Details

Autor(en) / Beteiligte

• Ochi, Yukino
• Otani, Ayano
• Katakami, Rika
• Ogura, Akihiro
• Takao, Ken-ichi
• Iso, Yoshiki
• Isobe, Tetsuhiko

Titel

Open system massive synthesis of narrow-band blue and green fluorescent graphene quantum dots and their application in water sensing

Ist Teil von

• Journal of materials chemistry. C, Materials for optical and electronic devices, 2024-05, Vol.12 (18), p.6548-6558

Ort / Verlag

Cambridge: Royal Society of Chemistry

Erscheinungsjahr

2024

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Graphene quantum dots (GQDs) are environmentally friendly fluorescent carbon-based nanomaterials. However, there is no report on the massive synthesis of GQDs with narrow-band fluorescence and a high photoluminescence quantum yield (PLQY) using a simple liquid-phase method under atmospheric conditions. In this study, GQDs were successfully synthesized in ∼100% product yield by heating phloroglucinol (PG) with Na 3 PO 4 ·12H 2 O in 1,2-pentanediol at 180 °C for 6 h in an open system with air flow, followed by dialysis purification. The high product yield was attributed to the addition of Na 3 PO 4 ·12H 2 O as a base catalyst, which promoted the dehydration-condensation reaction between PG molecules. The dispersion of PG derived GQDs (PG-GQDs) in ethanol resulted in blue fluorescence with a full width at half maximum of 32 nm and a PLQY of 54%. Further purification of PG-GQDs by silica gel column chromatography improved the PLQY to 75%. Fourier-transform infrared spectroscopy, 1 H nuclear magnetic resonance spectroscopy, and X-ray photoelectron spectroscopy confirmed that dehydration-condensation reactions occurred not only between PGs but also between GQDs and 1,2-pentanediol. The binding of 1,2-pentanediol to the edges of GQDs suppressed the stacking of GQDs and prevented concentration quenching, resulting in a high PLQY. PG-GQDs exhibited negative fluorescence solvatochromism, i.e. , the fluorescence wavelength blue-shifted with increasing solvent polarity. Dispersion of PG-GQDs in N -methyl-2-pyrrolidone (MP) resulted in green fluorescence with a PLQY of 96%. Dispersion of PG-GQDs in water resulted in blue fluorescence and a low PLQY of 6% at pH 7, while the PLQY was more than 50% at pH ≥ 11. Using these properties, the sensing of water (pH 13) in MP was investigated. The results showed that as the water content was increased from 0% to 100%, the fluorescence color gradually changed from green to blue and the fluorescence wavelength continuously shifted from 514 nm to 466 nm, indicating their applicability in water sensing. PG-derived graphene quantum dots (GQDs) were obtained with 99.4% product yield and exhibited narrow-band blue fluorescence with a high quantum yield.