Reversible Fusion-Fission MXene Fiber-Based Microelectrodes for Target-Specific Gram-Positive and Gram-Negative Bacterium Discrimination.

Inaccurate or cumbersome clinical pathogen diagnosis between Gram-positive bacteria (G+) and Gram-negative (G-) bacteria lead to delayed clinical therapeutic interventions. Microelectrode-based electrochemical sensors exhibit the significant advantages of rapid response and minimal sample consumption, but the loading capacity and discrimination precision are weak. Herein, we develop reversible fusion-fission MXene-based fiber microelectrodes for G+/G- bacteria analysis. During the fissuring process, the spatial utilization, loading capacity, sensitivity, and selectivity of microelectrodes were maximized, and polymyxin B and vancomycin were assembled for G+/G- identification. The surface-tension-driven reversible fusion facilitated its reusability. A deep learning model was further applied for the electrochemical impedance spectroscopy (EIS) identification in diverse ratio concentrations of G+ and G- of (1:100-100:1) with higher accuracy (>93%) and gave predictable detection results for unknown samples. Meanwhile, the as-proposed sensing platform reached higher sensitivity toward E. coli (24.3 CFU/mL) and S. aureus (37.2 CFU/mL) in 20 min. The as-proposed platform provides valuable insights for bacterium discrimination and quantification.

Spin-state Conversion by Asymmetrical Orbital Hybridization in Ni-doped Co3 O4 to Boost Singlet Oxygen Generation for Microbial Disinfection.

Singlet oxygen (1 O2 ) plays a significant role in environmental and biomedical disinfection fields. Electrocatalytic processes hold great potential for 1 O2 generation, but remain challenging. Herein, a facile Ni doping converted spin-state transition approach is reported for boosting 1 O2 production. Magnetic analysis and theoretical calculations reveal that Ni occupied at the octahedral site of Co3 O4 can effectively induce a low-to-high spin-state transition. The high-spin Ni-Co3 O4 generate appropriate binding strength and enhance electron transfer between the Co centers with oxygen intermediates, thereby improving the catalytic activity of Ni-Co3 O4 for effective generating 1 O2 . In neutral conditions, 1×106  CFU mL-1 Gram-negative ESBL-producing Escherichia coli (E. coli) could be inactivated by Ni-Co3 O4 system within 5 min. Further antibacterial mechanisms indicate that 1 O2 can lead to cell membrane damage and DNA degradation so as to irreversible cell death. Additionally, the developed Ni-Co3 O4 system can effectively inactivate bacteria from wastewater and bioaerosols. This work provides an effective strategy for designing high-spin electrocatalysis to boost 1 O2 generation for disinfection process.

Moisture-Enabled Electricity from Hygroscopic Materials: A New Type of Clean Energy.

Water utilization is accompanied with the development of human beings, whereas gaseous moisture is usually regarded as an underexploited resource. The advances of highly efficient hygroscopic materials endow atmospheric water harvesting as an intriguing solution to convert moisture into clean water. The discovery of hygroelectricity, which refers to the charge buildup at a material surface dependent on humidity, and the following moisture-enabled electric generation (MEG) realizes energy conversion and directly outputs electricity. Much progress has been made since then to optimize MEG performance, pushing forward the applications of MEG into a practical level. Herein, the evolvement and development of MEG are systematically summarized in a chronological order. The optimization strategies of MEG are discussed and comprehensively evaluated. Then, the latest applications of MEG are presented, including high-performance powering units and self-powered devices. In the end, a perspective on the future development of MEG is given for inspiring more researchers into this promising area.

Rapid and Sensitive Detection of Fungicide-Resistant Crop Fungal Pathogens Using an Isothermal Amplification Refractory Mutation System.

Fungicide abuse leads to the emergence of fungicide-resistant fungal pathogens, thus posing a threat to agriculture and food safety. Here, we developed an isothermal amplification refractory mutation system (termed iARMS) allowing us to resolve genetic mutations, enabling rapid, sensitive, and potentially field-applicable detection of fungicide-resistant crop fungal pathogens. iARMS yielded a limit of detection of 25 aM via a cascade signal amplification strategy of recombinase polymerase amplification (RPA) and Cas12a-mediated collateral cleavage at 37 °C within 40 min. Specificity for fungicide-resistant Puccinia striiformis (P. striiformis) detection was guaranteed by RPA primers and the flexible sequence of gRNA. The iARMS assay allowed us to detect as low as 0.1% cyp51-mutated P. striiformis that showed resistance to the demethylase inhibitor (DMI), which was 50 times more sensitive than the sequencing techniques. Thus, it is promising for the discovery of rare fungicide-resistant isolates. We applied iARMS to investigate the emergence of fungicide-resistant P. striiformis in western China and found that its proportion was over 50% in Qinghai, Sichuan, and Xinjiang Province. iARMS can serve as a molecular diagnostic tool for crop diseases and facilitate precision plant disease management.

Activity Regulating Strategies of Nanozymes for Biomedical Applications.

On accounts of the advantages of inherent high stability, ease of preparation and superior catalytic activities, nanozymes have attracted tremendous potential in diverse biomedical applications as alternatives to natural enzymes. Optimizing the activity of nanozymes is significant for widening and boosting the applications into practical level. As the research of the catalytic activity regulation strategies of nanozymes is boosting, it is essential to timely review, summarize, and analyze the advances in structure-activity relationships for further inspiring ingenious research into this prosperous area. Herein, the activity regulation methods of nanozymes in the recent 5 years are systematically summarized, including size and morphology, doping, vacancy, surface modification, and hybridization, followed by a discussion of the latest biomedical applications consisting of biosensing, antibacterial, and tumor therapy. Finally, the challenges and opportunities in this rapidly developing field is presented for inspiring more and more research into this infant yet promising area.

Photothermal Regulated Nanozyme of CuFeS2 Nanoparticles for Efficiently Promoting Wound Healing Infected by Multidrug Resistant Bacteria.

Peroxidase-mediated chemokinetic therapy (CDT) can effectively resist bacteria; however, factors such as the high dosage of drugs seriously limit the antibacterial effect. Herein, CuFeS2 nanoparticles (NPs) nanozyme antibacterial system with the photothermal effect and peroxidase-like catalytic activity are proposed as a combined antibacterial agent with biosafety, high-efficiency, and broad-spectrum antibacterial ability. In addition, the as-obtained CuFeS2 NPs with a low doses of Cu+ and Fe3+ can change the permeability of bacterial cell membranes and break the antioxidant balance by consuming intracellular glutathione (GSH), which results in more conducive ROS production. Meanwhile, the photothermal heating can regulate the CuFeS2 NPs close to their optimal reaction temperature (60 °C) to release more hydroxyl radical in low concentrations of H2O2 (100 µM). The proposed CuFeS2 NPs-based antibacterial system achieve more than 99% inactivation efficiency of methicillin-resistant Staphylococcus aureus (106 CFU mL-1 MRSA), hyperspectral bacteria ß-Escherichia coli (106 CFU mL-1 ESBL) and Pseudomonas aeruginosa (106 CFU mL-1 PA), even at low concentration (2 µg mL-1), which is superior to those of the conventional CuO NPs at 4 mg mL-1 reported in the literature. In vivo experiments further confirm that CuFeS2 NPs can effectively treat wounds infected by MRSA and promote the wound healing. This study demonstrates that excellent antibacterial ability and good biocompatibility make CuFeS2 NPs a potential anti-infection nanozyme with broad application prospects.

Oxygen-regulated carbon quantum dots as an efficient metal-free electrocatalyst for nitrogen reduction.

An electrocatalytic nitrogen reduction reaction under ambient conditions provides a wonderful blueprint for the conversion of nitrogen to ammonia. However, current research on ammonia synthesis is mainly focused on metal-based catalysts. It is still a great challenge to realize the effective activation of N2 on non-metallic catalysts. Herein, carbon quantum dots are reported to reduce dinitrogen to ammonia under ambient conditions. Benefiting from its numerous defect sites, this metal-free catalyst shows excellent catalytic performance in 0.1 M HCl with a faradaic efficiency of 17.59%. In addition, both experimental and theoretical results confirm that the catalytic performance of the catalyst can be improved by appropriately controlling the oxygen content of samples at different temperatures, and the utmost ammonia yield is 134.08 µg h-1 mg-1cat., which is almost three times higher than that of a reported metal-free material. The proposed oxygen regulation provides a new method to optimize the surface properties of metal-free catalysts for ammonia synthesis.

Electrochemistry in Carbon-based Quantum Dots.

Electrochemistry belongs to an important branch of chemistry that deals with the chemical changes produced by electricity and the production of electricity by chemical changes. Therefore, it can not only act a powerful tool for materials synthesis, but also offer an effective platform for sensing and catalysis. As extraordinary zero-dimensional materials, carbon-based quantum dots (CQDs) have been attracting tremendous attention due to their excellent properties such as good chemical stability, environmental friendliness, nontoxicity and abundant resources. Compared with the traditional methods for the preparation of CQDs, electrochemical (EC) methods offer advantages of simple instrumentation, mild reaction conditions, low cost and mass production. In return, CQDs could provide cost-effective, environmentally friendly, biocompatible, stable and easily-functionalizable probes, modifiers and catalysts for EC sensing. However, no specific review has been presented to systematically summarize both aspects until now. In this review, the EC preparation methods of CQDs are critically discussed focusing on CQDs. We further emphasize the applications of CQDs in EC sensors, electrocatalysis, biofuel cells and EC flexible devices. This review will further the experimental and theoretical understanding of the challenges and future prospective in this field, open new directions on exploring new advanced CQDs in EC to meet the high demands in diverse applications.

Ti3C2Tx MXene-derived TiO2/C-QDs as oxidase mimics for the efficient diagnosis of glutathione in human serum.

Nanozyme-based colorimetry was suggested to be a rapid method for biomarker (e.g. glutathione) detection, but this method suffers from lack of efficiency and low-toxicity nanozymes till now. Herein, quantum dots of TiO2 loaded on carbon (TiO2/C-QDs) oxidase-like nanozymes were prepared via a hydrothermal treatment of tiny and few-layered Ti3C2Tx MXene nanosheets, which possess abundant thermodynamic metastable Ti atoms on MXene margins as raw materials for the preparation of TiO2/C-QDs. The oxygen vacancy in TiO2 on the surface of the carbon matrix can facilitate O2 adsorption in the solution and generate reactive oxygen species (ROS), thereby quickly oxidizing 3,3',5,5'-tetramethylbenzidine (TMB) to its oxidized form (TMBox) in the absence of H2O2. After adding glutathione (GSH), TMBox was able to be restored to TMB, which resulted in a corresponding decrease in the UV-vis absorbance value at 652 nm. Furthermore, this assay possesses good selectivity, excellent specificity and high sensitivity (limit of detection: 0.2 µM), which made it possible to efficiently detect GSH in complex biological samples such as human serum.

A 3D-graphene fiber electrode embedded with nitrogen-rich-carbon-coated ZIF-67 for the ultrasensitive detection of adrenaline.

A novel nitrogen-rich-carbon-coated ZIF-67 embedded three-dimensional-graphene (ZIF-67/NC/3DG) fiber was fabricated via a facile one-pot electrodeposition self-assembly method, and used as a prominent electrode for the non-enzymatic detection of adrenaline (Ad). In this design, the prepared ZIF-67 adsorbs Ad through hydrogen bonding and electrostatic interaction, while polypyrrole functions as the precursor of the conductive NC that seamlessly connects ZIF-67 with the 3DG fiber electrode to ameliorate the poor conductivity of the ZIF-67 moiety and thus improve the sensitivity of the ZIF-67/NC/3DG fiber electrode for detecting Ad. The constructed fiber sensor shows a double linear response over the Ad concentration range of 0.06-95 µM with a high sensitivity of 44.6 mA mM-1 cm-2 and 95.0-5900 µM with a good sensitivity of 11.0 mA mM-1 cm-2, giving a low detection limit of 0.02 µM and excellent repeatability. The ZIF-67/NC/3DG fiber electrode was further successfully applied for the determination of Ad in a real sample of human serum, indicating that this fiber electrode is a promising miniaturized sensor for electrochemical analysis.

Ultra-small dispersed Cu x O nanoparticles on graphene fibers for miniaturized electrochemical sensor applications.

A graphene microfiber (GF) modified with ultrafine Cu x O nanoparticles (Cu x ONPs/GF) has been fabricated by direct annealing of electrodeposited nano-sized copper-based metal organic frameworks (HKUST-1) and used as an electrode for nonenzymatic H2O2 sensing. Benefiting from the unique microfiber architecture and synergetic effects, as well as strong coupling between components with many active sites and boosted electron transport, the Cu x ONPs/GF electrode shows prominent sensitivity, selectivity and long-term operational stability for the detection of H2O2. Further work successfully applied this Cu x ONPs/GF electrode to detection of H2O2 in real samples such as milk and human serum. These results indicate that the Cu x ONPs/GF is a promising mini-sized sensor in electrochemical analysis.

Intrinsic poorly-crystallized Fe5O7(OH)·4H2O: a highly efficient oxygen evolution reaction electrocatalyst under alkaline conditions.

As the bottleneck of electrochemical overall water splitting, the oxygen evolution reaction (OER) needs efficient catalysts to lower the required overpotential. Electrocatalysts with an amorphous form are highly active but suffer with low structural stability. Poorly crystallized materials with activity like amorphous forms, while maintaining the mechanical robustness of crystalline forms, are expected to be ideal materials. Towards this direction, we, for the first time, developed low-crystalline Fe5O7(OH)·4H2O as an excellent OER electrocatalyst with an overpotential of 269 mV, in order to drive a current density of 100 mA cm-2 in a 1.0 M KOH environment, and this outperforms most of the reported Fe-based electrocatalysts. Notably, its activity can be maintained for at least 100 hours. A one-pot synthesis for the poorly-crystallized material using one of the most abundant metal elements to obtain effective OER catalysis will provide great convenience in practical applications.

Electric Power Generation through the Direct Interaction of Pristine Graphene-Oxide with Water Molecules.

Converting ubiquitous environmental energy into electric power holds tremendous social and financial interests. Traditional energy harvesters and converters are limited by the specific materials and complex configuration of devices. Herein, it is presented that electric power can be directly produced from pristine graphene oxide (GO) without any pretreatment or additives once encountering the water vapor, which will generate an open-circuit-voltage of up to 0.4-0.7 V and a short-circuit-current-density of 2-25 µA cm-2 on a single piece of GO film. This phenomenon results from the directional movement of charged hydrogen ions through the GO film. The present work demonstrates and provides an extremely simple method for electric energy generation, which offers more applications of graphene-based materials in green energy converting field.

Dimensional confinement of graphene in a polypyrrole microbowl for sensor applications.

A polypyrrole microbowl with dimensionally confined graphene is fabricated through electrochemical polymerization of pyrrole with a gas bubble template and reduction of graphene oxide in situ. The unique assembly of graphene within the polypyrrole microbowl presents much enhanced sensor performance, which will be attractive as a micro detection system, in which only a few microliter sample solution is needed.

Direct spinning of fiber supercapacitor.

A direct wet spinning approach is demonstrated for facile and continuous fabrication of a whole fiber supercapacitor using a microfluidic spinneret. The resulting fiber supercapacitor shows good electrochemical properties and possesses high flexibility and mechanical stability. This strategy paves the way for large-scale continuous production of fiber supercapacitors for weavable electronics.