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Nanocellulose has become a hotspot in the field of green and sustainable materials. The research status of nanocellulose in cleaner production and its environmental assessments were reviewed.

A facile and green process based on pre-phosphorylation and mechanical fibrillation is proposed and optimized for P-CNC production, and the obtained P-CNCs with high charge content and high crystallinity exhibited superior flame retardancy.

Conductive self-healing hydrogels (CSHs) are a class of materials that possess both electrical conductivity and the ability to autonomously repair mechanical damage.

The construction of a nanozyme that mimics a natural enzyme is a promising strategy to obtain a highly stable catalyst. Laccases are members of copper-containing oxidases, as environmental catalysts, and show significant potential in biotechnology and environmental remediation. In this study, inspired by the active site and electron transfer of laccase, a new laccase mimic (defined as CA-Cu) was synthesized via the coordination of copper with a cysteine (Cys)–aspartic acid (Asp) dipeptide. The as-prepared CA-Cu nanozyme exhibits significant laccase-like activity and catalytic oxidation of a wide range of phenolic pollutants, such as 2,4-dichlorophenol, phenol, p-chlorophenol, 2,6-dimethoxyphenol, hydroquinone, o-nitrophenol and o-aminophenol hydroquinone. It has a similar Km (Michaelis constant), a higher vmax (maximum rate) and better recyclability than laccase at the same mass concentration. In addition, the CA-Cu nanozyme is robust in a broad temperature range (0–100 °C), at extreme pH and under long-term storage. Surprisingly, the catalytic performance of the CA-Cu nanozyme was enhanced under high-salt conditions or at high concentrations of heavy metal ions, which lead to severe loss in the catalytic activity of laccase. We believe that this nanozyme is a promising environmental catalyst for the treatment of phenolic pollutants under high-salt or heavy metal ion conditions.

The application of protein units and architectures as supports in the synthesis of metal and metal oxide nanoparticles (NPs) is a relatively new emerging issue. While avoiding toxic stabilizers and solvents, this new synthesis route mostly fulfils the long-desired prospect of designing and synthesizing size- and morphology-controlled nanocatalysts with long-term stability towards maintaining their catalytic activity during reactions and facilitating their separation and recycling. Biotemplates of protein units and architectures with different dimensions, such as protein cages, bacteriophages, protein fibers, protein membranes, and protein crystals, have been widely adopted for the controllable synthesis and immobilization of metal and metal oxide NPs, owing to their abundant functional surface groups for NP anchoring and well-defined structures for accommodating NPs. Various bioinorganic nanohybrids have been constructed and applied in electrocatalysis for fuel cells, photocatalysis for clean energy and pollutant remediation, hydrogenation and oxidation reactions, catalytic syntheses of organic chemicals, etc. This review is meant to present several pivotal aspects of nanocatalysts, their protein-assisted synthesis and their catalytic applications, providing a description of common protein biotemplates, synthesized NPs and applied catalytic reactions.

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).

To analyze multiple analytes in trace samples, low-dosage and high efficiency are crucial in many common cases. Herein, we developed a facile method using a single-channel surface plasmon resonance (SPR)-based biosensor for the simultaneous detection of gentamicin (GEN) and melamine (MEL) in milk and serum with only one sample injection. Based on a sandwich immunoassay, non-interfering antibodies against GEN from mouse (AbGEN) and against MEL from rabbit (AbMEL) were chosen to capture the analytes. Secondary antibodies against mouse (AbM) and rabbit (AbR) were used to bind with AbGEN and AbMEL to determine the concentrations of GEN and MEL on a single channel of an SPR sensor. All of the detection process could be done in 10 min with 50 μL of sample injection. According to the response shifts of AbM and AbR, two standard curves for GEN and MEL were obtained successively, with the limit of detection (LOD) values at 4.4 ng mL-1 and 1.3 ng mL-1, respectively. Moreover, the feasibility was determined by spiking milk and serum samples with GEN and MEL, with recoveries in the range of 81.6%-118.0%. Importantly, the analytes can be substituted by others for much more applications. This method is also expected to multiply the detection efficiency of multi-channel SPR biosensors with low-dosage samples in the future.

Mercapto functionalized Zr-MOFs have been developed via a one-pot synthesis for the selective adsorption of Hg2+ ions. Mercaptoacetic acid (MAA) or alpha lipoic acid (ALA) was used as the modulators and functionalized molecules to synthesize mercapto functionalized Zr-MOFs (Zr-MOFs-SH(O)). In comparison with the mercapto functionalized Zr-MOFs via the traditional postsynthetic modification (Zr-MOFs-SH(P)), Zr-MOFs-SH(O) had a much higher content of –SH groups, thus leading to a much higher adsorption capacity for Hg2+ ions. In particular, PCN-224-MAA(O) had an adsorption capacity for Hg2+ ions up to 843.6 mg g−1, which is much higher than that of PCN-224-MAA(P) (138.5 mg g−1). Additionally, PCN-224-MAA(O) can be used to reduce Hg2+ ion concentrations (5–20 μg L−1) in water to the limit acceptable (1 μg L−1) for drinking water. Moreover, PCN-224-MAA(O) also exhibited good selectivity, recyclability, and chemical stability.

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.

We herein report a novel strategy for the removal of heavy metals and the subsequent preparation of a metal ceramic for immobilizing enzymes. To demonstrate this concept, Ni2+ ions were removed from an aqueous solution via entrapment by chitosan nanoparticles, and the resulting Ni(II)-containing precipitate was mixed with the ceramic matrix to give the Ni-doped ceramic (Ni-CP), which was subsequently applied in lipase immobilization. Under optimized conditions, Ni2+ removal reached 99.4%, and the Ni-CP showed significant chelation towards lipase following immobilization. In addition, a lipase activity yield of 164% was obtained under optimal conditions. Furthermore, the thermal and storage stabilities of Ni-CP-lipase exhibited a wider applied range, and the Ni-CP reusability was maintained at 97.5% following 20 cycles, suggesting high stability and excellent recyclability. Hence, the entrapped Ni2+ exhibited improved stability, thus reducing leakage into the environment. Furthermore, the chelation between Ni2+ and lipase improved enzyme activity and stability, and thus, may be suitable for application in large-scale production. It is therefore expected that this novel approach for enzyme immobilization has the potential to serve as an important technique in the field of biocatalysis.

Herein, we design and synthesize a novel hydrolase model by integrating the supramolecular self-assembly of an amphiphilic short peptide (Fmoc-FFH) and electrostatic complexation (with PEI) at an aqueous liquid–liquid interface to synthesize stable peptide–polymer Fmoc-FFH/PEI hybrid capsules (FPCs). After treatment with glutaraldehyde as a crosslinking agent, we can obtain novel Fmoc-FFH/PEI/GA hybrid capsules (FPGCs). The FPGCs with imidazolyl groups as the catalytic centers exhibit high catalytic activity for the hydrolysis of p-nitrophenyl acetate (PNPA). The resulting hydrolase model (FPCs or FPGCs) shows kinetics behavior typical of natural enzymes, and the catalytic activity is higher than that of a Fmoc-FFH hydrogel. The enhanced catalytic activity may be attributed to the high density of catalytic sites on the inner surface of the hybrid capsule. Additionally, the FPGCs retained 93% of their productivity after fifteen cycles, suggesting high stability and excellent recyclability. This novel hybrid capsule is expected to be applied as a substitute for natural hydrolases in industrial production applications.

A novel signal amplification strategy for quartz crystal microbalance (QCM) based on catalytic gas generation was developed to construct an ultrasensitive immunosensor for the detection of proteins (immunoglobulin G, IgG, used as a model). A catalase modified immunoparticle was prepared to form a sandwich-type immunocomplex with the IgG and anti-IgG antibodies that were immobilized on the QCM sensor. The amount of immunoparticles on the sensor surface was thus controlled by the IgG concentration. Then H2O2 was added and catalyzed by catalase for oxygen generation. The generated oxygen replaced some of the liquid on the sensor surface, leading to the change in the shear modulus of the immunocomplex layer and the apparent viscosity and density of the liquid layer. Due to the ultrasensitive response of QCM to these changes, a significant frequency shift related to the IgG concentration was achieved. Different parameters, including the flow cell structure, operation temperature, immunoparticle concentration, and H2O2 concentration were optimized to achieve steady and efficient frequency shifts. Under the optimal conditions, the proposed gas-phase amplified QCM sensor could achieve up to 72 times improvement of detection sensitivity compared to the label-free sensor as a control, in the concentration range of 0.1-3.0 μg mL(-1). The detection limit was also reduced from 236 ng mL(-1) to 51.0 ng mL(-1) at the 3Sblank level.

Hydrogen bonding is one of dominant forces in crystalline cellulose and lignocellulose, however, it is still a big challenge to evaluate the changes in the hydrogen bonding strength. Here, we reported a new method for measuring the changes in the hydrogen bonding strength of cellulose-based materials by terahertz time domain spectroscopy (THz-TDS). Avicel, corncob and their residual substrates after enzymatic hydrolysis were chosen as the targeted cellulose to demonstrate this method. THz adsorption in the range 0.5–2.5 THz and refractive index in the range 0.5–1.0 THz provided a direct signal corresponding to an increase in the hydrogen bonding strength for the residual samples (Avicel and corncob) after enzymatic hydrolysis. The THz results were further compared with those obtained from X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis. As a quick and non-invasive technique, THz spectroscopy provides unique information about the changes in the hydrogen bonding strength of cellulose-based materials. Therefore, it is a promising way to directly evaluate the hydrogen bonding strength of cellulosic macromolecules.

High solids enzymatic hydrolysis is a promising process to increase the concentrations of fermentable sugars for ethanol production. Here, we reported an integrated strategy incorporating decrystallization and fed-batch operation to enhance the enzymatic hydrolysis of lignocellulose at high solid loadings. The effect of concentration of phosphoric acid on the decrystallization and enzymatic hydrolysis of cellulose was investigated. The results showed that 86 wt% phosphoric acid could completely break the crystalline structure, achieving a high cellulose conversion and hydrolysis rate (89% within 4 h) in batch operation (5% solid loading). In the fed-batch operation, we designed two different enzyme feeding strategies, in which the enzymes were added either at start-up or along with the fresh substrate. The results indicated that fed-batch hydrolysis can be carried out at a final high solids loading of 30%, resulting in a glucose concentration as high as 143.5 g L−1 within 27 hours. Meanwhile, a stable and high cellulose conversion was achieved in fed-batch operation with the enzymes divided over the substrate feed, which should be dependent on the decrystallization of the substrate. Our findings provide a practical way to enhance enzymatic hydrolysis at high solid loadings and also propose a feasible enzyme feeding strategy in fed-batch operation.

Multifunctional nanoprobes with excellent reusable capability for practical detection can not only increase the resource utilization rate, but also reduce the discharge of toxic nanoparticles into the environment. In this paper, novel magnetic–fluorescent nanocomposites (Fe3O4@CdTe) have been successfully fabricated through layer-by-layer (LBL) self-assembly. The particles were used to develop a reusable fluorescence method to detect hydrogen peroxide and glucose with high sensitivity. The obtained core–shell Fe3O4@CdTe nanocomposites were characterized by transmission electron microscopy and fluorescence spectroscopy. The results indicated the successful formation of a CdTe shell on the surface of the magnetic Fe3O4 core. Its sensing performance towards H2O2 and glucose was then discussed in detail. The emission of the nanocomposites gradually reduced with the increasing analyte concentration. High sensitivity and good selectivity were observed from the composites. More importantly, these composites can be easily recovered and reused for several cycles due to their magnetism and high stability. Furthermore, we demonstrated that this fluorescent sensor can be used for glucose detection in human urine samples. As a multifunctional nanoplatform, the present nanoprobe holds genuine potential in future biosensing applications.

A novel concept integrating supramolecular self-assembly and electrostatic complexation at an aqueous liquid–liquid interface to synthesize stable peptide–polymer hybrid capsules was developed. The concept was further applied for enzyme immobilization to give stable and active biocatalysts with low enzyme leakage and high encapsulation efficiency, enzyme loading, and recyclability.

Liquid crystallinity of graphite oxide (GtO) flakes prepared without the need for sonication was found. Therefore, the scalable processing of GtO liquid crystals (LCs) became promising. The spontaneous highly-ordered alignment of GtO LCs was observed, as verified by SEM and TEM. The effects of electric fields on GtO LCs were demonstrated.

The measurement of molecular parameters, such as molecular weight and degrees of polymerisation, in lignocellulosic feedstock are critical during the hydrolysis process, because following the changes in these parameters can provide insight into the mechanism of hydrolysis. This work employs SEC-MALLS to monitor the changes in the absolute values of these parameters of lignocellulosic samples during enzymatic hydrolysis. The lignocellulosic samples were directly dissolved in 8.0% LiCl/DMAc without any change. The number- and weight-average molecular weights of the cellulose fraction decreased initially and increased slightly thereafter, indicating that a “layer-by-layer” mechanism is adapted for enzymatic hydrolysis of the cellulose fraction of lignocellulose. Similar changes in the molecular weights of the hemicellulose fraction indicates that hemicellulose and cellulose are always together in the recalcitrant substrates during enzymatic hydrolysis. Finally, the reaction mechanism of cellulase on lignocellulose was defined by SEC-MALLS analysis combining HPLC and XRD data.

A convenient and cost-efficient method featuring the integration of enzymatic and acid catalysis has been developed for the selective conversion of glucose into HMF, which provides a new strategy for HMF production from glucose.

Self-assembly of molecular units at an interface has been an active area of research over the past few decades because of its advantages to prepare highly ordered materials. Here we demonstrated jet flow directed supramolecular self-assembly at the interface between two aqueous solutions, one containing a cationic polyacrylamide (CPAM) and the other, a small self-assembling Fmoc-diphenylalanine (Fmoc-FF) peptide bearing opposite charge. By controlling the jet flow of CPAM solution, we can fabricate macroscopic sac membranes, or microfibers composed of well-aligned Fmoc-FF nanofibers at the interface between two solutions. Moreover, the structure of microfibers may be hollow or solid depending on the intensity of jet flow. The entrainment of the jet flow will enhance the mixing between Fmoc-FF and CPAM solutions, which can be utilized for the fast fabrication of well-defined Fmoc-FF/CPAM microfibers. These microfibers can encapsulate functional components facilely for controlled drug release. Moreover, functional components such as QDs can also be integrated into the self-assembling system to easily achieve additional functionalities. We believe that the organization of components at the aqueous liquid–liquid interface will have great potential for the discovery of highly ordered and functional materials with potential applications in areas such as controlled drug release, wound dressing, enzyme immobilization, biosensors and other non-biological applications.

A new approach based on solvent and surface effects was developed for controlling the self-assembly of diphenylalanine peptide into microtubes and nanofibers. The HBD/HBA ability and surface tension may be major determinants in the formation of these peptide assemblies. Our results will lead to a better understanding of the molecular mechanisms involved in diphenylalanine self-assembly process.

Here we report a novel peptide–polysaccharide hybrid hydrogel as a potential carrier for sustained delivery of hydrophobic drugs. The hybrid hydrogel composed of Fmoc-diphenylalanine (Fmoc-FF) peptide and konjac glucomannan (KGM) was prepared through molecular self-assembly of Fmoc-FF in the KGM solution. The physicchemical properties of the Fmoc-FF–KGM hybrid hydrogel were further evaluated. This hybrid hydrogel exhibited a highly hydrated, rigid and nanofibrous gel network in which self-assembled peptide nanofibers were interwoven with the KGM chains. The results of a stability test and rheology study showed that the hybrid hydrogel has much higher stability and mechanical strength compared to Fmoc-FF hydrogel alone. Both CD and FTIR analysis indicated an anti-parallel β-sheet arrangement of Fmoc-FF peptide in self-assembled nanofibers, regardless the presence of KGM. Moreover, docetaxel was chosen as a model of hydrophobic drugs and incorporated into hydrogels to study the in vitro release behavior. The sustained and controlled drug release from this hybrid hydrogel was achieved by varying the KGM concentration, molecular weight, aging time or β-mannanase concentration. Our results not only provide a new strategy for fabricating Fmoc-FF–KGM hybrid hydrogel as a sustained-release drug carrier but also open an avenue for the design of new self-assembling peptide–polysaccharide hybrid hydrogels.