A Simple Route to Alloyed Quaternary Nanocrystals Ag–In–Zn–S with Shape and Size Control

Abstract

A convenient method of the preparation of alloyed quaternary Ag-In-Zn-S nanocrystals is elaborated, in which a multicomponent mixture of simple and commercially available precursors, namely, silver nitrate, indium(III) chloride, zinc stearate, 1-dodecanethiol, and sulfur, is used with 1-octadecene as a solvent. The formation of quaternary nanocrystals necessitates the use of an auxiliary sulfur precursor, namely, elemental sulfur dissolved in oleylamine, in addition to 1-dodecanethiol. Without this additional precursor binary ZnS nanocrystals are formed. The optimum reaction temperature of 180 °C was also established. In these conditions shape, size, and composition of the resulting nanocrystals can be adjusted in a controlled manner by changing the molar ratio of the precursors in the reaction mixture. For low zinc stearate contents anisotropic rodlike (ca.3 nm x 10 nm) and In-rich nanocrystals are obtained. This is caused by a significantly higher reactivity of the indium precursor as compared to the zinc one. With increasing zinc precursor content the reactivities of both precursors become more balanced, and the resulting nanocrystals are smaller (1.5-4.0 nm) and become Zn-rich as evidenced by transmission electron microscopy, X-ray diffraction, and energy-dispersive spectrometry investigations. Simultaneous increases in the zinc and sulfur precursor content result in an enlargement of nanocrystals (2.5 to 5.0 nm) and further increase in the molar ZnS content (up to 0.76). The prepared nanoparticles show stable photoluminescence with the quantum yield up to 37% for In and Zn-rich nanocrystals. Their hydrodynamic diameter in toluene dispersion, determined by dynamic light scattering, is roughly twice larger than the diameter of their inorganic core.

Luminophores of tunable colors from ternary Ag–In–S and quaternary Ag–In–Zn–S nanocrystals covering the visible to near-infrared spectral range

“…Somewhat less popular methods involve the use of a mixture of single element precursors. 19,22 In general, by varying the composition of ternary Ag-In-S nanocrystals and alloyed quaternary Ag-In-Zn-S ones, it is possible to cover the whole visible part of the spectrum as far as photoluminescence is considered; however QY values depend heavily on l max . An additional improvement of the QY values is possible by appropriate surface modifications.…”

“…In the second approach (mixture of simple precursors) different sources of metals and sulfur were used in the preparation of Ag-In-S and Ag-In-Zn-S nanocrystals. AgNO 3 20,22,25-28 and silver(I) acetate 29 were used as precursors of silver whereas InCl 3 , 22 In(OAc) 3 20,25,27,29 and In(acac) 3 26,28 as precursors of indium. Zinc was usually introduced into the reaction mixture in the form of zinc stearate 20,22,[25][26][27][28] or Zn(OAc) 2 .…”

Core Nanoparticle Engineering for Narrower and More Intense Band-Edge Emission from AgInS2/GaSx Core/Shell Quantum Dots

“…Although the "heating up" approach achieved better PL QY, it was still difficult to regulate the particle size because the growth process mainly occurred by Ostwald ripening [22,23]. At the same time, the method of particle size control by the rapid injection of precursors into a hot solvent, which has been commonly used for binary semiconductor QDs, was also adopted for the AgInS 2 NPs synthesis and achieved good size distribution with a PL QY as high as 59% [24][25][26]. Although the control over particle size and composition was achieved, none of these attempts generated a narrow band-edge emission corresponding to common II-VI semiconductor QDs.Recently, we have successfully demonstrated a narrow band-edge PL from AgInS 2 NPs by coating them with a gallium sulfide (GaS x ) shell to passivate the surface of AgInS 2 NPs [27,28].…”

Encapsulation of lanthanides in ternary I–III–VI AgInS2 nanocrystals and their physical properties

“…Among the known nanoscale particles, semiconductor crystals have raised significant concerns in the fabrication of corresponding nanodevices because they played critical roles in assembling new materials for the application in biological probes, solar cells and light-emitting diodes [4]. Particularly, the type of I-III-VI ternary semiconductor such as AgInS 2 has been paid much attention and it is a direct band gap material with high extinction coefficients in a broad region [5]. In addition, they avoid the encapsulation of toxic elements like cadmium or selenium.…”