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Nowadays, consumers can estimate the condition of packaged foods only by checking the expiration date on the label. However, this approach is inefficient when it comes to assessing the actual edibility of fresh products, since the events that accelerate the onset of degradation phenomena, such as a rise in temperature, cannot be continuously assessed. In this context, the detection of a different parameter, such as low concentration of amines, can reveal the onset of degradation processes. Here, a colorimetric photonic multilayer sensor is reported for detecting low amine concentrations suitable for sealed packages. The sensor consists of alternating layers of poly(N‐vinylcarbazole) and polyacrylic acid, and its response is based on the selective interaction between the latter and amines. This interaction causes the polymer layers to swell and introduce disorder into the photon structure, resulting in fading its bright color. Since the reaction of these systems is usually reversible, manipulation or false readings are possible due to inapt sealing of the package. It is shown that the activation of carboxylic acid residues of the sensitive polymer with N‐hydroxysuccinimide produces an irreversible response to amine vapor concentrations as low as 3 parts per billion. [ABSTRACT FROM AUTHOR]

A holistic detection system, in principle sensitive to any molecular species in the vapor phase is proposed. The sensor consists of a polymeric multilayered distributed Bragg reflector made of a perfluorinated polar polymer, Aquivion, and a nonpolar polymer, poly(N‐vinylcarbazole). Alternated layers of the two polymers provide a characteristic optical response that depends on the chemical species intercalating within the structure. Such differences arise from Flory–Huggins polymer–solvent interactions. Then, the presence of polar, nonpolar, and perfluorinated moieties in the structures, potentially, allows sensitivity to any molecular species, providing a detection system with no need for any additional chemical receptors. As a proof of concept, the study demonstrates the sensitivity of the sensor to very diverse classes of molecules in the vapor phase including perfluorinated, nonpolar hydrophobic, and hydrophilic species and the capability to distinguish them, even in binary mixtures. Additionally, a connection between the dynamic temporal response of the sensors and the chemical–physical properties of the analytes, their concentration, and effective diffusion coefficient within the polymer structure is revealed. [ABSTRACT FROM AUTHOR]

Multilayered photonic sensors that rely on polymer‐solvent Flory–Huggins interactions are drawing increasing interest owing to their broad‐band selectivity, even among mixtures, without the need for chemical targeting. Moreover, these sensors provide simple colorimetric responses, and easy, quick fabrication both on laboratory and industrial scales. However, complex optical responses and slow response times are limiting their development. In this work, the behavior of different photonic sensor architectures is analyzed to speed up response time and define a strategy to simplify their spectral behavior. To this end, the effect of interfaces, materials order, and thickness on the diffusion kinetics of a single reference analyte in the multilayered sensors is studied to design the optimal structure. [ABSTRACT FROM AUTHOR]

Keywords: diffusion coefficient; distributed Bragg reflectors; Flory-Huggins; polymer photonic crystals; vapor photonic sensors EN diffusion coefficient distributed Bragg reflectors Flory-Huggins polymer photonic crystals vapor photonic sensors 1 1 1 02/26/21 20210224 NES 210224 In article number 2009626, Paola Lova, Davide Comoretto, Heba Megahd propose general guidelines for designing multi-layered colorimetric vapor sensors using commodity polymers. Diffusion coefficient, distributed Bragg reflectors, Flory-Huggins, polymer photonic crystals, vapor photonic sensors Photonic Vapor Sensors: Universal Design Rules for Flory-Huggins Polymer Photonic Vapor Sensors (Adv. Funct. [Extracted from the article]