Photoluminescencequantum yield (PL QY) is one of the most important properties of luminescent materials. The best method for absolute PL QY measurement so far is recognized as using the optical integrating sphere system. However, measuring the absolute PL QY in high accuracy and stability is still challenging. Herein, both the experimental setup and analytical method for PL QY measurment are systematically studied. Two sets of absolute PL QY measurement systems based on two different integrating spheres have been built and optimized in two aspects, i.e. the light path and cuvette holder. A rationally designed cuvette holder has been fabricated using 3D printing technology. For quantum dot solution samples with constant PL QYs in a wide range of concentrations, a multi-point measuring method is developed. By plotting the remaining excitation photon number after absorbed versus the emission photon number for a series of quantum dot solutions with various concentrations, PL QY can be calculated as the absolute value of the slop of the linear fitting of the experimental data points. The reliability of the multi-point method can be evaluated by the fitting deviation. The R<sup>2</sup> of the linear fitting of more than six points reaches 0.999 for CdSe/CdS core-shell quantum dots. Comparing to the commonly used single-point method, multi-point method has much lower system error and higher repeatability. The PL QYs of the standard dyes, such as Rhodamine 6G and Nile Red, determined using the new method is found to be in good agreement to the values reported in literature. For the quantum dots with small Stokes shift or with weak-binding ligands, the PL QY would reduce at very high or low concentrations. The multi-point method with a series of quantum dot concentrations could be used to evaluate the self-absorption effect and the desorption of ligands on the surface of colloidal quantum dots. The concentration gradient method for PL QY measurement introduced here can be further used for quantitatively studying the ligand dynamics of colloidal quantum dots.

Measuring the absolute photoluminescence quantum yield of colloidal nanoparticles with multipoint method

2019 Fall National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.