Pyrrolic-N-rich carbon dots (CDs) that exhibit an absorption peak in the first near-infrared (NIR) window region were developed using a one-step microwave-assisted hydrothermal synthesis. A high concentration of urea enabled the introduction of a large amount of pyrrolic-nitrogen on the CD surfaces. Upon optimization of the experimental conditions, the absorption peak of the CDs red-shifted from 550 to 650 nm. The resulting pyrrolic-N-rich CDs exhibited photothermal effects with high NIR photothermal efficiency (54.3%) and photoluminescence. The prepared CDs, which show a first NIR window absorption peak, photoluminescence, and negative surface charge, have the potential to be used as multifunctional nanocarriers for cell imaging and drug delivery and as photothermal agents in cancer therapy.

Synthesized transparent CQD–PVA composite films performed stable UV-A blocking, even after exposure to UV light for several days and elevated temperature.

This work demonstrated the production of highly crystalline, monodisperse fine metal particles with high density and purity using a simple, facile rapid spray heating process. In this technique, a starting solution including fine Ag particles, prepared using a liquid phase method, is sprayed into a horizontal furnace. After this spray heating step, the crystallinity and purity of the particles are greatly improved relative to those of the initial particles, while the morphology and size distribution are maintained. Consequently, the volume resistivity of the Ag particles is decreased from 6.4 × 10–3 Ω·cm (before spray heating) to 3.6 × 10–5 Ω·cm (after spray heating at 500 °C). Detailed analyses show that this significant increase in conductivity results from the improved crystallinity, purity, and density of the material. The rapid spray heating method proposed in this research could be applied to other metals with the potential to produce high-quality fine metal particles.

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