Increase In Doping Concentration Research Articles

Tuning the potentials of aluminum phosphide nanotube photocatalyst for wastewater treatment through band gap engineering: a DFT study

Abstract The photocatalytic properties of semiconductor materials, which are controllable through the design of the bandgap structure, make them a promising catalyst for wastewater treatment. This work investigated the photocatalytic properties of single-walled aluminum phosphide nanotube (SWAlPNT) doped with different concentrations of boron (B) atoms for wastewater treatment. Analysis of the structural, electronic and optical properties of the SWAlPNT photocatalyst was performed using the density functional theory approach in terms of plane wave basis set and pseudopotential. The SWAlPNT was found to be stable to B doping with 3.6% and 7.1% concentrations. Cohesive energy decreases with an increase in concentration of dopant which results in efficient thermal stability. An indirect band gap value of 1.4 eV was obtained with B-doped SWAlPNT with 3.6% concentration which agreed with band gaps of other photocatalysts used for wastewater purification. Analysis using optical absorption spectra revealed that 3.6% B-doped system absorbs visible light while 7.1% doped system absorbs both visible and ultraviolet light. This study found both 3.6% and 7.1% B-doped SWAlPNT as suitable photocatalysts for wastewater treatment under solar irradiation, while the 3.6% B-doped system shows relatively better performance for wastewater treatment.

Structural, Optical, and Magnetic Properties of Mn Doped Zn3P2 Diluted Magnetic Semiconductor Nanoparticles

Mn-doped Zn3P2-diluted magnetic semiconducting nanoparticles (Zn0.98Mn0.02P2, Zn0.96Mn0.04P2, Zn0.94Mn0.06P2, and Zn0.92Mn0.08P2) were synthesized by a conventional solid-state reaction followed by a subsequent vacuum annealing process. The formation of a tetragonal structure of pure and Mn-doped Zn3P2 was confirmed by X-ray diffraction studies, with no evidence of any further phases. Lattice parameters dicrease from a = b = 8.133 Å, c = 11.459 Å to a = b = 8.041 Å, c = 11.410 Å with increasing dopant concentration. Scanning electron microscpy analysis indicated that all samples that underwent doping exhibited agglomeration in the scanned range of 500 nm. Energy-dispersive X-ray analysis confirmed the presence of Zn, P, and Mn in the samples, and all of the synthesized samples achieved a nearly atomic ratio. In the diffused reflectance spectra, the optical band gap increases from 1.398 to 1.418 eV with increasing dopant concentration. PL has provided evidence indicating that the emission intensity of all doped samples remains constant with increasing dopant content from x = 0.02 to 0.08, with different excitation wavelengths (215 and 290 nm). Vibrating sample magnetometer tests confirmed the presence of ferromagnetic behavior at room temperature, and a positive correlation between saturation magnetization and Mn content, with the magnetic moment increasing from 0.0640 to 0.1181 emu g−1 with an increase in dopant content.

Fabrication, characterization and application of W/N co-doped zinc oxide nanoparticles as a promising photoanode for dye-sensitized solar cells

In the present investigation, undoped, W doped, and W/N co-doped ZnO nanoparticles were prepared by sol–gel route. Here, the ZnO layers were fabricated via the doctor blade method. Hexagonal wurtzite structure is determined by XRD studies. The formation of a hexagonal wurtzite structure was observed from X-ray powder diffraction (XRD) resulting in a slight increase in crystallite size with an increase in doping content. The UV observation shows that W/N co-doping shifted the absorption spectra towards a higher wavelength and reduces the band gap energy. The EDS spectra confirms the high purity and triumphant doping of the W(tungsten) and N(nitrogen) into the ZnO lattice. The morphology of undoped and W/N co-doped ZnO nanoparticles was demonstrated by using FESEM and HRTEM. The 2 % W and 1.5 % N co-doped ZnO photoanode based DSSC (dye-sensitized solar cells) gained the highest short circuit current density of 8.44 mAcm−2 having an open-circuit voltage of 0.65 V, and PCE (power conversion efficiency) of 3.60 %.

Structures and properties of carbon-doped silicon as anode material for lithium ions battery: A first-principles study

Anode materials for lithium ions battery have been much less investigated than the cathode materials. Recently, silicon-based anode materials have attracted attentions for its high theoretical capacity. In the present work, the structures and properties of carbon doped silicon as the anode materials of lithium ions battery were investigated by first-principles method. In the doping concentration range from 1.56 % to 15.6 %, the results show that the stronger Si–C covalent bond leads to a higher bulk modulus of the carbon-doped silicon structures. The band gap of the doped structure decreases with increased doping concentration. The volume expansion can be suppressed by the doping of the carbon atom, and the structures with higher carbon concentrations had a better suppression effect. Meanwhile, the lithium diffusion energy barrier increases with the carbon doping concentration.

Effect of Different Concentrations of Co Doping on the Properties of η′‐Cu6Sn5 and Ni3Sn4: First‐Principles Study

In the field of electronic packaging, Ni3Sn4‐based and η′‐Cu6Sn5‐based compounds are common Sn‐based intermetallic compounds into which doping of other appropriate elements has been widely studied. Herein, the structural stability, mechanical properties, and electronic structures of (Ni,Co)3Sn4 and η′‐(Cu,Co)6Sn5 are systematically investigated using first‐principles calculations. By comparing the heat of formation of the doped and undoped intermetallic compounds, it is found that the doped Ni3Sn4 structure has a higher heat of formation and a less stable structure, while the doped η′‐Cu6Sn5 structure has a lower heat of formation and a more stable structure. The doped Ni3Sn4 exhibits an increasing bulk modulus (B) and Young's modulus (E), and the doped η′‐Cu6Sn5 exhibits a gradually increasing bulk modulus (B). These findings suggest that doping improves the rigidity and elastic deformation properties of the two intermetallic compounds. And yet the anisotropy of both intermetallic compounds is decreasing as doping concentration increases. According to the calculations of the electronic structures, the doped (Ni,Co)3Sn4 structure and the doped η′‐(Cu,Co)6Sn5 structure exhibit stronger metallicity. In addition, stronger Co–Sn ionic bonds are formed in the doped Ni3Sn4 and η′‐Cu6Sn5 structures. This suggests that the doped Ni3Sn4 and η′‐Cu6Sn5 structures are harder.

Evolution of Ni-induced orthorhombic phase in SnO2: Influence of Ni on the optical and photocatalytic properties

This paper presents the impact of nickel doping on the structural, optical and photocatalytic characteristics of Sn1-xNixO2 (x = 0, 0.3, 0.05, 0.07) nanoparticles. The samples are synthesized via the chemical co-precipitation method. Information on the structural properties of the samples is obtained via the Rietveld refinement technique. As the dopant concentration increases, a partially stable orthorhombic phase emerges and becomes prominent, indicating a correlation with the amount of Ni dopant. This orthorhombic phase arises during the transformation from the amorphous state to a more stable crystalline phase. The FESEM-EDAX analysis demonstrates the uniform distribution of agglomerated particles. Additionally, the Raman data provides information related to surface defects and vacancies. A minor increase in the band gap value is detected, and this observed blue shift can be attributed to the Burstein-Moss effect. The samples exhibit a strong blue emission, primarily attributed to surface defects and states, particularly due to the oxygen vacancies. The CIE coordinates show an increase in blue colour purity, making the samples suitable for blue components in white-light emitting diodes. However, the photocatalytic study reveals only partial degradation of methylene blue under visible light conditions.

Room temperature ferromagnetism in undoped and Fe doped Zn3P2 nanoparticles: Structural, optical and magnetic properties

In the current study, the structural, optical, and magnetic characteristics of Fe-doped Zn3P2 nanoparticles prepared by the solid-state reaction technique with various concentrations of Fe (x = 0.00, 0.02, 0.04, 0.06, and 0.08) were investigated. Studies using X-ray diffraction (XRD) verified that all of the produced samples had a tetragonal structure without any other phase, and that the lattice parameters increased (a = 8.090 Å, c = 11.421 Å to a = 8.120 Å, c = 11.499 Å) as the amount of dopant increased. The scanning electron microscopy (SEM) performed on the sample demonstrates that the grain size is almost spherical. The size of agglomerations slightly increases with increasing dopant concentration. The results of an energy dispersive X-ray analysis (EDAX) are almost exactly what was anticipated for the atomic weight ratios. The optical bandgap of the samples went from being 1.406 eV to being 1.453 eV when the dopant concentration was raised. When excited at wavelengths of 210 nm and 240 nm, rather than 307 nm, very intensity Photoluminescence (PL) emission spectra were detected in all of the samples. Vibrating sample magnetometer (VSM) verified that magnetic moment is found to increase (0.08829 emu/g to 0.23125 emu/g) with increase of dopant concentration from 0.02 to 0.08.

Analysis of CdS/CdTe Thin Film Solar Cells as a Function of CdS Doping Concentration: A Numerical Simulation Perspective

Cadmium Telluride (CdTe) photovoltaics, incorporating a thin film of Cadmium Sulfide (CdS), present a costeffective yet less efficient solar cell technology. Improving CdS/CdTe solar cell efficiency involves optimizing parameters like doping concentration and CdS layer thickness. However, limited research on cell defects necessitates a comprehensive analysis, including the often-overlooked impact of temperature. This study aims to analyze defect-free and defective CdS/CdTe solar cells, exploring the effects of doping concentration and other parameters. Using the SCAPS-1D simulator, design parameter variations will be investigated, and key metrics— open-circuit voltage (Voc), short-circuit current density (Jsc), fill factor (FF), and efficiency (η)—will be extracted. Simulation results indicate minimal efficiency impact from increased doping concentration in the ntype CdS layer for defect-free devices. The optimal doping concentration for CdS is 5 × 10<sup>18</sup> cm<sup>-3</sup>, with an optimum electron affinity of 4.0 eV. CdS thickness shows no significant efficiency impact, with the chosen optimum at 10 nm. In the defect-free CdS/CdTe solar cell, key metrics were Voc: 1.06 V, Jsc: 24.60 mA cm<sup>-2<sup>, FF: 87.89%, and η: 23.01%. Analysis of defects revealed single acceptor defects significantly impacting solar cell performance in both interfacial and bulk defects. Defect structure simulations demonstrated that increasing doping concentration, decreasing electron affinity, and thickness enhance efficiency. New optimum values for these parameters—1 × 10<sup>18</sup> cm<sup>-3</sup>, 4.0 eV, and 10 nm—yielded Voc: 1.03 V, Jsc: 23.88 mA cm<sup>-2</sup>, FF: 87.15%, and η: 21.40%. Additionally, a temperature decrease was associated with increased efficiency.

Band gap, ferromagnetic resonance and strong microwave absorption of BaFe12-2xZnxSnxO19 compounds and enhanced dielectric loss in BaFe12-2xZnxSnxO19/carbon nano tube composites

The forbidden bandgap energy, magnetic properties, natural ferromagnetic resonance and microwave absorption are studied on the Zn2+ and Sn4+ doped BaFe12-2xZnxSnxO19. The forbidden band gap of BaFe12-2xZnxSnxO19 increases with the increasing doping content x from 1.80 eV up to 1.97 eV. The coercive field, the anisotropy field and the magnetocrystalline constant of BaFe12-2xZnxSnxO19 decreases with the increasing doping. The natural ferromagnetic resonance is observed. The high permeability, accompanied with the ferromagnetic resonance, enables strong microwave absorption. BaFe10.4Zn0.8Sn0.8O19 has a wide effective microwave absorption bandwidth (RL≤-10dB) of 6 GHz with the material thickness below 2.5 mm in 11.4–17.4 GHz. The dielectric loss has little contribution to the excellent microwave absorption of BaFe12-2xZnxSnxO19. The BaFe12-2xZnxSnxO19/carbon nanotube (CNT) composites significantly increase the permittivity. The high dielectric loss and the high magnetic loss further improve the microwave absorption. With a very thin thickness of 1.8 mm, BaFe10.4Zn0.8Sn0.8O19/CNT has a bandwidth of 7.1 + GHz of 10.9–––18 + GHz. With the material thickness thinner than 3 mm, BaFe12-2xZnxSnxO19/CNT composites have very broad effective microwave absorption bandwidth of 11.4+, 10.7 and 10.7 GHz, with x = 0.6, 0.8 and 1.0, respectively. It illustrates that both BaFe10.4Zn0.8Sn0.8O19 and BaFe12-2xZnxSnxO19/CNT composites are very promising microwave absorbers.

Composition-dependent structure and bandgaps in HfxZr1−xO2 thin films

ZrO2 as a wide-bandgap semiconductor with high dielectric constant and ferroelectric properties has been extensively studied. To explore the impact of chemical doping on the structure and optical performance of ZrO2, HfxZr1−xO2 (x = 0, 0.25, 0.5, 0.75, 1) thin films were prepared through pulsed laser deposition. X-ray diffraction reveals that the orthorhombic phase (o) (111) gradually transforms into the monoclinic phase (m) (−111) with the increase in Hf content from 0 to 1. Furthermore, optical property analysis demonstrates an increase in the optical bandgap from 5.17 to 5.68 eV with the increase in Hf doping content. Density functional theory calculations and x-ray photoelectron spectroscopy suggest that the widening of the bandgap in HZO films is associated with the hybridization of Zr 4d and Hf 5d orbitals.

Multifunctional Ce+3 doped nickel-cobalt mixed ferrites via co-precipitation method for photocatalytic and antibacterial activity

The overuse of industrial dyes and anti-bacterial drugs are destroying fresh water reservoirs and making bacteria more resistant, respectively. To sort out these problems, we have synthesized Cerium doped Nickel-Cobalt mixed ferrites (Ce-@NCMF) with chemical composition [Ni0.4Co0.6CexFe2-xO4 (where x = 0.00, 0.10, 0.15, 0.20 and 0.25)] via co-precipitation method. Influence of cerium doping on the structural, optical, electrical, magnetic, photocatalytic and anti-bacterial properties of Ce-@NCMF studied. Powder x-ray diffraction analysis (PXRD) confirmed the synthesis of Ce-@NCMF. Decrease of crystallite size from 29.71 to 24.95 nm was observed with increase in dopant concentration. Tauc’s plot indicated the decrease of energy bandgap from 2.10 to 1.89 eV with increase in dopant concentration, which revealed the absorption of light in visible region to generate electron–hole pairs for photocatalytic applications. FTIR spectra indicated the presence of M-O bonds as major functional group present in Ce-@NCMF. Electrical properties demonstrated the prominent increase of electrical conductivity with increase of Ce-doping. VSM analysis was performed to analyse the magnetic properties of materials and showed prominent decrease in saturation magnetization value from 84.66 to 19.85 emu g−1. Owing to optical bandgap in the visible region, all the synthesized samples were evaluated for their photocatalytic potential for the degradation of methylene blue. Ce-@NCMF at x = 25% dopant value showed maximum degradation efficiency (95%) under sunlight irradiation of 90 min. Kinetic studies of dye degradation followed pseudo-1st order kinetics with maximum rate constant (k) value of 2.78×10−2 min−1. Antibacterial activity results showed the bioactive nature of Ce-@NCMF against all strains of bacteria in consistent with the crystallite size of samples. Smallest crystallite size Ce-@NCMF were found most active against gram-negative bacterial strains.

Display and energy storage applications of copper doped nanoceria

In the current study CeO2: Cu2+ (0–11 mol%) NPs were synthesized by Aloevera mediated solution combustion method followed by calcination. The synthesized samples were described and their multifunctional characteristics, including photoluminescence, sensor, and supercapacitor features were covered thoroughly. Bragg reflections confirmed single-phased CeO2: Cu2+ NPs with cubic spinel structure belonging to space group Pm3m(221). Crystal size was estimated using both the Scherrer and W-H plot method. The energy gap was computed from the Wood-Taucs relation. The crystallite size increases whereas the energy band gap increases with an increase in dopant concentration. The photoluminescence emission peaks of CeO2:Cu2+ (1–11 mol%) NPs, CIE, and CCT λex= 340 nm unambiguously show that the current nanophosphor might be a promising nanophosphor material for white and blue LEDs. The Cyclic voltammetry analysis was performed on as obtained CeO2: Cu2+ NPs for oxidation and redox peaks. EIS revealed that ion transport kinetics and super-capacitance values were obtained from GCD analysis. Specific capacitance values are found to be in the range 18 to 61 F/g for CeO2: Cu2+ 1 to 11 mol % NPs respectively which are in good agreement with the values obtained from CV analysis. Thus, the present synthesized material might find applications in the field of display technology and energy storage materials.

High-efficiency TOPCon solar cell with superior P + and P++ layer via one-step processing

The boron diffusion process in the front field of N-type tunnel oxide passivated contact (TOPCon) solar cells is crucial for PN junction formation and the creation of a selective emitter. This study presents a theoretical model of boron diffusion in silicon using molecular dynamics. The research examines the mean square displacement and diffusion coefficient of boron atoms at varying temperatures, confirming their diffusion behavior. The simulations indicate predominant boron diffusion in the z-direction within the silicon matrix, with the diffusion depth being temperature dependent. The optimal temperature range for boron diffusion in silicon is identified as 950 °C to 1050 °C. Using boron-doped silicon paste and boron trichloride as dopants, thermal diffusion experiments were conducted to fabricate the front-field PN junction (p+ layer) and selective emitter (p++ layer) by one step. Subsequent processing and performance evaluation were performed on a production line. Experimental findings reveal a decrease in boron diffusion at higher temperatures, reduced sheet resistance, increased doping concentration, and deeper junction formation. The ideal boron concentration in the p+ layer is 8.68 × 1018 atom/cm3 with a depth of 0.53 μm, while the p++ layer is 2.35 × 1019 atom/cm3 and 0.82 μm. The efficiency of the optimized TOPCon + cell production line reaches up to 25.17 %, marking an improvement of 0.23 % over the standard cell production line. This research contributes to elucidating the mechanism of boron diffusion and offers insights for enhancing the efficiency of TOPCon solar cells.

Bi–Er–O pre-synthesized phase (Bi1-xErx)2O3 doped ZnO varistors with high nonlinear coefficient and low leakage current

The content of free oxygen Oad at the ZnO grain boundaries has an important impact on the double Schottky barrier and electrical properties of ZnO varistors. In this work, Bi–Er–O pre-synthesized (BE) phase (Bi1-xErx)2O3 (0.25 < x < 0.455) with high conductivity of Oad was prepared using Bi2O3 and Er2O3 as raw materials, and the effects of the BE phase doping on the phase, grain boundary properties, and electrical properties of ZnO–Bi2O3–Sb2O3–Co2O3–MnO2–Cr2O3–SiO2 varistors were studied. XRD analysis shows that the lattice constant of the BE phase (Bi1-xErx)2O3 is between (Bi0.75Er0.25)2O3 and BiErO3. With increasing doping content of the BE phase from 0 to 0.75 wt%, part of Er3+ still exists in the form of the BE phase (Bi1-xErx)2O3 at the ZnO grain boundaries, and its content increases with increasing doping content of the BE phase. The conductivity of Oad in (Bi1-xErx)2O3 is much higher than that in Bi2O3, resulting in the generation of a large number of negative O′ and O″ at the ZnO grain boundaries, and decreasing concentration of the intrinsic point defect zinc interstice Zni. So the donor concentration Nd decreases, the height of the grain boundary barrier increases, the depletion layer widens, and the electrical properties are improved. By analyzing the low-temperature permittivity spectra, it was calculated that with increasing doping content of the BE phase from 0 to 0.75 wt%, the concentration of oxygen vacancy VO• decreases inappreciably, but the concentration of zinc interstice Zni•• decreases by about 23%. When the doping amount of the BE phase is 0.75 wt%, the nonlinear coefficient α of the obtained ZnO varistors is 73.9 ± 0.6, and the leakage current density JL is only 0.3 ± 0.1 μA/cm2. This study provides an important reference for improving the electrical properties of ZnO varistors by manipulating the Bi-rich phase structure to improve the double Schottky barrier characteristics.

Effect of nickel doping on magnetic and dielectric properties of orthorhombic calcium ferrite nanoparticles

Nickel (10∼50 mol%) doped calcium ferrite nanoparticles (NPs) are synthesized by the solution combustion method using lemon juice extract as a reducing agent, followed by calcination at 500°C. The calcined samples are characterized with different techniques. The Bragg reflections of Nickel doping confirm the formation of a single orthorhombic calcium ferrite phase. The crystallite size is estimated using both Scherrer's and the W-H plot method. The surface morphology consists of irregular size and shaped agglomerated NPs along with pores and voids. A blueshift and a broad absorption spectrum is observed with an increase in the direct energy band gap. The direct energy band gap estimated from Wood and Tauc's relationship was found to be 2.91∼2.97 eV with an increase in dopant concentration. The magnetic analysis provided values for saturation magnetization (Ms), remanence (Mr), and coercivity (Hc), while dielectric studies demonstrated a dielectric constant of 2.81, 2.14, and 1.67 with increasing dopant concentration. The variation of dielectric properties of the sample as a function of frequency in the range 0.1∼20 MHz has been studied at room temperature. The dielectric properties of CaFe2O4: Ni (1∼9 mol%) NPs clearly indicate that there is a more pronounced dispersion at lower frequencies, gradually reaching saturation as the frequency increases. The dielectric loss was found to decrease from 4.62, 3.22, and 2.32 with an increase in Ni2+ substitution (10, 30, and 50 mol%) respectively. These results indicate the suitability of these samples for applications in memory devices and high-frequency applications.

Effects of manganese doping on the lattice structure and iron ion states in La2/3Ca1/3Fe1-xMnxO3-δ

In this paper, La2/3Ca1/3Fe1-xMnxO3-δ(x = 0–0.6) nano particles have been prepared by the sol-gel method. X-ray diffraction (XRD) analysis revealed that with the increase of Mn doping content, the main diffraction peak shifted to the right, the lattice parameters decreased overall, and the degree of lattice distortion gradually reduced. X-ray photoelectron spectroscopy (XPS) analysis indicates that the valence states of Fe and Mn in the system coexist as trivalent and tetravalent, and with the increase in Mn doping, the ratio of Fe3+/Fe4+ decreases, while the ratio of Mn3+/Mn4+ slightly increases. The results of Mössbauer spectrum analysis revealed that as the Mn doping content increased, some Fe ion valence states in the system gradually changed from Fe3+ to Fe4+, and the presence of the paramagnetic phase became increasingly prominent. Furthermore, with the increase of Mn doping content, the degree of lattice distortion in the system decreased, which is consistent with the results obtained from the XRD analysis. This work will provide a reference for future research on the effects of manganese doping in similar systems.

Preparation and photoluminescence study of rare-earth-free red emitting La3Ga5SiO14:Mn4+ phosphors

Given the growing interest in eco-friendly lighting solutions, the use of high-quality phosphors has become integral to the advancement of all-solid white light-emitting diodes (WLEDs). One novel phosphor, La3Ga5SiO[Formula: see text]:Mn[Formula: see text] (LGS), has been successfully synthesized via a high-temperature solid-state reaction. The crystal structure of LGS is classified as belonging to the trigonal phase, with a space group P321. The excitation spectrum exhibits a wide peak within the wavelength range of 280–440 nm. It emits a highly intense red light, with a peak emission occurring at 715 nm within the spectral range of 670–740 nm is attributed to the transition of Mn[Formula: see text] from 4A2g to 4T2g. LGS:Mn[Formula: see text] demonstrates a favorable quantum efficiency of 16% when doped with a concentration of 0.25 mol% Mn. The decay curve of LGS:Mn[Formula: see text] exhibits a pattern of decreasing lifetime as the dopant concentration increases. Additionally, the LGS:Mn[Formula: see text] products demonstrate a CIE chromaticity of (0.688, 0.2644), which is located within the deep red light region. All the aforementioned findings support the potential application of LGS:Mn[Formula: see text] specimens in WLEDs, thereby contributing to the progress of environmentally friendly and energy-efficient lighting.

Influence of Hf doping on structural, morphological, optical and electrochemical properties of NiO thin films: Electrochromic application

In this study, the authors investigated the influence of hafnium doping on the properties of NiO thin films using the spray pyrolysis (SP) method. A comprehensive analysis was conducted to evaluate the structural, morphological, optical, and electrochemical characteristics of the deposited films. Techniques such as X-ray diffraction analysis (XRD), Raman spectroscopy, scanning electron microscopy (FESEM), energy dispersive analysis by X-ray (EDS), UV–Vis–NIR spectrophotometry, cyclic voltammetry (CV), and chronoamperometry (CA) were employed. XRD examination revealed that the NiO thin films exhibit a polycrystalline cubic phase, with a preferred orientation along the (111) plane. The successful integration of Hf ions into the NiO matrix was confirmed by the Raman spectrum. SEM images depicted the formation of dense and uniform nanograins on all film surfaces, free from any cracks. EDS analysis and elemental mapping indicated uniform and homogeneous distribution of Ni, O, and Hf elements across the films. The optical analysis suggested a decrease in the optical band gap energy from 3.54 eV to 3.49 eV with an increase in hafnium doping concentration. Electrochemical results revealed a continuous improvement in specific capacitance with Hf doping. The NHf6 sample reached 65 F. g−1 at 5 mV s−1, compared to 46 F. g−1 at 5 mV s−1 for the NHf0 sample. However, the NHf4 film exhibited the highest optical density variation (49%), shortest response times (tb = 3.58 s, tc = 4.67 s), and the largest coloration efficiency (63.39 cm2/C), indicating enhanced electrochromic performance at this Hf doping rate. These findings suggest that Hf-doped NiO holds promise as a candidate for use as a counter-electrode in electrochromic devices.

Enhanced Photo/Electrocatalytic Hydrogen Evolution by Hydrothermally Derived Cu-Doped TiO2 Solid Solution Nanostructures.

Highly efficient nanocatalysts with a high specific surface area were successfully synthesized by a cost-effective and environmentally friendly hydrothermal method. Structural and elemental purity, size, morphology, specific surface area, and band gap of pristine and 1 to 5% Cu-doped TiO2 nanoparticles were characterized by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), electron paramagnetic resonance (EPR), energy dispersive X-ray analysis (EDAX), inductively coupled plasma mass spectrometry (ICP-MS), liquid chromatography-high resolution mass spectrometry (LC-HRMS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET surface area, Raman spectroscopy, photoluminescence spectroscopy (PL) and UV-visible diffused reflectance spectroscopy (UV-DRS) studies. The XPS and EPR findings indicated the successful integration of Cu ions into the TiO2 lattice. UV-DRS and BET surface area investigations revealed that with an increase in dopant concentration, Cu-doped TiO2 NPs show a decrease in band gap (3.19-3.08 eV) and an increase in specific surface area (169.9-188.2 m2/g). Among all compositions, 2.5% Cu-doped TiO2 has shown significant H2 evolution with an apparent quantum yield of 17.67%. Furthermore, the electrochemical water-splitting study shows that 5% Cu-doped TiO2 NPs have superiority over pristine TiO2 for H2 evolution reaction. It was thus revealed that the band gap tuning with the desired dopant concentration led to enhanced photo/electrocatalytic sustainable energy applications.

Effects of Rare-Earth Elements Doping on Micro-Structure and Fluorescence Performances of Fluorapatite

For purposes of optimizing the microstructure and fluorescence properties of rare-earth elements (REEs)-doped fluorapatites (FAps), various kinds of REEs (La, Pr, Sm, Eu, Gd, Ho, Er, and Yb) with the concentration of 2~20 mol.% have been inserted into the FAps framework via hydrothermal method, in order to investigate the influential mechanism of the REEs on the crystal structure, morphology, and fluorescence under the excitation of the near-ultraviolet light of the FAps. Experimental results show that the wavelength of the emitted light of the REEs-doped FAps is decided by the type of REEs. Unlike the Pr/Yb- and Ho-doped FAps and with the fluorescence of red and green emitted light, respectively, the Er-doped FAps show a blue light emission with wavelengths of 296, 401, and 505 nm, which is, moreover, different with the Eu-doped Faps, showing an orange light emission with wavelengths of 490, 594, and 697 nm. The emission luminous color is related to the lattice defects of the FAps doped with the various types and the effective doping concentration of the REEs. The luminous intensity increases with the increase in the effective doping concentration of the REEs. Nevertheless, the formation of rare-earth fluoride results in the decrease in the effective doping concentration of the REEs and the luminous intensity. The FAps with an effective doping concentration of 7 mol.% Er and 3 mol.% Eu show relative excellent fluorescence properties.