Ultrasensitive Dual-Mode Visual/Photoelectrochemical Bioassay for Antibiotic Resistance Genes through Incorporating Rolling Circle Amplicons into a Tailored Nanoassembly.

As emerging contaminants in the environment, antibiotic resistance genes (ARGs) have aroused a global health crisis and posed a serious threat to ecological safety and human health. Thus, efficient and accurate onsite detection of ARGs is crucial for environmental surveillance. Here, we presented a colorimetric-photoelectrochemical (PEC) dual-mode bioassay for simultaneous detection of multiple ARGs by smartly incorporating rolling circle amplification (RCA) into a stimuli-responsive DNA nanoassembly, using the tetracycline resistance genes tetA and tetC as models. The tailored DNA nanoassembly containing RCA amplicons hybridized with specific signal probes: CuO nanoflowers-anchored signal DNA1 and HgO nanoparticles-anchored signal DNA2, respectively. Upon exposure to an acidic stimulus, numerous Cu2+ and Hg2+ were released, serving as the reporting agent of colorimetric/PEC dual-mode assay. The released Cu2+ and Hg2+ induced localized surface plasmon resonance shifts in Au nanorods and triangular Ag nanoplates through an etching process, respectively, enabling visual analysis of ARGs with distinguishing color changes. Meanwhile, numerous Cu2+ and Hg2+ triggered the amplified PEC variations via reacting with the photoactive layers of CuS/CdS and ZnS, respectively. Thus, a rapid and ultrasensitive colorimetric/PEC dual-mode detection of multiple ARGs was achieved with the detection limit down to 17.2 aM. Furthermore, such dual-mode bioassay could discriminate single-base mismatch and successfully determine ARGs in E. coli plasmids and sludge samples, holding great promise for point-of-care genetic diagnostics.

Efficient degradation of atrazine through in-situ anchoring NiCo2O4 nanosheets on biochar to activate sulfite under neutral condition.

Sulfite (S(IV)) is a promising substitute for sulfate radical-based advanced oxidation processes. Here, a composite of in-situ anchoring NiCo2O4 nanosheets on biochar (BC) was firstly employed as a heterogeneous activator for sulfite (NiCo2O4@BC-sulfite) to degrade atrazine (ATZ) in the neutral environment. The synergistic coupling of BC and NiCo2O4 endows the resulting composite excellent catalytic activity. 82% of the degradation ratio of ATZ (1 mg/L) could be achieved within 10 min at initial concentrations of 0.6 g/L NiCo2O4@BC, 3.0 mmol/L sulfite in neutral environment. When further supplementing sulfite into the system at 20 min (considering the depletion of sulfite), outstanding degradation efficiency (∼ 100%) were achieved in the next 10 min without any other energy input by the NiCo2O4@BC-sulfite system. The features of the prepared catalysts and the effects of some key parameters on ATZ degradation were systematically examined. A strong inner-sphere complexation (Co2+/Ni2+-SO32-) was explored between sulfite and the metal sites on the NiCo2O4@BC surface. The redox cycle of the surface metal efficiently mediated sulfite activation and triggered the series radical chain reactions. The generated radicals, in particular the surface-bound radicals were involved in ATZ degradation. High performance liquid chromatography-tandem mass spectrometry (LC-MS) technique was used to detect the degradation intermediates. Density functional theory (DFT) calculations were performed to illustrate the possible degradation pathways of ATZ. Finally, an underlying mechanism for ATZ removal was proposed. The present study offered a low-cost and sustainable catalyst for sulfite activation to remove ATZ in an environmentally friendly manner from wastewater.

Temperature-Responsive Nanocarrier-Regulated Alternative Release of "Cargos" for a Multiplex Photoelectrochemical Bioassay of Antibiotic-Resistant Genes.

A smart temperature stimuli-driven multiplex photoelectrochemical (PEC) assay was constructed for antibiotic resistance genes (ARGs) detection, where the stimuli-responsive gatekeeping by regulating the alternative release of "cargo" allowed for the simultaneous detection of multiple tetracycline resistance gene, using tetA (TDNA1) and tetC (TDNA2) as the model. Dual temperature-responsive nanoassemblies were embedded in the PEC bioassay as signal DNA tages: one thermoresponsive polymer (poly(N-isopropylacrylamide), PNIPAM)-capped mesoporous silica nanoparticles (MSN) with loading the "cargo" of HgO nanoparticles as signal DNA1 tags (SDNA1-PNIPAM@MSN@HgONPs) and the other antimony tartrate (SbT)-anchored silica nanospheres as signal DNA2 tags (SDNA2-SbT@SiO2NSs). At 20 °C, below the lower critical solution temperature (LCST) of PNIPAM, the "gatekeeper" PNIPAM in SDNA1-PNIPAM@MSN@HgONPs was in an ON state, igniting Hg2+ release through the pore of SiO2. While at above LCST (40 °C), it was in an OFF state. Likewise, the thermo-dependent dissociation of SbT endowed the grafted SDNA2 tags switching from the OFF (at 20 °C) to ON state (at 40 °C), igniting SbO+ release. The released Hg2+ and SbO+ triggered the amplified photocurrents due to the structure evolution of the photoactive layer into HgS/ZnS or Sb2S3/ZnS heterostructure, thus achieving sensitive detection of multiple ARGs: tetA, tetC, tetG, tetM, tetO, tetZ, tetX, and tetW. Combined with heat map analysis, rapid screening of the ARGs profiles in 12 samples could be realized. This bioassay is simple and accessible for multiple genes analysis with the detection limit down to 0.50 nM. And it was successfully applied for measuring tetracycline ARGs in real sludge samples.

Smart pH-Regulated Switchable Nanoprobes for Photoelectrochemical Multiplex Detection of Antibiotic Resistance Genes.

Antibiotic resistance, encoded via particular genes, has become a major global health threat and substantial burden on healthcare. Hence, the facile, low-cost, and precise detection of antibiotic resistance genes (ARGs) is crucial in the realm of human health and safety, especially multiplex sensing assays. Here, a smart pH-regulated switchable photoelectrochemical (PEC) bioassay has been created for ultrasensitive detection of two typical subtypes of penicillin resistance genes bla-CTX-M-1 (target 1, labeled as TDNA1) and bla-TEM (target 2, labeled as TDNA2), whereby pH-responsive antimony tartrate (SbT) complex-grafted silica nanospheres are ingeniously adopted as signal DNA1 tags (labeled as SDNA1-SbT@SiO2NSs). The operations of the PEC bioassay depend on the switchable dissociation of the pH-responsive SDNA1-SbT@SiO2NSs complex under the external pH stimuli, thus initiating the pH-regulated release of ions pre-embedded in sandwich-type DNA nanoassemblies. At acidic conditions, the dissociation of SDNA1 tags (ON state) triggers the release of the embedded SbO+. Under alkaline conditions, the dissociation of SDNA1 tags is inhibited (OFF state). The detection of TDNA2 was achieved via DNA hybridization-triggered metal ion release. The unwinding of the introduced hairpin T-Hg2+-T fragment, hybridized with the second anchored signal DNA (SDNA2), ignites the release of Hg2+. The released SbO+ or Hg2+ ions would trigger the formation of Sb2S3/ZnS or HgS/ZnS heterostructure through ion-exchange with the photosensitive ZnS layer, giving rise to the amplified photocurrents and eventually realizing the ultrasensitive detection of penicillin resistance genes subtypes, bla-CTX-M-1 and bla-TEM. The as-fabricated pH-regulated PEC bioassay, smartly integrating the pH-responsive intelligent unit as SDNA tags, pH-regulated release of embedded ions, and the subsequent ion-exchange-based signal amplification strategy, exhibits high sensitivity, specificity, low-cost, and ease of use for multiplex detection of ARGs. It can be successfully used for measuring bla-CTX-M-1 and bla-TEM in real E. coli plasmids, demonstrating great promise for developing a new class of genetic point-of-care devices.

Single-Atom Iron Boosts Electrochemiluminescence.

The traditional luminol-H2 O2 electrochemiluminescence (ECL) sensing platform suffers from self-decomposition of H2 O2 at room temperature, hampering its application for quantitative analysis. In this work, for the first time we employ iron single-atom catalysts (Fe-N-C SACs) as an advanced co-reactant accelerator to directly reduce the dissolved oxygen (O2 ) to reactive oxygen species (ROS). Owing to the unique electronic structure and catalytic activity of Fe-N-C SACs, large amounts of ROS are efficiently produced, which then react with the luminol anion radical and significantly amplify the luminol ECL emission. Under the optimum conditions, a Fe-N-C SACs-luminol ECL sensor for antioxidant capacity measurement was developed with a good linear range from 0.8 µm to 1.0 mm of Trolox.

Visual and photoelectrochemical analysis of antibiotic resistance genes enabled by surface-engineered ZIF-8@Au cascade nanozymes.

The aggravation of antibiotic resistance genes (ARGs) in the environment has posed a significant global health crisis. Accurate evaluation of ARGs levels in a facile manner is a pressing issue for environmental surveillance. Here, we demonstrate a unique dumbbell-shaped cascade nanozyme for visual/photoelectrochemical (PEC) dual-mode detection of ARGs. Gold nanoparticles (AuNPs) with tunable exposed facets are controllably anchored onto ZIF-8 dodecahedrons, exhibiting glucose oxidase (GOx)-like (ZIF-8@Au/G) and peroxidase (POD)-like (ZIF-8@Au/P) activities. Upon the occurrence of ARGs, an asymmetric cascade-amplified "dumbbell" configuration is spontaneously generated via target-induced DNA hybridization, comprising GOx-like ZIF-8@Au/G with capture DNA on one side and POD-like ZIF-8@Au/P with signal DNA on the opposite side. Such a cascade nano-system can efficiently oxidize colorless 2, 2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) into its green oxidation state and synergistically decompose H2O2, realizing colorimetric/PEC dual-mode ARGs detection with a detection limit of 0.112 nM. The applicability of the present bioassay is validated through measuring ARGs in real sludge samples. This work suggests the possibility to rationally design task-specific nanozymes and develop target-responsive nano-cascade assays for environmental monitoring.

New multifunctional porous materials based on inorganic-organic hybrid single-walled carbon nanotubes: gas storage and high-sensitive detection of pesticides.

Single-walled carbon nanotubes (SWNTs) that are covalently functionalized with benzoic acid (SWNT-PhCOOH) can be integrated with transition-metal ions to form 3D porous inorganic-organic hybrid frameworks (SWNT-Zn). In particular, N(2)-adsorption analysis shows that the BET surface area increases notably from 645.3 to 1209.9 m(2) g(-1) for SWNTs and SWNT-Zn, respectively. This remarkable enhancement in the surface area of SWNT-Zn is presumably due to the microporous motifs from benzoates coordinated to intercalated zinc ions between the functionalized SWNTs; this assignment was also corroborated by NLDFT pore-size distributions. In addition, the excess-H(2)-uptake maximum of SWNT-Zn reaches about 3.1 wt. % (12 bar, 77 K), which is almost three times that of the original SWNTs (1.2 wt. % at 12 bar, 77 K). Owing to its inherent conductivity and pore structure, as well as good dispersibility, SWNT-Zn is an effective candidate as a sensitive electrochemical stripping voltammetric sensor for organophosphate pesticides (OPs): By using solid-phase extraction (SPE) with SWNT-Zn-modified glassy carbon electrode, the detection limit of methyl parathion (MP) is 2.3 ng mL(-1).

Nitrate promoted defluorination of perfluorooctanoic acid in UV/sulfite system: Coupling hydrated electron/reactive nitrogen species-mediated reduction and oxidation.

A significantly accelerated defluorination of recalcitrant perfluorooctanoic acid (PFOA) was explored with the co-present nitrate (20 mg L-1) by UV/sulfite treatment (UV/sulfite-nitrate). The deep defluorination of PFOA and complete denitrification of nitrate were simultaneously achieved in UV/sulfite-nitrate system. At the initial 30 min, PFOA defluorination exhibited an induction period, exactly corresponding to the removal of the co-existed nitrate. Upon the induction period passed, an accelerated removal of PFOA (5 mg L-1) occurred, nearly 100% defluorination ratio reached within 2 h. Compared with those in UV/sulfite, the kinetics of PFOA decay, defluorination, and transformation product formations were greatly enhanced in UV/sulfite-nitrate system. Reactive nitrogen species (RNS) generated from eaq--induced reduction of nitrate were found to play significant roles on the promoted defluorination apart from eaq--mediated reductive defluorination. The investigations on solution pH (7.0-11.0) confirmed that the reductive defluorination of PFOA was more efficient under alkaline conditions, however, the presence of nitrate can promote the defluorination even under neutral pH. Theoretical calculations of Fukui function demonstrated that RNS could easily launch electrophilic attack toward H-rich moieties of fluorotelomer carboxylates (FTCAs, CnF2n+1-(CH2)m-COO-), more persistent intermediates (formed via H/F exchange), and convert FTCAs into shorter-chain perfluorinated carboxylic acids, thus facilitating the deep defluorination. Along with the analysis on the denitrification products, the liberation of fluoride ions and generated intermediates, possible decomposition pathways were proposed. This work highlights the indispensable synergy from eaq-/RNS with integrated reduction and oxidation on PFOA defluorination and will advance remediation technologies of perfluorinated compound contaminated water.

Efficient removal of PFOA with an In2O3/persulfate system under solar light via the combined process of surface radicals and photogenerated holes.

The environmental persistence, high toxicity and wide spread presence of perfluorooctanoic acid (PFOA) in aquatic environment urgently necessitate the development of advanced technologies to eliminate PFOA. Here, the simultaneous application of a heterogeneous In2O3 photocatalyst and homogeneous persulfate oxidation (In2O3/PS) was demonstrated for PFOA degradation under solar light irradiation. The synergistic effect of direct hole oxidation and in-situ generated radicals, especially surface radicals, was found to contribute significantly to PFOA defluorination. Fourier infrared transform (FTIR) spectroscopy, Raman, electrochemical scanning microscope (SECM) tests and density functional theory (DFT) calculation showed that the pre-adsorption of PFOA and PS onto In2O3 surface were dramatically critical steps, which could efficiently facilitate the direct hole oxidation of PFOA, and boost PS activation to yield high surface-confined radicals, thus prompting PFOA degradation. Response surface methodology (RSM) was applied to regulate the operation parameters for PFOA defluorination. Outstanding PFOA decomposition (98.6%) and near-stoichiometric equivalents of fluorides release were achieved within illumination 10 h. An underlying mechanism for PFOA destruction was proposed via a stepwise losing CF2 unit. The In2O3/PS remediation system under solar light provides an economical, sustainable and environmentally friendly approach for complete mineralization of PFOA, displaying a promising potential for treatment of PFOA-containing water.

A controllable reduction-oxidation coupling process for chloronitrobenzenes remediation: From lab to field trial.

Chloronitrobenzenes (CNBs) are typical refractory aromatic pollutants. The reduction products of CNBs often possess higher toxicity, and the electron-withdrawing substituent groups are detrimental to the ring-opening during the oxidation treatment, leading to ineffective removal of CNBs by either reduction or oxidation technology. Herein we demonstrate a controllable reduction-oxidation coupling (ROC) process composed of zero-valent iron (ZVI) and H2O2 for the effective removal of CNBs from both water and soil. In water, ZVI first reduced p-CNB into 4-chloronitrosobenzene and 4-chloroaniline intermediates, which were then suffered from the subsequent oxidative ring-opening by ·OH generated from the reaction between Fe(II) and H2O2. By controlling the addition time of H2O2, the final mineralization rate of p-CNB reached 6.6 × 10-1 h-1, about 74 times that of oxidation alone (9.0 × 10-3 h-1). More importantly, this controllable ROC process was also applicable for the site remediation of CNBs contaminated soil by either ex-situ treatment or in-situ injection, and, respectively decreased the concentrations of p-CNB, m-CNB, and o-CNB from 1105, 980, and 94 mg/kg to 3, 1, and < 1mg/kg, meeting the remediation goals (p-CNB: < 32.35 mg/kg, o-CNB and m-CNB: < 1.98 mg/kg). These laboratory and field trial results reveal that this controllable ROC strategy is very promising for the treatment of electron-withdrawing groups substituted aromatic contaminates.

Efficient removal of heavy metal ions from aqueous systems with the assembly of anisotropic layered double hydroxide nanocrystals@carbon nanosphere.

We report on the efficient removal of heavy metal ions from simulated wastewater with a nanostructured assembly. The nanoassembly was obtained via direct assembling the performed anisotropic layered double hydroxide nanocrystals (LDH-NCs) onto the surface of carbon nanospheres (labeled as LDH-NCs@CNs). It was found that the maximum adsorption capacity of the nanoassembly toward Cu(2+) was ∼ 19.93 mg g(-1) when the initial Cu(2+) concentration was 10.0 mg L(-1), displaying a high efficiency for the removal of heavy metal ions. The Freundlich adsorption isotherm was applicable to describe the removal processes. Kinetics of the Cu(2+) removal was found to follow pseudo-second-order rate equation. Furthermore, the as-prepared building unit of the assembly, including LDH-NCs, CNs, and the assembly, as well as Cu(2+)-adsorbed assembly, were carefully examined by transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), nitrogen sorption measurements, and X-ray photoelectron spectroscopy (XPS). Based on the characterization results, a possible mechanism of Cu(2+) removal with the assembly of LDH-NCs@CNs was proposed. Comparison experiments show that the adsorption capacity of the resulting LDH-NCs@CNs assembly was much higher than its any building unit alone (CNs or LDH-NCs), exhibiting the deliberation of the assembly on water decontamination. This work provides a very efficient, fast and convenient approach for exploring promising nanoassembly materials for water treatment.

Enhanced electrochemiluminescence bioassay triggered by intracellular leakage for detection of Escherichia coli.

An intracellular leakage-trigged signal-on solid-state electrochemiluminescent (ECL) assay is developed for the detection of Escherichia coli (E. coli). A self-assembled multilayer ensemble of N, S co-doped carbon dots -poly dimethyl diallylammonium chloride grafted carbon nanospheres is used as ECL luminophores with peroxydisulfate (PS) ions as coreactants. The incorporation of molecularly imprinted electrospun nanofibers with the multilayer ensemble enables a robust, highly selective solid-state ECL probe without using any expensive and fragile biological receptor. Upon the imprinted E. coli exposed to the assay, under bactericidal effects of PS ions by destroying the integrity of E. coli cell membrane, intracellular leakage K+-triggered ECL enhancement is first disclosed via prompting the involved 1O2-mediated ECL process. Benefiting from the ECL enhancement upon increasing the concentration of E. coli, a unique intracellular leakage-trigged signal-on ECL system is created for sensing E. coli. Such a assay is proved to be highly specific and sensitive for sensing E. coli in the concentration range from 5 to 107 cfu mL-1, achieving a detection limit of 1 cfu mL-1 (S/N = 3). This label-free, simple and facile assay provides a promising point-of-care diagnostic tool for pathogen detection.

Stripping voltammetric detection of mercury(II) based on a bimetallic Au-Pt inorganic-organic hybrid nanocomposite modified glassy carbon electrode.

A new, highly sensitive and selective sensor for the electrochemical assay of Hg(II) by anodic stripping voltammetry has been developed, whereby a glassy carbon electrode is modified with a novel inorganic-organic hybrid nanocomposite, namely, bimetallic Au-Pt nanoparticles/organic nanofibers (labeled as Au-PtNPs/NFs). The sensor possesses a three-dimensional (3D) porous network nanoarchitecture, in which the bimetallic Au-Pt NPs serving as metal NP-based microelectrode ensembles are homogenously distributed in the matrix of interlaced organic NFs. The surface structure and composition of the sensor were characterized by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Its electrochemical performance was systematically investigated. Our results show that such a newly designed, Au-PtNPs/NF nanohybrid modified electrode provides remarkably improved sensitivity and selectivity for the stripping assay of Hg(II). The detection limit is found to be as low as 0.008 ppb (S/N = 3) that is much below the guideline value from the World Health Organization (WHO). Interferences from other heavy metal ions such as Cu(II), Cr(III), Co(II), Fe(II), Zn(II), and Mn(II) ions associated with mercury analysis are effectively inhibited. Toward the goal for practical applications, the sensor was further evaluated by monitoring Hg(II) in tap and river water specimens.

Rapid photochemical decomposition of perfluorooctanoic acid mediated by a comprehensive effect of nitrogen dioxide radicals and Fe3+/Fe2+ redox cycle.

Developing efficient methods to degrade perfluorochemicals (PFCs), an emerging class of highly recalcitrant contaminants, are urgently needed in recent years, due to their persistence, high toxicity, and resistance to most regular treatment procedures. Here, a UV-photolysis system is reported for efficient mineralization of perfluorooctanoic acid (PFOA) via irradiation of ferric nitrate aqueous solution, where in-situ generating •NO2 and the effective Fe3+/Fe2+ redox cycle synergistically play great roles on rapidly mediating the mineralization of PFOA. A fast PFOA removal kinetics with first-order kinetic constants of 2.262 h-1 is observed at initial PFOA concentration of 5 ppm (50 mL volume), reaching ∼ 92 % removal efficiency within only 0.5-h irradiation. Near-stoichiometric fluoride ions liberation and high total organic carbon (TOC) removal efficiency (∼100 %) further validated the capability for completely destructive removal of PFOA. A tentative pathway for PFOA destruction is proposed. This work, by UV photolysis of abundant existing iron/nitrate-based systems in natural environment, provides an economical, sustainable and highly efficient approach for complete mineralization of perfluorinated chemicals.

Dual-modal visual/photoelectrochemical all-in-one bioassay for rapid detection of AFP using 3D printed microreactor device.

An elaborated 3D printing "all-in-one" dual-modal immunoassay (3D-AIO) has been constructed for the colorimetric and photoelectrochemical (PEC) detection of alpha-fetoprotein (AFP), which integrates all step-analysis functional components (including immune/enzyme reaction, separation and detection) together using automatic microfluidics. The released ascorbic acid (AA) from the enzyme-linked immunoreactions can induce the aggregation of gold nanoparticles (AuNPs) by reducing cystine into cysteine, serving as the reporting agent of colorimetric assay. Meanwhile, the released AA induces hole-trapping of the photoactive nanostructured ZnIn2S4 (ZIS), thus triggering a noticeable photocurrent enhancement at ZIS modified screen printed electrode (labeled as ZIS/SPE) slotted in PEC detection chamber. By smart controlling, the colorimetric assays exhibits a distinguishable color change once AFP contents in serum exceed its cut-off value (20 ng mL-1), achieving fast screening and rapid identification purpose for plasma samples as negative or positive, especially in point of care (POC) analysis. And then the PEC immunoassay could be used for more accurate quantitative analysis with the detection limit as low as 0.01 ng mL-1 (S/N = 3). The proposed assay offered bimodal readout for realizing both qualitative fast screening and quantitative PEC determination of AFP concentration, thereby meeting the requirements of quick and precise POC analysis. The direct detection of AFP from human blood makes it promising for on-site POC diagnostics.

Bifunctional S, N-Codoped carbon dots-based novel electrochemiluminescent bioassay for ultrasensitive detection of atrazine using activated mesoporous biocarbon as enzyme nanocarriers.

A novel and ultrasensitive electrochemiluminescent (ECL) bioassay has been developed for the detection of atrazine (ATZ), whereby bifunctional S, N-codoped carbon dots (S, N-CDs) and activated mesoporous bicarbons (BCs) have been innovatively integrated to synergistically amplify the ECL signal. When endogenous dissolved O2 is used as a coreactant, its sluggish reduction hinders the enhancement of ECL intensity of the luminophore, thus restricting its further application in bioanalysis. Here, bifunctional S, N-CDs severe as not only the ECL luminophore but the coreaction accelerator of dissolved O2 to generate more intermediates to boost the coreaction without using any other coreactant and coreaction accelerator. The as-formed nanoarchitectures of BCs possess enlarged surface area as the nanocarriers. They could provide adequate active sites for immobilization of tyrosinase (Tyr), which greatly prompts the ECL bioassay applications. Such a smart integration of bifunctional S, N-CDs, activated mesoporous BCs and the enzyme inhibition reaction achieves a unique and attractive high-performance signal-on ECL bioassay, realizing ultrasensitive detection of ATZ. Under the optimal condition, this bioassay exhibits two linear ranges, from 0.0001 to 0.01 µg L-1 and 0.01-20 µg L-1 with a detection limit of 0.08 ng L-1 at signal to noise ratio of 3. The as-fabricated assay is sensitive and economical, opening a new way for the enhancement of ECL signal output and a versatile strategy for ultrasensitive ECL bioanalysis.

Boosted photoelectrochemical immunosensing of metronidazole in tablet using coral-like g-C3N4 nanoarchitectures.

A simple, facile and sensitive photoelectrochemical (PEC) bioassay protocol for metronidazole (MNZ) detection in common oral medicine samples has been proposed under visible-light irradiation, where novel hierarchical coral-like g-C3N4 nanoarchitectures (cg-C3N4) have been first explored as PEC sensing platform. Featured with the unique nanostructures (e.g., interlaced porous network architecture, and open boundaries), the as-formed cg-C3N4 nanoarchitectures not only efficiently inhibit the recombination of photogenerated electron-hole but also enable the immobilization of capture antibodies as well as the antibody-antigen binding efficiency fluently, thus amplifying the photocurrent response. This newly constructed PEC immunoassay displays excellent performance for MNZ determination with high sensitivity and selectivity. Under the optimal condition, this bioassay protocol exhibits a linear range of 0.01-100 µM with a detection limit of 0.005 µM at signal to noise ratio of 3. The resulting PEC immunoassay has been proved to be applicable for sensing MNZ in common oral medicine samples.

High-Throughput Signal-On Photoelectrochemical Immunoassay of Lysozyme Based on Hole-Trapping Triggered by Disintegrating Bioconjugates of Dopamine-Grafted Silica Nanospheres.

A unique split-type photoelectrochemical (PEC) immunoassay has been constructed for detection of low-abundance biocompounds (lysozyme, Lyz, used in this case) via a new trigger strategy by disintegrating bioconjugates of dopamine-grafted silica nanospheres (DA@SiO2NSs) for signal amplification. The preferred electron donor assembly of DA@SiO2NSs is first used as a molecular printboard for positioning anti-Lyz secondary antibody (Ab2) through an amide reaction. With specific immunoreactions in a high-binding microplate, a sandwich immunoassay, the DA@SiO2NSs-based bioconjugate is achieved. By initiating the disintegration of the bioconjugates via acid etching, numerous electron donors of DA are released, thus efficiently triggering hole-trapping with amplified signals obtained. The smart integration of ZnIn2S4-based heterojunctions as photoactive material, a split-type detection mode, and a new trigger strategy by disintegrating the DA@SiO2NSs-based bioconjugate offer an attractive high-throughput signal-on PEC immunoassay for detection of Lyz. Such an unusual PEC sensor exhibits an outstanding linear response to the concentration in the range between 0.002 and 500 ng mL-1, and the detection limit is as low as 0.6 ppt ( S/ N = 3). The as-fabricated assay is cost-effective and sensitive. It has been successfully used for measuring Lyz in real samples, which demonstrates great promise for practical applications.

Disposable photoelectrochemical sensing strip for highly sensitive determination of perfluorooctane sulfonyl fluoride on functionalized screen-printed carbon electrode.

Owing to the lack of chromophores and ionizable functional groups, it is a significant challenge to determine perfluorooctane sulfonyl fluoride (PFOSF) by traditional high-performance liquid chromatography or liquid chromatography/mass spectrometry, especially at a low concentration. In this work a unique photoelectrochemical (PEC) sensing strip has been developed for the first time for the detection of PFOSF. The sensing strip is cost effective and disposable, whereby BiOI nanoflake arrays are fabricated on a home-made screen-printed electrode through a facile one-step in-situ electrodeposition process, and then the molecule tags (i.e., molecularly imprinted polymers) for PFOSF are subsequently grafted on the surface. Benefitting from a three-dimensional interconnected framework, the as-fabricated sensing strip has a rapid response to the interfacial steric hindrance effect between the sensing platform and the target analyte of PFOSF. The elaborated PEC sensor exhibits a outstanding linear response to a concentration of PFOSF ranging from 0.05 to 500.0 ppb and a detection limit down to 0.01 ppb (S/N = 3) Furthermore, our low-cost and highly sensitive sensor has been further explored to detect PFOSF in real water samples, showing satisfactory results.

Electrospun template directed molecularly imprinted nanofibers incorporated with BiOI nanoflake arrays as photoactive electrode for photoelectrochemical detection of triphenyl phosphate.

Triphenyl Phosphate (TPhP), as a typical model of organophosphorus flame retardants (OPFRs), has been regarded as emerging environmental contaminants of health concern. In this study, a rapid and highly sensitive visible-light-response PEC sensor has been developed for the detection of Triphenyl Phosphate (TPhP) using electrospun template directed molecularly imprinted nanofibers modified BiOI nanoflake arrays (BiOINFs) as a photoactive electrode. The molecularly imprinted electrospun nanofibers (labeled as MI-ESNFs) were carefully characterized by scanning electron microscopy (SEM), UV spectra, FTIR spectra measurements and various electrochemical techniques. Under the optimized experimental conditions, the photoelectrochemical response was linearly proportional to the logarithm value of TPhP concentrations in the range of 0.01ngmL-1 to 500ngmL-1. Meanwhile, the sensor exhibited high selectivity and stability.