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Uranium extraction from seawater is regarded as the most promising strategy for solving the concerns regarding the increasing demands of the nuclear industry. Inspired by the functional proteins of natural biological entities like bacteria and proteins that can efficiently capture uranium, we have developed water-insoluble protein-based adsorbents via a one-step amyloid-like assembly process. This method could convert water-soluble commercial proteins like bovine serum albumin (BSA), lysozyme and ovalbumin into adsorbents via one-step methods, while maintaining plenty of adsorption sites on the outer surface. The results of molecular dynamics simulations confirm the strong binding affinity between uranium and oxygenic/nitrogen functional groups. The protein-based adsorbents can capture more than 1000 mg g−1 of uranium from ultralow concentration uranyl nitrate solutions (8 ppm) within 2 h. Both the adsorption capacity and adsorption rate are in the leading positions compared with those of other state-of-the-art adsorbents. Moreover, these adsorbents exhibit outstanding anti-fouling properties and recyclability. They could maintain more than 80% of their pristine performance even after ten cycles in a simulated marine environment. Furthermore, the adsorbents could be deposited on various porous substrates like sponges for dynamic adsorption, benefiting from the good adhesion property of the unfolded proteins. The modified sponges could adsorb 540.6 mg g−1 uranium from simulated seawater in 72 h, showing their great potential in the field of practical uranium extraction. [ABSTRACT FROM AUTHOR]

Design and development of flexible pressure sensors with high sensitivity, long-term stability and simple fabrication processes is a key procedure to fulfill the applications in wearable electronics, e-skin, medical monitoring, etc. Here, we present a highly sensitive, durable, cotton fabric-based pressure sensor by a simple cyclic dipping–drying approach of graphene dispersion. Gelatin, as a dispersant and stabilizer, is used for preparing graphene nanosheet (GN) dispersions. Strong interactions including hydrogen bonds and hydrophobic interactions firmly immobilized GNs on the surface of cotton fibers mediated by gelatin. Benefiting from the uniformly immobilized GNs and the interweaved microstructures of cotton fabrics, the resulting graphene/gelatin functionalized pressure sensor (GGFPS) exhibited low resistivity (34 Ω cm), a wide linear detection range (2.51–6800 Pa), fast response (60 ms), low hysteresis (degree of hysteresis: 3.06%) and excellent cyclic working stability (3000 cycles). The electrical properties remained almost the same after 10 cycles of washing in SDS aqueous solution, revealing good washing durability. The GGFPS also possessed increased tensile strength compared with pristine cotton fabrics. Furthermore, this flexible cotton fabric-based pressure sensor could sense various human motions and physiological signals such as finger bending, wrist movement and swallowing. Importantly, the GGFPS could monitor the pulse signals of jugular veins and wrist arteries in real-time. Thus, this work indicates the great application prospect of this pressure sensor in wearable electronics, flexible circuits, and medical diagnosis. [ABSTRACT FROM AUTHOR]

Metal–organic frameworks (MOFs) are micro/mesoporous crystalline materials with high surface area, tunability, and compositional diversity and have been widely used in diverse applications, including catalysis. The rigid framework built from organic and inorganic functional structures can offer the merits of both, providing a platform to convert solar energy into usable or storable energy. Various approaches such as bandgap engineering, modulating the charge separation and increasing the intrinsic activity have been developed to improve the photocatalytic performance. This frontier article summarizes the current state-of-the-art in the use of MOFs as photocatalysts, emphasizing the recent strategies to optimize their visible-light-driven catalytic activities. Hopefully, this review could foreshadow new guidelines for explaining the current interest in exploiting novel MOF-based photocatalysts. [ABSTRACT FROM AUTHOR]

As an important class of natural resources, lignin and its utilization receive more and more attention. However, it is treated as waste in paper industry and causes serious pollution of natural water bodies. Meanwhile, the uncontrollable surface topography and the crystal form of natural calcium carbonate (CaCO3) severely restrict its application in the industrial field. Biomineralization may provide a perfect solution for these two issues. In this work, two types of specific crystal forms, cinnamic acid & aragonite crystal (CAAs) and cinnamic acid & vaterite crystal (CAVs) were directly synthesized in the presence of cinnamic acid. Two kinds of polymorph states were also found in the growth process of CaCO3. The structural properties of CAAs and CAVs as well as their polymorph states were characterized by FESEM, AFM, FTIR spectroscopy, XRD and TGA. The results showed that CAAs and CAVs held the crystal forms of aragonite and vaterite, respectively. The crystal forms of CaCO3 followed the growth rule that they dynamically changed from calcite to aragonite and then to vaterite. The formation mechanism is illustrated in the nucleation and crystal growth processes of CaCO3; cinnamic acid first formed various surfaces with the change in ambient conditions. These made CaCO3 to form different crystal forms and surface structures. [ABSTRACT FROM AUTHOR]

Silk fibroin (SF) from Bombyx mori is a natural macromolecule with remarkable biocompatibility and adhesive ability. For wound healing bio-adhesive applications, good biodegradability is essential. The ideal bio-adhesive is expected to be fixed together in the early stage of wound healing, adhere to tissues to avoid cracking, and present slow and favorable degradation at the wound site after healing. The residual adhesive component should be completely degraded after the wound has healed either through being absorbed by the body or excreted through the biological metabolism. Herein, SF was functionalized with dopamine through a one-step method with crosslinkers to enhance its adhesive ability. Poly(ethylene glycol) (PEG) was selected to optimize the gelation time (NESFB-Dopa). The ratio of SF and PEG, the ratio of crosslinker, the amount of dopamine and the adhesive environment were tuned to determine the optimal conditions. Following the ASTM standard, when the weight ratio of SF to PEG was 5 : 5, the molar ratio of NHS to EDC was 2 : 1, and the content of dopamine was 5 weight%; also, the tensile strength of NESFB-Dopa achieved greater values of 460.44 ± 18.45 kPa and 503.32 ± 16.54 kPa in dry and wet conditions, respectively, which demonstrated superior adhesive properties compared with those of the clinically used fibrin sealants. [ABSTRACT FROM AUTHOR]

Infinite 1D Ti–O rod-based metal–organic frameworks (MOFs) are promising photocatalysts for water splitting due to their high optical response and favourable photo-redox properties and stability, but have not been explored yet. In this study, three isoreticular porous 1D rod-based Ti-MOFs ZSTU-1, ZSTU-2 and ZSTU-3 are successfully constructed from infinite [Ti6(μ3-O)6(μ2-OH)6]n secondary building units (SBUs) and tritopic carboxylate linkers 4,4′,4′′-nitrilotribenzoic acid (H3TCA), 1,3,5-tris(4-carboxyphenyl)benzene (H3BTB) and tris(4′-carboxybiphenyl)amine (H3BTCA), respectively. Their porosities systematically increase with the larger and longer organic linkers. The two MOFs ZSTU-1 and ZSTU-3 built from the triphenylamino-based ligands can absorb visible light, exhibiting much better photocatalytic performance than ZSTU-2 as shown by the H2 production rate of ZSTU-1 and ZSTU-3 being 3–4 times higher than that of ZSTU-2. The photocatalytic H2 production rates for ZSTU-1, ZSTU-2, and ZSTU-3 are 1060 μmol g−1 h−1, 350 μmol g−1 h−1 and 1350 μmol g−1 h−1, respectively. The extraordinary photocatalytic activity of ZSTU-3 is attributed to its visible light absorption, large surface area, and favorable charge separation. [ABSTRACT FROM AUTHOR]

Silk protein sericin based organic–inorganic hybrid microcapsules are fabricated by incubating sericin microcapsules with a supersaturated calcium phosphate solution containing citric acid. A mineral hydroxyapatite shell is formed on the surface of the microcapsules. The thickness of the mineralized shell is dependant on the mineralization time. The amylum as a model cargo is encapsulated into the microcapsules with/without the presence of a mineralized shell. The release behavior of amylum from the microcapsules is investigated under different external environments. The results show that the release speed of amylum from the hybrid microcapsules is slower than from the sericin microcapsules under different pH and ionic strength conditions. This indicates that the stability of the hybrid microcapsules is improved due to the presence of the hydroxyapatite shell. The mineral shell provides a good protection to the microcapsule structure and carries goods against external harsh environment. In addition, cell cultures show a good cytocompatibility of the hybrid microcapsules. The natural microcapsules having an inorganic mineral shell cover may potentially act as drug delivery and encapsulating bioactive molecule systems. [ABSTRACT FROM AUTHOR]

Green nanocomposites containing biodegradable poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) and cellulose nanocrystals/silver (CNC-Ag) nanohybrids were synthesized and their properties were investigated. It was found that homogeneously dispersed CNC-Ag could act as bifunctional reinforcements to improve the thermal, mechanical and antibacterial properties of PHBV. Compared to pristine PHBV, the tensile strength and the maximum decomposition temperature (T[sub max]) of the nanocomposite with 10 wt% CNC-Ag were enhanced by 140% and 24.2 °C, respectively. The nanocomposites displayed reduced water uptake and water vapor permeability along with lower migration level in both non-polar and polar simulants compared to the neat biopolymer, which can be related to the increased crystallinity and improved interfacial adhesion. Moreover, the nanocomposites showed strong antibacterial activity against both Gram-negative E. coli and Gram-positive S. aureus. The results of the study indicate that the high performance nanocomposites show great potential applications in the fields of food, beverage packaging and disposable overwrap films. [ABSTRACT FROM AUTHOR]

The intimate relationship of electrochemical sensors with high sensitivity and reliability has stimulated intensive research on developing versatile materials with excellent electrocatalytic activity. Here, we reported a novel strategy for the design of novel nanostructure-based electrochemical biosensors originating from an unexpected behavior of Au nanoparticles (AuNPs) embedded in the interior of polyacrylonitrile nanofibers (Au-PANFs), which can migrate to the external surfaces of the carbon nanofibers (Au-CNFs) during the graphitization process. Small and uniform AuNPs embedded in PANFs were synthesized via a combination of electrospinning and in situ reduction. With the conversion from the amorphous structures of PANFs to graphene layered structures of CNFs, the AuNPs can migrate from the interior of PANFs to the external surfaces of CNFs. The migration of AuNPs through the nanofiber matrix is strongly dependent on the graphitization temperature and heating rates. Three different heating rates of 2, 5, and 10 °C min-1 and graphitization temperatures of 600, 800, and 1000 °C were employed to investigate the migration and the exposed density of AuNPs on the CNFs. These novel nanomaterials were constructed as a nonenzymatic H2O2 electrochemical sensor and the sensors based on Au-CNFs with increased density of exposed AuNPs exhibit significantly promoted electrochemical activity. The Au-CNFs (1000 °C, 2 °C min-1) with high exposed density and small sizes of AuNPs possess higher specific surface area and active sites, leading to higher electrocatalytic activity. The present investigations provide a general route for the fabrication of nanostructures for novel electrochemical sensors, energy storage devices and so on. [ABSTRACT FROM AUTHOR]

Rose-petal-shaped MoS[sub 2] hierarchical nanostructures were designed and constructed using carbonized electrospun nanofibers as a template, which exhibit highly structure-sensitive properties for the hydrogen evolution reaction (HER). We first synthesized carbon nanofiber (CNF) mats by combining the electrospinning and carbonization processes, and then the CNF mats were used as a substrate for the direct growth of MoS[sub 2] nanocrystals via the CVD method. By controlling the MoS[sub 2] morphology at the nanoscale, we constructed evolutions in the structures and preferentially exposed more catalyt-ically active edge sites, enabling improved performance for electrochemical catalytic activity. Because of their highly exposed edges and excellent chemical and electrical coupling to the underlying CNFs, MoS[sub 2]-CNF fiber mats exhibited excellent HER activity with a small overpotential of ~0.12 V and a small Tafel slope of 45 mV per decade. Our findings provide a feasible way to design and engineer advanced nanostructures for catalysis, electronic devices, and other potential applications. [ABSTRACT FROM AUTHOR]

Taking the inspiration from the biomineral, the silk sericin was selected to modulate the assembly of nanosized hydroxyapatite crystals viaa modified co-precipitation method. The effect of silk sericin concentration and mineralization time on the formation of hydroxyapatite nanocrystals, including their nucleation, growth, aggregation, especially assembly dynamics, were investigated using the transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy. The results revealed that both the concentration of silk sericin and the mineralization time could affect the size, morphology and assembly of hydroxyapatite crystals. Higher concentration of silk sericin in the reaction system was apt to form the larger hydroxyapatite crystals and longer mineralization time helped to improve the crystallinity of hydroxyapatite crystals together with an increase of crystal size. More interested thing was that an arrangement of nanocrystals in order was observed when the concentration of silk sericin was kept at 1(w/v)% in the reaction system. The larger rod-like hydroxyapatite crystals of 300–500 nm in length and 50–80 nm in diameter were assembled along the c-axis by the smaller crystals of ca.20 nm under the control of silk sericin, whose arrangement method was similar to the natural enamel. A proposed formation mechanism of the special structure was elucidated. In addition, the biocompatibility of obtained crystals was evaluated in vitroand their strong ability to promote the cell differentiation and proliferation was proved in the paper, which may be important for the biomedical applications and also for the fundamental studies of cell–matrix interactions. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) are micro/mesoporous crystalline materials with high surface area, tunability, and compositional diversity and have been widely used in diverse applications, including catalysis. The rigid framework built from organic and inorganic functional structures can offer the merits of both, providing a platform to convert solar energy into usable or storable energy. Various approaches such as bandgap engineering, modulating the charge separation and increasing the intrinsic activity have been developed to improve the photocatalytic performance. This frontier article summarizes the current state-of-the-art in the use of MOFs as photocatalysts, emphasizing the recent strategies to optimize their visible-light-driven catalytic activities. Hopefully, this review could foreshadow new guidelines for explaining the current interest in exploiting novel MOF-based photocatalysts.

S-rich MoS2-NCNF hybrid nanomaterials exhibiting extraordinary HER activity, with a very low onset potential of 30 mV and a small Tafel slope of 38 mV per decade, were successfully fabricated by combining N-doped carbon nanofibers and single-layered MoS2 nanostructures with abundant edge active sites.