Dopant-Induced Shape Evolution of Colloidal Nanocrystals: The Case of Zinc Oxide

Abstract

The electrical, optical and other important properties of colloidal nanocrystals are determined mainly by the crystals' chemical composition, size and shape. The introduction of specific dopants is a general approach of modifying the properties of such nanocrystals in well-controlled ways. Here we show that in addition to altering the atomic composition of the nanocrystals the introduction of specific dopants can also lead to dramatic changes in morphology. The creation of Mg-doped ZnO nanocrystals provides an excellent example of this procedure; depending on the molar ratio of dopant precursor in the reagents, doped nanocrystals with well-defined shapes, from tetrapods to ultrathin nanowires, which exhibit tunable optoelectronic properties, are obtained for the first time. We find that the Mg dopants play an important role in the primary growth stage, resulting in initial growth seeds having diverse crystallographic structures, which are critical for the generation of doped nanocrystals with different shapes. We demonstrate that this "greener" synthetic scheme can be extended to other dopant systems and provides an attractive and effective strategy for fabricating doped ZnO nanocrystals with interesting compositional and spatial complexity.

Different magnetic properties of rhombohedral and cubic Ni2+ doped indium oxide nanomaterials

“…The similar phenomenon was also found in Mg doepd ZnO nanocrystals. 20 However, the orientation growth could not be observed in all Ni 2+ doped C-In 2 O 3 samples for their cubic structures were more difficult to grow directionally than rhombohedral structures.…”

Ligand Exchange of Colloidal ZnO Nanocrystals from the High Temperature and Nonaqueous Approach

“…The higher reaction temperature, generally above 250℃, led to improve crystalline features of ZnO nanocrystals [11]. This approach also allows effective size control in a wide range from about 3 nm up to 15 nm [11][12][13]. In addition, a few recent studies demonstrated the syntheses of doped ZnO nanocrystals by this approach, which generated materials with tailored electrical properties.…”

“…In addition, a few recent studies demonstrated the syntheses of doped ZnO nanocrystals by this approach, which generated materials with tailored electrical properties. For example, our group demonstrated the syntheses of alloyed Mg x Zn 1-x O [12] and Cd x Zn 1-x O [13] nanocrystals having tunable opti-cal bandgaps. Buonsanti et al prepared Al 3+ doped ZnO nanocrystals which had high free carrier concentrations [14].…”

“…It was found that ZnO nanocrystals by the hightemperature approach were generally capped by ligands with long alkyl-chains, such as stearate ions [11,12]. These bulky ligands act as insulating barriers and block charge transport between neighboring particles.…”

Synthesis of Doped and non-Doped Nano MgO Ceramic Membranes

“…This paper deals with the preparation of doped and non-doped nano MgO membranes using a polymeric sol-gel method that offers the possibility of controlling the synthesis of thin film hierarchical internal structure (Crisan et al 2000). Doping MgO with ZnO is studied in order to create doped nanocrystals and nanostructures with unprecedented properties (Yang et al, 2010). The effect of ZnO doping on thermal, surface and structural properties is studied.…”