Radiolytic Synthesis of Pt-Particle/ABS Catalysts for H2O2 Decomposition in Contact Lens Cleaning

Abstract

A container used in contact lens cleaning requires a Pt plating weight of 1.5 mg for H2O2 decomposition although Pt is an expensive material. Techniques that decrease the amount of Pt are therefore needed. In this study, Pt nanoparticles instead of Pt plating film were supported on a substrate of acrylonitrile–butadiene–styrene copolymer (ABS). This was achieved by the reduction of Pt ions in an aqueous solution containing the ABS substrate using high-energy electron-beam irradiation. Pt nanoparticles supported on the ABS substrate (Pt-particle/ABS) had a size of 4–10 nm. The amount of Pt required for Pt-particle/ABS was 250 times less than that required for an ABS substrate covered with Pt plating film (Pt-film/ABS). The catalytic activity for H2O2 decomposition was estimated by measuring the residual H2O2 concentration after immersing the catalyst for 360 min. The Pt-particle/ABS catalyst had a considerably higher specific catalytic activity for H2O2 decomposition than the Pt-film/ABS catalyst. In addition, sterilization performance was estimated from the initial rate of H2O2 decomposition over 60 min. The Pt-particle/ABS catalyst demonstrated a better sterilization performance than the Pt-film/ABS catalyst. The difference between Pt-particle/ABS and Pt-film/ABS was shown to reflect the size of the O2 bubbles formed during H2O2 decomposition.

Strong Biomimetic Immobilization of Pt-Particle Catalyst on ABS Substrate Using Polydopamine and Its Application for Contact-Lens Cleaning with H2O2

“…When an ABS substrate is coated with a PDA film, the number of sites for immobilizing Pt particles also increases, resulting in an increased Pt-loading weight. The Pt-loading weight of the Pt/ABS-PDA(24h) material (11.2 μg/substrate) was approximately twice that of the Pt/ABS-untreated sample, but at least 130 times lower than that of an ABS substrate coated with an electroless-plated Pt film (Pt-film/ABS) (1500 μg/substrate), which had been studied earlier [16].…”

“…Therefore, EBIRM was selected in this study. The mechanism of metal ion reduction by a radiochemical approach has been described in previous reports [31,32], and the methods applied for washing the ABS substrate and depositing the Pt particles on its surface were the same here as those reported previously [16,17]. The differences between this report and previous ones are the plasma pre-treatment and the use of a PDA coating to improve the catalytic durability during H 2 O 2 decomposition.…”

“…To remove the unimmobilized Pt particles, the ABS substrates were taken out of the solution, washed with pure water for 10 min using an ultrasonic cleaner, and finally dried with N 2 gas. In a previous report [16], XPS and water contact angle (WCA) measurements were performed for untreated ABS substrates before and after electron beam irradiation to investigate the immobilization mechanism; however, this mechanism is not yet clear. Those XPS and WCA results suggest two models: the first model assumes the chemical adhesion of Pt nanoparticles through a chemical reaction of functional groups (C-O) and/or carbon radicals with Pt ions and/or Pt 0 , and the second model assumes the unreactive immobilization of Pt nanoparticles through a C-C crosslinking network under EB irradiation.…”

“…The residual H 2 O 2 concentrations were measured after immersion times of 1, 2, 5, 10, 30, 60, 120, 240, and 360 min to obtain the decomposition curves. The method for measuring the H 2 O 2 concentration was the same as that reported in a previous article [16]. The optical absorbance of a H 2 O 2 solution, colored using diluted (5 wt%) titanium sulfate (Ti(SO 4 ) 2 ; 30 wt%, Fujifilm Wako Pure Chemical), was measured using a deuterium-halogen and tungsten lamp (DH-2000, Ocean Optics, Largo, FL, USA), a fiber multichannel spectrometer (HR-4000, Ocean Optics), and optical fiber (P600-1-UV/VIS, Ocean Optics).…”

“…Pt is very expensive, so there is a strong need to decrease the amount of Pt used in contact-lens cleaners. We have suggested replacing the Pt film with Pt particles, which results in a drastic decrease in the amount of Pt required (Figure 1b) [16]. However, some problems remain regarding the catalytic durability, although we pretreated the surface by etching, electric charge control, or both [17].…”