在色氨酸存在下利用多壁碳纳米管糊电极和萘酚介质构成的伏安传感器测定N-乙酰半胱氨酸(英文)

A multiwall carbon nanotube modified electrode prepared by incorporating multiwall carbon nanotubes in the electrode of a sensor and naphthol green as a homogeneous mediator was used as a voltammetric sensor for the determination of N‐actylcysteine(N‐AC) in the presence of trypto-phan(Trp). The voltammograms of differential pulse voltammetry of N‐AC in a mixture with Trp were separated from each other by a potential difference of 200 mV, which allowed the determina-tion of both N‐AC and Trp simultaneously. Under the optimum conditions, the electrocatalytic cur-rents increased linearly with N‐AC concentration in the range of 0.25–400 μmol/L(two linear seg-ments with different slopes). The detection limit for N‐AC was 0.08 μmol/L. The kinetic parameters of the system were determined using electrochemical methods. The method was applied for the determination of N‐AC in drug and urine samples.     

Time-dependent density functional theory investigations on structural modification in carbazole-based organic photosensitizers to improve electron injection in dye-sensitized solar cell

The time-dependent density functional theory approach, implemented at hybrid-B3LYP, GGA-PBE, and density functional-based tight binding levels of theory, was used to model photoinjection in organic dye/TiO₂ quantum dot to explore the prospects of improvement of dye-sensitized solar cell (DSSC). The photosensitizer used in this study consisted of six carbazole-based organic dyes, a cyanoacrylic acid group as an acceptor and an oligothiophene π-bridge spacer. The modifications were made in the dyes by increasing the length of the spacer by adding thiophene and oxadiazole rings at different positions of the donor-acceptor bridge. The structural variations appeared to alter the electronic and optical properties of dyes studied via energy levels and excitation spectra. The UV-Vis spectra calculated for all the dyes in solvents exhibited a red shift in spectral peaks with an increase in the polarity of the solvents. The findings of the study pointed toward the indirect photoinjection of the dye-(TiO₂)₉₆ complex for six different dyes. The substitution of the oxadiazole ring at the center and addition of a thiophene ring at the edge of the spacer produced two dyes that exhibited the lowest injection energies of 0.11 and 0.17 eV, along with the regeneration energies of 1.18 and 1.12 eV, respectively. The dyes reported here may have promising applications in photoanode for enhancing the performance of DSSC.     

ZnO nanorods as efficient catalyst for the green synthesis of thiophene derivatives: Investigation of antioxidant and antimicrobial activity

In this work, thiophene derivatives were synthesized in good yields via multicomponent reaction of isoquinoline, alkyl bromides, activated acetylenic compounds, isothiocyanates, and catalytic amounts of ZnO nanorods (NRs) at room temperature under solvent-free conditions. This procedure for the synthesis of thiophene derivatives is green, easy, and simple with excellent yield. In addition, DPPH radical scavenging and ferric reduction power experiment has been studied for the evaluation of the antioxidant activity of some prepared thiophenes, for example, 5b , 5d , 5e , and 5f . As outcome, the compound 5d exhibited a noteworthy radical trapping activity and excellent reducing ability than synthetic antioxidants such as butylated hydroxytoluene (BHT) and 2-tertbutylhydroquinone (TBHQ). Moreover, the antimicrobial activity of some synthesized thiophenes was confirmed by employing the disk diffusion test on Gram-positive and Gram-negative bacteria. The obtained results of disk diffusion test showed that compounds 5b , 5d , 5e , and 5f prevented bacterial growth.     

Electrical field-induced extraction and separation techniques: Promising trends in analytical chemistry – A review

Sample preparation is an important issue in analytical chemistry, and is often a bottleneck in chemical analysis. So, the major incentive for the recent research has been to attain faster, simpler, less expensive, and more environmentally friendly sample preparation methods. The use of auxiliary energies, such as heat, ultrasound, and microwave, is one of the strategies that have been employed in sample preparation to reach the above purposes. Application of electrical driving force is the current state-of-the-art, which presents new possibilities for simplifying and shortening the sample preparation process as well as enhancing its selectivity. The electrical driving force has scarcely been utilized in comparison with other auxiliary energies. In this review, the different roles of electrical driving force (as a powerful auxiliary energy) in various extraction techniques, including liquid-, solid-, and membrane-based methods, have been taken into consideration. Also, the references have been made available, relevant to the developments in separation techniques and Lab-on-a-Chip (LOC) systems. All aspects of electrical driving force in extraction and separation methods are too specific to be treated in this contribution. However, the main aim of this review is to provide a brief knowledge about the different fields of analytical chemistry, with an emphasis on the latest efforts put into the electrically assisted membrane-based sample preparation systems. The advantages and disadvantages of these approaches as well as the new achievements in these areas have been discussed, which might be helpful for further progress in the future.     

Reaction of Isonitriles with Dibenzoylacetylene Leading to Furan and Difuropyran Derivatives

A mixture of an isocyanide and dibenzoylacetylene in dry CH₂Cl₂ undergoes a smooth addition reaction at ambient temperature to furnish 3‐[5‐(alkylimino)‐3,4‐dibenzoyl‐2‐phenylfuran‐2(2H)‐yl]‐ 1‐phenylprop‐2‐yn‐1‐ones (1 : 2 adduct) and {2,5‐bis(alkylimino)‐4,7,8a‐triphenyl‐5H‐difuro[2,3‐b:3′,4′‐e]pyran‐3(8aH)‐yl}(phenyl)methanones (2 : 2 adduct). Single‐crystal X‐ray analyses conclusively confirmed the structures of the adducts.     

Palladium‐ and Solvent‐Free Synthesis of Ynones by Copper(I)‐Catalyzed Acylation of Terminal Alkynes with Acyl Chlorides under Aerobic Conditions

Air‐stable Cu^I/cryptand‐22 complex was found to be a highly active catalyst for the solvent‐free cross‐coupling reaction of terminal alkynes with different acyl chlorides in the presence of Et₃N as base to give the corresponding ynones in quantitative yields.     

Efficient Synthesis and Antibacterial Activities of Some Novel 1,2,3‐Triazoles Prepared from Propargylic Alcohols and Benzyl Azides

A simple and effective procedure for regioselective preparation of 1,2,3‐triazoles from benzyl azides and propargylic alcohols is described using CuSO₄.5H₂O and sodium ascorbate. To screen the antibacterial activity of some newly synthesized triazole derivatives, minimum inhibitory concentration of 3d and 3k was evaluated against gram positive Staphylococcus aureus and Bacillus subtilis and gram negative Escherichia coli and Pseudomonas aeruginosa.     

Heteroatom effects in XC5H5C Arduengo-type carbenes (X = CH,N, P,and As) in singlet and triplet states

Internal energy difference, ΔE _s-t; enthalpy difference, ΔH _s-t; Gibbs free energy difference, ΔG _s-t, between the singlet (s) and triplet states (t) of XC₅H₅C, 1X (X = CH, N, P, and As) were computed at B3LYP/6-311++G** and MP2/6-311++G**//B3LYP/6-311++G** levels of theory. The ΔG _s-t between the singlet and triplet states of 1 _X were changed in the order: 1 _P > 1 _As > 1 _N .     

The anti-adherence and bactericidal activity of sol–gel derived nickel oxide nanostructure films: solvent effect

This study presents the characterization and antibacterial activity of nanostructure NiO films synthesized by sol–gel dip coating method using solvents of different polarities and viscosities without any catalysts, templates or surfactants. Methanol, 1,4-butanediol, ethanol, and 2-propanol were used as solvent. The antibacterial activity was tested against two common foodborne pathogenic bacteria Staphylococcus aureus (ATCC 25922) and Escherichia coli (ATCC 29213) using the so-called antibacterial drop test. X-ray diffraction, scanning electron microscopy, atomic force microscopy, UV–vis spectroscopy and static contact angles test were used to analysis the structure and morphology character, surface topography, optical property and surface wettability of different coatings, respectively. The characterization results showed different preferred crystallographic orientations, particle sizes, surface properties and optical band gap of NiO films according to the solvent physicochemical properties. The antibacterial efficiencies were affected by the physiological status of the bacterial cells and degree of bacteria adherence, morphologies and crystal growth habits, surface and optical properties of NiO samples.