①动态光散射的基本原理与数据解析

主 讲 人：李牧 助理研究员

深圳综合粒子设施研究院

深圳市光明区新湖街道圳园路268号

Email: limu@mail.iasf.ac.cn

简介：

动态光散射是一种利用溶液中粒子布朗运动对光的准弹性散射来对粒子进行表征的方法。动态光散射可以对溶液中的粒子进行原位测试，可获得有关扩散系数、粒径以及粒径分布等丰富信息，在化学、生物、材料等领域应用广泛。然而动态光散射原理较为复杂，并且由于病态问题的特性，其数据解析具有一定的主观性与不确定性。因此，本报告将从基础的动态光散射理论出发，对动态光散射的原理与常用数据解析方法进行介绍。并介绍新发展的基于机器学习框架的多角度动态光散射数据联合分析方法。

李牧，2022年博士毕业于华南理工大学，获理学博士学位，现在深圳综合粒子设施研究院参与同步辐射光源的相关工作。他的主要研究方向为小角散射与动态光散射理论、方法学与软件开发，及其在物质表征中的应用。已发表SCI论文6篇，并开发了小角散射与动态光散射数据分析软件，获得软件著作权一项。

②带电大分子在受限环境下的非扩散型拓扑动力学

主 讲 人：贾迪 研究员

中科院化学研究所

高分子物理与化学国家重点实验室

简介：

过去70多年以来人们认为高分子链在受限环境下总是可以自由扩散运动的，并且遵从爱因斯坦扩散方程。高分子链在不同的受限环境下有不同的运动模型。即使是在最强烈的受限环境下，高分子链的运动符合由P. G. de Gennes和S. F. Edwards提出的著名的管道模型 （reptation），在此模型中，高分子链仍然可以像蛇一样向前爬行，符合一维无规自由扩散运动（one-dimensional random walk），因此，无论是在弱受限环境还是强受限环境中，高分子链都是可以自由运动的，并且遵从爱因斯坦扩散方程。

本报告将介绍一种新型动力学，即“非扩散型拓扑动力学（Non-diffusive Topologically Frustrated Dynamics）”。在此受限环境中高分子整链是不能自由扩散运动的，但是一条链内的局部链段可以在每个凝胶网格内做多级局部松弛运动，其本质是多熵位垒造成的一种能长存的亚稳态。本报告会详细阐明为什么在更强的受限环境下（reptation管道模型）高分子链能够进行一维自由扩散运动，而在较弱的拓扑受限环境下，高分子链反而不能进行自由扩散运动，并深入对比了我们这一新发现与著名的管道模型的区别。利用这一新型动力学可以在室温下把DNA链“困”在高含水量的水凝胶中，且DNA等生物大分子仍可保持其生物功能性。因此，这一新型动力学对基因工程，药物释放等领域具有重大价值。

贾迪研究员2021年加入中科院化学所。2021年获得“国家海外优秀青年科学基金”资助、“中科院百人计划”资助。2019 年荣获 Journal of Chemical Physics期刊“年度最佳审稿人”称号。具有散射技术与高分子物理的专业特长，主要研究方向为多尺度自组装带电软物质----从基础研究到创新应用。具体包括带电高分子与带电软物质体系的动力学、结构、相行为、反应动力学等，并将基础研究上取得的成果应用到生物医疗工程、能源、环境等领域中，力争以基础研究创新带动应用创新。

③Applications of Diffusing-wave Spectroscopy in Food

主 讲 人：潘伟春教授

The School of Food Science and Biotechnology,

Zhejiang Gongshang University, Hangzhou, China

简介：

The complexity of food, high heterogeneity with hierarchical structure, non-equilibrium with unceasing spatiotemporal changes of its compositions, and intrinsically complex interactions, hampers its study1. On the other hand, the tremendous impact of food on human being health encourages this kind of research. Long time practice suggests that micro-structure of food is a promising candidate to mitigate this dilemma2. However, how long time and how big area to capture this food structure is highly uncertain. In addition, what is the technique suitable to fulfill this job?

Researches in soft materials suggest that Diffusing-wave Spectroscopy is an ideal one3. In this presentation, several samples in food research have been given4. I hope that all these cases could shed light on the applications of this innovative technique in food.

REFERENCES

1. Mezzenga, R.; Schurtenberger, P.; Burbidge, A.; Michel, M., Understanding foods as soft materials. Nature Materials 2005, 4, 729-740.

2. Joardder, M. U. H.; Kumar, C.; Karim, M. A., Food structure: Its formation and relationships with other properties. Critical Reviews in Food Science and Nutrition 2017, 57, 1190-1205.

3. Weitz, D. A., Soft materials evolution and revolution. Nature Materials 2022, 21, 986-988.

4. (a) Niu, F.; Ahmad, M.; Fan, J.; Ritzoulis, C.; Chen, J.; Luo, Z.; Pan, W., The application of diffusing wave spectroscopy (DWS) in soft foods. Food Hydrocolloids 2019, 96, 671–680; (b) Li, F.; Zhang, Y.; Guo, B.; Wei, Y.; Don, C.; Pan, W.; Zhang, B., The mesoscopic structure in wheat flour dough development Journal of Cereal Science 2020, 95, 103087; (c) Niu, F.; Yu, J.; Fan, J.; Zhang, B.; Ritzoulis, C.; Pan, W., The Role of Glycerol on the Thermal Gelation of Myofibrillar Protein from Giant Squid (Dosidicus gigas) Mince. Food Chemistry 2022, 371, 131149.

   
   

Dr. Weichun Pan got the PHD of chemical Engineering from the University of Houston and worked with Dr. Peter Vekilov. His dissertation topic focused on the interactions between protein molecules and its application in protein phase transitions. He is one of the contributors for two-step mechanism. Then he went to Tohoku University and worked with Dr Katsou Tsukamoto. His research topic in Japan focused on the influence of microgravity condition on protein crystal nucleation and growth. In 2011, He joined in the School of Food Science and Biotechnology, Zhejiang Gongshang University. He tried to build a picture of intermolecular interactions between food protein and other bio-macromolecules. He revealed the salting-in mechanism of muscle protein, and found nano protein particles in food. This kind of structure could be used to judge food quality and to guide food process development.

④Advanced Light Scattering Techniques and their Applications

主 讲 人：Dr. Coline Bretz

LS Instruments, Fribourg, Switzerland

Email: Coline.bretz@lsinstruments.com

web: http://www.lsinstruments.ch

简介：

Light scattering is a powerful characterization technique routinely used in research and formulation development in diverse area such as life sciences, food, personal care products or advanced materials. Depending on the specific technique employed, it provides a measure of the size (DLS) or shape (SLS) or determines the viscoelasticity of a sample (DWS) [1].

While these are well-established characterization techniques, several significant improvements have gained traction over the past decade. This presentation will feature a short review of novel techniques enabling a wider range of applications, such as Depolarized DLS [2], Non-Ergodic DLS [3], Modulated 3D DLS [4] or Echo-DWS [5].

REFERENCES

[1] Weitz & Pine, Diffusing-Wave Spectroscopy. In Dynamic Light Scattering; Brown, W., Ed.; Oxford University Press: New York, 652-720 (1993).

[2] Balog & al., Characterizing nanoparticles in complex biological media and physiological fluids with depolarized dynamic light scattering, Nanoscale, 2015, 7, 5991-5997

[3] Pusey & van Megen, Dynamic light scattering by non-ergodic media, Physica A: Statistical Mechanics and its Applications 1989, 157, 2, 705-741

[4] Block & Scheffold, Modulated 3D cross-correlation light scattering: Improving turbid sample characterization, Rev. Sci. Instrum. 81, 123107 (2010).

[5] Zakharov & al., Multispeckle diffusing-wave spectroscopy with a single-mode detection scheme, Phys. Rev. E 73, 011413, 2006

Dr. Coline Bretz is an expert in advanced light scattering technologies. She studied colloidal science at the Paris 7 University (France) as well as the University of Pennsylvania (USA) and holds a PhD in physical chemistry. She joined LS Instruments as a product scientist in 2017 and now leads the Sales & Marketing business unit. She was the winner of the 2019 MDPI-Polymers Prize awarded by ECIS, the European Colloid and Interface Society. (The prize was created by ECIS and the MDPI journal Polymers for young scientist to acknowledge top level scientific activity of young researchers in the field of polymer physics, chemistry, or technology.)

⑤Characterization of Soft Materials by 3D Cross Correlation Light Scattering and Diffusing Wave Spectroscopy

主 讲 人：Prof. Dr. Frank Scheffold

Physics Department and Fribourg Center for Nanomaterials, University of Fribourg, Chemin du Musée 3, CH-1700 Fribourg, Switzerland

Board of LS Instruments AG, CH-1700 Fribourg, Switzerland

Email: Frank.Scheffold@unifr.ch

web: https://www.unifr.ch/phys/en/research/groups/scheffold/

简介：

I
nformation on mesoscopic length scales is required to characterize the structural and dynamic properties of soft materials, polymers, liquid crystals, small particles and droplets. Static and dynamic light scattering (SLS/DLS) experiments in the single scattering regime can provide such information [1]. In many systems, however, these powerful techniques or affected or fail due to multiple scattering of light. Here I will discuss several experimental innovations that have emerged over the last two decades [2,3] to overcome such limitations. New concepts and technological advances have led to a more widespread application of methods such as 3D static and dynamic light scattering (3D LS) [2,3] as well as diffusing wave spectroscopy (DWS) [4]. To illustrate their use and range of applications, I will discuss some examples taken from our research and of others. The examples I will discuss are the study of thermosensitive microgel particles [5], strongly interacting charged colloids and emulsions [4,6,7], and the microrheology of protein and polyelectrolyte solutions [8,9].

Figure 1. 3D Light Scattering – 3D LS. (a) Original 3D-Cross Light Scattering Goniometer [2]. Inset: Principle of time gating the beam-detector pair using a Pair of acousto-optical modulators (AOM) (b) employed as MHz-frequency shutters when inserted into the beam bath (Pictures courtesy of LS Instruments AG, Fribourg, Switzerland).

REFERENCES

[1]Neutron, X-rays and Light. “Scattering Methods Applied to Soft Condensed Matter” (North-Holland, 2002), Th. Zemb & P. Lindner (Editors)

[2] F. Scheffold and R. Cerbino, “New trends in light scattering”, Current Opinion in Colloid & Interface Science 12 (1), 50-57 (2007)

[3] Block, I. and Scheffold, F., “Modulated 3D cross-correlation light scattering: Improving turbid sample characterization”, Review of Scientific Instruments 81, 123107 (2010)

[4] Kim H.S., Şenbil N., Zhang C., Scheffold F., Mason T.G. “Diffusing wave microrheology of highly scattering concentrated monodisperse emulsions”, PNAS 116(16), 7766-71 (2019)

[5] Reufer, M., Diaz-Leyva, P., Lynch, I., & Scheffold, F. “Temperature-sensitive poly (N-Isopropyl-Acrylamide) microgel particles: A light scattering study,” EP E, 28(2), 165-171. (2009)

[6] Rojas-Ochoa, L. F., Castaneda-Priego, R., Lobaskin, V., Stradner, A., Scheffold, F., & Schurtenberger, P., “Density dependent interactions and structure of charged colloidal dispersions in the weak screening regime,” Physical Review Letters 100 (17), 178304 (2008)

[7] Xu, Y., Scheffold, F. and Mason, T.G., Diffusing wave microrheology of strongly attractive dense emulsions. Physical Review E, 102(6), p.062610. (2020)

[8] Garting, Tommy, and Anna Stradner. "Optical microrheology of protein solutions using tailored nanoparticles,” Small 14 (46), 1801548 (2018)

[9]Matsumoto, A., Zhang, C., Scheffold, F., and Shen, A.Q. Microrheological Approach for Probing the Entanglement Properties of Polyelectrolyte Solutions. ACS Macro Letters, 11(1), pp.84-90 (2021)

Frank Scheffold, born in 1969, holds a chair in experimental physics at the University of Fribourg (Switzerland). He studied at the University of Konstanz (Germany) and the Weizmann Institute of Science (Israel, with Prof. Jacob Klein). He received his Ph.D. from the University of Konstanz in 1998 for research he had carried out at the Institut Charles Sadron (Strasbourg, France) and in Konstanz with Prof. Georg Maret. After his habilitation at the University of Fribourg in the group of Prof. Peter Schurtenberger, he was appointed associate professor in 2004. Since 2009 he has held the chair of "Soft Matter and Photonics." Since 1996 he has authored about 120 peer-reviewed scientific articles.  He was a visiting scholar for several months at UC Los Angeles (2009), the University of Queensland (2014), and New York University (2019).  His research interests include the optics of complex systems, static and dynamic light scattering, diffuse light propagation, the dynamics of colloidal systems, aggregation and phase behavior, and the fabrication and characterization of soft materials. From 2011-2019 he served as a member of the Swiss National Research Council. He is co-founder and currently chairman of LS Instruments AG, Fribourg. He was a founding member of the Swiss National Centre of Competence in Research "Bioinspired Materials" based in Fribourg and was a member of the Centre's Executive Board from 2014 to 2022.