Nanozymes, defined as nanomaterials with enzyme-like activity, have attracted extensive interest in both fundamental and applied research. Laccases are members of the multi-copper oxidases, which are utilized as green catalysts in the environmental catalysis and biochemical industry. In this paper, we report a facile strategy for the preparation of a new class of nanozyme (denoted as CH-Cu) with laccase-like activity inspired by the structure of the active site and the electron transfer pathway of laccase via the coordination of Cu+/Cu2+ with a cysteine (Cys)-histidine (His) dipeptide. The CH-Cu nanozymes exhibit excellent catalytic activity, recyclability and substrate universality and have a similar Km (Michaelis constant) and a higher vmax (maximum rate) than laccase at the same mass concentration. They are robust under a variety of conditions, such as extreme pH, high temperature, long-term storage and high salinity, which can cause severe loss in the catalytic activity of laccase. Higher efficacy of the CH-Cu nanozymes compared with laccase in the degradation of chlorophenols and bisphenols is also demonstrated in a batch reaction. Furthermore, a method for the quantitative detection of epinephrine by a smart phone is established based on the CH-Cu nanozymes. We believe that this nanozyme has promising applications in environmental catalysis and rapid detection and expect that combining key peptides as metal ligands with metal ions to mimic the structure of the catalytic center of a natural enzyme will be a general and important strategy for the design and synthesis of a new type of nanozyme that can be used in various applications.

Construction of a bioinspired laccase-mimicking nanozyme for the degradation and detection of phenolic pollutants

Immobilization of laccase on hollow mesoporous carbon nanospheres: Noteworthy immobilization, excellent stability and efficacious for antibiotic contaminants removal.

Tunable gating graphene oxide (GO) membranes with high water permeance and precise molecular separation remain highly desired in smart nanofiltration devices. Herein, bioinspired by the filtration function of the renal glomerulus, we report a smart and high-performance graphene oxide membrane constructed via introducing positively charged polyethylenimine-grafted GO (GO-PEI) to negatively charged GO nanosheets. It was found that the additional GO-PEI component changed the surface charge, improved the hydrophilicity, and enlarged the nanochannels. The glomerulus-inspired graphene oxide membrane (G-GOM) shows a water permeance up to 88.57 L m-2 h-1 bar-1, corresponding to a 4 times enhancement compared with that of a conventional GO membrane due to the enlarged confined nanochannels. Meanwhile, owing to the electrostatic interaction, it can selectively remove positively charged methylene blue at pH 12 and negatively charged methyl orange at pH 2, with a removal rate of over 96%. The high and cyclic water permeance and highly selective organic removal performance can be attributed to the synergic effect of controlled nanochannel size and tunable electrostatic interaction in responding to the environmental pH. This strategy provides insight into designing pH-responsive gating membranes with tunable selectivity, representing a great advancement in smart nanofiltration with a wide range of applications.

Bioinspired Graphene Oxide Membranes with pH-Responsive Nanochannels for High-Performance Nanofiltration.

Organic light‐emitting diodes (OLEDs) are the most successful product of organic electronics in the market and continually receive attention from scientific and industrial communities. Imidazoles have been extensively investigated for OLED applications, and demonstrated their versatility in molecular design for different functions. This review presents a summary of recent studies on imidazole (including imidazole derived moieties) derivatives, with special focus on discussing various molecular design tactics, for applications as electron‐transporting materials, emitters, and host materials in OLEDs. At last, perspectives and challenges regarding to imidazole semiconductors for electroluminescence applications are also discussed.

Organic Light-Emitting Diodes Based on Imidazole Semiconductors

Improving laccase activity and stability by HKUST-1 with cofactor via one-pot encapsulation and its application for degradation of bisphenol A.

Functionalized membranes provide versatile platforms for the incorporation of biocatalysts and nanostructured materials for efficient and benign environmental remediation. The existing techniques for remediating chloro-organics in water consist of both physical and chemical means mostly using metal oxide-based catalysts, despite associated environmental concerns. To offer bioinspired remediation as an alternative, we herein demonstrate a layer-by-layer approach to immobilize laccase enzyme onto pH-responsive functionalized membranes for the degradation of chloro-organics in water. The efficacy of these bioinspired membranes toward dechlorination of 2,4,6-trichlorophenol (TCP) is demonstrated under a pressure-driven continuous flow mode (convective flow) for the first time to the best of our knowledge. Over 80% of the initial TCP was degraded at an optimum flow rate under an applied air pressure of about 0.7 bar or lower. This corresponds to degradation of a substantial amount of the initial substrate in only 36 s residence time, whereas it takes hours for degradation in a batch reaction. This, in fact, demonstrates an energy efficient flow-through system with potentially large-scale applications. Comparison of the stability of the enzyme in the solution phase versus immobilized on the membrane phase showed a loss of some 65% of enzyme activity in the solution phase after 22 d, whereas the membrane-bound enzyme lost only a negligible percentage of the activity in a comparable time span. Finally, the membrane was exposed to rigorous cycles of TCP degradation trials to study its reusability. The primary results reveal a loss of only 14% of the initial activity after 4 cycles of use in a period of 25 d, demonstrating its potential to be reused. Regeneration of the functionalized membrane was also validated by dislodging the immobilized enzyme, followed by immobilization of fresh enzyme onto the membrane.

/pdf/layer-by-layer-assembled-laccase-enzyme-on-stimuli-2df4bq6mqs.pdf

Layer-by-Layer-Assembled Laccase Enzyme on Stimuli-Responsive Membranes for Chloro-Organics Degradation

Role of membrane pore polymerization conditions for pH responsive behavior, catalytic metal nanoparticle synthesis, and PCB degradation.

Pore functionalized membranes with appropriate ion exchange/chelate groups allow toxic metal sorption under convective flow conditions. This study explores the sorption capacity of ionic mercury in a polyvinylidene fluoride-poly(acrylic acid) (PVDFs-PAA) functionalized membrane immobilized with cysteamine (MEA). Two methods of MEA immobilization to the PVDF-PAA membrane have been assessed: (i) ion exchange (IE) and (ii) carbodiimide cross-linker chemistry using 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS), known as EDC/NHS coupling. The ion exchange method demonstrates that cysteamine (MEA) can be immobilized effectively on PVDF-PAA membranes without covalent attachment. The effectiveness of the MEA immobilized membranes to remove ionic mercury from the water was evaluated by passing a dissolved mercury(II) nitrate solution through the membranes. The sorption capacity of mercury for MEA immobilized membrane prepared by the IE method is 1015 mg/g PAA. On the other hand, the sorption capacity of mercury for MEA immobilized membrane prepared by EDC/NHS chemistry is 2446 mg/g PAA, indicating that membrane functionalization by EDC/NHS coupling enhanced mercury sorption 2.4 times compared to the IE method. The efficiencies of Hg removal are 94.1 ± 1.1 and 99.1 ± 0.1% for the MEA immobilized membranes prepared by IE and EDC/NHS coupling methods, respectively. These results show potential applications of MEA immobilized PVDF-PAA membranes for industrial wastewater treatment specifically from energy and mining industries to remove mercury and other toxic metals.

Thiol-Functionalized Membranes for Mercury Capture from Water.

We have developed an integrated, multienzyme functionalized membrane reactor for bioconversion of a lignin model compound involving enzymatic catalysis. The membrane bioreactors were fabricated through the layer-by-layer assembly approach to immobilize three different enzymes (glucose oxidase, peroxidase and laccase) into pH-responsive membranes. This novel membrane reactor couples the in situ generation of hydrogen peroxide (by glucose oxidase) to oxidative conversion of a lignin model compound, guaiacylglycerol-β-guaiacyl ether (GGE). Preliminary investigation of the efficacy of these functional membranes towards GGE degradation is demonstrated under convective flow mode. Over 90% of the initial feed could be degraded with the multienzyme immobilized membranes at a residence time of approximately 22 s. GGE conversion product analysis revealed the formation of oligomeric oxidation products upon reaction with peroxidase, which may be a potential hazard to membrane bioreactors. These oxidation products could further be degraded by laccase enzymes in the multienzymatic membranes, explaining the potential of multi enzyme membrane reactors. The multienzyme incorporated membrane reactors were active for more than 30 days of storage time at 4 °C. During this time span, repetitive use of the membrane reactor was demonstrated involving 5–6 h of operation time for each cycle. The membrane reactor displayed encouraging performance, losing only 12% of its initial activity after multiple cycles of operation.

/pdf/multienzyme-immobilized-polymeric-membrane-reactor-for-the-2eis45mvny.pdf

Multienzyme Immobilized Polymeric Membrane Reactor for the Transformation of a Lignin Model Compound

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Layer-by-Layer-Assembled Laccase Enzyme on Stimuli-Responsive Membranes for Chloro-Organics Degradation

Role of membrane pore polymerization conditions for pH responsive behavior, catalytic metal nanoparticle synthesis, and PCB degradation.

Thiol-Functionalized Membranes for Mercury Capture from Water.

Multienzyme Immobilized Polymeric Membrane Reactor for the Transformation of a Lignin Model Compound