Here, we report a one-pot solvothermal synthesis that enables Fe₇C₃ nanoparticles (NPs) to direct the in situ formation of conformal graphitic carbon shells under comparatively mild conditions. Comprehensive structural analyses reveal that the resulting Fe₇C₃@C nanostructures consist of a crystalline carbide core encapsulated within a few-layer graphitic carbon shell, with small γ-Fe₂O₃ NPs by-products. Systematic variation of reaction parameters shows that both a reducing atmosphere and the Fe₇C₃ phase are essential for promoting graphitization, while Fe₅C₂ and Fe₃C NPs prepared under analogous solvothermal conditions develop only amorphous carbon shells. This structural feature directly translates into superior photothermal behavior: Fe₇C₃@C NPs exhibit enhanced photothermal heating under 808 nm irradiation, even after 10 irradiation cycles, and a photothermal conversion efficiency (PCE) exceeding those of other iron carbides and several noble-metal nanostructures. These findings establish Fe₇C₃ as a uniquely capable phase for promoting in situ carbon ordering and highlight phase-dependent surface chemistry as a powerful tool for designing high-performance photothermal materials.

Secondary Bonding Interactions (SBIs), particularly chalcogen bonding interactions (ChBIs), offer powerful opportunities to direct the assembly of functional organic materials on surfaces. Here we combine Te-based ChBIs with F⋯H hydrogen bonds (HBs) to drive the hierarchical engineering of supramolecular nanoribbons on Au(111) using a chalcogenazolo-pyridine derivative. Low-temperature scanning tunnelling microscopy imaging reveals that the molecules first undergo directional Te⋯N chalcogen-bonded dimerisation, followed by HB-mediated polymerisation into robust nanoribbon architectures. Density functional theory calculations confirm the adsorption geometries and intermolecular binding modes. The Au(111) herringbone reconstruction templates the nanoribbon orientation and maximum attainable length, with the face-centred cubic regions being the preferred adsorption sites. Scanning tunnelling spectroscopy reveals two intrinsic electronic fingerprints at +0.6 V and +1.8 V, corresponding to the LUMO and LUMO+1 of the dimeric repeat unit, respectively. The dI/dV mapping visualises their distinct spatial distributions along the ribbon backbone and edges. Control experiments with a non-pyridyl congener that cannot engage in Te⋯N ChBIs yield only simple linear assemblies, confirming the pivotal role of ChBIs in enabling hierarchical ordering.

Donor–acceptor (D–A) architectures underpin many high-performance conjugated polymers but remain largely unexplored in atomically precise nanoribbons. Here, we report the on-surface synthesis of ultra-narrow D–A nanoribbons using two complementary brominated precursors based on the electron donor peri-xanthenoxanthene and the acceptor anthanthrone. High-resolution scanning tunnelling microscopy, non-contact atomic force microscopy and scanning tunnelling spectroscopy reveal submolecular structural and electronic features of the resulting nanoribbons. Homopolymerisation of each precursor yields structurally well-defined donor-only and acceptor-only nanoribbons, whose electronic character strengthens with length. Co-deposition of both precursors produces mixed D–A nanoribbons with tuneable electronic structures governed by monomer sequence. The spatial character and energetic alignment of their frontier orbitals match gas-phase density functional theory calculations, while a simplified linear combination of molecular orbitals model captures dominant trends. This bottom-up synthetic strategy enables precise control over nanoribbon composition and functionality, offering a versatile platform for engineering π-conjugated nanostructures with tailored optoelectronic properties.

On Au(111), an alkyne-terminated borazine derivative undergoes thermally induced cyclotrimerisation, forming nanoporous boronnitrogen-carbon networks featuring regular BN-doped patterns, with borazine cores preserved during the reaction as characterised by scanning tunnelling microscopy (STM) and X-ray photoelectron spectroscopy (XPS).