Spyros N. Yannopoulos

Spyros N. Yannopoulos
University of Patras | UP · Department of Chemistry

Doctor of Engineering

About

222
Publications
42,845
Reads
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5,373
Citations
Introduction
[1] Laser synthesis of high-quality graphene-based structures from metal carbides and organic compounds [2] Developing rational bottom-up synthetic routes for the controlled growth of 1-D nanostructures based mainly on ZnO and heterostructures (water splitting, solar cells) [3] CVD/PVD growth of 2-D TMDCh crystals (tribology, energy harvesting) [4] Photoinduced phenomena in non-crystalline chalcogenides: • athermal photoplastic phenomena • reversible amorphous-to-crystal phase transitions
Additional affiliations
March 2010 - present
University of Patras
Position
  • Professor (Associate)
Description
  • Teaching the elective course: "Glasses and Ceramics"

Publications

Publications (222)
Article
Polyacrylonitrile (PAN) is a hard, rigid, thermoplastic substance with various applications, including carbon fiber production for the aerospace and automotive sectors, textile manufacturing, and water and air filtration. Its usage as a synthetic resin is particularly notable in its stabilized form. Stabilization ensures thermal stability during gr...
Article
Conventional synthetic sorbents for oil spill cleanup are the most widely employed materials, although a major drawback is the extensive chemical modification that they have undergone, making them economically and environmentally non‐sustainable. The use of inexpensive, abundant, non‐toxic, biodegradable, and reusable lignocellulosic materials migh...
Article
The transcendence toward smarter technologies and the rapid expansion of the Internet of Things requires miniaturized energy storage systems, which may also be shape-conformable, such as microflexible supercapacitors. Their fabrication must be compatible with emerging manufacturing platforms with regard to scalability and sustainability. Here, we m...
Article
Photocorrosion of a photocatalyst’s surface, leading to degradation of its catalytic efficiency/cyclability, is a major concern which must be tackled for designing efficient processes. Despite that the photocorrosion of ZnO has been widely explored, a deep understanding of the mechanism involved is still elusive. Here, a detailed investigation of t...
Article
In the present study, we show that PtSe2 films, prepared by soft selenization of pre-deposited Pt, is a very efficient counter electrode (CE) in dye sensitized solar cells (DSSCs). Devices based on PtSe2 achieve better photoconversion efficiency (9.5 ± 1.2 %) than those employing bare Pt CE (9.18 ± 0.21 %), even if the latter use three times more P...
Article
Full-text available
Following the long-standing experience of the liquid exfoliation of graphite for the production of graphene, a number of analogous van der Waals 2D nanomaterials have been also produced and studied...
Article
Lasers offer a versatile means towards the single-step, binder-free synthesis of three-dimensional graphene-like porous networks, providing an enticing alternative over energy intensive, multi-step traditional synthesis protocols creating unwanted waste streams. Here, we report on a novel laser-assisted method for the one-step preparation of the el...
Article
Full-text available
Production of high-grade graphene-like materials using a simple, reliable processes and its simultaneous transfer onto soft surfaces have not yet achieved; hence impeding wide-ranging graphene applications. Even more complex processes are required to prepare graphene-based nanohybrids, which offer additional synergistic functionalities in relation...
Article
The energy performance of the building stock and the resulting emissions of greenhouse gases must be taken seriously into account for securing a sustainable future. Smart windows can transform a building to reach the standards of the Net Zero Emissions by 2050 Scenario. Among the currently available technologies, the Photoelectrochromic Devices (PE...
Article
Research studies on biomass derived graphene-like carbon materials for use in novel energy storage applications, has increased significantly in the last decade. It is a promising approach to a more sustainable energy future, as the synthesis of graphene-like structures from biomass is cost-effective and almost carbon neutral. In addition, they are...
Article
Diverse types of nanoparticles dispersed in various mineral and natural oils are under systematic investigation over the last years, in an effort to develop insulating nanofluids towards enhancing the lifetime and improvement of the operation conditions of power transformers. The moderate stability of the nanofluids (NFs) is a major obstacle in adv...
Article
Synthesis of high-quality graphene-like structures by means of an eco-friendly, cost effective, one-step and scalable method is highly sought after. Some of these traits have been successfully addressed in recent studies employing laser irradiation in the synthesis process, however, reports on laser-assisted high-quality graphene growth overwhelmin...
Article
Full-text available
The rational synthesis of semiconducting materials with enhanced photoelectrocatalytic efficiency under visible light illumination is a long-standing issue. ZnO has been systematically explored in this field, as it offers the feasibility to grow a wide range of nanocrystal morphology; however, its wide band gap precludes visible light absorption. W...
Article
Undoped and aluminum-doped ZnO nanowire (NW) arrays with high aspect ratio and doping concentration up to 2.0 at.% in Al, were prepared by chemical bath deposition (CBD) technique onto FTO/glass substrates. The morphological, structural, and optical properties of the as-grown NWs were investigated by using electron microscopy, diffraction, and spec...
Article
Full-text available
The utilization of tungsten disulfide (WS2) nanomaterials in distinct applications is raising due to their unique physico-chemical properties, such as low friction coefficient and high strength, which highlights the necessity to study their potential toxicological effects, due to the potential increase of environmental and human exposure. The aim o...
Article
Full-text available
Boron nitride (BN) nanomaterials have been increasingly explored for potential applications in chemistry and biology fields (e.g., biomedical, pharmaceutical, and energy industries) due to their unique physico-chemical properties. However, their safe utilization requires a profound knowledge on their potential toxicological and environmental impact...
Article
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This study addresses the effect of nanoparticles' conductivity and surface charge on the dielectric performance of insulating nanofluids. Dispersions of alumina and silicon carbide nanoparticles of similar size (~50 nm) and concentration (0.004% w/w) were prepared in natural ester oil. The stability of the dispersions was explored by dynamic light...
Article
Preparing high-quality graphene-like structures and materials in a consistent and environmentally friendly way is still elusive. Recent advances have revealed that laser irradiation of proper precursors presents great potential and versatility towards realizing high-quality growth of graphene-like materials at low cost. Here, we present a detailed...
Article
Full-text available
Thermosetting resins, such as poly (furfuryl alcohol), are efficient precursors for preparation of carbon membranes with molecular sieving properties. Polymerization of furfuryl alcohol is catalyzed by Bronsted or Lewis acids. FeCl3, showing Lewis-acid behavior, is an interesting polymerization catalyst, because it gets reduced into metallic iron d...
Article
Full-text available
The physicochemical properties and the toxicological potential of commercially available MoS2 nanoparticles with different lateral size and degradation stage were studied in the present research work. To achieve this, the structure and stoichiometry of fresh and old aqueous suspensions of micro-MoS2 and nano-MoS2 was analyzed by Raman, while X-ray...
Article
In the present work, we propose for the first time, the use of a carbon-based perovskite solar cell (PSC) in a “partly covered” photoelectrochromic (PEC) device, with a three-electrode architecture that de-couples the photovoltaic (PV) and electrochromic (EC) operation, thus enabling better control of the device optical modulation. The proposed con...
Article
The synthesis of insulating nanofluids by integration of nanoparticles in insulating oils has been employed over the last two decades by many researchers in an effort to improve both the dielectric strength and the thermal conductivity of dielectric liquids. In this paper, nanofluids with different volume concentrations of the nanoparticles were pr...
Article
Full-text available
The relaxation properties of supercooled AsxS100−x liquids are investigated using a combination of infrared photon correlation spectroscopy and topological constraint theory. Results reveal two channels of relaxation for sulfur-rich compositions that manifest by an unusual profile in the density-density autocorrelation function involving two typica...
Preprint
Much progress has been made over a long period, spanning more than a century, in understanding the atomic arrangement on various length scales of noncrystalline chalcogens and their transitions upon certain external stimuli. However, it is broadly admitted that there are still several unsettled issues that call for proper rationalization. The curre...
Article
Full-text available
Much progress has been made over a long period, spanning more than a century, in understanding the atomic arrangement on various length scales of non-crystalline chalcogens and their transitions upon certain external stimuli. However, it is broadly admitted that there are still several unsettled issues that call for proper rationalization. The curr...
Article
We report an investigation of the optical properties, structure, and vibrational modes of Sb x As37-xS48I15 glasses (0 at. % < x < 37 at. %). Optical parameters such as the refractive index, the absorption coefficient, and the optical band gap are correlated with the glass composition. All parameters were found to follow an almost linear dependence...
Preprint
Full-text available
The current critical review aims to be more than a simple summary and reproduction of previously published work. Many comprehensive reviews and collections can be found in the literature. The main intention is to provide an account of the progress made in selected aspects of photoinduced phenomena in non-crystalline chalcogenides, presenting the cu...
Article
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We demonstrate a simple and cost-effective method for the synthesis of elemental Se and Te nanoparticles. The method employs irradiation of bulk Se and Te by visible light, continuous wave sources and results in uniform deposition of nanoparticles on various substrates. The process is fast and avoids the steps of pre- and post-treatment involved in...
Article
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Carbon-based mesoscopic perovskite solar cells (PSCs) and photodetectors were fabricated with the application of double-layered ZrO 2 films, consisting of zirconia nanoparticles and microparticles for the first and the second layer, respectively. This assembly exploits the ability of the zirconia microparticles to scatter and hence diffuse the inci...
Article
Full-text available
The paper reports on ≈1.5 μm Stokes photoluminescence (PL) emission and upconversion photoluminescence (UCPL) emission in the visible and near-infrared spectral region in Er ³⁺ -doped Ge 25 Ga 8 As 2 S 65 chalcogenide glasses at pumping wavelengths of 980 and 1550 nm. The ≈1.5 μm PL emission spectra are broadened with increasing concentration of Er...
Article
Well aligned ZnO NWs arrays served as a scaffold for the deposition of Pt by evaporation and their electrocatalytic properties were examined against the iodide/triiodide redox shuttle. By varying the amount of deposited Pt and the aspect ratio of the NWs arrays, an increment in the peak current density (up to 87%) and in the reaction rate for I3- r...
Article
In the present study, based on potentiodynamic and potentiostatic measurements as well on specific surface area analysis data we present a detailed study on the photoelectrochemical properties of ZnO nanorod (NR) arrays aiming to shed light on the photo-electrokinetics of oxygen evolution reaction (OER) on the ZnO surface interfaced with 0.1 M NaOH...
Article
The complex dielectric function, the Er3+ Stokes emission at ≈1540 nm and the upconversion photoluminescence at ≈990 nm of pulsed-laser deposited thin-film GeGaSbS:Er3+ are studied. The linear-refractive-index dispersion is obtained by fitting spectroscopic ellipsometry data to the Sellmeier and the Cody-Lorentz parametrizations. The former model i...
Article
Full-text available
Surface Enhanced Raman Spectroscopy (SERS) belongs to the techniques of ultra-sensitive chemical analysis and involves both identification and quantification of molecular species. Despite the fact that theoretically derived enhancement factors imply that even single molecules may be identified, which in some cases has indeed been experimentally obs...
Article
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Laser processing of carbon containing compounds towards the formation of graphene-based structures gains ground over the last years in view of the practicality that lasers offer against other conventional graphene preparation methods. The current work explores the viability of low-cost lasers, operating at ambient conditions, for the transformation...
Article
Societies worldwide are investing considerable resources into the safe development and use of nanomaterials. Although each of these protective efforts is crucial for governing the risks of nanomaterials, they are insufficient in isolation. What is missing is a more integrative governance approach that goes beyond legislation. Development of this ap...
Article
Reduction of graphene oxide (GO) to a low-resistance product is one of the most versatile routes to obtain large volume graphene-based materials. A number of chemical and thermal methods are being applied to achieve this goal, albeit each one is bound to certain disadvantages and limitations. Laser-assisted reduction has emerged as a promising meth...
Article
Full-text available
A comparative assessment of nanowire versus nanoparticle-based ZnO dye-sensitized solar cells (DSSCs) is conducted to investigate the main parameters that affect device performance. Towards this aim, the influence of film morphology, dye adsorption, electron recombination and sensitizer pH on the power conversion efficiency (PCE) of the DSSCs is ex...
Article
Defect-free ZnO nanowire arrays were synthesized and assessed as photoanodes in photoelectrochemical cells. Several tens of samples classified into five different average diameters in the range 40-260 nm were prepared to explore the role of morphology and polar surfaces. The photoelectrochemical performance of the NWs was studied in basic aqueous e...
Article
Time-resolved Raman measurements reveal a three-stage mechanism of photostructural changes in Ge25.0Ga9.5Sb0.5S65.0 (containing 0.5 at.% of Er3+) glass under continuous-above-bandgap illumination. These changes are reversible and effectively athermal, in that the local temperature rises to about 60% of the glass-transition temperature and the phase...
Article
Full-text available
The time-resolved Raman measurements reveal a three-stage mechanism of the photostructural changes in Ge25.0Ga9.5Sb0.5S65.0 (containing 0.5 at. % of Er3+) glass under continuous-above-bandgap illumination. These changes are reversible and effectively athermal, in that the local temperature rises to about 60% of the glass-transition temperature and...
Article
Full-text available
Oxygen-deficient pristine (LMNO) and microwave-treated LiMn1.5Ni0.5O4-δ (LMNOmic) cathode materials have been synthesized with modified thermo-polymerization synthesis technique. The XRD, XPS, CV and charge/discharge voltage profile analysis confirm that the microwave treatment enhance the electrochemical property by adjusting the lattice parameter...
Article
Full-text available
The current work attempts to provide a proof of concept for the achievement of semi-quantitative measurements by applying Surface Enhanced Raman Scattering (SERS) on thermally dewetted Au-films. In order to probe the anticipated advanced (device) material, Mitoxantrone (MTX) that exhibits strong SERS signal was utilized as a relevant prototype acti...
Article
Photocatalytic (PC) methods based on advanced oxidation processes have shown great potential for removal of water pollutants. Oxide semiconductors stand out as the most promising materials for UV-mediated photodegradation of persistent pollutants in wastewater. Although an immense number of studies have appeared so far concerning the PC activity mo...
Article
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Tuning the properties of van der Waals heterostructures based on alternating layers of two-dimensional materials is an emerging field of research with implications for electronics and photonics. Hexagonal boron nitride (h-BN) is an attractive insulating substrate for two-dimensional materials as it may exert less influence on the layer’s properties...
Article
Full-text available
In this work we present a structural and spectroscopic analysis of a copper(II) N-acetyl-5-arylidene tetramic acid by using both experimental and computational techniques. The crystal structure of the Cu(II) complex was determined by single crystal X-ray diffraction and shows that the copper ion lies on a centre of symmetry, with each ligand ion co...
Article
Full-text available
ZnO nanowire arrays represent an important multifunctional platform in nanotechnology with a diverse set of emerging applications. Many parameters and conditions are involved in the growth process affecting quality and reproducibility and hence the functionality of the nanowire arrays. Therefore, the fabrication of high-quality arrays is challengin...
Article
Full-text available
The growth of MoS2 films by sulfurization of Mo foils at atmospheric pressure is reported. The growth procedure provides, in a controlled way, mono- and few-layer thick MoS2 films with substrate-scale uniformity across square-centimeter area on commercial foils without any pre- or post-treatment. The prepared few-layer MoS2 films are investigated a...
Article
Full-text available
Thin (AsSe)100–xAgx (x = 0–25 mol.%) films have been deposited on glass substrates and silicon cantilevers by vacuum thermal evaporation from the corresponding bulk materials. The mechanical stability was investigated by measuring the stress of the films deposited on silicon cantilevers. The correlation between the stress and the composition has be...
Article
Full-text available
A novel method for the laser-assisted, template-free and surfactant-free fabrication of low-dimensional nanomaterials, i.e. nanotubes, nanowires, nanospheres, of elemental Te, hybrid Te/TeO2and GeTe structures is presented. Owing to the high light absorption at visible wavelengths and the low melting points of chalcogen-based materials, simple cw l...
Article
Carbon deposition during CO methanation from biomass-derived gas is a significant challenge in terms of catalyst lifetime. It results from the severe reaction conditions imposed by the presence of unsaturated hydrocarbons in the gasified feedstock. This work investigated the structure of boron-modified Ni/Al2O3 catalysts exhibiting enhanced carbon...
Article
Full-text available
Reversible and reproducible formation and dissolution of silver conductive filaments are studied in Ag-photodoped thin-film Ge 40S60 subjected to electric fields. A tip-planar geometry is employed, where a conductive-atomic-force microscopy tip is the tip electrode and a silver patch is the planar electrode. We highlight an inherent “memory” effect...
Research
Full-text available
REVIEW Much of our knowledge about structure and dynamics in solids, liquids or gasses comes from the interaction (scattering) between externally imposed stimuli and the system under study. Light has proved to be one of the best such stimuli that can furnish a great deal of important information over wide spatial and temporal range. This us the sub...
Chapter
One-dimensional anisotropic nanostructures, and in particular nanowires, are under intensive investigations over the last decade owing to their unique physical properties and their documented performance in a wide range of opto-electronic and nano-photonic devices. Here, we present a short overview of the main assets of nanowire arrays with particu...
Article
Full-text available
Controlled photo-induced oxidation and amorphization of elemental trigonal tellurium are achieved by laser irradiation at optical wavelengths. These processes are monitored in situ by time-resolved Raman scattering and ex situ by electron microscopies. Ultrathin TeO2 films form on Te surfaces, as a result of irradiation, with an interface layer of...
Conference Paper
Full-text available
We experimentally demonstrate a novel method which allows deposition of solution-based soft-glass films (chalcogenide) inside the holes of commercially available solid and hollow core photonic crystal fiber (PCF). The transmission spectra are recorded using a supercontinuum source indicating ARROW type guidance in the solid core PCFs while initial...
Article
Full-text available
Raman scattering has been employed to study the temperature and polarization dependence of the vibrational modes for the glass-forming halide salt mixtures xZnCl 2 -(1 ; x)AlCl 3 , with x = 0.8 and 0.6. The analysis has shown that the vibrational modes of the mixtures arise from a contribution of the vibrational modes of the pure components salts....
Article
Full-text available
Raman scattering has been employed to study the temperature and polarization dependence of the vibrational modes for the glass-forming halide salt mixtures xZnCl2-(1 - x)AlCl3, with x = 0.8 and 0.6. The analysis has shown that the vibrational modes of the mixtures arise from a contribution of the vibrational modes of the pure components salts. Emph...
Article
Carbon nanotubes (CNTs) have attracted great attention for their potential use in many applications because of their intrinsic properties. The importance other than the impact of the application of CNT-embedded membranes in the area of water technology development is immense. In this context, the identification and quantification of CNTs in aqueous...