In-Situ SAXS study of temperature dependence in the synthesis of Ag 2 S nanoparticles

JOAQUÍN SILVEIRA; FERNANDO PSCHUNDER; BEATRIZ H. JUAREZ; BAVA, YANINA B.; GIOVANETTI LISANDRO; FABIO D. SACCONE; REQUEJO FELIX G.

Campinas, San Pablo

Congreso; XVIII International Small-Angle Scattering Conference 2022; 2022

The Brazilian Synchrotron Light Laboratory is part of the Brazilian Center for Research in Energy and Materials (CNPEM)

Great efforts have been made during recent years to enhance the photovoltaic performance of the quantum dots-sensitized solar cells (QDSSCs) to meet the increasing demands of clean energy. In the third generation of solar cells, QDs play the role of sensitizer due their novel optical properties such as appropriated energy band gap, high absorption coefficient and multiple exciton generation. In this context, Ag2S nanoparticles are a promising material for this devices because of their low toxicity, the high absorption coefficient (∼104 cm-1) [1] and relatively narrow energy band gap (Eg ∼ 1.0 eV) [2], which can extend the light absorption spectrum to near-infrared regions.In order to achieve a fine tuning of the optical properties of this material, a fine control over the shape and size is crucial as well as a deep understanding of their process of formation. In this regard, non-invasive in situ characterization techniques, such as small angle x-ray scattering (SAXS), allow to study the process of nucleation and growth by following the shape and sizes of the products and sub-products during the reaction.For the synthesis, the Ag precursor, silver diethyldithiocarbamate (Ag(DDTC)), is reacted with a surfactant, 1-dodecanethiol (DCT), in a hot solution at 210 ºC under vigorous stirring and N2 atmosphere, forming sub 5 nm Ag2S nanoparticles [3,4]. In this work, we follow the synthesis process of Ag2S nanoparticles by in-situ temperature dependent SAXS measurements using the previously mentioned wet-chemistry method with slight modifications adapted to our set up. We also study the effect of the synthesis temperature on the final product of the reaction. Transmission electron microscopy (TEM) images and UV-vis measurements were performed for a complementary characterization. For the synthesis performed at 210 ºC we found that a Ag-DDT metal-organic polymeric lamellar phase with a lattice parameter of 3.5 nm is formed at the beginning of the reaction, as previously reported [5]. After few minutes at 210 ºC, ∽ 1 nm nanoparticles are formed and grow up to an average size of 5 nm . No significant difference was observed between the final product obtained during in situ experiment, without stirring, with respect to the ex-situ synthesis.