Antifouling and Photocatalytic Antibacterial Activity of the AquaSun Coating in Seawater and Related Media

Comparative Investigation of AquaSun Eco-Friendly Antifouling Coating via Rheological and Mechanical Characterization

Rheological and mechanical comparative tests of the new AquaSun antifouling sol-gel coating coated on shipbuilding steel compared to a commercial silyl acrylate antifouling top coat containing cuprous oxide and copper pyrithione show further evidence of the practical viability of this multifunctional coating for the protection of the immersed surfaces from biofouling. AquaSun is a less rigid or less viscous material than commercial top coat but more adherent to the steel substrate. These results support further investigation of this multifunctional sol-gel coating as an eco-friendly antifouling paint.

Green Synthesis of TiO2 Nanoparticles Using Natural Marine Extracts for Antifouling Activity

Titanium dioxide (TiO₂) nanoparticles were synthesized via a novel eco-friendly green chemistry approach using marine natural extracts of two red algae (Bostrychia tenella and Laurencia obtusa), a green alga (Halimeda tuna), and a brown alga (Sargassum filipendula) along with a marine sponge sample identified as Carteriospongia foliascens. X-ray diffraction (XRD), scanning electron microscope (SEM), UV-Vis, X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared spectroscopy (FTIR) were employed to characterize the crystal structure, surface morphology, and optical properties of the synthesized nanoparticles. Each of the as-synthesized marine extract based TiO₂ nanoparticles was individually incorporated as an antifouling agent to form a newly fabricated marine paint formulation. The newly prepared formulations were applied on unprimed steel panels. A comparative study with a commercial antifouling paint (Sipes Transocean Coatings Optima) was carried out. After 108 days of the coated steel panels' immersion in the Eastern Harbour seawater of Alexandria-Egypt, the prepared paints using B. tenella and C. foliascens extracts demonstrated an excellent antifouling performance toward fouling organisms by inhibiting their settlement and controlling their adhesion onto the immersed panels. In contrast, heavy fouling with barnacles was observed on the surface of the coated panel with the commercial paint. The physicochemical parameters of the seawater surrounding the immersed coated panels were estimated to investigate the influence of the fabricated paint formulations. Interestingly, no effects of the immersed coated panels on the physicochemical characteristics of the surrounding seawater were observed. Based on the obtained results and a comparison with commercially available antifouling products, the marine extract based TiO₂ nanoparticle preparations of B. tenella and C. foliascens are promising candidates for eco-friendly antifouling agents. Based on the obtained results and a comparison with commercially available antifouling products, the marine extract based TiO₂ nanoparticle preparations of B. tenella and C. foliascens are promising candidates for eco-friendly antifouling agents, which could be attributed to the small crystallite sizes of 22.86 and 8.3 nm, respectively, in addition to the incorporation of carbon in the crystal structure of the nanoparticles.

Design and Development of Fluorinated and Biocide-Free Sol–Gel Based Hybrid Functional Coatings for Anti-Biofouling/Foul-Release Activity

Biofouling has destructive effects on shipping and leisure vessels, thus producing severe problems for marine and naval sectors due to corrosion with consequent elevated fuel consumption and higher maintenance costs. The development of anti-fouling or fouling release coatings creates deterrent surfaces that prevent the initial settlement of microorganisms. In this regard, new silica-based materials were prepared using two alkoxysilane cross-linkers containing epoxy and amine groups (i.e., 3-Glycidyloxypropyltrimethoxysilane and 3-aminopropyltriethoxysilane, respectively), in combination with two functional fluoro-silane (i.e., 3,3,3-trifluoropropyl-trimethoxysilane and glycidyl-2,2,3,3,4,4,5,5,6,6,7,7,8,8,9,9-hexadecafluorononylether) featuring well-known hydro repellent and anti-corrosion properties. As a matter of fact, the co-condensation of alkoxysilane featuring epoxide and amine ends, also mixed with two opportune long chain and short chain perfluorosilane precursors, allows getting stable amphiphilic, non-toxic, fouling release coatings. The sol–gel mixtures on coated glass slides were fully characterized by FT-IR spectroscopy, while the morphology was studied by scanning electron microscopy (SEM), and atomic force microscopy (AFM). The fouling release properties were evaluated through tests on treated glass slides in different microbial suspensions in seawater-based mediums and in seawater natural microcosms. The developed fluorinated coatings show suitable antimicrobial activities and low adhesive properties; no biocidal effects were observed for the microorganisms (bacteria).

Development of Eco-Friendly Hydrophobic and Fouling-Release Coatings for Blue-Growth Environmental Applications: Synthesis, Mechanical Characterization and Biological Activity

The need to ensure adequate antifouling protection of the hull in the naval sector led to the development of real painting cycles, which involve the spreading of three layers of polymeric material on the hull surface exposed to the marine environment, specifically defined as primer, tie coat and final topcoat. It is already well known that coatings based on suitable silanes provide an efficient and non-toxic approach for the hydrophobic and antifouling/fouling release treatment of surfaces. In the present work, functional hydrophobic hybrid silica-based coatings (topcoats) were developed by using sol-gel technology and deposited on surfaces with the "doctor blade" method. In particular, those organic silanes, featuring opportune functional groups such as long (either fluorinated) alkyl chains, have a notable influence on surface wettability as showed in this study. Furthermore, the hydrophobic behavior of this functionalized coating was improved by introducing an intermediate commercial tie-coat layer between the primer and the topcoat, in order to decrease the wettability (i.e., decreasing the surface energy with a matching increase in the contact angle, CA) and to therefore make such coatings ideal for the design and development of fouling release paints. The hereby synthesized coatings were characterized by optical microscopy, contact angle analysis and a mechanical pull-off test to measure the adhesive power of the coating against a metal substrate typically used in the nautical sector. Analysis to evaluate the bacterial adhesion and the formation of microbial biofilm were related in laboratory and simulation (microcosm) scales, and assessed by SEM analysis.

Sustainability Evaluation of AquaSun Antifouling Coating Production

Relying on a cost-effective and green process that is technically and economically feasible on large scale is not enough to call a technology “sustainable”. We thus evaluate the sustainability of the production of the new “AquaSun” antifouling sol–gel coating with reference to each of the three main dimensions (economic, social, and environmental) of sustainable development. This study will hopefully assist in overcoming the “not invented here” syndrome that still affects many sol–gel technologies, including antifouling coatings derived via the sol–gel process.

A review of recent and emerging antimicrobial nanomaterials in wastewater treatment applications

In this paper, we present a critical review on antimicrobial nanomaterials with demonstrated potential for application as a disinfection technology in wastewater treatment. Studies involving fabrication and testing of antimicrobial nanomaterials for wastewater treatment were gathered, critically reviewed, and analyzed. Our review shows that there are only a few eligible candidate nanoparticles (NPs) (metal and metal oxide) that can adequately serve as an antimicrobial agent. Nanosilver (nAg) was the most studied and moderately understood metal NPs with proven antimicrobial activity followed by ZnO (among antimicrobial metal oxide NPs) which outperformed titania (in the absence of light) in efficacy due to its better solubility in aqueous condition. The direction of future work was found to be in the development of antimicrobial nanocomposites, since they provide more stability for antimicrobial metal and metal oxides NPs in water, thereby increasing their activity. This review will serve as an updated survey, yet touching also the fundamentals of the antimicrobial activity, with vital information for researchers planning to embark on the development of superior antimicrobial nanomaterials for wastewater treatment applications.

DNA-Based Nanofabrication for Antifouling Applications

This paper reports antifouling properties of nanostructured SiO₂ substrates patterned by DNA lithography. We used DNA triangle nanostructures as templates to produce triangular-shaped trenches ca. 130 nm in size on SiO₂ surfaces. Using B. subtilis as a bacterial model, we found that such nanopatterned surface showed a 75% reduction in bacterial adhesion and 72% reduction in biofilm density at 35% surface coverage of the nanoscale triangular trenches. DNA-based nanofabrication can produce high-resolution designer patterns, but aligning these patterns has been one of the major technical challenges for its applications in nanoelectronics. This work demonstrates the potential of DNA-based nanofabrication in antifouling applications, where surface patterning of micro/nanostructures is required but not their precise alignment.