Food wastage due to spoiling is a global economic issue and contributes to over-farming and overfishing with real environmental consequences. Smart food packaging is a promising solution to this problem, the concept of which is to incorporate responsive sensors that allow direct monitoring of the gasses released from the decay of food into a label that provides a visual indicator to the consumer as to whether the food is fresh or has spoiled. Here we report two dicyanovinyl-fluorene-benzothiadiazole-based fluorescent compounds, K12 and K12b, both of which showed rapid response to biogenic amines via two independent mechanisms. When primary alkyl amines were present in solution, they underwent an aza-Michael addition with the dicyanovinyl group of the sensing material, resulting in a rapid colour change. The reaction products of K12 and K12b with primary amines showed a decrease and increase in the fluorescence quantum yield, respectively, enabling a unique dual-sensor array with turn-off/turn-on response. In addition, fluorescence quenching via photoinduced hole transfer was observed in the solid-state sensor films with a wide range of primary, secondary and tertiary amines, enabling rapid and sensitive detection of amine vapours. Finally, we show as proof-of-concept that the fluorescence quenching response of sensing films was observable at cadaverine concentrations relevant to the food industry.

Dicyanovinyl-based fluorescent sensors for dual mechanism amine sensing

Volatile amine vapors are toxic and corrosive irritants and can cause serious health problems. In addition, the biologically amine vapor produced by microorganisms is also an important indicator of food spoilage. Therefore, the development of simple, sensitive, and selective amine vapor detection methods is of great significance. A new ESIPT-based fluorescent probe HBTAc has been developed as a rapid, highly sensitive, and selective sensor for amine vapors in this work. The HBTAc sensor exhibits an obvious fluorescence turn-on response at 514 nm toward amine vapors with a large Stokes shift (180 nm), and a low detection limit (12.7 ppm). Taking advantage of its portability and high sensitivity to amine vapors, the HBTAc sensor can be used for food spoilage monitoring by detecting volatile amines produced by microbial growth. Finally, agar gels based on the HBTAc probe were fabricated, which could act as a solid optical sensor to conveniently and efficiently detect amine vapors.

A new ESIPT-based fluorescent probe for the highly sensitive detection of amine vapors

Manipulation from multi-physical quantity aspect to steer molecular photophysical property is of great significance in improving sensing performance. Here, an investigation on how physical quantity rooted from molecular structure induce optical behavior change to facilitate an ultrasensitive detection to ethylenediamine (EDA) is performed by varying a set of thiols. The model molecule consisted of a thiol with dual-carboxyl exhibits the strongest fluorescence ascribed to the electron-donating ability prompted larger orbital overlapping and oscillator strength. The elevated fluorescence positively corelated to the increased EDA, endowing an ultrasensitive response to nanomolar-liquid/ppm-vapor. A gas detector with superior performances fulfills a contactless and real-time management to EDA. We envisage this electron tuning strategy enabled fluorescence enhancement can offer an in-depth insight in advancing molecule customized design, further paving the way to widen applicable scenes.

Electronic Tuning in Reaction-based Fluorescent Sensing for Instantaneous and Ultrasensitive Visualization of Ethylenediamine.

A new fast-responding fluorimetric “turn-on” sensor based on benzothiazole-phenanthridine for the sensitive, selective, and reversible detection of Cu2+ in real water samples and its use in bio-imaging

Balijapalli Umamahesh

Papers

A colorimetric and ratiometric fluorescent sensor for biogenic primary amines based on dicyanovinyl substituted phenanthridine conjugated probe