Vassiliki Belessi - Academia.edu (original) (raw)

Papers by Vassiliki Belessi

Applied Catalysis B: Environmental, 2000

Mixed oxidic and perovskite-type materials based on the La, Sr, Ce and Fe elements were prepared ... more Mixed oxidic and perovskite-type materials based on the La, Sr, Ce and Fe elements were prepared using a mixture of nitrates salts and heating at 1000 • C. Three groups of solids were synthesized: (i) La 1−y Ce y FeO 3 (y=0.2, 0.3, 0.5), (ii) La 1−x Sr x FeO 3 (x=0.2, 0.3, 0.5) and (iii) La 1−x−y Sr x Ce y FeO 3 (x/y=0.

Nanomaterials

Graphene/metal nanocomposites have shown a strong potential for use in electronic applications. I... more Graphene/metal nanocomposites have shown a strong potential for use in electronic applications. In particular, the combination of silver nanowires (AgNWs) with graphene derivatives leads to the formation of an efficient conductive network, thus improving the electrical properties of a composite. This work focused on developing highly conductive hydrophilic hybrids of simultaneously functionalized and reduced graphene oxide (f-rGO) and AgNWs in different weight ratios by following two different synthetic routes: (a) the physical mixture of f-rGO and AgNWs, and (b) the in situ reduction of GO in the presence of AgNWs. In addition, the role of AgNWs in improving the electrical properties of graphene derivatives was further examined by mixing AgNWs with a hybrid of few-layered graphene with functionalized multiwalled carbon nanotubes (FLG/MWNT-f-OH). The studied materials showed a remarkable improvement in the overall electrical conductivity due to the synergistic effect of their compon...

Chemistry - A European Journal, 2017

The present article describes the preparation and characterization of highly conductive carbon in... more The present article describes the preparation and characterization of highly conductive carbon inks based on nanocomposites that combine a polystyrene-acrylic resin or watersoluble polymers with a hydrophilic graphene/carbon nanotube hybrid. The water-based carbon inks show high electrical conductivity and can be effectively used in advanced technologies such as gravure printing for printed electronics. Moreover, the conductivity is shown to be increased with a power law of the nanohybrid volume fraction, with an exponent close to that predicted from the percolation theory, indicating a limited impact of the polymer tunnelling barrier on the electrical conductivity of such nanocomposites.

The Role of Colloidal Systems in Environmental Protection, 2014

Abstract Adsorption and photocatalysis have been proposed as effective technologies for the treat... more Abstract Adsorption and photocatalysis have been proposed as effective technologies for the treatment of wastewater. This review discusses the effectiveness of modified and nonmodified TiO 2 as adsorbent and/or photocatalyst for its use in wastewater treatment technologies. A disadvantage is the need of an additional separation step involving the removal of the photocatalyst from the treated water. In this respect, magnetically separable photocatalysts have been developed that enable the easy recovery of the adsorbent/photocatalyst by an external magnetic field. We review various synthetic methods for their preparation and their photoactivity toward the degradation of various substances. Another approach to obviate the need for an additional separation step is the dispersion of TiO 2 on layered clays, as the resulting composite materials sediment much faster than raw or commercial TiO 2 nanoparticles. A brief presentation of papers focused on the synthesis of TiO 2 silicate nanocomposites with environmental applications is included.

Biomaterials, 2009

Nearly monodispersed superparamagnetic maghemite nanoparticles (15-20 nm) were prepared by a one-... more Nearly monodispersed superparamagnetic maghemite nanoparticles (15-20 nm) were prepared by a one-step thermal decomposition of iron(II) acetate in air at 400 C. The presented synthetic route is simple, cost effective and allows to prepare the high-quality superparamagnetic particles in a large scale. The as-prepared particles were exploited for the development of magnetic nanocomposites with the possible applicability in medicine and biochemistry. For the purposes of the MRI diagnostics, the maghemite particles were simply dispersed in the bentonite matrix. The resulting nanocomposite represents very effective and cheap oral negative contrast agent for MRI of the gastrointestinal tract and reveals excellent contrast properties, fully comparable with those obtained for commercial contrast material. The results of the clinical research of this maghemite-bentonite contrast agent for imaging of the small bowel are discussed. For biochemical applications, the primary functionalization of the prepared maghemite nanoparticles with chitosan was performed. In this way, a highly efficient magnetic carrier for protein immobilization was obtained as demonstrated by conjugating thermostable raffinosemodified trypsin (RMT) using glutaraldehyde. The covalent conjugation resulted in a further increase in trypsin thermostability (T 50 ¼ 61 C) and elimination of its autolysis. Consequently, the immobilization of RMT allowed fast in-solution digestion of proteins and their identification by MALDI-TOF mass spectrometry.

Sensors

Thermal sensors are mainly based on the selective heating of specific areas, which in most cases ... more Thermal sensors are mainly based on the selective heating of specific areas, which in most cases is a critical feature for both the operation and the performance of the thermal device. In this work, we evaluate the thermoelectrical response of two graphitic materials, namely (a) a commercial 2.4%wt graphene–ethyl cellulose dispersion in cycloxehanone and terpineol (G) and (b) a custom functionalized reduced graphene oxide (f-rGO) ink in the range of −40 to 100 °C. Both inks were printed on a flexible polyimide substrate and the Thermal Coefficients of Resistance (TCR) were extracted as TCRG = −1.05 × 10−3 °C−1 (R2 = 0.9938) and TCRf-rGO = −3.86 × 10−3 °C−1 (R2 = 0.9967). Afterward, the inkjet-printed devices were evaluated as microheaters, in order to exploit their advantage for cost-effective production with minimal material waste. f-rGO and G printed heaters reached a maximum temperature of 97.5 °C at 242 mW and 89.9 °C at 314 mW, respectively, applied by a constant current source...

Nanomaterials, 2021

The present work reports on the detailed electro-thermal evaluation of a highly water dispersible... more The present work reports on the detailed electro-thermal evaluation of a highly water dispersible, functionalized reduced graphene oxide (f-rGO) using inkjet printing technology. Aiming in the development of printed electronic devices, a flexible polyimide substrate was used for the structures’ formation. A direct comparison between the f-rGO ink dispersion and a commercial graphene inkjet ink is also presented. Extensive droplet formation analysis was performed in order to evaluate the repeatable and reliable jetting from an inkjet printer under study. Electrical characterization was conducted and the electrical characteristics were assessed under different temperatures, showing that the water dispersion of the f-rGO is an excellent candidate for application in printed thermal sensors and microheaters. It was observed that the proposed f-rGO ink presents a tenfold increased temperature coefficient of resistance compared to the commercial graphene ink (G). A successful direct interc...

Green Chemistry, 2021

Carbon nanotubes functionalized by a solvent free reaction are mixed with graphene nanosheets int... more Carbon nanotubes functionalized by a solvent free reaction are mixed with graphene nanosheets into a water dispersible all carbon hybrid, which combined with a resin from renewable materials leads to an eco-friendly conductive all carbon ink.

Biosorption can be defined as the removal of substances, such as metal or metalloid species, comp... more Biosorption can be defined as the removal of substances, such as metal or metalloid species, compounds and particulates from solution by biological material or their products, especially bacteria, algae, yeast and fungi by physico-chemical binding. Among these biosorbents, biopolymers have been preferred over other materials because of its advantages including biodegradability, hydrophilicity and presence of carboxylic groups. The increase in the nuclear industry and other anthropogenic activities has intensified environmental pollution, with the accumulation of radioactive elements as uranium and thorium. So, it is very important to identify potential effective and environmentally being sorbents for the remediation/removal of uranium and thorium in order to protect the environment. This article reviews the state of art of biosorption of uranium and thorium by biopolymers and to compare the results found in the literature and obtained biosorption results of uranium and thorium by Ca...

Herein we present the development and printability of three different categories of nanostructure... more Herein we present the development and printability of three different categories of nanostructured water-based inks and namely, conductive, fluorescent and simultaneously conductive and fluorescent inks. These specific products are very promising materials for advanced applications in the field of anti-counterfeiting applications, printed electronics and smart packaging. The preparation of conductive materials was based on functionalized graphene derivatives and hybrids with strong hydrophilic character that combine high dispersibility in water and remarkable electrical conductivity affording highly conductive inks. The fluorescent inks were prepared by dispersing carbon dots (C dots) in water based resins. In the third case, conductive reduced graphene oxide was effectively decorated with fluorescent C dots in order to induce more security features to the derived inks. The fluorescent C dots were synthesized using hydrothermal heating or microwave-assisted pyrolysis; a low-cost, fa...

Advanced Functional Materials, 2011

... www.MaterialsViews.com wileyonlinelibrary.com By Sung Min Kang , Sungjin Park , Daewon Kim , ... more ... www.MaterialsViews.com wileyonlinelibrary.com By Sung Min Kang , Sungjin Park , Daewon Kim , Sung Young Park , Rodney S. Ruoff , and Haeshin Lee * 1. Introduction ... Mater. 2009, 19, 1884 . [ 13 ] H. Lee , J. Rho , K. Holmburg , PB Messersmith , Adv. Mater. 2009, 21, 431 . ...

SN Applied Sciences

A simple and effective preparation method for the simultaneous reduction and functionalization of... more A simple and effective preparation method for the simultaneous reduction and functionalization of graphene oxide (rGO) by 2,4-diamino benzene sulfonic acid has been developed. The derivatives exhibit excellent conductivity and high dispersibility in various solvents. The successful preparation of rGO and the presence of the sulfonated aromatic diamine on rGO surface has been confirmed by infrared and X-ray photoelectron spectroscopy, while, the analysis by micro-Raman spectroscopy indicated that the reduction/functionalization alters the lattice structure of GO by the increment the defect density when the 2,4-diamino benzene sulfonic acid is used. Moreover, the study of the dried products by X-ray diffraction spectroscopy suggested the turbostratic restacking of the exfoliated rGO into graphite-like nanostructures. The obtained derivative of simultaneous reduction and functionalization of GO was used for the preparation of highly conductive water-based gravure ink, which in turn, was successfully applied in printing on various flexible substrates, demonstrating its great potentiality in graphene-based flexible and printed electronics applications.

In the present article, we describe the use of highly fluorescent carbon dots (CDs) for the prepa... more In the present article, we describe the use of highly fluorescent carbon dots (CDs) for the preparation of an effective water-based carbon dot ink (CD-ink) for gravure printing. Carbon dots were prepared hydrothermally from citrate and triethylenetetramine, and mixed properly with certain resins that are used in gravure inks. The as-produced CD gravure ink was used successfully for printing high quality fluorescent images.

Studies in Surface Science and Catalysis, 2000

ABSTRACT This chapter illustrates the concept of mesoporous materials based on manganese and enri... more ABSTRACT This chapter illustrates the concept of mesoporous materials based on manganese and enriches them with other heterocations, such as A1, La, Ce, at will. The materials thus formed have been tested for important environmentally catalytic reactions: CH4/NO/O2 (lean de-NOx) and CH4/O2 (combustion). Their corresponding catalytic performances were found superior to those reported in the open literature for a large number of catalysts tested under similar experimental conditions. A large number of techniques were employed for the surface and bulk characterization of the present materials. These include X-ray photoelectron spectroscopy (XPS) for surface composition, X-ray diffraction (XRD) for crystal phases, surface area measurements (BET) and AFM/Tapping mode experiments for surface texture, and transient methods for in situ determination of adsorption capacities and interaction characteristics of the reaction molecular species with the catalyst surface. The results obtained from these techniques were correlated with the catalytic performance results obtained.

Solar Energy

Nanocrystalline titania thin films were prepared by screen printing in order to efficiently contr... more Nanocrystalline titania thin films were prepared by screen printing in order to efficiently control and optimize the main step of the dye-sensitized solar cells (DSSCs) fabrication process. Different compositions of nanocrystalline titanium dioxide screen-printing pastes are described, based on 2-ethyl-1-hexanol solvent and commercial Degussa P25 TiO2. The rheological properties of the prepared pastes are presented as the crucial parameter of the deposition procedure. The produced titania thin films are extensively characterized by means of spectroscopy (Raman, XRD) and microscopy (SEM, AFM). The performance (induced photon-to-current efficiency—IPCE% and overall energy conversion efficiency—g%) of the corresponding DSSCs is also reported. � 2005 Elsevier Ltd. All rights reserved.

Applied Catalysis B-environmental, 2009

Mixed oxides of the general formula La0.8Sr0.2FeO3−x were prepared by ceramic and surfactant meth... more Mixed oxides of the general formula La0.8Sr0.2FeO3−x were prepared by ceramic and surfactant methods and tested towards the NO/H2/O2 and NO/CH4/O2 lean-deNOx reactions in the 200–450°C range. The materials were characterized for their bulk and surface composition by XRD, Mössbauer and XPS techniques. The main crystal phases detected were perovskites LaFeO3 and SrFeO3−x, and α-Fe2O3. The Mössbauer technique allowed the