Templated Mesoporous Silica Outer Shell for Controlled Silver Release of a Magnetically Recoverable and Reusable Nanocomposite for Water Disinfection

Journal Article · 01 October 2021 · ACS Applied Materials and Interfaces

DOI: https://doi.org/10.1021/acsami.1c14669 · OSTI ID:1841115

Furlan, Ping Y.  ^[1]; Furlan, Alexander Y. ^[1]; Kisslinger, Kim  ^[2]; Melcer, Michael E. ^[1]

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1. United States Merchant Marine Academy, Kings Point, NY (United States)
2. Brookhaven National Lab. (BNL), Upton, NY (United States). Center for Functional Nanomaterials (CFN)

Here, we encapsulated Fe₃O₄@SiO₂@Ag (MS-Ag), a bifunctional magnetic silver core–shell structure, with an outer mesoporous silica (mS) shell to form an Fe₃O₄@SiO₂@₂Ag@mSiO₂ (MS-Ag-mS) nanocomposite using a cationic CTAB (cetyltrimethylammonium bromide) micelle templating strategy. The mS shell acts as protection to slow down the oxidation and detachment of the AgNPs and incorporates channels to control the release of antimicrobial Ag⁺ ions. Results of TEM, STEM, HRSEM, EDS, BET, and FTIR showed the successful formation of the mS shells on MS-Ag aggregates 50–400 nm in size with highly uniform pores ~4 nm in diameter that were separated by silica walls ~2 nm thick. Additionally, the mS shell thickness was tuned to demonstrate controlled Ag⁺ release; an increase in shell thickness resulted in an increased path length required for Ag⁺ ions to travel out of the shell, reducing MS-Ag-mS’ ability to inhibit E. coli growth as illustrated by the inhibition zone results. Through a shaking test, the MS-Ag-mS nanocomposite was shown to eradicate 99.99+% of a suspension of E. coli at 1 × 10⁶ CFU/mL with a silver release of less than 0.1 ppb, well under the EPA recommendation of 0.1 ppm. This high biocidal efficiency with minimal silver leach is ascribed to the nanocomposite’s mS shell surface characteristics, including having hydroxyl groups and possessing a high degree of structural periodicity at the nanoscale or “smoothness” that encourages association with bacteria and retains high Ag⁺ concentration on its surface and in its close proximity. Furthermore, the nanocomposite demonstrated consistent antimicrobial performance and silver release levels over multiple repeated uses (after being recovered magnetically because of the oxidation-resistant silica-coated magnetic Fe₃O₄ core). It also proved effective at killing all microbes from Long Island Sound surface water. The described MS-Ag-mS nanocomposite is highly synergistic, easy to prepare, and readily recoverable and reusable and offers structural tunability affecting the bioavailability of Ag⁺, making it excellent for water disinfection that will find wide applications.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• Grant/Contract Number: SC0012704
• OSTI ID: 1841115
• Report Number(s): BNL-222613-2022-JAAM
• Journal Information: ACS Applied Materials and Interfaces, Journal Name: ACS Applied Materials and Interfaces Journal Issue: 40 Vol. 13; ISSN 1944-8244
• Publisher: American Chemical Society (ACS)Copyright Statement
• Country of Publication: United States
• Language: English