Fourier transform Raman spectroscopy and chemometric tools have been used for exploratory analysis of pure corn and cassava starch samples and mixtures of both starches, as well as for the quantification of amylose content in corn and cassava starch samples. The exploratory analysis using principal component analysis shows that two natural groups of similar samples can be obtained, according to the amylose content, and consequently the botanical origins. The Raman band at 480 cm(-1), assigned to the ring vibration of starches, has the major contribution to the separation of the corn and cassava starch samples. This region was used as a marker to identify the presence of starch in different samples, as well as to characterize amylose and amylopectin. Two calibration models were developed based on partial least squares regression involving pure corn and cassava, and a third model with both starch samples was also built; the results were compared with the results of the standard colorimetric method. The samples were separated into two groups of calibration and validation by employing the Kennard-Stone algorithm and the optimum number of latent variables was chosen by the root mean square error of cross-validation obtained from the calibration set by internal validation (leave one out). The performance of each model was evaluated by the root mean square errors of calibration and prediction, and the results obtained indicate that Fourier transform Raman spectroscopy can be used for rapid determination of apparent amylose in starch samples with prediction errors similar to those of the standard method.
Nanorattles, comprised of a nanosphere inside a nanoshell, were employed as the next generation of plasmonic catalysts for oxidations promoted by activated O2 . After investigating how the presence of a nanosphere inside a nanoshell affected the electric-field enhancements in the nanorattle relative to a nanoshell and a nanosphere, the SPR-mediated oxidation of p-aminothiophenol (PATP) functionalized at their surface was investigated to benchmark how these different electric-field intensities affected the performances of Au@AgAu nanorattles, AgAu nanoshells and Au nanoparticles having similar sizes. The high performance of the nanorattles enabled the visible-light driven synthesis of azobenzene from aniline under ambient conditions. As the nanorattles allow the formation of electromagnetic hot spots without relying on the uncontrolled aggregation of nanostructures, it enables their application as catalysts in liquid phase under mild conditions using visible light as the main energy input.
Metallic nanomaterials displaying hollow interiors as well as sharp tips/branches at their surface (such as hollow nanodendrites) are attractive, because these features enable higher surface-to-volume ratios than their solid and/or rounded counterparts. This paper describes a simple strategy for the synthesis of Ag-Au nanodendrites in 15 s using Ag nanospheres prepared in a previous synthetic step as seeds. Our approach was based on the utilization of Ag nanospheres as seeds for Au deposition by a combination of galvanic replacement reaction between Ag and AuCl4(-)(aq) and AuCl4(-)(aq) reduction using hydroquinone in the presence of polyvinylpyrrolidone (PVP) as a stabilizer and water as the solvent. The produced Ag-Au nanodendrites presented monodisperse sizes, and their surface morphologies could be tuned as a function of growth time. Owing to their hollow interiors and sharp tips, the Ag-Au nanodendrites performed as effective substrates for surface-enhanced Raman scattering (SERS) detection of 4-MPy (4-mercaptopyridine) and R6G (rhodamine 6G) as probe molecules. We believe that the approach described herein can serve as a protocol for the fast and one-step synthesis of Ag-Au hollow nanondendrites with a wide range of sizes, compositions, and surface morphologies for applications in SERS and catalysis.
In this work, a simple but powerful method for controlling the size and surface morphology of AgAu nanodendrites is presented. Control of the number of Ag nanoparticle seeds is found to provide a fast and effective route by which to manipulate the size and morphology of nanoparticles produced via a combined galvanic replacement and reduction reaction. A lower number of Ag nanoparticle seeds leads to larger nanodendrites with the particles' outer diameter being tunable in the range of 45-148 nm. The size and surface morphology of the nanodendrites was found to directly affect their catalytic activity. Specifically, we report on the activity of these AgAu nanodendrites in catalyzing the gas-phase oxidation of benzene, toluene and o-xylene, which is an important reaction for the removal of these toxic compounds from fuels and for environmental remediation. All produced nanodendrite particles were found to be catalytically active, even at low temperatures and low metal loadings. Surprisingly, the largest nanodendrites provided the greatest percent conversion efficiencies.
Background: Oncological pain is one of the most prevalent and difficult-to-treat symptoms in patients with cancer. p-cymene (PC) is a monoterpene found in more than 100 different plant species, endowed with various pharmacological properties-particularly antinociceptive. Hypothesis/Purpose: PC has antinociceptive effect in a model of oncologic pain due to the activation of the descending inhibitory pathway of pain. Study Design: A pre-clinical, longitudinal, blind and randomized study. Methods: Male Swiss mice were induced with S180 cells in the right hind paw, then treated daily with PC (12.5, 25 and 50 mg/kg, s.c.) and screened for mechanical hyperalgesia, spontaneous nociception, nociception induced by non-noxious palpation, tumor growth, changes in the neuromuscular function and existence of bone degradation in the tumor area. The effect of PC on Ca 2+ currents (electrophysiological records), histological and neurochemical changes (immunofluorescence for Fos) were also evaluated. Results: PC reduced (p < 0.05) the mechanical hyperalgesia, the spontaneous (p < 0.001) and non-noxious palpation (p < 0.001) nociceptions, not changing the tumor development, neuromuscular function or histopathological aspects of the paw affected. PC reduced Fos expression in the spinal cord (p < 0.001) and increased this expression in the PAG (p < 0.05) and in the NRM (p < 0.01). PC decreased the density of calcium channel currents (p < 0.05). Conclusion: These results suggest the antinociceptive effect of PC on oncologic pain, probably acting in both ascending and descending pain pathways, and modulating the calcium channel currents in order to exert its effects.
Nanorattles,c omprised of an anosphere inside an anoshell, were employed as the next generation of plasmonic catalysts for oxidations promoted by activated O 2 . After investigating how the presence of an anosphere inside an anoshell affected the electric-field enhancements in the nanorattle relative to an anoshell and an anosphere,t he SPRmediated oxidation of p-aminothiophenol (PATP) functionalized at their surface was investigated to benchmark howt hese different electric-field intensities affected the performances of Au@AgAu nanorattles,A gAun anoshells and Au nanoparticles having similar sizes.T he high performance of the nanorattles enabled the visible-light driven synthesis of azobenzene from aniline under ambient conditions.A st he nanorattles allowt he formation of electromagnetic hot spots without relying on the uncontrolled aggregation of nanostructures,i t enables their application as catalysts in liquid phase under mild conditions using visible light as the main energy input.Oxidation reactions play ap ivotal role in industrial processes and academic research, [1][2][3] in which the activation of molecular oxygen (O 2 )a tt he catalyst surface represents apromising alternative to achieve high activities. [4][5][6] Interestingly,i th as been demonstrated that the surface plasmon resonance (SPR) excitation in silver (Ag) and gold (Au) nanostructures can generate activated O 2 at the metal surface. [7][8][9][10][11][12] This process occurs through the charge transfer of SPR-excited hot electrons to adsorbed O 2 molecules,allowing the use of visible-light to drive oxidation reactions. [7][8][9][10][11][12] Most studies on SPR-mediated transformations have focused on first-generation plasmonic catalysts,t hat is,c onventional Ag and Au nanoparticles such as quasi-spheres, cubes,wires,plates,among others. [7][8][9][10][11][12] Herein, we propose the utilization of metallic nanorattles,comprised of ananosphere inside of an anoshell, as the next generation of plasmonic catalysts towards SPR-mediated oxidations by taking advantage of the plasmon hybridization concept. [13,14] In nanorattles, plasmon hybridization between the nanoshell and nanosphere components can lead to much higher electric field (E-field) enhancements relative to its individual counterparts. [15][16][17] Nanorattles also enable the generation of electromagnetic hot spots in ac ontrollable manner without relying on the uncontrolled aggregation among individual nanostructures. [18,19] This is not possible in first-generation plasmonic catalysts,a nd aggregation leads to ad ecrease in surface area and thus catalytic performance.P reviously,h igh efficiencies towards SPR-mediated transformations were described at junctions between Ag nanocubes supported over Al 2 O 3 . [20] Although these junctions could present higher E-field enhancements relative to the nanorattles,t heir formation still relies on the uncontrolled aggregation and the synthesis of nanocubes is more complex relative to spherical nanoparticles.F inally,p rocedures for...
Together, these results demonstrated that CARV may be an interesting option for the development of new analgesic drugs for the management of cancer pain.
New AgAu tadpole nanocrystals were synthesized in a one-step reaction involving simultaneous galvanic replacement between Ag nanospheres and AuCl4(-)(aq.) and AuCl4(-)(aq.) reduction to Au in the presence of citrate. The AgAu tadpoles display nodular polycrystalline hollow heads, while their undulating tails are single crystals. The unusual morphology suggests an oriented attachment growth mechanism. Remarkably, a 1 nm thick Ag layer was found to segregate so as to cover the entire surface of the tadpoles. By varying the nature of the seeds (Au NPs), double-headed Au tadpoles could also be obtained. The effect of a number of reaction parameters on product morphology were explored, leading to new insights into the growth mechanisms and surface segregation behavior involved in the synthesis of bimetallic and anisotropic nanomaterials.
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