Sodium Doping Research Articles

Effects of Na/Al ratio on phonon sideband spectra and luminescent characteristics of Eu3+ doped sodium aluminosilicate glasses

In this work, sodium aluminosilicate (NAS) glass systems were fabricated via traditional melting technique with various Na/Al ratios. Structure and surface morphology of the fabricated glasses were investigated by X-ray diffractometer, Raman spectroscopy and SEM images. Optical characteristics of the fabricated glasses were inspected by photoluminescence (PL) and photoluminescence excitation (PLE) spectra, and the observations showed that intensity of the excitation peak of Eu3+ ions in the NAS glasses at 392 nm increases while one at 463 nm decreases with the increasing of Na/Al ratio. Analysis of the phonon sideband spectra shown a change of multiphonon relative rate (Wmp/W0) of the synthesized glasses relates to Na/Al ratio. By applying the Judd-Ofelt theory, Ωλ = 2,4,6 parameters were evaluated from the PL spectra and used these parameters to estimate the radiative parameters like calculated lifetime (τcal), effective line width (Δλeff), transition probability rate (A), emission cross-section (σp) and branching ratio (βR). Decay curves were measured to investigate luminescence quantum efficiency (η) of Eu3+ emission and η gets value in the 53%–65% region. The color coordinates (x, y) and correlated color temperature (CCT) were also estimated for the synthesized NAS glasses.

Lamellar sodium titanium silicate assembled by nanostrips decorated with N-rich 3D carbon for sodium dual-ion batteries

Sodium dual-ion batteries have received tremendous attention owing to their appealing operating voltage (i.e. >4.0 V) and eco-friendly features. However, the exploitation of efficient sodium ion storage anode materials is one of the keys for driving the application of sodium dual-ion batteries in the grid-scale energy storage. Herein, a lamellar sodium titanium silicate (NTSO) woven by plentiful nanostrips grown in situ on the surface of N-rich 3D carbon has been prepared via a convenient synthetic strategy. Based on the synergistic effect both micro-nano composite spatial structure and energy storage mechanism based on conversion reaction of material bulk phase, the NTSO/3DC-N composite as anode delivers a high special capacity of 540.6 mAh/g at 0.05 A/g and 163.1 mAh/g at 5.0 A/g in sodium ion half-cell. More impressively, the sodium dual-ion batteries built with NTSO/3DC-N as anode and a N-rich 3D carbon as cathode exhibits a high reversible capacity of about 123.6 mAh/g at 0.05 A/g. The elaborate designing an interconnecting framework composed of layered titanium silicate sodium and heterogeneous atom doping carbon substrate provides a generally applicable strategy for enhancing the anode performance of sodium dual-ion batteries.

Wearable and self-powered triboelectric sensors based on NaCl/PVA hydrogel for driver multidimensional information monitoring

Dangerous behaviors during driving such as fatigue or making phone calls may seem common in daily life. However, these behaviors are the actual "culprit" of many traffic accidents and pose a serious threat to traffic safety. Therefore, it is necessary to effectively detect dangerous driving behaviors by scientific and technological means. The present detection methods still face many bottlenecks, including individual differences, complex lighting changes, battery power supply, poor wearability, et al. Here, we designed a green and stretchable triboelectric sensor (TES) to monitor dangerous driving behaviors. The performance of the sensor was improved by about 9.99 and 3.58 times through doping sodium chloride solution in PVA hydrogel and introducing a curved contact surface between the electrode and friction layer, respectively. The proposed sensor has a high sensitivity of 1.95 V/kPa in the linear range of 0–11.28 kPa. By employing different machine learning models, we developed an intelligent neck ring based on the proposed sensor array to recognize different neck movements, which has achieved the highest accuracy of 96.10%. Finally, the intelligent neck ring was used to construct a sensing system for driver status monitoring. By collecting detailed driver information, the system can detect dangerous driving behaviors, monitor drivers’ health conditions, and provide appropriate reminders to improve driving safety and prevent the spread of viruses.

Thermalization and relaxation mediated by phonon management in tin-lead perovskites

Understanding and control of ultrafast non-equilibrium processes in semiconductors is key to making use of the full photon energy before relaxation, leading to new ways to break efficiency limits for solar energy conversion. In this work, we demonstrate the observation and modulation of slow relaxation in uniformly mixed tin-lead perovskites (MASnxPb1-xI3 and CsSnxPb1-xI3 nanocrystals). Transient absorption measurements reveal that slow cooling mediated by a hot phonon bottleneck effect appears at carrier densities above ~1018 cm−3 for tin-lead alloy nanocrystals, and tin addition is found to give rise to suppressed cooling. Within the alloy nanoparticles, the combination of a newly introduced high-energy band, screened Fröhlich interaction, suppressed Klemens decay and reduced thermal conductivity (acoustic phonon transport) with increased tin content contributes to the slowed relaxation. For inorganic nanocrystals where defect states couple strongly with carriers, sodium doping has been confirmed to benefit in maintaining hot carriers by decoupling them from deep defects, leading to a decreased energy-loss rate during thermalization and an enhanced hot phonon bottleneck effect. The slow cooling we observe uncovers the intrinsic photophysics of perovskite nanocrystals, with implications for photovoltaic applications where suppressed cooling could lead to hot-carrier solar cells.

Sodium doping and trapped ion mobility spectrometry improve lipid detection for novel MALDI-MSI analysis of oats

Oat (Avena sativa L.) is an important cereal grain with a unique nutritional profile including a high proportion of lipids. Understanding lipid composition and distribution in oats is valuable for plant, food and nutritional research, and can be achieved using MALDI mass spectrometry imaging (MALDI-MSI). However, this approach presents several challenges for sample preparation (hardness of grains) and analysis (isobaric and isomeric properties of lipids). Here, oat sections were successfully mounted onto gelatin-coated indium tin oxide slides with minimal tearing. Poor detection of triacylglycerols was resolved by applying sodium chloride during mounting, increasing signal intensity. In combination with trapped ion mobility spectrometry (TIMS), lipid identification significantly improved, and we report the separation of several isobaric and isomeric lipids with visualisation of their “true” spatial distributions. This study describes a novel MALDI-TIMS-MSI analytical technique for oat lipids, which may be used to improve the discovery of biomarkers for grain quality.

Surface-Modification of Doping and Coating Li1.2Ni0.2Co0.08Mn0.52O2 as a Long Life Cathode Material of Lithium-Ion Battery by Sodium Salt Treatment

Lithium-rich layered oxides are considered to be the most promising next-generation lithium-ion cathode materials due to their high specific capacity and energy density. However, its commercialization is limited due to its poor cycling stability and severe voltage decay. A NaH2PO4 molten salt treatment is designed, which simultaneously realizes Na+ doping and phosphate coating to improve the defects of lithium-rich materials. Sodium dihydrogen phosphate is of good contact with lithium-rich materials in the process of high temperature melting to facilitate surface sodium doping which is conducive to stabilizing the surface structure through lithium-sodium exchange. At the same time, the phosphate coating produced by lithium-sodium exchange and dehydration on the outer surface of the material can effectively inhibit the corrosion of the electrolyte. The modified material obtained by the synergistic effect of doping and coating has a capacity of 262.4 mAh·g−1 at 0.1 C and 169.6 mAh·g−1 at 5 C, the capacity retention rate of 73.6% after 500 cycles, and the voltage decay is significantly improved. A simple and effective method for improving the electrochemical performance of Li-rich layered materials is provided.

Alkali-Induced Phase Transition to β-Spodumene along the LiAlSi2O6-LiAlSi4O10 Join

Due to the refractory nature of α-spodumene (LiAlSi2O6) and petalite (LiAlSi4O10), two major lithium minerals, conventional lithium recovery processes involve a high-temperature pre-treatment (>1000 °C) to induce a phase transition to tetragonal β-spodumene, an open structure allowing easier access to lithium through ion exchange. Considering that these high temperatures are not dictated by thermodynamics but rather sluggish kinetics, the study investigates the mechanisms enhancing the rate of transformation to β-spodumene at lower temperatures while minimizing the growth of metastable hexagonal β-quartz typically observed at the onset of the conversion. The heat treatment of natural α-spodumene revealed that rapid growth of β-spodumene veinlets is achieved at ≤600 °C by activation of alkali-rich fluid inclusions, through a dissolution–recrystallization process. For petalite, the mechanism of the phase transition, initiated at ≈750 °C is a solid-state transformation keeping crystallographic coincidence with the mineral host. Synthetic growth experiments along the LiAlSi2O6-LiAlSi4O10 join indicate a compositional dependence on the resulting β-phase structure, where minor sodium doping strongly favors β-spodumene, as the tetrahedral framework of β-quartz does not allow the extent of deformation to accommodate the larger alkali. These findings open opportunities for energy-efficient lithium recovery pathways where the phase transition and ion exchange can be achieved simultaneously without a high-temperature pre-treatment.

Deposition of Thin Electroconductive Layers of Tin (II) Sulfide on the Copper Surface Using the Hydrometallurgical Method: Electrical and Optical Studies.

Thin films of tin (II) sulfide (SnS) were deposited onto a 500 µm thick copper substrate by a chemical bath method. The effect of sodium (Na) doping in these films was studied. The synthesis of the films was performed at temperatures of 60, 70, and 80 °C for 5 min. The microstructure of the SnS films analyzed by scanning electron microscopy (SEM) showed a compact morphology of the films deposited at 80 °C. The edges of the SnS grains were rounded off with the addition of a commercial surfactant. The thickness of different SnS layers deposited on the copper substrate was found to be 230 nm from spectroscopic ellipsometry and cross-section analysis using SEM. The deposition parameters such as temperature, surfactant addition, and sodium doping time did not affect the thickness of the layers. From the X-ray diffraction (XRD) analysis, the size of the SnS crystallites was found to be around 44 nm. Depending on the process conditions, Na doping affects the size of the crystallites in different ways. A study of the conductivity of SnS films provides a specific conductivity value of 0.3 S. The energy dispersive analysis of X-rays (EDAX) equipped with the SEM revealed the Sn:S stoichiometry of the film to be 1:1, which was confirmed by the X-ray photoelectron spectroscopy (XPS) analysis. The determined band-gap of SnS is equal to 1.27 eV and is in good agreement with the literature data.

Influence of High Content of Sodium Doping in Bi(Pb)2212 Superconductors

We study here, the effect of high content of sodium doping on structural and electrical properties of Bi(Pb)2212 superconducting. The X-ray analysis results showed that all the prepared samples mainly belong to the superconducting tetragonal phase Bi–(Pb)2212. SEM micrographs show that the grains are closely related and have a characteristic flat shape for the superconductor Bi (Pb) 2212. For the undoped sample, the grains are randomly distributed with an average size of 5 μm. For doped samples, the morphology changes with sodium concentration. Resistivity measurements show that all samples have a superconducting character.

Boron and Sodium Doping of Polymeric Carbon Nitride Photoanodes for Photoelectrochemical Water Splitting.

Polymeric carbon nitride is a promising photoanode material for water-splitting and organic transformation-based photochemical cells. Despite achieving significant progress in performance, these materials still exhibit low photoactivity compared to inorganic photoanodic materials because of a moderate visible light response, poor charge separation, and slow oxidation kinetics. Here, the synthesis of a sodium- and boron-doped carbon nitride layer with excellent activity as a photoanode in a water-splitting photoelectrochemical cell is reported. The new synthesis consists of the direct growth of carbon nitride (CN) monomers from a hot precursor solution, enabling control over the monomer-to-dopant ratio, thus determining the final CN properties. The introduction of Na and B as dopants results in a dense CN layer with a packed morphology, better charge separation thanks to the in situ formation of an electron density gradient, and an extended visible light response up to 550nm. The optimized photoanode exhibits state-of-the-art performance: photocurrent densities with and without a hole scavenger of about 1.5 and 0.9mA cm-2 at 1.23V versus reversible hydrogen electrode (RHE), and maximal external quantum efficiencies of 56% and 24%, respectively, alongside an onset potential of 0.3V.

Uniformly sodium ions doped LiNi0.84Co0.11Mn0.05O2 cathode material with high performance for lithium-ion batteries

Nickel-rich ternary cathode material is widely used in various fields due to its superior operating voltage and theoretical specific capacity. However, the nickel-rich cathode material undergoes cation mixing in highly delithiated state, which leads to rapid capacity decay and poor cycling stability. In this study, sodium ions were uniformly doped into the nickel-rich cathode material (Na-LNCM) using a hydrothermal method to overcome the problems mentioned above. Na-LNCM exhibits better cycling and rate performance, and lower electrochemical polarization compared with those of pristine material. The specific capacity of the Na-LNCM material was 138.3 mAh∙g−1 at 10 C current density, and the capacity retention ratio was 82.9% after 100 cycles at 1 C. The apparent enhancement in electrochemical performances is attributed to the truth that sodium ions occupy Li sites in the Li slab, which can broaden Li layer spacing, widen the diffusion channels of Li+, reduce cation mixing, and support the crystal structure of nickel-rich ternary cathode material. Moreover, compared with other methods, the doped sodium ions can be distributed more uniformly by the hydrothermal method, which could further enhance the electrochemical performance of the cathode material.

Luminescent properties of Tb3+ doped sodium silica germanate glasses

Luminescent properties of Tb3+ doped sodium silica germanate glasses

Lead Vacancy Promotes Sodium Solubility to Achieve Ultra-High zT in Only Ternary Pb1- x Nax Te.

Chemical doping of sodium is an indispensable means to optimize thermoelectric properties of PbTe materials, while a bottleneck is that an aliovalent atom doping leads to spontaneous intrinsic defects in the PbTe matrix, resulting in low dopant solubility. Therefore, it is urgent to improve the doping efficiency of Na for maximizing optimization. Here, an amazing new insight that the intentionally introduced Pb vacancies can promote Na solubility in ternary Pb1- x Nax Te is reported. Experimental analysis and theoretical calculations provide new insights into the inherent mechanism of the enhancement of Na solubility. The Pb vacancies and the resultant more dissolved Na not only synergistically optimize the carrier concentration and further facilitate the band convergence, but also induce a large number of dense dislocations in the grains. Consequently, benefiting from the self-enhancement of Seebeck coefficient and the minimization of lattice thermal conductivity, an 18% growth is obtained for the figure of meritzTin vacancy-containing Pb0.95 Na0.04 Te sample, reaching maximumzTmax ≈ 2.0 at 823 K, which achieves an ultra-high performance in only Na-doped ternary Pb1- x Nax Te materials. The strategy utilized here provides a novel route to optimize PbTe materials and represents an important step forward in manipulating thermoelectrics to improve dopant solubility.

Tuning band gap, structural and optical properties of tin selenide nanoparticles by alkali metal doping

The layered chalcogenide semiconductor, Tin monoselenide is an extraordinary candidate among chalcogenide materials because of their novel physical and chemical properties and tremendous applications in thermoelectrics, solar cells, energy storage devices, i.e. metal–ion batteries, supercapacitors etc. In this work, we synthesized polycrystalline SnSe by a simple hydrothermal method using sodium borohydride as a reducing agent for the single phase formation of SnSe nanostructures. X–ray diffraction spectroscopy has been done to confirm the orthorhombic structure and single phase formation. Fourier transform infrared characterization has been done to observe the linkage of groups among the precursors and solvents used. Further, Photoluminescence characterization has been done to estimate the band gap values and radiative recombination mechanism of the material. Ultraviolet–Visible (UV–Vis) spectroscopy has been used to study the optical properties of the material. Moreover, extrinsic heteroatom doping of sodium and potassium have been done to form NaxSnx-1Se and KxSnx-1Se respectively, which further decreases the band gap of the host material. The absorbance spectra, percentage of transmittance, extinction coefficient, direct band gap values depend upon photonic interactions and has been determined by UV–Vis spectroscopy. Elemental composition of each sample has been confirmed by EDX spectroscopy. All these properties have made the material a potential candidate for opto–electronic and photovoltaic applications.

Optical Properties of Sodium-doped Carbon Dots Made of Urea and Trisodium Citrate

Carbon dots are very interesting carbon-based nanoparticles. Carbon dots have unique optical properties, especially luminescence properties upon light excitation. Improving optical quality is the challenge in carbon dots research. Doping is one of the methods to improve the quality of carbon dots. In this work, we used sodium, which is an active ion, as doping in the carbon dots. We studied the optical properties of sodium-doped carbon dots. We found that absorbance, FTIR, and photoluminescence spectra changed due additional surface energy level of carbon dots. Furthermore, the quantum yield of carbon dots improved significantly due to sodium doping. In addition, the phosphorescence of sodium-doped carbon dots was slightly longer. Electron behavior was also changed. In conclusion, sodium-doped carbon dots showed very good optical properties for further applications.

Luminescence characteristics of Dy3+ doped sodium alumina borate glass: Role of silver

Metallic nanoparticle (NP) doped glasses have been studied as promising candidates for various technological applications due to their ability to improve the luminescence properties of rare earth ions. In this work, Dy2O3 and Ag2O co-doped sodium alumina borate glasses were synthesized by conventional melt-quenching technique. Raman analysis verified the existence of [BO3] and [BO4] groups with B–O stretching vibrations in the prepared glasses. Transmission electron microscope images confirmed the presence of spherical Ag NPs, whose average diameter is about 7.60 nm, in H-0.5Dy1Ag glass matrix. The optical and luminescence properties were investigated according to Ag concentrations. The negative value of the bonding parameters, calculated from the absorption spectra, indicates the ionic nature between the Dy3+ ions and its surrounding ligands. In order to determine the nature of the Dy-O bond and the symmetry around the Dy3+ ion environment, Judd–Ofelt intensity parameters (Ω λ, λ = 2, 4, 6) were obtained from the absorption spectra. The luminescence spectra obtained under 350 nm excitation exhibits four emission bands at 481 (4F9/2→6H15/2), 572 (4F9/2→6H13/2), 662 (4F9/2→6H11/2), and 750 (4F9/2→6H9/2) nm. The intensity of emission spectra increases with Ag2O content until 1.0 wt% in H-0.5Dy-yAg glasses and then decreases due to the back-energy transfer (ET) from Dy3+ to Ag+. The ET mechanism from Ag+ to Dy3+ ion for H-1Ag-xDy glasses were investigated through Forster-Dexter’s theory and were found to be quadrupole-quadrupole type. The various radiative properties were calculated by using Judd-Ofelt intensity parameters and emission spectra. It was found that the 572 nm emission band, located in the yellow region, has higher radiative parameters. As a function of Ag concentration, the Y/B values, Commission Internationale d’Eclairage (CIE) chromaticity coordinates (x,y) and correlated color temperatures (CCT) were evaluated. The CIE chromaticity coordinates and CCT values of all glasses are located in the white light region. The decay time values of 1S0→3D1 transition of Ag+ ions and 4F9/2→6H13/2 transition of Dy3+ ions confirm the ET from Ag+ to Dy3+ ions. Overall, the present study indicates that the synthesized glasses with Ag addition exhibits improved luminescence, making them potential candidate for white LEDs.

Contrasting thermoelectric properties in cubic SnSe-NaSbSe2 and SnSe-NaSbTe2: High performance achieved via increasing cation vacancies and charge densities

Cubic SnSe has been recognized as one of the most promising mid-temperature thermoelectric candidates. Herein, the cubic-phase SnSe has been stabilized at room temperature by alloying NaSbSe2 and NaSbTe2, respectively, and the contrasting thermoelectric properties of SnSe-NaSbSe2 and SnSe-NaSbTe2 were systematically investigated. NaSbTe2-alloyed SnSe demonstrates better performance with especially higher electrical properties. According to the DFT calculations, the introduction of NaSbTe2 can bring the lattice parameter of cubic-phase SnSe closer to SnTe, leading to a lower cation vacancy formation energy and producing an ultra-high hole carrier concentration. Meanwhile, Te has a more developed charge density compared with that of Se, providing additional channels for charge transport when bonded to Sn atoms in cubic lattice. Limited by the electrical transport properties, the ZTmax for SnSe-NaSbSe2 only reaches ∼ 0.50 at 773 K, while the ZTmax for SnSe-NaSbTe2 approaches ∼ 0.95. Furthermore, sodium doping was utilized to tune the carrier mobility and carrier concentration of SnSe-NaSbTe2. Resultantly, the PFmax and ZTmax values reach ∼ 11 μW cm−1 K−2 and ∼ 1.20 at 773 K in sodium-doped SnSe-NaSbTe2, 4.4 and 3.0 times higher than those of pure SnSe, respectively. Our study further promotes cubic-phase SnSe thermoelectrics for mid-temperature energy harvesting applications.

Effect of Sodium Additives on the Kinetics of the Solid-State Oxidation of Lead Babbitt PbSb15Sn10Na

A study is performed of the kinetics of oxidation of lead babbitt with 1.0 wt % of sodium in the 373–473 K range of temperatures. The kinetic and energy parameters of the oxidation of the alloys are determined. It is found that the weight gain of the alloys grows rapidly during the first 15–20 min of oxidation and then acquires an almost constant value. Oxide films that form at the beginning of oxidation have no protective properties, as is confirmed by an increase in the alloys’ rate of oxidation along with temperature in the initial period. It is revealed that sodium dopant additives taken in concentrations of 0.01–1.0 wt % enhance the oxidizability of the original alloy and considerably refine its microstructure. X-ray diffraction analysis shows that the alloys’ products of oxidation consist of oxides (Pb3Sb2O8.47)6.4, PbO, Pb3O4, Pb0.828O2, Sb2O4, Na3SbO3, NaSbO3, and PbSb2O6.

Revani diffusion model in Cu(In,Ga)Se2

Sodium doping has multifaceted effects in Cu(In,Ga)Se2, some of which remain unsolved since 1993. Here, we propose a thought experiment to unravel them. The Frank–Turnbull alkali ion diffusion hypothesis brings about anisotropy-induced fluctuations.

Enhancing the Catalytic Activity of Eggshell-Derived CaO Catalyst and Its Application in Biodiesel Production from Waste Chicken Fat

The comparatively greater cost of producing biodiesel in comparison to petroleum diesel is one of the key drawbacks. Eggshells and leftover chicken fat are examples of poultry wastes that can be used to produce biodiesel at a low cost as catalysts and oil, respectively. In this study, eggshell-derived CaO and its doping with sodium methoxide catalyst for enhancing catalytic activity was synthesized for the transesterification of waste chicken fat and characterized by FT-IR and XRD analyses. XRD studies confirmed the crystalline structure of the developed catalyst and doping of sodium with eggshell-derived CaO. The transesterification reaction was performed at different reaction parameters such as the catalyst loading, the methanol to oil ratio, the reaction temperature, and the reaction time. The biodiesel produced at the maximum yield was evaluated by gas chromatography mass spectrometry analysis. A maximum yield of 96% biodiesel was obtained with catalyst loading of 2 wt% of oil, as well as a methanol to oil ratio of 13:1 at 60 °C in 1 h. The output demonstrates that eggshell waste is a potentially accessible source of biomass-derived nano catalyst for the synthesis of biodiesel using chicken fat as a feedstock.