Insight into (Electro)magnetic Interactions within Facet-Engineered BaFe12O19/TiO2 Magnetic Photocatalysts

A series of facet-engineered TiO2/BaFe12O19 composites were synthesized through hydrothermal growth of both phases and subsequent deposition of the different, faceted TiO2 nanoparticles onto BaFe12O19 microplates. The well-defined geometry of the composite and uniaxial magnetic anisotropy of the ferrite allowed alternate interfaces between both phases and fixed the orientation between the TiO2 crystal structure and the remanent magnetic field within BaFe12O19. The morphology and crystal structure of the composites were confirmed by a combination of scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses together with the detailed study of BaFe12O19 electronic and magnetic properties. The photocatalytic activity and magnetic field effect were studied in the reaction of phenol degradation for TiO2/BaFe12O19 and composites of BaFe12O19 covered with a SiO2 protective layer and TiO2. The observed differences in phenol degradation are associated with electron transfer and the contribution of the magnetic field. All obtained magnetic composite materials can be easily separated in an external magnetic field, with efficiencies exceeding 95%, and recycled without significant loss of photocatalytic activity. The highest activity was observed for the composite of BaFe12O19 with TiO2 exposing {1 0 1} facets. However, to prevent electron transfer within the composite structure, this photocatalyst material was additionally coated with a protective SiO2 layer. Furthermore, TiO2 exposing {1 0 0} facets exhibited significant synergy with the BaFe12O19 magnetic field, leading to 2 times higher photocatalytic activity when ferrite was magnetized before the process. The photoluminescence emission study suggests that for this particular combination, the built-in magnetic field of the ferrite suppressed the recombination of the photogenerated charge carriers. Ultimately, possible effects of complex electro/magnetic interactions within the magnetic photocatalyst are shown and discussed for the first time, including the anisotropic properties of both phases.

ZnO-decorated green-synthesized multi-doped carbon dots from Chlorella pyrenoidosa for sustainable photocatalytic carbamazepine degradation

The promising green synthesis of carbon dots (CDs) from microalga Chlorella pyrenoidosa was achieved using simple hydrothermal and microwave-assisted methods. Doping of nanomaterials by nonmetals (N, S, and P) was confirmed by X-ray photoelectron spectroscopy (XPS), while the existence of metals in the CDs was confirmed by inductively coupled plasma optical emission spectroscopy (ICP-OES) and transmission electron microscopy (TEM), and Mg, Ca, K, and Na were found as the dominant doped metals. The novel nanomaterials with excellent photoluminescence (PL) properties were used for the modification of ZnO obtained by a simple hydrothermal process. In this regard, a series of ZnO decorated with multi-doped carbon dots (xCDs) was prepared and their photocatalytic properties were evaluated. The ZnO-xCD photocatalysts were characterized by various advanced techniques including X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), XPS, Brunauer-Emmett-Teller (BET), PL, ultraviolet-visible (UV-vis) spectroscopy and electrochemical impedance spectroscopy (EIS) analysis. The photocatalytic behaviour of the obtained materials was investigated in the degradation of carbamazepine (CBZ). The influence of the synthesis method of xCDs and their content on the activity of the photocatalyst was examined. The photocatalyst ZnO modified with 3% xCDs obtained by the microwave-assisted method revealed the highest effectiveness for CBZ degradation and allowed for a first-order degradation rate of 2.85 times in comparison with non-modified ZnO. The improvement of the photocatalytic process was achieved by support with peroxymonosulphate resulting in up to 3.18 times a first order kinetic rate constant compared with that of simple photocatalysis in the presence of ZnO-xCDs. Taken together, our synthesized multi-doped CDs and their nanohybrids with ZnO, can be considered as promising candidates for photocatalytic applications.

Synthesis, characterization, and application of 2D/2D TiO2-GO-ZnFe2O4 obtained by the fluorine-free lyophilization method for solar light-driven photocatalytic degradation of ibuprofen

In this study, we report the potential of 2D/2D TiO2-GO-ZnFe2O4 photocatalyst obtained using the fluorine-free lyophilization technique for the degradation of ibuprofen belonging to the group of active pharmaceutical ingredients (API). The improved ibuprofen degradation under simulated solar light was achieved in the presence of a composite of 2D TiO2 combined with GO and embedded ZnFe2O4, which additionally provides superparamagnetic properties and enables photocatalyst separation after the photodegradation process. After only 20 min of the photodegradation process in the presence of 2D/2D TiO2-GO-ZnFe2O4 composite, more than 90% of ibuprofen was degraded under simulated solar light, leading to non-toxic and more susceptible to biodegradation intermediates. At the same time, photolysis of ibuprofen led to the formation of more toxic intermediates. Furthermore, based on the photocatalytic degradation analysis, the degradation by-products and possible photodegradation pathways of ibuprofen were investigated. The photodegradation tests and electronic spin resonance analyses indicated the significant involvement of superoxide radicals and singlet oxygen in the ibuprofen photodegradation process.

Fibrillar aggregates in powdered milk

This research paper addresses the hypothesis that powdered milk may contain amyloid fibrils. Amyloids are fibrillar aggregates of proteins. Up to this time, research on the presence of amyloids in food products are scarce. To check the hypothesis we performed thioflavin T fluorescence assay, X-ray powder diffraction, atomic force microscopy and fluorescence microscopy imaging. Our preliminary results show that commercially available milks contain fibrils that have features characteristic to amyloids. The obtained results can be interpreted in two opposite ways. The presence of amyloids could be considered as a hazard due to the fact that food products may induce amyloid related diseases. On the other hand, the presence of amyloids in traditionally consumed foodstuffs could serve as proof that fibrils of food proteins do not pose a threat for consumers.

Novel composite of Zn/Ti-layered double hydroxide coupled with MXene for the efficient photocatalytic degradation of pharmaceuticals

In the present study, a hybrid photocatalyst of Zn/Ti layered double hydroxide (LDH) coupled with MXene - Ti₃C₂ was synthesized for the first time and applied in photocatalytic degradation of acetaminophen and ibuprofen, two commonly present in the natural environment and prone to accumulate in the aquatic ecosystem pharmaceuticals. The effect of MXene content (0.5 wt%, 2.5 wt%, and 5 wt%) on the photocatalytic activity of LDH/MXene composite was investigated. The composite of LDH/MXene containing 2.5 wt% of MXene revealed the highest photocatalytic activity in the degradation of acetaminophen (100% within 40 min) and ibuprofen (99.7% within 60 min). Furthermore, an improvement in acetaminophen and ibuprofen mineralization was observed for the composite material. Meanwhile, the introduction of interfering ions (Na⁺, Ca²⁺, Mg²⁺, Cl^-, SO₄^2-) in the model seawater did not affect the removal efficiency of both pharmaceuticals. The photocatalytic experiment performed in the four subsequent cycles, as well as FTIR, TEM, and XPS analyses after the photodegradation process confirmed the excellent stability and reusability of the prepared composite material. In order to evaluate the effect of various reactive oxidizing species (ROS) on the photocatalytic process, the trapping experiment was applied. It was noticed that •O₂^- had the main contribution in photocatalytic degradation of acetaminophen, while •OH and h⁺ mainly affected the degradation of ibuprofen. Finally, based on the results of Mott Schottky analysis, bandgap calculation, and ROS trapping experiment, the possible mechanism for pharmaceuticals degradation was proposed. This research illustrates the feasibility and novelty of the treatment of pharmaceuticals by LDH/MXene composites, implying that MXene plays a significant role in the electron-hole separation and thus high photocatalytic activity.

Modification of structured bio‑carbon derived from spongin-based scaffolds with nickel compounds to produce a functional catalyst for reduction and oxidation reactions: Potential for use in environmental protection

Three different 3D fibrous-like NiO/Ni(OH)₂/Ni‑carbonized spongin-based materials were prepared via a simple sorption-reduction method. Depending on the support used, the catalysts were composed of carbon, nickel oxide, nickel hydroxide and zero-valent nickel, with the surface content of the nickel-containing phase in the range 15.2-26.0 wt%. Catalytic studies showed promising activity in the oxidation of phenolic compounds in water and in the reduction of 4-nitrophenol. The oxidation efficiency depends on the substrate used and ranges from 80% for phenol at pH 2 to 99% for 4-chlorophenoxyacetic acid (4-CPA) and methylchlorophenoxypropionic acid (MCPP). In the reduction reaction, all catalysts exhibited superior activity, with rate constants in the range 0.648-1.022 min^-1. The work also includes a detailed investigation of reusability and kinetic studies.

Nitrofurazone Removal from Water Enhanced by Coupling Photocatalysis and Biodegradation

(1) Background: Environmental contamination with antibiotics is particularly serious because the usual methods used in wastewater treatment plants turn out to be insufficient or ineffective. An interesting idea is to support natural biodegradation processes with physicochemical methods as well as with bioaugmentation with efficient microbial degraders. Hence, the aim of our study is evaluation of the effectiveness of different methods of nitrofurazone (NFZ) degradation: photolysis and photodegradation in the presence of two photocatalysts, the commercial TiO₂-P25 and a self-obtained Fe₃O₄@SiO₂/TiO₂ magnetic photocatalyst. (2) Methods: The chemical nature of the photocatalysis products was investigated using a spectrometric method, and then, they were subjected to biodegradation using the strain Achromobacter xylosoxidans NFZ2. Additionally, the effects of the photodegradation products on bacterial cell surface properties and membranes were studied. (3) Results: Photocatalysis with TiO₂-P25 allowed reduction of NFZ by over 90%, demonstrating that this method is twice as effective as photolysis alone. Moreover, the bacterial strain used proved to be effective in the removal of NFZ, as well as its intermediates. (4) Conclusions: The results indicated that photocatalysis alone or coupled with biodegradation with the strain A. xylosoxidans NFZ2 leads to efficient degradation and almost complete mineralization of NFZ.

Mono- and bimetallic (Pt/Cu) titanium(IV) oxide photocatalysts. Physicochemical and photocatalytic data of magnetic nanocomposites' shell

Surface modification of titania with noble and semi-noble metals resulted in significant enhancement of photocatalytic activity. Presented data, showing the photocatalytic properties of TiO₂-M (where M is Pt and/or Cu) photocatalysts were further used as Fe₃O₄@SiO₂/TiO₂-M magnetic nanocomposites shells in "Mono- and bimetallic (Pt/Cu) titanium(IV) oxide core-shell photocatalysts with Vis light activity and magnetic separability" [1]. Platinum and copper were photodeposited on four different titania matrices (commercial and self-obtained ones). The prepared photocatalysts were characterized by X-ray diffraction (XRD) analysis, specific surface area measurements using the Brunauer-Emmet-Teller (BET) isotherm, diffuse reflectance spectroscopy (DR-UV/Vis) analysis as well as scanning transmission electron microscopy (STEM) analysis. Photocatalytic properties were investigated in three different reactions: H₂ generation, acetic acid oxidation to CO₂, and phenol degradation.

Improved degradation of etodolac in the presence of core-shell ZnFe2O4/SiO2/TiO2 magnetic photocatalyst

In the present study, susceptibility to photocatalytic degradation of etodolac, 1,8-diethyl-1,3,4,9 - tetrahydro pyran - [3,4-b] indole-1-acetic acid, which is a non-steroidal anti-inflammatory drug frequently detected in an aqueous environment, was for the first time investigated. The obtained p-type TiO₂-based photocatalyst coupled with zinc ferrite nanoparticles in a core-shell structure improves the separation and recovery of nanosized TiO₂ photocatalyst. The characterization of ZnFe₂O₄/SiO₂/TiO₂, including XRD, XPS, TEM, BET, DR/UV-Vis, impedance spectroscopy and photocatalytic analysis, showed that magnetic photocatalyst containing anatase phase revealed markedly improved etodolac decomposition and mineralization measured as TOC removal compared to photolysis reaction. The effect of irradiation and pH range on photocatalytic decomposition of etodolac was studied. The most efficient degradation of etodolac was observed under simulated solar light for a core-shell ZnFe₂O₄/SiO₂/TiO₂ magnetic photocatalyst at pH above 4 (pKa = 4.7) and below 7. The irradiation of etodolac solution in a broader light range revealed a synergetic effect on its photodegradation performance. After only 20 min of degradation, about 100% of etodolac was degraded. Based on the photocatalytic analysis in the presence of scavengers and HPLC analysis, the transformation intermediates and possible photodegradation pathways of etodolac were studied. It was found that ∙O₂^- attack on C2-C3 bond inside pyrrole ring results mostly in the hydroxylation of the molecule, which next undergoes -CH₂COOH detachment to give 1,9-diethyl-3,4-dihydro-pyrano[3,4-b]indol-4a-ol. The obtained compound should further undergo subsequent hydropyran and pyrrole ring breaking to give a family of benzene derivatives.

Preparation and Characterization of Defective TiO2. The Effect of the Reaction Environment on Titanium Vacancies Formation

Among various methods of improving visible light activity of titanium(IV) oxide, the formation of defects and vacancies (both oxygen and titanium) in the crystal structure of TiO2 is an easy and relatively cheap alternative to improve the photocatalytic activity. In the presented work, visible light active defective TiO2 was obtained by the hydrothermal reaction in the presence of three different oxidizing agents: HIO3, H2O2, and HNO3. Further study on the effect of used oxidant and calcination temperature on the physicochemical and photocatalytic properties of defective TiO2 was performed. Obtained nanostructures were characterized by X-ray diffractometry (XRD), specific surface area (BET) measurements, UV-Vis diffuse reflectance spectroscopy (DR-UV/Vis), photoluminescence spectroscopy (PL), X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) spectroscopy. Degradation of phenol as a model pollutant was measured in the range of UV-Vis and Vis irradiation, demonstrating a significant increase of photocatalytic activity of defective TiO2 samples above 420 nm, comparing to non-defected TiO2. Correlation of EPR, UV-Vis, PL, and photodegradation results revealed that the optimum concentration of HIO3 to achieve high photocatalytic activity was in the range of 20-50 mol%. Above that dosage, titanium vacancies amount is too high, and the obtained materials' photoactivity was significantly decreased. Studies on the photocatalytic mechanism using defective TiO2 have also shown that •O2- radical is mainly responsible for pollutant degradation.

Pseudo-superparamagnetic behaviour of barium hexaferrite particles

The effect of hexadecyltrimethylammonium bromide (CTAB) addition on the crystal structure, morphology, and magnetic properties of co-precipitated hexagonal barium ferrite was investigated. For a fixed amount of surfactant, different Fe³⁺ concentrations and Fe³⁺/Ba²⁺ ratios were used to optimize the formation of single-phase barium ferrite particles. The results indicated that the obtained ferrite particles exhibited coercivity changes similar to those of superparamagnetic particles with larger than theoretically calculated particle sizes. This results from the softening of the material due to the size reduction of the grains and incorporation of excess barium, localized on the surface of the particles. Therefore, lowering the energy barrier required to reverse the magnetization was observed, while high magnetization saturation was preserved. The precipitation of barium ferrite particles from a surfactant-rich solution allowed control of BaFe₁₂O₁₉ magnetic properties without introducing any modifications inside the crystal structure.

Hybrid TiO2-Polyaniline Photocatalysts and their Application in Building Gypsum Plasters

Hybrid materials of conjugated polymer and titanium(IV) oxide have attracted considerable attention concerning their potential benefits, including (i) efficient exploitation of visible light, (ii) a high adsorption capacity for organic contaminants, (iii) and effective charge carriers separation. The new class of the photocatalysts is promising for the removal of environmental pollutants in both aqueous and gaseous phases. For the first time, in this study, the polyaniline (PANI)-TiO2 hybrid composite was used for the degradation of phenol in water and toluene in the gas phase. Polyaniline-TiO2 was prepared by the in situ polymerization of aniline on the TiO2 surface. The obtained hybrid material was characterized by diffuse reflectance spectroscopy (DR/UV-Vis), X-ray diffraction (XRD), fast-Fourier transformation spectroscopy (FTIR), photoluminescence (PL) spectroscopy, microscopy analysis (SEM/TEM), and thermogravimetric analysis (TGA). An insight into the mechanism was shown based on the photodegradation analysis of charge carrier scavengers. Polyaniline is an efficient TiO2 photosensitizer for photodegradation in visible light (λ > 420 nm). The trapping experiments revealed that mainly h+ and ˙OH were the reactive oxygen species that were responsible for phenol degradation. Furthermore, the PANI-TiO2 hybrid nanocomposite was used in gypsum plaster to study the self-cleaning properties of the obtained building material. The effect of PANI-TiO2 content on the hydrophilic/hydrophobic properties and crystallographic structure of gypsum was studied. The obtained PANI-TiO2-modified gypsum plaster had improved photocatalytic activity in the reaction of toluene degradation under Vis light.

Gas-phase removal of indoor volatile organic compounds and airborne microorganisms over mono- and bimetal-modified (Pt, Cu, Ag) titanium(IV) oxide nanocomposites

The photocatalytic deactivation of volatile organic compounds and mold fungi using TiO₂ modified with mono- and bimetallic (Pt, Cu, Ag) particles is reported in this study. The mono- and bimetal-modified (Pt, Cu, Ag) titanium(IV) oxide photocatalysts were prepared by chemical reduction method and characterized using XRD, XPS, DR/UV-Vis, BET, and TEM analysis. The effect of incident light, type and content of mono- and bimetallic nanoparticles deposited on titanium(IV) oxide was studied. Photocatalytic activity of as-prepared nanocomposites was examined in the gas phase using LEDs array. High photocatalytic activity of Ag/Pt-TiO₂ and Cu/Pt-TiO₂ in the reaction of toluene degradation resulted from improved efficiency of interfacial charge transfer process, which was consistent with the fluorescence quenching effect revealed by photoluminescence (PL) emission spectra. The photocatalytic deactivation of Penicillium chrysogenum, a pathogenic fungi present in the indoor environment, especially in a damp or water-damaged building using mono- and bimetal-modified (Pt, Cu, Ag) titanium(IV) oxide was evaluated for the first time. TiO₂ modified with mono- and bimetallic NPs of Ag/Pt, Cu, and Ag deposited on TiO₂ exhibited improved fungicidal activity under LEDs illumination than pure TiO₂ .

UV-Vis-Induced Degradation of Phenol over Magnetic Photocatalysts Modified with Pt, Pd, Cu and Au Nanoparticles

The combination of TiO₂ photocatalyst and magnetic oxide nanoparticles enhances the separation and recoverable properties of nanosized TiO₂ photocatalyst. Metal-modified (Me = Pd, Au, Pt, Cu) TiO₂/SiO₂@Fe₃O₄ nanocomposites were prepared by an ultrasonic-assisted sol-gel method. All prepared samples were characterized by X-ray powder diffraction (XRD) analysis, Brunauer-Emmett-Teller (BET) method, X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), Mott-Schottky analysis and photoluminescence spectroscopy (PL). Phenol oxidation pathways of magnetic photocatalysts modified with Pt, Pd, Cu and Au nanoparticles proceeded by generation of reactive oxygen species, which oxidized phenol to benzoquinone, hydroquinone and catechol. Benzoquinone and maleic acid were products, which were determined in the hydroquinone oxidation pathway. The highest mineralization rate was observed for Pd-TiO₂/SiO₂@Fe₃O₄ and Cu-TiO₂/SiO₂@Fe₃O₄ photocatalysts, which produced the highest concentration of catechol during photocatalytic reaction. For Pt-TiO₂/SiO₂@Fe₃O₄ nanocomposite, a lack of catechol after 60 min of irradiation resulted in low mineralization rate (CO₂ formation). It is proposed that the enhanced photocatalytic activity of palladium and copper-modified photocatalysts is related to an increase in the amount of adsorption sites and efficient charge carrier separation, whereas the keto-enol tautomeric equilibrium retards the rate of phenol photomineralization on Au-TiO₂/SiO₂@Fe₃O₄. The magnetization hysteresis loop indicated that the obtained hybrid photocatalyst showed magnetic properties and therefore could be easily separated after treatment process.

Magnetic semiconductor photocatalysts for the degradation of recalcitrant chemicals from flow back water

In the present study treatability of persistent organic compounds from the flow back water after hydrauling fracturing was investigated. The combination of TiO₂ photocatalyst and magnetic oxide nanoparticles enhance the separation and recoverable property of nanosized TiO₂ photocatalyst. Fe₃O₄/TiO₂ and Fe₃O₄@SiO₂/TiO₂ nanocomposites were prepared by heteroagglomeration. The photocatalysts' characteristics by X-ray diffractometry (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS) showed that sample with the mass ratio of Fe₃O₄ to TiO₂ equal 1:4 and molar ratio of TEOS:Fe₃O₄ = 8:1 and NH₄OH:TEOS = 16:1 obtained by deposition TiO₂ P25 (Evonik) on magnetite core had about 124 m² g^-1 specific surface area and superparamagnetic properties. The prepared composites contained TiO₂ and Fe₃O₄ crystal phases. The photocatalytic activity was estimated by measuring the decomposition rate of three model pollutants identified in the flow back water from one of the Baltic Shale Basin. Regarding flow back water treatment after shale gas exploration, the progress of photocatalytic degradation of organic compounds was measured by chemical oxygen demand (COD) concentration. The Fe₃O₄@SiO₂/TiO₂_P25 composite nanoparticles were recovered and re-used without significant reduction of efficiency.

Transparent thin films of Cu–TiO2 with visible light photocatalytic activity

Thin films of Cu–TiO₂ with high transparency were prepared using a low-cost dip-coating method. The visible light activity of Cu–TiO₂ in the aqueous solution was confirmed in relation to model organic compounds.