Influence Of Dopant Concentration Research Articles

New Na5Y(MoO4)4: Yb3+, Er3+ phosphors: Up-conversion luminescence and temperature sensing characteristics

Currently, the development of new up-converting fluorescent materials for manufacturing optical temperature sensing device with high accuracy and precision has always been significant pursuits of many researchers. In this work, we have synthesized new Na5Y(MoO4)4: Yb3+/Er3+ phosphors via solid-state reaction route, and the influences of dopant concentration on UCL performance were discussed. The results revealed that the introduction of Yb3+ enhanced the luminescence intensity, and the optimal concentration combination was 0.20Yb3+/0.04Er3+. Doping Yb3+ and Er3+ did not affect the phase structure of the phosphor. Several emission peaks at 529, 552 and 668 nm of Er3+ were found to be temperature-dependent within the scope of 298–573 K. Through the utilization of fluorescence intensity ratio technique (FIR, I529/I552 and I529/I668), dual-mode temperature measurement was realized. The maximum relative sensitivity (Sr-max) of 1.77 % K−1 (@298 K) utilizing thermally coupled energy levels (TCELs) and the maximum absolute sensitivity (Sa-max) of 12.0 % K−1 (@573 K) based on the non-TCELs were achieved. Furthermore, Yb3+/Er3+ co-doped Na5Y(MoO4)4 phosphors exhibited excellent photothermal repeatability and temperature resolution. The results indicated that the novel Na5Y(MoO4)4 phosphor provided the possibility for the development of temperature sensing materials with high sensitivity.

Tunable X-ray-induced luminescence in lanthanide-doped LaPO4 nanoparticles

X-ray luminescent nanoparticles have gained significant attention as promising tools for implementing multimodal imaging and radiation-based treatments in theragnostics. The intricate comprehension of their properties and the underlying mechanisms driving the conversion of X-rays into light is critical for their success in various applications. LaPO4 nanoparticles doped with various individual luminescence centers, gadolinium (Gd3+), europium (Eu3+), dysprosium (Dy3+), and terbium (Tb3+), were produced via co-precipitation and investigated for their behavior upon X-ray excitation using energies of up to 225 kV. These materials evidenced a radioluminescent response dependent on the dopant concentrations, with emission lines from 300 to 700 nm, providing insights into the luminescence quenching effect in these structures. The luminescent characteristics of the nanoparticles were studied under continuous irradiation, evidencing the materials’ ability to withstand high absorbed doses and preserve their properties. Furthermore, the influence of dopant concentrations on crystallite size and the dependence of luminescence on thermal treatments was investigated. The assessment of nanoparticle stability in aqueous suspension was evaluated over a broad pH range, revealing a tendency of the LaPO4 surface to selectively interact with electropositive species. This insight enhances our comprehension of the colloidal stability of the material, positioning it for extended applications and in vitro evaluations, along with further surface functionalization.

Modulating Co[sbnd]Co bonds average length in Co0.85Se1−xSx to enhance conversion reaction for potassium storage

While alloying transition metal chalcogenides (TMCs) with other chalcogen elements can effectively improve their conductivity and electrochemical properties, the optimal alloying content is still uncertain. In this study, we study the influence of dopant concentration on the chemical bonds in TMC and reveal the associated stepwise conversion reaction mechanism for potassium ion storage. According to density function theory calculations, appropriate S-doping in Co0.85Se (Co0.85Se1−xSx) can reduce the average length of CoCo bonds because of the electronegativity variation, which is thermodynamically favourable to the phase transition reactions. The optimal Se/S ratio (x = 0.12) for the conductivity has been obtained from experimental results. When assembled as an anode in potassium-ion batteries (PIBs), the sample with optimized Se/S ratio exhibits extraordinary electrochemical performance. The rate performance (229.2 mA h g−1 at 10 A g−1) is superior to the state-of-the-art results. When assembled with Prussian blue (PB) as a cathode, the pouch cell exhibits excellent performance, demonstrating its great potential for applications. Moreover, the stepwise K+ storage mechanism caused by the coexistence of S and Se is revealed by in-situ X-ray diffraction and ex-situ transmission electron microscopy techniques. Hence, this work not only provides an effective strategy to enhance the electrochemical performance of transition metal chalcogenides but also reveals the underlying mechanism for the construction of advanced electrode materials.

Facile Synthesis of Ni-Doped ZnO Nanoparticles Using Cashew Gum: Investigation of the Structural, Optical, and Photocatalytic Properties

This work adopted a green synthesis route using cashew tree gum as a mediating agent to obtain Ni-doped ZnO nanoparticles through the sol–gel method. Structural analysis confirmed the formation of the hexagonal wurtzite phase and distortions in the crystal lattice due to the inclusion of Ni cations, which increased the average crystallite size from 61.9 nm to 81.6 nm. These distortions resulted in the growth of point defects in the structure, which influenced the samples’ optical properties, causing slight reductions in the band gaps and significant increases in the Urbach energy. The fitting of the photoluminescence spectra confirmed an increase in the concentration of zinc vacancy defects (VZn) and monovacancies (Vo) as Zn cations were replaced by Ni cations in the ZnO structure. The percentage of VZn defects for the pure compound was 11%, increasing to 40% and 47% for the samples doped with 1% and 3% of Ni cations, respectively. In contrast, the highest percentage of VO defects is recorded for the material with the lowest Ni ions concentration, comprising about 60%. The influence of dopant concentration was also reflected in the photocatalytic performance. Among the samples tested, the Zn0.99Ni0.01O compound presented the best result in MB degradation, reaching an efficiency of 98.4%. Thus, the recovered material underwent reuse tests, revealing an efficiency of 98.2% in dye degradation, confirming the stability of the photocatalyst. Furthermore, the use of different inhibitors indicated that •OH radicals are the main ones involved in removing the pollutant. This work is valuable because it presents an ecological synthesis using cashew gum, a natural polysaccharide that has been little explored in the literature.

Enhanced electrical performance of Ag/Ba–Sn/n-Si/Ag hetero junction diode for photodiode applications

In this work, a new photodiode has been using Barium (Ba) and Tin (Sn) films which were prepared by Jet Nebulizer Spray Pyrolysis (JSNP) technique, and the influence of dopant concentration on structural, surface morphology, and optical property were extensively analyzed. As well, Copper/Barium and Tin n-type Silicon photodiodes were fabricated, and their I–V characteristics parameters were calculated and analyzed in detail. As a result, the performance of formation of Ag/Ba–Sn/n-si/Ag photodiode was significantly enhanced at optimized experimental conditions. The improved performance of the prepared photodiode was evidenced from I–V evaluation. The excellent optoelectronic properties of the fabricated photodiode make them suitable for the application of the future Opto-electronics industry.

Ambient- and calcination- temperature induced color-tunable upconversion luminescence in Yb3+/Er3+ co-doped Y2(MoO4)3 phosphors for optical thermometer

Trivalent lanthanides (Ln 3+ )-doped upconversion luminescent (UCL) materials with negative thermal expansion (NTE) property are endowed an exciting thermal enhancement performance. Hitherto, selectively thermal enhancement for the multi-narrow-band emissions of phosphor with NTE property is not implemented. Herein, Y 2 Mo 3 O 12 :Yb 3+ /Er 3+ phosphor synthesized by the modified sol-gel method is explored in selectively enhanced green emission (Er 3+ : 2 H 11/2 / 4 S 3/2 → 4 I 15/2 ) due to the formation of Yb-MoO 4 dimer at high ambient-temperature. The 54-fold selectively enhancement of green emission is obtained from 298 K to 523 K. In addition, the influences of dopant-concentration and calcination-temperature on UCL properties are analyzed. Accordingly, based on the fluorescence intensity ratio (FIR) of non-thermally coupled levels (NTCLs) for 2 H 11/2 / 2 F 9/2 and 4 S 3/2 / 2 F 9/2 as well as ( 2 H 11/2 + 4 S 3/2 )/ 2 F 9/2 , the optimal relative sensitivity of temperature sensing in the Y 2 Mo 3 O 12 :Yb 3+ /Er 3+ sample could reach 0.14 K −1 at 298 K. All these indicate that this Y 2 Mo 3 O 12 :Yb 3+ /Er 3+ material is a promising candidate for high-sensitivity optical temperature sensing.

Green synthesis of Mn-doped TiO2 nanoparticles and investigating the influence of dopant concentration on the photocatalytic activity

• An environmentally friendly method for preparing photocatalysts to treat organic dyes. • A green synthesis approach is adopted to prepare Mn-doped TiO 2 nanoparticles. • Methylene blue is degraded most efficiently using a 0.05% Mn-TiO 2 catalyst. • 0.1 g L -1 of catalyst is found to remove 86% of Methylene blue after 35 minutes. • The regeneration of the Mn 4+ /Mn 2+ cycle is crucial for photocatalytic activity. A tea plant extract is used in the presence of titanium and manganese sources to synthesize three different concentrations of Mn x Ti 1-x O 2 (x=0.03, 0.05, and 0.1). By substituting Ti atoms for Mn, the lattice of TiO 2 is successfully incorporated with Mn. The degradation of Methylene Blue (MB) in the presence of visible light is used to test the photocatalytic activity of the synthesized samples. Among the Mn-doped TiO 2 samples, the highest degradation ratio is observed for samples with a dopant concentration of 0.05 at%. A dose of 0.1 g L -1 and 5 mM of Mn-TiO 2 is found to remove 86% of MB after 35 minutes of reaction. Mn x Ti 1-x O 2 is critically important for speeding up the MB degradation because of electron transfer between Mn and TiO 2 , and for the regeneration of the Mn 4+ /Mn 2+ cycle on its surface. Optical irradiation of the photocatalytic system under visible light led to higher visible photocatalytic activity than pure TiO 2 . We propose a novel and environmentally friendly method for preparing photocatalysts to treat organic dyes.

Influence of Dopant Concentration and Annealing on Binary and Ternary Polymer Blends for Active Materials in OLEDs.

Obtaining white light from organic LEDs is a considerable challenge and, to realize white light emission, many studies have been conducted, primarily addressing two- or three-color blend systems as a promising strategy. In this work, pristine films, grown by spin coating, consisting of commercial blue Poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO), green Poly(9,9-dioctylfluorene-alt-benzothiadiazole) (F8BT), and red spiro-copolymer (SPR) light-emitting materials, were studied as reference materials. Afterward, binary (SPR doped in host PFO) and ternary (SPR and F8BT doped in host PFO) thin films were successfully prepared with various ratios. The characterization of the as-grown and thermally-treated blend films was focused on their optical and photophysical properties. After, the fabrication of OLED devices on glass substrates was carried out for the evaluation of a blend's composition and annealing in terms of the devices' electrical characteristics and electro-emission properties in order to achieve white light emission. Their analysis provided insights into the energy transfer mechanisms between the constituent materials, which were correlated to host-guest interactions as well as to the structural changes originated by thermal treatment, leading to the crystallization of PFO. Finally, the OLEDs based on ternary blends approach the white light emission with (x, y) of (0.272, 0.346). These fabricated devices also exhibit turn-on voltages as low as 3 V, accompanied by remarkable luminance values above 3000 cd/m2.

Tailoring the optical characteristics and band-gap of BG doped PMMA/FTO nanocomposite films for laser power attenuation: New approach

Herein a good adherent film of PMMA doped with the various ratio of BG-dye deposited on optically flat FTO-substrates by using a well-controlled spin coating process. The average crystallite size and microstrain were determined by X-ray diffraction pattern analysis and were found to be 21.7219 nm and 0.0016, respectively, with a significant change with the amount of BG-dye doping in the matrix of PMMA film. Both linear and nonlinear optical characteristics, as well as their related parameters, were measured using a UV–Vis–NIR spectrophotometer. As a result of doping BG-dye molecules into the host PMMA matrix system, optical absorption studies revealed significant changes in optical characteristics. BG-dye doped PMMA film revealed impressive absorption bands in the range of 350–750 nm, depending on the degree of doping of BG-dye into the PMMA film. Another distinguished property is the attenuation of the complete absorption in the range of 552–688 nm and observed as a cut-off-absorbance. The point of the art of this contribution is the various applications for optical limitation systems like Cut-off filters and other related optical devices due to the remarkable optical features. The BG-dye doping influenced all optical metrics, including the absorption band, absorption edge, and direct and/or indirect energy band gap. The direct energy gap's first region is in the range of 1.77–1.97 eV, whereas the second is in the range of 2.68–2.82 eV, and the third is in the range of 3.67–4.09 eV. The indirectly allowed transitions are divided into two regions, the first of which is in the 1.74–1.82 eV range and the second of which is in the 3.69–3.98 eV range. The appearance of extra energy levels is confirmed by fluctuations in the optical band gap, which are aided by the influence of dopant concentration of BG-dye dopant wt.%. The ratio of BG-dye into the PMMA film is promising for the optical respective of the green light for the cut-off filter as well as optoelectronic device applications.

Influence of dopant concentration on the ammonia sensing performance of citric acid-doped polyvinyl acetate nanofibers.

The chemical modification of polymer nanofiber-based ammonia sensors by introducing dopants into the active layers has been proven as one of the low-cost routes to enhance their sensing performance. Herein, we investigate the influence of different citric acid (CA) concentrations on electrospun polyvinyl acetate (PVAc) nanofibers coated on quartz crystal microbalance (QCM) transducers as gravimetric ammonia sensors. The developed CA-doped PVAc nanofiber sensors are tested against various concentrations of ammonia vapors, in which their key sensing performance parameters (i.e., sensitivity, limit of detection (LOD), limit of quantification (LOQ), and repeatability) are studied in detail. The sensitivity and LOD values of 1.34 Hz ppm-1 and 1 ppm, respectively, can be obtained during ammonia exposure assessment. Adding CA dopants with a higher concentration not only increases the sensor sensitivity linearly, but also prolongs both response and recovery times. This finding allows us to better understand the dopant concentration effect, which subsequently can result in an appropriate strategy for manufacturing high-performance portable nanofiber-based sensing devices.

Influence of dopant concentration on powder morphology and photoluminescence characteristics of red-emitting Eu3+-doped ZnO

A well-defined morphology is highly required to obtain richness in red colour with improved photoluminescence characteristics of phosphor materials. In this work, different concentrations of Eu3+-doped ZnO red-emitting materials with well-established morphologies were prepared through precipitation using sodium borohydride. The morphology of pure phase of Eu3+-doped ZnO samples varied from agglomerated spherical particles to elliptical/elongated rod-like structures with the incorporation of Eu3+ ions. The Raman spectra exhibited the defects such as oxygen vacancy with zinc interstitial in all the samples. The emission spectra revealed the dominance of 5D0→7F2 electric dipole transition at 613 nm. The elongated rods with flower-like morphology of 1 mol% Eu3+-doped ZnO sample exhibited the highest emission intensity. It was mainly due to the less defects introduced in the larger particle size i.e. elongated rods with flower-like morphology. This led to decrease the nonradiative rate and eventually increases the emission intensity. The R/O ratio revealed the higher asymmetry in nature around the Eu3+ ions in the ZnO for all the samples. The CIE coordinates of Eu3+-doped ZnO samples were lie in the reddish-orange and red region. The elongated rods with flower-like nanostructures show a higher colour purity among the other nanostructures. Further, the Judd-Ofelt intensity parameters were determined with the help of emission spectra. The obtained results suggested that the Eu3+-doped ZnO samples may be used as a red-emitting light source in the solid-state lighting application.

Spectroscopic investigation of defects in spin coated titania based thin films for photocatalytic applications

The present work focuses on Raman and photoluminescence spectroscopic study of spin coated Nd doped titania thin films annealed at 350 and 450 ​°C. For all the samples, the penetration depth of laser was evaluated to be about 300–350 ​nm. The lifetime of phonon was in the range 0.46–0.52 ps for different samples and its variation is discussed in detail. Photoluminescence (PL) spectra of Nd doped titania revealed the influence of dopant concentration on defect sites and strong emission in near infrared (NIR) region confirms Nd doping in titania matrix. The effect of Nd doping on photocatalytic behavior of titania films was studied by degrading methyl orange (MO) under UV light. The Nd doped titania thin films enhance the photocatalytic activity as compared to pristine titania. The enhancement in efficiency is correlated to the formation of surface defects.

Enhanced Electrochemical Performance of Li4Ti5O12 by Niobium Doping for Pseudocapacitive Applications

Niobium-doped nanocrystalline Li4Ti5O12 (LTO) is synthesized by the solid-state reaction method, and the influence of dopant concentration (x = 2–10 mol%) on microstructural and electrochemical properties is studied. The X-ray diffraction and Raman patterns assessed the cubic spinel structure of Li4Ti5−xNbxO12 phase in all samples. Marginal changes in the lattice parameters, unit cell volume and dislocation density of LTO are observed with Nb substitution. The higher ionic radius of Nb induces a lattice expansion, which may be favorable for more ion intercalation/deintercalation. The SEM and TEM images display uniformly distributed nano-sized cubical particles. The represented (hkl) orientations of the SAED pattern and d-spacing (0.46 nm) between bright fringes confirm the well-crystallized LTO phase. The EDS and elemental mapping results demonstrate that Nb elements are uniformly doped in LTO with a proper stoichiometric ratio. The optimized 8%Nb-doped LTO electrode exhibits pseudocapacitive behavior and delivers a high specific capacitance of 497 F g−1 at a current density of 1 A g−1 with 92.3% of specific capacitance retention even after 5000 cycles.

The Influence of Dopant Concentration on Optical-Electrical Features of Quantum Dot-Sensitized Solar Cell.

In this study, TiO2/CdS/CdxCu1−xSe, TiO2/CdS/CdxMn1−xSe, and TiO2/CdS/CdxAg2−2xSe thin films were synthesized by chemical bath deposition for the fabrication of photoanode in quantum-dot-sensitized solar cells. As a result, the structural properties of the thin films have been studied by X-ray diffraction, which confirmed the zinc Blende structure in the samples. The optical films were researched by their experimental absorption spectra with different doping concentrations. Those results were combined with the Tauc correlation to estimate the absorption density, the band gap energy, valence band and conduction band positions, steepness parameter, and electron–phonon interaction. Furthermore, the electrical features, electrochemical impedance spectrum and photocurrent density curves were carried out. The result was used to explain the enhancing performance efficiency.

Thin Zn1 – xMnxO Films (x = 1–4 at %) by Chemical Bath Deposition: Influence of Dopant Concentration

Thin Zn1 – xMnxO Films (x = 1–4 at %) by Chemical Bath Deposition: Influence of Dopant Concentration

Investigation on dielectric properties of iron oxide nanoparticles-embedded binary transition metals-doped polyaniline-metal hybrid nanocomposites

Dielectric material based on hybrid PANI-metal nanocomposites always gained an immense research interest due to its unique properties. Herein, we have synthesized iron oxide nanoparticles embedded two different binary transition metal doped PANI nanocomposites via simple in situ rapid mixing chemical oxidative polymerization method. Morphological, structural, electronic and chemical composition of the composites were systematically studied. The influence of dopant concentration in tuning PANI surface from flake like to spherical bead like morphology was analysed by high resolution transmission electron microscopy. Moreover, dielectric parameters as function of frequency have been investigated at room temperature in a frequency range 100Hz–2MHz and the result showed that the as prepared flake like nanocomposites - 0.3 M Cu-Fe-PANI and 0.7 M Mn-Fe-PANI systems are promising dielectric materials.

Influence of dopant concentration on the electronic band gap energy of Yb-ZrSe2 thin films for photovoltaic application via electrochemical deposition technique

This research focus on the Influence of Dopant Concentration on Polycrystalline Ytterbium-doped ZrSe (Yb-ZrSe) material for possible photovoltaic application using the electrochemical deposition method. The cationic precursor was an aqueous solution of 0.01 mol ZrOCl2.8H2O while the anionic precursor was 0.15 mol selenium was prepared by dissolving with 5 ml of Hydrochloric acid (HCl), and then 0.05 mol Yb (NO3)3.5H2O was used as the dopant. The films were characterized using UV-1800 Visible Spectrophotometer, Bruker D8 Advance x-ray diffractometer with Cu Kα line (λ = 1.54056 Å) in 2θ range from 10°–90°and Scanning Electron Microscopy. X-ray diffraction (XRD) of the deposited films on FTO substrate studies reveals that films are polycrystalline by exhibiting diffraction peaks at (111), (200), (200) and (210) corresponds to the following angle (27.00°), (38.01°), (46.02°), (66.02°). (SEM) revealed that the grain size was uniformly distributed on the surface of the substrate. The optical band gap energy was obtained.

Composition-driven phase boundary and electromechanical properties in Bi0.5Na0.5TiO3-A(Mg1/3Nb2/3)O3 binary solid solutions

A(Mg1/3Nb2/3)O3 (abbreviated as AMN, A=Ba, Sr and Ca) complex perovskite with tolerance factor t of 0.937–1.03 was incorporated into Bi0.5Na0.5TiO3 (BNT) matrix with tBNT = 0.977 to form binary solid solutions, and the influence of dopant concentration and type on their ferroelectric and piezoelectric properties were investigated. It is found that the BNT-xCaMN system has a higher driving field, probably due to the co-contribution from smaller A-site ionic radius and larger atomic electronegativity. This study also revealed a relationship between t value of morphotropic and polymorphic phase boundary compositions for the BNT-xAMN systems and AMN end-members with tBaMN = 1.03 > tBNT, tSrMN = 0.972 ≈ tBNT and tCaMN = 0.937 < tBNT, which complements a MPB-t relation for quick predicting the approximate morphotropic and polymorphic phase boundary regions of BNT-based systems.

Co doped ZnO thin films deposited by spin coating as antibacterial coating for metallic implants

Pure and Co doped ZnO thin films were deposited on Ti substrates by spin coating and further thermally treated at 500 or 600 °C in order to achieve implantable metallic materials with improved biocompatibility and antibacterial effect. The influence of dopant concentration on the physical, chemical and biological characteristics was also approached, namely values of 0.5, 1.0, 1.5, 2.0 and 5.0 mol% Co. The coated structures were investigated in terms of composition, structure, morphology, wetting properties, antibacterial activity and biological response in the presence of amniotic fluid stem cells. The results proved that all deposited samples are nanostructured, with thicknesses below 1 μm, show a very good antimicrobial effect and prove to be suitable supports for cellular adhesion and proliferation.

Influence of Dopant Concentration on Dislocation Distributions in 150mm 4H SiC Wafers

Shifts in the spatial distribution of threading dislocations in 150 mm 4H SiC wafers were examined as a response to intentional changes in both the flow of the nitrogen source gas used to control resistivity during bulk crystal growth, and the growth rate. The density of threading edge and screw dislocations was found to be more evenly distributed in wafers produced under a high-growth rate, low-resistivity process. This result corresponded to a flattening of the resistivity distribution, and a ~34% reduction in on-and off-facet resistivity differential. The effect was attributed to regularized 4H island coalescence due to modulation of step terrace width.