Influence of Ligand–Precursor Molar Ratio on the Size Evolution of Modifiable Iron Oxide Nanoparticles

During the synthesis of nanoparticles via thermal decomposition of iron precursors, the capping ligand–precursor ratio influences the resulting size of the iron oxide nanoparticles. As the molar ratio of aliphatic amines to iron precursor is increased, the average diameter of the synthesized iron oxide nanoparticles decreases. This trend is opposite to previously reported results. We investigated this phenomenon by independently varying the ligand chain length, the ligand–precursor molar ratio, and the degree of saturation of the aliphatic chain. Nuclear magnetic resonance spectra of the precursor illustrated the presence of a primary amine peak before heating and the peak absence after heating, potentially indicating that the primary amine acts as reducing agent to promote the decomposition of the iron precursor. We hypothesize that the amine groups play a dominant role in the nucleation of the particles, while the chain length and degree of aliphatic saturation have only a minor effect on particle size. The nanoparticles’ size and crystallinity were characterized with high-resolution transmission electron microscopy, dynamic light scattering, and X-ray diffraction, and the magnetic properties were characterized by magnetometry

An Early Mesozoic transcontinental palaeoriver in South China: evidence from detrital zircon U–Pb geochronology and Hf isotopes

<p>Detrital zircon geochronology reveals that Late Triassic–Early Jurassic fluvial sandstones from the major basins of the South China Craton have similar age patterns and define four populations at 2.6–2.4 Ga, 2.0–1.7 Ga, 850–700 Ma and 480–210 Ma. The late Palaeoproterozoic group is predominant in all of the five samples, and yielded remarkable age peaks at <em>c</em>. 1.85 Ga. These zircons have ϵ_Hf(t) values between −22.5 and +3.6, suggesting derivation from reworked Archaean crust and minor juvenile crustal additions in the late Palaeoproterozoic. These characteristics differ from those of the Yangtze Block but correlate well with those of samples from the eastern Cathaysia Block. Palaeocurrent analysis of the Early Mesozoic sandstones shows predominant west- and NW-directed palaeoflows, supporting derivation of the sediments from the Cathaysia Block. The remarkable similarities in provenance signatures and spatial changes of lithofacies of the Triassic–Jurassic around the South China Craton delineate an east–west-trending sedimentary zone extending from Korea to West China. Accumulation of these sediments was probably related to the development of an active continental margin produced by westward subduction of the Palaeo-Pacific Plate. A <em>c</em>. 2000 km long westerly draining transcontinental palaeoriver probably had existed in the Early Mesozoic and fed the basins in Korea, South China and West China. </p