Deng Liu

This paper demonstrated for the first time a simple wet-chemical strategy for synthesizing hemin-graphene hybrid nanosheets (H-GNs) through the π-π interactions. Significantly, this new material possesses the advantages of both hemin and graphene and exhibits three interesting properties. First, H-GNs have intrinsic peroxidase-like activity, which can catalyze the reaction of peroxidase substrate, due to the existence of hemin on the graphene surface. Second, their dispersion follow the 2D Schulze-Hardy rule, that is to say, the coagulation of H-GNs in electrolyte solution results from the interplay between van der Waals attraction and electric double-layer repulsion. Third, H-GNs exhibit the ability to differentiate ss- and ds-DNA in optimum electrolyte concentration, owing to the different affinities of ss- and ds-DNA to the H-GNs. On the basis of these unique properties of the as-prepared H-GNs, we have developed a label-free colorimetric detection system for single-nucleotide polymorphisms (SNPs) in disease-associated DNA. To our knowledge, this is the first report concerning on SNPs detection using functionalized graphene nanosheets. Owing to its easy operation and high specificity, it was expected that the proposed procedure might hold great promise in the pathogenic diagnosis and genetic diseases.

Hydroxyl radicals (•OH) play a crucial role in the fate of redox-active substances in the environment. Studies of the •OH production in nature has been constrained to surface environments exposed to light irradiation, but is overlooked in the subsurface under dark. Results of this study demonstrate that abundant •OH is produced when subsurface sediments are oxygenated under fluctuating redox conditions at neutral pH values. The cumulative concentrations of •OH produced within 24 h upon oxygenation of 33 sediments sampled from different redox conditions are 2-670 μmol •OH per kg dry sediment or 6.7-2521 μM •OH in sediment pore water. Fe(II)-containing minerals, particularly phyllosilicates, are the predominant contributor to •OH production. This production could be sustainable when sediment Fe(II) is regenerated by the biological reduction of Fe(III) during redox cycles. Production of •OH is further evident in a field injection-extraction test through injecting oxygenated water into a 23-m depth aquifer. The •OH produced can oxidize pollutants such as arsenic and tetracycline and contribute to CO2 emissions at levels that are comparable with soil respiration. These findings indicate that oxygenation of subsurface sediments is an important source of •OH in nature that has not been previously identified, and •OH-mediated oxidation represents an overlooked process for substance transformations at the oxic/anoxic interface.

Significance Massive Paleozoic and Precambrian dolostone successions have long puzzled geologists in light of the kinetic barriers that inhibit low-temperature dolomite nucleation and precipitation (i.e., the “dolomite problem”). Significantly, the widely accepted hypothesis that such massive dolomites are the product of burial–hydrothermal dolomitization challenges their validity as archives of Earth surface environments. Here, we place constraints on the formation of massive dolomicrite deposits of the Ediacaran Doushantuo Formation (South China), demonstrating their syndepositional (i.e., early diagenetic) formation over a >63-My interval. Our findings suggest that the “dolomite problem” may be a product of specific conditions common if not persistent in Paleozoic and Precambrian oceans, and that massive dolostone successions may be faithful recorders of environmental conditions in the early oceans.