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Herein, we developed a rhodium(III)‐catalyzed synthesis of indenones from 2‐aryl‐3‐nitrosoindoles and alkynes in a redox‐neutral manner. The reaction did not require harsh conditions or any external oxidants. Mechanistic experiments and DFT calculation revealed that the reaction involved directed C−H activation, dearomative spirocyclization, N−O/C−C bond cleavage and ketimine hydrolysis cascade processes. [ABSTRACT FROM AUTHOR]

Herein, we develop a Rh(III)-catalyzed intermolecular regioselective dearomative spirocyclization of 2-aryl-3-nitrosoindoles with alkynes, featuring the redox-neutral and atom-economic construction of spiroindoline-3-one oximes bearing a C2 spirocyclic quaternary carbon center under mild conditions. Both aryl alkyl alkynes and 1,3-diynes generally proceeded smoothly in the reaction with moderate to good regioselectivities. DFT calculations provided in-depth insights into the reaction mechanism and disclosed the origins of the regioselectivities. [ABSTRACT FROM AUTHOR]

The stoichiometric coupling of readily available methylarenes and diverse acid chlorides into α-aryl ketones, a valued structural motif present in pharmacologically relevant molecules, has been developed. The utility of this protocol is demonstrated by the late-stage acylation of biologically active molecules in a stoichiometric manner. Mechanistic investigation reveals that the photocatalytically generated bromine radical acts as a hydrogen atom abstraction reagent and delivers a nucleophilic benzyl radical, which is intercepted by nickel-catalyzed cross coupling to accomplish benzylic acylation. [ABSTRACT FROM AUTHOR]

A synthetic method of o‐sulfanylanilines from cyclohexanones, amines, and thiophenols under transition‐metal‐free conditions is disclosed. This is the first report on the direct thioamination of cyclohexanones via N‐iodosuccinimide (NIS) promoted oxidative dehydroaromatization. Non‐aromatic cyclohexanones were smoothly dehydrogenated, and acted as an aryl source using oxygen as a green oxidant. The capacity of the resultant o‐sulfanylanilines for synthesis of N‐arylphenothiazines has been further demonstrated. [ABSTRACT FROM AUTHOR]

A tyrosinase-activatable fluorescent probe with endoplasmic reticulum targetability was developed for the first time. It can ratiometrically fluoresce and hence be used to monitor refluxed tyrosinase into the endoplasmic reticulum. [ABSTRACT FROM AUTHOR]

As a key reactive oxygen species (ROS), hypochlorous acid (HClO) plays a vital role in living systems. Ratiometric and endoplasmic reticulum-targeting probes for highly sensitive detection of hypochlorous acid are in demand. In this paper, we constructed a novel reticulum-targeting and ratiometric fluorescent probe for determining hypochlorous acid. The probe applied 4-aminonaphthalimide as the fluorescent group, employed the (2-aminoethyl)thiourea group as a specific recognition unit, and used the p-toluenesulfonamide group as the localization group of the endoplasmic reticulum. When HClO is absent, the probe underwent an intramolecular charge transfer (ICT) process and displayed green emission. In the presence of HClO, the ICT process was inhibited, which induced a 49 nm blue-shift of fluorescence emission from 533 nm to 484 nm. The ratiometric fluorescent probe exhibited high sensitivity and selectivity for HClO. Furthermore, the ratiometric fluorescent probe could work in a wide pH range. The fluorescence intensity ratios (I484nm/I533nm) exhibited a linear response to the concentration of HClO from 5.0 × 10−7 to 1.0 × 10−5 mol L−1. The detection limit was evaluated to be 1.0 × 10−7 mol L−1 for HClO. In addition, the probe displayed an excellent endoplasmic reticulum-targeting ability, and has been successfully applied for the confocal imaging of HClO in the endoplasmic reticulum of PC-12 cells with almost no cell toxicity. All of such outstanding properties demonstrated that it could be employed to sense HClO in the endoplasmic reticulum of living cells. [ABSTRACT FROM AUTHOR]

[Display omitted] • A lysosome-targetable fluorescent probe for H 2 O 2 has been reported. • The probe displays high sensitivity and high selectivity for H 2 O 2. • The probe can be utilized for determination of H 2 O 2 within the lysosomes of living cells. As an important member of reactive oxygen species, hydrogen peroxide (H 2 O 2) plays a key role in oxidative stress and cell signaling. Abnormal levels of H 2 O 2 in lysosomes can induce damage or even loss of lysosomal function, leading to certain diseases. Therefore, real-time monitoring of H 2 O 2 in lysosomes is very important. In this work, we designed and synthesized a novel lysosome-targeted fluorescent probe for H 2 O 2 -specific detection based on a benzothiazole derivative. A morpholine group was used as a lysosome-targeted unit and a boric acid ester was chosen as the reaction site. In the absence of H 2 O 2 , the probe exhibited very weak fluorescence. In the presence of H 2 O 2 , the probe showed an increased fluorescence emission. The fluorescence intensity of the probe for H 2 O 2 displayed a good linear relationship in the concentration range of H 2 O 2 from 8.0 × 10−7 to 2.0 × 10−4 mol·L−1. The detection limit was estimated to be 4.6 × 10−7 mol·L−1 for H 2 O 2. The probe possessed high selectivity, good sensitivity and short response time for the detection of H 2 O 2. Moreover, the probe had almost no cytotoxicity and had been successfully applied to confocal imaging of H 2 O 2 in lysosomes of A549 cells. These results illustrated that the developed fluorescent probe in this study could provide a good tool for the determination of H 2 O 2 in lysosomes. [ABSTRACT FROM AUTHOR]

A direct strategy for the preparation of fused thienoindoles from substituted indoles and elemental sulfur has been reported. The present approach produces a range of structurally valuable fused thienoindoles in 51–78% yield under transition‐metal‐free conditions, which may have potential applications in pharmaceutical industry and organic functional materials. In this work, the double C−S bonds formation is achieved via base promoted direct sulfuration of C−H bonds with elemental sulfur. [ABSTRACT FROM AUTHOR]

A regioselective synthesis of 2‐amino‐para‐iminonaphthoquinones and 4‐amino‐1,2‐naphthoquinones was described via the substrate‐dependent divergent multi‐functionalization of β‐tetralone with primary and secondary amines under metal‐free conditions. This developed strategy features extremely green and mild conditions (O2 as oxidant, ethanol as solvent under ambient temperature), broad substrate scope, and various pharmaceutical derivatizations. [ABSTRACT FROM AUTHOR]

[Display omitted] • A colorimetric-based SPD method was developed to sensitively quantify melamine (Mel) by Au@MnO 2 NPs. • Due to strong hydrogen bonding between Mel and gallic acid, the etching of MnO 2 shellis inhibited and the single Au@MnO 2 NPs shows yellow with DFM. • Through quantitatively counting the ratio of yellow Au@MnO 2 NPs, trace amount of Mel can be determined. • The detection limit can reach 16.7 nM and a satisfactory recovery is obtained in milk sample. In this work, we demonstrate a simple and label-free single particle detection (SPD) method for the quantification of melamine (Mel) based MnO 2 -modified gold nanoparticles (Au@MnO 2 NPs). Without Mel, MnO 2 shell of Au@MnO 2 NPs are able to be directly decomposed by gallic acid. In the existence of Mel, the decomposition process is restrained due to the strong hydrogen bonding between Mel and gallic acid. The selective etching of MnO 2 shell on AuNPs surface results in evident color change from single Au@MnO 2 NPs. Through quantitatively enumerating the number of color coded particles, trace amounts of Mel can be accurately detected. A linear range from 0.02 to 1 μM (R2 = 0.98) and a limit of detection of 16.7 nM are acquired. In milk sample, satisfactory recovery was acquired. Therefore, the SPD method is expected to be used for the detection of various chemical contaminants in food. [ABSTRACT FROM AUTHOR]

A four-component synthesis of 2-phenyl-9H-pyrimido[4,5-b]indoles was developed using indole-3-carboxaldehydes, aromatic aldehyde and ammonium iodide as the raw materials under transition-metal-free conditions. The pyrimidine ring was formed in one pot through [4 + 2] annulation reaction. Four C–N bonds were formed in one pot promoted by iodine and iodide additives. This work is highlighted by using two ammonium iodides as the sole nitrogen source. [ABSTRACT FROM AUTHOR]

[Display omitted] Photocatalytic CO 2 reduction and H 2 production are a competitive reaction, and existing active sites cannot take into account the simultaneous gas-solid and liquid-solid reaction processes. Hence, a metallic aerogel (CuAg 2.5) with dual active sites was constructed via straightforward in-situ reduction process. CuAg 2.5 aerosol has larger porosity and CO 2 adsorption capacity, which enables H 2 O and CO 2 to fully contact it. The CuAg 2.5 can also construct the cooperative dual active sites, which can conduct CO 2 reduction reaction on Ag surface and proton reduction reaction on Cu surface, respectively, thereby efficiently guiding the rapid migration of photogenerated carriers. The yields of CO (18533 µmol g−1) and H 2 (20340 µmol g−1) for CuAg 2.5 are much higher than those of single metals. The ratio of CO and H 2 can also regulated via changing the ratio of Ag and Cu. This work gives new insights into the fabrication of unique high-efficiency plasmonic photocatalysts. [ABSTRACT FROM AUTHOR]

A visible and sensitive assay for the quantitative detection of β-glucosidase (β-glu) activity based on Au@CeO2 core-shell nanoparticles (Au@CeO2 NPs) is described. As a hydrolytic enzyme, β-glu can promote the hydrolysis of β-arbutin to hydroquinone (HQ), which can trigger the decomposition of the CeO2 shell. With the single-particle enumeration (SPE) strategy coupled with dark field optical microscopy (DFM), an obvious color alteration of single Au@CeO2 NPs during the etching process can be observed in real-time. By statistically calculating the number of the etched nanoparticles, the β-glu activity level can be quantified accurately. This assay displays a broad linear range from 0.5 to 50 mU⋅mL−1 and low detection limit of 0.12 mU⋅mL−1. In addition, this method was successfully used to determine β-glu in real samples and acquires satisfactory recoveries in the range of 97.1-102.0%. This study provides a visualization analysis method for β-glu, which may be helpful for monitoring other targets in the future. [ABSTRACT FROM AUTHOR]

Fe‐catalyzed three‐component strategy have been developed for the synthesis of 2,3′‐biquinolines from readily available 2‐methyl quinolines, anthranils and N, N‐dimethylacetamide (DMA), This annulation procedure undergoes C(sp3)−H activation, amination, nucleophilic addition, dehydration and oxydehydrogenation steps. DMA acts not only as a solvent but also as a one carbon donor in the reaction. [ABSTRACT FROM AUTHOR]

The reactive nitrogen species (RNS) in lysosomes play a major role during the regulation of lysosomal microenvironment. Nitroxyl (HNO) belongs to active nitrogen species (RNS) and is becoming a potential diagnostic and therapeutic biomarker. However, the complex synthesis routes of HNO in biosystem always hinder the exact determination of HNO in living cells. Here, a rhodamine-based fluorescent probe used to determine nitroxyl (HNO) in lysosomes was constructed and synthesized. 2-(Diphenylphosphino)benzoate was utilized as the sensing unit for HNO and morpholine was chose as the targeting group for lysosome. Before the addition of HNO, the probe displayed a spirolactone structure and almost no fluorescence was found. After the addition of HNO, the probe existed as a conjugated xanthene form and an intense green fluorescence was observed. The fluorescent probe possessed fast response (3 min) and high selectivity for HNO. Furthermore, fluorescence intensity of the probe linearly related with the HNO concentration in the range of 6.0 × 10−8 to 6.0 × 10−5 mol L−1. The detection limit was found to be 1.87 × 10−8 mol L−1 for HNO. Moreover, the probe could selectively targeted lysosome with excellent biocompatibility and had been effectually utilized to recognize exogenous HNO in A549 cells. [Display omitted] • A lysosome-targetable fluorescent probe for HNO has been reported. • The probe displays high sensitivity and high selectivity for HNO. • The probe can be utilized for determination of HNO within the lysosomes of living cells. [ABSTRACT FROM AUTHOR]

Nitrogen-enriched carbon dots (NCDs) with green fluorescence were prepared with an average diameter of 4.8 nm by a room temperature self-polymerization method using catechol and ethylenediamine as precursors. It was found that the green fluorescence of NCDs can be quenched directly by uric acid (UA). A facile and fast fluorescent enzyme-free sensor has been developed for the detection of UA in the linear concentration range of 0–30 μM, with a limit of detection of 0.22 μM. High sensitivity, stability and selectivity can also be achieved for the detection of UA. In addition, the mechanism of fluorescence quenching of NCDs induced by UA was the dynamic quenching type according to the linearity of the Stern–Volmer equation and the change of the lifetime of NCDs after adding UA. Furthermore, UA in saliva samples was successfully detected using this established fluorimetric method, showing the feasible detection of UA in complicated body fluid samples. This NCD-based fluorimetric non-invasive method can be used for the highly selective determination of UA in the clinical laboratory. [ABSTRACT FROM AUTHOR]

A metal‐ and solvent‐free strategy for the preparation of maleimide‐fused carbazoles has been developed. This protocol started from 2‐(indol‐3‐yl)cyclohexanones and maleimides, providing various maleimide‐fused carbazoles in 45–90% yields. The present approach was catalyzed by trimethylsulfoxonium iodide and involved a cascade of oxidation, [4+2] annulation, and dehydrogenative aromatization. Moreover, these maleimide‐fused carbazole products could be further transformed into other polycyclic aromatic hydrocarbons. [ABSTRACT FROM AUTHOR]

Nowadays, test strips are widely applied, but their use is mostly limited to the qualitative or half-quantitative analysis of targets. The main reason for their limited use is the "Coffee Ring Effect" (CRE) of probe materials, which leads to a heterogeneous probe distribution and poor testing reproducibility and sensitivity. In the present work, a fluorescent test strip was fabricated with a suppressed CRE of silver nanocluster (AgNC) probes coated by gelatin (Gel) under vacuum-aided fast lyophilization. Uniform and stable deposition of AgNC probes was achieved onto the test strips with a high loading capacity. The AgNCs displayed specific responses to Hg2+ ions, allowing sensitive and quantitative analysis in the linear concentration ranges from 0.20 to 50000 nM with a limit of detection of 0.10 nM. Given the advantages of rapid and facile preparation, CRE suppression, high biocompatibility, and cost-effectiveness, such a fabrication protocol may pave the way for the design of various test strips-based devices for point-of-care analytical applications in the fields of environmental monitoring, food quality analysis, and clinical diagnostics. [ABSTRACT FROM AUTHOR]

[Display omitted] • An ICT-FRET-based fluorescent probe for the ratiometric detection of HNO has been reported. • The probe displays high sensitivity and high selectivity for HNO. • The probe had been applied for the ratiometric detection of HNO in A549 cells. Nitroxyl (HNO) is an important reactive nitrogen that is associated with various states in physiology and pathology and plays a unique function in living systems. So, it is important to exploit fluorescent probes with high sensitivity and selectivity for sensing HNO. In this paper, a novel ratiometric fluorescent probe for HNO was developed utilizing intramolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET) mechanisms. The probe selected coumarin as energy donor, naphthalimide as energy receptor and 2-(diphenylphosphino)benzoate as the sensing site for detecting HNO. When HNO was not present, the 2-(diphenylphosphino)benzoate unit of the probe restricted electron transfer and the ICT process could not occur, leading to the inhibition of FRET process as well. Thus, in the absence of HNO the probe displayed the intrinsic blue fluorescence of coumarin. When HNO was added, the HNO reacted with the 2-(diphenylphosphino)benzoate unit of the probe to yield a hydroxyl group which resulting in the opening of ICT process and the occurring of FRET process. Thus, after providing HNO the probe displayed yellow fluorescence. In addition, the probe showed good linearity in the ratio of fluorescence intensity at 545 nm and 472 nm (I 545 nm /I 472 nm) with a concentration of HNO (0.1–20 μM). The probe processed a detection limit of 0.014 μM and a response time of 4 min. The probe also specifically identified HNO over a wide pH scope (pH = 4.00–10.00), including physiological conditions. Cellular experiments had shown that this fluorescent probe was virtually non-cytotoxic and could be applied for ratiometric sensing of HNO in A549 cells. [ABSTRACT FROM AUTHOR]

Hydrogen polysulfide (H 2 S n , n≥2), as a kind of active sulfur species (RSS), has become a hot topic in RSS. It can regulate the biological activity of many proteins through S-sulfhydrylation of cysteine residues (protein Cys-SSH), and has a protective effect on cells. Although there have been some studies on hydrogen polysulfide, its production, degradation pathway and regulation mechanism still need further be researched. In presented study, an original lysosome-localized fluorescent probe for determining H 2 S n was developed utilizing rhodamine as the fluorogen. The probe used morpholine as the locating unit of lysosomes and chose 2-fluoro-5-nitrobenzoate as the recognizing group. Before adding H 2 S n , the proposed probe displayed a spironolactone structure and emitted very weak fluorescence. After adding H 2 S n , a conjugated xanthene was formed and the probe demonstrated green fluorescence. When the H 2 S n concentration was varied from 6.0×10−7 mol·L−1 to 10.0×10−5 mol·L−1, the fluorescence intensity of the probe was linearly dependent on the H 2 S n concentration. And the detection limit was 1.5×10−7 mol·L−1. The presented probe owned a fast response speed, good selectivity, excellent sensitivity and broad pH work scope. In addition, the probe had been well utilized to sense endogenic and exogenic H 2 S n in lysosomes. [Display omitted] • A lysosome-targetable fluorescent probe for H 2 S n has been reported. • The probe displays high sensitivity and high selectivity for H 2 S n. • The probe can be utilized for determination of H 2 S n within the lysosomes. [ABSTRACT FROM AUTHOR]

Photo-Fenton-like technology based on H 2 O 2 is considered as an ideal strategy to generate reactive oxygen species (ROS) for antibiotic degradation, but O 2 overflow in the process severely limits the utilization efficiency of H 2 O 2. Herein, we fabricate Bi 2 MoO 6 (BMO) photocatalyst modified with Frustrated Lewis pairs (FLPs) as a Fenton catalyst model for enhancing reuse of spilled O 2. The FLPs created by the introduction of cerium and oxygen vacancy were found to contribute to regulate the electronic structure of BMO and further improve the acidic and basic properties of photocatalyst surface. More importantly, the frustrated acid and base sites can enhance the H 2 O 2 and O 2 interfacial adsorption process and provide an Ce4+-O v -O2− active site on the surface of Ce-BMO nanosheets, which can promote O 2 /•O 2 −/1O 2 /H 2 O 2 redox cycles to achieve high H 2 O 2 utilization efficiency. Specifically, in the experiment using tetracycline as a photocatalytic degradation object, the degradation activity of Ce-BMO was 2.15 times higher than that of BMO pure phase. Quenching experiments and EPR assays also confirmed that 1O 2 and •O 2 − were the dominant oxidative species. This study systematically reveals the design of Fenton photocatalytic active sites at the atomic scale and provides new insights into constructing FLPs photocatalysts with high H 2 O 2 utilization efficiency. The mechanism of Bi 2 MoO 6 and Ce-doped Bi 2 MoO 6 /H 2 O 2 photocatalytic system for TC degradation. [Display omitted] • A universal strategy based on FLPs was proposed for efficient H 2 O 2 utilization. • Interaction of LA and LB contributed to the adsorption and activation of escaped O 2. • Ce-BMO presented enhanced photo-Fenton performance and high H 2 O 2 utilization. • Reaction mechanism of Ce-BMO/H 2 O 2 photo-Fenton system was established. [ABSTRACT FROM AUTHOR]

Zeolitic Imidazolate Frameworks (ZIFs) derived nitrogen‐doped porous carbon (NPC) materials have been proposed as promising metal‐free electrocatalysts for oxygen reduction reactions (ORR). Herein, we report a strategy to control the morphology of ZIF‐8 and ZIF material‐derived NPC materials by the amount of L‐cysteine. The prepared NPC electrocatalysts exhibit different morphologies and ORR properties. The best of these catalysts exhibited a nanosheet‐like morphology with an onset potential of 0.95 V and a half‐wave potential of 0.87 V in alkaline media, which are comparable to those of commercial Pt/C (20 wt%) catalysts. In addition, this catalyst exhibited high stability and methanol resistance. This work not only reveals the effect of L‐cysteine amount on the growth process of ZIF, but also provides a strategy for designing various excellent catalysts in the fuel cell field. [ABSTRACT FROM AUTHOR]

Hypochlorous acid (HOCl) was crucial for maintaining the homeostasis in cells and plays vital roles in many physiological and pathological processes. In this work, a highly selective fluorescent probe for hypochlorous acid in living cells was constructed and prepared based on a naphthalene derivative. A naphthalene derivative was utilized as the fluorescent group, and N,N-dimethylthiocarbamate was applied as the selective recognition site for HOCl. Before adding HOCl, the fluorescent probe exhibited weak fluorescence. Upon adding HOCl, the fluorescent probe displayed remarkable fluorescence enhancement. The fluorescence intensity at 502 nm showed a linear response to the concentration of HOCl from 3.0 × 10−7 to 1.0 × 10−5 mol·L−1. The detection limit was estimated to be 1.5 × 10−7 mol·L−1 for HOCl. The fluorescent probe showed fast response and outstanding selectivity toward HOCl. It owned good biocompatibility and had also been successfully applied in the confocal imaging of exogenous and endogenous HOCl in living cells. [ABSTRACT FROM AUTHOR]

Rapid emergence of new strains of drug-resistant H1N1 influenza viruses calls for effective drugs for the controls prior to their outbreaks. In the present work, electrochemical H1N1 RNA beacons have been newly designed for exploring the potentiality of an anticancer agent of Bleomycin (BLM) with Fe (ΙΙ) ions (BLM-Fe(ΙΙ)) alternatively the treatment of drug-resistant H1N1 strains with H274Y gene mutation. Herein, biotinylated (−) ssRNA of H1N1 virus and its complementary (+) ssRNA were labeled with electrochemical signal probes of ferrocene and anthraquinone, respectively. The resultants were hybridized and conjugated with avidin-modified magnetic beads to create electrochemical RNA beacons. The electrochemical signal variation of the H1N1 RNA beacon treated with the RNA degradation agent of BLM-Fe(ΙΙ) were monitored. Results indicate that the BLM-Fe(ΙΙ) agent could effectively cleave both H1N1 dsRNAs and ssRNAs at selective cutting sites, as evidenced by the mass spectrometry analysis. This indicates that the BLM-Fe(II) agent could be utilized to block the viral-host infection process by curbing the host-cell viral RNA-mRNA transcription or inactivate the viruses through the cleavage of viral genomes. The efficiency of the BLM-Fe(ΙΙ) agent was verified with clinical seasonal H1N1 samples using real-time polymerase chain reaction. The therapeutic gene drug of BLM-Fe(ΙΙ) holds great potential for controlling new strains of H1N1 virus resistant to clinical antiviral drugs. More importantly, the so designed RNA beacons may provide a rapid, sensitive and cost-effective platform of drug screening by monitoring the drug-DNA/RNA interactions. [Display omitted] • H1N1 RNA beacons are designed to be labeled separately with electrochemical probes. • The cleavage efficiency of the BLM-Fe(II) agent is confirmed for seasonal H1N1 samples. • BLM-Fe(ΙΙ) agent cleaves both H1N1 dsRNAs and ssRNAs at selective cutting sites. • BLM-Fe (ΙΙ) agent is verified with potentiality for treating drug-resistant H1N1 strains. [ABSTRACT FROM AUTHOR]

The multifunctional hemin@carbon dot hybrid nanozymes (hemin@CD) with simultaneous peroxidase-like activity and fluorescence signalling property was prepared for the first time. Based on these properties, hemin@CD was applied to develop a dual-channel fluorescent probe for H2O2 and H2O2-based biocatalytic systems. By virtue of the peroxidase-like activity, hemin@CD can catalyze the oxidative coupling of 4-aminoantipyrine with phenol in the presence of H2O2 to form a pink-red quinoneimine dye with a maximum absorbance at 505 nm. Under the excitation wavelength of 480 nm, the green fluorescence of hemin@CD peaks at 540 nm and is quenched by the generated quinoneimine dye due to an inner filter effect, and also by H2O2 because of dynamic quenching. Thus, a colorimetric and fluorimetric dual-channel optical probe for H2O2 is obtained. Due to the glucose/xanthine transformations under formation of H2O2 by the relevant oxidase catalysis, the probe can be applied for detection of glucose and xanthine. The colorimetric detection limits for H2O2, glucose and xanthine are 0.11, 0.15, 0.11 μM, and the and fluorimetric detection limits are 0.15, 0.15, 0.12 μM, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • A color-coded single particle enumeration assay is built to quantify E. coli based Au@MnO 2 NPs. • This assay is achieved through monitoring endogenous β-gal activity of E. coli. • The detection limit can reach as low as 15 CFU/mL. Au@MnO 2 nanoparticles (NPs), as core–shell nanostructures, have been widely used in ions, molecules and enzyme activities detection due to their stable properties and easy preparation, but their application in bacterial pathogens detection is rarely reported. In this work, Au@MnO 2 NPs is employed for Escherichia coli (E. coli) detection through monitoring and measuring β-galactosidase (β-gal) activity based enzyme-induced color-code single particle enumeration (SPE) method. In the existence of E. coli , p-aminophenylβ-D-galactopyranoside (PAPG) can be hydrolyzed to generate p-aminophenol (AP) by the endogenous β-gal of E. coli. MnO 2 shell reacts with AP and produces Mn2+, causing the blue shift of the localized surface plasmon resonance (LSPR) peak and color change of the probe from bright yellow to green. With the SPE method, the amount of E. coli can be quantified readily. The detection limit reaches 15 CFU/mL with dynamic range from 100 to 2900 CFU/mL. Besides, this assay is effectively employed to monitor E. coli in river water sample. The designed sensing strategy provides an ultrasensitive and low cost way for E. coli detection and has the possibility to detect other bacteria in environmental monitoring and food quality analysis. [ABSTRACT FROM AUTHOR]

Abstract Nanozymes' activities could be regulated by a simple and effective pH change in an in situ manner. In this work, for the first time, the peroxidase-like activity of Ni/Co layered double hydroxides (LDHs) was regulated via the alkaline-promoted reaction of fluorogenic substrate homovanillic acid and H 2 O 2 , and a promising tool for pH sensing was developed over the pH range of 8.3–9.6. As peroxidase nanozyme model, Ni/Co LDHs showed ease of preparation, low-cost, and water-solubility, which played an important role in this luminescence system. Based on the pH-dependent regulation of the Ni/Co LDHs activity, we constructed the bioassay platform for the determination urea, urease, penicillin G, and penicillinase with a wide linear range of 17–1000 µM, 3.3–270 mU mL−1, 3.3–1300 µM and 3.3–100 mU mL−1, respectively. This study not only demonstrated the alkaline-promoted modulation the nanozymes' activities, but also established a facile approach to develop novel bioassays. Graphical abstract fx1 Highlights • The alkaline-promoted regulating Ni/Co LDHs' peroxidase-like activity has been explored. • A pH sensor was developed based on the system of Ni/Co LDHs-HVA-H 2 O 2. • A platform for the detection urea, urease, penicillin G, and penicillinase was established. [ABSTRACT FROM AUTHOR]

Schematic presentation of a novel assembled G-wire-induced pyrene excimer switching probe for the amplified detection of microRNA based on exonuclease III-assisted target recycling and Fe 3 O 4 @PDA nanoparticles. This work proposes a promising method for G-wire-based biosensing in disease-related biomarkers detection. [Display omitted] • A new fluorescence method for amplified detection of microRNA was developed. • The method used a novel assembled G-wire-induced pyrene excimer switching probe. • The probe was based on Exo III-assisted target recycling and Fe 3 O 4 @PDA NPs. • The approach shows high sensitivity and specificity. • The approach was successfully applied in cancer cell lysates and serum samples. We reported a novel assembled G-wire-induced pyrene excimer switching probe for microRNA (miRNA) amplified detection on the basis of exonuclease III (Exo III)-assisted target recycling and Fe 3 O 4 @PDA nanoparticles. The multifunctional hairpin (HP) probe recognized and effectively bound to target miRNA, which formed a 3′-blunt terminal for Exo-III digestion and miRNA regeneration to initiate another Exo III-mediated cycling cleavage. After digestion, numerous HP-caged c-myc sequences were released, which were positively related to target miRNA and folded to the parallel G-quadruplex with K+. Additionally, Fe 3 O 4 polydopamine nanoparticles (Fe 3 O 4 @PDA NPs)-based magnet separation was conducted to reduce background fluorescence signal, and parallel G-quadruplexes self-asembled into filamentous G-wires with Mg2+. G-wires generated from 5′-terminal pyrene-labeled c-myc sequences made close distance between two labeled pyrene molecules, and induced the "turn-on" fluorescence signal of pyrene excimer switching. Moreover, gamma-cyclodextrin (γ-CD) was added, which promoted pyrene moiety, causing signal amplification in pyrene excimer fluorescence. Therefore, miRNA was efficiently measured within the homogeneous solution. This method detected miRNA within the dynamic range of 1 pM to 5 nM, with the miR-141 limit of detection (LOD) being 99 fM. It distinguished perfect-matched and mismatched target miRNAs, and showed an accurate detection of miRNA levels in different cell lines and favorable reproducibility when analyzing miRNAs within spiked serum samples. We propose a promising method for G-wire-based biosensing in disease-related biomarkers detection. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H 2 S) plays a cytoprotective role during mitophagy by detoxifying superfluous reactive oxygen species (ROS), and its concentration fluctuates in this process. However, no work has been reported to reveal the variation in H 2 S levels during autophagic fusion of lysosomes and mitochondria. Herein, we present a lysosome-targeted fluorogenic probe, named NA-HS, for real-time monitoring of H 2 S fluctuation for the first time. The newly synthesized probe exhibits good selectivity and high sensitivity (detection limit of 23.6 nM). Fluorescence imaging results demonstrated that NA-HS could image exogenous and endogenous H 2 S in living cells. Interestingly, the colocalization results revealed that the level of H 2 S was upregulated after autophagy began because of the cytoprotective effect, and was finally gradually reduced during subsequent autophagic fusion. This work not only affords a powerful fluorescence tool to monitor the variations in H 2 S levels during mitophagy, but also offers new insights into targeting small molecules for elaborating the complex cellular signal pathways. The variation of H 2 S during autophagic fusion of lysosome and mitochondria was revealed by a lysosome-targeting fluorogenic probe. [Display omitted] • H 2 S fluctuation during mitophagy was revealed by a synthetic fluorescence probe. • The endogenous and exogenous H 2 S can be imaged with this fluorescence probe. • The level of H 2 S was revealed to upregulate and then reduced during mitophagy. [ABSTRACT FROM AUTHOR]

A microdots array-based fluoremetric method with superwettability profile has been developed for the simultaneous and separate detection of Fe3+ and Cu2+ ions in red wine samples. A wettable micropores array was initially designed with high density by using polyacrylic acid (PAA) and hexadecyltrimethoxysilane (HDS), followed by the NaOH etching route. Zinc metal organic frameworks (Zn-MOFs) were fabricated as the fluorescent probes to be immobilized into the micropores array to obtain the fluoremetric microdots array platform. It was found that the fluorescence of Zn-MOFs probes could decrease significantly in the presence of Fe3+ and/or Cu2+ ions towards their simultaneous analysis. Yet, the specific responses to Fe3+ ions could be expected if using histidine to chelate Cu2+ ions. Moreover, the developed Zn-MOFs-based microdots array with superwettability profile can enable the accumulation of targeting ions from the complicated samples without any tedious pre-processing. Also, the cross-contamination of different samples droplets can be largely avoided so as to facilitate the analysis of multiple samples. Subsequently, the feasibility of simultaneous and separate detection of Fe3+ and Cu2+ ions in red wine samples was demonstrated. Such a design of microdots array-based detection platform may promise the wide applications in analyzing Fe3+ and/or Cu2+ ions in the fields of food safety, environmental monitoring, and medical diseases diagnostics. A wettable microdots array with the hydrophobic-hydrophilic interfaces was fabricated with the fluorescent probes of Zn-MOFs for the detection of Fe3+ or Cu2+ ions in red wine. [Display omitted] • A microdots array-based fluoremetric method is fabricated with superwettability profile. • Zn-MOFs are prepared and immobilized into superwettable micropores array yielding the fluoremetric platform. • The Zn-MOFs probes can simultaneously responses to Fe3+ and Cu2+ ions. • Accumulation of targeting ions and avoiding of any cross-contamination of samples droplets can be expected. • This fluoremetric method can facilitate the simultaneous and separate detection of Fe3+ and Cu2+ ions in red wine. [ABSTRACT FROM AUTHOR]

Lysosomes, important acidic organelles, under hypoxia status are closely associated with many diseases. The development of a molecular tool for the precise monitoring of lysosomal hypoxia is of great significance but remains challenging. Herein, we present a novel fluorescence probe HPFR, which is consisted of anthocyanidin fluorophore incorporated with quenching and hypoxia-sensitive azobenzene group, pH-switchable spirolactam moiety, and morpholine as lysosome targetable unit. Due to its hypoxia and acid dual-activatable characteristics, the proposed probe displays a highly sensitive and selective fluorescence response to azoreductase under a lysosomal pH environment but remains silent under neutral or alkaline conditions. Furthermore, it is confirmed to be biocompatible and could be employed to accurately visualize the hypoxia level of acidic lysosomes, offering a promising imaging tool for investigating hypoxic lysosome-related physiopathology. • A hypoxia-sensitive and pH-switchable fluorescence probe was developed. • The probe can specifically detect hypoxia-related azoreductase under acidic solution. • The probe enables to precisely monitor lysosome-confined hypoxia level. [ABSTRACT FROM AUTHOR]

[Display omitted] • A lysosome-targetable fluorescent probe for cysteine has been reported. • The probe displays high sensitivity and high selectivity for cysteine. • The probe can be utilized for determination of cysteine within the lysosomes of living cells. An essential sulfhydryl amino acid in the human body is cysteine (Cys). Its abnormal level is related to coronary heart disease, hypertension, growth retardation, sleepiness, liver injury and AIDS. At present, although many cysteine fluorescent probes have been synthesized, there are relatively few fluorescent probes for sensing cysteine in lysosomes. Therefore, based on a rhodamine derivative, we constructed a fluorescent probe with high selectivity for detecting cysteine in lysosome. The probe chose acrylate as the recognition group and morpholine as the positioning group. The probe was in spirolactone state and displayed very weak fluorescence when cysteine was absent. After adding cysteine, the conjugated xanthene structure was formed through the conversion of the closed spirolactone structure and strong green fluorescence appeared. Compared with glutathione (GSH) and homocysteine (Hcy), the probe had better selectivity to Cys. When the Cys concentration was altered from 1.0 × 10−7 to 6.0 × 10−6 mol·L−1, there was a good linear relationship between fluorescence intensity of the probe and Cys concentration. The detection limit had been evaluated to be 7.5 × 10−9 mol·L−1 for Cys. The probe can work under a wide pH range, including pH under physiological conditions. The probe also has a good effect in non-cytotoxic confocal imaging of endogenous and exogenous cysteine in A549 cells. These findings showed that the fluorescent probe synthesized in this study could be a useful tool for the detection of endogenic and exogenic cysteine. [ABSTRACT FROM AUTHOR]

Nanomaterial-based peroxidase-mimetics are an emerging research field that promises to produce alternatives to horseradish peroxidase for a variety of applications. Generally, some peroxidase-mimetics substrates are used in acidic condition (pH ≤ 7). Then, it is necessary to screen some peroxidase-mimetics substrates suitable for basic condition because that some peroxidase-mimetics leached ions in acidic solution. In this paper, using Ni/Co layered double hydroxides (LDHs) as a nano-peroxidase mimic model, we evaluated three fluorogenic substrates suitable for basic condition though experimental conditions, reaction kinetic and glucose detection assay. And the detection of glucose method based on homovanillic acid (HVA) as fluorescent substrate gave wide linear range (0.02–20 μM) and low detection limit (0.01 μM). We also developed a novel platform that could study the inhibitory effects of ascorbic acid and glutathione based on the system of Ni/Co LDHs-HVA-H 2 O 2 . [ABSTRACT FROM AUTHOR]

The synthesized NiCo 2 O 4 mesoporous spheres (MS) displayed intrinsic peroxidase and oxidase-like activity were firstly reported. The catalytic mechanism of the oxidase-like activity of NiCo 2 O 4 MS was analyzed in detail using the electron spin resonance (ESR) method. It is found that NiCo 2 O 4 MS could directly oxidize 3,3′,5,5′-tetramethylbenzidine (TMB) but did not produce 1 O 2 and ·OH. And the mechanism of the peroxidase-like activity of NiCo 2 O 4 MS was also verified that the oxidation of TMB stemmed from not only ·OH but also 1 O 2 . Based on the NiCo 2 O 4 MS showed excellent peroxidase-like activity over a broad temperature range, especially at normal body temperature, a detection tool was designed for glucose determination in diabetics' serum samples. And this detection method based on NiCo 2 O 4 MS gave a lower limit of detection than the method using Co 3 O 4 NPs and NiO NPs, as the single-component oxides of NiCo 2 O 4 . Our study may open up the possibility to make a great influence on the next generation of enzyme mimetics system. [ABSTRACT FROM AUTHOR]

[Display omitted] • An engineered biomimetic-compartmented nanoprobe (APO@CDs) has been constructed through self-assembly. • The response sensitivity and specificity to iron ions have been improved by using APO@CDs. • In-situ Imaging of the iron storage/release from ferritin in cells was achieved. Ferritin plays an important role in regulating the homeostasis of iron in cells by storing/releasing iron. Current methods usually explored the determination of iron content, but in-situ imaging of the iron storage/release from ferritin in cells cannot be achieved. Hence, an engineered self-assembled biomimetic-compartmented nanoprobe (APO@CDs) has been constructed. The protein shell of APO (apoferritin) acted as ion channel module to control iron ions entering/exiting ferritin cavity; the inner core of CDs (carbon dots) acted as signal module for iron ions response. Compared with CDs, the response sensitivity and specificity to iron ions (Fe3+) have been improved by using APO@CDs, and the cytotoxicity was significantly reduced. Additionally, compared with cells containing APO@CDs alone, the normalized fluorescence gray value of Fe3+-treated cells was significantly decreased (0.275), indicating that Fe3+ has effectively entered the ferritin. Furtherly, that of Fe3+-treated cells incubated with deferoxamine (DFO) was significantly enhanced (0.712), showing that Fe3+ was released from ferritin under the mediation of DFO. The results demonstrate that APO@CDs can be successfully applied to in-situ imaging of iron storage/release from ferritin in cells, providing a potential platform for the in-situ dynamic study of the iron storage/release in biomedical field. [ABSTRACT FROM AUTHOR]

[Display omitted] • Donor-acceptor organic polymers with different bridges are obtained by a facile synthesized strategy. • The CH 4 -producing activity of as-obtained polymers varies with the change of the linking bond. • TOA-PC sample furnishes a CH 4 evolution rate of 2748 µmol g−1 with ultra-high selectivity (near 100 %). • The efficient electron transport channel and the excellent CO 2 adsorption/ activation are constructed by the sulfur bridge. Much progress has been made in the design and preparation of organic polymers for photocatalytic CO 2 reduction. However, potocatalytic reduction of CO 2 to CH 4 using organic polymers is still a great difficulty due to poor CO 2 adsorption/activation and eight electron transfer. A donor-acceptor (D-A) organic polymer (TOA-PC) was synthesized by combining cyclotriphosphazene (donor) with s-triazine (acceptor) via sulfur bridge. The photocatalytic activity of as-obtained polymers is remarkably dependent on the electron bridges between the donor and acceptor, effectively changing the photogenerated carrier mobility and CO 2 adsorption/activation property of the polymers. When the electron bridge is sulfur atom, the TOA-PC exhibits a high CH 4 yield of 2748 μmol g−1 (selectivity: near 100 %) under visible light irradiation without photosensitizers and cocatalysts, which represents the latest CH 4 -producing yield of photocatalysts. This study demonstrates that implantation of novel electron bridges in polymers is an effective way to enhance CH 4 yields. [ABSTRACT FROM AUTHOR]

Ultra-thin MoS 2 nanosheets were treated by nitrogen (N 2) plasma to mediate the photo-reduction deposition of silver forming N/Ag@MoS 2 nanozymes for the catalysis-based colorimetric assay of hydrogen sulfide (H 2 S) in aquaculture water. [Display omitted] • MoS 2 nanosheets were treated by N 2 plasma to mediate the robust deposition of silver. • Enhanced electron transferring of N/Ag@MoS 2 can be achieved. • The deposited silver can act as a specific probe to recognize H 2 S. • N/Ag@MoS 2 can present the enhanced catalysis for the colorimetric analysis of H 2 S. • N 2 plasma treatment route promises the design of various nanozymes with 2D structures. Ultra-thin MoS 2 nanosheets were treated by nitrogen (N 2) plasma to mediate the photo-reduction deposition of silver forming N/Ag@MoS 2 nanozymes for the catalysis-based colorimetric assay of hydrogen sulfide (H 2 S) in aquaculture water. It was found that the as-produced N/Ag@MoS 2 could display a greatly enhanced peroxidase-like catalytic activity than that of MoS 2 nanosheets (about three times higher). Also, in the presence of H 2 S, a strong Ag-S interaction could occur to form non-conductive Ag 2 S onto N/Ag@MoS 2 nanocomposites towards the rationally reduced catalysis depending on H 2 S concentrations. Herein, on the one hand, the plasma treatment-aided doping of N elements into MoS 2 nanosheets might facilitate the robust deposition of silver onto MoS 2 nanosheets through the strong Ag-N chelation, and the enhanced internal electron transferring of N/Ag@MoS 2 nanozymes. On the other hand, the so deposited silver could not only enhance the catalytic properties of nanozymes, but also act as a specific probe for recognizing H 2 S to trigger the decreased catalysis of nanozymes. Importantly, such a N 2 plasma treatment pathway that mediates the deposition of silver onto two-dimensional structures like MoS 2 nanosheets may pave the way toward the design of various nanozymes for the analysis of different targets in the biomedical, food, and environmental monitoring fields. [ABSTRACT FROM AUTHOR]

A nanozyme with 2D/1D heterostructure has been fabricated by the in-situ growth of molybdenum disulfide nanosheets (MoS 2 NSs) onto single-walled carbon nanotubes (SWCNTs). It was discovered that the so-obtained SWCNTs@MoS 2 nanozyme could exhibit greatly improved peroxidase-like catalysis, due to that the formed 2D/1D interfacial coupling in the heterostructure might provide more active sites and exhibit enhanced charge transferring during the catalytic reactions, as confirmed by the X-ray photoelectron spectroscopy, photoluminescence, electrochemical impedance spectra and radical capturing experiments. Furthermore, the catalysis of the developed nanozyme could be selectively inhibited by glutathione (GSH) through the competitive consumption of hydroxyl radicals with enzyme substrate in the catalytic reaction system. A SWCNTs@MoS 2 catalysis-based colorimetric strategy was further proposed for the quantitative analysis of GSH with the concentrations linearly ranging from 0.01 to 1000.0 μM. Besides, the feasibility of the developed colorimetric method was evaluated by monitoring GSH separately in the extractions from hela cells and human serum, promising the extensive applications for monitoring various biological species like GSH in the clinical laboratory. Importantly, such a fabrication route for nanozyme with 2D/1D heterostructure may pave the way towards the wide applications for designing various nanzymes with improved catalysis. [Display omitted] • A nanozyme with 2D/1D heterostructure was synthesized by in-situ growing MoS 2 nanosheets on SWCNTs forming SWCNTs@MoS 2. • The SWCNTs@MoS 2 can exhibit greatly improved catalysis performances due to the formed 2D/1D interfacial coupling in the heterostructure. • SWCNTs@MoS 2 with 2D/1D heterostructure may possess enhanced charge transfer and more active sites during the catalytic reaction on the improved catalysis. • The competing reaction between GSH and chromogenic substrate triggered by the hydroxyl radical could be revealed toward the highly selective detection of GSH. • The SWCNTs@MoS 2 catalysis-based colorimetric strategy enables the evaluation of GSH in the extractions of hela and human serum with pretty high sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

[Display omitted] • ZnS/CdS was fabricated with type-II heterostructure by growing ZnS QDs on CdS NWs. • Low-bandgap CdS NWs and wide-bandgap ZnS QDs act separately as photosensitizer and Hg2+ probe. • A selective PEC sensor was developed for the analysis of Hg2+ with "turn-on" signal output. • Hg2+ induces the in-situ formation of HgS/ZnS/CdS with double type-II heterostructure. • The PEC sensor can detect Hg2+ with concentrations down to about 0.40 pM. An ultrasensitive and selective photoelectrochemical (PEC) platform has been developed for determining Hg2+ with "turn-on" signal output by synergistically using CdS nanowires (NWs) and ZnS quantum dots (QDs). CdS NWs was first prepared and then deposited with ZnS QDs to yield ZnS/CdS nanocomposite with type-II heterostructure. It was found that the as-constructed ZnS/CdS heterostructure can exhibit excellent photoelectrochemical characteristics by separately employing CdS NWs and ZnS QDs as the photosensitizer and Hg2+-recognition probe. What's more, the constructed analysis platform could display specifically enhanced photocurrent responses to Hg2+ under the visible light via the selective ion-exchange reaction. The in-situ formation of ternary HgS/ZnS/CdS could be thus expected with double type-II heterostructures so as to further enhance the transferring and separation of charges. A linear response can be achieved for Hg2+ in the concentration range from 0.0010 to 5.0 nM, with a detection limit of 0.40 pM. Moreover, the application feasibility of the developed sensor with ZnS/CdS heterostructure could be testified by detecting Hg2+ ions in environmental waters. Such a route of in-situ formation of double type-II heterostructure might promise the wide applications for designing different visible light-driven PEC sensors for probing heavy metals like Hg2+ with the "turn-on" signal output. [ABSTRACT FROM AUTHOR]

• Fe 3 O 4 QDs can present higher peroxidase-like catalysis than Fe 3 O 4 NPs. • Enhanced catalysis can be achieved for Fe 3 O 4 QDs if coated with sodium alginate. • Fe 3 O 4 QDs were coated onto capillary tubes by SA with film-forming capacity. • Automatic fetching of multiple samples can be expected by the capillarity power. • Capillary array-based colorimetric platform enables high-throughput detection of H 2 O 2. A simple and high-throughput colorimetric analysis array has been constructed for quantifying H 2 O 2 in milk using Fe 3 O 4 quantum dots (QDs), which were coated with sodium alginate (SA) and chromogenic substrate onto the arrayed capillary tubes. It was discovered that the Fe 3 O 4 QDs could present larger peroxidase-like catalysis than Fe 3 O 4 nanoparticles (NPs). Particularly, dramatically enhanced catalysis activity could be achieved for Fe 3 O 4 QDs if coated with SA films. Moreover, the use of SA could protect Fe 3 O 4 QDs to expect the improved environmental stability. A capillary arrays-based high-throughput colorimetric platform was thereby developed for the detection of H 2 O 2 in milk, with levels linearly ranging from 10 to 400 μM. Importantly, the developed colorimetric platform with the capillarity power for automatic fetching of multiple samples may promise the practical applications for extensive monitoring of multiple H 2 O 2 samples for food safety. [ABSTRACT FROM AUTHOR]

C@MoS 2 nanocomposites with hollow nanotube structures were synthesized through the hydrothermal sulfuration of molybdenum precursor along with the carbonization of glucose. Interestingly, it was found that the so-obtained C@MoS 2 nanzymes could specifically exhibit much enhanced oxidase-like catalysis after the addition of Hg2+. Herein, carbon might not only play a role in accelerating charge transfer, but also conduct the synergistic effects with MoS 2 to provide more catalytic active sites of nanzymes as compared with pristine MoS 2. Especially, the introduction of Hg2+ could induce C@MoS 2 nanozyme to produce more quantities of highly oxidative superoxide radicals through the strong Hg-S chelation in the catalysis reactions, as confirmed by the electron spin-resonance spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectra, and radical capturing experiments. A catalysis-based colorimetric platform with C@MoS 2 nanozyme was thereby constructed for the quantitative analysis of Hg2+ ions, showing linear responses to Hg2+ in the range of 0.010–100 μM with the detection limit of 2.7 nM, which is lower than those of current analysis methods. More importantly, the proposed colorimetric assay could be applied for detecting Hg2+ in environmental wastewater with the satisfactory detection recoveries, showing great potential applications for environmental monitoring, biomedical sensing, and food detection fields. [Display omitted] • Hollow C@MoS 2 nanotubes with Hg2+-enhanced oxidase-like activity were synthesized. • Carbon might conduct the synergistic effects with MoS 2 yielding more active sites of C@MoS 2. • Hg2+ could endow C@MoS 2 nanozyme with more superoxide radicals by the Hg-S chelation. • An effective C@MoS 2 -based colorimetric assay is established for the analysis of Hg2+ ions. • The developed strategy enables the evaluation of Hg2+ ions in the wastewater. [ABSTRACT FROM AUTHOR]

Recently, using nanomaterials to enhance the endocytosis capability and sensitivity of probes for RNA imaging in living cells has gotten the attention of many researchers. Nanomaterials, as a reliable alternative to transfection reagents, could prevent nucleic acid probes from being degraded by DNase, and bring them into sub-cellular locations for efficient internalization. Therefore, nanomaterial-based fluorescent probes (NFPs) provide a promising sensing platform to realize in situ RNA detection and imaging, which can reveal the expression of RNA at single cell level and provide large amount of information about RNA spatial localization. Meanwhile, many RNAs are in low abundance in living cells, resulting in difficulty in sensitive detection. Thus, the incorporation of NFPs and signal amplification strategy offers a broader prospect for the detection of RNAs, that have been proven as predominant therapeutic targets or diagnostic biomarkers. Herein, the purpose of our review is to first introduce the general procedure of NFPs used for in situ RNA imaging and how nanomaterials deliver these probes into living cells. Further, we focused on different kinds of nanomaterials that are mainly used for sensitive detection of RNAs and those in low abundance, through different signal read-out modes. Nanomaterial-based fluorescent probe (NFP) provides a promising sensing platform to realize effectively cellular endocytosis and intracellular RNA Imaging in situ. In our review, we try to basically introduce the whole progress of NFPs used for in situ RNA imaging, particularly focusing on the endocytic pathways that nanomaterials deliver these probes into living cells, as well as different kinds of nanomaterials that are mainly used for sensitive signal detection of RNAs, especially for those in low abundance. [Display omitted] • Monitoring the level of RNA expression, can assist our understanding of the progression, diagnosis and further treatment of tumor. • NFPs has high internalization efficiency and excellent biocompatibility to achieve cellular uptake and RNA imaging in situ. • Different kinds of nanomaterials for detection of RNAs, especially for those in low abundance, are summarized. [ABSTRACT FROM AUTHOR]

Water-soluble non-conjugated polymer dots (PDs) have been synthesized using hyperbranched polyethyleneimine (PEI) and dihydroxybenzaldehyde (DHB) for the first time via the Schiff base reaction at room temperature. The yielded non-conjugated PDs of PEI-DHB could display the well-defined spheric structure and good water solubility. In contrast to the common PDs otherwise showing blue emission, the PEI-DHB PDs could give out strong green fluorescence in aqueous media. Especially, the fluorescence of the PEI-DHB PDs could be specifically quenched by MnO 2 nanosheets through the inner filter effects and further restored by the thiocholine that could reduce MnO 2 nanosheets into Mn2+. Herein, thiocholine could be produced in hydrolysis reaction of acetylthiocholine catalyzed by the acetylcholinesterase (AChE), of which the catalytic activity could be irreversibly inhibitted by the introduction of organophosphates. A highly selective fluorimetric method was thereby been developed for the detection of organophosphorus pesticides using dimethyl-dichloro-vinyl phosphate as a model. The linear concentrations ranges from 0.050 to 2.5 μM. Importantly, the non-conjugated PDs probes with strong green fluorescence and high water solubility may promise the extensive applications in the environmental, food, and clinical analysis fields. [Display omitted] • Water-soluble non-conjugated polymer dots (PDs) were made by Schiff base reaction. • The PDs can display the well-defined structure and strong green fluorescence in water. • MnO 2 -quenched PDs fluorescence is restored by AChE-catalyzed hydrolysis. • The detection of pesticides is performed via the AChE catalysis inhibition. [ABSTRACT FROM AUTHOR]

• LaPO 4 @Ag was fabricated with high conductivity and visible-light-driven photocatalysis. • The nanocomposites were applied as electrochemical probes and photocatalytic adsorbents • Selective electroanalysis for phoxim was expected at the potentials approaching to zero. • Photocatalytic removal of pesticides was realized with the efficiency up to 95.7%. • The enhanced photocatalysis might be attributed to the constructed Z-scheme strategy. Urchin-like LaPO 4 was fabricated and further deposited with silver through the citric acid-templated self-assembly and reduction, yielding LaPO 4 @Ag to serve as the electrochemical probes and photocatalytic adsorbents for pesticide residues of phoxim (Phox). It was discovered that the LaPO 4 @Ag-modified electrodes could allow for the signal output of Ag/AgCl electrochemistry at the low potential approaching to zero, which could rationally decrease in the presence of sulfide-containing Phox. A selective electroanalysis method was further developed for sensing Phox in vegetables with the linear concentrations range of 0.10–600 μM. Moreover, the LaPO 4 @Ag adsorbent with large surface-to-volume area could present the white light-driven photocatalysis for the removal of Phox under sunlight with the efficiencies up to 95.7%, due to the Z-scheme strategy constructed by the silver deposition on LaPO 4. Importantly, this citric acid-templated self-assembly and reduction strategy may promise the wide applications for designing of various silver-doped catalytic materials of multiple functions of electrocatalysis, photocatalysis, and absorption. [ABSTRACT FROM AUTHOR]

A magnet-renewable electroanalytical strategy has been initially developed for monitoring hydrogen sulfide (H 2 S) in aquaculture freshwater systems using magnetic Fe 3 O 4 -loaded silver metal-organic framework (Fe 3 O 4 @Ag-MOF). The magnetic composites were synthesized by a hydrothermal route and further attached onto the magnetic electrodes. It was discovered that the Fe 3 O 4 @Ag-MOF-based electrochemical sensors could exhibit the extremely sharp and steady signals of solid-state Ag/AgCl electrochemistry at a lower potential. Furthermore, the highly specific and irreversible S–Cl replacement reactions could occur in the presence of H 2 S, so as to induce the conversion of AgCl into non-electroactive Ag 2 S with the rational decline of Ag/AgCl signals. Importantly, the Fe 3 O 4 @Ag-MOF-modified electrodes could be renewed simply by the removal of the magnet after each of the detection cycles for the next immobilization of Fe 3 O 4 @Ag-MOF probes. The developed electroanalytical method could facilitate the detection of H 2 S in the linear range from 4.0 to 1400 nM, with a limit of detection down to 2.0 nM. Besides, it was employed to detect H 2 S in aquaculture freshwater samples of fish, crab, and shrimp, showing the satisfactory results. Fe 3 O 4 @Ag-MOF composites were synthesized step-by-step and further attached onto the magnetic electrodes, which were allowed for the selective electroanalysis of H 2 S using NaCl, based on the solid-state Ag/AgCl electrochemistry. [Display omitted] • A magnet-renewable electroanalytical strategy is developed for monitoring H 2 S using magnetic Fe 3 O 4 @Ag-MOF. • Τhe Fe 3 O 4 @Ag-MOF-based sensor can exhibit sharp and steady signals of solid-state Ag/AgCl electrochemistry. • H 2 S can trigger the decreased Ag/AgCl signals through the specific S–Cl displacement reaction. • The Fe 3 O 4 @Ag-MOF-modified electrode can be renewed magnetically after the detection. • The as-prepared sensor is employed to probe H 2 S in aquaculture freshwater samples with satisfactory results. [ABSTRACT FROM AUTHOR]

Nanozymes are more stable, economical, and easier to produce than natural enzymes; however, their low activity in non-acidic environments and lack of substrate selectivity severely limit the applications of nanozymes. In this study, we developed Co- and N-doped carbon dot nanozymes (CoNCDs) that specifically exhibited peroxidase-like activity toward o-phenylenediamine in a non-acidic environment. Based on the peroxidase-like activity and fluorescence property of CoNCDs in a neutral environment, a one-pot multi-mode sensing platform (colorimetric and ratiometric fluorescence imaging) was developed to detect cholesterol and xanthine in solution and human serum samples. This platform was simple to operate, and the CoNCDs demonstrated a reduced detection time and an improved analytical performance compared to most of the reported nanozymes. Moreover, the improved peroxidase activity at neutral pH, good biocompatibility, and photostability of CoNCDs facilitated their use for monitoring endogenous H 2 O 2 levels in vivo. This study not only provides a novel approach for developing an acid pH-independent and substrate selectivity nanozyme but also demonstrates the application of ratiometric fluorescence imaging using the developed CoNCDs both in vitro and in vivo. [Display omitted] • CoNCDs showed the peroxidase-like activity at neutral and alkaline pH. • CoNCDs showed the substrate selectivity toward OPD, but no activity toward TMB and ABTS. • The one-pot multi-mode sensing platform for cholesterol and xanthine were developed. • CoNCDs was firstly applied to monitor H 2 O 2 in vitro and in vivo. [ABSTRACT FROM AUTHOR]

Nanozymes are more stable, economical, and easier to produce than natural enzymes; however, their low activity in non-acidic environments and lack of substrate selectivity severely limit the applications of nanozymes. In this study, we developed Co- and N-doped carbon dot nanozymes (CoNCDs) that specifically exhibited peroxidase-like activity toward o-phenylenediamine in a non-acidic environment. Based on the peroxidase-like activity and fluorescence property of CoNCDs in a neutral environment, a one-pot multi-mode sensing platform (colorimetric and ratiometric fluorescence imaging) was developed to detect cholesterol and xanthine in solution and human serum samples. This platform was simple to operate, and the CoNCDs demonstrated a reduced detection time and an improved analytical performance compared to most of the reported nanozymes. Moreover, the improved peroxidase activity at neutral pH, good biocompatibility, and photostability of CoNCDs facilitated their use for monitoring endogenous H 2 O 2 levels in vivo. This study not only provides a novel approach for developing an acid pH-independent and substrate selectivity nanozyme but also demonstrates the application of ratiometric fluorescence imaging using the developed CoNCDs both in vitro and in vivo. [Display omitted] • CoNCDs showed the peroxidase-like activity at neutral and alkaline pH. • CoNCDs showed the substrate selectivity toward OPD, but no activity toward TMB and ABTS. • The one-pot multi-mode sensing platform for cholesterol and xanthine were developed. • CoNCDs was firstly applied to monitor H 2 O 2 in vitro and in vivo. [ABSTRACT FROM AUTHOR]

A highly sensitive and visible-light-driven photoelectrochemical (PEC) sensor has been constructed for the quantitative assay of organophosphorus pesticides like chlorpyrifos (Chlo) using hollow Co 9 S 8 @CdS heterostructures. The Co 9 S 8 @CdS heterostructures were created by growing CdS onto Co 9 S 8 surface via one-step oil-bath route, of which Co 9 S 8 was fabricated with hollow tubular structures through the Co(CO 3) 0.35 Cl 0.2 (OH) 1.1 -templated solvothermal method. It was discovered that the so-obtained Co 9 S 8 @CdS with direct Z-scheme heterojunctions could exhibit larger photocurrents than the Co 9 S 8 or CdS because of the greatly enhanced separation efficiency of photo-generated carriers. What's more, the photocurrent signal of Co 9 S 8 @CdS-based PEC sensor could be selectively inhibited with the addition of Chlo through the specific chelation between the N and S atoms of Chlo with C N and P S groups and Co sites of Co 9 S 8 @CdS so as to suppress the carriers transferring. The developed PEC sensor could exhibit a linear response for Chlo ranging from 0.050 to 1000 ppb, with the detection limit value down to 0.015 ppb, which was far below than those of currently reported PEC sensors. Besides, the proposed routes may provide guidelines for designing various direct Z-scheme heterojunction-based PEC analysis platforms for determining environmental pollutants like Chlo. [Display omitted] • A visible-light-driven photoelectrochemical sensor was developed for probing chlorpyrifos. • Hollow Co 9 S 8 @CdS heterostructures were constructed via one-pot oil-bath route. • Co 9 S 8 and CdS were separately utilized as chlorpyrifos-recognition probe and sensitizer. • The sensor can facilitate the detection of chlorpyrifos with concentration down to 0.015 ppb. [ABSTRACT FROM AUTHOR]