Nonlinear Optical Properties of Molybdenum Disulfide Nanocrystals for Luminescence-Based Sensor Applications

In this work, the nonlinear optical (NLO) properties of ca. 4.6 nm molybdenum disulfide nanocrystals (MoS₂ NCs) were examined. The spectrally resolved NLO response of the synthesized NCs was investigated across excitation wavelengths ranging from ∼600 to 1000 nm. The maximum σ₂ value of 4.0 × 10^-47 cm⁴·s·photon^-1 per NC was obtained at an excitation wavelength of 720 nm, indicating efficient two-photon absorption and strong NLO activity within the near-infrared region. Furthermore, the sensing capabilities of the water-dispersed MoS₂ NCs toward ferric ion and temperature variations were examined in the two-photon excitation regime. The results revealed that ion sensing remains comparably efficient under both one- and two-photon excitation, whereas temperature sensing in the two-photon regime demonstrates consistent and reliable performance. The findings provide insights into the NLO characteristics of colloidal MoS₂ NCs and highlight their potential as multifunctional nanomaterials for future advanced optical sensing technologies.