Assessment of structural, morphological, and figure of merit factors of small-sized cysteine-N and S co-doped graphene oxide nanoclusters for optical switching devices

This paper presents the synthesis of unique small-sized graphene oxide nanoclusters (GO-NCs) using a simple and rapid method. The one-step pyrolysis method was utilized to prepare fluorescent N and S co-doped nanoclusters with a cysteine capping agent. The dynamic light scattering (DLS) research indicates that the average size of nanoclusters is 1.1[Formula: see text]nm, exhibiting a narrow size distribution. The size of the nanoclusters was diminished to under 2[Formula: see text]nm in comparison to traditional graphene quantum dots. The investigation performed with Fourier transform infrared (FT-IR) spectroscopy confirms the presence of cysteine ligands, together with nitrogen and sulfur atoms, in the structural framework of GONCs. The nanoclusters emit in the blue wavelength range. This study also employed a nonlinear approach utilizing [Formula: see text]-scan technology with a continuous-wave (CW) Diode Pumped Solid State (DPSS) Nd:YAG laser at 532[Formula: see text]nm. [Formula: see text]-scan tests revealed negative values for both the nonlinear absorption coefficient and nonlinear refractive index of the synthesized Cys-GONCs, signifying the occurrence of two-photon absorption (TPA) and the self-defocusing effect, respectively. The findings of this research create opportunities to enhance nanoclusters and facilitate the advancement of nanophotonic devices. The results derived from the Figure of Merit (FOM) factors indicate that these nanoclusters possess potential for application in optical switching.