For nanocomposites composed of plasmonic nanocrystal and polymers, the plasmon‐induced electromagnetic field (EF) around the plasmonic nanocrystals can be used to change the dielectric environment around them, resulting in the optical and electrical properties of nanocomposites being adjustable. The electrical conductivities of ligand coated on plasmonic nanocrystal and polymer matrix play important roles in controlling the “local” and “overall” dielectric environment of nanocomposites under plasmon‐induced EF. The changes in the dielectric environment of nanocomposites are caused by the rearrangement of molecular chains of ligand and/or polymer matrix around the plasmonic nanocrystals. The optical properties of nanocomposites depend on the “local” and “overall” dielectric environment of nanocomposites, which show a significant change in the plasmon resonance wavelength (blueshift ≈10 nm) under plasmon‐induced EF. However, the electrical properties of nanocomposites depend only on the “overall” dielectric environment of the nanocomposite under plasmon‐induced EF. Nanocomposites are constructed in the conducting polymer matrix resulting in three orders of magnitude increase (from 4 × 10–14 to 10–10 s cm−1) in the electrical conductivity of nanocomposites under plasmon‐induced EF. Such plasmonic nanocrystal‐polymer nanocomposites with highly sensitive optical and electrical properties under external stimuli have potential applications in “electromagnetic field” or “photonic” 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...