Flexible Electrochemical Sensor Based on NiCu(OOH) for Monitoring Urea in Human Sweat

Wearable and flexible electrochemical sweat analysis for monitoring health-related urea concentrations with high sensitivity and selectivity is highly required for individual medical care and disease diagnosis. Herein, we report a sensitive and selective sweat sensor based on a flexible NiCu(OOH)/polystyrene (PS) electrode to detect a urea biomarker. The non-enzymatic sensor was fabricated using electrospinning PS containing carbon nanotube as a conductive component and co-sputtering Ni-Cu alloys as a catalyst. The flexible PS provided a porous structure, leading to sufficient active sites, easy access to reactants, and adequate water wettability for effective charge transfer. The sputtered Ni-Cu alloys deposited on the PS were transformed to a Ni-Cu oxyhydroxide form by cyclic voltammetry treatment, managing the detection of the urea molecule in a neutral pH environment. This urea sensor displayed an excellent linear response with a sensitivity of 10.72 μAmM–1cm–2 toward a physiologically appropriate linear range of 2.00–30.00 mM, and negligible interferences from co-existing common species. Furthermore, bending tests demonstrated excellent mechanical tolerance where electrochemical performance was not affected under 200 cycles and 150° bending. The flexible electrochemical urea sensor platform can provide noninvasive monitoring of urea levels in sweat fluids, ensuring clinical diagnosis for biomedical applications.

1-Naphthols as components for multifunctional material systems (MFMS): the molecular modeling approach

Increasing research interests have been paid to developing efficient multifunctional material systems (MFMS) by using various composite materials, owing to their useful properties and good stability. Here, we systematically studied 1-naphthols, especially how the type and position of a substituent influence the reactivity and properties, using different electron-directing groups. During computations, important preparation guidelines for thiol derivatives of 1-naphthol were obtained. It is very interesting to note that some molecules could exhibit intramolecular O–H–O interactions. Careful theoretical investigation reveals that all the tested compounds are stable and the molecules with substituents in positions 4 and 8 are the least reactive. It is also worth noting that for the stability and polarizability tensor values, it is more favorable when both substituents are in the same benzene ring. Among tested 1-naphthols, the greatest values of alpha, beta, and gamma are more than 5, 60, and 110 times better respectively, than in the urea molecule; the change of electron-withdrawing group (EWG) to electron-donating group (EDG) increases NLO effects. This study provided a new scope of 1-naphthols applicability by using them as anti-corrosion materials and as very good materials for NLO devices due to the high stability of the aromatic structure coupled with polarity given by the substituents. Also, the understanding of IR vibrations for more complex organic compounds with thiol substituent has been improved.

Non-linear optical properties of polystyrene and polyvinyl alcohol composites with 4-methoxy-1-naphthol

The analysis of the NLO properties of 4-methoxy-1-naphthol (4M1N) reveals that this molecule has the value of polarizability tensor, α, more than 340% greater than that obtained, at the same level of theory, for urea molecule. This improvement grows to 500% when the second-order hyperpolarizability is considered. Calculations performed within LR-PCM-B3LYP/6-311+G(3d,2p) model proved that embedding of 4M1N in the polymer matrix significantly improved these results suggesting applications of 4M1N as the cheap and effective NLO material. The molecule was also studied, both theoretically and experimentally, to determine its full vibrational characterisation and structural description. Calculations were performed with HF, MP2, SVWN and B3LYP methods, in two, varying in size, basis sets, to find optimized structures, conformational isomers and UV–VIS, IR and Raman spectra. The accordance of simulated oscillation and absorption spectra with experimental ones is very good; IR values are slightly red-shifted. NBO charge distribution analysis was made to generate frontier orbitals and find most reactive parts of the molecule.

A Novel One-Dimensional Copper Mellitate Complex Featured by {Cu(H2O)2(urea)[C6(COO)4(COOH)2]}n2n- Polyanions

Blue monoclinic single crystals of the novel one-dimensional [H3N-(CH2)6-NH3][Cu(H2O)2(urea)(µ2-C6(COO)4 (COOH)2)]*H2O coordination polymer have been prepared in aqueous solution at room temperature in the presence of 1,6-diaminohexane and urea. Space group P21/n (no. 14) with a = 958.48(9), b = 1465.74(11), c = 1821.14(12) pm, beta = 97.655(8)°. The Cu2+ cation is coordinated in a square pyramidal manner by two oxygen atoms stemming from the dihydrogen mellitate tetraanion, one oxygen atom from the urea molecule, and two water molecules. The Cu−O distances are between 193.3(2) and 229.4(2) pm. The connection between Cu2+ and [C6(COO)4(COOH)2]4-

Exploring the potential of a urea derivative: an AIE-luminogen and its interaction with human serum albumin in aqueous medium

A simple AIE active urea molecule (L1) can selectively interact with HSAviaturn-on fluorescence response in aqueous medium.

Facile Synthesis, Crystal Growth, Quantum Chemical Studies of Electronic Structure and of the Profoundly Persuasive NLO Organic Crystal: Ethyl 4-[N,N-bis(p-toluenesulfonyl)]- Aminobenzoate

In the present work, we synthesized Ethyl-4-[N,N-bis (p-toluene sulfonyl)amino]benzoate crystal and structurally characterized by X-ray diffraction (XRD) method. The optimized geometry and vibration wave numbers of the compound investigated was obtained by performing density functional theory (DFT) computations at the M06-2X level of theory and with the 6-311+G(d,p) basis set. The DFT findings show good agreement with the experimental XRD data. Natural bond orbital (NBO) study was performed at the M06-2X/6-311+G(d,p) level to find the stability due to charge delocalization and hyperconjugative interactions. Charge transfer properties and chemical activities at different sites of the synthesized compound was quantitatively determined by performing frontier molecular orbital (FMO) analysis and molecular electrostatic potential (MEP) surfaces at the M06-2X level of theory with 6-311+G(d,p) basis set. The global reactivity parameters were explored with use of the energy of the FMOs. These descriptors predicted the stability of the investigated molecule by revealing the larger hardness and less softness values. Nonlinear optical (NLO) properties was computed at the M06-2X level of theory and 6-311+G(d,p) basis set combination which is observed larger as compared to the urea molecule indicating the considerable NLO character.

BIS-DEACETYLATION OF TETRAACETYLGLYCOLURYL UNDER ACTION OF UREAS

It is established that tetraacetylglycoluril under the action of urea, some N-substituted ureas and benzylidenebisurea in the acid-catalyzed conditions undergoes only bis-deacetylation with the formation of syn- and anti-regio-substituted N,N-diacetylglycolurils, rather than N-acetylation as it was previously shown in a similar reaction for a number of aromatic and heterocyclic amines. In the course of individual experiments, the absence of independent effect of organic solvents during boiling for several hours (alcohols, dioxane, tetrahydrofuran, dimethylsulfoxide) on the deacetylation of tetraacetylglycoluril was revealed, since in these conditions the original substrate remained unchanged. Based on the NMR spectroscopy data, by comparison the integrated intensities of methine and acetyl protons of glycoluryl fragments, we found that the bis-deacetylation of tetraacetylglycoluril in the studied conditions occurs regioselectively with an overwhelming majority of anti-N,N-diacetylglycoluril (up to 92-94%) except for benzylidenebisurea, when the content of the trans-isomer reaches 75%. A marked increase in the cis-isomer (up to 25%) of N,N-diacetylglycoluril in the case of benzylidenebisurea seems to be dictated by the specific effect on the intermediates of reaction of phenylmethylureido carbocation from eliminating urea molecule in acid-catalyzed conditions. It is shown that N,N-diacetylglycoluril in similar conditions under the action of urea and its derivatives does not undergo further deacetylation to the progenitor of bicyclic bisureas – glycoluril, primarily related to the high hydrolytic and steric resistance of these compounds. On the basis of the above research results, the reaction mechanisms of bis-deacetylation of tetraacetylglycoluril in the acid-catalyzed conditions under the action of urea and its N-methyl (phenyl) derivatives through an intermediate process of nucleophilic addition of ureas is proposed.Forcitation:Hoang N.P., Bakibaev A.A., Malkov V.S. Bis-deacetylation of tetraacetylglycoluryl under action of ureas. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 7. P. 49-53

Structural and AC electrical properties study of solid metal urea complexes

The complexation of solid urea with (Co[Formula: see text]), (Cu[Formula: see text]) or (Ni[Formula: see text]) ions has been studied by using dielectric spectroscopy technique over a wide frequency range at different temperatures. Samples' structure were investigated by XRD, FTIR and FT-Raman spectroscopy. FTIR and Raman analysis indicated that the urea coordinates with the metal atoms through the same oxygen–metal bond (O–M). Furthermore, XRD analysis showed that the samples have polycrystalline structure with single phase. The permittivity of complexes was found at much higher values than that of the ligand (pure urea), showing structure dependency. Furthermore, two relaxation peaks were observed in the dielectric loss spectra corresponding to the orientation polarization of urea molecule, and some parts of urea molecule may be NH2 groups. Both relaxation peaks correspond to thermally activated because they were shifted to higher frequency with the temperature increase. The peak position for the low frequency relaxation peak was observed at the same relaxation time ([Formula: see text][Formula: see text]s), corresponding to the coordination mode through the same O–M bond. Novelty of this work is the successful finding of the relationship between the crystalline phase, coordination mode and the dynamic molecular behavior of solid urea and its complexes using the dielectric spectroscopy technique.

Crystal structures of the 2:2 complex of 1,1′-(1,2-phenylene)bis(3-m-tolylurea) and tetrabutylammonium chloride or bromide

The title compounds, tetrabutylammonium chloride–1,1′-(1,2-phenylene)bis(3-m-tolylurea) (1/1), C16H36N+·Cl−·C22H22N4O2or [(n-Bu4N+·Cl−)(C22H22N4O2)] (I) and tetrabutylammonium bromide–1,1′-(1,2-phenylene)bis(3-m-tolylurea) (1/1), C16H36N+·Br−·C22H22N4O2or [(n-Bu4N+·Br−)(C22H22N4O2)] (II), both comprise a tetrabutylammonium cation, a halide anion and anortho-phenylene bis-urea molecule. Each halide ion shows four N—H...X(X= Cl or Br) interactions with two urea receptor sites of different bis-urea moieties. A crystallographic inversion centre leads to the formation of a 2:2 arrangement of two halide anions and two bis-urea molecules. In the crystals, the dihedral angle between the two urea groups of the bis-urea molecule in (I) [defined by the four N atoms, 165.4 (2)°] is slightly smaller than that in (II) [167.4 (2)°], which is probably due to the smaller ionic radius of chloride compared to bromide.