Enhanced photocatalytic dye degradation and hydrogen production ability of Bi25FeO40-rGO nanocomposite and mechanism insight

Recent advances in designing and developing efficient sillenite-based materials for photocatalytic applications

Sillenite materials have been the subject of intense investigation for recent years due to their unique characteristics. They possess a distinct structure with space group I23, allowing them to exhibit distinctive features, such as an electronic structure ideal for certain applications such as photocatalysis. The present research delves into the structure, synthesis, and properties of sillenites, highlighting their suitability for photocatalysis. It explores also advanced engineering strategies for designing sillenite-based photocatalysts, including heterojunction formation, morphology modification, doping, and hybrid processes. Each strategy offers advantages and limitations that are critically discussed. The review then lists and discusses the photocatalytic performance of various sillenite-based systems recently developed for common applications, such as removing hazardous organic and inorganic contaminants, and even infrequent applications, such as microbial inactivation, H2 generation, CO2 reduction and N2 fixation. Finally, valuable insights and suggestions are put forward for future research directions in the field of sillenite-based photocatalysis. This comprehensive overview would provide a valuable resource for the development of efficient photocatalytic systems to address environmental and energy challenges.

Promising photocatalytic activity of Ag2SO4-modified BiOCl/BFO heterostructures under visible light

In this work, a simple co-precipitation method for the preparation of Ag2SO4@BiOCl@Bi25FeO40 (BFO) was developed. Ultraviolet-visible spectrophotometric analysis, X-ray diffraction patterns, Fourier transform infrared spectroscopy (FT-IR), and scanning field emission electron microscopy (FESEM) were performed to characterize the newly synthesized nanocomposite. In addition, the EDX method was used to determine the actual material quantities. The synthesized samples of Bi25FeO40 and Ag2SO4 Bi25FeO40 showed high absorption in the visible region. Furthermore, the photocatalytic activity was significantly improved by the addition of Ag2SO4. The results showed photcatalytic efficiency was reached to about 99% with 0.01 g of Ag2SO4@BiOCl@Bi25FeO40 in pH 4 under visible light. The isoelectric pH of the photocatalayst was obtained 5. Also, kinetic study showed a first order mechanism for photodegradation. Moreover, a mechanistic study was proposed for the newly synthesized heterostructures.

Using NIR irradiation and magnetic bismuth ferrite microparticles to accelerate the removal of polystyrene microparticles from the drinking water

Magnetic bismuth ferrite (BiFO) microparticles were employed for the first time for the removal of polystyrene (PS) nano/microplastics from the drinking water. BiFO is formed by porous agglomerates with sizes of 5-11 μm, while the PS nano/microparticles have sizes in the range of 70-11000 nm. X-ray diffraction studies demonstrated that the BiFO microparticles are composed of BiFeO3/Bi25FeO40 (the content of Bi25FeO40 is ≈ 8.6%). Drinking water was contaminated with PS nano/microparticles (1 g L-1) and BiFO microparticles were also added to the contaminated water. Later, the mixture of PS-particles + BiFO was irradiated with NIR light (980 nm). Consequently, PS nano/microparticles melted on the BiFO microparticles due to the excessive heating on their surface. At the same time, the NIR (near infrared) light generated oxidizing agents (∙OH and h+), which degraded the by-products formed during the photocatalytic degradation of PS nano/microparticles. Subsequently, the NIR irradiation was stopped, and a Neodymium magnet was utilized to separate the BiFO microparticles from the water. This last procedure also permitted the removal of PS nano/microparticles by physical adsorption. Zeta potential measurements demonstrated that the BiFO surface was positively charged, allowing the removal of the negatively charged PS nano/microparticles by electrostatic attraction. The combination of the photocatalytic process and the physical adsorption permitted a complete removal of PS nano/microparticles after only 90 min as well as a high mineralization of by-products (≈95.5% as confirmed by the total organic carbon measurements). We estimate that ≈23.6% of the PS nano/microparticles were eliminated by photocatalysis and the rest of PS particles (≈76.4%) by physical adsorption. An outstanding adsorption capacity of 195.5 mg g-1 was obtained after the magnetic separation of the BiFO microparticles from the water. Hence, the results of this research demonstrated that using photocatalysis + physical-adsorption is a feasible strategy to quickly remove microplastic contaminants from the water.

A review on degradation of organic dyes by using metal oxide semiconductors

The discharge of organic dye pollutants in natural water bodies has put forward a big challenge of providing clean water to a large part of the population. As the population is increasing with time, only underground water is not sufficient to complete the water requirements of everyone everywhere. Purification of wastewater and its reuse is the only way to fulfill the water needs. Nanotechnology has been used very efficiently for wastewater treatment via photocatalytic degradation of dye molecules. In the past few years, a lot of investigations have been done to enhance the photocatalytic activity of metal oxide semiconductors for water purification. In this review, we have discussed the different methods of synthesis of various metal oxide semiconductor nanoparticles, energy band gap, their role as efficient photocatalysts, radiations used for photocatalytic reactions, and their degradation efficiency to degrade the dye pollutants. We have also discussed the nanocomposites of metal oxide with graphene. These nanocomposites have been utilized as the efficient photocatalyst due to unique characteristics of graphene such as extended range of light absorption, separation of charges, and high capacity of adsorption of the dye pollutants.

Magnesium Bismuth Ferrite Nitrogen-Doped Carbon Nanomagnetic Perovskite: Synthesis and Characterization as a High-Performance Electrode in a Supercapacitor for Energy Storage

Bismuth ferrite (BiFeO₃) is regarded as an important ABO₃ perovskite in the areas of energy storage and electronics. A high-performance novel MgBiFeO₃-NC nanomagnetic composite (MBFO-NC) electrode was prepared using a perovskite ABO₃-inspired method as a supercapacitor for energy storage. The electrochemical behavior of the perovskite BiFeO₃ has been enhanced by magnesium ion doping in the basic aquatic electrolyte as the A-site. H₂-TPR revealed that the doping of Mg²⁺ ions at the Bi³⁺ sites minimizes the oxygen vacancy content and improves the electrochemical characteristics of MgBiFeO₃-NC. Various techniques were used to confirm the phase, structure, surface, and magnetic properties of the MBFO-NC electrode. The prepared sample showed an enhanced mantic performance and specific area with an average nanoparticle size of ∼15 nm. The electrochemical behavior of the three-electrode system was shown by cyclic voltammetry to have a significant specific capacity of 2079.44 F/g at 30 mV/s in 5 M KOH electrolyte. GCD analysis at a 5 A/g current density also showed an enhanced capacity improvement of 2159.88 F/g, which is 3.4× higher than that of pristine BiFeO₃. At the power density of 5284.83 W/kg, the constructed MBFO-NC//MBFO-NC symmetric cell showed an exceptional energy density of 730.04 W h/kg. The MBFO-NC//MBFO-NC symmetric cell was employed as a direct practical application of the electrode material to entirely brighten the laboratory panel, which had 31 LEDs. This work proposes the utilization of duplicate cell electrodes made of MBFO-NC//MBFO-NC in portable devices for daily use.

Magnetized inulin by Fe3O4 as a bio-nano adsorbent for treating water contaminated with methyl orange and crystal violet dyes

Current work focuses on fabricating a new bio-nano adsorbent of Fe₃O₄@inulin nanocomposite via an in-situ co-precipitation procedure to adsorb methyl orange (MO) and crystal violet (CV) dyes from aqueous solutions. Different physical characterization analyses verified the successful fabrication of the magnetic nanocomposite. The adsorbent performance in dye removal was evaluated by varying initial dye concentration, adsorbent dosage, pH and temperature in 5110 mg/L, 0.10.8 g/L, 111 and 283-338 K, respectively. Due to the pH of zero point of charge and intrinsic properties of dyes, the optimum pHs were 5 and 7 for MO and CV adsorption, respectively. The correlation of coefficient (R²) and reduced chi-squared value were the criteria in order to select the best isotherm and kinetics models. The Langmuir model illustrated a better fit for the adsorption data for both dyes, demonstrating the maximum adsorption capacity of 276.26 and 223.57 mg/g at 338 K for MO and CV, respectively. As well, the pseudo-second-order model showed a better fitness for kinetics data compared to the pseudo-first-order and Elovich models. The thermodynamic parameters exhibited that the dye adsorption process is endothermic and spontaneous, which supported the enhanced adsorption rate by increasing temperature. Moreover, the nanocomposite presented outstanding capacity and stability after 6 successive cycles by retaining more than 87% of its initial dye removal efficiency. Overall, the magnetized inulin with Fe₃O₄ could be a competent adsorbent for eliminating anionic and cationic dyes from water.

Simple Low Temperature Technique to Synthesize Sillenite Bismuth Ferrite with Promising Photocatalytic Performance

Sillenite-type members of the bismuth ferrite family have demonstrated outstanding potential as novel photocatalysts in environmental remediation such as organic pollutant degradation. This investigation has developed a low temperature one-step hydrothermal technique to fabricate sillenite bismuth ferrite Bi₂₅FeO₄₀ (S-BFO) via co-substitution of 10% Gd and 10% Cr in Bi and Fe sites of BiFeO₃, respectively, by tuning hydrothermal reaction temperatures. Rietveld refined X-ray diffraction patterns of the as-synthesized powder materials revealed the formation of S-BFO at a reaction temperature of 120-160 °C. A further increase in the reaction temperature destroyed the desired sillenite structure. With the increase in the reaction temperature from 120 to 160 °C, the morphology of S-BFO gradually changed from irregular shape to spherical powder nanomaterials. The high-resolution TEM imaging demonstrated the polycrystalline nature of the S-BFO(160) nanopowders synthesized at 160 °C. The as-synthesized samples exhibited considerably high absorbance in the visible region of the solar spectrum, with the lowest band gap of 1.76 eV for the sample S-BFO(160). Interestingly, S-BFO(160) exhibited the highest photocatalytic performance under solar irradiation, toward the degradation of rhodamine B and methylene blue dyes owing to homogeneous phase distribution, regular powder-like morphology, lowest band gap, and quenching of electron-hole pair recombination. The photodegradation of a colorless organic pollutant (ciprofloxacin) was also examined to ensure that the degradation is photocatalytic and not dye-sensitized. In summary, Gd and Cr co-doping have proven to be a compelling energy-saving and low-cost approach for the formulation of sillenite-phase bismuth ferrite with promising photocatalytic activity.

Structural, Optical and Photocatalytic Activity of Multi-heterojunction Bi2O3/Bi2O2CO3/(BiO)4CO3(OH)2 Nanoflakes Synthesized via Submerged DC Electrical Discharge in Urea Solution

In this research, a novel ternary multi-heterojunction Bi₂O₃/Bi₂O₂CO₃/(BiO)₄CO₃(OH)₂ photocatalyst is fabricated via submerged DC electrical arc discharge in urea solution. FT-IR, XRD, EDS and PL results confirm the formation of Bi₂O₃/Bi₂O₂CO₃/(BiO)₄CO₃(OH)₂ multi-heterojunction. Formation of nanoflake morphology is revealed by FE-SEM and TEM images. The optical properties and intense absorption edge of Bi₂O₃/Bi₂O₂CO₃/(BiO)₄CO₃(OH)₂ reveal the proper visible light absorbing ability. The photocatalytic performance of the sample is investigated via the degradation of methylene orange (MeO) and rhodamine B (RB) under visible light irradiation. The photocatalytic activity of Bi₂O₃/Bi₂O₂CO₃/(BiO)₄CO₃(OH)₂ is compared with the synthesized sample in water, Bi₂O₃/Bi/Bi(OH)_3, which exhibits much higher photocatalytic activity. Also, the stable photodegradation efficiency of Bi₂O₃/Bi₂O₂CO₃/(BiO)₄CO₃(OH)₂ after four cycles reveals the long-term stability and reusability of the synthesized photocatalyst. The PL intensity of Bi₂O₃/Bi₂O₂CO₃/(BiO)₄CO₃(OH)₂ shows an improved separation rate of electron-hole pairs and so enhanced photocatalytic performance. The improved photocatalytic activity can be ascribed to the formation of multi-heterojunctions, flake morphology and intrinsic internal electric field (IEF). Multi-heterojunction nanoflakes enhance the absorbance of visible light and facilitate the separation and transport of photogenerated electron holes through large IEF. Our work offers an effective method for the production of innovative bismuth-based photocatalyst with excellent prospects for the degradation of environmental pollutants and light harvesting for renewable energy generation under visible light.

Bismuth Sillenite Crystals as Recent Photocatalysts for Water Treatment and Energy Generation: A Critical Review

Photocatalysis has been widely studied for environmental applications and water treatment as one of the advanced oxidation processes (AOPs). Among semiconductors that have been employed as catalysts in photocatalytic applications, bismuth sillenite crystals have gained a great deal of interest in recent years due to their exceptional characteristics, and to date, several sillenite material systems have been developed and their applications in photoactivity are under study. In this review paper, recent studies on the use of Bi-based sillenites for water treatment have been compiled and discussed. This review also describes the properties of Bi-based sillenite crystals and their advantages in the photocatalytic process. Various strategies used to improve photocatalytic performance are also reviewed and discussed, focusing on the specific advantages and challenges presented by sillenite-based photocatalysts. Furthermore, a critical point of certain bismuth catalysts in the literature that were found to be different from that reported and correspond to the sillenite form has also been reviewed. The effectiveness of some sillenites for environmental applications has been compared, and it has demonstrated that the activity of sillenites varies depending on the metal from which they were produced. Based on the reviewed literature, this review summarizes the current status of work with binary sillenite and provides useful insights for its future development, and it can be suggested that Bismuth sillenite crystals can be promising photocatalysts for water treatment, especially for degrading and reducing organic and inorganic contaminants. Our final review focus will emphasize the prospects and challenges of using those photocatalysts for environmental remediation and renewable energy applications.

Broad Spectral Response Z-Scheme Three-Dimensional Ordered Macroporous Carbon Quantum Dots/TiO2/g-C3N4 Composite for Boosting Photocatalysis

Photocatalytic degradation technology is one of the effective protocols to solve environmental problems. TiO₂ has always been favored for its photostability and low cost. However, the insufficient photocatalytic activity of TiO₂ limits its application due to the severe recombination of photogenerated electrons and holes and a narrow light response range. Therefore, 3DTCN, a TiO₂/g-C₃N₄ composite with a three-dimensional ordered macroporous structure was prepared by a colloidal crystal template technique to form a heterojunction for inhibiting the photogenerated electron-hole recombination. On 3DTCN, carbon quantum dots (CQDs) were loaded by impregnation to obtain x % CQDs/3DTCN with a broad spectral response to light. The physical and chemical properties of samples were investigated by X-ray diffraction, scanning electron microscopy, transmission electron microscopy (TEM), high-resolution-TEM, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, Brunauer-Emmett-Teller analysis, photoluminescence spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy. The photocatalytic activity was evaluated via degrading the rhodamine B (RhB) dye, and the degradation efficiency of 1% CQDs/3DTCN (98%) was found to be much higher than that of 3DTCN (42%) in 80 min under simulated sunlight irradiation. Furthermore, it also possessed excellent durability. Meanwhile, the sample also showed an outstanding photoelectric property. Finally, the proposed mechanism of the composites had been mainly analyzed by density functional theory calculations. This work thus provides an idea to form a 3D structure heterojunction and further improve the photocatalytic activity.

Interfacial engineering in 3D/2D and 1D/2D bismuth ferrite (BiFeO3)/Graphene oxide nanocomposites for the enhanced photocatalytic activities under sunlight

3D-particulate and 1D-fiber structures of multiferroic bismuth ferrite (BiFeO₃/BFO) and their composites with 2D-graphene oxide (GO) have been developed to exploit the different scheme of interfacial engineering as 3D/2D and 1D/2D systems. Particulates and fibers of BFO were developed via sol-gel and electrospinning fabrication approaches respectively and their integration with GO was performed via the ultrasonic-assisted chemical reduction process. The crystalline and phase formation of BiFeO₃ and GO was confirmed from the XRD patterns obtained. The electron microscopic images revealed the characteristic integration of 3D particulates (with average size of 100 nm) and 1D fibers (with diameter of ~150 nm and few μm length) onto the 2D GO layers (thickness of ~27 nm). XPS analysis revealed that the BFO nanostructures have been integrated onto the GO through chemisorptions process, where it indicated that the ultrasonic process engineers the interface through the chemical modification of the surface of these 3D/2D and 1D/2D nanostructures. The photophysical studies such as the impedance and photocurrent measurements showed that the charge separation and recombination resistance is significantly enhanced in the system, which can directly be attributed to the effective interfacial engineering in the developed hetero-morphological composites. The degradation studies against a model pollutant Rhodamine B revealed that the developed nanocomposites exhibit superior photocatalytic activity via the effective generation of OH radicals as confirmed by the radical analysis studies (100% degradation in 150 and 90 min for 15% GO/BFO particulate and fiber composites, respectively). The developed system also demonstrated excellent photocatalytic recyclability, indicated their enhanced stability.

Designing a novel visible-light-driven heterostructure Ni-ZnO/S-g-C3N4 photocatalyst for coloured pollutant degradation

In this study, photocorrosion of ZnO is inhibited by doping Ni in the ZnO nanostructure and electron-hole recombination was solved by forming a heterostructure with S-g-C₃N₄. Ni is doped into ZnO NPs from 0 to 10% (w/w). Among the Ni-decorated ZnO NPs, 4% Ni-doped ZnO NPs (4NZO) showed the best performance. So, 4% Ni-ZnO was used to form heterostructure NCs with S-g-C₃N₄. NZO NPs were formed by the wet co-precipitation route by varying the weight percentage of Ni (0-10% w/w). Methylene blue (MB) was used as a model dye for photocatalytic studies. For the preparation of the 4NZO-x-SCN nanocomposite, 4NZO NPs were formed in situ in the presence of various concentrations of S-g-C₃N₄ (10-50% (w/w)) by using the coprecipitation route. The electron spin resonance (ESR) and radical scavenger studies showed that O₂ ^- and OH free radicals were the main reactive species that were responsible for MB photodegradation.

Carbon Dot-Doped Titanium Dioxide Sheets for the Efficient Photocatalytic Performance of Refractory Pollutants

Broad solar light harvesting and fast photoinduced electron-hole migration are two critical factors for the catalytic capacity of photocatalytic system. In this study, novel visible light-driven carbon dot-TiO₂ nanosheet (CD-TN) photocatalysts are successfully prepared by loading CDs on the surface of TNs through the hydrothermal method. The microstructure, chemical components, and optical properties of the prepared samples are characterized via X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, UV-visible diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy analysis. Congo red (CR), rhodamine B (RhB), and tetracycline (TC) are selected as pollutants to assess the catalytic performance of CD-TNs. As expected, the removal efficiencies of CD-TNs for CR, RhB, and TC are 94.6% (120 min), 97.2% (150 min), and 96.1% (60 min), respectively, obviously higher than that of pure TNs. The enhanced degradation efficiency of CD-TNs is predominantly ascribed to the merits of CDs (excellent up-conversion property and electron transfer property). Moreover, according to the several degradation cycles, CD-TNs possess the excellent stability, having removed 93.3% of CR after 120 min irradiation.

Effective Strategies, Mechanisms, and Photocatalytic Efficiency of Semiconductor Nanomaterials Incorporating rGO for Environmental Contaminant Degradation

The water pollution problems severely affect the natural water resources due to the large disposal of dyes, heavy metals, antibiotics, and pesticides. Advanced oxidation processes (AOP) have been developed using semiconductor nanomaterials as photocatalysts for water treatment as an essential strategy to minimize environmental pollution. Significant research efforts have been dedicated over the past few years to enhancing the photocatalytic efficiencies of semiconductor nanomaterials. Graphene-based composites created by integrating reduced graphene oxide (rGO) into various semiconductor nanomaterials enable the unique characteristics of graphene, such as the extended range of light absorption, the separation of charges, and the high capacity of adsorption of pollutants. Therefore, rGO-based composites improve the overall visible-light photocatalytic efficiency and lead to a new pathway for high-performance photocatalysts’ potential applications. This brief review illustrates the strategies of combining rGO with various semiconductor nanomaterials and focuses primarily on modification and efficiency towards environmental contaminants.

Enhanced UV-Vis Photodegradation of Nanocomposite Reduced Graphene Oxide/Ferrite Nanofiber Films Prepared by Laser-Assisted Evaporation

Nanocomposite films of rGO/MFeO3 (M = Bi, La) nanofibers were grown by matrix-assisted pulsed laser evaporation of frozen target dispersions containing GO platelets and MFeO3 nanofibers. Electron microscopy investigations confirmed the successful fabrication of MFeO3 nanofibers by electrospinning Part of nanofibers were broken into shorter units, and spherical nanoparticles were formed during laser processing. Numerical simulations were performed in order to estimate the maximum temperature values reached by the nanofibers during laser irradiation. X-ray diffraction analyses revealed the formation of perovskite MFeO3 phase, whereas secondary phases of BiFeO3 could not be completely avoided, due to the high volatility of bismuth. XPS measurements disclosed the presence of metallic bismuth and Fe2+ for BiFeO3, whereas La2(CO3)3 and Fe2+ were observed in case of LaFeO3 nanofibers. High photocatalytic efficiencies for the degradation of methyl orange were achieved for nanocomposite films, both under UV and visible light irradiation conditions. Degradation values of up to 70% after 400 min irradiation were obtained for rGO/LaFeO3 nanocomposite thin layers, with weights below 10 µg, rGO platelets acting as reservoirs for photoelectrons generated at the surface of MFeO3.

A 3D nitrogen-doped graphene aerogel for enhanced visible-light photocatalytic pollutant degradation and hydrogen evolution

The synergistic effect of the 3D structure and N-doping explain the high surface area of 536 m² g⁻¹ and excellent photocatalytic activity.

In situ construction of hybrid MnO2@GO heterostructures for enhanced visible light photocatalytic, anti-inflammatory and anti-oxidant activity

Hybrid MnO₂@GO heterostructure nano-composites with enhanced visible light photocatalytic, anti-oxidant and anti-inflammatory activity.

Pt nanoparticles decorated heterostructured g-C3N4/Bi2MoO6 microplates with highly enhanced photocatalytic activities under visible light

Exploring an efficient and photostable heterostructured photocatalyst is a pivotal scientific topic for worldwide energy and environmental concerns. Herein, we reported that Pt decorated g-C₃N₄/Bi₂MoO₆ heterostructured composites with enhanced photocatalytic performance under visible light were simply synthesized by one-step hydrothermal method for methylene blue (MB) dye degradation. Results revealed that the synthetic Pt decorated g-C₃N₄/Bi₂MoO₆ composites with Bi₂MoO₆ contents of 20 wt.% (Pt@CN/20%BMO) presented the highest photocatalytic activity, exhibiting 7 and 18 times higher reactivity than the pure g-C₃N₄ and Bi₂MoO₆, respectively. Structural analyses showed that Bi₂MoO₆ microplates were anchored on the wrinkled flower-like g-C₃N₄ matrix with Pt decoration, leading to a large expansion of specific surface area from 10.79 m²/g for pure Bi₂MoO₆ to 46.09 m²/g for Pt@CN/20%BMO. In addition, the Pt@CN/20%BMO composites exhibited an improved absorption ability in the visible light region, presenting a promoted photocatalytic MB degradation. Quenching experiments were also conducted to provide solid evidences for the production of hydroxyl radicals (^•OH), electrons (e⁻), holes (h⁺) and superoxide radicals (^•O²⁻) during dye degradation. The findings in this critical work provide insights into the synthesis of heterostructured photocatalysts with the optimization of band gaps, light response and photocatalytic performance in wastewater remediation.

MoS2 nanosheet incorporated α-Fe2O3/ZnO nanocomposite with enhanced photocatalytic dye degradation and hydrogen production ability

We have synthesized MoS₂ incorporated α-Fe₂O₃/ZnO nanocomposites by adapting a facile hydrothermal synthesis process. The effect of incorporating ultrasonically exfoliated few-layer MoS₂ nanosheets on the solar-light driven photocatalytic performance of α-Fe₂O₃/ZnO photocatalyst nanocomposites has been demonstrated. Structural, morphological and optical characteristics of the as-synthesized nanomaterials are comprehensively investigated and analyzed by performing Rietveld refinement of powder X-ray diffraction patterns, field emission scanning electron microscopy and UV-visible spectroscopy, respectively. The photoluminescence spectra of the as-prepared nanocomposites elucidate that the recombination of photogenerated electron–hole pairs is highly suppressed due to incorporation of MoS₂ nanosheets. Notably, the ultrasonicated MoS₂ incorporated α-Fe₂O₃/ZnO nanocomposite manifests 91% and 83% efficiency in degradation of rhodamine B dye and antibiotic ciprofloxacin respectively under solar illumination. Active species trapping experiments reveal that the hydroxyl (˙OH) radicals play a significant role in RhB degradation. Likewise the dye degradation efficiency, the amount of hydrogen produced by this nanocomposite via photocatalytic water splitting is also considerably higher as compared to both non-ultrasonicated MoS₂ incorporated α-Fe₂O₃/ZnO and α-Fe₂O₃/ZnO nanocomposites as well as Degussa P25 titania nanoparticles. This indicates the promising potential of the incorporation of ultrasonicated MoS₂ with α-Fe₂O₃/ZnO nanocomposites for the generation of carbon-free hydrogen by water splitting. The substantial increase in the photocatalytic efficiency of α-Fe₂O₃/ZnO after incorporation of ultrasonicated MoS₂ can be attributed to its favorable band structure, large surface to volume ratio, effective segregation and migration of photogenerated electron–hole pairs at the interface of heterojunctions and the plethora of exposed active edge sites provided by the few-layer MoS₂ nanosheets.

Novel few-layer MoS₂ nanosheets incorporated α-Fe₂O₃/ZnO photocatalyst nanocomposite is reported with high dye degradation and hydrogen evolution ability under solar illumination.

Morphology dependent nonlinear optical and photocatalytic activity of anisotropic plasmonic silver

Anisotropic nanoparticles are ideal building blocks for a number of functional materials due to their exceptional and anisotropic optical, electronic, magnetic and mechanical properties. In this work we present systematic studies on morphology dependent ultra-sensitive thermal diffusivity and photodegradation capability of anisotropic plasmonic silver for the first time. Hydrogen peroxide centered synthesis was performed to prepare anisotropic silver nanosystems spherical (14 nm), quasi-spherical (17 nm), elliptical (18 m), rods (aspect ratio 2.1), hexagonal (22 nm) and prisms (19 nm). The synthesized nanosystems were characterized using UV-VIS spectroscopy, high resolution transmission electron microscopy (HRTEM) and band gap analysis. A dual beam mode matched thermal lensing method was adopted for evaluating the thermal diffusivity of the anisotropic system. The present anisotropic nanoparticle system exhibited strong morphology based thermal diffusivity. An increase of 140% in the thermal diffusivity value points to the nonlinear optical application potential of the anisotropic systems. Sunlight mediated photodegradation of methylene blue showed a promising increase in the degradation rate for anisotropic systems compared to other similar systems reported in the literature.

Low temperature synthesis of BiFeO3 nanoparticles with enhanced magnetization and promising photocatalytic performance in dye degradation and hydrogen evolution

In this investigation, we have synthesized BiFeO₃ nanoparticles by varying hydrothermal reaction temperatures from 200 °C to 120 °C to assess their visible-light driven photocatalytic activity along with their applicability for hydrogen production via water splitting. The rhombohedral perovskite structure of BiFeO₃ is formed for hydrothermal reaction temperature up to 160 °C. However, for a further decrement of hydrothermal reaction temperature a mixed sillenite phase is observed. The XRD Rietveld analysis, XPS analysis and FESEM imaging ensure the formation of single-phase and well crystalline nanoparticles at 160 °C reaction temperature with 20 nm of average size. The nanoparticles fabricated at this particular reaction temperature also exhibit improved magnetization, reduced leakage current density and excellent ferroelectric behavior. These nanoparticles demonstrate considerably high absorbance in the visible range with a low band gap (2.1 eV). The experimentally observed band gap is in excellent agreement with the calculated band gap using first-principles calculations. The favorable photocatalytic performance of these nanoparticles has been able to generate more than two times of solar hydrogen compared to that produced by bulk BiFeO₃ as well as commercially available Degussa P25 titania. Notably, the experimentally observed band gap is almost equal for both bulk material and nanoparticles prepared at different reaction temperatures. Therefore, in solar energy applications, the superiority of BiFeO₃ nanoparticles prepared at 160 °C reaction temperature may be attributed not only to their band gap but also to other factors, such as reduced particle size, excellent morphology, good crystallinity, large surface to volume ratio, ferroelectricity and so on.

Multiferroic BiFeO₃ nanoparticles were synthesized using low temperature hydrothermal technique to assess their visible-light driven photocatalytic activity along with their applicability for the production of hydrogen via water splitting.