Bistable thermo-chromic and magnetic spin crossover microcrystals embedded in nata de coco bacterial cellulose biofilm

Bacterial cellulose (BC) is a unique biomaterial with interesting physico-chemical properties and potential technological applications (i.e. removal of heavy metals from wastewater, manufacturing electrical and electronic devices, papermaking and biomedical technologies among others). In this work, we describe the growth of well formed micro-crystals of the one-dimensional spin crossover (SCO) compound {[Fe(Htrz) 2 (trz)](BF 4 )} n in a matrix of BC. The thermal dependence of the magnetic, optical, calorimetric and vibrational properties associated with the SCO properties of the resulting composite material have been investigated and compare well with those of the bulk SCO. The SCO-BC composite films display reversible thermomagnetic (diamagnetic ↔ paramagnetic) and thermochromic bistability (purple ↔ pale-yellow) determined by a well-defined hysteresis in the temperature range ca. 345–380 K where these properties depend on the history of the sample (memory effect).