Oxidation degree dependent adsorption of ssDNA onto graphene-based surface

DNA/GO composite plays a significant role in the research field of biotechnology and nanotechnology,and attracts a great deal of interest.However,it is still unclear how the oxidation degree of the graphene-based surface affects the adsorption process of single-strand DNA(ssDNA).In this paper,based on the molecular dynamics simulations,we find that ssDNA molecule is absorbed on the GO surface in the most stable state with the oxidation degree around 15%.The microscopic mechanism is attributed to the van Der Walls and the electrostatic interactions between the ssDNA molecule and the graphene-based surface,which is accompanied with theπ-πstacking and hydrogen bond formation.The number ofπ-πstacking between ssDNA and GO reaches the maximum value when the oxidation degree is around 15%among all the GO surfaces.Our simulation results also reveal the coexistence of stretched and curved configurations as well as the adsorption orientation of ssDNA on the GO surface.Furthermore,it is found that the absorbed ssDNA molecules are more likely to move on the graphene-based surface of low oxidation degree,especially on pristine graphene.Our work provides the physics picture of ssDNA’s physisorption dynamics onto graphene-based surface and it is helpful in designing DNA/GO nanomaterials.

Preparation of graphene oxides with different sheet sizes by temperature control

The sheet size of a graphene oxide （GO） can greatly influence its electrical, optical, mechanical, electrochemical and catalytic property. It is a key challenge to how to control the sheet size during its preparation in different application fields. According to our previous theoretical calculations of the effect of temperature on the oxidation process of graphene, we use Hummers method to prepare GOs with different sheet sizes by simply controlling the temperature condition in the process of the oxidation reaction of potassium permanganate （KMnO4） with graphene and the dilution process with deionized water. The results detected by transmission electron microscopy （TEM） and atomic force microscopy （AFM） show that the average sizes of GO sheets prepared at different temperatures are about 1 μm and 7 μm respectively. The ultraviolet-visible spectroscopy （UV-vis） shows that lower temperature can lead to smaller oxidation degrees of GO and less oxygen functional groups on the surface. In addition, we prepare GO membranes to test their mechanical strengths by ultrasonic waves, and we find that the strengths of the GO membranes prepared under low temperatures are considerably higher than those prepared under high temperatures, showing the high mechanical strengths of larger GO sheets. Our experimental results testify our previous theoretical calculations. Compared with the traditional centrifugal separation and chemical cutting method, the preparation process of GO by temperature control is simple and low-cost and also enables large-size synthesis. These findings develop a new method to control GO sheet sizes for large-scale potential applications.

About an important problem in a melter-gasifier

Metallization degree of DRI（R;） reduces with rising oxidization degree of reduction gas（r;） and oxidization degree of reduction gas rises with falling metallization degree of DRI.This is a vicious circle exists in present operation of C3000.Fuel consumption（r;） in Corex increases with falling R;and decreases with rising r;. However,r;obviously increases with the integrated change of R;and r;.To increase R;and decrease r;,an analysis on energy consumption and its distribution was deployed in this paper.According to the results,proposal was tabled based on decreasing char bed height.

Oxidation behavior of low-grade vanadiferous titanomagnetite concentrate with high titanium

In order to clarify the oxidation mechanisms and make better use of the low-grade vanadiferous titanomagnetite concentrate with high titanium(LVTC),the oxidation behavior of LVTC was investigated.The results showed that oxidation degree was achieved within 90 min when temperature was not lower than 700°C,and the main phases of the oxidized LVTC consisted of Fe9TiO15,Fe2O3,CaSiTiO5 and a small amount of Fe2.75Ti0.25O4.Increasing temperature is favorable to the formation of Fe2TiO5.The surface of LVTC gradually becomes rough,with fine particles of needle-like and granular shape appearing on the surface,which finally turn from laminar to creamy,spread out,and are interspersed with many tiny holes.The phase oxidation paths in LVTC were as follows:(1)Fe2.75Ti0.25O4→Fe9TiO15+Fe2O3;(2)Fe2.75Ti0.25O4→Fe2O3+FeTiO3→Fe2TiO5;(3)FeTiO3→Fe2O3+Fe2Ti3O9→Fe2TiO5.LVTC is predominantly mesoporous whether oxidized or not,with the pores mainly distributed in the range of 2–40 nm,and the specific surface area of LVTC decreases significantly with increasing temperature.

Regulating the Nb_(2)C nanosheets with different degrees of oxidation in water lubricated sliding toward an excellent tribological performance

Novel two-dimensional(2D)Nb_(2)C nanosheets were successfully prepared through a simple lultrasonic and magnetic stirring treatment from the original accordion-like powder.To further study their water-lubrication properties and deal with common oxidation problems,Nb_(2)C nanosheets with different oxidation degrees were prepared and achieved long-term stability in deionized water.Scanning electron microscope(SEM),transmission electron microscope(TEM),scanning probe microscope(SPM),X-ray powder diffraction(XRD),Raman,and X-ray photoelectron spectrometer(XPS)experiments were utilized to characterize the structure,morphology,and dispersion of Nb_(2)C nanosheets with different degrees of oxidation.The tribological behaviors of Nb_(2)C with different degrees of oxidation as additives for water lubrication were characterized using a UMT-3 friction testing machine.The wear scars formed on the 316 steel surface were measured using three-dimensional(3D)laser scanning confocal microscopy.The tribological results showed that a moderately oxidized Nb_(2)C nanosheet,which owned the composition of Nb_(2)C/Nb_(2)O5/C,displayed excellent tribological performance,with the friction coefficient(COF)decreasing by 90.3%and a decrease in the wear rate by 73.1%compared with pure water.Combining the TEM and Raman spectra,it was shown that Nb_(2)O5 nanoparticles filled in the worn zone,and the layered Nb_(2)C and C were adsorbed into the surface of the friction pair to form a protective lubricating film.This combined action resulted in an excellent lubricating performance.

Tailoring thermal conductivity of bulk graphene oxide by tuning the oxidation degree

Bulk graphene oxide （GO） shows great potential in a variety of applications, such as sensors,photodetectors, supercapacitors, lithium ion batteries and catalysts. However, its thermal conductivity,one of the most important and fundamental physical properties, is still less known. Herein, we havesystematically investigated the thermal conductivity of bulk GOs and find that it can be tailored by tuningtheir oxidation degree during preparation process. Notably, the cross-plane thermal conductivity of bulkGO, in comparison with its precursor graphite, exhibits more than 100 times decrease at roomtemperature. The dependence of thermal conductivity of GO on oxidation degree is attributed to thechemical and structural changes by introducing oxygen atoms and oxygen-containing functional groups,which can lead to a significant enhancement in atomic- and nano-scale phonon scattering. Furthermore,we reveal that the thermal conductivity of bulk GOs exhibits evident anisotropic behavior. These resultsprovide fundamental understanding and valuable information on thermal transport properties of bulkGOs for various practical applications.

High-Temperature Oxidation Behavior of Vanadium,Titanium-Bearing Magnetite Pellet

By means of isothermal oxidation and chemical analysis, great importance was attached to the parameters that made effects on the oxidation degree of vanadium, titanium-bearing magnetite pellet in high-temperature processing （1 073- 1 323 K）. Based on the experimental data, oxidation kinetics of pellet was analyzed according to shrinking unreacted-core model subsequently. Experiment results display that the oxidation degree of pellet increases with increasing of oxidation time, oxidation temperature and oxygen content, as well as shrinking of pellet diameter. Under the condition of oxidation time 20 min, oxidation temperature 1223 K, oxygen content 15%, and pellet diameter 12 mm, oxidation degree of pellet reaches 92.92%. The analysis of oxidation kinetics indicates that oxidation process of pellet is controlled by chemical reaction with activation energy 68.64 kJ/mol at a relatively lower temperature （1073-1 173 K）. Oxidation process of pellet is mixed-controlled by chemistry reaction and diffusion with activation energy 39.66 kJ/mol in the temperature range of 1 173-1 273 K. When oxidation temperature is higher than 1 273 K, the limited link of oxidation reaction is the diffusion control with the activation energy 20.85 kJ/mol. These results can serve as a reference to the production of vanadium, titanium-hearing magnetite pellet.