32 No. 4
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Guidelines for Measurement of Luminescence Spectra and Quantum Yields of Inorganic Compounds, Metal Complexes, and Materials
Many fields of basic and applied chemistry, as well as material chemistry and the biosciences, employ luminescent inorganic compounds and materials. The number of researchers, who are synthetic chemists but carry out photophysical measurements, is continually increasing. While some experimental procedures have been published, there remains a need for standardized protocols, especially for quantitative measurements for such materials. Once accepted as standards, these will provide guidelines for such measurements and they can be available to all researchers, regardless of their previous experience in photophysics or theoretical chemistry, thereby allowing for objective comparisons of results generated in different laboratories.
This project aims to prepare a document describing guidelines for accurate measurements of luminescence spectra and quantum yields of metal complexes, inorganic compounds, and materials. The document will disseminate basic knowledge, rules, and protocols, not only to experts, but also to those new to this field.
In 1988, the IUPAC Organic Chemistry Division Commission on Photochemistry published “Reference Materials for Fluorescence Measurement”, D. F. Eaton, Pure Appl. Chem., 1988, 60, 1107-1114 (doi:10.1351/pac198860071107). This covers basic knowledge in fluorescence spectroscopy and quantum yield determination. However, there are some problems specific to inorganic compounds, which are not usually fluorescent but phosphorescent. Phosphorescence is generally air-sensitive and emits at longer wavelengths, and it may be temperature dependent. Therefore, the experiments require additional attention. For instance, the correction function for the spectrometer is generally difficult to establish in the near-infrared (NIR) range. Detectors such as CCD cameras are starting to replace the classical photomultiplier tube and reliable response curves are needed. Moreover, a major point in these experiments is the availability of highly reliable standards for relative-emission quantum-yield measurements.
Recently, some quantum yields of luminescent organic and inorganic compounds in solution have been reevaluated (Kengo Suzuki, et al., Phys. Chem. Chem. Phys., 2009, 11, 9850; doi:10.1039/b912178a). The emission quantum yield of ruthenium tris(bipyridine) complex, which is internationally used as a reference, has now been reevaluated to have a significantly higher value than previously reported.
For these reasons, new guidelines should be established for the measurement of luminescence spectra and quantum yields of inorganic compounds and metal complexes. The document should describe a precise methodology for establishing the correction function, particularly in the NIR. It should also provide adequate standards for quantum yield determination of both highly and poorly luminescent inorganic compounds and complexes.
The task group is hopeful that this project will result in an inspiring and enlightening pamphlet for chemists and material scientists who join the fast developing field of photochemistry and photophysics.
For more information, contact the Task Group Chair Hitoshi Ishida <[email protected]>.
last modified 23 July 2010.
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