Pheromone enclosed in halloysite with n-octadecane releases rhythmically under simulated diurnal temperature

Insect pheromone is a class of natural non-toxic and harmless biological pesticide. To improve the utilization efficiency of the pheromone pesticides, controlled release in response to circadian rhythm of insects is a feasible approach because some insects act and release pheromones with a circadian rhythm. Thus, myrcene, as the insect pheromone model, was first loaded into the hollow nano-cavity of halloysite nanotubes (Hal), which were further enclosed with melted n-octadecane as a coating to form a composite (PMHal). The latter was simply blended into chitosan solution to cast a chitosan composite film (PMHal@CS) for preventing n-octadecane leakage during the phase change process . The effects of temperature change on the release rate of myrcene from the composite film were evaluated. Results showed the combination of Hal with n-octadecane could significantly slow the release rate of myrcene from the composite film when the ambient temperature was below 15 °C. If the ambient temperature was near to the melting point of n-octadecane, the release rate of myrcene would be enhanced. In alternating temperature cycles test of PMHal@CS film, the average release rate of myrcene was 0.65 μg/h at 30 °C and 0.022 μg/h at 15 °C, the persistent temperature sensitivity and good temperature rhythm were still remained after 7 cycles. These results suggested that the composite film had a good controlled release effect on myrcene and could adapt well to the circadian rhythm activity of some insects.