Interactions of Aqueous Ag+ with Fulvic Acids: Mechanisms of Silver Nanoparticle Formation and Investigation of Stability

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• 作者：Nathaniel F. Adegboyega ; Virender K. Sharma ; Karolina Siskova ; Radek Zbo艡il ; Mary Sohn ; Brian J. Schultz ; Sarbajit Banerjee
• 刊名：Environmental Science & Technology (ES&T)
• 出版年：2013
• 出版时间：January 15, 2013
• 年：2013
• 卷：47
• 期：2
• 页码：757-764
• 全文大小：445K
• 年卷期：v.47,no.2(January 15, 2013)
• ISSN：1520-5851

文摘

This study investigated the possible natural formation of silver nanoparticles (AgNPs) in Ag⁺鈥揻ulvic acid (FA) solutions under various environmentally relevant conditions (temperature, pH, and UV light). Increase in temperature (24鈥?0 掳C) and pH (6.1鈥?.0) of Ag⁺鈥揝uwannee River fulvic acid (SRFA) solutions accelerated the appearance of the characteristic surface plasmon resonance (SPR) of AgNPs. The rate of AgNP formation via reduction of Ag⁺ in the presence of different FAs (SRFA, Pahokee Peat fulvic acid, PPFA, Nordic lake fulvic acid, NLFA) and Suwannee River humic acid (SRHA) followed the order NLFA > SRHA > PPFA > SRFA. This order was found to be related to the free radical content of the acids, which was consistent with the proposed mechanism. The same order of AgNP growth was seen upon UV light illumination of Ag⁺鈥揊A and Ag⁺鈥揌A mixtures in moderately hard reconstituted water (MHRW). Stability studies of AgNPs, formed from the interactions of Ag⁺鈥揝RFA, over a period of several months showed that these AgNPs were highly stable with SPR peak reductions of only 15%. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements revealed bimodal particle size distributions of aged AgNPs. The stable AgNPs formed through the reduction of Ag⁺ by fulvic and humic acid fractions of natural organic matter in the environment may be transported over significant distances and might also influence the overall bioavailability and ecotoxicity of AgNPs.