Tailoring the Surface and Solubility Properties of Nanocrystalline Titania by a Nonaqueous In Situ Functionalization Process

Abstract

The reaction between titanium tetrachloride and benzyl alcohol in the presence of enediol ligands such as dopamine and 4-tert-butylcatechol provides a simple nonaqueous route to in situ surface functionalization of titania nanoparticles. The as-prepared precipitates are resoluble either in water or in organic solvents, depending on the ligand used. The surface chemistry of the 4-tert-butylcatechol-functionalized particles dissolved in dimethylformamide was analyzed by 1 H NMR measurements revealing the presence of adsorbed 4-tertbutylcatechol, in addition to benzyl alcohol and water. Although the reaction temperatures of 70 or 80 °C are relatively low, XRD and HRTEM investigations give evidence that the as-synthesized nanoparticles are highly crystalline. Ultracentrifugation analysis of dopaminefunctionalized titania nanoparticles dissolved in water shows a particle size distribution of approximately 3.5-8 nm with the peak maximum at 5.5 nm. Furthermore, the UV-vis detector system of the ultracentrifuge allows the measurement of the absorption spectra dependent on the particle size, showing an unusual red shift with decreasing particle size.

Low temperature crystallisation of mesoporous TiO2

“…Non-hydrolytic sol-gel (NHSG) crystalline nanoparticle synthesis -Crystalline anatase nanoparticles were synthesised as described in the literature 5,27,29,32 . A dry flask was evacuated and floated with dry nitrogen several times before 5.75 ml absolute ethanol (Fisher Scientific) was added.…”

Amino Acid-Based Stabilization of Oxide Nanocrystals in Polar Media: From Insight in Ligand Exchange to Solution 1H NMR Probing of Short-Chained Adsorbates

“…30 Potentially useful procedures in this respect involve the use of stripping agents such as NOBF 4 , 31 RO 3 BF 4 , 32 and BF 3 33 which operate in acidic conditions, or dopamine, which stabilizes titania NCs by a positive surface charge. 34 The former approach however, does not lead to long term stable dispersions whereas dopamine is an important neurotransmitter, involved in addictive behavior, and therefore a restricted chemical. Also amino acids are known to stabilize NCs in water, [35][36][37][38] but no ligand exchange process took place in those examples as the NCs were synthesized in the water phase with the amino acids already present.…”

Functionalisation of Colloidal Transition Metal Sulphides Nanocrystals: A Fascinating and Challenging Playground for the Chemist

“…Ligands can be also used to direct the growth of the forming NCs [289][290][291][292]. In the ligand-assisted growth of NCs, the surface ligand dynamics is affected by the growth temperature, the ligand concentration and the ligand chain length, as outlined by Peng et al [240], and as shown in Figure 5.…”

“…Ligands can be also used to direct the growth of the forming NCs [289][290][291][292] [240], and as shown in Figure 5. Also the intermolecular interactions among the ligands can affect the growth of the NCs.…”

“…Among the most employed ligands for metal nanoparticles, thiols [39,[322][323][324][325][326][327][328] have to be mentioned, whereas metal oxides NP can be conveniently derivatised by carboxylates or, even stronger, by multifunctional ligands such as dopamine-derivatives and cathecols [280,283,292,[329][330][331]. A further distinction can be carried out accordingly to the chemical nature of the surface to be derivatised, which can be noble metal NPs [9,141,163,269,318, or metal oxides, the most commonly functionalised colloids, but also of other composition (halogenides, chalcogenides, phosphates, carbonates etc.…”