The identification of hydroxyl groups on ZnO nanoparticles by infrared spectroscopy

Abstract

The interaction of water with ZnO nanoparticles has been studied by means of diffuse reflectance infrared spectroscopy (DRIFTS) and ultra-high vacuum FTIR spectroscopy (UHV-FTIRS). Exposing clean ZnO powder to water at 323 K leads to both molecular and dissociative adsorption of H2O forming a number of hydroxyl species. All the OH bands are clearly identified by the adsorption of D2O showing the expected isotopic shifts. According to the vibrational and thermal stability data obtained from single crystal surfaces, the OH species observed on ZnO nanoparticles are identified as follows: (1) OH group (3620 cm(-1)) on the polar O-ZnO(0001[combining macron]) surface formed via dissociation of water on oxygen vacancy sites; (2) partial dissociation of water on the mixed-terminated ZnO(101[combining macron]0) surface yielding coexistent H2O ( approximately 3150 and 3687 cm(-1)) and OH species (3672 cm(-1)), where the molecularly adsorbed H2O is further identified by the characteristic scissoring mode at 1617 cm(-1); (3) isolated OH species (3639 and 3656 cm(-1)) formed on the mixed-terminated ZnO(101[combining macron]0) surface; (4) interaction of water with defects forming hydroxyl (or O-HO) species (3564 and 3448 cm(-1)).

Bismuth oxide aqueous colloidal nanoparticles inhibit Candida albicans growth and biofilm formation

“…[32][33][34] As previously mentioned, Bi 2 O 3 has a marked basic character, and when this compound is suspended in water, it tends to be associated with hydroxyl ions and water molecules on its surface, similar to titanium dioxide, zinc oxide, tin dioxide, and other metal oxides. [35][36][37][38][39] When Bi 2 O 3 is nanostructured, its ionic character is enhanced compared with the same bulk material, ie, it becomes a "harder" species with respect to its electrons (according to Pearson's theory of hard and soft acids and bases). 40 As a consequence, when Bi 2 O 3 is nanostructured, its dissociating character increases, as does the overall surface of the material.…”

Hydrogen Loading of Oxide Powder Particles: A Transmission IR Study for the Case of Zinc Oxide

“…[18] The successful application of this new apparatus to oxide surfaces exposed by single crystals as well as by powder particles has been demonstrated for several systems. [19][20][21][22][23][24] ZnO powder samples were first pressed into a stainless steel grid covered by gold and then mounted on a sample holder which was specially designed for the FTIR transmission measurements under UHV conditions. The base pressure in the measurement chamber was 2 10 À10 mbar.…”

Hydroformylation of 1-Hexene over Rh/Nano-Oxide Catalysts

“…In our supported Rh systems, it is likely that the impregnated Rh 3+ is reduced by the syngas, subsequent to which the reaction follows a route similar to that suggested by Zhou et al and Rosales et al for the heterogeneous olefin hydroformylation [34,49]. The hydroxyl groups on metal oxide surfaces are also known to have an impact on the catalytic activity [50][51][52], but their role was not studied in detail in the current work.…”