Laboratorio Nacional Of Nanotecnologia Lnnano Cnpem

Campinas, Brazil

Laboratorio Nacional Of Nanotecnologia Lnnano Cnpem

Campinas, Brazil

Time filter

Source Type

Da Silva S.F.C.,Laboratorio Nacional Of Nanotecnologia Lnnano Cnpem | Da Silva S.F.C.,Federal University of Viçosa | Lanzoni E.M.,Laboratorio Nacional Of Nanotecnologia Lnnano Cnpem | Malachias A.,Federal University of Minas Gerais | Deneke C.,Laboratorio Nacional Of Nanotecnologia Lnnano Cnpem
Journal of Crystal Growth | Year: 2015

Partly released InGaAs layers forming a wrinkled network are used as templates for InAs growth. A systematic growth study was carried out, where InAs amounts from 0 ML to 3 ML were deposited on the patterned samples. The material migration during growth is evaluated by distinct microscopy techniques. We find a systematic accumulation of the deposited material on the released, wrinkled areas of the sample, whereas no material accumulation or formation of three-dimensional nanostructures is observed on the unreleased areas of the sample. © 2015 Elsevier B.V. All rights reserved.


Marcal L.A.B.,Federal University of Minas Gerais | Rosa B.L.T.,Federal University of Minas Gerais | Rosa B.L.T.,Brazilian National Institute of Technology | Safar G.A.M.,Federal University of Minas Gerais | And 7 more authors.
ACS Photonics | Year: 2014

(Graph Presented). Semiconductor nanomembranes are promising systems for many applications, since the band structure of a given material can be tailored to achieve specific configurations, which are not feasible by conventional growth procedures on rigid substrates. Here we show that optically active III-V membranes containing InAs quantum dots exhibit a pronounced photoluminescence enhancement with respect to equivalent systems grown on top of flat substrates. The effect is explained by the formation of carrier depletion regions symmetrically located with respect to the optically active layer. This leads to the filling of excited states of the quantum dots and the overall spectra are enhanced at higher energies. Changes on the strain field that are expected to lead to a red-shift of the quantum dot emission play a reduced role in the final emission spectra in comparison with the depletion effects. These effects can be considered as another degree of freedom and a key ingredient for band engineering of extremely thin semiconductor membranes. © 2014 American Chemical Society.


Marcal L.A.B.,Federal University of Minas Gerais | Richard M.-I.,European Synchrotron Radiation Facility | Richard M.-I.,Aix - Marseille University | Magalhaes-Paniago R.,Federal University of Minas Gerais | And 7 more authors.
Applied Physics Letters | Year: 2015

Semiconductor heteroepitaxy on top of thin compliant layers has been explored as a path to make inorganic electronics mechanically flexible as well as to integrate materials that cannot be grown directly on rigid substrates. Here, we show direct evidences of strain transfer for InAs islands on freestanding Si thin films (7 nm). Synchrotron X-ray diffraction measurements using a beam size of 300 × 700 nm2 can directly probe the strain status of the compliant substrate underneath deposited islands. Using a recently developed diffraction mapping technique, three-dimensional reciprocal space maps were reconstructed around the Si (004) peak for specific illuminated positions of the sample. The strain retrieved was analyzed using continuous elasticity theory via Finite-element simulations. The comparison of experiment and simulations yields the amount of strain from the InAs islands, which is transferred to the compliant Si thin film. © 2015 AIP Publishing LLC.


Barcelos I.D.,Federal University of Minas Gerais | Barcelos I.D.,Laboratorio Nacional Of Nanotecnologia Lnnano Cnpem | Cadore A.R.,Federal University of Minas Gerais | Campos L.C.,Federal University of Minas Gerais | And 6 more authors.
Nanoscale | Year: 2015

We observed the coupling of graphene Dirac plasmons with different surfaces using scattering-type scanning near-field optical microscopy integrated into a mid-infrared synchrotron-based beamline. A systematic investigation of a graphene/hexagonal boron nitride (h-BN) heterostructure is carried out and compared with the well-known graphene/SiO2 heterostructure. Broadband infrared scanning near-field optical microscopy imaging is able to distinguish between the graphene/h-BN and the graphene/SiO2 heterostructure as well as differentiate between graphene stacks with different numbers of layers. Based on synchrotron infrared nanospectroscopy experiments, we observe a coupling of surface plasmons of graphene and phonon polaritons of h-BN (SPPP). An enhancement of the optical band at 817 cm-1 is observed at graphene/h-BN heterostructures as a result of hybridization between graphene plasmons and longitudinal optical phonons of h-BN. Furthermore, longitudinal optical h-BN modes are preserved on suspended graphene regions (bubbles) where the graphene sheet is tens of nanometers away from the surface while the amplitude of transverse optical h-BN modes decrease. © The Royal Society of Chemistry 2015.


Sarveena,H P University | Muraca D.,University of Campinas | Muraca D.,Federal University of ABC | Zelis P.M.,National University of La Plata | And 9 more authors.
RSC Advances | Year: 2016

This article presents the effect of oxidation temperature on shape anisotropy, phase purity and growth of core-shell heterostructures and consequently their effect on structure-property relationships. Iron oxide and Au-iron oxide nanocomposites were synthesized by a thermal decomposition method by passing pure oxygen at different temperatures (125-250 °C). The prepared nanoparticles were surface functionalized by organic molecules; the presence of the organic canopy prevented both direct particle contact as well as further oxidation, resulting in the stability of the nanoparticles. We have observed a systematic improvement in the core and shell shape through tuning the reaction time as well as the oxidizing temperatures. Spherical and spherical triangular shaped core-shell structures have been obtained at an optimum oxidation temperature of 125 °C and 150 °C for 30 minutes. However, further increase in the temperature as well as oxidation time results in core-shell structure amendment and results in fully grown core-shell heterostructures. As stability and ageing issues limit the use of nanoparticles in applications, to ensure the stability of the prepared iron oxide nanoparticles we performed XRD analysis after more than a year and they remained intact showing no ageing effect. Specific absorption rate values useful for magnetic fluid hyperthermia were obtained for two samples on the basis of detailed characterization using X-ray diffraction, high-resolution transmission electron microscopy, Mössbauer spectroscopy, and dc-magnetization experiments. © 2016 The Royal Society of Chemistry.


Meiorin C.,CONICET | Londono O.M.,University of Campinas | Muraca D.,University of Campinas | Socolovsky L.M.,University of Buenos Aires | And 4 more authors.
Materials Chemistry and Physics | Year: 2016

The aim of this work is to study the influence of the polymeric matrix composition on particle aggregation, magnetic interparticle interactions and nanoparticle surface effects, which affect the magnetic and structural properties of different ultra-diluted magnetite nanocomposites (MNCPs). Bio-based matrices were selected as a possible response to the increasing demand for renewable materials. To investigate the influence of different bio-based polymeric matrices on the magnetic behavior, three different bio-based polymers were used to prepare MNCPs with 1 wt.% of magnetite nanoparticles (MNPs). One of them was prepared using a tung oil (TO)/styrene (St) weight ratio of 70/30, a second one was prepared by replacing the styrene with methylester (green comonomer obtained from tung oil, ME, 70TO/30ME) and a third one that incorporated a green modifier, acrylated epoxidized soybean oil (AESO), using a tung oil/AESO weight ratio of 90/10. Structural features as nanoparticle aggregation state, nanoparticle and cluster sizes, and fractal dimension were studied and determined from small-angle X-ray Scattering (SAXS). The experimental SAXS data were analyzed by means of fractal aggregate model. Results indicate differences in nanoparticle arrangement depending of the containing matrix. The magnetic characterization of these materials indicates that the matrix strongly affects the physical and chemical properties of the MNCPs. All samples display superparamagnetic behavior at room temperature, but the blocking temperature varies from 75 K (tung oil/styrene with 1 wt.% MNPs) to 126 K (tung oil/AESO 1 wt.% MNPs). Furthermore, the temperature dependence of the coercive field changes for all samples, suggesting a strong influence of the polymer properties on the magnetic properties of the MNCPs. © 2016 Elsevier B.V.


Cendula P.,Leibniz Institute for Solid State and Materials Research | Cendula P.,University of Zürich | Malachias A.,Federal University of Minas Gerais | Deneke Ch.,Leibniz Institute for Solid State and Materials Research | And 4 more authors.
Nanoscale | Year: 2014

Self-positioned nanomembranes, such as rolled-up tubes and wrinkled thin films, have been potential systems for a variety of applications and basic studies on elastic properties of nanometer-thick systems. Although there is a clear driving force towards elastic energy minimization in each system, the exploration of intermediate states, in which specific characteristics could be chosen by a slight modification of a processing parameter, have not been experimentally realized. In this work, arrays of freestanding III-V nanomembranes (NM) supported on one edge and presenting a coexistence of these two main behaviors were obtained by design of strain conditions in the NMs and controlled selective etching of patterned substrates. As the etching process continues, a mixture of wrinkled and rolled-up states is achieved. For very long etching times an onset of plastic cracks was observed in the points with localized stress. The well-defined morphological periodicity of the relaxed NMs was compared with finite element simulations of their elastic relaxation. The evolution of strain in the NMs with etching time was directly evaluated by X-ray diffraction, providing a comprehensive scenario of transitions among competing and coexisting strain states. © The Royal Society of Chemistry 2014.


Filipe Covre Da Silva S.,Laboratorio Nacional Of Nanotecnologia Lnnano Cnpem | Filipe Covre Da Silva S.,University of Vic | Lanzoni E.M.,Laboratorio Nacional Of Nanotecnologia Lnnano Cnpem | De Araujo Barboza V.,Laboratorio Nacional Of Nanotecnologia Lnnano Cnpem | And 3 more authors.
Nanotechnology | Year: 2014

Partly released, relaxed and wrinkled InGaAs membranes are used as virtual substrates for overgrowth with InAs. Such samples exhibit different lattice parameters for the unreleased epitaxial parts, the released flat, back-bond areas and the released wrinkled areas. A large InAs migration towards the released membrane is observed with a material accumulation on top of the freestanding wrinkles during overgrowth. A semi-quantitative analysis of the misfit strain shows that the material migrates to the areas of the sample with the lowest misfit strain, which we consider as the areas of the lowest chemical potential of the surface. Material migration is also observed for the edge-supported, freestanding InGaAs membranes found on these samples. Our results show that the released, wrinkled nanomembranes offer a growth template for InAs deposition that fundamentally changes the migration behavior of the deposited material on the growth surface. © 2014 IOP Publishing Ltd.


Duran N.,University of Campinas | Duran N.,Laboratorio Nacional Of Nanotecnologia Lnnano Cnpem | Islan G.A.,National University of La Plata | Duran M.,Laboratorio Nacional Of Nanotecnologia Lnnano Cnpem | And 2 more authors.
Journal of the Brazilian Chemical Society | Year: 2016

United Nations Children's Fund (UNICEF)/United Nations Development Programme (UNDP)/ World Bank/World Health Organization (WHO) implemented the Training in Tropical Diseases (TDR) program with excellent results; however, due to current challenges, this active program requires new and innovative solutions. Nowadays, Aedes aegyptis-borne diseases can be added among neglected diseases. Surveillance and control must be considered owing to a great risk of infection with dengue, chikungunya and zika viruses. Although investigations on several vaccines are in progress, new insights in term of development of drugs that evade from resistance are of paramount importance. Nanobiotechnology appears as one of the most innovative strategy in the search of new uses for old pharmaceuticals or in the development of innovative and intelligent nanomedicines for neglected diseases. Liposomes, solid lipid nanoparticles, nanoemulsions, polymeric nanoparticles, metallic nanoparticles, quantum dots, carbon dots and carbon nanotubes were the focus of the current advances. In this direction, we have focused this overview on new advances in diagnostic assays as nanobiosensors, antivirus and nanoinsecticides on Aedes aegyptis control. © 2016 Sociedade Brasileira de Qúmica.

Loading Laboratorio Nacional Of Nanotecnologia Lnnano Cnpem collaborators
Loading Laboratorio Nacional Of Nanotecnologia Lnnano Cnpem collaborators