Singlet Oxygen Generation on Porous Superhydrophobic Surfaces: Effect of Gas Flow and Sensitizer Wetting on Trapping Efficiency

Abstract

We describe physical-organic studies of singlet oxygen generation and transport into an aqueous solution supported on superhydrophobic surfaces on which silicon–phthalocyanine (Pc) particles are immobilized. Singlet oxygen (1O2) was trapped by a water-soluble anthracene compound and monitored in situ using a UV–vis spectrometer. When oxygen flows through the porous superhydrophobic surface, singlet oxygen generated in the plastron (i.e., the gas layer beneath the liquid) is transported into the solution within gas bubbles, thereby increasing the liquid–gas surface area over which singlet oxygen can be trapped. Higher photooxidation rates were achieved in flowing oxygen, as compared to when the gas in the plastron was static. Superhydrophobic surfaces were also synthesized so that the Pc particles were located in contact with, or isolated from, the aqueous solution to evaluate the relative effectiveness of singlet oxygen generated in solution and the gas phase, respectively; singlet oxygen generated on particles wetted by the solution was trapped more efficiently than singlet oxygen generated in the plastron, even in the presence of flowing oxygen gas. A mechanism is proposed that explains how Pc particle wetting, plastron gas composition and flow rate as well as gas saturation of the aqueous solution affect singlet oxygen trapping efficiency. These stable superhydrophobic surfaces, which can physically isolate the photosensitizer particles from the solution may be of practical importance for delivering singlet oxygen for water purification and medical devices.

A simple, inexpensive method for gas-phase singlet oxygen generation from sensitizer-impregnated filters: Potential application to bacteria/virus inactivation and pollutant degradation

“… Kim et al (2020) showed that 1 O 2 inactivated micro-organisms in air up to a distance of 10–15 cm away from the source. Several researchers have presented different experimental set-ups based on this heterogeneous system and demonstrated 1 O 2 generation from them with further application of the generated 1 O 2 for substrate degradation or bacteria/virus inactivation ( Bartusik et al, 2012a , Bartusik et al, 2012b ; Zamadar et al, 2009 ; Aebisher et al, 2010 ; Carpenter et al, 2015 ; Zhao et al, 2014 ; Hettegger et al, 2015 ). Nevertheless, the potential application of 1 O 2 for the purpose of improved air quality has not been well explored.…”

Recent advances in surface‐functionalised photosensitive antibacterials with synergistic effects

“…In this way, the structural stability and safety can be improved. Furthermore, similar structures have been reported to discuss the difference in the activity of PS particles immobilised on different sites of PDMs, the influence of oxygen flux [48] and the resulting 1 O 2 utilisation rate [49], and the practical application of this material in dental, water treatment and wound disinfection.…”

“…In spite of some PSs that can be activated by an infrared laser, most of the currently developed PSs molecules need to be activated at relatively short wavelengths and low extinction coefficients [49]. However, it is well known that the ray with shorter wavelength has higher energy, shallower penetration depth, and greater impact on human body [50].…”

“… Mechanism diagram and topography of UCNP a Tissue penetration depth of light with different wavelengths and the schematic principle of upconversion luminescence processes. Taken from [49, 50] b Energy‐level diagram of photon upconversion in the Yb 3+ ‐sensitised Er 3+ and Tm 3+ UCNP. Taken from [52] c TEM images of the LiYF 4 : Yb/Er.…”

Antimicrobial Photodynamic Inactivation Using Topical and Superhydrophobic Sensitizer Techniques: A Perspective from Diffusion in Biofilms†

“…1 mm tall posts on 0.5 mm pitch) (Fig. 3) (10)(11)(12). The polymer post-tips can be capped with silicone to prevent contact between photosensitizer particles and the biofilm while maintaining access to oxygen gas.…”