Title: Wet surface vibrational spectroscopy
Osawa, Derek Peak,
Bin Ren, Zhong-Qun
Tian, and Thomas
To promote the application of wet surface vibrational spectroscopies
(ATRIRS, SEIRAS, SERS) to problems in interfacial chemistry by selecting,
testing, and disseminating to universities a collection of experiments
suitable for undergraduate teaching laboratories and able to be performed
with inexpensive equipment.
Undergraduate experiments in interfacial chemistry are presently
dominated by measurements of macroscopic quantities such as surface
tension and amount adsorbed when increasingly spectroscopic and microscopic
data are presented in the corresponding lectures. IUPAC can take a
lead in encouraging a more modern molecular approach to interfacial
physical chemistry through international collaboration of leading
expertise to compile and test a series of appealing experiments which
can be readily carried out in undergraduate laboratories with relatively
This project brings together leading physical chemists
in the fields of attenuated total reflection infrared spectroscopy
(ATRIRS), surface enhanced infrared spectroscopy (SEIRAS), and surface
enhanced Raman spectroscopy (SERS), to select practicable experiments
which can be carried out in teaching situations throughout the world.
Both SERS and SEIRAS employ finely divided metal surfaces while the
ATRIRS particle film approach can be applied to any solid. All of
the chosen surface spectroscopies are applicable to solid/aqueous
interfaces that are of considerable interest in studies of natural
and technological systems. Examples include the study of adsorbed
electrode intermediates and the investigation of adsorbed collectors
used as flotation agents for mineral extraction.
The ATRIRS experiments will include the basis of ATR-IR
spectroscopy, the measurement of solution spectra, the preparation
of colloidal particles of substrate materials, the measurement of
spectra of adsorbed species including eg oxalic acid on TiO2,
sulfate on hematite, adsorption kinetics and adsorption isotherm determinations.
The SEIRAS experiments will include a brief introduction
to the mechanism of the IR absorption enhancement and the procedures
for preparing SEIRA-active thin metal films on a Si ATR prism. By
using a thin metal film as the working electrode, adsorption and reaction
of molecules on the electrode surface will be examined in aqueous
solution under electrochemical control. The electrocatalytic oxidation
of methanol on Pt will be used as a model system. By comparing the
SEIRA spectra of adsorbed CO and adsorbed formate with the cyclic
voltammogram acquired simultaneously, students can know that CO is
a poison and formate is a reaction intermediate in methanol electrooxidation.
The SERS experiments will include: introduction of basis
of Raman spectroscopy, instrumentation; measurement of liquid (CCl4
and H2O), and solid sample (Silicon as sensitivity and frequency
calibration standard); Electrochemical roughening of massive silver
electrodes; Preparation of Au sol, which will be used as it is or
dispersed as SERS substrate; SERS measurement on Silver surface, Au
sol and the sol dispersed surface; Preparation of SERS active Pt surface.
The probe species will be pyridine and SCN-.
Most undergraduates have access to infrared spectrometers
in teaching laboratories so that the ATRIRS and SEIRAS experiments
would be expected to find more widespread use. However, Raman instruments
are decreasing in cost and more frequently found in undergraduate
laboratories, which justifies the inclusion of SERS experiments.
The experiments will be tested and refined in their
laboratories of origin, followed by testing in at least two university
undergraduate laboratories elsewhere under normal laboratory conditions.