Recent advances in UV–vis spectroscopy of turbid solutions

报告题目：Recent advances in UV–vis spectroscopy of turbid solutions

报告人：Baptiste Auguié，School of Chemical and Physical Sciences, Victoria University of Wellington, New Zealand

报告时间：2025年3月10日10:00-11:00

报告地点：物理科技楼101

报告邀请人：倪卫海

报告摘要：UV–vis optical spectroscopy is a powerful nondestructive material characterisation technique for micro and nanoparticles in solution, ubiquitous in many fields—including foodstuffs, biochemicals, materials and medical research. The technique however requires that liquid samples cause minimal scattering to the probing light, and absorb sufficiently over the optical pathlength. Furthermore, traditional UV–vis

spectroscopy cannot distinguish between scattering and absorption contributions to extinction. We will describe our recent and on-going efforts using an integrating sphere technique to overcome these limitations [1,2]. Scattering can also be measured in a 90-degree configuration, providing a complementary characterisation to both transmission and absorption. We have applied these three techniques

on solutions of Au nanospheres (diameters 20–100 nm), checked the consistency of extinction as the sum of absorption and scattering, and validated the results against Mie theory (Fig. 1).

Figure 1: (a) Photograph of a cuvette with a solution of Au nanospheres, showing a strong colour variation along the beam path. (b) Schematic of extinction and scattering measurements of liquid samples in a standard cuvette. (c) Absorption spectroscopy setup enclosing a liquid sample inside an integrating sphere. (d) Extinction and scattering spectra for 60 nm Au spheres in water.

Scattered light measured at 90 degrees requires a calibration factor accounting for the collection geometry, and, more importantly, a non-trivial post-processing for the “inner-filter" effect of light undergoing scattering and absorption along the path [3]. Experimental access to all three types of spectra provides a much richer characterisation tool than extinction alone, and offers therefore a more stringent test of the parameters used in a theoretical fit. Notably, good agreement with Mie theory could only be obtained by considering the size polydispersity of the colloids and an accurate dielectric function for the metal [4]. The integrating sphere technique has also been applied to challenging samples consisting of low concentration dye molecules in the presence of resonant plasmonic nanoparticles. The method’s key strengths are: i) full angular and spatial averaging; ii) robust non-imaging optics; iii) recycling of scattered light inside the cavity; iv) increased pathlength. This combination enables the measurement of minute changes in absorption against a turbid reference sample [1,5,6].

References

[1] B.L. Darby, B. Auguié, M. Meyer, A. E. Pantoja, and E. C. Le Ru, Nat. Photon.10, 40–45 (2016).

[2] J. Grand, B. Auguié, and E. C. Le Ru., Anal. Chem.,91, 14639–14648 (2019).

[3] N. Micali, F. Mallamaceet al, Anal.Chem.,73, 4958–4963 (2001).

[4] A. Djorovi

, S. J. Oldenburg, J. Grand, and E C. Le Ru, ACS Nano,14, 17597–17605 (2020).

[5] S. Lee, H. Hwang, W. Lee, D. Schebarchov, Y. Wy, J. Grand,et al, ACS Energy Letters,5, 3881-3890 (2020).

[6] A. Stefancu, J. Gargiulo, G. Laufersky, B. Auguié, V. Chiş, E.C. Le Ruet alACS Nano17, 3119-3127 (2023).

报告人简介：Dr Baptiste Auguié  School of Chemical and Physical Sciences  Victoria University of Wellington, New Zealand