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Surface defect and rational design of TiO2?x nanobelts/ g-C3N4 nanosheets/ CdS quantum dots?hierarchical structure for enhanced visible-light-driven photocatalysis
摘要： TiO2-x/g-C3N4/CdS ternary heterojunctions are fabricated through thermal polymerization-chemical bath deposition combined with in-situ solid-state chemical reduction approach. The prepared materials are characterized by X-ray diffraction, Fourier transform infrared spectra, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption-desorption, and X-ray photoelectron spectroscopy. The results show that the ternary heterojunctions are formed successfully and CdS quantum dots (QDs) and TiO2 are anchored on surface of g-C3N4 nanosheets simultaneously. The visible-light-driven photocatalytic degradation ratio of Bisphenol A and hydrogen production rate are up to 95% and ~254.8 mmol h-1, respectively, which are several times higher than that of pristine TiO2. The excellent visible-light-driven photocatalytic activity can be ascribed to the synergistic effect of TiO2-x, g-C3N4 and CdS QDs which extend the photoresponse to visible light region and favor the spatial separation of photogenerated charge carriers.
关键词： Photocatalysis,Ti3+ self-doping,g-C3N4 nanosheets,CdS quantum dots,TiO2 nanobelts
更新于2025-09-04 15:30:14
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Deep level acceptors of Zn-Mg divalent ions dopants in β-Ga2O3 for the difficulty to p-type conductivity
摘要： β-Ga2O3 exhibits huge potential applications in next-generation power electronics with its wide band gap, large breakdown field and high Baligas’s figure of merit. The achievement of p-type conductive β-Ga2O3 faces hugely challenge due to the self-compensating process, while that is critically important to further extend its utility and applications. Although the acceptor deep levels of divalent ions dopants can explain the difficulty of p-type Ga2O3 theoretically, while the experimental evidence is lacked. Herein, Zn and Zn-Mg co-doped β-Ga2O3 thin films were prepared to investigate the acceptor levels of ZnGa and MgGa. The XPS results indicate that both Zn and Mg exhibit divalent ions when they replaced trivalent Ga ion. The doping concentration and band gap can modulate by solely changing the numbers of Zn and Mg pieces during the deposition process. The levels of ZnGa and MgGa are located at 0.79 eV and 1.00 eV respectively speculated by photoluminescence, such deep acceptor transition levels proved that it is difficult to obtain highly conductive p-type Ga2O3 by doping with divalent ions of Zn and Mg.
关键词： acceptor levels,p-type conductivity,photoluminescence,Zn-Mg doping,β-Ga2O3
更新于2025-09-04 15:30:14
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High germanium doping of GaN films by ammonia molecular beam epitaxy
摘要： Doping Gallium nitride (GaN) with elemental Germanium (Ge) grown by ammonia molecular beam epitaxy is presented. Growth studies varying the GaN growth rate, substrate growth temperature and the elemental Ge flux reveal several incorporation dependencies. Ge incorporation increases with flux, as expected, and a doping range from ~1017 cm-3 to 1020 cm-3 was readily achieved. A strong substrate temperature dependence on the electrical properties of films grown is observed, with an optimal growth temperature of 740 °C, lower than standard GaN growth conditions for the ammonia molecular beam epitaxy. Compensation effects at higher growth temperatures are suspected, as observed with other techniques. Crystallographic defects are apparent at the highest doping concentrations from electrical and optical measurements, however thin layers of such highly doped films are of great interest for contact layers and tunnel junctions in devices.
关键词： Ammonia Molecular Beam Epitaxy,Molecular Beam Epitaxy,Tunnel Junctions,Germanium Doping,Gallium Nitride
更新于2025-09-04 15:30:14
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Structural stability and electronic properties of XTO2 (X= Cu, Ag; T=Al, Cr): an ab initio study including X vacancies and Mg doping
摘要： Ab initio density functional theory-based calculations are used to study the structural and electronic properties of CuAlO2, AgAlO2, CuCrO2, and AgCrO2 transparent conducting oxides (TCOs). The hexagonal 2H delafossite polymorph is determined here to be one of the most stable polymorphs, by comparing total energies for different structural phases. The simple antiferromagnetic configuration is chosen to model magnetic effects in CuCrO2 and AgCrO2 due to it having one of the lowest ground state total energies and containing the most semiconductor like behavior of the magnetic configurations considered. Electronic structures of 2H CuAlO2 and AgAlO2 obtained from different approximations for the exchange-correlation functional, GGA (PBE), PBE+U, PBE+mBJ, PBE+mBJ+U, and the Hybrid HSE06 are compared. Supercells are employed to model 6.25% Cu and Ag vacancies, 3.13% O vacancies, and 6.25% Mg doping replacing Al and Cr, from which structural and electronic properties are obtained and used to predict on the effectiveness of these native defects and dopant on increasing the conductivity in all TCOs studied in this work. The obtained partial density of states for the pristine systems supports a model of hole conduction in the a – b plane, perpendicular to the O – X – O dumbbells of the delafossite structure. Additionally, the partial density of states of the defective and doped systems suggest a growth environment deficient in X and saturated in O may increase conductivity in these materials.
关键词： Delafossite,Density functional theory,Transparent conducting oxides,Mg doping,Structural stability,Ab initio,Vacancies,Electronic properties
更新于2025-09-04 15:30:14
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Significant improvement of the performance of ZrO2/V1-W O2/ZrO2 thermochromic coatings by utilizing a second-order interference
摘要： The paper deals with VO2-based thermochromic coatings prepared by reactive magnetron sputtering. We combine four ways how to improve the coating performance and to increase its application potential. First, reactive high-power impulse magnetron sputtering with a pulsed O2 flow control allowed us to prepare crystalline VO2 of the correct stoichiometry under highly industry-friendly deposition conditions: without any substrate bias at a low deposition temperature of 330 °C. Second, doping of VO2 by W (leading to V1-xWxO2, with x = 0.012 in this work) allowed us to shift the thermochromic transition temperature towards the room temperature (39 °C in this work), without concessions in terms of coating properties. Third, we employ ZrO2 antireflection layers both below and above the thermochromic V1-xWxO2 layer, and present an optimum design of the resulting ZrO2/V1-xWxO2/ZrO2 coatings. Most importantly, we show that while utilizing a first-order interference on ZrO2 leads one to a tradeoff between the luminous transmittance (Tlum) and the modulation of the solar transmittance (ΔTsol), utilizing a second-order interference allows one to optimize both Tlum and ΔTsol in parallel. Fourth, the crystalline structure of the bottom ZrO2 layer further improves the VO2 crystallinity and the process reproducibility. The optimum experimental values of ZrO2 thickness are in agreement with those predicted during the coating design. The results are important for the design and low-temperature fabrication of high-performance durable thermochromic VO2-based coatings for smart window applications.
关键词： Thermochromic coatings,Low deposition temperature,Antireflection layer,HiPIMS,Doping,VO2
更新于2025-09-04 15:30:14
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Ionic Radii and Concentration Dependency of RE <sup>3+</sup> (Eu <sup>3+</sup> , Nd <sup>3+</sup> , Pr <sup>3+</sup> and La <sup>3+</sup> ) Doped Cerium Oxide Nanoparticles for Enhanced Multi-Enzyme Mimetic and Hydroxyl Radical Scavenging Activity
摘要： The anti-oxidant activity of cerium oxide nanoparticles (CNPs) depends on the concentration of oxygen vacancies and Ce3+ active sites. In the present work, we report the impact of 5 mol% tri-valent rare earth doped (RE3+ = Eu3+, Nd3+, Pr3+ and La3+) CNPs on the oxidation state modulation and anti-oxidant property with respect to ionic radii. An increase in lattice parameter, strain and oxygen vacancy concentration was observed as a function of ionic radii. Among the various dopants in CNP, La3+ with higher ionic radii having smaller crystallite size (7.9 nm) and higher vacancy displayed better peroxidase, oxidase and hydroxyl radical (HO?) scavenging activity. The kinetic parameters for the peroxidase and oxidase activity was found to be superior with Km = 0.217 mM and 0.261 mM, respectively, for 5 mol% La3+ doped CNPs. In order to divulge the role of dopants concentration on structural properties, we also explored using 10 and 20 mol% La3+ doping in CNP. Due to smaller crystallite size (6.7 nm) and higher defect level (3.12 x 1021 cm-3), 20% La3+ doping showed superior peroxidase and oxidase activity as shown by the low Km values. CNPs exhibit both peroxidase and oxidase activity in a concentration dependent manner. Moreover, CNPs exhibit a concentration dependent peroxidase and oxidase activity that can be selectively activated for various theranostic applications. Thus, our results demonstrate the crucial role of ionic radii and concentration of RE3+ dopants on the defect formation in cerium oxide nanoparticles for improved anti-oxidant properties of ceria.
关键词： ionic radii,RE3+ doping,oxygen vacancies,peroxidase activity,oxidase activity,hydroxyl radical scavenging,cerium oxide nanoparticles,anti-oxidant properties
更新于2025-09-04 15:30:14
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Studies on Different Doped Zn Concentrations of CdSe Thin Films
摘要： Different Zn concentration was doped with CdSe thin films by Electron Beam Evaporation method. Crystallite variation was studied for doping effect and it was found to be about 40 to 50 nm respectively. Optical band gap values are found to be modified by doping as well as annealing. Annealed films showed considerable influence in their opto-elctronic and structural properties, which provided improvement in conversion efficiency of about 2.75% and 2.87% respectively.
关键词： PEC solar cells,Electron beam evaporation,Doping effect,XRD of CdSe
更新于2025-09-04 15:30:14
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Photocatalytic activity of gadolinium doped TiO <sub/>2</sub> particles for decreasing heavy metal chromium (VI) concentration
摘要： Titanium dioxide (TiO2) is among the most potential photocatalyst. However, TiO2 only works under UV light due to the relatively wide band gap energy. To overcome this, TiO2 is infiltrated (doped) by rare earth elements such as gadolinium (Gd). TiO2 was synthesized using sol gel method, while Gd/TiO2 photocatalyst was synthesized by the mixing methods of sol-gel and impregnation. The crystals are then characterized using XRD and SEM-EDX. The XRD diffractogram demonstrated that the crystallinity synthesized of TiO2 had an anatase structure similar to the structure of anatase P-25 as references. The SEM-EDX showed that Gd ion could not enter the crystal lattice, but only dispersed on the surface of TiO2 particles. The optimum result of decreased Cr(VI) concentration was reported using Gd/TiO2 1% w/w by a decrease of up to 94%, after irradiated with ultraviolet for one hour.
关键词： sol-gel method,gadolinium doping,TiO2,Cr(VI) concentration,photocatalyst
更新于2025-09-04 15:30:14
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Solution combustion synthesis and characterization of phosphorus doped TiO2–CeO2 nanocomposite for photocatalytic applications
摘要： Phosphorus doped TiO2-CeO2 nanocomposite (P-TiO2-CeO2) was synthesized by solution combustion method. The prepared sample has been heated at di?erent temperatures and characterized by X-ray di?raction (XRD), scanning electron microscopy (SEM), UV–vis absorption spectra, X-ray photoelectron spctroscopy (XPS). XRD analysis reveals the retarded phase transition by increased thermal stability due to phosphorus doping. FE-SEM shows the porous structure of the sample. The absorption edge of the P/TiO2-CeO2 nanocomposite exhibits redshift with increasing heating temperature with its value around 2.93 eV, 2.90 eV and 2.89 eV at 400 °C, 500 °C and 600 °C respectively. From the observed P2p XPS peak, it is con?rmed that the doped phosphorus enters substitutionally into Ce4+/Ti4+ site, which can play an important role in the photocatalytic activity of the sample. The binding energy of Ti 2p XPS peak increases slightly from 458.5 eV to 458.8 eV due to interaction between titanium and cerium.
关键词： Phosphorus doping,TiO2,CeO2,XPS,TiO2-CeO2 nanocomposite
更新于2025-09-04 15:30:14
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Quantum Cutting Luminescent Solar Concentrators Using Ytterbium Doped Perovskite Nanocrystals
摘要： We introduce and demonstrate the concept of quantum-cutting luminescent solar concentrators (QC-LSCs) using Yb3+-doped perovskite nanocrystals. These NCs feature a photoluminescence quantum yield approaching 200% and virtually zero self-absorption loss of PL photons, defining a new upper limit of 150% for the internal optical efficiency (ηint) of LSCs that is almost independent of LSC sizes. An unoptimized 25 cm2 QC-LSC fabricated from Yb3+-doped CsPbCl3 NCs already displayed an ηint of 118.1±6.7% that is 2-fold higher than previous records using Mn2+-doped quantum dots (QDs). If using CsPbClxBr3-x NCs capable of absorbing ~7.6% of solar photons, the projected external optical efficiency (ηext) of QC-LSCs can exceed 10% for >100 cm2 devices which still remains a big challenge in the field. The advantage of QC-LSCs over conventional QD-LSCs becomes especially obvious with increasing LSC sizes, which is predicted to exhibit more than 4-fold efficiency enhancement in the case of window size (1 m2) devices.
关键词： Luminescent solar concentrators,Solar energy,Doped nanocrystals,Quantum cutting,Ytterbium doping
更新于2025-09-04 15:30:14