Heterostructured ZnFe2O4/Fe2TiO5/TiO2 Composite Nanotube Arrays with an Improved Photocatalysis Degradation Efficiency Under Simulated Sunlight Irradiation

Ultrahigh Degree of Cationic Disorder, Configurational Entropy in New Type of High-Entropy Pseudobrookite Phase

High-entropy ceramics exhibit various excellent properties owing to their high configurational entropy, which is caused by multi-principal elements sharing one lattice site. The configurational entropy will further increase significantly if multi-principal elements randomly share two different lattice sites. For this purpose, pseudobrookite phase containing two cationic lattice sites (A and B sites) is selected, and corresponding high-entropy pseudobrookite (M2+ 0.4M3+ 1.2)Ti1.4O5 is synthesized. Herein, the distribution of the 2-valent and 3-valent cations in the A and B sites are analysed in depth. The distance between the A and B sites in the crystal structure models which are constructed by the Rietveld analysis is calculated and defined as distance d. Meanwhile, the atomic column positions in the STEM images are quantified by a model-based mathematical algorithm, and the corresponding distance d are calculated. By comparing the distance d, it is determine that the 2-valent and 3-valent cations are jointly and disorderly distributed in the A and B sites in high-entropy (M2+ 0.4M3+ 1.2)Ti1.4O5. The density functional theory (DFT) simulations also demonstrate that this type of crystal structure is more thermodynamically stable. The higher degree of cationic disorder leads to a higher configurational entropy in high-entropy (M2+ 0.4M3+ 1.2)Ti1.4O5, and endows high-entropy (M2+ 0.4M3+ 1.2)Ti1.4O5 with very low thermal conductivity (1.187-1.249 W m-1 K-1).

Photocatalytic behavior for removal of methylene blue from aqueous solutions via nanocomposites based on Gd2O3/CdS and cellulose acetate nanofibers

Efficient cleaning of contaminated water by photocatalysis has become an effective strategy in recent years due to its environmental and ecological designation. Cadmium sulfate (CdS) is an excellent photocatalyst in the visible region but has low quantum efficiency. In order to increase the photocatalytic efficiency, CdS was modified with gadolinium oxide (Gd2O3) and combined with graphene oxide (GO) nanoparticles. The estimated crystallite size (Ds) for Gd2O3, CdS/Gd2O3, and CdS/Gd2O3@GO was 29.6, 11.6, and 11.5 nm, respectively. The degradation of methylene blue (MB) reaches the highest values after 60 min under visible light irradiation with a dye concentration of (0.25 ppm). Whereas in powdered composition the efficiency of dye removal has been enhanced under UV irradiation, it reduced by increasing the MB concentration to 0.50 ppm with visible light irradiation. In addition, the CdS with/without Gd2O3 and GO were integrated into electrospun nanofibrous cellulose acetate (CA) through the electrospinning technique. The compounds of Gd2O3, CdS/Gd2O3, and CdS/Gd2O3/GO were encapsulated into CA nanofibers for the degradation of MB under visible and UV irradiation. The apparent rate constant (k) achieves a value of 0.006, 0.007, and 0.0013 min-1 while the removal efficiency reaches 41.02%, 54.71%, and 71.42% for Gd2O3@CA, CdS/Gd2O3@CA, and CdS/Gd2O3/GO@CA, respectively, after 60 min under UV irradiation.

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.

BiVO4/Fe2O3/ZnFe2O4; triple heterojunction for an enhanced PEC performance for hydrogen generation

n/n/n triple heterojunction photoanodes made up of Zr:W-BiVO₄, Fe₂O₃, and ZnFe₂O₄ metal oxides are fabricated through a simplistic spray pyrolysis method. Use of Zr and W as dopants in BiVO₄ plays an important role as Zr increases the carrier density and W reduces the charge recombination. Further, Fe₂O₃ and ZnFe₂O₄ serve as a protective layer for Zr:W-BiVO₄, which augmented the photoelectrochemical performance and achieved a 1.90% conversion efficiency in the triple heterojunction. XRD measurements display the crystalline nature and reduction in particle size due to strain in the sample, UV-vis absorbance shows an extended absorption towards the visible region and the FE-SEM imaging confirms the successful deposition of ZnFe₂O₄ over BiVO₄/Fe₂O₃. By analyzing the band edge position, it was observed that on formation, the triple heterojunction not only suppresses the charge carrier recombination but also utilizes the band edge offset for the water splitting reaction using solar energy.

n/n/n triple heterojunction photoanodes made up of Zr:W-BiVO₄, Fe₂O₃, and ZnFe₂O₄ metal oxides.

Recovery of syringic acid from aqueous solution by magnetic Fe–Zn/ZIF and its slow release from the CA-coated carrier based on the 3Rs concept

The excessive utilization of syringic acid (SA) has caused severe environmental pollution and economic waste.

pH and H2S Dual-Responsive Magnetic Metal-Organic Frameworks for Controlling the Release of 5-Fluorouracil

Along with the increasing cancer incidence, developing suitable drug delivery systems (DDSs) is becoming urgent to control drug release and further enhance therapeutic efficiency. Herein, a Fe-Zn bimetallic MOF-derived ferromagnetic nanomaterial was synthesized by a one-step method. The successful preparation of ferromagnetic Fe-ZIF-8 was verified by scanning electron microscopy, powder X-ray diffraction, Brunauer-Emmett-Teller, X-ray photoelectron spectroscopy, and physical property measurement system characterizations. Furthermore, the release behaviors of 5-FU from the ferromagnetic carrier were investigated in a simulative cancer microenvironment of PBS buffer solution (PBS = phosphate-buffered saline, pH = 5.8) and NaHS solution. The vehicle in PBS solution of pH = 5.8 and NaHS solution of 500 μM can rapidly release 5-FU with the cumulative release percentages of 68 and 36%, respectively, within two hundred minutes. The release mechanism in the weak acid environment can be mainly attributed to the decomposition of the Fe-ZIF-8. However, the strong interaction between Zn and Fe atoms in Fe-ZIF-8 and the S atom in H₂S plays an important role in the release process in the simulated H₂S cancer microenvironment. The investigation of release kinetic models indicates that the 5-FU release in the PBS solutions and NaHS solution of 500 μM can be accurately fitted by a second-degree polynomial model and first-order model, respectively. In addition, the decomposition products, zinc, iron, and 2-MeIM, are endogenous and show low toxicity values [LD₅₀ (Zn) = 0.35 g·kg^-1, LD₅₀ (Fe) = 30 g·kg^-1, and LD₅₀ (2-MeIM) = 1.4 g·kg^-1]. Therefore, the low-toxicity, pH and H₂S dual-stimuli-responsive, and ferromagnetic nature make the obtained Fe-ZIF-8 an ideal candidate in the field of bioactive molecule delivery.

A versatile switchable dual-modal colorimetric and photoelectrochemical biosensing strategy via light-controlled sway of a signal-output transverter

A design criterion to construct a versatile dual-modal colorimetric and PEC biosensing platform for switching the corresponding mode freely is proposed via integration of a natural enzyme, light-activated nanozyme and light-controlled swayable signal-output transverter. A switchable dual-modal platform toward DNA analysis is developed as a proof of concept.

Kinetic Study on the Crystal Transformation of Fe-Doped TiO2 via In Situ High-Temperature X-ray Diffraction and Transmission Electron Microscopy

Titanium dioxide (TiO₂) is widely used in various major industries owing to its different crystal forms and functions. Therefore, fabricating suitable crystalline TiO₂ through reasonable processes is necessary. In this study, Fe-doped TiO₂ precursors were prepared via hydrolysis. Further, in situ high-temperature X-ray diffraction and transmission electron microscopy were used to transform the synthesized precursor in its crystal form. The Rietveld full-spectrum fitting method could accurately yield two different crystal forms at instant temperatures. Additionally, the rate relation between the crystal form transformation and reaction conditions was obtained. Results showed that the addition of Fe increased the temperature of phase transition of TiO₂ anatase to rutile and accelerated the anatase → rutile transformation process. Further, crystal phase transition kinetic analysis showed that the phase transition kinetic model of Fe-doped TiO₂ matched the Johnson-Mehl-Avrami-Kohnogorov (JMAK) model and that its phase transition was affected by crystal defects. Finally, Fe³⁺ in Fe-doped TiO₂ was reduced to Fe²⁺ to generate oxygen vacancies, thus promoting the rate of transformation from titanium ore to rutile.

A comprehensive study on the application of FeNi3@SiO2@ZnO magnetic nanocomposites as a novel photo-catalyst for degradation of tamoxifen in the presence of simulated sunlight

Pharmaceutical compounds at trace concentrations are found in the environment, especially in drinking water and food, posing significant negative effects on humans as well as on animals. This paper aimed to examine the diagnostic catalytic properties and efficacy of a novel synthesized photocatalyst, namely FeNi₃@SiO₂@ZnO magnetic nanocomposite, for the removal of tamoxifen (TMX) from wastewater under simulated sunlight. According to the results, it was found that TMX was completely degraded operating under optimized conditions (i.e. pH = 7, catalyst dose = 0.01 g/L, initial TMX concentration = 20 mg/L and reaction time = 60 min). The reaction kinetics of TMX degradation followed a pseudo-first order kinetics model. The final by-products from the TMX photodegradation were water, carbon dioxide, acetic acid, nitroacetic acid methyl ester, 2-methyl-2-pentenal, and 4-methyl-2-pentanol. In addition, the synthesized photocatalyst could successfully performed five consecutive photodegradation cycles. The obtained results revealed that the synthesized FeNi₃@SiO₂@ZnO magnetic nanocomposite holds a great potential to be applied as a photocatalyst for the degradation of TMX on an industrial scale.

Engineering the coupling interface of rhombic dodecahedral NiCoP/C@FeOOH nanocages toward enhanced water oxidation

Hydrogen, regarded as one of the most promising green and sustainable energy resources, could be generated by splitting water with electrochemical methods. The challenge for efficient hydrogen generation is the sluggish kinetics at the anodes for the oxygen evolution reaction (OER). Here, a novel catalyst with remarkably enhanced OER activity was prepared by coupling FeOOH and NiCoP/C. The enhanced OER activity of the hybrid catalyst should be ascribed to the synergistic effect of the individual components. First, NiCoP/C derived from ZIF-67 with a hollow rhombic dodecahedral architecture not only allows exposure of numerous active sites but also provides high conductivity. Second, the re-localization of electrons at the coupling interface optimizes the adsorption/desorption nature of intermediate oxygenated species and imparts a high OER activity. The hybrid NiCoP/C@FeOOH catalyst exhibits very high OER activity with a low overpotential of 271 mV for producing a current density of 10 mA cm^-2 in 1 M KOH aqueous solution, markedly surpassing the individual counterparts of pure NiCoP/C nanocages and bare FeOOH. This work represents a universal strategy for boosting the OER kinetics of catalysts and pushing boundaries for high-efficiency water oxidation.

Microstructures and Photodegradation Performance toward Methylene Orange of Sputtering-Assisted Decoration of ZnFe₂O₄ Crystallites onto TiO₂ Nanorods

In this study, TiO₂⁻ZnFe₂O₄ (ZFO) core-shell nanorods with various ZFO crystallite thicknesses were synthesized through sputtering-deposited ZFO thin films onto the surfaces of TiO₂ nanorods. By coupling the ZFO narrow bandgap oxide with TiO₂, an enhanced photodegradation efficiency of methylene orange under irradiation was achieved. Structural analyses revealed that ZFO crystallites fully covered the surfaces of the TiO₂ nanorods. The sputtering-deposited ZFO crystallites on the head region of the composite nanorods were markedly thicker than those covering the lateral region of the composite nanorods. The coverage of ZFO crystallites on the TiO₂ nanorods led to an improved light harvesting, a decrease in the hole⁻electron recombination rate, as well as the enhanced photodegradation activity of the TiO₂⁻ZFO heterostructures under irradiation. The optimized ZFO thickness on the head region of the composite nanorods was approximately 43 nm on average and that at the lateral region of the composite nanorods was 15 nm, which exhibited superior photodegradation ability to methylene orange and retained a stable photodegradation efficiency of approximately 97% after cycling tests. The results herein demonstrate that sputtering deposition of ZFO crystallite with tunable thickness is a promising approach to designing TiO₂⁻ZFO composite nanorods with various ZFO coverage sizes and to adjust their photodegradation ability toward organic dyes.

Copper-nanoparticle-dispersed amorphous BaTiO3 thin films as hole-trapping centers: enhanced photocatalytic activity and stability

Nobel metal (Au and Ag) nanoparticles are often used in semiconductor photocatalysis to enhance the photocatalytic activity, while inexpensive Cu attracts less attention due to its easy oxidization. Herein, an elaborate study was conducted using Cu-nanoparticle-dispersed amorphous BaTiO3 films as photocatalysts. Photocatalytic and photoelectrochemical measurements demonstrated that the degradation efficiency and photocurrent density of the nanocomposite films are approximately 3.5 and 10 times as high as the pristine BaTiO3 film, respectively, which can be ascribed to a synergetic effect of the surface plasmon resonance and interband excitation. In addition, a good stability was also demonstrated by cyclic tests for the degradation of rhodamine B, which may be due to the amorphous nature of the BaTiO3 matrix providing hole-trapping centers. The high photocatalytic stability suggests that Cu is a promising alternative metal to replace Au and Ag for the development of cost-effective photocatalysts. Our work demonstrates a simple and promising strategy for improving the photostability of Cu nanomaterials and may provide a useful guideline for designing Cu-based composite materials toward various photocatalytic applications such as water pollution treatment.