Precious Metals Nanoparticles
Precious metal nanoparticles with properties different from bulk or molecules
TANAKA has been developing new materials that contribute to solving social issues by designing and synthesizing precious metal nanoparticles with new functions not found in conventional materials.
Polymer Coated Nanoparticles
Nanoparticles are generally defined as having a size between 1 and 100 nm and have unique properties that are different from both bulk metals and molecules. They are expected to be used in a variety of applications including catalysts. Nanoparticles can be stably dispersed in solvent by modifying their surface with polymers called protective agents.
■Precious Metal Nanoparticles
Typical nanoparticle solution provided as a sample by TANAKA
(wt.%) |
||||||
|---|---|---|---|---|---|---|
| Au PVP | Au | 5～10 | PVP※1 | 4 | Water | |
| Pt PVP | Pt | 2 | ||||
| Pd PVP large | Pd | 5～20 | ||||
| Pd PVP fine | 4 | |||||
| Pt PAA | Pt | 2 | PAA※2 | 2 | ||
| Pt PEI | Pt | 3～5 | PEI※3 | ～0.5 | ||
- ※1：PVP; Polyvinyl Pyrrolidone
- ※2：PAA; Polyacrylic Acid
- ※3：PEI; Polyethyleneimine
- Other products available upon consultation.
- *Please inquire regarding mass production.
■TEM Images
Pt PVP
Pd PVP
Gold Nanoshell Particles
Gold nanoshell with 10 nm thickness
Silica nanoparticles coated with Au (gold nanoshell particles). The overall size of gold nanoshell particles can be controlled between 80 nm and 250 nm to allow a wide range of optical characteristics.
■Features
- The extremely thin shell of less than 10 nm allows effective absorption of incident light energy. In addition, the specific gravity of the particles as a whole becomes lower, which contributes to stable dispersion.
- Possible to stably disperse in water and organic solvents.
- Particles protected by protective agents can be prepared with Au concentration of up to approximately 20 wt％.
- STEM image of gold nanoshell particles (220 nm)
The white contrast is gold
- Gold nanoshell particles dispersing liquid
Left: 100 nm, Right: 220 nm
This technology is expected to be used for optical materials that respond to visible light to light in the near-infrared range such as colloidal crystals, surface-enhanced Raman scattering, and photothermal conversion materials. Furthermore, it is expected to be applied in optical devices including optical displays used in LCDs that require high image quality, optical sensors, plasmonic nanoantennas, and biosensors used in cancer screening.
Anisotropic Precious Metal Nanoparticles
Gold nanocube with a side of approx. 50 nm
Precision-controllable gold nanocube
One side of the cube can be precisely controlled between about 20 and 100 nm. The edge shape can also be adjusted from sharp to rounded. Unlike an isotropic sphere, anisotropy occurs in the enhanced electric field due to localized surface plasmon resonance depending on the direction and angle of the incident light.
Simulation diagram of electric field enhancement of gold nanocube
The simulation of electric field enhancement of 50 nm gold nanocube shows that when light polarized in the x-axis direction is injected, light (electric field) with an intensity hundreds of times greater than the incident light is concentrated at the edge endpoints.
■Features
- In addition to cubes, other shapes such as rods and prisms can also be synthesized.
- The peak wavelength of localized surface plasmon resonance can be controlled from the visible to the infrared range by controlling the shape and size.
- Possible to add other metals to the surface using anisotropic particles as a nucleus.
This technology is expected to be used for optical materials that respond to visible light and light in the infrared range such as for photoelectric conversion, photothermal conversion, and photocatalysis. Furthermore, it is expected to be applied to bioimaging in combination with biomolecules.
Quantum Dot
Quantum dot that can use various light
Semiconductor nanoparticles called quantum dot. Multi-component semiconductor nanocrystals with a uniform particle size distribution that can be produced by appropriately mixing multiple metal species and chalcogens.
■Features
- The bandgap width (absorption wavelength) can be adjusted by controlling the core composition and particle size.
- A wide range of wavelengths from visible, near-infrared (NIR) to short wavelength infrared (SWIR) can be used.
- High-performance quantum dot can be obtained by core-shelling particles and doping specific atoms.
- Does not contain lead or other environmentally harmful substances.
- Film formation is possible using spin coating or other simple methods since ink stably dispersed in organic solvents can be produced.
-
Example of controlled quantum dot particle size
- Image of the cross-section of particles coated
with a film formed by spin coating
This technology is expected to be applied to various fields that use light. In particular, it is expected to be used for photoelectric conversion materials such as solar cells, optical sensors, and as well as luminescent materials for laser and imaging.
Metal Nano Cluster
Ag12 cluster molecules model
Precious metal nano cluster assembled by linker molecules
Metal nano clusters consisting of several to dozens of metal atoms bonded together are fine particles with a particle size of 4 nm or less. They are attracting attention as a constituent unit of functional nanomaterials. TANAKA is developing materials linked by organic molecules called linkers because, in general, particles become unstable as the particle size decreases.
■Features
- Achieved high structural stability by integration using linker molecules.
- Uniform physical properties can be expected by maintaining a constant distance between clusters.
- The clusters form a unique sheet structure arranged in a two-dimensional array that presents high crystallinity.
SEM image and molecule model of Ag12 cluster assembly
Relevant literature：
DAS, Saikat, et al. Silver cluster-assembled materials for label-free DNA detection.
Chemical Communications, 2023, 59.27: 4000-4003.
This technology is expected to be applied to chemical sensors, catalysts, and electronic device materials.