Cobalt ion (Co²⁺) is known to be harmful for human beings, and effectively portable sensor is one of the key for its prophylaxis and treatment. In this work, Zn(CH₃COO)₂·2H₂O, Na₂S·9H₂O and thioglycolic acid were used to prepare ZnS quantum dots through a facile water-bath method. The structure and morphology of the ZnS quantum dots were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. Scanning electron microscope (SEM) was also used to observe the surface morphology of the test paper prepared by a simple dipping-drying process. The Co²⁺ sensing properties of as-prepared test paper were investigated. And it was found that the color of as-fabricated test paper could change from white to brown within 1 min with addition of Co²⁺ aqueous solution, which makes it possible for qualitative detection of Co²⁺ through naked eyes. In this mode, a widely detectable range from 10 to 1000 mg L⁻¹ is reached by the test paper. In addition, through measuring the grey level of the test paper by ordinary smart phone and laptop, a semi-quantitative function of the test paper is realized. Moreover, the as-fabricated paper sensor can resist the interference of a serious cations and anions, and suits for a wide pH surrounding from 1.08 to 9.65, which makes it a promising Co²⁺ sensor for practical use. In addition, through X-ray diffraction and UV–vis spectra, the sensing properties of as-fabricated test paper are attributed to the chemical reaction between as-prepared ZnS quantum dots and Co²⁺ ions. And the formation of CoS₂ should be responsible for the color change from white to brown.

已知钴离子（Co ²⁺）对人类有害，有效的便携式传感器是其预防和治疗的关键之一。在这项工作中，Zn（CH ₃ COO）₂ ·2H ₂ O，Na ₂ S·9H ₂ O和巯基乙酸被用于通过简便的水浴法制备ZnS量子点。分别通过X射线衍射（XRD）和透射电子显微镜（TEM）研究了ZnS量子点的结构和形态。还使用扫描电子显微镜（SEM）观察通过简单的浸渍干燥过程制备的试纸的表面形态。钴²⁺研究了所制备试纸的感官特性。结果发现，加入Co ²⁺水溶液后，试纸的颜色可在1分钟内从白色变为棕色，这使得通过肉眼定性检测Co ²⁺成为可能。在这种模式下，试纸可达到10到1000 mg L ^-1的广泛检测范围。另外，通过用普通的智能手机和笔记本电脑测量试纸的灰度，可以实现试纸的半定量功能。而且，制成的纸传感器可以抵抗严重的阳离子和阴离子的干扰，并且适合在1.08至9.65的宽pH值范围内使用，这使其成为很有前途的Co ²⁺实际使用的传感器。此外，通过X射线衍射和UV-vis光谱，制成的试纸的感测特性归因于制成的ZnS量子点与Co ²⁺离子之间的化学反应。CoS ₂的形成应负责颜色从白色变为棕色。