Modification of optical absorption of molecule near metallic nanoparticles

We provide an analytical model for the enhancement of optical absorption of active molecules when they are placed in the vicinity of metal nanoparticles of subwavelength dimensions. Through Mie theory, in the context of plane wave expansion (PWE) of a single sphere, we have shown that for a fully random molecular orientation, the absorption enhancement factor is equal to the local field intensity enhancement factor and depends strongly on the nanoparticle size-enabling optimization and separation between the object and metal sphere. With this understanding to the modified absorption, we call for further efforts in the engineering of the perfect absorber.