magnetic nanoparticles, part 1. synthetic methods: from mechanochemistry to biomimetics

Transcription

1 magnetic nanoparticles, part 1. synthetic methods: from mechanochemistry to biomimetics Tanya Prozorov, Ph.D. US DOE Ames Laboratory e mail: tprozoro@ameslab.gov 1

2 outline some definitions what happens on the nanometer scale common trends in properties and applications making materials smaller: synthetic methods 2

3 Ames, Iowa, USA 3

4 some definitions material: the substance of which a thing is composed; structure of a material relates to the arrangement of its constituents; property is a kind and magnitude of material s response to a specific imposed stimulus; processing structure properties performance materials science studies the relationship between the structures and properties of materials materials engineering designs the structure of material to produce a desired set of properties on the basis of the structure property correlations; classification of solids: metals, ceramics, polymers, composites modern materials needs: advanced materials performance properties structure processing 4

5 defects and imperfections in solids vacancies and self interstitials; impurities, solid solutions and alloys; linear and interfacial defects: dislocations, external surfaces, grain boundaries and twin boundaries; external surface: surface energy bulk or volume defects: pores, cracks, foreign inclusions and heterophases; thermal fluctuations 5

6 what s special about the nanometer scale? Surface effects are accentuated. IYQntl9C0 Scaling laws can break down: ferrofluids IYQntl9C0 Quantum effects can appear. A stainless steel ball bounces much more elastically on a sample of amorphous metal than on crystalline stainless steel, a consequence of the different nanoscale arrangement of atoms; (see movie of this). A liquid sample of ferrofluid, comprising 10 nm ferrimagnetic magnetite particles suspended in oil or water with a surfactant, responds to a magnet (see movie). A reddish sample of gold nanoparticles suspended in aqueous has a completely different appearance than sample of gold foil and illustrates the striking effects of light scattering at this scale. 6

7 nanostructured material nanocomposite matrix nanoparticle Abundance of grain boundaries H. Gleiter, Acta Mater. 48, 1 (2000) Abundance of interfaces 7

8 one of the earliest magnetic devices 8

9 what happens on the nanometer scale surface effects Numbers of surface and interior atoms in the BCC structure Number of unit cells Surface (S) Interior (I) in the cube atoms atoms Ratio (S/I) (2 2 2) (3 3 3) (4 4 4) (5 5 5) (6 6 6) ,000,000 ( ) 60,002 1,970, small particles will have a majority of atoms at the surface 9

10 filling size and crystallinity gap nm nanocrystals still considered bulk on atomic level (50 nm magnetite particle contains ~1.7x10 6 Fe 3 O 4 unit formulae) superparamagnetic (monodomain) crystals n, e and ph diffraction study magnetic and structural transitions needed for: applications, where larger magnetic moment is desired studies of fundamental physics properties develop better controlled artificial systems (self assembly, templating, patterns, structuring etc) potential use in spintronics and quantum computing. 10

11 synthesis is an important consideration Top Down (Physical Methods) Bottom Up (Chemical Methods) Bulk Classical behavior Nanoparticles Quantum-size effects Macroscopic Mesoscopic Microscopic Metal and Metal-Alloy Nanoparticles 1. High-energy ball milling 2. Laser ablation 3. Ion sputtering 4. Thermal evaporation 5. etc. 100 nm 1 nm Metal and Metal-Oxide Nanoparticles Molecules Quantum behavior 1. Reduction of metal salts in solution 2. Thermal decomposition reactions 3. Hydrolysis 4. Bio-inspired methods 5. etc.. 11

12 synthetic magnetite nanoparticles Mechanochemical Routes Controlled atmosphere high energy ball milling submicron synthesis ball milling.html Chemical Routes Wet chemistry techniques Decomposition of volatile organometallics Microemulsion syntheses Aerosol/vapor, pyrolysis methods Biomineralization 2 20 nm nm Extracellular magnetite formation 2 20 nm Magnetosome biomineralization nm Biomimetic synthesis Templated growth (porous media, organic macromolecules) tunable 12

13 high energy ball milling Hadjipanayis, G., Neil, D. Gabay, A., EPJ Web of Conferences, 2013, 40, mill ultrafine grinding.html 13

14 nucleation and growth: general concepts + Nucleation and Critical Radii G n 0 r c r 0 G n = 4 r 2 G s (4/3) r 3 G v r Variation of Gibb s free energy of nucleation with cluster radius during synthesis. r c is the kinetic critical radius and r 0 the thermodynamic critical radius Stabilization of nanoclusters of various size requires a competitive reaction chemistry between core cluster growth and cluster surface passivation. LaMer, V. K. and Dinegar, R. H., J. Am. Chem. Soc., 1950, 72,

15 crystal growth mechanism in solution 15 S. H. Yu, Top. Curr. Chem., 2007, 271,

16 co precipitation synthesis 16

17 formation of uniform particles in solution single nucleation and uniform diffusion controlled growth nucleation, growth and aggregation of smaller subunits multiple nucleation events and Ostwald ripening growth nucleation events and growth of nanoparticles have to be separated Must either use a stabilizer, or proceed via the constrained synthesis 17

18 silica coated magnetite particles Magnetic particles encapsulated in silica via the Stöber sol gel method diethylenetriamine functionalized silica surface 18 L. L. Vatta, et al., Pure Appl. Chem., 2006, 78,

19 flame spray synthesis 19

20 laser spray pyrolysis 20

21 sonochemical direct immersion horn 21 K. S. Suslick, Scientific American, 1989, 2,

22 controlled decomposition of Fe(CO) 5 Fe(CO) 5 ))) + oleic acid alkanes, Ar/O nm 24 hrs reflux, Ar/O 2 Fe(CO) 5mesitylene, F 127 Pluronic precipitation, washing, resuspension in water 22

23 ultrasonic spray pyrolysis 500 nm 23 W. H. Suh, K. S. Suslick, J. Am. Chem. Soc., 2005, 127,

24 sonochemical synthesis with magnetic field 24 T. Prozorov, et al., J. Phys. Chem. B, 1999, 59, 6956

25 selected functions of various objects from nature variety of inorganic crystals 25

26 magnetic moment per bee 26