1,720,980 research outputs found
An overview of biopolymer-based nanocomposites for optics and electronics
No full textBiopolymer-based nanocomposites are materials composed mainly of biopolymer matrices in which nanofillers are dispersed. Biopolymers are polymers obtained from some living organisms; therefore they are biodegradable and biocompatible; moreover, they have a variety of functional groups allowing the control of the interface with nanofillers and the multiscale assembly. They have been employed in numerous applications also because of their flexibility under processing conditions and competitive cost of their end products. Most of the published work is focused on their electronic and biomedical applications. In this review we focus our attention on biopolymer-based composites with inorganic nanofillers like metal, metal oxides, semiconductor nanoparticles and carbon-based nanoparticles, for application in optics and electronics. Special attention is paid to synthesis strategies for integrating nanofillers in biopolymer matrices. This journal i
Enhancing Tungsten Oxide Gasochromism with Noble Metal Nanoparticles: The Importance of the Interface
No full textCrystalline tungsten trioxide (WO3) thin films covered by noble metal (gold and platinum) nanoparticles are synthesized via wet chemistry and used as optical sensors for gaseous hydrogen. Sensing performances are strongly influenced by the catalyst used, with platinum (Pt) resulting as best. Surprisingly, it is found that gold (Au) can provide remarkable sensing activity that tuned out to be strongly dependent on the nanoparticle size: devices sensitized with smaller nanoparticles display better H-2 sensing performance. Computational insight based on density functional theory calculations suggested that this can be related to processes occurring specifically at the Au nanoparticle-WO3 interface (whose extent is in fact dependent on the nanoparticle size), where the hydrogen dissociative adsorption turns out to be possible. While both experiments and calculations single out Pt as better than Au for sensing, the present work reveals how an exquisitely nanoscopic effect can yield unexpected sensing performance for Au on WO3, and how these performances can be tuned by controlling the nanoscale features of the system
Photoluminescence properties of silk–carbon quantum dots composites
Full text linkIn this paper, we report silk fibroin (SF) and carbon quantum dots (CQDs) nanocomposites obtained through a facile solution casting approach. The optical properties of the nanocomposites have been characterised by UV–vis absorption and photoluminescence spectroscopy. Crosslinking of SF and chemical interactions with the CQDs have been investigated by FTIR spectroscopy. In addition, water stability and degradability of the prepared composites have been investigated in terms of mass loss, important for applications in a real scenario. We observed that for a concentration of CQDs above 1%wt aggregation of nanoparticles occurs, affecting the photoluminescence of the material. The results show that the best composition in terms of photoluminescence intensity and water stability is 0.5%wt CQDs. [Figure not available: see fulltext.
Waste-derived glass as a precursor for inorganic polymers: From foams to photocatalytic destructors for dye removal
Full text linkSynthetic alumino-silicate glasses may yield inorganic polymers, through activation with alkali hydroxide solutions. In this framework, we formulated a glass prepared by the melting of red mud from bauxite refinement, combined with coal combustion fly ash, discarded pharmaceutical glass and a minor addition of sodium carbonate. The activation with 6 M NaOH aqueous solution allowed for the manufacturing of highly porous foams, by gas generation at the early stages of gelation. These foams featured an extensive formation of zeolite at cell walls which, combined with the presence of magnetite formed upon cooling of the melt, favoured the application of the foams as sorbents for dye removal from contaminated water. The powders prepared by crushing the highly porous foams showed an excellent water purification ability documented by efficient removal of methylene blue used as a model contaminant. The specific iron oxide polymorph facilitated both magnetic recovery of dispersed powders and photocatalytic destruction of the dye under UV irradiation
Nanomechanical and tribological characterization of silk and silk-titanate composite coatings
No full textThis paper investigates the tribological and mechanical properties of silk-based nanocomposite coatings which are finding applications in optics, biomedicine and dentistry, thanks to the exceptional mechanical/optical properties and associated biocompatibility of silk. Three different nanocomposite formulations were synthesized, and thin films were prepared by spin coating at different thicknesses and with different post-deposition annealing processes. Ellipsometry, FTIR spectroscopy, AFM, nanoindentation, scratch testing, continuous/reciprocating wear testing, confocal microscopy and SEM were used to characterize the coatings. The results reveal that their hardness and elastic modulus are in the range 0.56–1.30 GPa and 23.6–55.4 GPa, respectively, which are much higher than those reported for other silk films in literature. Incorporation of titanate nanosheets also improved coatings’ scratch resistance
SILAR Deposition of Metal Oxide Nanostructured Films
Full text linkMethods for the fabrication of thin films with well controlled structure and properties are of great importance for the development of functional devices for a large range of applications. SILAR, the acronym for Successive Ionic Layer Adsorption and Reaction, is an evolution and combination of two other deposition methods, the Atomic Layer Deposition and Chemical Bath Deposition. Due to a relative simplicity and low cost, this method has gained increasing interest in the scientific community. There are, however, several aspects related to the influence of the many parameters involved, which deserve further deepening. In this review article, the basis of the method, its application to the fabrication of thin films, the importance of experimental parameters, and some recent advances in the application of oxide films are reviewed. At first the fundamental theoretical bases and experimental concepts of SILAR are discussed. Then, the fabrication of chalcogenides and metal oxides is reviewed, with special emphasis to metal oxides, trying to extract general information on the effect of experimental parameters on structural, morphological and functional properties. Finally, recent advances in the application of oxide films prepared by SILAR are described, focusing on supercapacitors, transparent electrodes, solar cells, and photoelectrochemical devices
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Sol-Gel Pt-VO2 Films as Selective Chemoresistive and Optical H2 Gas Sensors
No full textIn this work, VO2 (M1/R) thin films were exploited as H-2 gas sensors. A flat film morphology, obtained by furnace annealing, was compared with a laser-induced nanostructured one. The combination of the environmentally friendly sol-gel approach with the ultrafast laser crystallization allows for significant reductions in energy consumption and related emissions during the fabrication of VO2 sensors. By decorating the sensors' surface with Pt nanoparticles (NPs), the sensor response was enhanced exploiting the hydrogen spillover effect. The Pt/VO2 sensors, tested at operating temperatures between 20 and 200 degrees C and for concentration of H-2 from few ppm to 50000 ppm, offered a dual chemoresistive and optical sensing mode. Low operating temperatures of 150 degrees C were achieved, along with a detection limit as low as 2 ppm and a perfect baseline recovery. Both sensors guaranteed specific selectivity toward H-2, without response to NO2 or humidity, and long-term stability over 500 h. The H-2 sensing mechanism, for both the monoclinic and rutile VO2 phases, was investigated through in operando X-ray Diffraction and in situ X-ray Photoelectron Spectroscopy tests. The interaction was found to be based on the reversible formation of HxVO2 bronze, along with the reversible variations in the oxidation state of V
Functionalization of LCD glass for the manufacturing of advanced 3D-printed translucent photocatalytic scaffolds
Full text linkIn this paper, we discuss the functionalization of translucent glass scaffolds obtained from LCD glass waste with a photocatalytic coating. Scaffolds were in the form of four-layer lattices and gyroids, depending on the printing technology, such as direct ink writing and masked stereolithography. The printed structures were dip-coated with a sol-gel TiO2 precursor solution followed by thermal annealing to induce crystallization. Preliminary tests were performed on LCD slides to optimize the process parameters such as withdrawal speed and annealing temperature. The physicochemical properties of the coatings were characterized by X-ray diffraction analysis, UV–VIS spectroscopy, ellipsometry, and SEM. The photocatalytic efficiency was evaluated by monitoring the degradation of methylene blue under UV light. Photodegradation kinetics were studied following a pseudo-first-order reaction. We found that the coated scaffolds show comparable photodegradation rate constant, despite the different topologies
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