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The development of electrochemiluminescent (ECL) emitters with both intense ECL and excellent film-forming properties is highly desirable for biosensing applications. Herein, a facile one-pot preparation strategy was proposed for the synthesis of a self-enhanced ECL emitter by co-doping Ru(bpy)32+ and (diethylaminomethyl)triethoxysilane (DEAMTES) into an in situ-produced silica nanohybrid (DEAMTES@RuSiO2). DEAMTES@RuSiO2 not only possessed improved ECL properties but also exhibited outstanding film-forming ability, which are both critical for the construction of ECL biosensors. By coupling branched catalytic hairpin assembly with efficient signal amplification peculiarity, a label-free ECL biosensor was further constructed for the convenient and highly sensitive detection of miRNA-21. The as-fabricated ECL biosensor displayed a detection limit of 8.19 fM, much lower than those in previous reports for miRNA-21 and showed superior reliability for detecting miRNA-21-spiked human serum sample, demonstrating its potential for applications in miRNA-associated fundamental research and clinical diagnosis.

Opposed rotary piston (ORP) engines have high power density and compact designs which meet the requirements of power sources of hybrid vehicles. Hydrogen applications to ORP engines can effectively decrease greenhouse gas emissions; however, hydrogen combustion in ORP engines around stoichiometric ratio generated large quantities of nitrogen oxides (NOx), especially for low engine speed conditions. Lean-burn as an effective method to decrease NOx emissions was adopted in this research. A 3D numerical simulation method was used to explore the effect of equivalence ratio (≤1) on combustion and NOx emission characteristics of this ORP engine fuelled with hydrogen. The results indicated that peak in-cylinder pressure increased with equivalence ratio for 1000 revolutions per minute (RPM); however, the value over the equivalence ratio of 0.9 was the maximum among 2000 RPM scenarios. The effect of equivalence ratio on heat release rates was greatly dependent on the engine speeds. Start of combustion over 1000 RPM engine speed was advanced with the increase of equivalence ratio; and it was the earliest over the equivalence ratio of 0.9 at 2000 RPM conditions. During the exhaust stroke, in-cylinder pressure of free discharge was much higher than atmosphere pressure, which significantly increased the pumping losses of exhaust stroke. Accumulated NOx emissions over the equivalence ratio of 0.9 reached the maximum value for given engine speeds; and the NOx emissions were almost zero for severe lean-burn (

Metal doping is a common strategy for the regulation of the structure of carbon nitride materials at the molecular level. A wide range of intriguing applications of metal-doped carbon nitride (M–CN) materials have recently been investigated from the mainstream of photocatalysis to other emerging fields, including electrocatalysis, organic synthesis, biosensors, and nanozymes. From a fundamental point of view, M–CN is an essential branch of carbon nitride materials and opens a new avenue for the preparation of single-atom catalysts and even endows the materials with new exciting properties. In particular, M–Nx structures as active sites in numerous M–CN materials have been widely demonstrated using both experiments and theoretical calculations. This review summarizes the state-of-the-art preparation methods, characterization techniques, and diverse applications of M–CN. Finally, future perspectives on the fabrication and application prospects of M–CN materials are discussed.

Covalently bonded carbon nitride (CN) has stimulated extensive attention as a metal-free semiconductor. However, because of the complexity of polymeric structures, the acquisition of critical roles of each molecular constituent in CN for photocatalysis remains elusive. Herein, we clarify the fundamental active units of CN in photocatalysis by synthesizing CN with more detailed molecular structures. Enabled by microwave synthesis, the as-prepared CN consists of distinguishable melem (M1) and its incomplete condensed form (M2). We disclose rather than the traditional opinion of being involved in the whole photocatalytic processes, M1 and M2 make primary contributions in light absorption and charge separation, respectively. Meanwhile, oxygen molecules are unusually observed to be activated by participating in the photoexcited processes via electronic coupling mainly to M2. As a result, such CN has a higher activity, which was up to 8 times that of traditional bulk CN for photocatalytic oxidation of tetracycline in water., The acquisition of critical roles of each molecular constituent in carbon nitrides for photocatalysis remains elusive. Here the authors synthesize carbon nitrides with distinguishable units and reveal the roles of the different units in light absorption and charge separation.

As a class of metal-free two-dimensional (2D) semiconductor materials, polymeric carbon nitrides have attracted wide attention recently due to its facile regulation of the molecular and electronic structures, availability in abundance and high stability. According to the different ratios of C and N atoms in the framework, a series of CxNy materials have been successfully synthesized by virtue of various precursors, which further triggers extensive investigations of broad applications ranging from sustainable photocatalytic reactions and highly sensitive optoelectronic biosensing. In view of topological structures on their electronic structures and material properties, the as-reported CxNy could be generally classified into two main categories with three- or six-bond-extending frameworks. Owing to the effective n→π* transition in most CxNy materials, the relative energy level of the lone-pair electrons on N atoms is high, which thus endows the materials with the capability of visible light absorption. Meanwhile, the different repeating units, bridging groups and defect sites of these two kinds of CxNy allow them to effectively drive a diverse of promising applications that require specific electronic, interfacial and geometric properties. This review paper aims to summarize the recent progress in topological structure design and the relevant electronic band structures and striking properties of CxNy materials. In the final part, we also discuss the existing challenges of CxNy and outlook the prospect possibilities.

The exceptional nature of WO3-x dots has inspired widespread interest, but it is still a significant challenge to synthesize high-quality WO3-x dots without using unstable reactants, expensive equipment, and complex synthetic processes. Herein, the synthesis of ligand-free WO3-x dots is reported that are highly dispersible and rich in oxygen vacancies by a simple but straightforward exfoliation of bulk WS2 and a mild follow-up chemical conversion. Surprisingly, the WO3-x dots emerged as co-reactants for the electrochemiluminescence (ECL) of Ru(bpy)3 2+ with a comparable ECL efficiency to the well-known Ru(bpy)3 2+ /tripropylamine (TPrA) system. Moreover, compared to TPrA, whose toxicity remains a critical issue of concern, the WO3-x dots were ca. 300-fold less toxic. The potency of WO3-x dots was further explored in the detection of circulating tumor cells (CTCs) with the most competitive limit of detection so far.

As an emerging 2D conjugated material, graphitic carbon nitride (CN) has attracted great research attention as important catalytic medium for transforming solar energy. Nanostructure modulation of CN is an effective way to improve catalytic activities and has been extensively investigated, but remains challenging due to complex processes, time consuming or low yield. Here, taking advantage of recent discovered good solvents for CN, a nanoprecipitation approach using poor solvents is proposed for preparation of CN nanoparticles (CN NPs). With simple processes of CN dissolution and precipitation, we can quickly synthesize CN NPs (˜40 nm) with a yield of up to 50%, the highest one to the best of our knowledge. As an example of potential applications, the as-prepared CN NPs were applied to photocatalytic degradation of dyes with an evident boosted performance up to 2.5 times. This work would open a new way for batch preparation of nanostructured CN and pave its large-scale industrial applications.

Recovery of β-carotene from n-hexane solution onto Zr-based metal organic frameworks (UiO-66)/graphene nanoplatelets (GPNPs) has been investigated. The nanocomposite has been characterized by X-ray...

Polymeric carbon nitride (CN) semiconductor by thermal condensation of N-rich precursors has attracted much attention for its capability ranging from photocatalytic and photoelectrochemical energy conversion to biosensing. However, the influence of condensation process on the final structure of CN was rarely studied, making the condensation kinetic far from be fully optimized. Herein, we report the preparation of CN by a simple condensation kinetics modulation using a faster ramping rate during the polymerization process. The modified condensation recipe was even simpler than the conventional one, but led to an improved photocatalytic H2 evolution up to 3 times without any additional chemicals or other complements. Detailed mechanism studies revealed the increase of crystallinity and surface area due to the rapid condensation played the key roles. This work would offer a more facile and effective way to prepare bulk CN for large-scale industrial applications of bulk CN with higher photocatalytic actives for sustainable energy, environmental and biosensing.

In this work, a dual catalyst composed of atomically ordered intermetallic PdZn and Co nanoparticles was synthesized and chemically bonded to nitrogen-doped carbon by simultaneously modulating the lattice spacing of the Pd nanoparticle guest and the metal centers of the zeolite imidazolate framework (ZIF) host through a one-step heating procedure. Results reveal that the ability of the PdZn alloy to catalyze the oxygen reduction reaction can be regulated by adjusting the lattice spacing of Pd–Pd through the formation of the ordered PdZn, resulting from Zn2+ in the ZIF-8 host lattice diffusing into the Pd phase. Meanwhile, the secondary active sites (Co nanoparticles) and N-doped carbon (particularly N-doped carbon nanotubes) carrier are obtained by doping Co2+ into the ZIF-8 host lattice, which can further improve the catalytic activity. The characterization results show the existence of Pd–N and Co–N bonds between the dual catalyst and the carrier, which can be regulated by controlling the synthesis conditions, such as the atomic ratios of the Pd guest to Zn in the ZIF-8 host, pyrolysis temperatures, and doping Co2+ into the ZIF-8 host lattice. The dual catalyst bonded to N-doped carbon exhibits high ORR catalytic activity with a desirable onset potential (0.916 V), and diffusion-limiting current density (∼5.70 mA cm−2), superior to other reported Pd-based catalysts and comparable to commercial Pt/C. Moreover, the chemical bonds between the dual catalyst and the carrier result in the dual catalyst with a small size of 5.9 nm and prolonged duration of electrochemical activity (no obvious change of the half peak potential after 10 000 cyclic voltammetry cycles and 90.6% current retention after a 4 h chronoamperometric test). Thus, the highly dispersed ordered-PdZn/Co on N-doped carbon is a promising substitute to commercial Pt/C for alkaline fuel cells.

NAD(P)H: Quinone Oxidoreductase 1 (hNQO1) is a cytosolic flavin two-electron reductase involved in many physiological and pathological processes that is overexpressed in many cancers and recognized as a potential cancer biomarker. However, it is still challenging for highly sensitive and selective monitoring hNQO1 in living cells. Here, we developed a highly selective and ultrasensitive hemicyanine-based near-infrared (NIR) fluorescence probe (probe HCYSN) for the sensing of hNQO1 activity and discrimination of human cancer cells. The fluorescent sensing system with NIR emission is low phototoxic to normal cells but is highly selective and ultrasensitive to hNQO1 in a linear range from 0.03 μg/mL to 0.6 μg/mL with detection limit (LOD) of 4.9 ng/mL (0.49 mU/mL), which is better than most of other hNQO1 probes reported. In particular, the NIR fluorescent probe was successfully applied to distinguish various cancer cells through the different distribution of endogenous hNQO1. All the present results demonstrated that the probe HCYSN exhibited great potential for human hNQO1 assay and in vivo imaging for the early cancers diagnosis and pathological studies.

Due to exceptional electron-accepting ability, light-absorption, and a delocalized conjugated structure, buckminsterfullerene (C60) has attracted fascinating interest in the field of organic solar cells. However, poor delocalization and accumulation of electrons for pristine C60 in physiological aqueous solution and difficulties in conjugation with biomolecules limit its extended photovoltaic applications in bioassay. Herein, we reported the noncovalent coupling of C60 to an electronically complementary porphyrin-derived metal-organic framework (PCN-224) with carboxyl-group terminals. Such assembly not only offered a friendly interface for bioconjugation but also resulted in a long-range ordering C60@PCN-224 donor-acceptor system that demonstrated an unprecedented photocurrent enhancement up to 10 times with respect to each component. As an example, by further cooperating with Nanobodies, the as-prepared C60@PCN-224 was applied to a photoelectrochemical (PEC) immunosensor for S100 calcium-binding protein B with by far the most promising detection activities. This work may open a new venue to unlock the great potential of C60 in PEC biosensing with excellent performances.

Semiconducting polymeric carbon nitride (CN) has drawn wide attention ranging from photocatalysis to more recent biosensing owing to unique defect-tolerated optoelectronic properties and being metal-free, cheap, and highly stable. However, at the core of electrical-optical interconversion, the preparation of the CN photoelectrode is still challenging. Now, the growth of CN on electrodes is achieved simply by microwave-assisted condensation in seconds. The ultrafast heating not only addressed the thermodynamic contradiction of precursor volatilization during polymerization but also led to strongly adhesive CN layer on electrodes with gradient carbon-rich texture, greatly accelerating the electron-hole separation and mobility. Consequently, the CN photoelectrode exhibited a remarkable photocurrent and a record cathodic efficiency of electrochemiluminescence up to 7 times that of benchmark Ru(bpy)3 Cl2 in aqueous solution.

Tailor-designed cathode materials are essential for Li-ion batteries with both high energy density and outstanding capacity retention. Here we have designed and fabricated coral-shaped hierarchical porous LiFePO4/graphene hybrids for lithium-ion batteries. These novel hybrid materials exhibit excellent electrochemical performance over a wide temperature range from −40 ​°C to +60 ​°C. Even at −40 ​°C, the hybrid cathode can deliver a high initial capacity of 120 ​mAhg−1 and still maintain a discharge capacity of 80 mAhg−1 after 500 cycles with a very low capacity loss of 0.066% per cycle. The excellent wide-temperature performance can be ascribed to the porous structure and fast ion/electronic transport kinetics of the high conductive framework.

Photocatalytic water splitting holds huge potential to meet the current challenges of energy and environments. Among them, polymeric carbon nitride (CN) has drawn much attention as a promising meta...

The efficient and low-cost platinum group metal (PGM)-free metal-nitrogen-carbon electrocatalysts (M-N-C) are potential alternatives for the oxygen reduction reaction (ORR) in artificial energy conversion devices. However, the solid-state reactions of M/C/N-containing precursors at high temperature was rather complicated, making the engineering of carbonization processes of M-N-C catalysts challenging and less explored. Herein, we report a way to modulate the pyrolysis processes of M-N-C by pre-organization of the molecular precursors via a simple solvation, in which, the simultaneous hydrogen bonding and coordination interactions played an important roles. It was revealed that the supramolecular precursors from different solvents had the same chemical compositions but quite different crystal structures. Accordingly, the pyrolysis processes were greatly altered, making the as-prepared Co-N-C exhibit distinct morphologies ranging from worm-nanotubes to bamboo-nanotubes and to porous nanosheets. The optimized Co-N-C showed competitive bifunctional electrocatalytic ORR and OER activities, which were further successfully applied to advance the rechargeable Zn–air batteries with excellent cycling stability over 600 h at a current density of 20 mA cm−2 and voltage gap (0.76 V). This work highlights the great potential of the pre-organization for the designing and selecting of precursors to engineer pyrolyzed M-N-C with higher electrocatalytic activities.

Electrochemiluminescent (ECL) performance and cytotoxicity of CdTe quantum dots (QDs)-based nanocomposites and its possible application for ECL immunoassay were investigated. Two types of CdTe-based nanocomposites, i.e., SiO2-coated CdTe (CdTe@SiO2) and CdTe-functionalized SiO2 (SiO2@CdTe), were synthesized and comprehensively compared in regarding of the cytotoxicity and ECL performance. The in vitro cytotoxicity of SiO2@CdTe and CdTe@SiO2 nanoparticles was assessed in L02 cells using standard CCK-8 assay, and their ECL performance was investigated by constructing sandwiched immunosensor using SiO2@CdTe and CdTe@SiO2 as tags for the labelled antibody, respectively. The results showed that CdTe@SiO2 exhibited much lower cytotoxicity and a higher ECL intensity than SiO2@CdTe. Taking the analysis of alpha-fetoprotein (AFP) as an example, the ECL immunosensor using CdTe@SiO2 as an emitter was proved to have a wide linear dynamic range from 1.0 pg mL−1 to 100 ng mL−1 with a low detection limit of 0.22 pg mL−1 (S/N ratio of 3). The ECL immunosensor also demonstrated satisfactory recovery and excellent reproducibility and stability, indicating that this method has prospects in practical application in the clinical diagnosis of AFP.

Antimony selenide (Sb2Se3) as a p-type semiconductor material has recently attracted extensive attention for its excellent photoelectric properties in applications of thin film solar cells. However, applying Sb2Se3 as a photoelectrochemically (PEC) active material for constructing biosensors has never been reported. In this work, by using Sb2Se3/graphene oxide (Sb2Se3–GO) as both the PEC probe and substrate for biomolecule conjugation, a “signal-off” sandwich-type PEC biosensor was proposed for DNA methyltransferase (Dam MTase) activity detection based on gold nanoparticles (Au NPs) as quenchers. In the presence of Dam MTase and Dpn I, hairpin probe DNA (hDNA) was cleaved into single-stranded DNA (ssDNA), which could be hybridized with Au NP-functionalized DNA (S1) to form a double-stranded DNA (dsDNA) complex. The formation of dsDNA shortened the distance between Au NPs and Sb2Se3 on the electrode and induced competitive absorption and exciton energy transfer (EET) between Sb2Se3 and the Au NPs, thus significantly reducing the photocurrent. The constructed PEC biosensor exhibited a superior performance compared to most reports with a wide detection range from 1 mU mL−1 to 100 U mL−1 and a low detection limit of 0.6 mU mL−1 for the detection of Dam MTase. This work opens a new avenue for Sb2Se3 in biosensing applications and provides a new technology for the early warning and early diagnosis of diseases.

Recently, the early screening of the genotoxicity of new chemicals and drugs calls for the envelope of micro-/nanoreactors for metabolic study. Herein, a novel light-driven enzymatic bionanoreactor is designed with the gold nanoparticle (NP)-modified carbon nanocage (Au@CNC) as a nanoreactor and meso-tetrakis(4-carboxyphenyl)porphyrin (TCPP) as a photosensitizer for cytochrome P450-mediated drug metabolism. By confining the cytochrome P450 3A4 (CYP3A4) enzyme and TCPP inside the pores of Au@CNC, a high metabolic activity is achieved by using 7-ethoxytrifluoromethyl coumarin as the substrate because of the three-dimensional hierarchical porous structure, large surface area, and fast electron transfer capacity of Au@CNC. It is noted that owing to the presence of AuNPs inside CNC, the surface hydrophilicity of CNC is much improved, which further promotes the catalytic activity of the CYP3A4 enzyme. To our knowledge, this is the first attempt to apply CNC as a bionanoreactor for NADPH-free and light-driven in vitro drug metabolism. In addition, the presented bionanoreactor exhibits a variety of advantages in terms of fast response, short assay time (10 min), high sensitivity, and good selectivity, which are expected to expedite drug screening and render potential advances in drug discovery and development.

Poly(ADP-ribose) polymerase-1 (PARP-1) monitoring has attracted extensive attention because it serves a vital role in human pathologies. However, only a few researches about its detection methods have been reported because PARP-1 and its catalyzed product poly(ADP-ribose) polymer (PAR) are lack of optical or electrochemical activity. Herein, a convenient fluorescence “turn-off-on” nanosensor based on cationic conjugated polymer (PFP) and MnO2 nanosheets has been designed for selective detection of PARP-1 in vitro. To the best of our knowledge, it is the first time to use manganese dioxide (MnO2) nanosheets for PARP-1 detection. The fluorescence intensity of PFP can be quenched by MnO2 nanosheets via a fluorescence resonance energy transfer (FRET). While the subsequently joined electronegative poly(ADP-ribose) polymer (PAR), catalysate of PARP-1, take positively charged MnO2 nanosheets away from PFP via electrostatic interaction, causing sufficient recovery of fluorescent signal. The sensing platform displayed a sensitive response to PARP-1 in a linear range of 0.03 − 1.5 U (0.024 − 1.2 nM), with a detection limit of 0.004 U (0.003 nM), which is 10–100 lower than reported methods. As expected, this method was successfully applied to the detection of PARP-1 in human serum samples with recoveries ranging from 97.6 − 102.7%. Especially, it has also been applied to the determination of PARP-1 in human breast cancer cells SK-BR-3 in the 40 to 1000 cells per mL range, with a detection limit as low as 25 cells per mL.

Electroluminescence (ECL) has been used in extensive applications ranging from bioanalysis to clinical diagnosis owing to its simple device requirement, low background, high sensitivity, and wide dynamic range. Nucleic acid is a significant theme in ECL bioanalysis. The inherent versatile selective molecular recognition of nucleic acids and their programmable self-assembly make it desirable for the robust construction of nanostructures. Benefiting from their unique structures and physiochemical properties, ECL biosensing based on nucleic acids has experienced rapid growth. This review focuses on recent applications of nucleic acids in ECL sensing systems, particularly concerning the employment of nucleic acids as molecular recognition elements, signal amplification units, and sensing interface schemes. In the end, an outlook of nucleic acid-based ECL biosensing will be provided for future developments and directions. We envision that nucleic acids, which act as an essential component for both bioanalysis and clinical diagnosis, will provide a new thinking model and driving force for developing next-generation sensing systems.

Lithium-ion battery packs are widely deployed as power sources in transportation electrification solutions. To ensure safe and reliable operation of battery packs, it is of critical importance to monitor operation status and diagnose the running faults in a timely manner. This study investigates a novel fault diagnosis and abnormality detection method for battery packs of electric scooters based on statistical distribution of operation data that are stored in the cloud monitoring platform. According to the battery current and scooter speed, the operation states of electric scooters are clarified, and the diagnosis coefficient is determined based on the Gaussian distribution to highlight the parameter variation in each state. On this basis, the K-means clustering algorithm, the Z-score method and 3σ screening approach are exploited to detect and locate the abnormal cells. By analyzing the abnormalities hidden beneath the external measurement and calculating the fault frequency of each cell in pack, the proposed algorithm can identify the faulty type and locate the faulty cell in a timely manner. Experimental results validate that the proposed method can accurately diagnose faults and monitor the status of battery packs. This theoretical study with practical implications shows the promising research direction of combining data mining technologies with machine learning methods for fault diagnosis and safety management of complex dynamical systems.

With the development of connected and automated vehicles, eco-driving control is reckoned to generate unprecedented potential on energy-saving in electrified powertrain. In this paper, a data-driven based eco-driving control strategy with efficient computation capacity is proposed for plug-in hybrid electric vehicles to achieve approximate optimal energy economy. An efficient hierarchical optimal control scheme is designed to mitigate the massive computational cost during velocity optimization and powertrain control. A data-driven optimal energy consumption cost model and an optimal battery current model are respectively constructed via two neural networks and served as the critic model and the system model during velocity optimization. Furthermore, the neural network-based dynamic programming is exploited to optimize the vehicle velocity by merging the data-driven models and Bellman optimality principle. The simulation results demonstrate that the proposed method can remarkably improve fuel economy by up to 16.7% in complicated driving conditions, compared with conventional sequential optimization methods. Furthermore, the data-driven control scheme can drastically improve the computational efficiency with slight sacrifice on fuel economy, compared with the optimum benchmark.

Emerging as a cost-effective and robust enzyme mimic, nanozymes have drawn increasing attention with broad applications ranging from cancer therapy to biosensing. Developing nanozymes with both accelerated and inhibited biocatalytic properties in a biological context is intriguing to peruse more advanced functions of natural enzymes, but remains challenging, because most nanozymes are lack of enzyme-like molecular structures. By re-visiting and engineering the well-known Fe-N-C electrocatalyst that has a heme-like Fe-Nx active sites, herein, it is reported that Fe-N-C could not only catalyze drug metabolization but also had inhibition behaviors similar to cytochrome P450 (CYP), endowing it a potential replacement of CYP for preliminary evaluation of massive potential chemicals, drug dosing guide, and outcome prediction. In addition, in contrast to electrocatalysts, the highly graphitic framework of Fe-N-C may not be obligatory for a competitive CYP-like activity.

This paper proposes a novel control framework and the corresponding strategy for power sources management in connected plug-in hybrid electric vehicles (cPHEVs). A mobile edge computation (MEC) based control framework is developed first, evolving the conventional on-board vehicle control unit (VCU) into the hierarchically asynchronous controller that is partly located in cloud. Elaborately contrastive analysis on the performance of processing capacity, communication frequency and communication delay manifests dramatic potential of the proposed framework in sustaining development of the cooperative control strategy for cPHEVs. On the basis of MEC based control framework, a specific cooperative strategy is constructed. The novel strategy accomplishes energy flow management between different power sources with incorporation of the active energy consumption plan and adaptive energy consumption management. The method to generate the reference battery state-of-charge (SOC) trajectories in energy consumption plan stage is emphatically investigated, fast outputting reference trajectories that are tightly close to results by global optimization methods. The estimation of distribution algorithm (EDA) is employed to output reference control policies under the specific terminal conditions assigned via the machine learning based method. Finally, simulation results highlight that the novel strategy attains superior performance in real-time application that is close to the offline global optimization solutions.

Nitrogen doped carbon nanomaterials are excellent electrode materials and catalysts due to their extraordinary conductivity, prolific structures, and abundant active sites. Herein, two kinds of waste biomass, catkins and Okara were used as precursors for the preparation of novel nitrogen doped carbon fibers via hydrothermal and pyrolysis process. The blend of nitrogen-rich Okara with catkins effectively enhanced the content of doped nitrogen in the product. The as-prepared sample (denoted as NCF900) exhibited a hollow fiber like structure with a diameter of 2 to 5 μm and had abundant highly active sites of pyridinic N and graphitic N, thereby improving its electrocatalytic activity in oxygen reduction reaction (ORR). The typical rotating disk electrode test proved that the NCF900 exhibited a high onset potential (0.82 V vs RHE) and a nearly four-electron pathway for ORR in alkaline solution as well as stronger methanol tolerance and better long-term durability than commercial Pt/C. The green, low cost synthetic method and the excellent ORR catalytic efficiency of NCF900 made it a promising electrocatalytic material for the ORR in fuel cells.

A simple photoelectrochemical (PEC) immunoassay based on an amino-terminated perylene derivative (PTCNH2) was developed for highly sensitive and specific detection of tumor necrosis factor-alpha (TNF-α). Simple grinding and sonication afforded a π-π stacked graphene oxide (GO)/PTCNH2 assembly exhibiting fast electron transfer kinetics and excellent photoelectric performance, and this assembly was applied as a PEC probe. The GO-PTCNH2 assembly provided not only a large surface area, fast electron transfer kinetics and abundant active sites for further biomolecule conjugation but also high PEC activity. A “signal-off” PEC immunoassay for TNF-α was developed by assembling GO-PTCNH2 on the electrode, followed by conjugation of anti-TNF-α with GO-PTCNH2 and subsequent capture of the target protein TNF-α. The linear detection range was from 10 pg/mL–100 ng/mL with a limit of detection (LOD) of 3.33 pg/mL. This method was also successfully applied for detecting TNF-α in human serum with recoveries ranging from 92.5% to 96.6% and a relative standard deviation of less than 9.99%. For the first time, this work reports a simple PEC immunoassay achieved by using PTC-NH2 as a photoelectrochemically active probe for the detection of a tumor biomarker. This assay could be applicable to the detection of other biomarkers for clinical diagnosis.

Telomerase is a basic nuclear protein reverse transcriptase and responsible for the elongation of telomeres in cells. It has attracted a lot of attentions and acted as an important sally port for cancer diagnosis and clinical therapy. Hence, accurate and efficient determination of telomerase activity is significant. In recent years, numerous sensitive and accurate techniques have been developed for in vitro or in situ detection of telomerase activity. These methods were mainly dependent on three unique properties of elongated telomerase primer (TS primer): 1) Plenty of negative charges play important role to change interactions between biomolecules and signal probes; 2) G-rich sequences have excellent peroxidase-like catalytic activity; 3) They can be used for DNA hybridization or strand displacement reaction, which are beneficial to construct biosensors. In this review, we conclude and enumerate these advanced methods for telomerase activity detection in recent years. Development trends of telomerase detection are also prospected.

Carbon dots (CDs) are an emerging fluorescent nano-imaging probe due to their unique characteristics, such as good conductivity, carbon-based chemical composition, and photochemical stability, which sets up the potential of outperforming the classic metal-based quantum dots (QDs). It is a timely effort to proactively investigate the biocompatibility feature of CDs with a view to safely utilize this emerging nanomaterial in biological systems. In this study, we assessed the safety profile of an in-house synthesized CDs in hepatocyte-like Hepa 1–6 cells, which represents an important target organ for CDs exposure through either particle uptake and/or accumulation and elimination from primary exposure sites post particle administration. We not only demonstrated a dose- and time-dependent compromised cell viability, but also observed the induction of autophagy at high concentration (i.e. 400 μg mL-1), authenticated by the conversion of microtubule-associated protein light chain 3 (LC3)-I to LC3-II. We attributed these changes as the protective mechanism by which the cells used to compensate for CDs-induced apoptosis and cytotoxicity. The involvement of autophagy was further confirmed because the cytotoxicity profile can be increased or reduced by the use of 3-MA (autophagy inhibitor) and NAC (ROS inhibitor), respectively. Collectively, our findings revealed dose-dependent moderate cytotoxicity in Hepa 1–6 cells. Mechanistic understanding of autophagy during the cellular process revealed the homeostasis when liver cells deal with CDs as an external insult.

Because of the extremely low solubility of gas pollution, elucidating the pathogenetic mechanism between air pollution and the lung inflammatory response has remained a significant challenge. Here, we develop a bioinspired nanoporous membrane (BNM) with a three-phase interface as a gas exposure model that mimicks the airway mechanism, gas molecules contacting with alveolar cells directly, enabling high cell viability and sensitive inflammatory response analysis. Specifically, the top side of the porous anodic alumina (PAA) membrane was in contact with the medium for cell culture, and the bottom side contacted the gas phase directly for gas exposure. Compared with the two-phase interface, the viability of cells on the BNM was enhanced up to 3-fold. Additionally, results demonstrated that the inflammatory responses of cells stimulated by gas pollution (formaldehyde and benzene as models) from the gas phase were more obvious than those induced by gas pollution from solution, especially the increment of interleukin-2 (IL-2), IL-6, and tumor necrosis factor α (TNF-α), which was almost 2 times greater than that induced by gas pollution from solution. Furthermore, an enzyme inhibitor was introduced to evaluate potential applications of the BNM.

The low solubility of oxygen in solution is the main obstacle for the biodegradation of organic pollutants in wastewater. To address this problem, inspired by the degradation mechanism of aerobic bacteria toward organic pollutants, a novel photodegradation system was presented and operated by a heterojunction photocatalyst combining with a hydrophobic triphase interface, allowing oxygen to directly diffuse from the gas phase to active catalytic sites submersed in polluted solutions. Especially, the heterojunction photocatalyst was fabricated by graphitic carbon nitride nanosheets (C

Aflatoxin B1 (AFB1 ), one of the most toxic mycotoxins, is classified as a group I carcinogen and ubiquitous in various foods and agriproducts. Thus, accurate and sensitive determination of AFB1 is of great significance to meet the criteria of food safety. Direct detection of AFB1 is difficult by monoclonal antibody (mAb) with large molecular size (≈150 kD) since the target is too small to produce a detectable signal change. Herein, by combining the electrochemical properties of nanomaterials and the advantages of nanobodies, we developed a direct, highly selective and sensitive electrochemical immunosensor for small molecule detection. The proposed immunosensor had a wide calibration range of 0.01 to 100 ng mL-1 and a low detection limit of 3.3 pg mL-1 (S/N=3). Compared with the immunosensor prepared with mAb which was applied in the typical indirect immunoassay, the immunosensor in this work possessed two orders of magnitudes wider linear range and 10-fold more sensitivity. The as-obtained immunosensor was further successfully applied for sensing AFB1 in real samples. This proposed assay would provide a simple, highly sensitive and selective approach for the direct immunoassay of small molecule AFB1 , and is extendable to the development of direct immunosensing systems for other small molecules detection by coupling nanocarbon and nanobody.

The sensitive simultaneous detection of multiple biomarkers is critical for the early diagnosis of diseases. Electrochemiluminescence (ECL) offers outstanding advantages, e.g., low background, over other optical sensing techniques. However, multiplexed ECL bioassay is hindered not only by the lack of generally available ECL spectrometers but also by the limited number of biocompatible monochromatic ECL luminophores for decades. Herein, we report addressing these issues by re-examination of the recent tabletop spectrofluorometer coupled potentiostat as a high-resolution ECL spectrum acquisition system and using carbon nitrides as monochromatic luminophores. A wavelength-resolved multiplexing ECL biosensor is demonstrated to simultaneously detect CA19-9 and mesothelin, two pancreatic cancer biomarkers, at a single-electrode interface. This work could initiate new opportunities for more general multiplex ECL biosensors with competitive performances.

Stable and sensitive detection of poly(ADP-ribose) polymerase-1 (PARP-1) is of great significance in many fields. Herein, a highly simple and sensitive colorimetric biosensor for label-free detection of PARP-1 based on counterions-induced gold nanorods (AuNRs) aggregation is put forward in this work. The specific DNA activated PARP-1 and resulted in the formation of electronegative poly(ADP-ribose) polymer (PAR) on the auto-modified domain of PARP-1 when nicotinamide adenine dinucleotide (NAD+) was used as substrate. Negative charged PAR induced the aggregation of CTAB-coated AuNRs which are employed as the colorimetric probe here, resulted in the obvious decrease of absorbance and the vivid color change. The aggregation process was visually observed by transmission electron microscope (TEM), and dark-field measurements (DFM). By utilizing the change of longitudinal absorption and vivid color variation of AuNRs, PARP-1 can be detected in a linear range of 0.05–1.0 U with a detection limit of 0.006 U (0.261 ng), which is two orders of magnitude improved compared with previously reported colorimetric methods based on AuNPs. This detection method is label-free, visualized and reliable. The used AuNRs probe is stable and their synthesis procedures are simple. The method has been used to detect PARP-1 in ovarian cancer cells A2780, human breast cancer cells SK-BR-3 and MCF-7, obtained with satisfactory results. Besides, it has also been applied to evaluate the PARP-1 inhibitors, detect the change of PARP-1 activity in the presence of various DNA damages.

Graphite-phase polymeric carbon nitride (CN) was reported to be a promising material in photoelectrochemical solar energy conversion. However, its high recombination rate of photogenerated carriers limits its potential applications. In this article, a heterojunction of CN and sulfur-doped CN (CNS) was constructed through a solution-based processing way. Interestingly, it was observed that the photocatalytic hydrogen production of the as-prepared composite was 32.6 times higher than that of bulk carbon nitride and 2.3 times higher than that of the composites by conventional impregnating method. This study opens a new avenue to construct heterojunction of CN for large-scale industrial applications in environmental remediation.

By coupling tyrosinase (Tyr) and β-galactosidase (Gal) into one redox-cycling scheme, an enzyme cascade-based electrochemical immunosensor with boosted selectivity and sensitivity was constructed using polydopamine-functionalized multiwalled carbon nanotube (MWCNTs-PDA) nanohybrid modified electrodes. The MWCNTs-PDA nanohybrid presented a 5 times enhanced capability for antibody conjugation, which was responsible for signal amplification. In the proposed enzyme cascade scheme, Gal was captured on the immunosensor surface by a sandwiched immunoreaction, which catalyzed phenyl β-d-galactopyranoside (P-GP) into phenol based on a hydrolysis reaction. The resulting phenol was used as a substrate of Tyr, which was catalyzed to catechol and subsequently to o-quinone. The o-quinone was then electrochemically reduced to catechol, forming a redox cycle between catechol and o-quinone. The enzyme cascade-based immunoassay not only significantly amplified the electrochemical signal, but also led to a high selectivity. Taking the detection of CEA as an example, the enzyme cascade-based electrochemical immunosensor showed a detectable range of 10 pg mL-1 to 10 ng mL-1 and a low detection limit of 8.39 pg mL-1 (S/N = 3), which was superior/comparable to those using other methodologies in previous reports. The selectivity of the enzyme cascade-based immunosensor was 44-80% higher than that of a single enzyme-based immunosensor. This work shows great potential of the coupling enzyme cascade in immunosensing for clinical diagnosis with boosted selectivity and sensitivity.

Early diagnosis and life-long surveillance are clinically important to improve the long-term survival of cancer patients. Telomerase activity is a valuable biomarker for cancer diagnosis, but its measurement often used complex label procedures. Herein, we designed a novel, simple, visual and label-free method for telomerase detection by using enzymatic etching of gold nanorods (GNRs). First, repeating (TTAGGG)x sequences were extented on telomerase substrate (TS) primer. It formed G-quadruplex under the help of Hemin and K+. Second, the obtained horseradish peroxidase mimicking hemin/G-quadruplex catalyzed the H2O2-mediated etching of GNRs to the short GNRs, even to gold nanoparticles (GNPs), generating a series of distinct color changes due to their plasmon-related optical response. Thus, this enzymatic reaction can be easily coupled to telomerase activity, allowing for the detection of telomerase activity based on vivid colors. This can be differentiated sensitively by naked eyes because human eyes are ...

Benzo[a]pyrene (BaP), one of polycyclic aromatic hydrocarbons (PAHs), is identified as a prime carcinogen. Enzymatic metabolite of BaP diol epoxide is one of the important factors in its carcinogenic effect. Herein, cytochrome P450 1A1 modified nitrogen-doped graphene was synthesized to study the BaP metabolism with electrochemically-driven pathway. The direct and reversible electron transfer of the immobilized CYP1A1 on pyrenebutyric acid modified nitrogen-doped graphene nanocomposites was observed with an apparent electron transfer constant of 0.53 s− 1, and formal potential of − 0.48 V. With addition of BaP to an air-saturated buffer, the reduction peak current of dissolved oxygen increased, which confirmed the catalytic behavior of CYP1A1 to BaP. The Michaelis-Menten constant (Kmapp) and heterogeneous reaction rate constant of the catalytical reaction were calculated to be 25.6 μM and 1.9 s− 1, respectively. The inhibition effects of alpha-naphthoflavone on CYP1A1 catalyze-cycle were also illustrated with the IC50 value of 1.2 μM. The enzyme-induced BaP metabolism could be further demonstrated by the high performance liquid chromatography (HPLC) and gas chromatography-mass spectra (GC/MS). All these results showed that the proposed system had potential application for the development of drug discovery and the prediction of the chemicals toxicity in food and environment.

As an emerging nitrogen-rich 2D carbon material, graphitic carbon nitride (CN) has drawn much attention for applications ranging from photo-/electrocatalysts to biosensors. Interfacial modification of CN is fundamentally vital but is still in its infancy and remains challenging due to the low reactivity of CN. Here we report that, in conjunction with a π-π stacking interaction, bulk CN could be simultaneously exfoliated via facile mechanical grinding. The obtained CN nanosheets (m-CNNS) not only retained the pristine optoelectronic properties of bulk CN but also enriched a friendly interface for further coupling biomolecules with advanced properties, overcoming the deficiencies of CN in surface science. The m-CNNS were further covalently linked to a DNA probe, and the resultant electrochemiluminescent biosensor for the target DNA exhibited much enhanced sensitivity with respect to that obtained by direct physical absorption of the DNA probe on unmodified CNNS. This noncovalent exfoliation and interfacial modification should greatly expand the scope of potential applications of CN in areas such as biosensing and should also be applicable to other 2D materials in interface modulation.

The low solubility of gases in aqueous solution is the major kinetic limitation of reactions that involve gases. To address this challenge, we report a nanochannel reactor with joint gas–solid–liquid interfaces and controlled wettability. As a proof of concept, a porous anodic alumina (PAA) nanochannel membrane with different wettability is used for glucose oxidase (GOx) immobilization, which contacts with glucose aqueous solution on one side, while the other side gets in touch with the gas phase directly. Interestingly, it is observed that the O2 could participate in the enzymatic reaction directly from gas phase through the proposed nanochannels, and a hydrophobic interface is more favorable for the enzymatic reaction due to the rearrangement of GOx structure as well as the high gas adhesion. As a result, the catalytic efficiency of GOx in the proposed interface is increased up to 80-fold compared with that of the free state in traditional aqueous air-saturated electrolyte. This triphase interface with ...

The label-free localized surface plasmon resonance (LSPR) detection technique has been identified as a powerful means for in situ investigation of biological processes and localized chemical reactions at single particle level with high spatial and temporal resolution. Herein, a core–satellites assembled nanostructure of Au50@Au13 was designed for in situ detection and intracellular imaging of telomerase activity by combining plasmonic resonance Rayleigh scattering spectroscopy with dark-field microscope (DFM). The Au50@Au13 was fabricated by using 50 nm gold nanoparticles (Au50) as core and 13 nm gold nanoparticles (Au13) as satellites, both of them were functionalized with single chain DNA and gathered proximity through the highly specific DNA hybridization with a nicked hairpin DNA (O1) containing a telomerase substrate (TS) primer as linker. In the presence of telomerase, the telomeric repeated sequence of (TTAGGG)n extended at the 3′-end of O1 would hybridized with its complementary sequences at 5′-en...

The detection of telomerase activity is important in cancer diagnosis and in screening for anti-cancer drugs. This work describes a fluorometric method for the determination of telomerase activity by using a cationic conjugated polymer (CCP). Telomerase substrate primers were labelled with carboxyfluorescein (FAM-TS) which display weak electrostatic interactions with the CCP. Hence, fluorescence resonance energy transfer (FRET) from photoexcited CCP to FAM is weak. However, in the presence of telomerase, telomeric repeats (TTAGGG)x were elongated to the 3′-end of FAM-TS to form multiple G-quadruplexes in the presence of potassium ion (K+). These G-quadruplexes trigger strong electrical interaction between the condensed G-quadruplexes and the CCP, and this results in closer proximity and in more efficient FRET. As a result, strong green fluorescence (peaking at 527 nm) is emitted by FAM. Fluorescence can be visually observed under a UV lamp and be used to quantify the activity of telomerase by using a fluorometer. The assay was applied to the determination of HeLa cells in the 30 to 1000 cells per mL range, with a detection limit as low as 5 cells per mL (at an S/N ratio of 3). The method was applied to the detection of various cancer cell lines in human urine samples. The method is simple, sensitive, selective and accurate.

Porous graphite-phase polymeric carbon nitride (GPPCN)/TiO 2 donor-acceptor heterojunction was facilely fabricated through the combination of a template technique with a co-calcination process, which exhibited much higher photoelectric activity compared to pristine carbon nitride and TiO 2 . The precursor of porous GPPCN (pGPPCN), porous melem, was prepared by using a green template, calcium carbonate, which could be easily removed by diluted hydrochloride. The pGPPCN/TiO 2 heterojunction was then obtained by the assembly and subsequent co-calcination of TiO 2 nanoparticles with porous melem. The formation of pGPPCN/TiO 2 donor-acceptor heterojunction prepared by this method showed improved surface area and light absorption. Moreover, the composite presented much higher photo-energy conversion activity than those of GPPCN, pGPPCN and TiO 2 , which could be mainly ascribed to the high charge carrier separation efficiency. This study provides a new approach for the design and development of various photocatalysts with high efficiency for applications in energy fields.

Telomerase has become one of the most typical tumor marker because it is closely related to cancers. In this paper, a simple label-free electrochemical detection of telomerase activity by using methylene blue (MB) as a G-quadruplex binding probe was proposed, avoiding commonly used complex label procedures, nano-probe synthesis, complicated electrode modification, probe immobilization or signal amplification. In the presence of telomerase substrate (TS) primer, the binding of MB on primer was weak. When repeats of (TTAGGG) were extended on the TS primer under the action of telomerase, they formed multiple G-quadruplexes with the help of K + . As a result, a large amount of MB bounded to multiple G-quadruplexes because they have more strong interaction with G-quadruplexes than TS primer. As a result, the diffusion current of MB decreased sharply, which was strongly dependent on the telomerase activity. The DPV current change has a linear correlation with the logarithm of HeLa cell number in the range of 10–10,000 cells, with the detection limit of 3 cells. The high sensitivity was due to the formed multiple G-quadruplexes. Using indium tin oxide (ITO) as working electrode without modification ensured the good reproducibility of the method. The method was also simple, rapid, and has been successfully applied in the telomerase activity detection in urine with good selectivity and reproducibility, which is significant for cancer diagnosis, anticancer drugs screening, and cancer therapy evaluation.

A heterojunction photocatalyst made up of a single substrate is reported. The heterointerfaces of carbon nitride (CN) are natively compatible due to their very similar chemical and crystalline structures. Moreover, the varieties in the nanostructures of CN led to different energy levels that not only matched well with each other but also enabled a sufficient internal electric field at their interfaces to suppress unwanted recombination of charge carriers in photocatalysis.

Owing to the well-defined molecular structure and tunable mono-, di- or multinuclearity, Cu–N complexes have recently drawn specific attention as emerging catalysts for sustainable electrocatalytic oxygen reduction reaction (ORR) and other reactions. However, compared to state-of-the-art Pt/C, most of these Cu-based molecular catalysts show low catalytic activity due to the intrinsically limited capability and challenges in electronic structure modulation and sequential electron transfer within a single small molecule. Herein, inspired by structure–property relationships of laccases (a type of macromolecular biological catalyst), we report a facile molecular assembly of Cu(3,3′-diaminobenzidine) polymeric complex on carbon black via Cu–N complexing and π–π interaction as a highly efficient bifunctional electrocatalyst for ORR and hydrazine oxidation reaction (HOR), two half reactions for hydrazine fuel cells. Similar to the function of the Cys–His group in natural laccases, the 3,3′-diaminobenzidine ligand in the proposed polymeric catalyst synergistically adjusted the electronic structure of the Cu–N complex center and mediated a multiple-electron transfer cooperatively with carbon black via a long-range π–π interaction, owing to its electron reservation and π-conjugated properties. This study may provide a new way to design highly efficient biomimetic noble-metal-free electrocatalysts with well-defined and tunable structures.

Pomelo peel, a waste biomass, was used as an all-in-one (carbon source, self-template, and heteroatom) precursor to develop a nanoporous N/C-electrocatalyst for highly selective and energy-saving H2O2 production, in which disordered carbonous defects and five-membered rings (pyrrolic-N) played vital roles.

In this work, a simple and accurate in vitro drug metabolism strategy was proposed by using macroporous ordered siliceous foam (MOSF) as a nanoreactor for confining the nanohybrid of CdTe quantum dots (QDs) and cytochrome P450 2D6 (CYP2D6). After CYP2D6 was coupled to QDs through the carbodiimide coupling chemistry, the resulting nanohybrid of CYP2D6/QDs exhibited fluorescence emission at 645 nm, which could be used as a photocatalyst for drug metabolism. The energy level of CYP2D6 was located between the conduction band (CB) and valence band (VB) of QDs, which provided the possibility of the electron transferring from the CB of QDs to CYP2D6. Tramadol was chosen as the model substrate. Under the irradiation of a white-light, the photocurrent increased with the addition of tramadol in a wide linear range from 4.0 μM to 100 μM. The apparent Michaelis–Menten constant was measured to be 3.6 μM. The high performance liquid chromatography coupled with mass spectrometry (HPLC–MS) confirmed the production of metabolite of o-desmethyltramadol. Such nanoreactor provided a suitable environment to confine a mass of enzyme, as well as to maintain their catalytic activities for highly effective drug metabolic reactions. This showed promising potential for immobilizing various enzymes and other biomolecules in biomimetic metabolism study.

Oxidative damage is an important factor in causing various human disease and injury. As an oxidative DNA damage product, 8-hydroxy-2′-deoxyguanosine (8-OHdG) is a key marker, which is widely used to study oxidative damage mechanism in diseases. Most reported electrochemical methods were based on oxidation current of 8-OHdG. In this work, a simple electrochemical biosensor for ultrasensitive detection of 8-OHdG was proposed based on it triggered polyaniline (PANI) deposition on tetrahedral DNA nanostructure (TDN). TDN was immobilized onto a gold electrode surface based on self-assembly between three thiolated nucleotide sequences. 8-OHdG-aptamer on the top of TDN formed a hemin/G-quadruplex structure in the presence of 8-OHdG and hemin, which have high catalytic activity to trigger PANI deposition. Numerous negative charges on the duplex DNAs contained in hemin/G-quadruplex and TDN supplied exquisite environment for PANI deposition, which improved the detection sensitivity greatly by increasing the DPV current to10-fold (∼3 μA) compared to our previously reported method without TDN. The response signals correlated linearly with the concentration of 8-OHdG ranging from 10 pM to 2 nM, with a detection limit of 1 pM (S/N = 3). The sensitivity was improved to almost 300-fold when compared with most of previously reported electrochemical methods. The method was also simple and reliable, avoiding complex, expensive label procedures and nanomaterial synthesized procedures. The method had been successfully applied to quantify 8-OHdG in urine and human serum samples with satisfactory results.