The authors describe a template-free method for the electrodeposition of ultra-long copper nanowires on titanium foils. Scanning electron microscopy shows that the nanowires are around 50 nm in diameter and 30 μm in length. The titanium foils enable nonenzymatic sensing of glucose in 0.1 M NaOH solution because the nanowire-modified electrodes exhibit excellent electrocatalytic activity towards glucose oxidation at a typical working voltage of 0.7 V (vs. Ag/AgCl). Figures of merit include (a) a sensitivity of 4985 μA·mM−1·cm−2, (b) a linear response extending from 1 μM to 6.0 mM of glucose, (c) good reusability (a 2.5% relative standard deviation of one electrode in five detections), and (d) an excellent reproducibility (a 3.3% RSD of five electrodes to one sample).

Perovskite LaCoO3 materials (LCO NPs) were prepared and found to possess both peroxidase-like and catalase-like catalytic activities. The LCO NPs can catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of H2O2 generating a blue color change under acidic conditions or decompose H2O2 under alkaline conditions with the generation of oxygen. Catalytic kinetics together with the possible mechanism of the peroxidase-like activity was investigated. The peroxidase-like catalytic properties of LaCoO3 nanoparticles were found to originate from their ability of accelerating electron transfer. Then based on their peroxidase properties, LCO NPs were applied to determine dopamine by using the colorimetric method with the dopamine-dependent successive inhibition reaction. The linear range of dopamine sensing was found to be 0.5–20 μM and the detection limit (LOD) was also discussed. The standard addition experiments were further performed with recoveries between 95.4% and 103.6%, and all the relative standard deviations (RSDs) were below 4.0%. The determination of dopamine therefore showed high accuracy and efficiency and has potential for the diagnosis of dopamine-related diseases.

Uniform and compact porous Ni@C nanosheet membranes derived from Ni-based metal organic frameworks were successfully anchored on a Ni foam substrate via hydrothermal treatment with successive pyrolysis. The Ni@C/Ni foam was employed as a self-supporting electrode for non-enzymatic glucose sensing and exhibited remarkable electrocatalytic activity. It can be attributed to the hierarchical structure composed of Ni@C nanosheet array membranes freestanding on Ni foam and mesoporous Ni@C nanosheets. An ultrahigh sensitivity of 32.79 mA mM−1 cm−2 and a low detection limit of 50 nM were realized, which were superior to some existing glucose sensors. Meanwhile, a reasonable linear range from 0.15 μM to 1.48 mM was achieved. Furthermore, the Ni@C/Ni foam possessed various merits, such as excellent selectivity, good reusability, acceptable reproducibility, satisfying long-term stability and high tolerance to chloride ions. We further demonstrated its practicability by detecting glucose concentrations in human blood serum samples. The results enable the Ni@C/Ni foam to be an attractive candidate for practical application in non-enzymatic glucose sensing.

•Cu-SBA-15 materials exhibit the peroxidase-like activity.•The catalytic ability of Cu-SBA-15 is derived from Cu incoporation in the framework.•Cu-SBA-15 is successfully used for H2O2 and glucose determination.•The method show high accuracy and selectivity for detection of glucose in human serum.The copper incorporated SBA-15 (Cu-SBA-15) materials with different amount of Cu in framework were synthesized, and the products were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) and N2 adsorption/desorption. The Cu contents incorporated into the framework of SBA-15 were measured by inductively coupling plasma atomic emission spectrometer (ICP-AES). Cu-SBA-15 samples were found to exhibit the peroxidase-like activity, similar to the natural peroxidase. The effect of various parameters such as the content of Cu incorporated, pH and temperature on the peroxidase-like activity was studied. Based on the peroxidase-like activity, the Cu-SBA-15 was applied to the determination of H2O2. The linear range for detecting H2O2 was from 0.8 to 60 mM with a detection limit of 3.7 µM. Coupled with glucose oxidase, the Cu-SBA-15 was successfully used for the determination of glucose with the linear range of 2–80 mM and a detection limit of 5.4 µM. The determination of glucose in human serum showed high accuracy, good reproducibility, as well as high selectivity against uric acid, ascorbic acid, dopamine and glucose analogs including fructose, maltose and lactose.

Exploring a tough, reusable and reproducible nonenzymatic sensor for glucose detection is required. Cu nanowire array electrodes on a Ti/Cr/Si substrate are prepared from an anodic aluminum oxide template film covered Ti/Cr/Si substrate by an electrodeposition method. The scanning electron microscope results indicate that Cu nanowires with a diameter of 50 nm and a length of hundreds of nm freestanding on the Ti/Cr/Si substrate are obtained. Electrochemical measurements indicate the freestanding nanowire array electrodes showing sensitivity of 1067 μA mM−1 cm−2 and detection limit of 1.87 μM when using the arrays as glucose sensors. The most attractive characteristics of the electrodes are the outstanding reusability and reproducibility, realizing a 1.77% relative standard deviation (RSD) of one electrode in five time tests and a 3.33% RSD of five electrodes for one sample. The application of the electrodes on determining the glucose concentration in human serum samples indicates the array electrode is a promising candidate as a practical sensor.

•A fluorescent chemosensor for Ba2+ was developed.•The effect of the molecular structure on metal ion detection was investigated.•The sensor has the advantages of high selectivity, high sensitivity and easy preparation.Development of a selective and sensitive sensor for Ba2+ is currently of great importance because of the adverse effects of Ba2+ on the human body. In this study, we developed an excellent fluorescence chemosensor for Ba2+ based on 3AP (N-salicylidene-3-aminopyridine). A fluorescence spectrophotometer is utilized to investigate the sensing properties of 3AP, and the results indicate that 3AP shows sensitive and selective detection of Ba2+ through the enhancement of fluorescence intensity. The detection limit is determined to be 7.08×10−7 mol/L. Background metal ions, such as Li+, Na+, K+, Cs+, Ca2+, Mg2+, Mn2+, Fe3+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Pb2+, Cd2+, Al3+ and Ag+, exhibit small or no interference with the detection of Ba2+.

A highly ordered mesoporous silica material (SBA-15) functionalized with 5-(4-carboxy-phenylazo)-8-hydroxyquinoline (CPA-8-HQL) for use as a fluorescence chemosensor for Pb2+ detection has been reported in this study. XRD, TEM, FT-IR, UV-vis diffuse reflectance spectra and TGA were used to characterize the grafting process. The results proved that CPA-8-HQL was successfully anchored into the channel of SBA-15 and that the primary ordered mesoporous structure of SBA-15 was well preserved. A fluorescence spectrophotometer was utilized to investigate the sensing properties, and a highly fluorescent enhancement at 429 nm was observed in the presence of Pb2+. Measurements of the sensitivity parameters demonstrated that the obtained organic/inorganic hybrid possessed excellent sensitivity and selectivity to Pb2+ in aqueous media. The lowest limit of detection was 4.90 × 10−7 mol L−1 for Pb2+.

The applications of inorganic nanomaterials as biomimetic catalysts are receiving much attention because of their high stability and low cost. In this work, Co3O4 nanomaterials including nanoplates, nanorods, and nanocubes were synthesized. The morphologies and compositions of the products were characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The catalytic properties of Co3O4 nanomaterials as catalase mimics were studied. The Co3O4 materials with different morphology exhibited different catalytic activities in the order of nanoplates > nanorods > nanocubes. The difference of the catalytic activities originated from their different abilities of electron transfer. Their catalytic activities increased significantly in the presence of calcium ion. On the basis of the stimulation by calcium ion, a biosensor was constructed by Co3O4 nanoplates for the determination of calcium ion. The biosensor had a linear relation to calcium concentrations and good measurement correlation between 0.1 and 1 mM with a detection limit of 4 μM (S/N = 3). It showed high selectivity against other metal ions and good reproducibility. The proposed method was successfully applied for the determination of calcium in a milk sample.Keywords: amperometric biosensor; calcium determination; catalase mimic; morphology effect; nanomaterials;

Nanomaterials as enzyme mimics have received considerable attention as they can overcome some serious disadvantages associated with the natural enzymes. In recently developed Co3O4 nanoparticles as peroxidase mimics, the influence of the crystal plane on the catalytic performance has not been demonstrated. In order to better understand their crystal plane-dependent catalysis, the present study was initiated using three different Co3O4 nanomaterials, nanoplates, nanorods and nanocubes, as model systems. According to HRTEM, the predominantly exposed planes of nanoplates, nanorods and nanocubes are {112}, {110} and {100} planes, respectively. The catalytic activities were explored by using H2O2 and different organic substrates as the substrates of peroxidase mimics, and were investigated in-depth by steady-state kinetics and electrochemistry methods in depth. The results show that the peroxidase-like activity increases from nanocubes to nanoplates, via nanorods. The effect of external conditions such as pH and temperature on the three nanomaterials is the same, which indicates that the difference in their catalytic activities originates from their different shapes. The peroxidase-like catalytic activities of Co3O4 nanomaterials are crystal plane-dependent and follow the order: {112} ≫ {110} > {100}. The three crystal planes have different arrangements of surface atoms, thus exhibiting different abilities of electron transfer, which induce their different peroxidase-like catalytic activities. This investigation clarifies that the peroxidase-like activity of Co3O4 nanomaterials can be enhanced by shape control. These findings show that Co3O4 nanomaterials can serve as catalyst models for designing other catalysts.

•The catalase-like activity of Co3O4 nanoparticles could be tunable by the pH.•Compared to catalase, Co3O4 nanoparticles had the efficient catalytic ability.•Hydroxyl radicals took part in the catalytic recycles.•Co3O4 nanoparticles were used as the amperometric sensor for the detection of H2O2.Nanomaterial-based enzyme mimics have recently attracted considerable interest due to their easy preparation, low cost, high stability and so on. Herein Co3O4 nanoparticles (NPs) were used as a catalase mimic, catalyzing the decomposition of hydrogen peroxide to oxygen. The catalytic activity of Co3O4 NPs increased dramatically by adjusting the pH from acid to neutral and alkaline conditions. The catalytic activities and the mechanisms were investigated using the procedures of thermodynamics, steady-state kinetics and hydroxyl radical detection. The activation energy of Co3O4 NPs was determined to be 43.3 kJ mol−1 which was similar to 42.8 kJ mol−1 of catalase. The catalytic behaviour of Co3O4 NPs showed a typical Michaelis–Menten kinetics and good affinity to H2O2. The turnover number and specificity constant of Co3O4 NPs were very close to those of catalase. Based on the above results, Co3O4 NPs were an efficient catalase mimic. A catalytic mechanism was proposed where hydroxyl radicals took part in the catalytic recycles. Co3O4 NPs had better stability than natural catalase when they were exposed to solutions with different pH values and temperatures. As an efficient and stable catalase mimic, Co3O4 NPs were used as the amperometric sensor for the detection of hydrogen peroxide.

Uniform and compact porous Ni@C nanosheet membranes derived from Ni-based metal organic frameworks were successfully anchored on a Ni foam substrate via hydrothermal treatment with successive pyrolysis. The Ni@C/Ni foam was employed as a self-supporting electrode for non-enzymatic glucose sensing and exhibited remarkable electrocatalytic activity. It can be attributed to the hierarchical structure composed of Ni@C nanosheet array membranes freestanding on Ni foam and mesoporous Ni@C nanosheets. An ultrahigh sensitivity of 32.79 mA mM−1 cm−2 and a low detection limit of 50 nM were realized, which were superior to some existing glucose sensors. Meanwhile, a reasonable linear range from 0.15 μM to 1.48 mM was achieved. Furthermore, the Ni@C/Ni foam possessed various merits, such as excellent selectivity, good reusability, acceptable reproducibility, satisfying long-term stability and high tolerance to chloride ions. We further demonstrated its practicability by detecting glucose concentrations in human blood serum samples. The results enable the Ni@C/Ni foam to be an attractive candidate for practical application in non-enzymatic glucose sensing.

Nanomaterials as enzyme mimics have received considerable attention as they can overcome some serious disadvantages associated with the natural enzymes. In recently developed Co3O4 nanoparticles as peroxidase mimics, the influence of the crystal plane on the catalytic performance has not been demonstrated. In order to better understand their crystal plane-dependent catalysis, the present study was initiated using three different Co3O4 nanomaterials, nanoplates, nanorods and nanocubes, as model systems. According to HRTEM, the predominantly exposed planes of nanoplates, nanorods and nanocubes are {112}, {110} and {100} planes, respectively. The catalytic activities were explored by using H2O2 and different organic substrates as the substrates of peroxidase mimics, and were investigated in-depth by steady-state kinetics and electrochemistry methods in depth. The results show that the peroxidase-like activity increases from nanocubes to nanoplates, via nanorods. The effect of external conditions such as pH and temperature on the three nanomaterials is the same, which indicates that the difference in their catalytic activities originates from their different shapes. The peroxidase-like catalytic activities of Co3O4 nanomaterials are crystal plane-dependent and follow the order: {112} ≫ {110} > {100}. The three crystal planes have different arrangements of surface atoms, thus exhibiting different abilities of electron transfer, which induce their different peroxidase-like catalytic activities. This investigation clarifies that the peroxidase-like activity of Co3O4 nanomaterials can be enhanced by shape control. These findings show that Co3O4 nanomaterials can serve as catalyst models for designing other catalysts.