Center of Excellence for Advanced Materials and Sensing Devices, Research Unit New Functional Materials, Ruđer Bošković Institute, Bijeničkacesta 54, 10000 Zagreb, Croatia.
Osnovna škola Antuna Gustava Matoša, Albrechtova bb, 10000 Zagreb, Croatia.
Spectrochim Acta A Mol Biomol Spectrosc. 2022 Jan 5;264:120326. doi: 10.1016/j.saa.2021.120326. Epub 2021 Aug 27.
The binding of glucosamine to gold in water solutions of glucosamine hydrochloride mixed with clean colloidal gold nanoparticles obtained by laser ablation in liquid was studied using surface-enhanced Raman scattering (SERS), dynamic light scattering (DLS) and UV-VIS spectroscopy. The purpose of this study was to establish whether the binding of charged aminogroup to gold nanoparticles (AuNPs) is taking place, and if it does, how can it be identified by means of SERS. The average size of dried gold nanoparticles was (20 ± 4) nm determined by averaging the sizes observed in transmission electron microscopy micrographs, which is smaller than the average size of gold nanoparticles in water solution as determined by DLS: (52 ± 2) nm. Upon adding the glucosamine solutions to gold colloid, average hydrodynamic diameter of ions was slightly larger for 0.1 mM glucosamine solution (55 ± 2 nm), while it increased to (105 ± 22) nm in the case of 1 mM solution, and was (398 ± 54) nm when 10 mM glucosamine solution was added. Most prominent Raman bands observed both for 0.1 mM and 1 mM glucosamine solutions were located at 1165 cm, 1532 and 1586 cm and assigned to C-N coupled with C-C stretching, and C-NH deformation angles bending. In SERS spectrum of 1 mM GlcN solution, two strong bands at 999 and 1075 cm were found and attributed to C-O stretching coupled with C-NH bending (999 cm) and to dominantly C-O stretching vibration. The differences in SERS spectra are attributed to different number of glucosamine molecules that attach to gold nanoparticles and their orientation with respect to the metal particle surface, partly due to presence of beta anomers protonated at anomeric oxygen position. The assignment of glucosamine bands was further corroborated by comparison with vibrational spectra of alpha and beta glucose and of polycrystalline powder of glucosamine hydrochloride. For all three substances comprehensive calculation of vibrational density of states was conducted using density functional theory. Benchmark bands for polycrystalline glucose anomers distinction are 846 and 915 cm for alpha glucose, and 902 cm for beta glucose. However, the bands observed in SERS spectra of 0.1 mM glucosamine solution at 831, 899, and 946 cm or in 1 mM solution at 934 cm cannot be easily identified as belonging either to alpha or beta glucosamine anomer, due to complexity of atomic motions involved. The identification of vibrational bands associated with -CNH group will aid SERS studies on amino acids, especially in cases when several atomic groups could possibly bind to AuNPs.
采用表面增强拉曼散射（SERS）、动态光散射（DLS）和紫外-可见光谱研究了盐酸氨基葡萄糖在混合有通过液相激光烧蚀获得的清洁胶体金纳米粒子的氨基葡萄糖水溶液中与金的结合。本研究的目的是确定带电荷的氨基是否与金纳米粒子（AuNPs）结合，如果是这样，如何通过 SERS 来识别。通过对透射电子显微镜照片中观察到的尺寸进行平均，确定干燥金纳米粒子的平均尺寸为（20±4）nm，这小于通过 DLS 确定的水溶液中金纳米粒子的平均尺寸：（52±2）nm。当向金胶体中加入氨基葡萄糖溶液时，对于 0.1mM 氨基葡萄糖溶液，离子的平均水动力直径稍大（55±2nm），而对于 1mM 溶液，它增加到（105±22）nm，当加入 10mM 氨基葡萄糖溶液时，它为（398±54）nm。对于 0.1mM 和 1mM 氨基葡萄糖溶液，都观察到最突出的拉曼带位于 1165cm、1532cm 和 1586cm，分配给 C-N 与 C-C 拉伸以及 C-NH 变形角弯曲。在 1mM GlcN 溶液的 SERS 光谱中，发现了两个位于 999cm 和 1075cm 的强带，并归因于 C-O 拉伸与 C-NH 弯曲（999cm）以及主要的 C-O 拉伸振动。SERS 光谱的差异归因于附着在金纳米粒子上的氨基葡萄糖分子的数量不同，以及它们相对于金属颗粒表面的取向，部分原因是存在在端基氧位置质子化的β端异构体。通过与α和β葡萄糖以及盐酸氨基葡萄糖多晶粉末的振动光谱进行比较，进一步证实了氨基葡萄糖带的分配。对于所有三种物质，都使用密度泛函理论对振动态密度进行了全面计算。用于区分多晶葡萄糖端异构体的基准带是α葡萄糖的 846cm 和 915cm，以及β葡萄糖的 902cm。然而，在 0.1mM 氨基葡萄糖溶液的 SERS 光谱中观察到的 831cm、899cm 和 946cm 处或在 1mM 溶液中观察到的 934cm 处的带不能轻易地被识别为属于α或β葡萄糖端异构体，因为涉及到复杂的原子运动。与-CNH 基团相关的振动带的识别将有助于 SERS 对氨基酸的研究，特别是在多个原子基团可能与 AuNPs 结合的情况下。
