Tuning the optoelectronic features of Poly(3-hexylthiophene-2,5-diyl) with oligoplatinaynes-functionalized gold nanoparticles

Hydrophobic gold nanoparticles (AuNPs) covalently functionalized with organometallic platinum-containing oligomers (Pt–DEBPn, DEBP = 4,4′-diethynylbiphenyl) with different chain lengths were synthesized and incorporated into a poly(3-hexylthiophene-2,5-diyl) (P3HT) matrix to obtain inorganic/organic AuNPs/P3HT blends with tuned optoelectronic properties. The Pt–DEBPn (n = 3, 4, 6) chain length was modulated by carefully controlling reaction conditions in a catalyst-free polycondensation reaction and monitored using UV–visible spectroscopy. Spherical AuNPs with a (3.3 ± 1.1) nm diameter from solid-state microscopies and narrow size distributions, evaluated in colloidal suspension by dynamic light scattering (DLS), were obtained by a two-phase wet chemical reduction in the presence of thiolate organometallic ligands. Structural analyses by FTIR and SR-XPS confirmed the functionalization via Au–S bonds. Platinum-containing ligand introduced additional emissive pathways, including long-wavelength emission, attributed to increased rigidity and reduced nonradiative decay in AuNPs. AuNPs/P3HT blends were obtained with different compositions (from 10 to 90 wt % AuNPs content) by a simple room-temperature mixing approach in organic solvents and spin-coated onto an interdigitated ITO substrate. Homogeneous films with a mean thickness of about 3 nm were revealed by atomic force microscopy (AFM). Electrical I/V measurements (range ±10 V) carried out on AuNPs/P3HT blends demonstrated a composition-dependent response. The blend containing 10 wt % AuNPs showed a ∼30-fold increase in the relative electrical response compared to pristine P3HT and a reduced optical band gap (2.13 → 2.06 eV). Photoluminescence studies revealed red-shifted and broadened P3HT emission with increasing AuNP content, highlighting strong AuNP plasmon–polymer interactions. Further grazing-incidence wide-angle X-ray scattering (GIWAXS) and nanofocused X-ray scattering measurements (nano-GIWAXS) revealed composition-dependent structural and thermal stability. It is noteworthy that low AuNPs wt % promoted a more effective interconnectivity with P3HT chains, responsible for enhanced electronic coupling in blends compared with pristine counterparts. Results showed that this nanoscale arrangement offers tunable properties for optoelectronic applications