Multi-wavelength Stellar Polarimetry of the Filamentary Cloud IC5146: I. Dust Properties

We present optical and near-infrared stellar polarization observations toward the dark filamentary clouds associated with IC5146. The data allow us to investigate the dust properties (this paper) and the magnetic field structure (Paper II). A total of 2022 background stars were detected in $R_{c}$-, $i'$-, $H$-, and/or $K$-bands to $A_V \lesssim 25$ mag. The ratio of the polarization percentage at different wavelengths provides an estimate of $\lambda_{max}$, the wavelength of peak polarization, which is an indicator of the small-size cutoff of the grain size distribution. The grain size distribution seems to significantly change at $A_V \sim$ 3 mag, where both the average and dispersion of $P_{R_c}/P_{H}$ decrease. In addition, we found $\lambda_{max}$ $\sim$ 0.6-0.9 $\mu$m for $A_V>2.5$ mag, which is larger than the $\sim$ 0.55 $\mu$m in the general ISM, suggesting that grain growth has already started in low $A_V$ regions. Our data also reveal that polarization efficiency (PE $\equiv P_{\lambda}/A_V$) decreases with $A_V$ as a power-law in $R_c$-, $i'$-, and $K$-bands with indices of -0.71$\pm$0.10, -1.23$\pm$0.10 and -0.53$\pm$0.09. However, $H$-band data show a power index change; the PE varies with $A_V$ steeply (index of -0.95$\pm$0.30) when $A_V < 2.88\pm0.67$ mag but softly (index of -0.25$\pm$0.06) for greater $A_V$ values. The soft decay of PE in high $A_V$ regions is consistent with the Radiative Aligned Torque model, suggesting that our data trace the magnetic field to $A_V \sim 20$ mag. Furthermore, the breakpoint found in $H$-band is similar to the $A_V$ where we found the $P_{R_c}/P_{H}$ dispersion significantly decreased. Therefore, the flat PE-$A_V$ in high $A_V$ regions implies that the power index changes result from additional grain growth.Comment: 31 pages, 17 figures, and 3 tables; accepted for publication in Ap

Enhancing Full Water-Splitting Performance of Transition Metal Bifunctional Electrocatalysts in Alkaline Solutions by Tailoring CeO₂–Transition Metal Oxides–Ni Nanointerfaces

Rational design of highly efficient bifunctional electrocatalysts for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is critical for sustainable energy conversion. Herein, motivated by the high activity of OER catalyst on water dissociation that is the rate-determining step of alkaline HER, a bifunctional catalyst of metallic nickel-decorated transition metal oxide nanosheets vertically grown on ceria film (ceria/Ni-TMO) is synthesized by composition controlling and surface engineering. Because of the idealized electronic structure of the active centers and the abundance of such sites, as well as a synergistic effect between the carbon cloth/ceria film and the in situ formed TMO/Ni nanoparticles, the as-synthesized ceria/Ni-TMO exhibited long-time stability and a low cell voltage of 1.58 V at 10 mA/cm² when applied as both the cathode and anode in alkaline solutions. Moreover, it is the first time that pH-independent four-proton-coupled-electron-transfer processes and multiple adsorption–desorption processes were found to occur at the interfaces of ceria/TMO and Ni/TMO in a single catalyst for catalyzing OER and HER, respectively

Data_Sheet_1_UPLC-MS/MS profiling, antioxidant and anti-inflammatory activities, and potential health benefits prediction of phenolic compounds in hazel leaf.PDF

Hazel leaf, one of the by-products of hazelnut, which is widely used in traditional folk medicine around the world. In the present study, the profile of free, conjugated, and bound phenolic compounds from hazel leaf was detected and their antioxidant and anti-inflammatory activities were investigated. The potential health benefits of different phenolic compounds were also predicted. The results showed that the 35 phenolic substances of free, conjugated and bound forms were identified including phenolic acids, flavonoids and catechins. Most of the hazel leaf phenolics were presented in free form, followed by conjugated and bound form. All the fractions effectively inhibited the production of reactive oxygen species and malondialdehyde in TBHP-stimulated human umbilical vein endothelial cells by enhancing endogenous superoxide dismutase, and accordingly alleviated inflammatory cytokines (NO, IL-1β, TNF-α, and IL-6) in LPS-stimulated RAW264.7 cells, showing obvious antioxidant and anti-inflammatory capacity. Moreover, combined with network pharmacology, the potential therapeutic effects and functional pathways of hazel leaf phenolics were predicted, which provided value basis for exploring their treatment on diseases and developing health products in the future.</p

The Diagnostics of Laser-Induced Fluorescence (LIF) Spectra of PAHs in Flame with TD-DFT: Special Focus on Five-Membered Ring

The electronic emission characteristics of 13 gas-phase PAHs, ranging from phenlylacetylene to rubicene, were investigated to diagnose laser-induced fluorescence (LIF) spectra of PAHs in flame by DFT, TD-DFT, and premixed flame modeling methods. It was found that the maximum emission wavelengths of the PAHs with five-membered ring are located in visible region and insensitive to the number of C atoms. However, the fluorescence wavelengths of the PAHs without five-membered rings increase with the number of C atoms due to the reduced HOMO–LUMO gap. In addition, the fluorescence wavelength of the PAHs without five-membered rings with linear arrangement is longer than that of PAHs with nonlinear arrangement. According to the Franck–Condon principle, the vibrationally resolved electronic fluorescence spectra were obtained. The results show that fluorescence bandwidth of the PAHs with five-membered rings is much broader than that of the PAHs without five-membered rings. The concentration of PAHs was calculated by using the premixed flat-flame model with KM2 mechanism. On the basis of the fluorescence bandwidth and the concentration of the PAHs, the potentially fluorescence distribution of PAHs in flame was mapped. One can distinguish the specific PAHs according to the mapped fluorescence distribution of PAHs in this study. It was found that naphthalene should be responsible for the fluorescence located in the 312–340 nm region in the flame. 1-Ethynylnaphthalene is the most possible candidate to emit the fluorescence located in the 360–380 nm region. The fluorescence signals with the wavelength longer than 500 nm are likely emitted by the PAHs with five-membered rings. This study contributes to enhance the selectivity of PAHs in LIF technology, especially in the visible region

Effects of Thermal Fluctuations on the Structure, Level Alignment, and Absorption Spectrum of Dye-Sensitized TiO₂: A Comparative Study of Catechol and Isonicotinic Acid on the Anatase (101) and Rutile (110) Surfaces

The adsorption of catechol and isonicotinic acid on the TiO₂ anatase (101) and rutile (110) surfaces has been studied by means of first-principles molecular dynamics simulations and time-dependent density functional calculations. Our results show that thermal fluctuations induce changes in the position of the molecular levels around the TiO₂ valence band edge. For the anatase (101) surface, the alignment of the molecular levels with the TiO₂ valence band edge has a significant effect on the absorption spectrum. For rutile (110), instead, the adsorption of catechol and isonicotinic acid induces only a minor sensitization. The sensitization of anatase (101) by catechol and isonicotinic acid can be enhanced by increasing the hybridization between the adsorbed dye and TiO₂ states

New Insights into Thermal Decomposition of Polycyclic Aromatic Hydrocarbon Oxyradicals

Thermal decompositions of polycyclic aromatic hydrocarbon (PAH) oxyradicals on various surface sites including five-membered ring, free-edge, zigzag, and armchair have been systematically investigated by using ab initio density functional theory B3LYP/6-311+G­(d,p) basis set. The calculation based on Hückel theory indicates that PAHs (3H-cydopenta­[<i>a</i>]­anthracene oxyradical) with oxyradicals on a five-membered ring site have high chemical reactivity. The rate coefficients of PAH oxyradical decomposition were evaluated by using Rice–Ramsperger–Kassel–Marcus theory and solving the master equations in the temperature range of 1500–2500 K and the pressure range of 0.1–10 atm. The kinetic calculations revealed that the rate coefficients of PAH oxyradical decomposition are temperature-, pressure-, and surface site-dependent, and the oxyradical on a five-membered ring is easier to decompose than that on a six-membered ring. Four-membered rings were found in decomposition of the five-membered ring, and a new reaction channel of PAH evolution involving four-membered rings is recommended

Investigating the Role of CH₂ Radicals in the HACA Mechanism

Detailed mechanisms of PAH growth involving methylene (CH₂) were studied using accurate ab initio density functional theory B3LYP/6-311+G­(d,p) calculations, as well as approximate QCISD­(T,full)/6-311++G­(3df,2pd) calculations. The PAH growth can be divided into five essential reaction steps, namely, addition C₂H₂ → intramolecular hydrogen migration → addition CH₂ → cyclization → H-elimination. The aliphatic species of indene and 1H-phenalene are found in the pathways of PAH growth, which is in accord with the experimental results that reveal the formation of aliphatic species in flames. It was found that the simultaneous removal of two H atoms in one reaction step is feasible in PAH evolution, and this can reasonably interpret the absence of a H atom in the post-flame region. The corresponding rate coefficients at 1 atm were evaluated by using TST and RRKM theory by solving the master equations in the temperature range of 500–2500 K. The calculated branching ratios suggest that the pathways involving CH₂ are competitive in PAH growth

One-Step Electrophoretic Deposition of Reduced Graphene Oxide and Ni(OH)₂ Composite Films for Controlled Syntheses Supercapacitor Electrodes

A facile, rapid, scalable, and environmentally friendly electrophoretic deposition (EPD) approach has been developed for the fabrication of reduced graphene oxide (RGO) and Ni­(OH)₂ syntheses based on EPD of graphene oxide (GO) and Ni­(NO₃)₂ colloidal suspension. Nickel ion decoration made GO positively charged and further made cathodic EPD feasible. Direct assembly by one-step EPD facilitated transformation from GO to RGO and resulted in multilayer or flower-like RGO/Ni­(OH)₂ hybrid films on different substrates. X-ray diffraction analysis suggested that the crystal structures of Ni­(OH)₂ depended on the colloidal suspension and the substrate. Further transmission electron microscopy characterization indicated that Ni­(OH)₂ nanoclusters composed of 5–10 nm nanoparticles in grain size were homogeneously dispersed and anchored on the RGO. The resulting 100% binder-free RGO/Ni­(OH)₂ electrodes exhibited excellent pseudocapacitive behavior with high specific capacitance of 1404 F g^–1 at 2 A g^–1, high rate capability, and good electrochemical cyclic stability. These results paved the way for EPD to produce RGO-based nanocomposite films for high-performance energy storage devices

Flame Spray Pyrolysis Synthesis of WO₃ Sensing Materials: Effects of Flame Parameters on Particle Size Distribution and NO₂ Sensing Performance

In this study, the flame spray pyrolysis (FSP) technique was employed to produce WO3 nanoparticles, which were subsequently used as sensing materials for NO2 sensors. To enhance the sensing performance, the effects of flame parameters on the particle properties and sensing performances for 150–1200 ppb NO2 at 125 °C were investigated. The results indicate that WO3 particles with an average crystal size of about 10–20 nm and a standard deviation of about 3–7.5 nm were generated by controlling the precursor and dispersion oxygen flow rate of FSP. Based on the evaluation of NO2 sensing performance, WO3 sensing materials synthesized under the 3/5 flame condition exhibited better sensitivity than sensors made under other flame conditions. In summary, the FSP method and the optimization of flame synthesis parameters could be an effective strategy to prepare the sensing materials with high sensing performance

Exploratory Study of Zn_<i>x</i>PbO_<i>y</i> Photoelectrodes for Unassisted Overall Solar Water Splitting

A complete photoelectrochemical (PEC) water splitting system requires a photocathode and a photoanode to host water oxidation and reduction reactions, respectively. It is thus important to search for efficient photoelectrodes capable of full water splitting. Herein, we report on an exploratory study of a new photoelectrode family of Zn_<i>x</i>PbO_<i>y</i>ZnPbO₃ and Zn₂PbO₄similarly synthesized by a simple and economical method and shown to be a promising photocathode (p-type semiconductor) and photoanode (n-type semiconductor), respectively. From PEC measurements, the bare ZnPbO₃ photocathode achieved a photocurrent density of −0.94 mA/cm² at 0 V versus reversible hydrogen electrode (RHE), whereas the pristine Zn₂PbO₄ photoanode delivered a photocurrent density of 0.51 mA/cm² at 1.23 V versus RHE. By depositing suitable cocatalysts onto the photoelectrodes established above, we also demonstrated unassisted overall PEC water splitting, a rare case, if any, wherein a single material system is compositionally engineered for either of the photoelectrodes