Role of water structure on phase separation in polyelectrolyte-polyethyleneglycol based aqueous two-phase systems

Partitioning of proteins in aqueous two-phase systems (ATPS) has emerged as one of the important downstream processing techniques in bioprocess technology. The phase separation behavior of polyelectrolyte-polyethyleneglycol (PEG) based ATPS have been studied to elucidate the mechanism controlling phase behavior. The effect of various inorganic salt additives revealed the importance of water structure as a major factor controlling phase separation in these systems. Nitrate and potassium (water structure breaking ions) elevated the binodial line while sulphate, phosphate and sodium (water structure making ions) depressed the binodial line in both polyacrylic acid-PEG as well as polyethylenimine-PEG based ATPS. The effect of increase in concentration of either of the constituent polymers in both systems (at constant salt concentration) always led to a greater propensity towards phase separation. These results point to a mechanism in which salt-assisted polymer-modified water structure interactions play a central role in phase separation in ATPS.     

Investigation of OPET Performance Using GATE, a Geant4-Based Simulation Software

A combined optical positron emission tomography (OPET) system is capable of both optical and PET imaging in the same setting, and it can provide information/interpretation not possible in single-mode imaging. The scintillator array here serves the dual function of coupling the optical signal from bioluminescence/fluorescence to the photodetector and also of channeling optical scintillations from the gamma rays. We report simulation results of the PET part of OPET using GATE, a Geant4 simulation package. The purpose of this investigation is the definition of the geometric parameters of the OPET tomograph. OPET is composed of six detector blocks arranged in a hexagonal ring-shaped pattern with an inner radius of 15.6 mm. Each detector consists of a two-dimensional array of 8 × 8 scintillator crystals each measuring 2 × 2 × 10 mm(3). Monte Carlo simulations were performed using the GATE software to measure absolute sensitivity, depth of interaction, and spatial resolution for two ring configurations, with and without gantry rotations, two crystal materials, and several crystal lengths. Images were reconstructed with filtered backprojection after angular interleaving and transverse one-dimensional interpolation of the sinogram. We report absolute sensitivities nearly seven times that of the prototype microPET at the center of field of view and 2.0 mm tangential and 2.3 mm radial resolutions with gantry rotations up to an 8.0 mm radial offset. These performance parameters indicate that the imaging spatial resolution and sensitivity of the OPET system will be suitable for high-resolution and high-sensitivity small-animal PET imaging.     

Modeling multilayered MEMS-based micro-fluidic systems

This article describes the design, fabrication, and simulation of two micro-electromechanical systems-based micro-fluidic systems. The first system, a lab-on-a-chip, enables electrochemical immunoassay-based chemical/biological detection. The second is a micro-fluidic bio-impedance sensor. The relevance of fluidic dynamics in micro-fluidic channels is discussed in context of fluid paths and misalignments in the channels that appear during multi-level structure integration. Also discussed is the effect of channel dimensions on the flow profile and on performance within the micro-systems. For more information, contact Shekhar Bhansali, University of South Florida, Nanomaterials and Nanomanufacturing Research Center, Department of Electrical Engineering, 4202 East Fowler Avenue ENB 118, Tampa, Florida 33620; e-mail bhansali@eng.usf.edu.     

Poly(indole-6-carboxylic acid) and tetracyanoquinodimethane-modified electrode for selective oxidation of dopamine

Poly(indole-6-carboxylic acid) (PICA) was synthesized electrochemically over glassy carbon electrode (GCE) through potentiodynamic mode of polymerization. The resulting polymer was soluble in Tris-HCl buffer (pH 7.0). The processable polymer was cast over desired electrode surface along with organic redox mediator tetracyanoquinodimethane (TCNQ) as an electron transfer relay using Nafion^®. Nafion^® was used to solubilize TCNQ as well as to introduce permselectivity to the blend of polymer and TCNQ. The above blend was cast over GCE and characterized by cyclic voltammetry followed by its application in electrochemical sensing of dopamine (DA) and ascorbic acid (AA). The modified electrode was found to be selective for DA analysis. The lowest detection limit of DA sensing was found to be 4 μМ with a sensitivity of 18 μA ± 6 nA/mM of DA.     

Synthesis of Aromatic Polyhedral Oligomeric SilSesquioxane (POSS) Dianilines for Use in High-Temperature Polyimides

A series of novel aromatic Polyhedral Oligomeric SilSesquioxane (POSS) dianiline molecules has been synthesized for use in the preparation of high temperature aromatic polyimides. A general synthetic strategy was devised to improve the structure, yield, and utility of POSS dianilines over those currently available. Peripheral aromatic functionality was specifically incorporated in order to improve thermal properties and to increase compatibility with aromatic polymers. Silyloxy and/or aromatic functional groups were used to link the aniline groups to the POSS cage in order to ensure that this linkage was not a thermal weak point. Additionally, the stereochemistry of the aniline functionality has been varied to produce both meta- and para- isomers. The new dianiline monomers can be used to produce high molecular weight polyimide polymers. These dianilines have been incorporated both as pendants to the polymer backbone, and in a ??bead-on-a-string?? fashion by insertion into the polymer main-chain. In addition to producing POSS polyimides with superior thermal stability, these new monomers will allow full characterization and comparison of POSS-polyimides with differing structures in order to delineate the structure-property relationships of POSS and polymer architectures.     

Structural and physical characteristics of Au2O3-doped sodium antimonate glasses – Part I

Na₂O-Sb₂O₃ glasses doped with different concentrations of Au₂O₃ were prepared by melt quenching technique and later were heat treated at 800°C for 6 hours. Structural analysis by XRD, XPS, SEM, EDS, and DSC techniques indicated that the samples are embedded with multiple crystallites composed of Sb³⁺, Sb⁵⁺, Au³⁺ ions, and Au⁰ metallic particles. These studies have further demonstrated a gradual increasing fraction of Au⁰ metallic particles with increasing Au₂O₃ concentration. IR spectral studies suggested increasing the degree of polymerization of the glass network (due to increasing concentration of Sb⁵⁺ ions that participate in the glass network with Sb^VO₄ structural units) with rise in the concentration of Au₂O₃. Optical absorption spectra of the titled samples have exhibited a broad absorption band at about 530 nm predicted due to the surface plasmon resonance (SPR) and exhibited a spectral red shift with increasing intensity with increase in Au₂O₃ content. Photoluminescence (PL) spectra of the samples recorded (at λ_exc = corresponding SPR band position) exhibited an emission peak at about 580 nm (identified as being due to interband transition between sp and d bands of gold particles). Overall, the analysis of these results has confirmed increasing concentration of Au metallic particles with increase in Au₂O₃ content in the titled material. Finally, it is predicted that the presence of higher concentration of gold particles in the polymerized antimonate glass network makes the materials useful for designing different nano dimensional optoelectronic devices.     

Macroporous WO3: Tunable morphology as a function of glycine concentration and its excellent acetone sensing performance

Materials-by-Design symbolizes the development of advanced materials with cost and time -effective experimentation. Here, we show the single and unique strategy of developing macroporous WO₃ with different morphologies (nano to micro) using glycine as structure assisting agent. The developed structures were analyzed with various characterizing tools, and tested for practical application as acetone gas sensor (83.87% for 10?ppm). The morphological correlation with the sensitivity is described.     

Detection of SARS-CoV-2 using dielectric modulated TFET-based biosensor

Journal of Materials Science: Materials in Electronics - Attributable to the rapid increase in human infection of Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome...     

Structural and dielectric properties of a novel Bi2O3-(1 −x)WO3-xCuO solid solution

A novel solid solution in the system Bi-W-Cu-O has been synthesized and its structural and dielectric properties studied. The solid solution Bi₂O₃-(1 −x)WO₃-xCuO exists up tox=0·7; the solid solutions up tox=0·65 are orthorhombic but stabilize in tetragonal structure in a narrow range aroundx=0·7. The solid solutions are non-centrosymmetric and exhibit ferroelectric behaviour similar to their parent phase Bi₂WO₆. The Curie point of the solid solution is found to decrease with increase inx.