Electrosynthesis and characterization of alloyed CdSxSe1−x ternary quantum dots

• Published in: Journal of alloys and compounds 2023-12, Vol.969, p.172315, Article 172315
• Main Authors: da Silva, José E., Freitas, Denilson V., Sousa, Felipe L.N., Caires, Anderson J., Escobar, Diana Maria Perez, Reis, Thompson J.A., Navarro, Marcelo
• Format: Article
• Language: English
• Subjects: Band gap; CdSxSe1−x; Electrosynthesis; Nanoalloys; Voltammetric analysis
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2023.172315

CdS, CdSe and CdSxSe1−x (x = 0.15, 0.35, 0.5, 0.65, 0.85) ternary quantum dots (QDs) were electrosynthesized in a cavity cell and aqueous medium, using 3-mercaptopropionic acid (MPA) as stabilizer. The electrochemical procedure was carried out by a paired electrolysis, where elemental sulfur and selenium were reduced in a graphite powder macroelectrode while a sacrificial cadmium rod was oxidized, giving the simultaneous generation of S2-, Se2- and Cd2+ ions for efficient production of the ternary QDs, in the S2-/Se2- ratio of choice. The CdSxSe1−x QDs were characterized by XRD, HRTEM, UV-Vis absorption and emission spectroscopies, and voltammetric analyses. XRD analysis showed lattice parameters of the cubic CdSxSe1−x nanoalloys with a linear drop tendency when the sulfide molar ratio increased in the crystalline structure. HRTEM analysis was used to determine nanoparticle sizes: 3.94 ± 0.70 nm (CdS), 4.23 ± 1.00 nm (CdS0.5Se0.5), and 4.12 ± 0.78 nm (CdSe), with interplanar distances of 0.348 nm, 0.341 nm, and 0.339 nm, respectively. The band gap energy (Eg opt) of the CdSxSe1−x QDs were determined by UV-Vis absorption spectroscopy: 2.42, 2.47, 2.53, 2.66, 2.63, 2.73 and 2.84 eV, respectively, showing a linear increasing according to the S2-/Se2- ratio. The same behavior was observed for the Eg Elect determined by cyclic and linear voltammetry analysis, presenting a nanoalloy nature of the ternary QDs electrosynthesized. [Display omitted] •The electrosynthesis allowed effective and convenient green production of ternary QDs.•S2-, Se2- and Cd2+ were electrogenerated in-situ from the corresponding elements.•The S2-/Se2- ratio controls the lattice parameters and band gap energy of the QDs.•Voltammetry analysis allowed determination of the band edges of the CdSxSe1−x QDs.•XRD, HRTEM, UV-Vis and voltammetry analyses of CdSxSe1−x QDs showed a nanoalloy nature.