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Single-component, metal-free white light emitters with integrated photonic functionalities are highly attractive for solid-state lighting and integrated photonic applications. Here, we report carbonized polymer microspheres that exhibit efficient singlecomponent white light emission (WLE) together with excitation-tunable visible-to-nearinfrared (VIS-NIR) whispering gallery mode (WGM) emission. The microspheres are synthesized via a hydrothermal crosslinking reaction between the natural peptide ε-poly-Llysine and citric acid, yielding smooth microcavities with bright cyan emission. Incorporation of ortho-phenylenediamine (OPD) during synthesis enables control over the internal structure and promotes the in-situ formation of phenazine-like polycyclic aromatic hydrocarbon (PAH) domains. The extended π-conjugation of the PAHs enhances visible-light absorption, leading to emission spanning the visible to NIR spectral region. Upon ultraviolet excitation, the microspheres exhibit broadband single-component WLE arising from efficient intracavity energy transfer. The smooth spherical morphology and heterogeneous aromatic domains provide strong optical confinement and excitation wavelength dependent emission, resulting in amplified spontaneous emission mediated by WGM resonances. By varying the excitation wavelength, WGM-assisted emission spanning the entire VIS-NIR spectral region is achieved. This work introduces a rare-earth-and metal-free carbonized polymer microcavity platform that integrates WLE with tunable WGM amplification, offering new opportunities for multifunctional optoelectronic and photonic devices.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: Carbonized polymer microspheres, white light emission, near-infrared, whispering gallery mode, microcavities, amplified spontaneous emission

Date published: 2026-09-04

Publisher: Royal Society of Chemistry (RSC)

Journal:

• RSC Applied Interfaces (ISSN: 27553701)

Funding:

• Japan Society for the Promotion of Science 24K17589

Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.8638

First published URL: https://doi.org/10.1039/d6lf00065g

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Updated at: 2026-10-05 19:33:08 +0900

Published on MDR: 2026-10-06 10:22:54 +0900