Highly monodispersed Ag embedded SiO₂nanostructured thin film for sensitive SERS substrate: growth, characterization and detection of dye molecules

Abstract

Highly monodispersed Ag embedded SiO 2 nanostructured thin films have been synthesized and their sensitivity towards SERS investigated. The possible mechanism for the formation of a highly monodispersed SiO 2 nanostructured thin film and its self-assembled nanogap with Ag are discussed. It is found that the architecture of Ag embedded SiO 2 (Ag@SiO 2 ) is drastically influenced by the concentration of the precursors and the reaction time. Morphology and monodispersity of the silica thin film were confirmed using FESEM and AFM. Crystallinity and existence of Ag on SiO 2 were confirmed using XRD and XPS. The substrate shows enhanced SERS efficiency due to the reduced size (around 15 nm) of the Ag nanoparticles and the nano gap of (below 3 nm) between SiO 2 and Ag. Based on the FDTD (finite-difference time-domain) simulation, the creation of hotspots was confirmed for the obtained nanogap. The prepared thin film possesses strong Surface Plasmon Resonance (SPR) with widely tunable peaks between 407-430 nm in the UV visible spectrum. The Ag@SiO 2 nanospheresbased SERS platform provides highly enhanced effects and reveals a reproducible enhancement (EF = 7.79 x10 8 ) of R6G (Rhodamine 6G), allowing a detection limit from a 10 -18 mol L -1 solution. The prepared substrate was also used to detect trace level of melamine from a 10 -8 mol L -1 solution. Fig.9. AFM 2D and 3D images of (a-b) SiO 2 nanospheres (d-e) Ag@SiO 2 nanospheres and (c & f) Histograms of SiO 2 and Ag@SiO 2 nanospheres [Note: Here Ag represents hydrosol A] Fig.10. Electric field ሺ〈|‫|ܧ‬ ଶ 〉ሻ distributions obtained from 3D FDTD calculations at wavelength 514 nm of (a) 2.5 nm gap (b) 5 nm gap.

Infused self‐assembly on Langmuir–Blodgett Film: Fabrication of highly efficient SERS active substrates with controlled plasmonic aggregates

“…The enhancement factors (EFs) of the SER bands of 4‐MPy molecule adsorbed on two different modified substrates of classes “A” and “B” have been separately calculated using the relation, where, N bulk and N SERS represent the number of probe molecule that contribute to the normal Raman and SERS signals. I bulk and I SERS are the corresponding normal Raman and SERS intensities measured from the baseline.…”

Analysis on superhydrophobic silver decorated copper Oxide nanostructured thin films for SERS studies

“…The SERS activity of the Ag-NP-decorated samples was evaluated using 20 ll volume of R6G dye molecule with molarity varying from 10 À12 M to 10 À9 M. The characteristic peaks of R6G molecules and their intensities strongly depend on superhydrophobicity with water contact angle of 150.4 after Ag deposition as shown in Table S1. The enhancement factor (EF) for SERS is determined to be of the order of 10 7 for the R6G peaks at 610 by using the formula [29].…”

Reductant‐Free Synthesis of Silver Nanoparticles by Functionalized Hollow Doughnut Mesoporous Silica Nanoparticles for Preparation of Catalytic Nanoreactor

“…The X‐ray diffraction pattern clearly identified the presence of amorphous silica and crystalline Ag in the Ag/hd‐MSN‐NH 2 , because the XRD pattern of Ag/hd‐MSN‐NH 2 matched the JCPDS 04–0783 for cubic Ag metal and the amorphous peak of silica present at same peak position with hd‐MSN nanoparticle. The characteristic peaks at 38.5°, 44.3°, 64.6°, 77.6°, and 81.8° were indexed to the (111), (200), (220), (311), and (222) planes of Ag . The XRD pattern of Ag/hd‐MSN‐NH 2 nanoparticles indicates that the Ag/hd‐MSN‐NH 2 nanoparticles were successfully formed via reduction of Ag + to Ag nanoparticles by amine functional groups grafted on hd‐MSN nanoparticles.…”