Bismuth-based Semiconductors Research Articles

Photovoltaic effects in BiVO4/ZnTiO3 multilayer films with high fill factor

Bismuth-based semiconductor materials have garnered significant attention because of their appropriate optical bandgap and substantial photoelectric conversion efficiency. Enhancing the photocurrent and fill factor of photovoltaic films is essential for developing high-performance optoelectronic devices. In this study, high-performance BiVO4-ZnTiO3 multilayer films were fabricated using a straightforward sol-gel method, where the incorporation of ZnTiO3 films significantly improved the photovoltaic performance of BiVO4. Through structural design aimed at enhancing light utilization, the BiVO4-ZnTiO3 multilayer film achieved a photocurrent density of 1.9 mA/cm2 at 450 nm, along with a fill factor of 46.8 % in the composite multilayer structure. The improvement in film performance is attributed to the overall multilayer stacking effect. This study offers a novel approach for utilizing bismuth-based semiconductors in optoelectronics.

Photocatalytic Degradation of Sulfamethoxazole by Cd/Er-Doped Bi2MoO6

Bi2MoO6 (BMO) is a typical bismuth-based semiconductor material, and its unique Aurivillius structure provides a broad space for electron delocalization. In this study, a new type of bismuth molybdate Cd/Er-BMO photocatalytic material was prepared by co-doping Er3+ and Cd2+, and the performance of the photocatalytic degradation of sulfamethoxazole (SMZ) was systematically studied. The research results showed that the efficiency of SMZ degradation by Cd/Er-BMO was significantly improved after doping Er3+ and Cd2+ ions, reflecting the synergistic catalytic effect of Cd2+ and Er3+ co-doping. Cd/Er-BMO doped with 6% Cd had the highest degradation efficiency (93.89%) of SMZ under visible light irradiation. The material revealed excellent stability and reusability in repeated degradation experiments. In addition, 6% Cd/Er-BMO had a smaller particle size and a larger specific surface area, which is conducive to improving the generation efficiency of its photogenerated electron-hole pairs and reducing the recombination rate, significantly enhancing the photocatalysis of the material. This study not only provides an effective photocatalyst for degrading environmental pollutants such as SMZ, but also provides an important scientific basis and new ideas for the future development of efficient and stable photocatalytic materials.

Design of a novel direct Z-scheme BiOIO3/Bi2WO6 heterojunction for enhanced photocatalytic degradation of norfloxacin under visible light

The unique electronic structure, appropriate bandgap energy, and excellent electron transfer capability make bismuth-based semiconductors hotspots in the field of photocatalysis. Novel BiOIO3/Bi2WO6 Z-scheme heterojunctions were fabricated via in-situ hydrothermal synthesis. The BIOBIW-3 heterojunctions (BiOIO3:Bi2WO6=0.25:0.8, mole ratio) exhibited excellent photocatalytic activity for norfloxacin (NOR), with a degradation efficiency of 90.41 % after 90 min of photoreaction and a reaction kinetic constant of 0.02132 min−1, which was 5.02 and 9.35 times higher than that of BIO and BIW, respectively. The superior photocatalytic performance can be attributed to the intimate interface between BiOIO3 and Bi2WO6, as well as the staggered energy band structure that facilitates the formation of a Z-type heterojunction. This not only widens the range of visible light absorption but also enhances the separation and transfer of photogenerated carriers while maintaining a high capacity for redox reactions. The dominant active species in the degradation process were photogenerated holes (h+) and superoxide (∙O2−) radicals, and an in-depth exploration of the possible mechanism was conducted. Furthermore, the effects of various parameters, including solution pH, catalyst dosage, and NOR concentration on the photocatalytic degradation of NOR were also investigated. The prepared BiOIO3/Bi2WO6 heterojunctions exhibited remarkable photocatalytic performance and chemical stability, presenting a novel research direction for employing layered bismuth-based materials in the degradation of fluoroquinolone antibiotic wastewater.

Investigation of the physical characteristics of Bi4Ti3O12, Bi2Ti4O11, Bi12TiO20, Bi2Ti2O7 ternary semiconductors

The mechanical, thermodynamics, electronic, optical properties of Bi4Ti3O12, Bi2Ti4O11, Bi12TiO20 and Bi2Ti2O7 ternary semiconductor materials were calculated and analyzed using first-principles calculations. The structural optimizations demonstrate that four ternary semiconductors are structurally stable. The mechanical parameters of Bi2Ti2O7 exhibit the highest resistance to deformation and average bonding strength, while Bi2Ti4O11 demonstrates the high shear deformation resistance. The Debye temperatures for these bismuth titanate semiconductors are in the following order: Bi2Ti4O11>Bi2Ti2O7>Bi4Ti3O12>Bi12TiO20. Both Bi12TiO20 and Bi2Ti2O7 exhibit high light absorption energies within specific ranges. Through the computational analysis presented in this paper, the theoretical data of bismuth-based semiconductors are enriched for further experimental investigations.

Regulating the crystal phase of bismuth-based semiconductors for promoted photocatalytic performance

Regulating the crystal phase of bismuth-based semiconductors for promoted photocatalytic performance

Bismuth oxyhalide as efficient photocatalyst for water, air treatment and bacteria inactivation under UV and visible light

Fifteen bismuth oxyhalides were synthetized, including BiOX, BiOX/BixOyXz, heterostructures and BiOXxY1−x (X, Y = Cl, Br, I) solid solutions. The photocatalytic activity and intermediates formation of as-prepared bismuth-based semiconductors (BBS) were compared with the benchmark TiO2 P25 photocatalyst for NOx air purification, phenol decomposition, and E.Coli bacteria inactivation. TiO2 P25 possessed the highest photocatalytic oxidation rate of phenol (K = 0.003 min−1) and NO degradation efficiency (η = 38 %) when exposed to UV light, but also the lowest performance under visible light on both photocatalytic process (K = 0.0007 min−1 and η = 14 %). Under visible light, BiOI/Bi4O5I2 or solid solutions (BiOI0.5Cl0.5 and BiOI0.5Br0.5) enhanced the photocatalyic for phenol degradation (K = 0.01–0.026 min−1) and NO (35–37 %). BBS samples generated more NO2 during NOx oxidation, but less typical intermediates (benzoquinone, hydroquinone and catechol) during phenol decomposition were detected. BiOCl0.5I0.5 and BiOBr0.5I0.5 composites exhibited the most outstanding antibacterial performance under both irradiation conditions resulting in E. coli 102-3 cfu/mL after 60 min irradiation. The differences can be mainly linked to a different ROS-mediated mechanism of TiO2 and BBS. The BBS photocatalytic results is closely related to the balance between effective light absorption and adequate redox potentials.

Research Progress on Bismuth-Based Semiconductors in Photocatalysis

Research Progress on Bismuth-Based Semiconductors in Photocatalysis

Bismuth-Based Z-Scheme Heterojunction Photocatalysts for Remediation of Contaminated Water.

Agricultural runoff, fuel spillages, urbanization, hospitalization, and industrialization are some of the serious problems currently facing the world. In particular, byproducts that are hazardous to the ecosystem have the potential to mix with water used for drinking. Over the last three decades, various techniques, including biodegradation, advanced oxidation processes (AOPs), (e.g., photocatalysis, photo-Fenton oxidation, Fenton-like oxidation, and electrochemical oxidation process adsorption), filtration, and adsorption techniques, have been developed to remove hazardous byproducts. Among those, AOPs, photocatalysis has received special attention from the scientific community because of its unusual properties at the nanoscale and its layered structure. Recently, bismuth based semiconductor (BBSc) photocatalysts have played an important role in solving global energy demand and environmental pollution problems. In particular, bismuth-based Z-scheme heterojunction (BBZSH) is considered the best alternative route to overhaul the limitations of single-component BBSc photocatalysts. This work aims to review recent studies on a new type of BBZSH photocatalysts for the treatment of contaminated water. The general overview of the synthesis methods, efficiency-enhancing strategies, classifications of BBSc and Z-scheme heterojunctions, the degradation mechanisms of Z- and S-schemes, and the application of BBZSH photocatalysts for the degradation of organic dyes, antibiotics, aromatics compounds, endocrine-disrupting compounds, and volatile organic compounds are reviewed. Finally, challenges and the future perspective of BBZSH photocatalysts are discussed.

Dye-augmented bandgap engineering of a degradable cascade nanoreactor for tumor immune microenvironment-enhanced dynamic phototherapy of breast cancer

Non-invasive precision tumor dynamic phototherapy has broad application prospects. Traditional semiconductor materials have low photocatalytic activity and low reactive oxygen species (ROS) production rate due to their wide band gap, resulting in unsatisfactory phototherapy efficacy for tumor treatment. Employing the dye-sensitization mechanism can significantly enhance the catalytic activity of the materials. We develop a multifunctional nanoplatform (BZP) by leveraging the benefits of bismuth-based semiconductor nanomaterials. BZP possesses robust ROS generation and remarkable near-infrared photothermal conversion capabilities for improving tumor immune microenvironment and achieving superior phototherapy sensitization. BZP produces highly cytotoxic ROS species via the photocatalytic process and cascade reaction, amplifying the photocatalytic therapy effect. Moreover, the simultaneous photothermal effect during the photocatalytic process facilitates the improvement of therapeutic efficacy. Additionally, BZP-mediated phototherapy can trigger the programmed death of tumor cells, stimulate dendritic cell maturation and T cell activation, modulate the tumor immune microenvironment, and augment the therapeutic effect. Hence, this study demonstrates a promising research paradigm for tumor immune microenvironment-improved phototherapy. Statement of significanceThrough the utilization of dye sensitization and rare earth doping techniques, we have successfully developed a biodegradable bismuth-based semiconductor nanocatalyst (BZP). Upon optical excitation, the near-infrared dye incorporated within BZP promptly generates free electrons, which, under the influence of the Fermi energy level, undergo transfer to BiF3 within BZP, thereby facilitating the effective separation of electron–hole pairs and augmenting the catalytic capability for reactive oxygen species (ROS) generation. Furthermore, a cascade reaction mechanism generates highly cytotoxic ROS, which synergistically depletes intracellular glutathione, thereby intensifying oxidative stress. Ultimately, this dual activation strategy, combining oxidative and thermal damage, holds significant potential for tumor immunotherapy.

Advances in the optical and electronic properties and applications of bismuth-based semiconductor materials

In recent years, bismuth-based semiconductors have become a research hotspot in the new semiconductor field due to their unique optical and electronic properties.

Advances in the structural engineering of layered bismuth-based semiconductors for visible light-driven photocatalytic water splitting.

Hydrogen production via the photocatalytic water splitting reaction on semiconductors presents a promising avenue to directly achieve solar energy conversion and storage. Bismuth-based semiconductors with layered structures, a hierarchical arrangement of components stacked in the form of two-dimensional extended layers where the atoms within each layer are typically strongly bonded, while the interactions between the layers are relatively weak, have emerged as an important series of photocatalyst candidates. In this review, we focus on the new emerging layered bismuth-based semiconductors with structures in Sillén, Aurivillius, Sillén-Aurivillius and bismuth chromate systems primarily employed in the photocatalytic water splitting reaction. From a crystal structure-oriented view, we delve into discussions on how the component and unit of a crystal structure influence the intrinsic properties, including light absorption and photogenerated charge transfer and separation, of materials as well as the corresponding photocatalytic performance of the water splitting reaction. The strategies for modulating the ferroelectricity and surface modification of these layered bismuth-based semiconductors are also involved. We also discuss the limitations of these materials accompanied by a forward-looking perspective, and we hope to provide some insights from the view of rational material design and engineering for the fabrication of high-efficiency photocatalytic water splitting systems.

Review on synthetic approaches and PEC activity performance of bismuth binary and mixed-anion compounds for potential applications in marine engineering.

Photoelectrochemical (PEC) technology in marine engineering holds significant importance due to its potential to address various challenges in the marine environment. Currently, PEC-type applications in marine engineering offer numerous benefits, including sustainable energy generation, water desalination and treatment, photodetection, and communication. Finding novel efficient photoresponse semiconductors is of great significance for the development of PEC-type techniques in the marine space. Bismuth-based semiconductor materials possess suitable and tunable bandgap structures, high carrier mobility, low toxicity, and strong oxidation capacity, which gives them great potential for PEC-type applications in marine engineering. In this paper, the structure and properties of bismuth binary and mixed-anion semiconductors have been reviewed. Meanwhile, the recent progress and synthetic approaches were discussed from the point of view of the application prospects. Finally, the issues and challenges of bismuth binary and mixed-anion semiconductors in PEC-type photodetection and hydrogen generation are analyzed. Thus, this perspective will not only stimulate the further investigation and application of bismuth binary and mixed-anion semiconductors in marine engineering but also help related practitioners understand the recent progress and potential applications of bismuth binary and mixed-anion compounds.

Metal-alcohol coordination promoted reduction of bismuth (III) in bismuth-based semiconductors for enhanced photocatalytic activity

Metal ion doping is an extensively researched method to enhance photocatalytic activity of bismuth-based semiconductors, but function of the metal ions need be further clarified. Herein, metal-alcohol coordination was evidenced to promote reduction of BiIII in Bi-based semiconductors (e.g., Bi2MoO6 hierarchical microspheres) to generated oxygen vacancies (Ovs) and Bi metal (Bi0). Ovs and Bi0, rather than widely recognized doping metal ions, play a key role for remarkable enhancement of photocatalytic activity of Bi2MoO6, for example of ∼16-fold higher photocatalytic nitrogen reduction activity, which arises from that the Ovs and Bi0 can enhance photoexcited charge separation and work as surface active sites. The Ovs possess much greater efficacy than the Bi0. Formation of Bi0 also induces prominent morphological variation of the microspheres. This work discloses an interesting but neglected phenomenon in alcohothermal synthesis of “metal-doped” Bi-based semiconductors and aims at drawing high attention of relevant researchers.

Topology-regulated nanocatalysts for ferroptosis-mediated cancer phototherapy

Ferroptosis-mediated tumor treatment is constrained by the absence of single-component, activatable multifunctional inducers. Given this, a topological synthesis strategy is employed to develop an efficient bismuth-based semiconductor nano-photocatalyst (Bi2O3:S) for tumor ferroptosis therapy. Photo-excited electrons can participate in the reduction reaction to produce harmful reactive oxygen species (ROS) when exposed to near-infrared light. Meanwhile, photo-excited holes can contribute to the oxidation reaction to utilize extra glutathione (GSH) in tumors. In the acidic tumor microenvironment, bismuth ions generated from Bi2O3:S may further cooperate with GSH to amplify oxidative stress damage and achieve biodegradation. Both promote ferroptosis by downregulating glutathione peroxidase 4 (GPX4) expression. Besides, sulfur doping optimizes its near-infrared light-induced photothermal conversion efficiency, benefiting its therapeutic effect. Thus, bismuth ions and holes synergistically drive photo-activable ferroptosis in this nanoplatform, opening up new avenues for tumor therapy.

Bandlike Transport and Charge-Carrier Dynamics in BiOI Films.

Following the emergence of lead halide perovskites (LHPs) as materials for efficient solar cells, research has progressed to explore stable, abundant, and nontoxic alternatives. However, the performance of such lead-free perovskite-inspired materials (PIMs) still lags significantly behind that of their LHP counterparts. For bismuth-based PIMs, one significant reason is a frequently observed ultrafast charge-carrier localization (or self-trapping), which imposes a fundamental limit on long-range mobility. Here we report the terahertz (THz) photoconductivity dynamics in thin films of BiOI and demonstrate a lack of such self-trapping, with good charge-carrier mobility, reaching ∼3 cm2 V-1 s-1 at 295 K and increasing gradually to ∼13 cm2 V-1 s-1 at 5 K, indicative of prevailing bandlike transport. Using a combination of transient photoluminescence and THz- and microwave-conductivity spectroscopy, we further investigate charge-carrier recombination processes, revealing charge-specific trapping of electrons at defects in BiOI over nanoseconds and low bimolecular band-to-band recombination. Subject to the development of passivation protocols, BiOI thus emerges as a superior light-harvesting semiconductor among the family of bismuth-based semiconductors.

Protoporphyrin-sensitized degradable bismuth nanoformulations for enhanced sonodynamic oncotherapy.

Decreasing the scavenging capacity of reactive oxygen species (ROS) and enhancing ROS production are the two principal objectives in the development of novel sonosensitizers for sonodynamic therapy (SDT). Herein, we designed a protoporphyrin-sensitized bismuth-based semiconductor (P-NBOF) as a sonosensitizer to generate ROS and synergistically depleted glutathione for enhanced SDT against tumors. The bismuth-based nanomaterial (NBOF) is a wide-bandgap semiconductor. Sensitization by protoporphyrin made it easier to excite electrons under ultrasonic stimulation, and the energy of the lowest unoccupied electron orbital in protoporphyrin was higher than the conduction-band energy of NBOF. Under ultrasound excitation, the excited electrons in the protoporphyrin were injected into the conduction band of the NBOF, increasing its reducing ability leading to the production of more superoxide anion radicals and also helping to increase the charge separation of protoporphyrin leading to the production of more singlet oxygen. Meanwhile, P-NBOF continuously depleted glutathione, which was not only conducive to breaking the redox balance of the tumor microenvironment to enhance the therapeutic efficacy of SDT, but also promoted its degradation and metabolism. The construction of this P-NBOF sonosensitizer thus provided an effective strategy to enhance SDT for tumors. STATEMENT OF SIGNIFICANCE: To enhance the efficacy of sonodynamic tumor therapy, we developed a degradable protoporphyrin-sensitized bismuth-based nano-semiconductor (P-NBOF) by optimizing the band structure and glutathione-depletion ability. Protoporphyrin in P-NBOF under excitation preferentially generates free electrons, which are then injected into the conduction band of NBOF, improving the reducing ability of NBOF and promoting the separation of electron-hole pairs, thereby enhancing the production capacity of reactive oxygen species. Furthermore, P-NBOF can deplete glutathione, reduce the scavenging of reactive oxygen species, and reactivate and amplify the effect of sonodynamic therapy. The construction of the nanotherapeutic platform provides an option for enhancing sonodynamic therapy.

The Quick Removal of Toxic Dye Molecules by an Efficient Adsorptive BiOI/Bi2MoO6 Heterostructure

Adsorption is a low-energy, economical, and efficient method for pollutant removal from water. Because of their unique structure, large specific surface area (SSA), and non-toxicity, bismuth-based semiconductors, usually researched for the photodegradation of organic molecules, are also excellent for dark adsorption processes. Here, a three-dimensional adsorbent with a heterostructure with a hydrangea-like shape made of Bi2MoO6 (BMO) and BiOI (BOI) was synthesized by a one-pot solvothermal process and investigated for the adsorption of toxic dyes. BOI/BMO with an I-to-Mo ratio of 2.0 adsorbed 98.9% of the model pollutant rhodamine B (RhB) within 5 min with a maximum adsorption capacity of 72.72 mg/g in the dark at room temperature. When compared to pure BMO, the BOI2/BMO heterostructure was 14.1 times more performant because of its flower-like morphology with multiple planes, an SSA that was 1.6-fold larger, increased porosity, the formation of heterojunctions, and a negative surface charge attracting RhB. Further investigation indicated that adsorption by BOI2/BMO fitted the pseudo-second-order kinetic and the Langmuir isotherm models. In addition, the thermodynamic analysis showed that it was a spontaneous exothermic process probably relying on physisorption. Thus, the BOI/BMO adsorbent developed here is promising for the fast removal of toxic dyes from industrial wastewater.

Elucidating Polaron Dynamics in Cs2AgBiBr6 Double Perovskite.

Lead-free Cs2AgBiBr6 double perovskites have recently emerged as a possible alternative to lead-based halide perovskites for photovoltaic and optoelectronic applications. Significant research efforts have been devoted toward device engineering to enhance the performance of Cs2AgBiBr6 double-perovskite-based photovoltaic and optoelectronic devices; however, less attention has been paid to address their intrinsic photophysical properties. In this work, we have shown that the small polaron formation under photoexcitation and polaron localization limits the carrier dynamics in Cs2AgBiBr6 double halide perovskites. Furthermore, temperature-dependent ac conductivity measurement reveals that single polaron hopping is the dominant conduction mechanism. Ultrafast transient absorption spectroscopy reveals that a deformed lattice under photoexcitation leads to the formation of small polarons which act as self-trapped states (STSs) and lead to the ultrafast trapping of charge carriers. Our findings provide an in-depth understanding of intrinsic limitations of Cs2AgBiBr6 perovskites, which can be applicable for other bismuth-based semiconductors.

Construction and Enhanced Efficiency of Bi2MoO6/ZnO Compo-Sites for Visible-Light-Driven Photocatalytic Performance.

Bi2MoO6 was one of the important bismuth-based semiconductors with a narrow bandgap, and has been widely used in selective oxidation catalysts, supercapacitors, and energy-storage devices. A series of Bi2MoO6/ZnO composite photocatalysts with different mass ratios were synthesized by the hydrothermal method. The synthesized samples were characterized by XRD, PL, UV-Vis, SEM, TEM, XPS, and BET analysis techniques. Under visible light conditions, Methylene blue (MB) was used as the target degradation product to evaluate its photocatalytic performance. The results showed that the degradation rate constant of Bi2MoO6/ZnO (0.4-BZO) was about twice that of the traditional photocatalysis of ZnO. The Bi2MoO6/ZnO composite catalyst maintained stable performance after four consecutive runs. The high photocatalytic activity of Bi2MoO6/ZnO was attributed to the efficient electron transport of the heterojunction, which accelerates the separation of electron-hole pairs and reduces the probability of carrier recombination near the Bi2MoO6/ZnO heterojunction. Bi2MoO6/ZnO nanocomposites have potential applications in the field of photodegradation.

Research progress of MOF/Bismuth-based semiconductor composites in photocatalytic technology

Photocatalysis has significant potential for environmental remediation and energy conversion, with a focus on designing and developing highly efficient photocatalysts. Composite materials consisting of bismuth-based semiconductors and metal-organic frameworks (MOFs) exhibit outstanding photocatalytic activity, and have garnered significant attention from researchers as a highly sought-after material. A review is conducted on recent advances in MOF/bismuth-based semiconductor composites. On this basis, the synthesis methods of MBCs are described in detail, and then the applications of MBCs in organic pollutant degradation, Cr (VI) reduction, water (H2O) splitting, nitrogen (N2) fixation discussed. Finally, this paper highlights the current challenges in photocatalysis using MBCs and provides insights into the future development direction for MBCs photocatalysis technology. The preparation and modification methods of MBCs, the improvement of photocatalytic efficiency, the mechanism of oxidative degradation of organic matter and the mechanism of photocatalytic complete hydrolysis of water need further study.