Ratiometric pH Sensing in Living Cells Using Carbon Dots

The ability to precisely sense physiological pH changes in the cellular environment is exceedingly difficult. Novel technologies are thus required to address this challenge. Fluorescent nanomaterials can be exploited to this effect because their optical properties can exhibit strong pH dependence. Herein, an intracellular pH-sensing probe is developed via a facile microwave-reaction synthesis method for the preparation of carbon dots (CDs) using glutathione and formamide. The CDs possess unique optical properties allowing for concomitant fluorescence in the blue and red regions of the spectrum. These dots are investigated as pH-sensors using the red fluorescence signatures at 650 and 680 nm. The two fluorescence bands respond differently following pH changes in their environment and could thus be used for ratiometric measurements. Cytotoxicity studies of the CDs in glioblastoma cells show no decrease in cell viability up to 100 μg mL⁻¹ (24 h). Fluorescence imaging reveals that the dots localize in lysosomal compartments. Moreover, they can sense changes in lysosomal pH in response to serum and amino acid starvation, as well as administration of diclofenac and metformin, drugs currently in clinical trials for combination treatments of cancer. These CDs offer a new self-referencing approach for live intracellular pH sensing in 2D- and 3D-cell models.     

Blue Highly Fluorescent Boranil Derived From Anil Ligand: Synthesis,Characterization, Experimental and Theoretical Evaluation of Solvent Effect on Structures and Photophysical Properties

In this study, we report the design and the synthesis of a Schiff base; Anil and its corresponding Boron Difluoride complexe; Boranil. The synthesis procedure was carried out adopting new, optimized reaction conditions. The Boranil dye presents the advantage to be emissive in solution. 1H and 19F NMR along with FTIR confirmed both compound's structure. To gain a better understanding of the solvatochromic behavior of Anil and Boranil, the dependence of the absorption spectra on the solvent's polarity was studied in depth. Thus, UV–Vis spectroscopy was performed in five selected solvents. In addition to the solvent's polarity effect, the influence of BF2 moiety introduction on the molecule's photophysical properties was also evaluated. When examining different absorption spectra, we found that the title fluorescent dye exhibited weak solvatochromic (11 nm in THF) as well as a slight redshift broader and relatively more structured absorption spectra after complexation. Besides, we investigate the obtained key structure–property relationships through DFT and TD-DFT calculations using a 6–311++ G (d, p) basis set. Quantum chemical calculations allowed confirming proposed structures and understanding their electronic structure in larger details. Theoretical results also showed good agreement with the experimental findings. Finally, the frontier molecular orbitals were investigated to illustrate the pi-conjugation and charge transfer effect.     

Further results of existence of positive solutions of elliptic Kirchhoff equation with general nonlinearity of source terms

The paper deals with some existence results for elliptic Kirchhoff equations with respect to general nonlinear source terms and changing sign data, where we have used three different methods: direct variational method, Galerkin approach, and subsolution–supersolution method.     

Synthesis,antioxidant and anticholinesterase activities of novel quinoline-aminophosphonate derivatives

A series of 20 novel α-aminophosphonate derivatives bearing quinoline or quinolone moiety was designed and synthesized via Kabachnik-Fields reaction in the presence of triethylammonium acetate as a solvent and catalyst under ultrasound irradiation. This procedure affords products in high yields and short reaction times. Molecular structures of the synthesized compounds 4a-g and 5a-m were confirmed using various spectroscopic methods. The antioxidant activity of these compounds was evaluated by eight complementary in vitro tests. The anticholinesterase activity (AChE, BChE) of these compounds were also evaluated. In addition, theoretical calculations of all compounds were investigated as corrosion inhibitors using density functional theory (DFT). The results revealed that 16 of these compounds exhibited high levels of antioxidant activities depending on the assay and that most compounds showed more potent inhibitory activities against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE).     

On the local corrosion in a thin layer of electrolyte separating two materials: specific aspects and their contribution to pad-to-disk stiction in automobile brake system

Journal of Solid State Electrochemistry - The stiction phenomenon which results in the adhesion of the brake pad to the disc brake of a vehicle has been investigated from a corrosion point of view....     

A Dynamic Frictionless Elastic-Viscoplastic Problem with Normal Damped Response and Damage

We consider a mathematical model for the process of a frictionless contact between an elastic-viscoplastic body and a reactive foundation. The material is elastic-viscoplastic with internal state variable which may describe the damage of the system caused by plastic deformations. We establish a variational formulation for the model and prove the existence and uniqueness result of the weak solution. The proof is based on arguments of nonlinear equations with monotone operators, on parabolic type inequalities and fixed point.     

Clay‐Na as a sorbent for the extraction of anti‐inflammatory compounds in water samples

In this work, clay‐Na particles are used as the adsorbent for the solid‐phase extraction of acidic compounds. The novel sorbent under study is based on high‐specific surface area, cation‐exchange capacity designed specifically to offer ion‐exchange properties with the goal being to selectively extract a group of acidic compounds. The effects of the extraction parameters including extraction elution solvent, sample volume and pH. In optimum conditions, the repeatability for one fiber (n = 3), expressed as % relative standard deviation, was between 0.3 and 4.3% for the acid compounds. The detection limits for the studied acidic compounds were between 0.1–0.6 μg/L. The developed method offers the advantages of being simple to use and having a low cost of equipment.     

Multistep deposition of Cu2Si(S,Se)3 and Cu2ZnSiSe4high band gap absorber materials for thin film solar cells

Cu₂ZnSi(S,Se)₄ and Cu₂Si(S,Se)₃ are potential materials to obtain cost effective high band gap absorbers for tandem thin film solar cell devices. A method to synthesize Cu₂SiS₃, Cu₂SiSe₃and Cu₂ZnSiSe₄thin film absorbers is proposed. This method is based on a multistep process, using sequential deposition and annealing processes. X‐ray diffraction analysis performed on the final thin films have confirmed the presence of the Cu₂Si(S,Se)₃ and Cu₂ZnSiSe₄phases. Scanning electron microscopy images revealed the formation of polycrystalline layers with grains size up to 1 µm. The band gap of the ternary Cu₂SiSe₃ and Cu₂SiS₃, and quaternary Cu₂ZnSiSe₄ based thin films as determined from optical and photoluminescence measurements are found to be close to their theoretical values. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)