Copper-poor Cu₂ZnSnS₄ (copper zinc tin sulfide, CZTS) inorganic semiconducting nanoparticles were synthesized by an environmentally friendly low-temperature (100 °C) synthetic path, which allows precise control of the Sn content without any relevant presence of Zn- and Sn-related secondary phases. The resulting nanoparticles are polycrystalline and quasi-spherical, with an average diameter of 10 nm. The shape and composition were assessed using a multitechnique approach based on X-ray photoelectron spectroscopy (XPS), energy-dispersive fluorescence X-ray spectroscopy (EDXRF), inductively coupled plasma atomic emission spectrometry (ICP-AES), and high-resolution transmission electron microscopy (HR-TEM). The presence of paramagnetic species associated with Cu²⁺ cations was highlighted by electron paramagnetic resonance (EPR) spectroscopy, pinpointing the presence of significant exchange interactions between Cu²⁺ ions. The mixed oxidation state of Cu induces the generation of free holes, which are confined in the nanoparticles, giving rise to a plasmonic resonance. The plasmonic properties were investigated as a function of Sn doping through vis–NIR absorption spectroscopy combined with magnetic circular dichroism (MCD). This approach enabled the extraction of charge carriers’ density and mass, a key step for further optimization of CZTS-based photovoltaic devices.

中文翻译：

---

锡含量受控的黄锡矿纳米粒子的环保途径：磁学和光学性质的深入研究


通过环境友好的低温（100°C）合成路径合成了贫铜Cu ₂ ZnSnS ₄ （铜锌锡硫化物，CZTS）无机半导体纳米颗粒，可实现精确的合成控制 Sn 含量，而不存在任何与 Zn 和 Sn 相关的第二相。所得纳米粒子是多晶的、准球形的，平均直径为10 nm。使用基于 X 射线光电子能谱 (XPS)、能量色散荧光 X 射线能谱 (EDXRF)、电感耦合等离子体原子发射光谱 (ICP-AES) 和高分辨率透射的多种技术方法评估形状和成分电子显微镜（HR-TEM）。电子顺磁共振 (EPR) 光谱强调了与 Cu ²⁺ 阳离子相关的顺磁性物质的存在，查明了 Cu ²⁺ 离子之间存在显着的交换相互作用。 Cu 的混合氧化态诱导自由空穴的产生，这些空穴被限制在纳米颗粒中，从而引起等离子体共振。通过可见近红外吸收光谱与磁圆二色性（MCD）相结合，研究了等离子体特性与锡掺杂的函数关系。这种方法能够提取载流子的密度和质量，这是进一步优化基于 CZTS 的光伏器件的关键一步。