In this study, the combination of novel valinomycin doped chitosan-graphene oxide (C-GO-V) thin film and surface plasmon resonance (SPR) system for potassium ion (K) detection has been developed. The novel C-GO-V thin film was deposited on the gold surface using spin coating technique. The system was used to monitor SPR signal for K in solution with and without C-GO-V thin film. The K can be detected by measuring the SPR signal when C-GO-V thin film is exposed to K in solution. The sensor produces a linear response for K ion up to 100ppm with sensitivity and detection limit of 0.00948°ppm and 0.001ppm, respectively. These results indicate that the C-GO-V film is high potential as a sensor element for K that has been proved by the SPR measurement.

Surface plasmon resonance sensor coated with hydrous ferric oxide-magnetite-reduced (Fe2H2O4-Fe3O4-rGO) graphene oxide nanocomposite film was demonstrated to detect two toxic heavy metals; Arsenic (III) [As(III)] and Arsenic (V) [As(V)] in aqueous solution. The proposed nanocomposite film exhibited successful absorption of As with enhanced sensitivity and selectivity. Resultantly, when tested with different concentrations of As(III) and As(V), (0.1-1.0 ppb) the sensor ranged linearly with sensitivity of 2.196 °ppb-1 and 0.960 °ppb-1, respectively, and achieved a detection limit as low as 0.1 ppb. These results validate the potential of Fe2H2O4-Fe3O4-rGO nanocomposite material for optical sensing applications in as detection.

The exponential escalation of dengue cases has indeed become a global health crisis. This work elaborates on the development of a biofunctionalized tapered optical fiber (TOF) based sensor with the integration of polyamidoamine (PAMAM) dendrimer for the detection of dengue E protein. The dimension of the TOF generated an evanescent field that was sensitive to any changes in the external medium while the integration of PAMAM promoted more adhesion of bio-recognition molecules; anti-DENV II E protein antibodies; that were complementary to the targeted protein. This in return created more active sites for the absorption of DENV II E proteins onto the tapered region. The resolution and detection limit of the sensor are 19.53 nm/nM and 1 pM, respectively with Kd = 1.02 × 10−10 M.

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