Synergistic optical limiting performance in covalently grafted Pt(II)–carbon nanotube hybrids

We report a covalent hybridization strategy to construct a robust optical limiting material by grafting Pt (II) complexes onto carboxylated multi-walled carbon nanotubes (MWCNTs). The Pt (II) moieties are stably anchored to the CNT surface via amide bonds, as evidenced by FT-IR, Raman, XPS, and TEM/EDS analyses. These results confirm covalent linkage formation and reveal strong interfacial electronic interactions between the two components. The covalent integration enhances dispersion stability and modulates interfacial charge transfer and excited-state energy dissipation pathways. Optical limiting performance was investigated at 532 nm with 80% linear transmittance using the F 50 value (incident fluence at which the output drops to 50% of the linear response) as the quantitative metric. The optimal hybrid (Pt–NH 2 400 mg in 13% MWCNTs-COOH) shows a significantly lower F 50 of 0.8 J cm −2 compared with pristine Pt–NH 2 (F 50  > 4.0 J cm −2 ) and MWCNTs-COOH (F 50  = 2.1 J cm −2 ). This enhancement comes from synergistic interactions between the Pt (II) complexes and CNTs. The covalent bond enables efficient interfacial charge transfer and multipath energy dissipation, combining reverse saturable absorption (RSA) from Pt (II) complexes with nonlinear scattering and photothermal effects from CNTs. Transient absorption dynamics reveal that the covalently grafted Pt complex acts as an efficient photon sensitizer and reverse saturable absorber, while the MWCNT framework serves as a rapid energy acceptor and dissipater, validating the synergistic mechanism. This work provides a practical route for engineering high-performance broadband optical limiting materials through covalent grafting. It also offers mechanistic insights into cooperative nonlinear optical behavior in metal-complex-carbon-nanomaterial systems.