Utilizing Chemical Raman Enhancement: A Route for Metal Oxide Support-Based Biodetection

Abstract

Raman scattering enhancement was observed in systems where different metal oxide semiconductors (TiO 2 , Fe 2 O 3 , ZrO 2 , and CeO 2 ) were modified with enediol ligands. The intensity of Raman scattering was dependent on laser frequency and correlated with the extinction coefficient of the CT complex of the enediol ligands and nanoparticles. The mechanism of Raman enhancement was studied by varying both the chemical composition of the enediol ligand and the chemical composition (and crystal structure) of the nanoparticles. We found that the intensity of the Raman signal depends on the number of surface binding sites, electron density of the ligands, and their dipole moment. Changes in chemical composition caused variations in the intensity, frequency, and number of Raman bands observed. We also showed that Raman scattering is observed for the bioconjugated system, where a peptide is linked to the surface of the particle through a catechol linker, and further investigated the potential for such a system in the development of Raman-based in vivo and in vitro biodetection, cell labeling and imaging, and nanotherapeutic strategies.

Anatase nanoparticles surface modified with fused ring salicylate-type ligands (1-hydroxy-2-naphthoic acids): A combined DFT and experimental study

“…In contrast [36], the slower components of emission and fluorescence anisotropy decay are observed for salicylic acid, which forms a comparatively weaker CT complex with TiO 2 nanoparticles, indicating the delocalized nature of the excitation. Additionally, the formation of a CT complex and Raman scattering enhancement for TiO 2 nanoparticles functionalized with salicylic acid was observed by SERS [37,38], although this binding leads to less shifted absorption and a very different Raman spectrum. The Raman signal is lower in intensity than that for the systems employing catecholate-type modifiers, confirming that these are less stable complexes.…”

“…Several papers have investigated CT complex formation between catecholate [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39] and salicylate [27,[36][37][38]40,41] type ligands and colloidal TiO 2 nanoparticles (d $ 45 Å), where the binding of modifiers induces the surface reconstruction of the nanoparticles. Recently, combined theoretical (DFT) and experimental studies were performed, mainly on catecholate-type molecules as surface modifiers of rutile [32] and anatase [33][34][35] TiO 2 nanoparticles, reporting different adsorption geometries.…”

“…Recently, combined theoretical (DFT) and experimental studies were performed, mainly on catecholate-type molecules as surface modifiers of rutile [32] and anatase [33][34][35] TiO 2 nanoparticles, reporting different adsorption geometries. However, only a few papers have investigated the binding of salicylic acid [36][37][38]41]. Interfacial charge-transfer emission measurements and fluorescence anisotropy measurements [36] in catecholate-type molecule-TiO 2 nanoparticle complexes showed that the excitation is localized, with the charge transferred from the ligand to the localized Ti atom and not to the entire nanoparticle.…”

Do happy catalyst supports work better? Surface coating of silica and titania supports with (poly)dopamine and their application in hydrotreating

“…It is well documented in literature that titania binds strongly with the catechol groups of dopamine in a bidentate geometry [34]. The solid-state UV analysis of the Pdop/TiO 2 support showed the ligand-to-metal charge transfer complex formation between TiO 2 and catechol groups [35] extended the absorption into the visible light region as apparently indicated by the color change (Fig. S10).…”

Application of well-defined indium tin oxide nanorods as Raman active platforms

“…3,[10][11][12][13] And more recently, other systems involving either a metal oxide thin film or a hybrid system of a metal nanoparticle/metal oxide thin film have been demonstrated as SERS-active materials. 7,[14][15][16][17][18][19] Plasmonic characteristics similar to those observed from noble metals are found in some transparent conducting metal oxides such as indium tin oxide, fluorine-doped tin oxide, and aluminum-doped zinc oxide. 18,20 Despite many leading efforts on this aspect, only a small subset of research discusses Raman enhancement effects observed from nanomaterials that are precisely controlled for their physical, chemical, optical, or electrical properties during synthesis.…”