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Although evolving technology enables the production of sensors with excellent properties, the development of a fast-response, portable, and low-cost sensor is very important for food detection and also for disease diagnosis. Herein, zinc doped manganese oxide nanocomposites (Zn:MnO2 NCs) were designed as smartphone-integrated colorimetric and non-enzymatic electrochemical sensors with high sensitivity and selectivity. According to the Transmission electron microscopy (TEM) results showed that the Zn:MnO2 NCs had a spherical shape with a uniform particle size of less than 10 nm. As one of the most important results, the colorimetric sensing behavior of the Zn:MnO2 NCs was showed excellent fast and selective sensitivity against dopamine, ascorbic acid, gallic acid, and tannic acid among the various bio-analytes such as sugars, amino acids, hormones, and phenolic compounds. The Zn:MnO2 NCs were successfully used as smartphone supported paper based sensor against dopamine, gallic acid, and tannic acid using RGB analysis and with low limit of detection (LOD) values of 2.89, 3.88, and 7.81 μM, respectively. Moreover, Zn:MnO2 exhibited excellent a non-enzymatic electrochemical sensor performance against ascorbic acid with a low LOD of 239 nM and high sensitivity of 44.73 μA/cm2 mM in a concentration range of 0.52–11.35 mM. These findings emphasize that the designed Zn:MnO2 NCs based sensors has a potential as easily applicable and rapid sensor systems against of ascorbic acid, gallic acid, tannic acid and dopamine for real food and blood samples that as a point-of-care detection systems. [ABSTRACT FROM AUTHOR]

Abstract A vertically aligned Pd nanowire array was successfully fabricated on an Au/Ti substrate using an anodic aluminum oxide (AAO) template by a direct voltage electrodeposition method at room temperature using diluted neutral electrolyte. The fabrication of Pd nanowires was controlled by analyzing the current–time transient during electrodeposition using potentiostat. The AAO template and the Pd nanowires were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) methods and X-Ray diffraction (XRD). It was observed that the Pd nanowire array was standing freely on an Au-coated Ti substrate after removing the AAO template in a relatively large area of about 5 cm2, approximately 50 nm in diameter and 2.5 μm in length with a high aspect ratio. The nucleation rate and the number of atoms in the critical nucleus were determined from the analysis of current transients. Pd nuclei density was calculated as 3.55 × 108 cm−2. Usage of diluted neutral electrolyte enables slower growing of Pd nanowires owing to increase in the electrodeposition potential and thus obtained Pd nanowires have higher crystallinity with lower dislocations. In fact, this high crystallinity of Pd nanowires provides them positive effect for sensor performances especially.

In this study, ethanol detection performance of divanadium pentoxide (V2O5) nanowire array was investigated at various temperatures. The main purpose of this study is to develop a novel V2O5 nanowires-based sensor for the detection of ethanol using an Anodic Aluminum Oxide (AAO) template by direct voltage electrodeposition at room temperature. It was observed that the V2O5 nanowires were approximately 60 nm in diameter in a large area of 6 cm2. X-ray Diffraction (XRD) spectrum indicated the formation of V2O5. The XRD peak was indexed as V2O5 located at 2θ°≅ 20° that is attributed to the (001) lattice plane. The sensitivity of the V2O5 nanowire array was found 0.24 at 200 °C for 50 ppm ethanol. The results reveal that the diffusivity of the V2O5 molecules increases rapidly with increasing temperature, causing an increased sensitivity. The maximum sensor response was obtained at 200 °C. The limit of detection (LOD) of the V2O5 nanowire array sensor was 500 ppb at 200 °C. The response time (t90) of the V2O5 nanowire array sensor was calculated to be 52 s and the recovery time was 26 s at 200 °C. [ABSTRACT FROM AUTHOR]