Photochromic polymeric materials have been commercialized in ophthalmic lenses, however, there are many other potential uses for this technology. The photochromic transitions are extremely sensitive to environmental conditions, thus offering the potential for modifying the kinetics to suit different applications. There are a significant number of photochromic molecular families, with different characteristics. The spiro-compounds, both spirooxazines and spiropyrans, have received the most attention as they have good coloration properties and spirooxazines also display good fatigue resistance. Consequently this review focuses on the inclusion of these compounds into polymer matrices. In addition we discuss decoloration and coloration behaviors, solvatochromism, mechanism of fatigue, and unusual synthetic approaches.

A porous iron-based oxalate-phosphate-amine metal-organic framework material (OPA-MOF) was investigated as a microbially-induced slow-release nitrogen (N) and phosphorus (P) fertilizer. Seedling growth, grain yields, nutrient uptake of wheat plants, and soil dynamics in incubated soil, were investigated using OPA-MOF vs standard P (triple-superphosphate) and N (urea) fertilizers in an acidic Ferralsol at two application rates (equivalent 120 and 40 kg N ha^-1). While urea hydrolysis in the OPA-MOF treatment was rapid, conversion of ammonium to nitrate was significantly inhibited compared to urea treatment. Reduced wheat growth in OPA-MOF treatments was not caused by N-deficiency, but by limited P-bioavailability. Two likely reasons were slow P-mobilisation from the OPA-MOF or rapid P-binding in the acid soil. P-uptake and yield in OPA-MOF treatments were significantly higher than in nil-P controls, but significantly lower than in conventionally-fertilised plants. OPA-MOF showed potential as enhanced efficiency N fertilizer. However, as P-bioavailability was insufficient to meet plant demands, further work should determine if P-availability may be enhanced in alkaline soils, or whether central ions other than Fe, forming the inorganic metal-P framework in the MOF, may act as a more effective P-source in acid soils.

The mechanical recycling of solid plastic waste on a small-scale level can be accomplished with the correct approaches. Thermoplastics are the types of plastic mostly considered for mechanical recycling because of their physical properties and ease of reprocessing. This paper reviews the mechanical reprocessing techniques of selected thermoplastics (polyethylene terephthalate and polyolefins), since they constitute a significant proportion of the plastics used commercially. Furthermore, necessary considerations for the effective operation of small-scale plants, including energy requirements of machinery and optimisation in order to improve efficiency and product quality, are discussed. A clearer understanding and addressing of the process-related challenges will lead to the successful establishment and management of small-scale mechanical recycling facilities to benefit communities. Efficient small-scale mechanical reprocessing establishments have become essential in reducing the environmental impacts of solid plastic waste and for energy conservation.