Siti S. Mat Isa

The Effect of Different Reduction Methods on Conductivity of Reduced-Graphene Oxide (r-GO)

Large quantity of graphene oxide (GO) was prepared by Modified Hummer’s method, in which graphite was treated with a mixture of sulphuric acid, potassium permanganate and hydrogen peroxide. A chemically reduced graphene oxide (r-GO) was prepared using sodium borohydride (NaBH4), followed by thermal treatment and thermal treatment of chemically reduce using NaBH4. The electrical resistance of r-GO was measured using Keithley sourcemeter. The results revealed that r-GO show lower resistance on thermal reduction which is 2.39 kΩ compared to chemical reduction and thermal of NaBH4 reduction which is 2.18 MΩ and 3.16 kΩ respectively. It can be concluded that thermal reduction is the best method to produce high conductivity r-GO film.

Fiber Length Optimization of Ring Cavity Multi-Wavelength Brillouin Fiber Laser Utilizing Fiber Bragg Grating

In this paper, we experimentally investigated the performance of ring cavity multi-wavelength Brillouin fiber laser utilizing fiber Bragg grating which operated in the C-band wavelength region. The combination of stimulated Brillouin scattering and selective wavelengths gave a new invention in the optical fiber communication. Five different lengths of single mode fiber are used in order to get the best gain medium for stimulated Brillouin scattering effect. Up to 33 of Brillouin Stokes signals and 31 of anti-Stokes signals were obtained when 10 km fiber length was used in the laser system. The average value optical signal to noise ratio of 15 dB has been achieved. The broadening bandwidth of Brillouin Stokes signals also occurred at the center wavelength of 1550 nm based on the 3 dB bandwidth of 5 nm fiber Bragg grating.

Fabrication of multi-walled carbon nanotubes hydrogen sensor on plastic

Vacuum filtration method was applied to build optically homogeneous film of palladium (Pd) nanoparticles dispersed multi-walled carbon nanotubes (MWCNTs) networks on plastic substrate. Measurement of the sheet resistance as a function of MWCNTs concentration showed a transition from 2D percolation to 3D conduction behaviour when the concentration of MWCNTs exceeded 0.015 mg/ml. The electrical response to H2 gas exposure was investigated at room temperature.

Hybrid TiO2-Gigantochloa Albociliata Charcoal in Dye Sensitized Solar Cell

The Dye Sensitized Solar cell (DSSC) is an alternative to the silicon solar cell because it is low cost and easy to fabricate. In previous work, Remazol Orange (RO) was used as a dye sensitizer in DSSC but the efficiency is still low, 0.13%. In order to increase the device performance, TiO2 thin film as the working electrode is hybridized with high conducting and absorption material which is bamboo charcoal powder (BCP). It is founded that the nanoparticle size of TiO2-BCP composite was smaller compared to pristine TiO2. The ratio of TiO2 and BCP did not give any significant effect towards the particle size. The efficiency of RO DSSC was highly improved by 84.6% at higher carbonization temperature, 1100 °C compared to 500 °C during pyrolysis process due to its capability in absorbing more dye as it has larger specific area.

Remazol orange dye sensitized solar cell

Water based Remazol Orange was utilized as the dye sensitizer for dye sensitized solar cell. The annealing temperature of TiO2 working electrode was set at 450 °C. The performance of the device was investigated between dye concentrations of 0.25 mM and 2.5 mM at three different immersion times (3, 12 and 24 hours). The adsorption peak of the dye sensitizer was evaluated using UV-Vis-Nir and the device performance was tested using solar cell simulator. The results show that the performance was increased at higher dye concentration and longer immersion time. The best device performance was obtained at 0.2% for dye concentration of 2.5 mM immersed at 24 hours.

Optimization of Output Coupling Ratio for Multi-Wavelength Brillouin Fiber Laser Employing FBG and DCF as Gain Medium

A ring-cavity multi-wavelength Brillouin fiber laser by employing a fiber Bragg grating and dispersion compensating fiber was experimentally demonstrated. The multi-wavelength Brillouin fiber laser has been analyzed at different output coupling ratios at 1550 nm of Brillouin pump wavelength. A ring-cavity multi-wavelength Brillouin fiber laser has been designed with a 16 km long of dispersion compensating fiber which acts as gain medium for stimulated Brillouin scattering effect. Dispersion compensating fiber is designed to have small core size and has higher nonlinear coefficient. As a result, 8 Brillouin Stokes signals were produced at maximum Brillouin power of 21 dBm and output coupling ratio of 80%. The best performance of output coupling ratio was determined by 70% with the highest of signal to noise ratio at 38.39 dB.

S-shaped S-band multi-wavelength Brillouin Raman Fiber Laser employing Raman amplifier

The simulation demonstrated an S-shaped multi-wavelength Brillouin-Raman Fiber Laser employing Raman amplifier in the cavity. Raman amplifier- average power model is employed for signals amplification. This configuration is operated in the S-band wavelength region with tuning range between 1460 nm to 1530 nm. A laser signal at 1500 nm with 4 dBm of output power act as the Brillouin pump, while at output power of 90 mW with 1425 nm of wavelength act as the Raman pump. As a result, at 10 km of single mode fiber and output coupling ratio of 90%, 7 outputs of Brillouin Stokes signals are obtained with maximum output power of 33.88 dBm. Meanwhile, maximum gain values at 38. 07 dBm is recorded at 90 mW of injected Raman pump power. It is notable that the Raman gain broadening occurs around 1500 nm to 1530 nm in S-band wavelength region.

Wearable gas sensor utilising dye-functionalized single-walled carbon nanotubes

The suspension of single-walled carbon nanotubes (SWCNTs) that was functionalized by organic dye, was used as a sensing material. The Golden orange dye (Color Index : 40215) was used as the dispersion agent in order to establish a stable suspension of SWCNTs in water. The ratio of dye and deionized water (DI water) mixture is 1:1. Uniform thin film of SWCNTs was produced using vacuum filtration method where uniform thin film of SWCNTs network was formed. In this project, plastic was used as a substrate. The device was then being exposed to NO2 gas at three different temperatures which is room temperature, 200 °C and 300 °C.

L-band single-wavelength Brillouin fiber laser utilizing ring cavity

In this paper we demonstrate a single-wavelength Brillouin Fiber laser utilizing ring cavity which operated in the L-band wavelength region. The Brillouin gain medium is provided by 4 km long of Single Mode Fiber. Based on the experimental result, it shows that the maximum output Brillouin power of 9.73 dBm with an average value of 8.5 dBm was obtained as the Brillouin pump power of 16.0 dBm and pump wavelength of 1580 nm were applied to the system. The output Brillouin Stokes power was directly dependence on the value of output Brillouin power. The optical-to-noise ratio of 43.1 dB has been generated from the system. Furthermore, without any self-lasing cavity modes activities, single-wavelength BFL is able to operate freely across L-band wavelength region.

Single wall carbon nanotubes dispersion study of different dye molecules and chitosan

Carbon Nanotubes (CNTs) is known for their hydrophobicity ability. However, this ability can become the bottleneck for the application of CNTs where a highly dispersion of materials are needed. In this project, different dispersing agents were investigated namely dye molecules and chitosan. Three different dyes are studied with different concentration, including 0.05 % of chitosan. The dispersion quality is determined by examining through UV-Vis-NIR. The best dispersion quality investigated here is when the concentration of dye molecules is higher, which is around 2.5 mM.