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 ?. If the ambient tem-perature 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 mu g/h at 30 degrees C and 0.022 mu g/h at 15 degrees 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.