Effect of pH on Supramolecular Assemblies in Fulvic Acid Solutions

IF 1.1 4区化学 Q4 CHEMISTRY, PHYSICAL Doklady Physical Chemistry Pub Date : 2024-01-20 DOI:10.1134/S0012501623600316

G. N. Fedotov, S. A. Shoba, I. V. Gorepekin, O. A. Salimgareeva, A. I. Sukharev, T. A. Gracheva

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Abstract

The effect of alkalinization of fulvic acid (FA) solutions on an increase in their optical density has been studied. To explain this phenomenon, FA particles existing in solutions at different pH have been studied by scanning electron microscopy (SEM) and scanning tunneling microscopy (STM). It has been found that an increase in pH results in a noticeable decrease in the size of the supramolecular assemblies of FA molecules from ~200 to ~100 nm. An STM study of FA samples demonstrates that FAs exist in solutions as supramolecular assemblies of several hundred nanometers in size formed by 10–20 nm FA particle molecules. The observed phenomenon has been explained using the existing ideas about the supramolecular fractal cluster organization of humic substances. The explanation states that the upper layer of F-clusters degrades to give FA particle molecules, while the cluster size is seen to decrease. The FA particle molecules cannot be detected by SEM due to their small size, but they are readily visualized by STM.

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pH 值对富勒酸溶液中超分子组装的影响

摘要研究了富勒酸（FA）溶液碱化对其光密度增加的影响。为了解释这一现象，我们用扫描电子显微镜（SEM）和扫描隧道显微镜（STM）研究了存在于不同 pH 值溶液中的富勒酸颗粒。研究发现，pH 值的增加会导致 FA 分子超分子集合体的尺寸从 ~200 纳米明显减小到 ~100 纳米。对 FA 样品的 STM 研究表明，FA 存在于溶液中，是由 10-20 纳米 FA 粒子分子形成的几百纳米大小的超分子集合体。现有的关于腐殖质超分子分形簇组织的观点解释了所观察到的现象。该解释指出，上层的 F 簇会降解生成 FA 粒子分子，而簇的大小则会减小。由于 FA 粒子分子较小，因此无法通过扫描电镜检测到，但通过 STM 却很容易观察到。

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来源期刊

Doklady Physical Chemistry 化学-物理化学

CiteScore

1.50

自引率

0.00%

发文量

审稿时长

6-12 weeks

期刊介绍： Doklady Physical Chemistry is a monthly journal containing English translations of current Russian research in physical chemistry from the Physical Chemistry sections of the Doklady Akademii Nauk (Proceedings of the Russian Academy of Sciences). The journal publishes the most significant new research in physical chemistry being done in Russia, thus ensuring its scientific priority. Doklady Physical Chemistry presents short preliminary accounts of the application of the state-of-the-art physical chemistry ideas and methods to the study of organic and inorganic compounds and macromolecules; polymeric, inorganic and composite materials as well as corresponding processes. The journal is intended for scientists in all fields of chemistry and in interdisciplinary sciences.