Photocatalytic activity of silica and silica-silver nanocolloids based on photo-induced formation of reactive oxygen species

Abstract

Semiconductor nanomaterials are often proposed as photocatalysts for wastewater treatment; silica nanomaterials are still largely unexploited because their photocatalytic performances need improvements, especially under visible light. The present study is a proof-of-concept that amorphous silica colloids once submitted to the proper surface modifications change into an efficient photocatalyst even under low-energy illumination source. For this reason, silica-based colloidal nanomaterials, such as bare (SiO2 NPs), aminated (NH2-SiO2 NPs), and Ag NPs-decorated (Ag-SiO2 NPs) silica, are tested as photocatalysts for the degradation of 9-anthracenecarboxylic acid (9ACA), taken as a model aromatic compound. Interestingly, upon irradiation at 313 nm, NH2-SiO2 NPs induce 9ACA degradation, and the effect is even improved when Ag-SiO2 NPs are used. On the other hand, irradiation at 405 nm activates the plasmon of Ag-SiO2 NPs photocatalyst, providing a faster and more efficient photodegradation. The photodegradation experiments are also performed under white light illumination, employing a low-intensity fluorescent lamp, confirming satisfying efficiencies. The catalytic effect of SiO2-based nanoparticles is thought to originate from photo-excitable surface defects and Ag NP plasmons since the catalytic degradation takes place only when the 9ACA is adsorbed on the surface. In addition, the involvement of reactive oxygen species was demonstrated through a scavenger use, obtaining a yield of 17%. In conclusion, this work shows the applicability of silica-based nanoparticles as photocatalysts through the involvement of silica surface defects, confirming that the silica colloids can act as photocatalysts under irradiation with monochromatic and white light. Graphic abstract Silica and Ag-decorated silica colloids photosensitize the formation of Reactive Oxygen Species with 17% efficiencies. ROS are able to oxidase aromatic pollutants chemi-adsorbed on the surface of the colloids. Silica-silver nanocomposites present a photocatalytic activity useful to degrade aromatic compounds.

SiC Foams for the Photocatalytic Degradation of Methylene Blue under Visible Light Irradiation

“…After the cleaning process, the spectrum in Figure 4 e did not show any significant peaks related to MB and is very similar to the pristine SiC foam before use, indicating that the applied washing procedure efficiently regenerates the SiC foam and its photocatalytic properties are likely to be conserved. Interestingly, the signal coming from Si-O tends to decrease, which could reveal a reduction of surface silica species during the photocatalytic reaction as reactive oxygen species could be activated during the process [ 39 ].…”

Toxicity of metal-based nanoparticles: Challenges in the nano era

“…For instance, surface-bound free radicals on crystalline silica particles can enhance oxidative stress via a surface reaction to generate ROS (Fubini and Hubbard, 2003). Besides, studies have shown that some particular metalbased NPs, such as TiO 2 NPs can generate ROS through a photocatalytic process under light irradiation (Toloman et al, 2019;Balaji et al, 2020;Romolini et al, 2021). Additionally, transition metals in NPs such as copper (Cu), and chromium (Cr) can participate in ROS generation via Fenton and Haber-Weiss reactions, ultimately enhancing oxidative stress (Huang et al, 2010;Angele-Martinez et al, 2017).…”

Development of Transition Metal Incorporated Bismuth‐Based Oxide Semiconductors as Potential Candidates for Solar Assisted Water Splitting Applications

“…In the early 70's scientist Fujishima and Honda first demonstrated TiO 2 as an outstanding photocatalyst to achieve solar-assisted water splitting reaction [6] and later, various investigations have been performed with different types of semiconductors. [7][8][9][10][11][12][13][14][15] Being an n-type semiconductor with TiO 2 has the ability and adequate potential to split the H 2 O molecule into H 2 and O 2 if a photon is absorbed during illumination when an interaction occurs with the electrolyte. [16,17] However, the performance of TiO 2 is relatively poor due to its wide band gap energy (~3.2 eV) and is not being suitable for all purposes.…”

“…Due to easement of fabrication, better stability and appropriate electrical properties, all inorganic semiconductors are considered as promising materials for photo‐activated water splitting reaction. In the early 70’s scientist Fujishima and Honda first demonstrated TiO 2 as an outstanding photocatalyst to achieve solar‐assisted water splitting reaction [6] and later, various investigations have been performed with different types of semiconductors [7–15] . Being an n‐type semiconductor with TiO 2 has the ability and adequate potential to split the H 2 O molecule into H 2 and O 2 if a photon is absorbed during illumination when an interaction occurs with the electrolyte [16,17] .…”