Research Output
1 - 10 of 12
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PublicationAnalysis of power distribution in mach zehnder interferometer polymer-based waveguide for sensing applications( 2022-12)Two Mach Zehnder Interferometer (MZI) polymer-based waveguide designs namely MZI symmetrical and MZI asymmetrical structures were simulated and analyzed using Optiwave OptiBPM10. The two designs with device size of 4000μm x 300μm exhibit clear optical propagation path when light is simulated through them as well as displaying single mode profile. Highest output power was obtained by the MZI symmetrical design at 0.90 a.u, which suggests better waveguide design for sensing applications.
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PublicationElectrochemiluminescence of carbon dots and nitrogen-doped carbon dots from a microwave-assisted method( 2023-10)This research focuses on the use of carbon dots (CDs) and nitrogen-doped carbon dots (NCDs) synthesized using a microwave-assisted method as electrochemiluminescence (ECL) luminophores. CDs have been synthesized using citric acid, while various concentrations of nitrogen-doped CDs have been successfully obtained by varying the amount of urea from 1 to 3 g with citric acid to produce NCD1, NCD,2 and NCD3. The ECL mechanism of CDs and NCDs on screen-printed electrodes has been studied using cyclic voltammetry (CV). ECL emission from as-prepared CDs and NCDs was observed in PBS with potassium persulfate (K2S2O8) as a co-reactant. The addition of potassium chloride (KCl) as a supporting electrolyte displays fast electroreduction of CDs and K2S2O8 to expedite the generation of CDs and peroxydisulfate radicals that simultaneously increase ECL intensity. Furthermore, as the concentration of nitrogen-doped CDs increases, so does the intensity of the ECL. NCD3 shows the highest ECL intensity by an increment of 86.4% in comparison to CDs in PBS with the addition of K2S2O8 and KCl. Finally, optimization of ECL measurement was carried out in terms of CV potential range, concentration of luminophore, supporting electrolyte, and co-reactant using NCD3 luminophore. The CV potential range at 0 to -2 V shows 50 mV of early CV reverse onset potential that resulted in an increase of 52.9% ECL intensity. Meanwhile, 30x dilution of NCD3, 0.1 M of supporting electrolyte KCl, and 0.1 M of co-reactant K2S2O8 show the optimum value to obtain high ECL intensity.
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PublicationModification of photoanode surface structure via image analysis on organic polymer material based for dye-sensitized solar cell (DSSC) applications( 2021-12)In this study, the experiment on the modification of the photoanode with organic polymer material as copolymer template for dye-sensitized solar cell (DSSC) applications has been conducted. The two organic copolymer templates are polystyrene sphere (PS) and poly[2- methoxy-5(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV). The modification photoanodes were made using Dr. Blade’s method. These organic copolymer templates were added to improve the surface of the mesoporous titanium dioxide (TiO₂) layer, which is used as the main component in DSSC photoanode. The unmodified TiO₂ photoanode has poor aggregation and porosity of TiO₂. The addition of either MEH-PPV or PS sphere to the photoanode layer was found to affect the surface of mesoporous TiO₂ in terms of porosity, particle size distribution and shape. The analysis of the TiO2 modification was conducted using an image analysis processing method via a 2D scanning electron microscope (SEM) image. The image analysis processing method used was the ImageJ program. The DSSC of modified photoanode is fabricated using metal complex dye, Ruthenium (N719) dye. The data collected from the ImageJ program showed that by adding organic copolymer templates into TiO₂, the porosity of TiO₂ decreased from 45 % to 42 %. From the photovoltaic analysis obtained, the J-V characteristic is recorded with the photoanode of TiO₂ mixed with 1.00 wt% MEH-PPV gave the highest efficiency, which is 0.01 % with the following parameters – Voc = 0.43 V, Jsc = 0.17 mA/cm2 and FF = 0.20. Meanwhile, the photoanode of TiO₂ mixed with 0.50 wt% PS sphere gave the highest efficiency which is 0.08 % with the following parameters – Voc = 0.39 V, Jsc = 0.86 mA/cm2 and FF = 0.25.
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PublicationElectrochemical detection of heavy metal ions using gold nanoparticles on carbon dots extracted from curry leaves( 2024-06)Carbon dots (CDs) have attracted attention due to their versatility in electronic and optical properties based on precursor and type of synthesis process. Recently, many researchers have focused on using natural resources or wastes to form CDs. Four samples of CDs have been synthesized from curry leaves using a microwave-assisted approach at heating powers of 700 and 800 V with durations of 5 and 8 minutes. UV-Vis and FTIR spectra reveal the existence of carbon graphitic elements with carboxyl and hydroxyl functional groups on the surfaces of CDs. CVs of AuNPs/CDs/GS electrodes in ferricyanide disclosed that as-synthesized CDs produced using a lower heating power of 700 W exhibit pronounced electrocatalytic activity with sluggish electron transfer kinetics. Conversely, as-synthesized CDs created with a higher heating power of 800 W demonstrate reduced electrocatalytic activity but rapid electron transfer kinetics. Electrochemical detection of Pb2+ ions was observed through a sharp peak around -0.42 to -0.438 V, while detection of Hg2+ ions was observed through two anodic peaks around +0.334 to +0.408 V during a forward scan in acetate buffer (pH 4.5) on AuNPs/CDs/GS electrodes when tested individually. These distinct peaks also appeared in mixture solutions, with a slight reduction in peak current density that suggests the selectivity of the AuNPs/CDs/GS electrodes towards Pb2+ and Hg2+ ion detection. The optimum AuNPs/CDs/GS electrode for sensitive and selective detection of Pb2+ and Hg2+ was recorded using CDs D as a functional supporting matrix for AuNPs that was synthesized using a heating power of 800 W for 8 minutes.
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PublicationDyes extracted from Hibiscus Sabdariffa flower and Pandannus amaryllifolius leaf as natural dye sensitizer by using an alcohol-based solvent( 2021-03-01)The efficiency improvement of Dye sensitized solar cells (DSSC), the fabrication of DSSC by using metal-free organic natural dyes with a different type of solvents for the extraction of dye sensitizer was investigated. The metal-free organic Dye which comes from anthocyanin and chlorophyll dyes were dissolved by using different solvents, which are ethanol, methanol and mixture of ethanol and methanol. Anthocyanin dye was extracted from the petals of Hibiscus Sabdariffa (Roselle), and chlorophyll dye was extracted from the epidermal leaves of Pandannus amaryllifolius (Pandan). The purpose of using different solvents from alcohol-based was to determine which solvents that produce the highest effect in term of efficiency for DSSC. To confirm which solvents that produce the highest efficiency to the DSSC, the photovoltaic measurement was conducted, and the data was collected. From the photovoltaic analysis, the J-V characteristics under illumination are recorded. The sample that used anthocyanin dye extracted from Roselle flower diluted with methanol solvent gave the highest efficiency which is 0.0005% with the following parameters-Voc = 0.419 V, Jsc = 0.0057 mA/cm2 and FF = 0.24. Meanwhile, the sample that used chlorophyll dye extracted from Pandan leaves diluted with a mix of ethanol and methanol solvents gave the highest efficiency which is 0.00014% with the following parameters-Voc = 0.347 V, Jsc = 0.0016 mA/cm2 and FF = 0.25.
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PublicationOptimization of MEH-PPV based single and double-layer TOLED structure by numerical simulation( 2021-12)In this work, we simulated and characterized Poly [2-methoxy-5-(2’-ethylhexyloxy)-1, 4-phenylene vinylene] (MEH-PPV) based single and double-layer TOLED by using Silvaco ATLAS device simulator to achieve prominent values of electrical and optical properties of the device. MEH-PPV were used as the emitting layer (EML) in the single-layer, while addition of Poly [(3,4-ethylene dioxythiophene)-poly(styrene sulfonate)] (PEDOT-PSS) as the electron transport layer (ETL) were conducted in double-layer TOLED simulation. The EML and ETL thickness in both structures were varied between 10 – 150 nm, respectively, to observe and understand the underlying physics of the relation in the layer thickness to the electrical and optical characteristics. Furthermore, variation of the EML/ETL thickness ratio from 1:1 to 5:1 (with thickness in between 10 to 50 nm) had also been conducted. From this work, it is understood that the thickness of the EML layer plays the most important role in TOLED, and by balancing the carrier injections and recombination rate in appropriate EML/ETL thickness ratio, the electrical and optical properties can be improved. By optimizing the EML/ETL thickness and thickness ratio, an optimal forward current of 1.41 mA and luminescent power of 1.93e-18 W/μm has been achieved with both MEH-PPV and PEDOT-PSS layer thickness of 10 nm (1:1 ratio), respectively. The results from this work will assist the improvement of TOLED device to be implemented widely in low power and transparent electronic appliances.
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PublicationLow-cost tilt monitoring system for spin coater calibration( 2024-02-08)The spin coating process became the most widely used technique in the fabrication industry for thin film coating on a substrate by centrifugal force. Unfortunately, frequent usage of spin coater might induce a tilted surface of the chuck (i.e. the sample holder). A tilted chuck might induce inhomogeneity of the coating layer. Among the machine's calibration techniques, nullifying the tilt before the spin coating process is the most important step. However, to our knowledge, none of the spin coaters was introduced with the chuck's tilt monitoring during the spin coating process. Thus, investigating the discrete condition during the spin coating process is necessary. In this work, the tilt monitoring system for the spin coater was implemented based on an Arduino Uno microcontroller and distance sensor. A spin coater has been implemented to test the tilt surface monitoring during spinning ranges from 350rpm to 1000rpm. The measurement was done under two conditions: flat (0.00 degrees) and tilted (5.71 degrees). The setup was able to measure up to 0.01 degrees of the tilt.
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PublicationThe Effect of Different Solvents in Natural Dyes from Roselle (Hibiscus Sabdariffa) and Green Tea Leaves (Camellia Sinensis) for Dye-Sensitized Solar Cell( 2021-03-01)A dye-sensitized solar cell (DSSC) fabricated using anthocyanin or chlorophyll natural dye extract coming from Roselle (Hibiscus Sabdariffa) and Green Tea leaves (Camellia Sinensis). Both dye pigmentations were extracted using different alcohol-based solvent, namely, ethanol, methanol and mixed (ethanol + methanol) to identify whether the different solvents give the effect during the dye extraction. The performance of the electron transfer interaction between the natural dye and Titanium Dioxide (TiO2) was determined. The photovoltaic response of DSSC was collected by recording the data of I-V characteristic under illumination. The DSSC using the Roselle dye extract yielded the following results; Voc = 0.001 V, Jsc = 0.00868(mA/cm2), FF = 0.3554 and η = 0.00142% which is coming from the mixed solvent. On the other hand, the green tea dye extract yielded the following results; Voc = 0.3985, Jsc = 0.000797 (mA/cm2), FF = 0.3985 and η = 0.0000752% which is coming from the methanol solvent.
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PublicationAnalysis of Power Distribution in Mach Zehnder Interferometer Polymer-based Waveguide for Sensing Applications( 2022-12-01)Two Mach Zehnder Interferometer (MZI) polymer-based waveguide designs namely MZI symmetrical and MZI asymmetrical structures were simulated and analyzed using Optiwave OptiBPM10. The two designs with device size of 4000μm x 300μm exhibit clear optical propagation path when light is simulated through them as well as displaying single mode profile. Highest output power was obtained by the MZI symmetrical design at 0.90 a.u, which suggests better waveguide design for sensing applications.
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PublicationTemperature effects on electrical and structural properties of MEH-PPV/PEIE OLED Device( 2020-06-16)This paper explores the performance of configuration ITO/MEH-PPV/PEIE/Al OLED under the variations of temperature. The MEH-PPV and MEH-PPV/PEIE thin film were deposited on ITO substrates using spin coating technique with fixed spin speed of 3000 rpm and baked at low temperature ranging from 90 °C to 180 °C, respectively. The surface roughness values for MEH-PPV and MEH-PPV/PEIE films were analysed using AFM with 5 μm ' 5 μm scanning area. The roughness of MEH-PPV thin films were reduced from 2.825 nm to 1.625 nm when temperature increased. Contrary to MEH-PPV/PEIE films where the roughness increased linearly up to 3.397 nm when the temperature increased. The maximum absorption peak spectrum obtained from UV-Visible (UV-Vis) was found at 500 nm to 510 nm when baked temperature were varied. Furthermore, the turn on voltage from J-V characteristics gives no specific pattern across different temperature and agreed with the trend of surface roughness values. The turn-on voltage at T = 150 °C gives the lowest value of 3 V. Overall, the variations of low temperature gives an effects on structural and electrical properties of this OLED configuration.
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