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In this research, a hydroxyl group functionalized metal-organic framework (MOF), UiO-66-(OH)2, was synthesized as a “on-off-on” fluorescent switching nanoprobe for highly sensitive and selective detection of Fe3+, ascorbic acid (AA) and acid phosphatase (ACP). UiO-66-(OH)2 emits yellow-green light under ultraviolet light, when Fe3+ was added, Fe3+ was chelated with hydroxyl group, the electrons in the excited state S1 of the MOF transferred to the half-filled 3d orbits of Fe3+, resulting in fluorescence quenching because of the nonradiative electron/hole recombination annihilation. AA could reduce Fe3+ to Fe2+, which can destroy the electron transfer between UiO-66-(OH)2 and Fe3+ after AA adding, resulted in nonoccurrence of the nonradiative electron transfer, leading to the recovery of UiO-66-(OH)2 fluorescence intensity. The probe can also be used to detect ACP based on the enzymolysis of 2-phospho- l -ascorbic acid (AAP) to produce AA. Benefitting from the hydroxyl group and the characteristics of UiO-66, including the high porosity and large surface area, the developed UiO-66-(OH)2 showed extensive advantages as a fluorescent probe for detection of multi-component, such as high sensitivity and selectivity, colorimetric detection, fast response kinetics and easy to operate, economical and secure. This is the first time to use active group functionalized MOFs as a multi-component sensor for these three substances detection.

Photoelectrochemical (PEC) biosensors have shown great promise in bioanalysis and diagnostic applications in recent years. In this work, the CuO/Cu2O nanowire array (CuO/Cu2O Nanowire) supported on copper foam was prepared as a photocathode for detection of tyrosinase though quinone-chitosan conjugation chemistry method. The in-situ generated quinones that were the catalytic product of tyrosinase acted as electron acceptors, which were captured by the chitosan deposited on the surface of the electrode. Direct immobilization of electron acceptor on the electrode surface improved the photocurrent conversion efficiency and thus sensitivity. The as-prepared biosensor can realize a rapid response in a wide linear range of 0.05 U/mL to 10 U/mL with the detection limit as low as 0.016 U/mL of tyrosinase. The current work provides a new perspective to design and develop highly sensitive and selective PEC biosensor.

Mercury detection remains an important task because of its high toxicity. Herein a new dual-signal probe based on a boric acid (BA)-functionalized lanthanide metal-organic framework (BA-Eu-MOF) was developed for the detection of Hg2+ and CH3Hg+ ions for the first time. The BA-Eu-MOF was synthesized by coordination of Eu3+ with 5-boronobezene-1, 3-dicarboxylic acid (5-bop) through a one-pot method. The 5-bop ligand not only acted as the "antenna" to sensitize the luminescence of Eu3+ but also provided reaction sites for Hg2+ and CH3Hg+. Owing to the electron-withdrawing effect of the BA group, the "antenna" effect of the ligand was passivating and the BA-Eu-MOF showed weak red emission in water. Upon addition of Hg2+ or CH3Hg+ into the system, a transmetalation reaction took place, i.e., BA groups were replaced by Hg2+ or CH3Hg+; therefore, the "antenna" effect of the ligand was triggered, leading to the enhancement of red emission. As Hg2+ or CH3Hg+ concentration increased, the red emission was gradually enhanced, and the color change was also observed with the naked eye under 365 nm ultraviolet light. Owing to the porous characteristics and the surface effect of the MOF, as well as the unique transmetalation reaction between the BA group and Hg2+ or CH3Hg+, the developed nanoprobe showed excellent characteristics for simultaneous detection of Hg2+ and CH3Hg+, such as simple preparation, convenient operation, "turn-on" signal output, high sensitivity, and selectivity. The unique features of the BA-Eu-MOF make it an attractive probe for monitoring Hg2+ and CH3Hg+.

β-Glucuronidase (β-GCU) is closely related to the occurrence of multiple diseases, and it has been applied as a biomarker and therapeutic target in clinical diagnosis. However, reliable methods with high selectivity and sensitivity for monitoring β-GCU are still lacked. Herein, we designed a novel fluorescent nanoprobe, rhodamine B encapsulated MOF-5 (RhB@MOF-5) for the first time, to detect β-GCU through the synergistic effect of inner filter effect (IFE) and static quenching effect (SQE) by employing 4-nitrophenyl-β-D-glucuronide (PNPG) as the substrate. After encapsulating into MOF-5, the fluorescence emission of RhB at 550 nm excited by 320 nm was greatly enhanced. The major overlap between the fluorescence excitation spectrum of RhB@MOF-5 (about 320 nm) and the ultraviolet absorption spectrum of PNPG (about 310 nm) lead to PNPG being a good IFE absorber in this sensing system. Under the optimized conditions, the excitation spectrum of the RhB@MOF-5 could be absorbed by PNPG, resulting in the dramatically decrease of fluorescence emission. After adding β-GCU into the system, the substrate of PNPG would be enzymatic hydrolyzed to p-nitrophenol (PNP) and glucose, then the IFE disappearance and the fluorescence recovered. The current sensing platform was interference-free and exhibited a broad linearity relationship for β-GCU range of 0.1–10 U L−1 (R2 = 0.9957) with a limit of detection as low as 0.03 U L−1, which was reduced by more than one orders compared with the reported methods. Moreover, the encapsulation of dyes using porous nanoparticles to achieve some tailor-made characteristics will enrich experimental design inspiration.

Ferric ion (Fe3+) plays a vital role in cellular homeostasis. However, the detection of Fe3+ with rhodamine B (RhB) has potential problems, such as poor selectivity and low photostability. To address these problems, we rationally designed an RhB@MOF nanocomposite-based "on-off-on" fluorescent switching nanoprobe for highly sensitive and selective detection of Fe3+ and ascorbic acid. This RhB@MOF nanoprobe was prepared through a facile one-pot synthesis. Here MOF served as a selectivity regulator for the detection of Fe3+. By embedding RhB into the porous crystalline MOF, enhanced photostability and fluorescence lifetime of RhB to Fe3+ were achieved. The as-prepared RhB@MOF was demonstrated to be an ultrasensitive and selective nanoprobe for the detection of Fe3+ in human serum and ascorbic acid in rat brain microdialysate. Furthermore, inner filter effect (IFE) and photoinduced electron transfer (PET) were proposed and discussed to explain the selectivity and sensitivity of RhB to Fe3+ against other interfering substances. Our novel "on-off-on" nanoprobe provides insight into the rational design of MOF-based biosensors for selective and sensitive detection of analytes.

The composite of metal-organic frameworks (MOFs) and graphene aerogels (GAs) is getting growing attention in the field of electrochemical sensor owing to its interconnected meso-/macro-porous structure, high conductivity, and large surface area. How to effectively compound the two components in a simple way and maximize the performance advantages of materials is still a challenge. In this paper, a simple in-situ growth method was proposed by using polypyrrole (PPy) as a crosslinking agent for the synthesis of hierarchically porous PPy@ZIF-8/GAs. Wherein, PPy was initially decorated on GAs and then ZIF-8 nanocrystals were orderly grown on the surface of PPy/GAs through the coordination interaction between Zn2+ and amino ( NH ) groups in PPy chains. This hybrid 3D architecture provided open channels for electrolyte transportation and improved electron transfer between the electrode and the catalysts, which was exploited as electrochemical sensing platform for the detection of highly toxic 2, 2-methylenebis (4-chlorophenol) (dichlorophenol, Dcp). Benefiting from the synergistic effects between PPy, GAs and ZIF-8, the PPy@ZIF-8/GAs electrode showed high sensitivity for Dcp detection with a low detection limit down to 0.1 nM. In addition, the current sensor presented several merits, such as good reproducibility, high selectivity and long stability. More importantly, the sensor was successfully applied for the detection of Dcp in lake water samples.

Industrial production of NH3 from N2 and H2 significantly relies on Haber–Bosch process, which suffers from high energy consume and CO2 emission. As a sustainable and environmentally-benign alternative process, electrochemical artificial N2 fixation at ambient conditions, however, is highly required efficient electrocatalysts. In this study, we demonstrate that hexagonal boron nitride nanosheet (h-BNNS) is able to electrochemically catalyze N2 to NH3. In acidic solution, h-BNNS catalyst attains a high NH3 formation rate of 22.4 μg·h–1·mg–1cat. and a high Faradic efficiency of 4.7% at–0.75 V vs. reversible hydrogen electrode, with excellent stability and durability. Density functional theory calculations reveal that unsaturated boron at the edge site can activate inert N2 molecule and significantly reduce the energy barrier for NH3 formation.

The development of new electrocatalysts is critical for efficient water electrolysis to produce hydrogen. In this communication, we report a novel electrocatalyst for the oxygen evolution reaction (OER) which is realized via Fe doping in CoS2 nanosheets (Fe-CoS2). This catalyst shows an overpotential of 302 mV for a current density of 10 mA cm-2, 85 mV less than that for CoS2. In addition, Fe-CoS2 also exhibits high catalytic stability.

The fast and accurate real-time monitoring of hydrogen peroxide (H2O2) secreted from living cells plays a critical role in clinical diagnosis and management. Herein, we report low-cost and self-supported MoS2 nanosheet arrays for non-enzymatic eletrochemical H2O2 detection. Under the optimal test conditions, such MoS2 electrodes exhibit extremely promising electrocatalytic performance with a low detection limit of 1.0 μM (S/N = 3) and an excellent sensitivity of 5.3 mA mM−1 cm−2. Furthermore, the detection of the trace amount of H2O2 secreted from live A549 cancer cells was successfully performed with this biosensor.

Precision diagnosis and effective treatment are the cores of early cancer therapy. Here, for the first time, we report a hybridization chain reaction-based nanoprobe for selective and sensitive cancer cell recognition and amplified photodynamic therapy.

Hyaluronidase (HAase) has been reported as a diagnostic and prognostic urinary biomarker for bladder cancer. Simple and sensitive methods capable of quantitatively detecting HAase are desired for tumor diagnosis and therapy at its early stage. Herein, a label-free and fluorescence “turn-on” assay for sensitive detection of HAase was established based on the electrostatic assembly of a water-soluble cationic perylene diimide derivative (PDI) and hyaluronic acid (HA). The electrostatic assembly of HA–PDI between the positively charged PDI and the negatively charged HA resulted in an efficient aggregation-caused quenching (ACQ) of PDI. In the presence of HAase, the enzyme catalyzed hydrolysis of HA led to the failure of aggregation of PDI and thus the fluorescence of PDI was retained. HA was used to function not only as a scaffold to agglomerate PDI but also as a substrate for enzymatic reactions. The efficient ACQ and the specific enzymatic reaction induced failure of aggregation of PDI endowed the developed HA–PDI assembly with high sensitivity and specificity for the detection of HAase with a detection limit of 0.03 U mL−1. Moreover, the facile detection process and rapid response of the assay made it applicable for reliable detection of HAase in human serum and urine samples.

The development of sensitive methods for alkaline phosphatase (ALP) activity analysis is an important analytical topic. Based on the stimulus-responsive lanthanide coordination polymer, a simple ratiometric fluorescence sensing strategy was proposed to detect ALP activity. A carbon dot (CD) doped fluorescent supramolecular lanthanide coordination polymer (CDs@Tb-GMP) was prepared with Tb3+ and the ligand guanine single nucleotide (GMP). To construct a ratiometric fluorescence biosensor, the fluorescence of Tb-GMP was used as a response signal, and the fluorescence of CDs was used as a reference signal due to its good stability. When excited at 290 nm, the polymer network Tb-GMP emits characteristic fluorescence at 545 nm, while the CDs encapsulated in the polymer network emit fluorescence at 370 nm. After adding ALP to the system, the substrate GMP can be hydrolyzed by ALP, resulting in the destruction of the polymer network. Accordingly, the fluorescence of Tb-GMP significantly decreased, while the fluorescence of CDs slightly increased due to their release from the polymer network. By comparing the relationship between the fluorescence intensity ratio of the two signals and the concentration of ALP, sensitive detection of ALP could be achieved with the linear range from 0.5 to 80 U L−1 and a detection limit of 0.13 U L−1. Furthermore, the proposed ratiometric sensing system was applied to the detection of ALP in human serum samples with desirable results, indicating potential application in clinical diagnosis.

In the past decades, various nanomaterials with unique properties have been explored for bioapplications. Meanwhile, aptamers, generated from the systematic evolution of ligands by exponential enrichment technology, are becoming an indispensable element in the design of functional nanomaterials because of their small size, high stability, and convenient modification, especially endowing nanomaterials with recognition capability to specific targets. Therefore, the incorporation of aptamers into nanomaterials offers an unprecedented opportunity in the research fields of diagnostics and therapeutics. Here, we focus on recent advances in aptamer-embedded nanomaterials for bioapplications. First, we briefly introduce the properties of nanomaterials that can be functionalized with aptamers. Then, the applications of aptamer-embedded nanomaterials in cellular analysis, imaging, targeted drug delivery, gene editing, and cancer diagnosis/therapy are discussed. Finally, we provide some perspectives on the challenges and opportunities that have arisen from this promising area.

Branched Au nanocrystals with sub-10-nm arms are synthesized via a one-pot reduction in aqueous phase. The success of current work relies on the use of octadecyltrimethylammonium chloride as the shape-directing capping agent to facilitate the formation of branched products in high purity. Their overall size could be controlled in the range of 16–60 nm by varying the Au precursor amount or concentration of capping agent, and the diameter of arms is limited to sub-10-nm size range. Interestingly, Au nanocrystals with a unique morphology, sheet-wrapped dendrites, could be obtained when the concentration of a reductant was varied. The current strategy is also validated effective in the fabrication of dendritic products composed of other noble metals or alloys in addition to Au by simply using the alternative metal precursor. As compared to spherical counterparts, the current branched Au nanocrystals exhibited noticeable red-shift in UV-Vis extinction spectrum and enhanced catalytic activities for electrooxidation of ethanol in alkaline media.

We report the fabrication of concave gold (Au) nanocrystals with a set of morphologies and controlled sizes via seeded growth. Starting with Au seeds with a well-defined morphology and uniform size, cubic and rodlike Au nanocrystals with a noticeable concave feature could be successfully obtained, respectively. We also track the growth process and record the shape evolution process. The effect of several reaction parameters on product morphology, such as capping agent and concentration of Ag+, are systematically investigated. Their optical and electrochemical properties are investigated via UV-vis extinction spectroscopy and cyclic voltammetry, respectively. Compared to spherical counterparts, the current concave Au nanocrystals exhibit a noticeable red shift of the absorbance peak in UV-vis extinction spectra and characterized electrochemical behavior of stepped facets, illustrating the morphological advantage.

Flower-like graphene/CuO@Cu-BTC (GR/CuO@Cu-BTC) composite was employed as electrode material for the voltammetric determination of caffeic acid (CA) in the wine. The composite material was prepared via the self-template method. In this synthetic process, budlike CuO not only acts as the template, but also provides Cu2+ ions for in situ growth of the Cu-BTC shell. The utilization of GR as petal greatly boosts the stability and electronic conductivity of CuO@Cu-BTC. The GR/CuO@Cu-BTC composite possesses unique structural features with high specific surface area and good conductivity, exhibiting excellent electrocatalytic activity towards the oxidation of CA. Under optimized conditions, the sensor shows a good linear response to CA concentration over the range 0.020–10.0 μM, together with a low limit of detection (LOD) of 7.0 nM. Selectivity, reproducibility, and stability were investigated, and the method has been applied for the determination of CA in wine samples.

It is highly attractive to develop non-noble-metal nanoarray architecture as a high-active catalyst electrode for molecular detection due to its large specific surface area and easy accessibility to target molecules. In this paper, we demonstrate the development of cobalt nitride nanowire array on Ti mesh (Co 3 N NW/TM) as an efficient catalyst electrode for glucose oxidation in alkaline solutions and H 2 O 2 reduction in neutral solutions. Electrochemical tests suggest that such Co 3 N NW/TM possesses superior non-enzymatic sensing ability toward rapid glucose and H 2 O 2 detection. As a glucose sensor, this fabricated electrode offers a high sensitivity of 3325.6 μA mM −1 cm −2 , with a wide linear range from 0.1 μM to 2.5 mM, a low detection limit of 50 nM (S/N = 3), and satisfactory stability and reproducibility. Its application in determining glucose in human blood serum is also successful. Amperometric H 2 O 2 sensing can also been realized with a sensitivity of 139.9 μA mM −1 cm −2 , a linear range from 2 μM to 28 mM, and a detection limit of 1 μM (S / N = 3). This nanoarray architecture holds great promise as an attractive sensing platform toward electrochemical small molecules detection.

Recently, photoelectrochemical (PEC) biosensing has received considerable attention with wide applications in biotechnology and biomedicine. Here we report a novel PEC biosensing platform constructed via the combined strategy of both PEC analysis and bioetching. Urchin-like ZnO-Au@CdS microspheres were obtained by depositing Au nanoparticles (NPs) and CdS NPs on the surface of urchin-like ZnO microspheres. The introduction of intermediate electrotransfer of Au NPs to isolated ZnO and CdS systems significantly enhances the PEC property. CdS NPs can be irreversibly bioetched by an enzymatic reaction catalyzed by horseradish peroxidase (HRP) and H2O2. As a result, H2O2 detection is realized based on the decrease of the intensity of the PEC signal. This mediator-free and interference-free sensing platform has a linear range from 0.15 to 100 μM with a detection limit of 0.04 μM H2O2 at S/N = 3. Furthermore, glucose oxidase (GOD) was successfully immobilized on ZnO-Au@CdS microspheres to construct a glucose biosensor with a detection limit of 0.18 μM at S/N = 3. The PEC biosensor shows good sensing performance with low detection limit, mediator-free and accuracy, strong anti-interference, promising its application in PEC biosensing.

It is extremely desired to develop cost-effective and high-efficient water oxidation electrocatalysts in alkaline electrolytes. In this Letter, we report the topotactic conversion of Cu(tetracyanoquinodimethane) nanoarray, denoted as Cu(TCNQ), into Fe(TCNQ)2 nanoarray via low-temperature cationic exchange. As a 3D electrode, such Fe(TCNQ)2 possesses superior oxygen evolution reaction (OER) performance needing overpotentials as low as 321 and 353 mV to afford 20 and 50 mA cm–2 in 1.0 M KOH, respectively. Remarkably enough, such a catalyst shows good durability in the long term electrochemical process with its catalytic activity being retained for 25 h at lowest. This work demonstrates that Fe(TCNQ)2 nanoarray may open up new possibilities for OER application.

It is highly attractive to develop high-performance non-noble-metal electrocatalysts for water oxidation in alkaline media. In this communication, we report the hydrothermal growth of a Co-MOF nanosheet array on Ni foam (Co-MOF/NF) as a 3D oxygen evolution reaction catalyst in alkaline media. The Co-MOF/NF demonstrates superior activity and needs an overpotential of only 311 mV to drive a geometrical catalytic current density of 50 mA cm−2 in 1.0 M KOH. Notably, this catalyst also demonstrates superior long-term electrochemical durability for at least 105 h, and it achieves a high turnover frequency of 0.18 mol O2 s−1 at an overpotential of 400 mV.

Heparin (Hep) is widely used as a major anticoagulant in surgery. Simple and sensitive methods capable of quantitative detection of Hep are desired for better regulating its clinical use. Herein, a novel nanoassembly of amino-functionalized mesoporous silica nanoparticle-gold nanoclusters (MSN-AuNCs) with remarkable emission enhancement characteristics for sensitive fluorescence detection of Hep is developed. The electrostatic interaction between the positively charged amino-functionalized MSNs and the AuNC-stabilizing surface ligands triggers the self-assembly of MSN-AuNC nanocomposites which exhibit more than 5-fold fluorescence emission enhancement. However, the presence of negatively charged Hep inhibits the emission enhancement phenomenon due to the effective wrapping of Hep on the surface of MSNs, which blocks the interaction between AuNCs and MSNs. Benefitting from the remarkable emission enhancement and the competing binding of Hep, facile and ultrasensitive detection of Hep can be realized with a detection limit as low as 2 nM. Moreover, the successful application of the proposed method for detection of Hep in human serum samples shows promise for clinical applications.

It is highly desired to develop high-efficiency and low-cost catalysts for the hydrogen evolution reaction (HER). Herein, we report the development of an Al-doped Ni2P nanosheet array on Ti mesh as a high-performance and durable electrocatalyst for the HER in 1.0 M KOH. Such a catalyst demands an overpotential of 129 mV to afford 10 mA cm−2 and maintains its catalytic activity for at least 20 h. This work offers us a promising cost-effective catalyst for large-scale electrolytic production of hydrogen fuels.

The illegal adulteration of melamine in dairy products for false protein content increase is a strong hazard to human health. Herein, a simple and sensitive colorimetric method was developed for the quantification of melamine in dairy products based on a Cu2+-hydrogen peroxide (H2O2)-3,3′,5,5′-tetramethylbenzidine (TMB) system. In this strategy, Cu2+ exhibits peroxidase-like activity and can catalyze the oxidation of TMB to oxidized TMB (oxTMB) in the presence of H2O2 with a blue colour change of the solution. However, the presence of melamine quickly interacts with H2O2 leading to the consumption of H2O2 and thus strongly hinders the oxidation of TMB. Under the optimal conditions, the absorbance change of oxTMB has a linear response to the concentration of melamine from 1 to 100 μM with a detection limit of 0.5 μM for melamine. The proposed method has many merits including more simplicity, good selectivity, and more cost-effectiveness without using any nanomaterials. The method was further successfully applied to detect melamine in dairy products including milk and infant formula powder.

Developing earth-abundant and efficient catalysts for the hydrogen evolution reaction (HER) is highly desirable. In this communication, we report the development of a Mn-doped Ni3S2 nanosheet array on Ni foam (Mn-Ni3S2/NF) as a superior and durable catalyst for alkaline hydrogen evolution. Such Mn-Ni3S2/NF demands an overpotential of 152 mV to afford 10 mA cm-2 in 1.0 M KOH, 46 mV less than that for Ni3S2/NF. Furthermore, this catalyst also shows high long-term electrochemical durability. This work provides important guidance for exploring optimal HER catalysts.

It is highly attractive to develop efficient hydrogen evolution reaction (HER) electrocatalysts under alkaline conditions. In this communication, we report the preparation of amorphous Ni(OH)2 decorated Fe2P nanoarray on Ti mesh (Ni(OH)2-Fe2P/TM) via electrodeposition. As a 3D electrode for the hydrogen evolution reaction, such Ni(OH)2-Fe2P/TM demonstrates superior catalytic activity. Moreover, the as-prepares electrocatalyst requires an overpotential of only 76 mV to drive a current density of 10 mA cm-2, which is 94 mV less than that for Fe2P/TM. It also shows strong long-term electrochemical durability with its catalytic activity being maintained for at least 20 h.

NH3 synthesis heavily depends on the energy-intensive Haber–Bosch process, which produces serious carbon emission. Electrocatalytic N2 reduction emerges as an environmentally benign process for sustainable artificial N2 fixation but requires efficient, stable and selective catalysts for the N2 reduction reaction (NRR). Here, we report that Cr2O3 nanofiber behaves as a superb non-noble-metal NRR electrocatalyst for artificial N2 fixation to NH3, with excellent selectivity under ambient conditions. In 0.1 M HCl, this catalyst achieves a high Faradaic efficiency of 8.56% and a high NH3 formation rate of 28.13 μg h−1 mgcat.−1, placing it amongst the most active aqueous-based NRR electrocatalysts. Moreover, this catalyst also shows strong electrochemical durability during electrolysis and the recycling test. It opens a new avenue to explore the rational design of Cr-based nanostructures as advanced catalysts for N2 fixation and other applications.

Since bleomycins (BLMs) play a prominent role in the clinical treatment of various cancers, the development of convenient and sensitive detection assays for BLM is of great significance in cancer therapy and related biological mechanism research. Here, taking advantage of the easily controllable and excitation of the G-triplex DNA structure, we reported a facile, label-free G-triplex based functional molecular beacon (G3MB) sensing system for fluorescence "turn-on" detection of BLM based on BLM-Fe(ii) mediated DNA strand scission. In the presence of BLM, the stable hairpin structure of G3MB undergoes an irreversible cleavage in the loop region that contains a 5'-GT-3' recognition site for BLM. The released G-tract DNA fragment self-assembles into a G-triplex-ThT complex showing a strong fluorescence. Owing to the effective locking of G-tracts in the stem of the G3MB and the specific DNA strand scission by BLM which is like a key for the release of G-tracts, the assay shows high sensitivity and selectivity with a detection limit of 0.2 nM. In addition, satisfactory results were obtained for the detection of BLM in human serum samples. Critically, the convenient "mix-and-detect" protocol, fast response and no need for modifying DNA offered a potential application of the proposed strategy for BLM assay in biomedical and clinical studies.

It is extremely important to develop earth-abundant and stable oxygen evolution reaction (OER) electrocatalysts with excellent performance in alkaline media. In this work, we describe the in situ electrochemical conversion of microrod array of Ni(tetracyanoquinodimethane)2, Ni(TCNQ)2, into Ni(OH)2 nanoparticles embedded in a conductive TCNQ microrod array via anode oxidation. Such Ni(OH)2-TCNQ microarray shows OER activity needing overpotentials of 322 and 354 mV to attain current densities of 50 and 100 mA cm–2 in 1.0 M KOH, respectively. It is also extremely durable with its electrocatalytic performance being kept for at least 20 h. This work points out a stimulating approach to explore the utilization of TCNQ array as a conductive matrix for electrochemical applications.

The authors have synthesized spindle-like ZnO nanorods closely anchored to CdS nanoparticles (NPs) placed on gold NPs (ZnO-CdS@Au). It is shown that the ZnO-CdS@Au nanocomposite can serve as a photoactive material for use in photoelectrochemical (PEC) detection by efficiently absorbing light and then promoting electron transfer. A visible light-driven PEC detection platform for tetracycline (TET) was fabricated by placing the nanocomposite on an ITO and immobilizing the TET-binding aptamer as biorecognition element. PEC can be quantified by applying a bias potential of + 0.4 V (vs. SCE) and visible light irradiation. The aptamer on the electrode specifically captures the TET present in the solution to produce a restored photocurrent signal through the reaction between the captured TET and the photogenerated holes. The electrode has a linear response in the 50 to 200 nM TET concentration range, with a 4.5 nM detection limit (at an S/N ratio of 3). In our perception, this novel PEC detection strategy based on ZnO-CdS@Au nanocomposite demonstrated an ultrasensitive method for TET detection with high selectivity and good stability.

It is urgent but still remains challenging to boost the alkaline water oxidation activity of transition metal oxide electrocatalysts for applications. In this work, we report our recent finding that surface introduction of an amorphous nickel–borate (Ni-Bi) layer on a nickel oxide (NiO) nanosheet array on carbon cloth (NiO/CC) can greatly enhance its electrochemical water oxidation activity under alkaline conditions. In a 1.0 M KOH solution, the resulting core–shell NiO@Ni-Bi/CC shows superior electrochemical catalytic activity of only 290 mV to drive 10 mA cm–2, 100 mV less than that for NiO/CC. Meanwhile, this catalyst electrode shows great long-term durability for at least 25 h. The high activity can be ascribed to the Ni-Bi layer on NiO promoting NiOOH generation as the active species. This study provides us an abundant water oxidation catalyst in an alkaline water electrolysis device for high-performance, durable electrolytic hydrogen production.

As a promising candidate for photoelectrochemical (PEC) water oxidation, the photoelectrochemical water splitting efficiency of hematite (Fe2O3) is limited by its low electron mobility. In this work, we report a new strategy for great enhancement of PEC water oxidation activity on Fe2O3. The S-doped Fe2O3 (S:Fe2O3) nanorods array on a Ti plate shows a substantially increased photocurrent density of 1.42 mA cm–2 at 1.23 V vs RHE in 1.0 M NaOH under simulated sunlight irradiation (AM 1.5G, 100 mW cm–2), 2.45 times that of Fe2O3 counterpart (0.58 mA cm–2). Both density functional theory calculations and experimental measurements verify that the superior activity is contributed to the enhanced electron mobility after S doping. This study offers an attractive photoanode in water-splitting devices for solar hydrogen production application.

Searching for a simple and fast strategy to effectively enhance the oxygen evolution reaction (OER) performance of non-noble-metal electrocatalysts in alkaline media remains a significant challenge. Herein, the OER activity of NiFe-LDH nanoarray on carbon cloth (NiFe-LDH/CC) in alkaline media is shown to be greatly boosted by an amorphous NiFe-Borate (NiFe-Bi ) layer formation on NiFe-layered double hydroxide (NiFe-LDH) surface. Such a NiFe-LDH@NiFe-Bi /CC catalyst electrode only needs an overpotential of 294 mV to drive 50 mA cm-2 in 1.0 m KOH; 116 mV less than that needed by NiFe-LDH/CC. Notably, this electrode also demonstrates strong long-term electrochemical durability. The superior activity is ascribed to the pre-formed amorphous NiFe-Bi layer effectively promoting active species generation on the NiFe-LDH surface. This work opens up exciting new avenues for developing high-performance water-oxidation catalyst materials for application.

The design and development of earth-abundant electrocatalysts for efficient full water splitting under mild conditions are highly desired but still remain a challenging task. In this study, we describe the development of homologous Fe-doped Co-based nanoarray as complementary catalysts for high-performance and durable water splitting in near-neutral media. Fe-doped Co-phosphate-borate nanoarray on carbon cloth (Fe-Co-Pi-Bi/CC) derived from Fe-doped CoP nanoarray on CC (Fe-CoP/CC) via oxidative polarization behaves as a highly active bimetallic electrocatalyst for water oxidation with the demand of overpotential of 382 mV to afford a geometrical catalytic current density of 10 mA cm-2 in 0.1 M potassium borate (K-Bi, pH: 9.2). Fe-CoP/CC is also superior in activity for hydrogen evolution reaction, capable of driving 10 mA cm-2 at overpotential of only 175 mV in 0.1 M K-Bi. The two-electrode water electrolyser using Fe-Co-Pi-Bi/CC as anode and Fe-CoP/CC as cathode achieves 10 mA cm-2 water splitting current at a cell voltage of 1.95 V with strong long-term electrochemical durability.

The development of high-performance and cost-effective water oxidation catalysts operating under mild conditions is attractive for the conversion of electricity into chemical fuels. In this communication, we report the in situ electrochemical development of a Ni-Bi layer (5–8 nm thick) on a NiS2 nanoarray supported on carbon cloth (i.e., NiS2@Ni-Bi/CC) for efficient water oxidation in 0.1 m potassium borate electrolyte at pH 9.2. As a durable 3 D catalyst electrode, core–shell-structured NiS2@Ni-Bi/CC shows excellent catalytic activity for water oxidation and approaches a geometrical catalytic current density of 20 mA cm−2 at an overpotential of 486 mV, with long-term electrochemical stability for at least 24 h with a high turnover frequency of 0.28 mol O2 s−1 at an overpotential of 500 mV and nearly 100 % Faradic efficiency for oxygen evolution.

Glutathione (GSH) serves several vital biological functions and its abnormal levels are associated with many diseases. Simple and sensitive methods capable of detecting GSH are desired for better understanding the mechanism of diseases. In this work, a label-free MnO2 nanosheets assisted aggregation-induced emission (AIE)-silica nanospheres (SiO2 NPs) nanoprobe for fluorescent "turn-on" detection of GSH with high sensitivity was reported for the first time. The anionic tetraphenylethylene derivative 3 (TPE3) was synthesized and employed as the AIE-active probe, which can be aggregated on the uncoated amino-functionalized SiO2 NPs to form AIE-SiO2 NPs and emitted strong fluorescence. Negatively charged MnO2 nanosheets were employed as both positive charge protectors for amino-functionalized SiO2 NPs and recognition units for GSH. The presence of GSH could selectively reduce MnO2 nanosheets to Mn2+, thus releasing the amino-functionalized SiO2 NPs and exposure its positive charges. Accordingly, the TPE3 could be aggregated on the exposured amino-functionalized SiO2 NPs to form AIE-SiO2 NPs and emitted strong fluorescence. The proposed assay is simple, fast, low cost, and highly sensitive with a detection limit of 200nM for GSH. The assay was further applied in human serum samples for the detection of GSH with satisfactory results, demonstrating its promising application in practical biological samples.

Developing low cost and efficient anode and cathode materials toward electrocatalysis are regarded as one of the most desirable yet challenging research directions, which are intimately related to the pressing energy, environmental and human health issues. Currently, 3 D foam (such as Ni foam, Cu foam, and graphene foam) based heterogeneous catalysts have been intensively explored for actively catalyzing the electrode reactions. Their inherent characteristics of stereo-network structure, high specific area and large pore volume not only provide better mass transport of reactants to electrode surfaces, but also pave 3 D electron transport pathways. Herein, recent significant progress and rational design of foam-based electrocatalysts are reviewed. In addition, some insights into current challenges and future directions of foams for efficient electrocatalysis are proposed and discussed.

Nickel-borate nanosheets array on titanium mesh (Ni-Bi NA/TM) was derived from NiSe2 nanosheets array on titanium mesh (NiSe2 NA/TM) by electrochemical transformation. As a three-dimensional electrode, Ni-Bi NA/TM exhibited high catalytic activity toward the oxygen evolution reaction and required a low overpotential of 430 mV at 10 mAcm(-2) in 0.1 M potassium borate (pH 9.2), with outstanding long-term stability and high turnover frequency.

It is highly needed but still a difficult challenge to achieve energy-saving electrolytic hydrogen generation. In this communication, we describe the first use of iron phosphide nanosheets array on Ni foam as a high-active and durable catalyst for electrochemical hydrazine oxidation reaction (HzOR) in alkaline media. The high hydrogen-evolving activity of this catalyst electrode and the substitution of sluggish oxygen evolution with thermodynamically more favorable HzOR enables the construction of a stable two-electrode energy-efficient electrolytic hydrogen generation system capable of driving 125 mA cm−2 at a cell voltage of 0.5 V to in 1.0 M KOH with 0.5 M hydrazine.

Using sterculia lychnophora seeds as precursors for the first time, fluorescent carbon dots (CDs) were synthesized by simple hydrothermal treatment. The quantum yield of as-synthesized CDs was 6.9% by using quinine sulfate as the reference. The fluorescence of CDs could be effectively quenched by a MnO2 nanosheet based on fluorescence resonance energy transfer (FRET). Ascorbic acid (AA) could reduce MnO2 to Mn2+ and result in the destruction of the MnO2 nanosheets, which could induce the fluorescence recovery of the CDs. In particular, alkaline phosphatase (ALP) could bio-catalyze acid 2-phosphate (AAP) hydrolysis to AA. Here, an efficient fluorescence probe based on a CDs-MnO2 nanosheet for rapid and selective detection of ALP was reported for the first time. Excellent performance for the detection of ALP was observed with high sensitivity and a detection limit of 0.4U/L owing to the low background. The detection of ALP in human serum was conducted with satisfactory results, demonstrating its potential applications in clinical diagnosis.

Among reported electrode materials, a nanoarray is an attractive architecture for molecular detection because of its large specific surface area and easy accessibility for target molecules. Here, a new Fe3 N-Co2 N nanowires array grown on carbon cloth (Fe3 N-Co2 N/CC) is reported as a non-noble-metal bifunctional catalyst electrode for high-performance glucose oxidation and H2 O2 reduction. As an electrochemical non-enzymatic sensor for glucose detection, Fe3 N-Co2 N/CC shows a fast response time of 8 s, a low detection limit (LOD) of 77 nm (signal/noise=3), and a high sensitivity of 4333.7 μA mm-1 cm-2 . As an H2 O2 sensor, it shows a LOD of 59 nm (signal/noise=3) and a sensitivity of 2273.8 μA mm-1 cm-2 with a response time of 2 s. In addition, the proposed sensor is stable with high selectivity, specificity, and reproducibility, and its application for real sample analysis has been successfully demonstrated.

It is highly desired but still remains a key challenge to develop iron-based large-surface-area arrays as heterogeneous water oxidation catalysts that perform efficiently and durably under mild pH conditions for solar-to-hydrogen conversion. In this work, we report the in situ derivation of an iron phosphate–borate nanosheet array on carbon cloth (Fe–Pi–Bi/CC) from an iron phosphide nanosheet array via oxidative polarization in a potassium borate (KBi) solution. As a 3D catalyst electrode for water oxidation at mild pH, such a Fe–Pi–Bi/CC shows high activity and strong long-term electrochemical durability, and it only demands an overpotential of 434 mV to drive a geometrical catalytic current density of 10 mA cm–2 with maintenance of its activity for at least 20 h in 0.1 M KBi. This study offers an attractive earth-abundant catalyst material in water-splitting devices toward the large-scale production of hydrogen fuels under benign conditions for application.

Probe for α-ketoglutaric acid (α-KA) usually provides low sensitivity, invisible colour change and complex procedure with surfacants, which limits the accurate, sensitive quantification and mornitoring of α-KA in biological samples. Essentially different from the routine sensing mechanism, a special mechanism of photo-induced electron transfer (PET) combining with large absorption red-shift (rather than emission) has been designed to develop a facile yet multifunctional probe for the simultaneous fluorimetric, absorption-ratiometric and colorimetric detections of α-KA in biological samples. Effective inhibition of PET ensured the intense fluorescence turn-on (60 fold) and qutie low detection limit (0.9 μM) for α-KA without need of any surfacants. Dramatical colour change caused by the large absorption red shift (100 nm) from UV–vis region enabled the colormetric analysis of α-KA by naked-eye. Meanwhile, the large absorption red shift also contributed to the ratiometric detection, allowing for the accurate quantification of α-KA in complex biological sample. With this probe, ratiometric detection, naked eye mornitoring and imaging of α-KA in serum, living cells and tissues are realized for the first time.

Nanostructures possess distinct quenching ability toward fluorophores with different emission frequencies and have been intensively used as nanoquenchers for homogeneous nucleic acid detection. Complete understanding of such a sensing system will provide significant guidance for the design of superior sensing materials, which is still lacking. In this Letter, we demonstrate the development of FeP nanowires as a nanoquencher for high-performance fluorescent nucleic acid detection with much superior performance to α-Fe2O3 counterparts. The whole detection process is complete within 1 min, and this fluorosensor presents a detection limit as low as 4 pM with strong discrimination of single-point mutation. Electrochemical tests and density functional theory calculations reveal that FeP NWs are superior in both conductivity for facilitated electron diffusion and hydrogen-evolving catalytic activity for favorable electron depletion, providing further experimental and theoretical insights into the enhanced sensin...

In this Communication, we report a high-efficiency electrocatalyst for electrochemical water oxidation based on an Fe-doped Ni2P nanosheet array on a conductive carbon cloth. This catalyst shows a low onset overpotential of 190 mV, and it demands overpotentials of only 215 and 235 mV to drive 50 and 100 mA cm–2, respectively, with high electrochemical durability. This work offers us an attractive earth-abundant 3D catalyst electrode in water-splitting devices toward the mass production of hydrogen fuels for applications.

Developing high-performance water oxidation electrocatalysts working under mild conditions is highly desirable, but still remains challenging. In this communication, we report the in situ surface derivation of an Fe–Co–Bi layer (4–7 nm in thickness) on an Fe-doped Co3O4 nanowire array supported on carbon cloth (Fe–Co3O4/CC). As a 3D catalyst electrode for water oxidation, such a core–shell Fe–Co3O4@Fe–Co–Bi nanoarray (Fe–Co3O4@Fe–Co–Bi/CC) demonstrates superior activity over that of a Co3O4-derived nanoarray catalyst, with the need of an overpotential of 420 mV to drive a geometrical catalytic current density of 10 mA cm−2 in 0.1 M potassium borate (pH = 9.2). Notably, this catalyst also shows good long-term stability with high turnover frequencies.

It is highly desirable but still a challenging task to find a simple, fast and straightforward method to greatly improve the alkaline oxygen evolution reaction (OER) performance of a NiCo2O4 catalyst. In this communication, we demonstrate that developing an amorphous borate shell on a NiCo2O4 surface can boost its OER activity in alkaline media. As a 3D catalyst electrode, a NiCo2O4@Ni–Co–B nanoarray on carbon cloth needs an overpotential of only 270 mV to achieve a geometrical catalytic current density of 10 mA cm−2 in 1.0 M KOH, which is 100 mV less than that for a NiCo2O4 nanoarray. Notably, this electrode also demonstrates strong electrochemical durability, maintaining its activity for at least 100 h. The superior activity of NiCo2O4@Ni–Co–B is attributed to the amorphous Ni–Co–B shell on NiCo2O4 favoring the in situ electrochemical generation of more active species during water oxidation.

In this study, a coumarin-based probe (probe 1) bearing a maleimide group was used to rapidly and selectively detect thiols. After inducing thiols, this probe presented a significant fluorescence enhancement (≥22-fold), whereas other amino acids that had no sulfhydryl group just generated slight changes. The detection limits were determined to be as low as 7.41 nM for Cys, 6.06 nM for GSH, and 7.73 nM for Hcy based on S/N = 3. Furthermore, this probe possessed excellent water solubility and successfully detected thiols in PBS (pH 7.4, 99.5%). More importantly, the practical application of probe 1 for the selective detection of thiols was successfully demonstrated in living T24 cells.

It is highly attractive to construct cost-effective hybrid electrocatalysts with superior activity for the hydrogen evolution reaction (HER) in acids. In this communication, we report a novel structure consisting of a Cu3P-CoP hybrid nanowire array supported on carbon cloth (Cu3P-CoP/CC) as a superior HER electrocatalyst in acidic media. Owing to the synergistic effect between Cu3P and CoP, this Cu3P-CoP/CC catalyst exhibits superior catalytic HER performance, needing an overpotential of 59 mV to drive a current density of 10 mA cm-2 in 0.5 M H2SO4, 24 and 130 mV less than that for CoP/CC and Cu3P/CC, respectively. Moreover, this catalyst also shows high long-term electrochemical durability.

In this communication, we first report a fast and low-temperature preparation of Se doped Fe2O3 (Se-Fe2O3) nanorod arrays grown on a Ti plate with superior photoelectrochemical (PEC) performance for water oxidation. The Se-Fe2O3 offers a photocurrent density of 1.44 mA cm−2 at 1.23 V vs. the RHE in 1.0 M NaOH under simulated light (AM 1.5 G, 100 mW cm−2) irradiation, 3.13 times that of undoped Fe2O3, with a 90 mV cathodic shift of the onset potential. Experimental studies indicate that the superior PEC activity is ascribed to the increased electrical conductivity and carrier density arising from Se doping, which is of great benefit to improve the charge separation efficiency in bulk Se-Fe2O3. The present Se-doping offers an attractive approach to fabricate high-performance semiconductor photoanodes for applications.

It is highly attractive to develop efficient hydrogen-evolving electrocatalysts under neutral conditions. In this communication, we report an amorphous FeMoS4 nanorod array on carbon cloth (FeMoS4 NRA/CC) prepared by hydrothermal treatment of an FeOOH nanorod array on carbon cloth (FeOOH NRA/CC) in (NH4)2MoS4 solution. As a 3D electrode for hydrogen evolution electrocatalysis, this FeMoS4 NRA/CC demonstrates superior catalytic activity and strong long-term electrochemical durability in 1.0 M phosphate buffered saline (pH: 7). It needs an overpotential of 204 mV to drive a geometrical current density of 10 mA cm−2, which is 450 mV less than that for FeOOH NRA/CC. Density functional theory calculations suggest that FeMoS4 has a more favourable hydrogen adsorption free energy than FeOOH.