ABSTRACT
In this paper, we investigate localized surface plasmon resonance (SPR) detection based on nanoislands. Theoretical calculation performed with rigorous coupled-wave analysis and analytical transfer matrix method using effective medium theory suggests improvement on nanoislands in the limit of detection and sensitivity over conventional thin film-based SPR detection. Experimental results obtained with non-specific detection of ambient adenovirus confirm the improvement by more than one order of magnitude increase in the limit of detection. The enhancement achieved with nanoislands was explored in connection with efficient overlap between target and near-field distribution produced by nanoislands.
Subject(s)
Adenoviridae/chemistry , Adenoviridae/isolation & purification , Biosensing Techniques/instrumentation , Nanoparticles/chemistry , Nanotechnology/instrumentation , Surface Plasmon Resonance/instrumentation , Virion/chemistry , Virion/isolation & purification , Equipment Design , Equipment Failure Analysis , Nanoparticles/ultrastructure , Reproducibility of Results , Sensitivity and SpecificityABSTRACT
We demonstrated enhanced localized surface plasmon resonance (SPR) biosensing based on subwavelength gold nanoarrays built on a thin gold film. Arrays of nanogratings (1D) and nanoholes (2D) with a period of 200 nm were fabricated by electron-beam lithography and used for the detection of avian influenza DNA hybridization. Experimental results showed that both nanoarrays provided significant sensitivity improvement and, especially, 1D nanogratings exhibited higher SPR signal amplification compared with 2D nanohole arrays. The sensitivity enhancement is associated with changes in surface-limited reaction area and strong interactions between bound molecules and localized plasmon fields. Our approach is expected to improve both the sensitivity and sensing resolution and can be applicable to label-free detection of DNA without amplification by polymerase chain reaction.
Subject(s)
Biosensing Techniques/methods , DNA, Viral/chemistry , Influenza A virus/genetics , Nanotechnology/methods , Nucleic Acid Hybridization/methods , Surface Plasmon Resonance/methods , Gold , Influenza A virus/isolation & purification , Oligonucleotide Array Sequence Analysis , Sensitivity and SpecificityABSTRACT
We investigate optimum plasmon-enhanced total-internal-reflection fluorescence imaging by metallic thin films and nanostructures. The enhancement is based on the mismatch between the conditions of plasmon resonance and maximal near-field intensity. We have calculated plasmon-associated near-field and far-field characteristics using rigorous coupled-wave analysis. Near-field intensity was experimentally measured with fluorescent beads on silver thin films, nanogratings, and nanoislands. The results for nanostructure-based plasmon excitation confirm that momentum mismatching when exciting plasmons can increase the consequent emission of fluorescence substantially. The improvement can be critical depending on the specific structure.
