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Effect of metal doped and co-doped TiO2 photocatalysts oriented to degrade indoor/outdoor pollutants for air quality improvement. A kinetic and product study using acetaldehyde as probe molecule
摘要： This study demonstrates the photocatalytic decomposition of an indoor air pollutant, acetaldehyde (CH3CHO), over 0.04 mol% metal-doped TiO2 (Mn-, Co- and Mn/Co-) nanoparticles activated by ultraviolet and visible irradiation. The photocatalytic activity, the photodegradation kinetics, and the ?nal product analysis were examined using a Static Photochemical Reactor coupled with a FTIR spectrophotometer. CH3CHO undergoes ef?cient decomposition over all photocatalysts under UV irradiation in the presence of one atmosphere N2 or synthetic air (SA). Metal doping causes substantial in?uence to photocatalysis by altering the amount of electron/hole pairs generated and/or the electron/hole recombination rates. Simulating the experimental results with pseudo-?rst order kinetics the corresponding degradation rate coe?cients were determined for each photocatalyst under UV irradiation and SA environment: kd UV(Mn-TiO2) = (1.9 ± 0.2)×10 ?1 h ?1, kd UV(Co-TiO2) = (2.8 ± 0.3)×10 ?1 h ?1, and kd UV(Mn/Co-TiO2) = (6.0 ± 0.7)×10 ?1 h ?1. These degradation kinetics under UV light irradiation are signi?cantly faster than undoped TiO2 revealing that the transition metal doping of TiO2 nanomaterials boosts the photocatalytic degradation of organic pollutants. Substantial decomposition of CH3CHO was achieved under visible light in the presence of oxygen over Mn-TiO2 with kd Vis(SA) = (0.44 ± 0.04)×10 ?1 h ?1 while for other samples no visible light photocatalysis was observed. CO2, CO, and H2O were the main oxidation products, with CO2 yields almost 100% under UV excitation, and CO yields up to 20% under UV and < 1% under visible excitation. Our experimental results suggest that Mn-TiO2 (0.04 mol%) nanoparticles may be considered as a potentially safe photocatalyst to remove acetaldehyde particularly from indoor atmospheric environments under visible irradiation, without yielding signi?cant toxic by-products. Other possible atmospheric implications are also discussed in the paper.
关键词： Metal-doped TiO2,Visible-ultraviolet photocatalysis,Photodegradation kinetics,Acetaldehyde,Indoor air pollution
更新于2025-09-23 15:21:21
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Electrical characterization of HVPE GaN containing different concentrations of carbon dopants
摘要： A comprehensive study of the electrical characteristics in Schottky diodes made of GaN:C grown by HVPE technology has been reported. The Schottky junctions were made of Ni/Au (25/200 nm) metal stack and ohmic contacts were fabricated by the Ti/Al/Ni/Au (30/90/20/100 nm) e-beam deposition of the metal thin-films followed by the rapid thermal annealing. A good quality of the fabricated Schottky diodes has been proved by considering the transient shape using a pulsed technique of the barrier evaluation under linearly increasing voltage (BELIV). The concentrations of equilibrium carriers of 1×1011 cm-3 and of 2×1010 cm-3 have been evaluated for relatively low and high carbon density doped samples, respectively, using photo-capacitance characteristics dependent on excitation intensity. The effective mobility of carriers of μeff=610 cm2/Vs has been estimated by considering the serial resistance variations dependent on excitation density, through analysis of delay times appeared in formation of peaks within BELIV transients. The optical deep level transient spectroscopy has shown that thermal emission from the rather shallow centres prevails. The centres, ascribed to vacancies as well as to carbon on Ga site, have been identified. It has been demonstrated that Schottky junctions made of heavy carbon doped (NC≥1018 cm-3) HVPE GaN material are capable to withstand voltages of ≥300 V.
关键词： barrier evaluation by linearly increasing voltage pulsed technique,transient current technique,Schottky diodes,carbon doped HVPE GaN grown on Ammono substrates,deep level transient spectroscopy
更新于2025-09-23 15:21:21
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Nonperturbative nonlinear effects in the dispersion relations for TE and TM plasmons on two-dimensional materials
摘要： We analytically obtain the dispersion relations for transverse-electric (TE) and transverse-magnetic (TM) surface plasmon-polaritons in a nonlinear two-dimensional (2D) conducting material with inversion symmetry lying between two Kerr-type dielectric media. To this end, we use Maxwell’s equations within the quasielectrostatic, weakly dissipative regime. We show that the wavelength and propagation distance of surface plasmons decrease due to the nonlinearity of the surrounding dielectric. In contrast, the effect of the nonlinearity of the 2D material depends on the signs of the real and imaginary parts of the third-order conductivity. Notably, the dispersion relations obtained by naively replacing the permittivity of the dielectric medium by its nonlinear counterpart in the respective dispersion relations of the linear regime are not accurate. We apply our analysis to the case of doped graphene and make predictions for the surface plasmon wavelength and propagation distance.
关键词： Maxwell’s equations,quasielectrostatic regime,weakly dissipative regime,nonlinear two-dimensional materials,surface plasmon-polaritons,doped graphene,Kerr-type dielectric media
更新于2025-09-23 15:21:21
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Broadly Tunable Plasmons in Doped Oxide Nanoparticles for Ultrafast and Broadband Mid-Infrared All-Optical Switching
摘要： Plasmons in conducting nanostructures offer the means to efficiently manipulate light at the nanoscale with subpicosecond speed in an all-optical operation fashion, thus allowing for constructing high performance all-optical signal-processing devices. Here, by exploiting the ultrafast nonlinear optical properties of broadly tunable mid-infrared (MIR) plasmons in solution-processed, degenerately doped oxide nanoparticles, we demonstrate ultrafast all-optical switching in the MIR region, which features with subpicosecond response speed (with recovery time constant of ?400 fs) as well as ultrabroadband response spectral range (covering 3.0-5.0 μm). Furthermore, with the degenerately doped nanoparticles as Q-switch, pulsed fiber lasers covering 2.0-3.5 μm were constructed, of which a watt-level fiber laser at 3.0 μm band show superior overall performance among ever-reported passively Q-switched fiber lasers at the same band. Notably, the degenerately doped nanoparticles show great potential to work in the spectral range over 3.0 μm that is beyond the accessibility of commercially available but expensive semiconducting saturable absorber mirror (SESAM). Our work demonstrates a versatile while cost-effective material solution to ultrafast photonics in the technologically important MIR region.
关键词： tunable plasmons,ultrafast photonics,all-optical switching,doped oxide nanoparticles,mid-infrared
更新于2025-09-23 15:21:21
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Ultrathin Y <sub/>2</sub> O <sub/>3</sub> :Eu <sup>3+</sup> nanodiscs: spectroscopic investigations and evidence for reduced concentration quenching
摘要： Here, we report the synthesis and spectral properties of ultrathin nanodiscs (NDs) of Y2O3:Eu3+. It was found that the NDs of Y2O3:Eu3+ with a thickness of about 1 nm can be fabricated in a reproducible, facile and self-assembling process, which does not depend on the Eu3+ concentration. The thickness and morphology of these NDs were determined with small angle x-ray scattering and transmission electron microscopy. We found that the crystal field in these nanoparticles deviates from both the cubic and monoclinic characteristics, albeit the shape of the 5D0 → 7FJ (J = 0, 1, 2) transitions shows some similarity with the transitions in the monoclinic material. The Raman spectra of the non-annealed NDs manifest various vibration modes of the oleic acid molecules, which are used to stabilise the NDs. The annealed NDs show two very weak Raman lines, which may be assigned to vibrational modes of Y2O3 NDs. The concentration quenching of the Eu3+ luminescence of the NDs before annealing is largely suppressed and might be explained in terms of a reduction of the phonon density of states.
关键词： nanodiscs,small angle x-ray scattering,europium-doped yttrium oxide,Raman spectroscopy,concentration quenching,transmission electron microscopy,luminescence
更新于2025-09-23 15:21:21
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Effect of thermal oxidation temperatures on the phase evolution and photocatalytic property of tungsten-doped TiO <sub/>2</sub> thin film
摘要： Tungsten-doped titanium dioxide (W-TiO2) thin films were successfully prepared on glass substrates by sputtering thermally oxidized W-doped titanium films in air. Tungsten-doped titanium films were deposited using a DC and RF magnetron cosputtering system. The effects of annealing treatment and W content on the W-TiO2 film microstructure were investigated. The crystalline structures, morphological features, and photocatalytic activity of the annealed W-TiO2 films were systematically studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), and ultraviolet spectrophotometry. The results indicated that annealing at 550 °C clearly induced the formation of an anatase and rutile phase mixture in the 5.5 at. % W-TiO2 films, which directly affected photocatalytic activity. The W-TiO2 films showed good photocatalytic activity under UV-light irradiation, with a higher rate of methylene blue dye degradation than in the case of undoped TiO2.
关键词： photocatalytic activity,tungsten-doped titanium dioxide,thermal oxidation,methylene blue degradation,thin films
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Field Emission Properties of Indium-Doped ZnO Nanowires Prepared on ITO Glass Substrate
摘要： Doping is an important approach for improving the field emission properties of semiconductor nanowire field emitters. The indium-doped zinc oxide nanowires were prepared on ITO glass substrate by thermal oxidation method and field emission properties were measured. The prepared In-doped nanowire arrays shows excellent field emission performance with a turn-on field of 4.0 V/μm and current fluctuation of ~1.4%.
关键词： field emission,ZnO nanowire,indium doped
更新于2025-09-23 15:21:21
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Functionalized Holmium-Doped Hollow Silica Nanospheres for Combined Sonodynamic and Hypoxia-Activated Therapy
摘要： The oxygen concentration dependence of sonodynamic therapy (SDT) and bioreductive therapy can be utilized to design the strategy of synergistic therapy. Herein, holmium-doped hollow silica nanospheres are synthesized and then sequentially modified with chlorin e6, carboxyl poly(ethylene glycol) silane, and prostate stem cell antigen (PSCA) monoclonal antibody. The resultant nanocomposite designated as HHSN-C/P-mAb has good biocompatibility and can specifically target cancer cells overexpressing PSCA. Due to the inner cavity structure and Ho doping, HHSN-C/P-mAb shows high ultrasound (US) imaging contrast capability and excellent high-field magnetic resonance contrast performance. HHSN-C/P-mAb can act as a nanocarrier for loading the bioreductive prodrug tirapazamine (TPZ), and the degradation of the hollow nanospheres under the trigger of acidic microenvironment favors the pH responsive release of TPZ from the material. Upon US irradiation, HHSN-C/P-mAb produces reactive oxygen species to kill the cancer cells, and importantly, the oxygen consumption during SDT induces an intratumoral hypoxic environment to activate the therapeutic function of codelivered TPZ, resulting in a high-effective synergistic therapy. The findings of this study highlight that HHSN-C/P-mAb is a versatile theranostic nanoplatform for efficient cancer treatment.
关键词： magnetic resonance imaging,sonodynamic therapy,ultrasound imaging,holmium-doped hollow silica nanosphere,bioreductive therapy
更新于2025-09-23 15:21:21
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Point-by-Point Femtosecond-Laser Inscription of 2-μm-Wavelength-Band FBG through Fiber Coating
摘要： We propose a point-by-point inscription method for fiber Bragg grating (FBG) fabrication using a femtosecond pulsed laser focused through a fiber polyimide coating, realizing a 2-μm-wavelength-band FBG. A femtosecond laser acts as the inscription laser, focused by a 63× oil lens. A first-order FBG was fabricated with a grating interval of 700 nm. The 15- μW pulsed laser was focused directly on the fiber core through the polyimide coating and cladding. A first-order FBG for 2004.8-nm light with more than 56% reflectances was fabricated. High wavelength sensitivity and linearity of the FBG were demonstrated by temperature and strain-sensing testing. The first-order FBG of 2004.8 and 2000.2 nm resonant wavelengths could be realized simultaneously through parallel inscription method in 3000μm long grating area.
关键词： 2-μm-wavelength-band,Fiber Bragg grating,Erbium-doped fiber laser,Femtosecond pulsed laser
更新于2025-09-23 15:21:21
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Sulfur-doped porous graphitic carbon nitride heterojunction hybrids for enhanced photocatalytic H2 evolution
摘要： Graphitic carbon nitride (g-C3N4) is considered as an attractive, efficient and newly generated photocatalyst material owing to its distinct properties such as metal free, suitable band gap and high physicochemical stability. Nevertheless, the photocatalytic activity of pure g-C3N4 was limited by the fast recombination rate of photoinduced electron–hole pairs and relatively low specific surface area. In this study, we provide a new prospect to overcome the problem by using another suitable precursor urea-assisted copolymerization with thiourea which is expected to optimize the process of thermal condensation, inhibit agglomeration and improve the specific surface area; meanwhile, the formed isotype heterogeneous junction effectively inhibits charge carrier recombination. The formed g-C3N4 isotype heterojunction photocatalyst manifested significant improvement photocatalytic hydrogen production than the single and pure g-C3N4 sample. This significant enhanced photocatalytic performance is mainly ascribed to inhibited recombination, enriched active site and enlarged specific surface area.
关键词： porous graphitic carbon nitride,heterojunction hybrids,photocatalytic H2 evolution,Sulfur-doped
更新于2025-09-23 15:21:21