1、 Basic characteristics

1. Size effect

When the size of metal particles is reduced to the level of 10 nanometers, their physical and chemical properties are significantly different from bulk materials, mainly due to the "high dispersant effect" caused by an increase in the proportion of surface atoms.

Nanoscale metal particles can generate quantum confinement effects, and small changes in the number of atoms can significantly alter their electronic structure and optical properties.

2. Morphological features

The particle shape directly affects the process performance, and spherical particles are more conducive to preparing porous materials with uniform pores.

Non spherical particles may cause anisotropy in product performance, but can be quantitatively described by complex shape coefficients.

2、 Optical and Electrical Properties

1. Plasmon resonance

Gold nanoparticles exhibit characteristic surface plasmon resonance peaks in the ultraviolet visible region, which are widely used in sensing and photocatalytic fields.

Precious metal nanoparticles have extremely low light reflectivity and exhibit a black appearance.

2. Conductive properties

Reducing the size of nanoparticles can lead to an increase in resistance, for example, the resistivity of 10-25nm palladium particles is higher than that of bulk materials.

Gold nanoparticles can enhance electrode conductivity and, after modification, can be used to prepare high-sensitivity biosensors.

3、 Thermodynamic properties

1. Melting point and heat capacity

Nanoparticles have a significant decrease in melting point due to increased surface energy, which is present in precious metals such as silver and gold.

The specific heat capacity of nano palladium crystals at constant pressure is 5% higher than that of polycrystalline palladium, and it continues to increase with decreasing particle size.

2. Thermal expansion behavior

Nano silver exhibits abnormal thermal expansion above 373K, with an average coefficient of thermal expansion higher than bulk silver.

4、 Mechanical performance

Particle size influence: The pressing and sintering behavior of metal powders strongly depends on particle size distribution, and industrial porous materials typically use 1-500 μ m particles.

Ductility: Macroscopic metals generally have good ductility, but the mechanical behavior of nanoparticles depends more on their surface atomic arrangement.

5、 Typical applications

Catalysis: Utilizing quantum size effect to enhance surface activity. Composite materials with performance.