Carbon dots and fluorescein: The ideal FRET pair for the fabrication of a precise and fully reversible ammonia sensor

Abstract

Monitoring of ammonia in the human breath is of paramount importance to monitor diseases link to liver and kidney mulfunctioning. The present paper describes a solid-state optical ammonia sensor based on Förster resonance energy transfer (FRET) between narrowly dispersed blue-emitting carbon nanodots (CNDs) as FRET donor and fluorescein as FRET acceptor. The fluorophores were physically entrapped in a close to superhydrophobic sol-gel matrix, in turn deposited on a PVDF-HFP electrospun fiber membrane. The sensor shows a linear calibration with a remarkably low limit of detection, i.e., 110 ppb, and adequate reproducibility up to six N2/NH3 cycles.

Optical glucose sensing using ethanolamine–polyborate complexes

“…Such optical behaviour has also been previously observed in carbon nanodots (CNDs), 38 although in this study the formation of CNDs can be excluded as the complex was not retained by dialysis performed with the lowest cut-off membrane size (i.e. 100-500 Da) and AUC results shows a monodisperse size for the amino-polyborates of 5 Å. M. Fu et al 17 mimicked the CNDs excitation-dependent emission behaviour by mixing polycyclic aromatic fluorophores with different fluorescence properties, thus such feature might be the consequence of the heterogeneity in fluorescence emission of different boroxole-amine complexes.…”

Recent development in carbon dot-based gas sensors

“…Amphiphilic CDs have been found to exhibit solvatochromism which is a phenomenon where the absorption and emission spectra have a strong dependence with the solvent polarity [5,12]. On aggregation of CDs in unsupported solid powder or solution, no luminescence is observed due to non-radiative internal conversion of excitons within CDs energy traps and states as shown in figure 6b leading to agglomeration induced quenching [30,39,82].…”

“…Changes occurring in the energy gap, HOMO and LUMO levels of CD during adsorption of a target molecule was studied [49,88]. But optical sensors may suffer from drift in the final signal depending on loading of fluorophores into the sensor system which affects their reproducibility [82]. Modulation of different optical properties of CDs is adopted as a sensor signal.…”

Current Advancements in Transdermal Biosensing and Targeted Drug Delivery

“…Quantum dots are semiconductor nanocrystals in the size range of 0.2 to 100 nm (crystals in the size range of 2 to 10 nm are typically used). Due to the small size of these nanoparticles, they exhibit discrete energy levels with the behavior of the electrons and holes in their orbitals governed by quantum mechanics; as a result, small changes in their size (which can be controlled by fabrication techniques) cause changes in their fluorescence properties [30,31,32]. These nanostructures have tunable fluorescence properties by controlling their size, material composition, and fabrication temperature; consequently, they have the ability to outperform organic fluorophores due to their strong signal, tunable emission wavelengths, narrow emission profiles, and potential for use with only one light source for excitation for a variety of emission signals.…”

“…These nanostructures have tunable fluorescence properties by controlling their size, material composition, and fabrication temperature; consequently, they have the ability to outperform organic fluorophores due to their strong signal, tunable emission wavelengths, narrow emission profiles, and potential for use with only one light source for excitation for a variety of emission signals. While these nanocrystals have gained attention for a variety of biomedical applications (e.g., in vivo imaging, drug delivery systems), they also have applications in sensing technology [31]. The excellent optical properties of QDs have allowed them to function in various FRET assays for the detection of biologically relevant molecules (e.g., nucleic acids, proteins, and antibodies).…”