Nanoscale spinel zinc ferrite (ZNF) was prepared by sol-gel auto-ignition route and subsequently its surface was modified by oleic-acid (OA) coating. The pristine and surface modified ZNF ...nanoparticles (UC-ZNF and OA-ZNF) were characterized by standard techniques. XRD patterns of both the samples ensured the nanocrystalline mono-phasic cubic-spinel lattice structure with ‘Fd-3m space-group’. FT-IR spectra revealed the presence of vibrational frequency-modes of spinel structure and successful coating of OA over ZNF. The nano-size spherical grains with some agglomeration and OA coating over ZNF were visualized in FE-SEM images. The hydrophobic-to-hydrophilic surface-transition of ZNF was confirmed by water contact-angle measurements. The BET surface-area and distribution of pore-radius was evaluated by recording N2-isotherms. The M − H plots confirmed the superparamagnetic nature of both the samples. Optical properties were studied by UV–Vis and PL spectroscopy techniques. The colloidal-stability and distribution of particle-sizes were estimated by zeta-potential and DLS measurements. Magnetic hyperthermia studies were carried out for different concentrations (2, 4, 6, 8 and 10 mg/mL) of both the samples. The biocompatible nature of both the samples was studied by cell-viability studies. All these results ensure the implementation of OA-ZNF nanoparticles with minimum dose rate (8 mg/mL) in magnetic hyperthermia therapies for cancer treatment.
Nickel ferrite (NiFe2O4) nanoparticles were synthesized through the sol-gel auto-combustion method using urea and glycine as mixed fuel. The prepared nanoparticles were investigated for their ...structural, optical, and magnetic characterizations. Rietveld refined X-ray diffraction (XRD) patterns revealed the development of single-phase cubic spinel. The crystallite size was calculated by using Modified Scherrer's method and the W-H plot was found in the order of 26.6 nm and 25.4 respectively which are nearly the same. The infrared spectrum showed the typical characteristic absorption bands in the range of 400 cm-1 to 600 cm-1 belonging to cubic spinel structure. Scanning electron microscopy images showed the spherical nature of the nanoparticles along with agglomeration to some extent. As per the optical study, the prepared nanoparticles have an optical bandgap of 2.59 eV. The magnetic properties were studied through the M − H hysteresis curve showing superparamagnetic nature, the value of saturation magnetization (Ms), coercivity (Hc) was observed 46.20 emu/gm, and 383.2 Oe respectively. The photocatalytic activity of nickel ferrite was studied based on the degradation of methylene blue (MB) dye as a model compound, where the result showed that prepared nanoparticles possessed a good photocatalytic activity against dye degradation. Up to four times catalyst exhibits nearly the same reutilization.
Mn substituted ZnO nanoparticles with compositional formula Zn
1−
x
Mn
x
O where
x = 0.00, 0.04 and 0.08 were synthesized by sol-gel route. All the samples sintered at 650 °C for 12 h in a furnace ...followed by furnace cooling up to room temperature. X-ray diffraction (XRD) studies shows the presence of hexagonal crystal structure as same as parent compound (ZnO) in all samples. The lattice parameters ‘a’ and ‘c’ were determined from XRD data and found that they increase linearly with the Mn content, which suggests that doped Mn ions go to Zn sites. Grain size, X-ray density and Atomic packing fraction (APF) were evaluated using XRD data and found that grain size increases while X-ray density and Atomic packing fraction (APF) decreases with dopant concentration increases. The functional groups and chemical interactions of Mn substituted Zinc oxide samples were also determined at various peaks using FTIR data and observed the presence of function groups in the samples. Results of such an investigation presented in this paper.
► Mn substituted ZnO nanoparticles synthesized by sol–gel method. ► Maintained wurtzite structure of ZnO upto 8% of Mn doping without any extra peaks of impurities. ► Prominent IR peaks analyzed qualitatively.
In the present work, Al
3+
-Gd
3+
substituted (at iron site) cubic nickel ferrite nanoparticles having the formula NiFe
2-2x
Al
x
Gd
x
O
4
(
x
= 0.00–0.08 in the step of 0.02) were fabricated ...through wet chemical, low temperature sol–gel self-ignition method. Glycine (C
2
H
5
NO
2
) was used as a fuel; maintaining the metal nitrite to glycine ratio as 1:4.4. The as prepared nanoparticles were annealed at 850 ºC for 5 h for removal of the moisture and other impurities. The phase purity and the structural parameters were investigated using the powder X-ray diffraction technique, which indicates the presence of principle reflections (220) and (311) along with other reflections belonging to cubic structure which proves that the prepared samples possesses mono-phase and the crystal structure have cubic spinel symmetry. The ferrite phase formation was assured with the characteristic peaks driven by intrinsic
υ
1
= 546 cm
−1
, 557 cm
−1
, and extrinsic vibration
υ
2
= 401 cm
−1
, 417 cm
−1
studied in the FTIR spectroscopic analysis. The lattice constant (
a
) of NiFe
2-2x
Al
x
Gd
x
O
4
NPs was found to be increased gradually with an increasing composition of Al-Gd co-substitution under the influence of higher ionic radii. The average crystallite size (D) was estimated through Scherrer’s formula varies between 20.88 and 27.82 nm. The SEM and TEM observations of typical samples have suggested the well-defined spherical grain growth with dense structure and agglomeration with a particle size of ~ 28.56 nm to ~ 47.74 nm. From the Brunauer–Emmett–Teller analysis, the surface area of the samples with
x
= 0.02 and 0.04, was found to be in the range of 10.6–18 m
2
/g. The magnetic properties such as saturation magnetization (
M
s
) and magneton number (
n
B
) were decreased with an increasing Al-Gd content
X
. The remanence ratio (
M
r
/
M
s
) was found to be in the range of 0.25 to 0.37, indicating the multi-domain structure of the prepared samples. The Ultraviolet–Visible spectroscopy was employed to study the absorbance and determine the bandgap of the NiFe
2-2x
Al
x
Gd
x
O
4
NPs which is of the order ~ 2.80 eV.
The Zn
2+
–Cr
3+
substituted nickel ferrite nanoparticles with a chemical formula Ni
1−x
Zn
x
Fe
2−x
Cr
x
O
4
(0.0
≤
x
≤
1.0) were successfully synthesized by a sol–gel auto-combustion method. ...X-ray diffraction (XRD) patterns of all the samples confirm the single phase cubic spinel structure with
Fd-3m
space group. In the present system, the lattice constant was increased from 8.337 to 8.396 Å with increasing Zn
2+
–Cr
3+
concentration. The average crystallite size (t) determined using the Debye–Scherrer’s formula, which lies in the range of 19–28 nm. The surface morphology was examined with field emission scanning electron microscopy (FE-SEM) and it showed that the particle size of the samples lies in the nano regime with a moderate agglomeration. The compositional stoichiometry was confirmed by energy dispersive spectrum (EDS). FT-IR spectra indicates two fundamental absorption bands, the higher frequency band
ϑ
1
at 574–594 cm
−1
and the lower frequency band
ϑ
2
at 468–486 cm
−1
arising from tetrahedral (A) and octahedral B sites it confirm the spinel structure. The magnetic properties of all the samples were measured using a Vibrating sample magnetometer (VSM) at room temperature. The saturation magnetization (M
s
) was found to decrease due to B–B exchange and A–B superexchange interaction while remanent magnetization (M
r
) and coercivity (H
c
) decreases with increasing Zn
2+
–Cr
3+
concentration. The DC electrical resistivity as a function of temperature revealed the semiconducting nature of all the samples. The activation energy (E
a
) was found to increase from 0.371 to 0.478 eV with an increase in Zn
2+
–Cr
3+
concentration. Overall, the Zn
2+
and Cr
3+
ions are successfully incorporated in the nickel ferrite by sol–gel auto-combustion method, and the spinel structure was not disturbed by the substitution. The magnetic and electrical properties of nickel ferrites are strongly influenced by the substitution, which may useful in technological and industrial applications.
Aluminum substituted cobalt ferrite powders (CoFe2−xAlxO4) with varying composition from 0.0 to 1.0 in the step of 0.2 have been obtained by sol–gel auto combustion technique using citric acid as a ...fuel. The metal nitrate to fuel ratio was maintained 1:4 throughout the synthesis of CoFe2−xAlxO4. The thermal analysis of as prepared samples is done by TGA technique. The compositional stoichiometry of the prepared samples is confirmed by Energy dispersive X-ray analysis technique. Single phase cubic spinel structure and nano phase structure of the synthesized powders were confirmed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The crystallite size of 16–26nm was obtained using Scherrer formula. SEM analysis shows the formation of uniform grain growth. The grain size obtained from SEM results is of the order of 30nm. Maximum specific surface area was observed to be of the order of 52m2/gm. The highest value of saturation magnetization and coercivity was observed for pure cobalt ferrite sample and it decreases as the aluminum content x increases. A strong co-relation between the saturation magnetization and aluminum content was observed. The decrease in magnetic properties is due to the substitution of aluminum ions in place of Fe3+.
The silica aerogel was synthesized by simple and cost-effective sol-gel process under ambient pressure drying. The wet gel was modified by using trimethylchlorosilane (TMCS) as silylating agent. The ...prepared aerogel was characterized by X-ray diffractometer (XRD), thermogravimetric and differential thermal analyzer (TG-DTA), Fourier transform infrared spectrometer (FT-IR), Brunauer-Emmett-Teller (BET) analyzer, field emission scanning electron microscope (FE-SEM) and Ultraviolet-Visible (UV–Vis) spectrophotometer for structural, thermal, functional, surface, morphological and optical properties. The presence of hump in X-ray diffraction pattern revealed the amorphous nature of prepared silica aerogel. Thermal stability of silica aerogel investigated by TG-DTA show a hydrophobic nature up to 478 °C. FE-SEM images confirmed the porous nature of silica aerogel. The surface area and pore radius measured by BET analyzer disclosed as 792.308 m2/g and 5.779 nm respectively while the total pore volume is 2.289 cc/g. Superhydrophobic nature of silica aerogel sample was affirmed by contact angle measurements. The energy band gap calculated from UV–Vis spectra was found to be 4.25 eV confirming the insulating nature of prepared silica aerogel. The resulting silica aerogel possesses high thermal stability, Superhydrophobicity and large specific surface area which can be useful in various applications such as catalysis, coating materials, oil spill cleanup processes and insulating materials.
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•Synthesis of silica aerogel by simple and economic ambient pressure drying method.•Trimethylchlorosilane (TMCS) used as a silylating agent for surface modifications.•Prepared aerogels shown high thermal stability with respect to hydrophobicity.•Brunauer-Emmett-Teller analysis disclosed large surface area of prepared aerogel.•High contact angle value affirmed the superhydrophobic nature of the aerogel.
In situ polymerization of aniline is carried out in the presence of zinc ferrite to synthesize polyaniline/ZnFe2O4 composites (PANI/ZnFe2O4) by chemical oxidation method. The composite has been ...synthesized with various compositions (10, 20, 30, 40 and 50wt.%) of zinc ferrite in PANI. From the infrared spectroscopy (FTIR) studies on polyaniline/ZnFe2O4 composites, the peak at 1140cm−1 is considered to be measure of the degree of electron delocalization. The surface morphology of these composites is studied with scanning electron micrograph (SEM). The ac conductivity and dielectric properties are studied in the frequency range from 102 to 106Hz. The results obtained for these composites are of scientific and technological interest.
