Glasses system was fabricated using the chemical composition {[(TeO 2 ) 0.7 (B 2 O 3 ) 0.3 ] 0.8 (SiO 2 ) 0.2 } 1 − x (Er 2 O 3 ) x with x = 0.01, 0.02, 0.03, 0.04 and 0.05 by melt-quenching method. The glasses were subjected to FTIR and XRD to study the glass structural changes and amorphous nature respectively. The absorption spectrum of the glasses were obtained from UV–Vis spectroscopy and used to calculate the energy band gap. Using the Archimedes principle, the density and the molar volume were determined. From the density, molar volume, and energy band gap, other parameters such as refractive index, molar refractive index, metallization criterion, reflection loss, transmission coefficient, polarizability, optical basicity, polaron radius, dielectric constant, optical dielectric constant, electric susceptibility, average electronegativity and others parameters were obtained by calculation. The polarizability values and the optical basicity were found to increase with Er 3 + ions concentration increase. The dielectric constant, optical dielectric constant and the linear electric susceptibility decreased with increase in Er 3 + ions concentration. The properties studied for the erbium doped glass system suggest the glass system has a potential in the EDFA application.

Polarizability, optical basicity and electric susceptibility of Er 3+ doped silicate borotellurite glasses

B2O3 –TeO2 – Na2O – CaO glasses doped with small concentrations of TiO2, from 0.5 to 3 mol%, were prepared by traditional technique. The changes in the structure of studied glasses were observed by using FTIR technique and it was found that glasses containing different structure units of borate and tellurite groups. The change in the many optical and physical parameters such as density, molar volume, band gap, optical backing density, refractive index and others were studied. The density was found to increase with the addition of TiO2 till 1 mol% then begin to decrease and the opposite trend was observed to molar volume. Energy band gap was measured by two techniques ASF and Tauc's models and their values was very close to each other and to decrease with the addition of TiO2. The refractive index was found to increase with the addition of TiO2 from 2.4 for base glass to 2.59 for glass containing 3 mol% of TiO2. The ionic concentration of Ti, the interionic distance ri, field strength F, dielectric constant, molar refraction index rm, molar polarizability, average electronegativity, and the reflection loss (rL) were rise with increasing TiO2 content. On the other hand, there are some properties such as transmission coefficient (T) was found to decrease with increasing the concentration of Ti ions.

The influence of TiO2 on structural, physical and optical properties of B2O3 –TeO2 – Na2O – CaO glasses

Graphene, a two-dimensional single layered carbon atoms crystal lattice has grabbed much attention due to its unique electronic, surface, mechanical and optoelectronic characteristics. Owing to its unique structure and properties, graphene has opened new opportunities for the future systems and devices, which has led to increase its demand in numerous applications. However, scaling up its production is still a challenging job. Although there is a huge body of literature on the graphene synthesis using various techniques but eco-friendly and cost–effective processes for mass scale production are still needed. In order to conceptualize and develop the processes fulfilling the growing concerns, it is important to overview the existing literature. The current review summarizes the production of graphene using several approaches as well as the potential of various waste materials as graphene precursors. The methods used for graphene synthesis have been categorized into top down techniques such as chemical exfoliation, mechanical exfoliation and chemical fabrication processes, and bottom up techniques including pyrolysis, plasma synthesis, epitaxial growth and chemical vapor deposition (CVD) processes. Conversely, several limitations are considerate for an individual procedure such as toxicity of chemicals, high-cost, time consumption or inadequate quality of the product. Furthermore, mass production of graphene derivatives under low-cost can also be considered by utilizing a variety of wastes precursors such as plastic and batteries waste, newspaper, biomass, chitosan, coal, insects waste etc. This review designates the current advances in wastes-derived graphene synthesis to relief synthetic difficulties as well as predicts the future development in this area.

Advances in synthesis of graphene derivatives using industrial wastes precursors; prospects and challenges

One-Step Electrofabrication of Reduced Graphene Oxide/Poly(N-methylthionine) Composite Film for High Performance Supercapacitors

Effect of the band gap and the defect states present within band gap on the non-linear optical absorption behaviour of yttrium aluminium iron garnets

In this work, linear and nonlinear optical parameters of zinc borotellurite glasses doped with Gd3+ have been studied for all-optical switching applications. A series of gadolinium zinc borotellurite glasses were synthesized by using conventional melt quenching technique. Optical absorption spectra were recorded by UV–vis spectroscopy. From the optical absorption spectra, the cut-off wavelength, optical band gap, Urbach energy and refractive index have been determined and are related to the structural changes in the glass systems. The nonlinear optical properties of Gd3+ doped glasses are investigated by using Z-scan technique. The values of nonlinear refractive index and absorption coefficient with closed and opened apertures of the Z-scan, respectively, were determined for proper utilization in nonlinear optical devices.

Linear and nonlinear optical properties of Gd3+ doped zinc borotellurite glasses for all-optical switching applications

Graphene is an exceptional and versatile new material which having worldwide reputation due to its unique properties such as having extremely good electrical conductor, tunable energy band gap, and offers high mechanical strength. The process to derived graphitized carbon into the reduced graphene oxide (rGO) is facing a huge obstacle and the chemical method is proven to be the best choice in order to synthesis rGO in the big scale short amount of time. However, the current chemical method involved the usage of hazardous, toxic and corrosive chemical as reducing agent namely hydrazine to form the sheet layer of graphene. Thus, this will limit the various applications of graphene due to environmental impact and safety issues. As an alternative current research proposed the usage of palm oil leaves extract to replace the hazardous and toxic chemical used as reducing agent. In our project, graphite was used as starting material and was oxidized using modified Hummer’s method. The palm oil leaves extract with the mixture of graphene oxide (GO) solution was refluxed to produce rGO. The as-synthesized green approach rGO material were then characterized using X-ray diffraction (XRD), energy dispersive X-ray (EDX), transmission electron microscopy (TEM), and Raman spectroscopy. The results revealed that the interspace distance between plane increased proportionally as graphite was oxidized, increasing from 0.33 nm to 0.84 nm. The reduction process of GO using palm oil leave extract showed the successful in removing the hydroxyl group and amorphization of sp2 carbon structures. The reduction process found to be increased in C/O ratios from 1:1 to 3:1. Raman spectroscopy revealed that the G band position was restored comparable to graphite as the reduction process successful achieved. TEM images and selected area electron diffraction (SAED) patterns illustrated the confirmation of the successfully synthesized of the monolayer of graphene sheet. Electrochemical studies carried out for both GO and rGO have positively differentiated and concluded a better voltage-current response of rGO in comparison to GO. The as synthesized rGO in the current project holds various potential for further investigation and industrial applications not limited to just supercapacitor and photocatalyst.

Low cost and green approach in the reduction of graphene oxide (GO) using palm oil leaves extract for potential in industrial applications

In thepresent study, the conversionof teawastebiomasswas carried via carbonization athigh temperature and furtherused as startingmaterial toproduce grapheneoxide (GO). Theoxidation andexfoliationof graphitized carbonwas successfully achievedusingmodifiedHummer’smethod.Theas synthesizedGO havebeen loadedwith titaniumdioxide (TiO2)usinghydrothermalmethod toproducenanocomposite of rGO/TIO2.Thepreparednanocompositeswere characterizedbymeansofXRD,FTIR,RamanandFESEM analysis.The evaluation for rGO/TIO2nanocomposite photocatalytic activitywas carriedout basedon degradationofmethyl orange (MO)under theultraviolet (UV) light irradiation.Results obtainedusing FTIR results revealed the successful oxidationof graphitized carbonwith thepresenceof carboxyl and hydroxyl group. FESEMimages suggested the changes of surfacemorphology fromgraphiteflakes structure into few layers of graphene sheets.Therefore, it canbe indicated that teawaste suitable tobe sustainable alternative of graphite for the synthesis ofGO.Moreover,GOobtainedhas immensepotential for degradationof variouswater pollutions. Photocatalytic activity experiment inferred that the importanceof optimumratiobetween reduceGOtoTiO2materialswhich can resulted indifference in thedegradation efficiency; rGO/TiO21:8>rGO/TiO21:4>TiO2>rGO/TiO21:6>rGO/TiO21:10.

https://iopscience.iop.org/article/10.1088/2053-1591/ab689d/pdf

C.A. Che Azurahanim

Papers

Linear and nonlinear optical properties of Gd3+ doped zinc borotellurite glasses for all-optical switching applications

Low cost and green approach in the reduction of graphene oxide (GO) using palm oil leaves extract for potential in industrial applications

Preparation and characterization of graphene oxide from tea waste and it’s photocatalytic application of TiO2/graphene nanocomposite

Synergistic effect of complementary organic dye co-sensitizers for potential panchromatic light-harvesting of dye-sensitized solar cells