Confined assembly of size-tunable silver nanoprisms on flexible Teflon tapes as highly active SERS hotspots for ultralow-level sensing of DNA and glucose

Abstract

The design of smart and advanced sensors facilitates highly sensitive optical detection platforms for biomolecules. Herein, we attempted the confined assembly of silver nanoprisms (SNPs) on hydrophobic Teflon tapes to design a highly flexible and ultrasensitive biosensing platform for DNA and glucose. We investigated the sensor characteristics including morphological, optical, and SERS activities as a function of nanoparticle size. Pyramidal SNPs were synthesized, whose size was tuned by varying the bromide ion concentrations. The size of SNPs was decreased with an increase in bromide ion concentrations, where quasi-spherical nanoparticles were formed at higher bromide content. The hydrophobic Teflon surface caused considerable constrain during the evaporation of nanoparticle suspension, leading to highly confined SNPs. SERS activities of Teflon/SNP sensors were tuned by varying the size of SNPs, where a size of ∼34 nm exhibited the highest signal enhancement. The optimum Teflon/SNP sensor showed an enhancement factor of 1.3 × 109 with high stability and excellent reproducibility. Teflon/SNP sensor was further exploited to detect DNA and glucose in a label-free method, exhibiting sensitivities of approximately 13.6 fg/µL and 5 µM, respectively. Real-time monitoring of DNA and glucose from saliva was also investigated. Teflon/SNP substrates were found to be excellent biosensing platforms for ultralow-level sensing of biomolecules in a rapid and cost-effective manner.