Silver nanoparticle aggregation not triggered by an ionic strength mechanism

Botasini, Santiago; Méndez, Eduardo

doi:10.1007/s11051-013-1526-4

Cited by 21 publications

(18 citation statements)

References 36 publications

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“…The SPR absorbance at 396.3 nm decreases with an increase in NaCl concentration. The decrease in the SPR band at 396.3 nm and the appearance of a new absorption band in the region 700–900 nm is an indication of aggregation and has been observed in other similar studies . It is suggested that in the millimolar concentration range, as used in this study, that the aggregation effect is due to the formation of insoluble AgCl and is not due to an ionic strength mechanism.…”

Section: Resultssupporting

confidence: 87%

SERS and DFT study of 5F‐PB‐22

Alkaseem

Baron

2018

J Raman Spectroscopy

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In this work, a joint experimental and theoretical study on the synthetic cannabinoid, 5F-PB-22 (1-(5-fluoropentyl)-8-quinolinyl ester-1H-indole-3-carboxylic acid) is reported. The molecular vibrations of 5F-PB-22 were investigated by Raman and surface-enhanced Raman spectroscopy (SERS) spectroscopies. In parallel, quantum chemical calculations based on density functional theory (DFT) with the hybrid B3LYP exchange-correlation functional coupled with the standard 3-21G basis set were used to determine the geometrical and vibrational characteristics of 5F-PB-22 and to predict the adsorption geometry of the molecule on the silver colloidal surface. The SERS spectrum of 5F-PB-22 was recorded using a 532-nm laser line and a hydroxylamine phosphate reduced silver colloid as the SERS substrate. SERS and Raman spectral bands have been assigned by comparison with the DFT calculated spectrum. A self-aggregation spectrum was obtained, but in order to obtain a spectrum with NaCl as the aggregating agent, a two-step procedure was developed. It was found that 10-mM NaCl can be used as a trigger for aggregation before adding 5F-PB-22followed by the addition of 20-to 100-mM NaCl to complete aggregation. Using this procedure, 5F-PB-22 was easily detected at 2.12 × 10 −8 M. Based on a predicted molecular adsorption geometry from the calculated molecular electrostatic potential and the SERS spectrum, it is proposed that the quinoline moiety of the molecule lies in a preponderant parallel orientation to the silver surface with the plane of the indole ring being perpendicular to the surface.The molecular orientation is affected by the surface coverage by 5F-PB-22 and the presence of Cl − .

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Section: Resultssupporting

confidence: 87%

SERS and DFT study of 5F‐PB‐22

Alkaseem

Baron

2018

J Raman Spectroscopy

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“…High order resonance modes, typically associated with NP aggregates, may be hidden under the predominance of the dipolar peak corresponding to individual small NPs, and the attenuation of this peak as the fraction of single particle decreases due to the presence of aggregates can be considered as the main signature of the aggregation process, in particular at the initial stages. Similar behavior has been seen experimentally in other works for citrate stabilized Ag NPs [48,49]. From the optical model described above, and the results shown in Figure 6, it is possible to conclude that the aggregation of Ag NPs is not easily detectable by optical means, in particular when comparing with the case of Au NPs (Figure 6g, h).…”

Section: Models For Nanoparticle Aggregationsupporting

confidence: 88%

“…Under these circumstances, calculations based on Mie theory should be replaced by a more precise theoretical approximation such as the finite-difference time domain (FDTD) [51]. Finally, it is worth mentioning that numerous works aiming to evaluate the stability of Ag NPs by optical means end up with experimental observations not far from what has been described here [48,49].…”

Section: Models For Nanoparticle Aggregationmentioning

confidence: 99%

Modeling the Optical Responses of Noble Metal Nanoparticles Subjected to Physicochemical Transformations in Physiological Environments: Aggregation, Dissolution and Oxidation

Piella

Bastús

Puntes

2016

Zeitschrift Für Physikalische Chemie

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Herein, we study how optical properties of colloidal dispersions of noble metal nanoparticles (Au and Ag) are affected by processes such as aggregation and oxidative dissolution. The optical contributions of these processes to the extinction spectra in the UV-vis region are often overlapped, making difficult its interpretation. In this regard, modeling the UV-vis spectra (in particular absorbance curve, peaks position, intensity and full width at half maximum -FWHM) of each process separately offers a powerful tool to identify the transformation of NPs under relevant and complex scenarios, such as in biological media. The proper identification of these transformations is crucial to understand the biological effects of the NPs.

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“…On the other hand, with the methanol solvent, the absorbance peak is decreased and red-shifted. This phenomenon of agglomeration and precipitation of nanoparticles in different mediums has been observed by several authors [8][9]. Then, we changed the molar concentration of AgNO 3 from 0.0015 mole to 0.0035 mole under the same conditions at ambient temperature.…”

supporting

confidence: 67%

“…This increase of the nanoparticles can be explained by the agglomeration phenomenon, present in a methanol medium. Moreover, several authors have reported [9]- [11] that during the precipitation of two or more nanoparticles, the resulting absorption peak corresponds to the total volume of the new structure of the nanoparticles, which in most cases form a spheroidal shape with the corresponding volume and aspect ratio of initial nanoparticles.…”

mentioning

confidence: 99%