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Static and dynamic studies using linear reflectance and second harmonic generation of molecular and metallic nanoparticles films at the air/water interface. Gaëlle Gassin-Martin. Nonlinear Optics and interfaces Laboratoire de Spectrométrie Ionique et Moléculaire (LASIM) – Lyon -. Aims.

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Ga lle gassin martin

Static and dynamic studies using linear reflectance and second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

Gaëlle Gassin-Martin

Nonlinear Optics and interfacesLaboratoire de Spectrométrie Ionique et Moléculaire (LASIM) – Lyon -


Aims second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

General idea: Nanometric studies using nonlinear optics

  • Bi-dimensional films upon compression

    • Control of the average distance between nano-objects

    • Vary the amplitude of the interactions

  • Optical measurement of the electronic delocalisation

    • Molecular systems (molecular aggregates)

    • Metallic systems (nanoparticles)


Overview
Overview second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

  • Molecular film

    • Langmuir film formation

    • Importance of optical measurement

    • Properties upon compression

      • Polarisation resolved Second Harmonic Generation (SHG)

  • Metallic nanoparticles film

    • Evolution of interactions upon compression

      • Linear reflectance

      • SHG

    • Film dynamics at the air/water interface

      • Intensity correlation analysis


  • Molecule dia

    air second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    water

    Molecule :DiA

    hydrophobic tail

    hydrophilic head

    • Amphiphilic molecule

    • Large nonlinear response (electrons p delocalised, « push-pull » structure)

    • Excellent surface SHG probe


    Molecular films
    Molecular films second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    Langmuir trough

    • Control the densityin situ

    Densification


    Film isotherms
    Film isotherms second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    Expanded liquid

    Condensed liquid

    compression

    Compression

    • Knowledge of certain macroscopic states (S, P, T, pH…) all along the film formation

    • Control of interactions in the system


    Polarisation resolved shg of a film experimental set up

    Filter second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    Photon counter

    Laser

    femto

    Mirrors

    Chopper

    Langmuir trough

    70°

    Langmuir trough

    Polarisation resolved SHG of a film- Experimental set up -

    • Polarisation measurement

    • A l/2 wave plate permits the variation of the incident light polarisation

    • An analyser to select the emergent light polarisation

    • Experimental curves interpretation, exit S polarised

    l/2

    Lens

    Analyser

    Pressure Measurement

    Above

    Langmuir trough

    profile


    Second harmonic generation

    SHG second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    Second harmonic generation

    SHG process :brings into play

    the second order polarisation

    Excitation

    at 800 nm

    SHG

    measurement

    2 nd order susceptibility tensor


    Centrosymmetric property
    Centrosymmetric property second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    Centrosymmetric medium

    • The symmetry is very important for this process

    • SHG is always null in centrosymmetric medium

    • Wide interest with the surface which represents a symmetry break

    • exclusive measurement of surface properties ( )


    Microscopic dimension
    Microscopic dimension second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    Induced dipole defined by :

    Hyperpolarisabilty

    1st order

    polarisability

    • Hyperpolarisabilty tensor βmicroscopic parameter which characterises the molecule.

    • Susceptibility tensor χmacroscopic parameter which characterises the surface.


    Molecular film collapse dia molecular film

    Contre-ions second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    Micelle

    Molecular film collapse-DiA molecular film -

    • High monolayer compression

    • Simultaneous measurements :

    Molecular Density : 0.4 to 3 nmoles/cm²

    • Surface pressure : continuous growing

    • SHG: Signal falls at high density

    Some information remain inaccessible by surface pressure measurement.

    SHG technique convincing

    Non centrosymmetry

    SHG signal falls related to multilayer formation

    • DiA : 2 carbon chains

    • liquid film with a lot of defects

    centrosymmetry


    Polarisation analysis dia molecular film
    Polarisation analysis second harmonic generation of molecular and metallic nanoparticles films at the air/water interface. -DiA molecular film -

    ED Approximation (electric dipolar)

    Isotropic surface

    Molecular Density : 0.43 nmoles/cm²

    incident polarisation angle

    • High degree of symmetry


    Isotropic chiral Surface second harmonic generation of molecular and metallic nanoparticles films at the air/water interface. -DiA molecular film -

    isotropic surface

    ED Approximation

    • Monolayer compression

    Chiral

    Molecular Density : 0.8 nmoles/cm²

    (Chiral)

    • Chirality with ED approximation not sufficient

    Unique possible origin for 90° angle deformation is chirality's phenomenon


    Introduction of magnetic components second harmonic generation of molecular and metallic nanoparticles films at the air/water interface. -DiA molecular film -

    Isotropic chiral Surface

    Molecular Density : 0.8 nmoles/cm²

    ED Approximation

    (Chiral)

    MD Approximation

    (Chiral)

    • Chirality with MD approximation adapted


    Evolution of s polarised curves all along compression dia molecular film

    C second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    B

    A

    D

    F

    E

    G

    D

    C

    B

    A

    E

    G

    F

    Evolution of S-polarised curves all along compression -DiA molecular film -

    G

    F

    E

    D

    C

    A

    B

    • Progressive symmetrybreaking all along the compression

    Molecular Density : 0.2 to 1.4 nmoles/cm²

    threshold : 0.5 nmoles/cm²

    Fitting curves Tensor elements which translate surface state all along compression


    Chiral tensor element dia molecular film
    Chiral tensor element second harmonic generation of molecular and metallic nanoparticles films at the air/water interface. -DiA molecular film-

    • Increase chiral tensor element

    • Becomes comparable to

    Sign change

    • Uncertainty about the origin of chiral tensor evolution

    Compression


    Microscopic interpretation dia molecular film
    Microscopic Interpretation second harmonic generation of molecular and metallic nanoparticles films at the air/water interface. -DiA Molecular film -

    Even if we lack some information we know :

    DiA non chiral molecule

    attest an isotropic chiralsurface

    • Progressive formation of chiral structures upon compression

    • Microscopic models of chiral aggregates

    It drives us to think about:

    • Helix aggregates

    Model: an electron along an helix


    Conclusions second harmonic generation of molecular and metallic nanoparticles films at the air/water interface. -DiA molecular film-

    • Langmuir technique : squeeze the molecules to form a 2D film

      • Chiral aggregates formation

  • SHG technique : sensible to surface phenomenon

    • Measure electronicdelocalisation effects in these chiral aggregates upon compression

  • Molecular Films Nanoparticles Films


    Overview1
    Overview second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    • Molecular Film

      • Langmuir films

      • Importance of optical measurement

      • Proprieties under compression

        • SHG resolved in polarisation

  • Film of metallic nanoparticles

    • Evolution of interactions upon compression

      • linear reflectance

      • SHG

    • Film dynamic at the air/water interface

      • Intensity correlation analysis


  • Nanoparticles synthesis

    Thioalkanes second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    C12

    Nanoparticles Synthesis

    Metallic Nanoparticles

    Gold and Sliver

    Ø 7 nm

    Brust

    Method

    • Surface capped thioalkanes

    hydrophobic particles adapted to 2D film formation

    Silver Nanoparticles

    in chloroform

    Chain length variation:

    Nano

    Particle

    • Chains C18 limited interactions

    • Chains C12 , C6 … allowed interactions

    Collaboration LPCML ( Olivier Tillement, Stéphane Roux)


    Nanoparticles films aims

    Nanoparticles deposit thanks to a microlitric syringe second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    Nanoparticles Films -Aims-

    • Consequences on optical response (new resonances, field enhancement…)

    • Aggregates formation

    • Emergence of interactions upon compression

    Film compression


    Linear reflectance and shg of a film experimental set up

    Beam splitter second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    Objective

    Pressure Measurement

    Langmuir trough

    Detection

    Detection

    Filter

    Lampe

    HaDe

    femto Laser

    Dichroïc mirror

    Beam splitter

    Filter

    Objective

    Objective

    Langmuir trough

    Langmuir trough

    Linear reflectance and SHG of a film-experimental set up-

    Reflected Spectrum at 90° incidence on the surface

    Sources :

    Linear measurements : HaDe lamp

    Nonlinear measurements : femtosecond laser

    Metallic Nanoparticles

    capped C18


    Linear reflectance silver nanoparticles film
    Linear reflectance second harmonic generation of molecular and metallic nanoparticles films at the air/water interface. -Silver nanoparticles film-

    Surface density :

    3, 4 and 7x1014 particles /m²

    • Strong fluctuations of reflectance

    • Disappearance of fluctuations for high density

    Reflectance is the ratio between reflection spectrum of the film to the reference reflection spectrum

    2 consecutive measurements for each compression


    Linear reflectance silver nanoparticles film1
    Linear reflectance second harmonic generation of molecular and metallic nanoparticles films at the air/water interface. -Silver nanoparticles film-

    Surface density:

    3, 4 et 7x1014 particles /m²

    The behaviour is easily observed after normalised of the reflectance spectra

    • Maximum reflectance Amplitude increases at 660 nm with compression


    Linear reflectance modelling silver nanoparticles film

    50 nm second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    Linear reflectance modelling -Silver nanoparticles film-

    Simulations with hypothesis of particles aggregate

    Simulations with hypothesis of non aggregated particles

    Surface density : 9x1014 particles /m²

    Broaden

    =

    Effective film theory

    for spherical particles

    heterogeneous set

    of ellipsoid

    Isolated particles

    (weak surface

    fraction )

    Particles in strong interaction equivalent to an ellipsoid (model)

    High surface fraction

    Effective film

    theory for ellipsoidal particles

    • 2nd resonance shows the beginning of interactions


    Conclusions silver nanoparticles film
    Conclusions second harmonic generation of molecular and metallic nanoparticles films at the air/water interface. -Silver nanoparticles film-

    Diluted system (surface filling factor = 3%)

    Long alcane Chains C18

    Expect : No aggregation

    No interaction

    • Strong fluctuations at weak compression which disappear at high density

  • Prove :Inhomogeneous surface, existence of domains

    Domains movements frozen

    • 2nd plasmon resonance increases

  • Prove :Interactions appear upon compression

  • Modification of

    for the particles

    SHG

    Compression


    Shg of particles films gold nanoparticles film

    420 nm second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    Measured

    noise

    400 nm

    Measured SHG

    SHG of particles films -Gold nanoparticles film-

    • Continuous compression

    • Density: 2 to 11x1014 particles/m²

    Compression

    Few sharp picks


    Non linear signal gold nanoparticles film

    • For each average second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

      density:

    Non linear signal -Gold nanoparticles film-

    6 temporal domains

    Intensity histograms

    Log normal fit


    Nonlinear signal gold nanoparticles film
    Nonlinear signal second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.-Gold nanoparticles film-

    • Density variation N

    But do not decrease

    • Necessity to introduce the tensor . It proves the presence of interactions between particles


    Conclusion second harmonic generation of molecular and metallic nanoparticles films at the air/water interface. -Silver nanoparticles film-

    Diluted system (surface filling factor = 3%)

    Long alkane Chains C18

    Expect: No aggregation

    No interaction

    • Necessity to introduce the element at high compression

      Prove: Existence of interactions in compressed film

    • Link with the increase of the second resonance plasmon concerning reflectance measurements

      Recurrence of these fluctuations phenomenon

    • Reflectance

    • SHG


    Signal fluctuations
    Signal second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.Fluctuations

    To extract quantitative information from this systematic observation

    • Analysis using autocorrelation calculation

    Autocorrelationfunction

    SHG signal intensity

    2 distinct characteristic times

    hydrophilic silver Nanoparticles

    Ø 7 nm


    Autocorrelation calculation

    • Two characteristic values: second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    • Function at the origin g(0)

    • Decorrelation characteristic time

    Autocorrelation calculation

    Signal memory measurement between t et t +


    Reflectance fluctuation all along compression silver nanoparticles film

    Density : 1.7x10 second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.14 part/m²

    Density : 3.2x1014 part/m²

    Density : 4.4x1014 part/m²

    = 1 second

    = 2 seconds

    = 6 seconds

    = 40 seconds

    Density : 5.3x1014 part/m²

    Density : 8x1014 part/m²

    >> 100 seconds

    Reflectance fluctuation all along compression -Silver nanoparticles film-

    Signal intensity

    Autocorrelation function

    Linear signal study

    • Characteristic fluctuation time increases

    • g(0) value decreases

    Silver nanoparticles

    Ø 7 nm

    capped C12


    Evolution of the parameter g 0
    Evolution of the parameter g(0) second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    g(0) decreases

    g(0)

    • Density of particles aggregates increases under the laser spot

    g(0)

    Compression


    Evolution of the parameter t
    Evolution of the parameter second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.t

    Characteristic time increases

    • Frozen movements on the surface for high density

    Agreggate size evolution from nm to µm

    Compression


    Autocorrelation curve fitting silver nanoparticles film

    Spot light second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    Domain

    Autocorrelation function from a silver nanoparticles film

    density 2x1014 part/m²

    vi

    Autocorrelation curve fitting -Silver nanoparticles film-

    Checked : No disregard waves

    Autocorrelation function

    Brownian diffusion

    Lateral flow


    Conclusions nanoparticles films
    Conclusions second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.-Nanoparticles films-

    Compression

    Compression

    • Some interactions between particles appear when the surface is compressed :

      • Linear reflectance

      • SHG

    • Possibility to measure the dynamics of the film :

      • Presence of moving nanoparticulesdomains

      • Dynamic evolution during compression


    General conclusions
    General Conclusions second harmonic generation of molecular and metallic nanoparticles films at the air/water interface.

    • Bi-dimensional Langmuir films studies:

      • Control the distance between nano-objects

      • Modulate the interactions between nano-objects

    nano-objects

    without interaction

    2D system

    with interaction

    • Molecular films upon compression:

      • Molecular aggregates arrangement

      • Presence of chirality in aggregates

      • Evidence of electronic delocalisation in aggregates

    • Metallic nanoparticles films:

      • Beginning of interactions upon compression

      • Observation of the film dynamics


    Have a look to my phd group thank you every one
    Have a look to my PhD group … second harmonic generation of molecular and metallic nanoparticles films at the air/water interface. Thank you every one ! !

    Pierre-François Brevet, Emmanuel Benichou, Guillaume Bachelier,

    Isabelle Russier-Antoine, Christian Jonin,

    Guillaume Revillod, Chawki Awada, Yara El Harfouch, Julien Duboisset, Lin Pu


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