Plasmonically Enhanced Vibrational Biospectroscopy Using Low‐Cost Infrared Antenna Arrays by Nanostencil Lithography

Abstract

798 wileyonlinelibrary.com COMMUNICATION www.MaterialsViews.com www.advopticalmat.dePlasmonics [1][2][3][4][5][6][7][8] is leading to signifi cant advancements and innovations in photonic technologies including biomedicine, [ 9,10 ] energy harvesting [ 11,12 ] and telecommunications. [ 13 ] For biomedical applications, plasmon-based bio nanosensors [14][15][16][17] consisting of metallic structures could overcome limitations of conventional biosensors through their unique ability to manipulate light at nanoscale dimensions. Plasmonic biosensors could enable detection of medically important proteins and high throughput screening of their interactions. [ 18 ] One of the powerful and label free optical techniques for determining structural and conformational properties of proteins and protein interactions is Infrared (IR) Spectroscopy. [ 19 ] However, sensitivity of conventional IR spectroscopy is limited. Thus, relatively large quantities of analytes are required to have suffi cient absorption signal. Recently, resonant plasmonic nanoantennas have been used to enhance the absorption signals of surface bound protein monolayers. [20][21][22][23][24][25] The general concept is to electromagnetically couple the vibrational modes of the proteins to the optical modes of the nanoantennas. Plasmonic antennas boost the interaction between the light and the biomolecules through strongly enhanced near fi elds and increase the sensitivity to attomolar levels. [ 26 ] Such near fi eld interactions can be controlled through the geometry and composition of the metallic nanostructures in arrays. [ 27,28 ] Therefore even slight tailoring of the nanoantenna and its arrangement could signifi cantly alter the performance of surface enhanced IR spectroscopy technique. In order to realize precisely tailored plasmonic antennas, highly controllable nanofabrication techniques offering fl exible design capability are needed. Conventional electron and ion beam based lithography tools enable tremendous nanoscale feature fl exibility. However their limitations such as high operational cost and low throughput have motivated development of new nanofabrication techniques. There are a few inexpensive innovative approaches demonstrated recently including nano imprinting, [ 29 ] PEEL (a combination of phase-shifting photolithography, etching, electron-beam deposition and lift-off of the fi lm), [ 30 ] hole mask colloidal lithography, [ 31 ] and nano bridging. [ 32 ] However they either require multiple pattern transfer steps that limits the resolution or they lack the ability of precise arraying and shape control at nanoscale dimensions.Towards this end, we recently presented that nanostencil lithography (NSL) could be utilized for high resolution, high throughput, and low cost nanofabrication of plasmonic nanoantennas with great design fl exibility on conventional as well as fl exible and polymeric substrates. [ 33,34 ] Uniquely, NSL preserves the fl exibility of beam based lithography tools for creating nanoantennas in a variety of shapes and arran...

High resolution fabrication of nanostructures using controlled proximity nanostencil lithography

“…However, small gold particles, attributed to surface diffusion of gold following deposition, are visible 6,33 . If needed, previous reports have demonstrated the ability to selectively remove these smaller gold particles with a short dry etch 34 . The gold nanodot size was found to be consistently 2 -3 nm smaller than the corresponding hole in the stencil mask (Fig.…”

Plasmonic cross-junction ring antenna implementation for field enhancement

“…For optical imaging and spectrometry in bio sensing, the enhancement of E-field is important to achieve higher resolution and detection [16]. So to achieve this aim, different methods are implemented such as array antenna with FSS (frequency selective surface) by Altug et al [17][18], or multilayer nano ring structure [12]. Also, gap structures are noticed for this aim and different models are presented [19].…”

Periodic array-based substrates for surface-enhanced infrared spectroscopy

“…One of the alternative is nanostencil lithography [80]. The authors used this technique to fabricate arrays of linear nanoantennas and applied these for antibody assays and detection of immunologically important small proteins.…”