Concentration effect in surface plasmon-coupled phosphorescence (SPCP) emission engineering with augmented s-polarization from N-heterocyclic carbene platinum(II) complexes

Phosphorescent materials unlike fluorescent materials have limited use in sensing applications due to the lack of signal enhancements involving any kind of amplification schemes due to the restricted delocalization of triplet excitons in comparison to singlet excitons. We report the surface plasmon-coupled phosphorescence (SPCP) with enhanced quantum efficiency based on excimer-forming N-heterocyclic carbene (NHC) platinum(II) complexes with varied alkyne derivatives: (i) C₆H₄C(CH₃)₃, (ii) C₆H₅, (iii) C₆H₄F, and (iv) C₆H₃(CF₃)₂. Based on the square planar geometry of Pt(II) complexes that induce stacking and self-organization, we have achieved up to 18-fold enhancement in plasmon-coupled phosphorescence emission at increased concentrations, without the requirement of complex plasmonic architectures or other energy transfer schemes. We have also engineered SPCP substrates to achieve augmented s-polarized emission, a unique phenomenon to be achieved using this plasmonic platform. The study also captures the unique property of alteration of dispersive behavior for these (NHC) Pt(II) complexes based on the SPCP phenomenon. These studies are expected to open new avenues for phosphorescent materials and their applications in multi-analyte detection using the SPCP platform.