Blue luminescent graphene quantum dot conjugated cysteamine functionalized-gold nanoparticles (GQD-AuNPs) for sensing hazardous dye Erythrosine B

One-step synthesis of fluorescent graphene quantum dots as an effective fluorescence probe for vanillin detection

“…3 In addition, the quantum connement effect and the edge (armchair or zigzag) effect impart GQDs with special properties such as low toxicity, high biocompatibility, high uorescent activity, robust chemical inertness, and excellent photostability. [4][5][6] Owing to these properties, GQDs have immense potential applications in photovoltaic devices, 7 bioimaging instruments, 8 sensors and biosensors, 9,10 etc. Until now, GQDs have been used as a uorescent probe for the detection of a broad range of analytes such as metal ions, [11][12][13][14][15] organic matter, 16,17 proteins, 18 and other biomolecules.…”

Minute-scale detection of SARS-CoV-2 using a low-cost biosensor composed of pencil graphite electrodes

“…The ACE2 anchoring step was successfully confirmed by the presence of an amide band at 1,650 cm −1 in our Fourier transform Minute-scale detection of SARS-CoV-2 using a low-cost biosensor composed of pencil graphite electrodes infrared (FTIR) spectroscopy analysis (SI Appendix, Fig. S1) (26,27). The functionalization of GPE with AuNPs-cys led to decreased values of R CT (47.6 ± 1.3 Ω) and increased ip (410.5 ± 13.7…”

“…These data indicate that GA acts as an electrical insulator hindering the electron transfer at the interface of the WE by preventing the redox probe from reaching the GPE surface (24,25). AuNPs-cys were then anchored covalently to the surface of the GPE (blue line) through an amide bond between the amine group from the cys and the aldehyde groups from the glutaraldehyde (26). The ACE2 anchoring step was successfully confirmed by the presence of an amide band at 1,650 cm −1 in our Fourier transform Minute-scale detection of SARS-CoV-2 using a low-cost biosensor composed of pencil graphite electrodes infrared (FTIR) spectroscopy analysis (SI Appendix, Fig.…”

“…The cys presents an amine group (−NH 3 + ) and a mercaptan group (−SH) in its extremities, the latter of which favorably binds onto the AuNPs surface through an Au-S bond. Thus, cys serves to provide greater stability to the AuNPs due to the electrostatic repulsion process among the amine groups, which generates free positive charges (26,43,45).…”

“…This process allowed the graphite surface to be functionalized with aldehyde groups. Then, the modified graphite substrate was kept in a AuNPs-cys solution with protonated amine groups from cys at pH 7.4, which enabled covalent anchoring of the AuNPs to the substrate by the formation of an amide bond (26). The AuNPs-cys presented a maximum adsorption time of 75 min and, after 100 min, the AuNPs-cys presented low adsorption to the substrate, and its color gradually faded (SI Appendix, Fig.…”