29 and 0.25 nm correspond to the 222 and 400 lattice planes of the corundum-type In2O3, respectively. No nanocrystals that have crystal structures similar to that of SnO or SnO2 were found in the HRTEM observation, in line with the electron diffraction analyses (Additional S3I-201 in vitro file 1: Figure S6). These results are supported by the XRD characterizations (Figure 4d) that the diffraction pattern matches well with the structure of the corundum-type In2O3 (JCPDS: 06-0416). ICP-AES analyses on the aqueous solution coming from digestion of the ITO nanocrystals suggest a doping concentration ([Sn] / ([Sn] + [In])) of 9.9 mol.%. Figure 4 ITO nanocrystals (10 mol.% of tin precursor) from the hot-injection

approach. (a and b) A typical TEM image and the corresponding histogram of size distribution of the ITO nanocrystals. (c) A typical HRTEM image and the selleck kinase inhibitor corresponding FFT patterns. (d) XRD pattern, (e) XPS narrow scan spectrum of the Sn 3d peaks, and (f) UV-vis-NIR spectrum. The valence state of tin dopants is critical in terms of modifying the electronic properties of the ITO nanocrystals.

Note that aminolysis of pure tin(II) 2-ethylhexanoate, the tin precursor used in our experiments, by oleylamine may lead to tin(II) oxide or tin(IV) oxide depending on specific reaction conditions, as demonstrated by our controlled experiments (Additional file 1: Figure S7). XPS was employed to identify the chemical states of the tin dopants. As shown in Figure 4e and Additional file 1: Figure S8, the binding energy of Sn 3d5/2 peak locates at 487.1 eV, which corresponds to the Sn4+ bonding state [40, 41]. The incorporation of Sn4+ ions into the lattice of the nanocrystals led to high free electron concentrations, as confirmed by the characteristic near-infrared SPR peak (Figure 4f). We determined the extinction coefficient per molar of ITO nanocrystals at the SPR peak of 1,680 nm to be 4.5 × 107 M−1 cm−1, by assuming

that the nanocrystals are spherical and 11.4 nm in diameter. The hot-injection approach is readily applied to the syntheses of ITO nanocrystals with a broad range of tin dopants. ROS1 As shown in Figure 5a,b, the SPR peak of the ITO nanocrystals Linsitinib gradually blueshifted from 2,100 to 1,680 nm when the ratio of the dopant precursor increased from 3 to 10 mol.%. Further increasing the ratio of the dopant precursor to 30 mol.% resulted in the red shift of the SPR peak to 1,930 nm. The evolution of SPR peaks of ITO nanocrystals from the hot-injection approach is in agreement with that of the ITO nanocrystals from the Masayuki method. TEM observations (Figure 5c,d,e,f) indicated that the sizes of the ITO nanocrystals became smaller, and the standard derivation was kept as ≤10% when high concentrations of tin dopants were used. Nevertheless, when the Sn amount exceeded 15%, the shape of ITO nanocrystals became irregular (Figure 5e).