Gold nanoparticles (AuNPs) conjugated with carbon nanotubes (CNTs) and/or biomolecules such as DNA are synthesized by a novel plasma technique combined with the introduction of ionic liquids or aqueous solutions for application to life sciences. We successfully generated the gas- liquid interfacial discharge plasma (GLIDP) using an ionic liquid, in which a large sheath electric field was formed on the ionic liquid and highenergy plasma ion irradiation to the ionic liquid was realized. Using this GLIDP, it is found that the high-energy ion irradiation to the ionic liquid is effective for the synthesis of AuNPs. Furthermore, controlled ion irradiation to the ionic liquid including functional groups can realize distancecontrolled synthesis of AuNPs on CNTs by dissociation of the ionic liquid and the functionalization of CNTs by dissociated carboxyl and amino groups. On the other hand, DNA is used as the functional group that connects the AuNPs to the CNTs. Monodispersed and high-density AuNPs are synthesized on CNTs in the same way as the carboxyl and amino groups. # 2012 The Japan Society of Applied Physics.