Most commercially available controlled release materials of pheromones have a "wick" structure or a "core-shell" structure, and the mechanism of continuous release is temperature-sensitive control. However, materials with this structure cannot control the release time, so they have no effect on the pests flying at night. In recent years, the light-controlled release materials of active molecules based on photoremovable protecting groups have attracted extensive attention, which are temperature-independent slow-release materials of pheromones.
Photoremovable protecting groups
Photoremovable protecting groups (PRPGs), refer to a class of organic compounds containing chromophores. These compounds can form covalent bonds with specific chemical groups of biologically active small molecules, making the small molecules unable to combine with the targeted biological macromolecules and lose activities. The covalent bond between the photosensitive protecting group in electronically excited state and the small molecule is broken under a specific wavelength of light, thereby releasing the small molecule with biological activity.
Due to the controllability of light, photoremovable protecting group can realize the release of immobilized active molecules, which has unique advantages in the application of sustained release of pheromones. In 1983, the light-controlled release of active molecules was achieved for the first time by utilizing the photosensitivity of o-nitrobenzyl compounds. 
- (E)-(2-Hydroxyphenyl) acrylate was used as a photoremovable group, and the release of pheromone molecules was achieved by photo-controlled intramolecular lactonization. When acetophenone and 3-allyl-cyclohexanopropionate were used as active molecules, more pheromone molecules were released with the increase of illumination. 
- When coumarin derivatives are used as photosensitive protective groups, they have two-photon absorption ability. Due to this property, coumarin was used to design a low-power light-controlled pheromone trap with battery operation. The trap is used to hunt night-flying insects, since switching-on can trigger the coumarin-based PRPGs to release pheromone at night. The photo-controlled release technology of pheromone using coumarin derivatives as PRPGs has many advantages, such as controlled release rate, monitored release, and good hydrolytic stability of PRPGs. 
- When the four compounds 7-hydroxy-4-hydroxymethylcoumarin, 1-pyrenemethanol, 9-anthracenemethanol and 2-(hydroxymethyl) anthraquinone are respectively used as the photosensitive protecting group of the sex pheromone (Z)-11-hexadecen-1-ol of Chilo infuscatellus Snellen, they all resulted in the release of pheromones under both UV light (≥350 nm) and direct sunlight irradiation. Among them, PRPG based on 7-hydroxycoumarin showed good stability and insecticidal activity. 
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- Atta,S. et al. Photoremovable protecting groups as controlled-release device for sex pheromone. Photochem Photobiol. 2013. 12(2): 393-403
- Atta,S. et al. Application of photoremovable protecting group for controlled release of plant growth regulators by sunlight. J Photochem Photobiol B. 2012. 111. 39-49