catalysts). This photoreactor’s design implies in large amounts of chemicals - cost problems, considerable amount of co-generated waste - environmental issues, safety problems and the need of large laboratory space. Currently, there is an effort by the scientific community to apply the principles of “green chemistry”, tending to miniaturize reactors and formats [1-8] and use modern sources of radiation such as light-emitting diodes (UV-LEDs), which are much more environmentally friendly than mercury lamps [9-13]. Another disadvantage of classical photochemical reactors is the withdrawal of aliquots at several times intervals. This procedure modifies the total volume of solutions and, consequently, the total number of absorbed photons per chromophore. Besides that, this methodology is time and labor consuming, and sometimes it is unsafe. In this way, a low amount of experimental points can limit the full kinetic description and lead to misinterpretations in kinetic parameters such as reaction order and rate constants. Accurate determinations are also limited by temperature control, which is not commonly effective in classical photoreactors. Here in it is proposed an interesting mini-photoreactor constituted by one UV-LED and a traditional quartz cuvette of 1.00 cm optical length that allows the reaction execution and, simultaneously, continuous monitoring via UV-Vis spectrophotometry (real-time kinetic analysis). In order to validate the use of this new mini-photoreactor we employed the photodegradation of methylene blue (MB) and salicylic acid (SA) in homogeneous and heterogeneous systems. For the proposition, it is necessary a specific spectrophotometer apparatus with a detection system that is not influenced by external light [14] and a Peltier system for controlling temperature with a mini-bar magnetic agitation. Continuous kinetic monitoring was performed in a spectrophotometer with a xenon flash lamp and silicon diode detectors, which emit flashes only during data collection, which prevents extra photodegradation for very photosensitive samples. Another spectrophotometer’s type that can be employed is that one based on diode-array system, whose external light also does not affect the spectrophotometric measurement.
关键词： methylene blue,mini-photoreactor,UV-LED,real-time monitoring,salicylic acid,ZnO,photodegradation
更新于2025-09-04 15:30:14
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TiO2-catalyzed photodegradation of aromatic compounds: relevance of susceptibility to oxidation and electrophilic attack by hydroxyl radical
摘要： The application of nanostructured titanium dioxide (TiO2) as catalyst for the photodegradation of drugs and dyes is well established. We aimed to evaluate the importance of the reactivity of aromatic compounds submitted to photodegradation. Specifically, we were interested in the correlation between susceptibility to oxidation and/or to electrophilic attack and the efficiency of degradation. We demonstrated that hydroxyl radical (HO˙) is the most relevant species generated in the photodegradation process. Considering that HO˙ has both oxidizing and electrophilic features, the efficiency of degradation of selected aromatic compounds was performed. The choice was based on their susceptibility to oxidation and/or to electrophilic attack. Benzoic acid (C1), salicylic acid (C2), and protocatechuic acid (C3) were compared regarding their oxidability using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and were ranked as follows: C3 ? C2~C1. These compounds were efficiently photodegraded and no significant difference was observed among them. To assess the importance of susceptibility to electrophilic attack, anisole (C4), acetophenone (C5), and nitrobenzene (C6) were selected. Compared to C5 and C6, the higher susceptibility of C4 to electrophilic attack was demonstrated using hypochlorous acid, an electrophilic reagent. The photodegradation showed that C4 was also more susceptible to degradation compared to C5 and C6. In summary, we found that by acting as a powerful oxidant/electrophile agent, HO˙ was able to promote the degradation of aromatic moieties. Considering that the majority of drugs and dyes bear aromatic moieties, our findings explain the great success of photodegradation using metal oxides as catalysts.
关键词： Pharmaceutical drugs,Aromatic compounds,Titanium dioxide,Nanostructured catalysts,Electrophilic susceptibility,Photodegradation
更新于2025-09-04 15:30:14
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PPECu/NiFe2O4 as an efficient visible-light-driven difunctional photocatalyst for degradation of PPCPs and hydrogen production
摘要： A simple coprecipitation method has been used to prepare PPECu/NiFe2O4 composites. The as-prepared samples were studied by XRD, FE-SEM, TEM, EDS and UVevis Drs. The loading of NiFe2O4 not only enhanced the visible light absorption intensity of composites, but also promoted the separation of photogenerated electron-hole pairs. Cocatalyst NiFe2O4 made the PPECu/NiFe2O4 composites possessed better activities for TC degradation and hydrogen production than pure PPECu. Among the composite photocatalysts, P-NFO-5 exhibited the highest activity with the degrade ef?ciency of 98% (20 min) and hydrogen evolution yield of 35.8 mmol/g (3.0 h) under visible light irradiation. Furthermore, a possible mechanism for the ef?cient PPECu/NiFe2O4 composite has been discussed.
关键词： NiFe2O4,Photodegradation,PPECu,Photocatalytic hydrogen production,Difunctional photocatalyst
更新于2025-09-04 15:30:14
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In situ fabrication of α-Fe2O3/CaFe2O4 p-n heterojunction with enhanced VOCs photodegradation activity
摘要： a-Fe2O3/CaFe2O4 p-n heterojunctions were prepared via a simple in-situ hydrolysis process as highly ef?cient VOCs degradation photocatalyst, wherein no additional conditions such as high pressure, high temperature and surfactants were required. The structures and morphologies of the as-prepared samples were analyzed by XRD, SEM and TEM. The results revealed that a-Fe2O3/CaFe2O4 p-n heterojunctions exhibited superior photocatalytic activity of VOCs degradation compared to pure CaFe2O4 and a-Fe2O3 in both steady model and ?ow bed model. It can degrade more than 82% of acetaldehyde within 180 min in steady mode and 65% in ?ow mode under visible light irradiation. The prominent VOCs remove property could be attributed to the strong interfacial contact caused by the in-situ fabrication process and the promoted charge carrier separation ef?ciency due to the constructing of a-Fe2O3/CaFe2O4 p-n heterojunction. It provides some new insights into the design and fabrication of advanced photocatalytic materials with p-n heterojunction for high ef?ciency in VOCs photodegradation.
关键词： VOCs photodegradation,In-situ fabrication,a-Fe2O3/CaFe2O4,p-n Heterojunction
更新于2025-09-04 15:30:14
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Framework for predicting the photodegradation of adhesion of silicone encapsulants
摘要： We developed a framework to predict and model the photodegradation of adhesion and cohesion of a silicone encapsulant for concentrator photovoltaic applications. Silicone encapsulant specimens were artificially weathered under narrow band UV filters to determine the effects of individual wavelengths within the UV spectrum on the photodegradation of the cohesion of encapsulant material and its adhesion with adjacent interfaces. The threshold wavelength, signifying the upper bound of the damaging action spectrum for the silicone, was identified from the results. In addition, specimens were artificially weathered with different relative humidities to understand the effects of moisture on the rate of photodegradation. The adhesion energy was measured using a fracture mechanics approach. The complementary delaminated surfaces were characterized to determine the failure pathway and chemistry changes resulting from photodegradation. A previously developed model was modified to account for the effects of damaging wavelengths in the terrestrial solar spectrum and reciprocity law failure due to varying UV intensity during weathering. With these modifications, the model showed good agreement with the behavior of the silicone encapsulant exposed in an outdoor solar concentrator simulating concentrator photovoltaics operating conditions. Similar studies can be adopted to develop models that can have high predictive accuracies based on accelerated aging studies.
关键词： Accelerated aging,Concentrator photovoltaics,Photodegradation,Encapsulant,Lifetime prediction,Silicone
更新于2025-09-04 15:30:14
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Biosynthesis of Silver Nanoparticles Using <i>Selaginella bryopteris</i> Plant Extracts and Studies of Their Antimicrobial and Photocatalytic Activities
摘要： The present study focuses on the green synthesis of silver nanoparticles (AgNPs) using aqueous extract of S. bryopteris which is a lithophyte with remarkable resurrection capabilities. These biosynthesized NPs were characterized with the help of UV-vis spectrophotometer, X-ray diffraction (XRD), FT-IR and Transmission electron microscopy (TEM). Formation of AgNPs was confirmed by UV-Visible spectrophotometer analysis which showed surface plasmon resonance (SPR) at around 420 nm. The TEM images showed the nanoparticles to be polydispersed, nearly spherical in shape and have sizes in range 4–30 nm. The synthesized AgNPs possessed high antibacterial activity as well as photocatalytic dye degradation properties under solar light irradiation in the absence of chemical reducing reagents. Stability of bio-reduced silver nanoparticles was analyzed using UV-vis absorption spectra, and their antimicrobial activity was screened against various gram-positive bacteria.
关键词： Characterization,Photodegradation,Antimicrobial Activity,Biosynthesis,S. bryopteris Extract,Silver Nanoparticles
更新于2025-09-04 15:30:14
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Study of self cleaning fabric modified by Cu doped TiO2 with the addition of tetraethyl orthosilicate (TEOS)
摘要： Study of self – cleaning fabric modified by Cu doped TiO2 with the addition of TEOS has been done to achieve high performance of self – cleaning fabric. TiO2 doped Cu were made by using Photo Assisted Deposition (PAD) method. After that, certain compositions of the water, TEOS and Cu – TiO2 catalyst with the TEOS variated are prepared to be padded by the fabric and then dryed in the oven at certain temperature. The addition of TEOS in fabric coating is to improved the catalyst performance in self – cleaning ability and photodegradation of methylen blue. After the fabric is made, then analyzed it by using FTIR. The photodegradation is tested by puting a small amount of fabric to a methylen blue solution for 2 hours to see its absorbance using UV – Vis Spectroscopy and the self – cleaning ability test is to put the fabric in a sludge dirt for several minutes then spray it with water. FTIR result showed that the addition of TEOS cause Ti – O – Si bond to be applied in the fabric. The fabric coated with doped TiO2 has better performance than the undoped on both MB photodegradation and self – cleaning ability. The MB photodegradation performance of fabric increased with the amount of TEOS up to 74.4% within 2 hours and the efficiency of sludge dirt self – cleaning of fabric increased with the amount of fabric up to 83% efficiency, which is the type of fabric cotton Cu – TiO2 1,2% Si was the best among the other type of fabrics.
关键词： photodegradation,TEOS,methylene blue,self-cleaning fabric,Cu doped TiO2
更新于2025-09-04 15:30:14
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A Study on Photocatalytic Behaviors of Activated Carbon Fibers Impregnated with N-Doped Titania
摘要： Activated carbon ?bers (ACFs) impregnated with N-doped titania were prepared via the sol–gel method and sonochemical synthesis. The photocatalytic behavior of rhodamine B showed that N-doped TiO2/ACF nanocomposites exhibited enhanced photocatalytic activity. This result could be attributed to the synergistic effect between the high adsorption capacity of ACF and the visible light photocatalytic activity of N-doped TiO2. In particular, the N-doped TiO2/ACF nanocomposite that was sonicated four times had the highest photocatalytic ef?ciency and degradation rate, owing to the optimal N-doped TiO2 loading and nanocomposite pore structure.
关键词： N-doped TiO2,Sonochemical Synthesis,Activated Carbon Fibers,Photodegradation
更新于2025-09-04 15:30:14
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Photodegradtion of Methyl Orange in the Water on Undoped and Fe-doped TiO2 Nanotubes
摘要： Undoped and Fe-doped TiO2 nanotubes were fabricated by hydrothermally treating the sol-gel-derived undoped and Fe-doped TiO2 nanoparticles in a KOH aqueous solution. The light absorption edge the nanotubes extended to visible light region of ~449 nm at a maximal Fe molar content (3.86 %). Correspondingly, the optical bandgap narrowed to ~2.76 eV. The sunlight-excited degradation rate of methyl orange aqueous solution on the nanotubes increased as increasing Fe-doping content and initial solution pH. The photodegradation followed pseudo-first order reaction kinetics. The pseudo-kinetic rate constant increased from 0.133 to 0.513 h(cid:2)1 as the increase of Fe content and initial pH. A maximal value was achieved at Fe molar content of 3.86 % and initial solution pH=9. The measurement of oxidation-reduction potential revealed a dominant reductive photocatalytic behavior of the nanotubes. The mechanism of enhancing photocatalysis of TiO2 nanotubes by Fe-doping was proposed.
关键词： nanotubes,enviromant decontaimnant,Advanced oxidation,TiO2,photodegradation
更新于2025-09-04 15:30:14