Ion-induced agglomeration of Ag NPs for quantitative determination of trace malachite green in natural water by SERS

• Published in: Vibrational spectroscopy 2022-05, Vol.120, p.103360, Article 103360
• Main Authors: Khrushchev, A.Yu, Akmaev, E.R., Gulyaeva, A.Yu, Zavialov, A.V, Sidorenko, A.I., Bondarenko, V.O., Lvovskiy, A.I.
• Format: Article
• Language: English
• Subjects: Ag NPs; Environmental water; Hot spots; Malachite green; SERS; Synergetic mechanism
• ISSN: 0924-2031; 1873-3697
• DOI: 10.1016/j.vibspec.2022.103360

This article covers a simple one-step method that has been developed for ion-induced activation/agglomeration of silver nanoparticles. While using this method in Surface-enhanced Raman spectroscopy (SERS) we have recorded high values of signal enhancement factor (EF= 3.9 ×106). An important feature of the method is high stability of analytical signal (RSD of about 2% with analyte concentration at 1 ppb). We have shown, that in case of activation of nanoparticles with chlorides of alkaline earth metals the signal amplification proceeds according to a different mechanism rather than in case of NaCl. It was found that the synergistic action of two-charged cations (Ca2+, Mg2+, Ba2+) and chloride ions leads to the agglomeration of silver nanoparticles and the formation of “hot spots”, whereas in the case of NaCl at a concentration of up to 1 mM, only the surface modification of Ag NPs occurs. Kinetic studies have been carried out, and the mechanism of this process has been proposed. The obtained data served as a basis for the development of a simple and sensitive express method for the determination of trace amounts (in the range of 0.1–10 ppb, LOD = 0.002 ppb) of malachite green in water from natural sources. In order to compensate matrix effects we applied a standard addition method which simplified considerably the sample preparation process, increased method’s accuracy and reduced the time of analysis. •It is shown that chlorides of Ca, Mg, Ba are able to amplify SERS signal.•Ag NPs agglomerates in size of 176, 205 and 431 nm were obtained.•It was proposed the mechanism of “hot spot” formation.•It was developed a method of MG assay in environmental water using SERS (LOD 2 ppt).