# US 10,118,834 B2 · Superparamagnetic colloidal photonic structures

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- Number: US 10,118,834 B2
- Document ID: US10118834B2
- Status: Granted
- Kind: B2
- Application number: 12/597,794
- Filed: 2008-04-26
- Published: 2010-09-09
- Granted: 2018-11-06
- Earliest claimed: 2007-04-27
- Assignees: The Regents of the University of California
- Applicants: Yadong Yin; Jianping Ge
- Inventors: Yadong Yin; Jianping Ge
- Web page: https://patentgrep.com/patent/US10118834B2

## CPC

- C01G 49/08: Ferroso-ferric oxide [Fe3O4]
- B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites
- C09C 1/24: Oxides of iron
- G02F 1/09: based on magneto-optical elements, e.g. exhibiting Faraday effect
- C01P 2002/72: by d-values or two theta-values, e.g. as X-ray diagram
- C01P 2002/80: defined by measured data other than those specified in group C01P2002/70
- C01P 2004/04: obtained by TEM, STEM, STM or AFM
- C01P 2004/32: Spheres
- C01P 2004/62: Submicrometer sized, i.e. from 0.1-1 micrometer
- C01P 2004/64: Nanometer sized, i.e. from 1-100 nanometer
- C01P 2004/84: one phase coated with the other
- C01P 2006/42: Magnetic properties
- C01P 2006/60: Optical properties, e.g. expressed in CIELAB-values
- G02F 2202/32: Photonic crystals
- C01G: COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts or peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium, or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds containing nitrogen, other non-metals and metal C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanamide C01C3/16; thiocyanates C01C3/20)
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- C09C: TREATMENT OF INORGANIC MATERIALS, OTHER THAN FIBROUS FILLERS, TO ENHANCE THEIR PIGMENTING OR FILLING PROPERTIES (treatment of materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone C04B14/00, C04B18/00, C04B20/00); PREPARATION OF CARBON BLACK {; PREPARATION OF INORGANIC MATERIALS WHICH ARE NO SINGLE CHEMICAL COMPOUNDS AND WHICH ARE MAINLY USED AS PIGMENTS OR FILLERS}
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS

## Abstract

Monodisperse colloidal nanocrystal clusters of magnetite (Fe3O4) with tunable sizes from about thirty to about three hundred nanometers have been synthesized using a high-temperature hydrolysis process. The colloidal nanocrystal clusters are capped with polyelectrolytes, and highly water soluble. Each cluster is composed of many single magnetite crystallites, thus retaining the superparamagnetic behavior at room temperature. The combination of superparamagnetic property, high magnetization, and high water dispersibility makes the colloidal nanocrystal clusters ideal candidates for various important biomedical applications such as drug delivery and bioseparation. The present invention is further directed to methods for forming colloidal photonic crystals from both aqueous and nonaqueous solutions of the superparamagnetic colloidal nanocrystal clusters with an external magnetic field applied thereto. The diffraction of the photonic crystals can be tuned from near infrared to visible and further ultraviolet spectral region by varying the external magnetic field.

## Claims

### Claim 1

A method of forming chain-like colloidal assemblies that diffract light, consisting of:
mixing an iron salt precursor, a polar solvent, and a surfactant to form a first mixture;
introducing a precipitation agent into the first mixture to initiate a hydrolysis reaction, wherein the precipitation agent is a base;
controlling the hydrolysis reaction to occur at a temperature ranging from about 100° C. to about 320° C.;
obtaining monodisperse superparamagnetic magnetite colloidal particles from the hydrolysis reaction, wherein each of the superparamagnetic magnetite colloidal particles is formed from a plurality of nanocrystals;
controlling a size of the monodisperse superparamagnetic magnetite colloidal particles from about 30 nanometers to about 300 nanometers based on a concentration of the base;
dispersing the monodisperse superparamagnetic magnetite colloidal particles in a polar solution; and
applying an external magnetic field on the monodisperse superparamagnetic magnetite colloidal particles so as to assemble the magnetite colloidal particles in chain-like structures that diffract light in the polar solution,
wherein the colloidal particles within the chain-like structures are periodically arranged, with tunable periodicity and diffraction frequency by varying the external magnetic field.

### Claim 2 (depends on 1)

The method of claim 1, wherein the polar solution is chosen from the group comprising:
water and solutions of other polar solvents wherein the superparamagnetic magnetite colloidal particles are dispersed.

### Claim 3 (depends on 1)

The method of claim 1, wherein the diffraction frequency of the chain-like colloidal assemblies under varying the external magnetic field covers the entire visible region, the near-ultraviolet region, and the infrared region of the light spectrum.

### Claim 4 (depends on 1)

The method of claim 1, wherein when the external magnetic field is oscillating, the optical response of the chain-like colloidal assemblies follows the oscillation.

### Claim 5

A method of forming chain-like colloidal assemblies, consisting of:
mixing an iron salt precursor, a polar solvent, and a surfactant to form a first mixture;
introducing a precipitation agent into the first mixture to initiate a hydrolysis reaction, wherein the precipitation agent is a base;
controlling the hydrolysis reaction to occur at a temperature ranging from about 100° C. to about 320° C.;
obtaining monodisperse superparamagnetic magnetite colloidal particles from the hydrolysis reaction, wherein each of the superparamagnetic magnetite colloidal particles is formed from a plurality of nanocrystals;
controlling a size of the superparamagnetic magnetite colloidal particles from about 30 nanometers to about 300 nanometers based on a concentration of the base;
rendering a surface of the superparamagnetic magnetite colloidal particles to be dispersible in nonaqueous solvents;
dispersing the superparamagnetic magnetite colloidal particles in a nonaqueous polar solution; and
applying an external magnetic field on the superparamagnetic magnetite colloidal particles so as to assemble the magnetite colloidal particles in chain-like structures that diffract light in the nonaqueous solution,
wherein the colloidal particles within the chain-like structures are periodically arranged, with tunable periodicity and diffraction frequency under varying the external magnetic field.

### Claim 6 (depends on 5)

The method of claim 5, wherein the nonaqueous polar solution is chosen from a group consisting of alcohol solvents.

### Claim 7 (depends on 5)

The method of claim 5, wherein rendering the surface of the monodisperse superparamagnetic magnetite colloidal particles includes coating the monodisperse superparamagnetic magnetite colloidal particles with a layer of silica.

### Claim 8 (depends on 7)

The method of claim 7, further comprising the step of tuning a thickness of the silica layer for further tuning the diffraction frequency under the external magnetic field.

### Claim 9 (depends on 5)

The method of claim 5, wherein the diffraction frequency of the chain-like colloidal assemblies under varying the external magnetic field covers the entire visible region, the far-ultraviolet region, and the infrared region of the light spectrum.

### Claim 10 (depends on 1)

The method of claim 1, wherein the surfactant is chosen from the group consisting of polyelectrolytes.

### Claim 11 (depends on 1)

The method of claim 1, wherein the obtaining of the superparamagnetic magnetite colloidal particles comprises:
coating the particles with a layer of silica or polymer; and
linking a ligand to the surface of the coated colloidal particles.

### Claim 12 (depends on 5)

The method of claim 5, wherein the surfactant is chosen from the group consisting of polyelectrolytes.

### Claim 13 (depends on 5)

The method of claim 5, wherein the obtaining of the superparamagnetic magnetite colloidal particles comprises:
coating the colloidal particles with a layer of silica or polymer; and
linking a ligand to the surface of the coated colloidal particles.

### Claim 14 (depends on 1)

The method of claim 1, wherein each nanocrystal of the plurality of the nanocrystals is approximately 10 nanometers in size.

### Claim 15 (depends on 5)

The method of claim 5, wherein each nanocrystal of the plurality of the nanocrystals is approximately 10 nanometers in size.

### Claim 16 (depends on 1)

The method of claim 1, wherein upon removing the external magnetic field, the chain-like colloidal assemblies disassemble from the chain-like structures.

### Claim 17 (depends on 1)

The method of claim 1, wherein the base is sodium hydroxide (NaOH).

### Claim 18 (depends on 1)

The method of claim 1, wherein the surfactant is polyacrylic acid (PAA), the precursor is Iron (III) chloride (FeCl3), the polar solvent is diethylene glycol, and the base is sodium hydroxide (NaOH).

### Claim 19 (depends on 1)

The method of claim 1, comprising:
controlling the size of the monodisperse superparamagnetic magnetite colloidal particles by modulating the concentration of the base while keeping all other parameters fixed.