The present invention is for particulate compositions and methods for
producing them that can absorb or scatter electromagnetic radiation. The
particles are homogeneous in size and are comprised of a nonconducting
inner layer that is surrounded by an electrically conducting material.
The ratio of the thickness of the nonconducting layer to the thickness of
the outer conducting shell is determinative of the wavelength of maximum
absorbance or scattering of the particle. Unique solution phase methods
for synthesizing the particles involve linking clusters of the conducting
atoms, ions, or molecules to the nonconducting inner layer by linear
molecules. This step can be followed by growth of the metal onto the
clusters to form a coherent conducting shell that encapsulates the core.