Highly Sensitive Electrochemical Detection of Nitrite Based on Cationic Surfactant Modification of Conductive Carbon Black

Nitrite is a commonly used additive in cured foods and its sensitive detection is important to human health.In this work,a simple but sensitive electrochemical sensor for nitrite was developed.Conductive carbon black(VXC-72R)functionalized with a cationic surfactant cetyltrimethylammonium bromide(CTAB)was used as an electrode material,and was coated on a glassy carbon electrode(GCE)to fabricate the electrochemical sensor(CTAB/VXC-72R/GCE)for nitrite.Zeta potential characterization and a series of electrochemical tests were carried out on several materials.It was found that the present sensor showed an enhanced sensitivity towards nitrite detection due to the enhanced surface positive charge revealed by the Zeta potential.Under optimal conditions,the ranges of good linear relationship between the peak current and the nitrite concentration were obtained to be 0.5-5.0μmol/L and 5.0-1087.0μmol/L with a lower detection limit of 0.30μmol/L.It was also successfully used for the determination of nitrite in cured food samples with excellent reproducibility,stability and selectivity.

Novel conductive polypyrrole/silk fibroin scaffold for neural tissue repair

Three dimensional（3D） bioprinting, which involves depositing bioinks（mixed biomaterials） layer by layer to form computer-aided designs, is an ideal method for fabricating complex 3D biological structures. However, it remains challenging to prepare biomaterials with micro-nanostructures that accurately mimic the nanostructural features of natural tissues. A novel nanotechnological tool, electrospinning, permits the processing and modification of proper nanoscale biomaterials to enhance neural cell adhesion, migration, proliferation, differentiation, and subsequent nerve regeneration. The composite scaffold was prepared by combining 3D bioprinting with subsequent electrochemical deposition of polypyrrole and electrospinning of silk fibroin to form a composite polypyrrole/silk fibroin scaffold. Fourier transform infrared spectroscopy was used to analyze scaffold composition. The surface morphology of the scaffold was observed by light microscopy and scanning electron microscopy. A digital multimeter was used to measure the resistivity of prepared scaffolds. Light microscopy was applied to observe the surface morphology of scaffolds immersed in water or Dulbecco＇s Modified Eagle＇s Medium at 37℃ for 30 days to assess stability. Results showed characteristic peaks of polypyrrole and silk fibroin in the synthesized conductive polypyrrole/silk fibroin scaffold, as well as the structure of the electrospun nanofiber layer on the surface. The electrical conductivity was 1 × 10^-5–1 × 10^-3 S/cm, while stability was 66.67%. A 3-（4,5-dimethyl-2-thiazolyl）-2,5-diphenyl-2-H-tetrazolium bromide assay was employed to measure scaffold cytotoxicity in vitro. Fluorescence microscopy was used to observe Ed U-labeled Schwann cells to quantify cell proliferation. Immunohistochemistry was utilized to detect S100β immunoreactivity, while scanning electron microscopy was applied to observe the morphology of adherent Schwann cells. Results demonstrated that the polypyrrole/silk fibroin scaffold was not cytotoxic and did not affect Schwann cell proliferation. Moreover, filopodia formed on the scaffold and Schwann cells were regularly arranged. Our findings verified that the composite polypyrrole/silk fibroin scaffold has good biocompatibility and may be a suitable material for neural tissue engineering.

Fabric Defect Detection Technique Based on Two-double Neural Network

This paper introduces the identification of the defects on the fabric by using two-double neural network and wavelet analysis.The purpose is to fit for the automatic cloth inspection system and to avoid the disadvantages of traditional human inspection.Firstly,training the normal fabric to acquire its characteristics and then using the BP neural network to tell the normal fabric apart from the one with defects.Secondly,doing the two-dimensional discrete wavelet transformation based on the image of the defects,then wiping off the proper characteristics of the fabric,and identifying the defects utilizing the trained BP neural network.It is proved that this method is of high speed and accuracy.It comes up to the requirement of automatic cloth inspection.

Electrochemical Reduction Determination of N-Nitrosodiphenylamine in Food Based on Graphene Electrode Material

As a group of the most notorious carcinogens,N-nitrosamines(NAs)are highly toxic and usually involved in healthy issue of human daily life.An electrochemical sensor for N-nitrosodiphenylamine(NDPhA)detection was constructed based on graphene electrode material.The graphene was facilely obtained by direct reduction of graphene oxide(GO)with hydrazine hydrate,and further coated on the surface of the glassy carbon electrode(GCE)to fabricate the electrochemical sensor for NDPhA analysis in food samples.The present sensor showed excellent sensitivity and selectivity for the electrochemical determination of NDPhA under a reduction manner with the detection limit of 0.6μmol/L.It was also successfully used in beer and ham food samples with satisfactory recovery results.

Preparation of UV-curable Nano-silver Antimicrobial Agent and Its Application in Non-woven Fabric

Nano-silver and waterborne polyurethane(WPU)composite emulsion was synthesized.The average diameter of silver nanoparticles(SNPs)was about 20 nm,and the average diameter of WPU was 101.32 nm.The anti-bacteria finishing of a polypropylene non-woven fabric(NWF)was carried out by ultraviolet finishing technology and the double dipping twin-roll method.The standard AATCC100 was used to test the antimicrobial activity of the samples.The results showed that the antimicrobial rates of Klebsiella pneumoniae(K.pneumoniae)and Staphylococcus aureus(S.aureus)were above 90%,which indicated that the NWF finishing had good antimicrobial activity.In addition,the thermal stability,mechanical properties,whiteness and contact angle of antimicrobial finishing nonwovens were characterized.The results showed that the performance of antimicrobial nonwovens was stable at 300℃.The breaking strength was better than that of untreated nonwovens,and the contact angle reached 119.1°.

Structure and luminescent properties of luminous polypropylene fiber based on Sr_2MgSi_2O_7:Eu^(2+),Dy^(3+)

The luminous polypropylene fiber based on long afterglow luminescent material Sr2MgSi2O7：Eu^2＋,Dy^3＋was prepared by melt-spinning process. Micro-morphology, phase composition, crystal structure, spectral features and afterglow properties of the lu-minescent fiber were tested and analyzed. The results indicated that the fiber had independent superposition phase features of both Sr2MgSi2O7：Eu2＋,Dy3＋and polypropylene. The range of its excitation wavelength was located between 250-450 nm;therefore, the luminescent fiber could be excited by ultraviolet or visible light. It could emit blue light of 460 nm wavelength after excitation, which was caused by the 5d-4f transition of Eu^2＋ions within the host lattice. The initial luminescent intensity was more than 0.8 cd/m^2, and afterglow life lasted 7 h. The afterglow decay was composed of rapid-decaying and slow-decaying processes, and the decay charac-teristics depended on the depth and concentration of trap level in the Sr2MgSi2O7：Eu^2＋,Dy^3＋.

Synthesis of Phenanthridine and Quinoxaline Derivatives via Copper-Catalyzed Radical Cyanoalkylation of Cyclobutanone Oxime Esters and Vinyl Azides

Main observation and conclusion A copper-catalyzed radical cyclization of cyclobutanone oxime esters and vinyl azide is described.This method provides facile access to cyanoalkyl-substituted phenanthridines and quinoxalines with excellent isolated yields.Moreover,these reactions proceed under mild conditions with a board substrate scope and excellent functional group tolerance.

Synthesis and Properties of CF3(OCF3)CH-Substituted Arenes and Alkenes

A silver-mediated oxidative trifluoromethylation of easily accessibleαα-trifluoromethyl alcohols with TMSCF3 was developed to access novel CF3(OCF3)CH-containing compounds.Deprotonation of CF3(OCF3)CH-substituted arenes afforded synthetically useful CF3O-substituted gem-difluoroalkenes.Furthermore,evaluation of the lipophilicities(log P)indicated that CH(OCF3)CF3 is more lipophilic than the common fluorinated motifs such as CF3,OCF3,and SCF3,thus rendering the CH(OCF3)CF3 motif appealing in drug discovery.

Facile syntheses of 3-trifluoromethylthio substituted thioflavones and benzothiophenes via the radical cyclization

3-CF3 S substituted thioflavones and benzothiophenes were achieved via the reactions of AgSCF3 with methylthiolated alkynones and alkynylthioanisoles,respectively,promoted by persulfate.This protocol possesses good functional group tolerance and high yields.Mechanistic studies suggested that a classic two-step radical process was involved,which includes addition of CF3 S radical to triple bond and cyclization with SMe moiety.

Alkylamine-mediated synthesis and photocatalytic properties of ZnO

A simple approach to synthesize ZnO microstructures was reported using dodecylamine,hexadecylamine and oleylamine as template agents.The synthesized ZnO was characterized by XRD,FESEM,TEM,EDS mapping,FTIR,UV-vis DRS,Raman spectroscopy and BET analysis.Hierarchical oriented ZnO microstructures were obtained.The photocatalytic performance of ZnO prepared with different types of alkylamines was evaluated by the degradation of methylene blue(MB)and methyl orange(MO).The results suggested that alkylamine control the nucleation,growth and morphology of ZnO.The photocatalytic properties of ZnO on the degradation of MB and MO decreased with increasing the alkyl chain length in alkylamine.

Mechanically Strong Heterogeneous Catalysts via Immobilization of Powderous Catalysts to Porous Plastic Tablets

Main observation and conclusion We describe a practical and general protocol for immobilization of heterogeneous catalysts to mechanically robust porous ultra-high molecular weight polyethylene tablets using inter-facial Lifshitz-van der Waals Interactions.Diverse types of powderous catalysts,including Cu,Pd/C,Pd/Al2O3,Pt/C,and Rh/C have been immobilized successfully.The immobilized catalysts are mechanistically robust towards stirring in solutions,and they worked well in diverse synthetic reactions.The immobilized catalyst tablets are easy to handle and reused.Moreover,the metal leaching of immobilized catalysts was reduced significantly.

Synthesis of Acrylonitriles via Mild Base Promoted Tandem Nucleophilic Substitution-Isomerization ofα-Cyanohydrin Methanesulfonates

Main observation and conclusion We have developed an efficient synthesis of acrylonitriles via mild base promoted tandem nucleophilic substitution-isomerization ofα-cyanohydrin methanesulfonates with alkenylboronic acids.This transition metal-free protocol works under simple and mild conditions and offers good chemical yields for a wide range of substrates and demonstrates good functional group tolerance.