Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 35
Filtrar
Mais filtros

Base de dados
País/Região como assunto
Tipo de documento
Intervalo de ano de publicação
1.
J Chem Phys ; 160(11)2024 Mar 21.
Artigo em Inglês | MEDLINE | ID: mdl-38488084

RESUMO

In our study, we investigated the influence of the local structure of amorphous Li-La-Zr-O (a-LLZO) on Li-ion conductivity using ab initio molecular dynamics (AIMD). A-LLZO has shown promising properties in inhibiting the growth of lithium dendrites, making it a potential candidate for solid electrolytes in all-solid-state lithium batteries. The low Li-ion conductivity of a-LLZO is currently limiting its practical applications. Our findings revealed that the homogeneous distribution of Zr-O polyhedra within the pristine structure of a-LLZO contributes to enhanced Li-ion conductivity. By reducing the interconnections among Zr-O polyhedra, the AIMD-simulated a-LLZO sample achieved a Li-ion conductivity of 5.78 × 10-4 S/cm at room temperature, which is slightly lower than that of cubic LLZO (c-LLZO) with a Li-ion conductivity of 1.63 × 10-3 S/cm. Furthermore, we discovered that Li-ion conductivity can be influenced by adjusting the elemental ratios within a-LLZO. This suggests that fine-tuning the composition of a-LLZO can potentially further enhance its Li-ion conductivity and optimize its performance as a solid electrolyte in lithium batteries.

2.
Phys Chem Chem Phys ; 24(25): 15201-15207, 2022 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-35612307

RESUMO

Silicene, a competitive two-dimensional (2D) material for future electronic devices, has attracted intensive attention in condensed matter physics. Utilizing an adaptive genetic algorithm (AGA), we identify a topological allotrope of silicene, named tilted penta (tPenta) silicene. Based on first-principles calculations, the geometric and electronic properties of tPenta silicene and its isoelectronic substitutions (Ge, Sn) are investigated. Our results indicate that tPenta silicene exhibits a semimetallic state with distorted Dirac cones in the absence of spin-orbit coupling (SOC). When SOC is considered, it shows semiconducting behavior with a gap opening of 2.4 meV at the Dirac point. Based on the results of invariant ( = 1) and the helical edge states, we demonstrate that tPenta silicene is a topological insulator. Furthermore, the effect of isoelectronic substitutions on tPenta silicene is studied. Two stoichiometric phases, i.e., tPenta Si0.333Ge0.667 and tPenta Si0.333Sn0.667 are found to retain the geometric framework of tPenta silicene and exhibit high stabilities. Our calculations show that both tPenta Si0.333Ge0.667 and tPenta Si0.333Sn0.667 are QSH insulators with enlarged band gaps of 32.5 meV and 94.3 meV, respectively, at the HSE06 level, offering great potential for practical applications at room temperature.

3.
Chemistry ; 27(37): 9686-9693, 2021 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-33871112

RESUMO

Single Mn atom on nitrogen-doped graphene (MnN4 -G) has exhibited good structural stability and high activity for the adsorption and dissociation of an O2 molecule, becoming a promising single-atom catalyst (SAC) candidate for oxygen reduction reaction (ORR). However, the catalytic activity of MnN4 -G for the ORR and the optimal reaction pathway remain obscure. In this work, density-functional theory calculations were employed to comprehensively investigate all the possible pathways and intermediate reactions of the ORR on MnN4 -G. The feasible active sites and the most stable adsorption configurations of the intermediates and transition states during the ORR were identified. Screened from all the possibilities, three optimal four-electron O2 hydrogenation pathways with an ultralow energy barrier of 0.13 eV were discovered that are energetically more favorable than direct O2 dissociation pathways. Analysis of the free energy diagram further verified the thermodynamical feasibility of the three pathways. Thus, MnN4 -G possesses superior ORR activity. This study provides a fundamental understanding of the design of highly efficient SACs for the ORR.

4.
Proc Natl Acad Sci U S A ; 115(6): E1289-E1298, 2018 02 06.
Artigo em Inglês | MEDLINE | ID: mdl-29358399

RESUMO

Mixed pathology, with both Alzheimer's disease and vascular abnormalities, is the most common cause of clinical dementia in the elderly. While usually thought to be concurrent diseases, the fact that changes in cerebral blood flow are a prominent early and persistent alteration in Alzheimer's disease raises the possibility that vascular alterations and Alzheimer pathology are more directly linked. Here, we report that aged tau-overexpressing mice develop changes to blood vessels including abnormal, spiraling morphologies; reduced blood vessel diameters; and increased overall blood vessel density in cortex. Blood flow in these vessels was altered, with periods of obstructed flow rarely observed in normal capillaries. These changes were accompanied by cortical atrophy as well as increased expression of angiogenesis-related genes such as Vegfa, Serpine1, and Plau in CD31-positive endothelial cells. Interestingly, mice overexpressing nonmutant forms of tau in the absence of frank neurodegeneration also demonstrated similar changes. Furthermore, many of the genes we observe in mice are also altered in human RNA datasets from Alzheimer patients, particularly in brain regions classically associated with tau pathology such as the temporal lobe and limbic system regions. Together these data indicate that tau pathological changes in neurons can impact brain endothelial cell biology, altering the integrity of the brain's microvasculature.


Assuntos
Doença de Alzheimer/patologia , Peptídeos beta-Amiloides/metabolismo , Indutores da Angiogênese/metabolismo , Encéfalo/irrigação sanguínea , Circulação Cerebrovascular/fisiologia , Neurônios/patologia , Proteínas tau/metabolismo , Envelhecimento , Doença de Alzheimer/genética , Doença de Alzheimer/metabolismo , Animais , Encéfalo/metabolismo , Encéfalo/patologia , Células Cultivadas , Humanos , Camundongos , Camundongos Transgênicos , Neurônios/metabolismo , Proteínas tau/genética
5.
Molecules ; 23(1)2018 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-29320428

RESUMO

Monitoring reaction paths is not only a fundamental scientific issue but also helps us to understand and optimize the catalytic process. Infrared (IR) and Raman spectroscopies are powerful tools for detecting particular molecules or intermediate products as a result of their ability to provide the molecular "finger-print". However, theoretical modeling for the vibrational spectra of molecular adsorbates on metallic surfaces is a long-standing challenge, because accurate descriptions of the electronic structure for both the metallic substrates and adsorbates are required. In the present work, we applied a quasi-analytical IR and Raman simulation method to monitor the dehydrogenation of propane towards propylene on a Pd-doped Cu(111) surface in real-time. Different Pd ensembles were used to construct the single-atom catalyst (SAC). We found that the number of sublayer Pd atoms could only affect the intensity of the peak rather than the peak position on the vibrational spectra. However, with the dehydrogenation reaction proceeding, both IR and Raman spectra were changed greatly, which indicates that every reaction step can be distinguished from the point of view of vibrational spectroscopies. Additionally, we found that the catalytic process, which starts from different initial states, shows different spectral profiles. The present results suggest that the vibrational spectroscopies obtained by the high-precision simulations pave the way for identifying different catalytic reaction paths.


Assuntos
Alcenos/química , Cobre/química , Paládio/química , Propano/química , Análise Espectral/métodos , Catálise , Modelos Moleculares , Espectrofotometria Infravermelho , Análise Espectral Raman , Propriedades de Superfície , Vibração
6.
J Am Chem Soc ; 139(29): 9771-9774, 2017 07 26.
Artigo em Inglês | MEDLINE | ID: mdl-28693318

RESUMO

We report the discovery of a dramatically enhanced N2 electroreduction reaction (NRR) selectivity under ambient conditions via the Li+ incorporation into poly(N-ethyl-benzene-1,2,4,5-tetracarboxylic diimide) (PEBCD) as a catalyst. The detailed electrochemical evaluation and density functional theory calculations showed that Li+ association with the O atoms in the PEBCD matrix can retard the HER process and can facilitate the adsorption of N2 to afford a high potential scope for the NRR process to proceed in the "[O-Li+]·N2-Hx" alternating hydrogenation mode. This atomic-scale incorporation strategy provides new insight into the rational design of NRR catalysts with higher selectivity.

7.
Angew Chem Int Ed Engl ; 56(46): 14637-14641, 2017 11 13.
Artigo em Inglês | MEDLINE | ID: mdl-28963739

RESUMO

As the first example of a photocatalytic system for splitting water without additional cocatalysts and photosensitizers, the comparatively cost-effective Cu2 I2 -based MOF, Cu-I-bpy (bpy=4,4'-bipyridine) exhibited highly efficient photocatalytic hydrogen production (7.09 mmol g-1 h-1 ). Density functional theory (DFT) calculations established the electronic structures of Cu-I-bpy with a narrow band gap of 2.05 eV, indicating its semiconductive behavior, which is consistent with the experimental value of 2.00 eV. The proposed mechanism demonstrates that Cu2 I2 clusters of Cu-I-bpy serve as photoelectron generators to accelerate the copper(I) hydride interaction, providing redox reaction sites for hydrogen evolution. The highly stable cocatalyst-free and self-sensitized Cu-I-bpy provides new insights into the future design of cost-effective d10 -based MOFs for highly efficient and long-term solar fuels production.

8.
BMC Infect Dis ; 16: 107, 2016 Mar 03.
Artigo em Inglês | MEDLINE | ID: mdl-26939531

RESUMO

BACKGROUND: Tuberculosis remains a major public health problem in China. The Hebei province is located in the Beijing-Tianjin-Hebei integration region; however little information about the genetic diversity of Mycobacterium tuberculosis was available in this area. This study describes the first attempt to map the molecular epidemiology of MTB strains isolated from Hebei. METHODS: Spoligotyping and 15-locus MIRU-VNTR were performed in combination to yield specific genetic profiles of 1017 MTB strains isolated from ten cities in the Hebei province in China during 2014. Susceptibility testing to first line anti-TB drugs was also conducted for all strains using the L-J proportion method. RESULTS: Based on the SpolDB4.0 database, the predominant spoligotype belonged to the Beijing family (90.5%), followed by T family (6.3%). Using 15-locus MIRU-VNTR clustering analysis, 846 different patterns were identified, including 84 clusters (2-17 strains per cluster) and 764 individual types. Drug susceptibility pattern showed that 347 strains (34.1%) were resistant to at least one of the first line drugs, including 134 (13.2%) multi-drug resistance strains. Statistical analysis indicated that drug resistance was associated with treatment history. The Beijing family was associated with genetic clustering. However, no significant difference was observed between the Beijing and non-Beijing family in gender, age, treatment history and drug resistance. CONCLUSIONS: The Mycobacterium tuberculosis strains in Hebei exhibit high genetic diversity. The Beijing family is the most prevalent lineage in this area. Spoligotyping in combination with 15-locus MIRU-VNTR is a useful tool to study the molecular epidemiology of the MTB strains in Hebei.


Assuntos
Antituberculosos/farmacologia , Farmacorresistência Bacteriana , Mycobacterium tuberculosis , Tuberculose , China/epidemiologia , Genótipo , Humanos , Testes de Sensibilidade Microbiana , Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/genética , Mycobacterium tuberculosis/isolamento & purificação , Tuberculose/epidemiologia , Tuberculose/microbiologia
9.
Phys Chem Chem Phys ; 18(15): 9969-78, 2016 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-26947704

RESUMO

Using density functional theory (DFT) calculations, we performed a thorough theoretical investigation on the catalytic mechanism of oxidative self-coupling of methanol with molecular oxygen on Au-Ag catalysts. It is found that molecular oxygen can be activated via a hydroperoxyl (OOH) intermediate by taking a hydrogen atom from co-adsorbed methanol with an energy barrier of 0.51 eV, which is actually the rate determining step for the overall reaction. The O, OH and OOH oxidant formation proceeds via two channels of I and II with low barriers. We demonstrated that the oxidative coupling of methanol by OOH, atomic oxygen, and hydroxyl is much more favorable than the total oxidation of methanol, and is responsible for the high selectivity of Au-Ag catalysts in methanol oxidation. The revealed activation mechanism provides an efficient pathway for optimizing the selective coupling of methanol with dioxygen.

10.
Phys Chem Chem Phys ; 16(42): 23214-23, 2014 Nov 14.
Artigo em Inglês | MEDLINE | ID: mdl-25254929

RESUMO

Hydrogenation and fluorination provide promising applications for tuning the properties of graphene-based nanomaterials. Using first-principles calculations, we investigate the electronic and magnetic properties of zigzag graphene nanoribbons (ZGNRs) supported on hydrogenated and fluorinated ZGNRs. Our results indicate that the support of zigzag graphane nanoribbon with its full width has less impact on the electronic and magnetic properties of ZGNRs, whereas the ZGNRs supported on fluorographene nanoribbons can be tuned to metal with almost degenerated ferro- and anti-ferromagnetic states due to the intrinsic polarization of substrate. The ZGNRs supported on zigzag hybrid fluorographene-graphane nanoribbons are spin-polarized half-semiconductors with distinct band gaps for spin-up and spin-down channels. Interestingly, in the absence of an external electric field, the spin-polarized band gaps of supported ZGNRs can be well modulated in the opposite direction by changing the ratio of fluorination to hydrogenation concentration in hybrid substrates. Furthermore, the ZGNRs supported on hybrid nanoribbons exhibit the half-semiconducting to half-metallic behavior transition as the interlayer spacing is gradually reduced, which is realized more easily for the hybrid support with a relatively wide fluorographene moiety compared to its narrow counterpart. Present results provide a novel way for designing substrate-supported graphene spintronic devices.


Assuntos
Fluorocarbonos/química , Grafite/química , Nanotubos de Carbono/química , Semicondutores , Teoria Quântica
11.
Phys Chem Chem Phys ; 16(18): 8367-75, 2014 May 14.
Artigo em Inglês | MEDLINE | ID: mdl-24658397

RESUMO

The single atom alloy of extended surfaces is known to provide remarkably enhanced catalytic performance toward heterogeneous hydrogenation. Here we demonstrate from first principles calculations that this approach can be extended to nanostructures, such as bimetallic nanoparticles. The catalytic properties of the single-Pd-doped Cu55 nanoparticles have been systemically examined for H2 dissociation as well as H atom adsorption and diffusion, following the concept of single atom alloy. It is found that doping a single Pd atom at the edge site of the Cu55 shell can considerably reduce the activation energy of H2 dissociation, while the single Pd atom doped at the top site or in the inner layers is much less effective. The H atom adsorption on Cu55 is slightly stronger than that on the Cu(111) surface; however, a larger nanoparticle that contains 147 atoms could effectively recover the weak binding of the H atoms. We have also investigated the H atom diffusion on the 55-atom nanoparticle and found that spillover of the produced H atoms could be a feasible process due to the low diffusion barriers. Our results have demonstrated that facile H2 dissociation and weak H atom adsorption could be combined at the nanoscale. Moreover, the effects of doping one more Pd atom on the H2 dissociation and H atom adsorption have also been investigated. We have found that both the doping Pd atoms in the most stable configuration could independently exhibit their catalytic activity, behaving as two single-atom-alloy catalysts.


Assuntos
Ligas/química , Cobre/química , Nanopartículas Metálicas/química , Paládio/química , Catálise , Difusão , Hidrogênio/química , Hidrogenação
12.
Artigo em Inglês | MEDLINE | ID: mdl-38679933

RESUMO

The CO2 reduction reaction (CO2RR) is a promising method that can both mitigate the greenhouse effect and generate valuable chemicals. The 2D-M2C12 with high-density transition metal single atoms is a potential catalyst for various catalytic reactions. Using an effective strategy, we screened 1s-Mn2C12 as the most promising electrocatalyst for the CO2RR in the newly reported 2D-M2C12 family. A low applied potential of -0.17 V was reported for the CO2-to-CH4 conversion. The relative weak adsorption of H atom and H2O in the potential range of -0.2 to -0.8 V, ensures the preferential adsorption of CO2 and the following production of CH4. The different loading amounts of Mn atoms on γ-graphyne (GY) were also investigated. The Mn atoms prefer doping in the nonadjacent triangular pores instead of the adjacent ones due to the repulsive forces between d-orbitals when the Mn loading is less than 32.3 wt % (5Mn). As the Mn concentration further increases, adjacent Mn atoms begin to appear, and the Mn@GY becomes metallic or half-metallic. The presence of four adjacent Mn atoms increases the d-band center of Mn@GY, particularly the dz2 center involved in CO2 adsorption, thereby enhancing the adsorption capacity for CO2. These findings indicate that 1s-Mn2C12 with high Mn atomic loadings is an excellent CO2RR electrocatalyst, and it provides new insights for designing efficient CO2RR electrocatalyst.

13.
Vet Microbiol ; 295: 110161, 2024 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-38945021

RESUMO

Streptococcus suis (S. suis) type 2 (SS2) is an important zoonotic pathogen causing severe neural infections in pigs and causes serious threat to public health. Inflammasome activation plays an important role in the host against microbial infection but the role of inflammasome activation in the blood-brain barrier (BBB) integrity during S. suis infection is rarely studied. This study investigated the mechanism by which S. suis-induced NLRP3 inflammasome activation led to BBB disruption. Our results showed that S. suis infection activated NLRP3 inflammasome in brain microvascular endothelial cells (BMECs) leading to the secretion of pro-inflammatory cytokines (IL-1ß, IL-6 and TNF-α) and chemokines (CCL-2 and CXCL-2) as well as the cleavage of Gasdermin D (GSDMD) which were significantly attenuated by inflammasome inhibitor MCC950. Furthermore, S. suis infection significantly downregulated expression of tight junctions (TJs) proteins and trans-endothelial electrical resistance (TEER) while NLRP3 inhibition rescued S. suis-induced degradation of TJs proteins and significantly reduced the number of S. suis crossing BBB in transwell infection model. Moreover, recombinant IL-1ß exacerbated the reduction of TJs proteins in BMECs. In murine S. suis-infection model, MCC950 reduced the bacterial load and the excessive inflammatory response in mice brain. In addition, the integrity of the BBB was protected with increased TJ proteins expression and decreased pathological injury after the inhibition of NLRP3 inflammasome, indicating NLRP3 inflammasome plays a destructive role in meningitis induced by S. suis. Our study expands the understanding on the role of NLRP3 inflammasome in bacterial meningitis, which provide the valuable information for the development of anti-infective agents targeting NLRP3 to treat bacterial meningitis.


Assuntos
Barreira Hematoencefálica , Células Endoteliais , Inflamassomos , Proteína 3 que Contém Domínio de Pirina da Família NLR , Infecções Estreptocócicas , Streptococcus suis , Animais , Barreira Hematoencefálica/microbiologia , Proteína 3 que Contém Domínio de Pirina da Família NLR/metabolismo , Inflamassomos/metabolismo , Inflamassomos/imunologia , Camundongos , Infecções Estreptocócicas/imunologia , Infecções Estreptocócicas/microbiologia , Células Endoteliais/microbiologia , Citocinas/metabolismo , Citocinas/genética , Camundongos Endogâmicos C57BL , Encéfalo/microbiologia , Encéfalo/imunologia , Feminino
14.
J Phys Chem Lett ; 14(49): 11125-11133, 2023 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-38052049

RESUMO

On the basis of the especially tunable electronic property of Si, several kinds of nanomaterials with atomically dispersed Si were constructed and characterized by extensive first-principles calculations and ab initio molecular dynamics (AIMD) simulations. The new-type Si(X≡Y)n wide-bandgap semiconductors featuring through-space d-π* hyperconjugation exhibit unique properties in photoelectric conversion, photoconductivity, structural mechanics, etc. The SiC8 siligraphene with the planar tetracoordinate Si (ptSi) has a high lithium-storage capacity and comparably facile surface migration behaviors of both Li and Li+, making it a promising anode material for high-performance Li-ion batteries. The atomically dispersed Si sites of 2D monolayer materials, such as ptSi and three- and four-coordinated Si atoms, generally exhibit remarkable catalytic activity toward CO2 activation with different electron mechanisms, resulting in different scaling relations between the activity and the p-band center. The computational findings enrich the understanding of structural and chemical properties of silicon and open up avenues for developing Si-based functional materials.

15.
Xi Bao Yu Fen Zi Mian Yi Xue Za Zhi ; 39(9): 824-827, 2023 Sep.
Artigo em Zh | MEDLINE | ID: mdl-37732578

RESUMO

Objective To investigate the effect of blood group serology and polymerase chain reaction with sequence-specific primers (PCR-SSP) on identification and genotyping of ambiguous ABO blood group. Methods Eighty suspicious ABO blood group samples were identified by serology and polymerase chain reaction with sequence-specific primers (PCR-SSP). The final blood group type and the strategy of the transfusion of each case were determined according to the results of serology and PCR-SSP. Results 40 cases were confirmed to be subtypes, and the remaining 40 cases were normal types with weakened antigens or missing antibodies due to other reasons. The results of molecular genetic blood group typing based on PCR-SSP were 41 cases of subtypes (There were 3 discrepancies between two methods: one was Ael identified by serological methods, while its gene type was O2O2; one was common type O, while its gene type was BO1; one was type A, while its gene type was AB.) and 39 cases of normal ones. Conclusion Genotyping technology combined with serological typing has an important significance in identification of ABO blood groups.


Assuntos
Sistema ABO de Grupos Sanguíneos , Anticorpos , Sistema ABO de Grupos Sanguíneos/genética , Genótipo , Reação em Cadeia da Polimerase , Primers do DNA
16.
J Phys Chem Lett ; 14(2): 363-369, 2023 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-36606739

RESUMO

The utilization of atomically confined plasmonic fields has revolutionized the imaging technique. According to the fundamental position-momentum uncertainty principle, such a narrow spatial distribution certainly leads to a broad momentum distribution in the fields, which has however been overlooked. Here we propose a novel exploitation for the momentum distribution by adaptively satisfying the conservation law of momentum in inelastic Raman scatterings in periodic systems, providing a unique optical means of directly measuring the whole phonon dispersions. The proposed technique is particularly useful for measuring phonon dispersions of low-dimensional hydrogen-rich materials, which are completely inaccessible via other techniques. The numerical results for a single all-trans polyacetylene chain demonstrate that all phonon dispersion branches can be conclusively measured from their Raman images for the first time. Our findings highlight a unique advantage of the emerging momentum-based nanophotonics and open the door for exploiting highly confined plasmonic fields in another dimension.

17.
Mol Neurobiol ; 60(12): 6916-6930, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37516664

RESUMO

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used as analgesic agents. They have been detected in various environmental matrices. The degradation of environmental contaminants and the long-term adverse effects have become a major public concern. Prenatal exposure to acetaminophen can cause damage to the developing hippocampus. However, the molecular mechanisms behind hippocampal damage following prenatal acetaminophen exposure (PAcE) remain unclear. The present study shows an increased risk of adverse neurodevelopmental outcomes in offspring following exposure to acetaminophen during pregnancy on mice. The results revealed that different doses, timings, and duration of exposure to acetaminophen during pregnancy were associated with dose-dependent changes in the hippocampus of the offspring. Furthermore, exposure to high doses, multiple-treatment courses, and late pregnancy induced pathological changes, such as wrinkling and vacuolation, inhibited hippocampal proliferation and increased apoptosis. In addition, PAcE significantly decreased the expression of genes related to synaptic development in fetal hippocampal neurons and hippocampal astrocyte and microglia were also damaged to varying degrees. The significant reduction either in SOX2, an essential gene in regulating neural progenitor cell proliferation, and reduction of genes related to the SOX2/Notch pathway may suggest that the role of SOX2/Notch pathway in impaired hippocampal development in the offspring due to PAcE. In general, PAcE at high doses, multiple-treatment courses, and mid- and late gestation were associated with neurodevelopmental toxicity to the offspring.


Assuntos
Acetaminofen , Anti-Inflamatórios não Esteroides , Feminino , Animais , Camundongos , Gravidez , Acetaminofen/toxicidade , Astrócitos , Feto , Hipocampo
18.
ACS Appl Mater Interfaces ; 14(31): 35844-35853, 2022 Aug 10.
Artigo em Inglês | MEDLINE | ID: mdl-35904900

RESUMO

Graphitic carbon nitride (g-C3N4) is regarded as a promising potent photoelectrocatalyst for CO2 reduction. Here, extensive first-principles calculations and ab initio molecular dynamics (AIMD) simulations are performed to systematically explore the structural and electronic properties of nonprecious metal single-atom-embedded graphitic s-triazine-based C3N4 (M@gt-C3N4, M = Mn, Fe, Co, Ni, Cu, and Mo) monolayer materials and their catalytic performances as the single-atom catalysts (SACs) for CO2 hydrogenation to HCOOH, CO, and CH3OH. It is found that the atomically dispersed non-noble metal Mn, Fe, Co, and Mo sites anchored on gt-C3N4 can efficiently activate both H2 and CO2, and their coadsorbed state serves as a precursor to the hydrogenation of CO2 to different C1 products. Among these SACs (M@gt-C3N4, M = Mn, Fe, Co, and Mo), Co@gt-C3N4 was predicted to have the best catalytic performance for CO2 hydrogenation to C1 products, although their mechanistic details are somewhat different. The predicted energy barriers of the rate-determining steps for the conversion of CO2 into HCOOH, CO, and CH3OH on Co@gt-C3N4 are 0.58, 0.67, and 1.19 eV, respectively. The desorption of products is generally energy-demanding, but it can be facilitated remarkably by the subsequent adsorption of H2, which regenerates M@gt-C3N4 for the next catalytic cycle. The present study demonstrates that the catalytic performance of gt-C3N4 can be well regulated by embedding the non-noble metal single atom, and the porous gt-C3N4 is nicely suited for the construction of high-performance single-atom catalysts.

19.
ACS Omega ; 7(17): 14875-14886, 2022 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-35557692

RESUMO

Charge compensation mechanisms in the delithiation processes of LiNi1/3Co1/3Mn1/3O2 (NCM111) are compared in detail by the first-principles calculations with GGA and GGA+U methods under different U values reported in the literature. The calculations suggested that different sets of U values lead to different charge compensation mechanisms in the delithiation process. Co3+/Co4+ couples were shown to dominate the redox reaction for 1 ≥ x ≥ 2/3 by using the GGA+U 1 method (U 1 = 6.0 3.4 3.9 for Ni, Co, and Mn, respectively). However, by using the GGA+U 2 (U 2 = 6.0 5.5 4.2) method, the results indicated that the redox reaction of Ni2+/Ni3+ took place in the range of 1 ≥ x ≥ 2/3. Therefore, according to our study, experimental charge compensation processes during delithiation are of great importance to evaluate the theoretical calculations. The results also indicated that all the GGA+U i (i = 1, 2, 3) schemes predicted better voltage platforms than the GGA method. The oxygen anionic redox reactions during delithiation are also compared with GGA+U calculations under different U values. The electronic density of states and magnetic moments of transition metals have been employed to illustrate the redox reactions during the lithium extractions in NCM111. We have also investigated the formation energies of an oxygen vacancy in NCM111 under different values of U, which is important in understanding the possible occurrence of oxygen release. The formation energy of an O vacancy is essentially dependent on the experimental conditions. As expected, the decreased temperature and increased oxygen partial pressure can suppress the formation of the oxygen vacancy. The calculations can help improve the stability of the lattice oxygen.

20.
Front Microbiol ; 13: 898559, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35694317

RESUMO

Streptococcus pneumoniae is an invasive pathogen with high morbidity and mortality in the immunocompromised children and elderly. NOD-like receptor family pyrin domain containing 6 (NLRP6) plays an important role in the host innate immune response against pathogen infections. Our previous studies have shown that NLRP6 plays a negative regulatory role in host defense against S. pneumoniae, but the underlying mechanism is still unclear. The further negative regulatory role of NLRP6 in the host was investigated in this study. Our results showed that NLRP6-/- mice in the lung had lower bacterial burdens after S. pneumoniae infection and expressed higher level of tight junction (TJ) protein occludin compared to WT mice, indicating the detrimental role of NLRP6 in the host defense against S. pneumoniae infection. Transcriptome analysis showed that genes related to leukocytes migration and recruitment were differentially expressed between wild-type (WT) and NLRP6 knockout (NLRP6-/-) mice during S. pneumoniae infection. Also, NLRP6-/- mice showed higher expression of chemokines including C-X-C motif chemokine ligand 1 (CXCL1) and 2 (CXCL2) and lower gene expression of complement C3a receptor 1 (C3aR1) and P-selectin glycoprotein ligand-1 (PSGL-1) which are the factors that inhibit the recruitment of neutrophils. Furthermore, NLRP6-/- neutrophils showed increased intracellular bactericidal ability and the formation of neutrophil extracellular traps (NETs) during S. pneumoniae infection. Taken together, our study suggests that NLRP6 is a negative regulator of neutrophil recruitment and function during S. pneumoniae infection. Our study provides a new insight to develop novel strategies to treat invasive pneumococcal infection.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA