Antibacterial efficiency of magnetron sputtered TiO2 on poly(methyl methacrylate)

doi:10.1016/j.surfin.2017.04.003

Surfaces and Interfaces

Volume 8, September 2017, Pages 28-35

https://doi.org/10.1016/j.surfin.2017.04.003 Get rights and content

Highlights

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TiO₂ were deposited on PMMA by magnetron sputtering of Ti using a Compact Planar Magnetron sputtering device.
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XPS, FTIR and EDX analyses confirmed the presence of TiO₂ on the surface of PMMA.
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Deposited TiO₂ were relatively smooth with micro islands of titanium at the surface.
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Photoinduced hydrophilicity was observed after 10 min of UV irradiation.
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TiO₂-deposited PMMA samples exhibited antibacterial efficiency of 70% to 80%.

Abstract

Titanium dioxide (TiO₂) particles were deposited on poly(methyl methacrylate) (PMMA) by magnetron sputtering of Ti at varying O₂/Ar flow rate ratio and at varying discharge current using a Compact Planar Magnetron (CPM) sputtering device. The deposited TiO₂ on PMMA samples were characterized using X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive X-ray spectroscopy (EDX). The samples were tested for their photoinduced hydrophilicity, and antibacterial activity against Escherichia coli (E.coli). XPS, FTIR and EDX analyses confirmed the presence of TiO₂ on the surface of PMMA. XPS spectra revealed the presence of Ti 2p and O 1 s bands on the surface of the samples and the EDX spectra showed that the elemental ratio of Ti and O ranged from 26 to 30% and 69 to 73%, respectively. SEM showed that the deposited TiO₂ was relatively smooth with micro islands of titanium at the surface. Photoinduced hydrophilicity was observed for all samples after 10 min of UV irradiation; this was seen from the reduction of the water contact angles on the UV irradiated samples from 66° to as low as <5°. Antibacterial tests showed that all TiO₂-deposited PMMA samples exhibited antibacterial efficiency of 70% to 80%.

Introduction

TiO₂ has gained much attention in photocatalysis because of its oxidizing action to decompose organic compounds [1], [2], [3] and kill bacteria in water [4], [5], [6]. This material has found significant environmental applications due to its high surface area, self-cleaning function, strong oxidizing ability to degrade organic pollutants, and antibacterial activity [7], [8], [9], [10], [11]. In 1985, Matsunaga and his team reported for the first time the antibacterial effect of TiO₂ photocatalyst [12]. Microbial cells in water were brought in contact with TiO₂ powder and were killed within 1–2 h of near-UV light irradiation.

TiO₂ is a promising material for the treatment of wastewater. However, the most common TiO₂ used for wastewater treatment is the slurry type of TiO₂. This should be avoided because it requires separation of the TiO₂ particles from the suspension which will augment operation cost and may lower activity due to potential catalyst loss during treatment [13]. Recent trends now are focused on the immobilization of TiO₂ [14]. Different immobilization techniques have been studied in the past. These include sol-gel method [15], reverse micelle method [16], solvothermal method [17], [18], and magnetron sputtering [19], [20], [21]. For these immobilization techniques, the most common substrate used is glass but it is fragile and highly dense which can be a limitation for its application in photoreactors [14]. Other materials used as substrates are alumina, silicon, steel, cellulose, sponge, and ceramics [3], [20], [21], [22]. However, these can sometimes be opaque, heavy and fragile, which can be disadvantageous if they will be used in the fabrication of a photoreactor device. One alternative is PMMA due its high strength and stability [23], flexibility, chemical resistance, and durability [24]. PMMA has been used previously as the support for TiO₂ immobilization in the design of a photoreactor [25], [26]. However, sol-gel method and special binders were used as immobilization technique.

For polymeric substrates, sol-gel method is commonly used because it can deposit crystalline TiO₂ without further heat treatment which is suitable for polymers like PMMA due to their heat sensitivity [22], [27]. However, it requires a long time to coat polymers and being a wet process, it may have limitations [28]. It may also have poor throughput and poor reproducibility [29]. Sol-gel method on PMMA may lead to uncontrollable precipitation and a smoother surface morphology [30]. Some unreacted organic precursors may also be detected at the surface [31]. Magnetron sputtering is suitable because it does not use hazardous chemicals found in other processes and it can deposit on heat-sensitive substrates like PMMA [32]. Deposition parameters can also be varied in order to produce a material of the desired characteristics, depending on the needs, which makes it a versatile process. To the best knowledge of the investigators, no extensive study has been performed yet about the use of magnetron sputtering in coating PMMA with TiO₂ and its use in killing bacteria in simulated wastewater.

Antibacterial materials have also been synthesized using different methods including magnetron sputtering techniques. Francq et al. coated pure magnesium on Ti via magnetron sputtering for 7 days that exhibited excellent antibacterial and biocompatible properties [33]. Zaatreh et al. also coated Ti with magnesium via magnetron sputtering and showed a decrease in S. epidermidis on the surface by 4 orders of magnitude as compared to the Ti control [34]. Zhang et al. used Ag coatings on Ti via magnetron sputtering, micro-arc oxidation, and hydrothermal treatment to produce a surface with an excellent antibacterial activity [35]. Wang et al. reduced the technique into using only magnetron sputtering and micro-arc oxidation that produced Zn-ZrO₂/TiO₂ coating that exhibited excellent antibacterial ability against S. aureus [36]. Most of the studies in literature either combines magnetron sputtering with other techniques or by introducing known compounds or elements that possess antibacterial properties with metal substrates to synthesize materials with excellent antibacterial properties.

The main aim of this work was to deposit TiO₂ on PMMA via magnetron sputtering using the Compact Planar Magnetron device and study the effect of varying O₂/Ar flow rate ratio and discharge current on the antibacterial activity of the material against E. Coli.

Section snippets

Materials and plasma deposition

A compact planar magnetron (CPM) device shown in Fig. 1 was used to deposit TiO₂ on PMMA substrates. In this study, the tubular T-shaped deposition chamber has height and width of 300 mm and 350 mm, respectively. The chamber is connected to a rotary pump and a diffusion pump to decrease the pressure inside the chamber down to 10⁻⁵ torr. The 99.5% pure titanium target, 80 mm in diameter is placed on top of a metal cylinder with magnets inside. A combination of an annular and cylindrical magnets is

Results and discussion

Elemental analysis revealed the presence of titanium and oxygen at the surface of the substrate. Fig. 2 shows the characteristic peaks for Ti and O confirming the presence of these elements. Table 1 shows the calculated atomic % of Ti and O obtained from SEMQuant. During calculation, some peaks were omitted like those for gold near 2 keV, which was used to coat the samples. From the calculated values in Table 1, it can be said that the deposited TiO₂ samples are near stoichiometry.

Fig. 3 shows

Conclusions

Antibacterial TiO₂ was successfully deposited on PMMA using the Compact Planar Magnetron sputtering device using different flow rate ratios of O₂/Ar and different discharge currents. Characterization techniques such as XPS, FTIR and EDX analyses confirmed the presence of TiO₂ on the surface of PMMA. SEM revealed that the deposited TiO₂ on PMMA samples was smooth with titanium micro islands. Photoinduced hydrophilicity was observed in all samples after only 10 min of UV irradiation. All samples

Acknowledgments

We would like to express our sincerest gratitude to the Department of Science and Technology — Philippine Council for Industry, Energy and Emerging Technology Research and Development (DOST-PCIEERD) and the Japan Society for the Promotion of Science for the financial support.

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Antibacterial efficiency of magnetron sputtered TiO2 on poly(methyl methacrylate)

Highlights

Abstract

Introduction

Section snippets

Materials and plasma deposition

Results and discussion

Conclusions

Acknowledgments

Water Res.

Chem. Eng. J.

Surf. Coat. Technol.

Surf. Coat. Technol.

Physica B

Mater. Lett.

Surf. Coat. Technol.

Appl. Surf. Sci.

Mater. Sci. Eng.

FEMS Microbiol. Lett.

Water Res.

Desalination

Chem. Eng. J.

J. Mol. Catal. A

Mater. Lett.

Sol. Energy Mater. Sol. Cells

Appl. Surf. Sci.

Surf. Coat. Technol.

Catal. Today

Opt.-Int. J. Light Electron Opt.

Desalination

J. Environ. Manage.

Surf. Coat. Technol.

J. Alloys and Compd.

Mater. Chem. Phys.

Ceram. Int.

Appl. Surf. Sci.

Antibacterial efficiency of magnetron sputtered TiO₂ on poly(methyl methacrylate)