Insights into the Oxidative Degradation Mechanism of Solid Amine Sorbents for CO2 Capture from Air: Roles of Atmospheric Water

Direct air capture (DAC) processes for extraction of CO₂ from ambient air are unique among chemical processes in that they operate outdoors with minimal feed pretreatments. Here, the impact of humidity on the oxidative degradation of a prototypical solid supported amine sorbent, poly(ethylenimine) (PEI) supported on Al₂O₃, is explored in detail. By combining CO₂ adsorption measurements, oxidative degradation rates, elemental analyses, solid-state NMR and in situ IR spectroscopic analysis in conjunction with ¹⁸O labeling of water, a comprehensive picture of sorbent oxidation is achieved under accelerated conditions. We demonstrated that the presence of water vapor can play an important role in accelerating the degradation reactions. From the study we inferred the identity and kinetics of formation of the major oxidative products, and the role(s) of humidity. Our data are consistent with a radical mediated autooxidative degradation mechanism.     

Direct electrochemistry of hemoglobin and myoglobin at didodecyldimethylammonium bromide-modified powder microelectrode and application for electrochemical detection of nitric oxide

Hemoglobin (Hb) and myoglobin (Mb) were immobilized at the didodecyldimethylammonium bromide (DDAB)-modified powder microelectrode (PME) to fabricate Hb-DDAB-PME and Mb-DDAB-PME. Direct electrochemistry of Hb and Mb were achieved on the DDAB-modified PME. The formal potential was −0.224 V for Hb and −0.212 V for Mb (vs. SCE). The apparent surface concentration of Hb and Mb at the electrode surface was 2.83 × 10⁻⁸ and 9.94 × 10⁻⁸ mol cm⁻². The Hb-DDAB-PME and Mb-DDAB-PME were successfully applied for measurement of NO in vitro. The anodic current peaks for NO oxidation at +0.7 V and the cathodic current peaks for NO reduction at −0.85 V on the CV curves were obtained on the modified electrodes. For detection of NO at +0.7 V, the sensitivity is 3.31 mA μM⁻¹ cm⁻² for Hb-DDAB-PME and 0.6 mA μM⁻¹ cm⁻² for Mb-DDAB-PME. The detection limit is 5 nM for Hb-DDAB-PME and 9 nM for Mb-DDAB-PME. The linear response range is 9-100 and 28-330 nM for Hb- and Mb-modified PME, respectively. For the electrochemical detection of NO at −0.85 V by using Hb-DDAB-PME, the detection sensitivity is 39.56 μA μM⁻¹ cm⁻²; the detection limit is as low as 0.2 μM; and the linear response range is 1.90-28.08 μM.     

Assessment of hand-held Raman instrumentation for in situ screening for potentially counterfeit artesunate antimalarial tablets by FT-Raman spectroscopy and direct ionization mass spectrometry

Pharmaceutical counterfeiting has become a significant public health problem worldwide and new, rapid, user-friendly, reliable and inexpensive methods for drug quality screening are needed. This work illustrates the chemical characterization of genuine and fake artesunate antimalarial tablets by portable Raman spectroscopy and validation by FT-Raman spectroscopy and ambient mass spectrometry. The applicability of a compact and robust portable Raman spectrometer (TruScan™) for the in situ chemical identification of counterfeit tablets is reported.     

Direct electrogenerated chemiluminescence detection in high-performance liquid chromatography for determination of ofloxacin

Ofloxacin (OFLX) exhibited strong electrogenerated chemiluminescence (ECL) in NaNO₃ solution with a dual-electrode system when constant current was exerted. Based on this observation, a sensitive direct ECL method coupled with high-performance liquid chromatography (HPLC) separation was developed for determination of OFLX in human serum. Factors affected the ECL emission were investigated. Under the optimal conditions, the ECL intensity has a linear relationship with the concentration of OFLX in the range of 1.0 × 10⁻⁸ to 4.0 × 10⁻⁶ g mL⁻¹ and the detection limit was 4 × 10⁻⁹ g mL⁻¹ (S/N = 3). The proposed method was sensitive, simple and convenient to operate.     

Direct Electron Transfer of Hemoglobin on a Carbon Ionic Liquid Electrode with TiO2 Nanopatricle as Enhancer

Room temperature ionic liquids (RTILs) N‐butylpyridinium hexafluorophosphate (BPPF₆) modified carbon paste electrode (CILE) was fabricated and applied to adsorb the hemoglobin (Hb) and TiO₂ nanoparticles on the electrode surface step by step to form a Hb modified electrode noted as TiO₂/Hb/CILE. UV‐Vis and FT‐IR spectra showed that Hb in the film retained its native conformations. Cyclic voltammetric experiments indicated that a pair of well‐defined quasi‐reversible redox peaks appeared with the formal potential (E^0′) located at ?0.251 V (vs. SCE) at pH 7.0 phosphate buffer solution (PBS), which was the characteristic of heme Fe(III)/Fe(II) redox couples. Electrochemical parameters of the Hb in the film such as the electron transfer coefficient (α), the electron transfer number (n) and the standard electron transfer rate constant (k_s) were estimated as 0.469, 0.87 and 0.635 s^?1, respectively.     

Effect of silica nanoparticles on solid state polymerization of poly(ethylene terephthalate)

In the present study, the effect of silica nanoparticles, on the solid state polycondensation (SSP) kinetics of poly(ethylene terephthalate) (PET) is thoroughly investigated. At silica concentrations less than 1 wt% and reaction temperatures between 200 and 230 °C higher intrinsic viscosity (IV) values were measured, compared to neat PET at all reaction times. However, with 1 wt% of nanosilica (n-SiO₂), the IV increase of the nanocomposites was similar to that of neat PET and a further increase to 5 wt% n-SiO₂ resulted in significantly lower IV values. A simple kinetic model was also employed to predict the time evolution of IV, as well as the carboxyl and hydroxyl content during SSP. The kinetic parameters of the transesterification and esterification reactions were estimated at different temperatures with or without the addition of n-SiO₂. The activation energies of both reactions were determined together with the concentration of inactive end-groups. From the experimental measurements and the theoretical simulation results it was proved that n-SiO₂ in small amounts (less than 1 wt%) enhances both the esterification and transesterification reactions at all studied temperatures acting as a co-catalyst. However, as the amount of nanosilica increases a number of inactive hydroxyl groups were estimated corresponding to participation of these groups in side reactions with the nanosilica particles. These side reactions lead initially to branched PET chains and eventually (5 wt% n-SiO₂ concentration) to crosslinked structures.     

A Web services accessible database of turbulent channel flow and its use for testing a new integral wall model for LES

The output from a direct numerical simulation (DNS) of turbulent channel flow at Re_τ ≈ 1000 is used to construct a publicly and Web services accessible, spatio-temporal database for this flow. The simulated channel has a size of 8πh × 2h × 3πh, where h is the channel half-height. Data are stored at 2048 × 512 × 1536 spatial grid points for a total of 4000 time samples every 5 time steps of the DNS. These cover an entire channel flow-through time, i.e. the time it takes to traverse the entire channel length 8πh at the mean velocity of the bulk flow. Users can access the database through an interface that is based on the Web services model and perform numerical experiments on the slightly over 100 terabytes (TB) DNS data on their remote platforms, such as laptops or local desktops. Additional technical details about the pressure calculation, database interpolation, and differentiation tools are provided in several appendices. As a sample application of the channel flow database, we use it to conduct an a-priori test of a recently introduced integral wall model for large eddy simulation of wall-bounded turbulent flow. The results are compared with those of the equilibrium wall model, showing the strengths of the integral wall model as compared to the equilibrium model.     

Application of indium tin oxide (ITO) thin film as a low emissivity film on Ni-based alloy at high temperature

Indium tin oxide (ITO) films as the low emissivity coatings of Ni-based alloy at high temperature were studies. ITO films were deposited on the polished surface of alloy K424 by direct current magnetron sputtering. These ITO-coated samples were heat-treated in air at 600–900 °C for 150 h to explore the effect of high temperature environment on the emissivity. The samples were analyzed by X-ray diffraction (XRD), SEM and EDS. The results show that the surface of sample is integrity after heat processing at 700 °C and below it. A small amount of fine crack is observed on the surface of sample heated at 800 °C and Ti oxide appears. There are lots of fine cracks on the sample annealed at 900 °C and a large number of various oxides are detected. The average infrared emissivities at 3–5 μm and 8–14 μm wavebands were tested by an infrared emissivity measurement instrument. The results show the emissivity of the sample after annealed at 600 and 700 °C is still kept at a low value as the sample before annealed. The ITO film can be used as a low emissivity coating of super alloy K424 up to 700 °C.     

Approximate solution of the problem of scattering of surface water waves by a partially immersed rigid plane vertical barrier

The problem of scattering of two dimensional surface water waves by a partially immersed rigid plane vertical barrier in deep water is re-examined. The associated mixed boundary value problem is shown to give rise to an integral equation of the first kind. Two direct approximate methods of solution are developed and utilized to determine approximate solutions of the integral equation involved. The all important physical quantity, called the Reflection Coefficient, is evaluated numerically, by the use of the approximate solution of the integral equation. The numerical results, obtained in the present work, are found to be in an excellent agreement with the known results, obtained earlier by Ursell (1947), by the use of the closed form analytical solution of the integral equation, giving rise to rather complicated expressions involving Bessel functions.     

Rapid Prototyping of Sensors and Conductive Elements by Day‐to‐Day Writing Tools and Emerging Manufacturing Technologies

The growing demand for low cost and easy to use analytical devices requires the development of reliable and rapid deposition strategies suitable for changing easily planned designs and applicable to a wide range of materials for assembling conductive tracks and sensitive elements. Further important challenges to be pursued are the possibility of using readily available instrumentation and reducing power consumption and hazardous chemical waste. This review provides an overview of the use of portable day‐to‐day writing tools, such as pencils and pens, for the rapid and on‐demand deposition of conductive patterns on different substrates, with particular emphasis on the assembly of “Do It Yourself” sensors. Moreover, layer‐by‐layer deposition of simple or even complex three dimensional (3D) circuits, resorting to pressure driven extrusion of conductive filaments is considered. Future perspectives and potentiality of these emerging technologies for assembling sensors are also explored.