Surface phases and photocatalytic activity correlation of Bi2O3/Bi2O4-x nanocomposite

Hydrothermal synthesis of spindle structure copper ferrite-graphene oxide nanocomposites for enhanced photocatalytic dye degradation and in-vitro antibacterial activity

In this study, a one-step hydrothermal approach was used to make pure magnetic copper ferrite (CuFe2O4) and copper ferrite-graphene oxide (CuFe2O4-rGO) nanocomposites (NCs) and spinel structure CuFe2O4 with a single phase of tetragonal CuFe2O4-rGO-NCs was confirmed by the XRD. Then, characterization of CuFe2O4-rGO-NCs was done using ng Raman spectroscopy, FT-IR, TGA-DTA, EDS, SEM, and TEM. The synthesized NCs was exposed to UV light to evaluate its photocatalytic activity for the degradation of methylene blue (MB) and rhodamine B (RhB) with CuFe2O4 and CuFe2O4-rGO-NCs, respectively. The catalyst CuFe2O4-rGO-NCs provided higher degradation of MB (94%) than for RhB (86%) under UV light irradiation compared to CuFe2O4. Further, the antibacterial activities of CuFe2O4-NPs and CuFe2O4-rGO-NCs were tested against Gram-negative and -positive bacterial pathogens such as Vibrio cholera (V. cholera); Escherichia coli (E. coli); Pseudomonas aeruginosa (P. aeruginosa); Bacillus subtilis (B. subtilis); Staphylococcus aureus (S. aureus); and Staphylococcus epidermidis (S. epidermidis) by well diffusion method. At 100 μg/mL concentrations of CuFe2O4-rGO-NCs, maximal growth inhibition was shown against E. coli (18 mm) and minimum growth inhibition against S. epidermidis (12 mm). This study suggests that CuFe2O4-rGO-NCs as a high-efficacy antibacterial material and plays an important role in exhibiting higher sensitivity depending on concentrations. The results encourage that the synthesized CuFe2O4-rGO-NCs can be used as a promising material for the antibacterial activity and also for dye degradation in the water/wastewater treatment plants.

Ternary Polyaniline@Bi2O3-BiOCl Nanocomposites as Innovative Highly Active Photocatalysts for the Removal of the Dye under Solar Light Irradiation

Ternary PANI@Bi₂O₃-BiOCl nanocomposites were successfully synthesized during the oxidative polymerization of aniline monomer in the presence of Bi₂O₃. PANI@Bi₂O₃-BiOCl nanocomposites were characterized by several analytical techniques, including X-ray diffraction (XRD), Fourier Transform Infrared spectroscopy (FTIR), N₂ physisorption, UV-Vis Diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The effective PANI-semiconductor interaction promotes the fast separation and transfer of photogenerated electrons and holes, enhancing the photocatalytic efficiency of the materials towards methylene blue (MB) degradation under solar light irradiation. The best results were obtained by 0.5%PANI@Bi₂O₃-BiOCl, leading to 80% MB degradation in 2 h, four times higher than pristine Bi₂O₃-BiOCl. Moreover, 0.5%PANI@Bi₂O₃-BiOCl maintained stable photocatalytic performances for four cycles without significant activity loss. Various scavengers (isopropyl alcohol, formic acid, and benzoquinone) were used to identify the active species by trapping holes and radicals generated during the photocatalytic degradation process. Finally, a probable photocatalytic mechanism of PANI@Bi₂O₃-BiOCl photocatalyst was suggested.

Synthesis of Bimetallic BiPO4/ZnO Nanocomposite: Enhanced Photocatalytic Dye Degradation and Antibacterial Applications

Multidrug-resistant strains (MDRs) are becoming a major concern in a variety of settings, including water treatment and the medical industry. Well-dispersed catalysts such as BiPO₄, ZnO nanoparticles (NPs), and different ratios of BiPO₄/ZnO nanocomposites (NCs) were synthesized through hydrothermal treatments. The morphological behavior of the prepared catalysts was characterized using XRD, Raman spectra, PL, UV-Vis diffuse reflectance spectroscopy (UV-DRS), SEM, EDX, and Fe-SEM. MDRs were isolated and identified by the 16s rDNA technique as belonging to B. flexus, B. filamentosus, P. stutzeri, and A. baumannii. The antibacterial activity against MDRs and the photocatalytic methylene blue (MB) dye degradation activity of the synthesized NPs and NCs were studied. The results demonstrate that the prepared BiPO₄/ZnO-NCs (B1Z4-75:300; NCs-4) caused a maximum growth inhibition of 20 mm against A. baumannii and a minimum growth inhibition of 12 mm against B. filamentosus at 80 μg mL^-1 concentrations of the NPs and NCs. Thus, NCs-4 might be a suitable alternative to further explore and develop as an antibacterial agent. The obtained results statistically justified the data (p ≤ 0.05) via one-way analysis of variance (ANOVA). According to the results of the antibacterial and photocatalytic study, we selected the best bimetallic NCs-4 for the photoexcited antibacterial effect of MDRs, including Gram ve⁺ and Gram ve^- strains, via UV light irradiation. The flower-like NCs-4 composites showed more effectiveness than those of BiPO₄, ZnO, and other ratios of NCs. The results encourage the development of flower-like NCs-4 to enhance the photocatalytic antibacterial technique for water purification.

Fabrication of novel BiVO4/Bi2O3heterostructure with superior visible light induced photocatalytic properties

Heterostructure BiVO₄/Bi₂O₃nanocomposites with enhanced visible light activity are effectively synthesized through an easiest and single step hydrothermal route, using bismuth subnitrate and ammonium meta-vanadate as main raw materials in existence of citric acid. The phase and surface structure, topography and optical properties of synthesized composites are characterized by XRD, SEM, EDX, FTIR, UV-Visible and PL spectroscopy. It was found that 5%BiVO₄/Bi₂O₃(BOBV-5) nanocomposite exhibit excellent photocatalytic performance for rhodamine B dye degradation and tetracyclic under irradiation of visible light as compared to single component i.e. BiVO₄. The increased photocatalytic activity should be ascribed for making p-n heterojunction among p-type Bi₂O₃and n-type BiVO₄. This p-n heterojunction successfully reduce the recombination of photogenerated charge carriers. Furthermore, the BOBV-5 novel photocatalyst shows good stability in constructive five cycles and photocatalytic activity is best for conquering photo corrosion of a photocatalysts. To explain charge migration route, whole photocatalytic mechanism was described in terms of energy band structures. Furthermore, the present work is helpful effort for design of new visible light photocatalytic materials with heterojunction structures.

Solar-Driven Photocatalytic Films: Synthesis Approaches, Factors Affecting Environmental Activity, and Characterization Features

Solar-powered photocatalysis has come a long way since its humble beginnings in the 1990s, producing more than a thousand research papers per year over the past decade. In this review, immobilized photocatalysts operating under sunlight are highlighted. First, a literature review of solar-driven films is presented, along with some fundamental operational differences in relation to reactions involving suspended nanoparticles. Common strategies for achieving sunlight activity from films are then described, including doping, surface grafting, semiconductor coupling, and defect engineering. Synthetic routes to fabricate photocatalytically active films are briefly reviewed, followed by the important factors that determine solar photocatalysis efficiency, such as film thickness and structure. Finally, some important and specific characterization methods for films are described. This review shows that there are two main challenges in the study of photocatalytic materials in the form of (thin) films. First, the production of stable and efficient solar-driven films is still a challenge that requires an integrated approach from synthesis to characterization. The second is the difficulty in properly characterizing films. In any case, the research community needs to address these, as solar-driven photocatalytic films represent a viable option for sustainable air and water purification.

Release and transformation of phosphorus in sediment following seasonal freezing-thawing cycles

River ice in the upper Yarlung Zangbo River is characterized by seasonal freezing-thawing cycles (SFTC). It is important to explore the effects of SFTC on phosphorus release and transformation from upstream surface sediments to protect the ecosystem of the Yarlung Zangbo River. The process and mechanism of phosphorus release and transformation in sediments following SFTC were investigated in a laboratory simulation experiment. The results showed that after freezing, sediment particles were broken, the specific surface area was increased by 14%, and the particle size was decreased by 43%, which resulted in weakened adsorption of phosphorus by sediments. Moreover, the destruction of organic matter (OM) on the sediment surface will release more ion adsorption sites and promote the release of phosphorus. The bioavailabilities of exchangeable phosphorus (Ex-P), aluminum phosphorus (Al-P) and iron phosphorus (Fe-P) increased by 60.09%, 86.86% and 31.86%, respectively, after freezing. Organic phosphorus (O-P) is used indirectly by organisms, and O-P content showed a significant correlation with OM content. Water affected the oxygen content in sediments during the freezing period, and continuous hypoxia promoted the release and transformation of Fe-P and Al-P.

Zn-doped Bi2MoO6 supported on reduced graphene oxide with increased surface active sites for degradation of ciprofloxacin

The reduced graphene oxide supported Zn-doped Bi₂MoO₆ nanocomposites (Zn_xBi_2-xMoO₆/RGO) are synthesized by an easy one-step solvothermal method for the rapid degradation of ciprofloxacin (CIP). Characterization analyses show that Bi₂MoO₆ nanosheets are uniformly supported on RGO, for which the agglomeration of Bi₂MoO₆ is effectively inhibited, leading to more exposure of surface active sites. The degradation rate of Zn_0.1Bi_1.9MoO₆/RGO₅ on CIP reached 90% after 120 min of visible light irradiation, which was 10.4 times the rate of unsupported Bi₂MoO₆. Zn doping and RGO loading synergistically reduce the recombination rate of photogenerated electron-hole pairs and result in the enhanced photocatalytic performance. Compared with previously reported catalysts, Zn_0.1Bi_1.9MoO₆/RGO₅ can get higher degradation efficiency with shorter time and less dosage. In addition, after five cycles, the degradation efficiency is maintained at about 85%, showing perfect cycling stability of Zn_0.1Bi_1.9MoO₆/RGO₅. Photocatalytic mechanism suggests that the photogenerated •O₂^- and h⁺ are main species for degrading CIP based on Zn_xBi_2-xMoO₆/RGO complex.

Morphological and optical investigation of 2D material-based ternary nanocomposite: Bi2O3/MgO/GO synthesized by a co-precipitation technique

A ternary oxide nanocomposite based on Bi2O3/MgO/GO was prepared using a co-precipitation method taking into consideration of preparing the material for photoconductive device applications.

A review on the preparation, microstructure, and photocatalytic performance of Bi2O3 in polymorphs

In recent years, the semiconductor bismuth oxide (Bi₂O₃) has attracted increasing attention as a potential visible-light-driven photocatalyst due to its simple composition, relatively narrow bandgap (2.2-2.8 eV), and high oxidation ability with deep valence band levels. Owing to the symmetry of its unit cell, Bi₂O₃ exists in more than one crystal form and exhibits phase-dependent photocatalytic properties. However, the phase-selective synthesis of Bi₂O₃ is a complex process, and its phase transformation usually occurs in a wide temperature range. Therefore, the development of Bi₂O₃ phases with a controllable microstructure and good photocatalytic properties is a great challenge. Hundreds of articles have been reported on the phase-selective synthesis and photocatalytic performance of Bi₂O₃. However, an interacting and critical review has rarely been reported, and thus it is essential to fill the gap in the literature. In this review, the phase-dependent photocatalytic performance of Bi₂O₃ is presented in detail. The phase-selective synthesis and temperature-dependent phase stability of highly active Bi₂O₃ are explored. The phase junction in Bi₂O₃ is reviewed, and the future perspective with an outlook on contemporary challenges is provided finally.

Synthesis of BiF3 and BiF3-Added Plaster of Paris Composites for Photocatalytic Applications

A BiF3 powder sample was prepared from the purchased Bi2O3 powder via the precipitation route. The photocatalytic performance of the prepared BiF3 powder was compared with the Bi2O3 powder and recognized as superior. The prepared BiF3 powder sample was added in a plaster of Paris (POP) matrix in the proportion of 0%, 1%, 5%, and 10% by wt% to form POP–BiF3(0%), POP–BiF3(1%), POP–BiF3(5%), and POP–BiF3(10%) composite pellets, respectively, and activated the photocatalytic property under the UV–light irradiation,in the POP. In this work, Resazurin (Rz) ink was utilized as an indicator to examine the photocatalytic activity and self-cleaning performance of POP–BiF3(0%), POP–BiF3(1%), POP–BiF3(5%), and POP–BiF3(10%) composite pellets. In addition to the digital photographic method, the UV–visible absorption technique was adopted to quantify the rate of the de-colorization of the Rz ink, which is a direct measure of comparative photocatalytic performance of samples.

Bi2O3 nano-flakes as a cost-effective antibacterial agent

Bismuth oxide is an important bismuth compound having applications in electronics, photo-catalysis and medicine. At the nanoscale, bismuth oxide experiences a variety of new physico-chemical properties because of its increased surface to volume ratio leading to potentially new applications. In this manuscript, we report for the very first time the synthesis of bismuth oxide (Bi₂O₃) nano-flakes by pulsed laser ablation in liquids without any external assistance (no acoustic, electric field, or magnetic field). The synthesis was performed by irradiating, pure bismuth needles immerged in de-ionized water, at very high fluence ∼160 J cm^-2 in order to be highly selective and only promote the growth of two-dimensional structures. The x- and y-dimensions of the flakes were around 1 μm in size while their thickness was 47.0 ± 12.7 nm as confirmed by AFM analysis. The flakes were confirmed to be α- and γ-Bi₂O₃ by SAED and Raman spectroscopy. By using this mixture of flakes, we demonstrated that the nanostructures can be used as antimicrobial agents, achieving a complete inhibition of Gram positive (MSRA) and Gram negative bacteria (MDR-EC) at low concentration, ∼50 ppm.

Secondary Phosphine Oxide Functionalized Gold Clusters and Their Application in Photoelectrocatalytic Hydrogenation Reactions

Ligands in ligand-protected metal clusters play a crucial role, not only because of their interaction with the metal core, but also because of the functionality they provide to the cluster. Here, we report the utilization of secondary phosphine oxide (SPO), as a new family of functional ligands, for the preparation of an undecagold cluster Au11-SPO. Different from the commonly used phosphine ligand (i.e., triphenylphosphine, TPP), the SPOs in Au11-SPO work as electron-withdrawing anionic ligands. While coordinating to gold via the phosphorus atom, the SPO ligand keeps its O atom available to act as a nucleophile. Upon photoexcitation, the clusters are found to inject holes into p-type semiconductors (here, bismuth oxide is used as a model), sensitizing the p-type semiconductor in a different way compared to the photosensitization of a n-type semiconductor. Furthermore, the Au11-SPO/Bi₂O₃ photocathode exhibits a much higher activity toward the hydrogenation of benzaldehyde than a TPP-protected Au₁₁-sensitized Bi₂O₃ photocathode. Control experiments and density functional theory studies point to the crucial role of the cooperation between gold and the SPO ligands on the selectivity toward the hydrogenation of the C═O group in benzaldehyde.

Removal of elemental mercury by photocatalytic oxidation over La2O3/Bi2O3 composite

La₂O₃/Bi₂O₃ photocatalysts were prepared by impregnation of Bi₂O₃ with an aqueous solution of lanthanum precursor followed by calcination at different temperatures. The composite materials were used for the first time for the photocatalytic removal of Hg⁰ from a simulated flue gas under UV light irradiation. The results showed that the sample containing 6 wt.% La₂O₃ and calcined at 500°C has the highest dispersion of the active sites, which was promoted by the strong interaction with the support (i.e., the formation of Bi-O-La species). Since they are fully accessible on the surface, the material also exhibits excellent optical properties while the heterojunction formed in La₂O₃/Bi₂O₃ promotes the separation and migration of photoelectron-hole pairs and thus Hg⁰ oxidation efficiency is enhanced. The effects of the various factors (e.g., the reaction temperature and composition of the simulated flue gas (i.e., O₂, NO, H₂O, and SO₂)) on the efficiency of the Hg⁰ photocatalytic oxidation were investigated. The results demonstrated that O₂ and SO₂ enhanced the efficiency of the reaction while the reaction temperature, NO, and H₂O had an inhibitory effect.

Bi metal/oxygen-deficient BiO2-x with tetrahedral morphology and high photocatalytic activity

Vacancy-rich materials with high photocatalytic activity are of great interest for pollutants removal and play a significant role in green chemistry. Herein, we successfully synthesized Bi/BiO_2-x composite through hydrothermal route. In this case, the surface plasmon resonance effect of Bi and oxygen vacancies of BiO_2-x collectively increase the removal rate of pollutants. More importantly, the Bi/BiO_2-x composites have enhanced activity in the degradation of RhB, MO, BPA and CIP, and the reduction of Cr(VI) and PNA. Besides, an enhanced photocatalytic activity is due to the main reactive species of ·[Formula: see text] and h⁺ that is confirmed by trapping experiments and ESR analyses. The electronic structure and visible light harvesting of photocatalysts were measured and also theoretically calculated by using density functional theory and finite difference time domain calculations, DRS, VB x-ray photoelectron spectroscopy and Mott-Schottky plots, which allowed to propose a possible photocatalytic mechanism for the degradation process.

Highly efficient adhesion and inactivation of Escherichia coli on visible-light-driven amino-functionalized BiOBr hybrids

Amino groups are successfully introduced on the surface of BiOBr nanosheets through a facile ammonia functionalization method. The surface morphology of the modified BiOBr hybrids varies on the concentration of applied ammonia solution. The active {001}-facet-exposed feature of nanosheets is well retained after amino-functionalization. With generation of small Bi₂O₄ nanoparticles on the surface of BiOBr nanosheets, the light adsorption of hybrids gradually shifts to the near infrared range. Compared to pure BiOBr with negligible activity, BOB10 hybrids exhibit superior photocatalytic activity for bacterial inactivation, with 7-log cells reduction in 40 min under LED irradiation. Amino functionalization endows BOB10 hybrids excellent adhesion capability towards surface negatively-charged bacterium Escherichia coli, which can significantly shortened access distance of the predominant •O₂^- and h⁺ guaranteeing their inactivation ability on cells membrane, thus leading to remarkable bacterial inactivation performance.

Direct electrospinning preparation of Z-scheme mixed-crystal Bi2O3/g-C3N4 composite photocatalysts with enhanced visible-light photocatalytic activity

A novel Z-scheme mixed-crystal Bi₂O₃/g-C₃N₄ composite photocatalyst was successfully prepared by a simple electrospinning–calcination approach.

Recent Progress, Challenges, and Prospects in Two-Dimensional Photo-Catalyst Materials and Environmental Remediation

The successful photo-catalyst library gives significant information on feature that affects photo-catalytic performance and proposes new materials. Competency is considerably significant to form multi-functional photo-catalysts with flexible characteristics. Since recently, two-dimensional materials (2DMs) gained much attention from researchers, due to their unique thickness-dependent uses, mainly for photo-catalytic, outstanding chemical and physical properties. Photo-catalytic water splitting and hydrogen (H2) evolution by plentiful compounds as electron (e-) donors is estimated to participate in constructing clean method for solar H2-formation. Heterogeneous photo-catalysis received much research attention caused by their applications to tackle numerous energy and environmental issues. This broad review explains progress regarding 2DMs, significance in structure, and catalytic results. We will discuss in detail current progresses of approaches for adjusting 2DMs-based photo-catalysts to assess their photo-activity including doping, hetero-structure scheme, and functional formation assembly. Suggested plans, e.g., doping and sensitization of semiconducting 2DMs, increasing electrical conductance, improving catalytic active sites, strengthening interface coupling in semiconductors (SCs) 2DMs, forming nano-structures, building multi-junction nano-composites, increasing photo-stability of SCs, and using combined results of adapted approaches, are summed up. Hence, to further improve 2DMs photo-catalyst properties, hetero-structure design-based 2DMs' photo-catalyst basic mechanism is also reviewed.

Influence of TiO2 Morphology and Crystallinity on Visible-Light Photocatalytic Activity of TiO2-Bi2O3 Composite in AOPs

Solution combustion synthesis was used to produce a junction between different TiO2 supports (anatase TiO2 nanorods (TNR) and nanoparticles (TNP) and TiO2 with anatase core and amorphous shell (a-TNR)) and narrow bandgap (BG) semiconductor β-Bi2O3. β-Bi2O3 acted as a visible-light photosensitizer and enabled us to carry out photocatalytic oxidation of water dissolved bisphenol A (BPA) with TiO2 based catalysts under visible-light illumination. Heterojunction between TiO2 and β-Bi2O3 in TNR + Bi and TNP + Bi composites enables the transfer of visible-light generated holes from the β-Bi2O3 valence band (VB) to the upper lying TiO2 VB. A p–n junction, established upon close chemical contact between TiO2 and β-Bi2O3, enables the transfer of visible-light generated electrons in the β-Bi2O3 conduction band (CB) to the TiO2 CB. In TNR + Bi and a-TNR + Bi composites, the supplied heat energy during the synthesis of samples was not sufficient to completely transform (BiO)2CO3 into β-Bi2O3. A p–n junction between (BiO)2CO3 and β-Bi2O3 enables the transfer of electrons generated by β-Bi2O3 to (BiO)2CO3. Hindered charge carrier recombination originating from the crystallinity of TiO2 is a more important factor in the overall kinetics of BPA degradation than high specific surface area of the amorphous TiO2 and reduction/oxidation of surface adsorbed substrates.

Oxygen vacancy rich Bi2O4-Bi4O7-BiO2-x composites for UV-vis-NIR activated high efficient photocatalytic degradation of bisphenol A

To fully utilize the solar light, photocatalyst with broad spectrum response from UV to near-infrared (NIR) is desirable. In this work, ternary mixed valent Bi₂O₄-Bi₄O₇-BiO_2-x with rich oxygen vacancy has been synthesized through one-pot hydrothermal treatment of NaBiO₃. The results showed that through adjusting the hydrothermal conditions, oxygen vacancy-rich Bi₂O₄-Bi₄O₇-BiO_2-x nanocomposites with much higher efficiency than single or mixed bismuth oxides (Bi₂O₄, Bi₄O₇, BiO_2-x and Bi₄O₇-BiO_2-x,) can be synthesized for photocatalytic degradation of bisphenol A (BPA) under UV, visible, and NIR light irradiation. In addition, the liquid chromatography-mass spectrometer (LC-MS) characterization demonstrated that BPA was oxidized to 4-isopropenyphenol first and the rings were opened sequentially under NIR light irradiation. Further detection of reactive species indicated that holes, O₂^-, and OH were the main oxidizing species in the degradation system. The experimental observations and density functional theory (DFT) calculations suggested that both type-II and the Z-scheme charge transfer with oxygen vacancies as electrons and holes mediators were formed at the interfaces of Bi₂O₄, Bi₄O₇, and BiO_2-x, resulting in a very efficient separation of photogenerated charge carriers in the composite. This work adds to the growing potential of mixed valent bismuth oxides based photocatalysts and is expected to accelerate the pace of the development of new-generation photocatalysts with high efficiency utilizing full-spectrum solar light.

Investigating the efficiency of α-Bismuth zinc oxide heterostructure composite/UV-LED in methylene blue dye removal and evaluation of its antimicrobial activity

Heterostructured α-Bismuth zinc oxide (α-Bi₂O₃-ZnO) photocatalyst was fabricated by a facile and cost-effective, ultrasound assisted chemical precipitation method followed by hydrothermal growth technique. As synthesized α-Bi₂O₃-ZnO photocatalyst showed enhanced photocatalytic performance for the MB dye degradation in contrast to pure ZnO and α-Bi₂O₃. Light emitting diodes (UV-LED) were used in the experimental setup, which has several advantages over conventional lamps like wavelength selectivity, high efficacy, less power consumption, long lifespan, no disposal problem, no warming-up time, compactness, easy and economic installation. XRD study confirmed the presence of both the lattice phases i.e. monoclinic and hexagonal wurtzite phase corresponding to α-Bi₂O₃ and ZnO in the α-Bi₂O₃-ZnO composite photocatalyst. FESEM images showed that α-Bi₂O₃-ZnO photocatalyst is composed of dumbbell like structures of ZnO with breadth ranging 4-5 μm and length ranging from 10 to 11 μm respectively. It was observed that α-Bi₂O₃ nanoparticles were attached on the ZnO surface and were in contact with each other. Low recombination rate of photo-induced electron-hole pairs, due to the migration of electrons and holes between the photocatalyst could be responsible for the 100% photocatalytic efficiency of α-Bi₂O₃-ZnO composite. In addition, photocatalyst was also observed to show the excellent antimicrobial activity with 1.5 cm zone of inhibition for 1 mg L^-1 dose, against the human pathogenic bacteria (S. aureus).

Bioactive tri/dicalcium silicate cements for treatment of pulpal and periapical tissues

Over 2500 articles and 200 reviews have been published on the bioactive tri/dicalcium silicate dental materials. The indications have expanded since their introduction in the 1990s from endodontic restorative and pulpal treatments to endodontic sealing and obturation. Bioactive ceramics, based on tri/dicalcium silicate cements, are now an indispensable part of the contemporary dental armamentarium for specialists including endodontists, pediatric dentists, oral surgeons andfor general dentists. This review emphasizes research on how these materials have conformed to international standards for dental materials ranging from biocompatibility (ISO 7405) to conformance as root canal sealers (ISO 6876). Potential future developments of alternative hydraulic materials were included. This review provides accurate materials science information on these important materials. STATEMENT OF SIGNIFICANCE: The broadening indications and the proliferation of tri/dicalcium silicate-based products make this relatively new dental material important for all dentists and biomaterials scientists. Presenting the variations in compositions, properties, indications and clinical performance enable clinicians to choose the material most suitable for their cases. Researchers may expand their bioactive investigations to further validate and improve materials and outcomes.

Facile in situ generation of bismuth tungstate nanosheet-multiwalled carbon nanotube composite as unconventional affinity material for quartz crystal microbalance detection of antibiotics

Overuse and thus a constant presence of antibiotics leads to various environmental hazards and health risks. Thus, accurate sensors are required to determine their presence. In this work, we present a mass-sensitive sensor for the detection of rifampicin. We chose this molecule as it is an important antibiotic for tuberculosis, one of the leading causes of deaths worldwide. Herein, we have prepared a carbon nanotube reinforced with bismuth tungstate nanocomposite material in a well-defined nanosheet morphology using a facile in situ synthesis mechanism. Morphological characterization revealed the presence of bismuth tungstate in the form of square nanosheets embedded in the intricate network of carbon nanotubes, resulting in higher surface roughness of the nanocomposite. The synergy of the composite, so formed, manifested a high affinity for rifampicin as compared to the individual components of the composite. The developed sensor possessed a high sensitivity toward rifampicin with a detection limit of 0.16 μM and excellent specificity, as compared to rifabutin and rifapentine. Furthermore, the sensor yielded statistically good recoveries for the monitoring of rifampicin in human urine samples. This work opens up a new horizon for the exploration of unconventional nanomaterials bearing different morphologies for the detection of pharmaceuticals.

Recent Advances and Applications of Semiconductor Photocatalytic Technology

Along with the development of industry and the improvement of people’s living standards, peoples’ demand on resources has greatly increased, causing energy crises and environmental pollution. In recent years, photocatalytic technology has shown great potential as a low-cost, environmentally-friendly, and sustainable technology, and it has become a hot research topic. However, current photocatalytic technology cannot meet industrial requirements. The biggest challenge in the industrialization of photocatalyst technology is the development of an ideal photocatalyst, which should possess four features, including a high photocatalytic efficiency, a large specific surface area, a full utilization of sunlight, and recyclability. In this review, starting from the photocatalytic reaction mechanism and the preparation of the photocatalyst, we review the classification of current photocatalysts and the methods for improving photocatalytic performance; we also further discuss the potential industrial usage of photocatalytic technology. This review also aims to provide basic and comprehensive information on the industrialization of photocatalysis technology.

Highly effective and green microwave catalytic oxidation degradation of nitrophenols over Bi2O2CO3 based composites without extra chemical additives

A novel treatment technology of microwave catalytic oxidation degradation (MCOD) for nitrophenols (NPs) wastewater over green catalysts of gC₃N₄Bi₂O₂CO₃ and SiCBi₂O₂CO₃ was developed. This process is eco-friendly because the only used Bi₂O₂CO₃ is non-toxic (which can be used as stomach medicine), and no heavy metal pollution exists in g-C₃N₄ and SiC. The results show that these Bi₂O₂CO₃ based composites exhibited superior catalytic activity for the degradation of para-NP, as well as ortho-NP, with optimal removal ratio of 98.96%. In addition, the proportion of Bi₂O₂CO₃ and irradiation time were the key parameters that had greatly influenced the degradation performance. Moreover, O₂^- was confirmed to be primary contributor for the degradation, which was different from our previous work that OH was the main specie in carbon loaded metal oxide system. That is to say, the type of oxidative specie may be controlled by the type of catalyst system. Besides, separation and transfer efficiency of the charge carriers could be enhanced by the heterojunctions fabricated in the band structures of the composites. This work not only demonstrated that the Bi₂O₂CO₃ based composites coupled with MW irradiation can generate reactive oxidative species(ROS) which can degrade NPs high-effectively, but also developed a new and green idea for treating refractory industrial wastewater.

Structures and energetics of low-index stoichiometric BiPO4surfaces

Four low-index surfaces of monazite BiPO₄in the Wulff shape are investigated.

Deep Oxidation of NO by a Hybrid System of Plasma-N-Type Semiconductors: High-Energy Electron-Activated "Pseudo Photocatalysis" Behavior

A "pseudo photocatalysis" process, being initiated between plasma and N-type semiconductors in the absence of light, was investigated for NO removal for the first time via dynamic probing of reaction processes by FT-IR spectra. It was demonstrated that N-type semiconductor catalysts could be activated to produce electron-hole (e^--h⁺) pairs by the collision of high-energy electrons (e*) from plasma. Due to the synergy of plasma and N-type semiconductors, major changes were noted in the conversion pathways and products. NO can be directly converted to NO₂^- and NO₃^- instead of toxic NO₂, owing to the formation of O₂^- and ·OH present in catalysts. New species like O₃ or ·O may be generated from the interaction between catalyst-induced species and radicals in plasma at a higher SIE, leading to deep oxidation of existing NO₂ to N₂O₅. Experiments with added trapping agents confirmed the contribution of e^- and h⁺ from catalysts. A series of possible reactions were proposed to describe reaction pathways and the mechanism of this synergistic effect. We established a novel system and realized an e*-activated "pseudo photocatalysis" behavior, facilitating the deep degradation of NO. We expect that this new strategy would provide a new idea for in-depth analysis of plasma-activated catalysis phenomenon.

Time-dependent synthesis of BiO2-x/Bi composites with efficient visible-light induced photocatalytic activity

A series of BiO_2-x/Bi nanocomposites were prepared via a time-dependent aqueous method, with the induction of lactic acid. The interaction of Bi³⁺ and C₃H₆O₃ in stock solution determined the formation of nonstoichiometric BiO_2-x as the precursor, subsequent reduction reaction at acid circumstance (pH = 3) produced combined composition of BiO_2-x nanosheets and Bi particles. Multiple valence states of Bi element (Bi⁰, Bi³⁺ and Bi⁵⁺) in the composite sample make it possible to manipulate the band structures of photocatalysts. The BiO_2-x/Bi composites with appropriate composition exhibited superior photocatalytic performance in the degradation of colorless bisphenol A (BPA) under visible-light irradiation. The O₂^- and OH radicals were detected as valid active species in the degradation process from ESR analysis. The photocatalytic mechanism over BiO_2-x/Bi composites was proposed on the consideration of electron-hole separation and the interfacial charge transfer.

Phase control synthesis of α, β and α/β Bi2O3 hetero-junction with enhanced and synergistic photocatalytic activity on degradation of toxic dye, Rhodamine-B under natural sunlight

Nano particles of a few α/β Bi₂O₃ hetero-junctions of various compositions synthesized by one- pot hydrothermal method, exhibit exceptional and synergistic photo-catalytic activity for the degradation of Rhodamine-B in aqueous solution under natural sunlight. Pure α and pure β Bi₂O₃ are also synthesized by control post heating of synthesized hetero-junction. The nano-materials were characterized by diffraction (XRD), microscopic and spectroscopic techniques. The XRD reveals α-β phase hetero-junctions of Bi₂O₃ are made of α-Bi₂O₃ and β-Bi₂O₃ with average dimensions within 13-113 and 5-71 nm respectively and having band gap range of 2.4- 2.9 eV. The spectrophotometrically determined % degradation of the dye and associated rate constant on the best hetero-junction are increased by 4.5(/2.1) and 3.3(/1.2) times than these on pure α (/β). The effects of operational parameters and trapping agents have been analyzed. The maximum removal of the dye was achieved up to 99.6% in 3 h using 0.5 g/L photo-catalyst at pH 3. The reusability test shows that the photo-catalytic activity is retained excellently due to change in chemical nature of the catalyst from α -Bi₂O₃ to β-Bi₂O_3, Bi₂O₂CO₃ and BiOCl. A suitable mechanism is proposed.

Electronic Structure of Visible Light-Driven Photocatalyst δ-Bi11VO19 Nanoparticles Synthesized by Thermal Plasma

Size confinement for tailoring of electronic structures can in principle be explored for enhancement of photocatalytic properties. In the present work, vanadium-doped bismuth oxide nanoparticles, with an average particle size of 36 nm, are synthesized for the first time, using the thermal plasma method, in large scale with high yield to explore for photocatalytic applications. The electronic and crystallographic structures of the sample are studied experimentally and theoretically. Systematic investigations of the electronic structure of the fluorite type cubic phase of Bi₁₁VO₁₉ nanoparticles are reported for the first time. Enhancement is observed in the photocatalytic activity as compared to other delta phases of bismuth vanadate. The valence band is found to comprise mainly of O 2p states, whereas the conduction band arises from V 3d states giving rise to a band gap value of 2.26 eV. Absence of excess O in δ-Bi₂O₃ results in shrinking of the band gap because of O 2p, Bi 6s and 6p states from the surrounding atoms at doping sites. Bi₁₁VO₁₉ nanoparticles show an efficient visible light absorption and exhibit excellent photodegradation properties of methylene blue solution under visible light irradiation.