Abdul Mutalib Md Jani

Stimulus-Responsiveness and Drug Release from Porous Silicon Films ATRP-Grafted with Poly(N-isopropylacrylamide)

In this report, we employ surface-initiated atom transfer radical polymerization (SI-ATRP) to graft a thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAM), of controlled thickness from porous silicon (pSi) films to produce a stimulus-responsive inorganic-organic composite material. The optical properties of this material are studied using interferometric reflectance spectroscopy (IRS) above and below the lower critical solution temperature (LCST) of the PNIPAM graft polymer with regard to variation of pore sizes and thickness of the pSi layer (using discrete samples and pSi gradients) and also the thickness of the PNIPAM coatings. Our investigations of the composites thermal switching properties show that pore size, pSi layer thickness, and PNIPAM coating thickness critically influence the materials thermoresponsiveness. This composite material has considerable potential for a range of applications including temperature sensors and feedback controlled drug release. Indeed, we demonstrate that modulation of the temperature around the LCST significantly alters the rate of release of the fluorescent anticancer drug camptothecin from the pSi-PNIPAM composite films.

Nanoporous anodic aluminium oxide membranes with layered surface chemistry

A new and facile method is described to prepare Janus-like nanoporous anodic aluminium oxide (AAO) membranes with distinctly different internal and external surface chemistry.

Pore spanning lipid bilayers on silanised nanoporous alumina membranes

The preparation of bilayer lipid membranes (BLMs) on solid surfaces is important for many studies probing various important biological phenomena including the cell barrier properties, ion-channels, biosensing, drug discovery and protein/ligand interactions. In this work we present new membrane platforms based on suspended BLMs on nanoporous anodic aluminium oxide (AAO) membranes. AAO membranes were prepared by electrochemical anodisation of aluminium foil in 0.3 M oxalic acid using a custom-built etching cell and applying voltage of 40 V, at 1oC. AAO membranes with controlled diameter of pores from 30 - 40 nm (top of membrane) and 60 -70 nm (bottom of membrane) were fabricated. Pore dimensions have been confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). AAO membranes were chemically functionalised with 3-aminopropyltriethoxysilane (APTES). Confirmation of the APTES attachment to the AAO membrane was achieved by means of infrared spectroscopy, X-ray photoelectron spectroscopy and contact angle measurements. The Fourier transform infrared (FTIR) spectra of functionalised membranes show several peaks from 2800 to 3000 cm-1 which were assigned to symmetric and antisymmetric CH2 bands. XPS data of the membrane showed a distinct increase in C1s (285 eV), N1s (402 eV) and Si2p (102 eV) peaks after silanisation. The water contact angle of the functionalised membrane was 80o as compared to 20o for the untreated membrane. The formation of BLMs comprising dioleoyl-phosphatidylserine (DOPS) on APTESmodified AAO membranes was carried using the vesicle spreading technique. AFM imaging and force spectroscopy was used to characterise the structural and nanomechanical properties of the suspended membrane. This technique also confirmed the stability of bilayers on the nanoporous alumina support for several days. Fabricated suspended BLMs on nanoporous AAO hold promise for the construction of biomimetic membrane architectures with embedded transmembrane proteins.

Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) Perovskite Nanorods by Template Synthesis

Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) is a ceramic perovskite-type oxide that has attracted growing attention due to its high catalytic activity, mixed ionic/electronic conductivity and giant magnetic resistance. Improvement in the properties of BSCF can be achieved by tailoring its architecture such as nanoparticles (powdered form), nanotubes or nanorods as these nanostructured materials posses high surface-to-volume ratios with high sensitivity to surface adsorption and reactions. However, most of the studies conducted by means of conventional solid-state reaction methods or with wet chemistry techniques regularly produced BSCF in loose powdered form, non-uniform and the particle size is hard to be controlled. Herein in this work, an investigation on a synthetic approach using highly ordered nanoporous anodic aluminium oxide (AAO) as a template, focusing on the fabrication of BSCF perovskite nanorods is demonstrated. Sol-gel method is used to prepare the BSCF precursor solution or sol followed by filling the AAO template with the sol at different immersion time of 1 hr, 12 hrs and 24 hrs. After the following drying and calcination steps, the morphological structure and composition of the synthesized BSCF nanorods inside the AAO templates are examined by field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) analysis. The micrograph showed BSCF nanorods are successfully synthesized at immersion time of 24 hrs with the diameter of nanorods embedded in the AAO template is approximately 180 nm. The EDX analysis also confirmed the stoichiometry of Ba0.5Sr0.5Co0.8Fe0.2O3-δ. Possible formation mechanism of BSCF nanorods inside the AAO template is also discussed in this paper.

Microstructure control of SOFC cathode material: The role of dispersing agent

In the present works, La0.6Sr0.4Co0.2Fe0.8O3−δ (LSCF) cathode powders were synthesized by a sol-gel method with the aid of ethylene glycol which served as the dispersing agent. The phase formation and morphology of the powders were examined by X-Ray diffractometer (XRD) and field emission scanning electron microscopy (FESEM), respectively. The electrochemical properties of the synthesized cathode were obtained using an electrochemical impedance spectroscopy (EIS). The characteristic peaks for LSCF phase appears in the X-ray diffractogram after calcined at 500 °C and complete formation of LSCF single phase was attained at 700 °C. FESEM micrographs showed the presence of spherical particles of the powders with approximate particle size between 10 to 60 nm along with agglomerate morphologies. Well dispersed particles and fewer aggregates were observed for samples prepared with addition of ethylene glycol as the synthesizing aid. The surface area obtained for powder sample prepared with the aid of dispersing ...

The Effect of Applied Voltage and Anodisation Time on Anodized Aluminum Oxide Nanostructures

The use of anodized aluminum oxide (AAO) is vastly being explored in recent years. The application includes molecular separation, sensing, energy storage and template synthesis for various nanostructures. The reason AAO is preferred was because of the ability to control the nanopore structure by manipulating some factors during the anodisation process. This study will investigate the exploitation of voltage and anodisation time during the anodisation process and the effect it has on the nanopore structure of the AAO by examining the structure under Field Emission Scanning Electron Microscope (FE-SEM). The experiment was carried out by anodizing aluminum foil in 0.3 M oxalic acid as electrolyte under the constant temperature of 5 °C. The applied voltage was varied from 40, 60 and 100 V with different anodisation time. The outcome of this study demonstrates that applied voltage has a proportional relationship with the developed pore size. Increasing the applied voltage from 40 to 100 V had increased the pore size of the AAO from 38 nm to 186 nm, respectively. Aluminium oxide anodized at 60 V demonstrates pore size in the range of 76 nm. Prolong anodisation time had improved the pore morphology of anodized aluminium oxide in the case of 40 V, however, the pore wall starts to collapse when anodisation time is more than 4 minutes at 100 V.

Synthesis of Chitosan-Gold Nanoparticles for Drug Delivery

Gold nanoparticles (Au NPs) have potential applications in catalysis, drug delivery, sensors and environmental remediation. This wide range application is due to its amenability of synthesis and functionalization, less toxicity and ease of detection. The present work focuses on functionalization of Au NPs with chitosan for further application in biomedical research. Gold nanoparticles (Au NPs) functionalized chitosan were prepared by reducing gold salt solution at various pH medium in the presence of sodium borohydride. The effect of pH and chitosan concentration on the Au particle size and distribution are studied. The results revealed the dependence of Au particle size on the pH of the solution. The smallest Au particle size is found to form in a range of 10.22 ± 2.96 nm at 0.2% chitosan concentration. In this study, we anticipate the Au NPs functionalized chitosan can be used for drug delivery applications.

Preliminary study towards the fabrication of the nanoscale optical pH sensor with tailored pK/sub a/ value by using molecularly imprinting technique

Molecularly imprinting is an advanced technique for producing chemically selective binding sites, which recognize a particular molecule, in a macro porous polymer matrix. The pK/sub a/ value of the indicator is significantly changed up to several orders of magnitude by the imprinting synthesis. This fine-tuning of the reactivity of pH indicators by using the imprinting synthesis (molecularly imprinted polymer) may find novel applications in designing pH sensors with tailored pK/sub a/ value. Here, we try to describe a technique for the successful imprinting of different structural stages of a pH indicator in a hybrid sol-gel matrix. The proton affinity of the indicator is strongly dependent on this imprinting synthesis. The pH indicator used in this experiment is methyl red. The end result of the proton imprinting technique is the modification of the pK/sub a/ value of the indicator in the sol-gel matrix. The fabricated imprinted polymer is likely suitable for the construction of the nanoscale optical pH sensor due to the modified pK/sub a/ value, the large surface area and the pore size of the hybrid sol-gel used in this study.

Preparation of Nano-Structured Cathode for Proton-Conducting Fuel Cell by Dispersing Agent-Assisted Sol-Gel Method

The development of high-performance cathodes is essential towards the operation of proton-conducting fuel cells (PCFCs) at intermediate temperatures. To that end, the performance of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) cathodes is very attractive. In the present works, LSCF cathode powders were synthesized by a sol-gel method with the aid of ethylene glycol which served as the dispersing agent. The pristine and modified samples were each denoted as LSCF64 and LSCF-EG5. The phase formation and morphology of the cathode powders were examined by X-Ray diffractometer (XRD) and field emission scanning electron microscopy (FESEM), respectively. In order to evaluate the cathode performance, a symmetrical cell of electrolyte supported PCFCs were examined using an electrochemical impedance spectroscopy (EIS) at a 700 oC in atmosphere containing humidified air. The formation of LSCF single phase was attained at 700 °C for both prepared samples. The FESEM images confirms an improvement in the microstructure of the modified cathode. The impedance spectra obtained from the electrochemical impedance measurement were resolved by a fitting procedure using an equivalent circuit that consists of a combination of two parallel pairs of resistor-constant phase element (R-Q) in series. The area specific resistance (ASR) determined for LSCF64 and LSCF-EG5 is 1.55 and 0.23 Ωcm2 , respectively. The better performance exhibited by LSCF-EG5 is attributed to its higher cathode reaction site due the improved microstucture. This study reveals that the application of ethylene glycol as dispersing agent is effective in producing a high quality cathode material for better PCFCs performance.

Characterization of Acid Treated Activated Carbon From Oil Palm Empty Fruit Bunches (EFB)

Activated carbon (AC) has a high potential to act as dispersing agent as the surface of the activated carbon can be modified by chemical and/or physical treatments. In this work, several acid treatment methods have been conducted by using nitric acid (HNO3), hydrogen peroxide (H2O2) and a mixture of nitric acid and sulfuric acid To functionalize the activated carbon from oil palm empty fruit bunches (AC-EFB), those treatments were followed by washing with distilled water until neutral pH and dried overnight in an oven at 80 °C. A dispersion test was conducted by dispersing a small amount of the treated AC-EFB in distilled water using a sonicator for 5 minutes. The modified AC-EFB has been characterized by using, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) analysis. Based on observation, the treated AC-EFB with a mixture of acids has a stable suspension compared to other methods which indicate the presence of a hydroxyl group attached to the surface of AC-EFB. FTIR results further confirmed the presence of the functional group of hydroxyl. The SEM micrograph shows the formation of unique microstructure on the AC-EFB structure after treated with method M3 whereas the number of pores developed was increased. The atomic percentage of oxygen of treated AC-EFB was higher than untreated AC-EFB, which indicates the hydroxyl group was attached to the surface of activated carbon as proven by EDX analysis. Thus, acid treated method using HNO3/H2SO4 mixture shows a promising approach on synthesizing the activated carbon with unique properties and characteristics.