Doped Specimens Research Articles

The stability, electronic and optical properties of nonmetal doped g-GaN: A first-principles calculation

Doping is an effective strategy to modulate the electronic performance of materials by forming new chemical bonds and relaxing the neighboring bonds, which may change catalytic performance of materials. Herein, we demonstrate the effects of a series of nonmetal (NM) dopants on the electronic properties and photocatalytic activity of g-GaN monolayer using first-principle calculations. NM dopants prefer to substitute N atom under Ga-rich condition. C, O and F doped specimens are highly stable under both Ga-rich and N-rich conditions. NM dopants induce the generation of impurity levels, contributing to reduce the electronic transition energies. S, Se and Te doped specimens increase by about 11, 8 and 4 times for absorption intensity in the region of visible light, respectively. Remarkably, S, Cl, Se, Br, Te and I dopants can effectively decrease the recombination rate of photogenerated electrons and holes of the g-GaN in photocatalytic reaction. H, B, C Si, P and As doped system can induce more active sites. Remarkably, halogen dopants could increase the both redox and reduction ability of g-GaN monolayer. Thus, NM dopants can effectively tune redox potential of g-GaN monolayer and improve its photocatalytic performance.

Impact of oxygen vacancy on luminescence properties of dysprosium-doped zinc oxide thin films

Pristine and dysprosium-doped ZnO thin films, highly c-axis oriented, were grown on a c-Al2O3 substrate using the pulsed laser deposition technique. During the deposition process, the growth was impacted by changes in the oxygen partial pressure. The structural, optical, and compositional properties of the pristine and dysprosium-doped ZnO thin films were systematically characterized using various state-of-the-art experimental techniques. The crystallinity associated with these films was observed to be highly dependent on the oxygen partial pressure maintained during the growth process. An average optical transparency of more than ∼90% in the visible spectral range (i.e., 400–800 nm) was observed for all specimens. For doped specimens, expected intra-4fn emissions of (dysprosium) Dy3+ ions that emanated from the 4F9/2 energy state were observed in room-temperature photoluminescence spectra under direct excitation. The Jacobian-transformed wavelength-to-energy plot for Dy-doped ZnO thin films in the UV-Visible region revealed intriguing findings. Specifically, it depicted a prominent peak at 2.82 eV, indicative of the energy state of Dy3+ ions, alongside intense band-edge emission and various defect-related emissions. The intensity of these transitions was observed to depend on the oxygen partial pressure kept during deposition. An x-ray photoelectron spectroscopy analysis of the doped specimen confirmed the +3 oxidation state of dysprosium into the ZnO matrix. These results provide a promising approach for controlling the doping and growth strategy of Dy-doped ZnO thin films, thereby opening up a wide range of applications and enhancement for next-generation optoelectronic devices.

Effect of Sr and Ta co-substitution on microstructure and ionic conductivity of cubic-Li0.5La0.5TiO3 electrolyte for applications in Li batteries

All-solid-state lithium batteries (ASSBs) have gained significant attention in recent years because of their potential to offer higher energy density and enhanced safety compared to conventional liquid-electrolyte-based lithium-ion batteries (LIBs). Lithium lanthanum titanate (LLTO) is a promising solid electrolyte for next-generation lithium batteries owing to its high ionic conductivity of approximately 10−3 S·cm−1 at room temperature (RT). The Sr and Ta co-doped Li0.5-□La0.5−xSrxTi1−xTaxO3 perovskites were synthesized by solid-state reaction. In this study, Sr2+ and Ta5+ with larger ionic radii, were used for co-substitution in the La3+ and Ti4+ sites, respectively, to increase the bottleneck size of the A-site and expand the average bond length of the B-site on the perovskite structure (ABO3), thereby increasing the Li+ ion mobility. The LLSrxTTaxO3 (0 ≤ x ≤ 0.12) pellets have high relative densities, and high grain conductivities, where the total conductivity of LLSr0.09TTa0.09O3 reached 4.12 × 10−5 S·cm−1. Compared with the pure specimen, the total conductivities of the doped specimens are approximately more than 2.7 times at RT. The assembled semi-solid LFP/10 wt% LLSr0.09TTa0.09O3/Li full battery has a 0.1 C specific discharge capacity of 156 mAh⋅g−1 and a 1 C capacity retention rate of 86% after 290 cycles at RT.

Lithium and Cesium Doping on the Properties of ZTS Crystals (Tris (Thiourea) Zinc (II) Sulphate)

The influence of alkali metals (Cs and Li) doping on the properties and crystal growth of tris(thiourea)zinc(II)sulphate crystals by slow evaporation solution growth technique at 30ºC has been investigated. Each metals as dopant incorporate into the crystal lattice even at its low concentrations is well confirmed by energy dispersive X – ray spectroscopy (EDS). In the powder X –ray diffraction (XRD), high intense peaks are observed for all doped specimens due to stress developed in the crystal because of doping when compared to pure one. Single crystal XRD reveals a nominal increase in the cell parameter values of the doped samples compared to pure. Presence of each alkali metal (Li, Cs) quantitatively is confirmed by inductively coupled plasma (ICP) technique. It is interesting to observe the enhancement of fluorescence intensity of pure ZTS by the dopant in the photoluminescence (PL) spectra. The grown crystals are also characterized by FT-IR, UV-Visible and TG/DSC methods. The second harmonic generation (SHG) efficiency, an essential character required for the single crystals to identify the non-linear optical (NLO) property, was performed by kurtz powder technique. 2.The characterization results of influence of various concentration of Mn (II) ion on the properties and crystalline perfection of ammoniumdihydrogenphosphate (ADP) crystal are presented. Using water as a solvent pure, 1 and 20 mol % of Mn (II) ion in the form manganese (II) sulphate added ADP crystals are prepared by slow evaporation solution growth technique (SEST). Well faceted grown crystals are characterised by different experimental techniques. The presence of Mn (II) in the doped specimens is confirmed by energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma (ICP) technique. High resolution X- ray diffraction (HRXRD) study of the doped samples when compared with the pure ADP crystal reveals interesting features. In the single crystal XRD studies, the dopants have not altered the lattice parameter values and the crystal system of pure ADP. Reduction in the intensity of peaks is observed in the powder XRD of all the doped samples. It is interesting to enhancement of fluorescence intensity of pure ADP by the dopants in the photoluminescence (PL) spectra. The surface morphology of the crystals is studied by scanning electron microscopy (SEM). The grown crystals are also characterized by FT-IR, UV-Vis and TG/DTA methods. The second harmonic generation (SHG) efficiency, which is an essential character required for the single crystals to identify the nonlinear optical (NLO) property, is performed by Kurtz powder technique. Increasing in concentrations of dopant enhance the SHG efficiency of ADP crystal.

Antimicrobial potential and rhodamine B dye degradation using graphitic carbon nitride and polyvinylpyrrolidone doped bismuth tungstate supported with in silico molecular docking studies

The environmental-friendly hydrothermal method has been carried out to synthesize Bi2WO6 and g-C3N4/PVP doped Bi2WO6 nanorods (NRs) by incorporating different concentrations of graphitic carbon nitride (g-C3N4) as well as a specified quantity of polyvinylpyrrolidone (PVP). Bi2WO6 doped with g-C3N4 provides structural and chemical stability, reduces charge carriers, degrades dyes, and, owing to lower bandgap energy, is effective for antibacterial, catalytic activity, and molecular docking analysis. The purpose of this research is the treatment of polluted water and to investigate the bactericidal behavior of a ternary system. The catalytic degradation was performed to remove the harmful rhodamine B (RhB) dye using NaBH4 in conjunction with prepared NRs. The specimen compound demonstrated antibacterial activity against Escherichia coli (E. coli) at both high and low concentrations. Higher doped specimens of g-C3N4/PVP-doped Bi2WO6 exhibited a significant improvement in efficient bactericidal potential against E. coli (4.55 mm inhibition zone). In silico experiments were carried out on enoyl-[acylcarrier-protein] reductase (FabI) and β-lactamase enzyme for E. coli to assess the potential of Bi2WO6, PVP doped Bi2WO6, and g-C3N4/PVP-doped Bi2WO6 NRs as their inhibitors and to justify their possible mechanism of action.

Hydrated doped-BaZrO3 proton conductors studied by positron annihilation lifetime spectroscopy

The study of defect chemistry for doped BaZrO3 proton conductors is of particular interest because of defect interactions that can affect the proton conductivity of the material. Protons incorporated due to the material's hydration can be trapped by negatively charged immobile dopants, reducing proton mobility. The reduction of the proton conduction impedes the use of BaZrO3 materials in energy conversion applications at intermediate temperatures (300 °C – 600 °C). The probing of proton trapping in doped BaZrO3 is hindered by the limited availability of techniques sensitive to defect chemistries. In this work, we used positron annihilation lifetime spectroscopy (PALS) to study the defect chemistry of Y-doped and Sc-doped BaZrO3. Using a two-state positron trapping model we showed that PALS can be applied to study the defect chemistry of hydrated dense proton conductors. Positron trapping rates and lifetimes were correlated with doping levels of the materials. Probability significance t-tests were carried out for PALS parameters to verify whether there are differences/similarities for various populations: non-doped/doped, level and type of doping, high temperature, and surface effects. The results revealed that the initial doping generates a significant number of traps available for positrons. Doping with yttrium increased the positron trapping rate, while this effect was not observed with scandium. Low-temperature hydration affects specimens significantly inhibiting positron trapping at undoped BaZrO3 material and highly doped specimens. Positronium formation in rough surface layers, and highly doped specimens was detected but does not exceed 1%.

Effects of thermal and mechanical properties of Hf and Ta-doped NiCoCrAlY bonding layer alloys on the high-temperature oxidation resistance of thermal barrier coatings

The MCrAlY bonding layer alloy was prepared by vacuum melting, and the alloy composition was NiCoCrAlY and NiCoCrAlYHfTa. The high-temperature cyclic oxidation experiment was carried out in air at 1050∘C until it failed. The results show that Hf and Ta have a significant influence on the oxidation resistance of the alloy. The doped specimens have longer oxidation lifetimes compared to the undoped samples. The study also found that the Hf would diffuse out and combine with O to form HfO2 in the thermally grown oxide (TGO) layer, which would improve the adhesion and reduce the wrinkles of the oxide layer. Ta in the doped specimens hinders the diffusion of Al and reduces the oxidation rate, while improving the thermal mismatch. Therefore, the specimens doped with both Hf and Ta have the highest oxidation lifetimes, though the oxidation lifetime was 10 times longer than that of the undoped specimens. It is indicated that the doping of Hf and Ta is an important method to improve the oxidation lifetime of thermal barrier coatings (TBCs).

Efficient Photocatalytic Dye Degradation and Bacterial Inactivation by Graphitic Carbon Nitride and Starch-Doped Magnesium Hydroxide Nanostructures.

The removal of hazardous pollutants from water is becoming an increasingly interesting topic of research considering their impact on the environment and the ecosystem. This work was carried out to synthesize graphitic carbon nitride (g-C3N4) and starch-doped magnesium hydroxide (g-C3N4/St-Mg(OH)2) nanostructures via a facile co-precipitation process. The focus of this study is to treat polluted water and bactericidal behavior with a ternary system (doping-dependent Mg(OH)2). Different concentrations (2 and 4 wt %) of g-C3N4 were doped in a fixed amount of starch and Mg(OH)2 to degrade methylene blue dye from an aqueous solution with bactericidal potential against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) pathogens. The textural structures, morphological evolutions, and optical characteristics of the as-prepared samples were analyzed using advanced characterization techniques. X-ray diffraction confirmed the hexagonal phase of Mg(OH)2 with improved crystallinity upon doping. Fourier transform infrared spectroscopy revealed Mg(OH)2 stretching vibrations and other functional groups. UV-visible spectroscopy exhibited a red shift (bathochromic effect) in absorption spectra representing the decrease in energy band gap (E g). Photoluminescence patterns were recorded to study recombination of charge carriers (e- and h+). A significant enhancement in photodegradation efficiency (97.62%) and efficient bactericidal actions against E. coli (14.10 mm inhibition zone) and S. aureus (7.45 mm inhibition zone) were observed for higher doped specimen 4% g-C3N4/St-Mg(OH)2.

The role of Os substitution on structural, magnetic, and optical features of LuFeO3

The powders of LuFeO3 and LuFe1-xOsxO3 (x = 0.05 and 0.10) were fabricated by using solid-state technique. The presence of particle agglomeration as well as the porosity of the analyzed materials have been shown via scanning electron microscope (SEM) studies. The oxidation states of the constituted elements in the fabricated samples have been determined with X-ray photoelectron spectroscopy (XPS) studies. It has been realized that the Lu has 3+, Fe accommodates both 2+ and 3+ valence stated in three samples. In addition, the oxidation state of Os has been identified as 4+ in the Os doped samples. It has been demonstrated that the Raman peak intensity of the Os substituted samples declines with Os presence. Furthermore, it has been seen that the peaks shift to lower wavenumber values in the Os doped specimens. Magnetic studies performed via vibrating sample magnetometer (VSM) found that the Os doping increases not only Hc but also Mr values at 10 K and 100 K, yet Hc and Mr values for undoped LFO at 300 K are higher than the Os doped samples. This rise in Hc and Mr values might be attributed to 1) deviations in the tilted angles of Fe3+ moments and 2) the evolution of energy of magnetocrystalline anisotropy. Moreover, the influence of Os doping on the optical band gap of LFO was determined. It exhibited that the optical band gap of LFO increases as the Os doping ratio elevates from 2.19 eV to 2.22 eV.

Investigation Of The Effect Of Vermiculite (Yıldızeli/Sivas) Addition On The Properties Of Sanitaryware Ceramic

Sanitaryware is the generic term used to describe items which traditionally were made from pottery. i.e. toilets, washbasins, pedestals, bidet, urinals, sinks, bathtubs installed within a bathroom or washroom. Sanitaryware products are primarily made of clay, kaolin, feldspar and quartz but they may also include small quantities of other raw materials. Its high gloss, stain resistant surface is ideal for use in both bath-rooms and kitchens. Vermiculite, a mineral in which the hydromicas group occurs naturally, becomes a high-efficiency thermal insulation material when heated above 300 ℃. The expanded vermiculite can be used as a filler for heat insulating materials due to its unique properties, low bulk density, low thermal conductivity, relatively high melting point, chemical inertia, durability and environmental safety. In this study, the effects of vermiculite obtained from Yıldızeli/Sivas region on sanitaryware body properties were investigated. The materials used in this study are calcined vermiculite, quartz, clay, kaolin and feldspar ceramic raw materials. Sanitaryware compositions were prepared by using kaolin-feldspar-quartz ternary equilibrium diagram according to the appropriate recipe from the raw material. In accordance with this purpose; prepared sanitaryware bodies %0, 10 and 20 by weight calcined vermiculite (1050 oC 1 hour) was added to formed the body compositions. The samples were coded as S20V1100 (S: Sanitaryware; 20V: 20% vermiculite addition and 1100: 1100 °C firing temperature). Mixtures homogenized in Alumina ball mills (60 rpm, 24 hours) were shaped by uniaxial dry pressing (100 MPa). Then, the prepared pressed samples were fired at 1050-1100 and 1150 °C for 1 hour. Microstructure (SEM), phase analysis (XRD), mechanical (hardness, 3-point bending) and physical properties (% shrinkage, water absorption, porosity and density) tests were performed on the sanitaryware bodies produced. The obtained data were presented in graphs and tables and commented. Accordingly, the properties of the vermiculite doped specimens were successfully developed and the optimum parameters were clearly shown. According to the results, it has been shown that sanitaryware properties are improved with the increase of calcined vermiculite.

Structural Characterization of (Mg(1-x)pbxO)-NPs by Modified Pechini Method

The structural characterization was discussed in the present paper of the pure MgO nanoparticles and the doped (Mg(1-x)pbxO) nanoparticles specimens, where (0 ≤ x ≤ 0.03). The modified Pechini method was used to prepare all the specimens. From (DTA), the convenient temperature of decomposition from Mg(OH)2 to MgO was above 375°C. The structure investigation (XRD) revealed that all the specimens have identical space groups and index well to cubic structures. The obtained crystallite size by Scherrer''s equation was increased with increasing the fraction of doping except for (Mg0.97Pb0.03O) due to the formation of PbO oxide. The molecular vibration by FTIR demonstrated that all the pure and doped specimens have the same framework. As the incorporation of Pb2+ ions increases, the bands get broader, and the intensities increase in the ranging 800-400 cm-1 due to vibrations of O-Mg and O-Pb bands, respectively.

Regulation of microstructure and physical properties of Tb-Dy-Fe-Cu alloys by doping with transition elements

The Tb-Dy-Fe alloy with superior magnetostrictive strain and excellent energy density is applied in various fields such as precise driving and intelligent sensing. However, the Laves phase of magnetostrictive alloys has severe brittleness and poor fracture toughness at room temperature, limiting the development of their engineering instruments. In the present study, the transition element doping method is proposed to regulate the elemental composition for the severe brittleness of Tb-Dy-Fe-Cu alloys. The values of Vickers hardness for Nb-doped and Ti-doped specimens were 520.82 HV and 531.90 HV, respectively, with an increase of 4.097% and 6.311% compared to the original specimens. The saturation magnetostriction coefficient is 800p.p.m. for the natural specimens and around 620p.p.m. for the doped specimens. On the one hand, the enhancement of the mechanical properties of doped specimens is mainly attributed to the growth twins and nanoprecipitates induced by doping the transition element. On the other hand, the weakened magnetic properties of the doped specimens ascribed to the accumulations consisting of nanoprecipitates, twins, and elemental aggregates. This doping method could provide an essential reference for developing novel magnetostrictive materials with more desirable and balance physical properties.

Bivalent Sr2+ doping to improve room-temperature TCR of La0.8-xSrxAg0.2MnO3 polycrystalline ceramics

Rare earth manganites have attractive wide attentions due to their promising applications in infrared bolometers and magnetic information storage. Their temperature coefficient of resistivity (TCR) need further improved so as to achieve its applications at room temperature. In this work, La0.8-xSrxAg0.2MnO3 (LSAMO, x = 0.00, 0.10, 0.15, 0.175, and 0.25) ceramics are fabricated by sol-gel method. Their structure and morphology as well as the optical, electrical and magnetic properties are studied. The structural distortion of Sr doped specimens is identified by the shift of the X-ray diffraction peaks toward the low angles and the red-shift of their Fourier transform infrared spectra. Meanwhile, the Mn4+ ion concentration increases, indicating that the double exchange effect enhances in the ceramics. Furthermore, the TCR values are obviously influenced by the doped Sr content. It enhances from 2.5% K−1 at 211.5 K for La0.8Ag0.2MnO3 to 16.9% K−1 at 299.8 K for La0.625Sr0.175Ag0.2MnO3. The origin of this improvement is attributed to the transformation of rare earth manganites from ferromagnetic metal to paramagnetic insulator and the distortion of MnO6 octahedra. These results uncover the effect of Sr2+ doping on the room-temperature TCR values of ceramics, making it suitable for advanced uncooling device applications.

Effect of alkali metals doping on the properties of ZTS crystals (tris(thiourea)zinc(II)sulphate)

The influence of alkali metals (Na, K, Cs, Li and Rb) doping on the properties and crystal growth of tris(thiourea)zinc(II)sulphate crystals by slow evaporation solution growth technique at 30 °C has been investigated. Each metals as dopant incorporate into the crystal lattice even at its low concentrations is well confirmed by energy dispersive X – ray spectroscopy (EDS). In the powder X –ray diffraction (XRD), high intense peaks are observed for all doped specimens due to stress developed in the crystal because of doping when compared to pure one. Single crystal XRD reveals a nominal increase in the cell parameter values of the doped samples compared to pure. Presence of each alkali metal quantitatively is confirmed by inductively coupled plasma (ICP) technique. It is interesting to observe the enhancement of fluorescence intensity of pure ZTS by the dopant in the photoluminescence (PL) spectra. The grown crystals are also characterized by FT-IR, UV-V is and TG/DSC methods. The second harmonic generation (SHG) efficiency, an essential character required for the single crystals to identify the non-linear optical (NLO) property, was performed by kurtz powder technique.

The influence of Mn (II) – Doping on the non-linear optical properties and crystalline perfection of ADP crystals

The characterization results of influence of various concentration of Mn (II) ion on the properties and crystalline perfection of ammonium di hydrogen phosphate (ADP) crystal are presented. Using water as a solvent, pure and 1, 5, 10 and 20 mol % of Mn (II) ion in the form manganese (II) sulphate added ADP crystals are prepared by slow evaporation solution growth technique (SEST). Well faceted grown crystals are characterised by different experimental techniques. The presence of Mn (II) in the doped specimens is confirmed by energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma (ICP) technique. The surface morphology of the crystals is studied by scanning electron microscopy (SEM). The grown crystals are also characterized by FT-IR, UV–Vis and TG/DTA methods. The second harmonic generation (SHG) efficiency, which is an essential character required for the single crystals to identify the nonlinear optical (NLO) property, is performed by Kurtz powder technique. Moderate concentrations of dopant enhance the SHG efficiency of ADP crystal.

Transport evidence of linear Dirac dispersion of non-trivial surface states in Fe-substituted PbBi2Te4 3D topological insulator

Abstract We report here the experimental realization of Dirac Fermions in electronic transport measurements through observation of Shubnikov-de Haas (SdH) oscillations with π-Berry phase in PbBi2−xFexTe4 3D topological insulators . Substitution of magnetic impurity Fe 2+ for Bi3+ ions have tuned the Fermi level towards the Dirac point, evident from the Hall measurements as well as from the SdH oscillations. SdH oscillations of all the single crystals reveal the existence of non-trivial topological surface states along with an elongated band for x = 0 outside the surface states, associated with the π-Berry phase of the carriers, and is absent for doped specimens. The massless nature of the carriers having Fermi velocity ~105 ms−1depicts their relativistic nature. The carrier's effective mass are successfully tuned with successive Fe substitution, showing linear dependency on the Fermi wave vector; indicating the linear Dirac dispersion of topological surface states. The observed weak antilocalization fitted with modified Hikami-Larkin-Nagaoka (HLN) equation corroborates the 2D surface states in which the pseudo spin of the carriers move round the Dirac point acquires π-Berry phase and is consistent with the SdH oscillations.

Unique magnetic properties of Nd based cuprate francisite: Major enhancement upon Co doping

To understand the physical mechanism of intralayer ferromagnetic (FM) and interlayer antiferromagnetic (AFM) interactions in quasi-two-dimensional model of a real three-dimensional system, rare earth (RE)-Nd based cuprate francisite, Cu3Nd(SeO3)2O2Cl (NdCufr) was doped with Co and studied using structural (X-ray diffraction technique), magnetic (temperature and field dependent magnetization and specific heat measurements) and local structural (X-ray absorption technique) techniques supported by first principle theoretical calculation. The structure of the samples is orthorhombic and doped specimens indicate more or less substitutional incorporation of Co at Cu site. The magnetic properties highlighted with two transitions, viz. AFM to paramagnetic (PM) transition around 30 K and a spin reorientation transition (SRT) below 10 K. Two phenomena viz. magnetic hysteresis below SRT and magnetic field induced metamagnetic transition (MMT) were observed. Co doping significantly enhanced these two phenomena in addition to change the transition temperatures. The concomitant change and enhancement of magnetic properties by Co doping has been interpreted using splitting scheme of Cu-d and Nd-f states. The local structure study corroborates the overall findings and detects the cause of unexpected trend of magnetism with increasing Co doping.

Al-doped Li1.21[Mn0.54Ni0.125Co0.125]O2 cathode material with enhanced electrochemical properties for lithium-ion battery

Layered Li-rich Mn-based oxides are believed to be a good candidate for cathode material in the next generation of lithium-ion batteries. However, they have some disadvantages, such as low initial coulombic efficiency, low rate capacity, and deficient cyclability. To overcome these shortcomings, various approaches, such as elemental doping, have been adopted. In this study, Al-doped Li1.21Mn0.54Ni0.125Co0.125O2 were successfully synthesized using the sol–gel method. Samples were characterized by thermal analysis (TGA/DTA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), surface-area analysis, field emission scanning electron microscopy and transmission electron microscopy (TEM). Measurements of galvanostatic charge discharge and electrochemical impedance spectroscopy were also performed to evaluate the electrochemical performance of the prepared samples. The XRD patterns showed that all the samples with the structure of 0.55Li2MnO3.0.45LiNi0.33Mn0.33Co0.33O2 had a composite material with two individual layered structures that are integrated with each other. By doping Al, the lattice parameters of the samples changed. The first discharge capacity of the Al-doped specimens was lower than that of the pristine sample. In cycling performance results, it is clear that cyclic behavior and capacity stability rate in doped samples have improved compared to the undoped sample, and in the meantime, the sample with 0.05 aluminum doping has shown the best performance. Optimal performance of the doped specimens can be related to lower load transfer resistance and better structural stability.

Molecular α-relaxation process of exopolysaccharides extracted from Nostoc commune cyanobacteria

Broadband dielectric spectroscopy was used to investigate the molecular α-relaxation of the exopolysaccharides (EPS) extracted from Nostoc commune cyanobacteria. The EPS were modified in different ways. EPS were carboxymethylated to obtain carboxymethyl-exopolysaccharides (CEPS). EPS and CEPS were doped with ammonium iodide and 1-butyl-3-methylimidazolium chloride. An α relaxation process was observed for all specimens. The temperature dependence of the relaxation times for pure and doped, EPS and CEPS polymers exhibited non-Arrhenius behavior. This relaxation process was associated with the glass transition of the complex heteropolysaccharides produced by the cyanobacteria. The molecular mobility at the glass transition, Tg, was affected by both the carboxymethylation treatment and the doping. The fragility index also decreased for the doped specimens, which may be attributed to an increase in the mobility of the polymer chains due to the plasticizing effect of the doping agents.

Employed Silver Doping to Improved Photocatalytic Properties of ZnO Micro/Nanostructures

In this study, undoped zinc oxide (ZnO) and silver (Ag) doped ZnO micro/nanostructures were successfully synthesized for photodegradation of Methylene Blue (MB) dye under visible-light. X-ray diffraction (XRD) patterns confirm appeared of the Ag phase and polycrystalline structure of ZnO with a wurtzite hexagonal phase growth in 101 direction. The energy dispersive spectra (EDX) study confirms homogeneity and purity of specimens. Field emission scanning electron microscopy (FESEM) results exhibited agglomeration of irregularly shaped nanoparticles (NPs), decreasing with increasing Ag doped concentration. UV–visible spectra revealed that the Ag leads to shifting in ZnO spectra and increased absorptance in a visible-light region. The photocatalytic result showed significantly enhanced with photodegradation activity 92.2%, 93.1%, 95.08%, and 96.7% for doped specimens, respectively, as compared to 73.8% for an undoped specimen. The enhance of photocatalytic performance may be attributed to increasing the aspect ratio of specimens, improve separation of charge carriers, surface Plasmon resonance (SPR) and high electron photogenerated efficiency