“…It could be concluded that more water aging time results in a thicker oxide shell because of reaction of zero valent iron with O 2 /H 2 O in the solution. The increase in shell thickness was also seen by Xue et al by preparing the core-shell nanocomposite, synthesized through the facile reflux method [17, 18]. Fig.…”
One of the big challenge of studying the core-shell iron nanostructures is to know the nature of oxide shell, i.e., whether it is γ-Fe2O3 (Maghemite), Fe3O4 (Magnetite), α-Fe2O3 (Hematite), or FeO (Wustite). By knowing the nature of iron oxide shell with zero valent iron core, one can determine the chemical or physical behavior of core-shell nanostructures. Fe core-shell nanochains (NCs) were prepared through the reduction of Fe3+ ions by sodium boro-hydride in aqueous solution at room atmosphere, and Fe NCs were further aged in water up to 240 min. XRD was used to study the structure of Fe NCs. Further analysis of core-shell nature of Fe NCs was done by TEM, results showed increase in thickness of oxide shell (from 2.5, 4, 6 to 10 nm) as water aging time increases (from 0 min, 120 min, 240 min to 360 min). The Raman spectroscopy was employed to study the oxide nature of Fe NCs. To further confirm the magnetite phase in Fe NCs, the Mössbauer spectroscopy was done on Fe NCs-0 and Fe NCs-6. Result shows the presence of magnetite in the sample before aging in water, and the sample after prolonged aging contains pure Hematite phase. It shows that prolonged water oxidation transforms the structure of shell of Fe NCs from mixture of Hematite and Magnetite in to pure hematite shell. The Magnetic properties of the Fe NCs were measured by VSM at 320 K. Because of high saturation magnetization (Ms) values, Fe NCs could be used as r2 contrasts agents for magnetic resonance imaging (MRI) in near future.
“…It could be concluded that more water aging time results in a thicker oxide shell because of reaction of zero valent iron with O 2 /H 2 O in the solution. The increase in shell thickness was also seen by Xue et al by preparing the core-shell nanocomposite, synthesized through the facile reflux method [17, 18]. Fig.…”
One of the big challenge of studying the core-shell iron nanostructures is to know the nature of oxide shell, i.e., whether it is γ-Fe2O3 (Maghemite), Fe3O4 (Magnetite), α-Fe2O3 (Hematite), or FeO (Wustite). By knowing the nature of iron oxide shell with zero valent iron core, one can determine the chemical or physical behavior of core-shell nanostructures. Fe core-shell nanochains (NCs) were prepared through the reduction of Fe3+ ions by sodium boro-hydride in aqueous solution at room atmosphere, and Fe NCs were further aged in water up to 240 min. XRD was used to study the structure of Fe NCs. Further analysis of core-shell nature of Fe NCs was done by TEM, results showed increase in thickness of oxide shell (from 2.5, 4, 6 to 10 nm) as water aging time increases (from 0 min, 120 min, 240 min to 360 min). The Raman spectroscopy was employed to study the oxide nature of Fe NCs. To further confirm the magnetite phase in Fe NCs, the Mössbauer spectroscopy was done on Fe NCs-0 and Fe NCs-6. Result shows the presence of magnetite in the sample before aging in water, and the sample after prolonged aging contains pure Hematite phase. It shows that prolonged water oxidation transforms the structure of shell of Fe NCs from mixture of Hematite and Magnetite in to pure hematite shell. The Magnetic properties of the Fe NCs were measured by VSM at 320 K. Because of high saturation magnetization (Ms) values, Fe NCs could be used as r2 contrasts agents for magnetic resonance imaging (MRI) in near future.
“…Figure 2 shows the Fourier transform infrared (FTIR) spectra of UiO‐66(Zr), NiFe 2 O 4 @AC, and NiFe 2 O 4 @AC/UiO‐66(Zr)‐ 2 photocatalysts. For UiO‐66(Zr) photomaterials, the vibrational peaks around 3420 cm −1 is attributed to the stretching vibration of O−H stretching vibration [32] . Besides, the C−O−C′s asymmetric and symmetric stretching frequencies can be observed at 1577 cm −1 and 1395 cm −1 , respectively.…”
In this study, NiFe2O4@AC/UiO‐66(Zr) composites were successfully prepared with different ratios of UiO‐66(Zr) as support for NiFe2O4@AC, (1 : 1), (2 : 1) and (3 : 1) named NiFe2O4@AC/UiO‐66(Zr)‐1, NiFe2O4@AC/UiO‐66(Zr)‐2 and NiFe2O4@AC/UiO‐66(Zr)‐3, respectively. The prepared composites were characterized by X‐Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X‐Ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET), ultraviolet‐visible diffuse reflectance (UV‐Vis/DRS) spectroscopy, PL (Photoluminescence) study. The synthesized composites′ efficiencies to enhance the photodegradation of alizarin yellow R (AYR) under visible‐light were evaluated. The results identified that NiFe2O4@AC/UiO‐66(Zr)‐2 is the most photoreactive photocatalyst with the lowest bandgap ∼1.7 eV. NiFe2O4@AC/UiO‐66(Zr)‐2 shows higher photodegradation efficiency (97.9 %) compared to NiFe2O4@AC/UiO‐66(Zr)‐1 and NiFe2O4@AC/UiO‐66(Zr)‐3 with photodegradation efficiency of 75.1 % and 89.9 %, respectively after 180 min under visible‐light. The photodegradation reaction of AYR was found to be pseudo first‐order reaction, and the rate constant (Ka) for NiFe2O4@AC/UiO‐66(Zr)‐1, NiFe2O4@AC/UiO‐66(Zr)‐2, and NiFe2O4@AC/UiO‐66(Zr)‐3 are 0.0072 min−1, 0.0204 min−1, and 0.0122 min−1, consecutively. The effects of various conditions such as initial concentration and photocatalyst dose on the photodegradation of AYR were determined. The high photodegradation efficiency of NiFe2O4@AC/UiO‐66(Zr)‐2 composite is because of the heterojunction and effective charge transfer between NiFe2O4@AC and UiO‐66(Zr). NiFe2O4@AC/UiO‐66(Zr)‐2 photocatalyst exhibits photocatalytic stability and reusability up to five cycles.
“…1,2 Among the various photocatalytic semiconductors, CdS was studied owing to the narrow band gap, strong light absorption coefficient and the appropriate band position. [3][4][5][6][7][8][9][10][11][12][13][14][15][16] In order to enlarge the specific surface and to promote the transfer of charge, various CdS have established nanostructures such as quantum dots (0D), nanorods (1D), nanoflakes (2D) and nanoparticles (3D) for solar water splitting. Compared to 0D and 3D nanostructures, 1D and 2D CdS exhibits less carrier recombination and faster charge transfer which leads to excellent photocatalytic property.…”
Section: Introductionmentioning
confidence: 99%
“…Photocatalytic water splitting as a regenerative green process for hydrogen production has attracted great attention in recent decades 1,2 . Among the various photocatalytic semiconductors, CdS was studied owing to the narrow band gap, strong light absorption coefficient and the appropriate band position 3‐16 . In order to enlarge the specific surface and to promote the transfer of charge, various CdS have established nanostructures such as quantum dots (0D), nanorods (1D), nanoflakes (2D) and nanoparticles (3D) for solar water splitting.…”
P-type Ni(OH) 2 has been combined with n-type CdS nanorods and nanocrystals for enhanced photocatalytic property due to the p-n junction. Though CdS nanosheets exhibit fast charge transfer and large superficial area, the decoration of Ni(OH) 2 was rarely reported up to now. In this work, the photodeposition of Ni(OH) 2 nanoparticles on CdS ultrathin nanoflakes was established for efficient photocatalytic H 2 generation. By changing the irradiation time of CdS, the reaction between Ni 2+ and OH À can be controlled for different loading density of Ni(OH) 2 . As the loading density-dependent morphology, light absorption, carrier separation and transfer were systematically studied for the composites, an obvious band gap narrowing from 2.28 to 2.08 eV was revealed, and the carrier separation and transfer between the CdS nanoflakes and Ni(OH) 2 nanoparticles have been enhanced for the composites with deposition time of 3 minutes. These together with the alignment of type "II" bands and the high specific surface area of the flakes and nanoparticles, lead to an optimum H 2 generation of 20.14 mmol/g/h, nearly three times of pure CdS (7.97 mmol/g/h). Such a study not only provides a deposition method of Ni(OH) 2 , but also sheds light on the enhancement strategy for photocatalytic property by controlling the microstructure and aligning the hetero-structured bands.
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