Naslov
Enhancement of Raman scattering on gold nanoparticles prepared in HEPES buffer

Autori
Kenđel, Adriana ; Radoslavić, Ivana

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
28th Croatian Meeting of Chemists and Chemical Engineers and 6th Symposium Vladimir Prelog : Book of Abstracts / Rogošić, Marko - Zagreb : Hrvatsko društvo kemijskih inženjera i tehnologa (HDKI), 2023, 85-85

Skup
28th Croatian Meeting of Chemists and Chemical Engineers

Mjesto i datum
Rovinj, Hrvatska, 28.03.2023. - 31.03.2023

Vrsta sudjelovanja
Poster

Vrsta recenzije
Međunarodna recenzija

Ključne riječi
SERS, nanoparticles, HEPES

Sažetak
Surface-enhanced Raman scattering (SERS) spectroscopy is very sensitive technique in which the intensity of scattered radiation is highly amplified, compared to normal Raman scattering, due to the adsorption of the analyte on rough metal surface [1]. Colloidal metal nanoparticles and nanoparticles immobilized on solid surfaces are most often used as substrates for SERS spectroscopy. Various compounds such as inorganic salts or buffers, used for the preparation of colloidal suspensions, can act not only as reducing agents for metal salts, but also as stabilizing agents, preventing oxidation and aggregation of metal nanoparticles [2]. Other substances, such as polymer molecules, can also be added to the colloids to stabilize the metal nanoparticles [3]. In this work, the SERS efficiency and stability of gold colloids prepared by reduction of tetrachloroauric(III) acid with 4-(2-hydroxyethyl)piperazine-1-ethanesulfonic acid (HEPES buffer) were investigated using rhodamine 6G (R6G) and (E)-1, 2-di(pyridin-4-yl)ethene (BPE) as model molecules. Colloids were synthesized in two ways using the "seedless" method [4]. In the first case, only the metal salt and buffer were mixed, while in the second synthesis, in addition to the metal salt and buffer, silver nitrate was also added. Silver nitrate is commonly used as a shape directing agent in gold nanoparticle synthesis procedures. For both prepared colloidal solutions, the influence of the addition of polyvinylpyrrolidone (PVP) on the stability of the metal nanoparticles and the enhancement of scattering were investigated. In all prepared gold colloids, the strongest SERS effect was found for the BPE molecules, most likely due to their lack of charge and optimal structural features. Unlike BPE, charged rhodamine 6G molecules were electrostatically repelled from the gold surface by HEPES molecules, which stabilize the nanoparticles, and were located on the metal surface in the form of zwitterion. The addition of silver nitrate during colloid synthesis resulted in a more efficient SERS substrate, probably due to the formation of nanoparticles with different morphology, that scattered radiation more efficiently, compared to the colloid obtained only from metal salt and buffer. By introducing the polymer PVP into the system, a steric barrier was created between the nanoparticles and the analyte, so the obtained spectra of the model molecules showed very weak bands. However, such modified colloidal nanoparticles were more stable over the time, compared to freshly prepared gold colloids.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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