Navegando por Autor "Silva, Glaura Goulart"
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Item Aerosol-printed MoS2 ink as a high sensitivity humidity sensor.(2022) Pereira, Neuma das Mercês; Rezende, Natália Pereira; Cunha, Thiago Henrique Rodrigues da; Barboza, Ana Paula Moreira; Silva, Glaura Goulart; Lippross, Daniel; Neves, Bernardo Ruegger Almeida; Chacham, Helio; Ferlauto, Andre Santarosa; Lacerda, Rodrigo GribelMolybdenum disulfide (MoS2) is attractive for use in nextgeneration nanoelectronic devices and exhibits great potential for humidity sensing applications. Herein, MoS2 ink was successfully prepared via a simple exfoliation method by sonication. The structural and surface morphology of a deposited ink film was analyzed by scanning electron microscopy (SEM), Raman spectroscopy, and atomic force microscopy (AFM). The aerosol-printed MoS2 ink sensor has high sensitivity, with a conductivity increase by 6 orders of magnitude upon relative humidity increase from 10 to 95% at room temperature. The sensor also has fast response/recovery times and excellent repeatability. Possible mechanisms for the water-induced conductivity increase are discussed. An analytical model that encompasses two ionic conduction regimes, with a percolation transition to an insulating state below a low humidity threshold, describes the sensor response successfully. In conclusion, our work provides a low-cost and straightforward strategy for fabricating a highperformance humidity sensor and fundamental insights into the sensing mechanism.Item Carbon nanotube/dendrimer hybrids as electrodes for supercapacitors.(2016) Trigueiro, João Paulo Campos; Figueiredo, Rute Cunha; Rojo Marcos, Francisco Javier; Viana, Renato Márcio Ribeiro; Schnitzler, Mariane Cristina; Silva, Glaura GoulartCarbon nanotubes (CNTs) were surface-modified by a glycodendrimer with four glucose units (4-Gl). Electrodes for supercapacitors based on CNT/4-Gl hybrids were used for the first time in this work. The preparation was conducted by casting eight alternating bilayers of two types of modified multiwalled carbon nanotubes (MWCNTs), MWCNT-COOH/4-Gl and MWCNT-NH2/4- Gl, from aqueous dispersions (pH= 6). The electrodes showed good cohesion, dimensional stability, and a homogeneous nanoscale structure because the carbon nanotube/dendrimer layers interact electrostatically. The supercapacitor was stacked with a separator embedded with a 1-ethyl-3- methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid electrolyte. The device with 20 wt% of dendrimer with respect to CNT content in the electrodes achieved a remarkable increase of 600 % in capacitance compared with the capacitance without the dendrimer.Item Theoretical study of solvent and temperature effects on the behaviour of poly(ethylene oxide) (PEO).(1999) Ferreira, Beatriz Alves; Santos, Helio Ferreira dos; Bernardes, Américo Tristão; Silva, Glaura Goulart; Almeida, Wagner Batista deMolecular mechanics and molecular dynamics simulations were applied in order to study the behaviour of poly ethylene. oxide PEO in different temperatures and solvents. It was found that over the temperature range of 50–500 K the equilibrium structure of PEO is folded. Both kinetic and potential energies increase with temperature. The behaviour of PEO . in two different solvents – CHCl « s5 and H O « s80 – was found to be similar, with the folded structure observed 32 in equilibrium. The solvation energy calculated using the GBrSA model yielded essentially the same value in CHCl and H2O.