Despite a significant surge in the number of investigations into chirality at the nanoscale, especially thiolated chiral molecules capping gold clusters, only limited knowledge is currently available to elaborate the alloying effect on chiroptical behavior of bimetallic nanoparticles (NPs). Also, few successful cases as to the efforts toward the development of chirality-dependent applications on the optically active nanomaterial have been made. Herein, as a positive test case for chiral alloy nanoparticle synthesis, the stable and large chiroptical ultrafine Au–Ag alloy NPs were prepared by reduction of different molar fractions of HAuCl₄ and AgNO₃ with NaBH₄ in the presence of d/l-penicillamine (d/l-Pen). Compared with those of monometallic Au and Ag counterparts with comparable size, the Au–Ag alloy NPs (Ag mole fraction, 70%) obviously displayed the largest optical activities with the maximum g-factors of ∼1.6 × 10^–3. Impressively, the Pen-mediated synthesis of chiral Au–Ag alloy NPs possesses a colorimetric self-recognition function and can be used as an incisive circular dichroism (CD) probe toward d- and l-Pen enantiomers. The plasmonic CD signal amplification (ΔI_CD) shows good linearity with the amount of Pen over the range of 5.0–80.0 μM with a detection limit (3σ) of 1.7 μM for l-Pen and 1.5 μM for d-Pen, respectively. In addition, the sensing system exhibits good selectivity toward d- and l-Pen in the presence of other enantiomers; therefore, it is highly expected that the approach described here would open new opportunities for design of more novel enantioselective analyses of important species related to biological processes.

中文翻译：

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光学活性超细Au-Ag合金纳米粒子用于比色手性识别和对映异构体的圆二色性传感

尽管在纳米级的手性研究，尤其是覆盖金簇的硫醇化手性分子的研究数量激增，但目前只有有限的知识来阐述合金化对双金属纳米粒子（NPs）的手性行为的影响。同样，关于在光学活性纳米材料上发展手性依赖的应用的努力的成功案例很少。在此，作为手性合金纳米粒子合成的积极测试案例，通过在d / l-青霉胺存在下用NaBH ₄还原HAuCl ₄和AgNO ₃的不同摩尔分数，制备稳定且大的手性超细Au-Ag合金NPs。（d / l -Pen）。与具有类似尺寸的单金属Au和Ag对应物相比，Au-Ag合金NPs（Ag摩尔分数为70％）明显显示出最大的光学活性，最大g因子约为1.6×10 ^–3。令人印象深刻的是，Pen介导的手性Au-Ag合金NP的合成具有比色自识别功能，可以用作针对d-和1- Pen对映异构体的尖锐圆二色性（CD）探针。等离激元CD信号放大（Δ我_CD）所示良好的线性度与笔超过5.0-80.0微米的范围内以1.7μM的用于检测限（3σ）的量升-Pen和1.5μM为d-笔，分别。另外，在其他对映异构体的存在下，传感系统对d-和1- Pen表现出良好的选择性。因此，人们高度希望本文所述的方法将为设计与生物过程相关的重要物种的更新颖的对映选择性分析提供新的机会。