Encapsulated dye coated noble metal nanoparticles with increased surface enhanced raman scattering properties as contrast agents

A method of producing enhanced Raman scattering with exitonic semiconductor noble metal composite nanoparticles for, comprising:

• preparing a solution of dye molecules and linker molecules;
• adding the solution of dye and linker molecules to a solution of noble metal nanoparticles under conditions selected to induce self-assembly of the linker and dye molecules to produce composite particles having a layer of the linker molecules attached to a surface of the noble metal nanoparticle and a layer of the dye molecules attached to the layer of linker molecules, the dye molecules being selected such that they interact cooperatively with each other and with the surface, when bound to the linker layer, to produce an optical absorption spectrum that is shifted in wavelength relative to an absorption spectrum of a single dye molecule;
• encapsulating the composite particles in a lipid bilayer layer;
• washing the encapsulated composite particles;
• identifying the optimal excitation wavelengths for field enhancement through a theoretical simulation that includes the complex dielectric constants of the metal and the molecular aggregate, wherein a wavelength near where the plasmon is observed is matched with the excitation wavelength (or stokes shifted wavelength) and a wavelength near where the real and imaginary components of are approximately equal and approach zero is matched with the Stokes shift (or excitation wavelength) and identifying the plasmon through a combination of theoretical simulation and experimental measurement, and depends on the size, shape, composition and environment of the metal nanoparticle.
• demonstrating the field enhancement by measuring Raman scattering strength with excitation at different wavelengths

A method of producing exitonic semiconductor noble metal composite nanoparticles for enhanced Raman scattering, comprising:

• preparing a solution of dye molecules and linker molecules;
• adding the solution of dye and linker molecules to a solution of noble metal nanoparticles under conditions selected to induce self-assembly of the linker and dye molecules to produce composite particles having a layer of the linker molecules attached to a surface of the noble metal nanoparticle and a layer of the dye molecules attached to the layer of linker molecules, the dye molecules being selected such that they interact cooperatively with each other and with the surface, when bound to the linker layer, to produce an optical absorption spectrum that is shifted in wavelength relative to an absorption spectrum of a single dye molecule;
• encapsulating the composite particles in a stabilizing coating layer;
• and
• washing the encapsulated composite particles.