Visible Irradiation Research Articles

Inactivation of Aspergillus Species and Degradation of Aflatoxins in Water Using Photocatalysis and Titanium Dioxide

Aflatoxins (AF) are highly toxic secondary metabolites produced by various species of Aspergillus, posing significant health risks to humans and animals. The four most prominent types are aflatoxin B1 (AFB1), aflatoxin B2 (AFB2), aflatoxin G1 (AFG1), and aflatoxin G2 (AFG2). These mycotoxins are prevalent in various environments, including water sources and food products. Among these mycotoxins, AFB1 is recognized as the most toxic, mutagenic, and carcinogenic to humans. Consequently, most efforts to mitigate the impact of AF have been focused on AFB1, with photocatalysis emerging as a promising solution. Recent research has demonstrated that using semiconductor photocatalysis, particularly titanium dioxide (TiO2), combined with UV–visible irradiation significantly enhances the efficiency of AF degradation. TiO2 is noted for its high activity under UV irradiation, non-toxicity, and excellent long-term stability, making it a favorable choice for photocatalytic applications. Furthermore, TiO2 combined with visible light has demonstrated the ability to reduce AF contamination in food products. This article summarizes the working conditions and degradation rates achieved, as well as the advantages, limitations, and areas of opportunity of these methodologies for the degradation of AF and preventing their production, thereby enhancing food and water safety.

Self-Sustaining Living Habitats in Extraterrestrial Environments.

Standard definitions of habitability assume that life requires the presence of planetary gravity wells to stabilize liquid water and regulate surface temperature. Here, the consequences of relaxing this assumption are evaluated. Temperature, pressure, volatile loss, radiation levels, and nutrient availability all appear to be surmountable obstacles to the survival of photosynthetic life in space or on celestial bodies with thin atmospheres. Biologically generated barriers capable of transmitting visible radiation, blocking ultraviolet, and sustaining temperature gradients of 25-100 K and pressure differences of 10 kPa against the vacuum of space can allow habitable conditions between 1 and 5 astronomical units in the solar system. Hence, ecosystems capable of generating conditions for their own survival are physically plausible, given the known capabilities of biological materials on Earth. Biogenic habitats for photosynthetic life in extraterrestrial environments would have major benefits for human life support and sustainability in space. Because the evolution of life elsewhere may have followed very different pathways from that on Earth, living habitats could also exist outside traditional habitable environments around other stars, where they would have unusual yet potentially detectable biosignatures.

Two-dimensional synchrotron beam characterization from a single interferogram

Two-dimensional synchrotron beam characterization from a single interferogram

High efficiency photocatalytic hydrogen evolution by black phosphorus quantum dots decorated 1D g-C3N4 nanotubes

Bare g-C3N4 (CN) encounters substantial charge recombination with strong fluorescence, which is detrimental to the photocatalytic reactions. In this work, g-C3N4 is curved into nanotubes then combined with black phosphorus quantum dots (BPQDs). The BPQDs decorated tubular CN (BPTCN) exhibits a stable and high photocatalytic hydrogen evolution rate of 507.51 μmolh−1g−1 under visible irradiation, which is four times higher than that of pure TCN. The apparent quantum yield (AQY) at 420 nm of BPTCN reaches 2.58%. The excellent photocatalytic ability of the BPTCN is attributed the suppressed recombination of electron-hole pair and improved carrier transport efficiency, which are introduced by the 1D tubular structure and the band alignment of the BPTCN heterojunction.

Hydrogen Production Through Water Splitting Reactions Using Zn-Al-In Mixed Metal Oxide Nanocomposite Photocatalysts Induced by Visible Light

In this study, the synthesis of hybrid photocatalysts of Zn-Al-In mixed metal oxides were activated by using visible light, derived from Zn-Al-In layered double hydroxide (ZnAlIn-LDH), and these nanocomposites demonstrated high efficiency for photocatalytic H2 production under UV light when using methanol as a sacrificial agent. The most active photocatalytic material produced 372 μmol h−1 g−1 of H2. The characterization of these materials included X-ray diffraction (DRX), infrared spectroscopy (FTIR), X-ray fluorescence spectroscopy (XRF), X-ray spectroscopy (XEDS), scanning electron microscopy analysis (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy, and N2- physisorption. In addition, the materials were characterized by photoelectrochemical techniques to explain the photocatalytic behavior. Subsequently, the photocatalytic performance for the water-splitting reactions under visible irradiation was evaluated. The ZnAlIn-MMOs with an In/(Al + In) molar ratio of 0.45 exhibited the highest photocatalytic activity in tests under visible light, attributed to the efficient separation and transport of photogenerated charge carriers originating from the new nanocomposite. This discovery indicates a method for developing new types of heteronanostructured photocatalysts which are activated by visible light.

A novel stratagem for synthesis of S-scheme Ag3PO4/ZnO nanocomposites by sol-gel assisted sonochemical route for removal of rhodamine B under visible light radiations

A novel stratagem for synthesis of S-scheme Ag3PO4/ZnO nanocomposites by sol-gel assisted sonochemical route for removal of rhodamine B under visible light radiations

Visible Light-Driven Photocatalysis of Al-Doped SrTiO3: Experimental and DFT Study.

Environmental problems associated with water pollution caused by organic dyes have raised serious concerns. In this context, photocatalytic processes have proven to be promising and environmentally friendly methods for water purification utilising abundant solar energy. In this study, a SrTiO3-based photocatalyst was modified by doping with Al ions and the deposition of dual co-catalysts (Rh/Cr2O3 and CoOOH) to enhance the photocatalytic decomposition efficiency of methylene blue (MB). Pure perovskite SrTiO3 was synthesised by chemical precipitation followed by calcination at 1100 °C. Al-doped SrTiO3 with deposited co-catalysts showed 3.2 times higher photocatalytic activity compared to unalloyed SrTiO3 with co-catalysts in MB decomposition under visible radiation. This study highlights the effectiveness of using dual co-catalysts and low-valence metal doping to enhance the efficiency of the photocatalytic decomposition of organic pollutants. The density functional theory analysis results show that the Al doping of SrTiO3 improves charge separation and increases the lifetime of photogenerated electrons and holes while maintaining the size of the forbidden band, which confirms its effectiveness for enhancing photocatalytic activity.

Photochemistry dominates over photothermal effects in the laser-induced reduction of graphene oxide by visible light

Graphene oxide (GO) possesses specific properties that are revolutionizing materials science, with applications extending from flexible electronics to advanced nanotechnology. A key method for harnessing GO’s potential is its laser-induced reduction, yet the exact mechanisms — photothermal versus photochemical effects — remain unclear. Herein, we discover the dominant role of photochemical reactions in the laser reduction of GO under visible light, challenging the prevailing assumption that photothermal effects are dominant. Employing a combination of Raman thermometry, X-ray photoelectron and photoluminescence spectroscopies, and electrical atomic force microscopy, we quantify the temperature and map the reduction process across micro and nano scales. Our findings demonstrate that the photochemical cleavage of oxygen-containing groups below a reduction threshold temperature is a decisive factor in GO reduction, leading to distinct characteristics that cannot be replicated by heating alone. This work clarifies the fundamental mechanisms of GO transformation under visible laser irradiation, highlighting the dominant role of photochemical processes. Distinguishing these subtleties enables the development of laser-reduced GO platforms for graphene-based applications compatible with industrial scales. We illustrate this potential by encoding information on GO surfaces as optical storage, allowing us to write binary sequences in long-term memory encoding invisible even through an optical microscope.

Indium-Iron Oxide Nanosized Solid Solutions as Photocatalysts for the Degradation of Pollutants under Visible Radiation.

A series of solid solutions of indium and iron oxides with different In/Fe ratios (InxFeyO3, with x + y = 2) were synthesized in the form of nanoparticles (diameter of ca. 30-40 nm) with the purpose of generating enhanced photocatalysts with an intermediate band gap compared to those of the monometallic oxides, In2O3 and Fe2O3. The materials were prepared by co-precipitation from an aqueous solution of iron and indium nitrates and extensively characterized with a combination of techniques. XRD analysis proved the formation of the desired InxFeyO3 solid solutions for Fe content in the range 5-25 mol%. UV-Vis absorption analysis showed that the substitution of In with Fe in the crystalline structure led to the anticipated gradual decrease of the band gap values compared to In2O3. The obtained semiconductors were tested as photocatalysts for the degradation of model organic pollutants (phenol and methylene blue) in water. Among the InxFeyO3 solid solutions, In1.7Fe0.3O3 displayed the highest photocatalytic activity in the degradation of the selected probe molecules under UV and visible radiation. Remarkably, In1.7Fe0.3O3 showed a significantly enhanced activity under visible light compared to monometallic indium oxide and iron oxide, and to the benchmark TiO2 P25. This demonstrates that our strategy consisting in engineering the band gap by tuning the composition of InxFeyO3 solid solutions was successful in improving the photocatalytic performance under visible light. Additionally, In1.7Fe0.3O3 fully retained its photocatalytic activity upon reuse in four consecutive cycles.

Magnetic Circular Dichroism of Oxide Films: Study of Electronic, Magnetic and Charge States

Semiconductor materials based on ZnO and RE3+MnO3 oxides are considered as potential candidates for spintronics. This article presents the methodology and results of studying the effect of magnetic circular dichroism for Zn1-xCoxO, Zn1-x-yCoxAlyO and RE1-x 3+Ax 2+MnO3 film structures in the visible radiation range. It has been shown that the magnetic circular dichroism behavior of the manganite films reflects not only the magnetic, but also the charge component of the material. This indicates the possibility of studying the magnetic and transport characteristics of the films using the magnetic circular dichroism spectroscopy. Since the magnetic circular dichroism effect also directly probes the ground and excited electronic states of the film, it has been obtained data that update calculated parameters for describing the manganites band structure. In the case of the Zn1-xCoxO and Zn1-x-yCoxAlyO films, the magnetic circular dichroism spectroscopy acts as a tool for detecting Co nanoparticles in the solid solution matrix of ZnO:Co and ZnO:(Co+Al).

Enhanced Photodegradation of Sulfamethoxazole Through Cutting-Edge Titania-Zirconia-Based Materials

ZrO2, TiO2, ZrO2-TiO2, and TiO2-ZrO2 were successfully prepared using the sol–gel method and fully characterized to check their physico-chemical features. X-ray diffraction showed the co-existence of monoclinic and tetragonal ZrO2 in addition to the Anatase phase for TiO2. The formation of mixed oxides led to a reduction in the band gap values and a modification of the textural characteristics, while the XPS evidenced an oxygen vacancy-rich surface. The ability of the synthesized materials to eliminate drug contaminants was checked using Sulfamethoxazole (SMX) as a model molecule under UV and BLUE-LED irradiation. The materials’ potential to decrease wastewater toxicity was also studied. The best photocatalyst was TiO2-ZrO2 with 76 and 100% conversion under visible and UV irradiation, respectively.

Dye Sensitized Photoactivation of ZnO/Zn(NCN) Nanocomposites Obtained via Solvent Free Mechanothermal Process and Their Photocatalytic Application

The current work describes the sustainable and ecofriendly synthesis of visible light active Zinc Oxide-Zinc Carbodiimide (ZnO/Zn(NCN)) nanocomposites under solvent free conditions via mechanothermal process. The photocatalytic proficiencies of the produced nanomaterials were investigated for the photo-mineralization of Rhodamine B (RhB) organic dye pollutant under visible light illumination. The synthesis of ZnO/Zn(NCN) nanocomposites were conducted using varying weight ratio of zinc acetate to urea as 1:2, 1:4, 1:6, and 1:8 and the resulting samples were named as ZnO/Zn(NCN) (1:2), ZnO/Zn(NCN) (1:4), ZnO/Zn(NCN) (1:6), and ZnO/Zn(NCN) (1:8), respectively. The XRD and FTIR results confirm that in the prepared nanocomposites, Zn(NCN) and ZnO nanoparticles coexist in a tetragonal lattice structure with a space group of . The addition of ZnO in the carbodiimide has surprisingly reduced the band gap of the later from 4.32 eV to ∼2.87 eV, thus enabling it photo-active under visible light radiation. In the present study, remarkable photo-mineralization activity for the prepared ZnO/Zn(NCN) nanocomposites was observed toward the RhB dye under visible light exposure. A maximum of 99% degradation of the dye was reported at a rate of 0.0505 min-1 over ZnO/Zn(NCN) (1:6) nanocomposite in acidic conditions (pH=2) with 20 mg catalyst dosage, 20 mg/L dye concentration and 90 min of visible light contact. The prepared nanocomposites were found to exhibit dye sensitized photoactivation under visible light irradiation. The photo-decolorization process was mainly regulated by •O2- followed by h+ oxidative species. The reusability experiment reveals the retention of 90.22% dye degradation capacity of the nanocomposite (1:6) even in the fourth cycle of reuse, demonstrating its good photostability and practical applicability.

Oxygen vacancy mediated TiO2-x-MoS2/FTO heterostructure as an efficient photoanode for photoelectrochemical water splitting

To achieve a complete water splitting cycle, solar-assisted oxidation plays a crucial role. Discovering efficient photoanodes capable of absorbing visible light is essential to enable cost-effective solar energy conversion. This study devised an efficient hydrothermal method to synthesize a TiO2-MoS2 heterostructure with an oxygen vacancy on FTO (fluorine-doped tin oxide). The structure, morphology, optical properties, and photoelectrocatalytic behavior of the TiO2-x-MoS2 heterostructure using various techniques. The oxygen vacancy state can create a new sublevel state below the conduction band of TiO2, which narrows the band gap to a lower level and thus extends the absorption edge into the visible region. The strategy of oxygen vacancy resulted in a photocurrent density of 0.6 mA cm-2, which is 3 times higher than pure TiO2. Also, the TiO2-x-MoS2 heterostructure exhibits a photocurrent density of 2.6 mA cm−2 and higher O2 evolution than pure TiO2 in a 1.0 M KOH solution under UV–Vis irradiation. Compared to unmodified TiO2 nanorods, TiO2-x-MoS2 electrodes exhibit an increase of 13 times in photoelectrochemical activity and have a low overpotential. This is due to accelerated electron transfer kinetics at the TiO2-x-MoS2 interface, an enhanced density of charge carriers, a reduced rate of charge recombination, and a highly wettable surface.

Arsenite removal by using ZnAlFe mixed metal oxides derived from layered double hydroxides

ZnAlFe mixed metal oxides (ZnAlFe-MMOs) were synthesized from layered double hydroxides (LDHs) prepared by the coprecipitation method at pH 9 using an initial weight composition of Zn2+ = 75%, Al3+ = 15% and Fe3+ = 10%, with or without the addition of citric or oxalic acid. The solids were calcined at 400 °C to obtain the respective MMOs, which exhibited relatively high specific surface areas (165.3–63.8 m2 g−1) and semiconductor properties active in the visible region (bandgap values (Eg) of 2.42–1.77 eV). The synthesized materials were tested for the removal of trivalent arsenic by adsorption and by photocatalysis under visible light irradiation (λ ≥ 420 nm). The best removal of As(III) by adsorption (65.9%) and by photocatalysis (99.9%) was obtained with the ZnAlFe-MMOs prepared in the absence of organic acids. The XPS results indicate the coexistence of As3+ and As5+ over ZnAlFe-MMOs after the photocatalytic reaction and also confirm the formation of Fe2+ sites on the hematite surface that enhances the removal of As(III). Raman measurements confirmed that, in the photocatalytic experiments, As is largely retained as As(V) on ZnAlFe-MMOs, bound to Fe. The results of fluorescence of 7-hydroxycoumarin suggest that the photocatalyst produces HO•, which can be the main species for As(III) oxidation under UV–Vis irradiation. Moreover, ZnAlFe-MMOs exhibited a good reusability after regeneration making ZnAlFe-MMOs a promising material for arsenic decontamination in polluted water.

Multifunctional TiO2(R)/Fe2O3 Photocatalytic Composites Obtained from Ilmenite Ore

AbstractThe commercialization of the photocatalysis technology requires that the synthesis of the photocatalytic material is easy to scale up. Thus, the synthesis from earth‐abundant minerals represents one plausible solution to obtain materials by a scalable process with a lower environmental impact. So far, the most promising photocatalyst for this application is titanium dioxide (TiO2), which can be obtained from ilmenite ore; however, its synthesis usually implies toxic solvents and complicated reaction conditions. Thus, here is proposed an optimized method to extract higher amounts of TiO2 by a multivariable Plackett‐Burman design of experiments considering the mass of the ore precursor, the addition of phosphoric acid (H3PO4), the digestion temperature, the amount of base to adjust the pH, and the final thermal treatment. From this design, it was possible to minimize the heat treatment and the amount of base used to favor higher TiO2 (rutile) content with the presence of additional phases of iron oxides (Fe2O3) that act as co‐catalyst to enhance the photocatalytic activity. The photocatalytic activity of the TiO2/Fe2O3 composites obtained was investigated in four model reactions to obtain solar fuels (H2 evolution and CO2 reduction) and to remove endocrine water pollutants (bisphenol A and dyeing water), using visible and natural solar irradiation, respectively.

Investigation on the overall performance of hydrogel-based thermochromic windows with various structures

Thermochromic (TC) windows have attracted extensive attention due to their potential for improving building performance through the variation of optical properties in response to temperature. However, past studies on TC windows at the building scale primarily focused on optimizing and evaluating the properties of TC materials, with little attention paid to the varying window structures frequently encountered in engineering applications. In this study, the building performance of hydrogel-based TC windows was investigated from the structural perspective. A comprehensive simulation framework was developed, integrating overall performance simulations of energy consumption and indoor comfort. Using a self-fabricated hydrogel TC glass and an office building as the case study, the impact of the optical properties of the substrate glass on single, double, vacuum, and ventilation TC windows was analyzed. The results indicated that the optimal extinction coefficients for the studied windows range from 55 to 105 m−1 for visible irradiation and from 155 to 255 m−1 for near-infrared irradiation. Subsequently, the overall performance improvements of these types of TC windows relative to corresponding static versions were calculated. It was found that the impacts of TC glass on these four windows varied significantly. The electricity usage was reduced by 33 ∼ 53 %, and the thermal comfort and visual comfort were enhanced by –22 ∼ 20 % and 72 ∼ 100 %, respectively. This study reveals in detail how the TC window structure affects various aspects of building performance, aiming to inspire and guide the consideration of window structure in the practical applications of TC glass.

Magnetic and visible light-induced novel green synthesized magnetic Co3O4 photocatalysts via sunflower seed meal extract for anionic and cationic dye removal by adsorption assisted photocatalytic degradation

This study was aimed at the preparation of m-Co3O4 NPs (magnetic Co3O4 nanoparticles) from sunflower seed meal (SFSM) which is the waste of sunflower seed oil factories, and their application as a photocatalyst for the adsorption assistant photocatalysis degradation of methylene blue (MB), and direct yellow-50 (DY-50) under the visible irradiations. Also, the photocatalytic performance of m-Co3O4 NPs was evaluated in synthetic wastewater. The produced m-Co3O4 NPs were ferromagnetic with a saturation magnetization value of 4.3 emu g−1 and the degradation of cationic MB and anionic DY-50 dyes by 100% and 93% in 20 min and 35 min, respectively, by adsorption-assisted photocatalytic process under visible light was achieved. The reactions were found to be pseudo-second-order equation for the adsorption-assisted photocatalytic process for both dyes. The photocatalytic activity of m-Co3O4 NPs decreased slightly even after five repeated cycles. These results show that the m-Co3O4 NPs can be used successfully in dye treatment in wastewater with their adsorption-assisted photocatalytic properties, activation by visible light, magnetic separability, and low-cost production.

Self-sacrificing template fabrication of mesoporous CuO micro/nanoplates for photo-Fenton-like oxidation of sulfathiazole

In this study, we offer a simple self-sacrificial template-directed method to prepare mesoporous CuO micro/nanoplates by using copper hydroxide acetate (Cu2(OH)3(CH3COO)·H2O) plates as a template. The as-prepared material was structurally, morphologically, optically and texturally characterized and its excellent catalytic activity in the LED-driven photo-Fenton-like process of sulfathiazole oxidation was demonstrated. Within 90 min, 100 % sulfathiazole degradation and 87.3 % TOC removal were achieved in the presence of H2O2 and visible LED irradiation. Moreover, the degradation of sulfathiazole can still reach 96.1 % after five cycles, which indicates exceptional performance of the catalyst.

Hydrothermal Synthesis of ZnO Nanoflowers: Exploring the Relationship between Morphology, Defects, and Photocatalytic Activity

Two forms of flower-like ZnO nanostructures were synthesized using hydrothermal methods at various growth times/temperatures and zinc precursors. The morphology, structure, chemical composition, and optical properties of these ZnO nanoflowers were studied using a scanning electron microscope (SEM), X-ray diffraction spectroscopy (XRD), X-ray photoelectrons spectroscopy (XPS), Raman spectroscopy, and UV–Vis spectroscopy. The SEM images revealed two forms of flower-like nanostructures, namely lotus- and tulip-like flower ZnO nanostructures. The XPS analysis revealed the oxidation state of the Zn and O elements, as well as the presence of OH groups on the surface of the lotus-like flower ZnO nanostructure. The XRD results revealed less crystallinity of the lotus-like ZnO nanoflowers (NFs) compared with the tulip-like ZnO NFs. The XRD results revealed the presence of Zn (OH)2 in the ZnO NFs. The Raman results confirmed less crystallinity of the lotus-like ZnO NFs. The estimated optical bandgap was 2.92 and 3.0 eV for the tulip- and lotus-like ZnO NFs, respectively. The tulip-like ZnO NFs showed superior photocatalytic degradation of methylene blue dye, verified via UV–Vis radiation, compared with the lotus-like ZnO NFs, which show the impact of the structure defects and OH- impurities on the photocatalytic performance of ZnO nanoflowers.

Enhanced band gap energy of one-pot mechano-synthesized Ag3PO4 for Orange G photodegradation under visible light irradiation: An in-depth experimental and DFT studies

The present study highlights the efficiency of Ag3PO4 photocatalyst with a band gap of 2.25 eV, synthesized by a green and one-pot simple mechanochemical method, towards photodegradation of orange G under visible irradiation. The phase structure, morphology, and optical properties of mechano-synthesized Ag3PO4 were investigated using X-ray diffraction, Scanning Electron Microscopy, Thermogravimetric Analysis, Fourier Transform Infrared, the Brunauer-Emmet-Teller surface area, and UV–vis diffuse reflectance spectroscopy. DFT calculations were also conducted for band gap energy prediction. The photocatalytic activity of the sample was evaluated using a central composite design for surface response methodology (CCD-RSM) to determine the optimal conditions for Orange G (OG) removal. The photocatalytic activity of Ag3PO4 was approximately 93 % within 20 min of reaction under irradiation for 24.6 mg/L and 11 mg/L of Ag3PO4 and Orange G, respectively. Trapping experiments confirmed that peroxides and hydroxyl radicals are the dominant active species in the photodegradation process.