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991.
J.T. Matsushima W.M. Silva A.F. Azevedo M.R. Baldan N.G. Ferreira 《Applied Surface Science》2009,256(3):757-762
Electrochemical response of nitrate reduction was analyzed using Boron Doped Diamond (BDD) films grown with different boron levels and it was correlated with the electrode physico-chemical properties. X-ray photoelectron spectroscopy and contact angle measurements showed the evolution of oxygen content and the weattability associated to the chemical surface modification as boron content increase in such films. Raman spectroscopy showed that the broad peaks at 1220 and 500 cm−1 become more evident with the boron addition. Electrochemical measurements by square wave voltammetry for nitrate reduction showed a strong dependence between the doping level of the BDD film and the nitrate detection. BDD film grown with B/C ratio of 20,000 ppm presented the best sensibility to low concentration of nitrate. This result was analyzed from the linear relationship between the peak currents as a function of the nitrate concentration. This behavior was attributed to the changes in the diamond surface chemical and the film grain size. 相似文献
992.
C. Ferreira P. Ventura C. Grinde R. Morais A. Valente C. Neves M.J.C.S. Reis 《Procedia Chemistry》2009,1(1):88-91
A fabricated micro-mechanical sensor to assess the condition of automotive shock absorbers is presented. The monolithic sensor, measures the oil temperature, acceleration and internal pressure of the shock absorber. A dual mass accelerometer with optimized beam geometry is used for acceleration readout. In addition, a 23.1 μm thickness square membrane and two buried resistors are used for pressure and temperature sensing respectively. The proposed miniaturized sensor can be effectively integrated with standard single- and dual-tube shock absorbers. The data acquired during normal vehicle operation can be continuously used to monitor the condition of the shock absorbers, allowing shock absorbers to be replaced before their degradation significantly reduce the comfort, performance and safety of the vehicle. 相似文献
993.
Geraldo D. Matos Edmagno B. dos Reis Antonio C.S. Costa Sergio L.C. Ferreira 《Microchemical Journal》2009,92(2):135-139
In the present work, a cloud point extraction (CPE) system has been proposed for determination of species de chromium in the natural water samples, Cr(III) and Cr(VI). The procedure was based on the reaction of Cr(III) with 1-(2-pyridilazo)-2-naphtol (PAN) in a surfactant solution (Triton X-114) yielding a hydrophobic complex, which then is entrapped “in situ” in the surfactant micelles. When the temperature of the system was higher than the cloud point of Triton X-114, the complex of Cr(III)-PAN entered the surfactant-rich phase and thus separation of the analyte from the matrix was achieved. Separation of the two phases was accomplished by centrifugation for 15 min at 2500 rpm. The Cr(VI) assay is based on its reduction to Cr(III) by ascorbic acid which subsequently reacts with PAN in a similar manner. The main factors affecting the cloud point extraction, such as complexation pH (7.7), buffer concentration (0.025 mol L− 1) and microwave irradiation time (10 min) were optimized by response surface methodology (RSM) using Box–Behnken design. Under the optimized conditions, the preconcentration system (50 mL sample) permitted an enrichment factor of 48, linear range of 2.5–80 μg L− 1, limit of detection and quantification of 0.7 and 2.5 μg L− 1, respectively, and the relative standard deviation (n = 10) of 2.0% for 50 μg L− 1 Cr(III) solution and (n = 10) 5.5% for 10 μg L− 1. The proposed procedure was applied to the speciation of chromium in river water samples. The procedure affords recoveries of 84–115% and a relative standard deviation lower than 4.2%. The analytical results of total chromium in the river water samples under study agreed well with those by electrothermal atomic absorption spectrometry (ET AAS). It is proved that the procedure can be successfully employed as an alternative to the commonly used preconcentration and speciation analytical techniques. 相似文献
994.
Keng H. Hsu Peter L. Schultz Placid M. Ferreira Nicholas X. Fang 《Applied Physics A: Materials Science & Processing》2009,97(4):863-868
In this letter we demonstrate the possibility of using the solid ionic conductor Ag2S for the fabrication of sub-100 nnm features in a Cu film. We also evaluate the physical properties of the Cu–Ag2S interface through an electroimpedance spectroscopy study. Cu meander lines of 60 nm in width were obtained and the screening
length and the surface adatom concentration of Cu on the interface were also evaluated to be 20 nm and 1012/cm2 respectively. 相似文献
995.
J. Ferreira P. F. C. Menezes C. H. Sibata R. R. Allison S. Zucoloto O. Castro e Silva Jr V. S. Bagnato 《Laser Physics》2009,19(9):1932-1938
We have investigated a possible correlation between the photostability and photodynamic efficacy for different photosensitizers; hematoporphyrin derivatives and chlorines. To perform such analysis, we combined the depth of necrosis (d nec) measurement, expressed by the light threshold dose and a photodegradation parameter, measured from investigation of photosensitizer degradation in solution. The d nec analysis allows us to determine the light threshold dose and compare its value with the existent results in the literature. The use of simple models to understand basic features of Photodynamic Therapy (PDT) may contribute to the solid establishment of dosimetry in PDT, enhancing its use in the clinical management of cancers and others lesions. Using hematoporphyrin derivatives and chlorines photosensitizers we investigated their properties related to the photodegradation in solution and the light threshold dose (D th) in rat livers. 相似文献
996.
da Silva Fernanda Gabrielle Soares Ferreira Andréia Rodrigues dos Santos Clenilton Costa de Menezes Alan Silva de Cássia Silva Luz Rita Damos Flávio Santos 《Journal of Solid State Electrochemistry》2021,25(8-9):2213-2224
Journal of Solid State Electrochemistry - Photoelectrochemical systems based on half-photoelectrochemical cells have been widely exploited in the development of analytical methods. However, the... 相似文献
997.
Adsorption processes are gaining interest as methods of purifying industrial effluents. Most industries discharge effluents containing several components. The adsorption of phenol and m-cresol mixtures from aqueous solutions onto a macroporous polymeric adsorbent, Duolite ES-861, was investigated experimentally in a fixed-bed adsorber for different flowrates, feed concentrations and bed initial conditions (clean or pre-saturated).The experimental results are presented in this work, where the major objective is placed on the modelling of these fixed bed adsorption experiments using an extended Langmuir isotherm equation for two components, based on single component equilibrium data obtained for phenol and m-cresol.The model presented in this paper takes into account axial dispersion of the liquid phase, film diffusion and intraparticle mass transfer and successfully simulates the adsorption behaviour of the phenol and m-cresol mixtures. 相似文献
998.
Nathlia Siso Ferreira Mrcia Moraes Cascaes Lourivaldo da Silva Santos Mozaniel Santana de Oliveira Maria das Graas Bichara Zoghbi Isabella Santos Araújo Ana Paula Trovatti Uetanabaro Eloisa Helena de Aguiar Andrade Giselle Maria Skelding Pinheiro Guilhon 《Molecules (Basel, Switzerland)》2022,27(6)
Chemical composition of the essential oils and extracts and the antimicrobial activity of Miconia minutiflora were investigated. The flavanone glycosides, pinocembroside and pinocembrin-7-O-[4″,6″-HHDP]-β-D-glucose, were identified, along with other compounds that belong mainly to the triterpene class, besides the phenolics, gallic acid and methyl gallate. Sesquiterpenes and monoterpenes were the major compounds identified from the essential oils. Screening for antimicrobial activity from the methanolic extract of the leaves showed that the MIC and MMC values against the tested microorganisms ranged from 0.625 to 5 mg·mL−1 and that the extract was active against microorganisms, Staphyloccocus aureus, Escherichia coli, and Bacillus cereus. 相似文献
999.
Simplified version of the sodium salicylate method for analysis of nitrate in drinking waters 总被引:1,自引:0,他引:1
M.I.C. Monteiro F.N. Ferreira N.M.M. de Oliveira A.K. Ávila 《Analytica chimica acta》2003,477(1):125-129
The salicylate method for determination of nitrate in drinking waters has been simplified by using the calibration solutions for 54 days, and therefore, reducing the work time. The results obtained can be considered satisfactory with regard to limit of determination (0.10 mg l−1 nitrate as nitrogen (NO3−-N)), precision (relative standard deviations <4% for five determinations were found) and accuracy (recoveries from 88 to 106% for nitrate in spiked drinking water were obtained). 相似文献
1000.
A new method is described for the determination of Ni based on the cathodic adsorptive stripping of Ni(II) complexed with hydroxynaphthol blue (HNB) at a static mercury drop electrode. Optimal conditions were found to be: accumulation potential -0.50 V (vs. Ag/AgCl); final potential -1.10 V; accumulation time 50 sec; scan rate 200 mV/sec; linear scan mode; filter 0.1 sec; supporting electrolyte acetic acid/acetate (0.25M, pH = 6.0) and concentration of HNB 3.3 x 10(-5)M. The response of the system was found to be linear in a range of Ni concentrations from 25 ppb to the detection limit. The detection limit was found to be 1.7 nM (0.10 ppb) with 2 mins of accumulation time. The effect of various potential interferences (including a variety of cations, anions and organic surfactants) were also studied. With the exception of Co, at less than equimolar concentrations no significant interferences were observed. Al was found to interfere at high concentrations with respect to Ni, but Al concentrations up to 1000 ppb may be masked by sodium citrate or sodium fluoride. The utility of the method is demonstrated by the recovery of Ni in a doped sample of commercial mineral water. 相似文献