Synthesis of TiO2 nanoparticles on the Au(111) surface

Abstract

The growth of titanium oxide nanoparticles on reconstructed Au(111) surfaces was investigated by scanning tunneling microscopy and X-ray photoelectron spectroscopy. Ti was deposited by physical vapor deposition at 300 K. Regular arrays of titanium nanoparticles form by preferential nucleation of Ti at the elbow sites of the herringbone reconstruction. Titanium oxide clusters were synthesized by subsequent exposure to O 2 at 300 K. Two-and three-dimensional titanium oxide nanocrystallites form during annealing in the temperature range from 600 to 900 K. At the same time, the Au(111) surface assumes a serrated, <110> oriented step-edge morphology, suggesting step-edge pinning by titanium oxide nanoparticles. The oxidation state of these titanium oxide nanoparticles varies with annealing temperature. Specifically, annealing to 900 K results in the formation of stoichiometric TiO 2 nanocrystals as judged by the observed XPS binding energies. Nano-dispersed TiO 2 on Au(111) is an ideal system to test the various models explaining the enhanced catalytic reactivity of supported Au nanoparticles. IntroductionMetal oxides are of considerable interest because of their technological importance, e.g. in the field of heterogeneous catalysis, where they are used as catalyst supports for a wide variety of metals. The interaction of the adsorbed metal particles with the oxide support is complex and gives rise to interesting phenomena such as the strong metal support interaction (SMSI). This term describes the change in catalytic activity (favoring hydrogenation) observed when group VIII B metals supported on reducible oxides (TiO 2 , TaO 5 , CeO 2 , NbO) are annealed in a reducing atmosphere [1]. Transition metal oxides are also used to support other oxides in the socalled monolayer catalysts. For example, V 2 O 5 /TiO 2 systems are used for the partial oxidation of methanol, and have been extensively studied in single crystal as well as in powder form [2][3][4][5].

Two-dimensional TiO x nanostructures on Au(111): a scanning tunneling microscopy and spectroscopy investigation

“…Also the "inverse system" TiO x /Au(111) has been observed to show an effective catalytic activity in promoting the water-gas shift (WGS) reaction [10], thus encouraging experimental work on the synthesis and characterization of TiO x structures supported by the Au(111) surface. After the oxidation of Ti clusters evaporated on Au(111), the formation of geometrically well-defined TiO 2 crystallites with triangular or hexagonal shape was reported by Biener et al [11] and Potapenko et al [12]. Hexagonal TiO x nanoparticles were also observed by Lauwaet et al [13] who revealed a semiconducting n-type character.…”

Growth of TiO2(B)(001) on Au(111) by chemical vapor deposition

“…The component labeled "1-2" is related to components "1" and "2" in the Ti 2p 3/2 spectra and component "3" in the O 1s appears in concomitance with "3" in the Ti 2p 3/2 . Component "4" is needed to obtain a satisfactory fit of the O 1s spectra and its origin is uncertain [34][35][36].…”

Activating antioxidant enzymes, hyoscyamine and scopolamine biosynthesis of Hyoscyamus niger L. plants with nano-sized titanium dioxide and bulk application

“…Metal oxide nanoparticles, represented by titanium dioxide (TiO 2 ), is of great technological importance in the field of heterogeneous catalysis for catalytic support of a wide variety of metals (Biener et al, 2005). The most important effects of TiO 2 compounds on plants are enhancement of the yield of various crops (~10-20%); an improvement of some essential element contents in plant tissues; an increase in the peroxidase, catalase, and nitrate reductase activities in plant tissues; and an enhancement of the chlorophyll content in paprika (Capsicum anuum L.) and green alga (Chlorella pyrenoidosa) (Hruby et al, 2002).…”