(669d) Colloidal Synthesis and Optical Characterization of Chalcogenide Non-Linear Optical (NLO) Particles, Na2Ba7Sn4S16 (NBTS)

Frequency conversion by non-linear optical (NLO) materials is of significant interest because of the need to produce coherent, monochromatic light at frequencies from UV to far-IR for various applications. A plethora of metal chalcogenides have been discovered experimentally as NLO materials, including the primary IR NLO materials available commercially with high second harmonic generation coefficients, AgGaS₂ and AgGaSe₂. [1] The ideal NLO material is characterized by: a large second order electro-optical response, high optical damage threshold, phase matching and high optical homogeneity, small dielectric loss, and transparency for appropriate wavelength ranges. [2]

Single crystal Na₂Ba₇Sn₄S₁₆ (NBTS), I3d space group, has been synthesized via solid state synthesis and the NLO properties measured by Abudurusuli et al. showing an optical band gap of 2.5 eV and second harmonic generation (SHG) response magnitude of 0.1 that of the reference AgGaS₂. [3]

In this work, a novel heat-up colloidal synthesis for Na₂Ba₇Sn₄S₁₆ is introduced using metal-dithiocarbamate precursors and oleylamine as solvent and ligand. Based upon synthesis conditions, particle morphology varies from 100 nm irregularly shaped particles to 5 μm tetrahedrons. Optoelectronic characterization of the varying particle morphologies, including Raman spectroscopy, SHG, photoluminescence, and absorption measurements, is employed to determine NBTS’s potential as a NLO material for the IR region.

[1] I. Chung and M. G. Kanatzidis, “Metal chalcogenides: A rich source of nonlinear optical materials,” Chem. Mater., vol. 26, no. 1, pp. 849–869, 2014, doi: 10.1021/cm401737s.

[2] C. Chen, “Nonlinear Optical and Electro-Optical Materials,” Ann. Rev. Mater.Sci., vol. 16, pp. 203–243, 1986.

[3] A. Abudurusuli, K. Wu, and S. Pan, “Four new quaternary chalcogenides A 2 Ba 7 Sn 4 Q 16 (A = Li, Na; Q = S, Se): syntheses, crystal structures determination, nonlinear optical performances investigation,” New J. Chem., vol. 42, no. 5, pp. 3350–3355, 2018, doi: 10.1039/C7NJ04288D.