Wan Mahmood Mat Yunus

Surface plasmon resonance sensing detection of mercury and lead ions based on conducting polymer composite

A new sensing area for a sensor based on surface plasmon resonance (SPR) was fabricated to detect trace amounts of mercury and lead ions. The gold surface used for SPR measurements were modified with polypyrrole-chitosan (PPy-CHI) conducting polymer composite. The polymer layer was deposited on the gold surface by electrodeposition. This optical sensor was used for monitoring toxic metal ions with and without sensitivity enhancement by chitosan in water samples. The higher amounts of resonance angle unit (ΔRU) were obtained for PPy-CHI film due to a specific binding of chitosan with Pb2+ and Hg2+ ions. The Pb2+ ion bind to the polymer films most strongly, and the sensor was more sensitive to Pb2+ compared to Hg2+. The concentrations of ions in the parts per million range produced the changes in the SPR angle minimum in the region of 0.03 to 0.07. Data analysis was done by Matlab software using Fresnel formula for multilayer system.

Fabrication and Crystallization of ZnO-SLS Glass Derived Willemite Glass-Ceramics as a Potential Material for Optics Applications

Willemite glass-ceramics were successfully derived from conventional melt-quench ZnO-SLS precursor glass by an isothermal heat treatment process. The effect of heat treatment temperatures on the physical properties was investigated by Archimedes principle and linear shrinkage. The generation of willemite crystal phase and morphology with increase in heat treatment temperature was examined by X-ray diffraction (XRD), Fourier transform infrared (FTIR), and field emission scanning electron microscopy (FESEM) techniques. X-ray diffraction revealed that the metastable -Zn2SiO4 and thermodynamically stable zinc orthosilicate α-Zn2SiO4 phases can be observed at temperatures above 700°C. The experimental results indicated that the density and shrinkage of the glass-ceramic vary with increasing the sintering temperature. FTIR studies showed that the structure of glass-ceramic consists of SiO2 and ZnO4 units and exhibits the structural evolution of willemite glass-ceramics. The characteristic of strong vibrational bands can be related to the tetrahedron corresponding to reference spectra of willemite.

Characterization of Electrosynthesized Conjugated Polymer-Carbon Nanotube Composite: Optical Nonlinearity and Electrical Property

The effects of multi-walled carbon nanotube (MWNT) concentration on the structural, optical and electrical properties of conjugated polymer-carbon nanotube composite are discussed. Multi-walled carbon nanotube-polypyrrole nanocomposites were synthesized by electrochemical polymerization of monomers in the presence of different amounts of MWNTs using sodium dodecylbenzensulfonate (SDBS) as surfactant at room temperature and normal pressure. Field emission scanning electron microscopy (FESEM) indicates that the polymer is wrapped around the nanotubes. Measurement of the nonlinear refractive indices (n2) and the nonlinear absorption (β) of the samples with different MWNT concentrations measurements were performed by a single Z-scan method using continuous wave (CW) laser beam excitation wavelength of λ = 532 nm. The results show that both nonlinear optical parameters increased with increasing the concentration of MWNTs. The third order nonlinear susceptibilities were also calculated and found to follow the same trend as n2 and β. In addition, the conductivity of the composite film was found to increase rapidly with the increase in the MWNT concentration.

Utilization of Chitosan-Based Sensor Thin Films for the Detection of Lead Ion by Surface Plasmon Resonance Optical Sensor

Chitosan-based sensor thin films were fabricated to detect trace amounts of lead ion using surface plasmon resonance (SPR) optical sensor. The gold surface used for SPR measure- ments was modified with chitosan and chitosan-tert-butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide) (chitosan-BCAT). Both chitosan and chitosan-BCAT layers were deposited on the gold surface by spin coating technique. The experiment has been carried out to monitor the SPR signals for lead ion with sensitive enhancement by chitosan and chitosan-BCAT layers. For both layers, the change in resonance angle (Δθ) is directly proportional to the concentration of lead ion solution. The higher amounts of Δθ were obtained for chitosan-BCAT film due to a specific binding of BCAT with lead ion. The chitosan-BCAT film enhanced the sensitivity of detection down to 0.03 ppm. Data analysis also has been done by Matlab software using Fresnel formula for multilayer system.

Preparation and elastic moduli of germanate glass containing lead and bismuth.

This paper reports the rapid melt quenching technique preparation for the new family of bismuth-lead germanate glass (BPG) systems in the form of (GeO2)60–(PbO)40−x–(½Bi2O3)x where x = 0 to 40 mol%. Their densities with respect of Bi2O3 concentration were determined using Archimedes’ method with acetone as a floatation medium. The current experimental data are compared with those of bismuth lead borate (B2O3)20–(PbO)80−x–(Bi2O3)x. The elastic properties of BPG were studied using the ultrasonic pulse-echo technique where both longitudinal and transverse sound wave velocities have been measured in each glass samples at a frequency of 15 MHz and at room temperature. Experimental data shows that all the physical parameters of BPG including density and molar volume, both longitudinal and transverse velocities increase linearly with increasing of Bi2O3 content in the germanate glass network. Their elastic moduli such as longitudinal, shear and Young’s also increase linearly with addition of Bi2O3 but the bulk modulus did not. The Poisson’s ratio and fractal dimensionality are also found to vary linearly with the Bi2O3 concentration.

Effect of Etching Time on Optical and Thermal Properties of p-Type Porous Silicon Prepared by Electrical Anodisation Method

The porous silicon (PSi) layers were formed on p-type silicon (Si) wafer. The six samples were anodised electrically with 30 mA/cm2 fixed current density for different etching times. The structural, optical, and thermal properties of porous silicon on silicon substrates were investigated by photoluminescence (PL), photoacoustic spectroscopy (PAS), and UV-Vis-NIR spectrophotometer. The thickness and porosity of the layers were measured using the gravimetric method. The band gap of the samples was measured through the photoluminescence (PL) peak and absorption spectra, then they were compared. It shows that band gap value increases by raising the porosity. Photoacoustic spectroscopy (PAS) was carried out for measuring the thermal diffusivity (TD) of the samples.

Thermal diffusivity measurement of Zn, Ba, V, Y and Sn doped Bi-Pb-Sr-Ca-Cu-O ceramics superconductors by photoacoustic technique

The simple open photoacoustic cell technique is demonstrated for measuring the thermal diffusivity of the Zn, Ba, V, Y and Sn doped Bi-Pb-Sr-Ca-Cu-O superconducting ceramic samples. It is based upon the measurement of the photoacoustic signal as a function of the modulation frequency in the region where the sample thickness, ls, equal to the thermal diffusion length of the sample, μs. The obtained thermal diffusivity values of Ba, V, Y and Sn doped in Bi-Pb-Sr-Ca-Cu-O system increase with the increasing dopant concentration at Ca side. However, the thermal diffusivity values of Zn doped sample decrease with the increasing of dopant concentration in the system. The measured thermal diffusivity value was found to be very dependent on the dopant atom and dopant concentration.

Thermal diffusivity measurement of black and metallic graphite paint coatings

The suitability of a single-access approach involving a pulsed laser technique for non-contact and non-destructive measurement of thermal diffusivity is further examined. It was used to measure the thermal diffusivity of black and metallic graphite paint coatings. The values obtained in the present work are and for black and metallic graphite paint coatings respectively. All measurements were performed at room temperature.

Infrared Study of Er3+/Yb3+ Co-Doped GeO2-PbO-Bi2O3 Glass

Heavy metal oxide glasses, containing bismuth and/or lead in their glass structure are new alternatives for rare eart (RE) doped hosts. Hence, the study of the structure of these vitreous systems is of great interest for science and technology. In this research work, GeO2-PbO-Bi2O3 glass host doped with Er3+/Yb3+ ions was synthesized by a conventional melt quenching method. The Fourier transform infrared (FTIR) results showed that PbO and Bi2O3 participate with PbO4 tetragonal pyramids and strongly distort BiO6 octahedral units in the glass network, which subsequently act as modifiers in glass structure. These results also confirmed the existence of both four and six coordination of germanium oxide in glass matrix.

Effect of Q-switched pulse laser temporal shape on induced temperature profile of laser absorbing materials

This paper examines the effect of a Q-switched pulsed lasers temporal output on the induced temperature change profile of laser absorbing materials. The effect was also discussed in the light of the case of the temperature profiles that were induced by ideal Dirac- function, square and Gaussian laser pulses. The induced temperature profiles were found to be unique with respect to the laser pulse temporal shape and therefore none of them resembled each other, even among the temperature profiles that were induced by Q-switched laser outputs with different pumping level.