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1.
Dalton Trans ; 2020 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-32412040

RESUMO

Herein we report the synthesis of novel 0D-nanocarbon-based silicon-containing ceramic composites by a facile salt-free synthesis method followed by polymer-to-ceramic transformation. 0D-nanocarbon-silica composites were synthesized via a one-pot sol-gel process using tetramethyl orthosilicate (TMOS) and functionalized nanodiamonds and converted subsequently via pyrolysis under an argon atmosphere into nanodiamond/silica nanocomposites. The thermal conversion of the nanodiamond phase to a multilayer fullerene phase was carefully investigated by integral and local characterization methods such as vibrational spectroscopy, X-ray diffraction, BET, SEM and HRTEM. The incorporation of nanodiamonds in a silica matrix enhances the crystallization temperature of the silica phase, as α-cristobalite, to 1500 °C, while their full graphitization is shifted to T > 1700 °C under an argon atmosphere. The thermal decomposition of the nanodiamond/silica composites leads to the formation of materials with a high specific surface area (up to 562 m2 g-1) and a mesoporous structure. No carbothermal reaction of composing phases was identified. The results obtained in the present study allow for designing advanced and highly-defined mesoporous 0D-nanocarbon-containing composites with tailored structural features and multifunctional property profiles.

2.
Angew Chem Int Ed Engl ; 59(14): 5756-5764, 2020 Mar 27.
Artigo em Inglês | MEDLINE | ID: mdl-31860759

RESUMO

Magnetic hysteresis is demonstrated for monolayers of the single-molecule magnet (SMM) Dy2 ScN@C80 deposited on Au(111), Ag(100), and MgO|Ag(100) surfaces by vacuum sublimation. The topography and electronic structure of Dy2 ScN@C80 adsorbed on Au(111) were studied by STM. X-ray magnetic CD studies show that the Dy2 ScN@C80 monolayers exhibit similarly broad magnetic hysteresis independent on the substrate used, but the orientation of the Dy2 ScN cluster depends strongly on the surface. DFT calculations show that the extent of the electronic interaction of the fullerene molecules with the surface is increasing dramatically from MgO to Au(111) and Ag(100). However, the charge redistribution at the fullerene-surface interface is fully absorbed by the carbon cage, leaving the state of the endohedral cluster intact. This Faraday cage effect of the fullerene preserves the magnetic bistability of fullerene-SMMs on conducting substrates and facilitates their application in molecular spintronics.

3.
Sensors (Basel) ; 19(23)2019 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-31757112

RESUMO

Understanding the mode of operation of gas sensors is of great scientific and economic interest. A knowledge-based approach requires the development and application of spectroscopic tools to monitor the relevant surface and bulk processes under working conditions (operando approach). In this review we trace the development of vibrational Raman spectroscopy applied to metal-oxide gas sensors, starting from initial applications to very recent operando spectroscopic approaches. We highlight the potential of Raman spectroscopy for molecular-level characterization of metal-oxide gas sensors to reveal important mechanistic information, as well as its versatility regarding the design of in situ/operando cells and the combination with other techniques. We conclude with an outlook on potential future developments.

4.
Small ; 15(41): e1902710, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31448574

RESUMO

Functionalized ordered mesoporous silica materials are commonly investigated for applications such as drug release, sensing, and separation processes. Although, various homopolymer functionalized responsive mesopores are reported, little focus has been put on copolymers in mesopores. Mesoporous silica films are functionalized with responsive and orthogonally charged block-co-oligomers. Responsive 2-dimethylamino)ethyl methacrylate)-block-2-(methacryloyloxy)ethyl phosphate (DMAEMA-b-MEP) block-co-oligomers are introduced into mesoporous films using controlled photoiniferter initiated polymerization. This approach allows a very flexible charge composition design. The obtained block-co-oligomer functionalized mesopores show a complex gating behavior indicating a strong interplay between the different blocks emphasizing the strong influence of charge distribution inside mesopores on ionic pore accessibility. For example, in contrast to mesopores functionalized with zwitterionic polymers, DMAEMA-b-MEP block-co-oligomer functionalized mesopores, containing two oppositely charged blocks, do not show bipolar ion exclusion, demonstrating the influence of the chain architecture on mesopore accessibility. Furthermore, ligand binding-based selective gating is strongly influenced by this chain architecture as demonstrated by an expansion of pore accessibility states for block-co-oligomer functionalized mesopores as compared to the individual polyelectrolyte functionalization for calcium induced gating.

5.
Angew Chem Int Ed Engl ; 58(42): 15057-15061, 2019 Oct 14.
Artigo em Inglês | MEDLINE | ID: mdl-31448864

RESUMO

SnO2 is the most widely used metal oxide gas-sensing material but a detailed understanding of its functioning is still lacking despite its relevance for applications. To gain new mechanistic insight into SnO2 gas sensors under working conditions, we have developed an operando approach based on combined UV/Vis, Raman, and FTIR spectroscopy, allowing us for the first time to relate the sensor response to the concentration of oxygen vacancies in the metal oxide, the nature of the adsorbates, and the gas-phase composition. We demonstrate with the example of ethanol gas sensing that the sensor resistance is directly correlated with the number of surface oxygen vacancies and the presence of surface species, in particular, acetate and hydroxy groups. Our operando results enable an assessment of mechanistic models proposed in the literature to explain gas sensor operation. Owing to their fundamental nature, our findings are of direct relevance also for other metal oxide gas sensors.

6.
ACS Sens ; 4(6): 1497-1501, 2019 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-31117364

RESUMO

Metal-oxide semiconductors are of great interest for gas-sensing applications. We provide new insights into the mode of operation of ceria-based gas sensors during ethanol gas sensing using combined operando Raman-gas-phase FTIR spectroscopy. Visible Raman spectroscopy is employed to monitor the presence of oxygen vacancies in ceria via F2g mode softening, while simultaneously recorded FTIR spectra capture the gas-phase composition. Such an experimental approach allowing the direct observation of oxygen vacancies in metal-oxide gas sensors has not been reported in the literature. By systematically varying the gas atmosphere and temperature, we can relate the sensor response to the spectroscopic signals, enabling us to obtain new fundamental insight into the functioning of metal-oxide semiconductor gas sensors, as well as their differences from heterogeneous catalysts.


Assuntos
Cério/química , Etanol/análise , Gases/análise , Oxigênio/química , Ouro/química , Espectroscopia de Infravermelho com Transformada de Fourier , Análise Espectral Raman
7.
J Phys Chem Lett ; 9(22): 6593-6598, 2018 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-30373369

RESUMO

Ceria is widely used in heterogeneous catalysis owing to its redox properties. Engineering the shape of ceria particles offers a powerful tool to develop materials with enhanced catalytic properties. In this study, we provide evidence for the shape-dependent dioxygen adsorption and activation of ceria nanoparticles with (111) and (100) facets by in situ Raman spectroscopy and relate these properties to unique adsorption sites employing density functional theory. Temperature- and gas-phase-dependent experiments demonstrate facilitated formation of peroxide, superoxide, and weakly bound dioxygen species on the (100) facets as rationalized by calculated vibrational frequencies of O22-, O2-, and O2 species on CeO2- x(100) surfaces. Our results show that localization of the excess charge, driving the Ce4+ → Ce3+ reduction, significantly affects the stretching vibrations. Our approach provides a powerful basis for future developments of ceria-based catalysts by bridging the materials gap between idealized and real catalytic systems.

8.
Phys Rev Lett ; 120(11): 117204, 2018 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-29601734

RESUMO

The honeycomb Kitaev-Heisenberg model is a source of a quantum spin liquid with Majorana fermions and gauge flux excitations as fractional quasiparticles. Here we unveil the highly unusual low-temperature heat conductivity κ of α-RuCl_{3}, a prime candidate for realizing such physics: beyond a magnetic field of B_{c}≈7.5 T, κ increases by about one order of magnitude, both for in-plane as well as out-of-plane transport. This clarifies the unusual magnetic field dependence unambiguously to be the result of severe scattering of phonons off putative Kitaev-Heisenberg excitations in combination with a drastic field-induced change of the magnetic excitation spectrum. In particular, an unexpected, large energy gap arises, which increases linearly with the magnetic field, reaching remarkable ℏω_{0}/k_{B}≈50 K at 18 T.

10.
Beilstein J Nanotechnol ; 8: 1127-1134, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28685113

RESUMO

We performed a study on the fundamental adsorption characteristics of Er3N@C80 deposited on W(110) and Au(111) via room temperature scanning tunneling microscopy and spectroscopy. Adsorbed on W(110), a comparatively strong bond to the endohedral fullerenes inhibited the formation of ordered monolayer islands. In contrast, the Au(111)-surface provides a sufficiently high mobility for the molecules to arrange in monolayer islands after annealing. Interestingly, the fullerenes modify the herringbone reconstruction indicating that the molecule-substrate interaction is of considerable extent. Investigations concerning the electronic structure of Er3N@C80/Au(111) reveals spatial variations dependent on the termination of the Au(111) at the interface.

11.
Langmuir ; 32(18): 4464-71, 2016 05 10.
Artigo em Inglês | MEDLINE | ID: mdl-27093097

RESUMO

Molecular anchoring and electronic properties of macrocyclic complexes fixed on gold surfaces have been investigated mainly by using scanning tunnelling microscopy (STM) and complemented with X-ray photoelectron spectroscopy (XPS). Exchange-coupled macrocyclic complexes [Ni2L(Hmba)](+) were deposited via 4-mercaptobenzoate ligands on the surface of a Au(111) single crystal from a mM solution of the perchlorate salt [Ni2L(Hmba)]ClO4 in dichloromethane. The combined results from STM and XPS show the formation of large monolayers anchored via Au-S bonds with a height of about 1.5 nm. Two apparent granular structures are visible: one related to the dinickel molecular complexes (cationic structures) and a second one related to the counterions ClO4(-) which stabilize the monolayer. No type of short and long-range order is observed. STM tip-interaction with the monolayer reveals higher degradation after 8 h of measurement. Spectroscopy measurements suggest a gap of about 2.5 eV between HOMO and LUMO of the cationic structures and smaller gap in the areas related to the anionic structures.

12.
Front Neurol ; 6: 211, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26528235

RESUMO

AIM: To describe structural covariance networks of gray matter volume (GMV) change in 28 patients with first-ever stroke to the primary sensorimotor cortices, and to investigate their relationship to hand function recovery and local GMV change. METHODS: Tensor-based morphometry maps derived from high-resolution structural images were subject to principal component analyses to identify the networks. We calculated correlations between network expression and local GMV change, sensorimotor hand function and lesion volume. To verify which of the structural covariance networks of GMV change have a significant relationship to hand function, we performed an additional multivariate regression approach. RESULTS: Expression of the second network, explaining 9.1% of variance, correlated with GMV increase in the medio-dorsal (md) thalamus and hand motor skill. Patients with positive expression coefficients were distinguished by significantly higher GMV increase of this structure during stroke recovery. Significant nodes of this network were located in md thalamus, dorsolateral prefrontal cortex, and higher order sensorimotor cortices. Parameter of hand function had a unique relationship to the network and depended on an interaction between network expression and lesion volume. Inversely, network expression is limited in patients with large lesion volumes. CONCLUSION: Chronic phase of sensorimotor cortical stroke has been characterized by a large scale co-varying structural network in the ipsilesional hemisphere associated specifically with sensorimotor hand skill. Its expression is related to GMV increase of md thalamus, one constituent of the network, and correlated with the cortico-striato-thalamic loop involved in control of motor execution and higher order sensorimotor cortices. A close relation between expression of this network with degree of recovery might indicate reduced compensatory resources in the impaired subgroup.

13.
Angew Chem Int Ed Engl ; 54(50): 15014-21, 2015 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-26538495

RESUMO

Controlled structuring of surfaces is interesting for a wide variety of areas, including microelectronic device fabrication, optical devices, bio(sensing), (electro-, photo)catalysis, batteries, solar cells, fuel cells, and sorption. A unique feature of atomic layer deposition (ALD) is the possibility to form conformal uniform coatings on arbitrarily shaped materials with controlled atomic-scale thickness. In this Minireview, we discuss the potential of ALD for the nanoscale structuring of surfaces, highlighting its versatile application to structuring both planar substrates and powder materials. Recent progress in the application of ALD to porous substrates has even made the nanoscale structuring of high-surface-area materials now feasible, thereby enabling novel applications, such as those in the fields of catalysis and alternative energy.

14.
Anasthesiol Intensivmed Notfallmed Schmerzther ; 50(10): 648-54; quiz 655-6, 2015 Oct.
Artigo em Alemão | MEDLINE | ID: mdl-26510110

RESUMO

Hyperbaric oxygen therapy (HBOT) is a scientifically justified and internationally established therapy, which is however not well-known thus rarely used in Germany. During a HBOT, the ambient pressure is raised while the patient breathes 100% O2, causing tissue partial oxygen pressure (ptO2) to increase distinctly. Through that, various pressure- and O2-associated processes are initiated. Herein 3 case studies are described that illustrate the mechanism of action and the range of applications of HBOT.


Assuntos
Doença da Descompressão/terapia , Mergulho/lesões , Oxigenação Hiperbárica/instrumentação , Medicina Esportiva/instrumentação , Doença da Descompressão/diagnóstico , Desenho de Equipamento , Análise de Falha de Equipamento , Feminino , Humanos , Oxigenação Hiperbárica/métodos , Masculino , Pessoa de Meia-Idade , Avaliação da Tecnologia Biomédica , Resultado do Tratamento , Adulto Jovem
15.
Nanotechnology ; 26(33): 335301, 2015 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-26225468

RESUMO

Low-temperature atomic layer deposition (ALD) of TiO2, SiO2, and Al2O3 was applied to modify the surface and to tailor the diameter of nanochannels in etched ion-track polycarbonate membranes. The homogeneity, conformity, and composition of the coating inside the nanochannels are investigated for different channel diameters (18-55 nm) and film thicknesses (5-22 nm). Small angle x-ray scattering before and after ALD demonstrates conformal coating along the full channel length. X-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy provide evidence of nearly stoichiometric composition of the different coatings. By wet-chemical methods, the ALD-deposited film is released from the supporting polymer templates providing 30 µm long self-supporting nanotubes with walls as thin as 5 nm. Electrolytic ion-conductivity measurements provide proof-of-concept that combining ALD coating with ion-track nanotechnology offers promising perspectives for single-pore applications by controlled shrinking of an oversized pore to a preferred smaller diameter and fine-tuning of the chemical and physical nature of the inner channel surface.

16.
Chem Commun (Camb) ; 51(58): 11697-700, 2015 Jul 25.
Artigo em Inglês | MEDLINE | ID: mdl-26104113

RESUMO

The near-field of surface plasmons is locally confined to nanometer dimensions. Here, we use surface plasmons to initiate polymer-functionalization of mesoporous silica films allowing subsequent ionic permselectivity gating based on polymer charge. We expect this functionalization approach to open a new dimension of functional miniaturization e.g. in nanofluidics.

18.
Beilstein J Nanotechnol ; 6: 472-9, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25821688

RESUMO

Polycarbonate etched ion-track membranes with about 30 µm long and 50 nm wide cylindrical channels were conformally coated with SiO2 by atomic layer deposition (ALD). The process was performed at 50 °C to avoid thermal damage to the polymer membrane. Analysis of the coated membranes by small angle X-ray scattering (SAXS) reveals a homogeneous, conformal layer of SiO2 in the channels at a deposition rate of 1.7-1.8 Å per ALD cycle. Characterization by infrared and X-ray photoelectron spectroscopy (XPS) confirms the stoichiometric composition of the SiO2 films. Detailed XPS analysis reveals that the mechanism of SiO2 formation is based on subsurface crystal growth. By dissolving the polymer, the silica nanotubes are released from the ion-track membrane. The thickness of the tube wall is well controlled by the ALD process. Because the track-etched channels exhibited diameters in the range of nanometres and lengths in the range of micrometres, cylindrical tubes with an aspect ratio as large as 3000 have been produced.

19.
Proc Natl Acad Sci U S A ; 112(7): 2000-5, 2015 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-25646460

RESUMO

The ability of antibodies to extravasate out of blood vessels is critical for therapeutic activity, because molecular targets for most diseases are located outside of the endothelial lining. By performing detailed biodistribution studies with a novel IL9-armed cancer-specific antibody, we identified a clear correlation between N-linked glycan structures and tumor-targeting efficiencies. Site-specific glycan analysis provided a detailed view of the glycan microheterogeneity present on the IL9 portion of the recombinant protein. Nonsialylated glycan structures have a negative impact on disease-homing activity, highlighting the importance of glycosylation control and characterization during process development.


Assuntos
Anticorpos/administração & dosagem , Extravasamento de Materiais Terapêuticos e Diagnósticos , Animais , Sequência de Bases , Primers do DNA , Feminino , Glicosilação , Camundongos , Reação em Cadeia da Polimerase , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz
20.
Cancer Immunol Immunother ; 64(5): 635-44, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25722088

RESUMO

We describe the expression and in vivo characterization of an antibody-cytokine fusion protein, based on murine Interleukin-13 (IL13) and the monoclonal antibody F8, specific to the alternatively spliced extra domain A of fibronectin, a marker of neo-angiogenesis. The IL13 moiety was fused at the C-terminal extremity of the F8 antibody in diabody format. The resulting F8-IL13 immunocytokine retained the full binding properties of the parental antibody and cytokine bioactivity. The fusion protein could be expressed in mammalian cells, purified to homogeneity and showed a preferential accumulation at the tumor site. When used as single agent at doses of 200 µg, F8-IL13 exhibited a strong inhibition of tumor growth rate in two models of cancer (F9 teratocarcinoma and Wehi-164), promoting an infiltration of various types of leukocytes into the neoplastic mass. This anticancer activity could be potentiated by combination with an immunocytokine based on the F8 antibody and murine IL12, leading to complete and long-lasting tumor eradications. Mice cured from Wehi-164 sarcomas acquired a durable protective antitumor immunity, and selective depletion of immune cells revealed that the antitumor activity was mainly mediated by cluster of differentiation 4-positive T cells. This study indicates that IL13 can be efficiently delivered to the tumor neo-vasculature and that it mediates a potent anticancer activity in the two models of cancer investigated in this study. The observed mechanism of action for F8-IL13 was surprising, since immunocytokines based on other payloads (e.g., IL2, IL4, IL12 and TNF) eradicate cancer by the combined contribution of natural killer cells and cluster of differentiation 8-positive T cells.


Assuntos
Anticorpos Monoclonais/administração & dosagem , Sistemas de Liberação de Medicamentos , Fibrossarcoma/tratamento farmacológico , Interleucina-13/administração & dosagem , Proteínas Recombinantes de Fusão/administração & dosagem , Teratocarcinoma/tratamento farmacológico , Animais , Anticorpos Monoclonais/genética , Anticorpos Monoclonais Humanizados , Linfócitos T CD4-Positivos/imunologia , Células CHO , Linhagem Celular , Cricetulus , Feminino , Fibrossarcoma/imunologia , Interleucina-13/genética , Ativação Linfocitária/efeitos dos fármacos , Ativação Linfocitária/imunologia , Depleção Linfocítica , Camundongos , Camundongos Endogâmicos BALB C , Transplante de Neoplasias , Proteínas Recombinantes de Fusão/biossíntese , Proteínas Recombinantes de Fusão/genética , Teratocarcinoma/imunologia
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