Papers by Author: Ramli Arifin

Abstract: Enhancing the optical performance of rare earth doped binary inorganic glasses is an ever-demanding quest. Samarium (Sm³⁺) doped zinc tellurite glasses containing Manganese (Mn) nanoparticles (NPs) with composition (59-x)TeO₂-20ZnCl₂-10ZnO-10Li₂O-1Sm₂O₃-(x)Mn₃O_4, where x = 0 to 0.06 mol% are prepared by melt quenching technique. The role played by Mn NPs in enhancing the optical behaviors are analyzed and discussed. The XRD patterns confirm the amorphous nature of the glass. The UV-Vis-NIR spectra reveal seven prominent absorption bands of Sm³⁺ ions. The photoluminescence spectra display four peaks corresponding to ⁴G_5/2→⁶H_5/2, ⁴G_5/2 →⁶H_7/2, ⁴G_5/2→⁶H_9/2 and ⁴G_5/2 →⁶H_11/2 transitions_. An enhancement in the luminescence intensity is observed up to 0.05 mol% concentration of NPs and the intensity quenches beyond it. The enhancement is attributed to local electric field effect of NPs in the proximity of Sm³⁺ ion. Our results on improved optical response via precise control of NPs contents may be useful for the development of solid state lasers and amplifiers.

Abstract: Obtaining enhanced up-conversion efficiency in rare earth ions doped inorganic glass by means of noble metal nanoparticles (NPs) embedment remains challenging. For the first time, we report the combined effects of silver (Ag) and titania (TiO₂) NPs embedment on the structural and absorption characteristics of dysprosium (Dy³⁺) doped tellurite glass. Transparent and thermally stable glass samples were prepared using conventional melt quenching method and characterized via spectroscopic techniques. The production of the strong electric field in the proximity of Dy³⁺ ion due to the localized surface plasmon (LSP) of embedded metallic NPs was found to improve the glass absorption properties. The effects of bimetallic NPs in changing the structure and absorption properties were found to be better than singly included metallic NP (either Ag or TiO₂). This improvement in the absorption behavior was attributed to the combined LSP resonance (LSPR) effects of Ag and TiO₂ NPs which transferred strong local electric field into the Dy³⁺ ions positioned in their vicinity. The UV-Vis-NIR spectra revealed six absorption bands centerted at 1690, 1283, 1097, 904, 800 and 755 nm which were allocated to the transition from ⁶H_15/2 ground state to various excited states (⁶H_11/2, ⁶F_11/2, ⁶F_9/2, ⁶F_7/2, ⁶F_5/2 and ⁶F_3/2) of Dy³⁺ ion. Furthermore, the Raman spectra of such bimetallic NPs included glass system exhibited Raman peak shift accompanied by intensity variations when compared to the glass system with only one type of NPs incorporation. This enhancement in the Raman signal was ascribed to the LSPR mediated mechansim. The synthesized glass comporition was asserted to be prospective for devices.

Abstract: Economically viable and maintenance free glass surfaces with improved hydrophobicity are highly demanding in the recent nanotechnology era. Deposition of pollutants and dirt on glass surface that not only causes visual obscurity but also damages the cultural heritages are still to be researched intensely. It is documented that excellent hydrophobic surfaces (with contact angle greater than 90^o) can be achieved by controlling the surface wettability, where liquid droplets remain spherical on such surfaces. Selection of materials and the preparation method play a significant role towards such accomplishments. Stirred by this idea, we explored the feasibility of fabricating super-hydrophobic tellurite glass systems by facilely varying the compositions of different constituents. Highly transparent and thermally stable ternary tellurite glass system with chemical composition of (80-x)TeO₂ – xSiO₂ – 20ZnO, where x = 0.00 to 0.20 mol% are synthesized via conventional melt-quenching method. Samples are characterized using Atomic Force Microscopy (AFM) and contact angle measurements. The impact of SiO₂ concentrations variation on the surface roughness, surface energy, and hydrophobic properties are inspected. Glass surface roughness as much as 9.885 nm is attained. The optimal value of water contact angle is discerned to be 101.02° for 0.1 mol% of SiO₂ incorporation into the amorphous tellurite host matrix. Besides, the surface energy revealed an inverse proportionality to the water contact angle. This achieved contact angle (greater than 90°) makes this hydrophobic glass surface beneficial for diverse applications. It is established that the present glass composition may be prospective for the development of super-hydrophobic surfaces.

Abstract: Despite several advantages of phosphate glass systems, their hygroscopic tendency (absorbing or attracting moisture from the atmosphere) remain a major limiting factor for widespread industrial applications. Dedicated efforts are made to improve the hygroscopic nature of such glasses for making them chemically durable and greatly resistant towards moisture attack. Guided by this requirement, we prepared five phosphate glass samples of composition (70-x) P₂O₅–xFe₂O₃–25ZnO–5CaO with controlled manipulation of iron-oxide contents (Fe₂O₃: x = 0 to 20 mol %) using melt-quenching method. The influence of Fe₂O₃ (as modifier) contents variation on the improvement of structural and chemical strength is determined. As-synthesized glass samples are immersed in acidic solutions for corrosion test. In this test, glass samples are engrossed in the aqueous hydrochloric acid (HCl) media at 90 °C and soaked for a period of 4 h. The corrosion rate (CR) was calculated from the weight loss obtained after the test. The least number of CR indicates that the inclusion of Fe₂O₃ in the glass network improved the network rigidity and made the glass much stronger as well as more water resistant. However, it is also established that there is an optimum limit of Fe₂O₃ content beyond which the durability cannot be further improved. The AFM analysis of pre- and post- chemically treated glass samples informed the surface roughness and 3D topography. Present observation must be validated with other supporting experiments and model calculation which is underway. In this study, it revealed that the lowest corrosion rate was sample S3 (10% of Fe₂O₃) which have CR value of 1.02±0.12 ´ 10^-3gcm^-2h^-1 .

Abstract: Borate glass system of composition (100-x)B₂O₃-15Al₂O₃-20CaO-0.4Fe₂O₃-xCeO₂ with x = 0, 0.25, 0.50, 0.75, and 1.0 mol% were prepared using conventional melt-quenching method. Optical measurements were carried out at room temperature to determine the Cerium (Ce³⁺) ions concentration dependent absorption and luminescence emission properties of such glass system. Optical energy band gap of the glass system were evaluated as a function of Ce³⁺ ions content. Indirect band gap energy was found to be lower than the direct band gap energy. Urbach energy was ranged between 0.12-0.17 eV. An increased broad absorption is observed in the UV region with increasing Ce³⁺ ions concentration. The emission spectra of the glass system recorded with 380 nm excitation wavelength revealed prominent cyan-green emission.

Abstract: Three lithium-sodium-phosphate glass samples with molar composition of (48.5–x)P₂O₅-20Na₂O-30Li₂O-0.5Sm₂O₃-1.0Er₂O₃-xAgNPs (where x = 0.01 g, 0.03 g and 0.05 g) are prepared using melt quenching method. The thermal stability and infrared absorption of synthesized samples are evaluated as a function of Ag NPs contents. Thermal and structural characterizations are made using differential thermal analysis (DTA) and Fourier transformed infrared (FTIR) spectroscopy, respectively. Thermal stability is found to vary in the range of 171 °C to 197 °C. FTIR spectra revealed various characteristic bonding vibrations related to the glass network structures. The IR absorption band around 570 cm^-1 is assigned to the P-O-P bending vibrations while the occurrence of bands around 759 cm^-1 and 913 cm^-1 are allocated to the P-O-P symmetric stretching vibrations. The asymmetric stretching vibrations of (PO₃)^2- and (PO₂)^- units are observed around 1045 cm^-1 and 1254 cm^-1 , respectively. The appearance of a band around 1735 cm^-1 is allocated to the free H₂O molecules because of moisture attack to the sample. Influences of Ag NPs in the host matrix are analyzed and explained.

Abstract: 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.

Abstract: The effects of Titania nanoparticles (TiNPs) sensitization on the self-cleaning, spectral, and physical properties of erbium-doped tellurite glass were determined. Five glass samples with composition (69-x)TeO₂-20ZnO-10Na₂O-1Er₂O₃-(x)TiO₂, where x = 0.0, 0.1, 0.2, 0.3 and 0.4 mol% were synthesized using melt quenching method. XRD pattern confirmed the amorphous nature of prepared samples and TEM images manifested the growth of nearly spherical TiNPs of average size ≈14 ± 1 nm inside the glass matrix. The observed decrease in the water contact angle from 68^o to 43^o with increasing TiNPs contents was ascribed to the increase of glass surface hydrophilicity. Meanwhile, enhanced degradation rate of methylene blue (MB) with increasing TiNPs contents up to 0.2 mol% indicated an improved photocatalytic activity of the glass sample. The UV-Vis-NIR absorption spectra exhibited ten significant bands of Er³⁺ ions. Two plasmon absorption bands were evidenced at 552 and 580 nm. The green band in the photoluminescence spectra of sample containing 0.2 mol% of TiNPs showed highest enhancement factor of 30 times. It is established that the present glass composition is prospective for making self-cleaning surfaces and other display devices.

Abstract: Glass samples with composition of (64-x)TeO₂ + (x)ZnO + 15 ZnCl₂ + 0.5 Sm₂O₃ + 0.5 Er₂O₃ (x = 20, 25 and 30 mol%) are prepared by melt quenching method. The season for co-doping with rare earth ions such as samarium (Sm³⁺) and erbium (Er³⁺) is to explore the feasibility of their simultaneous exploitation as high performing up-converted lasing materials. The role of varying modifier of ZnO concentration in improving the hardness and structural properties are evaluated. The density is observed to reduce and ionic packing density is augmented with increasing concentration of ZnO. Glass with 25 mol% of ZnO revealed the optimum hardness of 2830 N/mm². Incorporation of Zn²⁺ into the tellurite host matrix is found to shift the IR bands position slightly without altering their intensity. Bonding vibrations corresponding to bending of TeO₃ unit (784-762 cm^-1), stretching of TeO₄ units (678-676 cm^-1) and Zn-O bonds (462-452 cm^-1) are evidenced. Incorporation of ZnO as modifier is established to enhance the hardness and improved the structural properties. The proposed glass composition may be useful for industrial purposes.

Abstract: Glasses activated rare earth (RE) ions are demanding for photonic devices. Optimization of rare earth dopants, chemical composition of glass former and modifier decides spectra features. We synthesize a series of glass having composition (50-x)P₂O₅ - 30Li₂O - 20Na₂O - (x)Sm₂O_3, where x = 0 to 2.0 mol% (optimizing RE concentration) via melt-quenching technique. The effects of Sm₂O₃ concentration on significant enhancement of absorption and luminescence are scrutinized. The UV-Vis-NIR absorption spectra reveal ten band and the emission spectra exhibit four peaks specific to the dopant. The results suggest that samarium doped phosphate glasses are potential for laser and other applications.