MXene-Ti3C2, as a new class of two-dimensional (2D) transition metal carbides (or nitrides), has been synthesized by exfoliating pristine Ti3AlC2 phases with hydrofluoric acid. The SEM and XRD images ...show that the resultant MXene possesses a graphene-like 2D nanostructure. and the surface of MXene has been partially terminated with -OH, thus providing a favorable microenvironment for enzyme immobilization and retaining their bioactivity and stability. Considering the unique metallic conductivity, biocompatibility and good dispersion in aqueous phase, the as-prepared MXene was explored as a new matrix to immobilize tyrosinase (a model enzyme) for fabricating a mediator-free biosensor for ultrasensitive and rapid detection of phenol. The varying electrochemical measurements were used to investigate the electrochemical performance of MXene-based tyrosinase biosensors. The results revealed that the direct electron transfer between tyrosinase and electrode could be easily achieved via a surface-controlled electrochemical process. The fabricated MXene-based tyrosinase biosensors exhibited good analytical performance over a wide linear range from 0.05 to 15.5 μmol L−1, with a low detection limit of 12 nmol L−1 and a sensitivity of 414.4 mA M−1. The proposed biosensing approach also demonstrated good repeatability, reproducibility, long-term stability and high recovery for phenol detection in real water samples. With those excellent performances, MXene with graphene-like structure is proved to be a robust and versatile electrochemical biosensing platform for enzyme-based biosensors and biocatalysis, and has wide potential applications in biomedical detection and environmental analysis.
•Graphene-like MXene-Ti3C2 was prepared by exfoliating pristine Ti3AlC2 with HF.•MXene-Ti3C2 possesses unique metallic conductivity, biocompatibility and good dispersion in aqueous phase.•MXene was explored as a new biosensing platform for tyrosinase immobilization and phenol detection.•The nanostructure and surface -OH provide favorable microenvironments for retaining enzyme bioactivity and stability.•The MXene-Ti3C2 based biosensor exhibited excellent analytical performances.
A novel synergistic TiO2‐MoO3 (TO‐MO) core–shell nanowire array anode has been fabricated via a facile hydrothermal method followed by a subsequent controllable electrodeposition process. The ...nano‐MoO3 shell provides large specific capacity as well as good electrical conductivity for fast charge transfer, while the highly electrochemically stable TiO2 nanowire core (negligible volume change during Li insertion/desertion) remedies the cycling instability of MoO3 shell and its array further provides a 3D scaffold for large amount electrodeposition of MoO3. In combination of the unique electrochemical attributes of nanostructure arrays, the optimized TO‐MO hybrid anode (mass ratio: ca. 1:1) simultaneously exhibits high gravimetric capacity (ca. 670 mAh g−1; approaching the hybrid's theoretical value), excellent cyclability (>200 cycles) and good rate capability (up to 2000 mA g−1). The areal capacity is also as high as 3.986 mAh cm−2, comparable to that of typical commercial LIBs. Furthermore, the hybrid anode was assembled for the first time with commercial LiCoO2 cathode into a Li ion full cell, which shows outstanding performance with maximum power density of 1086 W kgtotal
−1 (based on the total mass of the TO‐MO and LiCoO2) and excellent energy density (285 Wh kgtotal
−1) that is higher than many previously reported metal oxide anode‐based Li full cells.
Synergistic TiO2‐MoO3 core–shell nanowire array anode is developed, showing high capacity (ca. 670 mAh g−1; 3.986 mAh cm−2), excellent cycleability (>200 times), and good rate performance. Ultrahigh energy density (285 Wh kgtotal −1) and power density (1086 W kgtotal −1) are further achieved for a full cell LIB device assembled using the TiO2‐MoO3 hybrid array as anode and commercial LiCoO2 film as cathode.
Gold nanoparticles (AuNP) dotted reduction graphene oxide (RGO-AuNP) is used as a platform for an aptamer biosensor to selectively detect 3,3'4,4'-polychlorinated biphenyls (PCB77). By anchoring ...aptamers onto the binding sites of RGO-AuNP and making use of the synergy effect of RGO and AuNP, the RGO-AuNP based biosensor exhibits superior analytical performances to AuNP based biosensor in terms of sensitivity and repeatability. The sensitivity of RGO-AuNP based aptamers (RGO-AuNP-Ap) biosensor (226.8 μA cm
) is nearly two times higher than that of Au based biosensors (AuNP-Ap/Au electrode, 147.2 μA cm
). The RGO-AuNP-Ap/Au biosensor demonstrated a linear response for PCB77 concentrations between 1 pg L
and 10 μg L
, with a low limit of detection (LOD) of 0.1 pg L
. The superb LOD satisfies the exposure thresholds (uncontaminated water < 0.1 ng L
) set out by International Agency for Research on Cancer (IARC) and the Environmental Protection Agency (EPA). The proposed biosensor can be a powerful tool for rapid, sensitive and selective detection of PCBs on site.
Wire‐shaped asymmetric pseudocapacitors with both pseudocapacitive cathode and anode are promising in facilitating device assembly and provide highly efficient power sources for wearable electronics. ...However, it is a great challenge to simultaneously obtain high energy and power as well as ultralong cycling life for practical demands of such devices. Herein, a device design with new cathode/anode coupling is proposed to achieve excellent comprehensive performance in a wire‐type quasi‐solid‐state asymmetric pseudocapacitor (WQAP). The hierarchical α‐MnO2 nanorod@δ‐MnO2 nanosheet array cathode and MoO2@C nanofilm anode are directly grown on flexible tiny Ti wires by well‐established hydrothermal and electrodeposition techniques, which ensures rapid charge/mass transport kinetics and the sufficient utilization of pseudocapacitance. The nanoarray/film electrode also facilitates integration with gel electrolyte of polyvinyl alcohol–LiCl, guaranteeing the durability. The resulting WQAP with 2.0 V voltage delivers high volumetric energy and power densities (9.53 mWh cm−3 and 22720 mW cm−3, respectively) as well as outstanding cycling stability over 100 000 times, surpassing all the previously reported WQAPs. In addition, the device can be facilely connected in parallel or in series with minimal internal resistance, and be fabricated at the 1 m scale with excellent flexibility. This work opens the way to develop high‐performance integrated wire supercapacitors.
A wire‐type quasi‐solid‐state asymmetric pseudocapacitor based on hierarchical biphase core–shell nano‐MnO2 array cathode and MoO2@C nanofilm anode is developed, which demonstrates high volumetric energy and power densities as well as ultralong cycling life of 100 000 times. The device can also be easily scaled up to 1 m, designed in parallel or in series, and power small electronics efficiently.
Extensive spatiotemporal analyses of long-trend surface ozone in the Yangtze River Delta (YRD) region and its meteorology-related and emission-related have not been systematically analyzed. In this ...study, by using 8-year-long (2015–2022) surface ozone observation data, we attempted to reveal the variation of multiple timescale components using the Kolmogorov–Zurbenko filter, and the effects of meteorology and emissions were quantitatively isolated using multiple linear regression with meteorological variables. The results showed that the short-term, seasonal, and long-term components accounted for daily maximum 8-hr average O3 (O3–8 hr) concentration, 46.4%, 45.9%, and 1.0%, respectively. The meteorological impacts account for an average of 71.8% of O3–8 hr, and the YRD's eastern and northern sections are meteorology-sensitive areas. Based on statistical analysis technology with empirical orthogonal function, the contribution of meteorology, local emission, and transport in the long-term component of O3–8 hr were 0.21%, 0.12%, and 0.6%, respectively. The spatiotemporal analysis indicated that a distinct decreasing spatial pattern could be observed from coastal cities towards the northwest, influenced by the monsoon and synoptic conditions. The central urban agglomeration north and south of the YRD was particularly susceptible to local pollution. Among the cities studied, Shanghai, Anqing, and Xuancheng, located at similar latitudes, were significantly impacted by atmospheric transmission—the contribution of Shanghai, the maximum accounting for 3.6%.
Owing to its unique chemical structure, natural pores, high structure defects, good surface hydrophilicity and biocompatibility, and favorable electrical conductivity, nitrogen-doped graphdiyne ...(NGDY) has been attracting attention in the application of electrochemical sensing. Taking advantage of these fascinating electrochemical properties, for the first time, two types of electrochemical enzymatic biosensors were fabricated for the respective detection of organophosphorus pesticides (OPs) and phenols based on the immobilization of acetylcholinesterase or tyrosinase with NGDY. Results revealed that the sensitivities of the NGDY-based enzymatic biosensors were almost twice higher than that of the matching biosensor in the absence of NGDY, proving that NGDY plays a vital role in immobilizing the enzymes and improving the performance of the fabricated biosensors. The effects of nitrogen doping on improving the biosensing performance were studied in depth. Graphitic N atoms can enhance the electrical conductivity, while imine N and pyridinic N can help to adsorb and accumulate the substance molecules to the electrode surface, all of which contribute to the significantly improved performance. Furthermore, these two types of biosensors also demonstrated excellent reproducibility, high stability, and good recovery rate in real environmental samples, which showed a valuable way for the rapid detection of OPs and phenols in the environment. With these excellent performances, it is strongly anticipated that NGDY has tremendous potential to be applied to many other biomedical and environmental fields.
The present study demonstrates the use of highly stable single-molecule enzyme nanocapsules (SMENs) instead of traditional native enzyme as biorecognition element in enzyme-based biosensors. The main ...purpose of this study is to resolve the major obstacle and challenge in the biosensor field, i.e., the poor stability of enzyme-based biosensors, including thermal stability, organic solvent tolerance, long-term operational stability, etc. Highly active and robust SMENs of glucose oxidase (GOx, as a model enzyme) were synthesized (nGOx) using an in situ polymerization strategy in an aqueous environment. The particle-size distribution, transmission electron microscopic (TEM) images, and UV–vis spectral characterization revealed the formation of a thin polymer layer around each enzyme molecule. The polymer shell effectively stabilized the GOx enzyme core while enabling rapid substrate transportation, resulting in a new class of biocatalytic nanocapsules. Multiple covalent attachments between a thin polymer layer and an enzyme molecule strengthened the encapsulated GOx molecule. Encapsulation created a favorable microenvironment to avoid any structural dissociation at high temperature and helped to retain essential water during the organic solvent operation. The present work reports a study implementing nGOx SMENs as highly stable nano(bio)sensors for point-of-care diagnostic applications. Prepared nGOx SMENs manifested significantly improved thermal stability (even at 65 °C) and organic solvent tolerance without any compromise in biocatalytic activity. For example, the native GOx-based biosensor lost its catalytic activity for glucose after 4 h of incubation at high temperature (65 °C), while the nGOx/N-CNTs-Chi/GCE nano(bio)sensor maintained ∼56% of its original catalytic activity for glucose oxidation. The proposed SMENs-based nano(bio)sensors with robust stability in variable working environment could promote the development and applications of biosensors in point-of care diagnostics, biomedical detection, wearable devices, implantable equipment, and biofuel cells.
Graphdiyne (GDY), a new two-dimensional all-carbon allotrope composed of benzene rings and alkyne unites, was successfully synthesized via a crossing-coupling reaction with much intriguing properties ...especially highly π-conjugated structure, attractive electronic and chemical properties, good biocompatibility and dispersion in aqueous solution. The as-prepared graphdiyne was explored for the first time as an extremely attractive matrix for tyrosinase (a model enzyme) immobilization to construct a mediator-free GDY-based biosensor for rapid detection of bisphenol A (BPA). The response of GDY-based tyrosinase biosensor is linear over the range of 1.0 × 10−7 to 3.5 × 10−6 mol L−1 with a high sensitivity of 2990.8 mA cm−2 M−1 and a low detection limit of 24 nmol L−1. The proposed GDY-based tyrosinase biosensor exhibited better analytical performances for BPA detection than CNTs and graphene based biosensors. The excellent performance of the biosensor should partially be ascribed to the strong π-π interactions between graphdiyne and BPA, which could enrich available BPA concentration on the electrode to react with tyrosinase. The robust GDY-based tyrosinase biosensor was used for BPA detection in drinking bottles and tap water with satisfactory results. As a new 2D all-carbon nanomaterial, graphdiyne is proved to be a powerful electrochemical enzyme biosensor platform for biomolecules (as recognition elements) immobilization and biosensor fabrication, and provides great application prospect for biomedical detection and environmental analyses.
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Flexible solid-state symmetric supercapacitor was fabricated using MnO2 nanofilms growing directly on carbon cloth as the electrodes and PVA/H3PO4 gel as the electrolyte/separator. The device can be ...operated at a stable cell-voltage up to 1.4 V, obviously larger than that of conventional solid-state symmetric supercapacitors (≤1 V). It exhibited excellent rate capability with a scan rate as high as 20 V s−1 and a long cyclability (∼60000 cycles) even under severe mechanical deformation. The charge storage mechanism at different scan rates was also quantitatively analyzed.
Bisphenol A (BPA), one of the most important endocrine disrupting chemicals, is a threat to human and wildlife health. Electrochemical enzyme biosensor has been regarded as ideal alternative ...analytical technique for ultrasensitive and rapid detection of BPA, while the unstable and easily deactivated nature of enzyme limits its development. In order to improve the stability of enzyme, tyrosinase was chosen as a model enzyme, and tyrosinase nanocapsules (nTyr) were prepared by encapsulating a single tyrosinase molecule into a thin network polymer shell through in-situ polymerization method in aqueous solution. The characterization of particle size distribution, TEM and FTIR indicated the successful formation of single tyrosinase molecule nanocapsule. And the porous network polymer shell of nTyr ensured the maintenance of tyrosinase activity and fast substrate transportation. The obtained nTyr was used to construct an electrochemical biosensor for BPA detection, exhibiting a low detection limit of 12 nmol L-1 and a wide linear range from 5 × 10-8 to 2 × 10-6 mol L-1. Compared with native tyrosinase, the nTyr based biosensor displayed dramatically enhanced stability including thermal stability, organic solvent tolerance and acid/base tolerance. The excellent performance of nTyr based biosensor was not only attributed to the protection of biocompatible rigid polymer shells, but also the multipoint covalent attachments between tyrosinase cores and polymer shells. The robust biosensor was further used for rapid detection of BPA leached from plastic products with satisfactory results. The nTyr based nano-biosensor provides a prospective solution to resolve the stability problem of enzyme biosensors in different application scenarios.
•Robust single molecule enzyme nanocapsules of Tyrosinase (nTyr) were firstly synthesized.•Polymer shell effectively stabilized the interior tyrosinase core while enabling rapid substrate transportation.•A new class of highly stable nTyr based biosensors was constructed for detecting BPA in different application scenarios.•The nTyr based biosensor displayed significantly enhanced stability in extreme operational conditions.•The nTyr based biosensor provides a prospective solution to resolve the stability problem of enzyme biosensors.
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