Abstract: This study systematically investigates the affinities of mononucleotides, i.e., adenine (A), thymine (T), guanine (G), and cytosine (C), and polynucleotides (20 bases, Poly A, Poly T, Poly G, Poly C) for lead sulfide (PbS) nanoparticles by evaluating the stability of mononucleotide- and polynucleotide-modified PbS nanoparticles in aqueous and salt solutions over time. Experimental results reveal distinct affinity trends between mononucleotides and polynucleotides. For mononucleotides, the affinity order is A>G>C>T, with C and T failing to stabilize PbS nanoparticles due to weak interactions. In contrast, the affinity order of polynucleotides differs from that of mononucleotides: Poly C>Poly G>Poly T>Poly A, indicating no direct correlation between the two systems. The discrepancy is attributed to the rigid length of polynucleotides, a critical factor reflecting the rigidity of oligonucleotide chains. Shorter rigid lengths enable more contact points between polynucleotides and the PbS surface, enhancing stability through cumulative interactions, even when individual nucleotide affinities are weak (e.g., Poly T). For example, Poly A's longer rigid length limits contact points, reducing stability despite A's strong single-nucleotide affinity. Transmission electron microscopy (TEM) confirms that Poly A-modified PbS nanoparticles (average size of 9.4 nm) exhibit good dispersibility and crystallinity, while high-concentration Poly G assemblies induce aggregation via intermolecular G-wire formation. These findings highlight the necessity of considering both nucleotide affinity and chain rigidity when designing oligonucleotide-stabilized semiconductor nanoparticles, thus providing a foundation for DNA-guided synthesis of PbS nanoparticles with tailored properties for applications in bioimaging and optoelectronics.

Key words: nucleotide, semiconductor nanocrystal, lead sulfide, nanoparticle, rigid length

摘要： 通过测量单核苷酸或多聚核苷酸修饰的硫化铅(PbS)纳米颗粒在不同浓度盐溶液中随时间变化的稳定性，本研究详细研究了单核苷酸与多聚核苷酸对PbS纳米颗粒的亲和力。实验结果表明，对于单核苷酸，亲和力按腺嘌呤(A)>鸟嘌呤(G)>胞嘧啶(C)>胸腺嘧啶(T)的顺序递减，其中C和T无法有效稳定PbS纳米颗粒。而多聚核苷酸的亲和力顺序则有所不同，表现为Poly C>Poly G>Poly T>Poly A。这两种排序的差异表明，不能依据单核苷酸的亲和力趋势推断多聚核苷酸的亲和力强弱，反之亦然。寡核苷酸的刚性长度是一个重要因素，研究中在确定多聚核苷酸与PbS纳米颗粒的整体相互作用时，必须将其与单个核苷酸的亲和力结合考虑。

关键词: 核苷酸, 半导体纳米晶, 硫化铅, 纳米颗粒, 刚性长度