The Langmuir-Blodgett technique was utilized and optimized to produce closed monolayers of cobalt-platinum nanoparticles over vast areas. It is shown that sample preparation, "dipping angle", and subphase type have a strong impact on the quality of the produced films. The amount of ligands on the nanoparticle's surface must be minimized, the dipping angle must be around 105 degrees , while the glycol subphase is necessary to obtain nanoparticle monolayers. The achieved films were characterized by scanning electron microscopy (SEM) and grazing incidence X-ray scattering (GISAXS). The electrical properties of the deposited films were studied by direct current (DC) measurements, showing a discrepancy to the variable range hopping transport from the granular metal model and favoring the simple thermal activated charge transport. SEM, GISAXS, as well as DC measurements confirm a narrow size distribution and high ordering of the deposited films.

We report an alternative procedure to incorporate gold nanoparticles into 3D ordered colloidal crystal film. The size of gold nanoparticles within the films can be controlled from about 10 nm to about 60 nm by simply varying the gold plating time. The application of the as-prepared films in surface-enhanced Raman spectroscopy (SERS) is investigated by using Rhodamine 6G (R6G) as probe molecules. It is found that the resultant gold-coated 3D ordered colloidal crystal films can be used as SERS substrates, exhibiting excellent enhancement ability.

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