Continuous Shape- and Spectroscopy-Tuning of Hematite Nanocrystals

Abstract

Uniform hexagonal hematite (α-Fe(2)O(3)) nanoplates have been synthesized by a facile alcohol-thermal reaction, and a new nanostructure of α-Fe(2)O(3) has been proposed. Each nanoplate is enclosed by (0001) basal planes and {1012} side surfaces. The phase, size, shape, and growth orientation of these nanocrystals were characterized by powder X-ray diffraction and electron microscopy. The thickness and diameter of these nanocrystals could be finely tuned by the selective use of alcohol solvent with increasing carbon atom number in the linear alkyl chain. A variety of nanocrystals with systemically changeable shapes from nanoplates to nanograins have been obtained. Specific adsorption of alcohol molecules on polar (0001) facets is proposed to be the main issue to modify the growth behavior of hematite nanocrystals. The presence of distilled water and the addition of sodium acetate have also been investigated. Either of them has a great influence on the growth of hematite nanocrystals, and shape-controlled growth can be rationally achieved. In addition, the post-aging of as-grown hematite nanocrystals in alcohol and distilled water has also been described. Both vibration spectroscopy (i.e., FTIR and Raman) and electronic spectra (diffused reflectance spectra) of these nanocrystals with a continuing shape change show a highly shape-dependent nature.

Facile Synthesis and Special Phase Transformation of Hydrophilic Iron Oxides Nanoparticles

“…The Fe 2p 3/2 binding energy of 710.9 eV and the corresponding satellite peak at 719.5 eV, a result of charge transfer screening, can be solely attributed to the presence of Fe 3+ of the solid samples, indicating that the as-synthesized sample is composed of -Fe 2 O 3 [14]. From the SEM and TEM image in Figures 1(c) and 1(d), we could see that the sample consists of nanoparticles with sizes of only less than 3 nm, which are greatly less than -Fe 2 O 3 in our previous work [13].…”

“…In our previous report, the side surface edges -Fe 2 O 3 nanoplates gradually redissolved into nanoparticles through "a mass transformation" during solvothermal processing [13]. We could speculated that other iron oxides particles should be obtained if we tune some experimental conditions during "a mass transformation."…”

“…Benefiting from previous study [13], we find a novel route to synthesize superparamagnetic iron oxide nanoparticles through -Fe 2 O 3 nanoparticles as precursor in this study, only in presence of ethylene glycol, without the presence of any other agents, surfactants, and additives. Herein, nanoscale -Fe 2 O 3 particles were obtained using a smaller particle size of -Fe 2 O 3 as precursors and the mild ethylene glycol as a solvent.…”

“…-Fe 2 O 3 precursors were synthesized by the modified solvothermal method as previously reported [13]: 0.273 g of FeCl 3 ⋅6H 2 O (0.1 mmol) was dissolved under vigorous magnetic stirring in ethanol (10.0 mL) and 2 mL of deionized water. Until completely dissolved, 0.6 g of sodium acetate was added while stirring.…”

Painting by Numbers: Nanoparticle‐Based Colorants in the Post‐Empirical Age

“…The spectra and photographs (inset) show the transition in optical properties as the shape changes. Panels (a) and (d) reproduced with permission from [77] and [84], respectively. Copyright 2010, American Chemical Society.…”