Papers by Emerson Camargo
Journal of Solid State Chemistry, 2004
Lead titanate was synthesized by the OPM wet-chemical route by the dissolution of Ti metal in H 2... more Lead titanate was synthesized by the OPM wet-chemical route by the dissolution of Ti metal in H 2 O 2 followed by the addition of Pb 2+ at high pH, resulting in a reactive and amorphous precipitate with (Pb:Ti=1:1) mole ratio, which was heat treated between 400 C and 700 C. The amorphous precipitate was characterized by DSC, and all of the powders were characterized by X-ray diffraction, Raman and XAS (EXAFS and XANES) spectroscopy at the Ti K edge. A metastable, stoichiometric and cubic pyrochlore phase (Pb 2 Ti 2 O 6 , Fd3m) was identified by XRD and Raman spectroscopy up to approx. 450 C. Only tetragonal PbTiO 3 was identified at higher temperatures. XAS spectra showed that the local structure around the absorbing Ti atom of the intermediate pyrochlore phase is similar to that observed in the amorphous precursor. This fact indicates that the metastable intermediate pyrochlore (Pb 2 Ti 2 O 6) is kinetically favored to be formed because of its similarity to the amorphous precipitate, instead of the slightly different and thermodynamically favored tetragonal (PbTiO 3 , P4/mmm) perovskite structure that is only formed at higher temperatures, after the crystallization of the metastable intermediate pyrochlore.
Journal of Materials Research, 2014
Colloids and Interfaces, 2017
The ability to control the assembly of nanoparticles on substrates used in plasmon-enhanced spect... more The ability to control the assembly of nanoparticles on substrates used in plasmon-enhanced spectroscopy continues to drive research in the field of nanofabrication. Here we describe the use of fungi as soft biotemplates to fabricate nanostructured microtubules with gold and gold-silver nanoparticles with potential applications as sensors and biosensors. In the first step, spores of the filamentous fungus Cladosporium sphaerospermum were inoculated in a suspension of gold nanoparticles, forming stable microtubules of gold nanoparticles during fungus growth. These materials were exposed to a second suspension of silver nanoparticles, resulting in complexes multilayers structures of gold and silver nanoparticles, which were evaluated as substrates for surface-enhanced Raman scattering (SERS) using small amounts of thiophenol as probe molecules directly on the microtubules. Both gold and the gold-silver substrates provide the SERS effect.
Antibiotics (Basel, Switzerland), Jan 26, 2018
The phytosynthesis of metal nanoparticles is nowadays attracting the increased attention of resea... more The phytosynthesis of metal nanoparticles is nowadays attracting the increased attention of researchers and is much needed given the worldwide matter related to environmental contamination. The antimicrobial activity of colloidal and spray formulation of silver nanoparticles (AgNPs) synthesized by pomegranate peel extract against and , and their cytotoxicity in mammalian cells were tested in the present study. Dry matter, pH, total phenolics, and ellagic acid in the extract were determined. Then, AgNPs were phytosynthesized and characterized by X-ray diffraction, electron transmission microscopy, dynamic light scattering, zeta potential, and Ag⁺ dosage. Spray formulations and respective chemical-AgNP controls were prepared and tested. The peel extract reduced more than 99% of Ag⁺, and produced nanoparticles with irregular forms and an 89-nm mean size. All AgNP presented antimicrobial activity, and the spray formulation of green-AgNP increased by 255 and 4 times the effectiveness aga...
Antibiotics (Basel, Switzerland), Jan 27, 2018
Nanobiomaterials combining remineralization and antimicrobial abilities would bring important ben... more Nanobiomaterials combining remineralization and antimicrobial abilities would bring important benefits to control dental caries. This study aimed to produce nanocompounds containing calcium glycerophosphate (CaGP) and silver nanoparticles (AgNP) by varying the reducing agent of silver nitrate (sodium borohydride (B) or sodium citrate (C)), the concentration of silver (1% or 10%), and the CaGP forms (nano or commercial), and analyze its characterization and antimicrobial activity against ATCC (10231) and (25175) by the microdilution method. Controls of AgNP were produced and silver ions (Ag⁺) were quantified in all of the samples. X-ray diffraction, UV-Vis, and scanning electron microscopy (SEM) analysis demonstrated AgNP associated with CaGP. Ag⁺ ions were considerably higher in AgCaGP/C. was susceptible to nanocompounds produced with both reducing agents, regardless of Ag concentration and CaGP form, being Ag10%CaGP-N/C the most effective compound (19.5⁻39.0 µg Ag mL). While ...
Future microbiology, Mar 14, 2018
To synthesize, characterize and evaluate the antimicrobial and antibiofilm activities of novel na... more To synthesize, characterize and evaluate the antimicrobial and antibiofilm activities of novel nanocomposites containing silver nanoparticles (AgNPs) associated or not to β-calcium glycerophosphate. These nanocomposites were produced through a 'green' route using extracts of different parts of pomegranate. Antimicrobial and antibiofilm properties against Candida albicans and Streptococcus mutans were determined by the minimum bactericidal/fungicidal concentration and biofilm density after treatments. All extracts used were successful in producing AgNPs. Composites made with peel extracts showed the highest antimicrobial and antibiofilm activity against both microorganisms tested and performed similarly or even better than chlorhexidine. AgNPs associated or not to calcium glycerophosphate produced by a 'green' process may be a promising novel antimicrobial agent against oral microorganisms.
Ceramics International, 2016
Bismuth titanate with sillenite structure (Bi 12 TiO 20) was prepared at lower temperatures and s... more Bismuth titanate with sillenite structure (Bi 12 TiO 20) was prepared at lower temperatures and shorter times using a modified oxidant peroxide method (OPM). Bi 12 TiO 20 was synthesized utilizing commercial Bi 2 O 3 and reactive titanium dioxide nanoparticles having peroxo-modified surfaces. Rather than depending on particle size, the reaction mechanism is related to the highly exothermic decomposition of peroxo groups, regardless the titanium source used, which locally releases a large amount of energy that can accelerate the reaction, similar to self-propagating high temperature routes (SHS).
Journal of endodontics, Jan 23, 2016
Silver nanoparticles have been used for different purposes in dentistry, including endodontic tre... more Silver nanoparticles have been used for different purposes in dentistry, including endodontic treatments. The aim of this study was to determine the cytotoxicity of different types of silver nanoparticles on mouse fibroblast cell line L929 and the reaction of subcutaneous connective tissue of Wistar rats to these nanoparticles. Silver nanoparticles of an average size of 5 nm were synthesized with ammonia (SNA) or polyvinylpyrrolidone (SNP). L929 was exposed to SNA and SNP (0.1-100 μg/mL), and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and enzyme-linked immunosorbent assays were performed after 6, 24, and 48 hours. Culture medium was used as the control. Sixteen rats received, individually, 3 polyethylene tubes filled with a fibrin sponge embedded in 100 μL SNA or SNP (1 μg/mL). A fibrin sponge with no embedding was the control. Tissue reaction was performed qualitatively and quantitatively after 7, 15, 30, and 90 days of implantation in the dorsal connective tissue...
Journal of Colloid and Interface Science, 2016
Distinct affinities between the organic and inorganic phases were observed in nanocomposites prep... more Distinct affinities between the organic and inorganic phases were observed in nanocomposites prepared through a colloidal route with carboxylated nitrile rubber and modified silica nanoparticles, which resulted in variable mechanical properties and improved thermal stability. Nanoparticles with modified surface affected the macromolecular arrangements of the elastomeric matrix, changing the final mechanical behavior of the nanocomposite, which could be predicted by the spin-lattice relaxation time measured by solid-state NMR. It was also possible to identify how each different nanoparticle affected the molecular dynamic of nanocomposite, correlating the dynamic-mechanical analysis with the NMR data of the saturated carbons of the elastomer.
Medical Mycology, 2014
Our aim in this study was to evaluate how the chemical stability of silver nanoparticles (SNs) in... more Our aim in this study was to evaluate how the chemical stability of silver nanoparticles (SNs) influences their efficacy against Candida albicans and C. glabrata biofilms. Several parameters of SN stability were tested, namely, temperature (50 o C, 70 o C, and 100 o C), pH (5.0 and 9.0), and time of contact (5 h and 24 h) with biofilms. The control was defined as SNs without temperature treatment, pH 7, and 24 h of contact. These colloidal suspensions at 54 mg/L were used to treat mature Candida biofilms (48 h) formed on acrylic. Their efficacy was determined by total biomass and colony-forming unit quantification. Data were analyzed using analysis of variance and the Bonferroni post hoc test (α = 0.05). The temperature and pH variations of SNs did not affect their efficacy against the viable cells of Candida biofilms (P > 0.05). Moreover, the treatment periods were not decisive in terms of the susceptibility of Candida biofilms to SNs. These findings provide an important advantage of SNs that may be useful in the treatment of Candida-associated denture stomatitis.
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2014
h i g h l i g h t s • We modified silica nanoparticles with a silane agent and with a polymeric s... more h i g h l i g h t s • We modified silica nanoparticles with a silane agent and with a polymeric shell. • SiO 2 nanoparticles induced arrangements in XNBR nanocomposites. • The SDS induced the polymeric macromolecules organization in the nanocomposites. • The silica nanoparticles dispersed in the polymer forming a mass fractal system. • The silica nanoparticles and XNBR chains formed three-dimensional network.
Journal of Nanoparticle Research, 2014
Pure (Bi 12 TiO 20) and niobium-doped (Bi 12 Ti 1-x Nb x O 20 , with ''x'' up to 0.15) bismuth ti... more Pure (Bi 12 TiO 20) and niobium-doped (Bi 12 Ti 1-x Nb x O 20 , with ''x'' up to 0.15) bismuth titanates were prepared by the oxidant peroxide method (OPM) and used to photodegradate rhodamine b (RhB) under UV and visible radiation. Rietveld refinements showed samples consisting mainly of sillenite structure with small amounts of a perovskite secondary phase in the Nb-doped materials. These bismuth-based catalysts exhibited superior performance than the commercial TiO 2 , with band gaps ranging from 2.53 of pure Bi 12 TiO 20 to 2.73 eV depending on the amount of niobium added, which seems to be responsible for the improved photoactivity of the doped catalysts under UV radiation.
Polymer Testing, 2009
The chemical behavior of styrene-butadiene rubber (SBR) and of the SBR/TiO 2 and photodegraded SB... more The chemical behavior of styrene-butadiene rubber (SBR) and of the SBR/TiO 2 and photodegraded SBR/TiO 2 nanocomposites was investigated through nuclear magnetic resonance spectroscopy (NMR) in the solid state with magic angle spinning (MAS). The 13 C cross polarization/magic angle spinning (CP/MAS) routine spectrum allowed us to obtain information on the polymer microstructure and also to evaluate the domain mobilities. The variation contact time and the proton spin-lattice relaxation time in the rotating frame (T 1 rH) were determinant factors to evaluate the dynamic molecular motion. The NMR spectrum of the nanocomposites was dislocated 5 ppm to higher chemical shift, indicating the presence of a strong interaction between the polymer chains and the TiO 2 nanoparticles. The VTC experiment showed a rigid domain in the SBR/TiO 2 photodegraded nanocomposite due to cross-linking reactions.
Mycoses, 2013
Although silver nanoparticles (SN) have been investigated as an alternative to conventional antif... more Although silver nanoparticles (SN) have been investigated as an alternative to conventional antifungal drugs in the control of Candida-associated denture stomatitis, the antifungal activity of SN in combination with antifungal drugs against Candida biofilms remains unknown. Therefore, the aim of this study was to evaluate the antifungal efficacy of SN in combination with nystatin (NYT) or chlorhexidine digluconate (CHG) against Candida albicans and Candida glabrata biofilms. The drugs alone or combined with SN were applied on mature Candida biofilms (48 h), and after 24 h of treatment their antibiofilm activities were assessed by total biomass quantification (by crystal violet staining) and colony forming units enumeration. The structure of Candida biofilms was analysed by scanning electron microscopy (SEM) images. The data indicated that SN combined with either NYT or CHG demonstrated synergistic antibiofilm activity, and this activity was dependent on the species and on the drug concentrations used. SEM images showed that some drug combinations were able to disrupt Candida biofilms. The results of this study suggest that the combination of SN with NYT or CHG may have clinical implications in the treatment of denture stomatitis. However, further studies are needed before recommending the use of these drugs safely in clinical situations.
Letters in Applied Microbiology, 2012
Aim: The purpose of this work was to evaluate the size-dependent antifungal activity of different... more Aim: The purpose of this work was to evaluate the size-dependent antifungal activity of different silver nanoparticles (SN) colloidal suspensions against Candida albicans and Candida glabrata mature biofilms. Methods and Results: The research presented herein used SN of three different average sizes (5, 10 and 60 nm), which were synthesized by the reduction of silver nitrate through sodium citrate and which were stabilized with ammonia or polyvinylpyrrolidone. Minimal inhibitory concentration (MIC) assays were performed using the microdilution methodology. The antibiofilm activity of SN was determined by total biomass quantification (by crystal violet staining) and colony forming units enumeration. MIC results showed that all SN colloidal suspensions were fungicidal against the tested strains at very low concentrations (0AE4-3AE3 lg ml)1). With regard to biomass quantification, SN colloidal suspensions were very effective only against C. glabrata biofilms, achieving biomass reductions around 90% at a silver concentration of 108 lg ml)1. In general, all SN suspensions promoted significant log 10 reduction of the mean number of cultivable biofilm cells after exposure to silver concentrations at or higher than 108 lg ml)1. Moreover, the results showed that the particle size and the type of stabilizing agent used did not interfere in the antifungal activity of SN against Candida biofilms. Conclusions: This study suggests that SN have antifungal therapeutic potential, but further studies are still required namely regarding formulation and delivery means. Significance and Impact of the Study: SN may contribute to the development of new strategies for the improvement of oral health and quality of life particularly of the complete denture wearers.
Journal of Prosthodontics, 2011
The aim of this study was to evaluate a denture base resin containing silver colloidal nanopartic... more The aim of this study was to evaluate a denture base resin containing silver colloidal nanoparticles through morphological analysis to check the distribution and dispersion of these particles in the polymer and by testing the silver release in deionized water at different time periods. Materials and Methods: A Lucitone 550 denture resin was used, and silver nanoparticles were synthesized by reduction of silver nitrate with sodium citrate. The acrylic resin was prepared in accordance with the manufacturers' instructions, and silver nanoparticle suspension was added to the acrylic resin monomer in different concentrations (0.05, 0.5, and 5 vol% silver colloidal). Controls devoid of silver nanoparticles were included. The specimens were stored in deionized water at 37 • C for 7, 15, 30, 60, and 120 days, and each solution was analyzed using atomic absorption spectroscopy. Results: Silver was not detected in deionized water regardless of the silver nanoparticles added to the resin and of the storage period. Micrographs showed that with lower concentrations, the distribution of silver nanoparticles was reduced, whereas their dispersion was improved in the polymer. Moreover, after 120 days of storage, nanoparticles were mainly located on the surface of the nanocomposite specimens. Conclusions: Incorporation of silver nanoparticles in the acrylic resin was evidenced. Moreover, silver was not detected by the detection limit of the atomic absorption spectrophotometer used in this study, even after 120 days of storage in deionized water. Silver nanoparticles are incorporated in the PMMA denture resin to attain an effective antimicrobial material to help control common infections involving oral mucosal tissues in complete denture wearers.
Journal of Nanoparticle Research, 2010
Nanocrystalline zirconium oxide was synthesized by hydrothermal treatment of ZrO(NO 3) 2 and ZrOC... more Nanocrystalline zirconium oxide was synthesized by hydrothermal treatment of ZrO(NO 3) 2 and ZrOCl 2 aqueous solutions at different temperatures and time in presence of hydrogen peroxide. Hydrothermal treatment of zirconium salts (0.25 and 0.50 mol L-1) produced nanocrystalline monoclinic ZrO 2 powders with narrow size distribution, which were formed by the attachment of the smaller particles with crystallites size of 3.5 nm, estimated by means of the Scherrer's equation and confirmed by transmission electronic microscopy. Typical monoclinic zirconium oxide X-ray powder diffraction patterns and Raman spectra were obtained for all the crystalline powders. It was observed that the crystallization depends strongly on the temperature, resulting in amorphous material when the synthesis was realized at 100°C, and crystalline with monoclinic phase when synthesized at 110°C, independently of the salt used. Zirconium oxide colloidal nanoparticles were formed only at hydrothermal treatments longer than 24 h. The stability of the colloids was successfully characterized of zeta potential, showing an initial value of ? 59.2 mV in acid media and isoelectric point at pH = 5.2, in good agreement with previous studies.
Journal of Colloid and Interface Science, 2011
A new method to stabilize silver nanoparticles by the addition of ammonia is proposed. Colloidal ... more A new method to stabilize silver nanoparticles by the addition of ammonia is proposed. Colloidal dispersions of silver nanoparticles were synthesized by the Turkevich method using sodium citrate to reduce silver nitrate at high pH and at 90°C. After approximately 12 min, a diluted ammonia solution was added to the reaction flask to form soluble diamine silver (I) complexes that played an important growth moderating role, making it possible to stabilize metallic silver nanoparticles with sizes as small as 1.6 nm after 17 min of reaction. Colloidal dispersions were characterized by UV-visible absorption spectroscopy, X-ray diffraction, and transmission electronic microscopy.
Journal of Applied Polymer Science, 2009
Journal of Applied Polymer Science, 2012
Much has been talking about the advantages of polymeric nanocomposites, but little is known about... more Much has been talking about the advantages of polymeric nanocomposites, but little is known about the influence of nanoparticles on the stability of these materials. In this sense, we studied the influence of both oxides of zirconium and titanium, known to have photocatalytic properties, as well as the influence of synthetic clay Laponite on the photodegradation of styrene-butadiene rubber (SBR). SBR nanocomposites were prepared by the colloidal route by mixing commercial polymer lattices and nanometric anatase TiO 2 , monoclinic ZrO 2 or exfoliated Laponite clays colloidal suspensions. To better understand the degradation mechanisms that occur in these nanocomposites, the efficiency of different photocatalysts under ultraviolet radiation was monitored by FT-IR and UV-vis spectroscopies and by differential scanning calorimetric. It was observed that TiO 2 and ZrO 2 nanoparticles undoubtedly acted as catalysts during the photodegradation process with different efficiencies and rates. However, when compared to pure SBR samples, the polymer degradation mechanism was unaffected. Unlike studies with nanocomposites montmorillonite, exfoliated laponite clay effectively acts as a photostabilizer of polymer UV photodegradation. V
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Papers by Emerson Camargo