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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.

Developing highly efficient and non-noble-metal catalysts is of great importance for electrochemical energy storage and conversion. In this communication, we report the development of a porous Ni3N nanosheet array on carbon cloth (Ni3N NA/CC) as a high-performance and durable electrocatalyst for urea oxidation. To drive 10 mA cm−2, this Ni3N NA/CC only demands a potential of 1.35 V in 1.0 M KOH with 0.33 M urea. The high catalytic activity of the hydrogen evolution reaction enables Ni3N NA/CC as a bifunctional catalyst electrode for electrochemical hydrogen production and the two-electrode electrolyzer is capable of offering 10 mA cm−2 at a cell voltage of only 1.44 V, 120 mV less than that for the urea-free counterpart.

In this Communication, cobalt phosphate (Co-Pi) has been successfully developed on a Co(CO3)0.5(OH)·0.11H2O nanoarray (CCH NA) on Ti mesh in neutral phosphate-buffered solution (PBS) via in situ electrochemical surface derivation. The resulting core@shell structured CCH@Co-Pi NA/Ti exhibits remarkable activity toward water oxidation with the need of an overpotential of 460 mV to achieve a geometrical catalytic current density of 10 mA cm−2 in 0.1 M PBS, with a high turnover frequency of and long-term electrochemical stability.

Designing and developing non-noble-metal electrocatalysts for efficient full water splitting at neutral pH is highly desired but still remains a huge challenge. In this communication, we report the development of homologous Co-based nanowire films, Co2N nanowire film on a Ti mesh (Co2N/TM) and Co-phosphate nanowire film on a Ti mesh (Co–Pi/TM), as complementary catalysts for stable electrochemical hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in neutral electrolyte. Co2N/TM shows remarkable HER activity with the need of an overpotential of 290 mV to drive 10 mA cm−2 in 1.0 M phosphate-buffered saline (PBS), and Co–Pi/TM is superior in OER activity affording 10 mA cm−2 at overpotentials of only 430 and 300 mV in 0.1 and 1.0 M PBS, respectively. The two-electrode water electrolyzer using Co2N/TM as a cathode and Co–Pi/TM as an anode affords a water-splitting current density of 10 mA cm−2 at a cell voltage of 1.78 V with 100% Faradaic efficiency in 1.0 M PBS, promising the practical uses of such homologous Co-based catalyst materials in technological devices.

Developing nanoporous nanoarray electrocatalysts for efficient water oxidation in environmentally benign media is highly desired but still remains a key challenge. In this communication, we report the fabrication of a nanoporous crystalline CoB2O4 nanowire array on Ti mesh (CoB2O4/TM) from a Co(OH)F nanowire array on Ti mesh (Co(OH)F/TM) via an anion-exchange reaction. As a three dimensional (3D) catalyst electrode for water oxidation, CoB2O4/TM exhibits superior catalytic activity and needs an overpotential of only 446 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 strong long-term electrochemical durability with high turnover frequency values of 0.19 and 0.81 mol O2 per s at overpotentials of 400 and 500 mV, respectively.

The development of cost-effective and high-performance water oxidation electrocatalysts operating in carbonate (Ci) electrolytes is highly desired but still remains a great challenge. In this communication, we report the in situ electrochemical development of an amorphous Ni–Ci layer on a NiO nanosheet array supported on carbon cloth (NiO@Ni–Ci/CC) as a 3D catalyst electrode for water oxidation in 1.0 M KHCO3 (pH: 8.3). To drive a geometrical catalytic current density of 15 mA cm−2, such core–shell structured NiO@Ni–Ci/CC only demands an overpotential of 387 mV, with its catalytic activity being maintained for at least 25 h. And at an overpotential of 500 mV, this catalyst electrode achieves a high turnover frequency of 0.18 mol O2 per s.

Developing non-noble-metal hydrogen evolution reaction electrocatalysts with high activity is critical for future renewable energy systems. Here we describe the development of a self-supported NiMoS4 nanosheet array on Ti mesh (NiMoS4/Ti) through a facile two-step hydrothermal strategy. As a 3D nanoarray electrode for electrochemical hydrogen evolution, NiMoS4/Ti shows exceptionally high catalytic activity and strong durability in 0.1 M KOH (pH: 13). It needs overpotentials of only 194 and 263 mV to drive geometrical catalytic current densities of 10 and 50 mA cm−2, respectively. Moreover, such a catalyst also demonstrates superior long-term stability with a high turnover frequency of 0.75 mol H2 s−1 at an overpotential of 148 mV. Density functional theory calculations suggest a more favorable hydrogen adsorption free energy on the NiMoS4 surface.

In this communication, we demonstrate the use of N-doped carbon dots (N-CDs) as a co-catalyst for hematite (α-Fe2O3) nanorod arrays on a Ti sheet for photoelectrochemical water oxidation. Under simulated light irradiation, the photocurrent density of the resulting N-CDs@α-Fe2O3/Ti as a photoanode exhibits a 3.4 times increase with a 280 mV cathode shift of the onset potential relative to that of pristine α-Fe2O3/Ti, with excellent photostability. The up-conversion fluorescent properties of N-CDs enable the absorption of longer wavelength irradiation with emission of short wavelength light to excite α-Fe2O3, leading to the generation of more electron–hole pairs.

Ammonia borane (AB) has been regarded as a promising candidate for chemical hydrogen storage but needs an efficient catalyst for hydrolytic hydrogen generation. In this communication, a CoP nanoarray in situ grown on a Ti mesh (CoP NA/Ti) is reported as a robust non-noble-metal catalyst for effective hydrogen generation from AB hydrolysis. The initial turnover frequency and activation energy of CoP NA/Ti for AB hydrolysis are 42.8 molH2 molCoP−1 min−1 and 34.1 kJ mol−1, respectively. Moreover, this catalyst shows only 0.15% loss in catalytic activity after 10 cycles and its easy separation nature from fuel solution enables its attractive use as an on/off switch toward on-demand hydrogen generation. The amazing catalytic activity and high durability of such a catalyst are attributed to the fact that the 3D nanoarray configuration not only allows for more efficient diffusion of the fuel and hydrogen gas but favors the exposure of more active sites, and on the other hand, in situ growth of CoP on a Ti mesh also ensures strong adhesion between them.

Zeolitic imidazolate frameworks (ZIF) are attracting considerable attention for their applications in adsorbents/separation as well as catalysis. In this article, we proposed a simple strategy to fabricate semiconductor–ZIF core–shell nanocomposites, which exhibited remarkable coherent function for adsorption and photocatalytic degradation of organic pollutants. The current nanocomposites were composed of ZnO/CdS and ZIF-8, where spindle-like ZnO nanoparticles not only acted as the seeding material but also worked as the Zn2+ source for the formation of ZIF-8. The as-prepared ZnO/CdS@ZIF-8 core–shell nanocomposites displayed distinct photocatalytic activity for methylene blue (MB) and rhodamine B (RhB) owing to the unique pore structure and thus absorption effect of the ZIF-8 shell. To this end, the ZnO/CdS@ZIF-8 core–shell nanocomposites could find important applications in photocatalytic degradation of pollutants.

It is attractive but still remains challenging to develop efficient water oxidation electrocatalysts working in a carbonate (Ci) electrolyte. In this communication, we report that a Ni–Co–Ci layer can be developed on a NiCo2O4 nanowire array supported on carbon cloth (NiCo2O4/CC) via electrochemical surface derivation of NiCo2O4. The resulting NiCo2O4@Ni–Co–Ci core–shell nanowire array on carbon cloth (NiCo2O4@Ni–Co–Ci/CC) exhibits high activity toward water oxidation in 1.0 M KHCO3 (K–Ci, pH = 8.3) with the overpotential requirement of 309 mV to drive 10 mA cm−2. NiCo2O4@Ni–Co–Ci/CC also shows long-term electrochemical stability for 20 h and a high turnover frequency of 0.464 mol O2 s−1 at an overpotential of 600 mV.

Nontoxic prodrugs, especially activated by tumor microenvironment, are urgently required for reducing the side effects of cancer therapy. And combination of chemo-photodynamic therapy prodrugs show effectively synergetic therapeutic efficiency, however, this goal has not been achieved in a single molecule. In this work, we developed a mitochondrial-targeted prodrug PNPS for near infrared (NIR) fluorescence imaging guided and synergetic chemo-photodynamic precise cancer therapy for the first time. PNPS contains a NIR photosensitizer (NPS) and an anticancer drug 5′-deoxy-5-fluorouridine (5′-DFUR). These two parts are linked and caged through a bisboronate group, displaying no fluorescence and very low cytotoxicity. In the presence of H2O2, the bisboronate group is broken, resulting in activation of NPS for NIR photodynamic therapy and activation of 5′-DFUR for chemotherapy. The activated NPS can also provide a NIR fluorescence signal for monitoring the release of activated drug. Taking advantage of the high H2O2 concentration in cancer cells, PNPS exhibits higher cytotoxicity to cancer cells than normal cells, resulting in lower side effects. In addition, based on its mitochondrial-targeted ability, PNPS exhibits enhanced chemotherapy efficiency compare to free 5′-DFUR. It also demonstrated a remarkably improved and synergistic chemo-photodynamic therapeutic effect for cancer cells. Moreover, PNPS exhibits excellent tumor microenvironment-activated performance when intravenously injected into tumor-bearing nude mice, as demonstrated by in vivo fluorescence imaging. Thus, PNPS is a promising prodrug for cancer therapy based on its tumor microenvironment-activated drug release, synergistic therapeutic effect and “turn-on” NIR imaging guide.

It is of great importance but still remains a key challenge to develop non-noble-metal bifunctional catalysts for efficient full water splitting under mild pH conditions. In this communication, we report the in situ electrochemical development of an ultrathin Ni–Bi layer on a metallic Ni3N nanosheet array supported on a Ti mesh (Ni3N@Ni–Bi NS/Ti) as a durable 3D core/shell structured nanoarray electrocatalyst for water oxidation at near-neutral pH. The Ni3N@Ni–Bi NS/Ti demands overpotentials of 405 and 382 mV to deliver a geometrical catalytic current density of 10 mA cm−2 in 0.1 and 0.5 M K–Bi (pH: 9.2), respectively, superior in activity to Ni3N NS/Ti and most reported non-precious metal catalysts under benign conditions. It also performs efficiently for the hydrogen evolution reaction requiring an overpotential of 265 mV for 10 mA cm−2 and its two-electrode electrolyser affords 10 mA cm−2 at a cell voltage of 1.95 V in 0.5 M K–Bi at 25 °C.

The exploration of high-performance and earth-abundant water oxidation catalysts operating under mild conditions is highly attractive and challenging. In this communication, core–shell CoFe2O4@Co–Fe–Bi nanoarray on carbon cloth (CoFe2O4@Co–Fe–Bi/CC) was successfully fabricated by in situ surface amorphization of CoFe2O4 nanoarray on CC (CoFe2O4/CC). As a 3D water oxidation electrode, CoFe2O4@Co–Fe–Bi/CC shows outstanding activity with an overpotential of 460 mV to drive a geometrical catalytic current density of 10 mA cm−2 in 0.1 M potassium borate (pH 9.2). Notably, it also demonstrates superior long-term durability for at least 20 h with 96% Faradic efficiency. Density functional theory calculations indicate that the conversion from OOH* to O2 is the rate-limiting step and the high water oxidation activity of CoFe2O4@Co–Fe–Bi/CC is associated with the lower free energy of 1.84 eV on a Co–Fe–Bi shell.

In this communication, we demonstrate the development of a MnCo2S4 nanowire array directly grown on Ti mesh (MnCo2S4 NA/TM) as an electrocatalyst for the oxygen evolution reaction in 1.0 M KOH which only needs an overpotential of 325 mV to drive 50 mA cm−2. At an overpotential of 500 mV, this electrocatalyst achieves a high turnover frequency of 0.81 mol O2 per s.

It is highly desirable but still remains a big challenge to develop earth-abundant bifunctional catalysts for urea oxidation and hydrogen evolution electrocatalysis towards more energy-efficient electrolytic hydrogen generation. In this study, we report that nickel phosphide nanoflake arrays on carbon cloth (Ni2P NF/CC) behave as a highly-active durable 3D catalyst electrode for the urea oxidation reaction (UOR) with the required potential of 0.447 V to achieve a geometrical catalytic current density of 100 mA cm−2 in a 1.0 M KOH with 0.5 M urea. Remarkably, the high hydrogen evolution reaction (HER) activity of Ni2P NF/CC enables it to be a bifunctional catalyst for both the UOR and HER towards energy-saving electrochemical hydrogen production, and its two-electrode alkaline electrolyzer requires a cell voltage of only 1.35 V to attain 50 mA cm−2, which is 0.58 V less compared with that required for pure water splitting to achieve the same current density, with remarkable long-term electrochemical durability and nearly 100% Faradaic efficiency for hydrogen evolution.

A luminescent metal organic framework (LMOF) of type UiO-66-NH2 was chosen for specific and sensitive detection of trace levels of hypochlorite. Hypochlorite causes the quenching of the blue fluorescence of nano-UiO-66-NH2 (with excitation/emission maxima at 325/430 nm), and this finding forms the basis for a fluorometric assay for hypochlorite. The method overcomes disadvantages of conventional redox-probes which are interfered by oxidants with oxidation capability stronger than that of hypochlorite. Compared with other fluorescent probes for sensing hypochlorite, UiO-66-NH2 has a comparable detection limit of 0.3 μmol L−1 and a broad linearity relationship in the range of 1–8 μmol L−1. The probe was successfully applied to the detection of hypochlorite in complex water samples and living Hela cells.

This study demonstrates a novel and convenient ratiometric fluorescent method for the detection of alkaline phosphatase (ALP) activity. Amino-functionalized mesoporous silica nanoparticle-gold nanoclusters (MSN-AuNCs) nanocomposites were integrated with o-phenylenediamine (OPD) to form a ratiometric fluorescence nanoplatform. The presence of ALP induced the generation of quinoxaline (QX) derivative which called 3-(dihydroxyethyl)furo[3,4-b]quinoxaline-1-one (DFQ) with strong fluorescence emission at 450 nm, while the orange-red fluorescence of MSN-AuNCs at 580 nm was slightly quenched. Meanwhile, an obvious fluorescence color change from orange-red to purple and finally to blue can be observed by naked eyes with the increasing of ALP concentration. Therefore, employing the fluorescence emission of DFQ at 450 nm as the reporter signal and the fluorescence emission of MSN-AuNCs at 580 nm as a reference signal, a sensitive ratiometric detection method for ALP was developed. Quantitative detection of ALP activity in the linear range from 0.2 to 80 U/L with a detection limit of 0.1 U/L can be realized in this way, which endows the assay with high sensitivity enough for practical detection of ALP in human serum samples.

Herein, a dual-emission metal-organic framework based ratiometric fluorescence nanoprobe was reported for detecting copper(II) ions. In particular, carbon dots (CDs) and gold nanoclusters (AuNCs) were embedded into ZIF-8 (one of the classical metal-organic frameworks) to form CDs/AuNCs@ZIF-8 nanocomposites, which exhibited dual-emission peaks at UV excitation. In the presence of Cu

A sensitive photoelectrochemical (PEC) aptasensor was constructed for prostate-specific antigen (PSA) detection using an enhanced photocurrent response strategy. The p-n heterostructure CdS-Cu

Ferric ion (Fe

An ultrasensitive photoelectrochemical (PEC) biosensor was constructed based on gold nanoparticles (Au NPs)/tungsten sulfide nanorod array (WS

G-triplexes have been reported recently with the similar function to G-quadruplex that can combine with thioflavin T (ThT) and emit strong fluorescence but easier to be controlled and excited. In this work, we report an Hg

The fast and accurate real-time monitoring of hydrogen peroxide (H

An enzyme-free electrochemical method is described for the determination of trace levels of malathion. It is based on a nanostructured copper-cerium oxide (CuO-CeO2) composite prepared by calcination of a Cu(II)/Ce(III) metal-organic framework. The morphology, crystal structure and elemental composition of composite was studied by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The principle for malathion determination is based on the fact that the redox signal of CuO (best measured at around −0.1 V vs. SCE) (at 100 mV/s) is inhibited by malathion due to affinity between CuO and the sulfur groups of malathion. The introduction of CeO2 into the composite system further improves the analytical performance. This is attributed to the unique microstructure and the synergistic effect between CuO and CeO2. Experimental parameters like solution pH value, Cu/Ce molar ratio, accumulation potential, accumulation time, and CuO-CeO2 volume on the electrode were optimized. The assay has a linear range of 10 fM to 100 nM and a 3.3 fM detection limit (at S/N = 3). The electrode is selectively inhibited by malathion even in the presence of potentially interfering substances.

A photoelectrochemical (PEC) method has been developed for sensitive detection of trypsin. It is based on the use of a composite consisting of MoS2 nanosheets and TiO2 nanorods (MoS2-TiO2). The material has a high specific surface area, superior electrical conductivity, excellent biocompatibility and good band gap matching. The composite was synthesized by a one-pot method using TiO2 as a template. This results in a uniform distribution of the MoS2 nanosheets (

Nanosheets of tungsten disulfide (WS2) were used to improve the physicochemical properties of reduced graphene oxide aerogel (rGA). The nanosheets were directly integrated into 3D hybrid architecture of rGA by a solvothermal mixing method by which the WS2 sheets were assembled onto the conductive graphene network. WS2 with highly exfoliated and defect-rich structure made the WS2/rGA composite possess plentiful active sites, and this enhanced the electrocatalytic capability of the composite. The introduction of poorly conductive WS2 into 3D rGA system decreases the background current of rGA when used as electrode material. This is advantageous in terms of signal to-noise ratio and analytical performance in general. The WS2/rGA electrode, best operated at a potential of 0.68 V (vs. SCE) has a linear response in the 0.01 to 130 μM nitrite concentration range with a low detection limit of 3 nM (at S/N = 3). It is selective, reproducible, stable and is successfully applied to the determination of nitrite in spiked bacon samples.

A fluorometric turn-on assay is described for ascorbic acid (AA). It is based on the controlled release of polyallylamine-stabilized gold nanoclusters (polyallylamine-AuNCs) from MnO2 nanosheets. In an aqueous solution of near-neutral pH value, the positively charged capped AuNCs are adsorbed on the surface of the negatively charged MnO2 nanosheets. The adsorption leads to the quenching of the fluorescence of the AuNCs. However, in the presence of AA, MnO2 is reduced to Mn2+. This causes the destruction of the MnO2 nanosheets. As a result, the fluorescence of the polyallylamine-AuNCs at 615 nm is recovered. This method for determination of AA is inexpensive, sensitive, and selective. It works in the 0.01 to 200 μM concentration range and has a 3.2 nM detection limit (for S/N = 3).

The level of alkaline phosphate (ALP) is a significant biomarker index in organism. In this work, a label-free and sensitive G-quadruplex fluorescence assay for monitoring ALP activity has been developed with the assistance of Cu

A method is described for photoelectrochemical determination of the activity of alkaline phosphatase (ALP). It employs an indium tin oxide (ITO) electrode modified a CdS quantum dots@graphene (CdS@GR) composite and hexagonal cobalt oxyhydroxide (CoOOH) nanosheets. The CdS@GR nanocomposite was synthesized by assembling the CdS quantum dots onto a GO film to receive a basic photocurrent response of the ITO. This is further improved by covering it with CoOOH nanosheets. Secondly, 2-phospho-L-ascorbic acid (AAP) is added as a substrate for ALP. Its hydrolysis yields ascorbic acid which reduces CoOOH to form cobalt(II) ion. As a result, the CoOOH nanosheets decompose. This is accompanied by a reduction of the photocurrent. The effect was used to design a selective and sensitive assay of determination of the activity of ALP. Under the optimized experimental conditions, response is linear in the 10 to 300 U·L−1ALP activity range. The detection limit is 1.5 U·L−1 at a signal-to-noise ratio of 3.

A fluorometric turn-on assay is described for ascorbic acid (AA). It is based on the controlled release of polyallylamine-stabilized gold nanoclusters (polyallylamine-AuNCs) from MnO

In this study, a composite nanosheet array (Co-MOF/TM) was developed by in-situ growing the cobalt-based metal-organic framework (Co-MOF) on titanium mesh (TM) to fabricate a non-enzymatic electrochemical sensor for detection of H2O2 released from living cells. The amperometric current in cyclic voltammetry (CV) enhanced linearly with the increase of H2O2 concentration. Due to the unique properties of Co-MOF, the proposed sensor showed excellent H2O2 detection performance, including low detection limits (0.25 μM, S/N = 3), wide linear range (1–13,000 μM, R > 0.995), high sensitivity (98.75 μA mM−1 cm−2), fast response within 3 s, and high selectivity in PBS solution. More importantly, the proposed electrode can be used to in situ sensing H2O2 released form A549 cells. This work provides a new design strategy of nonenzymatic electrochemical sensing method for amperometric determination of H2O2 in biological environment and also shows high perspective for sensing other biomolecules using other active MOFs as electrocatalytic electrodes.

Soft colloidal particles with multiple surface patches of differing composition are critical to the development of complex macroscopic structures that can serve as interfacial catalysts, macroscale surfactants, electronically responsive materials, and drug delivery vehicles. Here, we present a continuous process for the scalable formation of soft colloidal particles with multiple surface domains that employs well-established principles of polymer precipitation and phase separation to controllably shape particle architectures. Our results illustrate the broad range of particle morphologies, including Janus and Cerberus structures, and surface compositions accessible to our versatile solution-based assembly system. We also identify polymer diffusion, precipitation, and vitrification as the primary determinants of particle structure for the first time.

A zirconium-based metal–organic frameworks (MOF), with 2-aminoterephthalic acid as linkers, named UiO-66-NH2, has been synthetized and characterized in a dispersive solid-phase extraction (DSPE) procedure in combination with high-performance liquid chromatography (HPLC) with fluorescence detection (FLD) for the pre-concentration and detection of sialic acids (SAs) in serum samples. In this study, UiO-66-NH2 was employed for the first time as a novel DSPE sorbent for sample pretreatment. Parameters which influence the extraction efficiency such as the amount of MOF, nature of the desorption solvent and its amount, adsorption time and desorption time were investigated and optimized. Under the optimized conditions, better extraction results were obtained by UiO-66-NH2 based DSPE for the extraction of SAs from serum samples than traditional sample preparation methods. Detection limits of the method as low as 0.16 pmol for N-glycolylneuraminic acid (Neu5Gc) and 0.11 pmol for N-acetylneuraminic acid (Neu5Ac) were obtained, with determination coefficients (R2) higher than 0.9995 for the range 10–1000 pmol L−1, average recoveries of >91.3% at three different spiked levels (1, 5 and 10 ng mL−1), and relative standard deviation (RSD) values below 3.4%. The proposed method was demonstrated to be sensitive enough for determination of SAs from bio-samples.

In this work, a sensitive and selective fluorescence sensing platform was developed for the detection of tyrosinase (TYR) activity and its inhibitor screening using graphene quantum dots (GQDs) as probes. Upon excitation at 383 nm, GQDs displayed an intense emission at 445 nm. TYR, a typical polyphenol oxidase, can catalyze the oxidation of dopamine (DA) to dopaquinone and then a fluorescence resonance energy transfer (FRET) process between GQDs and dopaquinone took place. Therefore, the fluorescence of GQDs could be quenched. Thus, quantitative evaluation of TYR activity was established in terms of the relationship between fluorescence quenching efficiency and TYR activity. A linear range was obtained from 0.005 to 0.5 U mL−1 and from 0.5 to 5.0 U mL−1, respectively. A detection limit of 0.0015 U mL−1 was obtained, which was lower than those of reported papers. In addition, it constructed a useful platform for TYR inhibitor screening.

A novel, sensitive and convenient method, utilizing ultrasonic-assisted closed in-syringe hydrolysis and derivatization (UCSHD) prior to high performance liquid chromatography (HPLC) coupled with fluorescence detection (FLD) and online mass spectrometry (MS) identification, has been developed for determination of sialic acids. The pivotal parameters affecting the release of sialic acids from serum and the derivatization were investigated using a response surface methodology (RSM). Under optimized conditions, the maximum yield of sialic acids release were achieved and they were labeled successfully in a relatively short time of 72 min (traditional time > 3 h) for the reason of the combination of hydrolysis steps with derivatization in a closed system with the assistance of ultrasonication. Excellent linearity (R2 > 0.9991) in the calibration range of 0.5–16 μmol mL−1 and quite low detection limits (LODs) (0.30 pmol for Neu5Ac and 0.21 pmol for Neu5Gc) were achieved. When the established UCSHD-HPLC-FLD-MS method was applied to the analysis of sialic acids in various human sera, low relative error (RE: −3.4% to 2.5%), high recoveries (90–96%) and intra- and inter-day precisions (RSD, 0.9–2.2% for Neu5Ac and 1.4–2.8% for Neu5Gc) were also obtained, demonstrating obvious advantages for the accurate, sensitive and convenient determination of sialic acids in bio-samples.

We report an ultrasensitive electrochemical immunosensor designed for the detection of protein biomarkers using horseradish peroxidase (HRP)-loaded silica-poly(acrylic acid) brushes (SiO2-SPAABs) as labels. HRP could be efficiently and stably accommodated in the three-dimensional architecture of the SiO2-SPAABs and the SiO2-SPAABs-HRP exhibited high catalytic performance towards o-phenylenediamine (OPD) oxidation in the presence of H2O2, which resulted in significant differential pulse voltammetric (DPV) response change and color change. Using human IgG (HIgG) as a model analyte, a sandwich-type immunosensor was constructed. In particular, graphene oxide (GO) and SiO2-SPAABs-HRP were used to immobilize capture antibody (Ab1) and bind a layer of detection antibody (Ab2), respectively. The current biosensor exhibited a good linear response of HIgG from 100pg/mL to 100μg/mL with a detection limit of 50pg/mL (S/N=5). The sensitivity was 6.70-fold higher than the conventional enzyme-linked immunosorbent assays. The immunosensor results were validated through the detection of HIgG in serum samples.

The fluorescence intensity of gold nanoclusters (AuNCs) is inversely related to the length of a peptide immobilized on its surface. This finding has been exploited to design a turn-on fluorescent method for the determination of the activity of peptidase. The β-site amyloid precursor protein-cleaving enzyme 1 (BACE1) was chosen as a model peptidase. BACE1 cleaves the peptide substrates on AuNCs, and the fluorescence intensity of the AuNCs (at exCitation/emission wavelengths of 320/405 nm) carrying the rest of the cleaved peptide is significantly higher than that of the AuNCs with uncleaved peptide. Transmission electron microscopy revealed a decrease in the size of the AuNCs which is assumed cause fluorescence enhancement. The assay was applied to the determination of BACE1 activity in spiked cell lysates, and recoveries were between 96.9 and 104.0 %.

Construction of novel photoelectrochemical (PEC) materials with unique structures can effectively improve the photoelectric conversion efficiency. Here, a self-supported Cu2O@Cu-MOF/copper mesh (CM) nanobelt arrays with high specific surface area, high orientation, and high photoelectric conversion performance is obtained by in-situ grown strategy. Such PEC aptasensor is constructed based on the Cu2O@Cu-MOF/CM combined with rolling circle amplification and enzymatic biocatalytic precipitation for vascular endothelial growth factor 165 analysis. This strategy achieves excellent cooperative signal amplification, which greatly improves the detection sensitivity. The PEC aptasensor exhibited a wide calibration ranged from 10 to 1 × 108 fM with a detection limit down to 2.3 fM (S/N = 3). The construction of semiconductor@MOFs has developed the potential application of MOFs in photoelectrochemical and found a reliable path for ultrasensitive detection of biomarkers.