In the present work, the sensing capability of nitrogen-doped graphene quantum dots (N-GQDs) was explored for the first time toward hazardous heavy metal ions and they were found to be able to selectively detect cadmium ions (Cd(ii)).

No abstract

The influence of pad intrinsic properties on the removal rate profiles of ILD CMP with fumed silica abrasive slurry was studied by changing pad's polymer hardness, porosity, and pore size. Of these intrinsic properties, pore size is found to be most critical to removal rate profiles. By systematically changing the pore size from <1 μm to >100 μm, with porosity from 5% to 50%, of pad made of thermal-plastic urethane (TPU), removal rate profile of oxide polishing was studied. A flat removal rate profile cross wafer is desired for ILD CMP. It was found that when the pore size was larger than a certain threshold, flat removal rate profiles could be achieved. Below the threshold, severe edge-fast/center-slow removal rate profiles were observed and such profiles cannot be remedied by changing pad's other properties like porosity or polishing process conditions. A model is proposed to explain the non-flat removal rate profiles associated with the small pore size (<20 μm).

co-precipitation, [11] cloud point extraction, [12] flocculation, [13] reverse osmosis, [14] and adsorption, [15,16] the adsorption-based removal methodology is one of the most promising and widely applied methods to remove pollutants from the environment due to its cost-effectiveness, simple operation, and environmental friendliness. [17] However, the efficiency of adsorption in the removal of toxic metal ions such as Pb (II) depends on the selectivity of the materials used toward the particular ions because of the presence of other pollutants and common metal ions in relatively higher concentrations in water and the very low (safe) level of Pb (II) that need to be achieved. [16] For past decades, various adsorbents have been explored to remove heavy metal ions, which included activated carbon [18,19] from various sources and methods, zeolites, [20,21] clays, [22,23] and polymers [24,25] which exhibited lower removal efficiency for Pb (II) due to the weak binding affinity toward Pb (II) and lack of selectivity.Recently, ultrathin 2D nanomaterials such as graphene (Gr), and Gr-based compounds, molybdenum disulfide (MoS 2 ), [26,27] boron nitride, etc., have gained immense attention as adsorption materials due to their higher theoretical surface area (SA), enhanced catalytic and other unique properties. [28][29][30][31] With its high theoretical SA (≈2630 m 2 g −1 ), chemical stability, and outstanding physicochemical properties, Gr has shown high adsorption capacities for toxic metal ions [32] compared to the other commonly studied adsorbents. [33][34][35][36] Similarly, MoS 2 exhibits higher SA in its nanoforms and, in addition, can exhibit a significant advantage in the adsorption of heavy metal ions such as Hg (II), Ag (I), Cd (II), and Pb (II) because of the affinity toward S 2ions. [37][38][39][40] A previous work from our group utilized MoS 2 -HNR for the removal of toxic metal ions, and it demonstrated simultaneous removal of toxic metal ions: Hg (II), Pb (II), and Ag (I) from groundwater and seawater samples with adsorption capacities as high as ≈1991, 1350, and 1267 mg g −1 for Hg (II), Ag (I), and Pb (II). Even though the maximum adsorption capacity of MoS 2 -HNR toward Pb (II) was higher, the MoS 2 -HNR required ≤30 min to decrease the [Pb (II)] to the safe level (≤10 ppb) in water. The results were able to be explained based on affinity and electrochemistry mechanism. Cost-effective adsorbent materials with high Pb(II) removal efficiency and selectivity are considered necessary for successfully removing Pb(II) contamination from drinking water because of their high-level toxicity and the ultralow safe level of ≤10 ppb in water. This study demonstrates the synthesis and the ultrafast Pb(II) removal capability of a partially reduced graphene oxide-nano-molybdenum disulfide composite (prGO-MoS 2 ). The prGO-MoS 2 exhibits thin sheets of prGO covered more or less uniformly with nano-MoS 2 , and the open architecture gives enhanced accessibility to the S 2and oxygen moieties present in prGO-MoS 2 . A singl...

No abstract