Gold Nanoparticle Functionalized Carrageenan Polysaccharide and Zeolitic Imidazolate Framework-8: Biopolymer Nanocomposite for Selective Serotonin Sensing

Herein, a biopolymer, Carrageenan (CA), decorated with gold nanoparticles (Au NPs), showed a highly stable structure with more active sites for serving as an electrochemical sensing platform. Furthermore, the adsorption of Zeolitic imidazolate framework-8 (ZIF-8) on Au NPs decorated CA (Au@CA) structure resulted in a strong hybrid composite formation for the sensitive and selective electrochemical sensing of serotonin (5-HT), a neurotransmitter. The morphology of ZIF-8 decorated Au-modified CA (Au@CA/ZIF-8) based hybrid nanocomposite was studied by scanning electron microscopy and its affirmed interactions was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and UV–visible spectroscopy. After that, the electrochemical studies revealed its excellent conductivity and sensing behaviour towards 5-HT (0.15 V) at a sensitivity of 7.232 μA with a wide linear range of 10 nM to 1 mM and a lower detection limit of 2 nM. Also, the composite has achieved good cyclic and long-term stability, selectivity, and reproducibility. Furthermore, the real sample results have demonstrated its efficient sensing of 5-HT in urine samples with excellent recoveries, which suggests that the Au@CA/ZIF-8 hybrid composite is a perfect transducer material for a 5-HT biosensor.