Hybrids of gold nanoparticles and oligo(p-phenyleneethynylene)s end-functionalized with alkynylruthenium groups: Outstanding two-photon absorption in the second biological window

Oligo(p-phenyleneethynylene)s (OPEs) end-capped with (alkynyl)bis(diphosphine)ruthenium and thiol/thiolate groups stabilize ca. 2 nm diameter gold nanoparticles (AuNPs). The morphology, elemental composition and stability of the resultant organometallic OPE/AuNP hybrid materials have been defined using a combination of molecular- and nano-material chacterization techniques. The hybrids display long-term stability in solution (more than a month), good solubility in organic solvents, reversible ruthenium-centered oxidation, and transparency beyond 800 nm, and possess very strong nonlinear absorption activity at the first biological window, and unprecedented two-photon absorption activity in the second biological window (σ2 up to 38,000 GM at 1,050 nm).We thank the Australian Research Council (DP170100411: M. G. H. and M. S.) and the National Science Centre (NCN) Poland (UMO-2016/22/M/ST4/00275: J. K. Z. and M. S.) for support of this work. C. Q. thanks Becas Chile (Agencia Nacional de Investigación y Desarrollo) for financial support in the form of a PhD scholarship (2015-72160061), J. P. L. M. thanks the Australian Government for an Australian Postgraduate Award, J. D. thanks the China Scholarship Council and the Australian National University for a CSC-ANU scholarship, and J. K. Z. thanks the Foundation for Polish Science (FNP) for support. The authors acknowledge the facilities, and the scientific and technical assistance, of the Australian Microscopy & Microanalysis Research Facility and the Centre of Advanced Microscopy at the Australian National University