Plasmon-free Surface-enhanced Raman Spectroscopy on TiO\u3csub\u3e2\u3c/sub\u3e-graphene Oxide Inverse Opal Substrates

TiO2-graphene oxide (GO) inverse opal materials were shown to be active plasmon-free surface-enhanced Raman spectroscopy (SERS) substrates. The SERS activity of the substrates was analyzed using three different probe molecules: phenethylamine (PEA), methylene blue (MB), and 4-mercaptobenzoic acid (4-MBA). The morphology of the substrates was investigated by SEM and AFM. Prepared TiO2-GO inverse opals substrates can be reused up to five times with minimal loss of signal, rendering them perfect candidates to be used as highly stable, low-cost, metal-free, recyclable SERS substrates

Stabilization of DAPI in Base-Catalyzed Sol-Gels Using Surface Enhanced Raman Spectroscopy

Sol-gels can be used as substrates for sensory materials in solutions. A fluorescent dye that binds to DNA, 4’,6-diamidino-2-phenylindole (DAPI), could be used as a biosensor for a solution. Adsorption of DAPI onto silver nanoparticles causes rapid precipitation and loss of DAPI in solution. UV-vis and surface-enhanced Raman spectroscopy (SERS) were performed to observe a solution of silver nanoparticles and DAPI. Over time, spectra of the solution greatly diminished and could no longer be accurately observed. To facilitate the stabilization of DAPI in the solution, sol-gels were synthesized via base-catalyzed hydrolysis of tetramethyl orthosilicate while in the DAPI-silver solution. Sol-gels were successfully synthesized and DAPI precipitation was prevented as suggested by UV-vis and SERS

SERS Detection of Graphene Oxide in Acid Catalyzed Sol-Gels

Silica sol-gel and aerogel substrates were synthesized using a modified acid catalyzed hydrolysis of tetramethyl orthosilicate method that incorporated graphene oxide and silver nanoparticles into the matrix. The effectiveness of loading of graphene oxide was monitored by UV-vis and surface enhanced Raman spectroscopy (SERS). Characterization data suggests that graphene oxide is detectable through SERS while integrated into a sol-gel and that size of silver nanoparticles has an impact on the SERS spectrum of graphene oxide

Examination of Silica Sol-Gels and Aerogels Containing Silver Nanoparticles and 4-Mercaptobenzoic Acid Using Surface-Enhanced Raman Spectroscopy

Sol-gels and aero-gels containing silver nanoparticles have been investigated for use as substrates in surface-enhanced Raman spectroscopy (SERS). 4-Mercaptobenzoic acid (4-MBA) was chosen as the target molecule in this study, as it has been well-characterized using SERS. The orientation of the 4-MBA at different coverages in gels, and at differing concentrations of silver colloid, has not been well studied. For both base and acid-catalyzed sol-gels, xerogels, and aerogels, the concentration of 4-MBA was varied with a constant silver colloid concentration in the silica gels and the effects were measured with SERS. The effect of varying silver colloid concentration against a constant 4-MBA concentration was also investigated. The results of each process were compared

Investigation of silica Sol-gel Materials Doped with Graphene Oxide and TiO\u3csub\u3e2\u3c/sub\u3e as Substrates for Plasmon-Free Surface Enhanced Raman Spectroscopy

Silica sol-gel materials doped with graphene oxide (GO) and TiO2 were investigated as possible reusable substrates for plasmon-free surface enhanced Raman spectroscopy. Sol-gels were prepared by the base-catalyzed hydrolysis of tetramethyl orthosilicate in the presence of GO and titanium dioxide nanoparticles. The characteristic Raman spectrum of GO was enhanced in the sol-gel materials with low titanium dioxide concentrations. Sol-gels were air-dried or heated under a nitrogen atmosphere to obtain xerogels. Analysis of the Raman spectra of xerogels obtained using the latter method indicated that there was a decrease in the oxygen content and a decrease in the defect density for GO within the silica matrix. This suggests that the carbon sp2 network was partially reformed within the xerogels, forming reduced GO/graphene. GO can be detected and reduced within silica sol-gel materials in the presence of TiO2, potentially providing a stable surface for reduced GO/graphene to promote charge transfer and enhance Raman scattering alongside TiO2. GO/TiO2-doped sol-gel materials are potential candidates to be used as highly stable, reusable, biologically-compatible, plasmon-free SERS substrates