Structures of Water Molecules at the Interfaces of Aqueous Salt Solutions and Silica: Cation Effects

Structures of water molecules at water/silica interfaces, in the presence of alkali chloride, were investigated using infrared−visible sum frequency vibrational spectroscopy. Significant perturbations of the interfacial water structure were observed on silica surfaces with the NaCl concentration as low as 1 × 10−4 M. The cations, which interact with the silica surface via electrostatic interaction, play key roles in perturbing the hydrogen-bond network of water molecules at the water/silica interface. This cation effect becomes saturated at concentrations around 10−2 to 10−1 M, where the sum frequency generation peaks at 3200 and 3400 cm−1 decrease by 75%. Different alkali cation species (Li+, Na+, and K+) produce different magnitudes of perturbation, with K+ > Li+ > Na+. This order can be explained by considering the effective ionic radii of the hydrated cations and the electrostatic interactions between the hydrated cations and silica surfaces. The interfacial water structure associated with the 3200 cm−1 band is more vulnerable to the cation perturbation, suggesting that the more ordered water structure on silica is likely associated with the vincinal silanol groups, which create a higher local surface electrical field on silica

Table_1_Dynamic mechanism of eliminating COVID-19 vaccine hesitancy through web search.DOCX

This research focuses on the research problem of eliminating COVID-19 vaccine hesitancy through web search. A dynamic model of eliminating COVID-19 vaccine hesitancy through web search is constructed based on the Logistic model, the elimination degree is quantified, the elimination function is defined to analyze the dynamic elimination effect, and the model parameter estimation method is proposed. The numerical solution, process parameters, initial value parameters and stationary point parameters of the model are simulated, respectively, and the mechanism of elimination is deeply analyzed to determine the key time period. Based on the real data of web search and COVID-19 vaccination, data modeling is carried out from two aspects: full sample and segmented sample, and the rationality of the model is verified. On this basis, the model is used to carry out dynamic prediction and verified to have certain medium-term prediction ability. Through this research, the methods of eliminating vaccine hesitancy are enriched, and a new practical idea is provided for eliminating vaccine hesitancy. It also provides a method to predict the quantity of COVID-19 vaccination, provides theoretical guidance for dynamically adjusting the public health policy of the COVID-19, and can provide reference for the vaccination of other vaccines.</p

Fabrication of Flexible Thermoplastic Polyurethane/Coal Hydrogasification Semi-coke Composites with Low rGO Content for High-Performance Microwave Absorption

Semi-coke (SC), a residue of coal hydrogasification, is recycled and incorporated into thermoplastic polyurethane (TPU) to create composites for microwave absorption (MA). Herein, we developed porous reduced SC (rSC)–reduced graphene oxide (rGO) hybrids (SGHs) via in situ reduction of a preoxidized SC (oSC) and graphene oxide (GO) mixture. Low-content GO was introduced to considerably improve the dielectric properties of SGHs while decreasing the production cost. Then, a solution blending technique was applied to develop microwave absorbers using TPU as the matrix. The obtained TPU/SGH5 composite with a feed ratio of 5:1 (oSC:GO) showed an optimum reflection loss of −48.81 dB at a thickness of 2.5 mm and an effective absorption bandwidth of 4.30 GHz (7.74–12.04 GHz) in 2–18 GHz. However, the MA property of the obtained composites with the same amount of rSC or rGO alone was not comparable to that of the TPU/SGH5 composite. The inherent magnetism, heteroatoms, and abundance of heterogeneous surfaces of rSC and the considerable dielectric loss of rGO worked together to improve the MA performance of TPU/SGH composites. This study offers an easy and effective technical method for producing high-performance microwave absorbers with a low rGO content, illuminating the path toward achieving sustainable development by converting waste into wealth

Images of ATTO 425-tagged clathrin in a CHO cell.

<p>(a) regular 2PE microscope and (b) the 2PE-STED microscope. (c) Magnified view of the marked area for the 2PE image. (d) Magnified view of the marked area for the 2PE-STED image. (e) Intensity profiles (scattering dots) of the 2PE and 2PE-STED images, and fitting with a Lorentzian function (solid lines) in (c) and (d). The scale bars are 5 µm in (a) and (b) and 400 nm in (c) and (d). The pixel sizes are 40 nm for (c) and 20 nm for (d).</p

Temporal profile of the excitation pulse, fluorescence, and depletion beam.

<p>(a) In a CW STED configuration, the CW depletion beam at 532 nm illuminates the sample at all time. (b) In the modulated-CW STED configuration, the CW 532 nm laser is modulated by an acousto-optic Bragg cell to generate 10 ns pulses, which significantly reduce the laser exposure to the sample.</p

Two-photon excited fluorescence depletion of ATTO 425 depends on the 532 nm depletion beam.

<p>Two-photon excited fluorescence depletion of ATTO 425 depends on the 532 nm depletion beam.</p

Detection of lethal fake liquors using digitally labelled gas-phase Fourier transform infrared spectroscopy

Fake liquors have caused severe body injuries or even deaths worldwide, rapid detection of such lethal drinks is thus quite necessary. Methanol has been identified as a primary cause of the problem, so methanol monitoring is critical to the detection of fake liquors. The present work provides an effective strategy for rapid detection of different lethal fake liquors. Using gas-phase Fourier transform infrared spectroscopy in a digitally labeled approach, the spectral bands of methanol were extracted by the iterative discrete wavelet transform for classification, which is named as digitally labeled gas-phase Fourier transform infrared spectroscopy. In digitally labeled gas-phase Fourier transform infrared spectroscopy, principal component analysis and least square support vector machine were combined to discriminate problematic samples using the iterative discrete wavelet transform filtered signals. As a result, the method could cleverly extract spectral features of methanol from the alcoholic drinks in the presence of uncontrolled matrix effects. The recognition accuracy was higher than 97.0%, and each measurement was done within 3 min. The results illustrate that the digitally labeled gas-phase Fourier transform infrared spectroscopy method serves well to rapidly discriminate fake liquors as an efficient and promising tool, and could be well extended to detection of any other targeted volatile substance in complicated systems.</p

Energy diagram showing the photobleaching pathway via the triplet state.

<p>The fluorescence (fl) lifetime of the excited state S₀ is typically a few to several ns. When trapped in the triplet state (T₀), it will take ∼µs to relax to the ground state. Further excitations form the triplet states are more likely to bleach the fluorophore.</p

Experimental setup for 2PE-STED microscopy.

<p>(a) Schematic layout of modulated CW 2PE-STED microscopy. (b) The doughnut-shape intensity profile of the 532 nm depletion beam was obtained by using a spiral phase plate shown in (a). (c) The Gaussian intensity profile of the two-photon excitation beam at 860 nm.</p

Competitive Adsorption of Toluene and <i>n</i>-Alkanes at Binary Solution/Silica Interfaces

The competitive adsorption of toluene and n-alkanes at binary solution/silica interfaces was studied at room temperature using IR-visible sum frequency generation vibrational spectroscopy. The surface coverage of toluene for toluene−pentane, toluene−heptane, and toluene−tetradecane mixtures was measured over the complete mole fraction range from 0 to 1. The competitive adsorption process was reversible, and the toluene coverage only depended on the bulk mole fraction, not on the history of the system. The estimated molar adsorption free energy of toluene is 3.4 ± 0.3, 1.8 ± 0.3, and 0.84 ± 0.3 kJ/mol higher than pentane, heptane, and tetradecane, respectively. Overall, toluene competes favorably on silica, and the molar adsorption free energy of alkanes increases as the chain length increases. It is consistent with the observed SFG spectra, indicating that the alkanes lie flat on the silica surface