title: A time-temperature integrator based on fluorescent and polymorphic compounds.
abstract: Despite the variety of functional properties of molecular materials, which make them of interest for a number of technologies, their tendency to form inhomogeneous aggregates in thin films and to self-organize in polymorphs are considered drawbacks for practical applications. Here, we report on the use of polymorphic molecular fluorescent thin films as time temperature integrators, a class of devices that monitor the thermal history of a product. The device is fabricated by patterning the fluorescent model compound thieno(bis)imide-oligothiophene. The fluorescence colour of the pattern changes as a consequence of an irreversible phase variation driven by temperature, and reveals the temperature at which the pattern was exposed. The experimental results are quantitatively analysed in the range 20-200°C and interpreted considering a polymorph recrystallization in the thin film. Noteworthy, the reported method is of general validity and can be extended to every compound featuring irreversible temperature-dependent change of fluorescence.
authors.affiliation: Consiglio Nazionale delle Ricerche-Istituto per lo studio dei Materiali Nanostrutturati (CNR- ISMN), via P. Gobetti 101, 40129 Bologna, Italy.
authors.forename: Denis
authors.initials: D
authors.lastname: Gentili
authors.forename: Margherita
authors.initials: M
authors.lastname: Durso
authors.forename: Cristian
authors.initials: C
authors.lastname: Bettini
authors.forename: Ilse
authors.initials: I
authors.lastname: Manet
authors.forename: Massimo
authors.initials: M
authors.lastname: Gazzano
authors.forename: Raffaella
authors.initials: R
authors.lastname: Capelli
authors.forename: Michele
authors.initials: M
authors.lastname: Muccini
authors.forename: Manuela
authors.initials: M
authors.lastname: Melucci
authors.forename: Massimiliano
authors.initials: M
authors.lastname: Cavallini