## 8 Applications of Two-Dimensional Nanoscale SnS
The peak at 0.05 V is attributed to: 23 Sn + 4 K\({}^{+}\) + 4e\({}^{-}\)\(\rightarrow\) K\({}_{4}\)Sn\({}_{23}\), with peaks at 0.72 V and 1.04 V corresponding to dealloying reactions of K\({}_{x}\)Sn to Sn at 800 mA g\({}^{-1}\); a capacity of 176 mA g\({}^{-1}\) is maintained after 50 cycles [171]. Other energy storage devices have also been prepared using non-2D nanoscale/nanosheet SnS including supercapacitors [172; 173] with capacities up to 980 F g\({}^{-1}\), higher than activated carbon (100 F g\({}^{-1}\)) [174] and 3D rGO networks [175]. A review on SnS\({}_{x}\) materials in batteries has been conducted by [PERSON] et al. [160]. Electronic devices such as transistors have been created by [PERSON] et al. using 2D, etched layers of SnS. The SnS was produced via the Bridgman technique with subsequent exfoliation. The SnS produced was single crystalline, with flakes ranging from 40-120 nm thick, a representative flake of 64 nm thickness having a lateral size between 10-20 \(\upmu\)m. Thinning of the material via dry etching provided greater performance and an improved on/off ratio due to reduced carrier screening as the material was thinned from 40-45 nm to 20-25 nm. The SnS devices were doped using Cs\({}_{2}\)CO\({}_{3}\) to reduce holes near the SnS flakes' top surface. The on/off ratio of the devices was 10, with surface n-type doping increasing the on/off ratio to 100. The doped devices also possessed a hole mobility of 100 cm\({}^{2}\) V\({}^{-1}\)s\({}^{-1}\)[23]. Due to large surface area, biocompatibility, and strong absorption in the biological near-infrared region, SnS has also been found to have potential applications in the biomedical field. [PERSON] et al. have utilised polyethylene glycol-coated (PEGylated) SnS nanosheets synthesised via a solvothermal route followed by sonication in distilled water and ethanol for photothermal therapy. The SnS produced had lateral sizes of around 100 nm with negligible 2D (unmeasured) thickness. A total of 90% of SK-OV-3 human ovarian cancer cells were killed within 5 min with SnS at 100 ppm. SnS nanosheets were found to have an improved photothermal conversion efficiency compared to bulk (36.1% and 24.0%, respectively). The extinction coefficient of SnS also increased from 8.2 L g\({}^{-1}\) cm\({}^{-1}\) to 16.2 L g\({}^{-1}\) cm\({}^{-1}\) at 808 nm from bulk to nanoscale [176]. Comparable photothermal materials such as WS\({}_{2}\)-PEG nanosheets, gold nanorods, and rGO have extinction coefficients of 23.8 Lg\({}^{-1}\) cm\({}^{-1}\), 13.89 Lg\({}^{-1}\) cm\({}^{-1}\)[177] and 24.6 Lg\({}^{-1}\) cm\({}^{-1}\), respectively, at 808 nm [178]. SnS nanosheets prepared by liquid-phase exfoliation have been successfully used as a combined photothermal and chemotherapeutic agent by [PERSON] et al. A photothermal response of 39.3% at 808 nm was obtained, compared to black phosphorous quantum dots (28.4%) [179] and gold nanorods (23.7%) [180]. A 200% loading ratio of the chemotherapeutic agent doxorubicin to SnS nanosheets was obtained, owing to the buckled structure. The SnS produced was found to have an enhanced therapeutic effect in mice due to the dual photothermal and chemotherapy effects. After 10 h of irradiation, 14% of the SnS had degraded, as determined by UV-Vis and photothermal temperature measurements [181]. SnS has also been used in the creation of a wide variety of chemical detectors for various applications from safety, environmental protection, and biomedical fields, with detection being possible in either gaseous or liquid media. SnS has applications in sensors such as for the detection of methanol, ethanol, acetone, and 1-butanol, with a detectable air concentration of 10 ppm as shown by [PERSON] et al. The sensor consisted of SnS nanoflakes prepared by a solid-state reaction before compression into a pellet and addition of silver paste contacts. A maximum response of 1000% at 100 \({}^{\circ}\)C and rise and fall times of 3 s and 14 s, respectively, was found for acetone [24].