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Humidity and moisture effects, frequently called water poisoning, in surroundings are inevitable for various molecular sensing devices, strongly affecting their sensing characteristics. Here, we demonstrate a water-selective nanostructured dehumidifier composed of ZnO/TiO

In this study, we developed an odor sensor system using chemosensitive resistors, which outputted multichannel data. Mixtures of gas chromatography stationary materials (GC materials) and carbon black were used as the chemosensitive resistors. The interaction between the chemosensitive resistors and gas species shifted the electrical resistance of the resistors. Sixteen different chemosensitive resistors were fabricated on an odor sensor chip. In addition, a compact measurement instrument was fabricated. Sixteen channel data were obtained from the measurements of gas species using the instrument. The data were analyzed using machine learning algorithms available on Weka software. As a result, the sensor system successfully identified alcoholic beverages. Finally, we demonstrated the classification of restroom odor in a field test. The classification was successful with an accuracy of 97.9%.

Breath odor sensing-based individual authentication was conducted for the first time using an artificial olfactory sensor system. Using a 16-channel chemiresistive sensor array and machine learning, a mean accuracy of97% was successfully achieved. The impact of the number of sensors on the accuracy and reproducibility was also demonstrated.

Polymer-carbon nanocomposite sensor is a promising molecular sensing device for electronic nose (e-nose) due to its printability, variety of polymer materials, and low operation temperature; however, the lack of stability in an air environment has been an inevitable issue. Here, we demonstrate a design concept for realizing long-term stability in a polyethylene glycol (PEG)-carbon black (CB) nanocomposite sensor by understanding the underlying phenomena that cause sensor degradation. Comparison of the sensing properties and infrared spectroscopy on the same device revealed that the oxidation-induced consumption of PEG is a crucial factor for the sensor degradation. According to the mechanism, we introduced an antioxidizing agent (i.e., ascorbic acid) into the PEG-CB nanocomposite sensor to suppress the PEG oxidation and successfully demonstrated the long-term stability of sensing properties under an air environment for 30 days, which had been difficult in conventional polymer-carbon nanocomposite sensors.

Correction for ‘Breath odor-based individual authentication by an artificial olfactory sensor system and machine learning’ by Chaiyanut Jirayupat et al., Chem. Commun., 2022, DOI: https://doi.org/10.1039/D1CC06384G.

In this study, we have fabricated multichannel odor sensor using chemosensitive resistors. The chemosensitive resistors were made from complex of carbon black and gas chromatography stationary materials (GC materials). The electrical resistance of the chemosensitive resistor changed by sensing gas species. We have fabricated an odor sensor chip, which had 16 types of chemosensitive resistors. In addition, we developed a measurement instrument with compact size. The odor sensor chip was embedded in the instrument to construct an odor sensor system. The sensor system outputted the data of 16 channels if sensing gas species. The data have been analyzed using machine learning algorithms that were available on software Weka. As a result, it was successful to identify alcohol beverages by sensing their odor using the sensor system.

Mimicking the biological olfaction, large odor-sensor arrays can be used to acquire a broad range of chemical information, with a potentially high degree of redundancy, to allow for enhanced control over the sensitivity and selectivity of artificial olfaction systems. The arrays should consist of the largest possible number of individual sensing elements while being miniaturized. Chemosensitive resistors are one of the sensing platforms that have a potential to satisfy these two conditions. In this work we test viability of fabricating a 16-element chemosensitive resistor array for detection and recognition of volatile organic compounds (VOCs). The sensors were fabricated using blends of carbon black and gas chromatography (GC) stationary-phase materials preselected based on their sorption properties. Blends of the selected GC materials with carbon black particles were subsequently coated over chemosensitive resistor devices and the resulting sensors/arrays evaluated in exposure experiments against vapors of pyrrole, benzenal, nonanal, and 2-phenethylamine at 150, 300, 450, and 900 ppb. Responses of the fabricated 16-element array were stable and differed for each individual odorant sample, proving the blends of GC materials with carbon black particles can be effectively used for fabrication of large odor-sensing arrays based on chemosensitive resistors. The obtained results suggest that the proposed sensing devices could be effective in discriminating odor/vapor samples at the sub-ppm level.

The size and shape of nanoscale materials provide important control over many of the physics and chemical properties, including electric and thermal conductivity, luminescence, and catalytic activity.1 Colloidal chemists have obtained excellent controlled nanosized particles for several spherical metal and semiconductor compositions, which has led to the discovery of the quantum size effect in colloidal nanocrystals.2 However, various bottom-up approaches for making anisotropic-shaped colloidal nanoparticles have been found, with most of these solution methods being based on a thermal process. On the other hand, top-down approaches have been developed for producing metal and semiconductor nanowires, nanobelts, and nanoprisms.3-5 In particular, the laser-induced ablation method has become an increasingly popular approach for making nanoparticles from the viewpoint of the concise procedure and application of a variety of materials.6-11 The ripple structures have been observed on the surface of the metal and semiconductor caused by the interferences between the scattering incident laser field and the surface plasmon-polariton waves (SPWs).11,12 However, until now, there has been no observation of nanowire formation in a colloidal suspension by pulsed laser irradiation and the mechanism of its appearance has not been fully understood. We recently reported the first experimental evidence of the periodic nanostructures embedded in silica glass after irradiation by a single focused beam of a femtosecond Ti:sapphire laser.13 The phenomenon is interpreted in terms of interference between the incident laser light field and the generated bulk electron plasma waves, resulting in the periodic modulation of electron plasma concentration and the structural changes in transparent material. Here, we report the first observation of the photoconversion from copper flakes to nanowires and nanospheres formation via ultrafast pulse laser irradiation. This phenomenon has provided two distinct surface plasmon resonances based on the characteristic shape. The observed copper nanowires of 50 nm diameter are fragmented from the initial flakes as a result of the interference between the light field and the SPWs. Beyond the fundamental issues of basic science, applications are possible in the areas of an optical polarization control, an electroconductive nanomaterial, and a catalytic metal.

We report on spatially selective change of magnetism from paramagnetic to ferrimagnetic-like behaviors in normal spinel ZnFe2O4 thin film under irradiation with 780 nm femtosecond laser pulses. The distribution of Zn2+ and Fe3+ ions in the irradiated region on the film surface becomes disordered because of local heating to high temperatures, and the metastable phase of ZnFe2O4 is frozen in by the rapid quenching after irradiation, resulting in the formation of the ferrimagnetic phase. The ferrimagnetic phase reverts to the paramagnetic state by annealing at 800°C. The present technique is useful for two-dimensional patterning of magnetic thin films.