Bifunctional and Uniform Tungsten Nanoparticles as a Dual-Mode Sensor for Quercetin and Ratiometric Detection of Riboflavin

We report the successful synthesis of highly fluorescent tungsten nanoparticles (W NPs) featuring a cubic-like structure meticulously engineered through oleylamine functionalization. W NPs were synthesized using an integrated approach of solvothermal and ultrasonic methods, offering a cost-effective alternative to traditionally synthesized expensive nanoparticles. These W NPs exhibit robust blue emission at 439 nm with a quantum yield of 53%, serving as versatile dual-mode sensors for quercetin and riboflavin. For quercetin detection, fluorescence quenching yielded a low limit of detection (LOD) of 3 nM across a linear range of 30 nM to 76 μM. Additionally, a visible color shift from clear to yellow enables colorimetric detection with a LOD of 0.31 μM (linear range: 1 to 70 μM). The strategic functionalization of W NPs with oleylamine not only enhances their fluorescence properties but also introduces highly reactive surface sites. This modification facilitates the robust adsorption of quercetin, thereby driving a synergistic quenching effect that markedly improves sensitivity. Moreover, the W NPs serve as a remarkable bifunctional sensor for detecting riboflavin, showcasing impressive sensitivity. With a linear fluorescence response from 10 nM to 10 μM and a LOD of 4.4 nM, they embody the potential of innovation in sensing technology. Mechanistic investigations reveal that quercetin detection relies on the inner filter effect (IFE) and surface adsorption, while riboflavin detection likely involves IFE or Forster resonance energy transfer (FRET). This work establishes W NPs as a powerful platform for dual-mode selective sensing, showcasing the potential of strategic functionalization in advancing high-performance materials for optical sensing applications.