Asmahani Awang

Spectral investigation of Sm3+/Yb3+co-doped sodium tellurite glass

Sm 3+ /Yb 3+ co-doped tellurite glasses are prepared by melt-quenching technique. The density of the glasses varies between 4.65 and 4.84 g/cm 3 . The optical absorption spectra consist of eight bands in the wavelength range of 350-2 000 nm, which correspond to the transitions from ground level 6 H 5/2 to the various excited states of the Sm 3+ ion. Energy band gaps vary in the range of 2.73-2.91 eV, and the Urbach energy ranges from 0.21 to 0.27. Emission spectra exhibit four peaks originating from the 4 G 5/2 energy level centered at 576, 613, 657, and 718 nm. Quenches in emission bands may be due to the energy transfer from the Sm 3+ to Yb 3+ ions.

Growth of Au nanoparticles stimulate spectroscopic properties of Er3+ doped TeO2-ZnO-Na2O glasses

The changes in optical properties of 70TeO2-20ZnO-10Na2O-0.5Er2O3-0.2Au glass system are stimulated by varying the heat treatment duration. The XRD data reveals broad humps in range of 25-35 degree representing the amorphous nature of the glass materials. The optical absorption edge at room temperature is used to estimate the direct (Edir), indirect (Eindir) optical band gap and the Urbach energy (EU). The value of Edir lies between 2.937 to 2.943 eV, while the value of Eindir lies within 2.478 to 2.502 eV. The value of EU is found to increase with longer time of heat treatment and lies between 0.409 to 0.424 eV. The characteristic surface plasmon resonance (SPR) band of Au nanoparticles (NPs) was observed at ~630 nm of optical absorption spectra. The strong and medium green upconversion (UC) fluorescence from Er3+ centred at 547 and 533 nm were observed at room temperature, in addition to a weak red UC fluorescence from Er3+ centred at 637 nm. The SPR stimulated by the presence of Au NPs enhanced the luminescence intensity by four and five folds for 1 and 4 hours heat treatment, respectively. The results indicate that there is a large influence of growth of gold NPs on the optical and spectroscopic properties of glass samples. Our results may be useful for the fabrication of nanophotonic materials.

Luminescence from Erbium Doped Tellurite Glass: An Insight on Titania Nanoparticles Surface Plasmon Mediation

Weak stimulated emission cross-section of rare earth ions (REIs) as dopants inside various glass hosts are disadvantageous for practical applications and needs improvement. We determine the mechanism of Titania (TiO2) nanoparticles (TNPs) mediated Surface Plasmon Resonance (SPR) assisted modification in the spectral properties of tellurite glass doped with Erbium (Er3+) ions. Transparent and thermally stable glass samples with varying TNPs contents are synthesized using melt-quenching technique. TEM images revealed the existence of TNPs with average size ranged from 16 to 26 nm. Glass containing 0.4 mol% of TNPs displayed an enhancement in the Raman signal by a factor of 2.25, 1.83, 1.98, 1.56 and 3.58 for the bands centered at 388, 495, 673, 758, and 845 cm-1, which is attributed to the SPR assisted effects. Absorption spectra of TNPs embedded glass (devoid of erbium ions) manifested two surface plasmon (SP) bands at 552 and 580 nm. Up-conversion (UC) PL spectra showed three prominent bands centered at 525, 545, and 660 nm due to the Er3+ ion transition from the excited states to the ground state. Furthermore, glass containing 0.4 mol% of TiNPs exhibited an intensity enhancement by a factor of 30, and 28.57 (green bands) and 19.60 (red band), which are ascribed to the generation of strong local electric field mediated by SPR effect of TNPs situated in the vicinity of Er3+ ion. The presence of TNPs surface plasmon is asserted to be responsible for the alteration of the Er3+ ions absorbance and modification of the UC emission intensity. A correlation between SPR and Surface Enhance Raman Scattering (SERS) is established.

Effect of Au NPs on the Spectral Modification of Er-Doped Zinc Sodium Tellurite Glass

Optimizing of the spectroscopic features of rare earth (RE) doped inorganic glasses via tuneable growth of metallic nanoparticles (NPs) is demanding in plasmonic based nanophotonics. We report the gold (Au) NPs assisted sizeable enhancements in Er3+ luminescence in zinc-sodium tellurite glass. Glasses of the form 70TeO2-20ZnO-10Na2O-(x)Er2O3-(y)Au (x = 0.0 and 1.0 mol%; y = 0.0-0.6 mol% in excess) are synthesized via melt-quenching method and thoroughly characterized. Au concentration dependent variations in the physical and spectroscopic properties of glasses are determined. XRD data confirms the amorphous nature of all samples. UV-Vis-NIR spectra reveal seven absorption bands corresponding to the transitions from ground state (4I15/2) to 4I13/2, 4I11/2, 4I9/2, 4F9/2, 2H11/2, 4F7/2 and 4F5/2 excited states of Er3+. TEM micrograph manifests the existence of non-spherical Au NPs with average size of 8.6 nm. Prominent surface plasmon band of Au NPs is evidenced around 629 nm. Furthermore, Au NPs display a SPR mediated strong absorption in the visible region. Room temperature visible down-conversion emission (under 425 nm excitation) reveal three significant peaks centred at 532 (moderate green represent 2H11/2 → 4I15/2 transition), 550 (weak green represent 4S3/2 → 4I15/2 transition) and 588 nm (strong green represent 4S3/2 → 4I15/2 transition). Glass containing 0.4 mol% of Au exhibiting the highest luminescence intensity is ascribed to the NPs local field enhancement and energy transfer between RE ions and NPs. Variations in the physical properties of glass are explained in terms of the alteration in structures and ligand interactions with Au NPs present in the glass network. The intense field amplification discerned in the vicinity of Au NPs is attributed to the charge accumulation at the surface of the NPs. Surface plasmon resonance (SPR) of Au NPs and energy transfer (ET) from NPs to Er3+ ions are primarily attributed for the observed spectral modification. It is established that our glass composition displaying such significant enhancement may be beneficial for the development of up-converted solid state lasers and other plasmonic devices.

Gold Nanoparticles Stimulated Surface Plasmon Resonance Effects in Erbium-Zinc-Sodium-Tellurite Glass

Modifying the optical characteristics of rare earth (RE) doped inorganic glasses by stimulating surface plasmon resonance (SPR) via controlled growth of metal nanoparticles (NPs) is an outstanding quest in glass plasmonics. Glasses with composition 70TeO2-20ZnO-10Na2O-(x)Er2O3-(y)Au (x = 0.0 and 1.0 mol%; y = 0.0 and 0.6 mol% both in excess) are synthesized using melt-quenching technique and characterized. Influences of heat treatment temperature on the growth of Au NPs and their subsequent impacts on Raman spectral features modifications are inspected. The amorphous nature of glass is confirmed by using XRD. TEM reveal the non-spherical Au NPs with average diameter vary from 7.4 to 10.3 nm. Surface plasmon band is evidenced around 627 - 632 nm. Raman spectra demonstrate the presence of Er-O and Zn-O bond, anti-symmetric vibrations of Te-O-Te bonds and stretching modes of non-bonded oxygen exists in TeO3 and TeO3+1 unit. The amplifications in Raman signals by a factor of 1.39, 1.40, 0.88 and 1.29 and 1.25 corresponding to the peak centered at 262, 382, 536, 670 and 725 cm-1 are attributed to the contribution of a surface plasmon (SP) generating a strong, localized and secondary field. The excellent features of the results suggest that our systematic method of controlled NPs growth may constitute a basis for improving the spectral features of tellurite glasses useful for the development of efficient and economic up-converted lasers.