Doping Molar Research Articles

Preparation and optical properties of Co doped nano-ZnO arrays

Firstly, ZnO seed layer thin films were successfully prepared on silicon substrates by radio frequency magnetron sputtering method. The seed layer substrate was treated at high temperature of 400 °C and placed vertically on the substrate in a high-pressure reactor. Co/ZnO nanorod arrays with good dispersibility were synthesized by hydrothermal synthesis at 100 °C on the ZnO seed layer using Zn(CH3COO)2·2H2O as the zinc source, NaOH as the analytical reagent, and C4H6CoO4·4H2O as the cobalt source. The structure, morphology, and optical properties of the samples were characterized and analyzed in sequence. The results indicate that the sample exhibits strong diffraction peaks on the crystal plane (002, 101, 102) and the growth of the (002) crystal surface is preferred. The prepared samples are hexagonal wurtzite structure. With the increase of Co doping molar ratio, the uniformity of the samples gradually becomes worse, while the average diameter of ZnO nanorods becomes larger. The PL spectrum shows that the sample has a strong ultraviolet emission peak at around 372 nm, and a significant red shift has occurred. Besides, there is a relatively weak visible light emission peak appeared near 565 nm. Finally, the growth mechanism and luminescence mechanism of nano-Co/ZnO arrays are explained.

Engineered Sn-TiO2@SnO2 and SnO2@Sn-TiO2 heterophotocatalysts for enhanced As(III) remediation: A comprehensive bulk and surface characterization and precise photocatalytic oxidation rates determination

Arsenite, As(III), is a highly toxic form of arsenic that poses a significant risk to human health if present in drinking water. Oxidation of As(III) to the less toxic As(V) using TiO2 as photocatalyst is an attractive solution in water treatment applications but challenged the high bandgap energy. In this study, we investigate the potential of doping TiO2 with Sn to reduce the bandgap and hence to improve the photocatalytic oxidation (PCO). To this end, we studied first the effect of varying Sn:TiO2 molar doping on the structure of the newly synthesized SnO2@TiO2 and Sn-TiO2@SnO2 hetero photocatalysts. We found that at low Sn:TiO2 doping ratios (0.1Sn:1TiO2), SnO2 tends to float on the surface and form a coat around the TiO2 (SnO2@Sn-TiO2), whereas at higher doping ratio (1Sn:1TiO2) a Sn-TiO2 coat forms alongside SnO2 clusters in the core of the catalyst (Sn-TiO2@SnO2). We assessed the PCO and observed significant shifts to lower conduction and valence band edge energies and a reduction of the bandgap at higher doping ratios. The smallest bandgap was 2.87 eV with a doping ratio of 1Sn:1TiO2. Sn-TiO2@SnO2 and as SnO2@Sn-TiO2 improved the PCO of TiO2 by ∼30 and 46 %, respectively. We finally determined the rate constant (k) for the As(III) oxidation using a combination of spectrochemical and surface sensitive techniques and determined for a 1Sn:1TiO2 (i.e. Sn-TiO2@SnO2) catalyst a value of 0.055 ±0.002 min−1, i.e., 78 folds faster than using only TiO2. We conclude that Sn doping of TiO2 is a very promising approach for improving the PCO of As(III) in water treatment.

Ag-TiO2 Photovoltaic Synergistic Field-catalyzed Degradation Performance of Tetracycline

Background: Tetracycline (TC), a commonly used antibiotic, is extensively utilized in the medical sector, leading to a significant annual discharge of tetracycline effluent into the water system, which harms both human health and the environment. Objective: A novel technique was developed to address the issues of photogenerated carrier complexation and photocatalyst immobilization. Compared to traditional photocatalytic photoelectrodes, the suspended catalyst used in the photovoltaic synergy field is more stable and increases the solidliquid contact area between the catalyst and the pollutant. Methods: This paper uses sol-gel-prepared Ag-TiO2 materials for the photoelectric synergistic fieldcatalyzed degradation of TC. The study examined how the Ag doping ratio, calcination conditions, catalyst injection, pH, electrolytes, and electrolyte injection affected photoelectric synergistic fieldcatalyzed degradation. The experiments were performed in a photocomposite field with a constant 50 mA current and a 357 nm UV lamp for 60 minutes. The composites underwent characterization using XRD, TEM, and XPS techniques. Results: Ag-TiO2 photoelectric synergistic field-catalyzed reaction with 357 nm ultraviolet lamp irradiation for 60 min and a constant current of 50 mA degraded 5 mg/LTC under preparation conditions of molar doping ratio of Ti: Ag=100:0.5, roasting temperature of 500 °C, and roasting time of 2 h. The photoelectric synergistic field-catalyzed degradation process achieved a degradation rate of 90.49% for 5 mg/L TC, surpassing the combined degradation rates of electrocatalysis and photocatalysis. The quenching experiments demonstrated that the degradation rate of TC decreased from 90.49% in the absence of a quencher to 53.23%, 42.58%, and 74.52%. The presence of •OH had a more significant impact than h+ and •O2 -. Conclusion: The findings suggest that Ag-TiO2 significantly enhanced the efficacy of photoelectric synergistic field-catalyzed degradation and can be employed to treat high-saline and lowconcentration TC. This establishes a benchmark for using photoelectrocatalytic materials based on titanium in treating organic wastewater.

Charge balance in OLEDs: Optimization of hole injection layer using novel p‐dopants

AbstractCharge balance is one of the most important factors for realizing high performance organic light emitting devices (OLEDs). In this work, we provide a novel strategy to improve the charge balance in OLEDs by optimizing the hole injection layer (HIL) as well as the electron transporting layer (ETL) and thereby controlling the charge carrier supplies in the device. First, we develop a p‐dopant material (PD02), with a lowest unoccupied molecular orbit (LUMO) of −4.63 eV, much shallower than that of the commercial material (PD01) of which the LUMO is −5.04 eV. Nevertheless, this enables us to modulate the supply of holes to the emissive layer through tuning doping concentration. We demonstrate that device performances are significantly improved by employing such a scheme. With a 23% molar doping of PD02, a bottom emission red OLED achieves an external quantum efficiency (EQE) of over 30%, an operating voltage of 3.4 V and a LT95 ~15,000 h at 10 mA/cm2, with a Digital Cinema Initiative P3 (DCI‐P3) chromaticity of CIE (X, Y) = (0.68, 0.32). Moreover, the efficiency roll‐off is suppressed up till ~3500 cd/m2, a desirable feature in display applications. The lateral conductivity of by using such HIL is also found to be much lower than that of PD01, resulting in reduced crosstalk among RGB pixels. Next, a new electron transporting material (ETM‐02) with a deep LUMO of −2.86 eV is also introduced to further optimize the charge balance. Although devices with ETM‐02 shows lower voltage and higher EQE, lifetime is compromised. In order to improve lifetime, additional fine tuning of the charge balance is essential. Finally, a second p‐dopant PD03 with a LUMO of −4.91 eV is added to the HIL to further extend the modulation flexibility in the hole injection. A double‐layer HIL consisting of 8 nm of HTM:16% PD02 and 2 nm of HTM:3% PD03, where the former is in contact with anode, is adopted in the device structure. The bottom emission deep red device achieve EQE over 30%, an operating voltage of 3.2 V and an improved LT95 ~13,000 h at 10 mA/cm2 with a BT.2020 range chromaticity of CIE (X, Y) = (0.701, 0.299). In the double HIL configuration, the introduction of PD03 provides one more parameter for tuning and therefore improves the overall device performances.

Al- and Cr-doped Co3O4/CoO redox materials for thermochemical energy storage in concentrated solar power plants

The redox system of Co3O4/CoO is very promising for the thermochemical energy storage systems coupled to concentrated solar power plants because of its high energy storage density and reversibility. Nevertheless, the practical application of Co3O4/CoO system is limited by thermal hysteresis of the redox reaction and material sintering. Here, we synthesized Co-based metal oxides doped with Al and Cr, and studied the influence of the doping of these two metal elements on the thermochemical properties and sintering resistance of the pure Co3O4/CoO system. Both Al and Cr doping narrows the thermal hysteresis of the Co3O4/CoO system. In particular, when the molar doping rate of Al is 10%, the thermal hysteresis of Co–Al oxides is only 4.02 °C, which is much narrower than that of pure Co3O4, and the increase of its oxidation temperature also means that a higher level of thermal energy can be released during oxidation. In the redox cycle, the addition of Al inhibits material sintering and the formation of a loose porous structure facilitates the oxidation, ensuring the reversibility of the redox reaction. The 10% Al–Co honeycomb shows stable conversion behavior with an average conversion of 77.75% in 15 redox cycles. Co–Al oxides exhibit excellent oxidative exothermic characteristics and long-term cycle stability, making them suitable for efficient thermochemical energy-storage processes.

Efficient sulfur host based on Sn doping to construct Fe2O3 nanospheres with high active interface structure for lithium-sulfur batteries

Lithium-sulfur batteries are hampered by the shuttle effect and sluggish conversion kinetics of polysulfide, and give rise to serious capacity decay and poor rate performance, which is an important reason for limiting to commercialization applications. Herein, Sn-doped Fe2O3 nanospheres with high active interface structure adhere to adequate and high-efficiency catalytic sites have been designed by a facile hydrothermal reaction. Theoretical calculations of density of states (DOS), visualized detection, symmetric cyclic voltammetry and Li2S nucleation experiment can elucidate adsorption effect and the mechanism of promoting polysulfide conversion. When Sn@Fe2O3 with Sn doping molar ratio to 1:3, it can advance growth of Li2Sn (93.47 mAh·g−1), reduce the reaction energy barrier, and enhance the conversion of polysulfides. Thus, as a sulfur composite cathode active material, it shows low electrochemical charge transfer resistance (56.14 Ω) and great lithium-ion diffusion coefficient (DLi+ = 1.4 × 10−11 cm2·s−1). Meanwhile, it has a great initial discharge capacity of 1057 mAh·g−1 at 0.5 C along with 85 % discharge capacity retention at 1 C after 130 cycles. Encouragingly, even with a sulfur loading up to 1.2 mg cm−2, the sulfur composite cathode still can harvest high lithium-ion transfer efficiency and cyclic stability.

Studies on photocatalytic performance and supercapacitor applications of undoped and Cu-doped ZnO nanoparticles

The structural, morphology and optical properties were characterised using XRD, FTIR, SEM, TEM, and UV-DRS for the undoped and Cu-doped ZnO NPs with varying Cu doping molar concentrations from 0 wt% to 6 wt% through the co-precipitation method. The presence of a ZnO hexagonal wurtzite structure for all samples was confirmed by the structural study of the Cu-doped ZnO NPs, indicating the incorporation of Cu2+ ions into the ZnO lattice by substitution and average crystallite sizes of 25–22 nm. The surface morphology analysis of undoped and Cu-doped ZnO NPs indicated the growth of spherical nanocrystallites with fine particles. Optical studies of Cu-doped ZnO nanostructured particles revealed that increasing the Cu doping agent from 0 wt% to 6 wt% resulted in a blue shift of the absorption band with increasing band gap energy from 3.27 eV to 3.44 eV. The degradation efficiency of MB is 89.2% for Cu-doped ZnO photocatalyst, which performs much better than undoped ZnO under natural sunlight irradiation. The electrochemical analysis determined the specific capacitance of 10 to 100 mV/s scan rate for all the samples. Amongst the various concentrations, 6 wt% Cu-doped ZnO had the most excellent specific capacitance of 539.87 F/g at 10 mV/s. Compared with undoped ZnO NPs, Cu-doped into the ZnO matrix enhanced photocatalytic activities and electrochemical performance for wastewater treatment and supercapacitor applications.

Degradation of carbamazepine over MOFs derived FeMn@C bimetallic heterogeneous electro-Fenton catalyst

A highly efficient heterogeneous electro-Fenton (Hetero-EF) catalyst with core-shell structure was successfully prepared by calcination of Mn-doped Mil-53 (Fe) precursor at high temperature. FeMn@C-800/2 prepared at pyrolysis temperature of 800 °C and Fe:Mn molar doping ratio of 2:1 showed the best catalytic performance for the degradation of carbamazepine (CBZ). The characterization, properties and stability of FeMn@C-800/2 were systematically investigated, obtaining the apparent first-order reaction rate of Hetero-EF was 8.9 and 17.8 times higher than that on Fe@C-800 and Mn@C-800 at the optimized conditions of current density 10 mA cm−2, catalyst dosage of 50 mg L−1 and initial pH 4.0, respectively. The incorporation of Mn promoted the generation of more Fe0 and Fe3C during the pyrolysis process, and enhanced the internal micro-electrolysis between Fe0 and carbon shell. At the same time, the presence of Mn0 also promoted the regeneration of Fe2+, and improved the activity of iron-carbon heterogeneous catalysis in the EF process, so as to degrade organic pollutants more effectively. This work would help to gain insight into the design of MOFs derived Fe–Mn bimetal catalyst and its mechanism for enhanced heterogeneous electro-Fenton.

Enhanced visible light photo-Fenton catalysis by lanthanum-doping BiFeO3 for norfloxacin degradation

Efficient photo-Fenton removal of antibiotic effluent is a widely followed and significant attempt to deal with the growing environmental pollution. In this study, BiFeO3 and lanthanum doped BiFeO3 catalysts were synthesized via one-step hydrothermal method as hydrogen peroxide activator for mineralization of norfloxacin (NOR). Various characterization measurements were used to verify La was successfully doped into the lattice of perovskite and investigated the effect of La doping molar ratio on BiFeO3 through the characterization of the morphology and physicochemical properties. The degradation experiment and reaction rate constants showed that the La-doped BiFeO3 particle exhibited superior photo-Fenton catalytic performance to undoped BiFeO3. Especially, the degradation efficiency of 15% La-doped BiFeO3 could reach up to 84.94%. And the first order kinetic constant of optimized conditions was 0.01638 min−1, which was about 6.9 times than that of undoped BiFeO3.The influence of pH, oxidizer content and catalyst dosage in photo-Fenton reaction were investigated detailedly. Besides, the synthetic catalyst possessed favorable stability and reusability with little metal leaching after many cycles of use. Radical scavenger experiments and electron spin resonance tests were carried out to conclude that the ·OH and holes were regarded as the dominate active species in the catalytic process. The narrow band gap and excellent electron transfer efficiency were the key factors for La-doped BiFeO3 to have high catalytic efficiency in the photo-Fenton system. Current works demonstrated the great promise of La-doped BiFeO3 in the elimination of antibiotic organics.

Microstructural and electrical features of highly conducting indium co‐doped ZnO‐based ceramics

AbstractIn this work, we developed experimental approaches on indium co‐doped ZnO‐based ceramics from the synthesis to the characterizations and analysis of physical features in the aim to achieve the formation of highly conducting ceramics with controlled nonlinearity. Different doping molar ratios of indium were used and the synthesis of the ceramics was realized by the conventional solid‐state reaction method which was then followed by a sintering under air (A), nitrogen (N), or a mixture of nitrogen and carbon monoxide (NC) atmosphere with different reduction capabilities. The structure, morphology, electrical investigations, and the electronic transport analysis were conducted on the different ZnO co‐doped ceramics as functions of the indium incorporation and the used sintering atmosphere, A, N, or NC. Suitable indium doping of 0.3 mol% and the use of highly reducing sintering atmosphere (NC) ensure the formation of ZnO‐based ceramics with an electrical conductivity up to (103 S/cm) and a quasi‐linear behavior on the electrical characteristic I–V. We discussed the obtained performances by correlating the charge transport with the microstructure of the ceramics, the composition, and the structure of grain boundaries as well as the solubility of indium in the host ZnO ceramic grains.

(Digital Presentation) Effects of Cation Doping on the Stability and Charge Acceptance of Alpha Nickel Hydroxide for Energy Storage Applications

Nickel hydroxide is used as active material in nickel based batteries and capacitors. It has two phases which are alpha and beta, since alpha nickel hydroxide has higher capacity it attracts scientists attention. Although it has promising performance, low utilization and poor stability hinder commercialization of alpha nickel hydroxide. The most common strategy to improve stability is to dope nickel hydroxide with cobalt or aluminum. Aluminum is more prominent due to its lower price and environmental concern. Besides the stability, it is well known that discharge capacity of nickel hydroxide decreases with increasing amount of both aluminum and cobalt. Although capacity is decrasing, number of electrons which is involved in the reaction does not change with increasing amount of dopant. At the same molar doping levels, although aluminum doped samples had higher active mass (nickel) content, they had lower gravimetric capacity than cobalt doped samples. Therefore, it is not convenient to explain capacity loss by only decreasing amount of active mass.Since cobalt doping raises differences between oxygen evolution potential and oxidation potential of nickel hydroxide, it enhances chargeability of nickel hydroxide but the cyclic voltammetry results showed that higher cobalt doping causes decrease in cell voltage and energy density of battery. The results showed that higher amount of aluminum must be doped to improve stability and relatively small amount of cobalt must be used to improve chargeability of alpha nickel hydroxide. Therefore, both aluminum and cobalt are effective in improving stability but cobalt is advantageous at low doping level, as it is reported in the literature.

45‐1: Invited Paper: Charge Balance in OLEDs: Optimization of Hole‐Injection Layer

In this work, we provide a novel strategy to improve the charge balance in organic light emitting devices (OLEDs) by optimizing the hole injection layer (HIL) and thereby controlling the overall hole supply in the device. The lowest unoccupied molecular orbit (LUMO) of the p‐dopant proposed in this work, PD02, is ‐4.63 eV, much shallower than that of the commercial material (PD01). Nevertheless, this enables use of the doping concentration to modulate the supply of holes to the emissive layer to control the charge balance. We demonstrate that device performances are significantly improved by employing such a scheme. With 23% molar doping of PD02, a bottom emission red OLED achieves external quantum efficiency (EQE) over 30%, operating voltage of 3.4 V and LT95 ~ 15,000 h at 10 mA/cm2. Moreover, the efficiency roll‐off is also suppressed up till ~ 3,500 cd/m2, a desirable feature in display applications. A study of exciton distribution within the emissive layer suggests that improved charge balance is indeed achieved in the optimized structure. An additional benefit from the modified HIL is its lower lateral conductivity relative to the standard formula, which reduces crosstalk between RGB pixels.

Near-Infrared Shielding Performance of Tungsten-Doped Tin Dioxide Nanoparticles

Heat-insulating clear coatings have been widely studied and used in energy conservation of buildings. In this article, tungsten-doped tin dioxide (WTO) nanoparticles were synthesized by a facile hydrothermal approach. The effects of molar doping ratios of tungsten, calcination temperatures of the WTO precursor, and hydrothermal synthesis temperatures on the phase composition and optical properties of WTO powder were investigated. The conditions for the preparation of WTO with better optical properties are as follows: the hydrothermal temperature is 180 °C, the molar doping ratio of tungsten is 1%, and the hydrothermal product is calcined at 900 °C. A possible mechanism of the optical properties of nano-WTO powder was proposed, in which tungsten ions provide carriers for tin oxide. It is worth mentioning that this is the first report on the synthesis of WTO nanoparticles and the development of their near-infrared light shielding properties.

Preparation of Antibiotic-Loaded Copper-Doped Hydroxyapatite Microspheres and Evaluation of Their Antibacterial and Osteogenic Effect

To explore the preparation method of copper (Cu)-doped hydroxyapatite (HA) microspheres loaded with vancomycin (Van), and evaluate their antibacterial and osteogenic effects in vitro. The Cu doped HA microspheres (Cu-HA) with molar doping ratios of 1%, 5%, 10%, and 20% were prepared by hydrothermal synthesis. The microscopic morphology changes were observe with scanning electron microscope. X-ray diffractometer (XRD) was used to study the phase composition and analyze the crystallinity of the sample. Cu-HA with a molar doping ratio of 10% was selected for analysis of the elemental composition of the sample with energy dispersive X-ray spectroscopy (EDS), and was then coated with polydopamine (PDA) as the medium to prepare Cu-HA-PDA. XRD and Fourier infrared spectrometer were used to examine the coating effect of the sample. Van was load on Cu-HA-PDA to prepare Cu-HA-PDA-Van. HA, Cu-HA, HA-PDA, and Cu-HA-PDA-Van were added to α medium at 10 mg/mL to prepare different groups of extract solutions.The main components of the extract solutions were examined, and the Van concentration was checked. We examined the toxic effect of material extract solutions on osteogenic precursor cells and the proliferation and differentiation of bone marrow mesenchymal stem cells, and checked the expression of osteocalcin ( OCN), runt-related transcription factor 2 ( RUNX-2), and alkaline phosphatase ( ALP), the osteogenic related genes. Sterilized HA, Cu-HA, HA-PDA, Cu-HA-PDA, Cu-HA-DPA-Van microsphere materials were prepared, and the colony counting method was used to evaluate the antibacterial effect of the materials for Staphylococcus aureus. Various types of Cu-doped HA (Cu-HA) were successfully synthesized. As the proportion of Cu increased, the morphology gradually changed from being strip or belt-shaped to a uniform spherical shape. Cu-HA of 10% molar doping ratio showed a clearly microspherical shape and a petal-like porous micro-nano morphology on the surface. EDS and XRD analyses showed that the main structure of the material was still made up of hydroxyapatite crystals and Cu was successfully doped with HA. The infrared spectrometer showed that the PDA was successfully coated on the surface of the material. Examination of the main components of the extract solution once again verified that the Cu element had successfully entered and replaced part of the Ca element in the HA. The 10 mg/mL Cu-HA-PDA-Van extract solution contained 0.27 mg/mL of Van. In vitro cell experiments and bone-formation-related gene testing showed that Cu-HA-Van had good biological activity and promoted bone differentiation. The minimum inhibitory concentration (MIC) of Cu-HA-PDA-Van microspheres was 16 μg/mL. Compared with Cu-HA, HA-PDA and pure HA, Cu-HA-Van microspheres had significant and long-lasting antibacterial effects. Cu element was used to control the microscopic morphology of HA, and the Cu-HA-PDA-Van microspheres prepared by successfully coating of PDA and loading of Van had good antibacterial properties and biological activity.

Luminescence and tunable color properties of uniphase white-emitting Sr3B2SiO8:Tm3+/Dy3+/Eu3+phosphors by energy transfer for UV-excited white LEDs

Multi-color single-phase white emission Sr3B2SiO8:Tm3+/Dy3+/Eu3+ fluorescent powders were prepared by solid-state fritting method. The fluorescence performance of Tm3+, Dy3+ and Eu3+ ions single-activated Sr3B2SiO8 phosphors were investigated and they exhibit desirable behaviors in their characteristic emissions. Meanwhile, the energy required for migration from Tm3+ to Dy3+ and from Dy3+ to Eu3+ in co-doped fluorescent substance was determined by the aids of steady-state and transient-state photoluminescence spectra/decay measurements. The energy transmission process from Tm3+ to Dy3+and Dy3+ to Eu3+ has been explored to be a dipole–quadrupole interaction and a dipole–dipole interaction of the resonant type, respectively. More significantly, by tuning the molarity ratio of doping Dy3+/Eu3+ ions, multicolor emission from yellow to red shall be achieved in Sr3B2SiO8:Dy3+, Eu3+ phosphors for its potential adhibitions in solid-state lighting applications. The Sr3B2SiO8:Tm3+, Dy3+ samples can implement white light emission by the appropriate changeable doping molar quantity of Tm3+and Dy3+, applying potentially in white LEDs. The energy migrations between co-doped rare earth ions play a decisive role in these processes.

P-Type Chemical Doping-Induced High Bipolar Electrical Conductivities in a Thermoelectric Donor–Acceptor Copolymer

P-Type Chemical Doping-Induced High Bipolar Electrical Conductivities in a Thermoelectric Donor–Acceptor Copolymer

Mn2O3-Na2WO4 doping of CexZr1-xO2 enables increased activity and selectivity for low temperature oxidative coupling of methane

Ethylene in principle can be obtained via oxidative coupling of methane (OCM), but it is urgently calling for a low-temperature active and selective catalyst. To accomplish this goal, the CexZr1-xO2 solid solutions with varied Ce/Zr molar ratio were modified with Mn2O3-Na2WO4 to fabricate OCM catalysts. The effects of Ce/Zr ratio and Mn2O3-Na2WO4 doping were investigated on the catalyst reactivity for the OCM, showing that the reaction light-off temperature, activity and selectivity are subject to the Ce/Zr molar ratio and Mn2O3-Na2WO4 doping. The promising catalyst with Ce/Zr molar ratio of 0.15/0.85 achieves 25% CH4 conversion with 67% selectivity to C2-C3 at 660 °C and is stable for at least 100 h. The catalysts were systematically studied by CH4-TPSR, O2-TPO/-TPD, CH4-pulse, in-situ FT-IR, EPR and XPS, showing that the Mn2O3-Na2WO4 doped Ce0.15Zr0.85O2 can generate more O2– species thereby leading to a markedly improved activity and selectivity at much lowered reaction temperature.

Study on the color tunability and energy transfer mechanism in Tm3+/Dy3+ co-doped LiLaSiO4 phosphors

Many color-tunable LiLaSiO4: αTm3+, βDy3+ phosphors were prepared using the traditional high-temperature solid-phase method. The phase composition, surface morphology, fluorescence spectrum, fluorescence lifetime, energy transfer mechanism, and color coordinates of the samples were analyzed using XRD, SEM, TEM and fluorescence spectrometer. The results show that LiLaSiO4: αTm3+ phosphor emits high intensity blue light at 460 nm and the concentration quenching point of Tm3+, α = 0.015 mol. In LiLaSiO4: αTm3+, βDy3+ phosphors, as the doped Dy3+ doping increases, the luminescence intensity of Tm3+ gradually decreases, the luminescence intensity of Dy3+ first increases and then decreases. The concentration quenching point of Dy3+, β = 0.015 mol. Adjustable light-emitting color can be obtained by changing the doping molar mass of Dy3+ or the wavelength of the excitation light. There is an effective energy transfer between Tm3+→Dy3+. The energy transfer mechanism is the electric dipole-electric dipole interaction, and the energy transfer efficiency reaches 90.11% when β = 0.06 mol. The quantum yield of LiLaSiO4:0.015 Tm3+,0.015Dy3+ was 39.0%. The single-matrix white light LiLaSiO4: αTm3+, βDy3+ phosphors with excellent performance is a prospective material for of white LEDs.

Electrical and optical properties of W-doped V2O5/FTO composite films fabricated by sol–gel method

V2O5/FTO composite films with different tungsten doping molar ratios were fabricated on soda-lime glass substrates by sol–gel spin coating method followed with annealing process. The analysis on crystallinity and surface morphology shows that W doping would induce V2O5 lattice distortion and make the film surface rougher. The resistance and transmittance during the phase transition process were measured to explore the electrical and optical properties of W-doped V2O5/FTO films. The results show that 3% W doping molar ratio is the most effective in improving the properties of V2O5/FTO films. The resistance of the prepared films is reduced by about three orders of magnitude from room temperature to 320℃. Compared to the undoped films, the 1%, 3% and 5% W-doped V2O5/FTO films possess higher conductivity and the width of the thermal hysteresis loop is narrowed from 14℃ to 13℃, 10℃ and 8℃, respectively. For undoped, 1%, 3% and 5% W-doped V2O5/FTO films, the phase transition temperature is 245℃, 238℃, 222℃ and 223℃, and the average transmittance decreased 7.7%, 7.8%, 11.7% and 5.7% in the range of 900–1400 nm before and after the phase transition, respectively.

Improved acetone gas sensing performance based on optimization of a transition metal doped WO3 system at room temperature

This paper proposes an effective strategy of material system optimization to improve acetone gas sensing performance based on hydrothermally processed transition metal (Fe, Co or Ni)-doped WO3 materials. A detailed comparison of the capability of pure WO3 and X:WO3 (X = Fe, Co, Ni) to sense acetone gas at room temperature was performed. It was found that the sensitivity of Ni:WO3 nanoflowers to acetone was much higher than that of pure WO3, Fe:WO3 and Co:WO3 under white light irradiation. To obtain a highly sensitive acetone gas sensor, the molar doping ratio of Ni to WO3 was further optimized. It was found that 3%Ni:WO3 had the highest response–recovery speed and the best target gas selectivity. Acetone with a concentration as low as 2 ppm can be detected at room temperature (20 °C). The sensitivity enhancement mechanism of the Ni:WO3 gas sensor is also discussed. It is expected that under white light irradiation the proposed Ni-doped WO3 can be used as a highly sensitive and selective acetone gas sensor at room temperature.