Fig. 1. A descriptive plot (Baier curve) of the generally observed strength of biological adhesion to substrate of different initial critical surface tensions. The minimum is always found in the zone between 20 and 30 mN/m, although at different absolute levels depending upon the specific biological system, the time of contact, and the acting mechanical forces of removal [31].

Fig. 2. The number of published papers about “antifouling nanocomposites” and “antibacterial nanocomposites” during 2005-2020 based on the PubMed Central and Publisher web sites [60].

Fig. 3. A schematic to represent the overall state of the art concept of this review paper.

Fig. 4. Antibacterial activity of chitosan and chitosan/ZnO nanocomposite coatings on the growth of P. nigrifaciens after 1, 2, and 5 days of incubation in marine broth under (a) light and (b) dark conditions. Data are means ?+SD [46].

Fig. 5. Field test results of (A, A1, A2, and A3) bare PDMS foul-release coating, (B, B1, B2, and B2) silicone/ZnO nanorods composite coating (0.5 wt. % nanorods), and (C, C1, C2, and C3) silicone/ZnO nanorods composite coating (5 wt. % NRs) during 6 months immersion in natural seawater [96].

Fig. 6. Photographs of ZnO-APTES-DGEBA nanocomposite film against (a) Streptomyces, (b) S. aureus, (c) P. aeruginosa, and (d) Aspergillus niger [97].

Fig. 7. Photograph of specimens (a) before immersion in sea water, (b) after immersion in sea water for 3 months, (c) after immersion in sea water for 9 months, and (d) specimens’ surfaces after washing with water. E, EP1.5, EN1.5, EN3, EN4.5, EN4.5-Z0.5, EN4.5-Z1, and EN4.5-Z2 represent pure epoxy, epoxy/1.5% PANI, epoxy/1.5% PANI-ZnO, epoxy/3% PANI-ZnO, epoxy/4.5% PANI-ZnO, epoxy/4.5% PANI-ZnO and 0.5% ZnO, epoxy/4.5% PANI-ZnO and 1% ZnO, and epoxy/4.5% PANI-ZnO and 2% ZnO, respectively [104].

Fig. 8. (I) Biodegradability measurements for unfilled and filled PDMS/TiO2 nanocomposites using different microorganisms after UV irradiation. (II) (A-G) Field trials of fabricated nanofiller TiO2 (0.5%)/PDMS nanocomposites throughout 360 days of immersion in seawater [120].

Fig. 9. Antimicrobial activities of TiO2-APTES-DGEBA nanohybrid coatings against (I) S. aureus, (II) P. aeruginosa, and (III) A. nigerand; (IV) scanning electron microscopy (SEM) image of S. Aureus after treatment. Photograph are taken after the TiO2-APTES-DGEBA coated panels were immersed in seawater: (a) after 6th month, (b) after 12th month and SEM images taken, (c) after 6th month, and (d) after 12th months; C1, C2, C3, and C4 represent the epoxy coatings loaded with 1, 3, 5, and 7 wt.% APTES modified TiO2 nanoparticles, respectively [121].

Fig. 10. Relationships among relative adhesion, value of (γ·E)1/2, and nano-SiO2 additions: (a) relationship between nano-SiO2 additions and (γ·E)1/2; (b) relationship between relative adhesion and (γ·E)1/2 [128].

Fig. 11. Field experiment results: (A, A1 and A2) for the virgin PDMS foul-release coating; (B, B1 and B2) for the formulated PDMS/β-MnO2 nanorod composites (0.5 wt. % nanorods); (C, C1 and C2) for the formulated PDMS/β-MnO2 nanorod composites (3 wt. % nanofillers) up to 90 days of immersion in natural seawater [134].

Fig. 12. The pseudobarnacle adhesion strength to the surfaces of the coatings [159].

Fig. 13. Fluorescence images showing E. coli populations after 48 h: (a) the control surface, (b) the surface coated with the GO-nanopaint (viable cells are observed to be in green, and dead cells in red (scale bar - 8 μm)), and (c) the percentage of dead cells in the three different cultures on the GO-nanopaint-coated surfaces after 24 and after 48 h. (d) The GO-nanopaint coated substrates and the bare substrates were immersed in a lagoon with tidal water directly connected to Jeju Sea, and (e) the digital images of bare and painted substrates before immersion and after 3 weeks [178].

Fig. 14. Images of field-environment test: (a) and (b) before immersion, (c) and (d) after immersion, (e) and (f) optical micrographs of EPN and EPG-1 coating systems [179].

Fig. 15. The images of the field trial of the prepared virgin silicone (A-C) foul release coating formulation and (D-F) for the PDMS/GO-Al2O3 NRs hybrid sheet (1 wt.%) composite formulation up to 90 days of immersion in natural marine water [56].

Fig. 16. Comparison of the antibacterial properties with the previous literature of selected polymeric nanofibers with incorporated metal oxides and 2D materials. The antibacterial effects of electrospun polymer blends were also compared. The stars denote the materials from this study [191].

Fig. 17. SEM images of the bacteria on the surface (first column EVA and the second column EVA-halloysite formulations): (a) pure EVA, (c, e) EVA directly doped with TCPM, and (b) EVA composited with halloysite, (d, f) EVA with TCPM loaded halloysite. The samples were incubated in the bacterial suspension for 3 days (c, d) directly and (e, f) after shaking in seawater for 60 days [206].

Fig. 18. The photographs of the field tests for AF paints (Test period: 2012.07.14-2013.04.01; test site: the East Sea of China, Ningbo, Zhejiang province) [207].

Fig. 19. Schematic of three main strategies for antifouling coatings used in marine environment.

Fig. 20. Schematic of antifouling and antibacterial mechanisms of polymer coatings loaded with nanomaterials: (I) changing surface properties, which include (a) surface roughness, (b) wettability, (c) stiffness (surface energy), (d) topography, and (e) surface charge; (II) ROS and oxidative and oxidative stress; and (III) ion release.

Fig. 21. Length-scale and time-scale comparison for the above-mentioned computer simulation methods [246].

Fig. 22. Adhesion energy plots of modified polyesters interacting with amorphous carbon. The unmodified interface, polyester/AmCH, is also included as a reference point. The depth of the well in these curves provides a measure of the adhesion at the interface, and the greater the dip, the stronger the adhesion between coating (polymer) and contaminant (AmCH). Adhesion plots show that low-level hydroxyl (7OH) surface modifications reduce adhesion between coating and contaminant [271].

Fig. 23. The most stable complexes of (a) Gly, (b) Lys, (c) Phe, and (d) Asp upon the HEAA. The interactions distances (Å) of the more reactive atoms and their NBO charges (|e|) are reported by +/- sign. The intermolecular CH···O interactions are bolded.

Fig. 24. The most stable complexes of (a) Gly, (b) Lys, (c) Phe, and (d) Asp upon the HEA. The intermolecular interactions distances (Å) of the more reactive atoms and their NBO charges (|e|) are reported by +/- sign. The intermolecular CH···O interactions are bolded.

Fig. 25. The most stable complexes of (a) Gly, (b) Lys, (c) Phe, and (d) Asp upon the HPenAA. The interactions distances (Å) of the more reactive atoms and their NBO charges (|e|) are reported by +/- sign. The intermolecular CH···O interactions are bolded.

Fig. 26. Schematic of adsorption and growth of water molecules (clusters) on HEAA. The most important interaction distances (Å) are reported.

Fig. 27. Schematic of adsorption and growth of water molecules (clusters) on HEA. The most important interaction distances (Å) are reported.

Fig. 28. Schematic of adsorption and growth of water molecules (clusters) on HPenAA. The most important interaction distances (Å) are reported.

Fig. 29. The most stable complexes of Gly binding to (a) HEAA-8H2O, (b) HEA-8H2O, and (c) HPenAA-8H2O complex. The most important interaction distances (Å) are reported.