Fabrication of Pd-Co nanoparticles decorated graphitic carbon nitride/zinc ferrite platform for electrochemical estimation of vitamin D

• Synthesis of g-C 3 N 4 -ZnFe 2 O 4 (ZFCN) hybrid with enhanced surface area . • Elevated electrochemical aspect of Pd-Co nanoparticles modified ZFCN template. • Affinity based tethering of biotinylated-aptamer onto streptavidin/Pd-Co/ZFCN probe. • Sensitive impedimetric detection of 25(OH)D 3 upto 0.064 pg mL −1 level. • Adequate testing of real serum samples as validated by ELISA technique. High prevalence of vitamin D deficiency coupled with severe repercussions of its long-standing prevalence necessitates the regular detection of vitamin D levels. In this regard, some electrochemical aptasensing strategies have been developed, however the testing of biosensor with real serum samples is scarce which is fundamental to establish the clinical applicability of a biosensor. Hence, a novel Pd-Co/ZFCN/FTO based aptasensing platform has been designed for serum assessment of 25(OH)D 3 levels. Initially, ZFCN was obtained by reinforcing carboxylated graphitic carbon nitride (C-g-C 3 N 4 ) and zinc ferrite (ZnFe 2 O 4 ), leading to five-fold enhanced surface area. The formed ZFCN/FTO template was further decorated with Pd doped Co nanoparticles (Pd-Co NPs), generating Pd-Co/ZFCN/FTO platform as characterized by various surface characterization techniques including XRD, XPS and FESEM, and electrochemical techniques. Further, the biorecognition element (5′ biotinylated-aptamer) was incurred by leveraging robust streptavidin–biotin interactions. The resultant aptaelectrode was utilized for selective detection of 25(OH)D 3 using electrochemical impedance spectroscopy technique, delivering sensitivity, linear response range, limit of detection and shelf life of 196 % (pg mL −1 ) −1 cm −2 , 0.001–10 6 pg mL −1 , 0.064 pg mL −1 and 60 days, respectively. Moreover, the aptasensor marked satisfactory performance with serum samples as validated by ELISA technique, illuminating the potential of present aptasensing approach in biomedical field.