title: Green synthesis of graphene-silver nanocomposites and its application as a potent marine antifouling agent.
abstract: Fouling of marine surfaces has been a perpetual problem ever since the days of the early sailors. The tenacious attachment of seaweed and invertebrates to man-made surfaces, notably on ship hulls, has incurred undesirable economic losses. Graphene receives great attention in the materials world for its unique combination of physical and chemical properties. Herein, we present a novel 2-step synthesis method of graphene-silver nanocomposites which bypasses the formation of graphene oxide (GO), and produces silver nanoparticles supported on graphene sheets through a mild hydrothermal reduction process. The graphene-Ag (GAg) nanocomposite combines the antimicrobial property of silver nanoparticles and the unique structure of graphene as a support material, with potent marine antifouling properties. The GAg nanocomposite was composed of micron-scaled graphene flakes with clusters of silver nanoparticles. The silver nanoparticles were estimated to be between 72 and 86nm (SEM observations) while the crystallite size of the silver nanoparticles (AgNPs) was estimated between 1 and 5nm. The nanocomposite also exhibited the SERS effect. GAg was able to inhibit Halomonas pacifica, a model biofilm-causing microbe, from forming biofilms with as little as 1.3wt.% loading of Ag. All GAg samples displayed significant biofilm inhibition property, with the sample recording the highest Ag loading (4.9wt.% Ag) associated with a biofilm inhibition of 99.6%. Moreover, GAg displayed antiproliferative effects on marine microalgae, Dunaliella tertiolecta and Isochrysis sp. and inhibited the growth of the organisms by more than 80% after 96h. The marine antifouling properties of GAg were a synergy of the biocidal AgNPs anchored on the stable yet flexible graphene sheets, providing maximum active contact surface areas to the target organisms.
authors.affiliation: Centre of Nanotechnology and Advanced Materials, Faculty of Engineering, University of Nottingham Malaysia Campus, Jalan Broga, 43500 Semenyih, Selangor, Malaysia. Electronic address: kedx2ysn@nottingham.edu.my.
authors.forename: Maxine Swee-Li
authors.initials: MS
authors.lastname: Yee
authors.affiliation: Centre of Nanotechnology and Advanced Materials, Faculty of Engineering, University of Nottingham Malaysia Campus, Jalan Broga, 43500 Semenyih, Selangor, Malaysia. Electronic address: PoiSim.Khiew@nottingham.edu.my.
authors.forename: Poi-Sim
authors.initials: PS
authors.lastname: Khiew
authors.affiliation: Low Dimensional Materials Research Center, Department of Physics, Faculty of Science, University Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Wee Siong
authors.initials: WS
authors.lastname: Chiu
authors.affiliation: School of Postgraduate Studies, International Medical University, 126 Jalan 19/155B, Bukit Jalil 57000 Kuala Lumpur, Malaysia.
authors.forename: Yuen Fen
authors.initials: YF
authors.lastname: Tan
authors.affiliation: School of Health Sciences, International Medical University, 126, Jalan Jalil Perkasa 19, Bukit Jalil, 57000 Kuala Lumpur, Malaysia.
authors.forename: Yih-Yih
authors.initials: YY
authors.lastname: Kok
authors.affiliation: School of Pharmacy, International Medical University, 126 Jalan Jalil Perkasa 19, Bukit Jalil 57000 Kuala Lumpur, Malaysia.
authors.forename: Chee-Onn
authors.initials: CO
authors.lastname: Leong
mesh_terms: D000890:Anti-Infective Agents / Q000737:chemistry / Q000494:pharmacology*; D018441:Biofilms / Q000187:drug effects; D057219:Biofouling / Q000517:prevention & control*; D006108:Graphite / Q000737:chemistry*; D055772:Green Chemistry Technology / Q000379:methods*; D020632:Halomonas / Q000187:drug effects / Q000502:physiology; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D058086:Microalgae / Q000187:drug effects / Q000502:physiology; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D015203:Reproducibility of Results; D012623:Seawater / Q000382:microbiology; D012834:Silver / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D014961:X-Ray Diffraction
chemical_list: D000890:Anti-Infective Agents; D012834:Silver; D006108:Graphite
keywords: Biofilm inhibitor; Graphene nanocomposite; Halomonas pacifica; Marine antifouling; Silver nanoparticles