Detection of Anions by Normal Raman Spectroscopy and Surface-Enhanced Raman Spectroscopy of Cationic-Coated Substrates

Abstract

The use of normal Raman spectroscopy and surface-enhanced Raman spectroscopy (SERS) of cationic-coated silver and gold substrates to detect polyatomic anions in aqueous environments is examined. For normal Raman spectroscopy, using near-infrared excitation, linear concentration responses were observed. Detection limits varied from 84 ppm for perchlorate to 2600 ppm for phosphate. In general, detection limits in the ppb to ppm concentration range for the polyatomic anions were achieved using cationic-coated SERS substrates. Adsorption of the polyatomic anions on the cationic-coated SERS substrates was described by a Frumkin isotherm. The SERS technique could not be used to detect dichromate, as this anion reacted with the coatings to form thiol esters. A competitive complexation method was used to evaluate the interaction of chloride ion with the cationic coatings. Hydrogen bonding and pi-pi interactions play significant roles in the selectivity of the cationic coatings.

Perchlorate removal by quaternary amine modified reed

“…6 [61,62]. The perchlorate band in solid NaClO 4 salt occurred at 953 cm −1 , a figure also reported in several studies [63][64][65]. Yoon et al [23] reported a ClO 4 − peak at 951 cm −1 in NaClO 4 salt, and suggested that the peak corresponded to (Na + · · ·ClO 4 − · · ·Na + ) trimers, tetramers, or higher-order structures in the solid phase.…”

Preparation of Fe3O4@Ag SERS substrate and its application in environmental Cr(VI) analysis

“…In addition, a low Cr(VI) concentration at 5 lg L À1 can be clearly resolved (Fig. 6), which was an order of magnitude lower than reported SERS level of detection at 59.3 lg L À1 [32].…”

Perchlorate adsorption and desorption on activated carbon and anion exchange resin

“…Perchlorate in a 10% NaClO 4 solution had a characteristic perchlorate peak at 933 cm −1 . Mosier-Boss and Lieberman [33] reported a peak at 935 cm −1 for an aqueous perchlorate solution. The appearance of the strong band at 934 cm −1 was ascribed to the symmetric ( 1 ) vibration of the perchlorate anion [34].…”