Exceptional size-dependent property of TiS2 nanosheets for optical limiting

Transition metal dichalcogenides (TMDs), an emerging optical limiting material, exhibit excellent optical limiting properties for high energy laser. Generally, TMDs materials showed better laser protection with the decrease of lateral sizes. However, in this work, TiS2 nanosheets showed exceptional lateral size-dependent optical limiting property contrary to the reported TMDs nanosheets. TiS2 nanosheets with similar thickness and varied lateral sizes of 50 nm, 100 nm, 150 nm, 350 nm were obtained. Larger size TiS2 nanosheets displayed better optical limiting performance and TiS2 nanosheets with ultra-low normalized transmittance (as low as 12%) were developed. It was interesting to find that both two-photon absorption (TPA) and reverse saturable absorption (RSA) were exhibited in large TiS2 nanosheets (350 nm) with a bandgap of 2.67 eV, while in small TiS2 nanosheets (50 nm) with a bandgap of 3.51 eV, only TPA existed. Furthermore, the TiS2 nanosheets incorporated polymethyl methacrylate (PMMA) sample with an extremely low content of 0.066 wt%o TiS2 nanosheets exhibited a low normalized transmittance of 18%, along with a low initial threshold (0.03 J/cm(2)) and low optical threshold (0.57 J/cm(2)), which showed great potential for practical use of the TiS2 nanosheets in optical limiting field.

Automated summary

TiS2 nanosheets exhibit exceptional lateral size-dependent optical limiting properties, showing unique characteristics compared to other TMDs materials.