Noise Engineering

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Noise Engineering (ME324N)
Environment effect on the acoustic vibration of
metal nanoparticles
Submitted by Suman
Chandrawat Entry no2001498
Group03
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Introduction

• Frequency and damping of the quantized modes .
• Investigation of composite materials .
• Fundamental radial (breathing) acoustic vibration
  of nanoparticles .

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Acoustic mode frequency and damping

• Navier equation for sphere.
• Continuity conditions for spherematrix boundary
  .
• Eigenmodes divided into spheroidal and torsional
  vibrations.
• complex frequency eigenvalues,

Where vL(s) is the longitudinal sound velocity
l,n is the normalized eigenfrequency.
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Other equations used
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Normalized frequency
n
For first five radial modes in the complex plane
for free or embedded silver nanoparticles
For first five radial modes in the complex plane
for free or embedded gold nanoparticles
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Density
, acoustic impedance Z
vL, and longitudinal vL and
transverse vT sound velocities in bulk silver and
gold and in different materials
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Experimental setup

• Two-color femtosecond pumpprobe technique
• TiSapphire oscillator
• Membrane type diamond anvil cell
• Experiments were performed on spherical silver
  nanoparticles embedded in a 50BaO50P2O5 glass
  matrix

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Results and discussion

• Silver nanoparticles in glass

(a) Transmission change ?T/T in R12.1 nm Ag
nanoparticles for a probe photon energy 2.95 eV
at normal pressure and at 53 kbar .The inset
shows the oscillating part of the signal at 1 bar
on an enlarged scale and a fit (b) same as (a) on
an enlarged scale.
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(a) Measured oscillation period Tosc in Ag
nanoparticles in glass as a function of their
radius. The lines show the periodsof the n0
fundamental radial mode computed using (2) and
(4) with the average bulk silver sound velocities
(full line) and extremal (dotted lines). (b)
Measured homogeneous damping time as a function
of R. The dashed line is a fit, and the full and
dotted lines the computed
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• Nanoparticles in solution

• The oscillation damping rate in gold colloid
  has been found to be much smaller than in the
  glass embedded silver nanoparticles.
• For large nanoparticles in solution, the apparent
  damping thus measures the size distribution and
  is environment independent

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Conclusion

• Frequency is almost environment independent
• Damping depends on the nature and acoustic
  response of the surrounding material and
  particlematrix interface

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Thank you