Functionalization of fine particles using atomic and molecular layer deposition

The functionalization of fine primary particles, including nanoparticles and nanotubes, is easily carried out using atomic or molecular layer deposition (ALD or MLD, respectively) techniques. Particle ALD/MLD can be used to deposit conformal and pinhole-free films of refractory oxides, non-oxides, metals, and hybrid polymer-based materials, amongst others. Fluidized bed reactors are well-suited for large scale operations and can be operated at reduced pressures while using inert gases necessary for standard self-limiting, flow-based ALD/MLD processes. The continuous-flow processing allows for process control using an in-line mass spectrometer downstream from the reactor chamber. Many insulating, semiconducting, metallic, polymeric and hybrid inorganic/organic films have been successfully deposited on primary particle surfaces in fluidized bed reactors using a variety of precursor types. This paper reviews some of the Particle ALD/MLD work carried out by the authors, including techniques and measurements used in Particle ALD/MLD. Some current and future applications of functionalized or passivated nanomaterials are also highlighted here.