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This research is focused on the fabrication of a sensitive, durable and user-friendly polyaniline-Zn-Ag (PANI-Zn-Ag) nanocomposite thin film sensor for Leptospira bacterial detection. This study focuses on the performance of different concentration ratios of PANI-Zn-Ag nanocomposite thin films. The characterization of PANI-Zn-Ag nanocomposite thin films was carried out through field-emission scanning electron microscopy (FESEM), energy-dispersive x-ray (EDX) and atomic force microscopy (AFM). The sensitivity, selectivity, repeatability and stability performance of PANI-Zn-Ag nanocomposite thin films were studied using current–voltage (I–V) curves, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). FESEM results showed an irregular particle structure of PANI-Zn0.6-Ag0.4 with diameters ranging from 20 nm to 80 nm, with low agglomeration. AFM results showed that the PANI-Zn0.6-Ag0.4 nanocomposite thin film sensor had the highest average roughness and grain size. These specific morphological properties are required to maximize the reaction between the particles in PANI-Zn-Ag and the bacterial cells to increase the sensitivity. The repeatability and stability test showed a standard deviation range of 0.0005–0.001, which indicates that the PANI-Zn-Ag thin film sensor has high reusability. The selectivity test showed a large current gap between the deionized water test and the bacteria test. The sensitivity analysis showed that the PANI-Zn0.6-Ag0.4 nanocomposite thin film sensor had the highest sensitivity (26.2%). The results obtained confirm that the PANI-Zn-Ag nanocomposite thin film sensor has the potential for use as a biosensor for Leptospira bacterial detection. [ABSTRACT FROM AUTHOR]

This work reports on the effect of the morphology of ZIF-67 on its performance as a non-enzymatic electrochemical uric acid sensor. Three different structures were prepared using a simple co-precipitation method with different solvents. The characterization studies on ZIF-67 were carried out by several techniques including X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The characterization results showed that ZIF-67 which was prepared using methanol, water, and a mixture of methanol and water displayed dodecahedral, microplate, and irregular shapes, respectively. The three different structures are denoted as Me-ZIF-67, W-ZIF-67, and M-ZIF-67, respectively. The uric acid sensor performances were evaluated by conducting Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) measurements in PBS solution with a pH of 7.4 containing uric acid. The test results show that W-ZIF-67 has the highest electrocatalytic activity compared to the other two materials possessing the highest current and the lowest overpotential. As a uric acid sensor, W-ZIF-67 has a sensitivity of 0.0377 μA μM−1 cm−2 with a relatively wide linear detection range of 20–1000 μM, and a detection limit of 3.04 μM. W-ZIF-67 also has good reproducibility and is stable against interfering species such as urea, glucose, ascorbic acid, and NaCl. [ABSTRACT FROM AUTHOR]

The development of non-noble-metal sensing material for sensitive and selective detection of uric acid with a simple material synthesis technique has not been frequently reported in recent years. Taking advantage of the unique properties of highly porous materials of Metal-Organic Frameworks, which incomparable in their structural diversity and tunability as well as their range of chemical and physical properties, open up a chance for developing novel nanomaterial for electrochemical sensor applications. In this article, we evaluated MOF-71 as a sensing material on a glassy carbon electrode (GCE) in a three-electrode system for electrochemical detection of uric acid. The MOF-71 was synthesized by a simple solvothermal method. Its structural characteristics that are examined by scanning electron microscopy and X-ray diffraction confirmed the successful formation of MOF-71. Cyclic voltammetry (CV) and differential pulse voltammetry DPV) analysis showed the successful uric acid detection in a phosphate buffer solution and showed good electrochemical catalytic activity toward uric acid. DPV was selected for the determination of uric acid with a sensitivity of 0.4811 mA.mM-1.cm-2, the detection range of 50.0- $1000~\mu \text{M}$ , and detection limit of $15.61~\mu \text{M}$ at an S/N = 3. [ABSTRACT FROM AUTHOR]

A barium strontium titanate Ba0.65Sr0.35TiO3 and its lithium (Li) and copper (Cu) doped thin films have fabricated on quartz substrates based on sol-gel and spin-coating method. Chemical solution deposition with spin-coating technique deposited the thin films. The addition of Li and Cu dopants lead to the change of lattice constant and the change of grain size. From Scherrer's equation, it found that BLST and BCST thin films have larger and smaller grain size than that of BST, respectively. It also revealed that the crystal structures formed in a phase between cubic and tetragonal structure. Scanning electron microscopy was confirmed homogenous surfaces of thin film and energy dispersive x-ray was showed chemical composition according to the considered stoichiometry. [ABSTRACT FROM AUTHOR]

Present-day science indicates that developing sensors with excellent sensitivity and selectivity for detecting early signs of diseases is highly desirable. Electrochemical sensors offer a method for detecting diseases that are simpler, faster, and more accurate than conventional laboratory analysis methods. Primarily, exploiting non-noble-metal nanomaterials with excellent conductivity and large surface area is still an area of active research due to its highly sensitive and selective catalysts for electrochemical detection in enzyme-free sensors. In this research, we successfully fabricate Metal-Organic Framework (MOF) FeBDC-derived Fe3O4 for non-enzymatic electrochemical detection of glucose. FeBDC synthesis was carried out using the solvothermal method. FeCl2.4H2O and Benzene-1,4-dicarboxylic acid (H2BDC) are used as precursors to form FeBDC. The materials were further characterized utilizing X-ray Powder Diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier-Transform Infrared Spectroscopy (FTIR). The resulting MOF yields good crystallinity and micro-rod like morphology. Electrochemical properties were tested using Cyclic Voltammetry (CV) and Differential Pulse Voltammetry (DPV) with a 0.1 M of Phosphate Buffer Saline (PBS pH 7.4) solution as the supporting electrolyte. The measurement results show the reduction and oxidation peaks in the CV curve of FeBDC, as well as Fe3O4. Pyrolysis of FeBDC to Fe3O4 increases the peak of oxidation and reduction currents. The Fe3O4 sample obtained has a sensitivity of 4.67 µA mM−1.cm−2, a linear range between 0.0 to 9.0 mM, and a glucose detection limit of 15.70 µM. [ABSTRACT FROM AUTHOR]

This work reports a facile glycerol-assisted solvothermal method for synthesizing hierarchical three-dimensional (3D) wool-ball-like zinc oxide (ZnO) nanostructures and their subsequent modifications with multi-walled carbon nanotubes (MWCNTs) as modifiers for achieving sensitive and selective detection of toxic sulfur dioxide (SO 2 ) gas. Structurally, the as-synthesized 3D wool-ball-like ZnO is assembled of two-dimensional (2D) plate-like structures, which themselves are arranged by numerous small nanoparticles. Furthermore, in this work we observed an interesting new phenomenon in which when a high concentration of MWCNTs is introduced, many small nanorods grew on the surface of the plate-like structures which assemble the 3D wool-ball-like ZnO nanostructures. When evaluated for SO 2 detection, the ZnO/MWCNTs (10:1) composite (ZnO:MWCNTs = 10:1) shows a high response of 220.8 to 70 ppm of SO 2 gas (approximately three times higher than the response of pure wool-ball-like ZnO) at an optimum operating temperature of 300 °C. Additionally, the composite also displays good stability and selectivity to SO 2 with the response to 50 ppm of SO 2 being 7–14 times higher than the responses to other tested gases at a similar concentration. The excellent sensing performance of the wool-ball-like ZnO/MWCNTs (10:1) composite is mainly attributed to: (i) the formation of p - n heterojunctions at the ZnO/MWCNTs interfaces, which greatly enhance the resistance changes upon exposure to SO 2 gas and (ii) the increased amount of adsorption sites for O 2 and SO 2 gas molecules owing to the larger surface area of the composite and defects sites generated by the functionalization process of MWCNTs. [ABSTRACT FROM AUTHOR]

[Display omitted] • Image processing converts the digital images into morphological criteria. • The lamellae cross-sectional area ratio is calculated from the binary images. • Radial distribution function justifies the lamellae cross-sectional area ratio. • The lamellae cross-sectional area ratio is associated with lamellae density. • The morphology of spherical silica was quantitively validated by lamellae density. We developed an SEM image processing technique using ImageJ to overcome the complexity of the bicontinuous concentric lamellar (bcl) morphology. SEM images were converted into ready-to-analyze binary images. From there, the lamellae cross-sectional area ratio A L / A total was calculated and used to compare the lamellae density between different bcl silica particles. Based on the comparison of bcl silica synthesized via the reflux method with varying times of synthesis, we found no significant difference in lamellae density, which is in accordance with the qualitative observations of the SEM images. We also compared our results with spherical silica particles synthesized by other research groups within the confidence interval of 48 to 53%. The particles above the confidence interval were considered to have lost their bicontinuity features. Whereas the particles below the interval still demonstrate the bicontinuous lamellar morphology, though with a larger interlamellar distance. To further verify our technique, we calculated the narrowness of the V-groove between the lamellae (θ). The θ value of the particles within the confidence interval showed similar values, ranging from 4.3 to 5.1°. Based on the comparison of the θ value with < A L / A total > we established a trend where the smaller the θ value, the higher the lamellae density. [ABSTRACT FROM AUTHOR]

Titanate nanotubes (TiNT) were deposited over the surface of 100 pores per inch (ppi) reticulated vitreous carbon (RVC) by anodic electrophoresis at a cell voltage of 15 V, in an undivided cell, from an ethanol/water suspension containing TiNT coated with tetrabutylammonium hydroxide (TBAOH) surfactant. Scanning electron microscopy showed the open cell porous structure of TiNT/RVC coated by a uniform ca. 30 μm thick layer of TiNT. Calcination at 450 °C for 2 h in air improved the photocatalytic properties. The material was used as photocatalyst for the decolourisation of methylene blue (MB) dye. The 98% volumetric porosity of the RVC substrate provided good reactant access and large surface area for deposition of TiNT. The calcined TiNT/RVC substrate achieved a 91% dye degradation after 20 min, which was higher than uncoated, acid treated RVC and non-calcined TiNT/RVC substrate. The MB decolourisation improved at an increased thickness of 3D TiNT/RVC catalyst although the improvement was limited to 4 mm on 100 ppi RVC due to limited UV penetration. Unlabelled Image • Anodic electrophoresis produced a stable TiNT film on 100 ppi RVC. • SEM imaging showed uniform deposition of TiNT. • The acid treatment of RVC increased the ratio of I D / I G as seen in Raman spectra. • Decorated RVC was used as a photocatalyst for decolourisation of MB dye. [ABSTRACT FROM AUTHOR]