Silica−Void−Gold Nanoparticles: Temporally Stable Surface-Enhanced Raman Scattering Substrates

Abstract

Reproducible detection of a target molecule is demonstrated using temporally stable solution-phase silica-void-gold nanoparticles and surface-enhanced Raman scattering (SERS). These composite nanostructures are homogeneous (diameter = 45 +/- 4 nm) and entrap single 13 nm gold nanoparticle cores inside porous silica membranes which prevent electromagnetic coupling and aggregation between adjacent nanoparticles. The optical properties of the gold nanoparticle cores and structural changes of the composite nanostructures are characterized using extinction spectroscopy and transmission electron microscopy, respectively, and both techniques are used to monitor the formation of the silica membrane. The resulting nanostructures exhibit temporally stable optical properties in the presence of salt and 2-naphthalenethiol. Similar SERS spectral features are observed when 2-naphthalenethiol is incubated with both bare and membrane-encapsulated gold nanoparticles. Disappearance of the S-H Raman vibrational band centered at 2566 cm(-1) with the composite nanoparticles indicates that the target molecule is binding directly to the metal surface. Furthermore, these nanostructures exhibit reproducible SERS signals for at least a 2 h period. This first demonstration of utilizing solution-phase silica-void-gold nanoparticles as reproducible SERS substrates will allow for future fundamental studies in understanding the mechanisms of SERS using solution-phase nanostructures as well as for applications that involve the direct and reproducible detection of biological and environmental molecules.

Colloidal Mesoporous Silica Nanoparticles

“…230 By using this method, small bare gold nanoparticles can be encapsulated in the central cavity of hollowstructured silica nanoparticles. 203 On the other hand, some groups have reported that hollowstructured porous silica nanoparticles can be obtained without using stabilizers. Although the conversion process is quite slow, Zhang et al revealed that hollow-structured silica nanoparticles can be prepared successfully simply by immersing colloidal silica in a NaBH 4 solution without the involvement of PVP.…”

Recent advances in plasmonic nanostructures for sensing: a review

“…Structures fabricated with multiple materials have been exploited to tune the plasmonic characteristics of the substrates to increase local electric field strengths or add functionality. These mixed material substrates include (i) dielectric materials coated with metals, [62][63][64]70 (ii) metals coated with dielectrics, 53,[71][72][73][74] (iii) semiconductors coated with metals, 75,76 and (iv) multilayered metal structures separated by dielectrics. 57,[77][78][79][80] One of the earliest and most prominent classes of these mixed material nanostructures for SERS sensing is known as core-shell nanoparticles, which consist of a dielectric core structure coated with a metallic shell [see Fig.…”

Mesoporous titania based yolk–shell nanoparticles as multifunctional theranostic platforms for SERS imaging and chemo-photothermal treatment

“…However, for the production of SERS labeled multifunctional nanomedicine, this sequence would induce problems because the pre-generated SERS disappeared because several severe synthesis conditions (high concentration of CTAB at the mSiO 2 coating process and NaOH etching stage) could detach Raman reporters from the metal substrates. Herein, we proposed a versatile "up-down" strategy, in which SERS nanosubstrates were pre-stabilized by polymers 32 or mesoporous materials, 33,34 followed by Raman reporters' subsequent mixing and infiltration step. In our case, it was crucial to load the Raman reporter DTDC and the therapeutic drug DOX at appropriate positions of the nanoplatform (on AuNR and in mTiO 2 , respectively), which determined the optical and therapeutic properties.…”