Papers by Aristides Pavani Filho
Materials Today: Proceedings, 2019
Interaction between different molecules during formation of complex nanostructured films, which c... more Interaction between different molecules during formation of complex nanostructured films, which can be used as matrixes for fixing of macromolecules, plays important role in formation of sensitive films for biosensors. The Langmuir-Blodgett technique was used to obtain mixed films of dimethyldioctadecylammonium bromide (DODAB) and graphene oxide sheets (GO). Specific aptamers were subsequently attached. The obtained results after characterization of films on the air/water interface show that incorporation of GO sheets between lipid monolayers takes place. Transfer rates for mixed films indicates the formation of Z-type films after GO incorporation. Quartz Crystal Microbalance measurements of films density clearly demonstrated the presence of GO sheets in films. After drop casting method with the solution of aptamer marked with Cy5 fluorophores on the surface of the mixed films, measurements of fluorescence microscopy and contact angle were performed demonstrating the presence of these macromolecules even after cleaning procedures.
ECS Transactions, 2010
Inductively Coupled Plasma Discharges (ICP) currently are considered as the main tool for plasma ... more Inductively Coupled Plasma Discharges (ICP) currently are considered as the main tool for plasma processing in the microelectronics industry. A comprehensive understanding of ICP's functionality and behavior is fundamental for the evolution of this technology. This understanding requires its modeling as an electrical lumped circuit. Existing electrical models cannot explain all the characteristics of an ICP discharge, especially the E-to-H mode transition. In this work, preliminary results on the modeling of ICP plasma and the possibility to incorporate the plasma kinetics, particularly the effect of metastables on the transitions, is discussed.
Sensors and Actuators B: Chemical, 2007
Surface acoustic wave (SAW) humidity sensors have been constructed by using poly(p-diethynylbenze... more Surface acoustic wave (SAW) humidity sensors have been constructed by using poly(p-diethynylbenzene) (PDEB) and sodium polysulfonesulfonate (NaSPF) as the sensitive film. The 138MHz SAW sensors were configured as a delay line onto a 128° YX–LiNbO3 substrate with the SAW path covered by the LB membrane of PDEB and the spin-coated NaSPF film. The frequency responses of the SAW sensors have
Revista brasileira de aplicações de vácuo, 1987
Proceedings of SPIE, Aug 20, 2015
Lately, graphene oxide (GO) thin films have attracted much attention: they can be used as humidit... more Lately, graphene oxide (GO) thin films have attracted much attention: they can be used as humidity-sensitive coatings in the surface acoustic wave (SAW) sensors; being functionalized, they can be used in optoelectronic or biodevices, etc. In this research we study surface morphology of small-area thin GO films obtained on Si and quartz substrates by deposition of very small amounts of H2O-GO aerosols produced by the SAW atomizer. An important feature of this method is the ability to work with submicrovolumes of liquids during deposition that provides relatively good control over the film thickness and quality, in particular, minimization of the coffee ring effect. The obtained films were examined using AFM and electron microscopy. Image analysis showed that the films consist of GO sheets of different geometry and sizes and may form discrete or continuous coatings at the surface of the substrates with the minimum thickness of 1.0-1.8 nm which corresponds to one or two monolayers of GO. The thickness and quality of the deposited films depend on the parameters of the SAW atomization (number of atomized droplets, a volume of the initial droplet, etc.) and on sample surface preparation (activation in oxygen plasma). We discuss the structure of the obtained films, uniformity and the surface coverage as a function of parameters of the film deposition process and sample preparation. Qualitative analysis of adhesion of GO films is made by rinsing the samples in DI water and subsequent evaluation of morphology of the remained films.
Ambiente, Aug 31, 2021
Element contents in the lower São Francisco river assessed by inductively coupled plasma optical ... more Element contents in the lower São Francisco river assessed by inductively coupled plasma optical emission spectrometry (ICP OES) analysis. Análise elementar das águas do Baixo Rio São Francisco avaliados por espectrometria de emissão óptica de plasma indutivamente acoplada (ICP OES). RESUMO: A bacia do rio São Francisco, também conhecida como Velho Chico, tem uma extensão de mais de 640 mil km 2 e percorre 2.700 km de Minas Gerais até chegar à foz no Oceano Atlântico, na divisa dos estados de Alagoas e Sergipe. Os corpos d'água são classificados em classes de acordo com os usos a que se destinam e de acordo com os requisitos estabelecidos. No presente trabalho, o objetivo foi traçar o perfil dos teores de B, Ca, Fe, K, Mn, V, Zn e Mg, presentes no rio São Francisco, por meio de espectrometria de emissão óptica com plasma indutivamente acoplado (ICP OES). Assim, propomos avaliar a qualidade da água do rio São Francisco com base em seus conteúdos de micro e macroelementos. De acordo com os resultados obtidos, a potabilidade da água do rio é avaliada com base nos padrões do Ministério da Saúde do Brasil. Pelos dados obtidos, as concentrações desses elementos estão abaixo dos limites máximos de tolerância e, portanto, essas águas atendem aos padrões de potabilidade nas condições testadas.
Revista brasileira de aplicações de vácuo, 1987
Marine Pollution Bulletin, Nov 1, 2020
The characterization of petroleum or its products spilled in the environment in relation to its s... more The characterization of petroleum or its products spilled in the environment in relation to its source rocks is an important tool to assist in the resolution of issues of environmental impact and legal responsibility since it clarifies the possible region or the producing country of that type of petroleum. This article analyzes the application of analytical techniques for petroleum geochemistry to identify the type and origin of oily material collected from beaches in Northeast Brazil in 2019. Samples of the oily material collected on the beaches in the states of Bahia and Sergipe were analyzed and for comparison purposes, samples of crude oils produced in Brazil, Middle East, Nigeria and Venezuela were also analyzed. The analytical results showed that the oily material that reached the beaches has geochemical characteristics compatible with those of the Venezuelan oil, indicating it was severely weathered or a product made with heavy oil produced.
Ciências Agrárias: Conhecimentos Científicos e Técnicos e Difusão de Tecnologias 4, 2020
Variantes do Meio Ambiente: Atuação, interdisciplinaridade e Sustentabilidade 2, 2021
DEMOCRATIZAÇÃO DO CONHECIMENTO E VALORIZAÇÃO PROFISSIONAL: CAMINHOS PARA O DESENVOLVIMENTO TECNOLÓGICO E SOCIAL., 2019
Estudos têm reportado o potencial bioativo da Petiveria alliacea, espécime vegetal com compostos ... more Estudos têm reportado o potencial bioativo da Petiveria alliacea, espécime vegetal com compostos bioativos passíveis de serem utilizados no combate e controle de pragas e verminoses, bem como agente bactericida e fungicida. Dentre os agentes com potencial de provocar doenças encontra-se o Aedes aegypti, atualmente o mosquito com maior dispersão em áreas urbanas no mundo. Na agricultura o Lasiodiplodia theobromae, um fungo oportunista, osmopolita e polífago, que sobrevive na atmosfera e nos tecidos, vivos ou mortos, de vegetais encontra-se disseminado em todas as regiões tropicais e subtropicais do mundo. Desta forma, objetivo do presente trabalho é avaliar o limiar tóxico do extrato etanólico das folhas da espécie Petiveria alliacea L. (EEFPA) frente à Artemia salina com a finalidade de determinar a dose máxima a ser utilizada com segurança como planta medicinal, bem como, determinar os metabólitos secundários presentes no extrato através de testes fitoquímicos e avaliar o potencial antioxidante do extrato através do teste DPPH (difenil-picril-hidrazina), verificar o potencial larvicida frente ao mosquito Aedes aegypti e sua atividade fungicida frente ao fungo L. theobromae. A atividade larvicida foi determinada a partir do método Probitos de análise para obtenção da Concentração Letal Média (CL50). A determinação do percentual de crescimento micelial (PIC) do Lasiodiplodia foi realizada conforme metodologia descrita por Menten, 1976. O ensaio para avaliar a atividade antioxidante revelou que o extrato etanólico das folhas da P. alliacea apresentou baixa atividade antioxidante. Na atividade fungicida os resultados também revelaram que o extrato não apresenta atividade frente ao fungo L. thebromae. Contudo, não se
Sensors and Actuators B: Chemical, 2015
Symmetric surface acoustic wave (SAW) atomizer was used to deposit graphene oxide (GO) nanofilms ... more Symmetric surface acoustic wave (SAW) atomizer was used to deposit graphene oxide (GO) nanofilms from microdroplets of the aqueous GO dispersion onto the surface of the SAW humidity sensors. The sensors with the deposited GO films were tested in a wide range of relative humidity and showed the amplitude of the response in the range of 1-40 kHz sufficient for the majority of applications. The kinetics of the adsorption of water molecules was modeled using the assumption that two independent first order adsorption processes take place. Saturation amplitudes and rate coefficients for both processes were experimentally evaluated using LSQ fitting of the sensor response in the time domain for the films obtained by different number of depositions. The mechanism of the adsorption of water molecules to the GO flakes is proposed and discussed.
Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures Processing, Measurement, and Phenomena, 2001
Residual gas inside field emission displays (FED) is the most important issue related to the devi... more Residual gas inside field emission displays (FED) is the most important issue related to the device lifetime. Increasing the display area while maintaining the display thickness unchanged results in lifetime decrease, since the pressure gradient is fostered. Therefore, improvement of vacuum properties is a mandatory step towards large area displays. In a prior publication we have demonstrated that porous diamond membranes show good vacuum performance, while requiring low emitter switching voltage. In this work, we continue the porous membrane development by using polyimide as the base material for the membrane. The use of polyimide instead of diamond allows for easier production of large area porous FEDs. In addition, we present results of preliminary field emission experiments showing a direct correlation between the emitted current and the number of pores. This result strongly suggests that the emission sites are located at the pore edges in the polyimide membranes, similar to our...
IOP Conference Series: Materials Science and Engineering, 2015
Due to its ability to absorb water molecules, graphene oxide (GO) is considered a promising mater... more Due to its ability to absorb water molecules, graphene oxide (GO) is considered a promising material for sensitive coatings in fast surface acoustic wave (SAW) humidity sensors. In this work, we characterize GO films obtained by the SAW atomization technique. It is shown that the atomized submicroliter droplets of aqueous suspension of GO can be deposited onto the surface of Si, LiNbO 3 or quartz substrates forming discrete or continuous films of nanometer thickness. The deposited films were examined using AFM and electron microscopy. We discuss the dependence of thickness and structure of the obtained GO films on the parameters of deposition: the number of atomized droplets, a volume of the initial droplet, a distance between the atomizer and the sample, etc. To evaluate the adsorption characteristics of the obtained GO films, we used them as sensitive coatings of the SAW humidity sensors. We found that the adsorption characteristics of the GO films are determined by fast adsorption on the surface of GO sheets and slow adsorption, attributed to limited penetration of water molecules between the sheets, and depend on the number of deposited layers.
28th Symposium on Microelectronics Technology and Devices (SBMicro 2013), 2013
ABSTRACT Atomization of one or two microliter droplets of aqueous dispersion of graphene oxide (G... more ABSTRACT Atomization of one or two microliter droplets of aqueous dispersion of graphene oxide (GO) by the surface acoustic wave (SAW) atomizer was used to deposit GO sensitive films of 15-30-nm thickness onto the surface of the SAW humidity sensor. Sensitivity of the sensors with these films as sensitive elements was calibrated over a wide range of humidity using a special procedure of preparation of standards, and adsorption kinetic curves for this process were obtained. The first-order rate kinetic equation with special additional linear term was shown to be adequate for modeling the kinetics of water adsorption onto the GO thin film. All parameters of this equation were calculated from least-squares fitting of experimental data. It was shown that the sensor partially coated with the graphene oxide film has good sensitivity and very short response time. The developed approach of experimental data treatment can be used for calibration of various types of portable SAW sensors.
2013 IEEE SENSORS, 2013
ABSTRACT Graphene oxide (GO) thin films with partial surface coating were deposited onto the surf... more ABSTRACT Graphene oxide (GO) thin films with partial surface coating were deposited onto the surface of 160 MHz quartz SAW delay lines by SAW atomization of submicroliter droplets of GO aqueous dispersions. The delay lines were used as sensitive elements of the SAW relative humidity (RH) sensors for monitoring the process of saturation of vapor pressure of water in an enclosed volume. To explain the RH time dependence, we suggest a model, which takes into account two processes: fast adsorption of water molecules by the surface of GO, described by the first order kinetic equation, and slow volumetric adsorption, described by linear kinetic equation. The parameters of kinetic equations of the saturation process were estimated experimentally for the coatings obtained by different number of atomizations and for eleven different RH standards.
ECS Transactions, 2011
A new approach for design of SAW sensors and tags is discussed. We propose to use a two-path SAW ... more A new approach for design of SAW sensors and tags is discussed. We propose to use a two-path SAW oscillator as a sensor. This structure does not require a reference channel as a traditional SAW sensor does. Also we show that the use of fan-shaped transducers in sensors and RF ID tags allows one to utilize different frequency bands in the same propagation path for reference and code parts of the signal. In the article we present prototypes of SAW chemical alarm sensor and SAW RF tag.
Thin Solid Films, 1999
We have shown previously that porous diamond membranes can be fabricated using a method based on ... more We have shown previously that porous diamond membranes can be fabricated using a method based on growing diamond on a patterned silicon substrate. The technique used to pattern the silicon is conventional lithography. In this work we present a method for reducing the pore size using diamond post-deposition over the membrane. An important concern in this work was to determine the pore-shutting rate, considering the time post-deposition and the pore morphology.
ECS transactions, Dec 17, 2019
Symmetric point and inline focused SAW atomizers on 128 deg. YX cut of the LiNbO3 were designed a... more Symmetric point and inline focused SAW atomizers on 128 deg. YX cut of the LiNbO3 were designed and fabricated for atomization of nanoliter single water droplet. Developed focused atomizers were experimentally proven to double SAW energy density in the region of the droplet comparable to traditional atomizer. It was shown that RF pulses with low duty factor give stable atomization in such structures. Detailed procedure of optimum matching for such devices is described.
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Papers by Aristides Pavani Filho