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In this work, the binary nanocomposite of crosslinked polyaniline nanorods (CPANINRs) and molybdenum disulfide (MoS2) is first synthesized by in situ polymerization, and CPANINRs/MoS2 on functionalized carbon cloth (CPANINRs/MoS2/FCC) is facilely constructed by a drop-casting method. The composition, morphology, and structure of the CPANINRs, MoS2, and CPANINRs/MoS2 binary nanocomposite are characterized by transmission electron microscope (TEM), scanning electron microscope (SEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The electrochemical properties of the MoS2/FCC, CPANINRs/FCC, and CPANINRs/MoS2/FCC are tested by cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD). The experiment results show that the CPANINRs/MoS2/FCC exhibits excellent stability and high specific capacitance, and its specific capacitance reaches 618.75 F g−1 at a current density of 0.5 A g−1. The CPANINRs/MoS2/FCC has a long cycling life and the capacity retention of 91.46% is obtained after 2000 cycles at a large current density of 10 A g−1. Moreover, the CPANINRs/MoS2/FCC-based symmetric supercapacitor also exhibits excellent rate performance and good cycling stability. The specific capacitance based on the total mass of the two electrodes is 106.4 F g−1 at a current density of 0.5 A g−1 and the capacitance retention of 93.6% is obtained after 2000 cycles.

In this paper, a new Co3O4–Ni nanocomposite-modified glassy carbon electrode (Co3O4–NiNPs/GCE) was successfully constructed and used to detect glucose and hydrogen peroxide (H2O2). The morphologies and structures of the Co3O4 and Co3O4–Ni nanocomposites were characterized via transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The construction process of the modified electrode was characterized via electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Co3O4–NiNPs/GCE shows more excellent electrocatalytic activity for the detection of glucose and H2O2 compared with Co3O4/GCE and NiNPs/GCE. The amperometric i–t method was used for the quantitative analysis of glucose and H2O2. The plots of current difference versus concentration of glucose and H2O2 were linear in the range of 0.3–550 μM and 0.5–89 μM, respectively. The corresponding limits of detection (LODs) were 0.086 μM and 0.23 μM for glucose and H2O2, respectively. This recommended sensor was successfully applied for the quantitative analysis of glucose in fruit and H2O2 in water samples.

A MoS2/PANI/functionalized carbon cloth (MoS2/PANI/FCC) was constructed by a drop-casting method. Its specific capacitances were higher than those of MoS2/CC and pure PANI/CC.

In this paper, an electrochemical sensor based on depositing acid chrome blue K on the surface of glassy carbon electrode was developed for detection of nitrofurazone. The obtained poly-ACBK film was characterised by atomic force microscope. The experimental results indicated that the Poly-ACBK/GCE showed good electrocatalytic activity to the redox reactions of nitrofurazone by differential pulse voltammetry and cyclic voltammetry in Britton-Robinson buffer solution, and the different redox peak currents were observed in different pH ranges (2.0–6.0, 7.0–12.0). Base on these, electrochemical reaction mechanism of nitrofurazone was presented in different pH ranges. Under the optimal conditions, a linear relationship between the reduction peak currents and concentrations for nitrofurazone is figured out in the range of 0.75‒192 μM, with detection limits of 0.25 µM (S/N = 3). This sensor produced satisfactory reproducibility and stability and was successfully applied to monitor of nitrofurazone in real samples (nasal drops).

A novel electrochemical non-enzymatic sensor for glucose and H2O2 based on metal organic framework (MOF)-derived cobalt-nickel bimetallic oxides (NiCo2O4) and gold nanoparticle (AuNPs) composite modified glassy carbon electrode (GCE) was fabricated in this paper. The structure and morphology of the prepared materials was successfully characterised by X-ray diffraction (XRD), element mapping images and scanning electron microscopy (SEM). Moreover, the electrocatalytic activity for glucose and H2O2 was investigated at the NiCo2O4/AuNPs/GCE using cyclic voltammetry (CV) and amperometric i–t technique. The catalytic currents for glucose and H2O2 are proportional to their concentrations in the range of 0.2 μM–581 μM and 0.5 μM–1774.5 μM, respectively. The corresponding limits of detection (LOD) were calcuated be 0.0081 μM and 0.181 μM for glucose and H2O2. Furthermore, the NiCo2O4/AuNPs/GCE shows excellent stability, reproducibility and anti-interference ability.

Based on the previous research, we found that the magnetic nanocomposite Fe

In this paper, a new Co3O4-Ni nanocomposite-modified glassy carbon electrode (Co3O4-NiNPs/GCE) was successfully constructed and used to detect glucose and hydrogen peroxide (H2O2). The morphologies and structures of the Co3O4 and Co3O4-Ni nanocomposites were characterized via transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The construction process of the modified electrode was characterized via electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. Co3O4-NiNPs/GCE shows more excellent electrocatalytic activity for the detection of glucose and H2O2 compared with Co3O4/GCE and NiNPs/GCE. The amperometric i-t method was used for the quantitative analysis of glucose and H2O2. The plots of current difference versus concentration of glucose and H2O2 were linear in the range of 0.3-550 μM and 0.5-89 μM, respectively. The corresponding limits of detection (LODs) were 0.086 μM and 0.23 μM for glucose and H2O2, respectively. This recommended sensor was successfully applied for the quantitative analysis of glucose in fruit and H2O2 in water samples.

In the work, a ratiometric electrochemical sensor for tert-butylhydroquinone (TBHQ) detection is constructed based on the modified electrode consisting of manganese dioxide (MnO2) and electrochemically reduced graphene oxide (ERGO) nanocomposite film. MnO2 was electrodeposited onto the electrochemically reduced graphene oxide (ERGO) placed on a glassy carbon electrode (GCE) to form the MnO2/ERGO/GCE. The construction process of the MnO2/ERGO/GCE electrode was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The electrochemical signal responses of the TBHQ sensor were recorded by differential pulse voltammetric measurements. The experimental results demonstrate that MnO2 can be used as the inner reference electrochemical probe, and ERGO can improve the sensitivity for TBHQ detection. It can be found that as the TBHQ concentration increases, the anodic peak current of TBHQ at the MnO2/ERGO/GCE increases, but the anodic peak current of MnO2 at such the modified electrode almost remains unchangeable. The net peak current ratio between TBHQ and MnO2 is chosen for quantitative detection of TBHQ. The developed ratiometric sensor exhibits two linear ranges of 1.0–50.0 μM and 100.0–300.0 μM for detecting TBHQ. The detection limit for TBHQ detection is estimated to be 0.8 μM on the basis of signal-to-noise (S/N) of 3. Moreover, the ratiometric electrochemical sensor is successfully applied for TBHQ detection in real edible oil samples.

Fluorescent tremella-like carbon nanosheets (TCNs) were hydrothermally synthesized using citric acid and adenosine as the starting materials. The resulting product had high quantum yield, water-sol...

Nanocomposite of Co3O4 and multiwalled carbon nanotube (MCNT) was synthesised using one step solvothermal method, and an electrochemical non-enzymatic glucose sensor (Co3O4-MCNT/GCE) was successfully constructed by a dropping method. The obtained Co3O4 and Co3O4- MCNT were characterized and investigated by transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS). Quantitative analysis of glucose was performed using the amperometric (i–t) method, and plot of current difference versus concentration of glucose was linear in the range of 1.0–122 μmol/L, with a linear correlation coefficient (R2) of 0.9983 and limit of detection (LOD) of 0.28 μmol/L. Sensitivity of this sensor was evaluated as 2550 μA L mmol−1 cm−2. This new sensor produced satisfactory reproducibility and stability and was applied to monitor trace amounts of glucose in human serum samples.

In the work, water-soluble bovine serum albumin-protected fluorescent nickel nanoclusters (BSA-NiNCs) are used as fluorescent probes to construct a label-free fluorescence quenching sensor for sensitive and selective detection of tartrazine. The fluorescent BSA-NiNCs are synthesized in one pot using BSA as both the template and reducing agent, and hydrogen peroxide as the additive. The as-prepared NiNCs are characterized by using various analytical techniques like transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV–Vis absorption spectroscopy, circular dichroism spectroscopy, and fluorescence spectroscopy. The synthesized BSA-NiNCs have a quantum yield of ca. 8% by using quinine sulfate as a standard. The sensor for tartrazine detection shows a wide linear range of 0.01–3.5 μM, with a low detection limit of 4 nM. The fluorescence quenching very likely results from the combination of the intermolecular interactions and the secondary inner filter effect between BSA-NiNCs and tartrazine. Then, the proposed sensor is successfully employed for tartrazine detection in drink samples, and the results are comparable with those based on a reference HPLC method.

Terbutaline sulfate (TBS) is a β2-adrenoceptor agonist, overdoses of which can cause serious harm and even be life-threatening to humans. Herein, we demonstrate a simple and facile method for the preparation of a molybdenum disulfide–gold nanoparticle composite (MoS2/AuNPs). The obtained MoS2 and MoS2/AuNPs were characterized and investigated by X-ray powder diffraction, scanning electron microscopy, and transmission electron microscopy. An MoS2/AuNPs-modified glassy carbon electrode (MoS2/AuNPs/GCE) was constructed using the dropping method and used to study the electrochemical behavior of TBS. The results indicated that the sensor had excellent electrocatalytic activity for TBS, with detection sensitivity for TBS more than 100 times higher compared with the bare GCE. With the successive addition of TBS, the peak current of the differential pulse stripping voltammogram (DPSV) of TBS was proportional to its concentration within a certain range, with a linear range of 1–85 nmol L−1 and limit of detection (LOD) of up to 0.47 nmol L−1. Furthermore, the modified electrode showed good stability, reproducibility, and anti-interference ability, meaning that it could be used to detect TBS in real samples.

A hydrothermal synthetic approach is developed for the preparation of graphitic carbon nitride quantum dots (g-C3N4 QDs) from human urine. The reported synthetic method is green, simple, low-cost, less time-consuming, and can be used for the large-scale production of the g-C3N4 QDs. The as-prepared g-C3N4 QDs possess a high quantum yield of 15.7% by using quinine sulfate as a reference, and display excitation-wavelength dependent fluorescent emission. In addition, the g-C3N4 QDs exhibit high photostability, low cytotoxicity. and are successfully used as fluorescent probes for cell multicolor imaging. It is believed that the valuable nanomaterials, g-C3N4 QDs, which are transformed from the human bodily wastes, are promising in diverse chemical applications.

In this paper, graphite phase carbon nitride (g-C3N4) was prepared by one-step high temperature thermal decomposition method, and layered g-C3N4 was prepared by protonation with concentrated hydrochloric acid. The morphology and composition of g-C3N4 were characterised by transmission electron microscope (TEM), energy dispersive spectroscopy (EDS) and X-ray powder diffraction (XRD). Furthermore, the AuNPs-g-C3N4/GCE was constructed by coating method and potentiostatic deposition method, and the construction process and resistance change of the electrodes were characterised by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The experimental results indicated that the AuNPs-g-C3N4/GCE has excellent electrocatalytic performance for bisphenol A (BPA) and 4-n-octylphenol (OP). Under optimized experimental conditions, BPA and OP were detected by differential pulse voltammetry (DPV) at the AuNPs-g-C3N4/GCE. The linear ranges were 0.1–6.5 µmol L−1 and 0.1–3.8 µmol L−1 for BPA and OP, wtih the detection limits of 0.0176 µmol L−1 and 0.0324 µmol L−1, respectively. In addition, the AuNPs-g-C3N4/GCE showed satisfactory reproducibility and stability and can be successfully applied to monitor of BPA and OP in baby formula samples.

Magnetic nanoparticles have been widely used in the field of nanomedicine as drug delivery vehicles for targeted imaging-guided and controlled drug uptake and release actions. In this work, the loading of curcumin on Fe3O4/rGO nanocomposites and their interaction mechanism were investigated by multispectral methods including resonance light scattering (RLS), atomic force microscopy (AFM), circular dichroism (CD) and Fourier transform infrared (FT-IR). Results revealed that the drug loading was a complex process which is not governed by a simple adsorption. The interactions of vitro human serum albumin (HSA) with free curcumin and/or curcumin-Fe3O4/rGO complex have been studied. Outcomes from the fluorescence quenching showed that the binding constant of curcumin to HSA increased significantly in the presence of Fe3O4/rGO, confirming the enhanced effect of Fe3O4/rGO besides its low toxicity towards HSA. Findings from this work verified that Fe3O4/rGO nanocomposite has a promising potential as a good drug loading carrier that can be used and broad range of therapies.

In this study, molybdenum disulfide (MoS

In this work, a novel CoMn2O4@CoMn2S4 core-shell nanocluster@nanosheet was successfully grown onto Ni foam via a hydrothermal reaction, which omitted the addition of a binder and conductive additive and the need for a complicated electrode preparation process. CoMn2S4 nanosheets as "shells" were found to be uniformly distributed on the surface of CoMn2O4 nanoclusters as "cores" to form a typical core-shell structure. These structures possess a high specific surface area and abundant active sites, which not only shorten the transmission path for electrons and ions, but also prevent collapse of the structure, thus improving its cycling stability. The specific capacity of CoMn2O4@CoMn2S4 is 1542.0 C g-1 at a current density of 1 A g-1, which is 3.1 times higher than that obtained for CoMn2O4. Moreover, CoMn2O4@CoMn2S4 shows excellent electrochemical cycling performance, and the specific capacity retention rate for CoMn2O4@CoMn2S4 reaches 95.81% after 5000 cycles at a current density of 20 A g-1. The specific energy of the CoMn2O4@CoMn2S4 reaches 44.30 Wh kg-1 at a specific power of 774.98 W kg-1. Therefore, the CoMn2O4@CoMn2S4//AC device shows excellent practical application capability.

In this work, a novel 3D MnNi2O4@MnNi2S4 core-shell nano array was successfully grown on nickel foam (NF) via in-situ growth method, which omitted the addition of binder and conductive additive and the complicated electrode preparation process. The MnNi2O4@MnNi2S4 possesses a unique nanorod@nanosheet core-shell structure, which can provide abundant active sites near the electrode interface for rapid electrochemical reaction, so the MnNi2O4@MnNi2S4 electrode materials exhibit high specific capacitance and excellent electrochemical properties. It is worth noting that the specific capacitance of the MnNi2O4@MnNi2S4 reaches 3578.57 F g−1 at the current density of 1 A g−1, and 1009.52 F g−1 at the current density of 20 A g−1. When the current density is 15 A g−1, the specific capacitance retention rate reaches 93.1% after 5000 cycles, showing good cycling performance. Moreover, the MnNi2O4@MnNi2S4//AC asymmetric device also exihibits low leakage current and excellent self-discharge characteristics. So, the MnNi2O4@MnNi2S4 is an excellent electrode material for supercapacitors.

Three structurally similar catecholamines, adrenaline (AA), dopamine (DA) and noradrenaline (NA), which are neurotransmitters well known for their treatment of neural disorders and many other diseases, were investigated at a glassy carbon electrode (GCE) with the use of differential pulse stripping voltammetry (DPSV). The aim was to develop a simple, rapid and cost effective method of simultaneous analysis of these three substances in typical samples such as human urine. Each analyte showed typical reversible redox behaviour with the use of cyclic voltammetry in aqueous medium in the pH range of 4.0–7.9, and composite voltammograms of the three analytes were found to consist of three significantly overlapping peaks corresponding to the three individual substances. Thus, two- and three-way multi-variate data analysis methods were investigated. These included unfolding methods such as—partial least squares (UPLS), principal component regression (UPCR) and radial basis function-artificial neural networks (URBF-ANN), as well as trilinear models, such as parallel factor analysis (PARAFAC) and N-way PLS (NPLS). The results were compared with those obtained from two-way voltammetric data matrix with the use of conventional models, PLS, PCR and RBF-ANN. It was found that most of the three-way models, such as PARAFAC and UPLS, performed somewhat better than others on the basis of the %RPET (5.6∼5.9) and mean %Recovery (94∼102). The proposed methods were then applied for the determination of human urine samples spiked with the three catecholamines, and the results were satisfactory.

Adenine-stabilized carbon dots (A-CDs) are shown to be a viable fluorescent probe for highly sensitive detection and imaging of Cu2+. The probe has a linear fluorometric response in the 1–700 nM concentration range and a 0.3 nM detection limit. The probe, with excitation/emission maxima at 380/435 nm, is highly selective for Cu2+ over other metal ions, anions, amino acids, and biomolecules. The fluorescence quenching mechanism of the A-CDs by Cu2+ is investigated using transmission electron microscopy images coupled with elemental mapping, X-ray photoelectron spectroscopy, X-ray-excited Auger electron spectroscopy, fluorescence lifetime, UV–visible spectroscopy, and cyclic voltammetry. The experimental results show that the fluorescence quenching is caused by the combination of Cu2+-coordination-induced aggregation of the A-CDs, the reduction of Cu2+ by the A-CDs, and the nonradiative photoinduced electron transfer process from the A-CDs to Cu2+ or metallic Cu. The high sensitivity and high selectivity of the sensor are ascribed to the chemical interactions between the A-CDs and Cu2+, the photophysical process between the A-CDs and Cu2+, and the high fluorescence quantum yield of the A-CDs (44.6%). The A-CDs have excellent water solubility, good stability to variation of pH values, high photostability, fast response time, and low cytotoxicity. They are successfully employed for intracellular imaging of Cu2+ in HepG2 cells and Cu2+ detection in the tap water samples.

Foods generally contain special ingredients which easily to interact with drugs human intaking, thus affecting drug efficacy and excretion, and even cause adverse reactions. Vitamin C (Vit. C) is abundant in fresh fruits and vegetables. It plays a regulatory role in redox metabolism, and its absence can cause scurvy. Aspirin (ASP) can be used to treat many diseases, is the earliest, common and widely used as antipyretic, analgesic and antirheumatic medicine. Human serum albumin (HSA) is the most abundant protein in vertebrate plasma and has the property of combining and transporting endogenous and exogenous substances. In this paper, the effects of Vit. C on the combination of ASP and HSA were studied by multi-spectra and voltammetric approaches. Fluorescence spectra showed that the quenching mode between Vit. C and HSA is dynamic, and the main binding force is hydrophobic force. The quenching mode between ASP and HSA is static one, and the main binding force is hydrogen bond and van der Waals force. For ternary biological system of (HSA-ASP)-Vit. C, the binding constant decreases compared with HSA-Vit. C system. However, for (HSA-Vit. C)-ASP system, the binding constant does not change when compared with binary system of HSA-ASP. Based on the technology combination of voltammetry, infrared, three-dimensional fluorescence and circular dichroism (CD), it is proved that the existence of ASP will influence the binding process of Vit. C to HSA. It could be concluded that taking Vit. C first doesn't affect the absorption of ASP and may be good for health; in contrast, it is not good to take Vit. C immediately as one have just taken ASP, because the existence of ASP reduce the absorption of Vit. C for human body.

Most of the conventional multidimensional differential sensors currently need at least two-step fabrication, namely synthesis of probe(s) and identification of multiple analytes by mixing of analytes with probe(s), and were conducted using multiple sensing elements or several devices. In the study, we chose five different nucleobases (adenine, cytosine, guanine, thymine, and uracil) as model analytes, and found that under hydrothermal conditions, sodium citrate could react directly with various nucleobases to yield different nitrogen-doped carbon nanodots (CDs). The CDs synthesized from different nucleobases exhibited different fluorescent properties, leading to their respective characteristic fluorescence spectra. Hence, we combined the fluorescence spectra of the CDs with advanced chemometrics like principle component analysis (PCA), hierarchical cluster analysis (HCA), K-nearest neighbor (KNN) and soft independent modeling of class analogy (SIMCA), to present a conceptually novel "synthesis-identification integration" strategy to construct a multidimensional differential sensor for nucleobase discrimination. Single-wavelength excitation fluorescence spectral data, single-wavelength emission fluorescence spectral data, and fluorescence Excitation-Emission Matrices (EEMs) of the CDs were respectively used as input data of the differential sensor. The results showed that the discrimination ability of the multidimensional differential sensor with EEM data set as input data was superior to those with single-wavelength excitation/emission fluorescence data set, suggesting that increasing the number of the data input could improve the discrimination power. Two supervised pattern recognition methods, namely KNN and SIMCA, correctly identified the five nucleobases with a classification accuracy of 100%. The proposed "synthesis-identification integration" strategy together with a multidimensional array of experimental data holds great promise in the construction of differential sensors.

Three-dimensional copper hydroxide nanosupercages and electrochemically reduced graphene oxide were used to modify the glassy carbon electrode for the selective determination of hydrogen peroxide. ...

In this paper, we constructed a novel label-free analytical strategy for highly sensitive and selective detection of nitrofurantoin (NFT) based on adenosine-stabilized copper nanoclusters (CuNCs) as nanoprobes. It was found that NFT caused a rapid decrease in the photoluminescence intensity of CuNCs. The photoluminescence quenching was likely attributed to the inner filter effect between NFT and CuNCs. The CuNCs exhibited a wide linear range of 0.05-4.0μM with the detection limit of 30nM (7.1ngmL-1) for detection of NFT. And it was successfully applied for NFT detection in lake water samples.

A facile, simple, and relatively environment-friendly hydrothermal approach was developed for one-step synthesis of graphitic carbon nitride nanosheets (GCNNs) using melamine and sodium citrate as the precursors. The prepared GCNNs emit strong fluorescence with a high quantum yield of 48.3%. The GCNNs were then characterized by various techniques including transmission electron microscopy, atomic force microscopy, X–ray diffraction, Fourier transform infrared spectroscopy, and UV–Vis absorption spectroscopy. In addition, the fluorescence quenching behavior of the GCNNS by mercuric ions (Hg 2+ ) was exploited to fabricate a label-free fluorescence quenching sensor for sensitive and selective detection of Hg 2+ . The results showed that there existed a linear relationship between the fluorescence intensity and the concentration of Hg 2+ from 0.001 to 1.0 μM with a detection limit of 0.3 nM. Finally, the sensor was successfully used to detection of Hg 2+ in water and milk samples.

An electrochemical biosensor capable of direct detection of DNA damage induced by clenbuterol (CLB) has been developed. A glassy carbon electrode (GCE) was modified using reduced graphene oxide-Nafion and dsDNA to produce a dsDNA/RGO-Nafion/GCE sensor. The modified electrode was characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV), and the results at each stage of the electrode construction were interpreted. They indicated that the electrochemical oxidation peak currents of guanine and adenine at the electrode (dsDNA/RGO-Nafion/GCE) significantly increased as compared with those at the untreated electrode (dsDNA/GCE). Based on this, the sensor was used to measure the change of the oxidation peak currents for guanine and adenine between the intact and damaged dsDNA in the sensor films, and the DNA damage was successfully detected. Furthermore, the plot of peak current decline for the guanine and adenine versus the concentration of CLB was linear in the range of 5.0 × 10−7 to 4.0 × 10−6 mol L−1, with a limit of detection (LOD) of 3.2 × 10−7 mol L−1, which provided a good method to determine CLB indirectly.

Lotus has been widely cultivated and consumed in Asia, Oceania and America, and it is not only used as an ornamental plant but also as a dietary staple. In this work, fingerprinting techniques based on NIR spectroscopy and HPLC chromatography were used to discriminate four important kinds of lotus seed cultivars, Xianglian, Jianlian, Ganlian and Hulian. By the use of the NIR spectra and the aid of genetic algorithm-partial least squares (GA-PLS) and principal component analysis (PCA), cored lotus seed samples were successfully discriminated into four cultivars. High performance liquid chromatographic (HPLC) characteristic peaks detected at different wavelengths can also be used for PCA analysis to differentiate the lotus seed cultivars. Furthermore, quantitative prediction analysis of total sugar, total polysaccharide, liensinine and rutin in cored lotus seed (liensinine and rutin are mainly in lotus plumule) can be successfully performed with the use of the combined data matrix of 30 common characteristic HPLC peaks and 37 GA-PLS selected NIR spectral variables (wavelengths). The results suggested that the combination of NIR and HPLC supported by chemometrics is suitable for the discrimination of the plant cultivars and quantitative prediction of the active constituents in lotus seed samples.

Nanostructured Co3O4 with near-cubic morphology was synthesised using the solvothermal method, and a non-enzymatic electrochemical glucose sensor (Co3O4–CuNPs/Pt) was successfully constructed by dropping and potentiostatic depositing technologies. The obtained Co3O4 and Co3O4–CuNPs were characterised and investigated by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. Quantitative analysis of glucose was performed using the amperometric (i–t) method, and a plot of current difference versus concentration of glucose was linear in the range 0.5–336 μM, with a linear correlation coefficient (R2) of 0.9989 and limit of detection (LOD) of 0.43 μM. When the linear range was reduced to 0.5–76.5 μM, R2 and LOD were 0.9997 and 0.17 μM, respectively. The sensitivity of the sensor was evaluated as 3.58 × 104 and 4.03 × 104 μA μM−1 cm−2 for the above two linear ranges, respectively. This novel sensor produced satisfactory reproducibility and stability and was applied to monitor trace amounts of glucose in human serum samples.

The interactions of typical nitrofuran antibiotics, nitrofurazone (NFZ) and nitrofurantoin (NFT), with bovine serum albumin (BSA) have been studied using fluorescence and FT-IR spectroscopy, circular dichroism (CD), atomic force microscopy (AFM) and molecular docking investigation. The results revealed that the fluorescence of BSA was quenched by nitrofurans with a static quenching mechanism. The conformation of BSA was changed and unfolded with the addition of nitrofurans because the alpha-helix and beta-sheet were varied to beta-turn and random structure. This study also indicated that the impact on the conformational changes of BSA caused by NFZ was more conspicuous than that of NFT. The molecular simulation studies were carried out to clearly describe the nature of the interaction between nitrofurans and BSA.

A novel modified electrode has been successfully constructed with the use of a nano-composite mixture consisting of molybdenum disulfide (MoS2) and gold nanoparticles (AuNPs). Its application as a cholesterol biosensor was investigated. The morphology of the prepared MoS2-AuNPs nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscope (AFM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). The physicochemical properties of the modified electrode at each stage of the construction were characterized by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Quantitative analysis of cholesterol was carried out with the use of the amperometric i–t method, and the calibration plot for cholesterol was linear in the range of 0.5–48 μM with a limit of detection (LOD) of 0.26 ± 0.015 μM. The apparent Michaelis-Menten constant ( K M a p p ) and sensitivity were estimated to be 0.325 mM and 4460 μA mM−1 cm−2, respectively. This novel sensor produced satisfactory reproducibility and stability, and was used successfully for the quantitative analysis of cholesterol in egg yolk and pork liver samples.

A strong red fluorescent nanocomposite, consisting of graphite-like carbon nitride nanosheets (g-C3N4 NSs) and serum albumin-capped Au nanoclusters (AuNCs), was synthesized. Dopamine (DA) can quench the red fluorescence of the nanocomposite, based on the Forster resonance energy transfer (FRET) mechanism. In this quenching process, the energy is transferred from the fluorescent g-C3N4 NSs-AuNCs to the oxidized DA quinine molecules (DA is easily oxidated to form DA quinine in air). The red fluorescence emission at 420 nm decreases dramatically and the quenching ratio (F0 – F)/F0 is linearly related to the concentration of DA in the range of 0.05–8.0 μmol L−1 with a detection limit of 0.018 μmol L−1 (S/N = 3). Additionally, this sensor has a potential of application to assay the DA in the real samples, such as human serum and human urine.

In this work, the electrochemical behavior of hydrochlorothiazide and pyridoxine on the ethylenediamine-modified glassy carbon electrode were investigated by differential pulse voltammetry. In pH 3.4 Britton-Robinson (B-R) buffer solution, both hydrochlorothiazide and pyridoxine had a pair of sensitive irreversible oxidation peaks, that overlapped in the 1.10 V to 1.20 V potential range. Under the optimum experimental conditions, the peak current was linearly related to hydrochlorothiazide and pyridoxine in the concentration range of 0.10&ndash, 2.0 &mu, g/mL and 0.02&ndash, 0.40 &mu, g/mL, respectively. Chemometrics methods, including classical least squares (CLS), principal component regression (PCR) and partial least squares (PLS), were introduced to resolve the overlapped signals and determine the two components in mixtures, which avoided the troublesome steps of separation and purification. Finally, the simultaneous determination of the two components in commercial pharmaceuticals was performed with satisfactory results.

In the present study, we demonstrated that the luminescent molybdenum disulfide (MoS 2 ) nanosheets, which were prepared hydrothermally by using sodium molybdate and thiourea as precursors, possessed peroxidase-like activity, and could catalyze the oxidation of peroxidase substrate o-phenylenediamine (OPD) in the presence of hydrogen peroxide (H 2 O 2 ) to produce a yellow color reaction. Further addition of Fe 2+ into the nanosheets led to peroxidase mimetics with greatly enhanced catalytic activity. The observation was exploited to develop a label-free colorimetric nanozyme sensor for detection of Fe 2+ . The fabricated MoS 2 /OPD/H 2 O 2 sensor showed a wide linear range of 0.01–0.8 µM with a detection limit of 7 nM. Moreover, it was found that the MoS 2 /OPD/H 2 O 2 sensor displayed enhanced sensitivity and selectivity toward Fe 2+ compared with the OPD/H 2 O 2 sensor, suggesting that the MoS 2 nanosheets could improve the performance of the Fe 2+ sensor. An advanced chemometrics algorithm, multivariate curve resolution by alternating least squares (MCR-ALS), was further applied to interpret the origin of enhancing sensitivity and selectivity in the Fe 2+ sensor with the MoS 2 nanosheets. The time-dependent UV–vis spectral data of the studied systems were collected, and submitted to the MCR-ALS. The results showed that the increased sensitivity and selectivity of the MoS 2 /OPD/H 2 O 2 sensor for Fe 2+ detection likely arose from its large reaction rate constant. Finally, the proposed MoS 2 /OPD/H 2 O 2 sensor was successfully applied for detection of Fe 2+ in water samples.

A novel 3D nano-flower-like Cu/multi-layer molybdenum disulfide composite (CuNFs/MoS2) modified glassy carbon electrode (GCE) has been successfully constructed. It was a highly sensitive and selective non-enzymatic hydrogen peroxide (H2O2) and glucose biosensor. The morphology of the obtained CuNFs-MoS2 nano-particles was investigated with the use of a scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDS). The physicochemical properties of the modified electrode were characterized at each of the construction stages with the use of an electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) techniques. The new sensor combined the advantages of MoS2 and CuNFs, and exhibited high electro-catalytic activity toward H2O2 and glucose. Quantitative analysis of H2O2 and glucose was carried out with the use of the amperometric i-t method. Linear ranges were obtained between 0.04-1.88 μM and 1.88-35.6 μM for H2O2 and 1-20 μM and 20-70 μM for glucose, and their corresponding limits of detection (LOD) were 0.021 μM and 0.32 μM. This novel sensor was successfully applied for the quantitative analysis of H2O2 in tap water and glucose in human serum samples.

Fluorescent molybdenum disulfide (MoS2) nanosheets were synthesized hydrothermally by employing sodium molybdate and thiourea as the starting materials. Lead(II) ion was introduced as a chemical dopant into the fluorescent nanosheets for the first time, and it was found that the fluorescence of the doped MoS2 nanosheets showed a considerable enhancement compared with that of initial MoS2 nanosheets, implying that lead(II)-doping into the MoS2 nanosheets could result in an increase in the fluorescence quantum yield. In parallel, we exploited the lead(II)-induced fluorescence enhancement of MoS2 nanosheets to design a green and facile fluorescent “turn on” nanosensor for lead(II) detection. Moreover, we found that the fluorescent intensity of the doped MoS2 nanosheets was drastically quenched by the successive addition of sulfide ions. Hence, the “turn off” process was used to fabricate a green fluorescence quenching sensor for detection of sulfide ions. Finally, we elucidated the origin of the lead(II)-ind...

The interactions of the sugars glucose and lactose with the transport protein bovine serum albumin (BSA) were investigated using fluorescence, FT-IR and circular dichroism (CD) techniques. The results indicated that glucose could be bonded and transported by BSA, mainly involving hydrogen bonds and van der Waals interactions (ΔH = -86.13 kJ mol(-1)). The obtained fluorescence data from the binding of sugar and BSA were processed by the multivariate curve resolution-alternating least squares (MCR-ALS) method, and the extracted concentration profiles showed that the equilibrium constant, rglucose:BSA, was about 7. However, the binding of lactose to BSA did not quench the fluorescence significantly, and this indicated that lactose could not be directly transported by BSA. The binding experiments were further performed using the fluorescence titration method in the presence of calcium and BSA. Calcium was added so that the calcium/BSA reactions could be studied in the presence or absence of glucose, lactose or hydrolysis products. The results showed that hydrolyzed lactose seemed to enhance calcium absorption in bovine animals. It would also appear that for children, lactose provides better nutrition; however, glucose is better for adults.

Near-infrared spectroscopy (NIRS) calibrations were developed for the discrimination of spectra of the jujube (Zizyphus jujuba Mill.) fruit samples from four geographical regions. Prediction models were developed for the quantitative prediction of the contents of jujube fruit, i.e., total sugar, total acid, total phenolic content, and total antioxidant activity. Four pattern recognition methods, principal component analysis (PCA), linear discriminant analysis (LDA), least squares-support vector machines (LS-SVM), and back propagation-artificial neural networks (BP-ANN), were used for the geographical origin classification. Furthermore, three multivariate calibration models based on the standard normal variate (SNV) pretreated NIR spectroscopy, partial least squares (PLS), BP-ANN, and LS-SVM were constructed for quantitative analysis of the four analytes described above. PCA provided a useful qualitative plot of the four types of NIR spectra from the fruit. The LS-SVM model produced best quantitative prediction results. Thus, NIR spectroscopy in conjunction with chemometrics, is a very useful and rapid technique for the discrimination of jujube fruit.

Near-infrared (NIR) spectroscopy is a well-known, rapid and non-destructive technique suitable for analyses of many different food products. In this work, it was used to develop a novel method for the analysis of dehydrated tomato samples, collected from four different producers. The NIR spectra from such samples were discriminated according to the four production sources, with the use of principal component analysis (PCA). Also, hierarchical cluster analysis (HCA), linear discriminant analysis (LDA) and K-nearest neighbors (KNN) were successfully used for pattern recognition. The prediction rates were 100% for assigning producers to samples. Two multivariate calibration models—partial least squares regression (PLSR) and radial basis function neural networks (RBF-NN), were applied for quantitative analysis. NIRS calibration models were established for the determination of lycopene and total acid, sugar, phenols and antioxidant activity in dehydrated tomatoes. These calibrations were then used for prediction of unknown, dehydrated tomato samples with satisfactory results. The RBF-NN results were better than those obtained from the PLSR models, and the better predictions suggested that the novel NIR spectroscopic method supported by chemometrics, is suitable for the discrimination and prediction of the five quality parameters in the dehydrated tomato products.

An uncomplicated and sensitive kinetic spectrofluorometric method was developed for the simultaneous analysis of sibutramine, indapamide, and hydrochlorothiazide commonly found in weight-reducing health foods. The mentioned compounds were oxidized by cerium(IV) ammonium sulfate dissolved in an acidic solution. The kinetic-fluorescence spectrum of the produced cerium(III) was recorded between 0 and 600 s reaction time at the excitation wavelength of 250 nm. It was found that the fluorescence intensity was proportional to the concentration of the compounds, and their linear ranges were 0.005–0.12, 0.03–1.44 and 0.01–0.20 μg mL−1; the corresponding detection limits were 1.6, 8.3 and 6.0 ng mL−1 for sibutramine, indapamide and hydrochlorothiazide, respectively. The measured three- and two-way data of the mixtures were processed by chemometrics (included methods: parallel factor analysis (PARAFAC), partial least squares (PLS), principal component regression (PCR), and radial basis function-artificial neural network (RBF-ANN)). The proposed method was applied for the simultaneous determination of the analytes in weight-reducing food samples, and the results were comparable with those from the reference HPLC method.

Bulk graphitic carbon nitride (g-C3N4) was obtained by pyrolysis of urea at 600 °C. The material was then subjected to protonation and exfoliation to obtain strongly fluorescent g-C3N4 nanosheets. These nanosheets are representing a two-dimensional layered material that emits strong blue fluorescence peaking at 434 nm, and their quantum yield of up to 10.3 % is much higher than that of bulk g-C3N4 (6.0 %). It was found that Cu(II) ions quench the fluorescence of the nanosheets due to photo-induced electron transfer (PET), probably the result of the stronger binding affinity between Cu(II) and the nitrogen and oxygen functional groups of the nanosheets. The probe responds to Cu(II) in the 0.01 to 0.4 nM concentration range, with a 8 pM detection limit. The method was applied to the determination of Cu(II) in spiked water samples.