Development of an optical chemical sensor based on 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol in Nafion for determination of nickel ion

An optical chemical sensor based on immobilization of 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol (Br-PADAP) in Nafion membrane is described. The membranes were cast onto glass substrates and were used for the determination of nickel in aqueous solutions by spectrophotometry. The sensor system is highly transparent, mechanically stable and showed no evidence of reagent leaching. The influence of several parameters such as pH, ligand concentration, and type and concentration of regenerating solution were optimized. The sensor system showed good sensitivity in the range 0.5-20 μg ml⁻¹ with a detection limit of 0.3 μg ml⁻¹ Ni(II). The sensor has been incorporated into a home-made flow-through cell for determination of nickel in flowing streams with improved sensitivity, precision and detection limit. The calibration curve in the flow system was linear in the range 0.1-16 μg ml⁻¹ with a detection limit of 0.07 μg ml⁻¹. The sensor is easily regenerated by dilute nitric acid solution. The proposed method was successfully applied to the determination of nickel content in vegetable oil and chocolate samples and the results were compared with those obtained using atomic absorption spectrometry.     

Synthesis of Polyfunctionalized 1,4‐Dihydropyridine‐Fused‐1,3‐Diazaheterocycles: One‐Pot Reaction of 1,1‐Bis(methylthio)‐2‐nitroethylene, 1,n‐Diamine,Arylaldehyde, and Malononitrile

An efficient, one‐pot synthetic protocol for polyfunctionalized 1,4‐dihydropyridine‐fused‐1,3‐diazaheterocycles, a class of biologically active compounds, starting from 1,1‐bis(methylthio)‐2‐nitroethylene, 1,n‐diamine, arylaldehyde, and malononitrile is described. The reactions are completed within 12–15 h under refluxing conditions and in the presence of 10 mol % of piperidine as a basic catalyst to produce the title compounds in 60–75% yields.     

Synthesis of magnetic nanoparticles Fe3O4@CQD@Si(OEt)(CH2)3@melamine@TC@Ni(NO3) with application in the synthesis of 2-amino-3-cyanopyridine and pyrano[2,3-c]pyrazole derivatives

Research on Chemical Intermediates - In the present study, magnetic nanocatalysts coated by carbon quantum dots (CQDs) and organic functional groups (Fe3O4@CQD@Si(OEt)(CH2)3@melamine@TC@Ni(NO3))...     

Imidazolium-based ionic liquid derivative/Cu<Superscript>II</Superscript> complexes as efficient catalysts of the lucigenin chemiluminescence system and its application to H<Subscript>2</Subscript>O<Subscript>2</Subscript> and glucose detection

The effects of six synthetic imidazolium-based ionic liquids (ILs) on the Cu^II-catalyzed chemiluminescence of lucigenin (Luc-CL) in the pH range 6.0–11 were investigated. Preliminary experiments found that the CL emission was strongly enhanced or inhibited in the presence of the ILs. The degree of enhancement or inhibition of the CL intensity in the presence of each IL was related to the molecular structure of the IL, the medium used, and the pH. The maximum enhancement of the CL intensity was observed at pH 9.0 (amplification factor?=?443). This decrease in the pH at which maximum CL enhancement occurred and the substantial signal amplification of the Luc-CL may be related to a strong interaction between Cu^II and the imidazolium ring of superior ILs at this pH. Additionally, the formation of IL microdomains in semi-aqueous media permitted more solubility of the product yielded by the Luc-CL reaction (N-methylacridone), which could increase the CL intensity. To obtain consistent data on the catalytic efficiency of Cu^II in the presence of various ILs as well as the corresponding CL emission intensities, fluorescence quantum yields (Φ _F) of lucigenin were measured under the same conditions. Comparison of the data pointed to the mechanism that controls the properties of Luc-CL in the presence of the Cu^II/IL complexes. Based on the catalytic effect of the Cu^II/IL complex and the measurement of the enzymatically generated H₂O₂, a novel, simple, and sensitive CL method for determining glucose with a detection limit (LoD) of 6.5 μM was developed. Moreover, this method was satisfactorily applied to the determination of glucose in human serum and urine samples.

Open image in new window

Graphical Abstract The lucigenin chemiluminescence assay for H₂O₂ and glucose using imidazolium–based ionic liquid derivatives/Cu^II complexes as efficient catalysts at pH 9.0

     

Synthesis,Characterization and Crystal Structure of the Dimeric Silver(I) Complex containing 4‐Amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione

The reaction of 4‐amino‐5‐methyl‐2H‐1,2,4‐triazole‐3(4H)‐thione (AMTT, 1 ) with AgNO₃ and triphenylphosphane in a molar ratio 1:1:2 in ethanol led to the dimeric complex {[Ag(AMTT)(PPh₃)₂]NO₃}₂·4EtOH ( 2 ). 2 was characterized by elemental analyses, IR, ³¹P NMR spectroscopy as well as single crystal X‐ray diffraction. Crystal data for 2 at ?80 °C: space group with a = 1265.5(2), b = 1300.9(2), c = 1509.5(2) pm, α = 83.77(2)°, β = 79.22(2)°, γ = 62.89(2)°, Z = 2, R₁ = 0.0330.     

Organic-ligand-assisted supercritical hydrothermal synthesis of titanium oxide nanocrystals leading to perfectly dispersed titanium oxide nanoparticle in organic phase

Titanium oxide (TiO₂) nanocyrstals which are perfectly dispersed in organic solvents are synthesized by organic-ligand-assisted supercritical hydrothermal synthesis. The addition of hexaldehyde to the supercritical hydrothermal synthesis of TiO₂ leads to the in-situ surface modification, which enables the synthsized TiO₂ nanocrystals to be perfectly dispersed in iso-octane because of its hydrophobic nature. Further, the one-pot synthesis of hybrid materials results in the significant reduction of the particles size, probably due to the capping effect of hexaldehyde to suppress the particles growth.     

Antimicrobial activity of nanocellulose conjugated with allicin and lysozyme

In this study, cellulose nanoparticles were prepared by acid hydrolysis, separately conjugated with allicin and lysozyme by a carbodiimide cross-linker, and characterized by scanning electron microscopy, dynamic light scattering, and Fourier transform infrared spectroscopy. Then, their antimicrobial properties were evaluated by the microdilution method and compared with allicin, lysozyme, and nanocellulose alone. The results showed that nanocellulose had few antimicrobial activities, but allicin-conjugated nanocellulose (ACNC) and lysozyme-conjugated nanocellulose (LCNC) had good antifungal and antibacterial effects against standard strains of Candida albicans, Aspergillus niger, Staphylococcus aureus, and Escherichia coli. Noticeably, although allicin and lysozyme had different minimum inhibitory concentrations (MICs) against all strains, the same quantity of MIC₅₀ and MIC₉₀ was observed for both ACNC and LCNC. The authors suggest that both ACNC and LCNC can be used in industries as an antimicrobial agent in food packaging, inside foodstuffs, and in textile materials.