Surface enhanced Raman spectroscopic readout on heavy metal ions based on surface self assembly

Abstract

A new method is reported for detecting heavy metal ions by using the self assembled monolayer (SAM) technique and surface enhanced Raman spectroscopy (SERS). The p-mercaptobenzoic acid (MBA) served as the SERS readout molecule and the modified tag to attach on the smooth gold substrate as well as the tag of nanoparticles by the SAM method. Two carboxyl groups from MBA molecules which were attached respectively to gold substrate and gold nanoparticles were linked through the heavy metal ions (Cu 2+ , Pb 2+ and Zn 2+ ) as bridge, and thus sandwich structure of 'MBA modified gold substrate/heavy metal ions/MBA modified gold nanoparticles' was built for detection. The observation of the oxidation peak of metal nanoparticles from cyclic voltammetry (CV) curve, gold nanoparticles from scanning electron microscopy (SEM) images and SERS signal of MBA from the sandwich structure indicated the existence of heavy metal ions. The difference in the wavenumbers of vibrational modes from MBA in the sandwich structure constructed by different could be used to identify different heavy metal ions. The assembled structure was rinsed by strong chelator of EDTA solution to remove the heavy metal ions from the sandwich structure and thus to obtain a fresh gold substrate modified with MBA for the cyclic detection.

TiO2 and Al2O3 nanoporous oxide layers decorated with silver nanoparticles—active substrates for SERS measurements

“…The intensity of the recorded SERS spectra for adsorbed MBA also depends on the diameter of the titania nanotubes (as a consequence on V max ). As in the case of pyridine, we do not observe any significant shifts in the position of the characteristic signals for MBA, in particular for the bands which can be assigned to the ν 12 -1,080 cm −1 and ν 8a -1,593 cm −1 vibrations of the aromatic ring [41][42][43][44]. The other characteristic band well [45,46].…”

Anomalous behavior of B1g mode in highly transparent anatase nano-crystalline Nb-doped Titanium Dioxide (NTO) thin films

“…The shift in peak position towards higher frequency and broadening in the FWHM of the main low frequency E g(1) mode of anatase has been widely reported. [30][31][32] Typically, in the agreement of PCM and is dominated when crystallite size is less than 20 nm. 12 However, a large shift and broadening in the peak for the size below 20 nm may not be explained by PCM alone.…”

Recent advances in linear and nonlinear Raman spectroscopy II

“…18 Comparison was made between the adsorption of laccaic acid and carminic acid, another anthraquinone dye. Yuan et al 19 reported a new method for detecting heavy metal ions by using a SAM technique and SERS. P-mercaptobenzoic acid served as the SERS readout molecule in this case.…”