A fluorometric sensor for detection and identification of biogenic amines with carboxylic acid modified tetraphenylethenes (TPEs) based on aggregation-induced emission (AIE) is reported. A mixture of the carboxylic acid substituted TPE and biogenic amines displayed a blue emission on aggregation, which serves as a “turn-on” fluorescent sensor for the amines, the degree of fluorescence enhancement being dependent on the amine. The chromic responses were utilized to distinguish the amines. A fluorometric sensor array of three TPEs with carboxylic acid groups was shown to identify accurately 10 different amines, including biogenic amines. The response patterns were systematically classified by using linear discriminant analysis (LDA) with 98 % classification accuracy. Additional information on the concentration of histamine in a “tuna fish matrix” as an example was assessed by the further analysis of the fluorescence intensity, demonstrating a test for food freshness and quality.

The synthesis of mannose-substituted tetraphenylethenes (TPEs) and their aggregation-induced emission (AIE) behavior, induced by interactions with concanavalin A (Con A), are reported. A mixture of the mannose-TPE conjugates and Con A in a buffer solution displays an intense blue emission on agglutination within a few seconds, which serves as a “turn-on” fluorescent sensor for lectins. The sensing is also selective: the conjugates act as a sensor for Con A, but do not sense a galactose-binding lectin, PNA. Con A-recognition is not affected even in the presence of other proteins in a mixture. The conjugates also exhibit high sensitivity to detect Con A. An increased sensitivity of the conjugates results if mannopyranoside substituents are linked to the TPE-core unit with a flexible chain and/or when the number of mannose residues increases.

Control of the helical sense in α-sexithiophene (6T) through pH-responsive wrapping with left-handed-helical amylose is demonstrated. A change in pH of the medium caused a significant conformational change in amylose as the host polymer, which resulted in either supramolecular complexation with 6T as the guest molecule to induce optical activity or decomplexation leading to loss of optical activity. Furthermore, we observed that chirality reversal in 6T does not require hosts of opposite helical chirality, but can be made possible simply by taking advantage of the pH sensitivity of the amylose folding, which is dependent on the pH history of the aqueous medium. In helical amylose, 6T assumes a clockwise-twisted conformation when the pH is changed from acidic to neutral, but assumes an anticlockwise-twisted conformation when the aqueous solution is acidified from very basic conditions.