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We have developed a highly sensitive colorimetric probe based on starch–iodine (I[sub.2]) crystallization for the precise discrimination of ethanol–water clusters (E-Wc) within binary ethanol–water solutions (E-Ws). This probe enables the identification of specific E-Wc species and their corresponding transition points. Notably, two distinct transition points were identified at ethanol volume fractions of 40–45% and 75–77%. The former corresponds to the structural transition from (H[sub.2]O)[sub.m](EtOH) to (H[sub.2]O)[sub.m](EtOH)[sub.n], characterized by a significant loss of blue coloration, while the latter signifies the transition from (H[sub.2]O)[sub.m](EtOH)[sub.n] to (H[sub.2]O)(EtOH)[sub.n], as evidenced by alterations in the absorption intensity of the starch–I[sub.2] complex. Mechanistic studies demonstrate that the observed starch–I[sub.2] crystallization is governed by supramolecular E-Wc rather than individual ethanol or water molecules in the binary solution. By leveraging starch–I[sub.2] crystallization as a colorimetric bridge, we establish a direct correlation between E-Wc transitions and the iodine chromogenic effect. This approach enables the visual detection of transitions in colorless supramolecular assemblies, offering new insights into supramolecular science. Furthermore, as a simple, rapid, and visually interpretable detection method, this colorimetric probe holds promising applications in fields such as the food industry and supramolecular science.

Response and recovery times are among the most important parameters for gas sensors. Their optimization has been pursued through several strategies, including the control over the morphology of the sensitive material. The effectiveness of these approaches is typically proven by comparing different sensors studied in the same paper under the same conditions. Additionally, tables comparing the results of the considered paper with those available in the literature are often reported. This is fundamental to frame the results of individual papers in a more general context; nonetheless, it suffers from the many differences occurring at the experimental level between different research groups. To face this issue, in the present paper, we adopt a statistical approach to analyze the response and recovery times reported in the literature for chemiresistors based on pure SnO[sub.2] for ethanol detection, which was chosen as a case study owing to its available statistic. The adopted experimental setup (of the static or dynamic type) emerges as the most important parameter. Once the statistic is split into these categories, morphological and sensor-layout effects also emerge. The observed results are discussed in terms of different diffusion phenomena whose balance depends on the testing conditions adopted in different papers.

Ag-LaFeO.sub.3 was prepared by chemical reduction method with NaBH.sub.4 ethanol solution. It can be seen from X-ray diffraction (XRD) that all samples are still perovskite structure. Two distinct Ag peaks were observed in X-ray photoelectron spectroscopy (XPS). The experimental results show that at 190 °C, the gas response of Ag-LaFeO.sub.3 sensor to 100 ppm ethanol is 155, which is much higher than that of LaFeO.sub.3 sensor. Meanwhile, the response time and recovery time are 30 s and 5 s, respectively. The results show that Ag-LaFeO.sub.3 has excellent ethanol gas-sensing properties.