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Study of Holmium Doped Lithium Nano-Structured Ferrites: Synthesis, Characterization and Application

Thesis Info

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Author

Manzoor, Alina

Program

PhD

Institute

The Islamia University of Bahawalpur

City

Bahawalpur

Province

Punjab

Country

Pakistan

Thesis Completing Year

2018

Thesis Completion Status

Completed

Subject

Physics

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/11013/1/Alina%20Manzoor_Phy_2018_IUB_PRR.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727375593

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In this work we have studied the influence of Ho-substitution on various properties of Li1.2Me0.4Fe2-xHoxO4 (Me: Co, Ni, Mn, Zn; x = 0.00-0.15) spinel ferrites synthesized by sol-gel auto-combustion method. The thermo-gravimetric analysis (TGA) of the as prepared samples was carried out to estimate the annealing temperature essential for complete decomposition of precipitates and spinel phase formation which was seen to be around 950 °C. It is seen that face centered cubic phase is obtained by this method of preparation. The overall average crystallite sizes as determined from X-ray diffraction (XRD) fall in the range of 29-17 nm, relatively smaller than those reveal from transmission electron microscopy (TEM). The densities are seen to increase, whereas the porosity is reduced by the substitution of Ho ions. X-ray photoelectron spectroscopy (XPS) has confirmed the presence of all metal ions in the required valence states. Fourier transform infrared (FTIR) spectra featured two intrinsic vibrational bands (υ1) and (υ2) in a wave number range 400-600 cm-1 due to the tetrahedral and octahedral stretching vibrations, respectively. We found that the Ho-substituted lithium ferrites show low dielectric losses for all samples. The effective contribution of grain-interior mechanism to dielectric behavior has confirmed by complex impedance study. The saturation magnetization is seen to decrease while coercivity is effectively increased with increasing the Ho-content proposing these ferrites for magnetic recording media. Ferromagnetic resonance (FMR) studies at X-band show the reduction in FMR line width with Ho substitution. However, the effects are to be related to the densification of the material since we find that the more dense samples actually lead to decreased microwave losses (narrow linewidth), which is prerequisite for their use in microwave applications. Electrical measurements revealed that the resistivity is higher in samples with smaller grains possessing a greater number of thin insulating grain boundaries. In high temperature resistivity measurements, a decrease in dc resistivity is observed with increasing the temperature. Most significantly we observed a change in slope around the Curie transition temperature (Tc) separating the ferromagnetic region from the paramagnetic with the activation energies being higher for paramagnetic region (Ep > Ef). The substitution of Ho3+ for Fe3+ at octahedral sites causes a decrease in Tc due to the damping of A-B exchange interactions. The drift mobility is seen to decrease with increase in resistivity and vice versa.
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اسلامی ریاست میں غیر مسلم رعایا کے حقوق

“Minority” is a word which is considered a challenge for any political system. This article discusses how a certain political system deals with the idea and rights of a minority. If a minority enjoys the privileges in a society that political system is considered as perfect. Islam, the revealed religion, has not overlooked the status of a minority. Rights of a minority is one of the top priorities in Islam. This article brings to the fore the very status which Islam gives to the minorities and which they enjoyed while living in the Islamic poltical and social set up. Islam not only gives minorities the right to live in an Islamic Society, but also gives them protection. The word “Dhimmis” gives minorities the protection in an Islamic society which they never entertain in their own society. Whether it was the time of the Holy Prophet, the Abbasid’s or Umayyad, everywhere in the Islamic society they enjoyed not only as minorities but also they were allowed to build churches, join Islamic forces and to become viziers, etc. It clearly reveals that Islam is a religion of peace that not only gives good tidings to the believers but aslo to the minorities who live among them. This article is a small replica of what the minorities enjoyed in the Islamic society.

Redox Behavior, Spectroscopic Characterization and Biological Activities of Some New Robustly Electro-Active Compounds

The correlation of biological activities of compounds with their redox properties is the subject of extensive investigations of bioelectrochemists. Schiff bases, quinones and naphthalenes contain electroactive moieties and their broad range biological activities are closely related with the ability of these compounds to donate and/or accept electrons. We synthesized Schiff bases 1-((4-bromophenylimino) methyl) naphthalen- 2-ol (BPIMN) and 1-((2,4-dimethylphenylimino)methyl)naphthalen-2-ol (HL) and used HL as a ligand for the preparation of its metallic complexes. All the synthesized compounds were confirmed by 1 H NMR, 13 C NMR, FTIR, TGA and UV–Vis spectroscopy. Structures of Schiff bases were also characterized by X-ray analysis and the experimental findings were supported by quantum mechanical calculations. The results of BPIMN were compared with a structurally related Schiff base, 1-((4- chlorophenylimino) methyl) naphthalen-2-ol (CPIMN). The photometric and electrochemical fate of all these Schiff bases were investigated in a wide pH range and the obtained results helped in proposing the redox mechanistic pathways. The synthesized compounds were subjected to numerous biological applications and the results revealed that Schiff base HL and its metal complexes other than oxovanadium complex remarkably decrease the blood glucose, triglyceride and cholesterol levels. The metal complexes were found to exhibit significant inhibition against alkaline phosphatase enzyme as compared to Schiff bases. The zinc complex was found as the most potent inhibitor of bacteria/fungi while the vanadyl product displayed the least activity among all the metal coordinated products. Quinones, another biologically important class were also investigated due to their robust electrochemical properties and wide range of biological activities. The laxative and therapeutic activities of quinones are related to their redox characteristics. Electrochemically unexplored hydroxy substituted quinones including 4-hydroxy-5-methoxynaphthalene-1-ylacetate (HMNA), 1,4-dihydroxy-2-(3-hydroxy- 3-(trichloromethyl)pentyl)-8-methoxyanthracene-9,10-dione 2(hydroxymethyl)anthracene-9,10-dione anthracenedione acetate (DHDN) (HACAD), (HAC), (HCAQ), 1-hydroxy- 1,8-dihydroxy-4,5-dinitro 4,8-dihydroxy-9,10-dioxo-9,10-dihydroanthracen-1-yl 1,4,5-trihydroxyanthracene-9,10-dione (HAD) and 1,4,5- trihydroxy-2-methyl-3-(3-oxobutyl)anthracene-9,10-dione (HOAD) were selected and their redox behavior was studied in a wide pH range using modern electrochemical techniques. Kinetic parameters such as diffusion coefficient and iiiheterogeneous electron transfer rate constant and thermodynamic parameters of the electron transfer processes such as ∆G # , ∆H # and ∆S # were electrochemically evaluated. Their redox mechanisms were proposed on the basis of experimental findings supported by computational calculations. Moreover, a detailed UV–vis spectroscopy was carried out in a wide pH range for photometric characterization and acid-base dissociation constant, pK a determination. Though naphthalene by itself is toxic, however, some of its derivatives are bestowed with medicinal properties. Two biologically important naphthalene derivatives, naphthalene-2,3-dicarboxylic acid (NDA) and 1,8-dimethoxynaphthalene (DMN) were characterized by electrochemical techniques and screened for their antioxidant and anti-diabetic activities. NDA was found less toxic to HeLa cells and biological antioxidant studies revealed it as a more effective antioxidant as compared to DMN and standard antioxidant, ascorbic acid. Both NDA and DMN significantly increased the cholesterol level in blood but showed varied biological activities as regards to glucose and triglyceride concentrations. The cytotoxicity results evidenced DMN to significantly inhibit the cell proliferation in a dose dependent manner. Like the biological antioxidant studies, the electrochemical results also witnessed NDA as stronger antioxidant than DMN. pH dependent oxidation of NDA revealed its antioxidant role to be exerted both by the donation of electrons and protons. Although the oxidation potential of NDA is greater than the widely used natural antioxidant, ascorbic acid, yet it is capable of donating two electrons as compared to one electron donating ability of ascorbic acid. The redox mechanistic pathways proposed in this work are expected to provide useful insights about the unexplored mechanisms by which Schiff bases, quinones and naphthalenes exert their biochemical actions.