Impact of Cr3+ substitution on the nephelauxetic ratio and Racah parameter of Cr-Mn-Zn nanoferrites

For the first time, we present the ligand field splitting (10Dq) nephelauxetic ratio (β), Racah parameter (B) and stability of Cr3+ within Mn–Zn nanoferrite which synthesized using the citrate route. These parameters were determined via optical absorption spectra. The obtained bands in the significance range of optical absorption spectra are wide as well as asymmetric; therefore the deconvolution process becomes a necessary task. The values of 10Dq and B have been estimated from the produced bands. The values of 10Dq are observed to increase from 16366.61 to 16447.37 cm-1 whereas, B values are observed to decrease from 829.81 to 760.80 cm-1 with additional Cr3+ substitution. The increasing 10Dq and decreasing B values, evidence for bonds between Cr3+ ions with their environments became a further covalent (less ionic). Moreover, the values of β are observed to decrease for further Cr3+ substitution. This decrease of β produces less stability between Cr3+ and its ligand. Furthermore, Dq/B values declare that Cr3+ centers are in the low-field sites by a slight tendency towards the high-field sites with further Cr/Fe substitution process. Therefore, it was suggested that Cr3+ substituted Mn–Zn nanoferrites are excellent candidates for diverse optical applications such as a tunable laser.

Racah Parameter and Nephelauxetic Effect on Er3+/Nd3+ Codoped Lithium Niobate Tellurite Glass

The modification of absorption characteristics in rare-earth doped tellurite glasses is important in photonics application. The Er3+/Nd3+ doped glasses of the form (69-x)TeO2-15Li2CO3-15Nb2O5-1Er2O3-(x)Nd2O3 with x= 0.4, 0.8 and 1.0 mol % are successfully made by using conventional melt-quenching technique. Physical properties such as polaron radius, interionic distance, field strength and average distance between acceptors and donors are determined. The absorption spectra reveal eleven prominent peaks centered at 6535.9 cm-1, 10245.9 cm-1, 11415.5 cm-1, 12437.8 cm-1, 13369.0 cm-1, 15267.2 cm-1, 15949.2 cm-1, 17127.1 cm-1, 19084.0 cm-1, 20449.9 cm-1 and 22271.7 cm-1 which corresponding to the transitions from ground state to various states of Nd3+ ions. The crystal field site increases from 8.120 to 8.169 cm-1 due to increase in contraction of Nd3+-ligand. The nephelauxetic function, increase 0.104 to 0.107. The increasing in value describes, the increasing in ionic bond from-0.0004 to-0.0011. The increment in exhibits the increase in the number of effective positive charge connected to neodymium atom and attracts the electrons from ligands as it increases from 1.0004 to 1.0011. These present glass shows the potential candidate of broadband amplifiers and lasers as it is comparable with other Nd3+ doped another host.

Photoluminescence Properties of the Magnetoplumbite-Type BaMg6Ti6O19:Mn4+ and Spinel-Type Mg2TiO4:Mn4+

Mn4+-doped magnetoplumbite-type BaMg6Ti6O19 and spinel-type Mg2TiO4 red phosphors were synthesized by a solid-state reaction. BaMg6Ti6O19:Mn4+ and Mg2TiO4:Mn4+ were formed as main phase above 1200 oC. Although the emission peak of BaMg6Ti6O19:Mn4+ and Mg2TiO4:Mn4+ were almost the same, the excitation peak of BaMg6Ti6O19:Mn4+ and Mg2TiO4:Mn4+ were different. The 4A2→4T1 transition peak of Mg2TiO4:Mn4+ shifted to a shorter wavelength side than that of BaMg6Ti6O19:Mn4+ and 4A2→4T2 shifted to a longer wavelength side. The crystal field splitting energy of Mg2TiO4:Mn4+ was lower than that of BaMg6Ti6O19:Mn4+. By the additional of R block, the racah parameter B increased and C decreased. Although the increase of B causes a blue-shift of the emission wavelength and the decrease of C causes a red-shift of the emission wavelength, PL emission wavelength was little different due to the influence of both racah parameter. Thus, it was suggested that the existence of R block results in a difference of photoluminescence properties.

The Ligand Fields Characterizations within Erbium-Tellurite Glass Network via Gold Nanoparticles Concentration Variation

Glass samples of composition 79TeO2 – 15PbO – 5PbCl2 – 1Er2O3 – (x)AuCl3 with (0.0 ≤ x ≤ 0.1 mol%) were successfully synthesized by using melt-quenching technique. The impacts of gold nanoparticles (GNPs) concentration in stimulating the ligand field interaction inside the erbium-tellurite glass network were inspected. Amorphous nature of the sample was confirmed through XRD pattern. TEM images display the existence of GNPs with average diameter ~1.24 nm. Optical absorption spectra were recorded in the UV-Visible range. The absorption displays several prominent peaks corresponding to the transitions from the ground state to the excited states of Er3+ ion. The compositional dependence of the ligand parameters in terms of crystal field strength and Racah parameter were determined.

Preparation , charactarazition and biological activity of some complexes of potassium 2-carbomethoxy amino-5- trithiocarbonate 1,3,4-thiadiazole

In this study a new ligand ,(potassium 2-carbomethoxy amino-5-trithiocarbonate 1,3,4-thiadiazole) (L) has been prepared from 2-carbomethoxy amino-5-mercapto 1,3,4-thiadiazole with CS2 in alkali media . The product has been isolated and characterized by appropriate physical measurements, vibrational and electronic spectroscopy. The ligand was used to prepare a number of complexes with some metal ions Co(II), Ni(II) and Cu(II). These complexes have been characterized by FT-IR, UV-Vis spectra, molar conductivity, magnetic susceptibility, melting points and atomic absorption measurements. The nickel and copper complexes have an octahedral geometry while cobalt complex has a tetrahedral geometry. The nature of bonding between the metal ion and the donor atom of the ligand was demonstrated through the calculated Racah parameter and other ligand field parameters, which have been calculated by using a suitable Tanaba-Sugano diagram The biological activity of the ligand and it’s complexes have been examined against two selected microorganisms Pseudomonas aeruginsa and Staphylococcus aureus using (10mM) and (5mM) in nutrient agar medium. The results were showed enhancement of activity of some complexes compared to that of the respective ligand, which were attributed to the synergetic effect between the metal ion and the ligand in addition to the difference in the structural varieties.