Carrageenan/polyvinyl alcohol composite film reinforced with spermidine carbon dots: An active packaging material with dual-mode antibacterial activity.

Exploring biopolymer-based antibacterial packaging materials is promising to tackle the issues caused by petroleum plastic pollution and microbial contamination. Herein, a novel packaging material with two antibacterial modes, continuous and efficient, is constructed by dispersing positively charged spermidine carbon dots (Spd-CDs) in a carrageenan/polyvinyl alcohol (CP) composite biopolymer. The obtained nanocomposite film (CP/CDs film) not only gradually releases the ultra-small Spd-CDs but also rapidly generates reactive oxygen species to inhibit the reproduction of E. coli and S. aureus. Benefiting from the complementary advantages of carrageenan and polyvinyl alcohol, as well as the addition of Spd-CDs, the CP/CDs films exhibit high transparency, good mechanical performance, water vapor barrier ability, low migration, etc. The CP/CDs film as a packaging material is validated to be effective in preventing microbial contamination of pork samples. Our prepared nanocomposite film with sustainability and efficient antibacterial properties is expected as food active packaging.

Accelerated Oxygen Evolution Kinetics by Engineering Heterojunction Coupling of Amorphous NiFe Hydr(oxy)oxide Nanosheet Arrays on Self-Supporting Ni-MOFs.

Designing definite transition metal heterointerfaces is considered an effective strategy for the construction of efficient and robust oxygen evolution reaction (OER) electrocatalysts, but rather challenging. Herein, amorphous NiFe hydr(oxy)oxide nanosheet arrays (A-NiFe HNSAs) are grown in situ on the surface of a self-supporting Ni metal-organic frameworks (SNMs) electrode via a combination strategy of ion exchange and hydrolytic co-deposition for efficient and stable large-current-density water oxidation. The existence of the abundant metal-oxygen bonds on the heterointerfaces can not only be of great significance to alter the electronic structure and accelerate the reaction kinetics, but also enable the redistribution of Ni/Fe charge density to effectively control the adsorption behavior of important intermediates with a close to the optimal d-band center, dramatically narrowing the energy barriers of the OER rate-limiting steps. By optimizing the electrode structure, the A-NiFe HNSAs/SNMs-NF exhibits outstanding OER performance with small overpotentials of 223 and 251 mV at 100 and 500 mA cm-2 , a low Tafel slope of 36.3 mV dec-1 , and excellent durability during 120 h at 10 mA cm-2 . This work significantly provides an avenue to understand and realize rationally designed heterointerface structures toward effective oxygen evolution in water-splitting applications.

Bimetallic-MOF-derived crystalline-amorphous interfacial sites for highly efficient nitrite sensing.

Considering the importance of rapid and effective detection of nitrite in food samples, herein, we report a multistep heterophase synthetic strategy for constructing crystalline-amorphous zinc/cobalt iron porous nanosheets (C-A Zn/Co-Fe PNSs) on carbon cloth. Notably, the C-A Zn/Co-Fe PNSs@CC electrochemical interface consists of interlaced carbon fibers with many uniformly distributed hybrid nanosheets containing crystalline-amorphous interfacial sites. This particular hybrid structure permits local enrichment of nitrite for enhanced nitrite capture efficiency, laying a solid foundation for the ultrasensitive detection of nitrite. In proof-of-concept experiments, we verified that C-A Zn/Co-Fe PNSs@CC could be used to analyze nitrite with good sensitivity and reproducibility. It is worth mentioning that an ultra-low LOD of 0.44 µM was obtained for the detection of nitrite. The designed electrochemical sensor worked well in complex samples such as sausages and tap water under optimal parameters.

Analysis of the composition of culturable airborne microorganisms in the archaeological excavation protection site of the Nanhai No. 1 Ancient Shipwreck.

After the recovery of the ship from the sea on 2007, the Nanhai No. 1 Ancient Shipwreck is currently exposed to the air. Air microorganisms settle on wooden shipwrecks, and they can use wood matrix to grow and multiply, causing biocorrosion and biodegradation. In this study, a systematical survey of the composition of culturable airborne microorganisms was performed at the conservation site of the Nanhai No. 1 Ancient Shipwreck. Airborne microorganisms were collected from seven sites in the preservation Nanhai No. 1 area over five periods. Molecular identification of the culturable microorganisms isolated from the air was done by sequencing both 16S rRNA (bacteria) and ITS (fungi) gene regions. The biodegradability of these strains was evaluated by degradation experiments with cellulose and lignin as substrate. The results showed that the composition of the isolated microbial communities was different in each period, and microbial spatial distribution was dissimilar in the same period. In the recent 2020, the dominant bacterial genus was Acinetobacter, and the dominant fungal genera were Penicillium, Aspergillus, and Cerrena. Acinetobacter spp. can degrade cellulose and lignin. Penicillium spp., Aspergillus spp., and Cerrena spp. degraded cellulose but only Cerrena spp. could utilize lignin. These dominant strains may have a harmful effect on the Nanhai No. 1 Ancient Shipwreck. This study provides data on the airborne microbial community found inside the protective chamber where Nanhai No. 1 Shipereck is placed, which can be used as a reference basis for the future conservation of the ship.

Analysis and control of fungal deterioration on the surface of pottery figurines unearthed from the tombs of the Western Han Dynasty.

In April 2020, 232 tombs of the Western Han Dynasty were found in Sundayuan, Heze City. In total, 141 pottery figurines of significant historical, cultural, and artistic value were unearthed from the tombs. Some of the figurines are currently being stored in warehouses, and the surface of some of the figurines show fungal deterioration. To thoroughly analyze the fungal deterioration on the surface of the pottery figurines and find appropriate control methods, we used high-through sequencing, scanning electron microscopy observation, pure cultures of culturable fungi, and optical microscopy observation and molecular identification of culturable fungi. We conducted fungistatic and simulation experiments in the laboratory to find appropriate control methods. We found that the fungi on the surface of the figurines were mainly of the phylum Ascomycota, and a few fungi were of the phyla Basidiomycota and Mucoromycota. We isolated seven culturable fungal strains and observed their colony morphology. The seven fungal strains were Lecanicillium aphanocladii, Penicillium aurantiogriseum, Clonostachys rosea, Mortierella sp., Mortierella alpina, Aspergillus flavus, and Cladosporium halotolerans. Through the fungistatic and simulation experiments conducted in the laboratory, we found that 50 mg/ml cinnamaldehyde and 0.5% K100 (2-methyl-4-isothiazolin-3-one) have a good fungistatic effect. They can not only inhibit the growth of fungi on medium, but also inhibit the growth of fungi on the surface of pottery figurines. This study has good reference significance for the analysis and control of fungal deterioration of unearthed pottery figurines.

Simple high-temperature annealing affords commercial carbon cloth with enhanced electrochemical performance for highly sensitive detection of imidacloprid.

Imidacloprid (IDP) residue in modern agricultural production seriously endangers human health and environmental safety. The establishment of a rapid and efficient method for the detection of IDP residue can effectively prevent its harm to human health. Herein, we demonstrate the carbon cloth (CC) prepared by a high-temperature annealing strategy possesses enhanced electrochemical performance, which could be directly used in electrochemical IDP sensing. Annealed carbon cloth (ACC) is endowed with higher defects, rougher surfaces, more functional groups, more hydrophilic surface, and increased ion-accessible surface area. Furthermore, the ACC electrode shows superior electrocatalytic reduction activity towards IDP, possessing a wide linear range of 5-100 µM, a low detection limit of 0.04 µM, and high sensitivity of 35.58 µA mM-1 cm-2. Meanwhile, this sensor can be applied for sensing IDP in grapes and apples with a good recovery of 96.8-104.1%. Compared with other modified electrodes, the ACC electrode has the advantages of no binder, no complicated modification, excellent detection effect, low cost, and easy large-scale production. Consequently, this work designs a self-supporting metal-free electrode with high electrochemical performance, providing a new idea for the development of environmentally friendly IDP sensors.

A Naturally Derived Nanocomposite Film with Photodynamic Antibacterial Activity: New Prospect for Sustainable Food Packaging.

Food packaging with efficient antibacterial ability is highly desirable and challenging in facing the crisis of microbial contamination. However, most present packaging is based on metal-based antibacterial agents and requires a time-consuming antibacterial process. Here, the unique packaging (CC/BB films) featuring aggregation-induced emission behavior and photodynamic inactivation activity is prepared by dispersing self-assembled berberine-baicalin nanoparticles (BB NPs) into a mixed matrix of sodium carboxymethylcellulose-carrageenan (CC). The superiority of this design is that this packaging film can utilize sunlight to generate reactive oxygen species, thus eradicating more than 99% of E. coli and S. aureus within 60 min. Also, this film can release BB NPs to inactivate bacteria under all weather conditions. Surprisingly, the CC/BB nanocomposite film presented excellent mechanical performances (29.80 MPa and 38.65%), hydrophobicity (117.8°), and thermostability. The nanocomposite film is validated to be biocompatible and effective in protecting chicken samples, so this work will provide novel insights to explore safe and efficient antibacterial food packaging.

Bi Doping-Enhanced Reversible-Phase Transition of α-MnO2 Raising the Cycle Capability of Aqueous Zn-Mn Batteries.

Rechargeable aqueous zinc-manganese oxide batteries have attracted extensive attention in energy-storage systems owing to their high safety and low cost but still suffer from the lack of advanced cathode materials with both high capacity and a long cycle life. Here, the bismuth-doped α-MnO2 was synthesized by a hydrothermal method. The preintercalation of Bi3+ effectively enlarges the lattice spacing and boosts the electrochemical performance of Zn/MnO2 batteries. The systematical studies suggest that Bi doping significantly optimized the electrochemical behavior and especially enhanced the reversibility of dissolution-deposition and phase transition processes. As a result, the Bi-doped α-MnO2 cathode achieves a superior performance: high reversible specific capacity (325 mA h g-1 at 300 mA g-1) and long cycling stability (90.9% capacity retention after 2000 cycles at 1000 mA g-1). By comparison with the α-MnO2 electrode, the Bi-doped α-MnO2 electrode exhibits a longer and stabler discharge plateau. It is different from most anionic doping methods, which attribute the performance improvement to superior ion diffusion kinetics and enhanced structural stability. Therefore, this work offers a new viewpoint and approach to improve the electrochemical property of Zn/MnO2 batteries.

A hafnium oxide-coated dendrite-free zinc anode for rechargeable aqueous zinc-ion batteries.

In aqueous zinc-ion batteries, metallic zinc is widely used as an anode because of its non-toxicity, environmental benignity, low cost, high abundance and theoretical capacity. However, growth of zinc dendrites, corrosion of zinc anode, passivation, and occurrence of side reactions during continuous charge-discharge cycling hinder development of zinc-ion batteries. In this study, a simple strategy involving application of a HfO2 coating was used to guide uniform deposition of Zn2+ to suppress formation of zinc dendrites. The HfO2-coated zinc anode improves electrochemical performance compared with bare Zn anode. Therefore, for zinc-zinc symmetric cells, zinc anode with HfO2 coating (48 mV) shows lower voltage hysteresis than that of bare Zn anode (63 mV) at a current density of 0.4 mA cm-2. Moreover, cell with HfO2 coating also shows good cycling performance in Zn-MnO2 full cells. At a constant current density of 1.0 A g-1, discharge capacity of bare Zn-MnO2 full cell is only 37.9 mAh g-1 after 500 cycles, while that of Zn@HfO2-MnO2 full cell is up to 78.3 mAh g-1. This good electrochemical performance may be the result of confinement effect and reduction of side reactions. Overall, a simple and beneficial strategy for future development of rechargeable aqueous zinc-ion batteries is provided.

Fungal Community and Biodeterioration Analysis of Hull Wood and Its Storage Environment of the Nanhai No. 1 Shipwreck.

The Nanhai No. 1 shipwreck is a Chinese merchant ship in the Southern Song Dynasty, and now it is stored in a huge enclosed glass warehouse in Maritime Silk Road Museum in Guangdong Province. At present, the hull of the Nanhai No. 1 shipwreck is still being excavated, and a small part of the hull wood is soaked in a specific solution to desalt. Through long-term exploration, we found that the above two states of hull wood had undergone biodeterioration, so the purpose of this study is to analyze the fungal community of exposed and soaked wood from the Nanhai No. 1 shipwreck. We sampled 10 exposed hull wood and sea mud samples, two wood storage water samples, and air samples in the glass warehouse. We used scanning electron microscope and optical microscope to find that there were obvious fungal structures in exposed wood and wood storing water samples. High-throughput sequencing of fungi revealed that the most abundant genera in exposed and soaked wood were Fusarium sp., and Scedosporium sp., respectively. In addition, Fusarium solani and Scedosporium apiospermum were successfully isolated from the hull wood surface and wood storing water samples, and the degradation tests of lignin and cellulose, the sensitivity tests of biocides and growth curve assay were carried out. We also found that Penicillium sp. and Cladosporium sp. are the most abundant in the glass warehouse air. Our research results show that F. solani and S. apiospermum should be regarded as a major threat to the preservation of the Nanhai No. 1 shipwreck. These results provide a reference for our protection of shipwrecks and other similar artifacts.

Graphene Oxide Wrapped CuV2O6 Nanobelts as High-Capacity and Long-Life Cathode Materials of Aqueous Zinc-Ion Batteries.

Rechargeable aqueous zinc-ion batteries are considered as a promising alternative of lithium-ion batteries for stationary energy storage because of their economical and high safety quality. However, their widespread application is still impeded by the development of cathode materials with poor energy density and limited long-term stability. Herein, we report a high-performance CuV2O6 cathode material for aqueous zinc-ion batteries and elucidate the zinc-storage mechanism. The reversible phase transformation between CuV2O6 and ZnV2O6, accompanied by zinc ion insertion/extraction and the reduction/oxidation of metallic Cu nanoparticles, all contribute to excellent battery performance: an impressively high specific capacity of 427 mA h g-1 at current density of 0.1 A g-1, long-term cycling stability with minor capacity loss (0.7%) after 3000 cycles at a high current density of 5 A g-1, and a high energy density of 317 Wh kg-1 at a power density of 210 W kg-1. Furthermore, graphene oxide wrapped CuV2O6 nanocomposites are successfully fabricated, which demonstrates the significantly enhanced specific capacity (at least 30% improvement). This work provides an intriguing cathode material and expands available options of transition metal vanadate materials for zinc-ion batteries.

Boosting the Cyclic Stability of Aqueous Zinc-Ion Battery Based on Al-Doped V10O24·12H2O Cathode Materials.

Rechargeable aqueous zinc-ion batteries (ZIBs) are considered an alternative energy storage system to lithium-ion battery because of its low price and high safety. However, the development of zinc-ion battery is limited by positive materials, which usually show poor cycling life because of the strong electrostatic interaction between divalent Zn2+ ions and crystal structure of materials. Developing a cathode material with a stable structure upon cycling is still a big challenge for researchers worldwide. Doping foreign elements, which can solidify the lattice, is an effective approach to improve the structural stability of materials. However, hardly any research based on the doping method for aqueous ZIBs has been reported. Here, we develop an Al-doped layer material of V10O24·12H2O as cathode material for aqueous ZIBs. Benefitting from the stable layered structure, the material exhibited an excellent cycling life with 98% capacity retention after 3000 cycles, which is much higher than the 65% in the pure V10O24·12H2O. The great enhancement on the cycle performance indicates that Al-doping can help build an advanced zinc-storage system.

Magnetic solid-phase extraction of pyrethroid pesticides in environmental water samples with CoFe2 O4 -embedded porous graphitic carbon nanocomposites.

Magnetic CoFe2 O4 -embedded porous graphitic carbon nanocomposites were prepared through a facile solid-phase thermal reaction with NaCl as a template. The material was applied in the magnetic solid-phase extraction process coupled with high performance liquid chromatography with a diode array detector to detect the trace fenpropathrin, cyhalothrin, S-fenvalerate, and bifenthrin in different water samples. The synthesis conditions of nanomaterial including glucose concentration and calcination time on extraction performance for pyrethroid pesticides have been investigated. Different magnetic solid-phase extraction parameters have been studied, such as the nanomaterial amount, solution pH, eluent types, adsorption time, and the reusability. Under the optimum conditions, good recoveries (80.2-110.9%) were achieved with relative standard deviations of 0.2-5.8%. There are probably hydrophobic interactions and dipole-dipole attractions between nanocomposites and the analytes.

Preparation of magnetic carbon/Fe3O4 supported zero-valent iron composites and their application in Pb(II) removal from aqueous solutions.

Nanoscale zero-valent iron (NZVI) was first assembled on magnetic carbon/Fe3O4 (CM) with a combination of hydrothermal and liquid phase reduction methods. The novel NZVI@CM magnetic nanocomposites have the merits of large surface area, unique magnetic property, low cost and environmental friendliness. They can be used for Pb(II) removal in aqueous solution. The materials were characterized by using transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), vibrating sample magnetometry (VSM), X-ray photoelectron spectroscopy (XPS) and Brunauer-Emmett-Teller (BET) adsorption. The various parameters, such as reaction time, dosage of catalyst, solution pH and acid ions concentrations were studied. The removal efficiency of Pb(II) can be obviously increased by the combination of appropriate CM and NZVI. The removal efficiency of Pb(II) is 99.7% by using 60 mg of NZVI@CM at pH 7. The kinetics study indicates that the Pb(II) removal accords to pseudo-second-order kinetics model.