Carboxymethyl chitosan/graphene oxide/silver nanotriangles nanohybrid as the sensing materials for the enhancement of ammonia localized surface plasmon resonance sensor

Abstract

This work reports the application of silver nanotriangles (AgNT) incorporated with chitosan/graphene oxide (Chit/GO) and carboxymethyl chitosan/graphene oxide (CMChit/GO) for the enhancement of ammonium localized surface plasmon resonance (SPR) sensor. The ammonium is detected through the hydrogen bonding between the hydroxyl functional group on the sensing material surface with ammonium. AgNT was successfully synthesized via the direct chemical reduction method. The appearance of three peaks in UV–visible analysis, 334, 486 and 677 nm corresponded to the out of plane quadrupole resonance, anisotropic nanoparticles, and in-plane dipole resonance formations, respectively. The morphology analysis by FESEM exhibits that the AgNT has a diameter of 45.16 nm. Zeta analysis depicts the average size distribution and surface potential of AgNT with 16.53 d.nm and −34.5 mV, respectively. Meanwhile, Chit/GO derivatives were synthesized via the solution mixing method. The AFM analysis resulted in the surface roughness for Chit/GO and CMChit/GO with 28.65 nm and 20.43, respectively, due to the abundance of electronegative groups on their surface, which provides more active sites for ammonium attachment. Chit/GO and CMChit/GO were incorporated with AgNT before the sensor performance analysis. In localized SPR sensing, Chit/GO/AgNT and CMChit/GO/AgNT exhibit the sensitivity of 0.39 and 2.41 nm ppm−1, respectively.