Papers by Priscila Alessio
Palavras-chave: ligninas; filmes evaporados a vácuo, sensores.
Quality and safety have become important food attributes within the last years. With the expansio... more Quality and safety have become important food attributes within the last years. With the expansion of food industry and food fabrication on a big scale is not infrequent to found adulterant and contaminant on food, i.e. of harmful chemicals and microorganisms, which can cause consumer illness. Increasingly, the public authorities are charging the food industry to develop quality management systems and restructure the food inspection system to improve food quality and safety. However, contamination can be taking place during all steps of food manufacturing. For instance, even during storage, the products can experience a significant degradation in quality due to a variety of physical, chemical, and biological interactions. Consequently, fast and inexpensive ways to control the food freshness, contamination or adulteration are requested to keep the quality control. Thus, there is an increasing demand for analytical methods easily operate with highly sensitive, selective and accurate f...
Com o aumento da populacao mundial, intensificou-se a aplicacao de pesticidas em todo o mundo ger... more Com o aumento da populacao mundial, intensificou-se a aplicacao de pesticidas em todo o mundo gerando debates amplos, pois interage com diferentes areas do conhecimento e quando aplicado sem controle traz consequencias para o ecossistema e tambem para os seres humanos. Entre os pesticidas mais consumidos no Brasil, o paraquate (PQT) ja foi banido da comunidade europeia, e com previsao de sair das prateleiras brasileiras em setembro de 2020, segundo a Anvisa. O PQT e um herbicida nao-seletivo de acao rapida amplamente utilizado na agricultura, quando aplicado de maneira abusiva pode causar danos severos como fibrose pulmonar, dermatites, ulceras, danos cerebrais e outros. Por essas razoes, o interesse por novos estudos em sensores e biossensores tem aumentado consideravelmente. Esse trabalho tem como objetivo a deteccao do pesticida PQT atraves de medidas de voltametria ciclica utilizando filme LbL ( Layer-by-Layer ) de poli(alilaminahidrocloridrica) e ftalocianina de niquel PAH/NiT...
Anais da Academia Brasileira de Ciencias, 2021
The immobilization of the enzyme tyrosinase (Tyr) in lipid matrices can be explored to produce bi... more The immobilization of the enzyme tyrosinase (Tyr) in lipid matrices can be explored to produce biosensors for detecting polyphenols, which is relevant for the food industry. Herein, we shall demonstrate the importance of the lipid composition to immobilize the enzyme tyrosinase in Langmuir-Blodgett (LB) films. Tyr could be incorporated into Langmuir monolayers of arachidic acid (AA), 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and 1,2-dipalmitoyl-sn-glycero-3-phospho-(1'-rac-glycerol) (sodium salt) (DPPG), having as the main effect an expansion in the monolayers. Results from polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS) pointed to electrostatic interactions between the charged residues of Try and the lipid headgroups, in addition to changes in the order of lipid chains. The interaction between Tyr and DPPC in Langmuir monolayers can be correlated with the superior performance of DPPC/Tyr LB films used as biosensors to detect catechol by cy...
Materials Chemistry and Physics
The P3HT and P3OT polymers were scattered on a water-air surface of a Langmuir trough. • Through ... more The P3HT and P3OT polymers were scattered on a water-air surface of a Langmuir trough. • Through isotherms (π-A) one can identify the organization phases of the molecules. • The thin films presented linear growth through of Langmuir Schaefer technique. • The thin films on the interdigitated electrode quickly detected the organic vapor. • Raman mapping detected the physical interactions between organic polymers and vapors.
Physical Chemistry Chemical Physics
Organic thin films supramolecular architecture plays an essential factor in the performance of op... more Organic thin films supramolecular architecture plays an essential factor in the performance of optical and electronic organic devices.
Sensors
Detection of the drug Levodopa (3,4-dihydroxyphenylalanine, L-Dopa) is essential for the medical ... more Detection of the drug Levodopa (3,4-dihydroxyphenylalanine, L-Dopa) is essential for the medical treatment of several neural disorders, including Parkinson’s disease. In this paper, we employed surface-enhanced Raman scattering (SERS) with three shapes of silver nanoparticles (nanostars, AgNS; nanospheres, AgNP; and nanoplates, AgNPL) to detect L-Dopa in the nanoparticle dispersions. The sensitivity of the L-Dopa SERS signal depended on both nanoparticle shape and L-Dopa concentration. The adsorption mechanisms of L-Dopa on the nanoparticles inferred from a detailed analysis of the Raman spectra allowed us to determine the chemical groups involved. For instance, at concentrations below/equivalent to the limit found in human plasma (between 10−7–10−8 mol/L), L-Dopa adsorbs on AgNP through its ring, while at 10−5–10−6 mol/L adsorption is driven by the amino group. At even higher concentrations, above 10−4 mol/L, L-Dopa polymerization predominates. Therefore, our results show that adso...
This thesis presents the results obtained from
Journal of Electroanalytical Chemistry
Sensors
The recent development of silver nanostars (Ag-NSs) is promising for improved surface-enhanced se... more The recent development of silver nanostars (Ag-NSs) is promising for improved surface-enhanced sensing and spectroscopy, which may be further exploited if the mechanisms behind the excitation of localized surface plasmon resonances (LSPRs) are identified. Here, we show that LSPRs in Ag-NSs can be obtained with finite-difference time-domain (FDTD) calculations by considering the nanostars as combination of crossed nanorods (Ag-NRs). In particular, we demonstrate that an apparent tail at large wavelengths ( λ ≳ 700 nm) observed in the extinction spectra of Ag-NSs is due to a strong dipolar plasmon resonance, with no need to invoke heterogeneity (different number of arms) effects as is normally done in the literature. Our description also indicates a way to tune the strongest LSPR at desired wavelengths, which is useful for sensing applications.
Journal of nanoscience and nanotechnology, 2018
The supramolecular arrangement in thin film technology has been explored through different deposi... more The supramolecular arrangement in thin film technology has been explored through different deposition techniques aiming to control the film properties at the molecular level. We report on the formation of iron phthalocyanine (FePc) films using both Langmuir-Schaefer (LS) and electrodeposition methods. The multilayer formation was monitored with ultraviolet-visible absorption spectroscopy (UV-vis) and electrochemical measurements. According to Raman spectroscopy, atomic force microscopy (AFM), and scanning electron microscopy (SEM), the surface morphology of electrodeposited films is more homogeneous than LS films at micro and nanometer scales. From FTIR spectroscopy, the FePc molecules in the electrodeposited films are oriented preferentially with the macrocycle parallel to the substrate surface (flat-on), while a slight tilt is suggested in LS films, being both films crystalline. Therefore, the use of different deposition techniques allowed the fabrication of thin films from FePc w...
Colloids and Surfaces B: Biointerfaces
The persistence of steroid hormones disposed of in the environment may pose risks to the health o... more The persistence of steroid hormones disposed of in the environment may pose risks to the health of humans and wildlife, which brings the need of understanding their mode of action, believed to occur in cell membranes. In this study, we investigate the molecular-level interactions between the synthetic hormone 17 ␣-ethynylestradiol (EE2) and Langmuir monolayers that represent simplified cell membranes. In surface pressure isotherms, EE2 was found to expand the monolayers at low surface pressures of the positively charged dimethyldioctadecylammonium bromide (DODAB), zwitterionic 1,2-dipalmitoyl-sn-glycerol-3-phosphocholine (DPPC), negatively charged 1,2-dipalmitoyl-sn-glycero-3phosphoglycerol (DPPG), and partially anionized stearic acid (StAc). The largest effects were observed for the charged DODAB and DPPG. At the pressure (30 mN.m −1) corresponding to the molecular packing of a cell membrane, EE2 caused the compressibility modulus to decrease, again with the largest changes occurring for DODAB and DPPG. The effects from EE2 on the packing of the lipid molecules at this high pressure depended essentially on the size of the headgroups, with EE2 contributing to the area per lipid for StAc and DODAB, whose headgroups are small. EE2 interacted with the headgroups of all lipids and StAc, also affecting the ordering of the tails for DODAB, DPPG and DPPC, according to in situ polarizationmodulated infrared reflection absorption spectroscopy (PM-IRRAS). Based on the analysis with the two characterization methods, we propose a model for the EE2 positioning and molecular groups involved in the interaction, which should be relevant to unveil the endocrine disrupting action of EE2.
Cerâmica
O resíduo (lodo) gerado nos decantadores das Estações de Tratamento de Água (ETA) possui composiç... more O resíduo (lodo) gerado nos decantadores das Estações de Tratamento de Água (ETA) possui composição variada, de acordo com a região onde ela está localizada, com o mês de coleta e com o coagulante usado. Neste trabalho foram feitas caracterizações, física, química e mineralógica, deste lodo e ensaios tecnológicos em corpos de prova, com a finalidade de avaliar a possibilidade de incorporação deste resíduo em massa cerâmica para produção de tijolos. Retração linear, absorção de água, porosidade e massa específica aparente e ensaios de resistência à flexão em corpos-de-prova, com diferentes concentrações de lodo, foram avaliadas. Também, foi avaliado o efeito do tipo de floculante usado na ETA, sobre as propriedades dos corpos-de-prova. A análise mineralógica mostrou que estes lodos apresentaram composição parecida com as das argilas usadas pelas cerâmicas. Em geral, a adição destes materiais à massa cerâmica piorou suas propriedades, entretanto, os valores obtidos para as propriedade...
Uploads
Papers by Priscila Alessio