Influence of the Capping Ligand on the Band Gap and Electronic Levels of PbS Nanoparticles through Surface Atomistic Arrangement Determination

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1 Supporting Information Influence of the Capping Ligand on the Band Gap and Electronic Levels of PbS Nanoparticles through Surface Atomistic Arrangement Determination Diana Fabiola Garcia-Gutierrez a,, b Laura Patricia Hernandez-Casillas a,b, Maria Victoria Cappellari c, Fernando Fungo c, Edgar Martínez-Guerra d, Domingo Ixcoatl García- Gutiérrez a,b*, a Universidad Autónoma de Nuevo León, UANL, Facultad de Ingeniería Mecánica y Eléctrica, FIME, Av. Universidad S/N, Cd. Universitaria, San Nicolás de los Garza, Nuevo León, C.P , México. b Universidad Autónoma de Nuevo León, UANL, Centro de Innovación, Investigación y Desarrollo en Ingeniería y Tecnología, CIIDIT, Km. 10 de la nueva carretera al Aeropuerto Internacional de Monterrey,PIIT Monterrey, Apodaca, Nuevo León, C.P , México. c Universidad Nacional de Rio Cuarto, UNRC. CONICET. Departamento de Química, RN36 601, X5804BYA Río Cuarto, Córdoba, Argentina d Universidad Autónoma de Nuevo León, UANL, Facultad de Ciencias Físico Matemáticas, FCFM, Av. Universidad S/N, Cd. Universitaria, San Nicolás de los Garza, Nuevo León, C.P , México. *Corresponding author domingo.garciagt@uanl.edu.mx Address: Km. 10 de la nueva carretera al Aeropuerto Internacional de Monterrey, PIIT Monterrey, C.P , Apodaca, Nuevo León, México. Phone: +52 (81) x 1525 S1

2 TEM Data Figures S1, S2 and S3 show TEM images at different magnifications of the nanoparticles PbS-HA, PbS-MA and PbS-OA, respectively. EDXS Spectra Figure S4 shows the EDXS spectra and calculated composition for the samples PbS-HA and PbS-MA. FTIR Spectra Figure S5 shows the FTIR data for the three nanoparticle systems, PbS-OA, PbS-HA and PbSMA. EELS Data Figure S6 shows the EELS data acquired for the samples PbS-MA-2.94nm and PbS-OA- 4.18nm. Once the spectra were acquired, the procedure followed to perform the background adjustment and subtraction was the same as the one reported in reference [1]. Briefly, a region of the zero loss peak energy tail is selected right before the signal associated to the energy gap, this tail is fitted to a curve using a power-law function, then it is extrapolated to higher energies and subtracted from the experimental data. The E g can be identified as the value in energy where the spectrum s signal starts to rise, right after the zero loss peak contribution [2]. All synthesized samples were analyzed with these conditions; being able to obtain reliable values for the E g only for two of them. S2

3 Figure S1 Figure S1. TEM images of the PbS-HA nanoparticles observed at different magnifications, a) 20 kx, b) 70 kx, c) 115 kx and d) 200 kx. Higher size dispersion and the presence of small nanoparticles agglomerates can be observed in this system. S3

4 Figure S2 Figure S2. TEM images of the PbS-MA nanoparticles observed at different magnifications. a) 20 kx, b) 70 kx, c) 115 kx and d) 200 kx. Improved size dispersion can be observed compared to the PbS-HA system; no clear agglomerates can be seen in this system. S4

5 Figure S3 Figure S3. TEM images of the PbS-OA nanoparticles observed at different magnifications. a) 20 kx, b) 70 kx, c) 115 kx and d) 200 kx. This system displayed the smallest size dispersion; no clear agglomerates can be seen in this system. S5

6 Figure S4 Figure S4. EDXS spectra from the PbS-HA (a) and PbS-MA (b) samples, with their corresponding composition, are shown. The composition of the PbS nanoparticles for the three different capping ligands used are very similar, within their standard deviation. S6

7 Figure S5 Figure S5. FTIR spectra of PbS nanoparticles with different capping ligands. S7

8 Figure S6 Figure S6. EELS spectra of PbS nanoparticles a) PbS-MA-2.94nm and b) PbS-OA- 4.18nm. Blue line shows the original signal, red line shows the background extrapolation, and the green line shows the signal after the background subtraction. References 1. Erni, R.; Browning, N. D. Quantification of the size-dependent energy gap of individual CdSe quantum dots by valence electron energy-loss spectroscopy. Ultramicroscopy (2007), 107, Lazar, S.; Botton, G.A.; Wu, M.-Y.; Tichelaar, F.D.; Zandbergen, H.W. Materials science applications of HREELS in near edge structure analysis and low energy loss spectroscopy. Ultramicroscopy (2003), 96, S8