A Citric Acid-Derived Ligand for Modular Functionalization of Metal Oxide Surfaces via “Click” Chemistry

Abstract

Citric acid is a widely used surface-modifying ligand for growth and processing of a variety of nanoparticles; however, the inability to easily prepare derivatives of this molecule has restricted the development of versatile chemistries for nanoparticle surface functionalization. Here, we report the design and synthesis of a citric acid derivative bearing an alkyne group and demonstrate that this molecule provides the ability to achieve stable, multidentate carboxylate binding to metal oxide nanoparticles, while also enabling subsequent multistep chemistry via the Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction. The broad utility of this strategy for the modular functionalization of metal oxide surfaces was demonstrated by its application in the CuAAC modification of ZnO, Fe(2)O(3), TiO(2), and WO(3) nanoparticles.

Applying Mechanochemistry for Bottom‐Up Synthesis and Host–Guest Surface Modification of Semiconducting Nanocrystals: A Case of Water‐Soluble β‐Cyclodextrin‐Coated Zinc Oxide

“…The high-resolutiont ransmission electron microscopy (HRTEM) images of the resultingZ nO NCs showed the presence of aggregateds pherical particles of (3.3 AE 0.6) nm in diameter ( Figure 2b). The cross-polarization/ magic-angle spinning (CP-MAS) 15 NNMR spectra ( Figure 3) as well as FTIR (the Supporting Information, Figure S6), and thermogravimetric (TG) analysis (Figures S7, S8, and S11i nt he Supporting Information) indicatedt hat the ZnO NCs were coated by benzamide. Thus, during ball-milling of 2 the benzamidate moieties were protonated, whiche nabled them to act as Ltype ligands [24] stabilizing ZnO NCs.…”

“…It also provides ZnO NCs that are insufficiently shielded against the environment, which is reflected in the documented toxicity, [14] as well as observed quenching of photoluminescence upon functionalization through copper(I)-catalyzed click reactions. [15] Some of these drawbacks can be overcome by using organometallic precursors.…”

High frequency magneto-dielectric effects in self-assembled ferrite-ferroelectric core-shell nanoparticles

“…41 Following this, the functionalized particles were heterogeneously linked together in the presence of a Cu(I) catalyst via the "click" reaction forming heterogeneous nanocomposites. [39][40][41] The core-shell structure was confirmed with electron microscopy and magnetic force microscopy. The magnetic and ferroelectric nature of the composites was confirmed with magnetization, ferromagnetic resonance and polarization P vs. E measurements.…”

“…Azide modification of nanoparticles and functionalization with alkyne group by attaching O-propargyl citrate was conformed using FTIR (KBr pellet) spectroscopy. 40 (iii) The generation of hetero-assemblies between nanoparticles was effected by Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction (commonly known as "click" chemistry). [38][39][40][41] Sample characterization in terms of structure, composition, and ferroic order parameters are detailed in Ref.…”

“…We synthesized these core-shell nanocomposites by coating the ferroic nanoparticles with complementary coupling groups and allowing them to self-assemble. [38][39][40][41] We employed BTO (diameter = 50 nm) and NFO (diameter = 100 nm) nanoparticles for the assemblies. One of the nanoparticles, BTO or NFO, was functionalized azide groups and the other with alkyne groups.…”