Korir Daniel K, Gwalani Bharat, Joseph Abel, Kamras Brian, Arvapally Ravi K, Omary Mohammad A, Marpu Sreekar B
Department of Chemistry, University of North Texas, Denton, TX 76203, USA.
Department of Materials Science and Engineering, University of North Texas, Denton, TX 76203, USA.
Nanomaterials (Basel). 2019 Apr 11;9(4):596. doi: 10.3390/nano9040596.
A simple photochemical method for making conjoined bi-metallic gold-silver (Au/Ag) nanotwins, a new breed of nanoparticles (NPs), is developed. To the best of our knowledge, the photochemical method resulted in distinct, conjoined, bimetallic nanotwins that are different from any well-established alloyed or core-shell nanostructures in the literature. The conjoined Au-Ag NPs possessed surface plasmon resonance (SPR) properties of both metals. The bimetallic nanostructures possessing distinctive optical properties of both metals were obtained using Au NPs as seeds in the first step, followed by the addition of a silver precursor as feed in the second step during a photochemical irradiation process. In the first step, small, isotropic or large, anisotropic Au NPs are generated by photoinduced reduction within a biocompatible chitosan (CS) polymer. In the second step, a silver precursor (AgNO₃) is added as the feed to the AuNPs seed, followed by irradiation of the solution in the ice-bath. The entire photochemical irradiation process resulting in the formation of bimetallic Au-AgNPs did not involve any other reducing agents or stabilizing agents other than the CS polymer stabilizer. The small, conjoined Au-Ag bi-metallic NPs exhibited SPR with peak maxima centering at ~400 nm and ~550 nm, whereas the large conjoined nanoparticles exhibited SPR with peak maxima centering at ~400 nm, 550 nm, and 680 nm, characteristic of both gold and silver surface plasmons in solution. The tunability in the SPR and size of the bimetallic NPs were obtained by varying the reaction time and other reaction parameters, resulting in average sizes between 30 and 100 nm. The SPR, size, distribution, and elemental composition of the bi-metallic NPs were characterized using UV-Vis absorption, electron microscopy, and energy dispersive X-ray spectroscopy (EDS) studies.
开发了一种制备连体双金属金 - 银（Au/Ag）纳米孪晶的简单光化学方法，纳米孪晶是一种新型纳米颗粒（NPs）。据我们所知，该光化学方法产生了独特的、连体的双金属纳米孪晶，与文献中任何已确立的合金或核壳纳米结构都不同。连体的Au - Ag NPs具有两种金属的表面等离子体共振（SPR）特性。在光化学辐照过程中，第一步以Au NPs为种子，第二步添加银前驱体作为原料，从而获得了具有两种金属独特光学特性的双金属纳米结构。第一步，通过在生物相容性壳聚糖（CS）聚合物中光诱导还原生成小的、各向同性的或大的、各向异性的Au NPs。第二步，将银前驱体（AgNO₃）作为原料添加到Au NPs种子中，然后在冰浴中对溶液进行辐照。导致形成双金属Au - Ag NPs的整个光化学辐照过程除了CS聚合物稳定剂外，不涉及任何其他还原剂或稳定剂。小的、连体的Au - Ag双金属NPs表现出SPR，其峰值最大值集中在约400 nm和~550 nm处，而大的连体纳米颗粒表现出SPR，其峰值最大值集中在约400 nm、550 nm和680 nm处，这是溶液中金银表面等离子体的特征。通过改变反应时间和其他反应参数，获得了双金属NPs的SPR和尺寸的可调性，平均尺寸在30至100 nm之间。使用紫外 - 可见吸收、电子显微镜和能量色散X射线光谱（EDS）研究对双金属NPs的SPR、尺寸、分布和元素组成进行了表征
