Silver nanoparticles embedded on mesoporous-silica modified reduced graphene-oxide nanosheets for SERS detection of uremic toxins and parathyroid hormone

Silver nanoparticles (AgNPs) were successfully immobilized onto mesoporous silica (MPS)-modified reduced graphene oxide (mrGO) nanosheets to form AgNPs@mrGO surface-enhanced Raman scattering (SERS)-active substrates for bio-detection. Using the highly porous structure of MPS with the beneficial Raman enhancement of rGO nanosheets as templates, the homogeneous dispersion of AgNPs was self-assembled on a floating 2D platform of mrGO nanosheets. These were evaluated by transmission electron microscopy, X-ray diffraction, and UV-Vis spectroscopy. The pore-channels (similar to 5 nm) of mrGO could be applied as templates to manipulate the interparticle gaps and particle size of AgNPs to obtain uniform nanoparticle arrays. Compared with AgNPs@mrGO and AgNPs@rGO (rGO substrate without MPS), the signal-to-background ratio (S/B ratio) was enhanced 6.9 times by mrGO addition. This indicates that the increase in SEAS intensity and reduction in the background by using the template of the mrGO. AgNPs@mrGO SERS-active substrate can be exploited for rapid and sensitive detection of uremic toxins (creatinine, uric acid, and urea) and parathyroid hormone (PTH) for chronic kidney disease. The rapid, reproducible, and ultrasensitive detection of uremic toxins (< 10(-6) M of uric acid) and PTH (< 0.2 ng/mL) could be achieved without labeling.