Silver nanocube dimer nanojunctions as plasmon-enhanced Raman sensors

Here, we demonstrated that the enhancement factor of the Raman signal in dimer nanojunctions under the plasmon-induced electromagnetic field can be tuned by the following parameters: (1) the conformations of the dimer nanojunction (vertical dimer or horizontal dimer); (2) the electrical conductivity of the ligands (thiol terminated poly-p-triphenylamine, HS-poly-p-TPA or thiol terminated poly(3,6-N-vinylcarbazole), HS-PVK) and/or matrices (poly-p-triphenylamine, PTPA or poly(3,6-N-vinylcarbazole, PVK) used to fabricate the dimer nanojunctions; (3) the irradiation intensity used to trigger the plasmonic-induced electromagnetic field around the dimer nanojunction. For dimer nanojunctions composed of high-conductivity ligand (HS-PVK)-coated AgNCs and high-conductivity matrix (PVK), the Raman signal enhancement factor of dimer nanojunctions under external stimulus can reach ∼500%. The significant increases in the enhancement factor of Raman signals under the plasmon-induced electromagnetic field can be attributed to the reducing the spacing between nanocrystals in the dimer nanojunction, which was caused by changing the configuration of the conducting ligand and the polymer matrix around the dimer nanojunction. The highly sensitive Raman response of dimer nanojunctions to external stimulus makes these dimer nanojunctions ideal for use in “electromagnetic field” or “photonic” sensors.