Molecularly Imprinted Chemiresistive Sensor for Specific Recognition of Furaneol as a Biomarker of Strawberry Flavor Conditions.

This work introduces the concept of a molecularly imprinted gas sensor to monitor the condition of naturally ripened strawberries. Furaneol, 2,5-dimethyl-4-hydroxy-3(2H)-furanone, is considered as an important biomarker related to the strawberry flavor. Identification of furaneol concentration is still a challenge because of its weak adsorption, nonpolar, and unreactive properties. Therefore, no study has been reported yet to measure furaneol gases via a simple chemiresistive mechanism. Herein, we demonstrate the sensor based on molecularly imprinted polymer (MIP)-based polyaniline (PANI). The sensitive and selective detection of furaneol gas with a MIP-PANI gas sensor was observed at room temperature and under different humidity conditions. The comparison between MIP and the nonimprinted (NIP)-based PANI shows a strong interaction between furaneol and the molecularly imprinted polymer. The furaneol gas sensing mechanism is explained based on the interaction between the gas molecules and the charge carriers of MIP-PANI, which results in the functional group change in the carboxylic group. Furthermore, the developed MIP-chemiresistive sensor for real strawberries was compared with a commercial e-nose system. The results show the potential to offer a rapid and cost-effective platform for specific recognition of furaneol.

Polyaniline/Graphene-Functionalized Flexible Waste Mask Sensors for Ammonia and Volatile Sulfur Compound Monitoring.

A flexible resistive-type polyaniline-based gas sensor was fabricated by simple dip-coating of graphene combined with in situ polymerization of aniline on a flexible waste mask substrate. The prepared polypropylene/graphene/polyaniline (PP/G/PANI) hybrid sensor demonstrated a fast response (114 s) and recovery time (23 s), ppb-level detection limit (100 ppb), high response value (250% toward 50 ppm NH3, which is over four times greater than that of the pristine PANI sensor), acceptable flexibility, excellent selectivity, and long-term stability at room temperature. The morphological and structural properties of the composite sensor materials were characterized by scanning electron microscopy and energy-dispersive spectroscopy characterization, and the surface chemistry of the hybrid sensors was analyzed by Fourier transform infrared spectroscopy. The excellent sensing performance was mainly ascribed to the larger specific surface area and efficient conducting paths of the porous PP/G/PANI network. Moreover, the PP/G/PANI hybrid gas sensor exhibited excellent sensing capability on volatile sulfur compounds contained in human breath, indicating that the hybrid sensor can be applied to breath analysis and kidney disease diagnosis.

Electrically Tunable Solution-Processed Transparent Conductive Thin Films Based on Colloidally Dispersed ITO@Ag Composite Ink.

Silver (Ag) introduced colloidal Sn-doped In2O3 (ITO) ink for transparent conductive electrodes (TCEs) was prepared to overcome the limitation of colloidally prepared thin film; low density thin film, high resistance. ITO@Ag colloid ink was made by controlling the weight ratio of ITO and Ag nanoparticles through ball-milling and fabricated using spin coating. These films were dried at 220 °C and heat-treated at 450−750 °C in an air atmosphere to pyrolyze the organic ligand attached to the nanoparticles. All thin films showed high crystallinity. As the thermal treatment temperature increased, films showed a cracked surface, but as the weight percentage of silver increased, a flattened and smooth surface appeared, caused by the metallic silver filling the gap between the nano-particles. This worked as a bridge to allow electrical conduction, which decreases the resistivity over an order of magnitude, from 309 to 0.396, and 0.107 Ω·cm for the ITO-220 °C, ITO-750 °C, and ITO@Ag (7.5 wt.%)-750 °C, respectively. These films also exhibited >90% optical transparency. Lowered resistivity is caused due to the inclusion of silver, providing a sufficient number of charge carriers. Furthermore, the work function difference between ITO and silver builds an ohmic junction, allowing fluent electrical flow without any barrier.

Morphological Effect on Electrochemical Properties of BaSnO3 as an Anode Material for Lithium Ion Batteries.

In this study, we investigated the electrochemical effects of morphological changes using BaSnO3 (BSO) of various shapes (columns, hollow rods, spheres) as anode materials for Li-ion batteries. The BSOs were prepared by hydrothermal method and their electrochemical properties were evaluated using galvanostataic charge/discharge and CV test. As a results, columnar BSO exhibits the best electrochemical properties, as an inert material, BaO can contribute to Li storage because of higher electrical conductivity. This results suggest that the formation of column shape can lead to improved electrochemical properties as anode materials of secondary battery.

Synthesis of Mn-, Ni-Doped LiAlO2 Matrix for Molten Carbonate Fuel Cell.

The phase stability of electrolyte matrix was improved by metal dopant materials which are Ni and Mn. The Ni-, Mn-doped LiAlO2 and dopant-free LiAlO2 were prepared by the mechanochemical process (MCP). The effects of dopant material, molar ratio and type of precursor were investigated after heat treatment at 700 and 800 °C. As a results, the Mn-doped LiAlO2 prevents phase transition even at higher operating temperature. Also, the stability was increased when Mn4+ ion was adapted as a precursor source than Mn3+ ion and the minimum Mn content to maintain the α-phase after heat treatment at 800 °C is found to be LiAl0.75Mn0.25O2. This result suggested that the formation of nano-sized particles confirmed the applicability as a matrix material with excellent electrolyte impregnation.