Here, we show a simple approach to synthesize cobalt and cobalt oxide nanoparticles in an organic solvent. We find that the cubic Co 3 O 4 nanoparticles can be easily obtained, even at temperatures as low as 80 °C. Moreover, exactly the same reaction at 180 °C leads to metallic Co nanoparticles. Thus, in addition to the synthetic efforts, we study the mechanism of occurrence of oxidation and reduction of a Co 2+ precursor in benzyl alcohol. Remarkably, the in situ X-ray absorption and diffraction measurements of the synthesis at 140 °C reveal that oxidation of Co 2+ to Co 3+/2+ and reduction of Co 2+ to Co 0 reactions take place simultaneously. It is followed by a rapid formation of Co 3 O 4 nanoparticles and its consecutive solid-state reduction to CoO. In parallel, metallic Co nanoparticles begin to grow. In addition, Multicomponent Curve Resolution−Alternating Least Squares (MCR-ALS) analysis of X-ray absorption spectroscopy (XAS) data efficiently reveals the nontrivial interdependence between four different reactions. Our strategy to control reduction and oxidation of Co-based nanoparticles as they grow opens up an elegant pathway for the one-pot-synthesis of the hybrid materials for energy-related applications.

Closing the loop: initially, the reactivity of benzyl alcohol determines the nucleation of Cu nanoparticles, but as soon as they start to form they begin to catalyze the condensation of benzyl alcohol to dibenzylether.

New chemical pathways are of fundamental interest for materials synthesis. Here, we report a novel surfactant-free, solution-phase, low-temperature route to crystalline, ultrasmall (∼2 nm) Cu 3 N nanoparticles via a one-step reaction between copper(II) methoxide and benzylamine. We propose a reaction mechanism for Cu 3 N formation based on the gas chromatography− mass spectrometry (GC−MS) analysis of the organic reaction byproducts. The reaction pathway involves reduction of the Cu(II) to Cu(I) by benzylamine, in situ generation of ammonia, and finally, the reaction between Cu(I) and ammonia to form Cu 3 N. We tested the Cu 3 N nanoparticles as an anode material for Li-ion batteries (LIBs). According to cyclic voltammetry, the Cu 3 N nanoparticles quickly undergo a phase transformation to Cu 2 O, but then stably deliver a capacity of ∼290 mAh/g at 1 A/g in the following 150 cycles.

Depth resolved X-ray photoelectron spectroscopy (XPS) combined with a 25 μm liquid jet is used to quantify the spatial distribution of 3 nm SnO2 nanoparticles (NPs) from the air-water interface (AWI) into the suspension bulk. Results are consistent with those of a layer several nm thick at the AWI that is completely devoid of NPs.

Here, we present a synthesis of MoO 2 nanoparticles doped with 2 at% of Ni in a mixture of acetophenone and benzyl alcohol at 200 °C. Based on in situ X-ray absorption nearedge structure (XANES) and ex situ extended X-ray absorption fine structure (EXAFS) measurements at Ni K-edge and Mo Kedge, we discuss scenarios on how the "doping" reaction, that is, the incorporation of Ni in the MoO 2 , proceeds. We can clearly exclude the formation of NiO or Ni nanoparticles. Moreover, within the resolution of our in situ XANES experiments, we observe that the ternary compound Ni:MoO 2 nucleates directly in the final composition. Although the local structure around the Ni ion adopts the MoO 2 crystal structure pointing at the substitution of tetravalent Mo by Ni, we find that Ni remains divalent. This aliovalent substitution results in the relaxation of the local structure, which is additionally reflected in the slight shrinking of the total volume of the unit cell of Ni:MoO 2 . Interestingly, such a small amount of divalent Ni has a tremendous effect on the performance of the material as anode in Li-ion batteries. The initial discharge capacity of Ni:MoO 2 based anodes almost doubles from 370 mAh/g for MoO 2 to 754 mAh/g for Ni:MoO 2 at 0.1 C (1 C = 300 mA/g). Additionally, we observed an atypical increase of capacity for both MoO 2 and Ni:MoO 2 anodes upon cycling with increasing cycling rate.

We use in situ X-ray absorption and diffraction studies to directly monitor the crystallization of different titania polymorphs in one and the same solution. We find that, despite the commonly accepted polymorphic-crossover from anatase to rutile triggered by the critical size of nanoparticles, in the solution their respective nucleation and growth are independent processes. Moreover, we find that 5.9 nm rutile nanoparticles are formed prior to the formation of 8.4 nm anatase nanoparticles. Our results suggest that the origins of this crystallization mechanism lie in the formation of an intermediate non-crystalline phase and in time-dependent changes in the chemical environment.

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