Transition-metal sulfide (TMS)/porous-reduced graphene oxide (p-rGO)-based nanocomposite materials exhibiting intrinsic peroxidase enzyme-like activity have been synthesized adopting simple solvothermal techniques and characterized with the help of different analytical techniques. The synthesized CuS/p-rGO and NiS/p-rGO artificial nanozymes can catalyze the oxidation process of chromogenic substrates like 3,3′,5,5′ tetramethyl benzidine (TMB) converted to a blue-colored oxidized TMB product (oxTMB) on addition of H₂O₂. It is observed that the presence of Hg(II) ions can inhibit the catalytic activity of nanozymes for the oxidation process of TMB because Hg(II) can easily bind with −S-containing sites of the nanozymes and thus block the catalytic active sites and reduce the catalytic efficiency. This mechanism is utilized for development of a simple colorimetric sensor for visual naked eye detection of Hg(II) ions in a water medium. The synthesized CuS/p-rGO and NiS/p-rGO nanozymes have excellent selectivity and sensitivity toward Hg(II) ions up to the lower concentrations of 13.05 and 48.73 nM, respectively. Moreover, we have reported here a portable, simple, cost-effective, and easy detection process of Hg(II) ions up to the lower limit of 50 nM using a CuS/p-rGO-based paper strip sensor.

中文翻译：

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CuS 和 NiS 纳米颗粒装饰的多孔还原氧化石墨烯片作为高效的过氧化物酶纳米酶，可轻松比色检测水介质中的 Hg(II) 离子并使用纸条

采用简单的溶剂热技术合成了具有内在过氧化物酶样活性的过渡金属硫化物（TMS）/多孔还原氧化石墨烯（p-rGO）基纳米复合材料，并借助不同的分析技术对其进行表征。合成的 CuS/p-rGO 和 NiS/p-rGO 人工纳米酶可以催化显色底物如 3,3',5,5' 四甲基联苯胺 (TMB) 转化为蓝色氧化 TMB 产物 (oxTMB) 的氧化过程加入 H ₂ O ₂. 观察到 Hg(II) 离子的存在可以抑制纳米酶对 TMB 氧化过程的催化活性，因为 Hg(II) 可以很容易地与纳米酶的含 -S 位点结合，从而阻断催化活性位点和降低催化效率。这种机制用于开发一种简单的比色传感器，用于水介质中 Hg(II) 离子的肉眼视觉检测。合成的 CuS/p-rGO 和 NiS/p-rGO 纳米酶对 Hg(II) 离子具有出色的选择性和灵敏度，分别高达 13.05 和 48.73 nM 的较低浓度。此外，我们在此报告了使用基于 CuS/p-rGO 的纸条传感器对高达 50 nM 下限的 Hg(II) 离子进行便携式、简单、经济高效且容易检测的过程。