▎ 摘　　要

In the current scenario, the dominance of cancer is becoming a disastrous threat to mankind. Therefore, an advanced analytical approach is desired as the need of the hour for early diagnosis to curb the menace of cancer. In this context, the present work reports the development of nano surface energy transfer (NSET) based fluo-rescent immunosensor for carcinoembryonic antigen (CEA) detection utilizing protein functionalized graphene quantum dots (anti-CEA/amine-GQDs) and a nanocomposite of nanostructured gold and reduced graphene oxide (AuNPs@rGO) as energy donor-acceptor pair, respectively. The obtained AuNPs@rGO nanocomposite has been characterized by different advanced analytical techniques. The functionality of the biosensor depends on quenching the fluorescence of anti-CEA/amine-GQDs donor species by AuNPs@rGO acceptor species, followed by the gradual recovery of GQDs' fluorescence after CEA addition. The efficient energy transfer kinetics have been envisaged by utilizing the AuNPs@rGO nanocomposite as a dual-quencher nanoprobe that revealed improved energy transfer and quenching efficiency (-62 %, 88 %) compared to AuNPs (-43 %, 81 %) as a single quencher. Further, the developed biosensing platform successfully detected CEA biomarker with notable bio-sensing parameters, including a wider linear detection range (0.001-500 ng mL-1), fast response time (24 min), and a significantly low detection limit (0.35 pg mL-1).