Particulate material comprising rough mesoporous hollow nanoparticles. The rough mesoporous hollow nanoparticles may comprise a mesoporous shell, the external surface of which has projections thereon, the projections having smaller sizes than the particle size. The particulate material may be used to deliver active agents, such as insecticides and pesticides. The active agents can enter into the hollow core of the particles and be protected from degradation by sunlight. The rough surface of the particles retains the particles on plant leaves or animal hair. Methods for forming the particles are also described. Carbon particles and methods for forming carbon particles are also described.