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1
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Activation of Silver Colloids for Enhancement of Raman Scattering

100%
Kruszewski S., Cyrankiewicz M.
Acta Physica Polonica A
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2011
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vol. 119
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issue 6A
1018-1022
EN
Obtaining of systems that provide ever-increasing enhancement of the Raman scattered light is a big challenge. The silver colloids obtained by reduction of silver nitrate by trisodium citrate are the most promising enhancement systems. Nanoparticles of silver forming fresh colloid obtained by this way exhibit in extinction spectrum the absorption band proving of the surface plasmons excitation, but do not enhance the Raman scattered light, are not surface enhanced Raman scattering active. Adding of KCl or HNO_3 causes the surface enhanced Raman scattering activation, i.e. causes that the conditions for aggregation of nanoparticles and for adsorption on their surface of molecules providing Raman scattering are created. Increasing amount of added KCl or HNO_3 leads to significant changes in the extinction spectrum and to significant increase in intensity of surface enhanced Raman scattering. The observed changes in extinction spectrum are mainly due to progressive aggregations of nanoparticles. In junctions between nanoparticles existing inside aggregates the condition for single molecule surface enhanced Raman scattering are fulfilled and therefore aggregation leads to increase in average surface enhanced Raman scattering intensity. Silver colloid activated by using KCl provides about 10-fold higher surface enhanced Raman scattering than that treated with HNO_3.
2
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Rhodamine 6G as a Mediator of Silver Nanoparticles Aggregation

100%
Kruszewski S., Cyrankiewicz M.
Acta Physica Polonica A
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2013
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vol. 123
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issue 6
965-969
EN
Surface-enhanced Raman scattering is the phenomenon where a huge increase of Raman scattering intensity from molecules situated close to the metal nanoobjects is observed. Our study is focused on the method of SERS-activation of silver nanoparticles and, in the future, the application of thus obtained SERS substrates for biomedical purposes. As expected, the intensity of Raman scattering from rhodamine 6G used here as a SERS probe strongly increase during the early stages of aggregation of silver sol. Moreover, the evolution of extinction spectra and changes in the degree of the colloid aggregation observed in DLS measurements point out that molecules of the dye do not participate passively in the aggregation process but greatly affect its course.
3
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Aggregated Silver Sols as SERS Substrates

100%
Kruszewski S., Cyrankiewicz M.
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EN
The unique plasmonic properties of the noble metal colloidal nanoparticles make them promising enhancement substrates for surface-enhanced Raman scattering. Obtaining of systems that provide ever-increasing enhancement of the Raman scattered light is a big challenge. Silver colloids studied here are prepared by Lee-Meisel's method. Rhodamine 6G and rhodamine B are used as probe adsorbates. The "raw" colloids obtained in this way exhibit a characteristic extinction band proving surface plasmons excitation, but do not enhance the Raman signal. Theoretical calculations indicate that the extremely large electromagnetic field is induced in the junctions between metallic nanostructures so some degree of their aggregation is necessary to achieve a sufficient gain value. The addition of aggregating agents (KCl or HCl) leads to significant changes in the extinction spectrum and to significant increase in the intensity of surface-enhanced Raman scattering. The experiments show that chloride can not only promote the aggregation process but also effectively affect chemical mechanisms contributing to surface-enhanced Raman scattering.
4
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Determination of the Protein-Binding Properties of Camptothecins by Means of Optical Spectroscopy Methods

81%
Ziomkowska B., Cyrankiewicz M., Wybranowski T., Kruszewski S.
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vol. 125
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issue 4A
A-61-A-65
EN
Optical spectroscopy methods are widely used in studies of drugs. The affinity of camptothecins - anticancer agents - to human serum albumin (HSA) was determined in this work. Camptothecins (CPTs) exist in two forms: active lactone and open ring inactive carboxylate. In blood, the hydrolysis process of lactone form occurs which leads to deactivation of CPTs. Research is being done on biophysical properties of synthesized CPT compounds, in particular on binding to albumin. The affinity to plasma proteins is an important determinant of stability of CPTs in blood. The following analogues of CPT were tested in this paper: irinotecan, SN-38, topotecan, and 9-amino camptothecin. Using the method of fluorescence anisotropy measurement, the association constants of the studied compounds to HSA were determined. The authors attempted to determine the deactivation rate of topotecan in HSA solution using Principal Component Analysis and Factor Analysis of absorption spectra recorded during hydrolysis process of lactone form.
5
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Silver Nanoparticles as Enhancing Substrates for Raman and Fluorescence Spectroscopy

81%
Cyrankiewicz M., Wybranowski T., Kruszewski S.
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vol. 125
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issue 4A
A-11-A-15
EN
The enhancing properties of silver nanoparticles in surface-enhanced Raman scattering (SERS) and metal-enhanced fluorescence (MEF) are studied in this work. The obtained results confirm that the partial aggregation of nanoparticles leads to a great increase of Raman scattering cross-section but there are significant differences in SERS-activity of colloidal silver treated with various aggregating compounds. The differences are interpreted through the analysis of both experimental and computational results. The same silver colloid covered with silica shell preventing the fluorescence quenching makes possible a several-fold increase in fluorescence emission. The effect strongly depends on thickness of the outer layer of nanoparticles. Geometrical parameters of nanoparticles (radius or radius and thickness of the adsorption layer in core-shell systems) are determined on the basis of the dynamic light scattering (DLS) data and extinction spectra analysis.
6
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Enhancement of FITC Fluorescence by Silver Colloids and Silver Island Films

71%
Kruszewski S., Wybranowski T., Cyrankiewicz M., Ziomkowska B., Pawlaczyk A.
Acta Physica Polonica A
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2008
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vol. 113
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issue 6
1599-1608
EN
Silver colloids and silver island films as fluorescence enhancement systems are the subject of this paper. Enhancement of fluorescence of molecules placed near metallic nanoparticles is a result of resonance interaction of exciting and emitted lights with surface plasmons. Two models explaining this phenomenon are presented. Processes of silver colloids and silver island films forming are described. Results of extinction, absorption and scattering studies of fluorescence enhancement systems are presented. The influence of these systems, i.e. silver colloids and silver island films on the fluorescence of fluorescein-5-isothiocyanate was studied. 7-fold increase in fluorescence intensity of fluorescein-5-isothiocyanate molecules placed near silver nanoparticles was observed.
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