Tailoring Optical Absorption Properties of Carbon Nanothreads

Year: 2024

Authors: Romi S., Santoro M., Fanetti S., Strobel T.A., Dunning S.G., Bini R.

Autors Affiliation: Univ Firenze, Dipartimento Chim Ugo Schiff, I-50019 Sesto Fiorentino, FI, Italy; Consiglio Nazl Ric Ist Nazl Ottica, Ist Nazl Ottica INO, I-50019 Sesto Fiorentino, FI, Italy; European Lab Nonlinear Spect LENS, I-50019 Sesto Fiorentino, FI, Italy; Consiglio Nazl Ric Ist Chim Composti OrganoMetall, I-50019 Sesto Fiorentino, FI, Italy; Carnegie Inst Sci, Earth & Planets Lab, Washington, DC 20015 USA; Univ Dist Columbia, Dept Chem, Washington, DC 20008 USA.

Abstract: Carbon nanothreads form a novel class of hydrogenated, diamond-like materials synthesized at high pressure from simple aromatic substances, theoretically predicted to exhibit unique mechanical properties, some of which may also exhibit optical and transport properties of potential technological interest, depending on the particular aromatic precursor. Our study focuses on cocrystals of two very similar aromatic molecules: diphenylacetylene and stilbene, both comprised of two rings connected by two-carbon units featuring triple and double bonds, respectively. We prepared the cocrystals by recrystallization from solution, producing six different compositions between the two end-member values of 100% diphenylacetylene and 100% stilbene. These samples were then compressed to final pressures of similar to 30 GPa, in diamond anvil cells, at room temperature. The compression induced copolymerization results in the formation of double-core carbon nanothreads. These nanothreads are comprised of two one-dimensional diamond-like cores connected through cis-polyacetylene-like backbones of variable length, produced from the topochemical polymerization of the acetylene moieties of diphenylacetylene. The resulting materials were characterized via optical absorption spectroscopy and X-ray diffraction. Very interestingly, the recovered materials exhibited variable optical absorption in the visible and near-infrared spectral region, resembling the low-energy edges of HOMO-LUMO band gaps in dielectric materials. Particularly, the absorption edge of our materials shifts to lower energies with increasing the diphenylacetylene content within the cocrystal precursor and, consequently, with increasing the lengths of the conjugated carbon chains. The materials properties range from semiconductor behavior to wide band gap insulating behavior at the two extremes of 100% and null diphenylacetylene content. Pressure-induced copolymerization thus represents a methodology for synthesizing novel carbon nanothreads with finely variable optical properties.

Journal/Review: JOURNAL OF PHYSICAL CHEMISTRY C

More Information: We acknowledge financial support under the National Recovery and Resilience Plan (NRRP), Mission 4, Component 2, Investment 1.1, Call for tender No. 104 published on 2.2.2022 by the Italian Ministry of University and Research (MUR), funded by the European Union – NextGenerationEU- Project Title NEw MatErials by high-presSure chemIStry- CUP B53D23015760006 – Grant Assignment Decree No. 1064 adopted on 18/07/2023 by the Italian Ministry of University and Research (MUR). This study was also supported by the Deep Carbon Observatory (DCO) initiative under the project Physics and Chemistry of Carbon at Extreme Conditions and by Fondazione Cassa di Risparmio di Firenze under the project Utilizzo dell’anisotropia strutturale nella sintesi di nanofili di carbonio diamond-like ad alta pressione and the project SALUS. S.G.D. acknowledges funding support from the Arnold and Mabel Beckman Foundation. T.A.S. acknowledges support from the National Science Foundation, Division of Materials Research (NSF-DMR) under Grant No. 2226699.
KeyWords: Effective Conjugation Length; High-pressure Synthesis; Polymerization
DOI: 10.1021/acs.jpcc.4c06125