Sharifah Bee Abdul Hamid

Progress on implantable biofuel cell: nano-carbon functionalization for enzyme immobilization enhancement.

Biofuel cells are bio-electrochemical devices, which are suitable for the environmentally friendly generation of energy. Enzymatic biofuel cell (EBFC) operates at ambient temperature and pH. Biofuel cells utilize vegetable and animal fluids (e.g. glucose) as a biofuel to produce energy. Fundamental part of each Glucose biofuel cell (GBFC) is two bioelectrodes which their surface utilizes as an enzyme immobilized site. Glucose oxidase (GOx) or glucose dehydrogenase (GDH) were immobilized on bioanode and oxidize glucose while oxygen reduced in biocathode using immobilized laccase or bilirubin oxidase in order to generate sufficient power. Glucose biofuel cells are capable to generate sufficient power for implanted devices. The key step of manufacturing a bioelectrode is the effective enzyme immobilization on the electrode surface. Due to the thin diameter of carbon nanomaterials, which make them accessible to the enzyme active sites, they are applicable materials to establish electronic communication with redox enzymes. Carbon nanomaterials regenerate the biocatalysts either by direct electron transfer or redox mediators which serve as intermediated for the electron transfer. Nano-carbon functionalization is perfectly compatible with other chemical or biological approaches to enhance the enzyme functions in implantable biofuel cells. Efficient immobilization of enzyme using the functionalized nano-carbon materials is the key point that greatly increases the possibilities of success. Current review highlights the progress on implantable biofuel cell, with focus on the nano-carbon functionalization for enzyme immobilization enhancement in glucose/O2 biofuel cells.

Base Catalytic Approach: A Promising Technique for the Activation of Biochar for Equilibrium Sorption Studies of Copper, Cu(II) Ions in Single Solute System

This study examines the feasibility of catalytically pretreated biochar derived from the dried exocarp or fruit peel of mangostene with Group I alkali metal hydroxide (KOH). The pretreated char was activated in the presence of carbon dioxide gas flow at high temperature to upgrade its physiochemical properties for the removal of copper, Cu(II) cations in single solute system. The effect of three independent variables, including temperature, agitation time and concentration, on sorption performance were carried out. Reaction kinetics parameters were determined by using linear regression analysis of the pseudo first, pseudo second, Elovich and intra-particle diffusion models. The regression co-efficient, R2 values were best for the pseudo second order kinetic model for all the concentration ranges under investigation. This implied that Cu(II) cations were adsorbed mainly by chemical interactions with the surface active sites of the activated biochar. Langmuir, Freundlich and Temkin isotherm models were used to interpret the equilibrium data at different temperature. Thermodynamic studies revealed that the sorption process was spontaneous and endothermic. The surface area of the activated sample was 367.10 m2/g, whereas before base activation, it was only 1.22 m2/g. The results elucidated that the base pretreatment was efficient enough to yield porous carbon with an enlarged surface area, which can successfully eliminate Cu(II) cations from waste water.

Thermally decomposed mesoporous Nickel Iron hydrotalcite: An active solid-base catalyst for solvent-free Knoevenagel condensation

Thermal decomposition of co-precipitated Ni-Fe-HT materials led to the formation a mesoporous Ni-Fe-HT catalyst and we have demonstrated here its active role as solid and active catalyst for the Knoevenagel condensation reaction of various aldehydes with active methylene compounds (R-CH2-CN, where R=CN or CO2Et). High product yields are obtained at moderate temperature under solvent-free conditions and the catalyst can be easily separated from the reaction mixture, simply by filtration and reused several times without a significant loss of its activity. Since these mesoporous metal oxides derived from the NiFe hydrotalcites, their basicity mediated abstraction of the acidic protons from the active methylene compounds was responsible for their catalytic activity under solvent-free conditions.

Effect of reduced graphene oxide-hybridized ZnO thin films on the photoinactivation of Staphylococcus aureus and Salmonella enterica serovar Typhi

The immobilization of photocatalyst nanoparticles on a solid substrate is an important aspect for improved post-treatment separation and photocatalyst reactor design. In this study, we report the simple preparation of reduced graphene oxide (rGO)-hybridized zinc oxide (ZnO) thin films using a one-step electrochemical deposition, and investigated the effect of rGO-hybridization on the photoinactivation efficiency of ZnO thin films towards Staphylococcus aureus (S. aureus) and Salmonella enterica serovar Typhi (S. Typhi) as target bacterial pathogens. Field-emission scanning electron microscopy (FESEM) revealed the formation of geometric, hexagonal flakes of ZnO on the ITO glass substrate, as well as the incorporation of rGO with ZnO in the rGO/ZnO thin film. Raman spectroscopy indicated the successful incorporation of rGO with ZnO during the electrodeposition process. Photoluminescence (PL) spectroscopy indicates that rGO hybridization with ZnO increases the amount of oxygen vacancies, evidenced by the shift of visible PL peak at 650 to 500nm. The photoinactivation experiments showed that the thin films were able to reduce the bacterial cell density of Staph. aureus and S. Typhi from an initial concentration of approximately 10(8) to 10(3)CFU/mL within 15min. The rGO/ZnO thin film increased the photoinactivation rate for S. aureus (log[N/No]) from -5.1 (ZnO) to -5.9. In contrast, the application of rGO/ZnO thin film towards the photoinactivation of S. Typhi did not improve its photoinactivation rate, compared to the ZnO thin film. We may summarise that (1) rGO/ZnO was effective to accelerate the photoinactivation of S. aureus but showed no difference to improve the photoinactivation of S. Typhi, in comparison to the performance of ZnO thin films, and (2) the photoinactivation in the presence of ZnO and rGO/ZnO was by ROS damage to the extracellular wall.

Facile Synthesis Polyethylene Glycol Coated Magnetite Nanoparticles for High Colloidal Stability

Polyethylene glycol PEG is one of the most frequently used synthetic polymers for surface modifications of magnetite nanoparticles MNPs to provide a new opportunity for constructing high colloidal stability. Herein, a facile in situ coprecipitation technique is described for the synthesis of PEG coated MNPs using ammonium hydroxide as the precipitating agent. The structure and morphology of the prepared PEG coated MNPs samples were characterized by Fourier transform infrared FTIR spectroscopy, X-ray spectroscopy, thermogravimetric analysis TGA, and the high resolution transmission electron microscopy HRTEM. In this study, all samples demonstrated hydrodynamic size in the range of 32 to 43 nm with narrow size distribution. In addition, the magnetic properties of resultant samples were investigated using a vibrating sample magnetometer VSM to reveal the superparamagnetic behaviour with saturation magnetization. The saturation magnetization of PEG coated MNPs samples was in the range of 63 to 66 emu/g at 300 K. Interestingly, it was found that 1.0 g of PEG coated MNPs exhibited high colloidal stability in a basic solution pH = 10 and nitrile NBR latex up to 21 days as compared to the unmodified MNPs during the sedimentation test.

A study on growth formation of nano-sized magnetite Fe3O4 via co-precipitation method

Abstract A simple and cost-effective chemical co-precipitation of aqueous ferrous and ferric salts was used to synthesis controlled size of magnetite iron oxide nanoparticles. The titration reactions between the aqueous Fe2+/Fe3+ salt solutions were controlled by an autotitrator unit with continuous addition of 1 M sodium hydroxide under different heating temperatures from 30 up to 80°C in oxidising atmosphere. Then, further investigation on the degree of crystallinity of magnetite iron oxide nanoparticles was conducted by altering the concentration of Fe2+/Fe3+ ions in the ratio of 1:1, 1:1·25, 1:1·5 and 1:2. The resultant magnetite iron oxide nanoparticles were characterised by using X-ray diffraction, field emission scanning electron microscopy and Fourier transform infrared spectroscopy. The ratio of Fe2+/Fe3+ salt solutions and heating temperatures played a crucial role in controlling the morphology, crystallinity and particle sizes of magnetite magnetite iron oxide.

The Role of Surface Area of ZnO Nanoparticles as an Agent for some Chemical Reactions

Synthesising zinc oxide nanoparticles (ZnO-NPs) to get certain characteristics to be applied in Enhanced Oil Recovery (EOR) is still challenging to date. In this work, the importance of high surface area of ZnO nanoparticles as EOR agent was highlighted. A simulation on density of state (DOS), band structure and adsorption energy of hydrogen and nitrogen gases on the surface of ZnO was carried out; it is observed that from the band structure of the band gap value for ZnO is 0.808ev. For the ZnO, Zn 4s states contribute to conduction band and O 2p states contribute to valence band. ZnO-NPs were synthesised using the sol-gel method by dissolving zinc nitrate hexahydrate in nitric acid and varying the stirring time (1 and 24h) and sintering time (30 and 40 min). A microwave oven was used for annealing ZnO without insulating the samples in any casket. The results show that 30 and 40 min of annealing and stirring for 1 & 24 h influenced the morphology and size of ZnO-NPs. These parameters could be tailored to generate a range of nanoparticle morphology (flask and/with agglomerated nanoparticles in a corn shape) obtained by Field Emission Scanning Electron Microscope (FESEM) and hexagonal crystal, determined by X-ray diffractometer (XRD), with the mean size of 70.5 & 74.9 nm and a main growth at the peak (101). The prepared sample via stirring for 24h and sintering for 40 min was chosen to prepare ZnO nanofluid because it has the highest surface area (BET) among the rest of samples, 0.23 m2/g. 10% of Original Oil In Place (OOIP) was recovered successfully to prove that ZnO is a good candidate to be applied in some chemical reactions. Moreover, it was found that ZnO is a promising catalyst for ammonia synthesis based on the adsorption energy of hydrogen and nitrogen gases (-1.05 and-1.60 kcal/mol respectively).

Facile Remediation Method of Copper Sulfide by Nitrogen Pre-Treatment

The deactivation and destabilization of copper sulfide when exposed to an oxidizing environment has led to the economical concerns as this sulfidic material can be easily destroyed by a series of oxidation processes. A promising and effective remediation technique in limiting the contact between covellite (CuS) and oxygen has been developed using a simple, hassle-free, non-corrosive, and eco-friendly pre-treatment of nitrogen approach. This remediation technique is remarkably effective as various techniques such as powder XRD, EDX, elemental mapping, and TGA-MS analyses have confirmed that covellite prepared with the pre-treatment of nitrogen does not oxidize to any mixed phase compound. Meanwhile, the study also shows that covellite stored without the pre-treatment of nitrogen has transformed to a mixed phase of pentahydrate copper sulfate and covellite. Hence, this method can be practically exercised not only on covellite, but possibly on other metal sulfides which are prone to be attacked by oxygen and water molecules in oxidizing environment.

Progress on synthesis, functionalisation and applications of graphene nanoplatelets

Carbon is the fifteenth most abundant element in Earths crust, and the fourth most abundant element in the universe. Carbon nanostructures, or nanocarbons, i.e. the low-dimensional nanomaterials, are being extensively researched for the past two decades because of their unique structure and electronic properties, prompting a huge interest in its fundamental research and applications in molecular electronics, materials science, energy storage and conversion, bio-medicine, sensing, and bio-sensing. Graphene was recently touted as a wonder material, because of its high-mechanical strength, high-electron mobility, lightness, flexibility, single-atom thickness, and near-transparency. These properties make graphene a very promising material for composites, thin films, electromagnetic shielding, barrier films, and sensors. This review focuses on the latest progress on the preparation and functionalisation of graphene nanoplatelets, and discusses its potential applications, future prospects, and challenges in the context of theranostic applications.

One-dimensional TiO2 nanotubes arrays: Influence of anodisation voltage and their photocatalytic activity performance

Abstract A systematic study of titanium dioxide (TiO2) nanotube arrays grown by electrochemical anodisation in an ethylene glycol electrolyte containing 0·5 wt-% ammonium fluoride has been carried out, with a range of anodisation voltage of 15–60 V for 1 hour. Among all of the applied anodisation voltages, 60 V resulted in the highest aspect ratio TiO2 nanotube arrays with the tube length of approximately 2 μm and pore size of 105 nm. The diameter and length of nanotubes were found to be increased with anodisation voltage because of the high electric field dissolution at the barrier layer of nanotubes. Besides, the anatase phase of TiO2 could be detected from the X-ray diffraction patterns after subjecting the annealing process at 400°C in argon atmosphere for 4 hours. Based on the photocatalytic studies, it was observed that TiO2 nanotube arrays with the highest aspect ratio (length/pore’s size) exhibited preferably high photocatalytic activity among the samples owing to the larger active surface area to generate more photo-induced electron–hole pairs. This condition will enhance the photocatalytic degradation efficiency of methyl orange.