Luminescent-plasmonic core–shell microspheres,doped with Nd3+ and modified with gold nanoparticles,exhibiting whispering gallery modes and SERS activity

Multifunctional core/shell type,luminescent-plasmonic material composed of lanthanide doped microspheres(≈50 μm) and gold nanoparticles(Au NPs;≈10-20 nm) deposited onto their surface,were successfully prepared(Nd~(3+):YAS@Au).The material was synthesized to combine the luminescence properties of the Nd~(3+)-doped microspheres,i.e.whispering resonance with plasmonic activity of the surface Au NPs,i.e.surface enhanced Raman scattering(SERS) effect,within a single,micro-sized material.The luminescent-plasmonic microspheres were used as the active SERS substrate for detection of the organic probe,and for generation of Whispering Gallery Modes(WGM),which red-shift together with increasing laser power(temperature elevation).The products obtained were analysed with optical,scanning and transmission electron microscopy(SEM and TEM),as well as by Raman,absorption and photoluminescence spectroscopies.     

Optical,thermal and luminescence properties of La2O3–Ga2O3–ZrO2 glasses co-doped with Tm3+/Yb3+ prepared by containerless technique

Bulk La₂O₃–Ga₂O₃–ZrO₂ (LGZ) glass and Tm³⁺/Yb³⁺ co-doped LGZ glasses were synthesized successfully using containerless technique. Raman spectra result reveals that the matrix sample possesses the low maximum phonon energy of ～642 cm^?1. The glasses show good compatibility between large Abbe numbers (>31) and high refractive indices (n_d > 1.93). Moreover, transmittance measurements reflect that the glasses have high infrared transmittance of ～81.9%, small OH^– absorption coefficient and long mid-infrared cut-off wavelengths (～7.5 μm). The surface morphology of host glass was characterized by scanning electron microscopy (SEM) micrograph and energy dispersive spectroscopy (EDS) tests reflect that the doped compositions are distributed into the matrix glass homogeneously. The results of thermal analysis show that the glasses have good thermal properties (T_g > 769 °C). Excited by 980 nm laser, an intense 1810 nm fluorescence is obtained originating from the transition: ³F₄ → ³H₆ of Tm³⁺ ion, accompanied by upconversion emission. It can be observed that 1810 nm fluorescence has the highest intensity at 1 mol% Yb₂O₃ and owns broad full width at half-maximum (>245 nm), the luminescence intensity of ³F₄ → ³H₆ transition increases with rising temperature from 300 to 550 K. Furthermore, the value of energy transfer efficiency shows that Yb³⁺ can transfer energy to Tm³⁺ effectively. By fitting the attenuation curves, the lifetimes of 1810 and 474 nm emission can be acquired.     

Influence of manganese rate on structural,optical and electrochemical properties of CeO2 thin films deposited by spray pyrolysis: Supercapacitor applications

The present work aimed to investigate the electrochemical properties of ITO substrates in propylene carbonate (PC) with 0.5 mol/L lithium perchlorate (LiClO₄) medium in the presence of elaborated thin films of cerium dioxide pure and doped with manganese at varying percentages. Ce_1–xMn_xO₂ (x = 0 wt%, 2 wt%, 4 wt% and 6 wt%) were successfully deposited by the spray pyrolysis (SP) technique on the glass substrate and ITO at 450 °C. The effects of manganese (Mn) doped thin films Ce_1–xMn_xO₂ were studied and investigated by using different analyses namely X-ray diffraction (XRD) analysis, Raman spectroscopy method, UV–Vis spectrophotometer technique, atomic force microscopy (AFM) analysis and electrochemical properties. XRD data obtained present a polycrystalline with a face-centred cubic structure of fluorite type. Raman results of undoped and Mn doped thin films show two peaks at 465 and 600 cm^?1, due to the formation of extrinsic oxygen vacancies by the incorporation of Mn into Ce_1–xMn_xO₂ matrix. Energy dispersive spectroscopy (EDS) data show the presence of Ce, O, and Mn elements in the elaborated films. The AFM results reveal that the surface roughness decreases with increasing Mn rate. Further, band gap energy of thin films decreases with increasing in Mn rate due to the formation of defect state between valence and conduction band. The storage capacity of the elaborated Ce_1–xMn_xO₂/ITO/PC + LiClO₄ electrode reaches a maximum of 1.997 mF in the presence of 6 wt% of Mn.     

Anti-corrosion performance of Si-surface-alloying NdFeB magnets obtained with magnetron sputtering and thermal diffusion

Si alloying in the surface layer of NdFeB magnets was realized by thermal diffusion combined with magnetron sputtering. The surface composition, phase structure and morphology of NdFeB(S–Si) specimens were characterized by an X-ray diffractometer, an X-ray photoelectron spectrometer and a field emission scanning electron microscope, respectively. The corrosion resistance of bare NdFeB(S–Si) was analyzed by static full immersion corrosion test and electrochemical experiments. Effects of sputtering and thermal diffusion on the microstructure and corrosion resistance of the surface layer were studied. Results show that surface alloying layer can effectively improve the corrosion resistance of bare NdFeB with the optimized static total immersion corrosion test time in NdFeB(1S–Si)-800 of 36 h, which is much longer than that of the pristine NdFeB (less than 0.5 h). The E_corr of NdFeB(1S–Si)-800 positively shifts from −1.05 to −0.92 V, indicating that the corrosion tendency is obviously lower. The J_corr is 1.45 × 10⁻⁶ A/cm² which is 2 orders of magnitude lower than that of the pristine NdFeB (5.25× 10⁻⁴ A/cm²). The intergranular composite oxides existing in Nd-rich phase contribute to the enhancement of corrosion resistance of Si-surface-alloying NdFeB.     

Catalytic action of rare earth oxide (La2O3, CeO2, Pr6O11) on electrochemical oxidation of activated carbon in molten KOH–NaOH

The oxidation of anode carbon fuel directly affects the electrochemical performance of molten hydroxide direct carbon fuel cell (MHDCFC). In general, the anode carbon fuel can be oxidized at high temperature, thus the direct carbon fuel cell (DCFC) can show great electrochemical performance. In this study, rare earth oxides (La₂O₃, CeO₂, Pr₆O₁₁) were prepared by the method of precipitation. Activated carbon was prepared by pretreatment of lignite. Rare earth oxides and activated carbon were mixed as anode carbon fuel, and rare earth oxides were used to catalyze the electrochemical oxidation of anode carbon fuel. The results show that CeO₂ has better electrocatalytic activity compared with La₂O₃ and Pr₆O₁₁ in the MHDCFC. The electrochemical test results show that the current density (at 0.4 V) increases from 81.02 to 112.90 mA/cm² and the maximum power density increases from 34.78 to 47.05 mW/cm² at 450 °C, when the mass fraction of CeO₂ is increased from 0 to 40%. When the mass fraction of CeO₂ is 30%, the current density (82.55 mA/cm² at 0.4 V) at 400 °C is higher than that (81.02 mA/cm² at 0.4 V) without CeO₂ at 450 °C. The electrochemical oxidation mechanism of CeO₂ catalyzed anode carbon fuel is discussed.     

Electrochemical co-reduction of Y(III) and Al(III) in a fluoride molten salt system and electrolytic preparation of Y–Al intermediate alloys

In this study, a molten salt co-reduction method was proposed for preparing Y–Al intermediate alloys and the electrochemical co-reduction behaviors of Y(III) and Al(III) and the reaction mechanism of intermetallic compound formation were investigated by transient electrochemical techniques. The results show that the reduction of Y(III) at the Mo electrode is a reversible electrochemical process with a single-step transfer of three electrons, which is controlled by the mass transfer rate. The diffusion coefficient of Y(III) in the fluoride salt at a temperature of 1323 K is 5.0238 × 10^?3 cm²/s. Moreover, the thermodynamic properties associated with the formation of Y–Al intermetallic compounds were estimated using a steady-state electrochemical method. Y–Al intermediate alloy containing 92 wt% yttrium was prepared by constant current electrolysis at 1323 K in the LiF–YF₃–AlF₃–Y₂O₃ (6 wt%)–Al₂O₃ (1 wt%) system at a cathodic current density of 8 A/cm² for 2 h. The Y–Al intermediate alloy is mainly composed of α-Y₂Al and Y phases. The development and application of this innovative technology have solved major technical problems, such as a long production process, high energy consumption, and serious segregation of alloy elements at this stage.     

Ce(Ⅲ)-modulation over non-enzymatic Pt/CeO2/GO biosensor with outstanding sensitivity and stability for lactic acid detection

A series of non-enzymatic graphene functionalized biosensors was developed via deposition precipitation method for lactic acid(LA) detection,which we re characterized by transmission electron micro scopy(TEM),Raman spectroscopy,X-ray photoelectron spectroscopy(XPS),gas chromatography-mass spectrometry,liquid chromatography-mass spectro metry,and proton nuclear magnetic re sonance(¹H NMR).The electrochemical performances of the non-enzymatic biosensors were measured by means of the ele...     

Reduction of iron oxides from liquid slags using a graphite rotating disc

Research work has been carried out on the reduction of FeO from liquid slags of the CaO‐FeO‐SiO₂ ternary system using a graphite rotating disc technique. The investigations were conducted on slags with a basicity of CaO/SiO₂ = 1.27 and FeO contents of 20 and 60%, at temperatures of 1350 and 1420°C. The calculated viscosity range for these slags is within 2.53 – 0.43 dPa·s. It has been found that the factor controlling the reduction process is diffusion of FeO towards the disc surface, both in the case of the reduction from the slag with 20% FeO and in the case of the reduction from the slag with 60% FeO fraction. The diffusion coefficient of FeO at the reduction temperature of 1350°C is of the order of magnitudes of 10^?7 cm²/s, while at 1420°C it reaches the order of 10^?6 cm²/s. The calculated thickness values for the limiting diffusion layers range from 8.54·10^?3 to 0.70·10^?3 cm. It has been found that with increasing reduction rate also Boudouard's reaction starts to be important to the overall reduction rate. The limiting reduction rate at which Boudouard's reaction starts to be important to the entire process is dependent on temperature, being approximately 10.0·10^?6 mol FeO/cm² s at 1350°C, and approximately 15.0·10^?6 mol FeO/cm² s at 1420°C.     

Leaching of waste battery paste components. Part 1: Lead citrate synthesis from PbO and PbO2

In this study, as part of developing a new process which can avoid smelting and electro-winning, citric acid based reagents in aqueous media were reacted with PbO and PbO₂. These two oxides are important components in the spent lead-acid battery paste and together account for up to 50% of the paste by weight. PbSO₄, the main component in a spent battery paste accounting for the remaining 50%, is dealt with in Part 2 in a separate paper. Reaction between PbO and C₆H₈O₇·H₂O or PbO₂ with a mixture of C₆H₈O₇·H₂O and H₂O₂ yielded lead citrate, Pb(C₆H₆O₇)·H₂O, which was characterised by XRD, SEM and FT-IR analysis. Optimal synthesis conditions were determined by investigating the effect of time, temperature, concentration, and the starting Pb oxide/water ratio. The optimal condition for leaching a mol of PbO at room temperature (20 °C) was found to be: 1 mol of (C₆H₈O₇)·H₂O solution; 1/3 as the starting PbO/water ratio and 15 min of reaction time. Pure citrate product, Pb(C₆H₆O₇)·H₂O was rapidly crystallized from the solution, in the leaching process. Leaching of PbO₂ required the use of a mild reducing agent. For each mole of PbO₂, the optimum condition at 20 °C was found to be: a solution containing 4 mol of C₆H₈O₇·H₂O and 2 mol of H₂O₂; 1/5 as the starting solid PbO₂/water ratio; and 60 min of reaction time. The product, as with PbO, was pure Pb(C₆H₆O₇)·H₂O compound. The remaining lead content of the filtrate solution was 0.017% and 1% corresponding to recoveries of 99.98% and 99% of lead as citrate, after the leaching/crystallization/filtration process with PbO and PbO₂, respectively. Asymmetric stretching vibrations between 1599 and 1662 cm^? 1, whereas symmetric vibrations between 1520 and 1327 cm^? 1 for lead citrate synthesised from PbO and asymmetric stretching vibrations between 1600 and 1642 cm^? 1 as well as symmetric vibrations between 1517 and 1326 cm^? 1 for the product obtained from PbO₂ revealed the strong IR adsorptions associated with a carboxylate structure. XRD data was identical to the well documented crystalline Pb(C₆H₆O₇)·H₂O compound from both the oxides. SEM revealed the formation of plate/sheet like morphologies. The difference in the column size of the Pb(C₆H₆O₇)·H₂O formed from the two lead oxides can be related to difference in the rate of the respective reactions.     

Synthesis and characterization of yttrium and antimony codoped SnO2 conductive nanoparticles

Y was used as a dopant in preparing conductive powder to improve its performance. Y and Sb co-doped SnO₂ conductive nanoparticles were prepared by the complexation-coprecipitation method with Sn, Sb₂O₃ and Y₂O₃ as the raw materials. Crystal phase, thermal behavior and structure of the prepared conductive nanoparticles were characterized by X-ray diffraction (XRD), thermal analysis (TG-DSC), Fourier transform infrared (FTIR) and transmission electron microscopy (TEM) techniques, respectively. The Y and Sb co-doped SnO₂ conductive nanoparticles with a structure of tetragonal rutile had intense absorption in 4000-2500 cm^?1, and the diameter ranged from 10 to 30 nm. The resistivity of Y and Sb co-doped SnO₂ conductive nanoparticles was as low as 0.09 Ω·cm which was 4.6 times lower than that of Sb doped SnO₂ conductive nanoparticles.     

Electromagnetic wave absorption properties of cobalt-zinc ferrite nanoparticles doped with rare earth elements

Traditional ferrites are of poor electromagnetic wave (EMW) absorption while doping rare earth elements (REEs) can greatly enhance their permeability to improve the EMW loss performance. In this study, Co-Zn ferrite nanoparticles doped with various amounts of REEs (Gd³⁺, Nd³⁺ and Pr³⁺) were synthesized by a hydrothermal method, and their particle morphology and an EMW absorption performance were characterized by using transmission electron microscopy (TEM) and a Vector network analyzer (VNA). The results show that the initial spherical Co-Zn ferrite nanoparticles present an irregular quadrilateral structure after Gd³⁺ doping, and the average particle size of Co_0.5Zn_0.5−xGd_xFe₂O₄ increases from 26 to 50 nm with x increasing from 0 to 0.35. At x of 0.25, the reflectivity absorbance achieves −27.94 dB at 18 GHz with the effective absorption bandwidth (EAB) of 4.08 GHz at a sample thickness of 2.5 mm. When Nd³⁺ doping amount reaches x = 0.3, the minimum reflection loss (RL) is −25.63 dB at 18 GHz and EAB is 3.91 GHz. Doping Pr³⁺ (x = 0.25) in the sample broadens EAB, and the minimum RL is −16.1 dB at 16.81 GHz and EAB is 7.31 GHz. This study shows that the magnetic moment produced by doping REES can form magnetic domains, which affects the incident EMW and improves the magnetic loss. It is expected that REEs-doped Co-Zn ferrite nanoparticles can be used as efficient electromagnetic shielding materials in aerospace.     

Spectroscopic properties of Er3+-doped fluoroindate glasses

The optical and thermal properties of a new class of fluoroindate glass with different erbium contents were investigated via Raman, transmission, and fluorescence spectroscopies, fluorescence decay curve analysis, and differential scanning calorimetry. The strength parameters of the samples were calculated using the Judd–Ofelt theory. The mid-infrared luminescence properties of erbium-doped fluoroindate glasses were studied, and a strong emission at 2.7 μm was obtained. Compared with the traditional ZBLAN glass, this glass has excellent emission properties, especially a longer fluorescence lifetime (7.09 ms) and larger emission cross-section (6.95 × 10^?21 cm²) at 2.7 μm. The results indicate that fluoroindate glass is an attractive host for mid-infrared lasers and as a gain medium for optical amplifier applications.     

Absorption behavior of lattice oxygen in Ce_(0.8)Y_(0.2)O_(2-δ) at intermediate temperature

The absorption behavior of lattice oxygen for Ce_(0.8)Y_(0.2)O_(2-δ)(YDC) crystal was investigated. Combined with TG-DSC, XRD, Raman and XPS characterization, lattice oxygen absorption occurs at intermediate temperature(from 500 to 800 ℃),which is related to the oxygen vacancies consumption,and no phase change is observed in this process. In electric conductivity relaxation(ECR) experiment, prolonged oxygen diffusion process is observed above 600 ℃, which may be caused by oxygen absorption process. And through ECR experiments,the bulk diffusion coefficient D_(chem) and surface exchange coefficient K_(ex) for YDC dense sample are measured as 6,5×10~(-5)-2×10~(-4)cm~2/s and K_(ex)=2×10~(-4)-9×10~(-4)cm/s at intermediate temperature range.     

Studies on Photocatalytic Performance of MgO Nanoparticles Prepared by Wet Chemical Method

In the present article, we explore a cost-effective and an environmentally benign route to prepare magnesium oxide (MgO) nanoparticles through thermal decomposition of magnesium hydroxide (Mg(OH)₂) nanoparticles. Mg(OH)₂ nanoparticles were prepared using different solvents namely ethylenediamine (EDA) and triethanolamine (TEA) by wet chemical method, and subsequently the as-synthesized Mg(OH)₂ nanoparticles were calcinated at 400°C for 2 h in air to obtain MgO nanoparticles. XRD pattern revealed that as-synthesized Mg(OH)₂ nanoparticles are polycrystalline in nature with hexagonal structure, and after annealing it transforms to MgO nanoparticles with cubic structure. FTIR spectrum of as-synthesized Mg(OH)₂ nanoparticles indicated the OH⁻ antisymmetric stretching vibration of the Mg(OH)₂ and after annealing the sharp peak at 3686 cm⁻¹ disappears, which confirms the complete transformation of hexagonal Mg(OH)₂ to cubic MgO. SEM analysis showed the formation of interfused Mg(OH)₂ nanoflakes and coral-like hierarchical MgO nanostructure made up of stacked nanoflakes. Optical band gap energy of Mg(OH)₂ and MgO nanoparticles prepared using different solvent were estimated using UV–Vis DRS. Degradation of methyl orange was performed to investigate the photocatalytic activity of coral-like hierarchical MgO nanostructure. Results demonstrate that coral-like hierarchical MgO nanostructure possessing large surface area and porous morphology exhibited good photocatalytic degradation of methyl orange.     

Comparison of Properties of Pristine and 200 MeV Ag15+ Ions Irradiated ‘Li’ 3 wt% Doped V2O5 Thin Films

Lithium (3 wt%) doped V₂O₅ thin film of thickness 97 nm was spray deposited over an ITO coated glass substrate at 450 °C. The deposited film was irradiated with 200 MeV Ag¹⁵⁺ swift heavy ions (SHI) at a fluence of 5 × 10¹² ions/cm². X-ray diffraction reveals the pristine and irradiated films to have an orthorhombic phase. The SHI irradiation induced thermal spike lead to texturing along the (400) direction along with partial amorphization. The 394 cm^?1 O–V–O Raman bending deformation is suppressed due to SHI irradiation induced oxygen vacancies. Optical transparency decreased from 80 to 50 % and the direct and indirect band gaps showed red shift upon SHI irradiation. Hall effect study revealed marginal variation in transport parameters upon SHI irradiation. The results are discussed.     

On the Prospects of Using Nanoindentation and Wear Test to Study the Mechanical Behavior of Fe-Based Metallic Glass Coating Reinforced by B4C Nanoparticles

In this study, Fe-based metallic glass was served as the matrix in which various ratios of hard B₄C nanoparticles as reinforcing agents were prepared using a high-energy mechanical milling. The feedstock nanocomposite powders were transferred to the coatings using a high-velocity oxygen fuel process. The results showed that the microstructure of the nanocomposite coating was divided into two regions, namely a full amorphous phase region and homogeneous dispersion of B₄C nanoparticles with a scale of 10 to 50 nm in a residual amorphous matrix. As the B₄C content is increased, the hardness of the composite coatings is increased too, but the fracture toughness begins to be decreased at the B₄C content higher than 20 vol pct. The optimal mechanical properties are obtained with 15 vol pct B₄C due to the suitable content and uniform distribution of nanoparticles. The addition of 15 vol pct B₄C to the Fe-based metallic glass matrix reduced the friction coefficient from 0.49 to 0.28. The average specific wear rate of the nanocomposite coating (0.48 × 10⁻⁵ mm³ Nm⁻¹) was much less than that for the single-phase amorphous coating (1.23 × 10⁻⁵ mm³Nm⁻¹). Consequently, the changes in wear resistance between both coatings were attributed to the changes in the brittle to ductile transition by adding B₄C reinforcing nanoparticles.

     

Temperature dependent behaviors of electro-elastic properties of NdCa4O(BO3)3 crystal with monoclinic symmetry

Rare-earth calcium oxyborate crystals (RECa₄O(BO₃)₃, RECOB, RE: rare-earth elements) are a kind of multifunctional crystal materials. In this work, the temperature dependent behaviors of the electro-elastic constants of NdCOB crystal were investigated over the temperature range of –80–200 ℃, and their temperature coefficients were evaluated. It is found that NdCOB crystal possesses minimal variation of relative dielectric permittivities (<3%). The temperature coefficient of frequency for ZY cut with width shear vibration mode is in the order of 0.07 × 10^?4/℃. The temperature coefficients of the elastic compliances are obtained to be in the range of ?33.0 × 10^?4/℃–32.2 × 10^?4/℃. Particularly, the s₄₄ and s₆₆ were found to show low temperature coefficients of the elastic compliances, i.e. 1.0 × 10^?4/℃ and ?0.4 × 10^?4/℃, respectively, indicating the existence of zero temperature coefficient of frequency crystal cut. Furthermore, the electromechanical coupling factors and piezoelectric coefficients as a function of temperature were studied. The electromechanical coupling factor k₂₆ and piezoelectric coefficient d₂₆ are determined to be ～30.8% and ～15.2 pC/N at room temperature, respectively. The large piezoelectric response and zero temperature coefficient of frequency indicate the potential usage of NdCOB crystal for piezoelectric frequency devices over a wide temperature range.     

Rh纳米粒子电化学制备及其表面增强拉曼效应

利用电化学手段在氧化铟锡(ITO)导电玻璃表面成功制备了Rh纳米粒子,并发现包裹剂、支持电解质以及电化学参数对产物的形貌及尺寸有着显著影响.通过对上述参数的调控实现了Rh纳米粒子的形貌可控制备,得到了准球形、岛状以及片层状的Rh纳米粒子.此外对岛状Rh纳米粒子在表面增强拉曼光谱中的应用进行了研究.结果表明该种结构具有良好的表面增强拉曼活性.