Papers by Keyword: Titanium Oxide Nanotubes

Abstract: Conventional physical sunscreens are formulated with titanium oxide (TiO₂), which reflects and scatters the UVA and UVB radiation, making them suitable for sensitive skin. However, its high refractive index can result in an undesirable white cast and potentially limit their cosmetic acceptability and effectiveness. Therefore, this study focuses on the formation of titanium oxide nanotubes (TNTs) as an alternative, since their nanoscale size minimizes light scattering and allows for a more transparent appearance when applied to the skin. TNTs were formed by anodic oxidation using an electrolyte based on ethylene glycol (EG), ammonium fluoride (NH₄F), and distilled water. Anodization was conducted at a constant voltage of 60 V for 1 h. TNTs were characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM), which confirmed the presence of Ti₂O and an inner diameter of 53 ± 4 nm. Biocompatibility was assessed using 3D spheroid cultures of hFOB 1.19 osteoblasts, and results showed that TNTs at concentrations of 0.2 mg/mL and 0.02 mg/mL were non-cytotoxic. The 0.2 mg/mL concentration exhibited a superior photoprotective effect, maintaining approximately 75% cell viability under UVB radiation conditions. These findings highlight the potential of TNTs as transparent, biocompatible UV filters for next-generation sunscreens.

Abstract: Increasing interest of attachment gold nanoparticles (AuNPs) on titanium oxide (TiO₂) nanotubes has been devoted to give tremendous properties suitable for catalysis application. Nevertheless, achieving precise control of attachment AuNPs on the TiO₂ nanotubes substrate by conventional methods such as thermal evaporation and conservative heating are far from satisfactory. Herein, in this work a new approach has been developed to synthesize controlled and uniformed attachment of AuNPs onto electrochemically-anodized TiO₂ nanotubes by deposition-precipitation method. The structural and elemental characterizations of the supported AuNPs are carried out by means of field emission scanning electron microscopy (FESEM) and energy dispersive X-ray spectroscopy (EDX) analysis. The FESEM image showed the anodized TiO₂ nanotube with good morphological structure is successfully fabricated at a voltage of 20 V and in a mixture electrolyte of ethylene glycol containing 0.5 wt% ammonium fluoride solutions with an average nanotubes diameter of 87 nm. Meanwhile, the attachment of AuNPs on the fabricated TiO₂ nanotubes has been effectively achieved for both calcined and uncalcined samples. The EDX analysis has confirmed the deposition of AuNPs over the TiO₂ nanotubes. The results showed that we had succeeded in synthesizing the AuNPs supported on the anodized TiO₂ nanotubes, which provide superior metal-metal oxide synthetic devices for diverse applications.

Abstract: The present paper deals with the investigation of the mechanisms of TiO₂ nanotubes formation on titanium surfaces during anodization process. The samples were made of pure Ti Grade-2 and Ti-6Al-4V alloy. They were grinded, etched with 0,5 wt. % HF acid and anodized. The anodization was done in electrolyte containing 0,5 wt. % HF acid using DC power supply with graphite electrode as cathode. The samples were investigated by SEM, EDAX and XRD analysis. The results show two different mechanisms of formation of TiO₂ nanotubes on the surfaces of both materials. During the anodization process the oxide formations, obtained on the pure Ti surface after etching, are oxidized to nanorods; the area between them is also oxidized and connects them. This thin oxide layer grows in the metal depth while the nanorods are dissolved thus forming the porous sponge-like structure which is further transformed in tubular. While on the surface of Ti-6Al-4V alloy oxide nanonuclei originate which transform their shape from nanoseed to bowl-like with clearly pronounced bottom and walls, growing in tubular structures. The type of the material defines the surface morphology after etching. Thus obtained morphology influences on the processes running rate in different micro-regions determining origination of the titanium nanotubes on different stage as well as by different mechanism. The field-enhanced oxidation and field-enhanced dissolution are the main processes for formation of TiO₂ nanotubes during anodization. In the regions with prevalent oxidation processes the TiO₂ nanotubes are formed earlier while in the regions with dominant dissolution processes the TiO₂ nanotubes are formed on the later stage.

Abstract: Effect of NaAc on the anodic growth of TiO2 nanotube arrays is described. NaAc-added approach yields longer nanotubes relative to samples grown from NaAc-free electrolyte. And the growth rate of TiO2 nanotubes has pH independency in NaAc-added electrolytes. The key to achieve a high aspect ratio TiO2 nanotube arrays is to decrease the chemical dissolution rate at the mouth of the tube by adding NaAc as protective coating. Adsorption of Ac- species on the TiO2 surface is shown to markedly decrease the chemical dissolution rate of the tube mouth, resulting in longer nanotube length.

Abstract: Titanium of 99.7% purity was anodized in 1M potassium phosphate monobasic (KH2PO4) water solution with 0.15M NH4F. Titanium oxide nanotubes were fabricated at anodization potential of 20 V and 4.64 pH. To control the pH of the solution, we have added weak acid such as citric acid because it has three dissociation constants (pKa) of 3.09, 4.75, and 5.41. Citric acid was very useful to control the pH of the 1M KH2PO4 water electrolyte solution within 3 to 5. The diameter and length of the titanium oxide nanotubes were independent on anodization time. The diameter of 120 nm and length of 2.8 μm at anodization time of 5 hrs were observed by field emission scanning electron microscope (FESEM). Undesired thin oxide layer blocking the top of titanium oxide nanotubes was wiped out by increasing the anodization potential with the multi step voltage by 1 V reached to 25 V. The titanium oxide nanotubes having a very large surface area are very attractive for the battery, gas sensor, photocatalytic application, and biomaterials.