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A general strategy for nanohybrids synthesis via coupled competitive reactions controlled in a hybrid process.

Wang R, Yang W, Song Y, Shen X, Wang J, Zhong X, Li S, Song Y - Sci Rep (2015)

Bottom Line: A new methodology based on core alloying and shell gradient-doping are developed for the synthesis of nanohybrids, realized by coupled competitive reactions, or sequenced reducing-nucleation and co-precipitation reaction of mixed metal salts in a microfluidic and batch-cooling process.The core alloying and shell gradient-doping strategy can efficiently eliminate the crystal lattice mismatch in different components.Consequently, varieties of gradient core-shell nanohybrids can be synthesized using CoM, FeM, AuM, AgM (M = Zn or Al) alloys as cores and transition metal gradient-doping ZnO or Al2O3 as shells, endowing these nanohybrids with unique magnetic and optical properties (e.g., high temperature ferromagnetic property and enhanced blue emission).

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, School of Mathematics and Physics, University of Science &Technology Beijing, Beijing 100083, China.

ABSTRACT
A new methodology based on core alloying and shell gradient-doping are developed for the synthesis of nanohybrids, realized by coupled competitive reactions, or sequenced reducing-nucleation and co-precipitation reaction of mixed metal salts in a microfluidic and batch-cooling process. The latent time of nucleation and the growth of nanohybrids can be well controlled due to the formation of controllable intermediates in the coupled competitive reactions. Thus, spatiotemporal-resolved synthesis can be realized by the hybrid process, which enables us to investigate nanohybrid formation at each stage through their solution color changes and TEM images. By adjusting the bi-channel solvents and kinetic parameters of each stage, the primary components of alloyed cores and the second components of transition metal doping ZnO or Al2O3 as surface coatings can be successively formed. The core alloying and shell gradient-doping strategy can efficiently eliminate the crystal lattice mismatch in different components. Consequently, varieties of gradient core-shell nanohybrids can be synthesized using CoM, FeM, AuM, AgM (M = Zn or Al) alloys as cores and transition metal gradient-doping ZnO or Al2O3 as shells, endowing these nanohybrids with unique magnetic and optical properties (e.g., high temperature ferromagnetic property and enhanced blue emission).

No MeSH data available.


Reaction solution color change and TEM image of the resulted particle at different resident time in microfluidic channels after the reductant solution is mixed with the mixed metal salt solution using FeAl@Al(1-x)FexOy (the FeCl2 and AlCl3 in NMP shows yellow color) as example.Color changes of the reaction solutions (a-i, b-i, c-i and d-i) and TEM images of the formed nanoparticle (a-ii, b-ii, c-ii, d-ii) after the reaction proceeds about 0.39 s (Ltotal = 10 cm), 0.44 s (Ltotal = 15 cm), 1.03 s (Ltotal = 35 cm) and 1.77 s (Ltotal = 60 cm), respectively. Ltotal: the total microchannel length after the Y-mixer (5) in Fig. s1.
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f1: Reaction solution color change and TEM image of the resulted particle at different resident time in microfluidic channels after the reductant solution is mixed with the mixed metal salt solution using FeAl@Al(1-x)FexOy (the FeCl2 and AlCl3 in NMP shows yellow color) as example.Color changes of the reaction solutions (a-i, b-i, c-i and d-i) and TEM images of the formed nanoparticle (a-ii, b-ii, c-ii, d-ii) after the reaction proceeds about 0.39 s (Ltotal = 10 cm), 0.44 s (Ltotal = 15 cm), 1.03 s (Ltotal = 35 cm) and 1.77 s (Ltotal = 60 cm), respectively. Ltotal: the total microchannel length after the Y-mixer (5) in Fig. s1.

Mentions: The mixed metal salt solution (FeCl2 and AlCl3) changes from yellow to white (Fig. 1a-i) as the reaction proceeds about 0.29 second (Ltotal = 10 cm) after it mixes with the reducing solution in the micro-mixer, indicating the formation of intermediates. As the intermediates were observed by TEM, most areas only show solute contaminating (local foggy areas) amorphous carbon film (Fig. 1a-ii). A few of nanocrystallinities (Fig. s2a) about 1.8 ± 0.4 nm (Fig. s2b) can be rarely found, which can be attributed to the localized initial nucleation due to the rapidly-increased local concentration by the solvent evaporation during the TEM sample preparation. The white intermediate solution will change to light-brown (Fig. 1b-i) and lots of highly-crystallized nanocrystals (Fig. 1b-ii) about 3.7 ± 0.6 nm (Fig. s2c) can be observed if the reaction proceeds for additional 0.15 second (Ltotal = 15 cm), indicating that the nucleation occurs. Since the nucleation is very fast, a slight growth of NPs in the microchannel and during the TEM sample preparation cannot be avoided. Thus, these nanoparticles are almost twice bigger than those observed in Figure 1a-ii and surface coatings can be clearly observed in many of them (inset in Fig. 1b-ii). The reaction solution becomes brown (Fig. 1c-i) as the reaction proceeds for additional 0.59 second (Ltotal = 35 cm). Interestingly, many of larger particles and lots of smaller particles can be observed (Fig. 1c-ii) in this stage. This is a common phenomena often observed during nanoparticle formation, where many larger particles will be formed by absorbing the solutes released from the smaller particles, or Ostwald ripening (OR), leading to a reduced mean diameter (3.1 ± 0.6 nm, Fig. s2d). The surface coatings of many NPs become thinner (inset in Fig. 1c-ii) than those NPs in Fig. 1b-ii. Clearly, these NPs preserve good crystalline cores but a little bit disordered surfaces, indicating that it is the surface coatings that firstly dissolve into the solution during OR, which can protect the cores from dissolving too fast. As the reaction proceeds for additional 1.33 seconds (Ltotal = 60 cm), the solution color becomes black (Fig. 1d-i). Surprisely, morphologies and crystal structures in NPs change dramatically (Fig. 1d-ii). Core shell morphology becomes more distinct, with cores of 3.1 ± 0.7 nm and the total diameter of 6.9 ± 2.5 nm (Fig. s2e, s2f). This result indicates that the elongated OR is mainly to increase the shell thickness (1.9 nm) since the core size changes little as comparing with that of the previous stage. Clearly, both shells and cores become amorphous (inset in Fig. 1d-ii) by comparing with those highly-crystallized NPs in the previous stages (Fig. 1b-ii and 1c-ii), indicating the reform of crystal structures both in cores and shells possibly due to the inclusion of metalloid boron and the doped second metal oxides (e.g., Al2FeO4) during OR. Therefore, termination of the growth at desired stage and the elimination of Ostwald ripening are very crucial in the morphology (size and surface coatings) and crystal structure control of nanohybrids. Otherwise, these NPs will experience Ostwald ripening where the random growth and reforming of surface coatings, interfaces and/or cores may occur, leading to broad size dispersion and/or structure change in each component.


A general strategy for nanohybrids synthesis via coupled competitive reactions controlled in a hybrid process.

Wang R, Yang W, Song Y, Shen X, Wang J, Zhong X, Li S, Song Y - Sci Rep (2015)

Reaction solution color change and TEM image of the resulted particle at different resident time in microfluidic channels after the reductant solution is mixed with the mixed metal salt solution using FeAl@Al(1-x)FexOy (the FeCl2 and AlCl3 in NMP shows yellow color) as example.Color changes of the reaction solutions (a-i, b-i, c-i and d-i) and TEM images of the formed nanoparticle (a-ii, b-ii, c-ii, d-ii) after the reaction proceeds about 0.39 s (Ltotal = 10 cm), 0.44 s (Ltotal = 15 cm), 1.03 s (Ltotal = 35 cm) and 1.77 s (Ltotal = 60 cm), respectively. Ltotal: the total microchannel length after the Y-mixer (5) in Fig. s1.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4377631&req=5

f1: Reaction solution color change and TEM image of the resulted particle at different resident time in microfluidic channels after the reductant solution is mixed with the mixed metal salt solution using FeAl@Al(1-x)FexOy (the FeCl2 and AlCl3 in NMP shows yellow color) as example.Color changes of the reaction solutions (a-i, b-i, c-i and d-i) and TEM images of the formed nanoparticle (a-ii, b-ii, c-ii, d-ii) after the reaction proceeds about 0.39 s (Ltotal = 10 cm), 0.44 s (Ltotal = 15 cm), 1.03 s (Ltotal = 35 cm) and 1.77 s (Ltotal = 60 cm), respectively. Ltotal: the total microchannel length after the Y-mixer (5) in Fig. s1.
Mentions: The mixed metal salt solution (FeCl2 and AlCl3) changes from yellow to white (Fig. 1a-i) as the reaction proceeds about 0.29 second (Ltotal = 10 cm) after it mixes with the reducing solution in the micro-mixer, indicating the formation of intermediates. As the intermediates were observed by TEM, most areas only show solute contaminating (local foggy areas) amorphous carbon film (Fig. 1a-ii). A few of nanocrystallinities (Fig. s2a) about 1.8 ± 0.4 nm (Fig. s2b) can be rarely found, which can be attributed to the localized initial nucleation due to the rapidly-increased local concentration by the solvent evaporation during the TEM sample preparation. The white intermediate solution will change to light-brown (Fig. 1b-i) and lots of highly-crystallized nanocrystals (Fig. 1b-ii) about 3.7 ± 0.6 nm (Fig. s2c) can be observed if the reaction proceeds for additional 0.15 second (Ltotal = 15 cm), indicating that the nucleation occurs. Since the nucleation is very fast, a slight growth of NPs in the microchannel and during the TEM sample preparation cannot be avoided. Thus, these nanoparticles are almost twice bigger than those observed in Figure 1a-ii and surface coatings can be clearly observed in many of them (inset in Fig. 1b-ii). The reaction solution becomes brown (Fig. 1c-i) as the reaction proceeds for additional 0.59 second (Ltotal = 35 cm). Interestingly, many of larger particles and lots of smaller particles can be observed (Fig. 1c-ii) in this stage. This is a common phenomena often observed during nanoparticle formation, where many larger particles will be formed by absorbing the solutes released from the smaller particles, or Ostwald ripening (OR), leading to a reduced mean diameter (3.1 ± 0.6 nm, Fig. s2d). The surface coatings of many NPs become thinner (inset in Fig. 1c-ii) than those NPs in Fig. 1b-ii. Clearly, these NPs preserve good crystalline cores but a little bit disordered surfaces, indicating that it is the surface coatings that firstly dissolve into the solution during OR, which can protect the cores from dissolving too fast. As the reaction proceeds for additional 1.33 seconds (Ltotal = 60 cm), the solution color becomes black (Fig. 1d-i). Surprisely, morphologies and crystal structures in NPs change dramatically (Fig. 1d-ii). Core shell morphology becomes more distinct, with cores of 3.1 ± 0.7 nm and the total diameter of 6.9 ± 2.5 nm (Fig. s2e, s2f). This result indicates that the elongated OR is mainly to increase the shell thickness (1.9 nm) since the core size changes little as comparing with that of the previous stage. Clearly, both shells and cores become amorphous (inset in Fig. 1d-ii) by comparing with those highly-crystallized NPs in the previous stages (Fig. 1b-ii and 1c-ii), indicating the reform of crystal structures both in cores and shells possibly due to the inclusion of metalloid boron and the doped second metal oxides (e.g., Al2FeO4) during OR. Therefore, termination of the growth at desired stage and the elimination of Ostwald ripening are very crucial in the morphology (size and surface coatings) and crystal structure control of nanohybrids. Otherwise, these NPs will experience Ostwald ripening where the random growth and reforming of surface coatings, interfaces and/or cores may occur, leading to broad size dispersion and/or structure change in each component.

Bottom Line: A new methodology based on core alloying and shell gradient-doping are developed for the synthesis of nanohybrids, realized by coupled competitive reactions, or sequenced reducing-nucleation and co-precipitation reaction of mixed metal salts in a microfluidic and batch-cooling process.The core alloying and shell gradient-doping strategy can efficiently eliminate the crystal lattice mismatch in different components.Consequently, varieties of gradient core-shell nanohybrids can be synthesized using CoM, FeM, AuM, AgM (M = Zn or Al) alloys as cores and transition metal gradient-doping ZnO or Al2O3 as shells, endowing these nanohybrids with unique magnetic and optical properties (e.g., high temperature ferromagnetic property and enhanced blue emission).

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, School of Mathematics and Physics, University of Science &Technology Beijing, Beijing 100083, China.

ABSTRACT
A new methodology based on core alloying and shell gradient-doping are developed for the synthesis of nanohybrids, realized by coupled competitive reactions, or sequenced reducing-nucleation and co-precipitation reaction of mixed metal salts in a microfluidic and batch-cooling process. The latent time of nucleation and the growth of nanohybrids can be well controlled due to the formation of controllable intermediates in the coupled competitive reactions. Thus, spatiotemporal-resolved synthesis can be realized by the hybrid process, which enables us to investigate nanohybrid formation at each stage through their solution color changes and TEM images. By adjusting the bi-channel solvents and kinetic parameters of each stage, the primary components of alloyed cores and the second components of transition metal doping ZnO or Al2O3 as surface coatings can be successively formed. The core alloying and shell gradient-doping strategy can efficiently eliminate the crystal lattice mismatch in different components. Consequently, varieties of gradient core-shell nanohybrids can be synthesized using CoM, FeM, AuM, AgM (M = Zn or Al) alloys as cores and transition metal gradient-doping ZnO or Al2O3 as shells, endowing these nanohybrids with unique magnetic and optical properties (e.g., high temperature ferromagnetic property and enhanced blue emission).

No MeSH data available.