Tailoring of strong orange-red-emitting materials for luminescence lifetime thermometry,anti-counterfeiting,and solid-state lighting applications

Strong orange-red-emitting Ba₂LaTaO₆:Eu³⁺ phosphors were designed and applied in various optical applications of luminescence lifetime thermometer, anti-counterfeiting film, and solid-state lighting applications. The crystal structure, elemental composition, asymmetry ratio, and other luminescent behaviors were investigated in detail. Especially, the optimal Ba₂LaTaO₆:0.1Eu³⁺ phosphor presented remarkable quantum yield (45.29%) and thermal stability (71.52% at 423 K). Based on the temperature-dependent luminescence decay curves, the maximum relative sensing sensitivity was 0.185 × 10^?2 K^?1 at 513 K. In addition, a novel anti-counterfeiting technique was introduced. The fabricated polydimethylsiloxane films exhibited three different colors under the irradiations of room light, 254 nm light, and 365 nm light, respectively. Eventually, the packaged light-emitting diode displayed the pure orange-red emission. Briefly, a series of the Eu³⁺-activated Ba₂LaTaO₆ phosphors with excellent luminescent properties were characterized and further applied in several optical fields for the first time.     

Single versus poly-crystalline layered oxide cathode materials for solid-state battery applications - a short review article

The recent developments in the application of single-crystalline (SC) cathode materials in solid-state batteries are discussed in this mini-review. The characteristics of SC and poly-crystalline (PC) cathode materials are explored, with emphasis on the kinetic and mechanical properties. The critical factors influencing their performance in liquid electrolyte and solid-state battery cells are investigated. Finally, the advantages and disadvantages of both morphologies are discussed and considerations to ensure a fair comparison between SC and PC cathodes in different systems are raised.     

Hybrid materials covalently incorporated with isophorone-based dyes through sol-gel process for nonlinear optical applications

Two new push-pull type second-order nonlinear optical (NLO) active isophorone-based alkoxysilane dyes with the same acceptor were synthesized and characterized. One silane (ICTES-HEMA) bears a chromophore with a hydroxyethyl methylamino donor and the other silane (ICTES-HMPP) is a bulkier analogue with a hydroxymethyl diphenylamino donor. Transparent, homogeneous films were prepared via the copolymerization of tetraalkoxysilane (TEOS) and different NLO silanes with the ratio of 5:1. The d(33) values obtained for the HEMA and HMPP films are 46.3 and 20.6 pm/V, respectively. Normalized UV-vis spectra reveal that the introduction of a diaryl group would help to prevent unfavorable organization of the chromophores. The reorientation dynamic stabilities of the samples were studied by second-harmonic generation (SHG) measurements, demonstrating that bulkier chromophores incorporated in sol-gel materials would not necessarily lead to higher stabilities over time.     

Hybrid organic/inorganic materials for photonic applications via assembling of nanostructured molecular units

Hybrid organic–inorganic materials exhibit so versatile properties that they can be considered one of the most interesting classes of materials for photonic applications, for the development of both passive and active devices. A synthetic route used for the preparation of nanostructured organic/inorganic (O/I) materials is the assembling of nano-building blocks (NBBs). This approach allows controlling the extent of phase interaction, which in its turn governs the structure-properties relationships. The non-hydrolytic sol–gel process is recognized as a useful route for the preparation of nanostructured molecular units. The condensation reaction of methacryloxypropyl trimethoxysilane and diphenylsilanediol in a non-hydrolytic sol–gel process has been exploited in order to synthesize nanostructured molecular units for the preparation of hybrid organic/inorganic coatings. The non-hydrolytic condensation reactions were run adding different compounds such as triethylamine, titanium isopropoxide, titanium chloride, and dibutyldilauryltin as condensation promoters. The NBB synthesis was also run under controlled hydrolitic conditions, by exploiting the in situ water production using an ethanol/acetic acid mixture. These reactions have been compared in terms of the influence of the employed reagents on the condensation degree and the product structure. Multinuclear NMR, ATR-FTIR and FT-Raman techniques have been used to study the reaction steps and characterize the final condensation products. Hybrid O/I materials have been prepared by assembling methacrylate-based NBBs in the presence of suitable thermal and photo-initiators. The study on the progress of the thermal polymerization process using differential scanning calorimetry (DSC) will be presented, as well as the preliminary results on the two photon polymerization (TPP) process for the preparation of patternable films.     

Hybrid nanocomposites for optical applications

Incorporating inorganic particles into conjugated polymer matrices is an area of current interest in the fields of optoelectronics and solar energy. The hybrid nanocomposites exhibit interesting physical properties thanks to good optical properties of polymers and to high carrier mobility of inorganic semiconductors. A judicious combination of organic/inorganic can therefore provide materials of low cost, ease processing, high stability, with specific electrical and optical properties.In the present study, we briefly review the composite materials that have been successfully utilized in the field of optoelectronics and photovoltaic conversion. We shall describe in particular a family of nanocomposites using polyhedral oligomeric silsesquioxanes (POSS) of general formula (RSiO_3/2)n where R is an organic group as a core. The composites are made by grafting functional polymer groups to the core, which allows the control of their optical properties. Such composites have high mechanical resistance and stability because of the special structure of the core. For illustration, we present a study of polyfluorene (PF)/POSS materials used as an active layer in organic light emitting diodes, with improved performance as compared to those using polymer only, and we discuss the role of the particles in the transport and emission processes in the devices studied.     

Hybrid materials for supercapacitor application

In the present study, a manganese oxide obtained by the acid treatment of LiMn₂O₄ spinel has been used as a positive electrode of supercapacitor. Removal of lithium from a spinel allowed to obtain MnO₂ compound with the pores partly distributed in atomic scale, hence, an efficient use of its pseudocapacitive properties could be reached. On the other hand, residual lithium remaining in the structure preserved layered framework of MnO₂ with pathways for ions sorption. Physical properties, morphology, and specific surface area of electrode materials were studied by scanning and transmission electron microscopy, and nitrogen sorption measurements. Voltammetry cycling, galvanostatic charge/discharge, and impedance spectroscopy measurements performed in two- and three-electrode cells have been applied in order to measure electrochemical parameters. Neutral Li₂SO₄ aqueous solution has been selected for electrolytic medium. Extension of operating voltage for supercapacitor has been realized through asymmetric configuration with an activated carbon as a negative electrode. The asymmetric capacitor was operating within a voltage range up to 2.5 V (limited to 2.0 V for cycling tests) and was able to deliver a specific capacitance of 60 Fg⁻¹ per capacitor at 100 mA g⁻¹ current density. High specific energy of 36 Wh kg⁻¹ was reached but with a moderate power density.     

Nanostructured materials for thermoelectric applications

Recent studies indicate that nanostructuring can be an effective method for increasing the dimensionless thermoelectric figure of merit (ZT) in materials. Most of the enhancement in ZT can be attributed to large reductions in the lattice thermal conductivity due to increased phonon scattering at interfaces. Although significant gains have been reported, much higher ZTs in practical, cost-effective and environmentally benign materials are needed in order for thermoelectrics to become effective for large-scale, wide-spread power and thermal management applications. This review discusses the various synthetic techniques that can be used in the production of bulk scale nanostructured materials. The advantages and disadvantages of each synthetic method are evaluated along with guidelines and goals presented for an ideal thermoelectric material. With proper optimization, some of these techniques hold promise for producing high efficiency devices.     

Ceramic-based materials for electrochemical applications

Novel catalytic ceramic-based materials that simultaneously possess high surface area and adsorptive capacity, with proton and/or electron conducting properties, were developed for electrocatalytic and waste-stream treatment processes. These novel inorganic proton conducting membranes were produced by incorporating inorganic low-temperature proton conductors such as polymeric phosphates of polyvalent metals into the porous structure of different active or inert substrates such as ceramics (in the form of tubes, discs and paper), zeolites or carbon cloth. Electrocatalytic activity was obtained by coating electroconductive surface layers that acted both as electrode and catalyst. Bench scale and pilot scale test reactors were built and commissioned. Comparison with existing technologies was undertaken for several applications. Such high surface-area inorganic materials that support nanoscale metal clusters are being tested as electrode materials in anodic oxidation, inorganic fuel cells and hydrogen generation.     

Polymer-filled nanoporous silica aerogels as hosts for highly stable solid-state dye lasers

New hybrid solid-state dye laser materials based on highly porous silica aerogels have been synthesized. The open porous network of the aerogel was saturated with laser dyes dissolved in appropriate organic monomers, and polymerization took place inside the silica structure. The resulting polymer-filled nanoporous aerogel (PFNPA) was cast in a cylindrical shape, forming monoliths that were used as gain media in solid-state dye lasers. When the PFNPA incorporated pyrromethene dyes, highly photostable laser emission with good lasing efficiency was obtained. Under the demanding conditions of tightly focused transversal pumping with 532 nm, 5 mJ pulses at 10 Hz repetition rate, the commercial dye Pyrromethene 567 exhibited laser action with only a 10% drop in the laser output after 10(6) pump pulses in the same position of the sample.     

A transparent solid-state ion gel for supercapacitor device applications

Journal of Solid State Electrochemistry - A feasibility study of the synthesis of gel polymer electrolytes based in methyl methacrylate (MMA) and 1-vinyl-2-pyrrolidone (VP) using [HEMIm][BF4] as...     

Hybrid cathode materials for lithium-sulfur batteries

This review demonstrates the approaches to fabricate hybrid cathode materials for lithium-sulfur batteries. This short review does not claim to cover all recently published data; instead, an effort is aimed to show how the critical issues on carbon – sulfur hybrid are addressed based on selected articles in last couple of years. The influence of porous structure of carbon, the confinement effect of polysulfides in narrow micropores, and importance of hierarchical porosity are explained. Besides, the heteroatom doping on carbon in carbon–sulfur hybrids plays a vital role on improvement of bulk electronic conductivity of electrode. This review presents the twin polymerization strategy for direct preparation of nanoscale intermixed hybrid materials. Finally, the formation of sulfur containing copolymers by reacting sulfur melt with functional vinyl monomers are shown in this review with selected examples postulating the respective potential for future generation energy storage technology from the viewpoint of industrial applications.     

Hybrid materials for optics and photonics

The interest in organic-inorganic hybrids as materials for optics and photonics started more than 25 years ago and since then has known a continuous and strong growth. The high versatility of sol-gel processing offers a wide range of possibilities to design tailor-made materials in terms of structure, texture, functionality, properties and shape modelling. From the first hybrid material with optical functional properties that has been obtained by incorporation of an organic dye in a silica matrix, the research in the field has quickly evolved towards more sophisticated systems, such as multifunctional and/or multicomponent materials, nanoscale and self-assembled hybrids and devices for integrated optics. In the present critical review, we have focused our attention on three main research areas: passive and active optical hybrid sol-gel materials, and integrated optics. This is far from exhaustive but enough to give an overview of the huge potential of these materials in photonics and optics (254 references).     

Azo dye doped polymer films for nonlinear optical applications

Azo dye doped polymer films were prepared on glass substrates using spin-coating technique. FTIR, UV-Vis spectra and PL measurements were recorded to characterize the structure of the metanil yellow doped PVA films. Surface morphology and thickness of the films were studied using AFM and FESEM. The magnitude of both real and imaginary parts of third-order nonlinear susceptibility χ3 of metanil yellow were determined by the Z-scan technique. The nonlinear refractive index n2 and the nonlinear absorption coefficient β of the azo dye doped polymer films were calculated respectively. The real part of the third-order susceptibility χ3 is much larger than its imaginary part indicating that the third-order optical response of the metanil yellow doped PVA films is dominated by the optical nonlinear refractive behavior.     

Two-photon laser photochemistry of a coumarin laser dye

Irradiation of 7-dimethylamino-4-methylcoumarin (1), a commercially available laser dye, in ethanol solution with the focused output of an XeCl excimer laser at 308 nm resulted in the formation of yellow oligomeric material derived from the ethanol solvent. The efficiency of formation of the yellow material was shown to be dependent on the intensity of the laser light, indicating that the photochemistry involved absorption of two photons. The oligomeric material is proposed to be a substance which interferes with stimulated emission in coumarin dye lasers. In addition, acetaldehyde and several gaseous products, principally hydrogen and butane, were formed. A product resulting from the coupling of 1 with the ethanol solvent was also isolated and characterized. Excimer laser irradiation of 1 in methanol yielded formaldehyde, hydrogen and solvent oligomers, while irradiation of 1 in benzene resulted in the formation of a black precipitate. The non-oligomeric products are similar to those observed from the direct irradiation of the solvent in the vacuum-UV region. A mechanism is proposed for the observed photochemistry in which 1 absorbs, sequentially, two photons from the laser pulse, resulting in the formation of a highly excited state which then transfers energy to the solvent.     

Multifunctional polymeric materials for biomedical applications

The work performed by our research group during the last few years in the area of bioerodible-biodegradable polymers as designed to the formulation of systems for the controlled delivery of drugs and as specific sorbents of uraemic toxins is broadly reviewed. In particular, attention has been focused on the strategies adopted in the preparation of functional polymers containing hydroxyl or carboxyl groups, suitable to establish specific bonding and non-bonding interactions with conventional and proteic drugs.     

Photo-responsive polymer materials for biological applications

In this review, we briefly summarized the remarkable progress of photo-responsive polymer materials from zero-dimensional micelles, twodimensional surfaces to three-dimensional hydrogels with irreversible or reversible moieties. Based on the photo-responsiveness, polymer have been designed, synthesized and applied for various biological fields including drug delivery and cell manipulation.     

Borazine materials for organic optoelectronic applications

Borazine materials have been demonstrated to be a new class of multifunctional and thermally stable materials with high electron (10(-3) cm2 V(-1) s(-1)) and moderate hole (10(-4) cm2 V(-1) s(-1)) mobilities for applications in electroluminescent devices.     

Polycarbonates as alternative electrolyte host materials for solid-state sodium batteries

This paper describes the first implementation of the aliphatic polycarbonate PTMC – that has previously been successfully applied to lithium polymer batteries – as a non-polyether host matrix in solid-state sodium batteries. Despite higher glass transition temperatures of PTMC–NaTFSI and PTMC–NaClO₄ electrolytes than their Li-containing counterparts, the ionic conductivities were found to be similar to the equivalent Li salt electrolytes. Finally, the functionality of PTMC–NaTFSI was demonstrated through cycling of Na/Prussian blue half-cells displaying high discharge capacities and limited polarization at C/10 and 60 °C.     

Spintronics: a challenge for materials science and solid-state chemistry

Spintronics is a multidisciplinary field involving physics, chemistry, and engineering, and is a new research area for solid-state scientists. A variety of new materials must be found to satisfy different demands. The search for ferromagnetic semiconductors and stable half-metallic ferromagnets with Curie temperatures higher than room temperature remains a priority for solid-state chemistry. A general understanding of structure-property relationships is a necessary prerequisite for the design of new materials. In this Review, the most important developments in the field of spintronics are described from the point of view of materials science.     

Incorporation of quadruply-bonded units into solid-state materials

The thirtieth anniversary of the quadruple bond marks a time in science when synthetic inorganic chemists are exploring molecular routes to new solid-state materials. Dinuclear transition metal complexes possessing , , and components to their M-M bonding present exciting opportunities for the design of macromolecular compounds with interesting optical, electronic, and magnetic properties. This brief review reports recent progress in the area of ordered molecular arrays incorporating quadruply bonded and other multiply bonded M₂ units.