Vibrational characterization of E102 food additive by Raman and surface‐enhanced Raman spectroscopy and theoretical studies

Abstract

The well-known food dye E102 could be detected in aqueous solutions by means of regular Raman and surface-enhanced Raman scattering (SERS) spectroscopy at micromolar and nanomolar levels, respectively. The changes observed in the profile of the band at 1365 cm −1 , characteristic of the n(-N N-) mode of the azo chromophore group, allowed us to establish the present species in the Raman and SERS solutions at different concentrations or pH values. Protonation at the azo group of the molecule was detected for acidic pH values <3. In the pH range 3-8, no changes in the molecular species were observed. Density functional theory (DFT)-calculated geometries, harmonic vibrational modes and Raman scattering activities for E102 were in good agreement with the experimental data, a complete vibrational assignment being proposed. A strong chemical interaction of E102 with colloidal particles was evidenced and an adsorbed geometry was proposed.

Identification and characterisation of the E951 artificial food sweetener by vibrational spectroscopy and theoretical modelling

“…This finding is supported by the medium intense band at 253 cm −1 as well as its shoulder at 236 cm −1 , which are assigned to the Ag-N stretching mode. [70,71] Moreover, one can observe the strong signal at 121 cm −1 together with its neighbouring shoulder at 139 cm −1 which are attributed to the Ag-O stretching modes. [72,73] …”

Characterization of indigo carmine with surface‐enhanced resonance Raman spectroscopy (SERRS) using silver colloids and island films, and theoretical calculations

“…These distances are specific for the phenyl rings. 43,47 In a different manner, the C-C bond lengths of five-membered rings, which are longer than those of both phenyl rings, have the calculated average between 147.3 and 149.2 pm (Table 1), values that have been given for rings containing nitrogen atoms. 48,49 The N-H proton is much more tightly bound than the carbonyl proton 50 and can, consequently, form hydrogen bonds.…”

Bio-organism sensing via surface enhanced Raman spectroscopy on controlled metal/polymer nanostructured substrates

“…The combination of the high sensia͒ Authors to whom correspondence should be addressed; electronic addresses: mdemirel@engr.psu.edu and dla3@psu.edu tivity and the fingerprint spectral capability of SERS has led to interest in a broad variety of biomedical types of applications including rapid DNA sequencing, 11 pathogen detection, 12 and food analysis. 13 Of particular interest to us has been the potential ability of SERS to obtain vibrational spectra from surface collected pathogens that could be used for detection and identification without reagents and further provides the chemical composition of pathogen membranes, which then could serve as a highly specific identification marker. There is significant interest in developing an optimum detection configuration in which a SERS sample collection surface in combination with a handheld spectrometer could provide a rapid, reagentless detection of pathogens with minimal sample preparation and ease of operation.…”