Khairul Arifah Saharudin

Fast-rate formation of TiO2 nanotube arrays in an organic bath and their applications in photocatalysis.

In this work, 18.5 microm titanium oxide (TiO(2)) nanotube arrays were formed by the anodization of titanium (Ti) foil in ethylene glycol containing 1 wt% water and 5 wt% fluoride for 60 min at 60 V. The fast growth rate of the nanotube arrays at 308 nm min(-1) was achieved due to the excess fluoride content and the limited amount of water in ethylene glycol used for anodization. Limited water content and excess fluoride in ethylene glycol inhibited the formation of a thick barrier layer by increasing the dissolution rate at the bottom of the nanotubes. This eased the transport of titanium, fluorine and oxygen ions, and allowed the nanotubes to grow deep into the titanium foil. At the same time, the neutral condition offered a protective environment along the tube wall and pore mouth, which minimized lateral and top dissolution. Results from x-ray photoelectron spectra revealed that the TiO(2) nanotubes prepared in ethylene glycol contained Ti, oxygen (O) and carbon (C) after annealing. The photocatalytic activity of the nanotube arrays produced was evaluated by monitoring the degradation of methyl orange. Results indicate that a nanotube with an average diameter of 140 nm and an optimal tube length of 18.5 microm with a thin tube wall (20 nm) is the optimum structure required to achieve high photocatalytic reaction. In addition, the existence of carbon, high degree of anatase crystallinity, smooth wall and absence of fluorine enhanced the photocatalytic activity of the sample.

Formation of TiO 2 nanotubes via anodization and potential applications for photocatalysts, biomedical materials, and photoelectrochemical cell

One-dimensional nanotube systems with high surface-to-volume ratios possess unique properties and are thus utilized in various applications. In this study, self-organized TiO2 nanotubes were prepared by anodization of a Ti foil in glycerol containing 5 wt% ammonium fluoride (NH4F) and 6 wt% ethylene glycol (EG). The surface morphology, average inner diameter, and average length of the nanotubes varied with the electrochemical anodization parameters. Nanotubes with uniform surface morphologies, an average diameter of 85 nm, and an average length of 1.1 µm were obtained at 30 V for 1 h. The as-prepared nanotubes were amorphous but they crystallized in the anatase phase after heating at about 400 °C for 2 h in an argon atmosphere. The photocatalytic activity of the TiO2 nanotubes was evaluated through the degradation of methyl orange (MO) and by investigating their bactericidal effect. Optimum photocatalysis of MO was achieved at a kinetic rate constant of 10 3 min 1 . Furthermore, cell viability rapidly decreased on UV illumination and complete killing was achieved at 60 min in the presence of TiO2 nanotubes. For biomedical applications, the cellular activity on TiO2 nanotubes was determined using PA6 cells. Higher cellular activities were achieved using the anatase phase of 85-nm-diameter nanotubes than the amorphous phase. Photoelectrochemical hydrogen generation was investigated using nanotube photoanodes in 1 M potassium hydroxide (KOH) containing 1 wt% EG and xenon lamp. The maximum photocurrent density was 0.55 mA/cm 2 . These findings demonstrate that TiO2 nanotubes are promising for use in multifunctional applications.

Bacteriostatic Activity of LLDPE Nanocomposite Embedded with Sol–Gel Synthesized TiO2/ZnO Coupled Oxides at Various Ratios

Metal oxide-polymer nanocomposite has been proven to have selective bactericidal effects against the main and common pathogens (Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli)) that can cause harmful infectious diseases. As such, this study looked into the prospect of using TiO2/ZnO with linear low-density polyethylene (LLDPE) to inactivate S. aureus and E. coli. The physical, structural, chemical, mechanical, and antibacterial properties of the nanocomposite were investigated in detail in this paper. The production of reactive species, such as hydroxyl radicals (•OH), holes (h+), superoxide anion radicals (O2•¯), and zinc ion (Zn2+), released from the nanocomposite were quantified to elucidate the underlying antibacterial mechanisms. LLDPE/25T75Z with TiO2/ZnO (1:3) nanocomposite displayed the best performance that inactivated S. aureus and E. coli by 95% and 100%, respectively. The dominant reactive active species and the zinc ion release toward the superior antibacterial effect of nanocomposite are discussed. This work does not only offer depiction of the effective element required for antimicrobial biomedical appliances, but also the essential structural characteristics to enhance water uptake to expedite photocatalytic activity of LLDPE/metal oxide nanocomposite for long term application.

Improved Adhesion of Nonfluorinated ZnO Nanotriangle Superhydrophobic Layer on Glass Surface by Spray-Coating Method

In this present work, a superhydrophobic glass surface comprising zinc oxide nanotriangles (ZnO-nt) and nontoxic silylating agent was developed via a cost-effective spray-coating technology. ZnO-nt was synthesized by a hydrothermal method. Poly(dimethylsiloxane) (PDMS) and dimethyldiethoxysilane (DMDEOS) were used as nontoxic (nonfluoro) silylating agents. The morphology and crystallinity of ZnO-nt were studied using X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. ZnO-nt with polymeric silane (PDMS) exhibited maximum wettability as compared to nonpolymeric silane (DMDEOS). The water contact angle (WCA), sliding angle (SA), and surface roughness of ZnO-nt/PDMS-coated glass substrate under UV treatment were 165 ± 1°, 3 ± 1°, and 791 nm, respectively. The WCA of ZnO-nt/PDMS was higher (165°) than that of commercial ZnO/PDMS (ZnO-C/PDMS). ZnO-nt/PDMS was strongly attached to the glass substrate with good stability and adhesion. The reasons for improved hydrophobicity, adhesion, and mechanism of hierarchical microstructure formation on the glass substrate were explained in detail. PDMS was attached to the glass substrate via hydrogen bonds from solvated zinc acetate.

Nucleation of octahedral titanate crystals using waste anodic electrolyte from the anodization of TiO2 nanotubes

This study aims to explore the structure of a yellowish electrolyte by-product that is obtained via the chemical recycling of post Ti-anodized electrolyte containing ethylene glycol and H2O2. The yellowish by-product was identified as highly crystalline ammonium oxofluorotitanate, (NH4)3TiOF5. Based on the evidence, it is deduced that the nucleation process is triggered by the use of the strong oxidizing agent, H2O2. Indeed, the anodization–nucleation process of the titanate crystals was captured.

P-Incorporated TiO2 Nanotubes for Methyl Orange Degradation

Highly ordered TiO2 nanotubes were successfully prepared via a facile anodization method in ethylene glycol and water mixture electrolyte (99 vol% EG + 5 wt% NH4F). The as-anodized TiO2 nanotubes were crystallized by annealing at 400 °C for 4 hours in argon atmosphere. A series of phosphorus incorporation with different phosphorus content have been prepared by soaking TiO2 nanotubes samples in H3PO4. The photocatalytic activity of TiO2 nanotubes and P-incorporated TiO2 nanotubes were evaluated by the photodegradation of methyl orange. It was found that the photocatalytic activity of P-incorporated TiO2 nanotubes was 34% higher than TiO2 nanotubes.

The Effect of Water Content on the Formation of TiO2 Nanotubes in Ethylene Glycol

In this paper, anodization of Ti foil was carried out in ethylene glycol (EG) containing 5 wt% NH4F solution and 0 to 1.5 wt% of water at 50 V for 60 min. The pH of the bath was kept constant at ~pH7. The crystal structure was studied by X-Ray Diffraction (XRD) analysis, and the morphology was observed via field emission scanning electron microscopy (FESEM). TiO2 nanotube with aspect ratio of 100 was obtained in EG containing less than 1wt % water. The nanotubes wall was very smooth. Increasing the water content > 1wt % results in short nanotubes of approximately 6.2μm with aspect ratio of 62. As anodized, nanotubes were amorphous and annealed at 400 °C promote 100 % anatase phase. Photocatalytic activity of the nanotubes produced at different water content was also evaluated by the degradation of methyl orange and the detail of the observation was discussed thoroughly in this paper.