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1.
Phys Chem Chem Phys ; 26(17): 13327-13334, 2024 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-38639877

RESUMO

Intrinsic half-metallic nanomaterials with 100% spin polarization are highly demanded for next-generation spintronic devices. Here, by using first-principles calculations, we have designed a class of new two-dimensional (2D) p-type half-metals, MSi2N4 (M = Al, Ga, In and Tl), which show high mechanical, thermal and dynamic stabilities. MSi2N4 not only have ultrawide electronic bandgaps for spin-up channels in the range of 4.05 to 6.82 eV but also have large half-metallic gaps in the range of 0.75 to 1.47 eV, which are large enough to prevent the spin-flip transition. The calculated magnetic moment is 1 µB per cell, resulting from polarized N1-px/py orbitals. Moreover, MSi2N4 possess robust long-range ferromagnetic orderings with Curie temperatures in the range of 35-140 K, originating from the interplay of N1-M-N1 superexchange interactions. Furthermore, spin dependent electronic transport calculations reveal 100% spin polarization. Our results highlight new promising 2D ferromagnetic half-metals toward future spintronic applications.

2.
Phys Chem Chem Phys ; 26(5): 4403-4411, 2024 Jan 31.
Artigo em Inglês | MEDLINE | ID: mdl-38240016

RESUMO

Nonlinear optical (NLO) crystals based on oxides typically have wide bandgaps and large laser damage thresholds (LDTs), which are important for generating high-power and continuous terahertz radiation. Recently, a new family of NLO materials α-A2BB'O6 including Li2TiTeO6 (LTTO) with a strong second harmonic generation (SHG) efficiency of 26 × KH2PO4 (KDP) and a large LDT of 550 MW cm-2 were reported. Herein, we systematically study the electronic structures and NLO properties of α-A2BB'O6 (A = Li, Na, K; B = Ti, Zr, Hf; B' = Se, Te) to explore the relationship between the structure and SHG coefficient. First, 15 members of the A2BB'O6 family are demonstrated to be highly stable and NLO materials, excluding K2TiTeO6, K2TiSeO6 and K2ZrSeO6. Then, the electronic band structure, dipole moment and distortion of BO6/B'O6 octahedrons, SHG coefficient and terahertz absorption spectrum are calculated comprehensively with the element variation of A-site, B-site and B'-site. Finally, the magnitude of the SHG coefficient is found to be directly proportional to the value of total dipole moment and distortion, and inversely proportional to the bandgap value. Most importantly, among the A2BB'O6 materials, K2HfSeO6 shows the smallest direct bandgap of 2.99 eV, the largest SHG coefficient d33 of about 5 × LTTO and low terahertz absorbance from 0.1 to 9 THz. Our results provide new NLO crystals that may have potential application in terahertz radiation sources and other nonlinear electronics.

3.
Phys Chem Chem Phys ; 25(34): 22920-22926, 2023 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-37591826

RESUMO

Na3PS4 crystals with high ionic conductivity are promising solid-state electrolytes. Here, a novel phase of Na3PS4 (ß'-NPS) crystallizing in a cubic lattice with a space group of P4̄3m was systematically investigated using first-principles calculations. First of all, ß'-NPS is determined to be thermodynamically, dynamically and mechanically stable. The phase transition from tetragonal Na3PS4(α-NPS) to a cubic ß'-NPS system occurs at approximately 480 K, suggesting high feasibility of experimental access. Moreover, the ß'-NPS is an insulator with a large band gap of 4.05 eV and a low migration energy barrier of 0.10 eV for an interstitial Na ion. Significantly, a novel Na ion diffusion mechanism, that is, interstitial diffusion, is proposed, in contrast to traditional vacancy diffusion or kick-off diffusion as observed in most solid electrolytes. This work proposes ß'-NPS as a promising superionic conductor for sodium ion batteries and provides theoretical guidance towards designing future ideal solid-state electrolytes.

4.
Phys Chem Chem Phys ; 25(48): 32875-32882, 2023 Dec 13.
Artigo em Inglês | MEDLINE | ID: mdl-38051151

RESUMO

Although the efficient separation of electron-hole (e-h) pairs is one of the most sought-after electronic characteristics of materials, due to thermally induced atomic motion and other factors, they do not remain separated during the carrier transport process, potentially leading to rapid carrier recombination. Here, we utilized real-time time-dependent density functional theory in combination with nonadiabatic molecular dynamics (NAMD) to explore the separated dynamic transport path within Ruddlesden-Popper oxysulfide perovskite Y2Ti2O5S2 caused by the dielectric layer and phonon frequency difference. The underlying origin of the efficient overall water splitting in Y2Ti2O5S2 is systematically explored. We report the existence of the bi-directional e-h separate-path transport, in which, the electrons transport in the Ti2O5 layer and the holes diffuse in the rock-salt layer. This is in contrast to the conventional e-h separated distribution with a crowded transport channel, as observed in SrTiO3 and hybrid perovskites. Such a unique feature finally results in a long carrier lifetime of 321 ns, larger than that in the SrTiO3 perovskite (160 ns) with only one carrier transport channel. This work provides insights into the carrier transport in lead-free perovskites and yields a novel design strategy for next-generation functionalized optoelectronic devices.

5.
Nano Lett ; 22(13): 5592-5599, 2022 Jul 13.
Artigo em Inglês | MEDLINE | ID: mdl-35729076

RESUMO

The number of semiconducting MXenes with direct band gaps is extremely low; thus, it is highly desirable to broaden the MXene family beyond carbides and nitrides to expand the palette of desired chemical and physical properties. Here, we theoretically report the existence of the single-layer (SL) dititanium oxide 2H-Ti2O MOene (MXene-like 2D transition oxides), showing an Ising superconducting feature. Moreover, SL halogenated 2H- and 1T-Ti2O monolayers display tunable semiconducting features and strong light-harvesting ability. In addition, the external strains can induce Weyl fermions via quantum phase transition in 2H-Ti2OF2 and Ti2OCl2 monolayers. Specifically, 2H- and 1T-Ti2OF2 are direct semiconductors with band gaps of 0.82 and 1.18 eV, respectively. Furthermore, the carrier lifetimes of SL 2H- and 1T-Ti2OF2 are evaluated to be 0.39 and 2.8 ns, respectively. This study extends emerging phenomena in a rich family of 2D MXene-like MOene materials, which provides a novel platform for next-generation optoelectronic and photovoltaic fields.

6.
Br J Surg ; 108(9): 1126-1132, 2021 09 27.
Artigo em Inglês | MEDLINE | ID: mdl-34037206

RESUMO

BACKGROUND: This study aims to assess the learning curve of robotic distal gastrectomy (RDG) and robotic total gastrectomy (RTG) for gastric cancer. METHODS: Data on consecutive patients who underwent robotic gastrectomy for gastric cancer by five surgeons between March 2010 and August 2019 at two high-volume institutions were collected. The learning curve was determined based on the analyses of operation time and postoperative complications within 30 days. Cumulative sum analysis (CUSUM) and risk-adjusted-CUSUM (RA-CUSUM) were applied to identify the turning points (TPs). RESULTS: A total of 899 consecutive patients were included. The mean number of patients needed to overcome the learning curve for operation time of RDG and RTG were 22 and 20, respectively. The number of patients needed to overcome the learning curve for postoperative complications after RDG and RTG were 23 and 18, respectively. The surgical outcomes in the post-TP group were better than in the pre-TP group and improved as surgeons' experience increased. Also, increased case numbers in RDG promoted the RTG learning process. CONCLUSION: The present study demonstrated a substantial influence of surgical cumulative volume on improved surgical outcomes in robotic gastrectomy. Increased experience in RDG may help surgeons to achieve proficiency faster in RTG.


Assuntos
Gastrectomia/métodos , Laparoscopia/métodos , Curva de Aprendizado , Procedimentos Cirúrgicos Robóticos/métodos , Neoplasias Gástricas/cirurgia , Humanos , Duração da Cirurgia , Estudos Retrospectivos
7.
Phys Chem Chem Phys ; 23(22): 12834-12841, 2021 Jun 02.
Artigo em Inglês | MEDLINE | ID: mdl-34060551

RESUMO

In this study, three stable two-dimensional beryllium diphosphide (2D-BeP2) structures with the wrinkle and planar monolayers, namely MoS2-like 6[combining macron]m-BeP2 phase (1H-BeP2), pentagonal 4[combining macron]2m-BeP2 (Penta-BeP2) and planar mm2-BeP2 (Planar-BeP2), have been successfully predicted through the first-principles calculation combined with a global structure search method. The structural stabilities, mechanical properties, electron properties and superconductivities are also systematically investigated. Results indicated that the 2D MoS2-like 1H-BeP2 showed higher stability than the Penta- and Planar-BeP2 structures. The 1H-BeP2 structure possessed an intrinsic metallic characteristics with the bands crossing the Fermi level. Notably, the Penta-BeP2 is a typical semiconductor, and the planar-BeP2 is semi-metal with Dirac corn. Based on the calculation results of the electron properties, phonon properties and electron-phonon coupling (EPC), the layer 1H-BeP2 sheet is a phonon-mediated superconductor with a critical temperature (Tc) of about 1.32 K.

8.
Phys Chem Chem Phys ; 21(28): 15327-15338, 2019 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-31259339

RESUMO

Two-dimensional (2D) superconductors, which can be widely applied in optoelectronic and microelectronic devices, have gained renewed attention in recent years. Based on the crystal structure prediction method and first-principles calculations, we obtain four novel 2D tungsten boride structures of tetr-, hex-, and tri-W2B2 and hex-WB4 and investigate their bonding types, electronic properties, phonon dispersions and electron-phonon coupling (EPC). The results show that both tetr- and hex-W2B2 are intrinsic phonon-mediated superconductors with a superconducting transition temperature (Tc) of 7.8 and 1.5 K, respectively, while tri-W2B2 and hex-WB4 are normal metals. We demonstrate that carrier doping as well as biaxial strain can soften the low-frequency phonon modes and enhance the strength of the EPC. While the Tc of tetr-W2B2 can be increased to 15.4 K under a compressive strain of -2%, the Tc of hex-W2B2 can be enhanced to 5.9 K by a tensile strain of +4%. With the inclusion of spin-orbit couping (SOC), the value of Tc decreases by 38.5% in our systems. Furthermore, we explore the stabilities and mechanical properties of tetr- and hex-W2B2 and indicate that they may be prepared by growing on ZnS(100) and ZnS(111), respectively. Our findings provide novel 2D superconducting materials and will stimulate more efforts in this filed.

9.
Ultrason Imaging ; 41(1): 49-58, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30803409

RESUMO

This retrospective study aimed to use preoperative and contrast-enhanced ultrasound (CEUS) factors to assess and reveal risk factors of early recurrence (ER) in patients with hepatocellular carcinoma (HCC). We enrolled 141 patients with primary HCC who had undergone surgical resection. The assessment of the CEUS scan includes (a) the maximum diameter of the lesion, (b) the tumor echogenicity of gray-scale ultrasound (US), (c) the morphology of the tumor, (d) the margin of the tumor, (e) the peripheral hypoechoic halo, (f) tumor necrosis, (g) nutritional arteries shown by tumors, (h) ultrasonography for diagnosis of cirrhosis, and (i) the timer on the US screen displayed the time elapsed from the saline flush and was used to determine time to washout. According to the degree of the phase, the washout rate is divided into four grades, namely, levels 1 to 4. ER is defined as the time between resection and recurrence within 12 months after surgery. Risk factors for ER HCC were analyzed. Predictors of ER on a univariate logistic regression analysis in CEUS are size, washout rate, morphology, center necrosis, and feeding artery appearing in the tumor. Multivariate analysis results indicated that feeding artery, microvascular invasion (MVI), and washout rate were independent risk factors for ER. The relative high risk of ER for washout rate 1, 2, 3, and 4 were 29.3%, 43.2%, 53.1%, and 71.4%, respectively. The appropriateness of hepatectomy in the treatment of single lesion HCC should be carefully considered when the washout rate was 4.


Assuntos
Carcinoma Hepatocelular/diagnóstico por imagem , Meios de Contraste , Aumento da Imagem/métodos , Neoplasias Hepáticas/diagnóstico por imagem , Recidiva Local de Neoplasia/diagnóstico por imagem , Ultrassonografia/métodos , Carcinoma Hepatocelular/cirurgia , Feminino , Humanos , Fígado/diagnóstico por imagem , Fígado/cirurgia , Neoplasias Hepáticas/cirurgia , Masculino , Pessoa de Meia-Idade , Valor Preditivo dos Testes , Estudos Retrospectivos
10.
Plant J ; 90(1): 147-163, 2017 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-28103409

RESUMO

Iron (Fe)-homeostasis in the plastids is closely associated with Fe transport proteins that prevent Fe from occurring in its toxic free ionic forms. However, the number of known protein families related to Fe transport in the plastids (about five) and the function of iron in non-green plastids is limited. In the present study, we report the functional characterization of Zea mays Fe deficiency-related 4 (ZmFDR4), which was isolated from a differentially expressed clone of a cDNA library of Fe deficiency-induced maize roots. ZmFDR4 is homologous to the bacterial FliP superfamily, coexisted in both algae and terrestrial plants, and capable of restoring the normal growth of the yeast mutant fet3fet4, which possesses defective Fe uptake systems. ZmFDR4 mRNA is ubiquitous in maize and is inducible by iron deficiency in wheat. Transient expression of the 35S:ZmFDR4-eGFP fusion protein in rice protoplasts indicated that ZmFDR4 maybe localizes to the plastids envelope and thylakoid. In 35S:c-Myc-ZmFDR4 transgenic tobacco, immunohistochemistry and immunoblotting confirmed that ZmFDR4 is targeted to both the chloroplast envelope and thylakoid. Meanwhile, ultrastructure analysis indicates that ZmFDR4 promotes the density of plastids and accumulation of starch grains. Moreover, Bathophenanthroline disulfonate (BPDS) colorimetry and inductively coupled plasma mass spectrometry (ICP-MS) indicate that ZmFDR4 is related to Fe uptake by plastids and increases seed Fe content. Finally, 35S:c-Myc-ZmFDR4 transgenic tobacco show enhanced photosynthetic efficiency. Therefore, the results of the present study demonstrate that ZmFDR4 functions as an iron transporter in monocot plastids and provide insight into the process of Fe uptake by plastids.


Assuntos
Deficiências de Ferro , Ferro/metabolismo , Proteínas de Plantas/metabolismo , Plastídeos/metabolismo , Zea mays/metabolismo , Regulação da Expressão Gênica de Plantas , Folhas de Planta/genética , Folhas de Planta/metabolismo , Proteínas de Plantas/genética , Raízes de Plantas/genética , Raízes de Plantas/metabolismo , Nicotiana/genética , Nicotiana/metabolismo , Zea mays/genética
11.
Zhejiang Da Xue Xue Bao Yi Xue Ban ; 46(2): 192-197, 2017 03 25.
Artigo em Chinês | MEDLINE | ID: mdl-28752712

RESUMO

Objective: To investigate the effect of glycyrrhizinate and phospholipids (DGPL) complex on inflammatory gene expression in cell inflammation model induced by palmitic acid (PA). Methods: Huh7 cells were divided into control, PA and PA+DGPL groups. For control group, cells were treated with BSA; for PA group, cells were incubated with 0.2 mmol/L saturated fatty acid PA, PA+DGPL group was given 20 µmol/L or 100 µmol/L DGPL in addition to 0.2 µmol/L PA. After 24 h, the expression of inflammation-related genes COX-2 and iNOS and endoplasmic reticulum (ER) stress-related gene GRP78 was determined by RT PCR. Oil red staining was conducted to observe the effect of DGLP on steatosis. Results: Compared with control group, the expression of COX-2, iNOS and GRP78 in PA group was enhanced to 6.07±0.73(P<0.05), 3.18±0.91 (P<0.01) and 3.21±1.00(P<0.05), respectively. Compared to control group, the expression of COX-2,iNOS and GRP78 in 100 µmol/L DGPL group was reduced to 2.40±0.76, 1.60±0.49 and 1.17 ±0.42 (P<0.05); and 20 µmol DGPL had similar inhibition effect on COX-2 and iNOS elevation induced by PA (P<0.01, P<0.05 respectively). In addition, DGLP enhances the steatosis of Huh7 cells as demonstrated by oil red staining. Conclusion: PA can induce the up-regulated expression of inflammation associated genes COX-2, iNOS and ER stress-associated gene GRP78 in Huh7 cells. DGPL is able to protect Huh7 cells from PA induced inflammatory gene expression and the beneficial effect may be partially due to its unsaturated phospholipid component, which may improve ER stress and enhance steatosis.


Assuntos
Regulação da Expressão Gênica , Ácido Glicirrízico , Inflamação , Ácido Palmítico , Fosfolipídeos , Linhagem Celular , Chaperona BiP do Retículo Endoplasmático , Fígado Gorduroso/fisiopatologia , Regulação da Expressão Gênica/efeitos dos fármacos , Ácido Glicirrízico/farmacologia , Proteínas de Choque Térmico/genética , Humanos , Inflamação/induzido quimicamente , Fosfolipídeos/farmacologia
12.
J Phys Chem Lett ; 15(28): 7191-7198, 2024 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-38968446

RESUMO

We investigate the electronic structure and linear and nonlinear [second-harmonic generation (SHG)] spectra of the NbOCl2 monolayer, bilayer, and bulk by using a real-time first-principles approach based on many-body theory. First, the interlayer couplings between NbOCl2 layers are very weak, due to the relatively large interlayer distance, saturation of the p orbital of Cl atoms, and high degree of localization of charge density around the Nb atom for both the lowest conduction band and the highest valence band. Second, the quasiparticle gaps and exciton binding energy for the three systems show layer-dependent features and decrease with an increase in layer thickness. Most importantly, the linear and SHG spectra of the NbOCl2 monolayer, bilayer, and bulk are dominated by strong excitonic resonances and exhibit layer-independent features due to the weak interlayer couplings. Our findings demonstrate that excitonic effects should be included in studying the optical properties of not only two-dimensional materials but also layered bulk materials with weak interlayer couplings.

13.
J Phys Chem Lett ; 15(28): 7221-7227, 2024 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-38975710

RESUMO

Intentional distortions of [BX6] octahedra within perovskite structures have been recognized as a potent strategy for precise band gap adjustments and optimization of their photovoltaic properties, yet information regarding charge carrier dynamics linked to octahedral distortion under ambient conditions for chalcogenide perovskites remains limited. In this study, we utilize ab initio nonadiabatic molecular dynamics to explore the dynamics of photogenerated carriers in a representative two-dimensional Ba3Zr2S7 material in the Ruddlesden-Popper phase. The theoretical results highlight the influence of octahedral rotation on the materials' stability and carrier recombination lifetime of the system. Specifically, the octahedrally rotating P42/mnm phase exhibits a prolonged nonradiative carrier recombination lifetime attributed to the stabilized electron-phonon coupling. These findings offer valuable insights into the fundamental physical characteristics of imposed octahedral distortion and its potential for optimizing the optoelectronic performance of 2D Ruddlesden-Popper Ba-Zr-S chalcogenide materials.

14.
Photoacoustics ; 32: 100535, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-37519337

RESUMO

In photoacoustic (PA) reconstruction, spatial constraints or real-time system requirements often result to sparse PA sampling data. For sparse PA sensor data, the sparse spatial and dense temporal sampling often leads to poor signal continuity. To address the structural characteristics of sparse PA signals, a data interpolation algorithm based on extremum-guided interpolation is proposed. This algorithm is based on the continuity of the signal, and can complete the estimation of high sampling rate signals without complex mathematical calculations. PA signal data is interpolated and reconstructed, and the results are evaluated using image quality assessment methods. The simulation and experimental results show that the proposed method performs better than several typical algorithms, effectively restoring image details, suppressing the generation of artifacts and noise, and improving the quality of PA reconstruction under sparse sampling.

15.
Micromachines (Basel) ; 14(2)2023 Feb 08.
Artigo em Inglês | MEDLINE | ID: mdl-36838105

RESUMO

Bulk III-nitride materials MN (M = Al, Ga and In) and their alloys have been widely used in high-power electronic and optoelectronic devices, but stable two-dimensional (2D) III-nitride materials, except h-BN, have not been realized yet. A new kind of 2D III-nitride material M2Si2N4 (M = Al, Ga and In) is predicted by choosing Si as the appropriate passivation element. The stability, electronic and optical properties of 2D M2Si2N4 materials are studied systematically based on first-principles calculations. The results show that Al2Si2N4 and Ga2Si2N4 are found to be indirect bandgap semiconductors, while In2Si2N4 is a direct bandgap semiconductor. Moreover, Al2Si2N4 and In2Si2N4 have good absorption ability in the visible light region, while Ga2Si2N4 is an ultraviolet-light-absorbing material. Furthermore, the carrier lifetimes of Ga2Si2N4 and In2Si2N4 are as large as 157.89 and 103.99 ns, respectively. All these desirable properties of M2Si2N4 materials make them attractive for applications in electronics and photoelectronics.

16.
J Colloid Interface Sci ; 652(Pt A): 627-635, 2023 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-37586949

RESUMO

Lithium (Li)-rich ternary alloy, comprising a multi-alloy phase as the built-in three-dimensional (3D) framework and a Li metal phase as a reversible Li reservoir, is a promising high-energy-density anode for rechargeable Li metal batteries. The introduction of metal/metalloid components to the alloy can effectively regulate Li deposition and maintain the dimensional integrity of the Li anode. Herein, the lithium-copper-zinc (Li-Cu-Zn) ternary alloy, as a new type of alloy anode, is synthesized via a facile thermal melting method. The fully delithiated 3D scaffold comprised two Cu-Zn alloy phases named CuZn and CuZn5. These alloy phases exhibit higher lithiophilicity and structural stability than Li-Zn and Li-Cu alloys. Moreover, the CuZn phase is electrochemically inert, ensuring the geometric stability of the anode, while the CuZn5 phase can readily undergo alloying reaction with Li to form the LiZn phase, thereby facilitating uniform Li nucleation and deposition. The hybridized multiphase alloy structure and specific energy storage mechanism of the Cu-Zn based alloy scaffold in the ternary alloy anode facilitate dendrite-free Li deposition and prolonged cycle lifetime. The Li metal full battery based on lithium iron phosphate (LiFePO4) cathode exhibits high cycling stability with high-capacity retention of 95.4% after 1000 cycles at 1C.

17.
J Phys Chem Lett ; 14(14): 3384-3390, 2023 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-36995147

RESUMO

The lack of efficient catalysts and research on the mechanism for the methanol oxidation reaction (MOR) impedes the development of direct methanol fuel cells. In this work, based on density functional theory calculations, we systematically investigated the activity trends of electrochemical MOR on a single transition-metal atom embedded in N-coordinated graphene (M@N4C). By calculating the free energy diagrams of MOR on M@N4C, Co@N4C was screened out to be the most effective MOR catalyst with a low limiting potential of 0.41 V due to the unique charge transfers and electronic structures. Importantly, one- and two-dimensional volcano relationships in MOR on M@N4C catalysts are established based on the d-band center and the Gibbs free energy of ΔG*CH3OH and ΔG*CO, respectively. In one word, this work provides theoretical guides toward the improved activity of MOR on M@N4C and hints for the design of active and efficient MOR electrocatalysts.

18.
Nanoscale ; 16(1): 373-383, 2023 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-38063775

RESUMO

With the expansion of global energy problems and the deepening of research on oxygen reduction reaction (ORR) in alkaline media, the development of low cost and high electrocatalytic performance catalysts has become a research hotspot. In this study, a hexagonal Pd-C-MnOOH composite catalyst was prepared by using the triblock copolymer P123 as the reducing agent and protective agent, sucrose as the carbon source and self-made MnOOH as the carrier under hydrothermal conditions. When the Pd load is 20% and the C/MnOOH ratio is 1 : 1, the 20% Pd-C-MnOOH-1 : 1 catalyst obtained by the one-step method has the highest ORR activity and stability in the alkaline system. At 1600 rpm, the limiting diffusion current density and half-wave potential of the 20% Pd-C-MnOOH-1 : 1 electrocatalyst are -4.78 mA cm-2 and 0.84 V, respectively, which are better than those of the commercial 20%Pd/C catalyst. According to the Koutecky-Levich (K-L) equation and the linear fitting results, the electron transfer number of the 20%Pd-C-MnOOH-1 : 1 electrocatalyst for the oxygen reduction reaction is 3.8, which is similar to that of a 4-electron process. After 1000 cycles, the limiting diffusion current density of the 20%Pd-C-MnOOH-1 : 1 catalyst is -4.61 mA cm-2, which only decreases by 3.7%, indicating that the 20%Pd-C-MnOOH-1 : 1 catalyst has good stability. The reason for the improvement of the ORR performance of the Pd-C-MnOOH composite catalyst is the improvement of the conductivity of the carbon layer formed by original carbonization, the regular hexagonal highly active Pd particles and the synergistic catalytic effect between Pd and MnOOH. The method of introducing triblock copolymers in the synthesis of oxides and metal-oxide composite catalysts is expected to be extended to other electrocatalysis fields.

19.
J Phys Chem Lett ; 14(40): 9075-9081, 2023 Oct 12.
Artigo em Inglês | MEDLINE | ID: mdl-37788153

RESUMO

The search for lead-free perovskite materials has triggered intensive interest. Here, we study the electronic structures and optical properties of cation-deficient Ruddlesden-Popper oxysulfide perovskites Ln2Ti2O5S2 (Ln = Sc, Y, or La), with a tunable band gap of 1.45-2.1 eV and a small exciton binding energy of ∼0.1 eV, among which Y2Ti2O5S2 has been synthesized experimentally. Sc2Ti2O5S2 possesses the largest light absorbance in the visible region. We further rationalize the light absorption via the transition dipole moment and suggest potential applications of Sc2Ti2O5S2 in solar cells and Y2Ti2O5S2 and La2Ti2O5S2 in water splitting. In addition, this family exhibits small effective masses within the x-y plane and large ones along the z direction. Most importantly, electron gas-like carrier behaviors are observed within the Ti-O bond region, offering a diffusion channel for electron transport. These findings greatly advance our understanding of lead-free perovskites and offer a novel material platform for future optoelectronic devices.

20.
Artigo em Chinês | MEDLINE | ID: mdl-22404013

RESUMO

To evaluate the feasibility and accuracy of contrast-enhanced ultrasonography (CEUS) for the measurement of hemodialysis access recirculation (AR) and access flow rate (Qa), a two pump system was used to simulate access and dialyzer flow. AR and Qa under different conditions, such as reversal connection of dialysis lines and the needle orientation, were compared with each other. The value of access flow and recirculation flow were calculated based on the formulas introduced in this paper, and the correlation and consistency between true flow rate and calculated values were analyzed. The measured R correlated well with true value of flow rate (r = 0.57, P = 0.038, Qa > Qb; r = 0.95, P = 0.001, Qa < Qb). The Bland-altman test showed good agreement between the calculated value based on CEUS and true values. The CEUS can be used as a new advanced technology for AR and Qa measurement.


Assuntos
Derivação Arteriovenosa Cirúrgica , Meios de Contraste , Falência Renal Crônica/terapia , Diálise Renal , Ultrassonografia , Velocidade do Fluxo Sanguíneo , Simulação por Computador , Humanos , Falência Renal Crônica/sangue , Modelos Biológicos , Monitorização Fisiológica/instrumentação , Fluxo Sanguíneo Regional , Diálise Renal/métodos
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