SPIN-CROSSOVER IRON(II) COORDINATION COM­POUNDS: FABRICATION OF FUNCTIONAL MATERIALS AND THEIR INTEGRATION INTO MICRO- AND NANOCONSTRUCTIONS

Development of micro- and nanosized spin-crossover (SCO) materials has become an important research direction within the past decade. Such an interest is associated with high perceptive of practical application of these materials in nanoelectronic devices. Therefore, researches working in the field of SCO put considerable efforts to obtain SCO complexes in various functional forms, such as nanoparticles, thin films, etc. Fabrication of these materials is realized through different chemical and/or lithographical approaches, which allow to adjust size, shape and even organization of nanoobjects. In this review theoretical background of SCO phenomenon is described, additionally different classes of coordination compounds exhibiting spin crossover are covered. It is demonstrated that electric field, temperature and light irradiation can be effectively used for switching and control of spin state in nanosized SCO systems. Cooperative SCO with transition close to room temperature, wide hysteresis loop and distinct thermochromic effect is most often observed for Fe(II) coordination complexes. Therefore, Fe(II) SCO compounds form one of the most perspective classes of compounds for obtaining functional materials. It is shown that integration of Fe(II) compounds into micro- and nanohybrid devi­ces allows to combine unique functional pro­perties in one material due to synergy between SCO and physical properties (luminescent, electrical, etc.) of the other component. As a result, SCO compounds are interesting not only from the fundamental point of view, but also from practical, thanks to the possibility of integration of SCO Fe(II) complexes as active materials in devices of different configurations. It is expected that obtaining of new Fe(II) coordination polymers with unique SCO cha­racteristics will favor the development of new functional materials and devices on their basis in the nearest future.

A smart material built upon the photo-thermochromic effect and its use for managing indoor temperature

We demonstrate a material by dispersing a thermochromic mixture of leuco dye, developer, and solvent as microspheres in a polymer matrix to improve the efficiency of building energy management. The...

Mechanical and chemical resistance of thermochromic packaging prints

Thermochromic inks are temperature-sensitive materials that change colour due to a temperature change. These inks are mostly printed on smart packaging applications where they are used in a form of temperature indicators. The colorants in these inks are microencapsulated which makes the prints obtained with these inks more sensitive to abrasion in comparison to the prints obtained with conventional inks. Thermochromic prints are also very sensitive to adverse environmental conditions, such as exposure to UV light, heat and certain chemicals and solvents. Abrasion and chemical resistance of thermochromic prints obtained on metallized label papers are discussed in this paper. For that purpose, two thermochromic UV screen inks were printed on two types of metalized papers that are commonly used as food packaging labels. The prints thus obtained were then subjected to a rub test in accordance with standard method BS 3110. Rub test was performed using Hanatek RT4 Rub and Abrasion Tester. The degree of rubbing was assessed by visual inspection and by detection of the colorimetric changes on the prints after their exposure to rubbing. Assessment of prints' resistance to various liquid agents (water, ethanol and citric acid) was done in accordance to standard method ISO 2836. Evaluation of chemical degradation on prints was done by the spectrophotometric measurements. The results of conducted research showed good rub resistance of these inks, as no rubbing was detected, but poor resistance to all liquid agents they were exposed to. Exposure to ethanol, particularly, caused severe damage to the prints. The bleeding of the colorants from the prints was also detected. However, even though the prints were not able to completely withstand exposure to specific liquid agents which was demonstrated by their optical deterioration, the thermochromic effect was still present in them after resistance tests were conducted.

Effect of Concentration of Thermochromic Ink on Performance of Waterborne Finish Films for the Surface of Cunninghamia Lanceolata

Using Cunninghamia lanceolata as a substrate, the thermochromic ink was added to the waterborne finish to test the optical properties and mechanical properties of the finish film. The results showed that the discoloration performance of the finish film with 15.0% and 30.0% of the thermochromic ink was better. The gloss of the finish film changes irregularly when the concentration increases. The finish film with a thermochromic ink concentration of 10.0% has the highest gloss, and with a concentration of 30.0% has the lowest gloss. When the thermochromic ink concentration exceeds 15.0%, the impact resistance of the finish film is slightly enhanced. The concentration is not related to the liquid resistance of the finish film. When the thermochromic ink concentration was 0–15.0%, the particle distribution uniform reunion was not much. The discoloration mechanism of discolored finish film can be considered to be as follows. After adding thermochromic ink, when the finish film temperature rises, it fades from red to colorless. When the temperature is lowered, the thermochromic ink changes to its original colour again, and the thermochromic effect is stable and sustainable. On the basis of the above results, when the thermochromic ink concentration is 15.0%, the general performance of the waterborne finish film on the Cunninghamia lanceolata surface is the best. This study provides new prospects in using thermochromic ink for waterborne finish film.