Sodium Tellurite Research Articles

Gold nanoparticles assisted structural and spectroscopic modification in Er3+-doped zinc sodium tellurite glass

Achieving enhanced spectroscopic properties of rare earth doped inorganic glasses by embedding metallic nanoparticles of controlled sizes is a challenging task. We report the gold (Au) NPs assisted modifications in structural and spectroscopic properties of melt-quench synthesized Er3+ doped zinc sodium tellurite glass. The growth of NPs is stimulated via time varying heat treatment at 300°C. XRD patterns confirm the amorphous nature of glasses and TEM images manifest the growth of gold NPs with sizes between 6.1 and 10.7nm. The heat treatment time dependent variations in physical properties are ascribed to the alteration in bonding of non-bridging oxygen ions. The UV–VIS–NIR spectra reveal six absorption peaks centered at 488, 523, 655, 800, 973 and 1533nm corresponding to the transition from ground state of 4I15/2 to 4F7/2, 2H11/2, 4F9/2, 4I9/2,4I11/2, and 4I13/2 excited states of Er3+ ions, respectively. Surface plasmon resonance (SPR) bands are observed in the range of 618–632nm. Judd–Ofelt analyses demonstrate a significant increase of spectroscopic quality factors (0.86–1.05) and branching ratio (0.62–92.38%). The up-conversion emission spectra of Er3+ exhibit three prominent peaks of reasonable green (502nm), a moderate green (546nm) and a strong red (629nm). An enhancement in the red band luminescence intensity by a factor of 8.19 and 8.54 times are achieved for 2 and 4h of heat treatments, respectively. This enhancement is attributed to the SPR effects of gold NPs producing an intense local field in the proximity of Er3+ ions and subsequent energy transfer between RE ions and NPs. The FTIR spectra display the presence of vibrational modes for ZnO4 bonds, Te–O bond in TeO3 (tp) and TeO4 (tbp) units and the hydroxyl groups. Excellent features of the results suggest that our method constitute a basis for tunable growth of gold NPs which is exceedingly useful for the optimization of optical and structural properties.

Alkali environments in tellurite glasses

Neutron diffraction measurements are reported for five binary alkali tellurite glasses, xM2O·(100−x)TeO2 (containing 10 and 20mol% K2O, 10 and 19mol% Na2O, and 20mol% 7Li2O), together with 23Na MAS NMR measurements for the sodium containing glasses. Differences between neutron correlation functions are used to extract information about the local environments of lithium and sodium. The Na–O bond length is 2.37(1) Å and the average Na–O coordination number, nNaO, decreases from 5.2(2) for x=10mol% Na2O to 4.6(1) for x=19mol% Na2O. The average Li–O coordination number, nLiO, is 3.9(1) for the glass with x=20mol% Li2O and the Li–O bond length is 2.078(2) Å. As x increases from 10 to 19mol% Na2O, the 23Na MAS NMR peak moves downfield, confirming an earlier report of a correlation of peak position with sodium coordination number. The close agreement of the maximum in the Te–O bond distribution for sodium and potassium tellurite glasses of the same composition, coupled with the extraction of reasonable alkali coordination numbers using isostoichiometric differences, gives strong evidence that the tellurium environment in alkali tellurites is independent of the size of the modifier cation used.

Two Lactococcus lactis thioredoxin paralogues play different roles in responses to arsenate and oxidative stress.

Thioredoxin (Trx) maintains intracellular thiol groups in a reduced state and is involved in a wide range of cellular processes, including ribonucleotide reduction, sulphur assimilation, oxidative stress responses and arsenate detoxification. The industrially important lactic acid bacterium Lactococcus lactis contains two Trxs. TrxA is similar to the well-characterized Trx homologue from Escherichia coli and contains the common WCGPC active site motif, while TrxD is atypical and contains an aspartate residue in the active site (WCGDC). To elucidate the physiological roles of the two Trx paralogues, deletion mutants ΔtrxA, ΔtrxD and ΔtrxAΔtrxD were constructed. In general, the ΔtrxAΔtrxD strain was significantly more sensitive than either of the ΔtrxA and ΔtrxD mutants. Upon exposure to oxidative stress, growth of the ΔtrxA strain was diminished while that of the ΔtrxD mutant was similar to the wild-type. The lack of TrxA also appears to impair methionine sulphoxide reduction. Both ΔtrxA and ΔtrxD strains displayed growth inhibition after treatment with sodium arsenate and tellurite as compared with the wild-type, suggesting partially overlapping functions of TrxA and TrxD. Overall the phenotype of the ΔtrxA mutant matches established functions of WCGPC-type Trx while TrxD appears to play a more restricted role in stress resistance of Lac. lactis.

Zingerone Protects the Tellurium Toxicity in the Brain Mitochondria of Rats

Tellurium (Te) has been reported to be toxic to humans but its application in industries is growing at rapid pace. Mitochondria are responsible to generate the chemical energy to regulate the fuelling of cellular processes. The decay of the mitochondria in the brain cells is a primary cause of all neurodegenerative disorders from Parkinson's to dementia. Animals were divided into 5 groups; group 1st was control. Group 2nd received Te as sodium tellurite (4.15 mg, 1/20th of LD50) orally once daily for 15 days. Groups 3rd and 4th were pretreated with zingerone (50 and 100 mg/kg b. wt respectively once daily for 15 days) followed by 15 days treatment with Te (orally once daily). On day 16, after the completion of Te dosing, the animals were sacrificed and brains were taken out to isolate the mitochondria. The content of lipid peroxidation (LPO) was increased significantly and the content of glutathione and activities of antioxidant enzymes; glutathione peroxidase (GPx) glutathione reductase (GR), glutathione-S-transferase (GST), superoxide dismutase (SOD) and catalase (CAT) were decreased significantly in the brain mitochondria of Te treated group as compared to the brain mitochondria of control group and these changes were protected significantly and dose dependently with the treatment of zingerone in Te+Z1 and Te+Z2 groups. The above study indicates that the zingerone which is part of our diet may be used as the best tool for the prevention of Te toxicity.

Toxicity of sodium tellurite (Na2TeO3) against Aedes caspius larvae in Gizan, Southwestern region, Kingdom of Saudi Arabia

The most common mosquito-borne diseases in Saudi Arabia are dengue, filaria, malaria and Rift valley fever. Rift valley fever /Dengue outbreaks in Mediterranean region have progressively increased, with recent reports of cases in Saudi Arabia. A serious out break had been seen in the southern coastal province of Jazan of Saudi Arabia. Tellurium is considered to be an important element in emerging world of corrosion resistance technology and glass ware technology. There was no literature available on mosquito larval toxicity. Thus this compound has stimulated our interest to evaluating the toxicity effect against mosquito larvae. The toxicity of Sodium tellurite was performed against Aedes caspius as per WHO methods. Preliminary toxicity of Sodium tellurite was evaluated at 200 ppm concentration in different time interval like 6 hrs, 12 hrs, 18 hrs and 24 hrs and percent mortality was recorded as 21.66%, 55%, 94% and 100% respectively against larvae.Therefore, further quantitative assay were carried out in different concentration of tellurite which was less than preliminary concentration such as 25 ppm, 50 ppm, 75 ppm, 100 ppm, 125 ppm, 150 ppm and 200 ppm. The LC50 and LC90 value was observed 37.5 ppm and 105 ppm respectively against the Ae. Caspius larvae. No mortality was observed in control group in all experiments. In conclusion, the Sodium tellurite are effective and may be developed as potent larvicides in future.

The TeO2‐Na2O System: Thermal Behavior, Structural Properties, and Phase Equilibria

Thermal behavior, structural properties, and phase equilibria of the (100−x)TeO2‐xNa2O system were studied in the 5 ≤ x ≤ 50 mol% composition range. Investigation of glass formation behavior in the binary system was realized, and the glass formation range was determined as 7.5 ≤ x ≤ 40 mol%. Differential thermal analysis (DTA) and Fourier transform infrared (FTIR) spectroscopy techniques were used for thermal and structural characterization of the glasses. Influence of Na2O content on glass transition temperature (Tg), glass stability (∆T), density (ρ), molar volume (VM), oxygen molar volume (VO), and oxygen packing density (OPD) values of sodium tellurite glasses was evaluated considering the structural transformations in the glass network. For the phase equilibria studies, DTA, X‐ray diffraction (XRD), and scanning electron microscopy/energy dispersive X‐ray (SEM/EDS) techniques were utilized to characterize the heat‐treated samples. According to the phase equilibria studies, three eutectic regions were detected in the 0 < x < 50 mol% composition range of the (100−x)TeO2‐xNa2O system. A new invariant endothermic reaction was detected for the compositions between 40 ≤ x ≤ 45 mol%. Na2O.8TeO2 (11.11 mol% Na2O) compound that was claimed to exist in the binary system in the literature was found to be the metastable δ‐TeO2 phase.

Gold nanoparticles assisted surface enhanced Raman scattering and luminescence of Er3+ doped zinc–sodium tellurite glass

Significant enhancements in Er3+ luminescence and Raman intensity mediated via surface plasmon resonance (SPR) of gold (Au) nanoparticles (NPs) embedded zinc–sodium tellurite glass are reported. The observed modifications in the physical and spectroscopic properties are ascribed to the alterations in the glass network. XRD pattern confirms the amorphous nature of prepared glass sample. UV–vis-NIR spectra reveal seven absorption bands. Surface plasmon band is evidenced around 626–630nm. TEM images manifest the growth of non-spherical Au NPs with average diameter between ~7.2nm and 8.6nm. The visible up-conversion (UC) emission for all samples under 779nm excitation exhibits three bands centered at 503nm (green), 546 (green) and 637nm (red) ascribed to 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions. Glass sample with 0.4mol% Au displaying the highest luminescence intensity with enhancement factor of 3.85 and 3.56 for green bands, and 7.61 for the red band is ascribed to the NPs local field enhancement and energy transfer between rare earth (RE) ions and NPs. FTIR spectra show the vibration of ZnO4 bonds, TeO bond in TeO3 (tp) and TeO4 (tbp) units and the hydroxyl groups. Raman spectra demonstrate the presence of ErO and ZnO bond, anti-symmetric vibrations of TeOTe bonds and stretching modes of non-bonded oxygen exists in TeO3 and TeO3+1 unit. The amplifications in Raman signals by a factor of 1.62, 1.58, 1.64, 1.68 and 1.69 corresponding to the peak centered at 262cm−1, 382cm−1, 521cm−1, 670cm−1 and 725cm−1 are attributed to the contribution of a surface plasmon generating a strong, localized and secondary field. We assert that our glass compositions offer favorable potential to develop solid state lasers and other versatile nanophotonic devices.

Synthesis of AS1411-aptamer-conjugated CdTe quantum dots with high fluorescence strength for probe labeling tumor cells.

In this paper, we report microwave-assisted, one-stage synthesis of high-quality functionalized water-soluble cadmium telluride (CdTe) quantum dots (QDs). By selecting sodium tellurite as the Te source, cadmium chloride as the Cd source, mercaptosuccinic acid (MSA) as the capping agent, and a borate-acetic acid buffer solution with a pH range of 5-8, CdTe nanocrystals with four colors (blue to orange) were conveniently prepared at 100 °C under microwave irradiation in less than one hour (reaction time: 10-60 min). The influence of parameters such as the pH, Cd:Te molar ratio, and reaction time on the emission range and quantum yield percentage (QY%) was investigated. The structures and compositions of the prepared CdTe QDs were characterized by transmission electron microscopy, energy-dispersive X-ray spectroscopy, selective area electron diffraction, and X-ray powder diffraction experiments. The formation mechanism of the QDs is discussed in this paper. Furthermore, AS1141-aptamer-conjugated CdTe QDs in the U87MG glioblastoma cell line were assessed with a fluorescence microscope. The obtained results showed that the best conditions for obtaining a high QY of approximately 87% are a pH of 6, a Cd:Te molar ratio of 5:1, and a 30-min reaction time at 100 °C under microwave irradiation. The results showed that AS1141-aptamer-conjugated CdTe QDs could enter tumor cells efficiently. It could be concluded that a facile high-fluorescence-strength QD conjugated with a DNA aptamer, AS1411, which can recognize the extracellular matrix protein nucleolin, can specifically target U87MG human glioblastoma cells. The qualified AS1411-aptamer-conjugated QDs prepared in this study showed excellent capabilities as nanoprobes for cancer targeting and molecular imaging.

Near infrared nonlinearity in silver telluride-core/carbon-sheath and tellurium-core/carbon-sheath nanostructures synthesized by reduction carbonization approach

A reduction-carbonization approach for the formation of one-dimensional (1D) silver telluride nanocables and tellurium nanorods with a sheath of amorphous carbon are proposed. Here the carbon shell is obtained with the assistance of glucose which behaves as carbonizing agent; silver nitrate and sodium tellurite are utilized as precursors and ethylene glycol acts as reducing agent. The results demonstrate the Ag2Te/C and Te/C nanostructures with average diameters of 150 and 100 nm, respectively. The crystal structures, morphology, and composition are studied using X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, and Energy-dispersive X-ray spectroscopy characterizations. The formation mechanism of amorphous carbon sheath and finally core–shell nanostructures is elaborated on the basis of the experimental results. In addition, nonlinear absorption and refraction coefficients along with 3rd order nonlinear optical properties are investigated by open/closed-aperture Z-scan measurements using femtosecond pulse laser at 800 nm in a systematic way. This study provides a guide to the nonlinear properties, which may hold promise as advanced materials for various applications.

Aqueous synthesis of luminescent cadmium telluride quantum dots using ascorbic acid as the reducing agent

A facile method for the synthesis of highly luminescent cadmium telluride (CdTe) quantum dots (QDs) in an aqueous solution is presented. Ascorbic acid and sodium tellurite were used as the reducing agent and tellurium source, respectively, to synthesise CdTe QDs under mild conditions. In this method, the preparation of the Te precursor and the growth of CdTe QDs were achieved with a one-step synthetic route. CdTe QDs with five different emission wavelengths of 506, 517, 541, 564 and 575 nm were obtained by tuning the refluxing time. The quantum yields of these QDs were 5.4, 10.9, 37.4, 53.3 and 40.1%, respectively. The X-ray powder diffraction and transmission electron microscopy characterisation indicated that the obtained QDs had a pure cubic zinc blended structure with spherical shape. The main advantage of the present method is that both the reducing agent and tellurium precursor are stable and cheap. Furthermore, no toxic gases are released in the preparation process. It is a low cost and green method suitable for large-scale synthesis.

Enhanced upconversion emission of Dy3+-doped tellurite glass by heat-treated silver nanoparticles

Dy3+-doped lead sodium tellurite glasses containing silver nanoparticles (NPs) were synthesized by a melt-quenching technique and treated for different annealing time intervals above the glass transition temperature. The glass samples were characterized by UV–vis–IR absorption spectroscopy, photoluminescence spectroscopy and transmission electron microscope imaging. Eight absorption peaks of Dy3+ ions were observed indicating the transitions from ground state to different excited states. The surface plasmon resonance (SPR) peak of silver NPs was probed at 522nm. Blue, yellow and red luminescence emissions were recorded at 485, 578 and 665nm. The intensity of emission peaks for heat-treated samples containing silver NPs found to be 1.7–4 times larger than their singly-doped counterpart. Such enhancements are attributed to the modification of the local field due to difference between dielectric constants of metal and surrounding medium as the major factor, and energy transfer from nano-metal particles to Dy3+ ions as the minor aspect. The size distribution of silver NPs has a Gaussian shape with a maximum around 18nm. The glasses can be nominated as promising materials for solid state lasers.

Simple one-pot aqueous synthesis of CdHgTe nanocrystals using sodium tellurite as the Te source

In this work, we systematically investigated the one-pot aqueous synthesis conditions of CdHgTe nanocrystals (NCs) using sodium tellurite (Na2TeO3) as the Te source, and found that the added content of Hg2+ and the initial pH value of reaction solutions significantly affected the photoluminescence quantum yield (PL QY) of alloyed CdHgTe NCs. When the concentration of Cd was 1.0mmolL−1, the mole ratio of Cd/Te/Hg/MPA was 1:0.5:0.05:2.4, and the initial pH value of the reaction solution was about 8.78, the PL QY of as-prepared CdHgTe NCs was up to 45%. Characterization by HRTEM and XRD confirmed the crystalline nature of CdHgTe NCs. Compared to other synthetic approaches of CdHgTe NCs, our experimental results indicate that Na2TeO3 could be an attractive alternative Te source to directly synthesize CdHgTe NCs in aqueous media.

Nano-silver enhanced luminescence of Eu3+-doped lead tellurite glass

Eu3+-doped lead sodium tellurite glasses containing silver nanoparticles (NPs) were synthesized by melt-quenching technique and annealed for different time intervals at above the glass transition temperature. The glasses were characterized by UV–Vis–IR absorption, photoluminescence spectroscopy and transmission electron microscope imaging. Four absorption peaks of Eu3+ ion were observed due to transitions from ground state to different excited states in 400–600nm region. The surface plasmon resonance (SPR) peak of silver NPs was probed at 632nm. Five emission lines were recorded at 568, 587, 614, 650 and 704nm which were intensified in the order of ∼1.9 times for heat-treated samples containing silver NPs. The average size of NPs was estimated to be ∼10nm. Different mechanisms for interaction of light with metal and luminescent ions are discussed. Such enhancements are attributed to the strong local electric field induced by SPR of silver NPs as the major factor, and energy transfer from surface of silver NP to Eu3+ ion. The glasses show promising properties for optical applications.

One-Pot Synthesis of DNA-CdTe:Zn2+ Nanocrystals Using Na2TeO3 as the Te source

DNA-functionalized quantum dots (QDs) are powerful tools for biosensing and bioimaging applications. Facile labeling methods with good fluorescence properties are desirable for the development of DNA-functionalized QDs. In this article, we describe a novel and simple approach that leads to the synthesis of DNA-functionalized CdTe:Zn(2+) QDs in one step. It is the first time that DNA-functionalized QDs have been prepared using sodium tellurite as the tellurium source by a hydrothermal method. This approach will greatly reduce the synthesis time (only about 1 h) and simplify the synthesis process as well as reduce the complexity of the required experimental techniques. The as-prepared QDs exhibit high quantum yield, small size, and low toxicity. UV-vis spectra and FTIR characterization proved that the abundance of DNA on the surface of the QDs increased with the increase in the concentration of the feed DNA. Most importantly, these QDs functionalized with DNA have great potential to bind specifically to DNA, protein, and cell surface receptors.

Luminescence Enhancement of Samarium-Doped Tellurite Glass Containing Silver Nanoparticles

Samarium-doped tellurite glass embedded with silver nanoparticles are synthesized by melt quenching technique and optically characterized. The effect of silver nanoparticles on the luminescent properties of the samarium-doped sodium tellurite glass is investigated. Upon pumping with 406 nm radiation, it is found that there are four distinctive emission bands centered at 562 nm, 599 nm, 645 nm and 705 nm. In the presence of silver nanoparticles in the glass substrates, we observe significant enhancement in the intensity of these emission bands. The enhancement tends to increase with the increasing of silver nanoparticles concentration. The mechanism of luminescence enhancement is discussed in terms of localized surface plasmon resonance.

The Influence of Yb<sup>3+</sup> Co-Doping on Optical Properties of Sm<sup>3+</sup>-Doped Sodium Tellurite Glasses

A series of Sm3+-doped sodium tellurite glasses co-doped with Yb3+were synthesized by melt quenching technique. The amorphous nature of the glasses was confirmed by X-Rays diffraction technique. From UV-Vis-NIR spectroscopy, eight absorption peaks of Sm3+ions are observed. The broad absorption band in the range of ~870-1100 nm corresponds to the superposition of Sm3+:6H5/26F11/2and Yb3+:2F7/22F5/2transitions. The experimental and theoretical oscillator strengths of these bands were calculated by Judd-Ofelt theory. The optical band gap energy (Eopt) values for direct allowed transition and Urbach energy were found to be in the range of 2.73-2.91 eV and 0.21-0.27 eV respectively. Four luminescence emission bands4G5/26H5/2,6H7/2,6H9/2and6H11/2were revealed under 406 nm excitation and intensity of all bands is found to be quenched with addition of Yb3+ions. The role of Yb3+co-doping in the optical properties is compared and understood.

Non-spherical gold nanoparticles mediated surface plasmon resonance in Er3+ doped zinc–sodium tellurite glasses: Role of heat treatment

Tuning the enhanced optical properties of rare earth (RE) doped inorganic glasses mediated via surface plasmon resonance (SPR) by embedding metallic nanoparticles (NPs) with controlled sizes is ever-demanding in photonics. Erbium (Er3+) doped zinc–sodium tellurite glasses containing gold NPs are prepared and spectroscopic characterization are made. The heat treatment temperature dependent variations in refractive index, density, molar volume, molar refraction and polarizability are ascribed to the alteration in bonding of non-bridging oxygen (NBO) ions originates from annealing processes between 325 and 400°C. X-ray diffraction pattern confirms the amorphous nature of the glass samples. TEM micrograph reveals the nucleation of heat treated Au0 NPs and SAED manifest their growth along the (111) crystallographic planes having average diameter in the range 7.4–10.3nm. The UV–vis spectra exhibit seven absorption bands corresponding to 4f–4f transitions of Er3+ ions. The SPR bands evidenced in the range 629–631nm validate the growth of gold NPs in the glass matrix. The glass annealed at 350°C displays maximum enhancement in the up-conversion (UC) emission intensity by a factor of 4.86 and 3.40 for green bands (2H11/2→4I15/2 and 4S3/2→4I15/2) and a strong enhancement by a factor of 4.91 for red band (4F9/2→4I15/2). The enhancement is primarily attributed to the local field effect of non-spherical NPs assisted SPR effects and the energy transfer processes between Er3+ ions and NPs. The excellent luminescence efficiency of proposed glasses nominates them potential for photonic devices and solid state lasers.

Hydrothermal Synthesis and Mechanism of Unusual Zigzag Ag2Te and Ag2Te/C Core‐Shell Nanostructures

A single step surfactant‐assisted hydrothermal route has been developed for the synthesis of zigzag silver telluride nanowires with diameter of 50–60 nm and length of several tens of micrometers. Silver nitrate (AgNO3) and sodium tellurite (Na2TeO3), are the precursors and polyvinylpyrrolidone (PVP) is used as surfactant in the presence of the reducing agent, that is, hydrazine hydrate (N2H4·H2O). In addition to the zigzag nanowires a facile hydrothermal reduction‐carbonization route is proposed for the preparation of uniform core‐shell Ag2Te/C nanowires. In case of Ag2Te/C synthesis process the same precursors are employed for Ag and Te along with the ethylene glycol used as reducing agent and glucose as the carbonizing agent. Morphological and compositional properties of the prepared products are analyzed with the help of scanning electron microscopy, transmission electron microscopy, and energy dispersive X‐ray spectroscopy, respectively. The detailed formation mechanism of the zigzag morphology and reduction‐carbonization growth mechanism for core‐shell nanowires are illustrated on the bases of experimental results.

Judd–Ofelt analysis of spectroscopic properties of Sm3+ doped sodium tellurite glasses co-doped with Yb3+

A spectroscopic Judd–Ofelt investigation of co-doped sodium tellurite glasses is a key issue in lasers. Sm3+-doped glasses co-doped with various Yb3+ concentrations have been prepared by the melt quenching technique. These glasses have been characterized using XRD, optical absorption and luminescence techniques at room temperature. The amorphous nature of glasses has been confirmed by XRD spectra. The optical absorption spectra exhibited seven absorption peaks corresponding to the transition from ground level 6H5/2 to the various excited state of Sm3+ ions. The broad absorption band in the range of ~870–1040nm due to the large contribution of the absorption from 2F7/2→2F5/2 transition of Yb3+ ion was also observed. Judd–Ofelt theory have been applied to absorption intensities of Sm3+ transitions to determine the phenomenological intensity parameters, Ωλ (λ=2, 4 and 6). Emission spectra consisted of four emission bands 4G5/2→6H5/2, 6H7/2, 6H9/2 and 6H11/2. The J–O parameters have been employed to predict various radiative properties such as transition probability (AR), radiative lifetime (τf), branching ratio (βR), effective bandwidth (λeff), stimulated emission cross-section σ(λp), gain bandwidth and optical gain of trivalent samarium ion in 4G5/2 excitation level. The maximum values of stimulated emission cross section, gain bandwidth and optical gain were 23.09×10–22, 28.54×10–28cm3 and 12.51×10–25, respectively, corresponding to 4G5/2→6H9/2 transition in present glasses. The comparative studies with other Sm3+ doped different glasses showed that present glasses could be a potential candidate for lasers and broadband amplifiers.

Concentration dependent structural and spectroscopic properties of Sm3+/Yb3+ co-doped sodium tellurite glass

Tuning the optical and structural behaviors of tellurite glasses with controlled dopants is the key issue in solid state lasers and amplifiers. Sm3+/Yb3+ co-doped sodium tellurite glasses are prepared by the melt quenching technique and characterized using XRD, FTIR and DTA, optical absorption and luminescence techniques. The XRD spectra reveals the amorphous nature of glasses and the presence of functional groups such as Te–O bond in trigonal bipyramids (TeO4), Te–O bending vibration of the trigonal pyramids (TeO3) and non-hygroscopic nature of the glasses are confirmed from FTIR spectra. The DTA measurement shows the thermal stability lies in the range of 106–123. The UV–vis–NIR spectra exhibit eight absorption bands corresponding to the transition from ground level 6H5/2 to the various excited state of Sm3+ ions and the broad absorption band in the range of ~825–1100nm is ascribed to the large contribution of the absorption from 2F7/2→2F5/2 transition of Yb3+ ion. The experimental oscillator strengths calculated from the absorption spectra are used to evaluate three phenomenological Judd–Ofelt (J–O) intensity parameters Ωλ (λ=2, 4 and 6). Emission spectra consist of four bands 4G5/2→6H7/2 (moderate green) 4G5/2→6H5/2 (intense orange), 4G5/2→6H7/2 (moderate orange-yellow) and 4G5/2→6H11/2 (feeble red). The J–O parameters are employed to calculate radiative parameters such as transition probability (AR), branching ratio (BR), effective bandwidth (λeff) and stimulated emission cross-section σ(λp) of these emission transition of trivalent samarium ion. The optical band gap energy value (Eopt) and Urbach energy values (ΔE) are calculated and compared. The concentration dependent spectroscopic behavior of Sm3+-doped and Sm3+/Yb3+co-doped glasses is understood. Our systematic study may contribute towards the development of optical device fabrication.