Question 1

Do platinum nanoparticles have a plasmon peak?

Accepted Answer

Not in the visible. Platinum's strong interband absorption damps its plasmon so much that the UV-vis spectrum of particles under about 60 nm is featureless, rising towards the UV. Only large particles (80 nm and up) show a broad maximum, from scattering: about 414 nm at 80 nm and 448 nm at 100 nm (table above).

Question 2

Why are platinum nanoparticle colloids dark brown or black?

Accepted Answer

They absorb across the whole visible range without a resonance to pick out one colour, so a colloid darkens from brown to black as the concentration grows.

Question 3

How do I find the concentration of platinum nanoparticles from UV-vis?

Accepted Answer

Use the extinction at a fixed wavelength, for example 400 nm, and the molar extinction coefficient for your size from the table (about 4.2 × 108 M−1 cm−1 at 400 nm for 20 nm spheres): c = A / (ε ℓ). The calculator gives ε at any wavelength from Cext.

Question 4

Are platinum nanoparticles good for photothermal heating?

Accepted Answer

They absorb broadband light efficiently, so they heat under white light or lasers of any colour, but without the resonant boost of gold. The nanoparticle heating calculator gives the temperature rise for any material and size.

Question 5

Can I compute platinum nanospheres, core–shell nanoparticles, arrays, near fields, heating or substrates?

Accepted Answer

Yes: platinum nanospheres and core–shell nanoparticles (add a shell) are available in every calculator, from spectra to optical properties: near-field enhancement maps, dimers and hot spots, nanoparticle arrays and lattice resonances, particles on a substrate, emitters and the Purcell factor, nanorods and laser heating.

Diameter	Visible maximum	Molar extinction coefficient	Scattering share
5 nm	none: featureless	5.80 × 10⁶ M⁻¹ cm⁻¹	< 1 %
10 nm	none: featureless	4.74 × 10⁷ M⁻¹ cm⁻¹	< 1 %
20 nm	none: featureless	4.15 × 10⁸ M⁻¹ cm⁻¹	2 %
30 nm	none: featureless	1.64 × 10⁹ M⁻¹ cm⁻¹	8 %
40 nm	none: featureless	4.82 × 10⁹ M⁻¹ cm⁻¹	16 %
50 nm	none: featureless	1.19 × 10¹⁰ M⁻¹ cm⁻¹	27 %
60 nm	none: featureless	2.46 × 10¹⁰ M⁻¹ cm⁻¹	38 %
80 nm	414 nm	6.22 × 10¹⁰ M⁻¹ cm⁻¹	60 %
100 nm	448 nm	9.83 × 10¹⁰ M⁻¹ cm⁻¹	78 %
150 nm	568 nm	1.75 × 10¹¹ M⁻¹ cm⁻¹	93 %
200 nm	732 nm	2.69 × 10¹¹ M⁻¹ cm⁻¹	96 %

Platinum nanoparticle UV-vis spectrum calculator

Questions & answers

Do platinum nanoparticles have a plasmon peak?

Why are platinum nanoparticle colloids dark brown or black?

How do I find the concentration of platinum nanoparticles from UV-vis?

Are platinum nanoparticles good for photothermal heating?

Can I compute platinum nanospheres, core–shell nanoparticles, arrays, near fields, heating or substrates?

Platinum nanoparticle size vs UV-vis spectrum

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