Herein,
an electrochemical technique as a cost-effective and one-step
approach was utilized to fabricate graphene quantum dots (GQDs). Different
amounts of GQDs (0, 0.2, 0.4, 0.8, and 1.2 wt %) were decorated uniformly
on the surface of anodized ZnO nanowires (NWs) forming GQD/ZnO NWs.
Transmission electron microscopy and atomic force microscopy confirmed
formation of GQDs on the ZnO NWs, 12–22 nm in width and 1–3
graphene layers thick. X-ray photoelectron spectroscopy and Fourier
transform infrared spectroscopy were employed to verify the functional
groups on the surface of GQDs, and the results indicated that GQDs
readily anchored on the surface of ZnO NWs. The GQD/ZnO NWs exhibited
a considerable improvement on the photocatalytic degradation of methylene
blue under solar irradiation, due to efficient light absorption. In
addition, the results indicated that the optimized GQD (0.4 wt %)/ZnO
NWs showed the highest photoactivity with about 3-fold enhancement
as compared to pure ZnO NWs. Finally, a mechanism of charge carrier
generation, transport, and separation was proposed using different
scavengers to probe the potential reaction pathway following a direct Z-scheme approach.
Amphiphilic surfaces, containing both hydrophilic and hydrophobic domains, offer desirable performance for many applications such as marine coatings or anti-icing purposes. This work explores the effect of the concentration of amphiphilic moieties on converting a polyurethane (PU) system to a coating having fouling-release properties. A novel amphiphilic compound is synthesized and added at increasing amounts to a PU system, where the amount of the additive is the only variable in the study. The additive-modified surfaces are characterized by a variety of techniques including ATR-FTIR, XPS, contact angle measurements, and AFM. Surface characterizations indicate the presence of amphiphilic domains on the surface due to the introduction of the selfstratifying amphiphilic additive. The fouling-release properties of the surfaces are assessed with three biological assays using Ulva linza, Cellulophaga lytica, and Navicula Incerta as the test organisms. A change in the fouling-release performance is observed and plateaued once a certain amount of amphiphilicity is attained in the coating system, which we call the critical amphiphilic concentration (CAC).
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