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Hydrogen peroxide (H2O2) is a powerful industrial oxidant and potential carbon-neutral liquid energy carrier. Sunlight-driven synthesis of H2O2 from the most earth-abundant O2 and seawater is highly desirable. However, the solar-to-chemical efficiency of H2O2 synthesis in particulate photocatalysis systems is low. Here, we present a cooperative sunlight-driven photothermal-photocatalytic system based on cobalt single-atom supported on sulfur doped graphitic carbon nitride/reduced graphene oxide heterostructure (Co–CN@G) to boost H2O2 photosynthesis from natural seawater. By virtue of the photothermal effect and synergy between Co single atoms and the heterostructure, Co–CN@G enables a solar-to-chemical efficiency of more than 0.7% under simulated sunlight irradiation. Theoretical calculations verify that the single atoms combined with heterostructure significantly promote the charge separation, facilitate O2 absorption and reduce the energy barriers for O2 reduction and water oxidation, eventually boosting H2O2 photoproduction. The single-atom photothermal-photocatalytic materials may provide possibility of large-scale H2O2 production from inexhaustible seawater in a sustainable way.

Nuclear energy has significantly promoted the development of human society. However, nuclear pollution caused by nuclear accidents can lead to significant hazards to the environment and human health. As a major radioactive product, radioactive iodine (mainly existing as I−) detection has attracted significant attentions. In this study, zirconium(IV) is used to enhance the oxidation of environmental I− to form I2. Subsequently, the generated I2 oxidizes the chemical chromogenic substrate 3,3′,5,5′-tetramethylbenzidine, which is used for I− detection and realizes an ultralow limit of detection (LoD) of 0.176 nM. The LoD of our method, to the best of our knowledge, is the lowest among those of the available chemical methods for I− detection. Furthermore, our detection method also shows high specificity and reliability, making it a promising technique for detecting I− in practical environments.

Highly functionalized materials at the nanoscale on optical fibers offer notable opportunities to construct "lab-on-fiber" functional devices with unusual properties. However, it is extremely difficult to fabricate nanostructures with special morphology on a thin cylindrical optical fiber surface using the commonly used physical lithography techniques. Meanwhile, it is vital to maintain the plasmonic properties of Ag-riched particles while improving their stability. Herein, we design a facile strategy for the fabrication of Au-Ag bimetallic nanorings (Au-Ag NRs) immobilized on optical fibers for enhanced plasmonic properties. Ag NPs are first grownin situon an optical fiber surface through chelation and redox of polydopamine (PDA) to metal ions, and then are quickly converted into Au-Ag NRs by a galvanic replacement reaction and metal deposition. This conversion only takes 3.5 min, while the formed Au-Ag NRs exhibit outstanding localized surface plasmon resonance (LSPR) sensitivity (2204 nm per RIU) and oxidation resistance, and Au and Ag atoms are distributed uniformly in the nanorings. Furthermore, a novel and interesting formation process of the nanorings including deformation, spallation, growth in the gaps, and ring formation is studied. These findings provide a way to grow bimetallic nanorings on optical fibers, which are promising candidates for photoelectric "lab-on-fiber" devices. This work was supported by the Hainan Provincial Natural Science Foundation of China (No. 519QN179) and the National Natural Science Foundation of China (No. 21621004 and 51473115).

Uranium is the main element for nuclear energy production and is one of the most hazardous radionuclides; its effective enrichment plays a key role in energy strategy and environmental safety. Oxime-functionalized nanostructures are the most promising candidates for uranium adsorption. However, current methods for their preparation mainly focus on multistep grafting and oximation processes, and the nanostructures usually show low efficiency. Here, we report a rapid one-step process to synthesize salicylaldoxime/polydopamine modified reduced graphene oxide (RGO-PDA/oxime) via the polymerization of dopamine (DA) and simultaneous deposition of oxime with an obviously decreased total synthesis time of 2 h. The obtained maximum uranium adsorption capacity of up to 1049 mg g−1 was 3–16 times larger than those of the reported single PDA or oxime modified nanostructures. The RGO-PDA/oxime followed the pseudo-second-order kinetics model and Langmuir isotherm equation with much higher adsorption selectivity and recyclability. The outstanding sorption performance is attributed to the electrostatic repulsion between GO and salicylaldoxime and the effective combination between PDA and oxime molecules. Finally, given the adhesion capability of DA to diverse surfaces, this rapid one-step method was used to prepare five other oxime/PDA modified materials, which also showed improved uranium adsorption efficiency. These findings provide a way to obtain oxime-functionalized nanostructures with promising uranium adsorption efficiency.

Massive uranium recovery from seawater is a key project to provide the long-time consumption of global nuclear power, while it is still greatly difficult to achieve high-efficient adsorbents with high mechanical property. In this work, a new nanoclay-poly(amidoxime) (NC-PAO) high-strength double-network (DN) composite hydrogel adsorbent with high-efficient and fast uranium extraction capacity has been explored. The uranium adsorbing performance can be significantly enhanced by the small content of added super-hydrophilic NC (Laponite RDS sheets), because of the largely improved hydrophilicity of the hydrogel. Compared with the blank PAO DN hydrogel without nanoclay, the uranium adsorbing capacity of this NC-PAO DN hydrogel can largely increase 73.4% from 4.97 mg/g to 8.62 mg/g, after in seawater only 25 days. The uranium adsorption rate of this hydrogel from natural seawater, can reached 0.345 mg/(g∙day), which is excellent among existing uranium adsorbents. Furthermore, this hydrogel has high mechanical performance with 2.42 MPa of tensile strength and 16.13 MPa of compressive strength, which can be used in seawater for relatively longer time than traditional low-strength single-network hydrogel, owing to its double network (DN) structure (the weakly crosslinked gelatin soft network and the strongly crosslinked cellulose nanofiber (CNF) hard network). This NC-PAO DN hydrogel adsorbent will be an excellent candidate for fast uranium recovery from seawater in largescale. Most importantly, this work will inspire the development of new hydrogel-based adsorbents and even other type of adsorbents for high-efficient uranium extraction, through compositing various low-cost and super-hydrophilic nanomaterials to significantly improve the hydrophilicity of the adsorbent and designing double-network structure to largely enhance the mechanical property.

To withstand the complex natural environment and ecological system in the ocean, adsorbents with high strength, rapid rate, and antifouling ability are urgently needed for uranium extraction. Herein, instead of the traditional poly(amidoxime) structures, we design an anti-adhesive adsorbent (Anti-LS/SA) by conjugating functional ligands of salicylaldoxime (SA) and hyaluronic acid (HA) on the porous biomass via a facile one-step process. The interconnected microchannels in the porous biomass can accelerate seawater transport, along with the micromolecular uranium-adsorbing ligand, endowing the Anti-LS/SA with a very fast uranium adsorption ability; the average adsorption rates reach up to 131 ± 1.8 mg g−1 hour−1 (in uranium spiked seawater with concentration of 8 ppm) and 0.1176 mg g−1 day−1 (in natural seawater) in the main adsorption stages, exceeding the currently used oxime-based adsorbents. Owing to the high hydration of HA, the adsorbents exhibit excellent hydrophilicity and anti-bacterial adhesion properties, as demonstrated by the bacteria adhesion testing and extraction experiments in bacteria-spiked seawater. Furthermore, the Anti-LS/SA displays a long service life and a very high tensile strength (62.63 MPa) to withstand strong ocean waves. Kinetics models and XPS data are used to analyze the extraction mechanisms. Considering its high efficiencies, structural advantages, as well as the facile and massive construction, we believe that the Anti-LS/SA will be a promising candidate for the large-scale uranium extraction from seawater.

For the uranium extraction from seawater in marine environments, the adsorbents need to possess sufficient mechanical strength to withstand the crashing force of the ocean waves, as well as anti-biofouling ability to prevent the blockage of the chelating sites by marine microorganisms. Herein, a facile one-step process is designed to massively construct robust and anti-biofouling poly(amidoxime) aerogels (Anti-PAO gels) for highly efficient uranium extraction. The gels display porosity, large surface area, flexibility, excellent mechanical strength to withstand the crash of the waves benefitting from the adhesive antibacterial compounds and the tight covalent bonding between the antibacterial compounds and PAO molecules, and the adsorption capacity reaches up to 1013 ± 9.7 mg-U/g-Ads in the 8 ppm uranium spiked solution. Significant inhibition zones are observed around the Anti-PAO gels, the adsorption amounts in bacteria-contained seawater reach 90.67%-94.82% of that in sterilized seawater, indicating the beneficial antifouling effects of the prepared aerogels for uranium extraction, providing an excellent extraction capacity of 9.29 ± 0.59 mg-U/g-Ads after a 30-day field test in natural seawater. More importantly, this developed strategy possesses universal applicability, and it can be used in other amidoxime molecules and other forms of uranium adsorbents to prepare the antifouling aerogels and fibers. Together with the economic analysis results, we believe that the developed amidoxime aerogels are promising in the industrialized uranium extraction from seawater.

This study presents a facile, rapid and effective method for the fabrication of optical fiber surface plasmon resonance (SPR) sensors via polydopamine (PDA)-accelerated electroless plating (ELP). The bioinspired PDA coating formed through the facile self-polymerization of dopamine (DA) was utilized as a versatile material for optic-fiber functionalization. Gold seeds were then rapidly and firmly adsorbed onto the PDA functional layer by amino and imino intermediates generated during the polymerization, and a gold film sensor was fabricated after metal deposition. The fabrication time of the sensor was decreased by 6–12 times, and the fabricated sensor exhibited higher sensitivity, better reproducibility and adhesion stability compared with those fabricated by the traditional ELP. Some key experimental parameters, including DA polymerization temperature, DA polymerization time, and plating time, were investigated in detail. The optimized sample exhibited high sensitivity ranging from 1391 nm per RIU to 5346 nm per RIU in the refractive index range of 1.328 to 1.386. Scanning electron microscopy images indicated that the sensor surface consisted of gold nanoparticles with a uniform particle size and an orderly arrangement, and the film thickness was approximately 60 nm. Another PDA layer was formed on the gold film for facile immobilization of antibodies. The sensor exhibited effective antibody immobilization ability and high sensitivity for human IgG detection over a wide range of concentrations from 0.5 to 40 μg mL−1, which indicate the potential applications of the fabricated sensor in immunoassays.