Latest ArticlesLightweight, highly strong and bio-based structural materials remain a long-lasting challenge. Here, inspired by nacre, a lightweight and high mechanical performance cellulosic material was fabricated via a facile and effective top-down approach and the resulting material has a high tensile strength of 149.21MPa and toughness of 1.91 MJ/m3. More specifically, the natural balsawood (NW) was subjected to a simple chemical treatment, removing most lignin and partial hemicellulose, follow by freeze-drying, forming wood aerogel (WA). The delignification process produced many pores and exposed numerous aligned cellulose nanofibers. Afterwards, the WA absorbed a quantity of moisture and was directly densified to form above high-performance cellulosic material. Such treatment imitates highly ordered "brick-and-mortar" arrangement of nacre, in which water molecules plays the role of mortar and cellulose nanofibrils make the brick part. The lightweight and good mechanical properties make this material promising for new energy car, aerospace, etc. This paper also explains the strengthening mechanism for making biomimetic materials by water molecules-induced hydrogen bonding and will open a new path for designing high-performance bio-based structural materials.
Immobilization of enzymes onto carriers is a rapidly growing research area aimed at increasing the stability, reusability and enzymolysis efficiency of free enzymes. In this work, the role of phase-separation and a pH-responsive "hairy" brush, which greatly affected the topography of porous polymer membrane enzyme reactors (PMER), was explored. The porous polymer membrane was fabricated by phase-separation of poly(styrene- co-maleic anhydride-acrylic acid) and poly(styrene-ethylene glycol). Notably, the topography and pores size of the PMER could be controlled by phase-separation and a pH-responsive "hairy" brush. For evaluating the enzymolysis efficiency of d-amino acid oxidase (DAAO) immobilized carrier (DAAO@PMER), a chiral ligand exchange capillary electrophoresis method was developed with d-methionine as the substrate. The DAAO@PMER showed good reusability and stability after five continuous runs. Notably, comparing with free DAAO in solution, the DAAO@PMER exhibited a 17.7-folds increase in catalytic velocity, which was attributed to its tailorable topography and pH-responsive property. The poly(acrylic acid) moiety of poly(styrene- co-maleic anhydride-acrylic acid) as the pH-responsive "hairy" brush generated topography changing domains upon adjusting the buffer pH, which enable the enzymolysis efficiency of DAAO@PMER to be tuned based upon the well-defined architectures of the PMER. This approach demonstrated that the topographical changes formed by phase-separation and the pH-responsive "hairy" brush indeed made the proposed porous polymer membrane as suitable supports for enzyme immobilization and fitting for enzymolysis applications, achieving high catalytic performance.
Metal–organic frameworks (MOFs) have a regular porous structure and high porosity, which make them ideal electrode materials for supercapacitors. However, their capacitance performance is greatly limited by their poor conductivity. In this study, a multi-component hierarchical structure was obtained by growing NiCoFeLDH on the surface of ZIF-67, which increased the electron transfer between the MOF particles and greatly improved the capacitance of ZIF-67. The formation mechanism of the multi-component layered hollow structure indicated that the hydrolysis acidity of metal ions and the coordination ability with ligands were the key factors for forming nanosheets and hollow structures. By controlling the type and valence state of the doped metals and the reaction time, the morphology transformation of MOF composites can be effectively controlled. Electrochemical studies showed that the specific capacitance of hollow NiCoFeLDH@ZIF-67 composite is 1202.08F/g (0.5 A/g). In addition, aqueous devices were assembled and carefully tested. This scheme is crucial for the design of MOF-based materials used in supercapacitor devices and serves as a guide for the design of MOF-based composites.
In order to reduce the greenhouse effect caused by the rapid increase of CO2 concentration in the atmosphere, it is necessary to develop more efficient, controllable, and highly sensitive adsorbing materials. In this study, the adsorption behavior of CO2 on BC3 nanosheets under an external electric field was explored based on density functional theory (DFT). It was found that CO2 experienced a transition from physisorption to chemisorption in the electric field range of 0.0060-0.0065 a.u.. In addition, the adsorption/desorption of CO2 is reversible and can be precisely controlled by switching on/off at the electric field of 0.0065 a.u.. The selective adsorption of CO2/H2/CH4 by BC3 can also be used to realize gas separation and purification under different electric fields. This study highlighted the potential application of BC3 nanosheets as a high-performance, controllable material for CO2 capture, regeneration, and separation in an electric field.
A novel flower-shaped zeolitic imidazolate framework (ZIF) doped organic-inorganic hybrid monolithic column (ZIF-HMC) was prepared by a simple sol-gel "one-step" method and utilized for efficient capillary microextraction (CME) of four brominated flame retardants. The prepared monolithic was characterized by Fourier transform infrared, scanning electron microscopy, X-ray photoelectron spectroscopy, energy disperse spectroscopy, and N2 adsorption-desorption. The parameters of CME were optimized by orthogonal array design. Under the optimal conditions, the ZIF-HMC showed excellent extraction efficiency, the limit of detection (LODs) and the limit of quantification (LOQs) were in the range of 0.52~3.1 μg/L and 1.7~10 μg/L, respectively, and the proposed method demonstrated good recovery (88.8%–116.6%) with the RSD less than 13.6% and a reusability of at least 30 times. The ZIF-HMC possessed great potential for separating organic pollutants and the strategy used here could be extended to prepare other derivatized HMC functionalized monoliths.
Increasing the charge separation and the utilization efficiency of sunlight are essential factors in a photocatalytic process. In this study, we prepared crystalline N-CQDs@W18O49 heterostructures, through the in situ growth of W18O49 nanocrystals on nitrogen-doped carbon quantum dots (N-CQDs). N-CQDs@W18O49 nanocomposites showed high activity in the photodegradation of ciprofloxacin (CIP) and methyl orange (MO). The photodegradation activity of the optimized N-CQDs@W18O49-5 sample was four times higher than that of W18O49 under ultraviolet-visible (UV–vis) light irradiation. The photodegradation activity of N-CQDs@W18O49-5 sample was two times higher than that of W18O49 under near-infrared (NIR) light irradiation. The enhanced photosensitivity of the nanocomposites was attributed to the promotion of charge separation by N-CQDs and the local surface plasmon resonance (LSPR) effect of W18O49 under NIR light irradiation. This work provides a promising approach for designing and manufacturing photocatalysts with full-spectral responsiveness and improved charge separation.
Intracellular pH is a key parameter related to various biological and pathological processes. In this study, a ratiometric pH fluorescent sensor ABTT was developed harnessing the amino-type excited-state intramolecular proton transfer (ESIPT) process. Relying on whether the ESIPT proceeds normally or not, ABTT exhibited the yellow fluorescence in acidic media, or cyan fluorescence in basic condition. According to the variation, ABTT behaved as a promising sensor which possessed fast and reversible response to pH change without interference from the biological substances, and exported a steady ratiometric signal (I478/I546). Moreover, due to the ESIPT effect, large Stokes shift and high quantum yield were also exhibited in ABTT. Furthermore, ABTT was applied for monitoring the pH changes in living cells and visualizing the pH fluctuations under oxidative stress successfully. These results elucidated great potential of ABTT in understanding pH-dependent physiological and pathological processes.
Covalent DNA–protein cross-links are toxic DNA lesions that interfere with essential biological processes, which can cause serious biological consequences, such as genomic instability and protein misexpression. 5-Formyluracil (5fU) as an important modification in DNA, which is mainly from oxidative damage, exists in a variety of cells and tissues. We have reported that 5fU mediated DNA–protein conjugates could exist in human cells [Zhou et al. CCS Chem. 2 (2020) 54-63]. We now aimed to explore its potential biological effects in vitro and in vivo. In this paper, we firstly reported that 5fU intermediated DNA–peptide or DNA–protein conjugates (both were called DPCs) could inhibit different polymerases bypass or cause mutations. Then we further investigated the functional impacts caused by 5fU-mediated DPCs, which appeared in different gene expression components [in the promoter sequence or 5′-untranslated regions (UTR)]. These results together may contribute to a broader understanding of DNA–protein interactions as well as the biological functions associated with 5fU.
Ammonia (NH3) is considered an attractive candidate as a clean, highly efficient energy carrier. The electrocatalytic nitrogen reduction reaction (NRR) can reduce energy input and carbon footprint; therefore, rational design of effective electrocatalysts is essential for achieving high-efficiency electrocatalytic NH3 synthesis. Herein, we report that the enzymatic mechanism is the more favourable pathway for NRR, due to lower limiting potential (−0.44 V), lower free energy (only 0.02 eV) of the first hydrogenation step (*N–N to *NH–N), and more electron transfer from Fe2B2 to the reaction species. In addition, both vacancies and dopants can be helpful in reducing the reaction energy barrier of the potential-determining step. Therefore, we have demonstrated that Fe2B2 is a potential new candidate for effective NRR and highlighted its potential for applications in electrocatalytic NH3 synthesis.
Water electrolysis is considered to be an effective and promising technology to make high-purity H2, however, the relationship between anion species and catalytic performance of electrocatalysts is still not completely clear. Herein, we report an anion engineering strategy to tune electrocatalytic water oxidation activity for Co-based materials. Novel hierarchical Co-based oxide/selenide/phosphide (Co-A, A = O, Se, P) hexagrams have been chosen as model materials. Electrochemical results and theoretical calculations reveal that the electron configuration, the electrical conductivity, and the oxidation potential of Co element in Co-A hexagrams could be moderated by the substitution of P atoms, which leads to the superior OER performance. Particularly, Co-P hexagram displays a low overpotential (η = 269 mV) at j = 10 mA/cm2 for the oxygen evolution reaction (OER) compared to Co-O hexagram (η = 399 mV) and Co-Se hexagram (η = 347 mV). This work is of great importance in understanding coordination atoms (O, Se and P) induced electrocatalytic properties of hierarchical Co-based materials.
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