The quantum yield (QY) is one of the most important quantitative properties of a luminescent sample, and robust ways to measure it are essential in the application of luminescence techniques. In the project we will perform an inter-laboratory comparison of the two main methods for QY measurements, the classical relative method based on standards, and the absolute method using integrating spheres which recently gained popularity.
The outcomes will be:
- insight into the reproducibility and inter-laboratory variability of QY measurements using the two methods
- an extended set of standards and protocols for QY measurement.
A previous IUPAC project (#2004-021-1-300; see Pure Appl. Chem. 2011, 83, 2213-2228; https://dx.doi.org/10.1351/PAC-REP-10-09-31) has clearly shown a shortage of standards for relative QY measurements of solutions. Recently, absolute measurements are becoming more popular as a result of the wider availability of integrating sphere equipment, but their reliability is still to be established.
More standards are needed to fully cover the wavelength range of interest, from ~250 to ~1000 nm. Preferred reference compounds have broad and featureless absorption spectra, and have proven emission quantum yields independent of the excitation wavelength. The reference values should preferably be those of air-equilibrated samples. The second purpose of the project is to establish the variability of independent QY measurements in different laboratories. We will ask ~10 laboratories world-wide to take part in this test. The laboratories should be well-equipped and experienced, but should not be specialists or method developers in the field. We are interested in what is practice in a normal good laboratory.
The accuracy of the integrating sphere measurements is best when the quantum yields are not too low or too high, and when overlap between absorption and emission is minimized. For relative measurements, it is advantageous if the QY of sample and reference are not very different. Thus, we should look in particular for standards that have QY of the order of 0.1 – 0.2. Other points to be addressed are standards for the long-wavelength range, up to 1000 nm.
Based on our previous experience, we propose a small task group that leads the project. A number of laboratories (ca. 10, distributed around the globe) will be invited to take part in the measurement of ca. 20 samples, to be selected in the first stage of the project. After the first round of measurements, laboratories that produced strongly deviating results will be informed before all the results are shared. This allows them to check their data. If a laboratory insists on results that deviate from those of others, they will be taking into account in the analysis. In fact, it is important to find out whether there is consensus.
The principal investigators of the laboratories participating in the project are:
Prof.Dr. Bo Albinsson, Chalmers University of Technology, Goteborg, Sweden
Prof.Dr. Fred Brouwer, University of Amsterdam, The Netherlands
Dr. Suzanne Fery-Forgues, ITAV, Toulouse, France
Prof. Ken Ghiggino, University of Melbourne, Australia
Dr. Stephan Landgraf, Graz University of Technology, Austria
Prof. Rachel Meallet-Renault, Universite Paris-Sud, France
Prof.Dr. Guillermo Orellana, Universidad Complutense de Madrid, Spain
Dr. Abhijit Patra, IISER Bhopal, India
Prof. Wenwu Qin, Lanzhou University, Lanzhou, P.R.China
Prof. Vivian Wing Wah Yam, University of Hongkong, China
In October 2014, a decision has been made which samples to measure, and samples have been shared among the labs during November 2014.
An announcement of this project was published in the Sep 2015 issue of Chemistry International, p. 31, https://dx.doi.org/10.1515/ci-2015-0521
By September 2015, most of the teams have delivered their results, and the task group expected to be able to start the analysis of the data.
April 2019 updated – The analysis of the data is in progress and a draft report is being prepared for submission to Pure Appl. Chem.
Page last updated 4 Apr 2019