Raman e Mineralogia, Parma, 12 febbraio 2009 Spettroscopia Raman e Grandi Sorgenti (Synchrotron...

Raman e Mineralogia, Parma, 12 febbraio 2009

Spettroscopia Raman e Grandi Sorgenti (Synchrotron Facilities)

Marco Milanesio

Dipartimento Scienze e Tecnologie AvanzateUniversità del Piemonte Orientale, Alessandria, Italy

E-Mail: [email protected]://www.mfn.unipmn.it/~marcomi

Nuove Applicazioni della Spettroscopia Raman nei MineraliParma 12 Febbraio 2009

Raman e Mineralogia, Parma, 12 febbraio 2009Marco Milanesio 2

Storage ring producing high brilliance X-ray (1000-1000000 more intense than in normal diffractometers)

What is a synchrotron facility?


Standard SNBL Beam line at ESRF

Optics A+BHRPD + XAFS PD + Single x-tal

B-Hutch A-Hutch Prep-lab


The good news: Synchrotron allows X-ray Powder Diffraction (XRPD) in situ studies (down to ms time res.)

Typical business at synchrotron facilities :

When a phase undergoes a phase transition its

diffraction pattern changes

Environmental chambers are used to condition the sample environment: Temperature,

pressure, atmosphere, irradiation, laser in situ

during XRPD

(a)


1) The availability of 3rd generation synchrotrons allowed the use of XRPD experiments at in situ conditions.

2) The addition of an extra dimension, such as time or temperature allowed the investigation of structural properties during solid-state transformations

IN SITU XRPD synchrotron facilities?

Template Burning inside TS-1 and Fe-MFI Molecular Sieves: An in Situ XRPD Study. Milanesio, M.; Artioli, G.; Gualtieri, A. F.; Palin, L.; Lamberti, C.

J. Am. Chem. Soc.; 2003; 125(47); 14549-14558


The bad news: the limits of in situ XRPD

amorphous phases

evolved gas

gel phases

liquid phases

nanoparticles

surface reactivity

disordered moieties

light elements (Z < 4)

Why Raman and synchrotron facilities?

Sometime overcame by Raman!!


Raman spectroscopy can give complementary information to XRPD, being extremely sensitive to small structural distortions, to changes in the hydration/protonation states, to surface modifications and to changes in the charge/defect distribution and short-range ordering.

Raman information


• Many non-simultaneous Raman-Xray diffraction/absorption studies have been performed for their complementarities.

• In situ induced sample modifications with multiple external stimuli such as:– Temperature and/or– Pressure and/or– UV or Visible Light, X-ray’s and/or– Oxidizing or reducing environments– ….

• On samples that show kinetic and non-reversible behaviors on one or more of these stimuli

Why Simultaneous RAMAN/XRPD? Because of the perfect space, time and reaction-coordinate correlation between Raman and XRPD and no bias due to different sample holder/conditioning modes

Difficult or impossible to synchronize separate XRPD and Raman experiments


The first example - Phase transitions of isobutyl-silsesquioxane (SNBL@ESRF, July 2004)

XRPD: phase transition from the triclinic to rhombohedral phase at 323 K

Raman spectroscopy: small variation of the peak at 775 cm-1

related to rotation of the side chain O-Si-C-C torsion angles

This case study allowed i) to test the first Raman/XRPD implementation with a NIR laser (1064 nm) and ii) to design the better setup for the permanent Raman installation at the SNBL


SNBL layout with Raman

Optics A+BHRPD + XAFS PD + Single x-tal

B-Hutch A-Hutch Prep-labRam

an

Excitation laserRaman return


The Experimental Set-up – Technical detailsReferences on the simultaneous experiments

- More info: E. Boccaleri, F. Carniato, G. Croce, D. Viterbo, W. van Beek, H. Emerich and M. Milanesio, In situ simultaneous Raman/high-resolution X-ray powder diffraction study of transformations occurring in materials at non-ambient conditions, J. Appl. Cryst. (2007). 40, 684-693.


Possible multi-technique experiments at the SNBL…

Raman/EXAFS

Raman/XRPD/EXAFS

Raman/XRPD/XAFS/Mass Spectroscopy

Raman/Single crystal XRD

Raman/XRPD


….. accessible non ambient conditions

Helium cryostat down to 5-10 K

Diamond Anvil cell: from 0 to 50 GP

Lamp- and laser- induced excitation: photo-reactivity

Gas blower + Cryostream nitrogen blower: from 80 to 1300 K

Gas pumping system: from vacuum to 30 bars


Case study 1 - The stearate-hydrotalcite (Mg/Al layered hydroxide) thermal treatment and decomposition (almost no mineralogy!)

Example of application to a low order synthetic

nanocomposite organic-inorganic material –

conformational/chemical sensitivity of Raman


Case study 1 - XRPD

At 362 K phase transition due to the swelling of the layers

A new peak appeared at 2θ=0.81° (d=42.4 Å). Its intensity increased up to 425 K and its 2θ moved to 0.72° (d=48.2 Å).


Case study 1 - Raman

The C-H stretching modes (2800-3000 cm-1) and the symmetric and asymmetric C-C stretching modes (at 1044 and 1110 cm-1) are sensitive to the changes in the trans-gauche conformation of the CH2 units and to the packing of the

embedded phase.


31.5 Å(XRPD at RT)

The phase transition characterizationRaman/XRPD the conformational features of the organic moiety and the structural rearrangement of the inorganic moiety

At room temperature: all-trans stearate chains form an inter-digitated bi-layer while (Raman).

45.0 Å (XRPD)

At high temperature: the chains assume folded gauche conformations and inter-digitation is reduced (Raman).

ΔT

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