Maity Subarna, Kolay Sarita, Chakraborty Sikta, Devi Aarti, Patra Amitava
Department of Chemistry, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan.
School of Materials Sciences, Indian Association for the Cultivation of Science, Kolkata 700032, India.
Chem Soc Rev. 2025 Feb 17;54(4):1785-1844. doi: 10.1039/d4cs00962b.
Atomically precise metal nanoclusters (MNCs) composed of a few to hundreds of metal atoms represent an emerging class of nanomaterials with a precise composition. With the size approaching the Fermi wavelength of electrons, their energy levels are well-separated, leading to molecule-like properties, like discrete single electronic transitions, tunable photoluminescence (PL), inherent structural anisotropy, and distinct redox behavior. Extensive synthetic efforts and electronic structure revelation have expanded applicability of MNCs in catalysis, optoelectronics, and biology. This review highlights the intriguing photophysical and electrochemical behaviors of MNCs and their regulatory parameters and applications. Initially, we present a brief discussion on the evolution of MNCs from gas-phase naked metal clusters to monolayer ligand-protected MNCs along with representative studies on their electronic structure. Due to their quantized molecular orbitals, they often exhibit PL, which can be regulated based on their capping ligands, number of atoms, crystal packing, presence of heterometal, and surrounding environment. Apart from PL, the relaxation pathways of MNCs on an ultrafast time scale have been extensively studied, which significantly differ from that of plasmonic metal nanoparticles. Moreover, their interaction with high-intensity light results in unique non-linear optical properties. The synergy between MNCs in a hierarchical self-assembled structure has been exploited to enhance their PL by precisely tuning their non-covalent interactions. Moreover, several NC-based hybrids have been designed to exhibit efficient electron or energy transfer in the photoexcited state. In the next section, we briefly focus on the redox behavior of NCs and facile electron transfer to suitable substrates, which result in enzyme-like catalytic activity. Utilizing these photophysical and electrochemical behaviors, NCs are widely employed in catalysis, optical sensing, and light-harvesting applications, which are also discussed in this review. In the final section, conclusions and open questions for the NC research community are included. This review will provide a comprehensive view of the emerging physicochemical properties of MNCs, thereby enabling an understanding for their precise modulation in future.
由几个到数百个金属原子组成的原子精确金属纳米团簇（MNCs）是一类新兴的具有精确组成的纳米材料。随着尺寸接近电子的费米波长，其能级被很好地分离，从而导致类似分子的性质，如离散的单电子跃迁、可调谐光致发光（PL）、固有的结构各向异性和独特的氧化还原行为。广泛的合成努力和电子结构揭示扩展了MNCs在催化、光电子学和生物学中的应用。本综述重点介绍了MNCs有趣的光物理和电化学行为及其调控参数和应用。首先，我们简要讨论了MNCs从气相裸金属团簇到单层配体保护的MNCs的演变，以及关于其电子结构的代表性研究。由于其量子化的分子轨道，它们通常表现出PL，这可以基于其封端配体、原子数、晶体堆积、异金属的存在和周围环境进行调控。除了PL，MNCs在超快时间尺度上的弛豫途径也得到了广泛研究，这与等离子体金属纳米颗粒的弛豫途径有显著不同。此外，它们与高强度光的相互作用导致独特的非线性光学性质。分层自组装结构中MNCs之间的协同作用已被用于通过精确调节其非共价相互作用来增强其PL。此外，已经设计了几种基于纳米团簇的杂化物，以在光激发态下表现出有效的电子或能量转移。在下一节中，我们简要关注纳米团簇的氧化还原行为以及向合适底物的 facile 电子转移，这导致了类似酶的催化活性。利用这些光物理和电化学行为，纳米团簇被广泛应用于催化、光学传感和光捕获应用，本综述也对此进行了讨论。在最后一节中，包括了对纳米团簇研究群体的结论和开放性问题。本综述将提供对MNCs新兴物理化学性质的全面观点，从而有助于未来对其进行精确调控。
