pubs.acs.org/JPCL
Preparation of Luminescent AgInS2-AgGaS2 Solid Solution Nanoparticles and Their Optical Properties Taro Uematsu,†,‡ Toshihiro Doi,†,‡ Tsukasa Torimoto,‡,§ and Susumu Kuwabata*,†,‡ †
Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan, Japan Science and Technology Agency, CREST, Kawaguchi, Saitama 332-0012, Japan, and §Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Chikusa-ku, Nagoya 464-8603, Japan ‡
ABSTRACT Luminescent AgInS2-AgGaS2 solid solution nanoparticles were synthesized by thermal decomposition of a single-source precursor, AgInyGa1-y(S2CN(C2H5)2)4 in oleylamine. Transmission electron microscopy showed formation of nanoparticles of good crystallinity with their size ranging from 4 to 5 nm. X-ray powder diffraction spectra showed peaks which were attributable to the chalcopyrite structure, and their peaks were continuously shifted to higher angle as the Ga to In ratio increased. Photoluminescence and absorption spectra were also blue-shifted as the ratio of Ga increased due to the larger band gap of AgGaS2 compared with that of AgInS2. The quantum yield was almost maintained in the composition range of 0.4 < y < 1.0, below which it decreased largely. The mechanism of such behavior was investigated using time-resolved photoluminescence spectra. SECTION Nanoparticles and Nanostructures
emiconductor nanoparticles (NPs) have attracted intense attention because they possess useful optical properties such as bright emission, photostability, and tunable band gap energy (Eg), which make them well-suited for use as biomarkers and optoelectronic devices.1-8 Numerous studies conducted on binary semiconductor NPs, for example, those consisting of II-VI and III-V semiconductors such as CdSe, CdTe, and InP, have revealed that the luminescence properties are improved by precise control of the size of NPs and by the optimization of surface conditions.9-12 Meanwhile, because I-III-VI ternary semiconductors possess a Eg suitable for harvesting sunlight, their use as photocatalysts and photovoltaics is attracting increasing attention.13,14 Recently, methods for synthesizing I-III-VI semiconductor NPs have been developed by slight modification of the methods for synthesizing conventional II-VI semiconductor NPs.15-17 A few of such ternary semiconductor NPs exhibited photoluminescence (PL), and their quantum yields (QY) have steadily improved by surface modification. Their Eg was tuned by controlling their particle size and/or by interfusing them with other I-III-VI or II-VI semiconductors.15,18,19 The low toxicity of I-III-VI semiconductor NPs compared with that of conventional II-VI and III-V semiconductor NPs increases their applicability in devices such as biomarkers, sensors, and wavelength converters. Recently, our group has developed ZnS-AgInS2 solid solution (ZAIS) NPs, whose emission color is tunable by changing the composition (value of x) of the precursor (AgIn)xZn2(1-x)(S2CN(C2H5)2)4.18,20,21 In the present study, we attempted to synthesize AgInS2-AgGaS2 solid solution (AIGS) NPs because AgInS2 and AgGaS2, both of which are direct semiconductors having a chalcopyrite structure, are anticipated to interfuse well with
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r 2010 American Chemical Society
each other. It was then discovered that with a little modification, a facile method to synthesize ZAIS NPs is applicable to AIGS NPs synthesis. The obtained AIGS NPs emitted intense fluorescence, the color of which was tunable by the composition, while keeping the low toxicity and stability of the resulting NPs. Their optical properties were investigated by using both steady-state and time-resolved PL measurements, and the mechanism of the emission correlated with the QY was discussed. The AIGS NPs were synthesized by the thermal decomposition of a metal ion-diethyldithiocarbamate complex in oleylamine. An aqueous solution containing silver, indium, and gallium nitrates with Ag/In/Ga=1/y/1-y (0.0
