Microbial-mediated transformation of anthropogenic Cd²⁺ controls its distribution, bioavailability, and potential risks. However, the processes readily form CdS nanoparticles (CdS-NPs), which exhibit dissolution behavior different from that of larger sized particles. Here, we investigated the effects of morphologies and facets of CdS-NPs on their photoinduced dissolution. Three CdS-NPs, CdS-sphere, CdS-rod, and CdS-sheet, and one nanosized biogenic CdS (Bio-CdS) were synthesized with different dominant facets of {101}, {100}, {001}, and {111} and thus distinct surface chemistry. As explored by HRTEM, EPR, and DFT calculations, photogenerated e^–/h⁺ pairs were more likely to generate on CdS-sheet surfaces due to higher surface energies and a narrower band gap, facilitating the formation of •OH and thereby faster dissolution (k_obs = 6.126–6.261 × 10^–2 h^–1). The wider band gaps of CdS-sphere and CdS-rod caused less formation of O₂^•– and •OH, leading to slower oxidative dissolutions (k_obs = 0.090–0.123 and 2.174–3.038 × 10^–2 h^–1, respectively). Given the similar surface energy as that of CdS-sheet, the dissolution rate of Bio-CdS was close to that of CdS-rod and CdS-sheet, which was 1.6–3.5 times faster than that of larger sized CdS, posing higher environmental risks than thought. Altogether, this work revealed the facet effects on the dissolution of CdS-NPs, manifesting a deeper understanding of metal sulfides’ environmental behaviors.

中文翻译：

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硫化镉 (CdS) 纳米粒子的面相关光致转化

人为 Cd ^{2+ 的}微生物介导转化控制其分布、生物利用度和潜在风险。然而，这些过程很容易形成 CdS 纳米颗粒 (CdS-NPs)，其表现出与较大尺寸颗粒不同的溶解行为。在这里，我们研究了 CdS-NPs 的形态和面对其光致溶解的影响。合成了三种 CdS-NPs、CdS-sphere、CdS-rod 和 CdS-sheet，以及一种纳米尺寸的生物 CdS（Bio-CdS），具有不同的主要晶面 {101}、{100}、{001} 和 {111 } 从而形成独特的表面化学。根据 HRTEM、EPR 和 DFT 计算，光生 e ^– /h ⁺由于更高的表面能和更窄的带隙，更容易在 CdS 片表面上生成，从而促进 •OH 的形成，从而更快地溶解（k _obs = 6.126–6.261 × 10 ^–2 h ^–1）。CdS 球和 CdS 棒的带隙较宽导致 O ₂ ^•–和 •OH 的形成较少，导致氧化溶解较慢（k _obs = 0.090–0.123 和 2.174–3.038 × 10 ^–2 h ^–1， 分别）。由于表面能与 CdS-sheet 相似，Bio-CdS 的溶解速度接近 CdS-rod 和 CdS-sheet，比更大尺寸的 CdS 快 1.6-3.5 倍，带来更高的环境风险比想。总之，这项工作揭示了对 CdS-NPs 溶解的多方面影响，表明对金属硫化物的环境行为有了更深入的了解。