Showing papers in "Materials horizons in 2015"
TL;DR: This review focuses on the fundamentals of flexible pressure sensors, and subsequently on several critical concepts for the exploration of functional materials and optimization of sensing devices toward practical applications.
Abstract: By virtue of their wide applications in personal electronic devices and industrial monitoring, pressure sensors are attractive candidates for promoting the advancement of science and technology in modern society. Flexible pressure sensors based on organic materials, which combine unique advantages of flexibility and low-cost, have emerged as a highly active field due to their promising applications in artificial intelligence systems and wearable health care devices. In this review, we focus on the fundamentals of flexible pressure sensors, and subsequently on several critical concepts for the exploration of functional materials and optimization of sensing devices toward practical applications. Perspectives on self-powered, transparent and implantable pressure sensing devices are also examined to highlight the development directions in this exciting research field.
940 citations
TL;DR: In this paper, the perovskite diode becomes polarised, providing a beneficial field, allowing accumulation of positive and negative space charge near the contacts, which enables more efficient charge extraction.
Abstract: High-efficiency perovskite solar cells typically employ an organic–inorganic metal halide perovskite material as light absorber and charge transporter, sandwiched between a p-type electron-blocking organic hole-transporting layer and an n-type hole-blocking electron collection titania compact layer. Some device configurations also include a thin mesoporous layer of TiO2 or Al2O3 which is infiltrated and capped with the perovskite absorber. Herein, we demonstrate that it is possible to fabricate planar and mesoporous perovskite solar cells devoid of an electron selective hole-blocking titania compact layer, which momentarily exhibit power conversion efficiencies (PCEs) of over 13%. This performance is however not sustained and is related to the previously observed anomalous hysteresis in perovskite solar cells. The “compact layer-free” meso-superstructured perovskite devices yield a stabilised PCE of only 2.7% while the compact layer-free planar heterojunction devices display no measurable steady state power output when devoid of an electron selective contact. In contrast, devices including the titania compact layer exhibit stabilised efficiency close to that derived from the current voltage measurements. We propose that under forward bias the perovskite diode becomes polarised, providing a beneficial field, allowing accumulation of positive and negative space charge near the contacts, which enables more efficient charge extraction. This provides the required built-in potential and selective charge extraction at each contact to temporarily enable efficient operation of the perovskite solar cells even in the absence of charge selective n- and p-type contact layers. The polarisation of the material is consistent with long range migration and accumulation of ionic species within the perovskite to the regions near the contacts. When the external field is reduced under working conditions, the ions can slowly diffuse away from the contacts redistributing throughout the film, reducing the field asymmetry and the effectiveness of the operation of the solar cells. We note that in light of recent publications showing high efficiency in devices devoid of charge selective contacts, this work reaffirms the absolute necessity to measure and report the stabilised power output under load when characterizing perovskite solar cells.
364 citations
TL;DR: In this article, the theoretical and practical aspects of CO2 conversion over semiconducting photocatalysts are discussed and an overview of the recently reported CO2-converting photocatalyst technologies is provided.
Abstract: Climate change and its impact on the Earth and Society has been recently reassessed by the International Panel on Climate Change. The panel estimates that the greenhouse gas emissions should be reduced by half by 2030 to mitigate climate change. Photocatalytic CO2 conversion is one of the promising technologies that can help with this modest goal. This review discusses the theoretical and practical aspects of CO2 conversion over semiconducting photocatalysts and overviews the recently reported CO2 conversion photocatalysts. A spectrum of photocatalysts reviewed in this work includes titania and its composites with metal oxides, metals, and advanced carbon allotropes; other solid photocatalysts, mostly based on germanium, gallium, tungsten, and niobium; graphitic carbon nitride; silver–silver halide plasmonic systems; photocatalytically active metal–organic frameworks; and graphene-based systems. Finally, a summary of the current state and an outlook for the future are provided.
357 citations
TL;DR: Inspired by the structures of the insect compound eyes, nanostructure arrays (NSAs) have been developed as effective antireflective surfaces, which exhibit promising broadband and quasi-omnidirectional properties together with multifunctions.
Abstract: Reducing the reflection and improving the transmission or absorption of light from wide angles of incidence in a broad wavelength range are crucial for enhancing the performance of the optical, optoelectronic, and electro-optical devices. Inspired by the structures of the insect compound eyes, nanostructure arrays (NSAs) have been developed as effective antireflective surfaces, which exhibit promising broadband and quasi-omnidirectional antireflective properties together with multifunctions. This review summarizes the recent advances in the fabrication and performance of antireflective surfaces based on NSAs of a wide variety of materials including silicon and non-silicon materials. The applications of the NSA-based antireflective surfaces in solar cells, light emitting diodes, detection, and imaging are highlighted. The remaining challenges along with future trends in NSA-based antireflective surfaces are also discussed.
312 citations
TL;DR: Nanoarchitectonic methods, and the materials that they produce, contrast strongly with those of conventional nanotechnology as mentioned in this paper, and illustrate the potential of nano-architectonics for future technologies.
Abstract: Nanoarchitectonics is introduced as a rising tide within current nanomaterials science. Physical phenomena operate quite differently at the nanoscale (compared to in the macroscopic and microscopic regimes) with behaviours of nanoscopic objects being strongly influenced by thermal/statistical fluctuations and mutual interactions between components. Nanoarchitectonic methods, and the materials that they produce, contrast strongly with those of conventional nanotechnology. In this review, to illustrate the potential of nanoarchitectonics for future technologies, examples of nanoarchitectonics are introduced which are categorized as (i) atomic or molecular manipulation as a route to leading nanotechnologies, (ii) materials creation in the realization of materials nanoarchitectonics, and (iii) advanced device materials.
231 citations
TL;DR: In this paper, the band offsets of methylammonium lead halides are reported, including relativistic corrections and using the Pb 1s core level as a reference state.
Abstract: Organic–inorganic halide perovskites efficiently convert sunlight to electricity in solar cells. The choice of halide (Cl, Br or I) can be used to chemically tune the spectral response of the materials and the positions of the valence and conduction bands (i.e. the ionisation potential and electron affinity). Here the band offsets of the methylammonium lead halides are reported, including relativistic corrections and using the Pb 1s core level as a reference state. The binding energy of the valence band decreases monotonically down the series, primarily due to the change from 3p to 4p to 5p valence orbitals of the halide. Type I band alignments are predicted, which implies that Br and Cl secondary phases in CH3NH3PbI3 thin-films would act as barriers to charge transport in photovoltaic devices.
230 citations
TL;DR: The goal of this review is to summarize the state-of-art research on universal polymer coatings and their biomedical applications, as well as to present their common features including some general rules for their further development.
Abstract: Universal polymer coatings have excellent potential for biomedical applications, because of their substrate-independent properties and versatile surface functionalization methods. The goal of this review is to summarize the state-of-art research on universal polymer coatings and their biomedical applications, as well as to present their common features including some general rules for their further development.
195 citations
TL;DR: In this article, the authors review the recent developments in three-component OSCs using various third components, such as light absorbing small molecules or polymers, fullerene or non-fullerene acceptors, metal- or carbon-based nanomaterials, quantum dots, and polymer or small molecule nonvolatile additives.
Abstract: Organic solar cells (OSCs) with a third component, consisting of a donor material, an acceptor material and a third component (organic or inorganic, semiconductor or insulator), received increasing attention in the last five years and the power conversion efficiencies approached 10%. Compared with the traditional binary (two-component) blend, three-component OSCs presented some advantages: broader and stronger absorption, more efficient charge transfer, more efficient charge transport pathways, better charge extraction at the electrodes and improved stability. Various types of third components, such as light-absorbing small molecules or polymers, fullerene or non-fullerene acceptors, metal- or carbon-based nanomaterials, quantum dots, and polymer or small molecule nonvolatile additives were used in OSCs. In this contribution, we review the recent developments in three-component OSCs using various third components. In particular, the absorption complementation, phase separation and the nanostructure in three-component OSCs are addressed.
166 citations
TL;DR: In this article, the authors divide low molecular weight gelators (LMWGs) with polymers into five categories: (i) polymerization of self-assembled LMWG fibres, (ii) capture of LMWGs fibres in a polymer matrix, (iii) addition of non-gelling polymer solutions to LMWg, (iv) systems with directed interactions between polymers and LMWgs, and (v) hybrid gels containing both LMWglers and polymer gels (PGs).
Abstract: Combining low molecular weight gelators (LMWGs) with polymers is a broad yet relatively recent field, in a phase of rapid expansion and with huge potential for exploitation. This review provides an overview of the state-of-the-art and reflects on new technologies that might be unlocked. We divide LMWG–polymer systems into five categories: (i) polymerisation of self-assembled LMWG fibres, (ii) capture of LMWG fibres in a polymer matrix, (iii) addition of non-gelling polymer solutions to LMWGs, (iv) systems with directed interactions between polymers and LMWGs, and (v) hybrid gels containing both LMWGs and polymer gels (PGs). Polymers can have significant impacts on the nanoscale morphology and materials performance of LMWGs, and conversely LMWGs can have a major effect on the rheological properties of polymers. By combining different types of gelation system, it is possible to harness the advantages of both LMWGs and PGs, whilst avoiding their drawbacks. Combining LMWG and polymer technologies enhances materials performance which is useful in traditional applications, but it may also yield major steps forward in high-tech areas including environmental remediation, drug delivery, microfluidics and tissue engineering.
166 citations
TL;DR: In this article, the authors reported the formation of vividly colorful hybrid organometal trihalide perovskite solar cells by a low-cost and scalable doctor-blade coating method.
Abstract: The colors of solar cells are very important when adopting them for future indoor and outdoor light energy harvesting devices with smart designs. Here we report the formation of vividly colorful hybrid organometal trihalide perovskite solar cells by a low-cost and scalable doctor-blade coating method. The perovskite films have a combination of a hundred micrometer size large domain structure and a concentric ring photonics structure in each domain which generates the vivid color. The convection during precursor solution drying in the doctor-blade coating process has been found to be responsible for the formation of the large domains and the coffee-ring like perovskite photonic structures after solvent drying, whose periodicity can be well tuned by the substrate temperature and the precursor solution concentration. Both the perovskite films and the finished devices are very colorful, and the efficiency of the vividly colorful solar cells is close to the optimized doctor-blade coated perovskite solar cell.
162 citations
TL;DR: A review of recent approaches to the preparation of carbon materials using ionic liquids (ILs) as versatile precursors can be found in this article, where the key structures and properties of ILs that enable successful carbonization are discussed.
Abstract: Carbon materials have been extensively used in diverse areas, especially in energy-related applications. Traditionally, these materials have been synthesized by carbonization of low-vapor-pressure natural or synthetic polymers. However, the polymer-related procedures are multistep and time consuming because of the limited solubility and complicated synthesis of polymers. Recently, ionic liquids (ILs), composed of entirely cations and anions, have emerged as a new family of carbon precursors. The carbon-rich nature of ILs, coupled with their attractive properties such as diverse cation–anion combinations, low volatilities, and high thermal stabilities, not only greatly simplifies the entire carbonization process, but also gives rise to carbons with attractive features, which are distinct from those of carbons obtained using conventional polymer precursors, such as very high nitrogen contents and conductivities. In this review, we highlight recent approaches to the preparation of carbon materials using ILs as versatile precursors. We begin with a brief introduction to these novel precursors, discussing the key structures and properties of ILs that enable successful carbonization, and then address synthetic techniques for the fabrication of advanced porous carbons from ILs by either self- or external-template methods, followed by a review of the potential applications of ionic-liquid-derived carbons such as electrocatalysis, Li-ion batteries, supercapacitors, CO2 capture and chemical catalysis. The review concludes with an overview of possible directions for future research in this field.
TL;DR: In this article, an asymmetric supercapacitors based on the GF + VO2/HMB cathode and neutral electrolyte are assembled and show enhanced performance with weaker polarization, higher specific capacitance and better cycling life than the unmodified GF +VO2 electrode.
Abstract: Hydrogen molybdenum bronze (HMB) is electrochemically deposited as a homogeneous shell on VO2 nanoflakes grown on graphene foam (GF), forming a GF + VO2/HMB integrated electrode structure. Asymmetric supercapacitors based on the GF + VO2/HMB cathode and neutral electrolyte are assembled and show enhanced performance with weaker polarization, higher specific capacitance and better cycling life than the unmodified GF + VO2 electrode. Capacitances of 485 F g−1 (2 A g−1) and 306 F g−1 (32 A g−1) are obtained because of the exceptional 3D porous architecture and conductive network. In addition, the GF + VO2/HMB electrodes are also characterized as the cathode of lithium ion batteries. Very stable capacities at rates up to 30 C are demonstrated for 500 cycles. This new type of shell material is expected to have its generic function in other metal oxide based nanostructures.
TL;DR: In this paper, a monolithic integration of perovskite and polymer subcells into a tandem structure is realized through a full solution process, where a small molecule additive, BmPyPhB, is added into the precursor solution to improve the uniformity of the initial nucleation process of the crystal by providing heterogeneous nucleation sites throughout the solution space.
Abstract: In the current study, a monolithic integration of perovskite and polymer subcells into a tandem structure is realized through a full solution process. The wide bandgap perovskite absorber (CH3NH3PbI3) is processed via a one-step deposition employing an additive-assisted solvent wash method. In particular, a small molecule additive, BmPyPhB, is added into the precursor solution to improve the uniformity of the initial nucleation process of the crystal by providing heterogeneous nucleation sites throughout the solution space. Next, a solvent wash method is employed to induce the fast crystallization of uniform and well-defined grains in the absorber layer as well as to reduce the requirement for thermal annealing. Thus, the highest power conversion efficiency (PCE) of 9.1% is obtained for a single junction, planar-structured CH3NH3PbI3 solar cell. For the polymer absorber, a new IR-sensitive block copolymer, PBSeDTEG8, with photosensitivity up to 950 nm is utilized to broaden the photoresponse of the tandem solar cell. More importantly, this polymer:PCBM blend exhibits improved thermal stability, which can endure thermal annealing process while fabricating the perovskite subcell. Subsequently, this hybrid tandem solar cell based on perovskite/polymer subcells achieves the highest efficiency of 10.2%.
TL;DR: In this paper, a superaerophobic surface was proposed to decrease the negative effect caused by the adhered gas bubbles. But, it was only applied to the target reactions of hydrogen evolution and oxygen evolution.
Abstract: Electrochemical gas evolution reactions are now of great importance in energy conversion processes and industries. Key to the improvement of catalytic performance lies the development of efficient catalytic electrodes. Besides the exploration of highly active catalysts, the fast removal of the gas products on the electrode surface should be realized because the adhered gas bubbles would block the following catalytic reactions and decrease the efficiency. In this paper, we introduce an ideal structure, a “superaerophobic” surface, to diminish the negative effects caused by the adhered gas bubbles. Several recent works focusing on addressing this issue are presented with the target reactions of hydrogen evolution and oxygen evolution. It is demonstrated that micro/nano-engineering of the catalyst directly on the current collector is a promising approach to minimize the negative effective induced by the gas bubble adhesion. In the last section, we also discuss the promise of this methodology for other energy related systems.
TL;DR: In this paper, the effects of nitrogen metal oxides on the physical and chemical properties of oxides have been investigated in specific fields such as photocatalysis in water splitting and other processes as the observed small band gaps lead to activity in the visible light range.
Abstract: Oxynitrides of transition metals, alkaline earth metals and rare earth metals are intensively investigated as a group of materials to expand and tune the properties of oxides. The differences in polarizability, electronegativity and anion charge of nitrogen and oxygen induce changes in the physical and chemical properties of oxides by nitrogen introduction. The effects on properties arise from the higher covalency of the metal–nitrogen bond and the changes in the energies of electronic levels, and are important in slightly doped nitrogen metal oxides as in stoichiometric oxynitrides. More intense recent progress in oxynitride research has been made in some specific fields such as photocatalysis in water splitting and other processes as the observed small band gaps lead to activity in the visible light range. The stabilization of new perovskite oxynitrides, with the oxidation states of cations tuned by N/O stoichiometry, has led to new magnetic and dielectric materials. The lower electronegativity of nitrogen and larger crystal field splitting induced by N3− shifts the emission wavelengths of phosphors to the red, and oxynitridosilicates have been investigated as components of white LEDs.
TL;DR: In this paper, a promising hole transporting material (HTM) using the 4,4′-spirobi[cyclopenta[2,1-b:3,4-b′]dithiophene derivative (spiro-CPDT) as the core and triarylamines as terminal units was presented.
Abstract: We present the design and synthesis of a promising hole transporting material (HTM) using the 4,4′-spirobi[cyclopenta[2,1-b:3,4-b′]dithiophene] derivative (spiro-CPDT) as the core and triarylamines as terminal units. The implementation of the new HTM in CH3NH3PbI3-based perovskite solar cells exhibited an excellent overall power conversion efficiency (PCE) of 13.4% without the use of any dopants and additives which is comparable to 15.0% obtained using p-doped spiro-MeOTAD-based devices. Furthermore, the device based on the new HTM generated a slightly higher open circuit voltage (VOC) of 971 mV compared to a spiro-MeOTAD (VOC = 951 mV) based device. The present results demonstrate that spiro-CPDT could be an excellent building block to prepare dopant-free HTMs for perovskite solar cells and holds promise to replace the p-doped spiro-OMeTAD, which is important for the fabrication of cost-effective devices in the future.
TL;DR: In this article, a family of highly active and durable perovskite oxides is proposed to lower the oxygen evolution reaction (OER) barriers in water splitting and further improvement of their activity and durability is an important objective.
Abstract: Development of highly active and cost-effective electrocatalysts is central to the large-scale electrolysis of water for renewable energy generation. Perovskite oxides are a group of promising candidates to lower the oxygen evolution reaction (OER) barriers in water splitting and further improvement of their activity and durability is an important objective. Here we report scandium and niobium cation (Sc3+ and Nb5+) doped strontium cobaltite perovskites (SrScxNbyCo1−x−yO3−δ) as a family of highly active and durable electrocatalysts for the OER in alkaline solution. These perovskites not only manifest up to a factor of 50 increase of the intrinsic activity compared to the gold-standard OER electrocatalysts (such as IrO2 and RuO2) and a factor of 5.8 enhancement to the perovskite-Ba0.5Sr0.5Co0.8Fe0.2O3−δ at an overpotential of 0.35 V, but also, more importantly, show excellent durability in alkaline solutions under operation.
TL;DR: In this paper, the authors outline the subsistent concerns on these adolescent anodes and systematically summarize the representative problem-solving designs, which are classified into two major categories totally including seven types, namely low-dimensional, inter-spatial, and composite design on materials; and ordered-array, cross-aligned, alternating-layer, and 3D porous design on electrodes.
Abstract: High performance anodes are of great significance to high energy-power lithium ion batteries (LIBs); however, challenges are still pervasive in advancing new materials beyond commercial graphite. In this review, we outline the subsistent concerns on these adolescent anodes and systematically summarize the representative problem-solving designs, which are classified into two major categories totally including seven types, namely low-dimensional, inter-spatial, and composite design on materials; and ordered-array, cross-aligned, alternating-layer, and 3D porous design on electrodes. After generalizing advantageous features, we further highlight the burgeoning design horizon from materials to electrodes as well as their competences and perspectives to push the energy storage of LIBs to the next-generation level. These designing rationales represent general models of advanced LIB anodes and can illuminate the material and electrode innovations in other energy storage realms.
TL;DR: The acceptor strength of the widely used acceptor benzothiadiazole (BT) by extending the heterocyclic core is a promising strategy for developing new and stronger acceptors for materials in organic electronics and photonics as discussed by the authors.
Abstract: Increasing the acceptor strength of the widely used acceptor benzothiadiazole (BT) by extending the heterocyclic core is a promising strategy for developing new and stronger acceptors for materials in organic electronics and photonics. In recent years, such heteroannulated BT acceptors have been incorporated into a wide variety of materials that have been used in organic electronic and photonic devices. This review critically assesses the properties of these materials. Although heteroannulation to form acceptors, such as benzo[1,2-c:4,5-c′]bis[1,2,5]thiadiazole (BBT), does result in materials with significantly higher electron affinity (EA) relative to BT, in many cases the extended BT systems also exhibit lower ionization energy (IE) than BT. Both the significantly higher EA and lower IE limit the efficacy of these materials in applications such as bulk heterojunction organic photovoltaics (BHJ-OPV) based on C60. Although the relatively high EA may enable some applications such as air stable organic field effect transistors (OFET), more widespread use of heteroannulated BT acceptors will likely require the ability to moderate or retain the high EA while increasing IE.
TL;DR: In this paper, the authors summarize the recent developments in perovskite solar cells (from April 2009 to December 2014), describe the unique properties of organometal halide perovsites leading to their rapid emergence, and discuss challenges such as stability and environmental issues to be faced in the future.
Abstract: Over the past several years, organic–inorganic hybrid perovskites have gained considerable research attention due to their direct band gap, large absorption coefficient, ambipolar diffusion and long carrier diffusion length, and have revolutionized the prospects of emerging photovoltaic technologies, with the highest power conversion efficiency of over 19% achieved under laboratory conditions. In this perspective, we summarize the recent developments in perovskite solar cells (from April 2009 to December 2014), describe the unique properties of organometal halide perovskites leading to their rapid emergence, and discuss challenges such as stability and environmental issues to be faced in the future.
TL;DR: In this article, a 10 cm long yarn supercapacitor with the optimum composition of 2.2 mg cm−1 activated carbon and 1 mg cm −1 carbon fiber yarns was demonstrated, yielding a high total capacitance of up to 1164 mF.
Abstract: Smart textiles are intelligent devices that can sense and respond to environmental stimuli. They require integrated energy storage to power their functions. An emerging approach is to build integratable fiber-/yarn-based energy storage devices. Here, we demonstrate all-carbon solid-state yarn supercapacitors using commercially available activated carbon and carbon fiber yarns for smart textiles. Conductive carbon fibers concurrently act as current collectors in yarn supercapacitors and as substrates for depositing large surface area activated carbon particles. Two hybrid carbon yarn electrodes were twisted together in polyvinyl alcohol/H3PO4 polymer gel, which is used as both an electrolyte and a separator. A 10 cm long yarn supercapacitor, with the optimum composition of 2.2 mg cm−1 activated carbon and 1 mg cm−1 carbon fiber, shows a specific length capacitance of 45.2 mF cm−1 at 2 mV s−1, an energy density of 6.5 μW h cm−1, and a power density of 27.5 μW cm−1. Since the yarn supercapacitor has low equivalent series resistance at 4.9 Ω cm−1, longer yarn supercapacitors up to 50 cm in length were demonstrated, yielding a high total capacitance of up to 1164 mF. The all-carbon solid-state yarn supercapacitors also exhibit excellent mechanical flexibility with minor capacitance decreases upon bending or being crumpled. Utilizing three long yarn supercapacitors, a wearable wristband was knitted; this wristband is capable of lighting up an LED indicator, demonstrating strong potential for smart textile applications.
TL;DR: In this article, a mechanism is proposed based on established fabric tearing theory, which will enable the development of mechanically robust composites based on fabrics, which can be used for developing soft biological prosthetics, and more generally for commercial applications such as tear resistant gloves and bulletproof vests.
Abstract: Ligaments are unique wet biological tissues with high tensile modulus and fracture stress, combined with high bending flexibility. Developing synthetic materials with these properties is a significant challenge. Hydrogel composites made from high stiffness fabrics is a strategy to develop such unique materials; however, the ability to produce these materials has proven difficult, since common hydrogels swell in water and interact poorly with solid components, limiting the transfer of force from the fabric to the hydrogel matrix. In this work, for the first time, we successfully produce extraordinarily tough hydrogel composites by strategically selecting a recently developed tough hydrogel that de-swells in water. The new composites, consisting of polyampholyte hydrogels and glass fiber woven fabrics, exhibit extremely high effective toughness (250 000 J m−2), high tear strength (∼65 N mm−1), high tensile modulus (606 MPa), and low bending modulus (4.7 MPa). Even though these composites are composed of water-containing, biocompatible materials, their mechanical properties are comparable to high toughness Kevlar/polyurethane blends and fiber-reinforced polymers. Importantly, the mechanical properties of these composites greatly outperform the properties of either individual component. A mechanism is proposed based on established fabric tearing theory, which will enable the development of a new generation of mechanically robust composites based on fabrics. These results will be important towards developing soft biological prosthetics, and more generally for commercial applications such as tear-resistant gloves and bulletproof vests.
TL;DR: In this article, the authors show that the large mobility difference between electrons and holes in XNiSn results in a significant correction to the Goldsmid-Sharp formula, which explains the difference in the thermopower band gap between n-type and p-type half-Heusler (HH) compounds.
Abstract: N-type XNiSn (X = Ti, Zr, Hf) half-Heusler (HH) compounds possess excellent thermoelectric properties, which are believed to be attributed to their relatively high mobility. However, p-type XNiSn HH compounds have poor figures of merit, zT, compared to XCoSb compounds. This can be traced to the suppression of the magnitude of the thermopower at high temperatures. Eg = 2eSmaxTmax relates the band gap to the thermopower peak. However, from this formula, one would conclude that the band gap of p-type XNiSn solid solutions is only one-third that of n-type XNiSn, which effectively prevents p-type XNiSn HHs from being useful thermoelectric materials. The study of p-type HH Zr1−xScxNiSn solid solutions show that the large mobility difference between electrons and holes in XNiSn results in a significant correction to the Goldsmid–Sharp formula. This finding explains the difference in the thermopower band gap between n-type and p-type HH. The high electron-to-hole weighted mobility ratio leads to an effective suppression of the bipolar effect in the thermoelectric transport properties which is essential for high zT values in n-type XNiSn (X = Ti, Zr, Hf) HH compounds.
TL;DR: In this article, a highly stable MOF luminescent switch {Cd3(L)(bipy)2·4DMA}n (1) has been successfully constructed, which exhibits clear fluorescence enhancement and quenching responses for benzene and nitrobenzene vapors, respectively, with high selectivity and sensitivity, as well as being fully reusable.
Abstract: In this work, a highly stable MOF luminescent switch {Cd3(L)(bipy)2·4DMA}n (1) has been successfully constructed, which exhibits clear fluorescence enhancement and “turn-off” quenching responses for benzene and nitrobenzene vapors, respectively, with high selectivity and sensitivity, as well as being fully reusable. Remarkably, the porous MOF (1) remains intact in aqueous solution over an extensive pH range of 2–13. This MOF sensor realizes fast detection for benzene vapor with a response time of less than one minute and ∼8-fold fluorescence enhancement. Furthermore, it as a porous multifunctional MOF also shows fully reversible adsorption behaviour for benzene vapor at room temperature. Thus the MOF material will be a promising luminescent sensor and adsorbent material for benzene vapor with important practical applications from environmental and health points of view.
TL;DR: In this article, a liquid organic phase consisting of a mixture of N,N-dimethylformamide and dimethyl sulfoxide was used for optical upconversion by triplet-triplet annihilation.
Abstract: We herein report new organogels that permit efficient optical upconversion (UC) by triplet–triplet annihilation. The materials studied consist of a liquid organic phase, composed of a mixture of N,N-dimethylformamide and dimethyl sulfoxide in which the UC chromophore pair Pd(II) mesoporphyrin IX and 9,10-diphenylanthracene was dissolved, and a three-dimensional polymer network formed by covalently cross-linking poly(vinyl alcohol) with hexamethylene diisocyanate. The new gels are highly transparent, shape-persistent, and display efficient green-to-blue upconversion with UC quantum yields of >0.6 and 14% under ambient and oxygen-free conditions, respectively. The design approach presented here permits the fabrication of a hitherto unexplored class of materials with a unique combination of properties. The framework can easily be extended to other materials based on other solvents, polymer networks, and/or chromophore pairs.
TL;DR: In this paper, a structural regularity and integrity of a melanin-based bioelectronic interface is reported, as the result of an ad hoc fabrication protocol involving ammonia-induced solid state polymerization (AISSP) technology of a 5,6-dihydroxyindole thin film.
Abstract: Relying on the water-dependent hybrid conductor properties of eumelanin biopolymers, a structurally controlled melanin thin film that can be reversibly switched-on and off by hydration–dehydration cycles and used as a biocompatible platform for stem cell growth and differentiation up to 11 days is reported. A key feature of the new eumelanin-based bioelectronic interface is its remarkable structural regularity and integrity, as the result of an ad hoc fabrication protocol involving ammonia-induced solid state polymerization (AISSP) technology of a 5,6-dihydroxyindole thin film. The AISSP technology is operationally simple and versatile, enabling the preparation of device-quality thin films (AFM and MALDI-MS evidence) on various substrates with efficient chemical control over molecular complexity. Overall the results of this study pave the way for the implementation of tailored eumelanin thin films for bioelectronic devices, e.g., in organic electrochemical transistors (OECTs).
TL;DR: In this paper, bilayer poly(divinyl benzene) p(DVB)/poly(perfluorodecylacrylate) (p-PFDA) is synthesized via iCVD on steel and silicon substrates.
Abstract: Thin films of bilayer poly(divinyl benzene) p(DVB)/poly(perfluorodecylacrylate) (p-PFDA) are synthesized via iCVD on steel and silicon substrates. Nanomechanical measurements reveal that the elastic modulus and hardness of the films are enhanced through the bilayer structure and that the adhesion of the films to the substrate is improved via in situ grafting mechanism. The strength of ice adhesion to the treated surfaces is reduced more than six-fold when the substrates are coated with these bilayer polymer networks.
TL;DR: In this paper, a single-phase Aurivillius compound, SrBi5Fe0.5Co 0.5Ti4O18 has been discovered that exhibits a plausible intrinsic magnetoelectric coupling at high temperature.
Abstract: A single-phase material where ferroelectricity and ferromagnetism coexist at room temperature (RT) is hardly available at present, and it is even more rare for such a material to further have an intrinsic and low magnetic field response magnetoelectric (ME) coupling at temperatures higher than RT. In this communication, a new single-phase Aurivillius compound, SrBi5Fe0.5Co0.5Ti4O18 has been discovered that exhibits a plausible intrinsic ME coupling. Remarkably, this property appears at a high temperature of 100 °C, surpassing all single-phase multiferroic materials currently under investigation. With a magnetocapacitance effect detectable at 100 °C and under a low response magnetic field, a RT functioning device was demonstrated to convert an external magnetic field variation directly into an electric voltage output. The availability of such a single-phase material with an intrinsic and low magnetic field response that is multiferroic at high temperature is important to the fundamental understanding of physics and to potential applications in sensing, memory devices, quantum control, etc.
TL;DR: In this article, the authors focus on PAF-1 and its derivatives in order to analyse the correlations between the nature of the material (e.g. pore size, surface area, pore volume, functional groups, metal sites, interpenetrated frameworks) and their properties such as gas sorption capacity, molecular recognition and separation.
Abstract: In materials design and preparative chemistry, it is imperative to understand the thought and logic behind synthesizing a particular kind of material. Computational modelling can help in this regard by not only optimizing the materials but also by simulating their properties. Furthermore, the experimental results fill the gap addressing complicated practical conditions that can't be covered using theoretical calculations. In this work, we focus on PAF-1 and its derivatives in order to analyse the correlations between the nature of the material (e.g. pore size, surface area, pore volume, functional groups, metal sites, interpenetrated frameworks) and their properties such as gas sorption capacity, molecular recognition and separation.
TL;DR: This study represents the first example of light-up AIE nanoparticle probe design and can switch to positive surface charge and thus significantly light up cancer cells, allowing for targeted imaging and selective suppression of cancer cells.
Abstract: A pH-responsive light-up nanoparticle probe with aggregation-induced emission (AIE) features was designed and synthesized. The probe carries negative charges and shows very weak fluorescence under physiological conditions. In a tumor acidic extracellular microenvironment, the nanoparticle probe can switch to positive surface charge and thus significantly light up cancer cells, allowing for targeted imaging and selective suppression of cancer cells. As AIE nanoparticles are known for high fluorescence in the aggregate state, this study represents the first example of light-up AIE nanoparticle probe design.