Investigations on the degradation of aspartame using high-performance liquid chromatography/tandem mass spectrometry

Aspartame is a widely used sweetener, the long-term safety of which has been controversial ever since it was accepted for human consumption. It is unstable and can produce some harmful degradation products under certain storage conditions. A high-performance liquid chromatography/tandem mass spectrometry method was developed for the simultaneous analysis of aspartame and its four degradation products, including aspartic acid, phenylalanine, aspartyl-phenylalanine and 5-benzyl-3,6- dioxo-2-piperazieacetic acid in water and in diet soft drinks. Aspartame and its four degradation products were quantified by a matrix matched external standard calibration curve with excellent correlation coefficients. The limits of detection were 0.16-5.8 μg/L, which exhibited higher sensitivity than common methods. This method was rapid, sensitive, specific and capable of eliminating matrix interferences. It was also applied to the study of the degradation of aspartame at various pH and temperatures. The results indicated that aspartame was partly degraded under strong acidic or basic conditions and the extent of degradation increased with increasing temperature.

Nitrogen-doped graphene nanosheets as high efficient catalysts for oxygen reduction reaction

It is of great significance in exploring alternative catalysts to platinum (Pt)-based materials for oxygen reduction reaction (ORR),because this reaction is invariably involved in various fuel cells and metal-air batteries.We herein reported the nitrogen doped graphene nanosheets (NGNSs) with pore volume of as high as 3.42 m 3 /g and investigated their potential application as ORR catalysts,it was demonstrated the NGNSs featured high activity,improved kinetics and excellent long-term stability for ORR.The NGNSs were successfully used as cathode catalysts of microbial fuel cells (MFCs) and performed even better than the commercial Pt/C (Pt 10%) catalysts at the maximum power output.

Porous cobalt oxide nanowires: Notable improved gas sensing performances

The porous Co3O4 nanowires have been successfully synthesized via modified template method. A possible growth mechanism governing the formation of such 1D nanowires is proposed. The as-prepared products have been characterized by X-ray Powder Diffraction (XRD), Extended X-ray Absorption Fine-structure (EXAFS), High-resolution Transmission Electron Microscopy (HRTEM) and N2 adsorption/desorption analysis. Our systematic studies have revealed that the porous Co3O4 nanowires show excellent gas sensing performances, which demonstrate the potential application of the 1D nanostructured Co3O4 in the detection of the ethanol gas as a sensor material. The improved performances are owing to its large specific surface area and porous morphology.

Controllable synthesis of well-ordered TiO_2 nanotubes in a mixed organic electrolyte for high-efficiency photocatalysis

Well-ordered TiO 2 nanotube arrays (TNAs) were fabricated by electrochemical anodization in a mixed organic electrolyte consisting of ethylene glycol and glycerol. The morphology, structure, crystalline phase, and photocatalytic properties of TNAs were characterized by using TEM, SEM, XRD and photodegradation of methylene blue. It was found that the morphology and structure of TNAs could be significantly influenced by the anodization time and applied voltage. The obtained tube length was found to be proportional to anodization time, and the calculated growth rate of nanotubes was 0.6 m/h. The microstructure analysis demonstrated that the diameter and thickness of the nanotubes increased with the increase of anodization voltage. The growth mechanism of TNAs was also proposed according to the observed relationship between current density and time during anodization. As expected, the obtained TNAs showed a higher photocatalytic activity than the commercial TiO 2 P25 nanoparticles.

Determination of benzoic acid in milk by solid-phase extraction and ion chromatography with conductivity detection

A simple, fast, precise and eco-friendly method, based on ion chromatography （IC） with a suppressed conductivity detector, was proposed for the determination of benzoic acid （BA） in milk in this paper. The chromatographic separation was accomplished by using an anion exchange column eluted with 3.2 mmol/L aqueous Na2C03 and 1.0 mmol/L aqueous NaHCO3 at a flow-rate of 0.7 mL/min. The method validation experiment provided excellent results with respect to linearity （correlation coefficient up to 0.9997）, limit of detection （0.1 ug/L）, recovery values （ranging from 88.0% to 93.0%） and relative standard deviation （RSD） （below 2.2%, n = 7）.

Y-Shaped Circular Aptamer–DNAzyme Conjugates for Highly Efficient in Vivo Gene Silencing

Oligonucleotide drugs have been used widely as therapeutic agents for gene therapy,while their instability in biological media and inefficiency for intracellular delivery remain major hurdles for practical in vivo applications.Herein,we report a circular Y-shaped aptamer–DNAzyme conjugate(cYAD)for highly efficient in vivo gene silencing via RNA cleavage,which can been employed in various disease treatments,including cancer,inflammation,as well as viral infections.Systematic studies revealed that cyclization of the DNA structure could improve the stability of oligonucleotide drugs in vivo.Besides,the bivalent aptamer motifs provided a specific and enhanced tumor cell targeting ability for accumulation and retention of the oligonucleotide drugs at the tumor site.As a proof of concept,a widely applicable Na+-dependent fluorescent sensor,NaA43 DNAzyme,was used to inhibit MET gene expression in mice tumor model tissues,which exhibited highly efficient gene silencing performance in vivo,which confirmed our findings with cYAD.This strategy provides a novel approach for the construction of oligonucleotide drugs for practical therapeutic applications.

DNA Induced FePt Bimetallic Nanoparticles on Reduced Graphene Oxide for Electrochemical Determination of Dopamine

FePt bimetallic nanoparticles were formed on reduced graphene oxide（rGO） with the help of double-stranded DNA（dsDNA） via a simple and universal route to obtain a FePt/DNA-rGO composite. The FePt nanoparticles with an average size of about 5 nm were well dispersed on rGO. FePt/DNA-rGO modified glassy carbon electrode（GCE） exhibited excellent electrocatalytic activity for the oxidation of dopamine（DA） with a detec- tion limit of 100 nmol/L（S/N = 3）. In addition, the FePt/DNA-rGO based electrochemical sensor showed an excellent selectivity for DA in the presence of ascorbic acid（AA）, uric acid（UA） and other interference reagents. The as-prepared electrochemical biosensor shows great promise in the application of clinical diagnostics.

Magnetic Co_3O_4 nanowires,preparation and properties

The Co3O4 nanowires have been successfully synthesized via modified template method.The as-prepared products have been characterized by EDS,TEM and HRTEM analysis.The magnetic behavior of it is investigated by a magnetic property measurement system.The nanowires exhibit some novel magnetic properties,which are different from its bulk material.The temperature dependence curves of magnetization in zero-field-cooling and field-cooling exhibit two peaks of antiferromagnetic at blocking temperature of～23 K and～31 K,respectively.The field dependent M（H） curves of the Co_3O_4 nanowires at T = 5 and 300 K both exhibit PM properties.Moreover,the diameter of nanowires is hence determined according to the finite size effect as approximately 7-11 nm,in consistent with the characterizations by HRTEM.

α型氧化铁与γ型氧化铁负载氮掺杂碳纳米管高效氧气还原反应催化剂(英文)

本论文采用空气煅烧与氮气/氨气退火两步法制备了α-Fe2O3/N-CNTs和γ-Fe2O3/N-CNTs高效氧气还原反应催化剂.X射线衍射与X射线光电子能谱等结果显示:球状的α-Fe2O3与立方体状的γ-Fe2O3较好地分散在氮掺杂的碳纳米管上;不同的退火温度造成γ-Fe2O3/N-CNTs中氮的掺杂量约为1.06%,而α-Fe2O3/N-CNTs中氮掺杂量约为1.94%.从拉曼光谱结果发现,α-Fe2O3/N-CNTs的ID/IG值(1.26)大于γ-Fe2O3/N-CNTs的ID/IG值(1.18),说明α-Fe2O3/N-CNTs表面可因较大的碳缺陷程度而产生更多的氧还原活性电位.电化学性能表征结果再次印证:相比较于γ-Fe2O3/N-CNTs,N-CNTs和CNTs,α-Fe2O3/N-CNTs具有更低的氧还原起始电位(-0.21 V)和峰值电位(-0.27 V).在碱性条件下,氧气在α-Fe2O3/N-CNTs表面更易发生接近4电子的还原反应.另外,与Pt/C相比,α-Fe2O3/N-CNTs和γ-Fe2O3/N-CNTs皆具有较好的催化耐久性与稳定性,进一步显示了二者在清洁能源电池领域的应用价值与潜力.