High-yield synthesis of well-crystalline alpha-Fe2O3 nanoparticles: structural, optical and photocatalytic properties

Switching of photoinduced proton transfer from one six-membered hydrogen-bonded ring to other: a molecule of hydrazine and pH sensor

The present study describes photophysical properties of 3-(benzo[d]oxazol-2-yl)-5-bromo-2-hydroxybenzaldehyde (HBOB) and (E)-2-(benzo[d]oxazol-2-yl)-4-bromo-6-(hydrazonomethyl)phenol (HBON) molecules with asymmetric two-way proton transfer sites. The purpose of this study is to know the direction of ESIPT out of the two-way proton transfer pathways in these molecules in both the solid and solution state. The steady state and time-resolved spectral behaviour of HBOB and HBON and a comparison of the spectral features with the two distinct control compounds 2-(benzo[d]oxazol-2-yl)-4-bromophenol (HBO) and (E)-4-bromo-2-(hydrazonomethyl)phenol (HBN) having single 6-membered hydrogen bonded network reveal that HBOB undergoes imine-amine photoisomerisation by proton transfer towards the oxazole side and HBON undergoes towards the hydrazone side with characteristic Stokes' shifted emission. Proton transfer forms with the red shifted emission of these molecules shows fast decay than the locally excited state. In the solid state, extremely high fluorescence intensity was observed, following a similar type of ESIPT pattern. Calculated ground (S0) and excited state (S1) energy barriers for the PT process obtained using density functional theory (DFT) and time-dependent density functional theory (TD-DFT) corroborate the unidirectional excited state intramolecular proton transfer (ESIPT) process for HBOB and HBON, and the theoretical spectral features validate our experimental absorption and emission spectra well. Interestingly, the unique unidirectional ESIPT behaviour of HBOB was utilised to detect hydrazine both in solution and solid phases. On the other hand, HBON was found to be a good fluorescence pH sensor with a ratiometric color change from yellow to green in acidic and basic media.

Effective degradation of tetracycline and real pharmaceutical wastewater using novel nanocomposites of biosynthesized ZnO and carbonized toner powder

In this study, novel nanohybrids of biosynthesized zinc oxide (ZnO) and magnetite-nanocarbon (Fe3O4-NC) obtained from the carbonization of toner powder waste were fabricated and investigated for persulfate (PS) activation for the efficient degradation of tetracycline (TCN). The chemical and physical properties of the synthesized catalysts were analyzed using advanced techniques. ZnO/Fe3O4-NC nanohybrid with mass ratio 1:2, respectively in the presence of PS showed the highest TCN removal efficiency compared to the individual components (ZnO and Fe3O4-NC) and other nanohybrids with mass ratios of 1:1 and 2:1. The results indicated that efficient degradation of TCN could be attained at pH 3-7. The optimum operating parameters were TCN concentration of 12.8 mg/L, PS concentration of 7 Mm, and catalyst dose of 0.55 g/L. The high stability of ZnO/Fe3O4-NC (1:2) nanocomposite was assured by the slight drop in TCN degradation percentage from 97.27% to 85.45% after five successive runs under the optimum conditions and the concentrations of leached iron and zinc into the solution were monitored. The quenching experiments explored that the prevailing reactive entities were sulfate radicals. Additionally, the degradation of TCN in various water matrices was investigated, and a degradation pathway was suggested. Further, degradation of real pharmaceutical waste was conducted showing that the removal efficiencies of TCN, total organic carbon (TOC), and chemical oxygen demand (COD) were 89.79, 80.65, and 78.64% after 2 h under the optimum conditions. The effectiveness of the proposed system (ZnO/Fe3O4-NC (1:2) @ PS) for the degradation of real samples compiled from industrial effluents as well as its inexpensiveness and green nature qualify this system for the full-scale application.

Conformance Control in Oil Reservoirs by Citric Acid-Coated Magnetite Nanoparticles

Reservoir conformance control methods may significantly improve enhanced oil recovery technologies through reduced water production and profile correction. Excessive water production in oil and gas reservoirs leads to severe problems. Water shutoff and conformance control are, therefore, financially and environmentally advantageous for the petroleum industry. In this paper, water shutoff performance of citric acid-coated magnetite (CACM) and hematite nanoparticles (NPs) as well as polyacrylamide polymer solution in a heterogeneous and homogeneous two-dimensional micromodel is compared. A facile one-step technique is used to synthesize the CACM NPs. The NPs, which are reusable, easily prepared, and environmentally friendly, are characterized using Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, dynamic light scattering, and X-ray diffraction. The results confirm uniform spherical Fe₃O₄ NPs of an average diameter of 40 nm, well coated with citric acid. CACM NPs provide a high pressure drop coupled with an acceptable resistance factor and residual resistance factor owing to NP arrangement into a solid-/gel-like structure in the presence of a magnetic field. A resistance factor and a residual resistance factor of 3.5 and 2.14, respectively, were achieved for heavy oil and the heterogeneous micromodel. This structure contributed to an appreciable plugging efficiency. CACM NPs respond to ∼1000 G of magnetic field intensity and display a constant resistance factor at intensities between 4500 and 6000 G. CACM NPs act as a gel, forming a solid-/gel-like structure, which moves toward the magnetic field and thereby shuts off the produced water and increases the oil fraction. The findings of this study suggest the ability to shut off water production using specially designed magnetic field-responsive smart fluids. The application would require innovative design of field equipment.

π-Extended Tetraphenylethylene Containing a Dicyanovinyl Group as an Ideal Fluorescence Turn-On and Naked-Eye Color Change Probe for Hydrazine Detection

A π-extended tetraphenylethylene derivative 1 was developed as a fluorescent "turn-on" and "naked-eye" color change probe for hydrazine detection. Probe 1 was composed of the representative AIE luminogen (AIEgen), tetraphenylethylene, and a dicyanovinyl group was adopted for hydrazine recognition. Upon exposure of hydrazine, probe 1 immediately gave a significant aggregation-induced emission around 575 nm and excellent photostability. A naked-eye color change was also observed from red to yellow. Moreover, probe 1 was simply coated with a glass-backed silica gel-coated thin-layer chromatography plate, showing rapid and on-site detection of hydrazine vapor.

The Synthesis of the Pomegranate-Shaped α-Fe2O3 Using an In Situ Corrosion Method of Scorodite and Its Gas-Sensitive Property

The release of hazardous gas increases with the development of industry. The research of gas-sensitive materials has attracted attention. Nanoscale iron oxide (α-Fe₂O₃) is one of the research hotspots of gas-sensitive materials because it is a cheap, non-toxic semiconductor material. In this study, pomegranate-shaped α-Fe₂O₃ was synthesized using an in situ corrosion method of scorodite. Spherical-shaped α-Fe₂O₃ nanoparticles were included in the octahedral shells. The forming process of the structure was analyzed by a variety of measurements. The shell was formed first through the deposition of Fe(OH)₃, which was produced by hydrolyzing scorodite. Then, the corrosion was continued and Fe(OH)₃ precipitation was produced below the shell. The particles aggregated and formed spheres. The pomegranate-shaped α-Fe₂O₃ was formed when the scorodite was hydrolyzed completely. The gas-sensing properties of α-Fe₂O₃ were investigated. The results showed that pomegranate-shaped α-Fe₂O₃ was responsive to a variety of gases, especially xylene. The value of R_a/R_g was 67.29 at 340 °C when the concentration of xylene was 1000 ppm. This indicated the pomegranate-shaped α-Fe₂O₃ has potential application as a xylene gas sensor.

Study of the iron nanoparticles phase transformation during thermal annealing

Change in structural properties and phase composition of nanoparticles based on iron oxide was researched in the paper. As a result of conducted studies it was found that during heat treatment oxide phases of (γ-Fe2O3) and α-Fe2O3 maghemite were formed in oxygen atmosphere. Researches of powder array magnetization were showed that the hysteresis loop movement had the form characteristic for ferromagnetic materials. Additionally, loops obtained at different directions of the magnetic field have different characters, which indicate the magnetic anisotropy presence in the samples.

Synthesis and characterization of Pt magnetic nanocatalysts with a TiO2 or CeO2 layer

The Pt magnetic nanocatalysts with a TiO₂ or CeO₂ layer have been fabricated successfully.

Photocatalytic degradation of methyl orange over nitrogen-fluorine codoped TiO2 nanobelts prepared by solvothermal synthesis

Anatase type nitrogen-fluorine (N-F) codoped TiO(2) nanobelts were prepared by a solvothermal method in which amorphous titania microspheres were used as the precursors. The as-prepared TiO(2) nanobelts are composed of thin narrow nanobelts and it is noted that there are large amount of wormhole-like mesopores on these narrow nanobelts. Photocatalytic activity of the N-F codoped TiO(2) nanobelts was measured by the reaction of photocatalytic degradation of methyl orange. Results indicate that the photocatalytic activity of the N-F codoped TiO(2) nanobelts is higher than that of P25, which is mainly ascribed to wormhole-like mesopores like prison, larger surface area, and enhanced absorption of light due to N-F codoping. Interestingly, it is also found that the photocatalytic activity can be further enhanced when tested in a new testing method because more photons can be captured by the nanobelts to stimulate the formation of the hole-electron pair.

Exploration of CeO₂ nanoparticles as a chemi-sensor and photo-catalyst for environmental applications

CeO₂ nanoparticles were synthesized hydrothermally and utilized as redox mediator for the fabrication of efficient ethanol chemi-sensor. The developed chemi-sensor showed an excellent performance for electrocatalytic oxidization of ethanol by exhibiting higher sensitivity (0.92 μA∙cm⁻²∙mM⁻¹) and lower limit of detection (0.124±0.010 mM) with the linear dynamic range of 0.17 mM-0.17 M. CeO₂ nanoparticles have been characterized by field emission scanning electron microscopy (FESEM), Energy dispersive spectroscopy (EDS), X-ray powder diffraction (XRD), Raman spectrum, Fourier transform infrared spectroscopy (FTIR), and UV-visible absorption spectrum which revealed that the synthesized CeO₂ is an aggregated form of optically active spherical nanoparticles with the range of 15-36 nm (average size of ~25±10 nm) and possessing well crystalline cubic phase. Additionally, CeO₂ performed well as a photo-catalyst by degrading amido black and acridine orange.