Papers by Author: Azlan Abdul Aziz

Abstract: This work investigates properties of Poly (3,4-ethylenedioxythiophene)–poly (styrene sulfonate) (PEDOT:PSS) on black silicon (nanotextured) and hybrid textured (nanotextured/microtextured) surfaces. The black silicon (b-Si) surface is fabricated using two-step metal-assisted chemical etching (MACE) process on crystalline silicon (c-Si) while the hybrid textures are fabricated using two-step MACE process on microscale pyramids. With PEDOT:PSS, weighted average reflection (WAR) reduces from 9.2% to 7.7% for b-Si and from 7.2% to 5.2% for hybrid textures. This is due to the anti-reflective (AR) property of the polymer. Electrical characterizations of the PEDOT:PSS layer reveal higher sheet resistance (R_s), lower hole concentration (n_h) and improved mobility (μ_h) with the presence of the surface textures on c-Si, in comparison to the results from planar c-Si reference.

Abstract: Development of bio-reduction techniques for nanoparticles (NPs) synthesis in medical application remains a challenge to numerous researchers. This work reports a novel technique for the synthesis of gold nanoparticles (AuNP) using palm oil fronds extracts (POFE) in the present of ultrasound radiation. The POFE is a waste material available in abundance in Asia and some African countries. The functional groups in the POFE operate as a persuasive capping and possibly reduced Au³⁺ to Au⁰. The prepared AuNPs were characterized by UV-vis spectrophotometry, FTIR, DLS, FESEM, and XRD. The analysis of FTIR validates the coating of alkynes and phenolic composites on the AuNPs. This shows a feasible function of biomolecules for efficient stabilization of the AuNPs. Field emission scanning electron microscopy (FESEM) clearly show the morphology of the prepared AuNPs. The XRD patterns display the peaks of fcc crystal structures at (111), (200), (220), (311) and (222). A physical and photometric detection effect of ten heavy metals (Pb, Zn, Ni, Co, Cu, Hg, As, Cr, Fe, and Mn) were investigated using the biosynthesized AuNPs and only Cr metal was detected by the AuNPs when it concentration increased from 1 ppm to 50 ppm with a rapit decrease of intensity measured using UV-vis spectrocopy at room temperature. While, almost all metals ions are detected at elevated tempeture (45 – 50 °C).

Abstract: This paper reports broadband anti-reflection in black silicon (b-Si) fabricated by two-step metal-assisted chemical etching (MACE) for potential photovoltaic (PV) applications. The method involves deposition of silver nanoparticles (Ag NPs) in aqueous solution of HF:AgNO₃, followed by etching in HF:H₂O₂:DI H₂O solution for different duration (10-25 s). Effects of etching time towards surface morphological and optical properties of b-Si nanowires are investigated. Surface morphological characterization confirms presence of b-Si nanowires with heights of 350-570 nm and diameter of 150-300 nm. The b-Si nanowires exhibit outstanding broadband anti-reflection due to refractive index grading effect. This is represented as weighted average reflection (WAR) in the 300-1100 nm wavelength region. After 20 s of etching, b-Si nanowires with height of 570 nm and width of about 200 nm are produced. The nanowires demonstrate WAR of 5.5%, which represents the lowest WAR in this investigation. This results in absorption of 95.6% at wavelength of 600 nm. The enhanced broadband light absorption yields maximum potential short-circuit current density (J_sc(max)) of up to 39.7 mA/cm², or 51% enhancement compared to c-Si reference. This facile b-Si fabrication method for broadband enhanced anti-reflection could be a promising technique to produce potential PV devices with high photocurrent.

Abstract: Superparamagnetic iron oxide nanoparticles (SPION) are routinely employed in biomedical and water treatment applications due to their inherent magnetic properties. However, for these applications a surface modified and functionalized SPION is required. Herein, for the first time we present an in-situ method of functionalizing decanethiol monolayer on thin silica coated SPION synthesised via a non-seeded process. Through physico-chemical analyses the grafting of decanethiol onto the composite nanoparticles were demonstrated. The alkane functional group in the monolayer molecule attached to the silanol group of the silica shell and became the tail and binding site to the magnetic composite nanoparticles.

Abstract: In this report, we discussed the physical properties of encapsulated Methylene Blue (MB) by Silica Nanoparticles (SiNPs) intended for photodynamic therapy application. The aim of this discussion is to determine the suitable concentration of MB which can be delivered to the target area. Results shows that the size of SiNP is not affected by the change in MB concentration from out-diffusion process even when the concentration of loaded MB were reduce by more than 50 percent. The applicability of the encapsulated MB in SiNP was demonstrated on Red Blood Cells (RBCs) and the results were compared to those obtained from naked MB.

Abstract: This paper reports the temperature dependent DC and RF characteristics of n-GaN Schottky diode simulated using Atlas/Blaze developed by Silvaco. It was found that as the temperature increases from 300K to 900K the forward current decreases due to lowering of the Schottky barrier with an increase in series-resistance and ideality factor. These observations indicates that tunneling behavior dominates the current flow rather than thermionic emission. Furthermore, the breakdown voltage decreases in reverse bias and insertion loss for RF behavior increases with respect to temperature due to the increase in capacitance near diode junction.Keywords: Atlas/Blaze, Schottky barrier, series resistance, ideality factor, insertion loss.

Abstract: Colloidal gold or also known as gold nanoparticle (AuNP) is a suspension of sub-nanometer-sized particle of gold in a fluid usually water. The synthesized AuNP have particle sizes ranging from, e.g. 10 nm to 100 nm with color changing from an intense red color (for particle less than 100 nm) to a dirty yellowish color (for larger particle). The size of AuNP determines their unique optic, electronic and magnetic properties. AuNP nowadays has widely used in material science [ and biomedical [2,. For many of this application, the AuNP need to be monodispersed and have a specific size. Generally, colloidal AuNP can be synthesis as monodispersed nanoparticles with core sizes ranging from 1nm to 250nm. The synthesis of AuNP can be controlled in different size and shapes due to their ability to react and agglomerate with other nanoparticles in their ambient condition [. Furthermore, AuNP can also becomes more prone to flocculation and aggregation [. As the size of colloidal AuNP increase so do their sensitivity to salt and environment. AuNP have increasingly gain interest due to their unique properties ofcontrolable morphology [ and size dispersion [6,, less toxicity and ease in synthesis and detection.

Abstract: Nanoscale particles of gold nowadays dominate a great deal of attention for biomedical applications. Better knowledge of the nano-bio interface will lead to advanced biomedical tools for diagnostic imaging and therapeutics. In this review, recent progress in the elucidating of how size and concentration of gold nanoparticles (AuNPs) affect cellular uptake will be discussed. Due to its small size, AuNPs can be administered conveniently via intravenous injection. The ability to enter cells is one of the factors that determine the clinical utility of nanoparti¬cles (NPs). The size of AuNPs is one of the limitations in the potential use of gold markers for medical imaging or tracking of harder tumors. Within the size range of 10-100 nm, AuNPs of diameter 50 nm demonstrate the highest uptake. Efficient accumulation of AuNPs into cells also can be achieved at higher concentration. The fewer AuNPs are in the solution, the lesser chance for a receptor to receive gold nanoparticle; “mem¬brane wrapping” time is longer, resulting to lower uptake by the cell. Theoretical models support the size- and concentration-dependent NP-uptake. Endocytosis is one of the major pathways for cellular uptake of NPs. NPs are internalized by cells through endocytosis process and trapped in endosomes, which is then fuse with lysosomes for processing before being transported to the cell periphery for excretion. Exocytosis of NPs is also dependent on the size and concentration of the NPs, however, the trend is different compared to endocytosis process. These findings provide useful information in the design and optimization of the NP-uptake at a single cell level for effective applications in imaging, diagnosis, therapeutics, and targeting.

Abstract: Superparamagnetic iron oxide nanoparticles (SPION) of sizes 5 to10 nm were synthesized by the co-precipitation method. They are coated with silica nanoparticles using sonication method. The SPION was produced under the optimum pH of 10, peptized in acidic medium and redispersed in water. The silica nanoparticles were produced through the Stöbermethod. Sonochemical coating of silica nanoparticle on the SPION was successfulat a pH value lower than 5. Otherwise, at higher pH value (but lower than point zero charge (PZC)), the SPION were found to be unstable. Fast hydrolysis of triethoxyvinylsilane(TEVS) shows that silica forms its own particles without coating onto the surfaces of the SPION. Under optimized experimental condition, sonochemical method of coating silica nanoparticles onto the SPION can be considered as an alternative for effective and prompt method that rely mainly on pH of the suspension.

Abstract: Aluminium (Al) thin films on polyimide (PI) plastic substrates prepared via thermal evaporation technique and annealed in nitrogen (N₂) ambient at different temperatures (250 - 400°C, for 30 minutes) have been investigated. Structural properties of the as-evaporated film have been studied by high resolution X-ray diffraction (HR-XRD). The result illustrates crystalline nature of the Al thin film with a dominant Al (111) peak at 2θ = 38.4°. Atomic force microscope (AFM) shows increased surface roughness root mean square (RMS) with increased annealing temperature (with roughness of 11.96 nm at 400°C). Sheet resistance drops with increased temperature and records the lowest reading (64 mΩ/) at 400°C. Besides, increased annealing temperature also results in reduced surface reflectance (with minimum reflectance of 73% reflectance in the visible region at 400°C). The effects of the resulting Al back contact properties towards thin film silicon (Si) solar cells on PI substrates were subsequently discussed.