A5056463710- Graphene research and applications
- Carbon Nanotubes in Composites
- Semiconductor Quantum Structures and Devices
- Quantum and electron transport phenomena
- Molecular Junctions and Nanostructures
- Mechanical and Optical Resonators
- Diamond and Carbon-based Materials Research
- Advanced biosensing and bioanalysis techniques
- Porphyrin and Phthalocyanine Chemistry
- Fullerene Chemistry and Applications
- Advanced Semiconductor Detectors and Materials
- Surface and Thin Film Phenomena
- Quantum Dots Synthesis And Properties
- Biosensors and Analytical Detection
- Silicon Nanostructures and Photoluminescence
- Graphene and Nanomaterials Applications
- 2D Materials and Applications
- Physics of Superconductivity and Magnetism
- Nanopore and Nanochannel Transport Studies
- Semiconductor materials and devices
- Advancements in Semiconductor Devices and Circuit Design
- GaN-based semiconductor devices and materials
- Semiconductor Lasers and Optical Devices
- Thermal properties of materials
- Spectroscopy and Laser Applications
Universidade Federal de Minas Gerais
2012-2024
Prefeitura Municipal de Belo Horizonte
2022
Ministério da Ciência e Tecnologia
2013
Hospital das Clínicas da Universidade Federal de Minas Gerais
2005
Massachusetts Institute of Technology
1996-1997
Universidade Estadual de Campinas (UNICAMP)
1989-1995
MIT Lincoln Laboratory
1995
Instituto de Ciencia de Materiales de Madrid
1993
Consejo Superior de Investigaciones Científicas
1993
Universidad Autónoma de Madrid
1993
The electronic structure of bilayer graphene is investigated from a resonant Raman study the ${G}^{\ensuremath{'}}$ band using different laser excitation energies. values parameters Slonczewski-Weiss-McClure model for are obtained analysis dispersive behavior features, and reveal difference effective masses electrons holes. splitting two TO phonon branches in also experimental data. Our results have implications devices.
Raman spectroscopy was used to determine the dispersion of longitudinal acoustic (LA) and in-plane transverse optic phonon branches near Dirac $K$ point monolayer graphene from analysis two second-order peaks involving LA TO phonons. We show that velocities phonons involved in double resonance process are given by ${v}_{\mathit{LA}}=7.70\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}{v}_{F}$ ${v}_{\mathit{TO}}=5.47\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}{v}_{F}$,...
By using a sample of DNA-wrapped single-wall carbon nanotubes strongly enriched in the $(6,5)$ nanotube, photoluminescence emissions observed at special excitation energy values were identified with specific mechanisms phonon-assisted excitonic absorption and recombination processes associated nanotubes, including one-phonon, two-phonon, some continuous-luminescence processes. Such detailed are not separately three-dimensional semiconducting materials. A general theoretical framework is...
We present direct experimental observation of exciton-phonon bound states in the photoluminescence excitation spectra isolated single-walled carbon nanotubes (SWNT) aqueous suspension. The from several distinct SWNTs show presence at least one sideband related to tangential modes, lying 0.2 eV above main absorption or emission peak. Both energy position and line shapes sidebands are excellent agreement with recent calculations [Phys. Rev. Lett. 94, 027402 (2005)] that predict existence...
In this work, we clarify the features of lateral damage line defects in single layer graphene. The were produced through well-controlled etching graphene using a Ga+ focused ion beam. length was obtained from both integrated intensity disorder induced Raman D band and minimum fluence. Also, characterized by polarized spectroscopy. It found that is resilient under conditions since defect peak exhibits dependence on direction lines relative to crystalline lattice also laser polarization lines....
The Raman spectrum of monolayer graphene deposited on the top a silicon oxide/silicon substrate was investigated as function temperature up to 515 K. An anomalous dependence features observed, including an important frequency upshift for G band at room temperature, after heating process. On other hand, G' is only slightly affected by thermal treatment. We discuss our experimental results in terms doping and strain effects associated with interaction presence water sample. conclude that...
The heterogeneous nature of mass-produced 2D material's nanoflakes requires analysis size and shape parameters: their distributions around the desired values are essential for production characterization. In this work, we obtain analytical expressions behaviors statistical experimentally extracted parameters obtained by liquid-phase exfoliation. collected data open can be mathematically handled to analyzed through different associations in scales, such as logarithm length/thickness (r)...
The observation of quantum-confined optical transitions in multiple δ doping GaAs, grown by molecular beam epitaxy, is reported. Doping efficiency and carrier confinement are investigated Hall photoluminescence measurements. measurement results for δ-doped samples show a dramatic enhancement concentrations compared to the uniform case. From spectra we observed that cutoff energy significantly affected spacing between dopant sheets. strong localization confined photoexcited holes layers these...
We studied confinement effects in CdTe quantum dots by means of photoluminescence excitation spectroscopy. show that changing the detection energy we can resolve spectrum different sizes inside their much broader size distribution CdTe-doped glass. The spectra obtained several well-resolved lines. There is excellent agreement between peak energies and calculations confined transitions based on a modified multiband envelope function model.
A series of nondegenerate pump-probe measurements were carried out on a DNA-wrapped single-walled carbon nanotube (SWNT) sample that is enriched with the (6,5) species. The pump pulse excites SWNTs at $\ensuremath{\sim}1.567\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$, which corresponds to an energy two $D$-band phonons above excitonic band edge SWNT. dynamics different channels exciton relaxation for SWNT analyzed in terms decay time-resolved differential transmission spectra. By systematically...
We have fabricated graphene devices on lightly doped Si substrates and show that pronounced changes in resistance versus gate voltage, R(Vg), characteristics of these at 77 K are induced by the variation charge distribution substrate with both voltage illumination. The R(Vg) dark shows remarkable as carriers underlying go through accumulation, depletion, inversion regimes. demonstrate possibility using a device an optical-latch.
In this work the authors establish use of photolithography technique by direct laser writing for fabrication devices on bilayer graphene coated with a photoresist. This is simple to use, versatile, reliable, and capable achieving good throughput. The alignment patterns flakes between different lithography steps can be performed an accuracy about 0.5 μm allowing placement electric contacts definition Hall-bar geometries in effective way. fabricated were characterized four-terminal resistance...
The association of organic molecules with two-dimensional (2D) materials, creating hybrid systems mutual influences, constitutes an important testbed for both basic science self-assembly studies and perspective applications. Following this concept, in work, we show a rich phenomenology that is involved the interaction thionine graphene, leading to material formed by well-organized self-assembled structures atop graphene. This composite system investigated atomic force microscopy, electric...
Zika virus (ZIKV) is a mosquito-borne that phylogenetically close to other medically important flaviviruses with high global public health significance, such as dengue (DENV) and yellow fever (YFV) viruses. Correct diagnosis of flavivirus infection can be challenging, particularly in world regions where more than one co-circulates YFV vaccination mandatory. Acid nucleic aptamers are oligonucleotides bind specific target molecule affinity specificity. Because their unique characteristics,...
The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), etiological agent for the disease 2019 (COVID-19), has resulted in over 775 million global infections. Early diagnosis remains pivotal effective epidemiological surveillance despite availability of vaccines. Antigen-based assays are advantageous early COVID-19 detection due to their simplicity, cost-effectiveness, and suitability point-of-care testing (PoCT). This study introduces a graphene field-effect transistor-based...
Abstract In this work we have measured the G′ Raman band of bilayer graphene using several laser lines. We show that from analysis experimental data in framework double resonance model can derive Slonczewski‐Weiss‐McClure parameters graphene. analyze behavior theoretical as a function these by comparing with results. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Abstract In this study, we develop a real-time PCR strategy to directly detect and quantify DNA aptamers on functionalized graphene surfaces using Staphylococcus aureus aptamer (SA20) as demonstration case. We show that allowed quantification in the range of 0.05 fg 2.5 ng. Using quantitative technique, it was possible determine functionalization with amino modified SA20 (preceded by surface modification thionine) much more efficient than process pyrene modification. also demonstrated...
A helium ion microscope is used to produce nanoscale patterns on different regions of a graphene device. The consist uniformly spaced strips with varying spacing in each region. Measurements the longitudinal magnetoconductivity region at temperatures and carrier densities reveal transition from metallic insulating regimes as density defects increases. We use weak localization theory Mott's for disordered two-dimensional systems analyze conductivity it crosses threshold value...
The relative intensity of photonic modes in microcavity pillars with embedded self-assembled quantum dots is shown to be a sensitive function dot dipole orientation and position. This deduced from comparison experiment calculated intensities light emission for many nominally identical pillars. We are able obtain the overall degree in-plane polarization ensemble also information on along growth axis.
A primitive cubic lattice composed of 1,000 atoms has 488 surface sites. By definition, every atom in a strictly two-dimensional single-layer composes its surface. These are the ones that undergo chemical interactions with surrounding medium, thereby defining functionalities nanostructure. As such, one most important morphological properties nano-objects is extremely large specific area enhances their levels reactivity. Here, we introduce an optical spectroscopy method to measure...