UV-Laser Interference Lithography for Local Functionalization of Plasmonic Nanostructures with Responsive Hydrogel

Abstract

A novel approach to local functionalization of plasmonic hotspots at gold nanoparticles with biofunctional moieties is reported. It relies on photocrosslinking and attachment of a responsive hydrogel binding matrix by the use of a UV interference field. A thermoresponsive poly(N-isopropylacrylamide)-based (pNIPAAm) hydrogel with photocrosslinkable benzophenone groups and carboxylic groups for its postmodification was employed. UV-laser interference lithography with a phase mask configuration allowed for the generation of a high-contrast interference field that was used for the recording of periodic arrays of pNIPAAm-based hydrogel features with the size as small as 170 nm. These hydrogel arrays were overlaid and attached on the top of periodic arrays of gold nanoparticles, exhibiting a diameter of 130 nm and employed as a three-dimensional binding matrix in a plasmonic biosensor. Such a hybrid material was postmodified with ligand biomolecules and utilized for plasmonenhanced fluorescence readout of an immunoassay. Additional enhancement of the fluorescence sensor signal by the collapse of the responsive hydrogel binding matrix that compacts the target analyte at the plasmonic hotspot is demonstrated.

Plasmonic nanomaterials with responsive polymer hydrogels for sensing and actuation

“… 117 Alternatively, lithography allows for the preparation of controlled shape of metallic nanoparticles at a solid surface and, for example, arrays of cylindrical gold nanoparticles were fabricated and wrapped by pNIPAAm-based hydrogel caps for their rapid actuating by applied external stimulus. 118 …”

“… 142 Similarly, this approach was adopted by using four-beam UV-LIL for the preparation of non-connected arrays of responsive pNIPAAm-based hydrogel domains with a diameter <200 nm that were wrapped around lithographically-made gold nanocylinders. 118 …”

Assembled Au/ZnO Nano-Urchins for SERS Sensing of the Pesticide Thiram

“…This technique consists in the use of plasmonic or hybrid (metal/semiconductor) nanostructures/nanoparticles [ 13 , 14 , 15 , 16 , 17 , 18 , 19 ] in order to improve the SERS signal of biochemical analytes via electric fields of the plasmonic or hybrid nanostructures/nanoparticles [ 20 ]. These plasmonic nanostructures/nanoparticles can be fabricated by chemical synthesis [ 21 , 22 , 23 , 24 ] or lithographic techniques [ 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]. Moreover, several groups have already investigated plasmonic or hybrid nanostructures/nanoparticles for thiram detection by SERS with detection limits varying from 10 M to 10 M [ 33 , 34 , 35 , 36 , 37 ].…”

Latest Novelties on Plasmonic and Non-Plasmonic Nanomaterials for SERS Sensing

“…The key point in order to obtain zones of strong electric field (called hotspots) is a precise control of the shape, size, and spatial organization of plasmonic nanostructures. The control of these parameters is enabled and realized thanks to a great number of lithographies such electron beam lithography [ 24 , 25 , 26 , 27 ], optical lithographies [ 28 , 29 , 30 ], nanosphere lithography [ 31 , 32 , 33 ], and nanoimprint lithography [ 34 , 35 , 36 ]. Several groups examined a broad number of designs as plasmonic nanodisks, nanodimers, and nanorods, which have reached important EF values (EF = 10 6 –10 9 ) [ 37 , 38 , 39 ].…”