Composite nanoparticles

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Composite nanoparticles are micro- or nanoparticles that are made up of several components, at least one of which is nanoscale, i.e. H. Has dimensions around or below about 100 nm. Due to their small size, the properties of the particles are largely determined by the surfaces and internal interfaces . Therefore, the properties of composite nanoparticles not only depend on the gross material composition, but also strongly on the shape, size and spatial arrangement of the components that make them up. While the term composite in materials engineering is mainly used for polymer materials in which other materials, e.g. B. inorganic particles are embedded, the term "composite nanoparticles" is often used for other material combinations.

Manufacture of composite nanoparticles

Gas phase processes are well established for the synthesis of nanoparticles. High temperatures are often used here. Flame syntheses are also suitable for the production of composite nanoparticles, e.g. B. for multicomponent particles of aluminum oxide / titanium dioxide , silicon dioxide / germanium oxide, vanadium oxide / titanium dioxide, vanadium oxide / aluminum oxide and for silicon dioxide / carbon powder. Microfluidic processes are e.g. B. used in continuous flow synthesis and in the nanoassembly of metal / polymer, polymer / oxide composite nanoparticles and composite nanoparticles from compound semiconductors . Micelle-like nanoparticles allow the encapsulation of organic and inorganic nanoparticles by amphiphilic block copolymers .

Multifunctional composite nanoparticles

The joint integration of different nanoparticles in a larger nanoparticle or a microparticle creates multifunctional composite nanoparticles that combine several special properties and functions. An example of this are nanoparticles that consist of a nanoporous silica gel matrix in which both fluorescent dyes and magnetic nanoparticles are embedded, which means that these composite particles have an optical marking function on the one hand, and can be moved magnetically and, if necessary, sorted on the other.

Combinatorial diversity, hierarchically structured nanoparticles

The combination of nanoparticles, which differ in their elementary or molecular composition, in shape and size, leads to a very large number of possible combinations. In addition, between the size level of small nanoparticles (approx. 2-3 nm) and the one-micrometer level, at least five intermediate levels of the size scales can be defined, each of which differs in volume by more than a power of ten. This enables an unmanageably large number of hierarchically structured nanoparticles with very different structural features and properties. The practically infinite variety of conceivable chemical substances can in future be transferred to the world of composite materials through a combinatorial synthesis of hierarchically structured composite nanoparticles.

Application examples

Carrier for drugs ("drug carrier")

Composite nanoparticles, which simultaneously contain non-contact manipulable or switchable nanoparticles and active ingredients , are interesting for new therapeutic strategies. These can be used to control the timing of the release of drugs in the body, or drugs can be brought to a site of action and specifically released there for local treatment. Therefore z. B. worked on magnetically controlled and thermally switchable composite nanoparticles for medical applications.

Adjustment of wetting properties

Microparticles or larger nanoparticles that have small nanoparticles on their surface are very suitable for adjusting the wetting properties of surfaces. In the case of water-repellent ( hydrophobic ) components, they represent a material that makes surfaces super- hydrophobic , i.e. it creates a strong lotus effect . Similarly, by using a hydrophilic material, particularly good wetting by water or aqueous solutions (superhydrophilicity) can be achieved.

Sensing and marking

Composite nanoparticles that work as sensor particles are particularly interesting for applications in sensor technology . H. that combine sensitive components with contact-free readout. So z. B. Hydrogel / precious metal core / shell particles are synthesized, which can be used as nanoscale temperature or pH sensors . Polymer composite particles, which are made up of a permeable matrix and contain silver and gold nanoparticles, are of interest as optical labels, as so-called plasmonic sensors and as sensors for surface- enhanced Raman spectroscopy (SERS) in small volumes.

Individual evidence

  1. ↑ HK Kammler et al., Flame synthesis of nanoparticles, Chem. Eng. Technol. 24 (200): 583-596
  2. ↑ H. Wang et al .: Continuous synthesis of CdSe-ZnS composite nanoparticles in a microfluidic reactor, Chem. Commun. (2004), 48-49
  3. ↑ ME Gindy et al., Langmuir 24 (2008), 83-90
  4. ↑ I. Kraus et al .: Continuous-microflow synthesis and morphological characterization of multiscale composite materials based on polymer microparticles and inorganic nanoparticles, J. Flow Chem 4 (2014), 72-78
  5. ↑ Y.-S. Lin et al .: Multifunctional composite nanoparticles: magnetic, luminescent, and mesoporous, Chem. Mater. 18: 5170-5172 (2006)
  6. ↑ M. Köhler: Microreaction technology as an instrument for nanotechnology, Lifis Online [28. June 2010]; http://www.leibniz-institut.de/archiv/koehler_28_06_10.pdf
  7. ↑ J. Liu et al .: Magnetic nanocomposites with mesoporous structures: synthesis and applications, Small 7 (2011), 425-443
  8. ↑ SRSershen et al .: Temperature-sensitive polymer-nanoshell composites for photothermally modulated drug delivery, J. Biomed. Mat. Res. 51 (2000), 293-298
  9. ↑ Xin Du, Xiangmei Liu, Hongmin Chen, Junhui He: Facile Fabrication of Raspberry-like Composite Nanoparticles and Their Application as Building Blocks for Constructing Superhydrophilic Coatings . In: Journal of Physical Chemistry C . tape 113 , no. 21 , May 28, 2009, pp. 9063-9070 , doi : 10.1021 / jp9016344 .
  10. ↑ J.-H. Kim and TR Lee: Thermo- and pH-responsive hydrogel-coated gold nanoparticles, Chem. Mater. 16: 3647-3651 (2004)
  11. ↑ N. Visaveliya et al .: Microflow SERS measurements using sensing particles of polyacrylamide / silver composite materials, Chem. Eng. Technol. 38 (2015), 1144-1149