Adsorption Configurations and Energetics of BClx (x = 0−3) on TiO2 Anatase (101) and Rutile (110) Surfaces

Ab Initio Investigation of Polyethylene Glycol Coating of TiO2 Surfaces

In biomedical applications, TiO₂ nanoparticles are generally coated with polymers to prevent agglomeration, improve biocompatibility, and reduce cytotoxicity. Although the synthesis processes of such composite compounds are well established, there is still a substantial lack of information on the nature of the interaction between the titania surface and the organic macromolecules. In this work, the adsorption of polyethylene glycol (PEG) on the TiO₂ (101) anatase surface is modeled by means of dispersion-corrected density functional theory (DFT-D2) calculations. The two extreme limits of an infinite PEG polymer [-(OCH₂CH₂) _n ], on one side, and of a short PEG dimer molecule [H(OCH₂CH₂)₂OH], on the other, are analyzed. Many different molecular configurations and modes of adsorption are compared at increasing surface coverage densities. At low and medium coverage, PEG prefers to lay down on the surface, while at full coverage, the adsorption is maximized when PEG molecules bind perpendicularly to the surface and interact with each other through lateral dispersions, following a mushroom to brush transition. Finally, we also consider the adsorption of competing water molecules at different coverage densities, assessing whether PEG would remain bonded to the surface or desorb in the presence of the aqueous solvent.

One-pot synthesis of 3-D dandelion-like architectures constructed by rutile TiO2 nanorods grown along [001] axis for high-rate lithium ion batteries

A novel 3-D dandelion-like TiO₂ anode constructed by rutile nanorods grown along [001] axis exhibits high-rate lithium ion battery behaviour.

Role of hydroxyl groups in the NH(x) (x = 1-3) adsorption on the TiO2 anatase (101) surface determined by a first-principles study

A spin-polarized density functional theory calculation was carried out to study the adsorption of NH(x) species (x = 1-3) on a TiO2 anatase (101) surface with and without hydroxyl groups by using first-principles calculations. It was found that the present hydroxyl group has the effect of significantly enhancing the adsorption of monodentate adsorbates H2N-Ti(a) compared to that on a bare surface. The nature of the interaction between the adsorbate (NH(x)) and the hydroxylated or bare surface was analyzed by the Mulliken charge and density of states (DOS) calculations. This facilitation of NH2 is caused by the donation of coadsorbed H filling the nonbonding orbital of NH2, resulting in an electron gain in NH2 from the bonding. In addition, the upper valence band, which originally consisted of the mixing of O 2p and Ti 3d orbitals, has been broadened by the two adjacent H 1s and NH2 sigma(y)(b) orbitals joined to the bottom of the original TiO2 valence band. The results are important to understand the OH effect in heterogeneous catalysis.

Ionic liquid-assisted synthesis of large-scale TiO2 nanoparticles with controllable phase by hydrolysis of TiCl4

Pure rutile and rutile-anatase composite TiO(2) nanoparticles have been successfully synthesized via an ionic liquid-assisted method by hydrolysis of titanium tetrachloride in hydrochloric acid. It is found that the phase composition (ratio of rutile to anatase) of the products increases with increasing the content of ionic liquid [Emim]Br (1-ethyl-3-methyl-imidazolium bromide), therefore, TiO(2) nanoparticles with controlled phase compositions can be obtained in high yields. The structural and morphological characterizations of the resulting samples are investigated by means of X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and Brunauer-Emmett-Teller (BET) analysis, and the results indicate that the diameters of the anatase nanoparticles are in the range of 4-6 nm and the well-defined rutile nanorods are about 3-6 nm in diameter and 20-60 nm in length. More importantly, we find that the [Emim](+) ions can serve as capping agents based on their strong interactions with the (110) facets of rutile, and the [Emim]Br favors the formation of the rutile structure with a rod-like shape due to the mutual pi-stacking interactions of imidazole rings. We believe that this method can be developed into a general way to synthesize other metal oxide nanoparticles on a large scale.