Tunable emission of AgIn5S8 and ZnAgIn5S8 nanocrystals: electrosynthesis, characterization and optical application

Ternary AgIn5S8 (AIS) and quaternary ZnAgIn5S8-alloy (ZAIS) nanocrystals, stabilized by L-glutathione, were produced by a clean and eco-friendly electrochemical method, eliminating the need of reducing agents. AIS-GSH colloidal solution was obtained by constant current electrolysis (i = 30 mA) in cavity cell. S2- ions (0.051 mmol) were generated into a graphite powder macroelectrode, reacting in the intermediate compartment of the cell containing Ag+/In3+ aqueous solution at different ratios (0.5, 0.28, 0.18, and 0.14), and 0.025 mmol/L-1 glutathione (GSH). ZAIS-GSH NCs were synthesized in the same cavity cell containing the previously prepared AIS-GSH solution. A paired electrolysis (i = 30 mA) was used for simultaneous production of Zn2+ and S2- (Zn-0 sacrificial anode and graphite powder macroelectrode/S-0 cathode). The electrochemical method promoted a high reproducibility and efficient luminescence in the preparations of NCs. The sizes of the AIS-GSH and ZAIS-GSH nanoparticles were determined by HRTM (3.4 and 4.0 nm, respectively), and quantum yields reaching 16% (AIS-GSH, Ag+/In3+ = 0.18). The spectrophotometric characterization showed that Ag+/In3+ ratio can be used for the tuning of the AIS-GSH nanoparticle emission wavelength, which is associated to electronic defects introduced in the NCs lattice. XRD/EDS analysis of ZAIS-GSH nanoparticles point out to Zn2+ ion-exchange into the AIS-GSH lattice. XPS analysis was carried out at different etching levels of the ZAIS nanocrystals surface, making possible to identify the 2p Zn doublet signal, indicating two different Zn2+ sites in the alloy structure. Time-resolved spectroscopy measurements/decay curves were carried out to evaluate the effect of silver amount on radioactive and non-radioactive terms. Additionally, the AIS-GSH and ZAIS-GSH photoluminescence and stability were used to produce the active parts of commercial white LEDs, and modulate the colour perception from the respective emission bands. (C) 2019 Elsevier Ltd. All rights reserved.