Search

In this work, a new reduced graphene oxide–poly(safranine T) (rGO–PST) film was prepared on glassy carbon electrode (GCE) via one-step polymerization using rGO as an electron transfer mediator. The uniform structure of rGO–PST film was exhibited by scanning electron microscopy. Electrochemical characterization indicated that rGO–PST/GCE possessed much larger surface area and faster electron transfer rate constant compared with GCE. Furthermore, the rGO–PST/GCE exhibited strong catalytic ability and sensitive response to the oxidation of methyl jasmonate (MeJA) using derivative linear scan voltammetry. Under optimal working conditions, the oxidation current of MeJA linearly increased with its concentration in the range of 1.0–10 μM and 30–3000 μM after 2-min accumulation, along with a low detection limit of 0.5 μM. As an example of practical application, the rGO–PST/GCE was successfully employed for the determination of MeJA in jasmine essential oil and rice spikelets samples. [ABSTRACT FROM PUBLISHER]

Oxytetracycline is a broad-spectrum antibiotic used in animal husbandry that may cause the occurrence of antibiotic residues in food-producing animals. A detailed study of the electrochemical properties of oxytetracycline was carried out at montmorillonite and acetylene black modified carbon paste microelectrode. The oxytetracycline underwent an irreversible oxidation at montmorillonite-acetylene black/carbon paste microelectrode, which was an adsorption-controlled process with one proton and one electron. Using differential normal pulse voltammetry with accumulation at a fixed potential of 0.3 V for 120 s, oxytetracycline yielded a well-defined voltammetric response at 0.6 V in pH 7.4 citric acid–Na2HPO4buffer. Furthermore, the oxidation peak current of oxytetracycline at the montmorillonite–acetylene black/carbon paste microelectrode linearly increased with concentration in the range of 0.5–50 µM with a low detection limit of 87 nM (S/N = 3). This methodology was successfully applied to the determination of oxytetracycline from food samples, suggesting that it has practical applications in monitoring oxytetracycline. [ABSTRACT FROM PUBLISHER]

Highlights: [•] We prepare graphene (GN) nanosheets and mesoporous TiO2 (M-TiO2) nanoparticle. [•] GN is thin and M-TiO2 has continuous ordered mesopores under electron microscope. [•] GN and M-TiO2 based sensor can simultaneous detect sunset yellow and tartrazine. [•] Sunset yellow and tartrazine contents in food samples are successfully determined. [Copyright &y& Elsevier]

Abstract: A new facile preparation method of graphene oxide–mesoporous MnO2 (GO–MnO2) nanocomplex was developed here. The GO–MnO2 was used as a new electrode material for the fabrication of voltammetric sensor for sensitive simultaneous determination of hydroquinone (HQ) and catechol (CC), which exhibited significantly decreased peak-to-peak separations of ca. 34 and 36mV for HQ and CC, respectively between oxidation and reduction waves in cyclic voltammetry. In differential pulse voltammetric measurements, the GO–MnO2 based sensor could separate the oxidation peak potentials of HQ and CC by about 115mV though the bare electrode gave a single broad response, which was related to the higher surface area and catalytic ability of GO–MnO2. The oxidation peak current of HQ was linear over the range from 0.01 to 0.7μM in the presence of 0.1μM CC, and the oxidation peak current of CC was linear over the range from 0.03 to 1.0μM in the presence of 0.13μM HQ. The detection limits (S/N =3) for HQ and CC were 7.0 and 10.0nM, respectively. The proposed sensor was successfully applied to the simultaneous determination of HQ and CC in artificial wastewater samples. [Copyright &y& Elsevier]

[Display omitted] • Molecularly imprinted electrochemical sensor was prepared for the electrochemical determination of atropine. • Hierarchical meso-microporous MSN@ZIF-8 was applied to enhance the density of imprinted sites and response signal. • Sensitive, specific quantification of atropine has been achieved. • The proposed sensor exhibited fine applicability for detection of atropine in real samples. Porous materials are of great interest for sensor design, while poor conductivity and single structure hinder their electrochemical application seriously, and the development of an effective way to improve their specificity for targets is another challenge. Herein, novel flower-like core-shell mesoporous silica nanospheres@zeolitic imidazolate framework-8 (MSN@ZIF-8) hybrid electrocatalyst with hierarchical framework, enhanced porosity, tunable functionality, and excellent stability was firstly attempted. Significantly, the electronic environment and dynamics were greatly enhanced in MSN@ZIF-8, owing to the abundant faradic active sites of MSN inner cores and plentiful pores for electrolyte permeation and analytes adsorption of ZIF-8 outer shell. Thereafter, the molecularly imprinted electrochemical sensor based on MSN@ZIF-8 nanocomposites was prepared with p-aminothiophenol as functional monomer, Au nanoparticles as cross-linker, and atropine as template molecule via electropolymerization technique, which had a wide linear range, subnanomolar detection limit, and specific selectivity for atropine monitoring. Our work will inspire further studies on developing porous electrocatalysts with improved stability and performance, which is highly expected for varieties of sensor applications. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile preparation method of ultrasmall conjugated polymer dots has been established based on the Schiff base condensation. • The synthesized polymer dots (OOPdots) show a variety of superior properties, such as uniform small size, red emission and high quantum yield. • The resulting OOPdots can serve as excellent pH fluorescent probe for labeling lysosomes in living cells and zebrafish. Developing new strategies for facile synthesis of conjugated polymer dots (CPdots) derived from novel monomer species is highly desirable to improve their application. This paper describes a super-simple method, based on Schiff base condensation, for facilely fabricating ultrasmall CPdots under room temperature. This novel CPdots, prepared by reacting the o-benzoquinone with o-phenylenediamine catalyzed by hydrochloric acid, defined as OOPdots, show a variety of superior properties, such as uniform small size, red emission and high quantum yield. With abundant imine and amino groups on the surface, the OOPdots exhibit an excellent pH responsiveness via modulation of the self-assemble or dissociation. Further experiments indicate that the resulting OOPdots are high-performance probes for labeling lysosomes in living cells and zebrafish. This work not only expands the application scope of OOPdots in the field of biological imaging, but also provides guidance for their rapid and large-scale preparation. [ABSTRACT FROM AUTHOR]

• Rational synthesis and characterization of hollow Mn 2 O 3 polycrystals with various morphologies. • Strong morphology-dependent electrocatalytic oxidation activity of Mn 2 O 3. • Signal enhancement of graphene oxide reinforced ellipsoidal Mn 2 O 3 crystals. • Construction of an electrochemical sensing platform for simultaneous detection of OPP and BP. In the present study, three-dimensional hollow Mn 2 O 3 polycrystals with various aggregation morphologies including spheres, dumbbells, cubes, and ellipsoids were selectively synthesized by modulating the shape of premade MnCO 3 precursors with different manganese sources. Structural and electrochemical analyses demonstrated that the ellipsoidal Mn 2 O 3 hollow structures had a higher specific surface area, wider pore diameter, and superior electron-transfer reactivity, thus, they exhibited greater electrocatalytic activity toward the oxidation of two phenolic endocrine disruptors, i.e., o-phenylphenol (OPP) and butylparaben (BP). In addition, the electro-oxidation of hollow Mn 2 O 3 ellipsoids for OPP and BP was further enhanced when they were physically wrapped with graphene oxide (GO). This remarkable property is attributable to the dramatical increase of active sites and surface-chemisorbed oxygen species in these unique nanostructures. Highlights are presented for the simultaneous determination of OPP and BP within wide linear ranges of 0.002-20 and 0.003-24 μM, with low detection limits of 0.63 and 0.88 nM, respectively. Our findings not only offer a novel morphology-controllable synthesis strategy to better understand the morphology impact on the electrochemical performances of Mn 2 O 3 , but also represent a facile design of robust, active, and easy-to-obtain catalysts for sensors and other electrocatalytic systems. [ABSTRACT FROM AUTHOR]

To understand the relationship between endoplasmic reticulum (ER) stress and the level of hypochlorous acid (HOCl), it is highly desired to develop an ER-targetable HOCl probe to monitoring the HOCl level. In this study, a new turn-on type of two-photon ER-targetable fluorescent probe (ER-NPA) is designed for fluorescent sensing and imaging HOCl in ER using 4-hydroxy-1,8-naphthalimide as the fluorophore, p-aminophenyl ether as the recognition receptor, and methyl sulfonamide as ER-targetable group. The probe ER-NPA exhibits some intrinsic features such as excellent water solubility, good biocompatibility, significantly fast and enhanced fluorescence response to HOCl within 60 s, and detection limit as low as 6.2 nM for HOCl determination. The probe ER-NPA is successfully applied to real-time monitoring of exogenous and endogenous HOCl fluctuations in HeLa cells and zebrafish during ER stress. The developed probe ER-NPA may provide a new strategy to reveal the chemical biology roles of HOCl in ER stress-related diseases. Image 1 • A new turn-on, two-photon, and endoplasmic reticulum (ER)-targetable fluorescent probe is designed for sensing and imaging HOCl in ER. • The probe exhibits excellent water solubility, good biocompatibility, fast response and detection limit for HOCl determination. • The probe is successfully applied to real-time monitoring of exogenous and endogenous HOCl fluctuations in living systems during ER stress. [ABSTRACT FROM AUTHOR]

We report an integrated ratiometric lysosomal nitric oxide (NO) nanoprobe based on engineered semiconducting polymer dots (Pdots), LyNO-Pdots, which consist of a newly designed NO-responsive dye, a fluorescent conjugated polymer and two functional polymers. The developed probe LyNO-Pdots exhibit high specificity and stability, good photostability and favorable blood–brain barrier (BBB) penetration ability. The LyNO-Pdots are successfully applied to ratiometric imaging of lysosomal NO variations in brain-derived endothelial cells, brain tissues and mice brains with Alzheimer's disease (AD). The results demonstrate that the NO content in the brains of AD mice is considerably higher than that in normal mice. [ABSTRACT FROM AUTHOR]

A template-activated strategy was developed to construct core/shell structured carbon sphere@silver composite based on one-pot hydrothermal treatment. The CS@Ag possessed a uniform three-dimensional interconnected microstructure with an enlarged surface area and catalytic activity, which was further mechanically protected by graphene oxide (GO) nanolayers to fabricate intriguing configuration, which was beneficial for efficiently preventing the aggregation and oxidation of AgNPs and improving the electrical conductivity through intimate contact. By immobilizing this special material on electrode surface, the CS@Ag@GO was further used for sensitive determination of chlorinated phenols including 2-chlorophenol, 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol. The tailored structure, fast electron transfer ability and facile preparation of CS@Ag@GO made it a promising electrode material for practical applications in phenols sensing. [ABSTRACT FROM AUTHOR]

A novel composite film based on carbon nanodots (CNDs) and chitosan was readily prepared and used as immobilization matrix to entrap a heme protein, hemoglobin (Hb) for direct electrochemistry and bioelectrocatalysis. A modified electrode was obtained by casting Hb–CNDs–chitosan composites on the glassy carbon (GC) electrode surface. Spectroscopic and electrochemical studies showed that Hb entrapped in the composite film remained in its native structures, and CNDs in the film can greatly facilitate DET between the protein and the GC electrode. The electron-transfer kinetics of Hb in composite film was qualitatively evaluated by using the Marcus theory, and the apparent heterogeneous electron-transfer rate constant (k s ) was estimated to be 2.39(±0.03)s−1 with Laviron equations. The modified electrode showed excellent electrocatalytic behavior to the substrate, hydrogen peroxide (H2O2). The linear current response for H2O2 was from 1×10−6 to 1.18×10−4 M with a detection limit of 0.27(±0.02)μM at the signal-to-noise ratio of 3, and the apparent Michaelis–Menten constant was 0.067(±0.02)mM. These important features of CNDs–chitosan film have implied to be a promising platform for elaborating bioelectrochemical devices such as biosensors and biofuel cells. [ABSTRACT FROM AUTHOR]

Abstract: A simple and novel electrochemical sensor for the determination of tetracycline (TC), a kind of antibiotic that may induce residue in the food chain, was developed by the modification of iron/zinc cation–exchanged montmorillonite (Fe/Zn–MMT) catalyst on glassy carbon electrode (GCE). The morphology and the structure of the Fe/Zn–MMT nanomaterial were characterized by scanning electron microscopy and X-ray diffraction, respectively. The results of electrochemical experiments demonstrated that the sensor exhibited excellent electrocatalytic activity to the oxidation of TC in the presence of sodium dodecyl sulfate. The sensor displayed a wide linear range from 0.30 to 52.0μM and a low detection limit of 0.10μM by using the derivative differential pulse voltammetry. Moreover, the electrochemical sensor was applied to the detection of TC in feedstuff and meat samples. [Copyright &y& Elsevier]

It is imperative to develop methods for quantifying and imaging hypochlorous acid/hypochlorite (HOCl/ClO−) in living systems to clarify its roles in physiological and pathological processes and optimize therapeutic interventions for related diseases. Herein, we develop a ratiometric semiconducting polymer dot (Pdot)-based fluorescent probe with dual-emission at blue and green regions, PFO–PFPV Pdot, which is prepared from two fluorescent conjugated polymers including poly(9,9-dioctylfluorenyl-2,7-diyl) (PFO) and poly[(9,9-dioctyl-2,7-divinylene-fluorenylene)-alt-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}] (PFPV), for detecting and imaging HOCl in living cells. The presence of HOCl can selectively oxidize PFPV components in Pdots and the oxidation reaction can be enhanced by UV irradiation, which interrupts the fluorescence resonance energy transfer (FRET) from PFO to PFPV and results in the fluorescence quenching of PFPV at green emission region and recovery of PFO at blue emission region. On the basis of the ratios of fluorescence intensities at PFPV and PFO as a function of HOCl concentrations, a ratiometric fluorimetry for HOCl detection with a low detection limit of 56.8 nM is proposed. Furthermore, the developed fluorescent probe is also used for ratiometric fluorescence imaging of exogenous and endogenous HOCl in RAW264.7 cells with satisfactory results. The developed PFO–PFPV Pdots show high specificity and sensitivity, low cytotoxicity, and good biocompatibility for HOCl detection. [ABSTRACT FROM AUTHOR]

The thiolysis of 7-nitro-1,2,3-benzoxadiazole amine (NBD-A) paves the way for specific sensing of H 2 S over biothiols and real-time imaging in living organisms. Rational fabrication of NBD-A-based probe with ratiometric mode and two-photon excitation is highly appealing to achieve high quality bioimaging. In this work, the NBD-A molecules are assembled with poly(9,9-dioctylfluorenyl-2,7-diyl) polymer nanoparticles, defined as NBD@PFO, to construct two-photon ratiometric probes for H 2 S detection through the fluorescence resonance energy transfer (FRET). For the construction of NBD@PFO nanohybrids, polymer nanoparticles are employed as the NBD-A molecular vehicle, energy donor and two-photon absorber, while NBD-A is served as the response unit and energy acceptor. Taking advantages of NBD-A and polymer nanoparticles, the obtained NBD@PFO probes exhibit high selectivity, fast response (<5 s), ratiometric detection and two-photon excitation. Our results indicate that NBD@PFO nanohybrids are successfully applied for monitoring of H 2 S concentration in living cells and zebrafish, exhibiting great potential of polymer nanoparticles to improve the imaging capability of an organic small molecular probe. [Display omitted] • A two-photon ratiometric H 2 S probe was developed based on FRET between SPNs and NBD-A dyes. • The obtained NBD@PFO probe exhibited high sensitivity, only for H 2 S detection as well as fast response. • The proposed probe was successfully applied for two-photon bioimaging in living cells and zebrafish. [ABSTRACT FROM AUTHOR]

Designing fluorescent probes to achieve sensitive and rapid detection of pesticide 2,6-dichloro-4-nitroaniline (DCNA) in a water environment is highly appealing. Here, anthracene-based fluorescent conjugated porous polymers (ACPP) with a partially π-extension wall have been synthesized via a Suzuki coupling reaction for sensitive and rapid detection of DCNA pesticide. The unique pore structure extending anthracene unit into the pore not only improve the host-guest interaction of the polymer and analytes, but also increase the possibility of photoinduced electron transfer (PET) by shortening the electron hopping distance, thus improving the fluorescence detection performance. Benefiting from the synergistic effects of competitive energy absorption, PET and host-guest interaction, the ACPP can be used to detect DCNA pesticide with fast response (<2 s) and high quenching constant (Ksv = 3.8 × 105 M−1). The ACPP-based portable test strips and sol-gel sensors were successfully applied to the portable detection of DCNA in real food samples. [Display omitted] • A conjugated porous polymer, ACPP, for pesticide DCNA detection was synthesized. • The unique pore structure improves PET efficiency and host-guest interaction. • The quenching constants Ksv was up to 3.8 × 105 M−1. • Portable test strips and sol-gel sensors were successfully constructed. [ABSTRACT FROM AUTHOR]

Acid stress is one of the most common adverse conditions during fermentation of fruit wines, and the acid tolerance of yeasts is, therefore, critical for fruit wine production. However, the biological mechanism underlying the acquired tolerance of yeasts against acid stress is poorly understood. We have previously obtained an evolved Saccharomyces cerevisiae strain ET008-c54 with increased tolerance against acid stress, and potentially, it serves as a promising yeast strain for greengage wine fermentation. In the current study, we further revealed the alterations responsible for the adaptation of ET008-c54 to low pH by whole-genome re-sequencing, transcriptomic, and metabolic analyses. Results confirmed the outstanding fermenting performance of ET008-c54 at low pH as compared with the parental ET008. More specifically, the growth rate of ET008-c54 at low pH was increased by 6.24 times and the fermentation time was shortened by 70%. Differences were also observed in the physiology of the strains through ergosterol, H+-ATPase activity, and aroma determinations. By integrating both RNA-seq and whole-genome re-sequencing data, we demonstrated some metabolic pathways in ET008-c54, namely ergosterol synthesis and ferrous iron uptake, in which several acid-responsive genes were involved being upregulated. Also, upregulation of the pathways responsible for aroma compound formation, including fatty acid ethyl ester synthesis and aromatic amino acid biosynthesis, was identified. Thus, the enhanced fermentation ability of ET008-c54 at low pH should be, at least partly, contributed by the altered gene expressions associated with the aforementioned pathways. By elucidating the biological mechanism of yeasts against acid stress, this current study allows better-defined targets for future studies of genetic improvement of wine yeasts and enhancement of the fermentation processes. Key points: • Metabolic analysis confirmed the excellent fermentation performance of ET008-c54. • Acid tolerance genes for ergosterol synthesis and ferrous iron uptake were upregulated. • Aroma genes for fatty acid ethyl ester and aromatic amino acid synthesis were upregulated. [ABSTRACT FROM AUTHOR]

A highly uniform and monodisperse silica-encapsulated Au@Ag multilayered core-shell nanorods (~ 80 nm in length) has been prepared with excellent electrocatalytic properties. Using the Au@Ag@SiO2 nanoassemblies to substantially enhance the sensitivity and the sol-gel molecularly imprinted polymer (MIP) with imprinted cavities to present special molecular recognition sites, a novel electrochemical sensing platform was rationally designed, fabricated, and tested for efficient theobromine (THB) quantification. The formation of final Au@Ag@SiO2@MIP was characterized by transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. The performance of the Au@Ag@SiO2@MIP modified electrode was evaluated by differential pulse voltammetry with the changes in peak current of hexacyanoferrate redox probe measured at a working potential of 0.2 V (vs. saturated calomel electrode) as determination signal. Under optimal conditions, the quantitation of THB was attained in a broad linear range from 10 nM to 100 μM with a detection limit of 8.0 nM. The selectivity of Au@Ag@SiO2@MIP was examined according to its recognition to THB and the interferents. Finally, the sensing platform was successfully applied to extract and determine THB from food, biological, and environmental samples with acceptable recoveries (92.20–107.1%) and relative standard deviation < 4%. The propsed sensor provides a robust means for monitoring alkaloids in complex matrices and a promising opportunity to develop sensitive and selective electrode materials with good reusability. [ABSTRACT FROM AUTHOR]

Acid tolerance and aroma profile are crucial factors for wine production in Saccharomyces cerevisiae. However, most wine yeasts to date fail to endure low-pH environments, therefore resulting in problems such as lengthened fermentation and poor flavor during acidic fruit wine production. In the present study, we established a multiple-step screening strategy, which was composed of atmospheric and room temperature plasma (ARTP), high-throughput screening (HTS), and laboratory adaptive evolution (ALE), to screen yeast strains for potential wine-producing with enhanced performances during low pH conditions. Importantly, we obtained the S. cerevisiae strain from the mutant library, ET008-c54, which displayed exhibited excellent performances in survival rate, fermentation time, aroma profile, and genetic stability. More specifically, the survival rate of ET008-c54 at low pH was increased by 10-fold, the fermentation time of greengage plum wine was shortened by about 70%, and the content of main aroma compounds was significantly increased by 52%. Collectively, we demonstrate the practical application of the screening platform designed for discovering mutant strains in winemaking technology. Key Points • A novel multi-step method was developed for screening wine-producing yeast. • Acid tolerance and aroma profiles of yeast were improved by the proposed method. • ET008-c54 showed excellent fermenting performance and stability at low pH. [ABSTRACT FROM AUTHOR]

In recent years, porous organic polymers (POPs) possess a remarkable potential as adsorbents for heavier halogen (I 2 and Br 2) capture in the fields of environmental treatment and industrial production. How to improve iodine adsorption properties through efficient molecular structure design is still worth exploring. In this work, a novel nitrogen-rich POP, defined as POP-TT, for iodine capture is designed and easily obtained by reacting 2,4,6-trichloro-1,3,5-triazine (TCT) and tris(4-aminophenyl) amine (TAPA) with the aid of dechlorination agent under mild condition, inspired by the significant enhancement of iodine capture with N-rich heterocyclic structure. The proposed POP-TT shows good stability and porosity even in high-salt solutions. Profiting from the nitrogen-rich skeleton and phenyl groups of POP-TT and strong charge-transfer interaction between polymer framework and adsorbed iodine, the proposed POP-TT exhibits excellent affinity with uptake capacity of 4.62 g g−1 for iodine vapor and removal efficiency of 86.8 % for iodine aqueous solution. Good retention behavior and recycling capacity are also observed for POP-TT. This work provides a practical guide for designing heavier halogen adsorbents by using dechlorinated porous organic polymers. [Display omitted] • N-rich porous organic polymers (POP-TT) were synthesized easily. • POP-TT exhibits significant promoted iodine vapor capacity (4.62 g g−1) and removal efficiency in aqueous solution (86.8 %). • Good retention behavior and recycling capacity are also observed for POP-TT. [ABSTRACT FROM AUTHOR]

In this work, the Ag@Cu particles with yolk–shell nanostructure was prepared by facile solvothermal method, which was modified on glassy carbon electrode (GCE) to fabricate electrochemical sensor for the convenient and fast determination of p-aminobenzoic acid (PABA). The surface morphology and electrochemical properties of the as-prepared Ag@Cu nanocomposite modified electrode were characterized by scanning electron microscopy, transmission electron microscopy, chronocoulometry, and electrochemical impedance spectroscopy. Further, the electrochemical sensing of PABA was performed on the Ag@Cu/GCE using cyclic voltammetry and differential pulse voltammetry techniques, showing high catalytic activity. Under the optimal conditions, the sensor exhibited a wide linear range, high sensitivity, and low detection limit of 0.315 μmol/L for PABA. The developed sensor was also successfully applied for PABA detection in anesthetic and cosmetics with satisfactory results. [ABSTRACT FROM AUTHOR]

In this study, a facile solution approach was developed for the synthesis of a series of core–shell structured Ag@Cu 2 O nanocrystals of various shapes including triangles, spheres, and cubes with well–defined stable heterojunctions. The electrooxidation of dopamine (DA), uric acid (UA), guanine (G), and adenine (A) using these hybrids revealed morphology–dependent sensing properties, with activities and accumulation ability following the order, triangular Ag@Cu 2 O > spherical Ag@Cu 2 O > cubic Ag@Cu 2 O. Further, we constructed a novel graphene oxide (GO) nanosheet–reinforced triangular Ag@Cu 2 O ternary hetero–nanostructure. Such a hybrid with a three–dimensional interconnected hierarchical architecture is suitable for catalysis, since it not only leads to improved interfacial electron transfer, but also readily exposes the highly catalytic Ag@Cu 2 O to the reactants. Therefore, more enhanced electrochemical activities were observed for the oxidation of DA, UA, G, and A. This study provides an efficient way to synthesize morphology–controlled Ag@Cu 2 O heterogeneous catalysts for the fabrication of potential biosensors, and also opens up attractive avenues in the design of multifunctional ternary noble metal–semiconductor–carbon hybrids. [ABSTRACT FROM AUTHOR]

The fluorescent nanohybrids of carbon dots and semiconducting polymer nanoparticles were used for ratiometric and visual determination of of copper ions. [Display omitted] • Carbon dots-based nanohybrids were fabricated for ratiometric detection of Cu2+ ion. • SPNs with clew-like structure were used to fabricate nanocomposites. • The obtained GCDs@RSPN probe was applied to detect the Cu2+ in actual samples. • The test strips were constructed by used GCDs@RSPN probe. Developing nanohybrid composition based fluorescent carbon dots (CDs) for ratiometric detection of copper ions is highly appealing. Herein, a ratiometric sensing platform (GCDs@RSPN) for copper ions detection has been developed by loaded green fluorescence carbon dots (GCDs) on the surface of red emission semiconducting polymer nanoparticles (RSPN) through electrostatic adsorption. The GCDs, featuring abundant amino groups, can selectively bind copper ions to induce the photoinduced electron transfer, leading to fluorescence quenching. A good linearity within the range of 0–100 μM is obtained, and the limit of detection (LOD) is 0.577 μM by using obtained GCDs@RSPN as ratiometric probe to detect copper ion. Moreover, the paper-based sensor derived from GCDs@RSPN was successfully applied for the visual detection of Cu2+. [ABSTRACT FROM AUTHOR]

The present work is focused on a typical core-shell-structured SiO@TiO-based imprinted polymer composite, employed as a molecular recognition and sensing interface in the construction of an innovative electrochemical sensor. Herein, the methacrylic acid and a bronchodilator drug, theophylline, were used as functional monomer and template, respectively. The SiO@TiO served as a potential signal transducer to shuttle electrons between the binding sites and the electrode. Such modification induced an electrocatalytic effect and thereby greatly improved the electrode kinetics. The analytical features of the developed theophylline sensor have been accessed, and the results have indicated that an increase of differential pulse voltammetric current as compared to the corresponding traditional imprinted polymer modified electrode. Moreover, the sensor has showed high sensitivity, wider linear range (0.01-40 μM), lower detection limit (1.2 nM), and satisfactory long-term stability, which was validated with the complex matrices of tea, human blood serum, and urine, without any matrix effect and cross-reactivity. [ABSTRACT FROM AUTHOR]

Graphene oxide−wrapped hierarchical hollow structured SnO 2 spheres were fabricated by hydrothermal strategy and applied to the sensitive electrochemical sensing of phenolic compounds. The as−prepared new nanocomposite modified electrode characterized by morphology, X−ray diffraction, Raman spectroscopy, electrochemical impedance, and electroactive surface area suggested its efficiency for the individual and simultaneous sensing of 4−aminophenol (4−AP) and 4−chlorophenol (4−CP), exhibiting as the remarkable increase in peak currents compared with SnO 2 or graphene oxide modified electrodes. After optimization of electrochemical parameters, the detection limits of 2.2 nM for 4−AP and 3.1 nM for 4−CP were obtained using differential pulse voltammetric method. Finally, the application of the modified electrode in real water samples was evaluated, indicating that it could be used as an excellent platform for the detection of phenolic pollutants. [ABSTRACT FROM AUTHOR]

Rational tailoring of hollow and porous bimetallic structures with excellent electrocatalytic performance is appealing yet challenging. Further, combining independent bimetallic nanoparticles with flexible two-dimensional substrate by forming stable heterocomplex is still highly desired for electrocatalysis. Herein, hierarchical PtCu alloy octahedrons with hollow interiors and nanosheet-assembled nanoshells were synthesized by a facile and efficient chemical transformation strategy using Cu 2 O as sacrificial templates. Such octahedral PtCu nanocages displayed significantly enhanced electrocatalytic activity owing to their unique hollow and porous architectures which provided easy access for analytes to the catalyst surface. Thereafter, introduction of Ti 3 C 2 T x MXene was realized via simple incubation of Ti 3 C 2 T x in solution containing the 3-aminopropyltriethoxysilane-capped PtCu, and their electrostatic interaction guaranteed the firm adsorption of PtCu nanocages on Ti 3 C 2 T x nanosheets. It turned out that the sensitivity of the hybrid sensor was remarkably improved for electrochemical monitoring of endocrine disrupting pollutants in water, exhibiting ultrawide linear ranges and sub-nanomole detection limits. The eminent electrode performance is attributed to the high specific area, fast electrochemical kinetics, decent electrical catalytic ability, and the synergistic effect between Pt, Cu, and MXene. [Display omitted] • Octahedral PtCu alloy nanocages with nanosheet−assembled shells were synthesized. • MXene−reinforced PtCu hybrid was fabricated for efficient electrocatalytic platform. • A sub−nanomole level sensing of endocrine disrupters was achieved. • The sensing platform can be applied to detect endocrine disrupters in waters. [ABSTRACT FROM AUTHOR]

A selective and sensitive electrochemical sensor has been prepared for the determination of 6-benzylaminopurine (BAP) in complex matrices. It was fabricated by thoroughly mixing multiwall carbon nanotube@SnS (MWNT@SnS) with molecularly imprinted chitosan (CHIT), and then covering on the surface of glassy carbon electrode (GCE). The core/shell-structured MWNT@SnS dramatically improved the sensitivity of the developed sensor through providing increased binding and preconcentration onto the modified GCE, while CHIT imprinted with BAP served as the selective recognition sites. Several experimental parameters such as pH, amount of modifier, extraction time, and incubation time were optimized. Under the optimal conditions, selective detection of BAP in a linear concentration range of 0.1 nM-10 mM was performed with the detection limit of 50 pM (3 S/ S). The relative standard deviation of repeatability and reproducibility of the sensor was 1.14 and 2.42 %, respectively. Furthermore, the sensor was successfully applied to the determination of BAP in vegetable and fruit samples, indicating the molecularly imprinted polymer-based electrochemical sensing platform might provide a rapid, sensitive, and cost-effective strategy for BAP determination and related food safety analysis. Graphical Abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

In this paper, we report a facile route to synthesize yolk–shell structured copper oxide@silica oxide (CuO@SiO 2 ) spheres and their application to construct an electrochemical Formoterol fumarate (FF) sensor. The CuO@SiO 2 was characterized by means of Fourier transform infrared spectroscopy, X-ray powder diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. Further, FF was electrocatalytically oxidized at the CuO@SiO 2 film modified glassy carbon electrode (GCE), which led to a sensitive determination of FF. The oxidation current of FF was linear with concentration in the range of 0.030–10 μM and the detection limit was found to be 5.0 nM (S/N = 3). The observed analytical parameters such as wide linear range, low detection limit and short response time were superior to previously reported FF sensors. Finally, it was demonstrated that the proposed sensor could be used for the selective determination of FF present in swine feed and tissues. [ABSTRACT FROM AUTHOR]

This work designed a simple, sensitive, low-cost, and disposable electrochemical platform for the detection of antibiotic rifampicin (RIF) by using a hollow manganese oxide@mesoporous silica oxide (Mn3O4@SiO2) core-shell nanohybrid as sensitive material. The Mn3O4@SiO2 core-shell nanohybrid, prepared by a facile polyacrylic acid soft templating method, was applied to modify a homemade carbon paste microelectrode, which provided a feasible pathway for electron transfer of RIF due to the low density, large surface area, excellent loading capacity, high permeability, and abundant amount of active sites. The electrocatalytic behavior was further used for sensitive detection of RIF by square wave voltammetry. Under optimal conditions, the calibration curve was linear in the range from 30 nmol/L to 3.0 μmol/L. The electrochemical method showed good stability, reproducibility, and selectivity. It could effectively be applied to the determination of RIF in human serum and urine samples. [ABSTRACT FROM AUTHOR]

We report a facile strategy for preparing Ag nanoparticles with a carbon shell by hydrothermal method, and the effect of Ag source concentration on the resultant stability and sphere sizes was investigated. The field emission scanning electron microscopy and field emission transmission electron microscopy show that the sphere sizes range from 130 nm to 2 μm with the gradual increase of Ag core and carbon shell simultaneously, energy dispersive spectrometry confirms the composition of core-shell-structured Ag@carbon, the face-centered cubic Ag phase is presented by X-ray diffraction analysis, and electrochemical impedance spectroscopy indicates that the conductivity of Ag@carbon changes with its sizes. Thereafter, a series of different sized Ag@carbon catalysts are used for the electrochemical sensing of bisphenol A (BPA). The results show that Ag@carbon sphere with a diameter of about 220 nm is a very effective and stable sensing material for the determination of BPA, which shows good prospects for sensor application. [ABSTRACT FROM AUTHOR]

Various morphologies of manganese dioxide (MnO 2 ) electrocatalysts, including nanoflowers, nanorods, nanotubes, nanoplates, nanowires and microspheres were prepared via facile hydrothermal synthesis and precipitation methods. By simply grinding with graphene oxide (GO), MnO 2 could be readily dissolved in water with high solubility and stability. The structures and electrochemical performances of these as–prepared MnO 2 –GO hybrids were fully characterized by various techniques, and the properties were found to be strongly dependent on morphology. As sensing materials for the simultaneous determination of guaiacol and vanillin for the first time, the nanoflowers–like MnO 2 , coupled with GO, exhibited relatively high sensitivity. The enhanced electrocatalytic activity was ascribed to the high purity, good crystallinity, and unique porous microstructure, which were favorable for transfer of electrons. These results may provide valuable insights for the development of nanostructured modified electrodes for next–generation high–performance electrochemical sensors. [ABSTRACT FROM AUTHOR]

Herein, we designed and fabricated hollow N-doped carbon polyhedrons with atomically dispersed Zn species (Zn@HNCPs) through a topo-conversion strategy by utilising metal-organic frameworks as precursors. Zn@HNCPs achieved efficient electrocatalytic oxidation of sulfaguanidine (SG) and phthalyl sulfacetamide (PSA) sulfonamides through the high intrinsic catalytic activity of the Zn-N 4 sites and excellent diffusion from the hollow porous nanostructures. The combination of the novel Zn@HNCPs with two-dimensional Ti 3 C 2 T x MXene nanosheets resulted in improved synergistic electrocatalytic performance for the simultaneous monitoring of SG and PSA. Therefore, the detection limit of SG for this technique is much lower than those of other reported techniques; to the best of our knowledge, this is the first detection approach for PSA. Moreover, these electrocatalysts show promise for the quantification of SG and PSA in aquatic products. Our insights and findings can serve as guidelines for the development of highly active electrocatalysts for application in next-generation food analysis sensors., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Monitoring the pH variation in lysosomes is very conducive to studying the autophagy process, and fluorescent ratiometric pH nanoprobes with inherent lysosome targeting ability are highly desirable. Here, a carbonized polymer dots-based pH probe (oAB-CPDs) was developed by self-condensation of o-aminobenzaldehyde and further carbonization at low temperature. The obtained oAB-CPDs display improved performance in pH sensing, including robust photostability, intrinsic lysosome-targeting ability, self-referenced ratiometric response, desirable two-photon-sensitized fluorescence property, and high selectivity. With the suitable pKa value of 5.89, the as-prepared nanoprobe was successfully applied to monitor the variation of lysosomal pH in HeLa cells. Moreover, the occurrence that lysosomal pH decreased during both starvation-induced and rapamycin-induced autophagy was observed by using oAB-CPDs as fluorescence probe. We believe that nanoprobe oAB-CPDs can work as a useful tool for visualizing autophagy in living cells., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

The pH environment in cancer cells has been demonstrated to display vital influences on the therapeutic effect of photodynamic therapy (PDT). It is very interesting to develop pH-responsive probes for simultaneous pH sensing and dynamics monitoring of the effects of PDT, and therefore assessing the correlation between them. In this study, a multifunctional fluorescence probe, dual-emission carbonized polymer dot (CPD) in blue and red regions, which uses ethylene imine polymer (PEI) and 4,4',4″,4‴-(porphine-5, 10, 15, 20-tetrayl) tetrakis (benzoic acid) (TCPP) as precursors through a one-step hydrothermal amide reaction, has been designed for ratiometric pH sensing, generating pH-dependent 1 O 2 for PDT of cancer cells, and investigating the dynamics effects of PDT through pH-guided imaging. The prepared CPDs were successfully used for ratiometric pH response, pH-dependent generation of 1 O 2 , and dynamics monitoring PDT in HeLa cells. This study may provide an alternative strategy to prepare CPD-based theranostic integrated nanoprobes for PDT through the rational design of precursors.

Novel dual-ratio semiconducting polymer dots (Pdots) with trichromatic-emission in the red, green and blue primary-color regions, are designed as lysosome-targeting nanoprobes for the simultaneous detection and multicolor imaging of pH and Cu 2+ in HeLa cells and zebrafish without cross-interference.

Ratiometric sensing systems transduced through independent analyte-sensitive response signals, which are simultaneously obtained from a single material, are highly desired to improve sensing reliability and sensitivity. In this study, a dual-model ratiometric sensing system with fluorescence and second-order light scattering (SOS) as transducing signals has been designed for the ratiometric detection of alkaline phosphatase (ALP). Semiconducting polymer nanoparticles (SPNs) made of poly[(9,9-dioctylfluorenyl-2,7-diyl)- co -(1,4-benzo-{2,1',3}-thiadiazole)] are prepared and used as reducing and stabilizing agents to prepare MnO 2 nanosheets in situ through the reduction of KMnO 4 . The formed SPNs@MnO 2 nanohybrids exhibit independent fluorescence and SOS response to ALP by using l-ascorbic acid 2-phosphate trisodium salt as the enzyme substrate. Benefiting from the simultaneous availability of fluorescence and SOS signals under the same excitation, a ratiometric probe has been constructed successfully for ALP sensing. Under optimal conditions, the SPNs@MnO 2 nanohybrids for ALP detection show a good linear detection range from 0.1 to 9.0 U L -1 with a detection limit of 0.034 U L -1 . Additionally, a visual and portable sensing device for ALP detection is also constructed based on the fluorescent performances of the SPNs@MnO 2 nanohybrids. We believe the proposed method with the in situ preparation of SPN-based hybrid probes via the reducing ability of SPNs will pave a new way for the construction of multifunctional sensing materials in chemo-/biosensing applications., Competing Interests: The authors declare no competing financial interest.

The rational surface functionalization of semiconducting polymer dots (Pdots) has attracted much attention to extend their applications in fabricating chemo/biosensing platform. In this study, a novel ratiometric fluorescent sensing platform using functionalized Pdots as probes for fluorescence signal transmission has been designed for sensing Cu(Ⅱ) and activity of alkaline phosphatase (ALP) with high selectivity and enhanced sensitivity. The highly fluorescent Pdots were firstly prepared with Poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-(1,4-benzo-{2,1',3}-thiadiazole)] (PFBT) via nanoprecipitation method, and then assembled with non-fluorescent rhodamine B hydrazide (RB-hy), which shows special binding activity to Cu(Ⅱ), through adsorption process to obtain functionalized nanohybrids, Pdots@RB-hy. As thus, a FRET donors/acceptors pair, in which PFBT Pdots act as energy donors while RB-hy-Cu(II) complexes act as energy acceptors were constructed. On the basis of the varies in fluorescence intensities of donors/acceptors in the presence of different amounts of Cu(II), a ratiometric method for sensing Cu(II) has been proposed. The proposed ratiometric Cu(II) sensor shows a good linear detection range from 0.05 to 5μM with a detection limit of 15nM. Furthermore, using the Pdots@RB-hy-Cu(II) system as signal transducer, a ratiometric sensing for alkaline phosphatase (ALP) activity has also been established with pyrophosphate (PPi) as substrates. The constructed ratiometric sensor of ALP activity displays a linear detection range from 0.005 to 15UL -1 with a detection limit of 0.0018UL -1 . The sensor was further successfully used for ALP activity detection in human serum with satisfactory results., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The study presents a new approach for rapid and ultrasensitive detection of maltol using a glassy carbon electrode (GCE) modified with graphene oxide-wrapped tin oxide@carbon nanospheres (SnO2@C@GO). The morphological and components properties of SnO2@C@GO nanocomposites were investigated by means of X-ray diffraction spectroscopy, Raman spectroscopy, field emission scanning electron microscopy, high resolution transmission electron microscopy, and electrochemical impedance spectroscopy. SnO2@C@GO nanocomposite on a GCE had a synergetic effect on the electrochemical oxidation of maltol by means of square wave voltammetry. Under the optimum conditions, anodic peak current response of maltol was linear with its concentration in the range of 80nM-10μM, and a detection limit of 12nM was achieved for maltol. The experiment results presented that the method showed good selectivity, sensitivity, reproducibility, and long-term stability, as well as excellent potential for use as an ideal inexpensive voltammetric method applicable for complex food matrices., (Copyright © 2016 Elsevier Ltd. All rights reserved.)