Plasmonic Silver Nanowire Structures for Two-Dimensional Multiple-Digit Molecular Data Storage Application

Abstract

The surface-enhanced Raman scattering (SERS) spectrum exhibits huge potential as an alternative data storage element. Using plasmonic nanostructures as the physical building blocks where probe molecules are adsorbed, their corresponding structural and SERS information are stored within a finite volume of plasmonic nanostructures. However, the current SERS development is hampered by the difficulty in fabricating quantitative and homogeneous SERS platforms. Here, we introduce the concept of "plasmonic molecular data storage" using SERS intensity as the basic data storage element (or digit). SERS signal is quantitatively tunable by manipulating the orientation (hence the localized surface plasmon modes) of the respective nanowire nanostructures to achieve multiple-digit SERS intensity data storage. We address the reproducibility problem by fabricating homogeneous plasmonic nanowire structures using two-photon lithography and thermal evaporation. Silver (Ag) nanowires of different orientations carrying different digits of molecular information can be combined to form sophisticated 2D geometrical structures, such as geometrical patterns, letters in the alphabet, and complex tessellated reptiles to impart multiple-digit-per-microstructure data storage. In particular, a 7-digit SERS information storage system has been achieved by tuning the Ag nanowires' orientation from 0° to 90° at 15° intervals. Spatial data, especially the coordinates and topology, brought about by the predefined Ag nanowire structures create an additional level of information to the plasmonic data storage system. Using 1 byte (8 binary digits) as the basis of comparison, our 7-digit platform is able to store 22 500-fold denser information than the binary system. In addition, our plasmonic nanowire data storage system also provides unique physical morphology and chemical Raman information. It is analogous to optical data storage, but it acquires richer multidimensional information and exhibits higher spectral resolution than the broader-band response of conventional optical spectroscopic techniques.