Facile synthesis of size and wavelength tunable hollow gold nanostructures for the development of a LSPR based label-free fiber-optic biosensor

Abstract

Hollow bimetallic nanostructures have recently emerged as attractive plasmonic materials due to the ease of optical tunability by changing their size/composition. Currently available methods, in addition to being tedious and time-consuming, result in polydispersed nanostructures, particularly due to polydispersed templates. In this study, optically tunable hollow gold nanostructures (HGNS) were synthesized by 10 galvanic replacement reaction between silver nanospheres (AgNS) templates and gold salt. Monodispersed AgNS were created using a gold seed-mediated heteroepitaxial growth. Since it is easier to ensure monodispersed gold nanosphere seeds, the resulting AgNS showed a tight control on size. Hollow gold nanostructures 43 -70 nm in size with extinction maxima ranging between 450 -590 nm were produced by varying the gold to silver molar ratio. The nanostructures were observed to be 15 monodispersed and uniform (SD ≤11%) in all the batches. Furthermore, the synthesized HGNS were immobilized on dendrimer-functionalized U-shaped fiber-optic probes to develop a localized surface plasmon resonance (LSPR) based sensor. Refractive index sensitivity of the HGNS based sensors was found to be 1.5-fold higher than solid gold nanosphere (GNS)-based fiber-optic sensors. These HGNSbased fiber-optic probes were subsequently used to develop an immunosensor with improved sensitivity 20 by using human immunoglobulin-G (HIgG) as receptor molecules and goat-anti-HIgG as a target analyte. 22 2572 3480; Tel: +91 22 2576 776 90 † Electronic Supplementary Information (ESI) available: Method of gold seed particle synthesis; Extinction spectrum and FEG-TEM image of gold seed particles; chemical reactions involved in the preparation diamine silver complex; Extinction spectra, FEG-TEM image and histogram of silver nanoparticles produced from heteroepitaxial growth method using 95

Hollow metal nanostructures for enhanced plasmonics: synthesis, local plasmonic properties and applications

“…As already stated, hollow nanostructures are known to be more effective in label-free sensing compared to their solid counterparts [14,133,190,199]. Sun and Xia [199] compared the sensitivity of solid Au nanospheres and Au nanoshells and reported almost a seven-fold increase in the SF while using the Au nanoshells.…”

“…Recently, we have reported a ~4-fold increase in the sensitivities of single-walled nanoboxes compared to solid Au nanoparticles against conjugation events with bovine serum albumin (BSA) protein and its antibodies thanks to the enhancement of the localized electromagnetic field around the hollow nanoboxes that allows easy and direct detection of binding events on their vicinity [133]. Satija et al [190] prepared hollow gold nanospheres based fiber-optic sensors having a 1.5-fold enhancement in sensitivity compared to solid Au nanoparticle-based sensors. They have been also used as immunosensors and reported a maximum of four-fold better detection limit compared to other Au-based biosensors [190].…”

“…Satija et al [190] prepared hollow gold nanospheres based fiber-optic sensors having a 1.5-fold enhancement in sensitivity compared to solid Au nanoparticle-based sensors. They have been also used as immunosensors and reported a maximum of four-fold better detection limit compared to other Au-based biosensors [190].…”

Plasmonic Fiber Optic Refractometric Sensors: From Conventional Architectures to Recent Design Trends

“…Besides tapering, polishing or splicing different fibers together, bending offers the easiest way of extracting the light propagating inside the fiber core. When a fiber is bent beyond its critical radius, the propagating modes inside the core can couple into the cladding [ 49 , 60 , 61 ]. If the bent region is coated with a metal, a portion of this radiation can excite SPs.…”

Light Absorption Enhancement by Employing A Plasmonic Nanobox Cavity Array

“…The cavity-type nanobox cavity array was fabricated via a sidewall deposition method, [33][34][35] which is the combination of various nanofabrication methods such as NIL, sputtering, and RIE. The cavitytype nanobox array platform poses the increased surface area with inner and outer surfaces compared to the solidtype counterpart, which can also enhance the sensitivity factors, 36,37 catalytic activity, 38,39 drug delivery, [40][41][42] Raman signal intensity. 3,14 The cavity-type nanobox architecture can be a suitable candidate for a label-free bio-chemical sensing platform compared to solid-type nanostructures such as nanobox array or spherical nanoparticles.…”