Near-infrared emitting AgInTe2 and Zn-Ag-In-Te colloidal nanocrystals

The synthesis of AgInTe2 nanocrystals emitting between 1095 nm and 1160 nm is presented. Evolution of the Ag:In:Te ratio shows progressive incorporation of In3+ in Ag2Te, leading to the formation of orthorhombic AgInTe2. When zinc is added to the synthesis, the photoluminescence quantum yield reaches 3.4 %. Electronic supplementary material The online version of this article (doi:10.1186/s11671-015-0951-y) contains supplementary material, which is available to authorized users.


Equipment and analysis method
Absorption spectra of the AIT NCs in TCE and the reference fluorophore were acquired with a Varian Cary 50 Conc UV-visible spectrophotometer. The suspensions were kept diluted enough to avoid self-absorption.
Photoluminescence spectra were recorded between 800 nm and 2000 nm with a Jobin Yvon Nanolog equipped with a Symphony-II CCD detector. The excitation wavelength was set to 488 nm for AgInTe 2 and Zn-Ag-In-Te NCs dispersed in TCE.
Fluorescence quantum yield (PL QY) was determined as presented by Williams et al. [1]. First, UV-visible absorption spectra were acquired for the indocyanine green (ICG) reference at four different concentrations. Measurements were taken at low concentrations in order to avoid reabsorption that would result in nonlinear effects affecting the calculated PL QY values. PL spectra were then recorded for each dilution and the integrated PL intensity (in photons) was plotted as a function of absorbance at λ abs = 795 nm for ICG and λ abs = 488 nm for AIT and Zn-Ag-In-Te NCs. PL QY was calculated with the following equation: where Grad is the gradient of the data plotted and η is the refractive index of the solvent.
Energy-dispersive x-ray spectroscopy measurements were obtained with a Quanta 3D FEG scanning electron microscope from the FEI Company using an EDAX Si(Li) detecting unit. Drops of well purified AIT NCs were put on a carbon surface and scanned with a 15 kV electron beam.
Powder X-ray diffractograms were acquired using a Siemens/Bruker X-ray diffractometer with a 2D Hi-Star XRD detector. The radiation source was a Kristalloflex 760 with a nickel window emitting the Cu K α line (λ = 1.5418 Å) with an accelerating voltage and current of 40 kV and 40 mA respectively. Diffractograms were recorded from 10° to 60°. The background signal was automatically subtracted by the diffraction pattern treatment software GADDS.
Transmission electron microscopy images were obtained with a JEOL JEM 1230. For each sample, 200 NCs were measured by fitting circles around NCs and extracting their diameter using an image treatment software (ImageJ). Slightly elongated NCs were also considered as spheres.
Most of the elongated NCs are actually composed of close smaller spherical NCs that were considered independently for the determination of the average size. Considering this, only a minority of larger elongated NCs were not considered for the determination of the average size.