Aqueous electrosynthesis of silver indium selenide nanocrystals and photothermal properties
The eco-friendly aqueous electrosynthesis of AgIn5Se8 (AISe) nanocrystals (NCs), and the respective core/shell structure AgIn5Se8/ZnS NCs (AISe/ZnS), was carried out by using L-glutathione (GSH) as stabilizer. Se0 direct reduction was carried out in a graphite powder macroelectrode of an electrochemical cavity cell; controlled by current (i = 30 mA) and electrical charge (Q = 11.6 C). The generated Se2- ions reacts with In3+ and Ag+ ions in the intermediary compartment of the cell to give AISe NCs. A paired electrolysis (Zn0 anode/S0 in graphite powder cathode) was carried out to prepare ZnS-GSH NCs, using the same electrochemical apparatus (i = 30 mA, Q = 9.6 C). The effect of the Ag+/In3+ ratio (0.5, 0.28 and 0.18) and ZnS shell over AISe NCs optical properties was investigated. The ternary AISe NCs were characterized by XRD and HRTEM as a AgIn5Se8 cubic phase structure (Ag+/In3+ = 0.18); the ZnS shell was a zinc blende structure. The shell growth promoted a heterojunction formation with different crystalline phases, leading to a quantum yield decrease (QY: AISe = 18.6 %; AISe/ZnS = 16.0 %). The NCs were irradiated by near-infrared laser at different power densities (λexc = 785 nm). AISe and AISe/ZnS samples showed photothermic response, reaching 381 K and 402 K, respectively.