Abstract
Here we report the rational development of a carbon dot (CDs)-based fluorescent pH nanosensor by employing an active surface preservation strategy. More specifically, citric acid, urea and fluorescein were subjected to a one-pot hydrothermal treatment, which preserved fluorescein-like structures on the surface of the CDs. The obtained CDs showed pH-sensitive green emission, which can be used to determine pH variations from 3.7 to 12.1 by fluorescence enhancement. Moreover, the obtained nanoparticles showed excellent selectivity toward pH, fluorescence reversibility in different pH values, photostability, while being compatible with human cell lines (even at high concentrations). Furthermore, their performance as pH sensors was comparable with reference pH determination procedures. Thus, an active surface preservation strategy was successfully employed to develop fluorescence pH nanosensors in a rational manner and without post-synthesis functionalization strategies, which show potential for future use in pH determination.
Highlights
Carbon dots (CDs) are carbon-based nanoparticles with photoluminescent properties [1]
The morphology of CDs was evaluated by a high-resolution transmission electron microscopy (HR-TEM) on a FEI Talos F200X
QY is the fluorescence quantum yield, Grad is the gradient from the plot of integrated fluorescence intensity versus absorbance and η is the refractive index
Summary
Carbon dots (CDs) are carbon-based nanoparticles with photoluminescent properties [1]. To provide rationality to the process of CDs-based sensor development, post-synthesis functionalization strategies can be employed to add to the surface of CDs specific sensing moieties. These modifications tend to require time-consuming and costly postsynthesis steps [12,13]. The use of these precursors gives rise to health and environmental concerns, as residual QDs may eventually contaminate the environment by releasing toxic metal ions during their decay process [30,31] Their toxicity depends on various physicochemical properties, and environmental conditions, impairing their applicability and leading to the necessity for the development of safer and greener materials and synthesis [32]. CDs are suitable for pH-sensing, showing potential for future biological applications
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