Plasmons are quanta of plasma oscillations that can be excited by light under certain conditions. There are two types of plasmons: bulk plasmons, which depend only on electron density, and surface plasmons, which are collective oscillations of electrons at a surface. Metallic nanoparticles support surface plasmons - when illuminated by light, the electromagnetic field causes electrons within the nanoparticle to oscillate at a resonant plasmonic frequency, generating an enhanced local electric field. Efficient energy transfer can occur between metal nanoparticles and semiconductors if their plasmons are resonantly coupled, allowing light absorption and energy transfer.

1. Plasmons
Presented By:
Anuradha Verma

2. Presentation Layout
What are plasmons
Plasma Frequency
Physical meaning of surface plasmon
Bulk plasmon and surface plasmon

3. What are Plasmons
Plasmons are a unit of collective oscillations of electrons
Or
Quantum of plasma oscillation
Photons-
electromagnetic
vibrations
Light is a wave that is oscillating electro-magnetic field, plasmons
can be excited by light under specific conditions. (And conversely,
in some cases light can be emitted by plasmons as well.)
Phonons-
mechanical
vibrations

4. Bulk Plasmon and Surface Plasmon
• Collective oscillation of conducting
electrons
• Bulk plasmon energy depends only on
electron density n
Bulk Plasmon
• Wave nature: Charge density waves
at surface.
Surface Plasmon
ωp= bulk plasmonfrequency
ωp(s)= surface plasmonfrequency

5. Physical Meaning of Surface Plasmons
Nanoparticles- Lattice
of ionic cores with
conduction electron
moving almost freely
inside the NP.
Particle illumination:
EMF of the light exerts
a force on these
conduction electrons
moving them towards the
NP surface.
Electrons are confined
inside NP, negative
charge and positive
charge accumulate on
opposite side, creating
an electric dipole
Dipole generates an electric
field inside the NP opposite
to that of the light that will
force the electrons to
return to the equilibrium
position.
electrons are displaced from the
equilibrium position and the field is
removed later, they will oscillate
with a certain frequency that is
called the resonant frequency called
plasmonic frequency.

6. Metallic nanoparticles (NPs)-
Electrons are confined in 3D.
Electron oscillations induce an electric field
around the NP that can be much larger than
the incident light one.

7.  Photoanode (Au-ZnO photoelectrode) capture solar light, simultaneously generates
photoelectrons that migrates to the CB of ZnO.
 Simultaneously, the Au nanostructure absorbs plasmon-induced irradiation,
generating hot electrons and an electromagnetic field.
 The plasmon-induced hot electrons were injected into CB of ZnO and they were
driven to the photocathode, where they reacted with protons to form H2 .
 Now excited Au nanoparticles can generate holes to accept electrons from
electrolyte (water) and form O2
Plasmon-induced electromagnetic field creates additional vacancies at the bottom of
the conduction band, facilitating the generation of photoelectrons by
photoexcitation.

8. Efficient energy transfer can occur between metal and
semiconductor if resonant coupling is present between the
plasmonic metal nanoparticles and semiconductor.
In case of low overall light absorption:
Plasmonic metal nanoparticles can be used to capture the light.
When the photons are not absorbed in the desired location,
metal nanoparticles can be used to absorb photons and then
transfer the energy to an adjacent semiconductor.
Metal nanoparticle be energetically coupled to the semiconductor
to transfer its excitation energy and produce an electron-hole pair
in the semiconductor.