Very Facile Polarity Umpolung and Noncovalent Functionalization of Inorganic Nanoparticles: A Tool Kit for Supramolecular Materials Chemistry

Abstract

The facile assembly of shell-by-shell (SbS)-coated nanoparticles [TiO2-PAC16]@shell 1-7 (PAC16 = hexadecylphosphonic acid), which are soluble in water and can be isolated as stable solids, is reported. In these functional architectures, an umpolung of dispersibility (organic apolar versus water) was accomplished by the noncovalent binding of ligands 1-7 to titania nanoparticles [TiO2-PAC16] containing a first covalent coating with PAC16. Ligands 1-7 are amphiphilic and form the outer second shell of [TiO2-PAC16]@shell 1-7. The tailor-designed dendritic building blocks 3-5 contain negative and positive charges in the same molecule, and ligands 6 and 7 contain a perylenetetracarboxylic acid dimide (PDI) core (6/7) as a photoactive reporter component. In the redox and photoactive system [TiO2-PAC16]@shell 7, electronic communication between the inorganic core to the PDI ligands was observed.

Electronic Communication in Confined Space Coronas of Shell‐by‐Shell Structured Al2O3 Nanoparticle Hybrids Containing Two Layers of Functional Organic Ligands

“…By using the grafting densities determined from the weight loss of the cleaved ligands, a Langmuir isotherm could be obtained. Such a behavior has been demonstrated to reflect successful monolayer functionalization . A linear fit was applied by plotting the reciprocal values of the grafting densities versus reciprocal concentrations of the phosphonic acid mixtures.…”

Quantitative Determination and Comparison of the Surface Binding of Phosphonic Acid, Carboxylic Acid, and Catechol Ligands on TiO2 Nanoparticles

“…Because of the sensitivity of nanostructures towards agglomeration and the necessity for surface passivation against external influences, am eans of effective and stable surface modification is imperative. [5] Ac ommonp athway is surface function-alizationw ith SAMs.I nt his context,a ne valuationo ft he stability of SAMs, particularly in post-functionalization processes, is necessary. [6] Aquantitative characterization of the bindingcharacteristics and in particulart he adsorbate-surface interaction of different adsorbates is vital for evaluation of the stability of SAMs.H owever,t his is particularly critical for aw et-chemical surfacef unctionalization, owing to the superimposition of several parameters, [7] including the bindingm ode of the ligand, the influence of other moieties presenti nt he SAM molecules, which may affect the anchor group functionality,a sw ell as the surfacec hemistry and solvation of the nanoparticles (surface accessibility).…”

Manufacturing Nanoparticles with Orthogonally Adjustable Dispersibility in Hydrocarbons, Fluorocarbons, and Water

“…The noncovalent nature of the second‐shell binding further resulted in desirable features such as reversibility (solubility in water and toluene) and exchangeability (exchange against other amphiphilic molecules). Demonstration experiments to prove that second‐shell amphiphiles were easily exchangeable, but, once formed, assembled in close proximity to the particle core, were conducted by employing fluorescent marker amphiphiles 10 (Figure a) . Colored assemblies of functionalized titanium oxide particles [TiO 2 ‐PA‐HC] with fluorescent amphiphiles 10 became colorless upon centrifugation and re‐dispersion in a solution of competing amphiphiles (Figure S6).…”

“…Surfactant stabilization is ap owerful technique for mixing and dispersing immiscible hydrophobic nanoparticles within a continuous aqueous phase. [22][23][24] As we demonstrated in ap revious publication, [25] dispersions of nanoparticles coated with an alkyl-SAM can be functionalized with ionic as wella sz witterionic surfactants in water.T os tudy this hydrophobic interaction drivens elf-assembly with nonionic surfactants, we synthesized as imple modela mphiphile HC-PEG 4 to investigate its ability to increase the dispersibility of metal oxide nanoparticles coated with alkyl-phosphonic acid [MO x -1]. The amphiphile HC-PEG 4 used in this study was synthesized through the esterification of lauric acid chloride 7 with triethylene glycol according to am odifiedl iterature procedure ( Figure 2).…”

“…Demonstratione xperiments to prove that second-shell amphiphiles weree asily exchangeable, but, once formed, assembled in close proximity to the particle core, were conducted by employing fluorescent marker amphiphiles 10 (Figure 4a). [25] Colored assemblieso f functionalized titaniumo xide particles [TiO 2 -PA-HC] with fluorescent amphiphiles 10 becamec olorless upon centrifugation and re-dispersion in as olutiono fc ompeting amphiphiles (Figure S6). By using hydrophobically coated superparamagnetic [Fe 3 O 4 -1]n anoparticles as scavengers, this mechanic extraction could be extendedt owards am agnetic removal of amphiphiles 10 from aqueouss olution (Figure 4b-e).…”