How to measure size of gold or silver nanoparticles using UV Vis Spectrum

There is the relationship between the optical absorption spectrum of gold or silver nanoparticles caused by surface plasmon absorption (in particular, the plasmon resonance and its brodening ) and their sizes. The surface plasmon resonance is the coherent excitation of all the `free ’ electrons within the conduction band. The resonance does not give rise to the most intense absorption for very small clusters. For the larger particles (several tens of nanometres) the excitation of the surface resonance absorption can occurs in visible light region ( 400 -600 nm for Ag and Au nanoparticles). Such absorption spectra can be analysed using Mie theory. In particular, according this theory for nanoparticles smaller than the mean free path of the conduction electrons there is the relationship between the resonance broadening (γ) and the sizes of nanoparticles γ (r ) = γo + AυF/r , where r is the size of nanoparticle, A=3/4 for silver, γo is the velocity of bulk scattering (5•10 to 12 degrees s(-1)), υF is the Fermi velocity (for silver 1.39 • 10 to 6 degrees m/s). Using the experimental absorption spectra and this relation we can determine the size of nanoparticle.

Instrument: Double Beam UV Visible Spectrophotometer UV1901S

Features

1. Holographic Blazed Grating 1200 lines/mm, which ensures the low stray light.

2. Automated control system, which ensures the high stability and low noise.

3. Detachable sample room, which makes it easy to change accessories.

4. Spacious open-type light source room, which makes it easy to replace lamps.

5. Real double beam optical system.

6. 320*240 Graphic LCD Screen.

Powerful Functions 

1. Photometric Measurement: it can measure the Transmittance and Absorbance at different wavelengths simultaneously (Max 6 wavelengths)

2. Spectrum Measurement: Scanning on the Transmittance, Absorbance and Energy in wavelength range, and can do kinds of data processing, such as peak & valley detection, derivative calculation and spectrum operation.

3. Quantitative Measurement: Single wavelength, Double wavelengths, Three wavelengths and Multi-wavelengths measurement.

4. Kinetics Measurement: Time scanning and kinds of values calculation on the transmittance and absorbance at any set wavelength.

Technique Parameters

1. Wavelength Range: 190-1100nm.

2. Spectral Bandwidth: 0.5nm/1nm/2nm/3nm/5nm.

3. Wavelength Accuracy: +/-0.1nm (D2 656.1nm); +/-0.3nm full range.

4. Work Mode: T; A; C; E.

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