Fabrication of Red-Light Emitting Organic Semiconductor Nanoparticles via Guidance of DNAs and Surfactants

Organic semiconductor materials for fabricating organic light emitting diodes (OLEDs) have attracted significant attention in the field of novel optical and optoelectronic devices. Particulation of OLEDs’ emitting materials in small-scale has been limited only to tris(8-hydroxyquinoline) aluminum (Alq₃) that emits green-light. In this study, we attempted to fabricate, for the first time, red-light emitting nanoparticles of phosphorescent organic semiconductor of bis(1-phenylisoquinoline) (acetylacetonate) iridium (Ir(piq)₂(acac)). Rectangular particles with length and thickness of ∼2 μm and ∼50 nm were fabricated with guidance of cetyltrimethylammonium bromide (CTAB) and micro-plates with length and thickness of ∼5 μm and ∼100 nm were fabricated by sodium dodecyl sulfate (SDS). By contrast, single-stranded DNA (ssDNA) induced nano-rods with dimension of ∼400 nm in length and 100 nm in thickness. Hence, the choice of guiding agents resulted in distinctive crystal characteristic so that the nanorods by ssDNAs showed UV absorption with a red-shift in metal-ligand charge transfer (MLCT) by 54 nm whereas the particles by surfactants did 35 nm compared to the dissolved precursor. Higher was the ssDNA-guided nanorods in relative phosphorescence of the intensity at 610 nm over that at 695 nm than the surfactant-guided particles. [Figure not available: see fulltext.].