Two-dimensional (2D) group-Ⅳ monochalcogenides MX (M = Ge, Sn; X = S, Se) are isoelectronic and isostructural analogues to phosphorene. Due to superior oxidation resistance relative to black phosphorus, MX are recently explored to be potentialsubstitute of phosphorene for highly sensitive gas sensor applications. In this work, nanoflakes of tin monosulfide (SnS) was synthesized by a one-step solvothermal method and then employed for methanol-sensing at room temperature. The as-synthesized SnS shows nanoflower-like hierarchical architecture assembled by 2D nanoflakes. To achieve satisfactory gas response magnitude, a KOH alkalization process for post-treatment of the synthesized SnS was developed further. It is proved that appropriate alkalization could induce the ultrathin nanoflakes and introduce additional –O function terminals on the surface, which are favorable for methanol adsorption and response. The resultant alkalized SnS sensor displays a ∼3.2-fold enhancement in gas response to 5 ppm methanol. And it is capable of sensing rarefied methanol vapor as low as 100 ppb. The response enhancement could attribute to the alkalization-induced ultrathin geometry of SnS nanoflakes, introduction of lattice defects and –O functional terminals available for active adsorption of gas molecules. Further first-principles calculations clarify the crucial contribution and underlying mechanism of attached –O terminal on methanol adsorption and reaction clearly.

二维 (2D) Ⅳ族单硫属化物 MX (M = Ge, Sn; X = S, Se) 是磷烯的等电子和同构类似物。由于相对于黑磷具有优异的抗氧化性，最近探索 MX 作为磷烯的潜在替代品，用于高度敏感的气体传感器应用。在这项工作中，通过一步溶剂热法合成了单硫化锡 (SnS) 纳米薄片，然后用于室温下的甲醇传感。合成的 SnS 显示出由 2D 纳米薄片组装的类似纳米花的分层结构。为了获得令人满意的气体响应幅度，进一步开发了用于合成 SnS 后处理的 KOH 碱化工艺。证明适当的碱化可以诱导超薄纳米薄片并在表面引入额外的-O功能终端，有利于甲醇的吸附和响应。由此产生的碱化 SnS 传感器对 5 ppm 甲醇的气体响应显示出约 3.2 倍的增强。它能够检测低至 100 ppb 的稀甲醇蒸汽。响应增强可能归因于碱化诱导的 SnS 纳米薄片的超薄几何形状、晶格缺陷的引入和可用于主动吸附气体分子的 -O 功能末端。进一步的第一性原理计算清楚地阐明了连接的-O末端对甲醇吸附和反应的关键贡献和潜在机制。响应增强可能归因于碱化诱导的 SnS 纳米薄片的超薄几何形状、晶格缺陷的引入和可用于主动吸附气体分子的 -O 功能末端。进一步的第一性原理计算清楚地阐明了连接的-O末端对甲醇吸附和反应的关键贡献和潜在机制。响应增强可能归因于碱化诱导的 SnS 纳米薄片的超薄几何形状、晶格缺陷的引入和可用于主动吸附气体分子的 -O 功能末端。进一步的第一性原理计算清楚地阐明了连接的-O末端对甲醇吸附和反应的关键贡献和潜在机制。