过氧化尿素的制备及产品中活性氧含量的测定——介绍一个基础化学综合实验

介绍一个基础化学小型综合实验——过氧化尿素的制备及产品中活性氧含量的测定。该实验以尿素和过氧化氢为原料制备过氧化尿素,并对其性质及含量进行鉴定和定量分析。实践结果表明本实验设计合理,可作为基础化学实验课程中的小型综合实验开设。

Insights into facet-dependent reactivity of CuO–CeO2 nanocubes and nanorods as catalysts for CO oxidation reaction

Copper–ceria(Cu O–CeO2) catalysts have been known to be very effective for the oxidation of CO, and their chemical behavior has been extensively studied during the last decades. However, the effect of different CeO2 crystal surfaces on the catalytic activity of Cu O–CeO2 for the oxidation of CO is still unclear and should be further elucidated. In this study, we deposited 1 wt% Cu on mostly {100}-exposed CeO2 nanocubes(1 Cu Ce NC) and mostly {110}-exposed CeO2 nanorods(1 Cu Ce NR), respectively. Both 1 Cu Ce NC and 1 Cu Ce NR have been used as catalysts for the oxidation of CO and achieved 100% and 50% CO conversion at 130 ℃, respectively. The differences in the catalytic activity of 1 Cu Ce NC and 1 Cu Ce NR were analyzed using temperature-programmed reduction of H2 and temperature-programmed desorption of CO techniques. The results confirmed the excellent reducibility of the 1 Cu Ce NC catalyst, which was attributed to the weak interactions between Cu and the CeO2 support. Moreover, in situ diffuse reflectance infrared Fourier-transform spectroscopy studies indicated that the {100} planes of 1 Cu Ce NC facilitated the generation of active Cu(I) sites, which resulted in the formation of highly reactive Cu(I)-CO species during the oxidation of CO. Both the excellent redox properties and effective CO adsorption capacity of the 1 Cu Ce NC catalyst increased its catalytic reactivity.

Effects of surface physicochemical properties on NH_3-SCR activity of MnO_2 catalysts with different crystal structures

α‐,β‐,δ‐,andγ‐MnO2nanocrystals are successfully prepared.We then evaluated the NH3selective catalytic reduction(SCR)performance of the MnO2catalysts with different phases.The NOx conversion efficiency decreased in the order:γ‐MnO2>α‐MnO2>δ‐MnO2>β‐MnO2.The NOx conversion with the use ofγ‐MnO2andα‐MnO2catalysts reached90%in the temperature range of140–200°C,while that based onβ‐MnO2reached only40%at200°C.Theγ‐MnO2andα‐MnO2nanowire crystal morphologies enabled good dispersion of the catalysts and resulted in a relatively high specific surface area.We found thatγ‐MnO2andα‐MnO2possessed stronger reducing abilities and more and stronger acidic sites than the other catalysts.In addition,more chemisorbed oxygen existed on the surface of theγ‐MnO2andα‐MnO2catalysts.Theγ‐MnO2andα‐MnO2catalysts showed excellent performance in the low‐temperature SCR of NO to N2with NH3.

The Effect of Oxidation/Reduction Disposing on Optical Properties of Mg:Fe:Mn:LiNbO_3 Crystals

The congruent tri-doped Mg:Mn:Fe:LiNbO 3 crystal has been grown by Czochralski method. Some crystal samples are reduced in Li 2CO 3 powder at 500 ℃ for 24 hours or oxidized for 10 hours at 1100 ℃ in Nb 2O 5 powder. Compared with As-grown Mg:Mn:Fe:LiNbO 3, the absorption edge in UV-Vis. absorption spectrum of the oxidized sample and the reduced shifts to the violet and the red, respectively. Reduction increases the absorption of crystals in visible light region. In two-wave coupling experiments, the writing time, maximum diffraction efficiency and the erasure time of crystal samples in the same conditions are determined. The results indicate that oxidation and reduction disposing has great effect on the holographic recording properties of these crystals. The reduced crystal exhibits the fastest response time of 160 s among the crystal series. The mechanism of post-disposing effect on the holographic recording properties of Mg:Mn:Fe:LiNbO 3 crystals are investigated.

Theoretical study on the structure and properties of five-membered cyclic carbonate-based electrolytes

Density functional theory is used to investigate the complexes structures and properties of poly(vinyl ethylene carbonate)(PVEC/LiTFSI)and poly(vinylene carbonate)(PVCA/LiDFOB)electrolytes containing five-membered ring carbonate groups under the polymer/Li^(+)model and the polymer/lithium salt model.In addition,the calculated and experimental values of the oxidation potentials of the two electrolytes were compared,and the reasons for the differences in the oxidation potentials of the two electrolytes are elucidated.The calculation results show that the PVEC/LiTFSI has more free ion structures and diverse coordination structures compared to PVCA/LiDFOB electrolyte.This provides a reasonable theoretical explanation for its higher ionic conductivity and lower cation mobility number.The PVEC/LiTFSI electrolyte has a lower oxidation potential compared to the PVCA/LiDFOB electrolyte,which is attributed to the proton transfer that occurs during its oxidation.

Water Energy and Antioxidant Properties of Water

The possibilities of changes of ORP （oxidation-reduction water potential） with the help of chemical and physical-chemical methods were explored. Distillation and membrane technology were used as physical-chemical methods. In the case of application of chemical methods well-soluble substances were added into water. It was ascertained that the application of membrane technology makes it possible to obtain antioxidant water with negative ORR. Different energy change in a time unit can be applied in a whole number of technological processes and reveals new possibilities for many branches of industry.

Conducting polymer-based peroxidase mimics:synthesis, synergistic enhanced properties and applications

The concept of artificial enzymes has been proposed for a long time and a large variety of materials have been exploited in enzyme-like catalytic field for decades. The emergence of nanotechnology provides increasing opportu- nities for the development of artificial enzymes. Conducting polymer-based nanocomposites are a new type of burgeoning functional materials as enzyme mimics owing to their nu- merous functional groups, excellent electrical conductivity and redox properties. This review summarizes the recent progress of the synthesis of conducting polymers and their nanocomposites, as well as their applications as efficient peroxidase mimics. After a brief description of the develop- ment of conducting polymers, we specifically introduce the fabrication of conducting polymers and their nanocomposites via diverse approaches and show the enhanced peroxidase-like catalytic properties. In addition, the mechanism of the en- hanced catalytic efficiency of the conducting polymer-based nanocomposites has been proposed. Finally, we highlight the applications of such conducting polymer-based nanocompo- sites in the sensitive detection of different types of substances. It is anticipated that this review will pave the way for devel- oping more intriguing functional nanomaterials as enzyme mimics, which shows promising applications in a great many technological fields.

Towards unlocking high-performance of supercapacitors: From layered transition-metal hydroxide electrode to redox electrolyte.

Both energy density and power density are crucial for a supereapacitor device, where the trade-off must be made between the two factors towards a practical application. Herein we focus on pseudocapacitance produced from the electrode and the electrolyte of supercapacitors to simultaneously achieve high energy density and power density. On the one hand, layered transition metal hydroxides （Ni（OH）2 and Co（OH）,,） are introduced as electrodes, followed with exploration of the effect of the active materials and the substrate on the electrochemical behavior. On the other hand, various redox electrolytes are utilized to improve the specific capacitance of an electrolyte. The roadmap is to select an appropriate electrode and a dedicated electrolyte in order to achieve high electrochemical performance of the supercapacitors.

Influence of Soil Properties on Zinc Solubility Dynamics Under Different Redox Conditions in Non-Calcareous Soils

Zinc(Zn) deficiency in paddy soils is often a problem for rice production.Flooding can decrease metal availability in some noncalcareous soils through different mechanisms associated with soil redox status.Laboratory experiments were performed in order to better understand the processes that governed the dynamics of Zn in non-calcareous paddy soils at varying redox potentials(Eh).Airdried non-calcareous soil samples collected from four different paddy field sites in the Philippines were submerged and incubated in a reaction cell with continuous stirring and nitrogen purging for 4 weeks,and then purged with compressed air for another week to reoxidize the system.The Eh of the four soils started at 120 to 300 mV,decreased to —220 to —300 mV after 100 to 250 h of reduction,and was maintained at this low plateau for about 2 weeks before increasing again upon reoxidation.Zinc solubility showed contrasting patterns in the four soils,with two of the soils showing a decrease in soluble Zn as the Eh became low,probably due to zinc sulfide(ZnS) precipitation.In contrast,the other two soils showed that Zn solubility was maintained during the reduced phase which could be due to the competition with iron(Fe) for precipitation with sulfide.Differences in the relative amounts of S,Fe,and manganese(Mn) oxides in the four soils apparently influenced the pattern of Zn solubility after flooding.

Presentation matters： Identity of gold nanocluster capping agent governs intracellular uptake and cell metabolism

Au nanoclusters （AuNCs） hold tremendous potential to be employed in a wide variety of biological applications. Despite the rapid development in the field of NCs synthesis, a comprehensive understanding of how cells interact with this class of ultra-small nanoparticles （〈2 nm） having defined sizes and surface chemistry, remains poorly understood. In this study, we show that the choice of the surface ligand used to protect AuNCs can significantly perturb cellular uptake and intracellular redox signaling. A panel of monodisperse, atomically precise AuNCs with different core Au atom number （i.e., Auls, Au18 and Au25） protected with either mercaptopropionic acid （MPA） or glutathione （GSH） capping agent were synthesized and their effects on the generation of intracellular reactive oxygen species （ROS）, cytotoxicity and genotoxicity of the NCs were assessed. Both mitochondrial superoxide anion （O2^-） and cytoplasmic ROS were found to be higher in cells exposed to MPA but not GSH capped AuNCs. The unregulated state of intracellular ROS is correlated to the amount of internalized AuNCs. Interestingly, MPA-AuNCs induction of ROS level did not lead to any detrimental cellular effects such as cell death or DNA damage. Instead, it was observed that the increase in redox status corresponded to higher cellular metabolism and proliferative capacity. Our study illustrates that surface chemistry of AuNCs plays a pivotal role in affecting the biological outcomes and the new insights gained will be useful to form the basis of defining specific design rules to enable rational engineering of ultra-small complex nanostructures for biological applications.

Synthesis and Electrocatalytic Oxygen Reduction Properties of Truncated Octahedral Pt3Ni Nanoparticles

Pt3Ni nanoparticles have been obtained by shape-controlled synthesis and employed as oxygen reduction electrocatalysts for proton exchange membrane fuel cells （PEMFC）. The effects of varying the synthesis parameters such as the types of the capping agent and the reducing agent, and the reaction time have been systematically studied. The as-prepared PtBNi nanoparticles were subjected to a butylamine-based surface treatment in order to prepare carbon-supported electrocatalysts. The Pt3Ni electrocatalysts show an area- specific activity of 0.76 mA/cm2（pt） at 0.9 V in an alkaline electrolyte, which is 4.5 times that of a commercial Pt/C catalyst （0.17 mA/cm2 （Pt））. The mass activity reached 0.30 A/mg（Pt） at 0.9 V, which is about twice that of the commercial Pt/C catalyst. Our results also show that the area-specific activities of these carbon-supported Pt3Ni electrocatalysts depend strongly on the （111） surface fraction, which is consistent with the results of a study based on Pt3Ni extended single-crystal surfaces.

A reciprocal inhibitory relationship between adiponectin and mammalian cytosolic thioredoxin

Thioredoxin is a redox protein while adiponectin is an adipokine. Their relationship has been less appreci- ated. Here we show that in serum of patients with acute exacerbations of chronic obstructive Pulmonary Disease, decreased activity of thioredoxin coexists with increased level of adiponectin as partial pressure of arterial oxygen decreases. From the results with adiponectin-knockout mice and in vitro experiments, we have found a reciprocal inhibitory relationship, by which adiponectin inhibits cytosolic thioredoxin （Trxl） expression, whereas serum Trxl influences adiponectin multimerization. The associa- tion between extracellular Trxl and adiponectin attenuates their functions. This relationship is dynamic, and correlated with a body＇s physiological conditions.