Spettroscopia Raman e Grandi Sorgenti (Synchrotron Facilities)

Presentazione sul tema: "Spettroscopia Raman e Grandi Sorgenti (Synchrotron Facilities)"— Transcript della presentazione:

1 Spettroscopia Raman e Grandi Sorgenti (Synchrotron Facilities)
Marco Milanesio Dipartimento Scienze e Tecnologie Avanzate Università del Piemonte Orientale, Alessandria, Italy Nuove Applicazioni della Spettroscopia Raman nei Minerali Parma 12 Febbraio 2009

2 What is a synchrotron facility?
Storage ring producing high brilliance X-ray ( more intense than in normal diffractometers) Marco Milanesio

3 Standard SNBL Beam line at ESRF
B-Hutch A-Hutch Prep-lab PD + Single x-tal Optics A+B HRPD + XAFS

4 Typical business at synchrotron facilities :
The good news: Synchrotron allows X-ray Powder Diffraction (XRPD) in situ studies (down to ms time res.) (a) Environmental chambers are used to condition the sample environment: Temperature, pressure, atmosphere, irradiation, laser in situ during XRPD When a phase undergoes a phase transition its diffraction pattern changes 4 Marco Milanesio

5 IN SITU XRPD synchrotron facilities?
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 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); 5 Marco Milanesio

6 The bad news: the limits of in situ XRPD
Why Raman and synchrotron facilities? Sometime overcame by Raman!! 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) 6 Marco Milanesio

7 Raman information 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.

8 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 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 Difficult or impossible to synchronize separate XRPD and Raman experiments Marco Milanesio

9 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 9 Marco Milanesio

10 SNBL layout with Raman B-Hutch A-Hutch Prep-lab Excitation laser
Raman return PD + Single x-tal Optics A+B HRPD + XAFS

11 The Experimental Set-up – Technical details
References 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,

12 Possible multi-technique experiments at the SNBL…
Raman/XRPD Raman/EXAFS Raman/XRPD/EXAFS Raman/XRPD/XAFS/Mass Spectroscopy Raman/Single crystal XRD 12 Marco Milanesio

13 ….. accessible non ambient conditions
Gas blower + Cryostream nitrogen blower: from 80 to 1300 K Helium cryostat down to 5-10 K Diamond Anvil cell: from 0 to 50 GP Lamp- and laser- induced excitation: photo-reactivity Gas pumping system: from vacuum to 30 bars 13 Marco Milanesio

14 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 Marco Milanesio

15 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). 15 Marco Milanesio

16 Case study 1 - Raman The C-H stretching modes ( 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. Marco Milanesio

17 The phase transition characterization
Raman/XRPD  the conformational features of the organic moiety and the structural rearrangement of the inorganic moiety 45.0 Å (XRPD) At high temperature: the chains assume folded gauche conformations and inter-digitation is reduced (Raman). ΔT 31.5 Å (XRPD at RT) At room temperature: all-trans stearate chains form an inter-digitated bi-layer while (Raman). Marco Milanesio