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The design of economical, efficient, and durable low-Pt catalysts is one of the directions in developing energy storage and conversion technologies. Herein, a Pt/WC1−x/WO3 self-supported electrode with a low Pt-loading (17.4 μg cm−2) was synthesized from bulk metals by an anodization coupled electrodeposition method followed by a carburization reduction process. The electrode exhibits an overpotential of 89.6 mV at 200 mA cm−2 for the hydrogen evolution reaction (HER) with excellent stability. Its highest mass activity for the methanol oxidation reaction (MOR) is 1.18 A mg−1 Pt, which is 2.46 times higher than that of a 20% Pt/C catalyst. This self-supporting electrode also shows excellent stability and resistance to CO poisoning. These can be attributed to the synergistic effects among Pt, WC1−x and WO3, and the heterogeneous interface between them, which accelerates the process of hydrogen absorption and desorption on their surface. These results suggest that the anodization coupled electrodeposition method is an efficient approach to design low Pt-loaded self-supporting electrodes with high activity and stability. [ABSTRACT FROM AUTHOR]

The occurrence of numerous neurodegenerative diseases is associated with abnormal levels of butyrylcholinesterase (BChE). The development of a probe for the real-time detection of butyrylcholinesterase in vivo and in vitro is beneficial for the diagnosis of related diseases. In this study, we designed and synthesized a novel fluorescent probe CnN to detect BChE activity. The probe CnN has numerous excellent properties for the real-time visualization of BChE with an ultrafast response (5 min), low detection limit (LOD of 0.07969 U mL−1) and good specificity. CnN also has a large Stokes shift (113 nm) and low cytotoxicity. Based on the excellent performance of CnN, we performed the endogenous imaging of apoptosis in LO2 cells, which can be used to assess stress changes in butyrylcholinesterase in apoptotic cells. [ABSTRACT FROM AUTHOR]

Inspired by porous smart gel materials, we designed pH-responsive polymer-modified silica microspheres as liquid chromatography stationary phase materials by a one-step strategy. The free radicals generated by the oxidation of dopamine are used to initiate the cross-linking polymerization of functional monomers. At the same time, the good adhesion of dopamine enables the polymer to be modified on silica. The hydrophilicity of this new stationary phase can change in response to the pH of the mobile phase and the stationary phase has weaker hydrophilicity under acidic (pH = 3.78) mobile phase conditions and stronger hydrophilicity under neutral mobile phase conditions. The hydrophilicity difference of the stationary phase leads to the selectivity difference in separation. To evaluate the chromatographic performance of this new stationary phase, 10 oligosaccharides and 9 nucleosides/bases were separated on this stationary phase. This paper will provide good guidance for us to achieve more pH-responsive hydrophilic/hydrophobic stationary phases in the future. [ABSTRACT FROM AUTHOR]

The development of highly efficient, low-cost and robust electrocatalysts for water splitting is urgently necessary to approach the energy crisis and environmental problems. In recent years, transition metal-based materials are commonly used as outstanding electrode materials for the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) due to their tunable electrocatalytic activity and earth-abundance. However, they are restrained from the disadvantages of low conductivity, easy agglomeration and poor stability. Therefore, it is a good choice to integrate transition metal compounds with carbon materials to address the aforementioned issues. In this review, we focus on the recent progress of the fabrication of a variety of transition metal-based materials integrated with carbon matrices for HER, OER and overall water splitting. First, the fundamentals of the water splitting process and the introduction of parameters to determine the water splitting performance are given. Then, the advantages of the integration of transition metals and compounds with carbon for electrolytic water splitting as well as the influence of the architecture, composition, electronic structure and interface engineering of the hybrid materials on their electrocatalytic activities are discussed. The experimental and theoretical simulation are complementary to investigate the mechanism of the enhanced HER, OER and overall water splitting processes. Finally, challenges, perspectives and opportunities for developing new transition metals and carbon-based electrocatalysts in water splitting are featured. [ABSTRACT FROM AUTHOR]

A new type of core–shell composite material was prepared and applied as a hydrophilic interaction liquid chromatography (HILIC) stationary phase. In this work, silica spheres were first modified with a bimetallic central metal–organic framework (ZnCoMOF) by a new strategy of static self-assembled in situ growth. This strategy was beneficial for increasing the electrostatic interaction between the MOF ligand and silica via introducing a sodium dodecylbenzenesulfonate (SDBS) group. The ZnCoMOF@silica stationary phase was characterized and evaluated in comparison with amino-modified and bare silica columns in terms of various polar analytes including eight nucleosides and nucleobases, seven carbohydrates, and multiple sulfonamides and antibiotics. The effects of organic solvent concentration, water content, the concentration of the salt and the pH of the buffer solution on the retention time were studied, which demonstrated the typical retention behavior of HILIC on the ZnCoMOF@silica column. Compared with most reported MOF-based stationary phases, the new composite material showed excellent hydrophilic properties and separation efficiency for various polar analytes. Moreover, the obtained stationary phase showed good reproducibility and stability. The relative standard deviation (RSD) of the retention time for repeatability was found to range from 0.1% to 0.6%, and the RSD of the retention time for stability was found to range from 0.3% to 0.7%. Furthermore, the column batch-to-batch reproducibility showed excellent preparation reproducibility, which few reported in most previous MOF@silica composite materials. This specific preparation method offers an easy and novel way to manipulate the amount of MOF particles on silica, which extends a universal way to produce various MOF@silica stationary phases by the method of static self-assembled in situ growth. [ABSTRACT FROM AUTHOR]

A magnetic solid-phase extraction (MSPE) technique coupled with high performance liquid chromatography (HPLC) was developed and used for bioaccumulation investigation of bisphenol A (BPA) in HepG2 cells and zebrafishes. Cobalt magnetic polystyrene microsphere derived carbon (C–Co@PST) as an adsorbent was prepared by in situ polymerization reaction and further annealing treatment. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy and X-ray diffraction were employed to confirm successful synthesis of C–Co@PST. A series of extraction parameters including the amount of the sorbent, the type of elute, extraction time and elution time were investigated to achieve high extraction efficiency. C–Co@PST based MSPE combined with HPLC was successfully established for bioaccumulation research of BPA in living creatures. It was found that the bioconcentration values of BPA in HepG2 cells underwent an increase, then a decrease, and finally reached an equilibrium level of 11.60 μg kg−1 at 8 h. The concentration of BPA in zebrafishes increased ranging from 6.05 μg kg−1 to 31.84 μg kg−1 over a culture time from 1 h to 12 h. Furthermore, linear and exponential models were employed to analyse the bioconcentration variation of BPA in organisms over the exposure time. Mathematical models have been developed to predict the transfer characteristics of BPA. [ABSTRACT FROM AUTHOR]

A metal organic framework (MOF-235) was fabricated by a simple solvothermal method and utilized as an adsorbent for the selective removal of electron-rich conjugated dyes. Parameters that influenced the adsorption process were investigated and the excellent adsorption properties of MOF-235 toward Congo red (CR) and lemon yellow (LY) are also exhibited in a wide range of pH 3–9. Moreover, the adsorption kinetics and thermodynamics were determined, indicating that the Langmuir model can well describe the adsorption isotherm and the pseudo-second order model can satisfactorily describe the adsorption kinetics. Thanks to the large hydrophobic effect between electron-deficient MOF and electron-rich conjugated dye molecules, the ultrahigh maximum adsorption capacity for CR and LY calculated by the Langmuir model is up to 1250 and 250 mg g−1, respectively, which surpass that of most reported adsorbents. Notably, the maximum adsorption capacity of adsorption of CR and LY is up to 1131 and 209 mg g−1 in fruit juice, respectively. Additionally, the synthesized MOF-235 has a high adsorptive selectivity and fast adsorption rate and can be regenerated for removal by washing with ethanol containing NaOH solution. These results demonstrated that MOF-235 would be an effective and easily reusable adsorbent for the adsorptive removal of CR and LY from fruit juice. [ABSTRACT FROM AUTHOR]

Herein, a novel, fusiform-like magnetic metal–organic framework material (Fe3O4-NH2@MOF-235) was fabricated by a facile two-step solvothermal approach. Then, Fe3O4-NH2@MOF-235 was applied as an adsorbent in magnetic solid-phase extraction (MSPE) coupled with high-performance liquid chromatography (HPLC) for the simultaneous extraction and determination of five kinds of benzoylurea insecticides (flufenoxuron, chlorbenzuron, teflubenzuron, diflubenzuron and triflumuron) from honey, fruit juice and tap water samples. Moreover, potential variables influencing the MSPE efficiency were optimized. Under the optimized conditions, an excellent linearity was achieved in the range of 1.0–300.0 μg L−1 for teflubenzuron and flufenoxuron and 2.0–300.0 μg L−1 for diflubenzuron, chlorbenzuron and triflumuron, with the correlation coefficients of 0.9991–0.9995. The limits of detection for the analytes were 0.25–0.5 μg L−1, and the recoveries at three fortified concentration levels ranged from 76.45% to 90.74% for the honey samples, 79.95–95.27% for the fruit juice samples, and 84.02–99.62% for the tap water samples. The π–π stacking and hydrophobic interactions between Fe3O4-NH2@MOF-235 and the analytes played an important role in the adsorption process. Moreover, maximum adsorption could be achieved within 5 minutes with very little adsorbent for all the samples. Therefore, the magnetic Fe3O4-NH2@MOF-235 composite combined with MSPE is a convenient approach to detect benzoylurea insecticides in actual samples. [ABSTRACT FROM AUTHOR]

Over the past ten years, considerable progress has been achieved in the field of nanomaterials-based enzymes (nanozymes). In comparison with natural enzymes, nanozymes demonstrate significant advantages such as facile synthesis procedure, low price, long storage period, and high environmental stability. A variety of nanomaterials including nanocarbons, metals, metal oxides, metal chalcogenides, halogen compounds, metal–organic frameworks (MOFs), and layered double hydroxides (LDHs) have been extensively investigated for enzyme mimicking. In this review, the recent progresses made in the development of the enzymatic properties of these nanozymes have been discussed. We comprehensively discuss strategies to improve catalytic activity and substrate specificity, enzyme-like catalytic mechanism, and novel application of nanozymes in sensing techniques. In addition, the remaining challenges and some future directions have been addressed. With the fast development of nanozyme applications in bioscience and technology, research in this field has become more and more attractive, which is expected to be a long-term exciting subject in the near future. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) is a remarkable endogenous gasotransmitter involved in numerous biological processes, and its noninvasive, rapid and accurate measurement in living cells and animals is urgently needed. Herein, we report a ratiometric fluorescent H2S-specific probe (CyT). This new probe can be readily prepared by modifying the triflate group (CF3SO3−) into hemicyanine, and it shows excellent sensing properties. First, CyT is highly selective against other biologically relevant anions, cations, reactive sulfur and small molecules; meanwhile, it has a low limit of detection (LOD) to H2S (7.33 nM) In addition, CyT exhibits rapid response to H2S (rate constant is 1464 M−1 s−1) and apparent color change from dark blue to very pale green, which is observed with the naked-eye. Furthermore, it exhibits low cytotoxicity to HeLa cells and can be successfully used for the detection of H2S activity in cells and zebrafish. [ABSTRACT FROM AUTHOR]

Nanomaterials with ABX3-type perovskite structure have attracted considerable and increasing attention due to their unique physical and chemical properties as well as promising applications in various fields. In this work, we have developed a simple electrospinning followed by a calcination process to prepare ABO3-type perovskite LaMnO3+δ nanofibers as efficient oxidase mimics for the detection of l-cysteine. The oxidase-like catalytic activity of the prepared LaMnO3+δ nanofibers is heavily dependent on the calcination temperature which results in different sizes of the LaMnO3+δ crystals and their crystallinity, and the maximum activity is achieved at the calcination temperature of 700 °C. Based on the high oxidase-like catalytic activity of the as-prepared perovskite LaMnO3+δ nanofibers, a simple and accurate colorimetric detection method towards l-cysteine has been developed. The detection limit is as low as 109.8 nM and an excellent selectivity for l-cysteine detection with common substances in human blood as interferents is also achieved. In addition, the LaMnO3+δ nanofibers can be retained as a monolithic membrane after the calcination process, making them an oxidase mimic for on-demand colorimetric sensing. This work reveals the promising prospects for the perovskite LaMnO3+δ materials in biosensing, medical diagnosis, food safety and environmental monitoring. [ABSTRACT FROM AUTHOR]

A self-templated approach has been developed for the preparation of FeMnO3 nanoparticles filled in the hollow core of polypyrrole (PPy) nanotubes by an in situ polymerization process accompanied by the etching of FeMnO3 nanofibers. The prepared FeMnO3@PPy nanotubes exhibited a superior peroxidase-like activity. The catalytic reaction system has been used for the sensitive colorimetric detection of glutathione with a low detection limit and good selectivity. [ABSTRACT FROM AUTHOR]

Synergistic effects play an important role in improving the catalytic activity for enzyme-like reactions. Compared to individual nanomaterials, a system consisting of multiple components usually exhibits enhanced catalytic activity as an enzyme mimic. Herein we describe the synthesis of CuFe2O4/Cu9S8/polypyrrole (PPy) ternary nanotubes as an efficient peroxidase mimic via a three-step approach involving an electrospinning process, annealing treatment and hydrothermal reaction. The remarkably enhanced catalytic activity of CuFe2O4/Cu9S8/PPy ternary nanotubes as peroxidase mimics over individual CuFe2O4 nanofibers, CuFe2O4/CuO composite nanofibers, CuFe2O4/CuS composite nanofibers, and PPy materials has been achieved, demonstrating the presence of a synergistic effect among the components. The steady-state kinetic experiment suggests a good catalytic efficiency of the CuFe2O4/Cu9S8/PPy ternary nanotubes. On the basis of high catalytic activity, a colorimetric platform for the sensitive detection of H2O2 and dopamine has been developed. This work not only offers a simple approach for the fabrication of a high performance peroxidase-like nanocatalyst, but also provides its promising potential applications in biosensors, medical diagnosis, and environmental monitoring. [ABSTRACT FROM AUTHOR]

The self-assembly of noble metal nanoparticles into new-fashioned one, two and three-dimensional structures is very important due to their superior properties in optics, electrics, catalysis, and chemical sensing compared with individual nanoparticles. Here, we first report a facile one-step approach that allows the fabrication of assembled Au nanorices induced by polyaniline (PANI). During the synthesis, a complex of HAuCl4-(3-aminopropyl)triethoxysilane (APTES) acts as both a soft template and an oxidant; then the reduction of HAuCl4 is accompanied by the oxidation of aniline, resulting in the formation of Au nanorices within a PANI matrix. The application of the prepared Au/PANI nanorices as enzyme mimics toward the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) is demonstrated. The resultant Au/PANI nanorices display an enhanced peroxidase-like catalytic activity compared with individual Au nanospheres and PANI nanofibers alone, revealing a synergistic effect between Au and PANI components in the Au/PANI nanorices. The Au/PANI nanorices are also used as efficient surface-enhanced Raman scattering (SERS) substrates for in situ monitoring of the oxidation process of TMB during the peroxidase-like catalytic reaction. On the basis of the SERS technique, a discernible detection level of H2O2 as low as 10−8 M is obtained. We envision that such a system may show more potential applications in biocatalysis, disease diagnosis and environmental monitoring. [ABSTRACT FROM AUTHOR]

A simple and low cost detection of l-cysteine is essential in the fields of biosensors and medical diagnosis. In this study, we have developed a simple electrospinning, followed by calcination process to prepare FeCo nanoparticles embedded in carbon nanofibers (FeCo-CNFs) as an efficient peroxidase-like mimic for the detection of l-cysteine. FeCo nanoparticles are uniformly dispersed within CNFs, and their diameters are highly influenced by the calcination temperature. The calcination temperature also influences the peroxidase-like catalytic activity, and the maximum activity is achieved at a calcination temperature of 550 °C. Owing to the high catalytic activity of the as-prepared FeCo-CNFs, a colorimetric technique for the rapid and accurate determination of l-cysteine has been developed. The detection limit is about 0.15 μM with a wide linear range from 1 to 20 μM. In addition, a high selectivity for the detection of l-cysteine over other amino acids, glucose and common ions is achieved. This study provides a simple, rapid and sensitive sensing platform for the detection of l-cysteine, which is a promising candidate for potential applications in biosensing, medicine, environmental monitoring. [ABSTRACT FROM AUTHOR]

In recent years, the fabrication of functional nanostructures with multicomponents for a variety of novel biosensors has received considerable attention due to their synergistic improved sensitivity. Herein, we report a facile approach for the preparation of Fe3O4/nitrogen-doped carbon (Fe3O4/N–C) hybrid nanofibers, and construct a sensing platform for the sensitive colorimetric detection of H2O2 and ascorbic acid (AA). During the synthetic process, a discontinuous layer of polypyrrole (PPy) is first polymerized in situ on the surface of the α-Fe2O3 nanofibers under hydrothermal reaction using α-Fe2O3 nanofibers as both a template and an oxidant. Then the prepared α-Fe2O3/PPy nanofibers are converted into Fe3O4/N–C hybrid nanofibers through pyrolysis with a thermochemical reduction process. The resulting Fe3O4/N–C hybrid nanofibers are used as a novel peroxidase mimic towards the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H2O2, with a superior catalytic activity over individual α-Fe2O3 nanofibers, α-Fe2O3/PPy nanofibers, Fe3O4/C nanofibers, and commercial Fe3O4 nanoparticles. Based on the high peroxidase-like activity of Fe3O4/N–C hybrid nanofibers, a sensing platform for the colorimetric detection of AA is developed. A good linear relationship from 0 to 50 μM and a detection limit of 0.04 μM are achieved. This work offers a new method for the preparation of Fe3O4/N–C hybrid nanofibers and presents new potential applications in biosensing, medical diagnostics and environmental monitoring. [ABSTRACT FROM AUTHOR]

Keggin-type phosphomolybdic acid (H3PMo12O40) promoted the formation of a cation radical of tetra(thienylthio)-tetrathiafulvalene (TT-TTF), consequently resulting in a cation radical complex [(TT-TTF)+•]3[(PMo12O40)3−](CH2Cl2), which shows self-assembly in solution and forms microtubes. The molecular level structure of the microtube is evaluated by X-ray diffraction analysis, which reveals that the microtube is produced via various non-covalent interactions in the hierarchical assembly process: the electrostatic interactions between (TT-TTF)+• and (PMo12O40)3− afford an organic–inorganic hybrid triangular nanocluster [(TT-TTF)+•]3[(PMo12O40)3−] as the building block; the strong π–π interactions between (TT-TTF)+• result in the cluster-based two-dimensional honeycomb nanosheet; the van der Waals forces between the nanosheets lead to the propagation along the third direction to form a three-dimensional supramolecular framework possessing nano-sized channels. [ABSTRACT FROM AUTHOR]

We have described a soft-template method that allows the one-pot fabrication of ring-like conducting polymer/noble metal nanocomposites. An insoluble complex of (CTA)2PdBr4 was used as a template and the composite nanorings were synthesized via the redox reaction between PdBr42 -- and the monomer. [ABSTRACT FROM AUTHOR]

TTF derivatives decorated with four aryls through the sulfur bridges are employed to form the donor–acceptor type inclusion complexes with fullerenes. The key factor for the formation of inclusion complexes is the introduction of structural flexibility in TTF molecules along with the molecular size matching with fullerenes. A crystallographic study indicates that the structures of the resulting complexes are stabilized by a multidimensional intermolecular interaction network consisting of TTF cores, peripheral aryls, and fullerenes, which in turn gives rise to the electronic communication between the donor and the acceptor as proved by the solid state absorption spectra. Moreover, the fullerene molecules form the two-dimensional sheet structure in the complexes. [ABSTRACT FROM AUTHOR]

V2O5-doped α-Fe2O3 composite nanotubes have been successfully fabricated via a simple one-step electrospinning technique followed by calcination treatment. For the first time, we found that the magnetic properties of the as-prepared samples were significantly dependent on the contents of the dopant. In comparison with pristine α-Fe2O3, perfect reversibility, more excellent capacitance and better cycling stability were simultaneously observed for the hybrid metal oxide with an appropriate mass ratio of V2O5 (VFNT1) when it was utilized for supercapacitor electrodes, indicating that the doped α-Fe2O3tubular nanostructures are fairly promising for practical applications not only in magnetic recording but also in the energy storage field. [ABSTRACT FROM AUTHOR]

Bulk VO2 (B) nanobelts with high quality have been fabricated via a simple one-step hydrothermal route and found to possess intrinsic peroxidase-like activity. The catalysts with excellent affinity to hydrogen peroxide (H2O2) and 3,3′,5,5′-tetramethylbenzidine (TMB) could be used for the colorimetric assay of H2O2 and glucose. [ABSTRACT FROM AUTHOR]

CuS-graphene nanosheet (GNS) composites with well-defined morphology have been successfully fabricated via a simple one-pot hydrothermal route by using thioacetamide (TAA) as both the sulfur source and reducing agent. The as-prepared CuS-GNS composites with an appropriate content of graphene exhibited an even higher peroxidase-like catalytic activity than pristine CuS nanoparticles in acetate buffer solution (pH = 4.0), which provided a facile method for the colorimetric detection of hydrogen peroxide (H2O2). It was calculated that H2O2 could be detected as low as 1.2 μM (S/N = 3) with a wide linear range from 2.0 to 20.0 μM (R2 = 0.992), indicating that the as-prepared catalyst as an artificial peroxidase is promising for application in biosensors and environmental monitoring. [ABSTRACT FROM AUTHOR]

Constructing highly efficient electrocatalysts via interface manipulation and structural design to facilitate rapid electron transfer in electrocatalytic nitrate-to-ammonia conversion is crucial to attaining superior NH 3 yield rates. Here, a Mott-Schottky type electrocatalyst of Co/In 2 O 3 with a continuous fiber structure has been designed to boost the electrocatalytic nitrate-to-ammonia performance. The optimized Co/In 2 O 3 -1 catalyst exhibits an impressive NH 3 yield rate of 70.1 mg cm -2 h -1 at -0.8 V vs. the reversible hydrogen electrode (RHE), along with an NH 3 faradaic efficiency (FE) of 93.34% at 0 V vs. RHE, greatly outperforming the single-component Co and In 2 O 3 samples. The yield rate of Co/In 2 O 3 -1 is also superior to that of most currently reported Co-based catalysts and heterostructured ones. Evidence from experiments and theoretical results confirms the formation of a Mott-Schottky heterojunction, which achieves a Co site enriched with electrons, coupled with an In 2 O 3 facet enriched with holes, inducing an electron redistribution to promote the utilization of electroactive sites. Consequently, the reaction energy barrier for nitrate-to-ammonia conversion is significantly reduced, further enhancing its yield efficiency., Competing Interests: The authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)

Nowadays, alkaline water electrocatalysis is regarded as an economical and highly effective approach for large-scale hydrogen production. Highly active electrocatalysts functioning under large current density are urgently required for practical industrial applications. In this work, we present a meticulously designed methodology to anchor Ir nanoparticles on Co 6 Mo 6 C nanofibers (Co 6 Mo 6 C-Ir NFs) bridging with nitrogen-doped carbon as efficient bifunctional electrocatalysts with both excellent hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) activity and stability in alkaline media. With a low Ir content of 5.9 wt%, Co 6 Mo 6 C-Ir NFs require the overpotentials of only 348 and 316 mV at 1 A cm -2 for the HER and OER, respectively, and both maintain stability for at least 500 h at ampere-level current density. Consequently, an alkaline electrolyzer based on Co 6 Mo 6 C-Ir NFs only needs a voltage of 1.5 V to drive 10 mA cm -2 and possesses excellent durability for 500 h at 1 A cm -2 . Density functional theory calculations reveal that the introduction of Ir nanoparticles is pivotal for the enhanced electrocatalytic activity of Co 6 Mo 6 C-Ir NFs. The induced interfacial electron redistribution between Ir and Co 6 Mo 6 C bridging with nitrogen-doped carbon dramatically modulates the electron structure and activates inert atoms to generate more highly active sites for electrocatalysis. Moreover, the optimized electronic structure is more conducive to the balance of the adsorption and desorption energies of reaction intermediates, thus significantly promoting the HER, OER and overall water splitting performance., Competing Interests: The authors declare no conflict of interest., (This journal is © The Royal Society of Chemistry.)

Nanomaterials with ABX 3 -type perovskite structure have attracted considerable and increasing attention due to their unique physical and chemical properties as well as promising applications in various fields. In this work, we have developed a simple electrospinning followed by a calcination process to prepare ABO 3 -type perovskite LaMnO 3+δ nanofibers as efficient oxidase mimics for the detection of l-cysteine. The oxidase-like catalytic activity of the prepared LaMnO 3+δ nanofibers is heavily dependent on the calcination temperature which results in different sizes of the LaMnO 3+δ crystals and their crystallinity, and the maximum activity is achieved at the calcination temperature of 700 °C. Based on the high oxidase-like catalytic activity of the as-prepared perovskite LaMnO 3+δ nanofibers, a simple and accurate colorimetric detection method towards l-cysteine has been developed. The detection limit is as low as 109.8 nM and an excellent selectivity for l-cysteine detection with common substances in human blood as interferents is also achieved. In addition, the LaMnO 3+δ nanofibers can be retained as a monolithic membrane after the calcination process, making them an oxidase mimic for on-demand colorimetric sensing. This work reveals the promising prospects for the perovskite LaMnO 3+δ materials in biosensing, medical diagnosis, food safety and environmental monitoring.

In recent years, the fabrication of functional nanostructures with multicomponents for a variety of novel biosensors has received considerable attention due to their synergistic improved sensitivity. Herein, we report a facile approach for the preparation of Fe 3 O 4 /nitrogen-doped carbon (Fe 3 O 4 /N-C) hybrid nanofibers, and construct a sensing platform for the sensitive colorimetric detection of H 2 O 2 and ascorbic acid (AA). During the synthetic process, a discontinuous layer of polypyrrole (PPy) is first polymerized in situ on the surface of the α-Fe 2 O 3 nanofibers under hydrothermal reaction using α-Fe 2 O 3 nanofibers as both a template and an oxidant. Then the prepared α-Fe 2 O 3 /PPy nanofibers are converted into Fe 3 O 4 /N-C hybrid nanofibers through pyrolysis with a thermochemical reduction process. The resulting Fe 3 O 4 /N-C hybrid nanofibers are used as a novel peroxidase mimic towards the oxidation of 3,3,5,5-tetramethylbenzidine (TMB) in the presence of H 2 O 2 , with a superior catalytic activity over individual α-Fe 2 O 3 nanofibers, α-Fe 2 O 3 /PPy nanofibers, Fe 3 O 4 /C nanofibers, and commercial Fe 3 O 4 nanoparticles. Based on the high peroxidase-like activity of Fe 3 O 4 /N-C hybrid nanofibers, a sensing platform for the colorimetric detection of AA is developed. A good linear relationship from 0 to 50 μM and a detection limit of 0.04 μM are achieved. This work offers a new method for the preparation of Fe 3 O 4 /N-C hybrid nanofibers and presents new potential applications in biosensing, medical diagnostics and environmental monitoring.

Polyaniline(PANI) microwires containing CdS nanoparticles have been prepared by introducing hydrogen bonding and/or electrostatic interaction between mercaptocarboxylic acid capped CdS nanoparticles and PANI. SEM and TEM proved them to be wire-like structures. PL spectra of the PANI/CdS complex is blue-shifted by 14 nm compared to CdS nanoparticles in N-methylpyrrolidinone(NMP).