Highly efficient one-step synthesis of carbon encapsulated nanocrystals by the oxidation of metalπ-complexes

Abstract

Various carbon encapsulated nanocrystals, including MnS and MnO, CrO, MoO, FeS and FeO, and ZrO, are prepared in one step and in situ by a simple and highly efficient synthesis approach. The nanocrystals have an equiaxed morphology and a median size smaller than 30 nm. Tens and hundreds of these nanocrystals are entirely encapsulated by a wormlike amorphous carbon shell. The formation of a core-shell structure depends on the strongly exothermic reaction of metal π-complexes with ammonium persulfate in an autoclave at below 200 °C. During the oxidation process, the generated significant amounts of heat will destroy the molecular structure of the metal π-complex and cleave the ligands into small carbon fragments, which further transform into an amorphous carbon shell. The central metal atoms are oxidized to metal oxide/sulfide nanocrystals. The formation of a core-shell structure is independent of the numbers of ligands and carbon atoms as well as the metal types, implying that any metal π-complex can serve as a precursor and that various carbon encapsulated nanocrystals can be synthesized by this method.

Confined space self-propagating room temperature synthesis of carbon-encapsulated Fe3O4 nanocrystals and its lithium storage performance

“…When the reaction took place in an autoclave, the large amount of heat and gases were confined in the space and cannot be released to the external environment, probably forming a propagating shock wave. The inner sudden high pressure and temperature would completely destroy the liquid intermediate phase into reactive radical species, which self-assembly transformed into the core-shell structure [11]. In addition, when the strong nitrate radical oxidized the hydrogen in the Cp ligand, the carbon shell was well preserved because the inadequate oxygen content in the autoclave and short high-temperature dwelling time could significantly alleviate its further oxidation.…”

Growth of metal nanoparticles in hydrocarbon atmosphere of arc discharge

“…One of the dominant methods for single-step production of metal-carbon nanoparticles at a large scale is the direct current (DC) arc discharge [12][13][14][15][16][17], although other techniques have been used [18][19][20][21][22][23]. In the DC arc, the discharge is maintained between two electrodes, where an anode is usually made of graphite, which ablates and provides a feedstock of carbon for nanomaterials synthesis.…”

Low temperature oxidation synthesis of carbon encapsulated Cr2O3 nanocrystals and its lithium storage performance

“…Recently, we have synthesized a dozen of carbon encapsulated metal oxide/sulfide nanocrystals with core-shell structure by the explosive reaction of metal -complex with oxidizing agent in an autoclave. [10][11][12] The synthesis finishes in 30 min and the temperature is as low as 200 ○ C. There is no need to consider the atmosphere in the reactor and only a pressure vessel is enough for the whole process rather than other complicated equipment. The large-scale production in quantity of tens of grams is also promising.…”