Optical sensing of hydrogen peroxide using starch capped silver nanoparticles, synthesis, optimization and detection in urine

Silver nanoparticles were synthesized using starch as a capping shell, AgNO₃ as a source of silver and sodium borohydride (NaBH₄) as a reducing agent. The nanoparticles were confirmed by their localized surface plasmonic resonance (LSPR) Ultraviolet-visible (UV–Vis) absorbance at 403 nm. Dynamic light scattering (DLS) reveals that starch capped silver nanoparticles (SAgNPs) mean size were 4.13 nm/diameter; the structure of SAgNPs was identified as face-centered cubic (FCC) using XRD analysis. HRTEM micrograph and contrast intensity profile confirms Ag atomic lattices at a distance of 2.35 Å and 2.03 Å corresponding to (111) and (200) hkl plane. The scope of SAgNPs to detect hydrogen peroxide (H₂O₂) in aqueous media and in urine samples was investigated. Volumes of SAgNPs, pH, temperature and time effect were used as parameters to optimize the detection of H₂O₂. The SAgNPs assay was compared with a commercially available assay kit. Linear responses were obtained with slopes and regression factors of (0.1025; r²=0.9883) and (0.0776; r²=0.9940) for SAgNPs and the assay kit respectively. Limit of detection (LOD) of 3.70 µM was obtained in the 0.45–121 µM range while, a LOD of 10.5 nM was obtained in the 4.70–32.0 nM range for the SAgNPs test. Values in the range of (9.22 ± 0.30 – 17.89 ± 0.28) and (8.43 ± 0.06 – 26.81 ± 0.19) μM of H₂O₂ were assessed by using SAgNPs and assay kit respectively, in urine samples collected from seven apparently healthy men aged between 20 and 40 years old.