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首页> 外文期刊>RSC Advances >Aggregation, dissolution and cyclic regeneration of Ag nanoclusters based on pH-induced conformational changes of polyethyleneimine template in aqueous solutions
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Aggregation, dissolution and cyclic regeneration of Ag nanoclusters based on pH-induced conformational changes of polyethyleneimine template in aqueous solutions

机译：基于pH诱导水溶液中聚乙烯亚胺模板的构象变化，Ag纳米团簇的聚集，溶解和循环再生

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This paper reports a dramatic cyclic regeneration of polyethyleneimine-templated silver nanoclusters (PEI-AgNCs) based on the pH-induced conformational changes of polyethyleneimine (PEI) in aqueous solution. The PEI-AgNCs have been synthesized and found to be highly sensitive to the pH of the solution in air. The studies show that small AgNCs would gather to form larger silver nanoparticles (AgNPs) by adjusting the pH to 1.5 with a nitric acid solution. The AgNPs in solution was then transformed gradually to Ag(I) ions with stirring in air. Subsequently, the above Ag(I) ions were reduced again to AgNCs by changing the pH to about 9 with a NaOH solution and adding a certain amount of formaldehyde as a reductant to solution. The fluorescence and UV-visible absorption spectra recorded this process in detail. The transmission electron microscopy images, X-ray powder diffraction patterns, and Fourier transform infrared spectra further demonstrated that the cyclic transformation existed among AgNCs, AgNPs, and Ag(I) ions. The amino-rich PEI plays a crucial role in the regeneration of PEI-AgNCs. A large number of amino groups on PEI could be reversibly protonated by adjusting the pH of solution, leading to a change of the interaction between Ag and PEI, which has laid foundation for this work.
机译：本文基于pH诱导的水溶液中聚乙烯亚胺（PEI）的构象变化，报道了聚乙烯亚胺为模板的银纳米簇（PEI-AgNCs）的剧烈循环再生。 PEI-AgNC已合成，发现对空气中溶液的pH值高度敏感。研究表明，通过用硝酸溶液将pH值调节到1.5，小的AgNC会聚集形成更大的银纳米颗粒（AgNP）。然后在空气中搅拌下将溶液中的AgNP逐渐转化为Ag（I）离子。随后，通过用NaOH溶液将pH值更改为约9并向溶液中添加一定量的甲醛作为还原剂，将上述Ag（I）离子再次还原为AgNCs。荧光和紫外可见吸收光谱详细记录了该过程。透射电子显微镜图像，X射线粉末衍射图和傅立叶变换红外光谱进一步表明，AgNCs，AgNPs和Ag（I）离子之间存在循环转化。富含氨基的PEI在PEI-AgNCs的再生中起关键作用。通过调节溶液的pH值可以使PEI上的大量氨基可逆地质子化，从而导致Ag和PEI之间相互作用的改变，这为这项工作奠定了基础。

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