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 inexpensive equipment.
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.
Project announcement published in Chem. Int. Jul/Aug 2007, p. 19
Jan 2016 update: Due to experimental complexities the SEIRAS component of the project has been discontinued. Work in the past few months has brought the ATRIRS experiments close to completion and the SERS experiments will follow in the coming months.
October 2019 update – A Technical Report by McQuillan, A., Osawa, M., Peak, D., et al. and entitled “Experiments on adsorption at hydrous metal oxide surfaces using attenuated total reflection infrared spectroscopy (ATRIRS)” is published PAC AOP 2 Oct 2019, https://doi.org/10.1515/pac-2019-0211
Cite Pure and Applied Chemistry, 91(12), pp. 2043-2061, 2019
Last update: 7 Dec 2019