Atomically precise surface chemistry of zirconium and hafnium metal oxo clusters beyond carboxylate ligands.

The effectiveness of nanocrystals in many applications depends on their surface chemistry. Here, we leverage the atomically precise nature of zirconium and hafnium oxo clusters to gain fundamental insight into the thermodynamics of ligand binding. Through a combination of theoretical calculations and experimental spectroscopic techniques, we determine the interaction between the MO (M = Zr, Hf) cluster surface and various ligands: carboxylates, phosphonates, dialkylphosphinates, and monosubstituted phosphinates.

Synthesis of zirconium(IV) and hafnium(IV) isopropoxide, -butoxide and -butoxide.

We revisited the synthesis of zirconium(IV) and hafnium(IV) alkoxides, namely the metal isopropoxide isopropanol complex (M(OiPr)·iPrOH, M = Zr, Hf) and the metal - and -butoxide (M(OBu) and M(OBu), M = Zr, Hf). We optimized the most convenient synthesis methods and compared the products with commercial sources. En route to the metal - and -butoxides, we synthesized the metal diethylamido complex (M(NEt), M = Zr, Hf).

Complexation and disproportionation of group 4 metal (alkoxy) halides with phosphine oxides.

Group 4 Lewis acids are well-known catalysts and precursors for (non-aqueous) sol-gel chemistry. Titanium, zirconium and hafnium halides, and alkoxy halides are precursors for the controlled synthesis of nanocrystals, often in the presence of Lewis base. Here, we investigate the interaction of Lewis bases with the tetrahalides (MX, X = Cl, Br) and metal alkoxy halides (MX(OR), = 1-3, R = OPr, OBu).

Monoalkyl Phosphinic Acids as Ligands in Nanocrystal Synthesis.

Ligands play a crucial role in the synthesis of colloidal nanocrystals. Nevertheless, only a handful molecules are currently used, oleic acid being the most typical example. Here, we show that monoalkyl phosphinic acids are another interesting ligand class, forming metal complexes with a reactivity that is intermediate between the traditional carboxylates and phosphonates.

Crystal structures of three ,,'-tris-ubstituted thio-ureas for reactivity-controlled nanocrystal synthesis.

The synthesis and single-crystal X-ray structures of three ,,'-tris-ubstituted thio-ureas are reported, namely ,,'-tri-benzyl-thio-urea, CHNS (), -methyl-,'-di-phenyl-thio-urea, CHNS (), and ,-di--butyl-'-phenylthio-urea, CHNS (). The influence of the different substituents on the thio-ureas is clear from the delocalization of the thio-urea C-N and C=S bonds, while the crystal structures show infinite chains of ,,'-tri-benzyl-thio-urea (), hydrogen-bonded pairs of -methyl-,'-di-phenyl-thio-urea () and hexa-mer ring assemblies of ,-di--butyl-'-phenylthio-urea () mol-ecules. The above-mentioned compounds were synthesized a mild, general procedure, readily accessible precursors and with a high yield, providing straightforward access to a whole library of thio-ureas.

Silica@zirconia Core@shell Nanoparticles for Nucleic Acid Building Block Sorption.

The development of delivery systems for the immobilization of nucleic acid cargo molecules is of prime importance due to the need for safe administration of DNA or RNA type of antigens and adjuvants in vaccines. Nanoparticles (NP) in the size range of 20-200 nm have attractive properties as vaccine carriers because they achieve passive targeting of immune cells and can enhance the immune response of a weakly immunogenic antigen via their size. We prepared high capacity 50 nm diameter silica@zirconia NPs with monoclinic/cubic zirconia shell by a green, cheap and up-scalable sol-gel method.

The Trouble with ODE: Polymerization during Nanocrystal Synthesis.

1-Octadecene is a widely used solvent for high-temperature nanocrystal synthesis (120-320 °C). Here, we show that 1-octadecene spontaneously polymerizes under these conditions, and the resulting poly(1-octadecene) has a comparable solubility and size to nanocrystals stabilized by hydrophobic ligands. Typical purification procedures (precipitation/redispersion cycles or size exclusion chromatography) fail to separate the poly(1-octadecene) impurity from the nanocrystal product.