Stelios Couris

University of Patras | UP · Department of Physics

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...

In the present work, the inorganic content of different milk samples is investigated by Laser Induced Breakdown Spectroscopy (LIBS) technique. Milk samples of different animal origin, in liquid, lyophilized powder, and ashed forms were studied using both infrared (1064 nm) and visible (532 nm) laser excitation conditions and the optimum experimenta...

Nonlinear optical (NLO) materials are the basis for several photonic and optoelectronic devices and applications. Among them, the 2D materials have attracted enormous interest due to their outstanding optoelectronic properties which endow them with great possibilities for a plethora of applications, as e.g. in ultrafast lasers, optical information...

The present work reports on the exceptional optical limiting performance of some recently synthesized nitrogen-doped graphene derivatives (NGs) by substitutional heteroatom doping. In particular, the optical limiting performance of NGs having different nitrogen contents and some NG-based quantum dots is investigated in a broad-band spectral range,...

WO3 nanostructured thin films were grown using spray deposition on FTO coated glass. The effect of the precursor concentration and the solution quantity, which determines the deposition time, on the electrochemical, electrochromic and optical properties of the WO3 films was investigated. The films were found to exhibit a good electrochromic activit...

The nonlinear optical properties of a functional Boron dipyrromethene (BODIPY) derivative, namely BODIPY 1, and its subsequent formed supramolecular romboidal cavitand BODIPY 2(OTf)4, formed by mixing 1 with the 90° platinum triflate Pt(dppp)(OTf)2 linker, were investigated under femtosecond (fs) and picosecond (ps) laser excitation conditions, usi...

In the present work the impact of in situ photoreduction, by means of ultraviolet (UV) irradiation, on the nonlinear optical response (NLO) of some graphene oxide (GO), fluorographene (GF), hydrogenated fluorographene (GFH) and graphene (G) dispersions is studied. In situ UV photoreduction allowed for the extended modification of the degree of func...

The present work reports on the transient nonlinear optical (NLO) responses of two different types of 2D silicon nanosheets (SiNSs), namely hydride-terminated silicon nanosheets (SiNS–H) and 1-dodecene-functionalized silicon nanosheets (SiNS–dodecene). The main motivation of this study was to extend the knowledge regarding the NLO properties of the...

In the present work, Laser Induced Breakdown Spectroscopy (LIBS) is used for the first time to investigate the effects of artificial feeding of bees on the honey. According to LIBS technique the emission spectral characteristics of the plasma created on the surface of honey samples are analyzed. Correlation plots indicating the importance of spectr...

We report a study related to the correlation between the texture coefficient and the electrochromism in vanadium pentoxide nanostructured films with orthorhombic symmetry obtained by spray pyrolysis technique. From a microstructural point of view, X-ray diffraction depicts that the size of the crystalline domains, evaluated from both Scherrer equat...

In the present work, the synthesis and characterization of polyelectrolyte-stabilized copper-based nanohybrids with tunable sizes and chemical composition are reported. More precisely, highly stable poly(sodium-4-styrenesulfonate) PSS-Cu(OH)2 and PSS-CuO/Cu(OH)2 nanohybrids are synthesized and characterized in terms of their chemical composition an...

Laser-Induced Breakdown Spectroscopy (LIBS), having reached a level of maturity during the last few years, is generally considered as a very powerful and efficient analytical tool, and it has been proposed for a broad range of applications, extending from space exploration down to terrestrial applications, from cultural heritage to food science and...

In the present work, laser-induced breakdown spectroscopy, aided by some machine learning algorithms (i.e., linear discriminant analysis (LDA) and extremely randomized trees (ERT)), is used for the detection of honey adulteration with glucose syrup. In addition, it is shown that instead of the entire LIBS spectrum, the spectral lines of inorganic i...

In this work Laser-Induced Breakdown Spectroscopy (LIBS) and absorption spectroscopy aided by machine learning are employed for discriminating some extra virgin Greek olive oils of different olive cultivars for the first time. LIBS and absorption spectra of extra virgin olive oils belonging to Kolovi and Koroneiki cultivars, as well as mixtures of...

Olive oil is a basic element of the Mediterranean diet and a key product for the economies of the Mediterranean countries. Thus, there is an added incentive in the olive oil business for fraud through practices like adulteration and mislabeling. In the present work, Laser Induced Breakdown Spectroscopy (LIBS) assisted by machine learning is used fo...

In the present work, the emission and the absorption spectra of numerous Greek olive oil samples and mixtures of them, obtained by two spectroscopic techniques, namely Laser-Induced Breakdown Spectroscopy (LIBS) and Absorption Spectroscopy, and aided by machine learning algorithms , were employed for the discrimination/classification of olive oils...

Laser-induced breakdown spectroscopy (LIBS) is used for the detection and determination of sulfur content in some organic soil samples. The most suitable sulfur spectral lines for such tasks were found to occur in the vacuum ultraviolet (VUV) spectral region and they were used for the construction of calibration curves. For the analysis, both univa...

Silicene, the silicon analogue of graphene, represents a new class of two-dimensional (2D) materials, which shares some of the outstanding physical properties of graphene. Furthermore, it has the advantage of being compatible with the current Si-based technology. However, this 2D material is not stable and is quite prone to oxidation. The hydride-t...

ABSTRACT In the present work, the nonlinear optical properties of some single- and few-layers graphene dispersions under femtosecond laser excitation were studied using Z-scan technique and are compared, in order to evaluate the effect of the number of graphenic layers and the influence of the laser excitation conditions on the measurements. The ex...

Nanostructured electrochromic V2O5 thin films were prepared using spray pyrolysis technique growth at a temperature of 250 °C using air-carrier spray deposition, starting from ammonium metavanadate precursor in water, followed by annealing at 400 °C in O2 atmosphere for 2 h. The V2O5 films were characterized by X-ray diffraction, scanning electron...

Fluorographene has been recently shown to be a suitable platform for synthesizing numerous graphene derivatives with desired properties. In that respect, N-octylamine-modified fluorographenes with variable degrees of functionalization are studied and their nonlinear optical properties are assessed using 4 ns pulses. A very strong enhancement of the...

Graphene derivatives and defect-engineered graphenes have attracted the interest of researchers owing to the excellent and tunable properties they exhibit. In this work the optical limiting performance of two defect-engineered boron- and nitrogen-doped reduced graphene oxides is investigated. Both graphenes are found to exhibit exceptional and broa...

Fluorographene (FG) is an uprising member of the graphene family as it combines high reactivity and stability. It presents various types of CF bonds (covalent, semi‐ionic, and ionic bonds) depending on its F‐atom content, which can be efficiently controlled by means of chemical synthesis. It is found that the chemical tweaking of the FG's structur...

In the present work, some recent results are presented concerning the use of UV laser reduction of fluorinated graphene and graphene oxide in order to modify their optical and nonlinear optical properties in a controlled way. The photo-reduction was achieved using 355 nm UV light from a 4 ns Nd:YAG laser, while the NLO properties of the derivatives...

Fluorinated graphene is an uprising member of the family of graphene derivatives, which, due to its high reactivity, can be easily modified chemically, resulting to modification of its wide bandgap and therefore allowing for the preparation of fluorographene derivatives exhibiting different and variable opto-electronic properties, while the choice...

A new approach regarding the development of nanostructured V2O5 electrochromic thin films at low temperature (250 °C), using air-carrier spray deposition and ammonium metavanadate in water as precursor is presented. The obtained V2O5 films were characterized by X-ray diffraction, scanning electron microscopy and Raman spectroscopy, while their elec...

In the present work Laser Induced Breakdown Spectroscopy (LIBS) is employed for the classification of honey samples assisted by different machine learning algorithms. Principal Component Analysis (PCA), Linear Discriminant Analysis (LDA), Support Vector Machines (SVMs) and Random Forest Classifiers (RFCs) were used for the treatment of the LIBS spe...

The present work reports on the broadband optical limiting performance and the enhancement of the nonlinear optical (NLO) response of a diethylamino‐modified fluorographene compared to pristine fluorographene and other modified fluorographenes. The present modified fluorographene was found exhibiting very efficient and broadband optical limiting ac...

The present study focuses on the in-situ analysis of slags from secondary copper production by means of laser-induced breakdown spectroscopy (LIBS) in order to improve the process efficiency and the end product quality. Synthetic slag samples, simulating secondary copper production slags, were melted in a laboratory induction furnace and were analy...

The classification of olive oils and the authentication of their geographic origin are important issues for public health and for the olive oil market and related industry. The development of fast, easy to use, suitable for online, insitu and remote operation techniques for olive oils classification is of high interest. In the present work, 36 oliv...

In the present work we report on the effect of the size and the degree of oxidation on the third-order nonlinear optical response and the optical limiting action of water dispersed graphene oxide (GO) sheets. The results show clearly that both the nonlinear optical third-order susceptibility χ(3) and the optical limiting threshold depend importantl...

In this work, the nonlinear optical (NLO) response of some graphene dispersions is investigated under low (i.e., 10 Hz) and high (i.e., 80 MHz) repetition rate femtosecond (fs) laser excitation conditions, using ${Z}$Z-scan, optical Kerr effect (OKE), and a combination of ${Z}$Z-scan and thermal lensing techniques. It is shown, that the NLO respons...

Laser Induced Breakdown Spectroscopy (LIBS) was combined with some machine learning techniques, such as Principal Components Analysis (PCA) and Linear Discriminant Analysis (LDA) in order to obtain useful information concerning the classification of olive oil samples (authentication of their geographic origin) and the detection of adulteration. Sin...

Fully fluorinated graphene (fluorographene) exhibits weak nonlinear optical response, in contrast to its unfunctionalized counterpart, that is graphene. However, diethylamino- functionalized fluorographene is shown to exhibit dramatic enhancement of its nonlinear optical response. Diethylamino-fluorographene is obtained by the reaction of fluorogra...

In the present work, Laser-Induced Breakdown Spectroscopy (LIBS) is used for the discrimination/identification of different plastic/polymeric samples having the same polymeric matrix but containing different additives (as e.g., fillers, flame retardants, etc.). For the classification of the different plastic samples, some machine learning algorithm...

Olive oil is an essential diet component in all Mediterranean countries having a considerable impact on the local economies, which are producing almost 90% of the world production. Therefore, the quality assessment of olive oil in terms of its acidity and its authentication in terms of PDO (Protected Designation of Origin) and PGI (Protected Geogra...

In this work, the synthesis and characterization of two novel thiophenol‐modified fluorographene derivatives, the methoxy‐thiophenol‐ and the dimethyl‐amino‐thiophenol‐modified fluorographenes, are reported while their third‐order nonlinear optical response were thoroughly investigated under visible (532 nm) and infrared (1064 nm), 35 ps and 4 ns l...

The third-order nonlinear optical response of hydrogenated fluorographene (CFH), a 2D counterpart of graphane, is presented in the visible and in the infrared, using ns laser excitation and compared to that of graphene fluoride (CF) and unfunctionalized graphene (G). All three graphenes, exhibit important nonlinear optical response, CFH exhibiting...

The third-order nonlinear optical response of hydrogenated fluorographene (CFH), a 2D counterpart of graphane, was investigated in the visible and in the infrared, using ns laser excitation and compared to that of graphene fluoride (CF) and (unfunctionalized) graphene (G). All three graphenes were found to exhibit important nonlinear optical respon...

The nonlinear optical response of some O-doped PAHs is systematically investigated in the present work aiming to understand the influence of structural effects on their nonlinear optical response. In that view, the third-order nonlinear optical properties of these PAHs were measured under 4 ns, visible (532 nm) and infrared (1064 nm) laser excitati...

The rapid development of nanoscience and nanotechnology has created a plethora of new opportunities for nonlinear optics. The growing number of nanomaterials shown to exhibit remarkable nonlinear optical properties has greatly enhanced the design and fabrication of new nano/nano-scale optoelectronic and photonic devices. Among these nanomaterials,...

During the last years, graphene and its derivatives have been in the spotlight of significant scientific research interest. This interest has been boosted up by the several potential applications envisaged for graphene in photonic and optoelectronic technologies. Graphene (G) is a 2D carbon allotrope with zero band gap. An interesting member of the...

Pd nanoparticles stabilized by polyvinylpyrrolidone were synthesized following mild reduction of palladium ion complexes. Their morphology and optical properties were characterized using Transmission Electron Microscopy, Dynamic Light Scattering and UV–Vis absorption spectroscopy to confirm the existence of monodispersed, low-dimensional single nan...

The nonlinear refractive index for 10 types of recently developed new soft glasses was measured under the same conditions using a pulsed Nd:YAG laser operating at 1064 nm with a 35 ps pulse duration. The study included various types of oxide-based soft glasses commonly used for nonlinear fiber optics, such as lead silicate, borosilicate, phosphatat...

We describe the benign wet chemical synthesis, characterization and third-order nonlinear optical properties of hydrogenated fluorographene, namely of a new 2D counterpart of hydrogenated graphene (graphane). The presence of hydrogen in hydrogenated fluorographene was confirmed using infrared spectroscopy, x-ray photoelectron spectroscopy and therm...

The preparation of the first soluble quaterrylene derivative featuring peripheral tert-butyl substituents and sterically hindering, core-anchored triflate groups has been achieved. This involves a facile synthetic route based on an oxidative coupling of perylene precursors in the presence of H2O2 as oxidant. The steric hindrance between the OTf sub...

Supplementary

The nonlinear optical properties of two graphene derivatives, graphene oxide and graphene fluoride, are investigated by means of the Z-scan technique employing 35 ps and 4 ns, visible (532 nm) laser excitation. Both derivatives were found to exhibit significant third-order nonlinear optical response at both excitation regimes, with the nonlinear ab...

The synthesis of O-doped polyaromatic hydrocarbons, in which two polycyclic aromatic hydrocarbon subunits are bridged through one or two O atoms, has been achieved. This includes high-yielding ring-closure key steps that, depending on the reaction conditions, yield the formation of either furanyl or pyranopyranyl linkages through intramolecular C-O...

Laser Induced Breakdown Spectroscopy (LIBS) was applied to homogenous methane–air mixtures of a wide range of compositions ranging from only air to only fuel in order to establish a new calibration scheme suitable for LIBS measurement of mixture fraction in turbulent non-premixed flames. Both a portable low resolution spectrometer equipped with a C...

Laser-induced breakdown spectroscopy (LIBS) is used for the mapping of local structures (i.e., reactants and products zones) and for the determination of fuel distribution by means of the local equivalence ratio ϕ in laminar, premixed air-hydrocarbon flames. The determination of laser threshold energy to induce breakdown in the different zones of f...

Ultrafast pump-probe spectroscopy on as-grown Graphene Oxide single sheet thin layers was employed in order to study their response following ultrafast excitation of electrons in the sp3 hybridized domains. The study of the transient spectra showed the existence of two wavelength regions with distinct responses: a saturable absorption region and a...

By means of different spectroscopic techniques, we investigate a novel series of free base porphyrin derivatives (H2TPP), connected to dibenzo-24-crown-8 (DB24C8) moieties, which undergo self-assembly with different methano[60]fullerene units bearing dibenzylammonium (DBA) cations. The formation of both [2] and [3]pseudorotaxanes was proved by mean...

We report on the effect of the degree of oxidation on the broadband non-linear optical response and magnetic behavior of graphene oxide, as well as on a route for obtaining reduced graphene oxide with enhanced optical properties without sacrificing the high dispersibility of the parent graphene oxide. As more sp 3 states evolved with the rise in ox...

We report on the effect of the degree of oxidation on the broadband non-linear optical response and magnetic behavior of graphene oxide, as well as on a route for obtaining reduced graphene oxide with enhanced optical properties without sacrificing the high dispersibility of the parent graphene oxide. As more sp3 states evolved with the rise in oxi...

Hybrids containing nanodiamonds with controllable content of gold nanoparticles (ND/Au) were prepared and characterized by XRD, TGA, and TEM/HRTEM techniques including STEM-EDS chemical mapping. For the first time, the nonlinear optical response of the prepared ND/Au dispersions in DMF was investigated by means of the Z-scan technique using 35 ps (...

The third order nonlinear optical parameters of a variety of organic solvents are determined under picosecond and femtosecond laser irradiation. Z-scan measurements have been carried out at 35 ps, 532 nm and at 40 fs, 800 nm, while Optical Kerr Effect studies were performed at 35 ps, 532 nm. The target of the present work is to provide a reference...

In the present work the third order nonlinear optical response of a series of pyrazoline derivatives has been experimentally investigated. All of the compounds have been prepared as doped poly(methyl methacrylate) thin polymeric films. For the needs of this study the third harmonic generation Maker fringes technique has been employed by using 30 ps...

In the present work the third order nonlinear optical response of a series of pyrazoline derivatives has been experimentally investigated. All of the compounds have been prepared as doped poly(methyl methacrylate) thin polymeric films. For the needs of this study the third harmonic generation Maker fringes technique has been employed by using 30 ps...