RESUMEN
Development of efficient bifunctional nonprecious metallic electrocatalysts for hydrogen electrochemistry in alkaline solution is of importance to enable commercialization of a low-cost alkaline hydrogen fuel cell and water electrolyzer, but it is very challenging. Two-dimensional (2D) MXene-based electrocatalysts hold tremendous potential for the applications of hydrogen fuel cell and water electrolyzer. Here, we successfully immobilized transition-metal-based NiMo nanoparticles (NPs) on 2D Ti3C2Tx (Tx: surface terminations, such as O, OH, or F) surfaces by a wet chemical method. Our results demonstrate that the NiMo NPs are monodispersed on Ti3C2Tx with surface functionalization. These monodisperse NPs resulted in superior hydrogen evolution reaction (HER) and hydrogen oxidation reaction (HOR) activities in an alkaline media. The NiMo NPs/Ti3C2Tx in 1.0 M KOH yielded an HER current of -10 mA cm-2 at -0.044 V vs reversible hydrogen electrode (RHE), nearly 232 mV smaller than that of the parent NiMo NPs. The NiMo NPs/Ti3C2Tx produced an HOR current density of 1.5 mA cm-2 at 0.1 V vs RHE. Density functional theory (DFT) results further reveal that Ti3C2Tx support can facilitate the charge transfer to metallic NPs and tailor the electronic structure of catalytic sites, resulting in optimized adsorption free energies of H* species for hydrogen electrochemistry. This work provides a facile and universal strategy in the development of 2D Ti3C2Tx with nonprecious metals for low-cost bifunctional hydrogen electrocatalysts.
RESUMEN
The growth of aerosol particles is intimately related to chemical reactions in the gas phase and particle phase and at gas-aerosol particle interfaces. While chemical reactions in gas and particle phases are well documented, there is very little information regarding interface-related reactions. The interface of gas-aerosol particles not only facilitates a physical channel for organic species to enter and exit but also provides a necessary lane for culturing chemical reactions. The physical and chemical properties of gas-particle interfaces have not been studied extensively, nor have the reactions occurring at the interfaces been well researched. This is mainly due to the fact that there is a lack of suitable in situ interface-sensitive analytical techniques for direct measurements of interfacial properties. The motivation behind this research is to understand how interfaces play a role in the growth of aerosol particles. We have developed in situ interface-specific second harmonic scattering to examine interfacial behaviors of molecules of aerosol particles under different relative humidity (RH) and salt concentrations. Both the relative humidity and salt concentration can change the particle size and the phase of the aerosol. RH not only varies the concentration of solutes inside aerosol particles but also changes interfacial hydration in local regions. Organic molecules were found to exhibit distinct behaviors at the interfaces and bulk on NaCl particles under different RH levels. Our quantitative analyses showed that the interfacial adsorption free energies remain unchanged while interfacial areas increase as the relative humidity increases. Furthermore, the surface tension of NaCl particles decreases as the RH increases. Our experimental findings from the novel nonlinear optical scattering technique stress the importance of interfacial water behaviors on aerosol particles in the atmosphere.
RESUMEN
BACKGROUND: Lupeol, a triterpene isolated from various herbal plants, possesses an anti-inflammatory function and has been proposed as a candidate for anticancer agents. The purpose of this research was to investigate the effect of lupeol on the viability, apoptosis, cell-cycle distribution, and migration of colorectal cancer cell lines and its molecular mechanism. METHODS: Lupeol was assessed for its anticancer effect using two human colorectal cancer cell lines: SW480 and HCT116. These cells were treated with lupeol, and their viability, apoptosis, migration, and cycle distribution were detected by CCK8, flow cytometry, and the transwell method. Quantitative PCR, Western blot, and immunofluorescence were applied to detect the expressions of CTNNB1, TCF4, cMYC, CCND1, CLDN1, and CCNA2. RESULTS: Lupeol suppressed cell viability and migration and induced cellular apoptosis of both cell lines, with increased p53 and decreased Bcl2 protein levels (P<0.05). Cell cycles of both lupeol-treated cell lines were arrested in the S phase (P<0.05). Quantitative PCR and Western blot analyses showed significantly reduced expressions of CTNNB1, TCF4, and downstream genes of the Wnt-ß-catenin pathway, including the cell-cycle-regulated genes of cMYC and CCND1 of both cell lines upon lupeol treatment (P<0.05). mRNA and protein levels of CLDN1 decreased in HCT116 cells, plus the expression of CCNA2 mRNA and protein decreased in SW480 cells (P<0.05). Immunofluorescence analysis confirmed decreased expression of Wnt-ß-catenin signaling. CONCLUSION: Our findings indicate that lupeol effectively inhibits proliferation and migration and induces apoptosis and cell-cycle arrest of two colorectal cell lines by inactivation of the Wnt-ß-catenin signaling pathway and downregulation of cMYC, CCND1, CCNA2, and CLDN1, thereby making it a promising anticancer candidate.
RESUMEN
The gas-aerosol particle interface is believed to contribute to the growth of secondary organic aerosols in the atmosphere. Despite its importance, the chemical composition of the interface has not been probed directly because of a lack of suitable interface-specific analytical techniques. The preliminary result in our early work has demonstrated direct observations of molecules at the gas-aerosol particle interface with the development of second harmonic scattering (SHS). However, the SHS technique is far away from being an analytical tool of chemical compositions at the gas-aerosol particle interface. In this work, we continued to develop the interface-specific SHS for in situ chemical analysis of molecules at the gas-aerosol particle interface. As an example, we demonstrated coherent SHS signal of a new SHS probe, crystal violet (CV), from interfaces of aerosol particles. The development of the SHS technique includes: (1) Optimization for a more efficient femtosecond laser system in the generation of SHS from aerosol particles. A near 5 MHz repetition rate of a femtosecond laser was found to be optimal for the generation of SHS; (2) exploration of a more effective detector for SHS of aerosol particles. We found that both a CCD detector and a single-photon counter produce similar signal-to-noise ratios of the interfacial SHS signals from aerosol particles. The CCD detector is a more effective option for the detection of SHS and could greatly reduce sampling time of the interfacial responses; (3) combination of the optimal laser system with the CCD detector, which has greatly improved the detection sensitivity of interfacial molecules by more than 2 orders of magnitude and could potentially detect interfacial SHS from a single aerosol particle. These experimental results not only provided a thorough analysis of the SHS technique but also built a solid foundation for further development of a new vibrational sum frequency scattering (SFS) technique for chemical structures at the gas-aerosol particle interface.
RESUMEN
Osteoarthritis (OA) is characterized by the degeneration and destruction of articular cartilage. Allicin, a dietary garlic active constituent, exerts anti-inflammatory effects on several diseases. However, its effects on OA have not been clearly elucidated. In this study, we explored the effects of allicin on OA in both in vitro and in vivo models. Allicin inhibited interleukin-1ß (IL-1ß) induced overproduction of nitric oxide, inducible nitric oxide synthase, prostaglandin E2, and cyclooxygenase-2, as well as pro-inflammatory cytokines tumor necrosis factor alpha and interleukin-6 in chondrocytes in a dose-dependent manner. Meanwhile, allicin reversed the overproduction of metalloproteinase-13 and a disintegrin and metalloproteinase with thrombospondin motifs-5 and the decrease of aggrecan and type II collagen. Furthermore, allicin dramatically suppressed IL-1ß-stimulated PI3K/Akt/NF-κB activation in chondrocytes. In vivo, treatment with allicin prevented the destruction of cartilage and inhibited PI3K/Akt/NF-κB activation in the cartilage of mice OA models. Taken together, these results indicate that allicin may be a potential therapeutic agent for OA.