Metal particles for surface-enhanced raman scattering and molecular sensing

A method for producing a metal nanoparticle material for molecular sensing, the method comprising:

• a) associating a single-stranded nucleic acid strand as a substrate with at least two single-stranded nucleic acid strands each having complementarity to a partial base structure in the nucleic acid strand and having one terminal with a thiol group to form a double helix, thereby obtaining a modified nucleic acid strand;
• b) reacting the thiol groups in the modified nucleic acid strand with a metal nanoparticle to bond the modified nucleic acid strand onto the surface of the metal nanoparticle, and then heating the resulting product at 60 to 100° C. to dissociate the double helix structure of the modified nucleic acid strand, thereby removing the single-stranded nucleic acid strand to obtain a metal nanoparticle bonded with the single-stranded nucleic acid strands through the thiol groups;
• c) reacting a single-stranded nucleic acid strand having complementarity to the nucleic acid strands, having one terminal with a thiol group, and having a base length equal to that of the nucleic acid strands with a metal nanoparticle, thereby obtaining a metal nanoparticle bonded with the single-stranded nucleic acid strand through the thiol group;
• d) mixing the metal nanoparticle bonded with the single-stranded nucleic acid strands and the metal nanoparticle bonded with the single-stranded nucleic acid strand to associate the single-stranded nucleic acid strands with the single-stranded nucleic acid strand, thereby forming a double helix to produce a metal nanoparticle aggregate;
• and
• bonding a Raman active molecule to:
• the single-stranded nucleic acid strands used in a);
• the single-stranded nucleic acid strand used in c);
• or
• the single-stranded nucleic acid strands used in a) and the single-stranded nucleic acid strand used in c);
• wherein:
• the metal nanoparticle material comprises a metal nanoparticle aggregate including three to ten metal nanoparticles connected to each other through an organic molecule so that adjacent metal nanoparticles are bonded and spaced apart a predetermined distance, the aggregate containing a Raman active molecule within a field applied to the aggregate;
• and
• the metal nanoparticle material emits enhanced Raman scattering light from the Raman active molecule in an enhanced electric field.