| 1. |
- Alberoni, Chiara, et al.
(författare)
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Ceria doping boosts methylene blue photodegradation in titania nanostructures
- 2021
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Ingår i: Materials Chemistry Frontiers. - : Royal Society of Chemistry. - 2052-1537. ; 5:11, s. 4138-4152
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Tidskriftsartikel (refereegranskat)abstract
- Ceria-doped titania photocatalysts (ceria loading 0.25–5.0 wt%) were synthesized by hydrothermal methods for water remediation. Nanotubes (CeTNTx) and nanoparticles (CeTNPx) were obtained. Ceria doping was applied to tune the electronic properties of nanostructured titania, boosting its photocatalytic activity. CeTNT nanostructures contained anatase as the only titania phase, whereas the CeTNP series consisted of both anatase and rutile polymorphs. The Ce addition induced a decrease in the energy gap, allowing enhancement of visible light harvesting. The photodegradation of methylene blue, MB, in aqueous solution was chosen to study the influence of the morphology and the ceria loading on the photocatalytic response, under UV and solar light. Both CeO2–TiO2 nanoparticles and nanotubes were found to be very active under UV light. The highest MB degradation rates were obtained for the 0.25 wt% CeO2 doping, for both nanotubes and nanoparticles (0.123 and 0.146 min−1, respectively), able to photodegrade completely the dye after 120 min. The two samples are stable after a 3-cycle reusability test. The photo-response under simulated solar light confirmed that doping titania with ceria allows harvesting visible light absorption, enhancing its photoactivity. A maximum efficiency of 85% under simulated sunlight at a degradation rate of 0.054 min−1 was obtained. Transient photoluminescence confirmed that MB acts as a charge scavenger for the composite system. These results pointed out ceria-doped titania nanostructures as a promising class of photocatalysts for the degradation of dyes and other hazardous organic compounds in wastewater.
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| 2. |
- Alkarsifi, Riva, et al.
(författare)
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Organic-inorganic doped nickel oxide nanocrystals for hole transport layers in inverted polymer solar cells with color tuning
- 2021
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Ingår i: Materials Chemistry Frontiers. - : ROYAL SOC CHEMISTRY. - 2052-1537. ; 5:1, s. 418-429
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Tidskriftsartikel (refereegranskat)abstract
- Polymer solar cells using non-fullerene acceptors are nowadays amongst the most promising approaches for next generation photovoltaic applications. However, there are still remaining challenges related to large-scale fully solution-processing of high efficiency solar cells as high efficiencies are obtained only for very small areas using hole transport layers based on evaporated molybdenum oxide. Solution-processable hole transport materials compatible with non-fullerene acceptor materials are still scarce and thus considered as one of the major challenges nowadays. In this work, we present copper-doped nickel oxide nanocrystals that form highly stable inks in alcohol-based solutions. This allows processing of efficient hole transport layers in both regular and inverted device structures of polymer solar cells. As the initial work function of these ionic doped materials is too low for efficient hole extraction, doping the nanocrystals with an organic electron acceptor, namely 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquino dimethane (F4-TCNQ), was additionally applied to make the work function more suitable for hole extraction. The resulting hybrid hole transport layers were first studied in polymer solar cells based on fullerene acceptors using regular device structures yielding 7.4% efficiency identical to that of reference cells based on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). For inverted device structures, the hybrid hole transport layers were processed on top of blends based on the non-fullerene acceptor IT-4F and PBDB-T-2F donor. The corresponding solar cells showed promising efficiencies up to 7.9% while the reference devices using PEDOT:PSS showed inferior performances. We further show that the hybrid hole transport layer can be used to tune the color of the polymer solar cells using optical spacer effects.
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| 3. |
- Casillas Trujillo, Luis, et al.
(författare)
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Experimental and theoretical evidence of charge transfer in multi-component alloys : how chemical interactions reduce atomic size mismatch
- 2021
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Ingår i: Materials Chemistry Frontiers. - : Royal Society of Chemistry. - 2052-1537. ; 5:15, s. 5746-5759
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Tidskriftsartikel (refereegranskat)abstract
- Ab initio simulations of a multi-component alloy using density functional theory (DFT) were combined with experiments on thin films of the same material using X-ray photoelectron spectroscopy (XPS) to study the connection between the electronic and atomic structures of multi-component alloys. The DFT simulations were performed on an equimolar HfNbTiVZr multi-component alloy. Structure and charge transfer were evaluated using relaxed, non-relaxed, as well as elemental reference structures. The use of a fixed sphere size model allowed quantification of charge transfer, and separation into different contributions. The charge transfer was generally found to follow electronegativity trends and results in a reduced size mismatch between the elements, and thus causes a considerable reduction of the lattice distortions compared to a traditional assumption based on tabulated atomic radii. A calculation of the average deviation from the average radius (i.e. the so-called δ-parameter) based on the atomic Voronoi volumes gave a reduction of δ from ca. 6% (using the volumes in elemental reference phases) to ca. 2% (using the volumes in the relaxed multi-component alloy phase). The reliability of the theoretical results was confirmed by XPS measurements of a Hf22Nb19Ti18V19Zr21 thin film deposited by sputter deposition. The experimentally observed core level binding energy shifts (CLS), as well as peak broadening due to a range of chemical surroundings, for each element showed good agreement with the calculated DFT values. The single solid solution phase of the sample was confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM) including energy dispersive spectroscopy (EDS) with nm-resolution. These observations show that the HfNbTiVZr solid solution phase is non-ideal, and that chemical bonding plays an important part in the structure formation, and presumably also in the properties. Our conclusions should be transferable to other multi-component alloy systems, as well as some other multi-component material systems, and open up interesting possibilities for the design of material properties via the electronic structure and controlled charge transfer between selected metallic elements in the materials.
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| 4. |
- Gond, Ritambhara, et al.
(författare)
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Phosphate-based polyanionic insertion materials for oxygen electrocatalysis
- 2024
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Ingår i: Materials Chemistry Frontiers. - : Royal Society of Chemistry. - 2052-1537. ; 8:5, s. 1153-1170
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Forskningsöversikt (refereegranskat)abstract
- Electrocatalyst-based energy storage technologies such as alkali metal–air batteries, fuel cells, and water splitting devices are the new holy grail in the next-generation energy storage landscape as they deliver higher energy densities than Li-ion/Na-ion batteries (LIBs/SIBs). The new chemistries of energy storage such as metal–air batteries under aqueous or non-aqueous conditions will complement existing LIBs/SIBs owing to the increasing requirement for batteries with high energy density in the present era. Phosphate-based polyanionic frameworks have long been known for their ability to (de)intercalate alkali metal ions. Because of their innate oxygen electrocatalytic activity, these insertion cathode materials have lately emerged as air electrodes in metal–air battery systems. In this review, the present status of phosphate-based polyanionic insertion materials for oxygen reduction and oxygen evolution reaction (ORR and OER) electrocatalysis is summarized. Factors influencing electrocatalytic activity in these materials, such as the presence of different types of alkali metal cations, transition metals, and the type of ligand/mixed anion as well as coordination around the transition metals are discussed. Finally, the development of metal–air batteries derived from phosphate-based polyanionic insertion materials as air electrodes is discussed.
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| 5. |
- Gong, Xiao, et al.
(författare)
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Eu-doped ZnO quantum dots with solid-state fluorescence and dual emission for high-performance luminescent solar concentrators
- 2021
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Ingår i: Materials Chemistry Frontiers. - : Royal Society of Chemistry. - 2052-1537. ; 5:12, s. 4746-4755
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Tidskriftsartikel (refereegranskat)abstract
- Heavy-metal-free quantum dots (QDs) are promising luminophores for luminescent solar concentrators (LSCs) because of environmental friendliness, which is essential for industrial applications. In order to keep high optical quality and inhibit aggregation-induced quenching, usually QDs can only be loaded at low concentration in a polymer optical waveguide material for LSCs, which significantly impairs the power conversion efficiency (PCE). Thus, it is a challenge to fabricate high-performance LSCs with high QD loading. Here, dual emission Eu-doped ZnO QDs with strong solid-state fluorescence are synthesized via a simple sol–gel method, which enables two characteristic photoluminescence peaks at 551 nm and 614 nm. Furthermore, Eu-doped ZnO QDs with dual fluorescence emission are for the first time reported to be applied in LSCs. The performance of LSCs can be influenced by the loading concentration of Eu-doped ZnO QDs in polyvinyl pyrrolidone (PVP) films. The obtained external optical efficiency (ηopt) of the LSCs based on Eu-doped ZnO QDs can be relatively high (4.37%) compared to the reported LSCs with a similar area when the loading concentration of Eu-doped ZnO QDs is up to 13.2% because of both their high photoluminescence intensity and dual fluorescence emission. Our results demonstrate that dual emission Eu-doped ZnO QDs with strong solid-state fluorescence are promising candidates as luminophores for LSCs.
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| 6. |
- Gordeyeva, Korneliya, 1989-, et al.
(författare)
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Lightweight foams of amine-rich organosilica and cellulose nanofibrils by foaming and controlled condensation of aminosilane
- 2018
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Ingår i: Materials Chemistry Frontiers. - : Royal Society of Chemistry (RSC). - 2052-1537. ; 2:12, s. 2220-2229
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Tidskriftsartikel (refereegranskat)abstract
- Organosilica foams are commonly formed by a multistep process involving hydrolysis and condensationof organosilanes followed by solvent exchange and e.g. supercritical CO2 drying. Here, we propose astraightforward route to synthesize lightweight hybrid foams from aqueous dispersions of a surfaceactiveaminosilane (AS) and TEMPO-oxidized cellulose nanofibrils (TCNFs). Air bubbles were introducedin the TCNF/AS dispersion by mechanical blending, and the foam was solidified by oven-drying.Evaporative drying at mild temperature (60 1C) resulted in dry foams with low densities (25–50 kg m3),high porosities (96–99%) and macropores of 150–300 mm in diameter. The foaming and foam stabilizationwere successful for a pH range of 10.4–10.8 for foams containing 55–65 wt% of organosilica inthe dry state. The protonation of AS increased the ionic strength of the dispersion and enhanced theinterparticle interactions with TCNFs and, in turn, the foam viscosity and foam stability upon drying. Theevaporation of water catalyzed the condensation of the AS to form low-molecular linear polymers,which resulted in an increased stiffness and strength of the foam lamella. The crosslinking of the ASpolymeric network with the TCNF matrix allowed lightweight and homogeneous macroporous foams tobe obtained with controlled densities and high amine content (amine content 44.5 mmol g1) using anenvironmentally friendly technique.
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| 7. |
- Li, Suyang, et al.
(författare)
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Highly homogeneous bimetallic core-shell Au@Ag nanoparticles with embedded internal standard fabrication using a microreactor for reliable quantitative SERS detection
- 2023
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Ingår i: Materials Chemistry Frontiers. - : Royal Society of Chemistry (RSC). - 2052-1537. ; 7:6, s. 1100-1109
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Tidskriftsartikel (refereegranskat)abstract
- Bimetallic gold core-silver shell (Au@Ag) surface-enhanced Raman scattering tags draw broad interest in the fields of biological and environmental analyses. Herein, an efficient hybrid microfluidic chip was designed to prepare uniform Au@Ag core-shell nanoparticles, and DTNB was used as the internal standard tag molecule to prepare Au@DTNB@Ag for SERS detection. Homogeneous core-shell nanoparticles with a particle size of 90 nm were prepared by mixing a silver precursor and a gold core in a microfluidic chip. The relative standard deviation (RSD) of the particle size distribution was close to 10%, and the detection limit of 4-MBA was as low as 10-10 M. In order to solve the influence of SERS signal fluctuation, a uniform Au@DTNB@Ag core-molecule-shell structure was synthesized in a microfluidic chip, and the characteristic peak of the analyte was corrected by the relative intensity of the DTNB characteristic peak (1335 cm−1). The experimental results showed that the SERS detection was achieved with high reproducibility, and the SERS peak intensity had a good linear correlation with the concentration. The homogeneous SERS substrate prepared using a microfluidic chip has potential for sensitive and reliable detection of environmental chemical contaminants.
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| 8. |
- Liao, Xunfan, et al.
(författare)
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The role of dipole moment in two fused-ring electron acceptor and one polymer donor based ternary organic solar cells
- 2020
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Ingår i: Materials Chemistry Frontiers. - : Royal Society of Chemistry. - 2052-1537. ; 4:5, s. 1507-1518
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Tidskriftsartikel (refereegranskat)abstract
- Fused-ring electron acceptor (FREA) based ternary organic solar cells (OSCs) have made significant progress and attracted considerable attention due to their simple device architecture and broad absorption range in devices. There are three key parameters that need to be fine-tuned in ternary OSCs including absorption, energy level and morphology in order to realize high efficiencies. Herein, a series of FREAs with diverse electron-rich cores or electron-deficient terminals are developed and rationally combined to achieve high performance ternary OSCs. The dipole moment of FREAs' terminals has been unveiled as an important factor and its working mechanism has been thoroughly investigated by systematically studying six ternary OSCs. These ternary blends all exhibit complementary absorption and cascade energy levels, which can facilitate efficient light-harvesting and charge transfer. Additionally, the morphological effects on ternary OSCs are eliminated through comparative studies while demonstrating distinctively different performance. The preliminary results show that compatible dipole moment between two FREAs is critical in ternary blends. Specifically, the performance of the ternary system with two FREAs having quite different dipole moment terminals is worse compared to that with similar terminal dipole moments. The pair with larger difference in the dipole moment will also negatively impact device performance. This interesting phenomenon is likely due to the fact that very different dipole moments of terminals in FREAs can significantly decrease the electron mobility as well as induce unbalanced hole/electron transport. Consequently, it results in increased charge recombination and reduced charge collection efficiency. This finding demonstrates that the dipole moment of FREAs should be taken into account in designing ternary OSCs.
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| 9. |
- Naimovičius, Lukas, et al.
(författare)
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Triplet-triplet annihilation mediated photon upconversion solar energy systems
- 2023
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Ingår i: Materials Chemistry Frontiers. - 2052-1537. ; 7:12, s. 2297-2315
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Forskningsöversikt (refereegranskat)abstract
- Solar energy harvesting is among the best solutions for a global transition toward carbon-neutral energy technologies. The existing solar energy harvesting technologies like photovoltaics (PV) and emerging molecular concepts such as solar fuels and molecular solar thermal energy storage (MOST) are rapidly developing. However, to realize their full potential, fundamental solar energy loss channels like photon transmission, recombination, and thermalization need to be addressed. Triplet-triplet annihilation mediated photon upconversion (TTA-UC) is emerging as a way to overcome losses due to the transmission of photons below the PV/chromophore band gap. However, there are several challenges related to the integration of efficient solid-state TTA-UC systems into efficient devices such as: wide band absorption, materials sustainability, and device architecture. In this article, we review existing work, identify and discuss challenges as well as present our perspective toward possible future directions.
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| 10. |
- Navarro-Pardo, F., et al.
(författare)
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Nanofiber-supported CuS nanoplatelets as high efficiency counter electrodes for quantum dot-based photoelectrochemical hydrogen production
- 2017
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Ingår i: Materials Chemistry Frontiers. - : Royal Society of Chemistry. - 2052-1537. ; 1:1, s. 65-72
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Tidskriftsartikel (refereegranskat)abstract
- We developed a hierarchically assembled hybrid counter electrode (CE) based on copper sulfide (CuS) nanoplatelets grown on polymer nanofibers. The resulting CE was used in a quantum dot (QD)-based photoelectrochemical (PEC) system for H2 generation in the presence of sacrificial agents (S2−/SO32−). The concept is to increase the specific surface area of the CE, aiming at maximizing charge exchange at the electrode, which boosts efficient generation of H2 and to obtain a stable structure for long-term operation of the device. Structural and morphological characterization indicated the presence of a covellite crystalline phase (CuS). PEC tests showed that the CuS nanoplatelets grown in the CEs could replace Pt CEs in either visible-active or near infrared (NIR)-active QD-based PEC systems. Specifically, saturation of the photocurrent density (∼7.5 mA cm−2) occurred at ∼0.6 V versus the RHE, when using a NIR QD-based TiO2 photoanode and a nanofiber-supported CuS as the CE. Stability tests of the nanofiber-supported CuS CE showed that 85% of the initial photocurrent density was maintained after ∼1 h, which is similar to that obtained with the Pt foil CE (86%). In contrast, CuS nanostructures directly deposited on FTO glass without nanofibers (CuS/FTO CE) exhibited poor stability. CuS/FTO CE degraded quickly, showing a 90% drop in the initial photocurrent within 200 s testing whereas a 14% drop in the initial photocurrent was observed for the CuxS on brass within 10 min of testing. Our new nanofiber supported-CuS CE stands out due to its higher performance compared to brass and its similar stability compared to Pt during long term PEC operation. Additionally, our hybrid CE showed a better catalytic performance than the Pt CE and good stability in cyclic voltammetry tests. These results demonstrate that the nanofiber-supported CuS is a promising cost effective alternative to Pt as a highly efficient CE for PEC H2 generation
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