Electrospun spiropyran-embedded nanofibers for fast photocontrollable and reversible optochemosensing of acidic vapors.

A completely green approach was adopted for the production of biocomposites of polylactic acid (PLA) and cellulosic fibers (CF) via functionalization of CF with an aqueous solution of poly­(ethylene oxide) (PEO) followed by extrusion with PLA and injection molding. The treatment with PEO improved the interfacial interaction among the components as well as the CF dispersion and free flow upon extrusion, allowing loading up to 30 wt % of CF. Moreover, the synergistic effect of PEO and CF greatly enhanced the physical–chemical properties of the biocomposites. Their storage modulus was higher with respect to pure PLA in the rubbery region. The stiffness and mechanical strength were found to be higher than those of PLA/PEO and remained comparable to pure PLA, whereas the elongation at break was 73–143% higher owing to the effective plasticizing and reinforcing effect exerted by PEO and CF respectively. Addition of PEO and CF had a great influence on the thermal properties, particularly on the glass transition and cold crystallization temperatures. Overall, the appealing properties of the proposed biocomposites combined with the sustainability of the developed process render them ideal for several technological applications within the plastic industry including food and cosmetic packaging, disposable items, and toys.

The acid vapor sensing properties of photochromic elastomeric composite films based on spiropyran molecules embedded in poly(dimethylsiloxane) matrices are investigated. The conversion of the spiropyran molecules to their zwitterionic merocyanine isomers upon UV irradiation is essential for the acidochromic response of the composite system, in order to detect vapors of hydrochloric, trifluoroacetic, formic and acetic acids by means of the protonation of the phenolate ions. The formation of the protonated merocyanine species is accompanied by a change in the absorption spectrum and a clear color transition of the film. Differences in the protonation rate are observed for different acids due to the relative acidity of the vapors, and for different concentrations of merocyanine. The acidochromic detection can be switched on and off several times by UV irradiation and subsequent thermal regeneration of the non-polar spiropyran form with an excellent resistance to photodegradation.The facile method of preparation combined with the fast and reversible optical response activated on demand upon photoexcitation renders this material suitable for the development of portable sensing devices for environmental and industrial applications. † Electronic supplementary information (ESI) available: Optimized molecular geometry of MCH, absorption spectra of a SP/PDMS lm at different irradiation times, lm thickness dependence of the kinetics of protonation of UV irradiated SP/PDMS lms with different thicknesses exposed to vapors of TFA, kinetics of the formation of MCH upon exposure of UV irradiated SP/PDMS lms to vapors of HCl, TFA, HCOOH and AcOH, time evolution of the absorption peak of a MCH/PDMS lm at 417 nm, time evolution of the absorbance at 550 nm of a MC/PDMS lm 0-60 minutes aer UV irradiation, variation of the absorbance at 417 nm during protonation of SP/PDMS lms (SP ¼ 0.5% wt) and of SP/PDMS lms (SP ¼ 0.3% wt) with the same content of MC, video of the protonation of a UV irradiated SP/PDMS lm exposed to vapors of TFA for 9 minutes. To reduce the le size the speed has been accelerated 20Â with respect to the original rate. See