Two different silver colloids were prepared by chemical reduction of silver nitrate with trisodium citrate and hydroxylamine hydrochloride to compare their characteristics in relation to their ...possible use in surface-enhanced Raman scattering (SERS) spectroscopy. The morphology and plasmon resonance of the single nanoparticles and aggregates integrating these colloids were characterized by means of UV−vis absortion spectroscopy and scanning electron microscopy, revealing important differences between each type of nanoparticle as concerns their physical properties. These metallic systems also manifested differences in the aggregation and the adherence to glass surfaces, revealing significant differences in the chemical surface properties of these nanoparticles. SERS and surface-enhanced IR also indicated the presence of interference bands which can overlap the spectra of the analyte, mainly in the case of the citrate colloid. All these differences have an important influence on the applicability of these nanostructured systems in SERS. In fact, the enhancement factor and spectral pattern of the SERS obtained by using alizarin as a molecule probe are different.
In this work we report the study of the chemical modifications undergone by flavonoids, especially by quercetin (QUC), under alkaline conditions by UV-visible absorption, Raman and surface-enhanced ...Raman scattering (SERS) spectroscopy, the study was performed in aqueous solution and also on Ag nanoparticles (AgNPs). Several processes are involved in the effect of alkaline pH both in solution and on AgNPs: autoxidation affecting mainly the C-ring of the molecule and giving rise to the molecular fragmentation leading to simpler molecular products, and/or the dimerization and further polymerization leading to species with a higher molecular weight. In addition, there exists a clear structure-instability correlation concerning mainly particular groups in the molecule: the C3-OH group in the C-ring, the catechol moiety in the B-ring and the C2=C3 bond also existing in the C-ring. QUC possesses all these groups and exhibits high instability in alkaline solution. The SERS spectra registered at different pH revealed a change in the dimerization protocol of QUC going from the A- and C-rings-like-condensation to B-ring-like-condensation. Increasing the knowledge of the chemical properties of these compounds and determining the structure-activity relationship under specific environmental factors allow us to improve their beneficial properties for health as well as the preservation of Cultural Heritage objects, for example, by preventing their degradation.
Surface-enhanced Raman scattering combines extremely high sensitivity, due to enhanced Raman cross-sections comparable or even better than fluorescence, with the observation of vibrational spectra of ...adsorbed species, providing one of the most incisive analytical methods for chemical and biochemical detection and analysis. SERS spectra are observed from a molecule-nanostructure enhancing system. This symbiosis molecule-nanostructure is a fertile ground for theoretical developments and a realm of applications from single molecule detection to biomedical diagnostic and techniques for nanostructure characterization.
The adsorption of beta2-adrenergic agonist (βAA) drugs clenbuterol, salbutamol, and terbutaline on metal surfaces has been investigated in this work by means of surface-enhanced Raman scattering ...(SERS). To assist in this investigation, a previous vibrational (IR and normal Raman) characterization of these drugs was performed, supported by ab initio density functional theory calculations. The application of SERS was aimed to apply this highly sensitive technique, based on localized surface plasmon resonance, in the detection of βAA at trace concentrations and as a possible alternative method which can be postulated in routine antidoping analysis. The adsorption of these drugs was studied in depth at different experimental conditions: on Au and Ag, at different pHs, and with varying adsorbate concentration. Moreover, plasmon resonance spectroscopy was employed to investigate the adsorption of these drugs on the metal nanoparticles as well as their aggregation. It was found that the adsorption of these molecules is more effective on gold nanoparticles and at acidic pH, based on the direct interaction of the aromatic or aliphatic moieties through ionic or coordination bonds with the metal. These drugs followed a Langmuir adsorption model from which the adsorption constant and the limit of detection can be determined.
This paper discusses the combined use of tools from dynamical systems theory and remote sensing techniques and shows how they are effective instruments which may greatly contribute to the decision ...making protocols of the emergency services for the real-time management of oil spills. This work presents the successful interplay of these techniques for a recent situation, the sinking of the Oleg Naydenov fishing ship that took place in Spain, close to the Canary Islands, in April 2015.
•Real-time response to a marine oil spill•Satellite detection of an oil spill•Lagrangian descriptors and the Lagrangian “skeleton” governing transport.•Dynamical systems analysis of satellite and model data.
Different Ag nanoparticles were prepared by four different methods (chemical reduction with trisodium citrate, chemical reduction with hydroxylamine hydrochloride, laser ablation and laser
in situ ...photoreduction) to compare their applicability in surface-enhanced Raman scattering (SERS), their stability and other interfacial characteristics such as the pH, surface availability and the surface potential. This study was conducted by using the anthraquinone dye alizarin as a molecular probe since this molecule is able to be adsorbed onto the metal through three different forms, which relative proportions depend on the interfacial properties of the exposed metal surfaces.
SERS enhancement factor (
G) of Ag nanoparticles prepared by four different methods: chemical reduction with hydroxilamine (SH), chemical reduction with citrate (SC), laser ablation (SA) and laser photoreduction (SP).
Abstract The superb image quality, stability, and sensitivity of JWST permit deconvolution techniques to be pursued with a fidelity unavailable to ground-based observations. We present an assessment ...of several deconvolution approaches to improve image quality and mitigate the effects of the complex JWST point-spread function (PSF). The optimal deconvolution method is determined by using WebbPSF to simulate JWST’s complex PSF and MIRISim to simulate multiband JWST/Mid-Infrared Imager Module (MIRIM) observations of a toy model of an active galactic nucleus (AGN). Five different deconvolution algorithms are tested: (1) Kraken deconvolution, (2) Richardson–Lucy, (3) the adaptive imaging deconvolution algorithm, (4) sparse regularization with the Condat–Vũ algorithm, and (5) iterative Wiener filtering and thresholding. We find that Kraken affords the greatest FWHM reduction of the nuclear source of our MIRISim observations for the toy AGN model while retaining good photometric integrity across all simulated wave bands. Applying Kraken to Galactic Activity, Torus, and Outflow Survey (GATOS) multiband JWST/MIRIM observations of the Seyfert 2 galaxy NGC 5728, we find that the algorithm reduces the FWHM of the nuclear source by a factor of 1.6–2.2 across all five filters. Kraken images facilitate detection of extended nuclear emission ∼2.″5 (∼470 pc, position angle ≃ 115°) in the SE–NW direction, especially at the longest wavelengths. We demonstrate that Kraken is a powerful tool to enhance faint features otherwise hidden in the complex JWST PSF.
Carbonation takes place in building materials when atmospheric CO
2 reacts with Ca
2+ present in the pore solution. Of the three crystallized forms of calcium carbonate, calcite is the most ...thermodynamically stable. Raman spectroscopy is a very useful technique for distinguishing between calcite, aragonite and vaterite. In the present study, micro-Raman techniques are used for the first time to establish the existence of various forms of calcium carbonate at different depths in fully carbonated lime mortar, in trials conducted at a temperature of 20 °C and 75% relative humidity in a chamber with atmospheric CO
2. A new model is introduced for samples containing two or three polymorphs. The size of the calcite crystals formed, also determined with this technique, was estimated to be between 25 and 30 μm.
Organochlorine pesticide endosulfan has been detected for the first time by using surface-enhanced Raman scattering (SERS) at trace concentrations. The bis-acridinium dication lucigenine was ...successfully used as a molecular assembler in the functionalization of metal nanoparticles to facilitate the approach of the pesticide to the metal surface. From the SERS spectra valuable information about the interaction mechanism between the pesticide and lucigenin can be deduced. In fact, endosulfan undergoes an isomerization upon adsorption onto the metal, while the viologen undergoes a rotation of the acridinium planes to better accommodate the pesticide molecule. An interaction between the N atom of the central acridinium ring and the pesticide Cl–C
C–Cl fragment is verified through a charge-transfer complex. The present study affords important information which can be applied to the design of chemical sensor systems of persistent organic pollutants based on the optical detection on functionalized metal nanoparticle.
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