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1.
Mikrochim Acta ; 191(6): 316, 2024 05 10.
Artigo em Inglês | MEDLINE | ID: mdl-38724679

RESUMO

An ultra-sensitive photoelectrochemical (PEC) sensor based on perovskite composite was developed for the determination of alkaline phosphatase (ALP) in human serum. In contrast to CsPbBr3 or Y6 that generated anodic current, the heterojunction of CsPbBr3/Y6 promoted photocarriers to separate and generated cathodic photocurrent. Ascorbic acid (AA) was produced by ALP hydrolyzing L-ascorbic acid 2-phosphate trisodium salt (AAP), which can combine with the holes on the photoelectrode surface, accelerating the transmission of photogenerated carriers, leading to enhanced photocurrent intensity. Thus, the enhancement of PEC current was linked to ALP activity. The PEC sensor exhibits good sensitivity for detection of ALP owing to the unique photoelectric properties of the CsPbBr3/Y6 heterojunction. The detection limit of the sensor was 0.012 U·L-1 with a linear dynamic range of 0.02-2000 U·L-1. Therefore, this PEC sensing platform shows great potential for the development of different PEC sensors.


Assuntos
Fosfatase Alcalina , Ácido Ascórbico , Técnicas Eletroquímicas , Eletrodos , Limite de Detecção , Óxidos , Processos Fotoquímicos , Titânio , Fosfatase Alcalina/química , Fosfatase Alcalina/sangue , Fosfatase Alcalina/metabolismo , Humanos , Técnicas Eletroquímicas/métodos , Técnicas Eletroquímicas/instrumentação , Ácido Ascórbico/química , Ácido Ascórbico/sangue , Ácido Ascórbico/análogos & derivados , Titânio/química , Óxidos/química , Compostos de Cálcio/química , Técnicas Biossensoriais/métodos
2.
Phys Chem Chem Phys ; 19(46): 31267-31273, 2017 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-29148556

RESUMO

The CO2 adsorption and dynamic behaviors on single crystal anatase TiO2(101) surfaces were investigated by UHV-FTIRS and first-principles calculations. The IRRAS results at 90 K show that the ν3(OCO) asymmetric stretching vibration of adsorbed CO2 exhibits band splitting at rather low CO2 coverage in p-polarized IR spectra for the IR beam incident along the [101[combining macron]] direction. Co-adsorbed CO can prevent such band splitting. Ab initio molecular dynamics (AIMD) simulations revealed that the adsorbed CO2 at finite temperature does not keep a stationary adsorption state but keeps a certain swing motion: one end of the linear CO2 molecule binds to surface Ti5c sites and the other end swings within the (010) plane with a tilted angle distribution ranging from 10° to 60° relative to the [101[combining macron]] direction. By suggesting a statistical model, we confirmed that it is the swing motion that results in the band splitting phenomenon of CO2 vibration in IR spectra. The co-adsorbed CO decreases the swing angle distribution ranging from 10° to 45° through the intermolecular interaction between CO and CO2, leading to the disappearance of CO2 band splitting.

3.
Phys Chem Chem Phys ; 18(26): 17660-5, 2016 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-27306113

RESUMO

The charge state of Au clusters deposited on rutile TiO2(110) single crystal surfaces was studied by UHV-FTIRS using CO as a probe. The as-deposited Au clusters on oxidized TiO2(110) surfaces are electrically neutral and are identified by the 2105-2112 cm(-1) vibrational frequency of adsorbed CO depending on Au coverage. Annealing Au/TiO2(110) in a moderate O2 atmosphere at 400 K blue shifts the CO vibrational frequency by only 2-3 cm(-1) both on bare TiO2(110) surfaces and on Au clusters. However, NO exposure blue shifts the CO vibrational frequency by 16-26 cm(-1) for CO adsorbed on Au atoms near the interface and by 3-4 cm(-1) for CO adsorbed on top of Au clusters. As the acceptors of the intense charge transfer from Au, the Oa atoms generated through (NO)2→ N2O + Oa reactions on the small fraction of the bare TiO2(110) surface reside around the Au/TiO2(110) interface perimeter, causing the neutral Au(0) to be cationic Au(δ+) states. This is a new approach to manipulate the charge state of Au clusters on oxide surfaces, which may be helpful in regulating the catalytic redox reactions on oxide supported metal systems.

4.
Phys Chem Chem Phys ; 17(37): 23994-4000, 2015 Oct 07.
Artigo em Inglês | MEDLINE | ID: mdl-26313610

RESUMO

CO2 adsorption and interaction on rutile TiO2(110) surfaces was studied by UHV-FTIRS combined with theoretical simulations. With increasing CO2 exposure, CO2 adsorbs in succession at the oxygen vacancy (Vo) sites, on the five-coordinated Ti cation (Ti5c) sites and the bridging oxygen (Obr) sites at low temperature. The coupling has occurred between neighboring CO2 adsorbed on Ti5c sites from rather low CO2 coverage (∼0.5 ML), leading the ν3(OCO) asymmetric stretching vibrations to split into two absorption bands in IR spectra. Two kinds of coupled geometries of adjacent CO2 on Ti5c sites are determined by theoretical simulations. For the higher CO2 coverage (∼1.5 ML), the horizontal adsorption configuration along the [11[combining macron]0] azimuth of CO2 adsorbed on Obr sites is identified for the first time using polarization- and azimuth-resolved RAIRS in experiments. The significant deviation of CO2 from the top of Obr sites demonstrates the strong coupling between CO2 adsorbed on Obr and Ti5c sites.

5.
Phys Chem Chem Phys ; 16(43): 23711-5, 2014 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-25272287

RESUMO

Competitive adsorption of prototype molecules such as (12)CO, (13)CO and CO2 at the two typical fivefold coordinated Ti5c(4+) cation sites of reduced rutile TiO2(110) surfaces was studied in a newly designed UHV-FTIR system. The measured binding energies of (12)CO, (13)CO or CO2 adsorbed at two kinds of Ti5c(4+) sites are different. The molecular occupying probability at these sites depends on the binding energy of the adsorbed molecules; while, the molecular exchanging probability at these sites depends on their binding energy difference due to the presence of competitive adsorption. A simple thermodynamic equilibrium model was proposed to qualitatively interpret the adsorption and competitive adsorption mechanisms. These results will contribute to the elucidation of the (photo)catalytic process on TiO2(110) surfaces.

6.
Phys Chem Chem Phys ; 16(28): 14682-7, 2014 Jul 28.
Artigo em Inglês | MEDLINE | ID: mdl-24916484

RESUMO

The adsorption and reaction of NO on both the oxidized and reduced single crystal rutile TiO2(110) surfaces were studied in a UHV-FTIRS system at low temperature. The monodentate adsorption configuration of the cis-(NO)2 dimer at bridge oxygen vacancy (Vo) sites was detected for the first time on reduced TiO2(110) surfaces. With the aid of (NO)2 dimer adsorption anisotropy, the bidentate configuration of the cis-(NO)2 dimer on fivefold coordinated Ti5c(4+) cation sites was clearly confirmed. The (NO)2 dimer converts to N2O on Ti5c(4+) cation sites at higher NO dosage on both oxidized and reduced surfaces, rather than at Vo sites. The (NO)2 → N2O conversion is independent of the presence of Vo on TiO2(110) surfaces. To explain the signs of absorption bands of the dimer monodentate configuration, the local optical constant at Vo sites was introduced.

7.
Phys Chem Chem Phys ; 16(30): 15968-78, 2014 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-24964160

RESUMO

We performed first-principles calculations to study the adsorption characteristics of alkali, alkali-earth, group III, and 3d transition-metal (TM) adatoms on germanene. We find that the adsorption of alkali or alkali-earth adatoms on germanene has minimal effects on geometry of germanene. The significant charge transfer from alkali adatoms to germanene leads to metallization of germanene, whereas alkali-earth adatom adsorption, whose interaction is a mixture of ionic and covalent, results in semiconducting behavior with an energy gap of 17-29 meV. For group III adatoms, they also bind germanene with mixed covalent and ionic bonding character. Adsorption characteristics of the transition metals (TMs) are rather complicated, though all TM adsorptions on germanene exhibit strong covalent bonding with germanene. The main contributions to the strong bonding are from the hybridization between the TM 3d and Ge pz orbitals. Depending on the induced-TM type, the adsorbed systems can exhibit metallic, half-metallic, or semiconducting behavior. Also, the variation trends of the dipole moment and work function with the adsorption energy across the different adatoms are discussed. These findings may provide a potential avenue to design new germanene-based devices in nanoelectronics.

8.
Anal Methods ; 15(3): 256-260, 2023 01 19.
Artigo em Inglês | MEDLINE | ID: mdl-36598084

RESUMO

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was used for the quantification of 7-nitroso-3-(trifluoromethyl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine (NTTP) in the sitagliptin phosphate monohydrate active pharmaceutical ingredient. Chromatographic separation was achieved using an Agilent-ZORBAX SB-C18 column, with 0.01 mol L-1 ammonium formate in water as mobile phase A and acetonitrile as mobile phase B in gradient elution mode at a 0.4 mL min-1 flow rate. Quantification of impurities was carried out using triple quadrupole mass detection with electrospray ionization in the multiple reaction monitoring mode. The method was fully validated with good linearity over the concentration range of 0.098-0.925 ppm of the sitagliptin phosphate monohydrate test concentration for NTTP. The correlation coefficient obtained in each case was >0.998. The recoveries were found to be satisfactory over the range between 80.0 and 120.0% for NTTP. The developed method was able to quantitate NTTP at a concentration level of 0.98 ng mL-1 (0.098 ppm with respect to 10 mg mL-1 sitagliptin phosphate monohydrate).


Assuntos
Fosfato de Sitagliptina , Espectrometria de Massas em Tandem , Cromatografia Líquida , Espectrometria de Massas em Tandem/métodos , Cromatografia Líquida de Alta Pressão/métodos , Preparações Farmacêuticas
9.
Cell Cycle ; 21(5): 477-488, 2022 03.
Artigo em Inglês | MEDLINE | ID: mdl-34979867

RESUMO

Proteasome 26S subunit, ATPase 2 (PSMC2) is a recently identified gene which is potentially associated with human carcinogenesis. However, the effects of PSMC2 on oral squamous cell carcinoma (OSCC) is still unclear. Here, we investigated PSMC2 expression in OSCC tissues and explored its effects on the biological behaviors of OSCC cells. PSMC2 expression was evaluated by immunohistochemistry in a tissue microarray containing 60 OSCC tissues and 9 normal tissues. PSMC2 was knocked down through lentivirus infection in OSCC cell lines. MTT, colony formation, flow cytometry, transwell, and scratch assays were performed to detect effects of PSMC2 knockdown on phenotypes of OSCC cells. Human apoptosis antibody array was used to screen potential downstream of PSMC2 in OSCC. Finally, the effects of PSMC2 knockdown on tumor growth were assessed in a tumor xenograft model using BALB/c nude mice. PSMC2 expression was significantly upregulated in OSCC tissues compared with normal tissues and correlated with poor prognosis. PSMC2 knockdown significantly suppressed cell proliferation, migration, but promoted apoptosis of OSCC cells. Additionally, we confirmed that PSMC2 knockdown can increase the expression of pro-apoptotic proteins. Furthermore, we found that PSMC2 knockdown downregulated expression of p100, p-Akt, CDK6, and upregulated of MAPK9. Xenograft experiments revealed that PSMC2 knockdown can suppress OSCC tumor growth and promote apoptosis. This study demonstrated that PSMC2 plays a critical role in OSCC progression through affecting pro-apoptotic protein expression and apoptosis pathways. It indicated that targeting PSMC2 might be a promising strategy for OSCC treatment.


Assuntos
Carcinoma de Células Escamosas , Neoplasias de Cabeça e Pescoço , Neoplasias Bucais , ATPases Associadas a Diversas Atividades Celulares/genética , Animais , Apoptose/genética , Carcinoma de Células Escamosas/patologia , Linhagem Celular Tumoral , Movimento Celular/genética , Proliferação de Células/genética , Regulação Neoplásica da Expressão Gênica , Humanos , Camundongos , Camundongos Nus , Neoplasias Bucais/patologia , Fosfatidilinositol 3-Quinases/metabolismo , Complexo de Endopeptidases do Proteassoma/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Carcinoma de Células Escamosas de Cabeça e Pescoço/genética
10.
Materials (Basel) ; 15(3)2022 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-35161184

RESUMO

In order to improve the energy dissipation capacity and to reduce the residual deformation of civil structures simultaneously, this paper puts forwards an innovative self-centering shape memory alloy (SMA) brace that is based on the design concepts of SMA's superelasticity and low friction slip. Seven self-centering SMA brace specimens were tested under cyclic loading, and the hysteresis curves, bond curves, secant stiffness, energy dissipation coefficient, equivalent damping coefficient, and the self-centering capacity ratio of these specimens were investigated, allowing us to provide an evaluation of the effects of the loading rate and initial strain on the seismic performance. The test results show that the self-centering SMA braces have an excellent energy dissipation capacity, bearing capacity, and self-centering capacity, while the steel plates remain elastic, and the SMA in the specimens that are always under tension are able to return to the initial state. The hysteresis curves of all of the specimens are idealized as a flag shape with low residual deformation, and the self-centering capacity ratio reached 89.38%. In addition, both the loading rate and the initial strain were shown to have a great influence on the seismic performance of the self-centering SMA brace. The improved numerical models combined with the Graesser model and Bouc-Wen model in MATLAB were used to simulate the seismic performance of the proposed braces with different loading rates and initial strains, and the numerical results are consistent with the test results under the same conditions, meaning that they can accurately predict the seismic performance of the self-centering SMA brace proposed here.

11.
Front Oncol ; 12: 877799, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35692763

RESUMO

Objective: The traditional lateral arm free flap (tLAFF) has the disadvantages of short vascular pedicle, small vascular diameter, and non-perforator flap. We used a new method to prepare modified LAFF (mLAFF) and evaluate its application value in the repair of oral and maxillofacial soft tissue defects. Methods: The anatomical features of the flap were recorded and compared between the tLAFF group and the mLAFF group. All the flaps in the modified group were perforator flaps. Statistical analysis was performed on the data using ANOVA on SPSS 22.0 statistical software package. Results: Forty-five mLAFFs were prepared as eccentric design rotation repair perforated flap, or multi-lobed or chimeric perforator flaps. Compared with the tLAFF, the vascular pedicle length of the mLAFF was increased, and the outer diameter of the anastomosis was thickened. The damage to the donor site was less. The difference was statistically significant. Conclusion: The mLAFF can effectively lengthen the vascular pedicle length and increase the anastomosis diameter. Perforator LAFFs in the repair of oral and maxillofacial defects have good application value.

12.
J Comput Chem ; 32(7): 1298-302, 2011 May.
Artigo em Inglês | MEDLINE | ID: mdl-21425287

RESUMO

First-principles calculations of undoped HfO(2) and cobalt-doped HfO(2) have been carried out to study the magnetic properties of the dielectric material. In contrast to previous reports, it was found that the native defects in HfO(2) could not induce strong ferromagnetism. However, the cobalt substituting hafnium is the most stable defect under oxidation condition, and the ferromagnetic (FM) coupling between the cobalt substitutions is favorable in various configurations. We found that the FM coupling is mediated by the threefold-coordinated oxygen atoms in monoclinic HfO(2) and could be further enhanced in electron-rich condition.


Assuntos
Cobalto/química , Háfnio/química , Magnetismo , Óxidos/química , Teoria Quântica , Termodinâmica
13.
Dis Markers ; 2021: 2821673, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34745386

RESUMO

To elucidate the mechanism of how the liver participates in PM2.5-caused insulin resistance. A novel Wistar rat model was developed in this study by instilling a suspension of lyophilized PM2.5 sample (2.5 mg/kg, 5 mg/kg, or 10 mg/kg) collected from the atmosphere. Systemic insulin resistance indicators, including serum fasting blood glucose (FBG), fasting insulin (FINS), Homeostatic Model Assessment for Insulin Resistance (HOMA-IR), and hemoglobin A1 (HbA1), were upregulated by the PM2.5 instillation. The area under the curve (AUCglu) calculated by intraperitoneal glucose tolerance testing (IPGTT) was also significantly greater in the PM2.5 instillation groups. Additionally, PM2.5 instillation was found to cause liver damage and inflammation. The serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin (TBIL), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were significantly elevated by PM2.5 instillation. PM2.5 also triggered IL-6 and TNF-α transcription but inhibited mRNA synthesis and suppressed signaling activation of the insulin-phosphoinositide 3-kinase- (PI3K-) Akt-glucose transporter 2 (GLUT2) pathway in the rat liver by reducing the ratio of phosphorylated Akt to phosphorylated insulin receptor substrate 1 (IRS-1). Thus, PM2.5-induced inflammation activation and insulin signaling inhibition in the rat liver contribute to the development of systemic insulin resistance.


Assuntos
Resistência à Insulina , Fígado/metabolismo , Material Particulado/toxicidade , Transdução de Sinais , Alanina Transaminase/sangue , Animais , Aspartato Aminotransferases/sangue , Bilirrubina/sangue , Glicemia/metabolismo , Transportador de Glucose Tipo 2/metabolismo , Hemoglobinas/metabolismo , Insulina/sangue , Interleucina-6/sangue , Fígado/efeitos dos fármacos , Masculino , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Ratos , Ratos Wistar , Fator de Necrose Tumoral alfa/sangue
14.
ACS Appl Mater Interfaces ; 13(35): 42074-42093, 2021 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-34428889

RESUMO

MXene sheets, as new 2D nanomaterials, have been used in many advanced applications due to their superior thin-layered architecture, as well as their capability to be employed as novel nanocontainers for advanced applications. In this research, intercalated Ti3C2 MXene sheets were synthesized through an etching method, and then they were modified with 3-aminopropyltriethoxysilane (APTES). Cerium cations (Ce3+) as an eco-friendly corrosion inhibitor were encapsulated within Ti3C2 MXene sheets to fabricate novel self-healing epoxy nanocomposite coatings. The corrosion protection performance (CPP) of Ce3+-doped Ti3C2 MXene nanosheets (Ti3C2 MXene-Ce3+) in a 3.5 wt % sodium chloride (NaCl) solution was studied on bare mild steel substrates using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The self-healing CPP of epoxy coatings loaded with 1 wt % undoped and doped Ti3C2 MXene was evaluated using EIS, salt spray, and field emission scanning electron microscopy (FE-SEM) techniques. The introduction of Ti3C2 MXene-Ce3+ into the corrosive solution and artificially scribed epoxy coating enhanced the total impedance from 717 to 6596 Ω cm2 and 8876 to 32092 Ω cm2, respectively, after 24 h of immersion compared to the control samples.

15.
Artigo em Chinês | MEDLINE | ID: mdl-33254312

RESUMO

Objective:To analyze the current status of newborn deafness gene screening from 2016 to 2017 in multiple regions of China, and to provide a reference for further promotion and application. Method:The "newborn deafness gene screening questionnaire" was sent to 41 institutions in eastern, central and western China after expert demonstration. The survey content included status of genetic screening, screening methods, the number of screenings, and the status of positive detections from January 1st, 2016 to December 31th, 2017. Each institution returned the questionnaire, the investigator conducted data verification and quality sampling. Finally, we performed analysis of screening methods and the positive detection rate of each gene on questionnaires with complete data. Result:Forty-one questionnaires were sent out and 41 were returned, the questionnaire return rate was 100%, in which 12 questionnaires were complete. Of the 41 institutions, 15 carried newborn deafness gene screening, with a rate of 36.59%(15/41). The highest rate was in the east(72.22%, 13/18), and the differences among the regions were statistically significant. As for the screening methods, among 12 questionnaires with complete data, 9 variants in 4 genes and 20 variants in 4 genes accounted for the highest proportion, both with the rate of 33.33%(4/12), followed by 15 variants in 4 genes(25%, 3/12) and 5 variants in 3 genes(8.34%, 1/12). A total of 340, 521 neonates were included in the study, and 17, 036 were positive for screening, with a positive rate of 5.00%. Among them, the single heterozygous mutation rate of GJB2 gene was 2.43%(8269/340, 521), the biallele mutation rate was 0.02%(56/340, 521),the single heterozygous mutation rate of SLC26A4 gene was 1.99%(6771/340, 521), the biallele mutation rate was 0.01%(39/340, 521),the single heterozygous mutation rate of GJB3 gene was 0.33%(1140/340, 521), the mitochondrial 12SrRNA gene mutation rate was 0.22%(746/340, 521) and the double-gene heterozygous mutation rate was 0.004%(15/340, 521). Conclusion:From 2016 to 2017, the newborn deafness gene screening is more extensive in the eastern region of China than in the central and western regions. In institutions that have carried out deafness gene screening, 9 variants in 4 genes and 20 variants in 4 genes are widely used; the GJB2 gene and SLC26A4 gene mutations are the most common. The results could provide references for areas where deafness gene screening is about to be performed.


Assuntos
Conexinas , Surdez , China/epidemiologia , Conexina 26 , Conexinas/genética , Análise Mutacional de DNA , Surdez/diagnóstico , Surdez/genética , Humanos , Recém-Nascido , Mutação , Transportadores de Sulfato
16.
Int J Pediatr Otorhinolaryngol ; 138: 110131, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32717628

RESUMO

OBJECTIVES: The present study aimed to determine the status of a universal newborn hearing screening (UNHS) program being conducted in parts of China, by comparing differences in the program findings between 2016 and 2017, as well as across regions in China. METHODS: This study investigated a nationally representative sample of newborns from 26 provinces, autonomous regions, and municipalities in mainland China. A ''Newborn Hearing Screening Survey'' questionnaire was sent to 43 hearing screening institutions throughout China and the data were analyzed, with appropriate quality control throughout the study process. RESULTS: Twenty-six questionnaires, covering 55.88% (19/34) of the provincial administrative regions in China were appropriately completed. The overall sampling frame comprised 238,795 (year 2016) and 229,185 (year 2017) newborns, respectively. We found differences between two years, the initial screening coverage in 2017 (96.10%) was higher than that in 2016 (94.96%); the referral rate at initial screening in 2017 (9.21%) was lower than that in 2016 (10.26%); and the rescreening rate in 2017 (73.50%) was higher than that in 2016 (68.44%). We found differences across three regions, the rescreening rate were highest in West China, the referral rate at rescreening and the referral rate to diagnostic audiological assessment diagnosis were both highest, while the hearing-loss rate was lowest, in the East China in two years. Overall, 61.54% (n = 16) reported using otoacoustic emissions (OAEs), while 38.46% (n = 10) reported using OAEs in combination with automated auditory brainstem response (AABR) tests, for the initial screening. For rescreening, most sites (n = 19, 73.08%) reported using OAEs in combination with AABR, followed by OAEs only (n = 4, 15.38%) and AABR only (n = 3, 11.54%). Of the twenty-six institutions, 57.69% (n = 15) were equipped with a digital information management system for UNHS program, East China had the highest rate of it (81.82%, 9/11). CONCLUSIONS: This study indicated that implementation of a UNHS program had essentially been achieved in many regions of China under the guidance of technical specifications for newborn hearing screening. Compared with 2016, the overall quality of the UNHS program had improved in 2017 and that in East China was better than in the Midland and West China. However, national quality control of the UNHS program is still required to enhance the quality of the program and public education needs to be emphasized to improve the rescreening and reception rate.


Assuntos
Testes Auditivos , Triagem Neonatal , China/epidemiologia , Potenciais Evocados Auditivos do Tronco Encefálico , Humanos , Recém-Nascido , Emissões Otoacústicas Espontâneas
17.
Materials (Basel) ; 11(10)2018 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-30326553

RESUMO

Ti3C2Tx MXene, a new 2D nanosheet material, is expected to be an attractive reinforcement of metal matrix composites because its surfaces are terminated with Ti and/or functional groups of ⁻OH, ⁻O, and ⁻F which improve its wettability with metals. Thus, new Ti3C2Tx/Al composites with strong interfaces and novel properties are desired. To prepare such composites, the chemical stability of Ti3C2Tx with Al at high temperatures should be investigated. This work first reports on the chemical stability of Ti3C2Tx MXene with Al in the temperature range 500⁻700 °C. Ti3C2Tx is thermally stable with Al at temperatures below 700 °C, but it reacts with Al to form Al3Ti and TiC at temperatures above 700 °C. The chemical stability and microstructure of the Ti3C2Tx/Al samples were investigated by differential scanning calorimeter, X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy.

18.
Nanoscale ; 10(33): 15545-15552, 2018 Aug 23.
Artigo em Inglês | MEDLINE | ID: mdl-30087972

RESUMO

One-dimensional (1D) nanowires (NWs) with robust half-metallicity are a rising star in spintronics. Herein, we theoretically investigate the magnetic and electronic properties of 3d transition-metal tribromide NWs, i.e. TMBr3 (TM = Sc, Ti, V, Cr, Co, and Cu). These systems represent repeated TMBr3 motifs with octahedral configuration, and are expected to be synthesized in a nanotube using an established method. Among these NWs, both VBr3 and CuBr3 NWs exhibit a ferromagnetic (FM) ground state, accompanied by sizable magnetocrystalline anisotropic energy, which is dominated by the superexchange coupling between the TM atoms. Strikingly, a half-metallic nature with a magnetic moment of 4.0µB per unit cell is predicted for the VBr3 NW. By combining with a tight-binding model, we demonstrate that the origin behind the half-metallicity is the half-filled e2 orbitals of the V atoms. The Curie temperature is evaluated to be up to 80 K using Monte Carlo simulations, which is comparable to the temperature of liquid nitrogen. We also find that the half-metallic behavior shows a favorable tolerance to the longitudinal elongation of the wire (∼10%). Additionally, a transition from FM semiconductor to half-metal can be realized in the CuBr3 NW through carrier doping. The coexistence of intrinsic high-temperature FM ordering and half-metallicity endows 1D TMBr3 NWs with great promise for spintronic and photoelectron device applications.

19.
Sci Rep ; 7(1): 6148, 2017 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-28733624

RESUMO

The polaron introduced by the oxygen vacancy (Vo) dominates many surface adsorption processes and chemical reactions on reduced oxide surfaces. Based on IR spectra and DFT calculations of NO and CO adsorption, we gave two scenarios of polaron-involved molecular adsorption on reduced TiO2(110) surfaces. For NO adsorption, the subsurface polaron electron transfers to a Ti:3d-NO:2p hybrid orbital mainly on NO, leading to the large redshifts of vibration frequencies of NO. For CO adsorption, the polaron only transfers to a Ti:3d state of the surface Ti5c cation underneath CO, and thus only a weak shift of vibration frequency of CO was observed. These scenarios are determined by the energy-level matching between the polaron state and the LUMO of adsorbed molecules, which plays a crucial role in polaron-adsorbate interaction and related catalytic reactions on reduced oxide surfaces.

20.
Sci Rep ; 7: 43442, 2017 03 06.
Artigo em Inglês | MEDLINE | ID: mdl-28262810

RESUMO

Clarifying the fundamental adsorption and diffusion process of CO2 on single crystal ZnO surfaces is critical in understanding CO2 activation and transformation over ZnO-based catalysts. By using ultrahigh vacuum-Fourier transform infrared spectroscopy (UHV-FTIRS), we observed the fine structures of CO2 vibrational bands on ZnO(100) surfaces, which are the combinations of different vibrational frequencies, originated from CO2 monomer, dimer, trimer and longer polymer chains along [0001] direction according to the density functional theory calculations. Such novel chain adsorption mode results from the relatively large attractive interaction between CO2 and Zn3c atoms in [0001] direction. Further experiments indicate that the short chains at low coverage evolve into long chains through Ostwald ripening by annealing. At higher CO2 coverage (0.7 ML), the as-grown local (2 × 1) phase of chains first evolve into an unstable local (1 × 1) phase below 150 K, and then into a stable well-defined (2 × 1) phase above 150 K.

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