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<p>Nitrogen-enriched graphene quantum dots (N-GQDs) were successfully synthesized via a one-step hydrothermal method using biomass as the carbon source and urea as the nitrogen dopant. The reaction was carried out in deionized water as a green solvent, promoting an environmentally friendly approach. The optical and structural properties of the resulting N-GQDs were characterized using UV–visible spectrophotometry, spectrofluorometry, attenuated total reflectance (ATR)/Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, x-ray diffraction (XRD), and transmission electron microscopy (TEM)/high-resolution TEM (HRTEM) analyses. The synthesized N-GQDs showed high quantum yield up to 28%. Notably, the synthesized N-GQDs showed enhanced sensitivity and distinct selectivity for Fe<sup>3+</sup> ions over other metal ions, as evidenced by a significant fluorescence quenching effect upon Fe<sup>3+</sup> addition. A linear decrease in fluorescence intensity was observed with increasing Fe<sup>3+</sup> concentrations, indicating a broad detection range (0–600&#xa0;μM) and a low detection limit of 0.023&#xa0;μM. The interaction mechanism between Fe<sup>3+</sup> and N-GQDs was further analyzed through density functional theory (DFT) calculations, revealing that nitrogen doping, along with oxygen-containing functional groups, plays a crucial role in stabilizing the coordination and electron transfer processes. Moreover, real water sample tests using tap water confirmed the practical applicability of N-GQDs, showing high recovery rates (96.8–103.4%), thereby demonstrating their reliability for detecting Fe<sup>3+</sup> contamination. These findings suggest that N-GQDs derived from biomass offer a promising platform for the development of sustainable, low-cost, and effective fluorescent sensors for ferric ion detection.</p> Graphical Abstract <p></p>

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Nitrogen-Enriched Graphene Quantum Dots from Biomass as Fluorescent Probes for Fe3+ Ions: A Combined Experimental and DFT Study

  • 期刊论文

  • 发表日期：

    2025年11月1日

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  • Fathah Dian Sari,
  • Bimo Isya Rohmatulloh,
  • Anis Febri Nilan Sari,
  • Puji Handayani Putri,
  • Arif Lukmantoro,
  • Moh. Adhib Ulil Absor

摘要

Nitrogen-enriched graphene quantum dots (N-GQDs) were successfully synthesized via a one-step hydrothermal method using biomass as the carbon source and urea as the nitrogen dopant. The reaction was carried out in deionized water as a green solvent, promoting an environmentally friendly approach. The optical and structural properties of the resulting N-GQDs were characterized using UV–visible spectrophotometry, spectrofluorometry, attenuated total reflectance (ATR)/Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy, x-ray diffraction (XRD), and transmission electron microscopy (TEM)/high-resolution TEM (HRTEM) analyses. The synthesized N-GQDs showed high quantum yield up to 28%. Notably, the synthesized N-GQDs showed enhanced sensitivity and distinct selectivity for Fe3+ ions over other metal ions, as evidenced by a significant fluorescence quenching effect upon Fe3+ addition. A linear decrease in fluorescence intensity was observed with increasing Fe3+ concentrations, indicating a broad detection range (0–600 μM) and a low detection limit of 0.023 μM. The interaction mechanism between Fe3+ and N-GQDs was further analyzed through density functional theory (DFT) calculations, revealing that nitrogen doping, along with oxygen-containing functional groups, plays a crucial role in stabilizing the coordination and electron transfer processes. Moreover, real water sample tests using tap water confirmed the practical applicability of N-GQDs, showing high recovery rates (96.8–103.4%), thereby demonstrating their reliability for detecting Fe3+ contamination. These findings suggest that N-GQDs derived from biomass offer a promising platform for the development of sustainable, low-cost, and effective fluorescent sensors for ferric ion detection.

Graphical Abstract