A DFT+U study of the catalytic degradation of 1,2-dichloroethane over CeO2.

The catalytic degradation of 1,2-dichloroethane (DCE) at CeO2(111) was investigated using periodic density functional theory calculations corrected by on-site Coulomb interactions. From thorough calculations of possible elementary steps, we are able to identify the lowest energy reaction pathway for the catalytic oxidation of DCE at CeO2(111). It proceeds via two successive C-Cl bond breaking processes to form adsorbed CH2CH2 species, and after further dehydrogenation and C-C bond scission, the surface species are finally oxidized to CO2 and H2O. The surface oxygen vacancies were found to be important for the catalytic decomposition of DCE, by providing the adsorption sites, as well as for charge transfer to favor C-Cl bond breaking. We are also able to illustrate the effect of H2O on the catalytic activity of CeO2(111) for DCE oxidation.

Crystal Structural Effect of AuCu Alloy Nanoparticles on Catalytic CO Oxidation.

Controlling the physical and chemical properties of alloy nanoparticles (NPs) is an important approach to optimize NP catalysis. Unlike other tuning knobs, such as size, shape, and composition, crystal structure has received limited attention and not been well understood for its role in catalysis. This deficiency is mainly due to the difficulty in synthesis and fine-tuning of the NPs' crystal structure. Here, Exemplifying by AuCu alloy NPs with face centered cubic (fcc) and face centered tetragonal (fct) structure, we demonstrate a remarkable difference in phase segregation and catalytic performance depending on the crystal structure. During the thermal treatment in air, the Cu component in fcc-AuCu alloy NPs segregates more easily onto the alloy surface as compared to that in fct-AuCu alloy NPs. As a result, after annealing at 250 °C in air for 1 h, the fcc- and fct-AuCu alloy NPs are phase transferred into Au/CuO and AuCu/CuO core/shell structures, respectively. More importantly, this variation in heterostructures introduces a significant difference in CO adsorption on two catalysts, leading to a largely enhanced catalytic activity of AuCu/CuO NP catalyst for CO oxidation. The same concept can be extended to other alloy NPs, making it possible to fine-tune NP catalysis for many different chemical reactions.

Significant enhancement of the selectivity of propylene epoxidation for propylene oxide: a molecular oxygen mechanism.

As an attractive and environmentally friendly process for propylene oxide (PO) production, direct epoxidation of propylene (DEP) with molecular oxygen catalyzed by metal-based catalysts such as Ag and Cu has drawn much attention, but remains one of the biggest challenges in chemistry. In this work, the crucial competitive reactions of propylene α-H stripping (AHS) versus the oxametallacycle formation (OMMP formation) using adsorbed atomic oxygen (O*) or adsorbed molecular oxygen (O2*) as an oxidant are extensively compared on IB group metal surfaces (Cu, Ag and Au) with varied electronic and structural effects in order to explore the possibility to enhance the PO selectivity by virtue of first-principles calculations. The determining factor for the PO selectivity is quantitatively revealed: it is found that with atomic O*, the AHS pathway was preferred, indicating the reason for low PO selectivity with current catalysts. By contrast, the undissociated molecular O2* species is found to prefer to electrophilically attack the C[double bond, length as m-dash]C double bond of propylene and form a special oxametallacycle intermediate (OOMMP) rather than nucleophilically abstracting the α-H. This OOMMP can readily cleave the O-O bond and transform into OMMP. These results demonstrate that the presence of undissociated O2* can efficiently promote the PO selectivity. Furthermore, the merit of such a molecular O2* mechanism can be rationalized by our quantitative barrier decomposition analyses, which reveal that the lower hydrogen affinity (ΔEH) of the O2* species dominantly contributes to the limited AHS reaction, and boosts the OMMP selectivity. Therefore, ΔEH can be applied as a selectivity descriptor. An efficient strategy to promote PO formation is presented. The insight obtained could pave the way for further development of catalysts for propylene epoxidation.

Surfactant-Assisted Stabilization of Au Colloids on Solids for Heterogeneous Catalysis.

The stabilization of surfactant-assisted synthesized colloidal noble metal nanoparticles (NPs, such as Au NPs) on solids is a promising strategy for preparing supported nanocatalysts for heterogeneous catalysis because of their uniform particle sizes, controllable shapes, and tunable compositions. However, surfactant removal to obtain clean surfaces for catalysis through traditional approaches (such as solvent extraction and thermal decomposition) can easily induce the sintering of NPs, greatly hampering their use in synthesis of novel catalysts. Such unwanted surfactants have now been utilized to stabilize NPs on solids by a simple yet efficient thermal annealing strategy. After being annealed in N2 flow, the surface-bound surfactants are carbonized in situ as sacrificial architectures that form a conformal coating on NPs and assist in creating an enhanced metal-support interaction between NPs and substrate, thus slowing down the Ostwald ripening process during post-oxidative calcination to remove surface covers.

A Sacrificial Coating Strategy Toward Enhancement of Metal-Support Interaction for Ultrastable Au Nanocatalysts.

Supported gold (Au) nanocatalysts hold great promise for heterogeneous catalysis; however, their practical application is greatly hampered by poor thermodynamic stability. Herein, a general synthetic strategy is reported where discrete metal nanoparticles are made resistant to sintering, preserving their catalytic activities in high-temperature oxidation processes. Taking advantage of the unique coating chemistry of dopamine, sacrificial carbon layers are constructed on the material surface, stabilizing the supported catalyst. Upon annealing at high temperature under an inert atmosphere, the interactions between support and metal nanoparticle are dramatically enhanced, while the sacrificial carbon layers can be subsequently removed through oxidative calcination in air. Owing to the improved metal-support contact and strengthened electronic interactions, the resulting Au nanocatalysts are resistant to sintering and exhibit excellent durability for catalytic combustion of propylene at elevated temperatures. Moreover, the facile synthetic strategy can be extended to the stabilization of other supported catalysts on a broad range of supports, providing a general approach to enhancing the thermal stability and sintering resistance of supported nanocatalysts.

Electronic storage capacity of ceria: role of peroxide in Aux supported on CeO2(111) facet and CO adsorption.

Density functional theory (DFT+U) was used to study the adsorption of Aux (x = 1-4) clusters on the defective CeO2(111) facet and CO adsorption on the corresponding Aux/CeO2-x catalyst, in this work Aux clusters are adsorbed onto the CeO2-x + superoxide/peroxide surface. When Au1 is supported on the CeO2(111) facet with an O vacancy, the strong electronegative Au(δ-) formed is not favorable for CO adsorption. When peroxide is adsorbed on the CeO2(111) facet with the O vacancy, Aux was oxidized, resulting in stable Aux adsorption on the defective ceria surface with peroxide, which promotes CO adsorption on the Aux/CeO2-x catalyst. With more Au atoms in supported Aux clusters, CO adsorption on this surface becomes stronger. During both the Au being supported on CeO2-x and CO being adsorbed on Aux/CeO2-x, CeO2 acts as an electron buffer that can store/release the electrons. These results provide a scientific understanding for the development of high-performance rare earth catalytic materials.

Role of oxygen vacancies in the surface evolution of H at CeO2(111): a charge modification effect.

Diffusion processes and reactions of H at stoichiometric and reduced CeO2(111) surfaces have been studied by using density functional theory calculations corrected by on-site Coulomb interactions (DFT + U). Oxygen vacancies on the surface are determined to be able to significantly affect the behavior of H by modifying the charge of surface lattice O through the occurrence of Ce(3+). It has been found that, at the reduced CeO2(111) surface, the adsorption strength of H as well as the H coupling barrier can be dramatically reduced compared to those at the stoichiometric surface, while H2O formation barrier is not significantly affected. Moreover, the diffusion of H at the reduced surface or into the bulk can occur more readily than that at stoichiometric CeO2(111).

A DFT + U study of NO evolution at reduced CeO2(110).

NO adsorption, diffusion and reaction at reduced CeO2(110) were studied by density functional theory calculations. NO accommodated by O vacancies can readily diffuse via alternate NO2 formation and dissociation, facilitating N2O2 formation and subsequent reduction to N2. Rare earth ceria plays an important catalytic role in both static and dynamic ways by tuning the electron distribution in adsorbates and reacting molecules.

Pd/NbOPO4 multifunctional catalyst for the direct production of liquid alkanes from aldol adducts of furans.

Great efforts have been made to convert renewable biomass into transportation fuels. Herein, we report the novel properties of NbO(x)-based catalysts in the hydrodeoxygenation of furan-derived adducts to liquid alkanes. Excellent activity and stability were observed with almost no decrease in octane yield (>90% throughout) in a 256 h time-on-stream test. Experimental and theoretical studies showed that NbO(x) species play the key role in C-O bond cleavage. As a multifunctional catalyst, Pd/NbOPO4 plays three roles in the conversion of aldol adducts into alkanes: 1) The noble metal (in this case Pd) is the active center for hydrogenation; 2) NbO(x) species help to cleave the C-O bond, especially of the tetrahydrofuran ring; and 3) a niobium-based solid acid catalyzes the dehydration, thus enabling the quantitative conversion of furan-derived adducts into alkanes under mild conditions.

Additional PD-1 inhibitor improves complete response to induction chemotherapy in locally advanced nasopharyngeal carcinoma.

Purpose: To investigate the treatment response and toxicity of the combination of induction chemotherapy (IC) and PD-1 inhibitor in locally advanced nasopharyngeal carcinoma (LANPC). Methods: Patients with stage III-IVA NPC who received IC or IC + PD-1 inhibitor were included. The chi-square test and multivariate logistic regression analysis were used for statistical analysis. Results: A total of 225 patients were identified, including 193 (85.8%) and 32 (14.2%) who received IC alone and IC + PD-1 inhibitor, respectively. The addition of PD-1 inhibitor to IC significantly improved the tumor response than those treated with IC alone. The complete response (CR), partial response, stable disease, and progressive disease rates of 4.7% vs. 31.3%, 69.4% vs. 62.5%, 24.9% vs. 6.3%, and 1.0% vs. 0% in patients receiving IC alone and IC + PD-1 inhibitor, respectively (P<0.001). The results of the multivariate logistic regression showed that receiving PD-1 inhibitor was an independent predictor influencing the CR rate of patients (odds ratio 9.814, P<0.001). The most common toxicity by using IC and PD-1 inhibitor was hematological toxicity. In terms of non-hematological toxicity, 7 (21.9%) patients experienced thyroid dysfunction and all of them were hyperthyroidism. No grade 5 toxicities were found. In those who received IC and PD-1 inhibitor, the one-year locoregional recurrence-free survival, distant metastasis-free survival, disease-free survival, and overall survival were 100%, 96.9%, 96.9%, and 100%, respectively. Conclusion: The addition of PD-1 inhibitor to IC has promise as an effective treatment approach for LANPC. More studies are expected to provide further insights into the optimal use of this treatment strategy, paving the way for more personalized and effective treatment options for patients with LANPC.

Addition of nimotuzumab to concurrent chemoradiotherapy after induction chemotherapy improves outcomes of patients with locally advanced nasopharyngeal carcinoma.

Purpose: To investigate the survival outcomes and toxicities associated with the addition of nimotuzumab to concurrent chemoradiotherapy (CCRT) in locally advanced nasopharyngeal carcinoma (LANPC) patients who received induction chemotherapy (IC). Methods: Patients with stage III-IVA nasopharyngeal carcinoma who received IC and CCRT between January 2017 and October 2021 were retrospectively included. We aimed to compare the locoregional recurrence-free survival (LRFS), distant metastasis-free survival (DMFS), disease-free survival (DFS), and overall survival (OS) between patients treated with CCRT+nimotuzumab and CCRT alone. Results: We included 411 patients in the analysis. Of these patients, 267 (65.0%) and 144 (35.0%) had CCRT+nimotuzumab and CCRT alone, respectively. Similar LRFS was found between those with and without nimotuzumab (92.9% vs. 92.6%, p = 0.855). The 3-year DMFS was 88.2% and 76.2% in those with and without nimotuzumab (p = 0.002). The 3-year DFS was 83.4% and 70.6% in those with and without nimotuzumab treatment (p = 0.003). The 3-year OS was 92.1% and 81.1% in those with and without nimotuzumab (p = 0.003). The multivariate Cox regression analysis indicated that the addition of nimotuzumab was independently associated with better DMFS (hazard ratio [HR] 0.606, p = 0.049), DFS (HR 0.613, p = 0.028), and OS (HR 0.497, p = 0.019). No significant differences in major toxicities were found between the two treatment arms, including hematologic toxicities, hepatoxicity, nephrotoxicity, gastrointestinal reactions, and mucositis (all p > 0.05). Conclusion: The addition of nimotuzumab to CCRT after IC in LANPC has shown promising results in improving treatment outcomes and acceptable toxicities.

Non-invasive measurement of rat auditory evoked fields using an optically pumped atomic magnetometer: Effects of task manipulation.

Optically pumped magnetometers (OPMs) have become a favorable tool for magnetoencephalography (MEG) measurement, offering a non-invasive method of measurement. OPMs do not require cryogenic environments, sensors can be more closely aligned with the brain. We employed a passive single-stimulus paradigm in conjunction with OPMs with a sensitivity of 20 fT/ Hz to investigate the auditory response of rats to inter-stimulus interval (ISI) and frequencies, recording the rat auditory event-related magnetic fields (ERMFs). Our findings include: (1) Auditory evoked fields can be detected non-invasively by OPMs; (2) The amplitude of the rat auditory ERMFs varies with changes in ISI, with more pronounced amplitude changes observed after 5 s; (3) When the sound stimulus frequency is altered at the same ISI, the amplitude of the rats ERMFs changes with frequency, indicating significant differences in attention. Our method offers a valuable tool for the clinical application of a single stimulus paradigm and opens up a new avenue for research on the brain magnetic field detections.

A DFT+U study of the lattice oxygen reactivity toward direct CO oxidation on the CeO2(111) and (110) surfaces.

Density functional theory calculations corrected by on-site Coulomb interaction have been carried out to track down the lattice oxygen reactivity of CeO(2)(111) and (110) surfaces in direct oxidation of a single CO. The possible elementary steps in CO adsorption and subsequent reactions with lattice oxygen were systematically studied. From calculated energetics, we determined that the lattice oxygen of the (110) surface is more reactive than that of the (111) surface. By calculating the reaction pathways leading to different final products, we found that the formation of carbonate species is competitive to CO(2) formation and desorption, and such an effect could be more significant at CeO(2)(110) compared to CeO(2)(111). More importantly, it has also been found that electron localization at the characteristic 4f orbital of Ce, directly determined by subtle structural relaxation, can give rise to a unique scenario of the overall reaction coordinates. These results may bring us one step ahead toward the comprehensive understanding of catalytic performance of CeO(2)-based materials.

Oxygen vacancy formation in CeO2 and Ce(1-x)Zr(x)O2 solid solutions: electron localization, electrostatic potential and structural relaxation.

Ceria (CeO(2)) and ceria-based composite materials, especially Ce(1-x)Zr(x)O(2) solid solutions, possess a wide range of applications in many important catalytic processes, such as three-way catalysts, owing to their excellent oxygen storage capacity (OSC) through the oxygen vacancy formation and refilling. Much of this activity has focused on the understanding of the electronic and structural properties of defective CeO(2) with and without doping, and comprehending the determining factor for oxygen vacancy formation and the rule to tune the formation energy by doping has constituted a central issue in material chemistry related to ceria. However, the calculation on electronic structures and the corresponding relaxation patterns in defective CeO(2-x) oxides remains at present a challenge in the DFT framework. A pragmatic approach based on density functional theory with the inclusion of on-site Coulomb correction, i.e. the so-called DFT + U technique, has been extensively applied in the majority of recent theoretical investigations. Firstly, we review briefly the latest electronic structure calculations of defective CeO(2)(111), focusing on the phenomenon of multiple configurations of the localized 4f electrons, as well as the discussions of its formation mechanism and the catalytic role in activating the O(2) molecule. Secondly, aiming at shedding light on the doping effect on tuning the oxygen vacancy formation in ceria-based solid solutions, we summarize the recent theoretical results of Ce(1-x)Zr(x)O(2) solid solutions in terms of the effect of dopant concentrations and crystal phases. A general model on O vacancy formation is also discussed; it consists of electrostatic and structural relaxation terms, and the vital role of the later is emphasized. Particularly, we discuss the crucial role of the localized structural relaxation patterns in determining the superb oxygen storage capacity in kappa-phase Ce(1-x)Zr(1-x)O(2). Thirdly, we briefly discuss some interesting findings for the oxygen vacancy formation in pure ceria nanoparticles (NPs) uncovered by DFT calculations and compare those with the bulk or extended surfaces of ceria as well as different particle sizes, emphasizing the role of the electrostatic field in determining the O vacancy formation.

Evaluation of Rheological and Anti-Aging Properties of TPU/Nano-TiO2 Composite-Modified Asphalt Binder.

Research on polyurethane-modified asphalt has become very popular. To this end, researchers have explored different ways, such as the use of polyurethane, to improve the road performance of asphalt. However, according to existing experimental research findings, it seems that the use of polyurethane alone cannot completely improve the road performance of asphalt. Therefore, the influence of nano-titanium dioxide and polyurethane on the rheological behavior and anti-ultraviolet aging properties of asphalt was studied. In this research, the rheological and microscopic tests of asphalt were conducted using Dynamic Shear Rheometer, Curved Beam Rheometer, and Fourier Infrared Spectrometer. The results show that the addition of TPU and nano-TiO2 to the asphalt not only improves the high- and low-temperature rheological behavior of the asphalt, but also improves the thermal oxygen resistance and UV aging resistance of the asphalt, and prolongs the use performance. Considering economic factors and environmental influences, among all the selected dosages, 4% TPU and 1% nano-TiO2 had the best performance.

A functional methylation signature to predict the prognosis of Chinese lung adenocarcinoma based on TCGA.

BACKGROUND: Lung cancer is the leading cause of cancer morbidity and mortality worldwide, however, the individualized treatment is still unsatisfactory. DNA methylation can affect gene regulation and may be one of the most valuable biomarkers in predicting the prognosis of lung adenocarcinoma. This study was aimed to identify methylation CpG sites that may be used to predict lung adenocarcinoma prognosis. METHODS: The Cancer Genome Atlas (TCGA) database was used to detect methylation CpG sites associated with lung adenocarcinoma prognosis and construct a methylation signature model. Then, a Chinese cohort was carried out to estimate the association between methylation and lung adenocarcinoma prognosis. Biological function studies, including demethylation treatment, cell proliferative capacity, and gene expression changes in lung adenocarcinoma cell lines, were further performed. RESULTS: In the TCGA set, three methylation CpG sites were selected that were associated with lung adenocarcinoma prognosis (cg14517217, cg15386964, and cg18878992). The risk of mortality was increased in lung adenocarcinoma patients with the gradual increase level of methylation signature based on three methylation sites levels (HR = 45.30, 95% CI = 26.69-66.83; p < 0.001). The C-statistic value increased to 0.77 when age, gender, and other clinical variables were added to the signature to prediction model. A similar situation was confirmed in Chinese lung adenocarcinoma cohort. In the biological function studies, the proliferative capacity of cell lines was inhibited when the cells were demethylated with 5-aza-2'-deoxycytidine (5-aza-2dC). The mRNA and protein expression levels of SEPT9 and HIST1H2BH (cg14517217 and cg15386964) were downregulated with different concentrations of 5-aza-2dC treatment, while cg18878992 showed the opposite result. CONCLUSION: This study is the first to develop a three-CpG-based model for lung adenocarcinoma, which is a practical and useful tool for prognostic prediction that has been validated in a Chinese population.

Sequential microfluidic flow synthesis of CePO4 nanorods decorated with emission tunable quantum dots.

CePO(4) nanorods decorated with QDs (QDs@CePO(4)) can be prepared in a sequential, aqueous procedure under continuous flow using a rotating tube processor and a narrow channel reactor. The emission from the QD@CePO(4) is tunable from green to red by simply adjusting the feeding rate, which in turn regulates the particle size of the QDs. The Ce(3+) ions in the QDs@CePO(4) serve as an efficient fluorescence resonance energy transfer (FRET) donor, effectively enlarging the Stokes shift of the QDs.

Photoelectrocatalytic degradation of methyl orange over mesoporous film electrodes.

Mesoporous TiO(2) films and ion-doped photocatalytic films, displaying a worm-like pattern, have been synthesized by dip-coating of ITO glass into an organic-inorganic sol followed by aging and calcination of the coating at different temperature. The prepared films were investigated by X-ray diffraction (XRD), UV-Vis reflectance spectra, scanning electron microscope (SEM), transmission electron microscopy (TEM) and photoelectrochemical measurement, and were confirmed to be of mesoporous characteristic. Degradation of methyl orange (MO) has been performed using the new film electrodes under UV light and artificial solar light illumination. The influence of variables, such as applied bias, pH, supporting electrolyte, MO concentration and the load of the films, on the degradation of the dye was investigated. More than 97% degradation of MO was achieved under the feasible experimental conditions in 2 h photoelectrocatalytic reaction with UV light illumination and mesoporous film TiO(2)/ITO as electrode. The activity of the mesoporous film V-TiO(2) was the highest of the newly synthesized films V-TiO(2), Ce-TiO(2), F-TiO(2) and pure TiO(2) under artificial solar light. The degradation ratio of MO was about 43% over 2 h reaction using V-TiO(2)/ITO as the electrode. The activity of the mesoporous film under artificial solar light needs to be increased further.

An understanding and implications of the coverage of surface free sites in heterogeneous catalysis.

The crucial roles of the coverage of surface free sites in determining catalytic activity trend are quantitatively addressed with the help of density functional theory and microkinetics. First, by analyzing activity trends of NO oxidation catalyzed by Ru, Rh, Pd, Os, Ir, and Pt surfaces with full kinetic considerations, we identify that the activity trend is in general determined by the competition between the reaction barrier and the coverage of surface free sites. Second, since the dissociation of many important molecules, such as the dissociation of N(2), O(2), and CO, follows the same Bronsted-Evans-Polanyi relationship, the coverage of surface free sites is usually a decisive term that affects the overall activity. Third, an equation is derived for the coverage of surface free sites and it is found that the coverage of surface free sites contains not only all the key thermodynamic parameters but also all the kinetic properties in the catalytic system.

Nanocasted synthesis of the mesostructured LaCoO3 perovskite and its catalytic activity in methane combustion.

Extremely high surface area, mesostructured LaCoO3 perovskite has been synthesized by nanocasting from mesoporous cubic (Ia3d) vinyl silica. Thus-prepared material was characterized by XRD, TEM, and N2-sorption, and its catalytic property was also tested in methane combustion. The catalytic results demonstrated that thus-prepared mesostructured LaCoO3 perovskite had higher activity than the conventional bulk LaCoO3 perovskite prepared by citrate method. Further analysis showed that both the high surface area and the existence of high valent cobalt ions (Co4+, XPS analysis) were contributed to the high activity.