We introduce a label-free biosensing
cellulose strip sensor with surface-enhanced Raman spectroscopy (SERS)-encoded bimetallic core@shell nanoparticles. Bimetallic nanoparticles consisting of a synthesis of core Ag nanoparticles (AgNP) and a synthesis of shell
gold nanoparticles (AuNPs) were fabricated on a
cellulose substrate by two-stage successive ionic layer absorption and reaction (
SILAR) techniques. The bimetallic nanoparticle-enhanced localized surface plasmon resonance (LSPR) effects were theoretically verified by computational calculations with finite
element models of optimized bimetallic nanoparticles interacting with an incident
laser source. Well-dispersed raspberry-like bimetallic nanoparticles with highly polycrystalline structure were confirmed through X-ray and electron analyses despite ionic reaction synthesis. The stability against
silver oxidation and high sensitivity with superior SERS enhancement factor (EF) of the low-cost SERS-encoded
cellulose strip, which achieved 3.98 × 108 SERS-EF, 6.1%-RSD reproducibility, and <10%-degraded sustainability, implicated the possibility of practical applications in high analytical screening methods, such as single-molecule detection. The remarkable sensitivity and selectivity of this bimetallic biosensing strip in determining aquatic toxicities for prohibited drugs, such as
aniline,
sodium azide, and
malachite green, as well as monitoring the
breast cancer progression for urine, confirmed its potential as a low-cost label-free point-of-care test chip for the early diagnosis of human diseases.