Vadym Prokopec - Academia.edu (original) (raw)

Papers by Vadym Prokopec

Research paper thumbnail of Preparation of SERS-Active Copper Substrates by Cathodic Reduction and Evaluation of their Structure by Atomic Force Microscopy

Copper substrates active in surface enhanced Raman scattering (SERS) were prepared by cathodic re... more Copper substrates active in surface enhanced Raman scattering (SERS) were prepared by cathodic reduction, using a massive platinum target as cathode. Two electrochemical baths (with 16-sulfanylhexadecanoic acid or 4-aminobenzene-1-thiol) and several steps with different current densities were tested. For testing SERS activity of the prepared substrates, model analytes were deposited from their methanolic solutions on the surface of each substrate. After deposition, Raman spectra of substrate surface were measured. If the substrate was SERS-active, the model analyte could be detected at monolayer level. Average roughness of substrate surface was evaluated and surface morphology was imaged using atomic force microscopy.

Research paper thumbnail of Preparation of SERS-active substrates with large surface area for Raman spectral mapping and testing of their surface nanostructure

Surface and Interface Analysis, 2008

Surface-enhanced Raman scattering (SERS) is a powerful technique of Raman signal detection of sub... more Surface-enhanced Raman scattering (SERS) is a powerful technique of Raman signal detection of substances at a low concentration level. It allows observation of structural details of films with very small thicknesses. It is possible to achieve the enhancement of Raman signal of species located on the surface of properly prepared SERS-active substrates of up to ca 10 6 . One of the main requirements for the substrate to be SERS-active is the proper roughness of the surface. In this work different SERS-active Au and Ag substrates suitable for spectral mapping were prepared using procedures which consisted of electrochemical deposition of metal layer and further roughening with oxidation-reduction cycles (ORC) treatment. The nanostructures of the metal surfaces were tested using atomic force microscopy (AFM). Monolayers formed both by covalent and noncovalent linkages to the metal surface were detected and Raman spectral maps were then measured. Roughening procedure of the substrates was optimized and its effect on the SERS enhancement was discussed. The relations among the surface nanostructure, optimal roughening, type of linkage of the analyte to the surface of the substrate and the Raman signal enhancement for the experimental conditions were studied.

Research paper thumbnail of Raman spectral detection and assessment of thin organic layers on metal substrates: systematic approach from substrate preparation to map evaluation

Journal of Raman Spectroscopy, 2008

Raman spectral mapping of thin organic layers on metal substrates is an important analytical tool... more Raman spectral mapping of thin organic layers on metal substrates is an important analytical tool to characterize these systems. Surface-enhanced Raman scattering (SERS) spectroscopy is a suitable technique for analysis of such layers. Development of new SERS-active surfaces with repeatable properties and without disturbing adsorbed species is one of the important steps for reliable assessment of the thin organic layers designed. This paper presents new SERS-active substrates suitable for both macro (millimeter scale) and microscopic (micrometer scale) spectral mapping, which allow easy regeneration for repetitive experiments. Both gold and silver SERS-active surfaces prepared by electrochemical deposition were tested. Complete map data evaluation utilities were newly designed and applied, using both ordinarily used and newly modified mathematical algorithms and chemometric procedures. Evaluation of data starts with finite impulse response (FIR) filtration algorithms to eliminate spectral interferences in individual spectra. Principal component analysis was used for transformation of multidimensional data to understandable dimensions. Various mathematical/statistical techniques were then used for data visualization as spectral maps and for similarity testing.

Research paper thumbnail of Comparison of SERS effectiveness of copper substrates prepared by different methods: what are the values of enhancement factors?

Journal of Raman Spectroscopy, 2012

ABSTRACT Surface-enhanced Raman scattering (SERS) spectroscopy is an analytical method for the de... more ABSTRACT Surface-enhanced Raman scattering (SERS) spectroscopy is an analytical method for the detection of low amounts of analytes adsorbed on an appropriate coinage metal (Au, Ag, Cu) surface. Generally, the values of the enhancement factor are the highest on silver, lower on gold and relatively very low on copper. In this study, we have focused on the estimation of the enhancement factors of copper surface/substrates formed by different preparation procedures. The SERS activity of large electrochemically prepared substrates and colloidal systems is compared. The surface morphology of the large substrates was studied using scanning electron microscopy and atomic force microscopy. The size distribution of colloidal nanoparticles was monitored by dynamic light scattering. The values of enhancement factor are in both cases more than 105 for the FT-SERS spectra, demonstrating the fundamental role of nanostructured copper as a substrate material at the excitation wavelength (1064 nm) used. Copyright (C) 2011 John Wiley & Sons, Ltd.

Research paper thumbnail of Spectroscopic study of SERS- and SEIRA-activity of copper large-scaled surface substrates prepared by electrochemical deposition: What is the role of oxidation–reduction cycle treatment?

Journal of Molecular Structure, 2011

Surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA) are pow... more Surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA) are powerful analytical techniques used for the study and characterization of ultrathin films and monolayers of organic compounds adsorbed on the nanostructured surface of several metals. The main requirement which has to be met for the SERS- and SEIRA-activity is the proper morphology of the surface in nanoscale, which can be

Research paper thumbnail of Effect of hydrophobic coating on the magnetic anisotropy and radiofrequency heating of γ-Fe2O3 nanoparticles

Journal of Magnetism and Magnetic Materials, 2013

ABSTRACT The effect of a hydrophobic (oleic acid) coating on the magnetic properties of maghemite... more ABSTRACT The effect of a hydrophobic (oleic acid) coating on the magnetic properties of maghemite (γ-Fe2O3) nanoparticles was investigated. The nanoparticles were prepared by a novel bi-phasic co-precipitation route and their properties compared with uncoated nanoparticles and nanoparticles prepared by a standard single-phase process. The oleic acid coated nanoparticles had a mean diameter of 6 nm when the two-phase precipitation procedure was used compared to 12 nm for nanoparticles prepared in a single phase under otherwise identical conditions. Super Quantum Interference Device measurements show superparamagnetism of the nanoparticles, with a saturation magnetization at 4 K to be 66.4 emu/g and 89.0 emu/g for the coated nanoparticles obtained by two- and single-phase procedure, respectively. Zero-field-cooled and field-cooled curves reveal a dramatic shift in the blocking temperature of the coated nanoparticles, and a significant change in their anisotropy. The hydrophobic nanoparticles were able to form stable ferrofluids in a range of organic solvents and show good heating rates in a 400 kHz alternating magnetic field.

Research paper thumbnail of Characterization of copper SERS-active substrates prepared by electrochemical deposition

Applied Surface Science, 2009

Research paper thumbnail of In situ SERS spectroelectrochemical analysis of antioxidants deposited on copper substrates: What is the effect of applied potential on sorption behavior?

The detection of p-coumaric acid and ferulic acid using a combined in situ electrochemical and su... more The detection of p-coumaric acid and ferulic acid using a combined in situ electrochemical and surface-enhanced Raman scattering spectroscopic technique in specially made electrode cell is described. New in situ spectroelectrochemical cell was designed as the three-electrode arrangement connected via positioning device to fiber-optic probe of Raman spectrometer Dimension P2 (excitation wavelength 785 nm). In situ SERS spectra of p-coumaric acid and ferulic acid were recorded at varying applied negative potentials to copper substrates. The spectral intensities and shapes of bands as well as spatial orientation of molecules on the surface depend significantly on varying values of the applied electrode potential. The change of electrode potential influences analyte adsorption/desorption behavior on the surface of copper substrates, affecting the reversibility of the whole process and overall spectral enhancement level. Principal component analysis is used to distinguish several stages of spectral variations on potential changes.

Research paper thumbnail of Preparation of SERS-Active Copper Substrates by Cathodic Reduction and Evaluation of their Structure by Atomic Force Microscopy

Copper substrates active in surface enhanced Raman scattering (SERS) were prepared by cathodic re... more Copper substrates active in surface enhanced Raman scattering (SERS) were prepared by cathodic reduction, using a massive platinum target as cathode. Two electrochemical baths (with 16-sulfanylhexadecanoic acid or 4-aminobenzene-1-thiol) and several steps with different current densities were tested. For testing SERS activity of the prepared substrates, model analytes were deposited from their methanolic solutions on the surface of each substrate. After deposition, Raman spectra of substrate surface were measured. If the substrate was SERS-active, the model analyte could be detected at monolayer level. Average roughness of substrate surface was evaluated and surface morphology was imaged using atomic force microscopy.

Research paper thumbnail of Preparation of SERS-active substrates with large surface area for Raman spectral mapping and testing of their surface nanostructure

Surface and Interface Analysis, 2008

Surface-enhanced Raman scattering (SERS) is a powerful technique of Raman signal detection of sub... more Surface-enhanced Raman scattering (SERS) is a powerful technique of Raman signal detection of substances at a low concentration level. It allows observation of structural details of films with very small thicknesses. It is possible to achieve the enhancement of Raman signal of species located on the surface of properly prepared SERS-active substrates of up to ca 10 6 . One of the main requirements for the substrate to be SERS-active is the proper roughness of the surface. In this work different SERS-active Au and Ag substrates suitable for spectral mapping were prepared using procedures which consisted of electrochemical deposition of metal layer and further roughening with oxidation-reduction cycles (ORC) treatment. The nanostructures of the metal surfaces were tested using atomic force microscopy (AFM). Monolayers formed both by covalent and noncovalent linkages to the metal surface were detected and Raman spectral maps were then measured. Roughening procedure of the substrates was optimized and its effect on the SERS enhancement was discussed. The relations among the surface nanostructure, optimal roughening, type of linkage of the analyte to the surface of the substrate and the Raman signal enhancement for the experimental conditions were studied.

Research paper thumbnail of Raman spectral detection and assessment of thin organic layers on metal substrates: systematic approach from substrate preparation to map evaluation

Journal of Raman Spectroscopy, 2008

Raman spectral mapping of thin organic layers on metal substrates is an important analytical tool... more Raman spectral mapping of thin organic layers on metal substrates is an important analytical tool to characterize these systems. Surface-enhanced Raman scattering (SERS) spectroscopy is a suitable technique for analysis of such layers. Development of new SERS-active surfaces with repeatable properties and without disturbing adsorbed species is one of the important steps for reliable assessment of the thin organic layers designed. This paper presents new SERS-active substrates suitable for both macro (millimeter scale) and microscopic (micrometer scale) spectral mapping, which allow easy regeneration for repetitive experiments. Both gold and silver SERS-active surfaces prepared by electrochemical deposition were tested. Complete map data evaluation utilities were newly designed and applied, using both ordinarily used and newly modified mathematical algorithms and chemometric procedures. Evaluation of data starts with finite impulse response (FIR) filtration algorithms to eliminate spectral interferences in individual spectra. Principal component analysis was used for transformation of multidimensional data to understandable dimensions. Various mathematical/statistical techniques were then used for data visualization as spectral maps and for similarity testing.

Research paper thumbnail of Comparison of SERS effectiveness of copper substrates prepared by different methods: what are the values of enhancement factors?

Journal of Raman Spectroscopy, 2012

ABSTRACT Surface-enhanced Raman scattering (SERS) spectroscopy is an analytical method for the de... more ABSTRACT Surface-enhanced Raman scattering (SERS) spectroscopy is an analytical method for the detection of low amounts of analytes adsorbed on an appropriate coinage metal (Au, Ag, Cu) surface. Generally, the values of the enhancement factor are the highest on silver, lower on gold and relatively very low on copper. In this study, we have focused on the estimation of the enhancement factors of copper surface/substrates formed by different preparation procedures. The SERS activity of large electrochemically prepared substrates and colloidal systems is compared. The surface morphology of the large substrates was studied using scanning electron microscopy and atomic force microscopy. The size distribution of colloidal nanoparticles was monitored by dynamic light scattering. The values of enhancement factor are in both cases more than 105 for the FT-SERS spectra, demonstrating the fundamental role of nanostructured copper as a substrate material at the excitation wavelength (1064 nm) used. Copyright (C) 2011 John Wiley & Sons, Ltd.

Research paper thumbnail of Spectroscopic study of SERS- and SEIRA-activity of copper large-scaled surface substrates prepared by electrochemical deposition: What is the role of oxidation–reduction cycle treatment?

Journal of Molecular Structure, 2011

Surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA) are pow... more Surface-enhanced Raman scattering (SERS) and surface-enhanced infrared absorption (SEIRA) are powerful analytical techniques used for the study and characterization of ultrathin films and monolayers of organic compounds adsorbed on the nanostructured surface of several metals. The main requirement which has to be met for the SERS- and SEIRA-activity is the proper morphology of the surface in nanoscale, which can be

Research paper thumbnail of Effect of hydrophobic coating on the magnetic anisotropy and radiofrequency heating of γ-Fe2O3 nanoparticles

Journal of Magnetism and Magnetic Materials, 2013

ABSTRACT The effect of a hydrophobic (oleic acid) coating on the magnetic properties of maghemite... more ABSTRACT The effect of a hydrophobic (oleic acid) coating on the magnetic properties of maghemite (γ-Fe2O3) nanoparticles was investigated. The nanoparticles were prepared by a novel bi-phasic co-precipitation route and their properties compared with uncoated nanoparticles and nanoparticles prepared by a standard single-phase process. The oleic acid coated nanoparticles had a mean diameter of 6 nm when the two-phase precipitation procedure was used compared to 12 nm for nanoparticles prepared in a single phase under otherwise identical conditions. Super Quantum Interference Device measurements show superparamagnetism of the nanoparticles, with a saturation magnetization at 4 K to be 66.4 emu/g and 89.0 emu/g for the coated nanoparticles obtained by two- and single-phase procedure, respectively. Zero-field-cooled and field-cooled curves reveal a dramatic shift in the blocking temperature of the coated nanoparticles, and a significant change in their anisotropy. The hydrophobic nanoparticles were able to form stable ferrofluids in a range of organic solvents and show good heating rates in a 400 kHz alternating magnetic field.

Research paper thumbnail of Characterization of copper SERS-active substrates prepared by electrochemical deposition

Applied Surface Science, 2009

Research paper thumbnail of In situ SERS spectroelectrochemical analysis of antioxidants deposited on copper substrates: What is the effect of applied potential on sorption behavior?

The detection of p-coumaric acid and ferulic acid using a combined in situ electrochemical and su... more The detection of p-coumaric acid and ferulic acid using a combined in situ electrochemical and surface-enhanced Raman scattering spectroscopic technique in specially made electrode cell is described. New in situ spectroelectrochemical cell was designed as the three-electrode arrangement connected via positioning device to fiber-optic probe of Raman spectrometer Dimension P2 (excitation wavelength 785 nm). In situ SERS spectra of p-coumaric acid and ferulic acid were recorded at varying applied negative potentials to copper substrates. The spectral intensities and shapes of bands as well as spatial orientation of molecules on the surface depend significantly on varying values of the applied electrode potential. The change of electrode potential influences analyte adsorption/desorption behavior on the surface of copper substrates, affecting the reversibility of the whole process and overall spectral enhancement level. Principal component analysis is used to distinguish several stages of spectral variations on potential changes.