Co-doping Concentration Research Articles

An investigation about the ability to change color and the way energy is transferred of NaYMgWO6:RE3+ (RE3+ = Tm3+, Dy3+, Tm3+/Dy3+): A new type of single-phase white phosphor for WLEDs

Novel NaYMgWO6:Tm3+, Dy3+ phosphor is synthesized by solid-state reaction method in air. The phase structure was meticulously analyzed through XRD and Rietveld refinement techniques. Dy3+ doped NaYMgWO6 phosphors emitted yellowish-white light, which was observed. Surprisingly, the introduction of Tm3+ ions resulted in white-emitting, which was further studied with the aid of a spectrometer. By fixing the concentration of Tm3+ ions and subsequently adjusting the co-doping concentration of Dy3+ ions or altering the excitation wavelength, the CIE coordinates of NaYMgWO6:Dy3+, Tm3+ phosphors shifted from the blue-violet region to the yellowish-white region. In particular, when b = 0.2 mol, there was efficient energy transfer from Tm3+ to Dy3+, with an energy transfer efficiency of 95.1 %. The gradual decrease of the lifetime at 454 nm monitoring implies that there is indeed an energy transfer process from Tm3+ to Dy3+ and that the probability of energy transfer from Tm3+ to Dy3+ gradually increases with increasing Dy3+ concentration. These findings indicate that NaYMgWO6: aTm3+, bDy3+ phosphors offer a novel approach to researching single-phase white phosphors.

Robust ferromagnetism and magneto-dielectric anomalies in (Al, Cr) co-doped iron oxide thin films-microwave mediated sol–gel approach

Research on thin films of iron oxide has gained interest in recent years because of its application in advanced spintronic and electronic devices. Technologically important iron oxide phases can be achieved by adopting novel methodologies and/or selecting suitable dopants. A cost-effective microwave assisted sol–gel approach is adopted in this work to prepare thin films of iron oxide. Undoped and doped sols (2–10 wt% of dopant concentration) are irradiated with MW power of 720 W. Maghemite phase (γ-Fe2O3) is observed to be stable up to a co-dopant concentration of 6 wt%. Further increase in dopant content leads to a phase transition to mixed (γ-Fe2O3+Al2O3) crystal phases. Values of dielectric constant (DC) and loss tangent exhibit normal dispersion response with high DC value (log f 5.5 = ∼92) observed for undoped sample. Cole–Cole plots indicate the effective grain boundary contribution for low dopant concentrations, whereas contributions from grains is observed at higher dopant concentrations. M−H curves show ferromagnetic response with high value of saturation magnetization (Ms) of ∼450 emu/cm3 witnessed at 6 wt%. (Al, Cr) co-doping results in tuning of magnetic response/parameters. MD coupling of (Al, Cr) co-doped thin films of iron oxide makes this material suitable for advanced spintronic and energy storage devices.

Effect of gadolinium and manganese on the physical properties of yttrium iron garnet

The Y3-xGdxFe5-yMnyO12 (x = y = 0.0, 0.2, 0.4, 0.6, 1.0, and 1.5) powders were synthesized by a co-precipitation method. The structural analysis confirmed the presence of the cubic structure of YIG, the formation of the secondary phase YFeO3 and the stoichiometry proposed for Y3-xGdxFe5-yMnyO12. The results of the FTIR spectroscopy show three prominent absorption bands that shift to lower wavenumber values with the increase of co-dopant concentrations. Energy bandgap values are found to be 2.96 eV for pure YIG and 3.02 ± 0.1 eV for doped powders. Photoluminescence spectra show that all the samples exhibit intense peaks around 530 nm. Moreover, Gd3+ and Mn2+ partial alternatives strongly influence the magnetic behavior of YIG nanoparticles. It is observed that coercivity is affected by the crystallite size of 0.0 ≤ x = y ≤ 0.6, confirming the multidomain nature of the powders, which could be acceptable in microwave applications and data storage uses.

Improving the quality of red light emitting from Eu3+ by Co-doping Tb3+ in LuBa3(BO3)3

The red light emitting from phosphors activated with Eu3+ is of great significance for optimizing the comprehensive performances of white light-emitting diodes (WLEDs) for solid-state lighting. Herein, LuBa3(BO3)3:Eu3+ and LuBa3(BO3)3:Tb3+,Eu3+ phosphors are synthesized via the high temperature solid-state reaction to investigate the effects of the doping concentration of Eu3+ and the co-doping of Tb3+ on the quality of red emission from Eu3+ in the host. Under the excitation of 392 nm light, the dominant emission peak of LuBa3(BO3)3:xEu3+ gradually shifts from 593 nm to 610 nm when the doping concentration of Eu3+ is increased from 0.02 to 0.10, and the quality of red light emitting from Eu3+ in the host is found to be further improved with increasing the co-doping concentration of Tb3+, both of which are explained with the Judd-Ofelt theory. The calculated results indicate that the enhancement of red emission is attributed to the decrease of the environment symmetry of Eu3+ by increasing the concentration of Eu3+ in LuBa3(BO3)3:Eu3+ or co-doping Tb3+ ions. The color purity of the emission from LuBa3(BO3)3:0.10 Tb3+,0.10Eu3+ is 94.11%, and the luminescent intensity of the phosphor at 425 K is 69% of that at room temperature. Moreover, a WLED device with the high color rendering index of 91.1 is obtained by fabricating LuBa3(BO3)3:0.10 Tb3+,0.10Eu3+ and other phosphors with a 365 nm LED chip. The good comprehensive performances suggest that LuBa3(BO3)3:Tb3+,Eu3+ has a great application prospect as a red phosphor in the field of high-quality solid lighting.

Antimicrobial activity of Cobalt doped Cerium Oxide (Co-CeO2) nanoparticles against selected food pathogens

This present work is to investigate the antibacterial activity of CeO2 nanoparticles on five foodborne pathogens. Low-temperature solid-state reactions were used to create co-doped CeO2 nanoparticles (Co-CeO2 NPs). In the current work, the impact of Co-doping on polycrystalline CeO2 samples synthesized using the co-precipitation method at room temperature for Co-doping concentrations of 0.5%, 1%, 3%, and 5% is discussed. Rietveld refinement of the X-ray diffraction patterns confirms that the Co-doped CeO2 samples have a face-centred cubic structure. This shows that the Co ions have been successfully integrated into the CeO2 lattice. Also, the UV-Vis-NIR absorption spectra confirm that redshifts do happen in the Co-doped CeO2 samples, which shows that the band gap energy decreases as the number of Co ions grows. In an antibacterial test against five pathogenic microbes, S. aureus, M. luteus, Enterobacter aerogenes, S. typhi, and Pseudomonas aeruginosa, Co-doped cerium oxide nanoparticles significantly slowed the growth of all five pathogens, both in liquid and solid growth conditions. These results show that Co-doped CeO2 nanoparticles have strong antibacterial properties against foodborne pathogens. This suggests that they could be used as promising bionanomaterials for in vivo therapeutic uses.

Design of B/N Co-doped micro/meso porous carbon electrodes from CNF/BNNS/ZIF-8 nanocomposites for advanced supercapacitors

Boron (B) and nitrogen (N) co-doped 3D hierarchical micro/meso porous carbon (BNPC) were successfully fabricated from cellulose nanofiber (CNF)/ boron nitride nanosheets (BNNS)/ zinc-methylimidazolate framework-8 (ZIF-8) nanocomposites prepared by 2D BNNS, ZIF-8 nanoparticles, and wheat straw based CNFs. Herein, CNF/ZIF-8 acts as versatile skeleton and imparts partial N dopant into porous carbon structure, while the introduced BNNS can help strengthen the hierarchical porous superstructure and endow abundant B/N co-dopants within BNPC matrix. The obtained BNPC electrode possesses a high specific surface area of 505.4 m2/g, high B/N co-doping content, and desirable hydrophilicity. Supercapacitors assembled with BNPC-2 (B/N co-doped porous carbon with a CNF/BNNS mass ratio of 1꞉2) electrodes exhibited exceptional electrochemical performance, demonstrating high capacitance stability even after 5 000 charge-discharge cycles. The devices exhibited outstanding energy density and power density, as well as the highest specific capacitance of 433.4 F/g at 1.0 A/g, when compared with other similar reports. This study proposes a facile and sustainable strategy for efficiently fabrication of rich B/N co-doped hierarchical micro/meso porous carbon electrodes from agricultural waste biomass for advanced supercapacitor performance.

The Effect of a Yb Co-Dopant on the Blue Upconversion and Thermoluminescent Emission of SrLaAlO4:Yb3+,Tm3+ Phosphors

In this study, we described the structural, morphological, optical, photoluminescence, and thermoluminescence properties of SrLaAlO4:Tm3+,Yb3+ (SLAO:Tm,Yb) blue-emitting phosphors made by combustion synthesis and a post-annealing treatment at 1200 °C. The Yb co-dopant concentration was varied (1.0, 3.0, 5.0, and 6.0 mol%) while the Tm dopant concentration was fixed at 5 mol%. According to the X-ray diffraction patterns, all the samples presented the pure tetragonal phase of SrLaAlO4. Scanning electron microscopy analysis showed that the SLAO powders had morphologies of irregular or bar grains with average sizes in the range of 0.5–1.07 µm. Photoluminescence emission under 980 nm excitation showed an intense blue emission peak at 481 nm. The phosphors also emitted red light at 654 nm and a prominent NIR emission at 801 nm. All those emissions correspond to 1G4 → 3H6, 1G4 → 3H4 and 3H4 → 3H6 transitions of Tm3+. The SLAO:Tm,Yb phosphors synthesized with 3.0 mol.% of the Yb co-dopant showed the highest emission intensity in the visible/near-infrared (NIR) range (400–800 nm), and its CIE coordinates corresponded to the blue color (0.19368, 0.15826). Additionally, thermoluminescence emissions were recorded for the SLAO:Tm,Yb phosphors. The samples were previously irradiated with UV wavelengths of 265 nm, 365 nm, and 385 nm prior to the thermoluminescent measurements. After this, the kinetic parameters such as frequency factors, activation energy (E), and order of kinetics were calculated using the Chen method. The thermoluminiscent emissions demonstrated that the SLAO:Yb,Tm phosphors can be used for UV dosimetry.

Realizing multicolor tunable photoluminescence in La2MgTiO6: Tb3+, Eu3+ phosphors via energy transfer and application for white light-emitting diodes

The achievement of multiple emission color phosphors has a significant importance in screen display, lighting devices, and multicolor imaging, but it still faces formidable challenges. In this work, double perovskite La2MgTiO6: Tb3+, Eu3+ phosphors with tunable emissions are designed and successfully synthesized. The obtained phosphors can emit intense green (Tb3+), red (Eu3+), and yellow emissions (Tb3+/Eu3+) via varying the co-doping concentration of Tb3+ and Eu3+. The CIE coordinates exhibit an excellent linear behavior in La2MgTiO6: Tb3+, Eu3+, revealing the possibility of linear adjustment of multiple emission colors. Detailed material characterization demonstrates that the multicolor tunable emission originates from energy transfer between Tb3+ and Eu3+. The decay dynamics analysis suggests that the multipole interaction between Tb3+ and Eu3+ is quadrupole-quadrupole interaction. A white light-emitting diode device with color rendering index of 84.7, correlated color temperature of 4684 K, and CIE coordinate of (0.3472, 0.3083) is fabricated by combining La2MgTiO6: Tb3+, Eu3+ yellow phosphor and BaMgAl10O17: Eu2+ blue phosphor. Our results reveal that La2MgTiO6: Tb3+, Eu3+ phosphors are promising luminescent materials in white light-emitting diodes.

Synthesis of diluted magnetic semiconductor ZnS:Cr and ZnS:(Cr+V) nanoparticles for spintronic applications

The design of optimally diluted magnetic semiconductors that exhibit strong ferromagnetism at room temperature is also imperative for developing spintronic devices. In this study, we describe the wet chemical preparation and characterization of ZnS, ZnS:Cr (1 at%), ZnS:Cr (1 at%) + V (1 at%), and ZnS:Cr (1 at%) + V (2 at%) NPs for spin-electronic device applications. Wide-ranging structural analyses suggested the incorporation of both Cr and V ions into the ZnS system. Morphological analysis revealed that the synthesized samples were in the nanoregime with a zero-dimensional alignment. Photoluminescence (PL) spectra displayed diminished luminescence intensity with doing and co-doping. and Electron paramagnetic resonance analysis revealed the presence and augmentation of spins with increasing V co-dopant concentration in the ZnS:Cr (1 at%) host lattice. Vibrating sample magnetometer analysis revealed that the ZnS:Cr (1 at%), ZnS:Cr (1 at%) + V (1 at%), and ZnS:Cr (1 at%) + V (2 at%) NPs exhibited strong ferromagnetism with clear hysteresis loops at room temperature.

High energy-power zinc-ion hybrid supercapacitors achieved by 3D channels enriched biomass-derived N/O co-doped 2D arcuate carbon nanosheets

Cost effective and safe zinc-ion hybrid supercapacitors (ZIHSCs), coupling the virtues of aqueous rechargeable supercapacitors and batteries, hold great potential in the energy storage field. However, ZIHSCs development is encumbered by the fatal obstacles of carbon cathodes, including inferior capacity and low energy and power densities. Herein, inspired by the intrinsic feature of well-developed metabolic channels, three-dimensional channels-enriched biomass is effectively converted into a novel N/O co-doped 2D arcuate carbon nanosheets cathode with robust 2D arcuate architecture, an optimized hierarchical porosity plus an ultrahigh surface area and high N/O co-doping contents for high energy-power ZIHSCs to conquer these barriers. The comprehensive integration of these properties affords extensive interfacial active sites for high energy density and fast kinetics for a high power output, thereby endowing remarkable Zn2+ storage capability, including specific capacity of 198.4 mAh/g at 0.2 A/g, capacity retention of 57.2% at a 100-fold enlarged current, and energy and power densities of 155.6 Wh/kg and 18.9 kW/kg, together with no loss in the capacity reservation of 10,000 cycles. Most excitingly, the resultant carbon-based quasi-solid ZIHSC device gave expressive specific capacity of 166.6 mAh/g, outstanding energy density of 123.4 Wh/kg, and excellent mechanical flexibility.

Magnetic, Optical and Phonon Properties of Ion-Doped MgO Nanoparticles. Application for Magnetic Hyperthermia

The influence of size and doping effects on the magnetization M, phonon ω and band gap energy Eg of MgO nanoparticles is studied using a microscopic model. The room-temperature ferromagnetism is due to surface or/and doping effects in MgO nanoparticles (NPs). The influence of the spin-phonon interaction is discussed. M increases with decreasing NP size. M and Eg can increase or decrease by different ion doping (Co, Al, La, Fe) due to the different strain that appears. It changes the lattice parameters and the exchange interaction constants. We found that MgO NP with size of 20 nm and Fe- or Co-doping concentration x = 0.1 and x = 0.2, respectively, have a Curie temperature TC = 315 K, i.e., they are appropriate for application in magnetic hyperthermia, they satisfy the conditions for that. The energy of the phonon mode ω = 448 cm-1 increases with decreasing NP size. It increases with increasing Co and Fe, or decreases with Sr ion doping.

Insights into visible luminescence and energy transfer mechanism of Eu3+/Dy3+ co-doped dolo-telluro-borate glasses

A series of Eu3+/Dy3+co-doped doro-telluro-borate (DTB) glasses were prepared using the melt-quenching approach and characterized. The absorption, excitation, emission, CIE1931 diagram and fluorescence decay profiles of these glasses were examined. The Judd-Ofelt model calculation was performed. These glasses showed prominent visible luminescence and lasing potency. The emission spectra and fluorescence lifetime decay profiles of the glasses with the increase of Dy3+ suggested an efficient energy transfer process between Eu3+ and Dy3+. The obtained chromaticity coordinates and color correlated temperature (CCT) of these glasses confirmed the emission of reddish-orange tone useful for cool white light displays. It was shown that the multicolor light emission from the studied glasses can be tuned by properly adjusting the Eu3+/Dy3+ co-doping contents. The proposed glass compositions may be advantageous for the construction of low-cost solid-state laser and cool white light emitting diodes.

Customized structural and mechanical characteristics of Eu3+ imbued boro-telluro-dolomite glasses: effect of Dy3+ co-doping

Inorganic oxide glasses with high mechanical strength and durability became demanding. Thus, a new type of Eu3+/Dy3+ co-doped boro-telluro-dolomite glass system with customized structures and mechanical properties were prepared by the melt-quenching method and characterized. The densities, FTIR and Raman spectra of the glasses revealed a significant modification in the network structure with the increase of Dy3+ contents. The values of microhardness and elastic moduli of the glasses were increased with the increase of co-doping contents. In addition, a correlation between the glass hardness and applied load was established. The proposed glasses were shown to withstand about 300 g applied force without any distortion, confirming their usefulness to design mechanically stable screen shield and high strength surfaces.

Production of p-CuO/n-ZnO:Co nanocomposite heterostructure thin films: An optoelectronic study

The p-n junction is the principal mode of optoelectronic semiconductor material. At present, we submit a solution-based attempt at the synthesis of nanostructured p-type CuO and n-type ZnO nanocomposite (NC) heterostructure films. Bare and Cobalt (Co)-doped CuO–ZnO NC films have been produced on glass slides using the SILAR (Successive Ionic Layer Adsorption and Reaction) method. The influence of Co-doping concentration on the physical characteristics of CuO–ZnO NC heterostructure films was investigated. XRD spectrums indicated the phase and structural purity of solution-based synthesized CuO–ZnO NC samples. The surface topographical, as well as optical and electrical properties of heterostructure films were, also investigated. While the bare CuO–ZnO NC film has a ∼38% transmission near 1000 nm wavelength region, the 2.0% Co-doped CuO–ZnO NC film has ∼31% of optical transmission. The sheet resistance value of the grown 2.0% Co:CuO–ZnO NC sample is almost 13 times lower than that of the bare CuO–ZnO NC sample at 400 K temperature. As a consequence, our attempt ensures a novel strategy for the production and performance optimization of CuO–ZnO NC heterostructures in the implementation of optoelectronics.

Antimicrobial, antioxidant, cytotoxicity and photocatalytic performance of Co doped ZnO nanoparticles biosynthesized using Annona Muricata leaf extract.

In the present study, ZnO nanoparticles doped with 3%, 5% and 7% of cobalt have been synthesized by green method using Annona muricata leaf extract. The obtained nanopowder was characterised by XRD, FTIR, XPS, HRTEM, SAED, SEM, EDAX and UV-Visible spectroscopy techniques. XRD patterns confirm the formation of pure and Co doped ZnO nanoparticles with a hexagonal wurtzite structure with high phase purity. FTIR spectra indicate the stretching vibration of Zn-O at 495cm-1. The incorporation of Co2+ ions into the ZnO lattice was identified by XPS analysis. EDX spectra confirm the existence of Co, Zn and O elements. The SEM and HRTEM micrographs show morphology of nanoparticles. The optical study specifies a decrease in energy band gap with an increase in Co-doping concentration. The photocatalytic performance of ZnO and Zn0.93Co0.07O has been examined for the degradation of methylene blue (MB) under sunlight irradiation. The antimicrobial activity of synthesized nanoparticles against s.aureus, p.aeruginosa, b.subtilis bacterial strains c.albicans and a.niger fungal strains as investigated. The Zn0.93Co0.07O nanoparticles exhibit good antioxidant properties. Moreover, the cytotoxicity of ZnO nanoparticles was evaluated against L929 normal fibroblast cells. So, this work suggests that Annona muricata leaf extract mediated pure and Co-doped ZnO nanoparticles are a potential candidate for biomedical and photocatalytic applications.

Theoretical and experimental investigation of the effects of Pr dopant on the electronic band structure, thermal, structural, in vitro biocompatibility of Er-based hydroxyapatites

Pr and Er co-doped hydroxyapatites (HAps) have undergone their first theoretical and experimental research. Pr content was changed in 0.13 percent increments from 0.13 to 0.78 percent. Er content was kept constant at 0.39 at.%. Theoretical results demonstrated an increase in the density from 3.154 to 3.179 g cm−3, as well as steady decreases in the bandgap from 4.1739 to 4.0618 eV. X-ray diffraction (XRD) patterns point out that all the samples consist of the single phase of the HAp. The crystallinity decreased steadily with adding of Pr. Pr-content has a considerable impact on all the XRD-related parameters, thermal behavior and morphology. The cell viability was affected by the co-dopant content, and this value was found to be higher than 83% for all the samples.

Superconductivity in the cobalt-doped V3Si A15 intermetallic compound

The A15 structure of superconductors is a prototypical type-II superconductor that has generated considerable interest since the early history of superconducting materials. This paper discusses the superconducting properties of previously unreported V3−x Co x Si (0 ⩽ x ⩽ 0.30) alloys. It is found that the lattice parameter decreases with increasing cobalt-doped content and leads to an decreased residual resistivity ratio value of the V3−x Co x Si system. Meanwhile, the superconducting transition temperature (Tc ) also decreases with increasing cobalt-doped content. Furthermore, the fitted data show that the increase of cobalt-doped content also reduces the lower/upper critical fields of the V3−x Co x Si system. Type-II superconductivity is demonstrated in all V3−x Co x Si samples. With higher Co-doped content, V3−x Co x Si (0.15 ⩽ x ⩽ 0.30) alloys may have superconducting and structural phase transitions in low-temperature regions. As the electron/atom ratio increases, the Tc variation trend of V3Si is as pronounced as in crystalline alloys and monotonically follows the trend observed for amorphous superconductors.

Solvothermal synthesis of magnetically separable Co–ZnO nanowires for visible light driven photocatalytic applications

Magnetically retrievable Cobalt doped ZnO nanowires were synthesised by simple solvothermal method. The prepared Co–ZnO nanowires were analysed with several characterization instruments such as FESEM, XRD, FTIR, VSM, UV–vis spectroscopy, XPS and PL spectroscopy. No other phase has been identified besides wurtzite phase, according to the structural analysis of pure ZnO and Co–ZnO nanowires. As the concentration of Co doping increased, ZnO nanowires' band gap energy dropped. Moreover, ZnO's absorption peak has a minor wavelength shift toward longer wavelengths. Green light emission was detected by PL analysis of ZnO nanowires and also the PL intensity of ZnO nanowires was decreased after cobalt doping. Co–ZnO nanowires exhibited ferromagnetic property. The coercivity and retentivity of Co–ZnO nanowires were increased with increase of Cobalt concentration. Improved visible light photocatalytic activity for the breakdown of methyl orange dye was achieved by Co–ZnO nanowires.

Investigation (Cd + Co) Co-Loading Impact on Physical Properties of Nano-Structured (CuO) Thin Films

Pure CuO and (Cd+Co) double doping CuO thin films were produced using the sol- gel method and the spin coating approach, with various (Cd+Co) co-doping concentrations ((1+1), (3+3), (5+5), and (7+7) wt.%) of (Cd+Co). XRD results showed that all prepared pure and metals co-doped CuO nanostructured thin films are polycrystalline and have a monoclinic structure with preferred planes on (002) and (111) without additional peaks related to Cd and Co. The surface morphology and layer thickness of synthesized thin films were analyzed by field emission Scanning Electron Microscopy. The SEM images showed Agglomerated spherical grains form at high co-doping concentrations. The existence of Cu, Cd, Co, and O elements was confirmed by EDS measurements., The energy gap decreased from 2.139eV to 2.02 eV was investigated by the Tauc’s and Davis-Mott relations.

Color-tunable luminescence based on the efficient energy transfer of a Tm-Dy system for optical thermometry and white LED lighting.

The development of phosphors with color-tunable luminescence including white emission is at the forefront of lighting and display technologies. Herein, Dy3+,Tm3+ single-doped or co-doped K3Y(PO4)2 phosphors are synthesized through the solid-state reaction method. By properly adjusting the ratio of Dy3+,Tm3+ co-doping concentrations, color-tunable luminescence from blue to yellow, including white luminescence, is realized under 359 nm excitation. The mechanism of energy transfer between Tm3+ and Dy3+ is further investigated via measuring the luminescence decay curve. Based on efficient energy transfer from Tm3+ to Dy3+, the emission of Dy3+ exhibits an abnormal thermal enhancement phenomenon as the temperature increases. The optical thermometry behaviors of various emission combinations for the Dy3+,Tm3+ co-doped system are analyzed. The maximum sensitivity can be obtained as a constant of 4.8 × 10-3 K-1, which is conducive to improve the measurement accuracy of optical temperature sensing at high temperatures. Furthermore, we also demonstrate the applicability of K3Y(PO4)2:Tm3+,Dy3+ phosphors in white LEDs, providing proof-of-concept for the lighting and display fields.