Preparation and characterization of corn starch-based antimicrobial indicator films containing purple corncob anthocyanin and tangerine peel essential oil for monitoring pork freshness.

A novel antibacterial indicator film was prepared by mixing corn starch with tangerine peel essential oil (TEO) Pickering emulsion emulsified by ultrasonic and esterified modified starch (UDSt), and then incorporated with purple corncob anthocyanin (PCA), which was used to monitor the freshness of pork. The results showed that the UDSt can effectively stabilize the TEO emulsion. PCA showed obvious color changes at different pH. With the increase of pH, the color of film changed from red to yellow, and its response to volatile ammonia changed from pink to cyan, showing better response ability. The loading of TEO conferred the film excellent bacteriostatic ability against E. coli and S. aureus. The film also had good ability of light blocking and free radical scavenging. In the process of pork deterioration, the antibacterial indicator film changed from pink to yellow, which was closely related to pork quality and had a good linear indicator correlation. The addition of TEO reduced the release of PCA in the antibacterial indicator film and helped to maintain the functional properties of the film. This type of antibacterial indicator film had considerable application potential in indicating food freshness.

Efficient Shaping of Cellulose Nanocrystals Based on Allomorphic Modification: Understanding the Correlation between Morphology and Allomorphs.

Cellulose nanocrystals (CNC) are green, safe, and renewable nanomaterials with a variety of excellent performances but their morphologies are notoriously difficult to control as this is unfavorable to the diversification of the end products. Allomorphic conversion plays an important role in diversifying the morphology of CNC. However, this further complicates the prediction, design, and control of the geometric dimensions of CNC. Herein, allomorphically modified cellulose (mercerized cellulose, ethylenediamine (EDA)-treated cellulose, and ball-milled cellulose) is designed and used as the starting material for CNC isolation. Subsequently, the morphological evolution of cellulose particles during acid hydrolysis is traced by scanning electron microscopy observations. A mechanism that facilitates further understanding of CNC shaping during sulfuric acid hydrolysis is proposed. According to the CNC shaping mechanism, precise prediction, design, and efficient control of the morphology of CNC (needle-like, ribbon-like, ellipsoid, and spherical) can be realized. CNC with various morphologies are favorable for their applications, such as templating synthesis of porous materials and Pickering emulsion dispersion.

Compressible Ionized Natural 3D Interconnected Loofah Membrane for Salinity Gradient Power Generation.

Large-scale salinity gradient power energy harvesting has generated broad attention in recent years, in which affordable ion-selective membranes (ISMs) are essential for its practical implementation. In this study, for the first time, ISMs derived from natural loofah sponge are reported, which have features of high hydrophilicity, superior ion conductivity, and 3D interconnected long fibers. The permselectivity and ion conductivity of loofah-based anion-selective membranes (ASMs) and cation-selective membranes (CSMs) are designed by chemical modification of the surface functional groups of loofah fibers and followed with compression and the resin filling. The charged nanochannels inside the ISMs are served as ion conductive and selective channels based on the nanofluidic effects and Donnan exclusion. Meanwhile, the unique isotropic structure endows excellent dimensional stability under the NaCl solution for months. When ISMs are used for salinity gradient power generation from the gradient of artificial seawater and river water, the maximum power density is 18.3 mW m-2 . When ten units of loofah-based ISMs are stacked in series, a voltage as high as 1.55 V is achieved. The results highlight the great potential of natural fibers for fabricating affordable, durable, and high performance ISMs, paving a sustainable pathway for developing high-performance, durable, and low-cost salinity gradient power generators.

Photocatalytic Rejuvenation Enabled Self-Sanitizing, Reusable, and Biodegradable Masks against COVID-19.

Personal protective equipment (PPE) has been highly recommended by the U.S. Centers for Disease Control and Prevention for self-protection during the disastrous SARS-CoV-2 (COVID-19) pandemic. Nevertheless, massive utilization of PPE encounters significant challenges in recycling and sterilizing the used masks. To tackle the associated plastic pollution of used masks, in this work, we designed a reusable, biodegradable, and antibacterial mask. The mask was fabricated by the electrospinning of polyvinyl alcohol (PVA), poly(ethylene oxide) (PEO), and cellulose nanofiber (CNF), followed by esterification and the deposition of a nitrogen-doped TiO2 (N-TiO2) and TiO2 mixture. The fabricated mask containing photocatalytic N-TiO2/TiO2 reached 100% bacteria disinfection under either 0.1 sun simulation (200-2500 nm, 106 W m-2) or natural sunlight for only 10 min. Thus, the used mask can be rejuvenated through light irradiation and reused, which represents one of the handiest technologies for handling used masks. Furthermore, intermolecular interactions between PVA, PEO, and CNF enhanced the electrospinnability and mechanical performance of the resultant mask, which possesses a 10-fold elastic modulus and 2-fold tensile strength higher than a commercial single-use mask. The porous structures of electrospun nanofibers along with strong electrostatic attraction enabled breathability (83.4 L min-1 of air flow rate) and superior particle filterability (98.7%). The prepared mask also had excellent cycling performance, wearability, and stable filtration efficiency even after 120 min wearing. Therefore, this mask could be a great alternative to current masks to address the urgent need for a sustainable, reusable, environmentally friendly, and efficient PPE under the ongoing COVID-19 contagion.

Biopolymers Derived from Trees as Sustainable Multifunctional Materials: A Review.

The world is currently transitioning from a fossil-fuel-driven energy economy to one that is supplied by more renewable and sustainable materials. Trees as the most abundant renewable bioresource have attracted significant attention for advanced materials and manufacturing in this epochal transition. Trees are composed with complex structures and components such as trunk (stem and bark), leaf, flower, seed, and root. Although many excellent reviews have been published regarding advanced applications of wood and wood-derived biopolymers in different fields, such as energy, electronics, biomedical, and water treatment, no reviews have revisited and systematically discussed functional materials and even devices derived from trees in a full scope yet. Therefore, a timely summary of the recent development of materials and structures derived from different parts of trees for sustainability is prsented here. A concise introduction to the different parts of the trees is given first, which is followed by the corresponding chemistry and preparation of functional materials using various biopolymers from trees. The most promising applications of biopolymer-based materials are discussed subsequently. A comprehensive review of the different parts of trees as sustainable functional materials and devices for critical applications is thus provided.

Antibacterial Performance of a Mussel-Inspired Polydopamine-Treated Ag/Graphene Nanocomposite Material.

Graphene-based nanocomposites have attracted tremendous attention in recent years. In this study, a facile yet effective approach was developed to synthesize reduced graphene oxide and an Ag-graphene nanocomposite. The basic strategy involved in the preparation of reduced graphene oxide includes reducing graphene oxide with dopamine, followed by in situ syntheses of the Ag-PDA-reducing graphene oxide (RGO) nanocomposite through adding AgNO3 solution and a small amount of dopamine. The nanocomposite was characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), FTIR spectra, Raman spectra, ultraviolet-visible (UV-vis), and X-ray photoelectron spectroscopy (XPS), results indicated that a uniform PDA film is formed on the surface of the GO and GO is successfully reduced. Besides, the in situ synthesized Ag nanoparticles (AgNPs) were evenly distributed on the RGO surface. To investigate antibacterial properties Ag-PDA-RGO, different dosages were selected for evaluating the antibacterial activity against Gram-positive bacteria Staphylococcus aureus and Gram-negative bacteria Escherichia coli. The Ag-PDA-RGO nanocomposites displayed excellent antibacterial property. The antibacterial ratio reached 99.9% against S. aureus and 90.9% against E. coli when the dosage of 100 mg/L Ag-PDA-RGO nanocomposites was 100 µL. The novel Ag-PDA-RGO nanocomposite prepared by a facile yet effective, environmentally friendly, and low-cost method holds great promise in a wide range of modern biomedical applications.