Functionalized carbon dots as sensors for gold nanoparticles in spiked samples: Formation of nanohybrids

• Functionalization via amidation reaction of the Carbon Dots (CDs).
• Interaction of CDs and AuNPs due to the high affinity of thiol ending groups to Au.
• A static mechanism is involved in the quenching phenomenon.
• Formation of CD–AuNP nanohybrids.
• A selective method to determine AuNPs versus others gold species is presented.

This paper reports the synthesis, passivation and functionalization of luminescent carbon dots (CDs) possessing surface thiol ending groups. A simple procedure involving amidation of passivated carbon dots (p-CDs) with cysteamine boosts their photoluminescent properties and enables their use as easily controlled fluorescent nanosensors for determining citrate–gold nanoparticles (AuNPs). The mechanism behind the quenching phenomenon was established from fluorescence measurements at high temperatures and lifetime tests, and found to involve static quenching leading to the formation of CD–AuNP nanohybrids. A method for determining AuNPs in complex matrices was developed and validated by application to spiked drinking water and mussel tissues. The limits of detection and quantitation for AuNPs thus obtained were 0.20 and 0.66 nmol L–1, respectively.

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