Modification of Nanocrystalline TiO₂ with Phosphonate‐ and Bis(phosphonate)‐Bearing Macrocyclic Complexes: Sorption and Stability Studies

Abstract

The first systematic study of chemical adsorption/desorption of phosphonic acid and geminal bis(phosphonic acid) on/ from the surface of anatase nanoparticles is reported. Stable TiO 2 colloidal nanodispersions were used in the study. The colloidal stability is preserved upon nanoparticle modification. A macrocyclic lanthanide(III) complex, attached through a phosphonic/bis(phosphonic) group to the TiO 2 surface allowed precise quantification of sorption parameters by means of inductively coupled plasma atomic emission spectroscopy (ICP-AES). Results show different behavior of phosphonate and bis(phosphonate) groups. For phosphonate, a IntroductionSurface modification of inorganic materials by organic molecules is widely used in many fields of research and industry as it can improve their performance in a wide range of applications. The modification proceeds through noncovalent or covalent interaction of the adsorbate with the surface. The noncovalent surface coatings are based mainly on van der Waals and electrostatic interactions and are typical for coatings of polymers. Grafting of low-molecular-weight molecules is usually carried out through interaction of the inorganic surface with specific chemical group that serves as a chemical anchor. These interactions are mostly based on the formation of covalent bonds between the anchoring group and substrate, and the sorption is called chemisorption in this case. The most typical example of chemisorption is a surface modification of oxidic materials such as SiO 2[1] or SnO 2 [2] with organosilanes/organostannanes or metals such as gold [3,4] with thiol-containing molecules.[ Phosphonates have been intensively studied as chemical anchors [5] and have been used for the modification of a wide variety of surfaces like iron oxides, [6] zirconium dioxide, [7] aluminum oxide, [7,8] oxides of rare earths, [9] and other oxidic [10,11] and metallic [12] substrates. Presence of more than one phosphonate group in the molecule can further improve sorption properties.[13] The most studied arrangement of two phosphonate groups, geminal bis(phosphonate), is used in clinical practice for the treatment of osteoporosis and other bone diseases [14] due to its extremely stable sorption onto the surface of bone tissue. The interaction of geminal bis(phosphonates) with various inorganic surfaces has also been studied to prepare new materials applicable, for example, as medical implants, [15] drug-delivery systems, [16] or medical-imaging probes. [17,18] Titanium dioxide is a highly stable, nontoxic, and chemically inert material. Phosphonate affinity towards the TiO 2 surface is high, and the adsorption proceeds under a wide variety of conditions in terms of reaction temperature, solvent, and pH. The grafting of bis(phosphonates) and phosphonates [19] onto the TiO 2 surface has been studied, and the resulting modified materials have been used for numerous applications. Tuning of the hydrophilicity/hydrophobicity of the surface by organophosphonate coating may improve the TiO 2 properties a...

Surface modification of alumina-coated silica nanoparticles in aqueous sols with phosphonic acids and impact on nanoparticle interactions

“…17 Greenwood et al found that silica sols could be efficiently grafted by slow addition of pre-hydrolyzed GPTMS. 32,33 Pautrot-d'Alençon et al modified CeO 2 sols stabilized by acetate groups using 2-carboxyethylphosphonic acid, ethylphosphonic acid, and phosphonoacetic acid in order to tune the acidic character of their surface. 4,18 Suspensions of positively charged silica particles stabilized at low pH (B4) are also commercially available.…”

“…4,18 Suspensions of positively charged silica particles stabilized at low pH (B4) are also commercially available. 33 The goal of the present article is to explore the modification of aqueous sols of alumina-coated silica stabilized by electrostatic repulsions with different phosphonic acids, and to assess the influence of this modification on interactions and colloidal stability. The presence of this alumina coating opens the road to surface functionalization in aqueous medium using phosphonic acids (PAs), as recently shown for aggregated silica nanoparticles.…”

High refractive index transparent nanocomposites prepared by in situ polymerization

“…The modier can be acids, amines, alcohols, silanes, phosphonates, sulfonates and so on. 6,12,13,15,19,[23][24][25] A combination of more than two different approaches is also feasible such as TiO 2 -ZrO 2 -acrylic acid. 12 In this research, we used a one-step approach to make nanoparticles of aromatic phenyl acetic acid modied TiO 2 (PAA-TiO 2 ) and aliphatic hexanoic acid modied TiO 2 (HA-TiO 2 ) that are compatible with poly(ethoxylated (6) bisphenol A dimethacrylate).…”

Visible and near-infrared luminescent mesoporous titania microspheres functionalized with lanthanide complexes: microstructure and luminescence with visible excitation

“…Recently, titania has been considered as a matrix material, which is attractive due to its thermal and mechanical stability. [31][32][33] In addition, the photocatalytic activity and energy conversion ability of titania make it promising for various potential applications. 19,33,34 For example, Li and coworkers have synthesized lanthanide hybrids through chemical modication of titanium alkoxide where lanthanide complexes can be anchored within the framework of inorganic titania materials.…”