Electrochemiluminescence behaviors of Eu3+-doped CdS nanocrystals film in aqueous solution

Eu3+ doped CdS nanocrystals (CdS:Eu NCs) were synthesized via a co-precipitation method. The doping of Eu3+ ions caused a 4-fold enhancement in electrochemiluminescence (ECL) intensity and more stable cathodic signals compared to pure CdS NCs. Such enhancement was mostly ascribed to doping-induced improvement in the stability of reduced NCs. A new emission peak around 620 nm was observed in ECL spectra of the doped NCs, which belongeded to the D-5(0) -> F-7(2) transition of Eu3+ ions in CdS NCs. Correspondingly, a pair of oxidation and reduction peaks occurred at +1.01 V and +0.61 V because of the formation of Eu3+-surface states complex when the CdS:Eu NCs solution underwent cyclic voltammogram scanning. Benefiting from the strong ECL emission of the doped NCs and high affinity of the doped Eu3+ ions to oxygen, the CdS:Eu NCs film showed a great oxygen-sensitivity. The intense red luminescence of the characteristic transitions of Eu3+ in CdS:Eu NCs would also have enormous potential in bioanlytical systems.

通过共沉淀法合成了铕离子（Eu³⁺）掺杂的硫化镉纳米晶体（CdS:Eu NCs）。与纯硫化镉纳米晶体相比，Eu³⁺离子的掺杂使电化学发光（ECL）强度提高了4倍，并且阴极信号更加稳定。这种增强主要归因于掺杂提高了还原态纳米晶体的稳定性。在掺杂纳米晶体的ECL光谱中观察到一个位于620 nm左右的新发射峰，该峰归属于硫化镉纳米晶体中Eu³⁺离子的⁵D₀→⁷F₂跃迁。相应地，当硫化镉:铕纳米晶体溶液进行循环伏安扫描时，由于形成了Eu³⁺ - 表面态络合物，在+1.01 V和+0.61 V处出现了一对氧化还原峰。得益于掺杂纳米晶体的强电化学发光发射以及掺杂的Eu³⁺离子对氧气的高亲和力，硫化镉:铕纳米晶体薄膜显示出良好的氧敏感性。硫化镉:铕纳米晶体中Eu³⁺特征跃迁的强烈红色发光在生物分析系统中也具有巨大潜力。