Iron (?) And Copper (?) Based Metal-organic Complexes In The Electrochemical Assay Of Tryptophan And Nitrite

Metal-organic frameworks(MOF)and metal-organic gels(MOG)are members of metal-organic complexes which connected by metal ions and suitable ligand through chemical force.Owning to the big surface area,excellent optical and electrical properties of these materials,MOF and MOG have been extensively used in adsorption,catalysis and sensing.In this paper,two kinds of metal-organic materials including Fe-based MOF and Cu-based MOG were introduced as the novel electrode-modified materials in the assay of small molecules.The detailed results are summarized as follows:AgNPs/MIL-101(Fe)composite as a novel electrocatalyst for tryptophan detection In this section,silver nanoparticle/metal-organic frameworks composite(AgNPs/MIL-101(Fe))was synthesized according to the previous report.We firstly utilized this composite as a novel electrocatalyst in tryptophan(Trp)detection.Firstly,the excellent adsorbability of MOF makes Trp gathered on the surface of MOF,which makes the oxide current of Trp higher than the bare electrode;Secondly,the outstanding electrically conductive properties of silver nanoparticles attached on the MOF further enhanced the current response.Under the optimum experimental conditions,the oxidation peak currents of Trp are proportional to the concentrations of tryptophan over the ranges of 1 ?M to 50 ?M and 50 ?M to 150?M,respectively.The detection limit is 0.14 ?M.Moreover,the presented method was successfully applied to the determination of Trp in urine samples with good recovery.Novel copper(II)-based metal-organic gels as electrocatalyst for selectively sensing of nitrite1.Synthesis and characterizationof Cu(II)-based metal-organic gels2,6-Bis(2-benzimidazolyl)pyridine(BBPY)was chosen to form MOG with copper(II)in this section.The formation of the MOG highly depended on the concentration of metal ions,ligand and the kinds of solvent.Powder Xray diffraction(XPRD)patterns and Fourier transform infrared spectra(FTIR)was carried out to discuss the possible aggregation model.The possible formation model might explained as: the bipyridine N may coordination with copper(II)and the two imine-NH groups may lead to aggregation of molecules through hydrogen bonding interactions.These interactions constitute the fibers together with ?-? stacking caused by the benzene ring in BBPY.The fibers were able to trap additional solvents,further forming the stable MOG.Through a simple freezing-dry treatment of the wet gel,the metal-organic xerogel was obtained and demonstrated well dispersibility in water with the morphology unchanged.2.MOG acted as a novel electrode modified material towards nitrite sensing The pyridine group and imine N-atom contained in BBPY could endow MOG excellent dispersibility in water,which significantly benefits the modification of electrodes.In this section,the well-dispersed metal-organic xerogels was utilized as a promising modified materials towards nitrite sensing,while there have not hitherto been anyreports about MOG material acted as electrocatalyst directly.Results showed the oxidation peak current of nitrite on MOG modified electrode were linearly correlated to the logarithmic value of their concentrations in the range of 2-150 ?M with a detection limit of 0.86 ?M.It was further demonstrated that the modified electrode could be successfully applied for determination of nitrite in sausage samples with satisfactory recovery.