inVia Raman microscope Sample environment accessories Introduction Electrochemical cell

SPD/PN/089 Issue 1.0 June 2003
Product note from the Spectroscopy Products Division
inVia Raman microscope
Sample environment accessories
Introduction
Electrochemical cell
Renishaw offers a wide range of sample
stages that enables in situ dynamic
Raman and photoluminescence
experiments in a variety of environments.
Renishaw's electrochemical cell is an
ideal tool for researchers investigating
electrochemistry.
Electrochemical cell: for studying in situ
corrosion, surface enhanced Raman
scattering, etc.
Humidity cell: for studying the effect of
humidity on materials such as
pharmaceuticals.
High pressure cell: diamond anvil cell for
compressing samples to 50 GPa (500 kbar)
Temperature control stages: heating and
cooling stages covering temperatures from
2.2 K (-271 °C) to over 1800 K (1500 °C)
0.1 V
0.6 V
500
1000
Raman shift / cm-1
1500
Spectra of corrosion inhibitors taken from
inside an electrochemical cell with an
electrochemically roughened silver working
electrode and 0.05 Mol dm-3 solution of
benzotriazole. The changes in the spectra are
attributable to changes in molecular orientation
in the region of the electrode surface.
Data courtesy UK Atomic Energy Authority.
It can be used for in situ corrosion studies,
where Raman spectroscopy can be used to
detect the chemical changes that occur
during cyclic voltammagram studies, for the
identification of electrochemically produced
intermediates, and for investigations of
catalysts. It can also be used to generate
electrochemically roughened surfaces that
use the phenomenon of surface enhanced
Raman scattering (SERS) to give greatly
enhanced Raman signals.
Electrochemical cell and
holder.
The glass electrochemical cell is securely
mounted in a metal holder that fits onto
Renishaw's macro sampling set. This enables
the user to use the standard microscope
stage controls to focus accurately and easily
into the cell.
The cell features ports for easy filling of the
cell with electrolye/reaction mixtures and for
venting gaseous reaction products, and a
side arm that contains the standard electrode
(a calomel mercury/mercurous chloride
electrode is normally supplied). The working
electrode face is held vertically to allow
gaseous reaction products to bubble away,
and the distance between the working
electrode and the window is adjustable to
accommodate a range of working distance
objectives.
Use Raman
spectroscopy to
monitor the changes
caused to samples
by:
• temperature
• pressure
• humidity
• electrochemistry
Humidity control cell
VGI humidity control cell.
The system is interfaced to a dedicated
digital process controller allowing manual
control and measurement of humidity in
addition to programmed humidity profiles. PC
based software allows greater programmable
functionality, together with data acquisition
and playback facilities.
Changes in humidity can affect the
structure and properties of many
materials, from catalysts and
semiconductors to microbiological cells
and pharmaceuticals. Chemical and
physical structure, as well as reaction
rates and degradation processes, can all
be influenced by changes in humidity.
Raman spectroscopy is ideal for studying the
reaction of samples with solvents and is
especially suited to aqueous studies since
water is a poor Raman scatterer and gives
rise to only very weak Raman signals. The
unrivalled sensitivity of Renishaw's Raman
microscopes means that even very subtle
changes can be monitored with ease.
The VGI humidity cell (supplied to Renishaw
by Surface Measurement Systems) allows
users to control precisely the temperature
and humidity environment of a microscopy
sample. For example, the influence of
humidity on chemical transformations in drug
samples, the stability of drug delivery
systems such as tablet coatings, the
efficiency of catalysts, growth rates for micro
biological samples, and electronic properties
of semiconducting materials can be studied.
B-05 high pressure (diamond
anvil) cell.
Temperature and pressure
The cell is designed for use with ultra-long
working distance objectives, using standard
microscope slides as the sample mounting.
Temperature and humidity around the sample
are controlled using an integrated Peltier
heat pump, circulating fluid pump, and water
reservoir to ensure uniform temperature
distribution and stable sample humidities
(see Table 1 for specifications). The sample
window is double-glazed to prevent
condensation of moisture when working at
temperatures above or below ambient. An
organic option is available for working with
solvents other than water.
90% RH
80% RH
70% RH
0% RH to 60% RH
TIme / s
300
200
100
0
820
840
860
Raman shift / cm-1
880
Temperature and pressure control cells are
therefore widely used for the study of phase
transitions (such as polymer melting,
crystallisation, and conformational changes
in proteins), and for the study of
degradation/oxidation in the pharmaceutical,
adhesive, polymer, and paints fields. They
are also used by materials scientists for
studies of photoluminescence in
semiconductors and other materials, and by
chemists for studies of catalysts and reaction
kinetics.
Renishaw's Raman microscopes are valuable
tools in this work as Raman spectra are
sensitive to molecular arrangement and can
differentiate different structures. The
microscopes' ability to acquire
photoluminescence spectra also enables
them to reveal detailed information about
defects and the effect of pressure and
temperature on them; these data are
especially useful in the semiconductor and
materials science fields.
95% RH
800
Changes in temperature and pressure can
cause changes to the phase, morphology,
and structure of materials, can cause
chemical degradation, and can modify the
mechanical, electrical, and catalytic
behaviour of materials.
900
Effect of humidity on an pharmaceutical tablet
(ibuprofen meltlet). Dramatic changes occur at
80% RH as the sucrose component deliquesces.
(Excitation: 830 nm)
High pressure cell
Temperature control cells
The high pressure cell operates by
forcing two diamond anvils together, and
can produce hydrostatic or nonhydrostatic pressures.
Customer's requirements are normally
satisfied by one or more of four cell types:
• hot cell (ambient to 1500 °C)
(Linkam Scientific Instrument’s TS1500)
• hot-cold cell (-196 °C to 600 °C)
(Linkam Scientific Instrument’s
THMS600)
For hydrostatic pressures the sample is
immersed in a pressure transmitting material
surrounded by a metal gasket with a central
hole, with the confinement being created by
the vertical walls of the gasket hole and the
two anvil faces. This configuration is useful
for high precision pressure measurements.
Non-hydrostatic pressures are generated if
the gasket is omitted. This gives a pressure
gradient, with the pressure gradually
dropping from the centre of the cell towards
its periphery, and is useful for visualizing
pressure induced phase changes.
• liquid nitrogen cell (77 K to 500 K)
(Oxford Instruments Superconductivity’s
MicrostatLN)
• liquid helium cell (2.2 K to 500 K)
(Oxford Instruments Superconductivity’s
MicrostatHe)
TS1500 hot cell supports
temperatures from ambient to
1500 °C.
Details of the cells are given in Table 2.
Please contact Renishaw if you require
further information, or have a requirement for
a custom temperature control cell.
The B-05 high pressure cell (supplied to
Renishaw by Diacell Products Ltd.) can
support pressures up to 50 GPa (500 kBar).
It normally operates at ambient
temperatures, but the addition of a ring
heater allows use to about 600 ºC.
THMS 600 hot-cold cell
supports temperatures from
–196 °C to 600 °C.
(A0,X)-LO
(D0,X)-LO
X-LO
The anvils can be adjusted for tilt to ensure
anvil faces are parallel. For convenience, all
adjustments necessary for alignment can be
made under the microscope.
GaN/Al2O3
T = 4.2 K
d = 200 µm
3.7 GPa
675
700
×100
A1 (LO)
MicrostatHe supports
temperatures from 2.2 K to
500 K
725
875
Raman shift / cm-1
(A0,X)
×5
0 GPa
650
X
DAP
6.3 GPa
E2 (high)
(D0,X)
X-2LO
9.7 GPa
900
925
950
Raman spectra of the (0001) face of AlN, as a
function of hydrostatic pressure.
Data courtesy M. Kuball, University of Bristol,
and D.J. Dunstan, Queen Mary, University of
London.
3.1
3.2
3.3
Energy / eV
3.4
3.5
325 nm excitation photoluminescence
spectrum of a 200 µm GaN layer on sapphire,
taken at 4.2 K.
Data courtesy of H. Siegle et al., Technical
University, Berlin, Germany.
MicrostatN supports
temperatures from 77 K to
500 K.
Renishaw plc
Spectroscopy Products Division
Old Town, Wotton-under-Edge,
Gloucestershire GL12 7DW
United Kingdom
T +44 (0) 1453 844302
F +44 (0) 1453 844236
E raman@renishaw.com
www.renishaw.com
Table 1: Humidity control stage
Temperature stabilitya
± 0.1 °C
Temperature Rangeb
+10 °C to +40 °C
Humidity stability
± 1.5% RH
Humidity Range:
0% RH to 95% RH
Notes:
a
Where difference between ambient and programmed temperature > ±2 °C
b
Assuming ambient temperature of 25 °C.
Table 2: Temperature control stages
Temperature range
Maximum sample size
Diameter
Height
Hot
Hot/cold
Liquid nitrogen
Liquid helium
ambient
to
1500 °C
-196 °C
to
600 °C
77 K
to
500 K
2.2 K
to
500 K
8 mm
2.5 mm
(6 mm deep
also available)
22 mm
3 mm
(lid extension
also available)
20 mm
2 mm
23 mm
8 mm
Light aperture (diameter)
1.7 mm
2.4 mm
20 mm
10 mm
Window thickness
Variousa
0.17 mm
Typicallya 0.5 mm
Typicallya 0.5 mm
Objective lens
working distance
> 6 mm
0.1 mm
to
4.5 mm
> 2 mm
> 3 mm
104 mm
95 mm
29 mm
137 mm
92 mm
22 mm
90 mm
190 mm
24 mm
110 mm
440 mm
44 mm
Stage body size
Length
Width
Height
Notes:
a
A variety of window thicknesses are available. Please contact Renishaw for more details.
Renishaw is continually improving its
products and reserves the right to change
specifications without notice.
© 2003 Renishaw plc