Spray-Drying Hydrophobic Cellulose Nanocrystal Coatings with Degradable Biocide Release for Marine Antifouling.

With increasing awareness about the ecological environment, increased attention has been paid to the application of eco-friendly materials in the field of marine antifouling. In this work, a novel coating having good mechanical strength and static marine antifouling characteristics was fabricated using cellulose nanocrystals (CNCs) as the skeleton material, with in situ growth of SiO2 as the basic superhydrophobic material and introducing hexadecyl trimethyl ammonium bromide (CTAB) and 4-bromo2-(4-chlorophenyl)-5-(trifluoromethyl)-1H-pyrrole-3-carbonitrile (Econea) into the coating. Due to the high strength and rod structure of CNCs, the coating maintained super-hydrophobicity after 50 cycles of abrasion tests. Moreover, the addition of CTAB during the synthesis of SiO2 led to the hydrolysis and polycondensation of tetraethyl orthosilicate at the micellar interface. Econea was fully mixed with SiO2 nanoparticles, thus slowing down the rate of release of Econea. Meanwhile, the adhesion between the coating and the substrate reached 1.9 MPa, which can meet the application requirements for marine environments. The bioassay using bacteria (Escherichia coli) and diatoms (Nitzschia closterium) showed that the rate of inhibition of the coating on bacteria and diatoms could reach 99 and 90%, respectively, after immersion in artificial seawater for 28 days. This research provides a facile and promising fabricating solution of an eco-friendly CNC-based coating having strong antifouling characteristics suitable for marine environments.

Eco-friendly marine antifouling coating consisting of cellulose nanocrystals with bioinspired micromorphology.

Nanomaterial-incorporated surfaces with microstructures have been widely used for marine antifouling coatings, yet limited green antifouling coatings are currently available for sustainable application, given the potential environmental effects of nanomaterial-based nanofillers. Here, by using natural sourced nanomaterials (cellulose nanocrystals, CNCs) as nanofillers, a nanocomposite superhydrophobic coating was fabricated via a simple sol-gel synthesis method. Notably, CNCs were firstly applied in the marine antifouling realm to form uniform and stable coatings, which were condensed with hydroxyl groups of hydrolyzed tetrapropyl zirconate, 3-glycidyloxypropyltrimethoxysilane, and methyltrimethoxysilane. The synthesized coatings gained a biomimetic microscopic ridge-like surface, where more CNCs contents contributed to finer microstructures. As a result of the influence of CNCs content on surface wettability and antifouling properties, the coating with CNCs accounting for 20 wt% of the total solid content (CNC20) delivered the best antifouling performance. Furthermore, 90-day marine field tests verified CNC20's excellent antifouling ability, reducing fouling by 82 % in comparison to the control group. Such a biomimicry study provides a novel strategy for the development of environmentally friendly coatings with CNCs nanofillers.

Efficient removal of Phaeocystis globosa from seawater with the persulfate activation by arbutin-modified cellulose nanocrystals.

Harmful algal blooms (HABs) from seawater have a severe threat to human health, aquaculture, and coastal nuclear power safety. Thus, it is highly desirable to explore environmentally friendly, efficient, and economic methods for controlling HABs. Herein, the arbutin-modified cellulose nanocrystals (AT-CNC) activated persulfate (PS), as a novel heterogeneous Fenton-like process, was proposed to remove Phaeocystis globosa (P. globosa) from seawater. The AT-CNC was synthesized via the surface modification of AT on CNC. The effects of AT dosage, CNC dosage, and PS dosage on the removal performance of P. globosa were investigated. With the addition of 530 mg/L AT-CNC (6 wt% AT/CNC of AT loading) and 120 mg/L PS, the removal percentage of chlorophyll a (Rc), optical density at 680 nm (Ro) and turbidity (Rt) reached 97.7%, 91.9% and 85.2% at 24 h. According to electron paramagnetic resonance (EPR) spectra and radical quenching tests, the predominant free radicals inactivating P. globosa were hydroxyl radicals (•OH). Additionally, the flocculation of the inactivated algae cells by AT-CNC was also critical for removing P. globosa. Moreover, a positive environmental impact was achieved in the AT-CNC-PS system due to the reduction of nitrogen, phosphorus and organic carbon contents. Based on the excellent removal performance for P. globosa, we believe that the AT-CNC activated persulfate is a promising option for HABs control.

Biomimetic surface coatings for marine antifouling: Natural antifoulants, synthetic polymers and surface microtopography.

Marine biofouling is a ubiquitous problem that accompanies human marine activities and marine industries. It exerts detrimental impacts on the economy, environment, ecology, and safety. Traditionally, mainstream approaches utilize metal ions to prevent biological contamination, but this also leads to environmental pollution and damage to the ecosystem. Efficient and environmentally friendly coatings are urgently needed to prevent marine devices from biofouling. Since nature is always the best teacher for humans, it offers us delightful thoughts on the research and development of high-efficiency, broad-spectrum and eco-friendly antifouling coatings. In this work, we focus on the research frontier of marine antifouling coatings from a bionic perspective. Enlightened by three distinctive dimensions of bionics: chemical molecule bionic, physiological mechanism bionic, and physical structure bionic, the research status of three main bioinspired strategies, which are natural antifoulants, bioinspired polymeric antifouling coatings, and biomimetic surface microtopographies, respectively, are demonstrated. The antifouling mechanisms are further interpreted based on biomimetic comprehension. The main fabrication methods and antifouling performances of these coatings are presented along with their advantages and drawbacks. Finally, the challenges are summarized, and future research prospects are proposed. It is believed that biomimetic antifouling strategies will contribute to the development of nontoxic antifouling techniques with exceptional repellency and stability.