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The direct synthesis of highly water-soluble nanoparticles has attracted intensive interest, but systematic size control has not been reported. Here, we developed a general method for synthesizing monodisperse water-soluble iron oxide nanoparticles with nanometer-scale size increments from 4 nm to 13 nm in a single reaction. Precise size control was achieved by continuous growth in an amphiphilic solvent, diethylene glycol (DEG), where the growth step was separated from the nucleation step by sequential addition of a reactant. There was only one reactant in the synthesis and no need for additional capping agents and reducing agents. This study reveals the “living growth” character of iron oxide nanoparticles synthesised in an amphiphilic solvent. The synthetic method shows high reproducibility. The as-prepared iron oxide nanoparticles are extremely water soluble without any surface modification. Surprisingly, the synthesized 9 nm iron oxide nanoparticles exhibit extremely high transversal and longitudinal relaxivities of 425 mM −1 s −1 and 32 mM −1 s −1 respectively, which is among the highest transversal relaxivity in the literature for sub-10 nm spherical nanoparticles. This study will not only shed light on the continuous growth phenomenon of iron oxide nanoparticles in an amphiphilic solvent, but could also stimulate the synthesis and application of iron oxide nanoparticles. The continuous growth method could be further extended to other materials for the controlled synthesis of water-soluble nanoparticles.
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Continuous Production of Water‐Soluble Nanocrystals through Anti‐Solvent Precipitation in a Fluidic Device
Abstract This paper describes a simple and robust method for the continuous production of water‐soluble nanocrystals using anti‐solvent precipitation under diffusion control in a fluidic device. We use sodium chloride (NaCl) as an example to demonstrate the concept. In a typical process, aqueous NaCl and ethanol (the anti‐solvent) serve as the focused and focusing phases, respectively, for the generation of a coaxial‐flow system. Upon contact with each other, the rapid diffusion between water and ethanol leads to the formation of NaCl nanocrystals at the interface while a gradient in NaCl concentration is created along the flow direction. The nucleation and growth of NaCl nanocrystals can be readily tuned by varying the hydrodynamic parameters such as the ratio between the flow rates of the two phases and the total volumetric rate. By optimizing these parameters, we are able to produce NaCl nanocubes and nanospheres as small as 20 nm and 6 nm, respectively, while attaining a narrow distribution in size. We have also successfully generated KCl nanocrystals with similar controls, demonstrating the generality of this method for the production of water‐soluble nanocrystals.
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- Award ID(s):
- 1634687
- PAR ID:
- 10116622
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- ChemNanoMat
- Volume:
- 5
- Issue:
- 9
- ISSN:
- 2199-692X
- Format(s):
- Medium: X Size: p. 1131-1136
- Size(s):
- p. 1131-1136
- Sponsoring Org:
- National Science Foundation
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