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1.
Sci Rep ; 9(1): 17805, 2019 11 28.
Artigo em Inglês | MEDLINE | ID: mdl-31780767

RESUMO

Long-term, minimally perturbative brain electrophysiology requires electrodes to seamlessly integrate into surrounding tissue. In this work, we demonstrate electrodes composed of covalently functionalized graphite, decorated with various functional affinity and epitope tags, and use them to detect changes in electrical potential on the surfaces of illuminated quantum dots and near fluorescing molecules. Affinity and epitope tagging of carbon was achieved using direct attachment of biotin and solid phase peptide synthesis (SPPS) of histidine (His)- and human influenza hemagglutinin (HA)-tags. Surface modification was confirmed with Auger, Energy-Dispersive X-ray (EDX), Raman, and fluorescence spectroscopy. Photoresponse was detected with compatible binding protein-surface tag combinations, confirming desired tag and electrode functionality. These results provide a path to organic, biofunctionalized, fully molecularly-defined electrodes for neuronal applications, and to a wide range of other secondary reactions and modifications of carbon; potential uses include affinity chromatography, DNA sequencing technologies, biomolecular sensors, and surfaces and scaffolds for targeted interfaces with biological tissues.

2.
Sci Rep ; 9(1): 8246, 2019 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-31160663

RESUMO

Water is the universal solvent and plays a critical role in all known geological and biological processes. Confining water in nano-scale domains, as encountered in sedimentary rocks, in biological, and in engineered systems, leads to the deviations in water's physicochemical properties relative to those measured for the non-confined phase. In our comprehensive analysis, we demonstrate that nano-scale confinement leads to the decrease in the melting/freezing point temperature, density, and surface tension of confined water. With increasing degree of spatial confinement the population of networked water, as evidenced by alterations in the O-H stretching modes, increases. These analyses were performed on two groups of mesoporous silica materials, which allows to separate pore size effects from surface chemistry effects. The observed systematic effects of nano-scale confinement on the physical properties of water are driven by alterations to water's hydrogen-bonding network-influenced by water interactions with the silica surface - and has implications for how we understand the chemical and physical properties of liquids confined in porous materials.

3.
Sci Rep ; 8(1): 14747, 2018 10 03.
Artigo em Inglês | MEDLINE | ID: mdl-30282990

RESUMO

Carbon-based stationary phases for chromatographic separation have been commercially available since the 1980s. Porous graphitic carbon liquid chromatography columns are known to be highly resistant to aggressive mobile phases and extreme pH values of solvents and eluents, an important advantage compared to conventional silica-based alternatives. In our work, we demonstrate a new variant of carbon-based stationary phases for liquid chromatography, specifically developed for chiral separation. Mesoporous three-dimensional graphene nanosheets (3D GNS), functionalized with tetracyanoethylene oxide (TCNEO) and (S)-(+)-2-pyrrolidinemethanol, demonstrate pharmaceutical-grade chiral separation of model ibuprofen and thalidomide racemic mixtures when used as Chiral Stationary Phases (CSPs), with performance parameters comparable to currently commercially available CSPs. Simple covalent attachment of functionalization groups to the surface of mesoporous three-dimensional graphene nanosheets makes these carbon-based CSPs chemically stable and up to an order of magnitude less expensive than standard silica-based analogues.


Assuntos
Cromatografia Líquida de Alta Pressão/instrumentação , Grafite/química , Ibuprofeno/isolamento & purificação , Nanoestruturas/química , Talidomida/isolamento & purificação , Adsorção , Cromatografia Líquida de Alta Pressão/métodos , Etilenos/química , Humanos , Nitrilas/química , Porosidade , Pirrolidinas/química , Soluções , Estereoisomerismo
4.
Nanotechnology ; 28(19): 195603, 2017 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-28358720

RESUMO

Thermal reduction of erbium nitrate and S-doped reduced graphene oxide (rGO) mixture resulted in the formation of small (∼3-18 nm sized) Er2O3-Er2SO2 nanoparticles with a high degree of surface coverage on the reduced GO support. The morphology, structure, and the chemical composition of the synthesized nanoparticles have been studied by scanning and transmission electron microscopy, x-ray photoelectron spectroscopy, x-ray diffraction, and by optical spectroscopies. The rGO-supported Er2O3-Er2SO2 nanoparticles (Er2O3-Er2SO2/rGO) demonstrate sufficiently strong light emission (luminescence and upconversion) in the visible and near-infrared range via intra-4f Er3+ optical transitions. The reported synthetic approach demonstrates a novel method for synthesizing Er-containing nanoparticles for sensor applications.

5.
J Nanosci Nanotechnol ; 15(7): 4883-6, 2015 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-26373051

RESUMO

Simultaneous chemical vapor deposition (CVD) of graphene and "in-situ" phosphorous or boron doping of graphene was accomplished using Triphenylphosphine (TPP) and 4-Methoxyphenylboronic acid (4-MPBA). The TPP and 4-MPBA molecules were sublimated and supplied along with CH4 molecules during graphene growth at atmospheric pressure. The grown graphene samples were characterized using Raman spectroscopy. Phosphorous and boron presence in phosphorous and boron doped graphene was confirmed with Auger electron spectroscopy. The possibility of obtaining phosphorous and boron doped graphene using solid-source molecule precursors via CVD can lead to an easy and rapid production of modified large area graphene.


Assuntos
Boro/química , Grafite/química , Compostos Organofosforados/química , Fósforo/química
6.
Carbon N Y ; 81: 216-222, 2015 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-25484371

RESUMO

The tetracyanoethylene oxide (TCNEO) functionalization of chemical vapor deposition grown large area graphene and graphite was performed using reaction of TCNEO with carbon surface in chlorobenzene. The successful functionalization has been confirmed by Raman and Auger spectroscopy, and by numerical modeling of the structure and vibrational modes of TCNEO-functionalized graphene. Raman spectra of TCNEO-functionalized graphene and graphite show several groups of lines corresponding to vibrations of attached carbonyl ylide. One of key signatures of TCNEO attachment is the high intensity Raman band at ~1450 cm-1, which represents the C-C=C in plane vibrations in functionalization-distorted graphene. Raman spectra indicate the existence of central (pristine) attachment of TCNEO to graphene surface.

7.
Carbon N Y ; 54: 192-200, 2013 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-23505324

RESUMO

The benzyne functionalization of chemical vapor deposition grown large area graphene and graphite was performed using a mixture of o-trimethylsilylphenyl triflate and cesium fluoride that react with the carbon surface. The reaction requires at least 2 days of treatment before the appearance of Raman and energy-dispersive X-ray spectral signatures that verify modification. Raman spectra of modified graphene and graphite show a rich structure of lines corresponding to C=C-C, C-H, and low frequency modes of surface-attached benzyne rings.

8.
ACS Nano ; 4(7): 3831-8, 2010 Jul 27.
Artigo em Inglês | MEDLINE | ID: mdl-20536187

RESUMO

Near-field scanning microwave microscopy is employed for quantitative imaging at 4 GHz of the local impedance for monolayer and few-layer graphene. The microwave response of graphene is found to be thickness dependent and determined by the local sheet resistance of the graphene flake. Calibration of the measurement system and knowledge of the probe geometry allows evaluation of the AC impedance for monolayer and few-layer graphene, which is found to be predominantly active. The use of localized evanescent electromagnetic field in our experiment provides a promising tool for investigations of plasma waves in graphene with wave numbers determined by the spatial spectrum of the near-field. By using near-field microwave microscopy one can perform simultaneous imaging of location, geometry, thickness, and distribution of electrical properties of graphene without a need for device fabrication.

9.
Nano Lett ; 7(4): 960-4, 2007 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-17385934

RESUMO

Three-terminal devices with conduction channels formed by quasi-metallic carbon nanotubes (CNTs) are shown to operate as nanotube-based field-effect transistors under strong magnetic fields. The off-state conductance of the devices varies exponentially with the magnetic flux intensity. We extract the quasi-metallic CNT chirality as well as the characteristics of the Schottky barriers formed at the metal-nanotube contacts from the temperature-dependent magnetoconductance measurements.


Assuntos
Campos Eletromagnéticos , Nanotecnologia/instrumentação , Nanotecnologia/métodos , Nanotubos de Carbono/química , Nanotubos de Carbono/efeitos da radiação , Transistores Eletrônicos , Condutividade Elétrica , Teste de Materiais
10.
Opt Lett ; 31(7): 969-71, 2006 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-16599227

RESUMO

We have analyzed the efficiency of coherent scattering of infrared radiation in molecular gases for the production of intense, short terahertz (THz) pulses by using stimulated Raman adiabatic passage for the preparation of coherence. We show that coherently driven molecular media potentially yield strong, controllable, short pulses of THz radiation. The pulses have energies ranging from several nanojoules to microjoules and time durations from several femtoseconds to nanoseconds at room temperature.

11.
Proc Natl Acad Sci U S A ; 102(42): 14976-81, 2005 Oct 18.
Artigo em Inglês | MEDLINE | ID: mdl-16217021

RESUMO

We use time-resolved coherent Raman spectroscopy to obtain molecule-specific signals from dipicolinic acid (DPA), which is a marker molecule for bacterial spores. We use femtosecond laser pulses in both visible and UV spectral regions and compare experimental results with theoretical predictions. By exciting vibrational coherence on more than one mode simultaneously, we observe a quantum beat signal that can be used to extract the parameters of molecular motion in DPA. The signal is enhanced when an UV probe pulse is used, because its frequency is near-resonant to the first excited electronic state of the molecule. The capability for unambiguous identification of DPA molecules will lead to a technique for real-time detection of spores.


Assuntos
Inibidores Enzimáticos/química , Ácidos Picolínicos/análise , Análise Espectral Raman/métodos , Esporos Bacterianos/química , Biomarcadores , Matemática , Análise Espectral Raman/instrumentação
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