Abstract
This work explores the alternative use of noble metal nanowire systems in large-scale array configurations to exploit both the nanowires’ conductive nature and localized surface plasmon resonance (LSPR). The first known nanowire-based system has been constructed, with which optical signals are influenced by the simultaneous application of electrochemical potentials. Optical characterization of nanowire arrays was performed by measuring the bulk refractive index sensitivity and the limit of detection. The formation of an electrical double layer was controlled in NaCl solutions to study the effect of local refractive index changes on the spectral response. Resonance peak shifts of over 4 nm, a bulk refractive index sensitivity up to 115 nm/RIU and a limit of detection as low as 4.5 × 10−4 RIU were obtained for gold nanowire arrays. Simulations with the Multiple Multipole Program (MMP) confirm such bulk refractive index sensitivities. Initial experiments demonstrated successful optical biosensing using a novel form of particle-based nanowire arrays. In addition, the formation of an ionic layer (Stern-layer) upon applying an electrochemical potential was also monitored by the shift of the plasmon resonance.
Highlights
In this work we present various designs for nanowire arrays, their fabrication, their optical characterization and their potential inelectrochemical sensing applications
To further characterize the sensor performance of the nanowire arrays and to compare different sensor architectures, the bulk refractive index sensitivity mLSPR was determined by the relation ∆λ = mLSPR ∙ ∆nmedium in units of nm/RIU (Refractive Index Unit)
As a first step towards biosensing, the use of nanofabricated particle-based nanowire/nanoline arrays to measure the adhesion of biomolecules has been demonstrated
Summary
In this work we present various designs for nanowire arrays, their fabrication, their optical characterization and their potential in (bio-)electrochemical sensing applications. The creation of a combined optical-electrical system designed for the nanoscale with noble metal nanowire arrays should offer a unique and powerful new platform, which will enable more complex chemical sensing and biosensing applications, as well as open new possibilities to explore the fundamental in situ behavior of nanowires. The favorable electrical properties of certain materials containing e.g., silicon [6,7,8,9], gallium [10], cadmium [11,12], titanium [13], or carbon (i.e., carbon nanotube-based FET devices) [4,5] have yielded promising results in chemical sensing, biosensing and integrated electronics Such nanowires represent very attractive bioelectrochemical transducer components, since their conductance is sensitive to surface perturbations induced by biochemical analytes [14,15]. Similar, yet alternative methods for self-assembled or particle-based nanowires can be found in the works of Blech et al and Hung et al [27,28]
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