Tuning the Hydrophilic, Hydrophobic, and Ion Exchange Properties of Mesoporous TiO₂

Abstract

Alkyl phosphonic acids (Pho-C(n)-R) of different chain length (6, 10, and 14 carbons) bearing neutral, positive, and negatively charged head groups (R = -H, R(-) = sulfonate, R(+) = pyridinium) were prepared and anchored to the inner walls of randomly sintered mesoporous TiO(2) thin films. Quartz crystal microbalance (QCM) and Fourier transform infrared (FT-IR) measurements show that a monolayer coverage was achieved. The monolayer crystallinity is lower as compared to alkyl thiols on gold, but it increases with the length of the carbon chain. The neutral phosphonic acid modifier makes the TiO(2) highly hydrophobic and suppresses electrochemistry in aqueous media, and the alkyl phosphonic acids with charged head groups render the TiO(2) film as an ion exchanger with a phase separated hydrophilic and hydrophobic portion. Different charged guest molecules were incorporated on top or into the supported membranes. The host-guest interactions were found to be electrostatic, hydrophobic, or both. Highly charged electroactive metal complexes ([Fe(CN)(6)](4-), [IrCl(6)](2-)) and purpose-synthesized organic electrochromophores (dialkylated viologens with variable chain length, C(1)-V(+2)-C(n), C(n)-V(+2)-C(n), n = 6, 10, and 14) were used as molecular guests, and the assemblies were characterized by cyclic voltammetry and FT-IR. Using the preconcentration phenomenon, [Fe(CN)(6)](4-) concentration as low as 200 nM can be detected on a Pho-C(14)-R(+) modified TiO(2) electrode by conventional cyclic voltammetry. The new surface modification technique simplifies the molecular requirements for functional surface modifiers considerably. Using a limited set of organic anchors with orthogonal coordination properties and adjustable hydrophobicity, a broad range of electrochromophores, redox active wiring compounds, or sensitizers can be adsorbed onto TiO(2).

Control of Charge Dynamics via Use of Nonionic Phosphonate Chains and Their Effectiveness for Inverted Structure Solar Cells

“…[ 14 ] 1 H NMR and 13 C NMR spectra were recorded on a Varian VNRS 400 MHz (Varian, USA) spectrometer using CDCl 3 as solvent and tetramethylsilane (TMS) as an internal reference. UV-vis spectra were taken using a UV-1800 (SHIMADZU) spectrometer.…”

“…The crude product was purifi ed by column chromatography (silica gel, ethyl acetate to 10% methanol in ethyl acetate) to afford 2.3 g (56%) of 2 as dark-red solid 167.89,145.82,132.75,131.36,126.94,125.35,120.55,111.42,61.60,40.25,30.44,27.35,26.65,25.07,22.54,16.66. Elemental analysis: C,50.25;H,5.86;N,3.26;O,14.87;Found: C,50.27;H,5.88;N,3.06;O,14. General Procedure for Synthesis of IIG-Based Polymers and Purifi cation through Stille Coupling : In a Schlenk fl ask, a solution of monomers 1 ( x mol), 2 ( y mol), and 3 ( x + y mol) in dry toluene (12 mL)/DMF (2 mL) were degassed with argon for 20 min. To this solution, tri-otolylphosphine (0.12 equiv.…”

Transition Metal Compounds Towards Holography

“…Up to now there are no reports on monolayers of SO on a thin film, but the environment used in Reference [18] could be modified to hold the positively charged OSO instead of negatively charged NP [63]. Unlike SNP, that compound should not alter its photofunctionality, while being attached to the TiO${}_2$, due to its larger size and, therefore, due to less influence of the electrostatic spacer it is attached to.…”

Synthesis and Antibacterial Evaluation of Bis‐thiazolium, Bis‐imidazolium, and Bis‐triazolium Derivatives

“…[13] In contrasttot his previous study,e ach even and odd linkers from n = 4t on = 12 werep repared. [19] Conversion into the diiodo counterparts allowed the preparation of longer analogues.B esides, O-methylation [13] prior to dimerizationa fforded three more compounds. [19] Conversion into the diiodo counterparts allowed the preparation of longer analogues.B esides, O-methylation [13] prior to dimerizationa fforded three more compounds.…”