Journal Article Improvement of photoluminescence stability of ZnS-AgInS2 nanoparticles through interactions with ionic liquids

Suzuki, Shushi  ,  Hattori, Yuuki  ,  Kuwabata, Susumu  ,  Torimoto, Tsukasa

Photoluminescence (PL) stability of ZnS-AgInS2 (ZAIS) nanoparticles (NPs) prepared via thermal decomposition of (AgIn)xZn2(1-x)(S2CN(C2H5)2)4 (x = 0.5, 0.8 and 1.0) was improved by ionic liquids (ILs) of 1-ethyl-3-metylimidazolium ethylsulfate (EMI-es) and tris (2-hydroxyethyl) methylammonium methylsulfate (HEMA-mes). Through ligand exchange processes from oleylamine (OLA) to sodium 2-mercaptoethanesulfonic acid (MES), hydrophilic NP’s surfaces changed into hydrophobic ones, resulting in that the ZAIS NPs could be dispersed in the ILs. UV irradiation caused the PL deterioration of ZAIS NPs in solutions, but MES-ZAIS NPs in the ILs exhibited higher PL stability than the OLA-ZAIS NPs in chloroform, the degree being more remarkable for NPs dispersed in HEMA-mes than in EMI-es. The improvement of PL stability could be interpreted as a result of stabilization of MES adsorbed on the NPs through electrostatic interaction between MES and the ILs. Exposing to the air and mixing with the water accelerated the PL deterioration of the NPs.

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