Bi Doping Research Articles

Pressure-Driven Reverse Intersystem Crossing: New Path toward Bright Deep-Blue Emission of Lead-Free Halide Double Perovskites.

Maximizing the regeneration of singlet excitons remains a considerable challenge in deep-blue emission systems to obtain low-cost, high-efficiency fluorescent materials. However, the formation of the long-lifetime triplet excitons generally dominates the radiative process, making it greatly difficult to harvest deep-blue emission with high color purity because of the depression of singlet excitons. Here, a very bright deep-blue emission in double perovskite Cs2Na0.4Ag0.6InCl6 alloyed with Bi doping (CNAICB) was successfully achieved by pressure-driven reverse intersystem crossing (RISC), an abnormal photophysical process of energy transfer from the excited triplet state back to the singlet. Therein, the inherently broad emission of CNAICB was associated with the self-trapped excitons (STEs) at excited triplet states, whereas the radiative recombination of STEs populated in excited singlet states was responsible for the observed deep-blue emission. Moreover, the deep-blue emission corresponds to Commission Internationale de L'Eclairage (CIE) coordinates (0.16, 0.06) at 5.01 GPa, which meets the requirement of Rec. 2020 display standards. Likewise, pressure was introduced as an efficient tool to rule out the possibility of the recombination of free excitons and clarify the long-standing conventional dispute over the origin of the low-wavelength emission of Cs2AgInCl6. Our study not only demonstrates that pressure can be a robust means to boost the deep-blue emission but also provides deep insights into the structure-property relationship of lead-free CNAICB double perovskites.

Bi-doped La1.5Sr0.5Ni0.5Mn0.5O4+δ as an efficient air electrode material for SOEC

Bi-doped La1.5-xBixSr0.5Ni0.5Mn0.5O4+δ (LBSNM-x, x = 0, 0.05, 0.1, 0.15) was investigated as a potential air electrode for solid oxide electrolysis cell (SOEC). The effect of Bi doping on the structure, electrical conductivity, chemical compatibility with GDC electrolyte, electrochemical performance and thermal expansion coefficients (TECs) were investigated. XRD characterization results show that the solid solution content of Bi is less than or equal to 0.1. XPS characterization results indicate that Bi doping increases the oxygen vacancy content of LBSNM-x air electrode and thus greatly benefits its oxygen evolution reaction. Among the Bi-doped samples, LBSNM-0.1 electrode has the best electrochemical performance with its lowest Rp (polarization resistance) of 0.28 Ω cm2 at 800 °C based on LBSNM-0.1/GDC half-cell. LBSNM-0.1 single cell with 70%CO2 + 30%CO fuel gas feed on the fuel electrode has achieved current density of 811 mA cm−2 at 800 °C and 1.4 V, a 62.2% increase relative to that of LSNM single cell. In addition, LBSNM-0.1 single cell exhibits excellent stability at 800 °C and 1.3 V with 70%CO2 + 30%CO feed gas on the fuel electrode. These results prove that Bi-doped LBSNM-0.1 is an efficient air electrode for SOEC.

Effect of Bi dopant on morphological and optical properties of ZnO semiconductor films produced by the sol-gel spin coating process

Abstract In this study, undoped semiconductor ZnO thin film and Bi-doped ZnO thin films were produced using the sol-gel spin coating method. By changing each parameter of the spin coating method, the best conditions for the formation of the film were determined via the trial and error method. When the appropriate parameter was found, the specified parameter was applied for each film. The structural, superficial, and optical properties of the films produced were characterized via atomic force microscope (AFM), UV-visible spectroscopy, and Fourier transform infrared (FTIR), and the effects of Bi dopant on these properties were investigated. When the morphological properties of the undoped and Bi-doped ZnO films were examined, it was observed that they had a structure in a micro-fiber shape consisting of nanoparticles. When the surface roughness was examined, it was observed that the surface roughness values became larger as the rate of Bi dopant increased. By examining the optical properties of the films, it was determined that they were direct band transition materials and Bi-doped thin films were involved in the semiconductor range. In addition, optical properties changed positively with Bi dopant. Since Bi-doped ZnO thin film has a wide bandgap and good optical properties, it is a material that can be used in optoelectronic applications.

Constructing 3D Bi/Bi4O5I2 microspheres with rich oxygen vacancies by one-pot solvothermal method for enhancing photocatalytic activity on mercury removal

A 3D hierarchical metallic Bi modified Bi4O5I2 microspheres with rich oxygen vacancies (Vos) was successfully prepared via a one-pot solvothermal method. In this work, the different morphologies of BiOI and Bi modified Bi4O5I2 were prepared by precipitation, hydrothermal and solvothermal methods. It was discovered that using the solvothermal method with ethylene glycol as the solvent could not only prepare microspheres Bi4O5I2 with rich oxygen vacancies but also control the content of Bi by changing the reaction duration. The doping of metallic Bi created a built-in electric field between Bi and Bi4O5I2, which is helpful to improve the efficiency of carrier separation. Benefited from the synergistic effect of oxygen vacancies and built-in electric field, the as-prepared Bi/Bi4O5I2 exhibits an excellent mercury removal efficiency, high-performance stability, and satisfactory sulfur resistance as well as nitric oxide resistance. Finally, the mechanism of catalytic oxidation reaction was proposed, photo-generated holes and superoxide radicals were predominant in the photocatalytic reaction.

Ambient electrosynthesis of NH3 from N2 using Bi-doped CeO2 cube as electrocatalyst

The synthesis of ammonia (NH3) from electrochemical nitrogen reduction reaction (NRR) under environmental conditions is a promising technology. Compared with the traditional artificial nitrogen fixation process by the Haber-Bosch process, electrochemical nitrogen reduction reaction (NRR) requires no harsh reaction conditions. In this work, we report that Bi-doped CeO2 nanocubes show high NRR activity as electrocatalysts. The NH3 yield of 17.83 μgh−1 mg−1cat. and the Faradaic Efficiency (FE) of 1.61% at −0.9 V are achieved in 0.1 M Na2SO4. The performance is much higher than that for the traditional CeO2 nanoparticles. The detailed analysis indicates that both the Bi doping and the cube morphology are critical for this encouraging NRR performance. The mechanism for improving NRR is further explored with first-principle calculations, demonstrating the importance of Bi-doping for performance enhancement.

Preparation, characterization and photocatalytic decolorization process for the removal of orange-green dye using perovskites Ba1-xBixFeO3-δ (x = 0, 0.05, 0.1)

Recently, the preparation of novel nano-sized photocatalysts and studying of the ability of the prepared materials for the photocatalytic degradation of the harmful pollutants which often present in industrial effluents as model substances under solar/visible light paid particular attention. In this frame, nano-sized Ba1-xBixFeO3-δ system was prepared using Pechini method. All the samples are characterized using XRD, FTIR, optical absorbance spectra, TEM and BET. Cubic fluorite phase of BaFeO2.75 was detected for BaFeO3, Ba0.95Bi0.05FeO3-δ samples while cubic fluorite phase of BaFeO3 was detected for Ba0.9Bi0.1FeO3-δ sample. Minor phases of Orthorhombic BaFe2O4, Monoclinic Ba2Fe2O5 and Orthorhombic BaCO3 were detected for all the samples. Bi doping had obvious effect on the cubic lattice parameter, the cubic unit cell volume, the optical properties, lattice spacing, surface area and the photocatalytic activity. pH, simulated solar irradiation time and catalyst dose were optimized to be 3, 420 min, and 1 g L−1 respectively for degradation of 50 mg L−1 dye, the highest decolorization efficiency was 92.2% using Ba0.95Bi0.05FeO3-δ while, TOC removal was 90% for a photocatalytic and ammonia concentration attained 0.53 mg L−1 under the optimum operating conditions. The photocatalytic decolorization of the dyes was fitted with pseudo first-order rate. According to scavenger experiment, the main oxidative species for the decolorization of orange green dye The analysis of experimental design results demonstrated the significant effect of the irradiation time and pH for orange green on photocatalytic degradation process.

Experimental and DFT studies of novel Z-scheme Bi-doped Bi2WO6/Bi2S3 p-n/n homo/heterojunction and its application in cathodic photoelectrochemical immunosensing

Doping, as an important strategy, can change the conductivity type of semiconductor and has been used to construct p-n homojunction. However, the effect of doping style on the conductivity type has not been well ascertained. Herein, taking Bi2WO6 with layered crystal structure as the model, the effect of Bi doping type on the conductivity type of Bi2WO6 is studied through density functional theory (DFT) and experiments. Detailed investigations reveal that Bi substitutes W site rather than fills O site or interlayer, is critical for changing the conductivity type of Bi2WO6 (i.e. from n to p), thus producing a p-n homojunction structure in Bi2WO6 and enabling it cathodic photoelectrochemical (PEC) performance. To further study and improve the PEC properties of Bi-doped Bi2WO6 (marked as Bi2+xWO6), a novel p-n/n homo/heterojunction photocathode material of Z-scheme Bi2+xWO6/Bi2S3 has been synthesized by an in-situ ion-exchange reaction. Benefiting from the internal built-in electric field of homojunction and Z-scheme heterojunction, the bulk and interface charges of Bi2+xWO6/Bi2S3-3 (i.e. treated with 1 mM of Na2S) are sufficiently separated and transferred, and thus a quite high cathodic photocurrent response occurs, which is about 5 and 100 times of those induced by Bi2+xWO6 and Bi2S3, respectively. To explore the applicability of this homo/heterojunction structure, a novel “signal-on” cathodic PEC immunosensor is constructed with Z-scheme Bi2+xWO6/Bi2S3-3 as substrate and self-assembled 3D Ti3C2@Au as label for the ultrasensitive detection of neuron-specific enolase (NSE). The immunosensor exhibits high sensitivity and selectivity.

Accurate guided alternating atomic layer enhance internal electric field to steering photogenerated charge separation for enhance photocatalytic activity

Bi4O5BrxI2-xCy solid solutions with simultaneous bismuth-enriched and low temperature homogeneous C doping were obtained by the phase crystal reforming of BiOI with solvothermal alkali assisted molten salt method. The internal electric field between alternating atomic layers was significantly enhanced due to the synergism of formation of solid solutions, enrichment Bi and homogeneous C doping. Driven by the strong internal electric field, the photogenerated electrons and holes of Bi2.8C1.2O5Br0.5I1.5 were confined to the [Bi2.8C1.2O5]2+ layer and the double [Br0.5I1.5]− layer, respectively, then effective separation of charge carriers was achieved. The removal rates over Bi2.8C1.2O5Br0.5I1.5 of phenol, 4-chlorophenol, resorcinol and hydroquinone were 100 % in 1 h under visible light irradiation, which followed the parallel attack mechanism of O2- and h+. This study provided a reference for the multiple coordinated regulation of internal electric field by formation of solid solutions, enrichment Bi and homogeneous doping.

Improving the photo-thermoelectric performance of CuAlO2via doping with Bi

The photothermoelectric (PTE) effect enables the conversion of temperature differences induced by absorbed light to electrical voltages. For the first time, we investigated the effect of Bi doping on the photothermoelectric properties of CuAlO2. In this study, delafossite CuAl1-xBixO2 (x = 0.01, 0.02, 0.03, 0.04, and 0.06) powders were synthesised. X-ray diffraction and X-ray absorption spectroscopy results indicated that the doping limit of Bi content was approximately 2.6–2.7 at% (x = 0.026–0.027). At x = 0.02, we successfully demonstrated the increase of electrical conductivity due to the reduced effective mass and the increased hole concentration, the increase of optical absorption due to the reduced band gaps, and lower thermal conductivity resulting from mass and strain fluctuations. At a Bi content of 2 at%, the photovoltage signals increased compared with the undoped CuAlO2. These results indicated that Bi doping could potentially improve the PTE properties of CuAlO2.

Synthesis and thermoelectric properties of Bi-doped SnSe thin films* *Project supported by the National Key Research and Development Program of China (Grant No. 2017YFB0405702) and the National Natural Science Foundation of China (Grant No. 51672179).

Bi doped n-type SnSe thin films were prepared by chemical vapor deposition (CVD) and their structure and thermoelectric properties were studied. The x-ray diffraction patterns, x-ray photoelectron spectroscopy, and microscopic images show that the prepared SnSe thin films were composed of pure SnSe crystals. The Seebeck coefficients of the Bi-doped SnSe were greatly improved compared to that of undoped SnSe thin films. Specifically, Sn0.99Bi0.01Se thin film exhibited a Seebeck coefficient of –905.8 μV⋅K−1 at 600 K, much higher than 285.5 μV⋅K−1 of undoped SnSe thin film. Further first-principles calculations reveal that the enhancement of the thermoelectric properties can be explained mainly by the Fermi level lifting and the carrier pockets increasing near the Fermi level due to Bi doping in the SnSe samples. Our results suggest the potentials of the Bi-doped SnSe thin films in thermoelectric applications.

Enhanced Photocatalytic Performance of One-Pot Flash Combustion Synthesized ZnO Nanoparticles: An Effect of Bi Doping

Enhanced Photocatalytic Performance of One-Pot Flash Combustion Synthesized ZnO Nanoparticles: An Effect of Bi Doping

Evaluation of bismuth doped La2-xBixNiO4+δ (x = 0, 0.02 and 0.04) as cathode materials for solid oxide fuel cells

Bismuth doped La2-xBixNiO4+δ (x = 0, 0.02 and 0.04) oxides are investigated as SOFC cathodes. The effects of Bi doping on the phase structure, thermal expansion, electrical conduction behavior as well as electrochemical performance are studied. All the samples exist as a tetragonal Ruddlesden-Popper structure. Bi-doped LBNO-0.02 and LBNO-0.04 have good chemical and thermal compatibility with LSGM electrolyte. The average TEC over 20–900°С was 13.4 × 10−6 and 14.2 × 10−6 K−1 for LBNO-0.02 and LBNO-0.04, respectively. The electrical conductivity was decreasing with the rise of Bi doping content. EIS measurement indicates Bi doping can decrease the ASR values. At 750 °C, the obtained ASR for LBNO-0.04 is 0.18 Ωcm2, which is 56% lower than that of the sample without Bi doping, suggesting Bi doping is beneficial to the electrochemical catalytic activity of LBNO cathodes.

Substitutional doping of WO3 for Ca-ion based supercapacitor

In the present work, we analyzed the effect of doping (Bi, Hf, and Nb) on the performance of tungsten oxide (WO3) based supercapacitor. Through substitutional doping, the properties were altered to enhance its electrochemical charge storage performance. The doped samples were tested in different electrolytes (H+, Li+, Na+, Ca2+ and Al3+). The cyclic voltammetry, galvanostatic charge–discharge, and EIS studies were performed to identify the best suitable anode material for the fabrication of asymmetric supercapacitor. Nb:WO3 yielded the highest specific capacitance (Csp) of 782 Fg−1 in Ca electrolyte. An asymmetric device with Nb:WO3 as anode and MnO2 as a cathode using an aqueous Ca ion electrolyte exhibited a high potential window of 2 V and capacitance of 126 Fg−1. The factors responsible for performance of electrode material in different electrolytes were identified through experimental results, theoretical calculations, and relevant simulations. The effect of doping on WO3 crystal structure and electronic properties along with their binding nature/interaction with different electrolyte ions were first postulated through density functional theory (DFT) calculations.

Electrochemical and Structural Behavior of Bi Doped ZnO Materials Obtained with Solvothermal Synthesis Method

In this study, Bi-doped ZnO and undoped ZnO nanomaterials have been synthesized by the solvothermal reaction method. The effect of Bi doping on the structural and electrochemical properties has been investigated by X-ray diffractions (XRD), X-ray photoelectron spectroscopy (XPS) and, scanning electron microscopy (SEM). As seen from X-ray diffraction spectra performed on the bulk material, it has been clearly observed that both Bi doping changed the preferred orientation of the nanopowder as (101) and Bi+3 ions were expectedly entered the lattice. Furthermore, this result has been supported by photoelectron spectra. Scanning electron microscopy images have shown the shapes and distributions of nanostructures of the samples. As a result, it is thought that Bi doping is suitable for obtaining p-type conductivity in ZnO materials for the experimental processes we applied to samples in the study.

Effect of Bi5O7I/calcined ZnAlBi-LDHs composites on Cr(VI) removal via adsorption and photocatalytic reduction

Bi5O7I/calcined Bi-doped ZnAl layered double hydroxides (Bi5O7I/ZnAlBi-CLDHs) composites were prepared using the ultrasonic-assisted wet-chemical method, and the removal efficiency of Cr(VI) in an aqueous solution—through the adsorption and photocatalytic reduction of Bi5O7I/ZnAlBi-CLDHs—was investigated. The Bi doping concentration and composition ratio of Bi5O7I/ZnAlBi-CLDHs influence the removal rate of Cr(VI), and the optimal removal ability of Bi5O7I/ZnAlBi-LDHs is attained with 3% Bi doping and a Bi5O7I/ZnAlBi-CLDHs ratio of 1/10. The adsorption rate of Cr(VI) reaches 84% when infiltrating Bi5O7I/ZnAlBi-CLDHs for 60 min, while a higher removal rate of 98%, is attained through photocatalysis with visible light irradiation. The experimental data fit well with the pseudo second-order kinetic model, Langmuir adsorption isotherm model and the first-order reaction equation, which explains the possible Cr(VI) removal mechanism based on the fitting data. XPS results prove that about 61% of the Cr(VI) is gradually reduced to safe Cr(III) through the photocatalysis of Bi5O7I/ZnAlBi-CLDHs by the light irradiation duration 6 h. These results indicated that harmful Cr(VI) can be effectively removed by as-prepared Bi5O7I/ZnAlBi-CLDHs for water security, and that Bi5O7I/ZnAlBi-CLDHs provide a new prospect for the removal of Cr(VI) through adsorption and photocatalysis.

Rational design of Bi-doped rGO/Co3O4 nanohybrids for ethanol sensing

Gas sensors based on metal oxide semiconductors (MOSCs) and reduced graphene oxide (rGO) for sensing of organic volatile compounds often suffer from high operation temperature, low responses, poor selectivity, or narrow detection range. Herein, we design and fabricate Bi-doped rGO/Co3O4 (BGCO) nanohybrids with a flower morphology, which have been applied as a sensing layer for an ethanol sensor. This BGCO sensor exhibits a maximum p-type response of 178.1 towards 500 ppm ethanol at an optimum working temperature of 120 °C. The sensor’s detection range for the ethanol concentration is from 500 ppb to 500 ppm, and the sensor has an excellent selectivity to ethanol compared to other types of organic volatile gases and oxidizing gas such as NO2. The enhanced ethanol sensing mechanism is attributed to the increased conductivity of Bi doped rGO/Co3O4 material. Additionally, incorporation of Bi dopant can promote the redox reaction, and the rGO/Co3O4 act as the catalyst.

Bi doping stimulation on the visible-light absorption of In2O3 ceramics

Bandgap engineering in semiconductors is a long-term subject in many interests. Doping Bi modifies the wide-bandgap semiconductor In2O3 by generating an in-gap state. The reflectance spectra show that an optical transition occurs at 1.2 eV inside the bandgap of In2O3 as a substitution of Bi atoms, which is in good agreement with the previously reported density functional theory (DFT) calculation by Sabino et al., Phys. Rev. Mater. 3 (2019) 034605. The detailed analyses illustrate that the trivalent Bi dopant sites on the In-site in a limited concentration maintaining the chemical state of In and O. For the higher doping concentration, the secondary phase of Bi2O3 forms even though no chemical state variation of the host In2O3. However, the free electron concentration decreases rapidly with increasing Bi doping concentration while unchanging oxygen vacancies. These results confirm that the trivalent Bi induces an occupied band in the In2O3 electronic structure and In-vacancy as an acceptor, promising host materials for the p-type doping. Furthermore, the extended DFT calculation to the other pnictogen atoms confirms the similar in-gap states and lower In vacancy formation energy, suggesting the possibility toward p-type oxide semiconductors using pnictogen doped In2O3.

Martensitic transformation and magnetocaloric effect of Mn<sub>1−</sub><sub><italic>x</italic></sub>Bi<sub><italic>x</italic></sub>CoGe alloys

<p indent="0mm">Quaternary alloys of MnCoGe with the partial addition of other elements can realize coupling between structural and magnetic transformations, and it can present apparent magnetocaloric effects during martensitic transformation. In this paper, we have prepared Mn₁₋_{<italic>x</italic>}Bi_{<italic>x</italic>}CoGe (<italic>x</italic>=0, 0.03, 0.04, 0.05, 0.055, 0.06) series alloys using arc melting in a protective argon atmosphere. Experimental results indicate that the structural transformation temperature (<italic>T</italic>_M) of the samples shifts to low temperatures with increasing elemental Bi doping. The Mn_0.945Bi_0.055CoGe alloy (valence electron concentration<italic>e</italic>/<italic>a</italic>=6.63) undergoes a first-order magnetostructural transition (FOMST) near room temperature, and a large magnetic entropy change of <sc>36.8 J kg⁻¹ K⁻¹</sc> is obtained under an external magnetic field of <sc>0–5 T,</sc> which proves that elemental Bi doping in MnCoGe alloys can effectively tune the martensitic transformation temperature and further improve the magnetic entropy change.

Single-atom Bi-anchored Au hydrogels with specifically boosted peroxidase-like activity for cascade catalysis and sensing

The complex structure of nanomaterial causes great difficulty in identifying active sites of nanozymes and getting to the bottom of the catalytic mechanism. In this report, single-atom Bi-anchored Au (BiSA@Au) hydrogels were synthesized through a one-step reduction strategy, which enables the precise regulation of the nanozyme activity and specificity at the atomic scale and the in-depth understanding of their catalytic nature. Due to the single-atom Bi doping, the BiSA@Au hydrogels showed previously unachieved peroxidase (POD)-like activity, while the doped single Bi atoms had negligible effects on the enhancements of the other closely related redox enzyme-like activities. Density functional theory verified that the introduction of single Bi atoms not only enhances the adsorption of H2O2 but also decreases the potential barriers for *OOH generation, leading to the boosted POD-like activity. Taking advantage of the unique porous nanowire networks of BiSA@Au hydrogels, a nanozyme/natural enzyme hybrid cascade reaction system was fabricated to achieve the sensitive colorimetric biosensor for glucose. This work paved a new route to rationally design functional nanozymes at the atomic scale, achieving the significant enhancement of POD-like activity with exceptional specificity.

Theoretical and experimental studies on electronic structure and optical properties of Bi-doped anatase TiO2

In this paper, Bi-doped TiO2 was prepared by electrochemical method. XRD results show that the crystal structure was not changed after Bi doping. All of them were anatase TiO2. And there were no strontium peak. The microscopic morphology of the nanotube has little effect. The optical property test results show that the Bi doping causes a significant red shift of anatase TiO2, which promotes light absorption in the visible range. This is consistent with the theoretical results. The band gap of pure anatase TiO2 calculated by GGA+U method is 3.22 eV. After Bi enters the lattice, it will introduce impurity level in the TiO2 bandgap and reduce the band gap of TiO2.