Characterization of Noncrystalline Nanomaterials: NMR of Zinc Phosphate as a Case Study

Abstract

Zinc phosphate nanoparticles are prepared via a polyol-mediated synthesis. The nanomaterial turns out to be nonagglomerated and very uniform in size and shape, in particular 20 nm in diameter. X-ray powder diffraction analysis and high-resolution transmission electron microscopy indicate as-prepared nanoparticles to be noncrystalline. To investigate the chemical composition (stoichiometry, material homogeneity, amount of ortho-/metaphosphate, water content, type of surface-allocated adsorbents, differentiation of surface/inner core), X-ray diffraction, NMR-spectroscopy, energy-dispersive X-ray analysis, infrared spectroscopy, and thermal analysis are performed. To validate the local structure and composition, we performed 1 H, 13 C, and 31 P magic angle spinning nuclear magnetic resonance spectroscopy and multidimensional homo-and heteronuclear multiple-pulse solid-state NMR experiments. Moreover, 31 P{ 1 H} rotational echo double-resonance experiments for various spin topologies are analyzed analytically and numerically, in order to differentiate between homogeneous nanoparticles and core-shell nanoparticles. The analysis gives a length scale to homogeneity and for bulk materials allows us to differentiate between mono-and dihydrogen phosphates, and phosphate hydrates.

Structural investigation of aluminium doped ZnO nanoparticles by solid-state NMR spectroscopy

“…The experiment used CX 1 X symmetries and a post-C-element 45,46 that corresponds to a 1 H nutation frequency n rf of 50 kHz at n MAS of 25 kHz. The C-REDOR data were plotted as DS/S 0 against the universal dephasing time t uds , 47,48 which is a pulse sequence-independent time scale defined by the product |k|t of the magnitude of the scaling factor k and the dipolar dephasing time t. The scaling factor 49 H during extra p/2 À t 1 À p/2 block, which is followed by a short zero-quantum filter of a few ms. Proton decoupling was implemented using continuous wave (cw) decoupling with a rf field strength corresponding to 100 kHz. The nutation frequency for the selective pulses applied to the 27 Al central transition was 50 kHz.…”

Outlining the mechanism of flame retardancy in polyamide 66 blended with melamine-poly(zinc phosphate)

“…This feature is due to Q 1 sites that are either chain terminals or found in isolated pyrophosphate dimers. α-Zn 2 P 2 O 7 (À 15.9, À 19.1, À 21.2 ppm) and γ-Zn 2 P 2 O 7 (À 5.5, À 7.1, À10.4 ppm) are reported to be found around the same region [52].…”

“…Pyrolysis of S400 additive. Degradation in S400 can be conveniently tracked by solid state NMR thanks to the presence of NMR sensitive nuclei in both inorganic ( 31 P of ZnPO) and organic components ( 13 C of melamine) as they provide information [46][47][48][49][50][51][52][53][54] about fragmentation in phosphorus polyhedra and melamine condensation/degradation, respectively. 31 P MAS-NMR of S400 and its pyrolysed products are displayed in Fig.…”

Sonochemical Synthesis of Amorphous Zinc Phosphate Nanospheres

“…5,6 In addition, the catalytic properties of zinc phosphate have been investigated in hydrocarbon conversion process, such as dehydration/dehydrogenation of sec-butanol and methanol conversion. 7,8 Since the first report on the synthesis of microporous zinc phosphates, 9 various techniques, including a solid-state reaction 10 and a polyol-mediated approach, 11 have been investigated for the synthesis of monodispersed and nonagglomerated zinc phosphate nanoparticles. A solid-state reaction is a simple room temperature process, but it requires very long reaction time (from several hours to several days) for the fabrication of zinc phosphate nanoparticles.…”

“…10,12 Unlike the solid-state reaction, a polyol-mediated approach is a relatively fast route (up to several hours) to the preparation of nonagglomerated zinc phosphate nanoparticles. 11,13,14 However, the polyol-mediated approach requires both a heating system due to the relatively high temperature process (up to 300 o C) and an additional cooling system for refluxing process.…”