Evangelia pavlatou - Academia.edu (original) (raw)

Papers by Evangelia pavlatou

Research paper thumbnail of ZnO Nanoparticles from Different Precursors and Their Photocatalytic Potential for Biomedical Use

Nanomaterials

Semiconductor photocatalysts, particularly ZnO nanoparticles, were synthesized via the precipitat... more Semiconductor photocatalysts, particularly ZnO nanoparticles, were synthesized via the precipitation method using four different precursors (zinc acetate/zinc nitrate/zinc sulfate/zinc chloride) and compared, according to their optical, structural, photocatalytic, and anticancer properties. The materials were characterized via X-ray Diffraction method (XRD), micro-Raman, Fourier Transform Infrared Spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET), Dynamic Light Scattering (DLS), and Field Emission Scanning Electron Microscope (FESEM) analysis. Photocatalysis was conducted under UV and visible light irradiation, using Rhodamine B as the organic pollutant. It was observed that the highest photocatalysis efficiency was obtained by the nanoparticles synthesized from the zinc acetate used as precursor material. A cell-dependent anticancer efficiency of the tested ZnO nanoparticles was also observed, that was also attributed to the different precursors and the synthesis method, revealing...

Research paper thumbnail of Biological Effect of Silver-modified Nanostructured Titanium Dioxide in Cancer

Cancer Genomics - Proteomics, 2021

Background/Aim: Nanomedicine is a promising scientific field that exploits the unique properties ... more Background/Aim: Nanomedicine is a promising scientific field that exploits the unique properties of innovative nanomaterials, providing alternative solutions in diagnostics, prevention and therapeutics. Titanium dioxide nanoparticles (TiO 2 NPs) have a great spectrum of photocatalytic antibacterial and anticancer applications. The chemical modification of TiO 2 optimizes its bioactive performance. The aim of this study was the development of silver modified NPs (Ag/TiO 2 NPs) with anticancer potential. Materials and Methods: Ag/TiO 2 NPs were prepared through the sol-gel method, were fully characterized and were tested on cultured breast cancer epithelial cells (MCF-7 and MDA-MB-231). The MTT colorimetric assay was used to estimate cellular viability. Western blot analysis of protein expression along with a DNA-laddering assay were employed for apoptosis detection. Results and Conclusion: We show that photo-activated Ag/TiO 2 NPs exhibited significant cytotoxicity on the highly malignant MDA-MB-231 cancer cells, inducing apoptosis, while MCF-7 cells that are characterized by low invasive properties were unaffected under the same conditions. Nanomedicine is an emerging inter-disciplinary scientific field that exploits the unique properties of innovative 425 This article is freely accessible online.

Research paper thumbnail of Developing Arduino Laboratory Instruments and Smart Devices in a School Makerspace

ICERI2021 Proceedings, 2021

Research paper thumbnail of Using Educational Strategies and Techniques Based on Interactive Cartoons, Animations and 3D Visualizations to Rebuild Scientific Knowledge in Chemistry in Higher Education

ICERI2018 Proceedings, 2018

Research paper thumbnail of Introducing “Makers” Movement in a Formal Chemistry Class

ICERI2019 Proceedings, 2019

Research paper thumbnail of Learning Chemistry with 3D Visualizations Employing Cartoons Agents in Higher Education

Students in higher education usually find it challenging to understand and picture the particulat... more Students in higher education usually find it challenging to understand and picture the particulate nature of matter in microscopic level. However, students often face difficulties in that field and how to link that knowledge to macroscopic behaviour. Therefore, the main purpose of this work is to present a specifically designed educational material that focus to the benefits of viewing visualizations to enhance students' conceptual understanding of chemistry concepts. Under this frame, educational material for specific basic chemistry concepts that are taught in the Chemistry course and supplied at the National Technical University of Athens, in which 3D visualizations with cartoons were constructed and employed. The material was designed for in class use from the educator or for core-concept use. Concepts that combine the microscopic level with the symbolic language were chosen. So, specifically 3D dimensional visualizations were made for the atomic orbitals (dxy, dxz, dzy, dz 2), types of solids-ionic structures (crystal of sodium chloride), molecular structures (water), covalent lattice structures (diamond, graphite structures), metallic structures (copper) etc. Since it was planned all constructed applications to run on all functional and most browsers in terms of 3D, so code three js (javascript that supports 3D) was used. Also, the interactive agents "cartoons" Einstein and Curie, were developed from scratch in programs that apply animation in 2D characters, giving them freedom of movement and realism at the same time. In the near future a planned research will be carried out to study and find out how the students' scientific knowledge can be reconstructed in the above mentioned concepts in the Inorganic-General Chemistry course, which is taught at three schools of the National Technical University of Athens, exploiting the developed cognitive and their metacognitive abilities, their spatial ability and their optical encoding.

Research paper thumbnail of Photo-activated N-doped/TiO2 nanoparticles with anticancer properties

Proceedings of The World Conference on Engineering and Technology, 2019

The aim of this study was the synthesis of titanium dioxide (TiO2) nanoparticles with photoinduce... more The aim of this study was the synthesis of titanium dioxide (TiO2) nanoparticles with photoinduced anticancer properties, under visible light irradiation. It is well established that when pure TiO2 nanoparticles are excited by ultraviolet light, the formed reactive oxygen species (ROS) can significantly damage cancer cells by inducing apoptosis and, thus, promoting TiO2 as a promising photosensitizer against cancer. Surface modification by TiO2 doping with nitrogen (N-doped) is proved to improve TiO2 photocatalytic activity, according to recent studies. This doping process is associated with the reduction of electron-hole recombination, resulting in efficient separation and stronger photocatalytic reactions, upon irradiation with visible light. Thus, synthesis of N-doped TiO2 was conducted, followed by surface and morphological characterization realized by micro-Raman spectroscopy, SEM (Scanning Electron Microscopy) microscopy and DLS (Dynamic Light Scattering) techniques. Additiona...

Research paper thumbnail of Ionic liquid – Assisted synthesis of silver mesoparticles as efficient surface enhanced Raman scattering substrates

Journal of Molecular Liquids, 2020

Abstract Surface-enhanced Raman Scattering (SERS) constitutes a powerful molecule detection and i... more Abstract Surface-enhanced Raman Scattering (SERS) constitutes a powerful molecule detection and identification method. However, the design of a suitable substrate, which combines ease of use with reproducibility, remains a major problem. In this study, the use of silver mesoparticles (AgMPs) as SERS substrate was investigated. A green methodology was applied for the synthesis of the AgMPs, using the novel hydroxyethylammonium ascorbate ionic liquid as the reducing agent and chitosan as the stabilising and homogenising matrix. Experimental design was applied for the optimisation of the AgMPs' synthesis. Scanning electron microscopy (SEM) revealed the flower-shape morphology of the materials. The potential application of AgMPs as SERS using Rhodamine B as the model molecule and promising and reproducible results were obtained in concentrations even at 10−9 M. Dynamic light scattering and SEM confirmed the stability of the synthesised AgMPs over a period of 18 months.

Research paper thumbnail of Using cartoons agents and 3D visualizations based on HTML5 for improving learning in crystal structures in engineers

Computer Applications in Engineering Education, 2019

This paper presents an educational digital material on "solid crystal structures," in which carto... more This paper presents an educational digital material on "solid crystal structures," in which cartoons agents direct undergraduate students on a learning cycle of understanding concepts from the submicroscopic level and correlate with the corresponding macroscopic-related properties. Specifically, undergraduate students are given the opportunity to study basic crystal structures starting from structural units, composing the unit cells in a three-dimensional (3D) pattern that are characterized and related with intermolecular forces within them, and finally leading to basic crystalline solids associated with the macroscopic behavior of solid materials expressed by physical and mechanical properties such as hardness, electrical conductivity, etc. The design of the digital material was focused on the cognitive benefits that students gained after viewing 3D visualizations for which students were able to manipulate the rotation or size of them, to enhance their conceptual understanding addressed to chemistry and engineering, accompanied by cartoons agents. Digital material was constructed to be accessible from and compatible with any web browser without any third-party plugin. A research using a properly designed questionnaire was conducted in the School of Chemical Engineering in Greece where the evaluation indicated that students preferred using this web material due to its simplicity and their active involvement by self-controlling the pace and the way of learning.

Research paper thumbnail of Development of Smart Composites Based on Doped-TiO2 Nanoparticles with Visible Light Anticancer Properties

Materials, 2019

In this study, the synthesis of smart, polymerically embedded titanium dioxide (TiO2) nanoparticl... more In this study, the synthesis of smart, polymerically embedded titanium dioxide (TiO2) nanoparticles aimed to exhibit photo-induced anticancer properties under visible light irradiation is investigated. The TiO2 nanoparticles were prepared by utilizing the sol gel method with different dopants, including nitrogen (N-doped), iron (Fe-doped), and nitrogen and iron (Fe,N-doped). The dopants were embedded in an interpenetrating (IP) network microgel synthesized by stimuli responsive poly (N-Isopropylacrylamide-co-polyacrylicacid)–pNipam-co-PAA forming composite particles. All the types of produced particles were characterized by X-ray powder diffraction, micro-Raman, Fourier-transform infrared, X-ray photoelectron, ultra-violet-visible spectroscopy, Field Emission Scanning Electron, Transmission Electron microscopy, and Dynamic Light Scattering techniques. The experimental findings indicate that the doped TiO2 nanoparticles were successfully embedded in the microgel. The N-doped TiO2 nan...

Research paper thumbnail of Embedding of hybrid MWCNT-Al2O3 particles in Ni matrix: Structural, tribological and corrosion studies

Surface and Coatings Technology, 2018

Composite nickel coatings, were produced under direct current (DC) and pulse current (PC) from a ... more Composite nickel coatings, were produced under direct current (DC) and pulse current (PC) from a Watt's type bath, containing 0.5g/L hybrid MWCNTs-Al 2 O 3 , in presence and absence of additive Sodium Dodecyl Sulfate-SDS. Surface morphology, crystallographic orientation, wear resistance and corrosion resistance were studied. The application of high frequency pulse current in combination with the presence of additive in the electrolytic bath, led to a more uniform distribution of the hybrids particles in the metallic matrix. Micro-Raman measurements revealed that MWCNTs-Al 2 O 3 are distributed at the whole depth of the cross-section profile analysis. The application of pulse current, in absence or presence of additive, favored a random crystallographic orientation of Ni crystallites with reduced grain sizes in comparison with pure Ni. The evaluation of the tribological data demonstrated that the composite coatings produced under pulse conditions in presence of additive, exhibited lower coefficient of friction, higher resistance to dry sliding accompanied by the presence of increased amounts of nickel oxide in wear tracks compared to pure Ni coatings. The behavior of pure and composite coatings in corrosive environment was evaluated by electrochemical impedance spectroscopy. It was found that composite coatings attained their corrosion resistance characteristics for 60 h in 0.6M NaCl solution. Differences between pure nickel and composite coatings were attributed mainly to morphological differences rather than differences on corrosion performance.

Research paper thumbnail of Production of copper powder form printed circuit boards by electrodeposition

Issue 2, 2013

During the last years, the waste electrical and electronic equipment (WEEE) are gathering attenti... more During the last years, the waste electrical and electronic equipment (WEEE) are gathering attention, as a very special section of waste. In fact, they have been proven to be source for the recovery of metals. In the present study printed circuit boards (PCBs) were cut and treated thermally at 500oC for 1 h in both air and nitrogen atmosphere. The obtained material was dissolved in three different acid media HNO3aq, HClaq and H2SO4aq, in order to extract copper. The achieved Cu recovery percentages were 97.5, 65 and 76.5% respectively. Electrodeposition technique was applied in order to recover copper in powder form. More than 98% of copper was recovered achieved by application of high current density resulting to dendritic structure of copper. The applied process was characterised by a high current efficiency and led to the production of copper powder of 80 μm mean diameter appropriate for powder metallurgy applications.

Research paper thumbnail of Raman Scattering from Alkali Metal Halide Melt Mixtures: Composition and Temperature Effects

ECS Proceedings Volumes, 1994

Reduced isotropic and anisotropic Raman spectra were measured for a series of molten alkali metal... more Reduced isotropic and anisotropic Raman spectra were measured for a series of molten alkali metal halides and their mixtures. The systems involving CsX and LiX (X=C1, Br, I) were investigated at different tem peratures and compositions. The spectra of the comm on anion mixtures show two bands which appear to be a superposition of the bands of the component salts. Similar is the spectral behavior o f the common cation salts. The data are interpreted in terms of the fluctuations o f the X" and C s+ polarizabilities induced by short range ionic interactions. The Li-X pair interactions appear to be im portant in determining the scattered light intensity and its temperature variation.

Research paper thumbnail of Structural Properties of Zinc Halide Melts

ECS Proceedings Volumes, 1992

Vibrational Raman spectroscopy has been used to identify and determine the structure o f species ... more Vibrational Raman spectroscopy has been used to identify and determine the structure o f species formed in the binary mixtures ZnC^ ACl (A=Cs, I i) and ZnCLj-ZnBr^ The data indicate that the network-like structure of the zinc halide melts breaks up with the addition of alkali metal halide and with increasing temperature. The tetrahedral structure around the Zn is preserved but one, two, three or four "terminal" halogen atoms having A + as nearest neighbors are formed. Different bridging bonding states are proposed to exist in the pure ZnC^ glass and liquid.

Research paper thumbnail of Electrodeposition and characterization of electroplated Ni/Graphene composite coatings

Materials Today: Proceedings, 2018

Pure nickel and composite nickel coatings were produced by using a Watts bath containing 0.1g/L G... more Pure nickel and composite nickel coatings were produced by using a Watts bath containing 0.1g/L Graphene platelets-GnPs in presence or absence of the surfactant Sodium Dodecyl Sulfate under both direct current-DC and pulse current-PC conditions. The surface morphology, crystallographic orientation, and micro-hardness as well as the wear mechanism of the produced coatings under dry sliding conditions were investigated. The results have shown that the presence of additive in the electrolytic bath led to a more uniform distribution of Graphene platelets in the nickel metal matrix. The simultaneous presence of additive in combination with the imposition of high pulse current frequency is accompanied by the predominance of a mixed Ni crystalline orientation [110 + 111], while for all composites an enhancement of the crystalline orientation through (111) axis was revealed. The presence of Graphene platelets increases the micro-hardness values of the coatings and enhances the wear resistance compared to pure nickel coatings produced under the same electrolytic conditions.

Research paper thumbnail of Usability evaluation of 3-D visualisations augmented by cartoons for teaching solids and crystal structures in chemical engineering

New Trends and Issues Proceedings on Humanities and Social Sciences, 2018

In chemical engineering, undergraduate students often have to face the highly demanding process o... more In chemical engineering, undergraduate students often have to face the highly demanding process of understanding concepts from the microscopic level (e.g., ionic crystals such as zinc sulphide or covalent lattice crystals diamond, graphite, graphene etc.) and then explain with certain physical–chemical properties their macroscopic behaviour. Therefore, the main idea was to construct a specifically designed educational material that focusses on the benefits of viewing visualisations to enhance students’ conceptual understanding of solids and crystal structures augmented by cartoons, and evaluate its usability. The interactive ‘cartoons’ agents were developed from scratch, giving them freedom of movement and realism at the same time. A research was conducted in the School of Chemical Engineering in Greece (National Technical University of Athens), evaluated the usability of the digital material and the contribution of the 3-D visualisations and the cartoons agents in the understanding...

Research paper thumbnail of Regeneration of HDTMA-modified minerals after sorption with chromate anions

Desalination and Water Treatment, 2016

Research objectives Stages: 1) to investigate Cr(VI) desorption possibility from organically modi... more Research objectives Stages: 1) to investigate Cr(VI) desorption possibility from organically modified-minerals using four different desorption agents (deionized H 2 O, NaCl, KCl and NaCN) 2) to examine Cr(VI) desorption kinetics 3) to evaluate the stability and reuse possibility of minerals employed after successive adsorption/desorption cycles  the regeneration study of various HDTMA-Br-modified minerals after their saturation with chromate anions

Research paper thumbnail of Nickel Matrix Composite Coatings: Application in Textile Machinery and Evaluation of Cotton Products Quality

Transactions of the IMF, 2000

Coatings applied to several mechanical parts involved in the cotton textile industry are expected... more Coatings applied to several mechanical parts involved in the cotton textile industry are expected to improve production efficiency and to decrease the relevant costs. The quality of cotton products is one of the most crucial parameters in the development of textile industry and is significantly associated with the mechanical and tribological properties of the coated machinery parts. For this purpose. nickel matrix coatings containing silicon carbide (SiC) micro-particles. prepared under pulse plating conditions were applied on several parts. Surface morphology, preferred orientation of the crystals. incorporated SiC percentage and mechanical properties of these coatings were investigated. Moreover, the influence of the surface coating on the cotton products quality was studied by the means of a prototypal method. which determines the extent of wear on a typical cotton fabric. under strictly controlled conditions. It has been proved that Ni/SiC coatings. prepared under very well defined conditions (pulse current density. frequency. duty cycle, etc), present relatively low roughness. high microhardness, low sliding .friction coefficient between the coating and typical cotton products and reduced wear against cotton fabrics or yarns.

Research paper thumbnail of Encapsulation of Antifouling Organic Biocides in Poly(lactic acid) Nanoparticles

Bioengineering, 2017

The scope of the current research was to assess the feasibility of encapsulating three commercial... more The scope of the current research was to assess the feasibility of encapsulating three commercial antifouling compounds, Irgarol 1051, Econea and Zinc pyrithione, in biodegradable poly(lactic acid) (PLA) nanoparticles. The emulsification-solvent evaporation technique was herein utilized to manufacture nanoparticles with a biocide:polymer ratio of 40%. The loaded nanoparticles were analyzed for their size and size distribution, zeta potential, encapsulation efficiency and thermal properties, while the relevant physicochemical characteristics were correlated to biocide-polymer system. In addition, the encapsulation process was scaled up and the prepared nanoparticles were dispersed in a water-based antifouling paint in order to examine the viability of incorporating nanoparticles in such coatings. Metallic specimens were coated with the nanoparticles-containing paint and examined regarding surface morphology.

Research paper thumbnail of Electrodeposition of Ni/SiC Composites by Pulse Electrolysis

Transactions of the IMF, 2002

Nickel matrix composite coatings containing micron-and nano-si=ed SiC particles were prepared in ... more Nickel matrix composite coatings containing micron-and nano-si=ed SiC particles were prepared in order to study the interdependence of the SiC particles embedding and the deposits' mechanical behaviour. SiC particles of two different si=es, namely 1 J.Lm and 20 nm, were codeposited with nickel from Watts solutions under pulse current conditions. It has been observed that the embedding of SiC particles in the nickel matrix and the pulse current application result in deposits with more uniform particle distribution and better surface morphology than those obtained under direct current conditions. The study of the composite deposits revealed that the microhardness is not only increased by the presence and the reduced si=e of the particles, but also influenced by the current conditions, i.e. duty cycle and pulse frequency. Moreover, microhardness of the deposits can be further ameliorated by specific thermal treatment.

Research paper thumbnail of ZnO Nanoparticles from Different Precursors and Their Photocatalytic Potential for Biomedical Use

Nanomaterials

Semiconductor photocatalysts, particularly ZnO nanoparticles, were synthesized via the precipitat... more Semiconductor photocatalysts, particularly ZnO nanoparticles, were synthesized via the precipitation method using four different precursors (zinc acetate/zinc nitrate/zinc sulfate/zinc chloride) and compared, according to their optical, structural, photocatalytic, and anticancer properties. The materials were characterized via X-ray Diffraction method (XRD), micro-Raman, Fourier Transform Infrared Spectroscopy (FT-IR), Brunauer–Emmett–Teller (BET), Dynamic Light Scattering (DLS), and Field Emission Scanning Electron Microscope (FESEM) analysis. Photocatalysis was conducted under UV and visible light irradiation, using Rhodamine B as the organic pollutant. It was observed that the highest photocatalysis efficiency was obtained by the nanoparticles synthesized from the zinc acetate used as precursor material. A cell-dependent anticancer efficiency of the tested ZnO nanoparticles was also observed, that was also attributed to the different precursors and the synthesis method, revealing...

Research paper thumbnail of Biological Effect of Silver-modified Nanostructured Titanium Dioxide in Cancer

Cancer Genomics - Proteomics, 2021

Background/Aim: Nanomedicine is a promising scientific field that exploits the unique properties ... more Background/Aim: Nanomedicine is a promising scientific field that exploits the unique properties of innovative nanomaterials, providing alternative solutions in diagnostics, prevention and therapeutics. Titanium dioxide nanoparticles (TiO 2 NPs) have a great spectrum of photocatalytic antibacterial and anticancer applications. The chemical modification of TiO 2 optimizes its bioactive performance. The aim of this study was the development of silver modified NPs (Ag/TiO 2 NPs) with anticancer potential. Materials and Methods: Ag/TiO 2 NPs were prepared through the sol-gel method, were fully characterized and were tested on cultured breast cancer epithelial cells (MCF-7 and MDA-MB-231). The MTT colorimetric assay was used to estimate cellular viability. Western blot analysis of protein expression along with a DNA-laddering assay were employed for apoptosis detection. Results and Conclusion: We show that photo-activated Ag/TiO 2 NPs exhibited significant cytotoxicity on the highly malignant MDA-MB-231 cancer cells, inducing apoptosis, while MCF-7 cells that are characterized by low invasive properties were unaffected under the same conditions. Nanomedicine is an emerging inter-disciplinary scientific field that exploits the unique properties of innovative 425 This article is freely accessible online.

Research paper thumbnail of Developing Arduino Laboratory Instruments and Smart Devices in a School Makerspace

ICERI2021 Proceedings, 2021

Research paper thumbnail of Using Educational Strategies and Techniques Based on Interactive Cartoons, Animations and 3D Visualizations to Rebuild Scientific Knowledge in Chemistry in Higher Education

ICERI2018 Proceedings, 2018

Research paper thumbnail of Introducing “Makers” Movement in a Formal Chemistry Class

ICERI2019 Proceedings, 2019

Research paper thumbnail of Learning Chemistry with 3D Visualizations Employing Cartoons Agents in Higher Education

Students in higher education usually find it challenging to understand and picture the particulat... more Students in higher education usually find it challenging to understand and picture the particulate nature of matter in microscopic level. However, students often face difficulties in that field and how to link that knowledge to macroscopic behaviour. Therefore, the main purpose of this work is to present a specifically designed educational material that focus to the benefits of viewing visualizations to enhance students' conceptual understanding of chemistry concepts. Under this frame, educational material for specific basic chemistry concepts that are taught in the Chemistry course and supplied at the National Technical University of Athens, in which 3D visualizations with cartoons were constructed and employed. The material was designed for in class use from the educator or for core-concept use. Concepts that combine the microscopic level with the symbolic language were chosen. So, specifically 3D dimensional visualizations were made for the atomic orbitals (dxy, dxz, dzy, dz 2), types of solids-ionic structures (crystal of sodium chloride), molecular structures (water), covalent lattice structures (diamond, graphite structures), metallic structures (copper) etc. Since it was planned all constructed applications to run on all functional and most browsers in terms of 3D, so code three js (javascript that supports 3D) was used. Also, the interactive agents "cartoons" Einstein and Curie, were developed from scratch in programs that apply animation in 2D characters, giving them freedom of movement and realism at the same time. In the near future a planned research will be carried out to study and find out how the students' scientific knowledge can be reconstructed in the above mentioned concepts in the Inorganic-General Chemistry course, which is taught at three schools of the National Technical University of Athens, exploiting the developed cognitive and their metacognitive abilities, their spatial ability and their optical encoding.

Research paper thumbnail of Photo-activated N-doped/TiO2 nanoparticles with anticancer properties

Proceedings of The World Conference on Engineering and Technology, 2019

The aim of this study was the synthesis of titanium dioxide (TiO2) nanoparticles with photoinduce... more The aim of this study was the synthesis of titanium dioxide (TiO2) nanoparticles with photoinduced anticancer properties, under visible light irradiation. It is well established that when pure TiO2 nanoparticles are excited by ultraviolet light, the formed reactive oxygen species (ROS) can significantly damage cancer cells by inducing apoptosis and, thus, promoting TiO2 as a promising photosensitizer against cancer. Surface modification by TiO2 doping with nitrogen (N-doped) is proved to improve TiO2 photocatalytic activity, according to recent studies. This doping process is associated with the reduction of electron-hole recombination, resulting in efficient separation and stronger photocatalytic reactions, upon irradiation with visible light. Thus, synthesis of N-doped TiO2 was conducted, followed by surface and morphological characterization realized by micro-Raman spectroscopy, SEM (Scanning Electron Microscopy) microscopy and DLS (Dynamic Light Scattering) techniques. Additiona...

Research paper thumbnail of Ionic liquid – Assisted synthesis of silver mesoparticles as efficient surface enhanced Raman scattering substrates

Journal of Molecular Liquids, 2020

Abstract Surface-enhanced Raman Scattering (SERS) constitutes a powerful molecule detection and i... more Abstract Surface-enhanced Raman Scattering (SERS) constitutes a powerful molecule detection and identification method. However, the design of a suitable substrate, which combines ease of use with reproducibility, remains a major problem. In this study, the use of silver mesoparticles (AgMPs) as SERS substrate was investigated. A green methodology was applied for the synthesis of the AgMPs, using the novel hydroxyethylammonium ascorbate ionic liquid as the reducing agent and chitosan as the stabilising and homogenising matrix. Experimental design was applied for the optimisation of the AgMPs' synthesis. Scanning electron microscopy (SEM) revealed the flower-shape morphology of the materials. The potential application of AgMPs as SERS using Rhodamine B as the model molecule and promising and reproducible results were obtained in concentrations even at 10−9 M. Dynamic light scattering and SEM confirmed the stability of the synthesised AgMPs over a period of 18 months.

Research paper thumbnail of Using cartoons agents and 3D visualizations based on HTML5 for improving learning in crystal structures in engineers

Computer Applications in Engineering Education, 2019

This paper presents an educational digital material on "solid crystal structures," in which carto... more This paper presents an educational digital material on "solid crystal structures," in which cartoons agents direct undergraduate students on a learning cycle of understanding concepts from the submicroscopic level and correlate with the corresponding macroscopic-related properties. Specifically, undergraduate students are given the opportunity to study basic crystal structures starting from structural units, composing the unit cells in a three-dimensional (3D) pattern that are characterized and related with intermolecular forces within them, and finally leading to basic crystalline solids associated with the macroscopic behavior of solid materials expressed by physical and mechanical properties such as hardness, electrical conductivity, etc. The design of the digital material was focused on the cognitive benefits that students gained after viewing 3D visualizations for which students were able to manipulate the rotation or size of them, to enhance their conceptual understanding addressed to chemistry and engineering, accompanied by cartoons agents. Digital material was constructed to be accessible from and compatible with any web browser without any third-party plugin. A research using a properly designed questionnaire was conducted in the School of Chemical Engineering in Greece where the evaluation indicated that students preferred using this web material due to its simplicity and their active involvement by self-controlling the pace and the way of learning.

Research paper thumbnail of Development of Smart Composites Based on Doped-TiO2 Nanoparticles with Visible Light Anticancer Properties

Materials, 2019

In this study, the synthesis of smart, polymerically embedded titanium dioxide (TiO2) nanoparticl... more In this study, the synthesis of smart, polymerically embedded titanium dioxide (TiO2) nanoparticles aimed to exhibit photo-induced anticancer properties under visible light irradiation is investigated. The TiO2 nanoparticles were prepared by utilizing the sol gel method with different dopants, including nitrogen (N-doped), iron (Fe-doped), and nitrogen and iron (Fe,N-doped). The dopants were embedded in an interpenetrating (IP) network microgel synthesized by stimuli responsive poly (N-Isopropylacrylamide-co-polyacrylicacid)–pNipam-co-PAA forming composite particles. All the types of produced particles were characterized by X-ray powder diffraction, micro-Raman, Fourier-transform infrared, X-ray photoelectron, ultra-violet-visible spectroscopy, Field Emission Scanning Electron, Transmission Electron microscopy, and Dynamic Light Scattering techniques. The experimental findings indicate that the doped TiO2 nanoparticles were successfully embedded in the microgel. The N-doped TiO2 nan...

Research paper thumbnail of Embedding of hybrid MWCNT-Al2O3 particles in Ni matrix: Structural, tribological and corrosion studies

Surface and Coatings Technology, 2018

Composite nickel coatings, were produced under direct current (DC) and pulse current (PC) from a ... more Composite nickel coatings, were produced under direct current (DC) and pulse current (PC) from a Watt's type bath, containing 0.5g/L hybrid MWCNTs-Al 2 O 3 , in presence and absence of additive Sodium Dodecyl Sulfate-SDS. Surface morphology, crystallographic orientation, wear resistance and corrosion resistance were studied. The application of high frequency pulse current in combination with the presence of additive in the electrolytic bath, led to a more uniform distribution of the hybrids particles in the metallic matrix. Micro-Raman measurements revealed that MWCNTs-Al 2 O 3 are distributed at the whole depth of the cross-section profile analysis. The application of pulse current, in absence or presence of additive, favored a random crystallographic orientation of Ni crystallites with reduced grain sizes in comparison with pure Ni. The evaluation of the tribological data demonstrated that the composite coatings produced under pulse conditions in presence of additive, exhibited lower coefficient of friction, higher resistance to dry sliding accompanied by the presence of increased amounts of nickel oxide in wear tracks compared to pure Ni coatings. The behavior of pure and composite coatings in corrosive environment was evaluated by electrochemical impedance spectroscopy. It was found that composite coatings attained their corrosion resistance characteristics for 60 h in 0.6M NaCl solution. Differences between pure nickel and composite coatings were attributed mainly to morphological differences rather than differences on corrosion performance.

Research paper thumbnail of Production of copper powder form printed circuit boards by electrodeposition

Issue 2, 2013

During the last years, the waste electrical and electronic equipment (WEEE) are gathering attenti... more During the last years, the waste electrical and electronic equipment (WEEE) are gathering attention, as a very special section of waste. In fact, they have been proven to be source for the recovery of metals. In the present study printed circuit boards (PCBs) were cut and treated thermally at 500oC for 1 h in both air and nitrogen atmosphere. The obtained material was dissolved in three different acid media HNO3aq, HClaq and H2SO4aq, in order to extract copper. The achieved Cu recovery percentages were 97.5, 65 and 76.5% respectively. Electrodeposition technique was applied in order to recover copper in powder form. More than 98% of copper was recovered achieved by application of high current density resulting to dendritic structure of copper. The applied process was characterised by a high current efficiency and led to the production of copper powder of 80 μm mean diameter appropriate for powder metallurgy applications.

Research paper thumbnail of Raman Scattering from Alkali Metal Halide Melt Mixtures: Composition and Temperature Effects

ECS Proceedings Volumes, 1994

Reduced isotropic and anisotropic Raman spectra were measured for a series of molten alkali metal... more Reduced isotropic and anisotropic Raman spectra were measured for a series of molten alkali metal halides and their mixtures. The systems involving CsX and LiX (X=C1, Br, I) were investigated at different tem peratures and compositions. The spectra of the comm on anion mixtures show two bands which appear to be a superposition of the bands of the component salts. Similar is the spectral behavior o f the common cation salts. The data are interpreted in terms of the fluctuations o f the X" and C s+ polarizabilities induced by short range ionic interactions. The Li-X pair interactions appear to be im portant in determining the scattered light intensity and its temperature variation.

Research paper thumbnail of Structural Properties of Zinc Halide Melts

ECS Proceedings Volumes, 1992

Vibrational Raman spectroscopy has been used to identify and determine the structure o f species ... more Vibrational Raman spectroscopy has been used to identify and determine the structure o f species formed in the binary mixtures ZnC^ ACl (A=Cs, I i) and ZnCLj-ZnBr^ The data indicate that the network-like structure of the zinc halide melts breaks up with the addition of alkali metal halide and with increasing temperature. The tetrahedral structure around the Zn is preserved but one, two, three or four "terminal" halogen atoms having A + as nearest neighbors are formed. Different bridging bonding states are proposed to exist in the pure ZnC^ glass and liquid.

Research paper thumbnail of Electrodeposition and characterization of electroplated Ni/Graphene composite coatings

Materials Today: Proceedings, 2018

Pure nickel and composite nickel coatings were produced by using a Watts bath containing 0.1g/L G... more Pure nickel and composite nickel coatings were produced by using a Watts bath containing 0.1g/L Graphene platelets-GnPs in presence or absence of the surfactant Sodium Dodecyl Sulfate under both direct current-DC and pulse current-PC conditions. The surface morphology, crystallographic orientation, and micro-hardness as well as the wear mechanism of the produced coatings under dry sliding conditions were investigated. The results have shown that the presence of additive in the electrolytic bath led to a more uniform distribution of Graphene platelets in the nickel metal matrix. The simultaneous presence of additive in combination with the imposition of high pulse current frequency is accompanied by the predominance of a mixed Ni crystalline orientation [110 + 111], while for all composites an enhancement of the crystalline orientation through (111) axis was revealed. The presence of Graphene platelets increases the micro-hardness values of the coatings and enhances the wear resistance compared to pure nickel coatings produced under the same electrolytic conditions.

Research paper thumbnail of Usability evaluation of 3-D visualisations augmented by cartoons for teaching solids and crystal structures in chemical engineering

New Trends and Issues Proceedings on Humanities and Social Sciences, 2018

In chemical engineering, undergraduate students often have to face the highly demanding process o... more In chemical engineering, undergraduate students often have to face the highly demanding process of understanding concepts from the microscopic level (e.g., ionic crystals such as zinc sulphide or covalent lattice crystals diamond, graphite, graphene etc.) and then explain with certain physical–chemical properties their macroscopic behaviour. Therefore, the main idea was to construct a specifically designed educational material that focusses on the benefits of viewing visualisations to enhance students’ conceptual understanding of solids and crystal structures augmented by cartoons, and evaluate its usability. The interactive ‘cartoons’ agents were developed from scratch, giving them freedom of movement and realism at the same time. A research was conducted in the School of Chemical Engineering in Greece (National Technical University of Athens), evaluated the usability of the digital material and the contribution of the 3-D visualisations and the cartoons agents in the understanding...

Research paper thumbnail of Regeneration of HDTMA-modified minerals after sorption with chromate anions

Desalination and Water Treatment, 2016

Research objectives Stages: 1) to investigate Cr(VI) desorption possibility from organically modi... more Research objectives Stages: 1) to investigate Cr(VI) desorption possibility from organically modified-minerals using four different desorption agents (deionized H 2 O, NaCl, KCl and NaCN) 2) to examine Cr(VI) desorption kinetics 3) to evaluate the stability and reuse possibility of minerals employed after successive adsorption/desorption cycles  the regeneration study of various HDTMA-Br-modified minerals after their saturation with chromate anions

Research paper thumbnail of Nickel Matrix Composite Coatings: Application in Textile Machinery and Evaluation of Cotton Products Quality

Transactions of the IMF, 2000

Coatings applied to several mechanical parts involved in the cotton textile industry are expected... more Coatings applied to several mechanical parts involved in the cotton textile industry are expected to improve production efficiency and to decrease the relevant costs. The quality of cotton products is one of the most crucial parameters in the development of textile industry and is significantly associated with the mechanical and tribological properties of the coated machinery parts. For this purpose. nickel matrix coatings containing silicon carbide (SiC) micro-particles. prepared under pulse plating conditions were applied on several parts. Surface morphology, preferred orientation of the crystals. incorporated SiC percentage and mechanical properties of these coatings were investigated. Moreover, the influence of the surface coating on the cotton products quality was studied by the means of a prototypal method. which determines the extent of wear on a typical cotton fabric. under strictly controlled conditions. It has been proved that Ni/SiC coatings. prepared under very well defined conditions (pulse current density. frequency. duty cycle, etc), present relatively low roughness. high microhardness, low sliding .friction coefficient between the coating and typical cotton products and reduced wear against cotton fabrics or yarns.

Research paper thumbnail of Encapsulation of Antifouling Organic Biocides in Poly(lactic acid) Nanoparticles

Bioengineering, 2017

The scope of the current research was to assess the feasibility of encapsulating three commercial... more The scope of the current research was to assess the feasibility of encapsulating three commercial antifouling compounds, Irgarol 1051, Econea and Zinc pyrithione, in biodegradable poly(lactic acid) (PLA) nanoparticles. The emulsification-solvent evaporation technique was herein utilized to manufacture nanoparticles with a biocide:polymer ratio of 40%. The loaded nanoparticles were analyzed for their size and size distribution, zeta potential, encapsulation efficiency and thermal properties, while the relevant physicochemical characteristics were correlated to biocide-polymer system. In addition, the encapsulation process was scaled up and the prepared nanoparticles were dispersed in a water-based antifouling paint in order to examine the viability of incorporating nanoparticles in such coatings. Metallic specimens were coated with the nanoparticles-containing paint and examined regarding surface morphology.

Research paper thumbnail of Electrodeposition of Ni/SiC Composites by Pulse Electrolysis

Transactions of the IMF, 2002

Nickel matrix composite coatings containing micron-and nano-si=ed SiC particles were prepared in ... more Nickel matrix composite coatings containing micron-and nano-si=ed SiC particles were prepared in order to study the interdependence of the SiC particles embedding and the deposits' mechanical behaviour. SiC particles of two different si=es, namely 1 J.Lm and 20 nm, were codeposited with nickel from Watts solutions under pulse current conditions. It has been observed that the embedding of SiC particles in the nickel matrix and the pulse current application result in deposits with more uniform particle distribution and better surface morphology than those obtained under direct current conditions. The study of the composite deposits revealed that the microhardness is not only increased by the presence and the reduced si=e of the particles, but also influenced by the current conditions, i.e. duty cycle and pulse frequency. Moreover, microhardness of the deposits can be further ameliorated by specific thermal treatment.