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1.
J Urban Health ; 100(2): 408-417, 2023 04.
Artigo em Inglês | MEDLINE | ID: mdl-36656439

RESUMO

This study used a natural experiment of a new metro line in Hong Kong to examine trade-offs between transit-related and non-transit-related physical activity (PA) among 104 older people (aged ≥ 65 years) based on longitudinal accelerometer data that distinguished transit-related and non-transit-related PA. Difference-in-difference (DID) analysis compared PA changes between treatment and control groups. We found that new metro stations have trade-off effects between transit and non-transit PA. After opening metro stations, transit-related PA increased by 12 min per day on average, but non-transit-related PA decreased by 18 min per day. In addition, the proportion of time spent in transit-related PA increased by 6%. The results suggested that new metro stations could generate transit-related PA, but it might shift from non-transit-related PA among older people. Our findings revealed trade-off effects of public transit interventions and have significant implications for transport and healthy ageing studies.


Assuntos
Exercício Físico , Meios de Transporte , Humanos , Idoso , Hong Kong , Acelerometria
2.
Biochem Genet ; 61(4): 1351-1368, 2023 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-36586008

RESUMO

Long noncoding RNAs (lncRNAs) are known to participate in the progression of several cancers, including esophageal carcinoma (EC), a common malignancy of the digestive system. Although the role of the lncRNA-miRNA-mRNA regulatory network is crucial for the growth and progression of EC, the regulation of lncRNA BBOX1-AS1 (BBOX1 antisense RNA1) remains unclear. We performed reverse transcription-quantitative PCR (RT-qPCR) and western blotting to evaluate miR-361-3p, collagen type V alpha 1 chain (COL5A1), and BBOX1-AS1 expression levels in EC cells and tissues. The colony formation assay (CFA) and Cell Counting Kit-8 (CCK-8) were employed to identify EC cell proliferation, while western blotting was used to examine EC cell apoptosis and Bax and Bcl-2 expression levels. The effect of BBOX1-AS1 on EC proliferation was determined using an in vivo carcinogenesis assay. Correlation between COL5A1, BBOX1-AS1, and miR-361-3p was examined using the luciferase reporter system and RNA immunoprecipitation assay (RIP). Herein, we observed that BBOX1-AS1 expression levels were upregulated in EC cells and tissues. BBOX1-AS1 knockdown inhibited EC cell proliferation and conferred a pro-apoptotic effect. These results indicated a positive interaction between BBOX1-AS1 and miR-361-3p in EC and a negative association with miR-361-3p. COL5A1 was recognized as a downstream miR-361-3p target and was inversely related to miR-361-3p in EC. Therefore, BBOX1-AS1 expression suppressed cell apoptosis and promoted cell proliferation via the downregulation of miR-361-3p and upregulation of COL5A1 expression. Overall, BBOX1-AS1 facilitates EC progression via the miR-361-3p or COL5A1 axis, indicating that BBOX1-AS1 might be a potential therapeutic target for EC therapy.


Assuntos
Carcinoma , MicroRNAs , RNA Longo não Codificante , Humanos , RNA Longo não Codificante/genética , RNA Longo não Codificante/metabolismo , Linhagem Celular Tumoral , Movimento Celular/genética , MicroRNAs/genética , MicroRNAs/metabolismo , Colágeno/metabolismo , Carcinoma/genética , Proliferação de Células/genética , Regulação Neoplásica da Expressão Gênica , Colágeno Tipo V/genética , Colágeno Tipo V/metabolismo
3.
Eur Arch Otorhinolaryngol ; 280(3): 1201-1207, 2023 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-36048296

RESUMO

BACKGROUND: Pregabalin supplementation may have some potential in improving pain relief in patients with septorhinoplasty, and this meta-analysis aims to explore the impact of pregabalin supplementation on pain control for septorhinoplasty. METHODS: PubMed, EMbase, Web of science, EBSCO and Cochrane library databases were systematically searched, and we included randomized controlled trials (RCTs) assessing the effect of pregabalin supplementation on pain control for septorhinoplasty. RESULTS: Six RCTs were finally included in the meta-analysis. Overall, when compared with control intervention for septorhinoplasty, pregabalin intervention showed significantly reduced pain scores at 1 h (SMD - 1.05; 95% CI - 1.85 to - 0.24; P = 0.01), 2 h (SMD - 1.01; 95% CI - 1.83 to - 0.20; P = 0.02), 6 h (SMD - 1.00; 95% CI - 1.47 to - 0.54; P < 0.0001) and 12 h (SMD - 0.69; 95% CI - 1.35 to - 0.02; P = 0.04), as well as rescue analgesics (OR 0.17; 95% CI 0.07 to 0.44; P = 0.0002), but had no notable influence on nausea and vomiting (OR 0.67; 95% CI 0.30 to 1.46; P = 0.31), or drowsiness (OR 1.22; 95% CI 0.64 to 2.35; P = 0.54). CONCLUSIONS: Pregabalin supplementation benefits to pain control after septorhinoplasty.


Assuntos
Analgésicos , Dor Pós-Operatória , Humanos , Pregabalina/uso terapêutico , Dor Pós-Operatória/tratamento farmacológico , Dor Pós-Operatória/etiologia , Analgésicos/uso terapêutico , Manejo da Dor , Suplementos Nutricionais
4.
BMC Cancer ; 21(1): 599, 2021 May 25.
Artigo em Inglês | MEDLINE | ID: mdl-34034705

RESUMO

BACKGROUND: The potential reversibility of aberrant DNA methylation indicates an opportunity for oncotherapy. This study aimed to integrate methylation-driven genes and pretreatment prognostic factors and then construct a new individual prognostic model in hepatocellular carcinoma (HCC) patients. METHODS: The gene methylation, gene expression dataset and clinical information of HCC patients were downloaded from The Cancer Genome Atlas (TCGA) database. Methylation-driven genes were screened with a Pearson's correlation coefficient less than - 0.3 and a P value less than 0.05. Univariable and multivariable Cox regression analyses were performed to construct a risk score model and identify independent prognostic factors from the clinical parameters of HCC patients. The least absolute shrinkage and selection operator (LASSO) technique was used to construct a nomogram that might act to predict an individual's OS, and then C-index, ROC curve and calibration plot were used to test the practicability. The correlation between clinical parameters and core methylation-driven genes of HCC patients was explored with Student's t-test. RESULTS: In this study, 44 methylation-driven genes were discovered, and three prognostic signatures (LCAT, RPS6KA6, and C5orf58) were screened to construct a prognostic risk model of HCC patients. Five clinical factors, including T stage, risk score, cancer status, surgical method and new tumor events, were identified from 13 clinical parameters as pretreatment-independent prognostic factors. To avoid overfitting, LASSO analysis was used to construct a nomogram that could be used to calculate the OS in HCC patients. The C-index was superior to that from previous studies (0.75 vs 0.717, 0.676). Furthermore, LCAT was found to be correlated with T stage and new tumor events, and RPS6KA6 was found to be correlated with T stage. CONCLUSION: We identified novel therapeutic targets and constructed an individual prognostic model that can be used to guide personalized treatment in HCC patients.


Assuntos
Biomarcadores Tumorais/genética , Carcinoma Hepatocelular/genética , Neoplasias Hepáticas/genética , Nomogramas , Carcinoma Hepatocelular/diagnóstico , Carcinoma Hepatocelular/mortalidade , Metilação de DNA , Conjuntos de Dados como Assunto , Epigênese Genética , Perfilação da Expressão Gênica , Regulação Neoplásica da Expressão Gênica , Hepatectomia , Humanos , Estimativa de Kaplan-Meier , Fígado/patologia , Fígado/cirurgia , Neoplasias Hepáticas/diagnóstico , Neoplasias Hepáticas/mortalidade , Neoplasias Hepáticas/cirurgia , Estadiamento de Neoplasias , Fosfatidilcolina-Esterol O-Aciltransferase/genética , Período Pré-Operatório , Curva ROC , Proteínas Quinases S6 Ribossômicas 90-kDa/genética , Análise de Sequência de RNA , Resultado do Tratamento
5.
Nanotechnology ; 32(41)2021 Jul 22.
Artigo em Inglês | MEDLINE | ID: mdl-34198269

RESUMO

Interaction volume of beam-resist is a basis unit of beam-lithography, directly determines the critical parameters of beam-lithography. We have visualized the interaction volume at the state-of-the-art sub-10 nm scale by a spot irradiation of sub-nanometer helium ion beam into an approximately free-standing resist. The visualized interaction volume suggests helium ion beam has an excellent capability in nanofabrication. Specifically, helium ion beam-lithography is 1000 times more efficient than electron beam-lithography (EBL), owns a sub-4 nm resolution, can achieve a large pattern aspect ratio (greater than 8), and does not suffer from backscattering effect at a normal exposure dose. Furthermore, the interaction volume has been theoretically studied by considering the spatial distribution of energy deposited in the resist, and eventually lead to a model for pattern prediction and proximity effect corrections. We expect that, our approach to visualize the interaction volume may be applied to study other high resolution lithographic techniques such as x-ray lithography and EBL, and it may open new possibilities in other applications, like beam-imaging, beam-milling, and beam-modification.

6.
J Chem Phys ; 154(3): 034705, 2021 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-33499634

RESUMO

Catalysts containing isolated single atoms have attracted much interest due to their good catalytic behavior, bridging the gap between homogeneous and heterogeneous catalysts. Here, we report an efficient oxygen reduction reaction (ORR) catalyst that consists of atomically dispersed single copper sites confined by defective mixed-phased TiO2-x. This synergistic catalyst was produced by introducing Cu2+ to a metal organic framework (MOF) using the Mannich reaction, occurring between the carbonyl group in Cu(acac)2 and the amino group on the skeleton of the MOF. The embedding of single copper atoms was confirmed by atomic-resolution high-angle annular dark-field scanning transmission electron microscopy and x-ray absorption fine structure spectroscopy. Electronic structure modulation of the single copper sites coupling with oxygen vacancies was further established by electron paramagnetic resonance spectroscopy and first-principles calculations. Significantly enhanced ORR activity and stability were achieved on this special Cu single site. The promising application of this novel electrocatalyst was demonstrated in a prototype Zn-air battery. This strategy of the stabilization of single-atom active sites by optimization of the atomic and electronic structure on a mixed matrix support sheds light on the development of highly efficient electrocatalysts.

7.
J Nanobiotechnology ; 19(1): 77, 2021 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-33741008

RESUMO

BACKGROUND: Although many treatments for breast cancer are available, poor tumour targeting limits the effectiveness of most approaches. Consequently, it is difficult to achieve satisfactory results with monotherapies. The lack of accurate diagnostic and monitoring methods also limit the benefits of cancer treatment. The aim of this study was to design a nanocarrier comprising porous gold nanoshells (PGNSs) co-decorated with methoxy polyethylene glycol (mPEG) and trastuzumab (Herceptin®, HER), a therapeutic monoclonal antibody that binds specifically to human epidermal receptor-2 (HER2)-overexpressing breast cancer cells. Furthermore, a derivative of the microtubule-targeting drug maytansine (DM1) was incorporated in the PGNSs. METHODS: Prepared PGNSs were coated with mPEG, DM1 and HER via electrostatic interactions and Au-S bonds to yield DM1-mPEG/HER-PGNSs. SK-BR-3 (high HER2 expression) and MCF-7 (low HER2) breast cancer cells were treated with DM1-mPEG/HER-PGNSs, and cytotoxicity was evaluated in terms of cell viability and apoptosis. The selective uptake of the coated PGNSs by cancer cells and subsequent intracellular accumulation were studied in vitro and in vivo using inductively coupled plasma mass spectrometry and fluorescence imaging. The multimodal imaging feasibility and synergistic chemo-photothermal therapeutic efficacy of the DM1-mPEG/HER-PGNSs were investigated in breast cancer tumour-bearing mice. The molecular mechanisms associated with the anti-tumour therapeutic use of the nanoparticles were also elucidated. RESULT: The prepared DM1-mPEG/HER-PGNSs had a size of 78.6 nm and displayed excellent colloidal stability, photothermal conversion ability and redox-sensitive drug release. These DM1-mPEG/HER-PGNSs were taken up selectively by cancer cells in vitro and accumulated at tumour sites in vivo. Moreover, the DM1-mPEG/HER-PGNSs enhanced the performance of multimodal computed tomography (CT), photoacoustic (PA) and photothermal (PT) imaging and enabled chemo-thermal combination therapy. The therapeutic mechanism involved the induction of tumour cell apoptosis via the activation of tubulin, caspase-3 and the heat shock protein 70 pathway. M2 macrophage suppression and anti-metastatic functions were also observed. CONCLUSION: The prepared DM1-mPEG/HER-PGNSs enabled nanodart-like tumour targeting, visibility by CT, PA and PT imaging in vivo and powerful tumour inhibition mediated by chemo-thermal combination therapy in vivo. In summary, these unique gold nanocarriers appear to have good potential as theranostic nanoagents that can serve both as a probe for enhanced multimodal imaging and as a novel targeted anti-tumour drug delivery system to achieve precision nanomedicine for cancers.


Assuntos
Neoplasias da Mama/diagnóstico por imagem , Ouro/química , Imagem Multimodal/métodos , Nanoconchas/química , Animais , Antineoplásicos/uso terapêutico , Apoptose/efeitos dos fármacos , Neoplasias da Mama/terapia , Linhagem Celular Tumoral , Liberação Controlada de Fármacos , Redução da Medicação , Tratamento Farmacológico , Feminino , Humanos , Células MCF-7 , Macrófagos , Maitansina/farmacologia , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Oxirredução , Terapia Fototérmica , Polietilenoglicóis/química , Porosidade , Receptor ErbB-2/metabolismo
8.
Nano Lett ; 20(5): 3442-3448, 2020 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-32324412

RESUMO

Designing low-cost, high-efficiency, platinum-free electrocatalysts for the hydrogen oxidation reaction (HOR) in an alkaline electrolyte is of great importance for the development of anion exchange membrane fuel cells. Herein, we report a novel HOR catalyst, RuNi1, in which Ni is atomically dispersed on the Ru nanocrystals. To note, the as-prepared RuNi1 catalyst exhibits excellent catalytic activity and stability for HOR in alkaline media, which is superior to those of Ru-Ni bimetallic nanocrystals, pristine Ru, and commercial Pt/C catalysts. Density functional theory (DFT) calculations suggest that isolation of Ni atoms on Ru nanocrystals not only optimizes the hydrogen-binding energy but also decreases the free energy of water formation, thus leading to excellent electrocatalytic activity of RuNi1 catalyst. The results show that engineering a catalyst at an atomic level is highly effective for rational design of electrocatalysts with high performance.

9.
Nanotechnology ; 31(34): 345302, 2020 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-32375133

RESUMO

We have studied nano-patterning of a two-dimensional (2D) material with an ultrafine helium ion beam considering shape-, size- and damage-control. The study reveals that the crystalline structure plays an important role in shape-control. Instead of commonly circular-shaped nanopores, spot irradiation onto a single layer of molybdenum disulfide (MoS2) gives rise to a rhombus-shaped nanopore, which is well explained by the sub-rhombus crystalline structure of MoS2. Helium ion beams also show promising capability to precisely control size using a delivered dose. However, the size of the nanopores is not linear with the delivered dose, due to the Gaussian distributed intensity profile of the helium ion beam. The intensity profiles are further estimated by considering aperture size, those results could be taken as a significant reference for size-control. In addition, we clarify that most of the damage is a result of re-deposition, thus controlling re-deposition might be a useful way to alleviate the damage.

10.
Endocr Pract ; 26(4): 369-377, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31859554

RESUMO

Objective: Goiter occurs at high frequency in acromegaly patients. Whether normalization of insulin-like growth factor 1 (IGF-1) levels could decrease goiter and thyroid volume remains unclear. Methods: Thyroid hormone levels and ultrasound measurements were assessed in 101 acromegaly patients, compared with 108 patients with nonfunctioning pituitary adenoma (NFPA) and 55 healthy controls. Thirty-four acromegaly patients underwent repeat evaluation 1 year post-transsphenoidal surgery. The effect of IGF-1 on thyroid cell proliferation, cell cycle, and apoptosis was evaluated in vitro. Results: Acromegaly patients showed larger thyroid volume than those with NFPAs (18.32 mL vs. 9.91 mL; P<.001) and healthy controls (18.32 mL vs. 9.63 mL; P<.001). Duration of acromegaly was shown to be independently associated with thyroid volume enlargement (B = 0.259; 95% confidence interval, 0.162 to 0.357) in multivariate analysis. At follow-up, the median thyroid volume decreased from 22.74 to 17.87 mL in the cured group (n = 20; P = .003), but the number of nodular goiters showed no significant change. Serum free thyroxine levels decreased from 13.76 to 10.08 pmol/L in the cured group (P = .006) but increased from 9.28 to 12.09 pmol/L in the active group (P = .013). Change in thyroid volume was significantly correlated with IGF-1 level (r = 0.37; P = .029). In vitro, IGF-1 time- and dose-dependently promoted proliferation and secretory function of thyroid cells by enhancing cell cycle shift from the G1/S to G2/M phase and suppressing apoptosis. Conclusion: Acromegaly-associated thyroid volume increase, but not nodular goiter, could be reversed in cured acromegaly. IGF-1 time- and dose-dependently promoted the proliferation and secretory function of thyroid cells. Abbreviations: CCK-8 = Cell Counting Kit-8; fT3 = free triiodothyronine; fT4 = free thyroxine; GH = growth hormone; IGF-1 = insulin-like growth factor 1; MRI = magnetic resonance imaging; NFPA = nonfunctioning pituitary adenoma; qRT-PCR = quantitative real-time-polymerase chain reaction; TSH = thyroid-stimulating hormone.


Assuntos
Acromegalia , Bócio , Hormônio do Crescimento Humano , Humanos , Fator de Crescimento Insulin-Like I , Estudos Prospectivos
11.
Nanomedicine ; 29: 102252, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32615336

RESUMO

Targeting cisplatin to the sites of action and decreasing its side effects are still major challenges. Here, we introduced a polyglutamic acid-platinum(IV) prodrug nanoconjugates (γ-PGA-CA-Pt(IV)) constructed by polyglutamic acid and modified platinum(IV) prodrug to reserve the anti-tumor efficacy of cisplatin with decreased side effects. We describe the synthesis, physico-chemical characterization, and redox- and pH-sensitive releasing behavior of the nanoconjugate. In vitro studies revealed that, when incubated with glutathione in advance, the γ-PGA-CA-Pt(IV) nanoconjugate induced significant apoptosis in human breast carcinoma MCF-7 cells. From in vivo antitumor efficacy evaluation, the γ-PGA-CA-Pt(IV) nanoconjugate obviously improved the survival rate of tumor-bearing mice with inhibition of the tumor growth compared with cisplatin. Meanwhile, the nanoconjugates showed remarkable improved safety profile than the free cisplatin.


Assuntos
Neoplasias da Mama/tratamento farmacológico , Sistemas de Liberação de Medicamentos , Nanoconjugados/química , Pró-Fármacos/farmacologia , Animais , Neoplasias da Mama/patologia , Cisplatino/química , Cisplatino/farmacologia , Feminino , Humanos , Concentração de Íons de Hidrogênio , Células MCF-7 , Camundongos , Oxirredução , Platina/química , Platina/farmacologia , Ácido Poliglutâmico/análogos & derivados , Ácido Poliglutâmico/química , Ácido Poliglutâmico/farmacologia , Pró-Fármacos/química , Ensaios Antitumorais Modelo de Xenoenxerto
12.
J Am Chem Soc ; 141(51): 19964-19968, 2019 Dec 26.
Artigo em Inglês | MEDLINE | ID: mdl-31804817

RESUMO

The efficient electrochemical hydrogen evolution reaction (HER) plays a key role in accelerating sustainable H2 production from water electrolysis, but its large-scale applications are hindered by the high cost of the state-of-the-art Pt catalyst. In this work, submonolayer Pt was controllably deposited on an intermetallic Pd3Pb nanoplate (AL-Pt/Pd3Pb). The atomic efficiency and electronic structure of the active surface Pt layer were largely optimized, greatly enhancing the acidic HER. AL-Pt/Pd3Pb exhibits an outstanding HER activity with an overpotential of only 13.8 mV at 10 mA/cm2 and a high mass activity of 7834 A/gPd+Pt at -0.05 V, both largely surpassing those of commercial Pt/C (30 mV, 1486 A/gPt). In addition, AL-Pt/Pd3Pb shows excellent stability and robustness. Theoretical calculations show that the improved activity is mainly derived from the charge transfer from Pd3Pb to Pt, resulting in a strong electrostatic interaction that can stabilize the transition state and lower the barrier.

13.
Small ; 15(31): e1901304, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31120188

RESUMO

2D mesoporous materials fabricated via the assembly of nanoparticles (NPs) not only possess the unique properties of nanoscale building blocks but also manifest additional collective properties due to the interactions between NPs. In this work, reported is a facile and designable way to prepare free-standing 2D mesoporous gold (Au) superstructures with a honeycomb-like configuration. During the fabrication process, Au NPs with an average diameter of 5.0 nm are assembled into a superlattice film on a diethylene glycol substrate. Then, a subsequent thermal treatment at 180 °C induces NP attachment, forming the honeycomb-like ordered mesoporous Au superstructures. Each individual NP connects with three neighboring NPs in the adjacent layer to form a tetrahedron-based framework. Mesopores confined in the superstructure have a uniform size of 3.5 nm and are arranged in an ordered hexagonal array. The metallic bonding between Au NPs increases the structural stability of architected superstructures, allowing them to be easily transferred to various substrates. In addition, electron energy-loss spectroscopy experiments and 3D finite-difference time-domain simulations reveal that electric field enhancement occurs at the confined mesopores when the superstructures are excited by light, showing their potential in nano-plasmonic applications.

14.
Nanomedicine ; 16: 195-205, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30597210

RESUMO

Up until now, hollow gold nanoparticles (HGNPs) with a spherical cavity have garnered much interest as theranostic agents in cancer therapy due to their high X-ray absorption and photothermal conversion ability. Herein, we describe the design of PEGylated hollow gold nanoparticles (mPEG@HGNPs) for combined X-ray radiation and photothermal therapy in vitro and enhanced computed tomography (CT) imaging in vivo using a breast tumor model. In vitro results revealed that mPEG@HGNPs could achieve a synergistic antitumor effect when irradiated by combined X-ray radiation and 808 nm near infrared laser light. Furthermore, mPEG@HGNPs exhibited a favorable tumor targeting effect and good CT contrast enhancement in both xenografted and orthotopic breast tumor models, due to the stealth effect of PEG which increased the enhanced permeability and retention (EPR) effect. These results suggest that mPEG@HGNPs may serve as multifunctional nanocomposites for cancer combination therapy and, thus, should be further studied.


Assuntos
Ouro/química , Hipertermia Induzida/métodos , Nanopartículas Metálicas/química , Tomografia Computadorizada por Raios X/métodos , Animais , Quebras de DNA de Cadeia Dupla , Feminino , Humanos , Camundongos Endogâmicos BALB C , Nanocompostos/química , Distribuição Aleatória
15.
J Am Chem Soc ; 140(8): 2773-2776, 2018 02 28.
Artigo em Inglês | MEDLINE | ID: mdl-29432012

RESUMO

Strain engineering has been a powerful strategy to finely tune the catalytic properties of materials. We report a tensile-strained two-to-three atomic-layer Pt on intermetallic Pt3Ga (AL-Pt/Pt3Ga) as an active electrocatalyst for the methanol oxidation reaction (MOR). Atomic-resolution high-angle annular dark-field scanning transmission electron microscopy characterization showed that the AL-Pt possessed a 3.2% tensile strain along the [001] direction while having a negligible strain along the [100]/[010] direction. For MOR, this tensile-strained AL-Pt electrocatalyst showed obviously higher specific activity (7.195 mA cm-2) and mass activity (1.094 mA/µgPt) than those of its unstrained counterpart and commercial Pt/C catalysts. Density functional theory calculations demonstrated that the tensile-strained surface was more energetically favorable for MOR than the unstrained one, and the stronger binding of OH* on stretched AL-Pt enabled the easier removal of CO*.

17.
J Am Chem Soc ; 139(21): 7294-7301, 2017 05 31.
Artigo em Inglês | MEDLINE | ID: mdl-28502173

RESUMO

Improving the catalytic selectivity of Pd catalysts is of key importance for various industrial processes and remains a challenge so far. Given the unique properties of single-atom catalysts, isolating contiguous Pd atoms into a single-Pd site with another metal to form intermetallic structures is an effective way to endow Pd with high catalytic selectivity and to stabilize the single site with the intermetallic structures. Based on density functional theory modeling, we demonstrate that the (110) surface of Pm3̅m PdIn with single-atom Pd sites shows high selectivity for semihydrogenation of acetylene, whereas the (111) surface of P4/mmm Pd3In with Pd trimer sites shows low selectivity. This idea has been further validated by experimental results that intermetallic PdIn nanocrystals mainly exposing the (110) surface exhibit much higher selectivity for acetylene hydrogenation than Pd3In nanocrystals mainly exposing the (111) surface (92% vs 21% ethylene selectivity at 90 °C). This work provides insight for rational design of bimetallic metal catalysts with specific catalytic properties.

18.
J Am Chem Soc ; 139(28): 9419-9422, 2017 07 19.
Artigo em Inglês | MEDLINE | ID: mdl-28661130

RESUMO

Here we report a precise control of isolated single ruthenium site supported on nitrogen-doped porous carbon (Ru SAs/N-C) through a coordination-assisted strategy. This synthesis is based on the utilization of strong coordination between Ru3+ and the free amine groups (-NH2) at the skeleton of a metal-organic framework, which plays a critical role to access the atomically isolated dispersion of Ru sites. Without the assistance of the amino groups, the Ru precursor is prone to aggregation during the pyrolysis process, resulting in the formation of Ru clusters. The atomic dispersion of Ru on N-doped carbon can be verified by the spherical aberration correction electron microscopy and X-ray absorption fine structure measurements. Most importantly, this single Ru sites with single-mind N coordination can serve as a semihomogeneous catalyst to catalyze effectively chemoselective hydrogenation of functionalized quinolones.

19.
Angew Chem Int Ed Engl ; 56(39): 11971-11975, 2017 09 18.
Artigo em Inglês | MEDLINE | ID: mdl-28710802

RESUMO

Tuning the selectivity of metal catalysts is of paramount importance yet a great challenge. A new strategy to effectively control the selectivity of metal catalysts, by tuning the lattice strain, is reported. A certain amount of Co atoms is introduced into Ru catalysts to compress the Ru lattice, as confirmed by aberration-corrected high-resolution transmission electron microscopy (HRTEM) and X-ray absorption fine structure (XAFS) measurements. We discover that the lattice strain of Ru catalysts can greatly affect their selectivity, and Ru with 3 % lattice compression exhibits extremely high catalytic selectivity for hydrogenation of 4-nitrostyrene to 4-aminostyrene compared to pristine Ru (99 % vs. 66 %). Theoretical studies confirm that the optimized lateral compressive strain facilitates hydrogenation of the nitro group but impedes the hydrogenation of the vinyl group. This study provides a new guideline for designing metal catalysts with high selectivity.

20.
J Am Chem Soc ; 138(42): 13850-13853, 2016 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-27740759

RESUMO

We report a one-pot synthesis of atomically dispersed Ru on ultrathin Pd nanoribbons. By using synchrotron radiation photoemission spectroscopy (SRPES) and extended X-ray absorption fine structure (EXAFS) measurements in combination with aberration corrected high-resolution transmission electron microscopy (HRTEM), we show that atomically dispersed Ru with content up to 5.9% was on the surface of the ultrathin nanoribbon. Furthermore, the ultrathin Pd/Ru nanoribbons could remarkably prohibit the hydrogenolysis in chemoselective hydrogenation of C═C bonds, leading to an excellent catalytic selectivity compared with commercial Pd/C and Ru/C.

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