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The key to developing new infrared nonlinear optical (NLO) materials is balancing second-order nonlinear optical effects and the laser-induced damage threshold (LIDT). In this paper, a new polymorph of HgBr2 (P212121) was synthesized by a "halogen-ion-induced effect" in solution, which features a crystal structure different from that of the original phase (Cmc21) and exhibits better NLO properties. Its powders show a strong SHG effect (9 × KDP), a high LIDT (30 × AgGaS2), a wide infrared transparent range, and stability in air, making it a prospective NLO material in the IR region. In addition, the above excellent NLO characteristics are well illustrated in DFT theoretical calculations. More importantly, experimental results show that the new infrared NLO polymorph with excellent comprehensive properties could be controllably obtained by using the halogen-ion-induced strategy.

We report temperature-dependent ultrafast hot carrier relaxation in graphene oxide (GO). At all temperatures in the range from ∼6 to 400 K, the time evolution of the photoexcited relaxation reveals...

Interanion hydrogen bonding (IAHB) and halogen bonding (IAXB) have emerged as a counterintuitive linker in a range of fascinating applications. Despite the overall repulsive (positive) binding energy, anions are trapped in a local minimum with its corresponding transition state (TS) preventing dissociation. In other words, the adduct of anions is metastable. Seemingly, the electrostatic paradigm and force field description of hydrogen/halogen bonding (HB/XB) are challenged, because of the preconceived Coulombic repulsion. Aiming at an insightful understanding of these interanion phenomena, we employed the energy decomposition approach based on the block-localized wavefunction method (BLW-ED) to investigate a series of exemplary interanion complexes. As expected, the key distinction from the conventional HB/XB lies in the electrostatic interaction, which is not increasingly repulsive as anions gradually approach to each other. Rather, there is a Coulombic barrier at a certain point. After this point, the electrostatic repulsion diminishes with the decreasing distance between anions. Differently, other energy components vary monotonically just like in conventional cases. The nonmonotonic characteristic of the electrostatic interaction in interanion complexes was reproduced using the multipole expansion in AMOEBA polarizable force field in which the state-specified atomic multipoles were adopted. This suggests that the nonmonotonicity can be well interpreted by classical electrostatic theory and there is no conceptual difference between conventional HB/XB and IAHB/IAXB. The stability of IAHB/IAXB depends on the competition between the local attractive HB/XB and the global Coulombic repulsion of net charges, though there is cooperativity between these two contrasting forces. This concise model was supported by the attractive IAHB/IAXB in modified molecular capsules, which exhibit strong quadruple HB/XBs and a considerable distance between charged substituents.

The photodissociation of methyl hydroperoxide (CH3OOH) at 193 nm has been studied using a direct dynamics trajectory surface-hopping (TSH) method. The potential energies, energy gradients, and nonadiabatic couplings are calculated on the fly at the MRCIS(6,7)/aug-cc-pVDZ level of theory. The hopping of a trajectory from one electronic state to another is decided on the basis of Tully's fewest switches algorithm. An analysis of the trajectories reveals that the cleavage of the weakest O-O bond leads to major products CH3O(2E) + OH(2Π), contributing about 72.7% of the overall product formation. This OH elimination was completed in the ground degenerate product state where both the ground singlet (S0) and first excited singlet (S1) states become degenerate. The O-H bond dissociation of CH3OOH is a minor channel contributing about 27.3% to product formation, resulting in products CH3OO + H. An inspection of the trajectories indicates that unlike the major channel OH elimination, the H-atom elimination channel makes a significant contribution (∼3% of the overall product formation) through the nonadiabatic pathway via conical intersection S1/S0 leading to ground-state products CH3OO(X 2A″) + H(2S) in addition to adiabatic dissociation in the first excited singlet state, S1, correlating to products CH3OO(1 2A') + H(2S). The computed translational energy of the majority of the OH products is found to be high, distributed in the range of 70 to 100 kcal/mol, indicating that the dissociation takes place on a strong repulsive potential energy surface. This finding is consistent with the nature of the experimentally derived translational energy distribution of OH with an average translational energy of 67 kcal/mol after the excitation of CH3OOH at 193 nm.

International audience; The Mo/W-bisPGD enzyme superfamily comprises a vast number of mononuclear molybdenum and tungsten enzymes that catalyze a great diversity of vital reactions in prokaryotes. In the past decades, much attention has been devoted to the immediate surroundings of the metal atom highlighting the importance of the inner coordination sphere but has failed to identify molecular determinants of the reactivity. Here, we report the mechanistic importance of a set of conserved residues that line the substrate entry tunnel in Escherichia coli nitrate reductase A (Nar), a paradigmatic enzyme of the Mo/W-bisPGD superfamily. Using mutagenesis, enzyme kinetics, electron paramagnetic resonance spectroscopy, and molecular dynamics, we unveil the pivotal role of Glu-581 motion and a number of polar residues in its close proximity in substrate affinity and proton transfer to the Mo active site. Motion of the side chain of Glu-581 exhibiting a strong acid–base cooperativity with Asp-801 and surrounded by several polar interactions controls the hydration inside the protein core, proton transfer, and substrate selectivity toward the active site. Overall, we identify an additional determinant that fine-tunes the reactivity and selectivity in Nar and propose that a gating mechanism is at play in several other members of the superfamily.

A Cu2O film is prepared on a flexible polyethylene terephthalate substrate for a bending sensor using the spin–spray method, a facile and low-environmental-load solution process. The Cu2O bending sensor shows high sensitivity and high resolution not only over a wide range of curvatures (0 < κ < 0.21 mm–1) but also for very small curvature changes (Δκ = ∼ 0.03 mm–1). The bending response of the sensor exhibited a curvature change of high linearity with a good gauge factor (18.2) owing to the grain-boundary resistance and piezoresistive effects of the fabricated Cu2O film. In addition, the sensor possesses good repeatability, stability, and long-term (>30 days) and mechanical fatigue durability (1000 bending–release cycles). The sensor is capable of detailed monitoring of large- and small-scale human motions, such as finger bending, wrist bending, nodding, mouth opening/closing, and swallowing. In addition, excellent stability and repeatability of the monitoring performance is observed over a wide range of motion angles and speeds. All of these results demonstrate the potential of the flexible bending sensor based on the Cu2O film as a candidate for healthcare monitoring and wearable electronics.

A Cu(II)-promoted synthesis of an aza-fused N-heterocycle having a benz-imidazopyridine scaffold is developed via an addition-cyclization reaction followed by an Ullmann-type C-N coupling between o-iodoanilines and γ-ketodinitriles. This protocol features a broad substrate scope, giving products in 32-84% yields. The compounds show excellent photoluminescence properties having two absorption maxima in the region between 270-280 and 338-350 nm and emission maxima in the range of 502-533 nm. The HOMO-LUMO energy gap of 3.49-3.57 eV was determined using Gaussian 09 at the B3LYP/6-31G (d, p) basis set level. We also demonstrated a few postsynthetic modifications.

High-performance piezoelectric polymers are promising for a broad range of practical applications, such as sensors, actuators, and energy generators in medical devices, wearable electronics, and so...

The dissociations of nascent Fe(CO)5++ ions created by 40.81 eV photoionization of iron pentacarbonyl have been examined using threefold and fourfold electron–ion coincidence measurements. The energies and forms of the ions have been explored by high-level calculations, revealing several new structures. The most stable form of Fe(CO)5++ has a quite different geometry from that of the neutral molecule. The dissociation pattern can be modeled as a sequence of CO evaporations followed by two-body charge separations. Each Fe(CO)n++ (n = 1–4) dication is stable in a restricted energy range; as its internal energy increases, it first ejects a neutral CO, then loses CO+ by charge separation at higher energy. In the initial stages, charge-retaining CO evaporations dominate over charge separation, but the latter become more competitive as the number of residual CO ligands decreases. At energies where ionization is mainly from the CO ligands, new Fe–C and C–C bonds are created by a mechanism which might be relevant to catalysis by Fe., Dissociations of nascent Fe(CO)5++ ions by sequential CO evaporations, leading (in restricted energy ranges) to stable Fe(CO)n++ (n = 1−4) dicationic species. At energies where ionization is mainly from the CO ligands, new Fe−C and C−C bonds are created by a mechanism which might be relevant to catalysis by Fe.

Gas adsorption properties of semiconductor-type gas sensors using porous (pr-) In2O3 powders loaded with and without 0.5 wt % Au (Au/pr-In2O3 and pr-In2O3 sensors, respectively) at 100 °C were examined by using diffuse reflectance infrared Fourier transform spectroscopy, and the effect of the Au loading onto pr-In2O3 on the NO2-sensing properties were discussed in this study. We found the following: the resistance of the Au/pr-In2O3 sensor in dry air is lower than that of the pr-In2O3 sensor; the DRIFT spectra of both the sensors show a broad positive band between 1600 and 1000 cm-1 in dry air (reference: in dry N2 at 100 °C), which mainly originates from oxygen adsorbates and/or lattice oxygen, and that this band is much larger for the Au/pr-In2O3 sensor than for the pr-In2O3 sensor; the Au loading also increases the adsorption amount of H2O and the reactivity of NO2 on the pr-In2O3 surface; and the NO2 response of the Au/pr-In2O3 sensor in dry air is marginally higher than that of the pr-In2O3 sensor in the examined concentration range of NO2 (0.6-5 ppm) in dry air. The obtained results strongly support the enhancement of the NO2 adsorption onto the pr-In2O3 surface by Au loading, which contributed to the improvement of the NO2-sensing properties.

Transition metal carbides find use in a wide range of advanced high-resilience applications including high-strength steels, heat shields, and deep-earth drills. However, carbides of the mid-to-late...

Metallic hydrogen is expected to exhibit remarkable physics. Of particular interest in this work is the possibility of high-temperature superconductivity. Comparing calculations of the superconducting critical temperatures of the solid phase to melting temperatures over a range of pressures leads to an interesting question: Will the solid, in a superconducting state, melt to a liquid that remains a superconductor? In this work, the possibility of liquid superconductivity in metallic hydrogen is investigated. This is done by first-principles simulations, and using the results of these to solve the Eliashberg equations. These are carried out over the pressure (and temperature) conditions where molecular dissociation is expected to first occur in the solid phase. Over the pressure range $386.8(4)$--$783.7(4)$ GPa, $T_c$ increases from $308(6)$ to $372(2)$ K with a maximum uncertainty of $10$ K; it then decreases to $356(2)$ K at $883.7(3)$ GPa. Comparisons to the solid phase show that the critical temperature is not significantly changed between the two phases, though the physics behind their superconductivity is different. Careful comparisons of these values to recent results in the context of the hydrogen phase diagram show that they are higher than the melting temperatures and that the solid will melt to liquid atomic hydrogen. The results of this work (in this context) therefore suggest that liquid atomic hydrogen will indeed exist in a superconducting state. They also provide the pressure and temperature conditions over which to look for it.

Based on the new 2A' and 4A' potential energy surfaces of NO2 fitted by Varga et al., we conducted a quasi-classical trajectory study on the N(4S) +O2(X3Σg- ) → NO(2Π) + O(3P) reaction, focusing on the high vibrational state up to ν = 25. For different rovibrational states of O2, within the relative translational energy (Ec) range of 0.1-30 eV, the total exchange cross section (ECS) is calculated, and it is found that the initial relative translational energy and vibration excitation have a significant effect on ECSs, while rotational excitation has little influence; the rate coefficient of the high rovibrational state of O2 molecules at high temperatures is studied, and it is found that when the vibrational level ν of O2 is in the range of 0-15, the value of log10k(T, ν, j) with the vibrational level ν is almost linear, while when ν is greater than 15, it becomes gentle with the increase in ν. Finally, the state-to-state rate coefficients are calculated; our results supply the advantageous state-to-state process data in the NO2 system, and they are useful for further studying the related hypersonic gas flow at very high temperature.

Upon treatment with Cs2CO3, S-methyl-N-ynonylsulfoximines undergo 5-exo-dig cyclizations to give three-dimensional heterocycles. The reactions proceed at ambient temperature with a wide range of substrates affording the corresponding products in good to excellent yields.

Understanding and broad screening Li interaction energetics with surfaces are key to the development of materials for a wide range of applications including Li-based electrochemical capacitors, Li sensors, Li separation membranes, and Li-ion batteries. In this work, we build a high-throughput screening scheme to screen Li adsorption energetics on 2D metallic materials. First, density functional theory and graph convolution networks are utilized to calculate the minimum Li adsorption energies for some 2D metallic materials. The data is then used to find a dependence of the minimum Li adsorption energies on the sum of ionization potential, work function of the 2D metal, and coupling energy between Li+ and substrate, and the dependence is used to screen all 2D metallic materials. Physics-simplified learning by splitting the property into different contributions and learning or calculating each component is shown to have higher accuracy and transferability for machine learning of complex materials properties.

In this work, radical anion photodetachment photoelectron (PD-PE) spectra of N-methylacridone (NM-AC) and N,N'-dimethyl-trans-quinacridone (NNM-QAC) are presented, from which we derived electron affinities and transition energies from S0 to the lowest excited triplet and singlet states (T1, T2, and S1). Because in molecules with extended π systems and heteroatoms the state density even in the energy range of the lowest excited electronic states is already high, assignment of most of the spectral structures in the PD-PE spectra was possible only on the basis of theoretical calculations. To this end, adiabatic transition energies including zero-point vibrational energy corrections were determined using a combination of density functional theory, time-dependent density functional theory, and multireference configuration interaction methods. Calculated Franck-Condon spectra proved to be particularly valuable for the assignment of the spectra. Surprisingly, the density of electronically excited states in the low-energy regime is smaller for NNM-QAC than for NM-AC. This is due to the fact that the nπ* energies remain nearly the same in the two molecules whereas the lowest ππ* excited singlet and triplet transitions are strongly red-shifted in going from NM-AC to NNM-QAC.

We use molecular dynamics to calculate the rotational and vibrational energy relaxation of C2H6 in Ar, Kr, and Xe bath gases over a pressure range of 10-400 atm and at temperatures of 300 and 800 K. The C2H6 is instantaneously excited by 80 kcal/mol randomly distributed into both vibrational and rotational modes. The computed relaxation rates show little sensitivity to the identity of the noble gas in the bath. Vibrational relaxation rates show a nonlinear pressure dependence at 300 K. At 800 K the reduced range of bath gas densities covered by the range of pressures does not yet show any nonlinearity in the pressure dependence. Rotational relaxation is characterized with two relaxation rates. The slower rate is comparable to the vibrational relaxation rate. The faster rate has a linear pressure dependence at 300 K but an irregular, nonlinear pressure dependence at 800 K. To understand this, a model was developed based on approximating the periodic box used in the molecular dynamics simulations by an equal-volume collection of cubes where each cube is sized to allow only single occupancy by the noble gas or the molecule. Combinatorial statistics then leads to a pressure- and temperature-dependent analytic distribution of the bath gas species the molecule encounters in a collision. This distribution, the dissociation energy of molecule/bath gas complexes and bath gas clusters, and the computed energy release per collision combine to show that only at 300 K is the energy release sufficient to dissociate likely complexes and clusters. This suggests that persistent and pressure-dependent clusters and complexes at 800 K may be responsible for the nonlinear pressure dependence of rotational relaxation.

Rapid and reliable processing methods for forming ordered block copolymer (BCP) materials with low defect density in a thin film geometry are required for many nanotechnology applications. Vertical...

Dioxygenation of alkenes was developed by the combination of electrochemical synthesis and aerobic oxidation, leading to easy accessibility of α-oxygenated ketones in an eco-friendly fashion. Using air as the oxygen source and the absence of transition metals were the critical features of this protocol. A wide range of alkenes and N-hydroxyimides were found to be compatible and provided α-oxygenated ketones in moderate to high yields.

The electronic g-tensor calculations are performed for dangling bonds (DBs) introduced into nanodiamonds (NDs) with four different functional groups on their surfaces. For hydrogenated and fluorinated NDs, it is found that g-shifts of the latter vary in a much wider range, and the same is also true for the total energy differences between the highest and the lowest energy DBs. In addition, it is shown that the shape of NDs significantly impacts the energetics and g-shifts of DBs, whereas the influence of the size is much less pronounced, as is the influence of the presence of one DB in the vicinity of the other, resulting in no substantial change on their magnetic behavior. For hydroxylated and aminated NDs, it is demonstrated that the variation range of g-shifts is larger for the former, whereas the opposite is seen regarding the total energy differences. On the whole, some of the positions of DBs can be energetically very costly in these NDs; besides, the lowest energy DBs are irregular, that is, formed by OH- and NH2-bonded C atoms, contrasting with hydrogenated and fluorinated NDs, for which irregular DBs are the most energetically unfavorable.

Compared with the electron donor of the bulk heterojunction (BHJ) organic/inorganic photodetectors (OPDs), there is less development in the field of electron acceptors that have strong absorption c...

The fast F reaction with NH3 poses a big challenge to experimental studies because of secondary chemical and collisional reactions. The quasi-classical trajectory method is utilized to investigate the mode specificity, product energy disposal, and temperature dependence of the thermal rate coefficient of F + ND3 → DF + ND2 on a recently developed potential energy surface. The effect of isotopic substitution is explored by comparing the F + ND3 reaction with the F + NH3 reaction. The computed results permit a better understanding of the F + ammonia reaction. The DF vibrational state has a Λ-type distribution, in accordance with the experimental measurement by the fast flow reactor technique. The product ND2 is dominantly populated in the ground state, and a considerable amount of ND2 is produced in the fundamental states of the bending mode. The similar vibrational state distributions of HF and NH2 in the F + NH3 reaction indicate a weak isotopic substitution effect on the product energy disposal. Exciting the umbrella mode of ND3 suppresses the reaction at low energies below 5 kcal mol-1, in sharp contrast to the observation in the F + NH3 reaction. These dynamical behaviors can be partially explained by the sudden vector projection model. In addition, the thermal rate coefficient of F + ND3 shows no temperature dependence in the range between 150 and 2000 K. There exists an inverse kinetic isotope effect at temperatures from 150 to 1500 K.

There is an intense race by the scientific community to identify materials with potential applications for the conversion of carbon dioxide (CO2) into new products. To extend the range of possibilities and explore new effects, in this work, we employ density functional theory calculations to investigate the presence of edge effects in the adsorption and activation of CO2 on pristine and Fe-decorated (WS2)16 nanoflakes. We found that Fe has an energetic preference for hollow sites on pristine nanoflakes, binding with at least two two-fold edge S atoms and one or two three-fold core S atoms. Fe adsorption on the bridge sites occurs only at the edges, which is accompanied by the breaking of W-S bonds in most cases (higher energy configurations). CO2 activates on (WS2)16 with an OCO angle of about 129° only at higher energy configurations, while CO2 binds via a physisorption mechanism, linear structure, in the lowest energy configuration. For CO2 on Fe/(WS2)16, the activation occurs at lower energies only by the direct interaction of CO2 with Fe sites located near to the nanoflake edges, which clearly indicates the enhancement of the catalytic activity of (WS2)16 nanoflakes by Fe decoration. Thus, our study indicates that decorating WS2 nanoflakes with TM atoms could be an interesting strategy to explore alternative catalysts based on two-dimensional materials.

Electrode calendering is a necessary process used in industry to improve the volumetric capacity of lithium-ion batteries. However, calendering high-nickel cathodes leads to electrode particle pulverization, raising concerns of a reduced cycle life due to parasitic side reactions. We present here an investigation of the impact of calendering on the morphology and electrochemical performance of the cobalt-free layered oxide cathode LiNi0.9Mn0.05Al0.05O2 (NMA-90). We find that secondary particle pulverization and fusion simultaneously occur at sufficiently high pressures. The initial surface area of the cathode is shown to increase with the degree of calendering, despite the higher likelihood of secondary particle fusion. Long-term cycling of full coin cells assembled with the NMA-90 cathode and the graphite anode indicates that cells with higher degrees of cathode calendering exhibit lower capacity fade compared to uncalendered cathodes. Hybrid pulse-power tests demonstrate that the usable capacity range of cells with calendered cathodes far exceeds those with uncalendered cells after long-term cycling. The improved capacity retention and pulse-power performance are attributed to the enhanced mechanical properties of the electrode after calendering that prevents loss of the primary particle contact during long-term cycling. We find that calendering high-nickel NMA-90 to industrially relevant densities does not have a detrimental effect on capacity fade, marking an important step toward commercial adoption.

In this contribution, we report an efficient approach to multiplex electrospray ionization (ESI) sources for applications in analytical and preparative mass spectrometry. This is achieved using up to four orthogonal injection inlets implemented on the opposite sides of an electrodynamic ion funnel interface. We demonstrate that both the total ion current transmitted through the mass spectrometer and the signal-to-noise ratio increase by 3.8-fold using four inlets compared to one inlet. The performance of the new multiplexing approach was examined using different classes of analytes covering a broad range of mass and ionic charge. A deposition rate of >10 μg of mass-selected ions per day may be achieved by using the multiplexed sources coupled to preparative mass spectrometry. The almost proportional increase in the ion current with the number of ESI inlets observed experimentally is confirmed using gas flow and ion trajectory simulations. The simulations demonstrate a pronounced effect of gas dynamics on the ion trajectories in the ion funnel, indicating that the efficiency of multiplexing strongly depends on gas velocity field. The study presented herein opens up exciting opportunities for the development of bright ion sources, which will advance both analytical and preparative mass spectrometry applications.

The thermal unimolecular decomposition of a methoxy radical (CH3O), a key intermediate in the combustion of methane, methanol, and other hydrocarbons, was studied using high-level coupled-cluster calculations, followed by E,J-resolved master equation analyses. The experimental results available for a wide range of temperature and pressure are in striking agreement with the calculations. In line with a previous theoretical study that used a one-dimensional master equation, the tunneling correction is found to exhibit a marked pressure dependence, being the largest at low pressure. This curious effect on the tunneling enhancement also affects the calculated kinetic isotope effect, which falls initially with pressure but is predicted to rise again at high pressures. These findings serve to reconcile a set of conflicting results regarding the importance of tunneling in this prototype unimolecular reaction and also motivate further experimental investigation. This study also exemplifies how changes in the energy redistribution due to collisions manifest in the tunneling rates.

Blanc's Law has served as a way to predict the mobilities of ions in mixed drift gases for over 100 years yet has remained largely unexplored using newer ion mobility spectrometry (IMS) configurations, including traveling wave and trapped IMS (TIMS) systems. Here, we evaluate a drift-tube IMS (DTIMS) and compare it to a similar set of experiments performed in TIMS. We found that Blanc's Law can be applied in a DTIMS to determine the mobility of an analyte in the minor gas component of a ternary mixed drift gas system within 2% error. Additionally, the calibration procedure for TIMS to convert elution voltages into a mobility value corrects for significant deviations (>4%) from Blanc's Law in the elution voltage domain. For the range of gas identities probed in this effort, up to an 11% error in calibrated mobilities was observed when using a gas mixture in the TIMS that differed from the gas used for the reference mobility. However, when the gas mixture within the TIMS was the same as the respective calibrant mobilities, calibration errors within the TIMS were as low as 0.01%. Interestingly, when probing the behavior of ions with argon-containing mixtures within the TIMS, the current accepted paradigm of elution voltage being proportional to inverse mobilities in TIMS calibrations procedures was shown to deviate substantially from the trends observed with DTIMS measurements. With this initial effort, foundations for future mixed drift gas measurements in TIMS are set for expanded analyte classes and larger molecules.

In radionuclide compounds undergoing electron capture (EC) decay, the electron density at the nucleus (ρ(0)) and half-life of the nucleus are inversely proportional. Thus, the decay can be accelerated by changing the chemical or physical conditions. A previous study reported a 1.1-1.5% reduction in the half-life of 7Be encapsulated in C60 compared with 7Be metal. However, 7Be was inserted into the fullerene using the rebound energy of the nuclear reaction, which may not be a practical method. This paper elucidates the mechanism of ρ(0) change in various Be compounds from density functional calculations and attempts to propose better systems that show faster EC decay (larger ρ(0)) and/or that are easier to generate than Be in C60. In typical Be compounds, ρ(0) decreases because Be donates electrons to other atoms through chemical bonds and, thus, is not effective. Among the various Be-encapsulated fullerenes (C20-C180), the largest increase in ρ(0) was obtained for C50 fullerene, but the magnitude was almost similar to that of C60. As new systems, we propose Be-encapsulated rare gas solids, which would be generated only by applying high pressure. An increase in ρ(0) from Be metal in the range 2-10%, which depends on the lattice constant, is obtained.

A full-dimensional global potential energy surface (PES) for the KRb + KRb → K2Rb2* → K2 + Rb2 reaction is reported based on high-level ab initio calculations. The short-range part of the PES is fit with the permutationally invariant polynomial-neural network method, while the long-range parts of the PES in both the reactant and product asymptotes are represented by an asymptotically correct form. The long- and short-range parts are connected with intermediate-range parts to make them smooth. Within a statistical quantum model, this PES reproduces both the measured loss rates of ultracold KRb molecules and the K2 and Rb2 product state distributions, underscoring the important role of tunneling in ultracold chemistry. The PES also correctly predicts the lifetime of the K2Rb2* intermediate complex within the Rice-Ramsperger-Kassel-Marcus limit. It thus provides a reliable platform for future dynamical studies of the prototypical reaction.

The addition of Fe2O3 into furnaces is a promising method for arsenic pollution control. Nevertheless, Fe2O3 particles undergo serious sintering under actual furnace temperatures. To improve its sintering resistance, Fe2O3 hollow microspheres were synthesized by the template method and were tested in flue gas containing SO2 and NO in the range of 1000-1300 °C. The results demonstrated that the amount of arsenic captured could be steadily maintained above 5 mg/g throughout the operating temperature range, and Fe2O3 microspheres could maintain the originally developed pore structure and hollow morphology well even at 1200 °C. Based on product analysis and density functional theory calculations, the fixation pathway of arsenic was proposed. In no oxygen conditions, As2O3 was first bound to the Fe2O3 surface by forming an -O-As-O-Fe stable structure and then was oxidized by lattice oxygen. The introduction of O2 could regenerate the consumed lattice oxygen and therefore promote arsenic capture. Finally, the oxidized arsenic was fixed in products in the form of FeAsO4. Additionally, the impact of acid gases was also investigated. SO2 showed a notable inhibiting effect on arsenic capture, while the impact of NO was less noticeable.

Despite the fact that nonlinear optical (NLO) crystals such as AgGaS2 and AgGaSe2 have been widely used in the infrared (IR) range due to their large second harmonic generation (SHG) coefficients and wide range of IR transparency windows, the small laser-induced damage threshold (LIDT) remains a great issue hindering their high-power applications. Herein, three noncentrosymmetric (NCS) chalcogenides AZn4Ga5Se12 (A = K, Rb, or Cs) are successfully obtained through an appropriate flux method after the extensive design and synthesis of the A/Zn/Ga/Q system. Single-crystal X-ray diffraction data demonstrate that they adopt trigonal space group R3 (No. 146) with three-dimensional diamond-like frameworks composed of [M9Se24] layers (M = Zn or Ga) stacking in the same direction and filled by charge-balancing A+ cations. Noticeably, they all exhibit strong powder SHG responses (2.8-3.7 × AgGaS2) and amazing LIDTs (19.2-23.4 × AgGaS2). In addition, theoretical calculations are performed to further determine the relationship between NCS structures and NLO properties. This work provides effective solutions for overcoming the trade-off between strong SHG and high LIDT in IR-NLO materials.

Controlling droplet deposition with a minute amount of polymer additives is of profound practical importance in a wild range of applications. Previous work ascribed the relevant mechanisms to extensional viscosity, normal stress, wetting properties, etc., but the mechanism remains controversial. In this paper, we employ molecular dynamics simulations systematically for the first time to investigate the origin of rebound suppression for dilute polymer solution droplets on a flat superhydrophobic substrate. The results demonstrate that polymer-substrate interactions and impact velocities dominate the antirebound phenomenon. For low impact velocities, the dynamic characteristics of droplets are insensitive to polymer additives. However, large impact velocities will enhance the stretch behavior of polymer chains and make the chains closer to the substrate, increasing the probability of polymer molecules contacting the bottom substrate. With the cooperation of strong polymer-substrate interactions, polymer molecules can be absorbed easily by the bottom substrate, resisting the retraction process and leading to the onset of the antirebound behavior.

Surfactant adsorption and ion exchange on calcite surfaces are investigated by means of flooding experiments in Estaillades limestone cores. We show that, in the 5000 mg/L salinity range, effluent ...

The mechanical adaptability of a family of six one-dimensional crystalline coordination polymers (CPs) of cadmium ([CdX2(3-X′py)2]n ; 1: X = Br, X′ = Cl, 2: X = I, X′ = Cl, 3: X = I, X′ = Br, 4: X = Cl, X′ = I, 5: X = Br, X′ = I, and 6: X, X′ = I) to applied external force was examined, and a plethora of flexible responses was noticed. While two of the six CPs (4 and 6) were slightly elastic, the remaining four CPs (1–3 and 5) presented variable plastic deformation ; three of these (1–3) displayed exceptional crystal flow, and one (2) demonstrated unprecedented ductility of crystalline metal–organic material. The feature was examined by theory and custom-designed experiments, and it was shown that specific and directional intermolecular interactions are not only the most influential structural feature in determining the type of mechanical responses (i.e., elastic vs plastic), with interlocking of adjacent molecules playing only a supportive role, but also an unavoidable tool for dialing-in a diversity of plastic responses in Cd(II) coordination polymers.

Hydrogen sulfide (H2S) solubility was experimentally quantified in aqueous N-methylpyrrolidone (NMP) solution. Mixtures of (NMP + H2O) were established in the whole composition range of xNMP = (0....

The acidity of acetylene CH is stronger than that of alkane CH, and the attractive interaction between an acetylene CH with π-electrons, which shows a clear hydrogen bond property, is called activated CH/π interaction. In this study, cooperative enhancement of the activated CH/π interaction has been probed through the cluster size dependence of the red shift of the acetylene CH stretching vibrational band in neutral phenol-(acetylene)n (∼16 ≤ n ≤ ∼30) and (acetylene)n+ (10 ≤ n ≤ 70). In both the clusters, the characteristic asymmetric (red-shaded) shape of the CH stretch band has been observed. This band shape means that the magnitude of the activated CH/π interaction is enhanced by its cooperativity in the interior moiety of the cluster. The red-shifted component of the band extends with increasing cluster size, and the edge of this component seems to reach to the CH stretch band position of crystalline acetylene at the size of n = 20-30, indicating that dozens of molecules need to interact each other to maximize cooperativity in the activated CH/π interaction of acetylene. On the other hand, the peak position of the band does not converge to that of crystalline acetylene in the observed size range. The present result suggests that the spectral convergence of acetylene clusters to the bulk may occur in the cluster size range of hundreds or larger.

Electrostatic interaction is widely considered to be the main driving force of the adsorption of polyelectrolytes (PEs) on an oppositely charged surface. Therefore, the alteration of charge distribution as a result of varying PE chain structures will directly affect the performance of the adsorption behaviors in the system at a certain monomer concentration. In this work, we studied the effects of chain structure (chain length, Nₘ) as well as sequence variables including charge fraction and blockiness on the adsorption behaviors of block-PEs on an oppositely charged planar surface in the salt-free system using PE-Poisson–Boltzmann equations. Due to the complicated competitions among the translational entropies of PEs and counterions, the conformational entropy of PEs, and the surface attractive interactions, we find that the adsorption amounts show rich behaviors. First, the adsorption amounts of charged ζc and neutral ζₙ monomers both show two-stage behaviors, that is, ζc and ζₙ drastically increase with Nₘ for short chains but moderately increase to an asymptotic value for relatively long chains. Second, the adsorption amounts of charged monomers show non-monotonic behaviors (increase first then decrease) with charge fraction. However, the adsorption amounts of neutral monomers monotonically decrease with charge fraction. Finally, when chain length and charge fraction are unchanged, the adsorption amounts of both neutral and charged monomers are independent of blockiness. Moreover, we find that overcharging can only appear when the bare surface charge density is low enough, while charge reversal and inversion can be observed in the entire range of the bare surface charge density with appropriate conditions. Additionally, our results indicate that the strength of charge reversal and inversion increases monotonically with chain length and charge fraction, while it changes non-monotonically with blockiness.

In recent years, increasing efforts have been devoted to widening the light response range of graphitic carbon nitride (g-C3N4) for photocatalytic environmental remediation and fuel production. To ...

The production of ammonia (NH 3 ) with low-pressure, radiofrequency plasmas is studied in this paper in a wide range of experimental conditions using tungsten as a catalyst. The relative position of the tungsten foil in the pyrex tube was observed to dramatically impact ammonia formation. By positioning the catalyst in the middle of the tube, the concentration of NH 3 peaked at 120 W with ≈20 mol %, while it decreased by more than a factor of 2 at 300 W. When the foil was placed close to the end of the tube, the production of NH 3 was rather stable beyond 120 W. These results provide clear evidence of the surface's role in the local enhancement of the NH 3 formation rates. In the plasma volume, at some distance from the foil, the decomposition of NH 3 is the major occurring process and the decomposition rate increases with the power primarily due to a higher electron density. The optimum production of NH 3 was found to be at 45 mol % N 2 and 120 W, and the position of the maximum was observed to slightly decrease to

For the majority of the water present on earth, the two most important factors influencing its behavior are confinement, in either inorganic or organic matrixes, and the presence of solutes. Here, we investigate the effect of confinement in 3 nm pores on water diffusivity in aqueous solutions with archetypical solutes, a structure making (kosmotrope) NaCl and a structure breaking (chaotrope) KCl, up to 1.0 M in concentration. The water diffusivity in bulk aqueous solutions in such a concentration range is known to decrease very slightly in the presence of NaCl and increase very slightly in the presence of KCl. However, here we observe the water diffusivity in confined H2O-KCl increases by a factor of 2 compared to the pure water diffusivity in the same confinement. This unusually strong cumulative effect of confinement and a structure breaking additive may have profound implications for the mobility and transport of aqueous species in nature.

To clarify the contentions about dissociative photoionization mechanism of nitrogen dioxide via the a3B2 and b3A2 ionic states, a new threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging has been conducted in the 12.8-14.0 eV energy range at the Hefei Light Source. The fine vibrational-resolved threshold photoelectron spectrum agrees well with the previous measurements. The ro-vibrational distributions of NO+, as the unique fragment ion in the dissociation of NO2+ in specific vibronic levels of a3B2 and b3A2 states, are derived from the recorded TPEPICO velocity images. A "cold" vibrational (v+ = 0) and "hot" rotational population is observed at the a3B2(0,3,0) and (0,4,0) vibronic levels, while the dissociation of NO2+ in b3A2(0,0,0) leads to the NO+ fragment with both hot vibrational and rotational populations. With the aid of the quantum chemical calculations at the time-dependent B3LYP level, minimum energy paths on the potential energy surfaces of the a3B2 and b3A2 states clarify their adiabatic dissociation mechanisms near the thresholds, and this study proposes reliable explanations for the observed internal energy distributions of fragment ions. Additionally, this study provides valuable insights into the application of the classical "impulsive" model on an overall slow dissociation process.

Organic aerosol can adopt a wide range of viscosities, from liquid to glass, depending on the local humidity. In highly viscous droplets, the evaporation rates of organic components are suppressed to varying degrees, yet water evaporation remains fast. Here, we examine the coevaporation of semivolatile organic compounds (SVOCs), along with their solvating water, from aerosol particles levitated in a humidity-controlled environment. To better replicate the composition of secondary aerosol, nonvolatile organics were also present, creating a three-component diffusion problem. Kinetic modeling reproduced the evaporation accurately when the SVOCs were assumed to obey the Stokes-Einstein relation, and water was not. Crucially, our methodology uses previously collected data to constrain the time-dependent viscosity, as well as water diffusion coefficients, allowing it to be predictive rather than postdictive. Throughout the study, evaporation rates were found to decrease as SVOCs deplete from the particle, suggesting path function type behavior.

Developing highly efficient photocatalysts to utilize solar radiation for converting CO2 into solar fuels is of great importance for energy sustainability and carbon neutralization. Herein, through an alkali-etching-introduced interface reconstruction strategy, a nanowire photocatalyst denoted as V-Bi19Br3S27, with rich Br and S dual-vacancies and surface Bi-O bonding introduced significant near-infrared (NIR) light response, has been developed. The as-obtained V-Bi19Br3S27 nanowires exhibit a highly efficient metallic photocatalytic reduction property for converting CO2 into CH3OH when excited solely under NIR light irradiation. Free of any cocatalyst and sacrificial agent, metallic defective V-Bi19Br3S27 shows 2.3-fold higher CH3OH generation than Bi19Br3S27 nanowires. The detailed interfacial structure evolution and reaction mechanism have been carefully illustrated down to the atomic scale. This work provides a unique interfacial engineering strategy for developing high-performance sulfur-based NIR photocatalysts for photon reducing CO2 into alcohol for achieving high-value solar fuel chemicals, which paves the way for efficiently using the solar radiation energy extending to the NIR range to achieve the carbon neutralization goal.

The oxidation of aldehydes is one of the most prevalent methods for the synthesis of a diverse range of carboxylic acids. We herein present a performic acid generator and its application for aldehy...

Self-assembled monolayers have been studied extensively due to their relative ease of synthesis and the broad range of applications for this class of materials. Monolayer-support interactions can range in strength from physisorption through covalent bond formation, with consequent variability in the robustness and fluidity of the monolayer. Monolayer-support bonding by metal ion complexation is especially attractive because of the ability to adjust the strength of interaction through metal ion identity. For such systems, both the exchange kinetics and thermodynamics of metal ion-complex formation contribute to the observed properties of the monolayer. We have synthesized metal-phosphate/phosphonate monolayers using Zr4+ and In3+ and have evaluated the metal ion dependence of monolayer dynamics for free and bound chromophores. Our findings reveal significant metal ion-dependent variations in monolayer dynamics and organization.