Swelling of Composite Films at Interfaces

Composite materials made of metallic nanoparticles embedded in an organic matrix are highly promising candidates as coatings for novel chemical sensors. Micromechanical cantilever measurements revealed that the Au-nanoparticle terphenyldithiol composite material swells upon dosing with toluene vapor. The mass increase was found to be linear with the toluene vapor concentration, ≈ 40 fg/ppm. Furthermore, significant differences in the mechanical transduction of ≈100 nm thick Au-nanoparticle terphenyldithiol composite material that was prepared on a 3-aminopropyldimethylmonoethoxysilane (APDMES) surface and on a Au surface were observed. The transduction of swelling of the composite film into a mechanical deflection was found to be more efficient for the composite film prepared on the Au surface attributed to covalent binding of the terphenyldithiol molecules with the Au surface. In contrast, the interface of the APDMES layer and the Au−terphenyldithiol composite material is based on electrostatic interaction between the Au nanoparticles and the amino interface. The analysis of the micromechanical cantilever sensor measurements lead to the conclusion that the composite film at the APDMES interface is more mobile compared to a similar film that was prepared on Au.