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The stability of formamidinium lead iodide (FAPbI3) perovskites is generally improved by incorporating cesium (Cs) into the crystal structure. However, the effectiveness of this approach is limited...

In this paper, a reduced graphene oxide/polypropylene (rGO/PP) dielectric composite with high dielectric constant and low dielectric loss at a low filler content was prepared

In order to obtain higher thermoelectric and mechanical properties in non-polar thermoplastic vulcanizates (TPVs), the Butyl rubber/Polypropylene (TPVs)/hydroxylated graphene (HGE) composites with nanosheet network were prepared through masterbatch technique and based on thermodynamic calculations, using polypropylene-graft-maleic anhydride (PP-MA) as a compatibilizer. The FTIR and Raman spectra revealed the introduced maleic anhydride group on PP-MA can form strong interfacial interaction with hydroxyl-containing functional groups on HGE. Morphology study indicated the rubber particles in the composites occupied the most volume of the PP phase, as expected to hinder the aggregation of HGE and form the effective nanosheet network. The nanosheet network can be combined with the IIR cross-linked particles during the dynamic vulcanization process to improve the interface bonding between PP and IIR, thus increasing the tensile strength of TPVs. When the content of HGE reached the percolation threshold (2 wt.%), the nanosheet network of HGE was formed, and the AC conductivity, dielectric permittivity and thermal conductivity increased sharply. The prepared TPVs/HGE nanocomposites have significantly improved in mechanical properties, thermal properties and dielectric properties, which provides a guarantee for their potential application as multifunctional TPVs polymers.

In order to obtain the unique properties of graphene-based composites, to realize homogeneous dispersion of graphene throughout the polymer matrix remains the key challenge. In this work, edge-oxidized graphene/polypropylene (EOGr/PP) composites with well-dispersed EOGr in PP matrix, synchronously exhibiting high electrical conductivity and thermal property, were simply fabricated for the first time using a novel strategy by in situ artificial PP latex preparation in the presence of EOGr based on solution-emulsification technique. The good dispersion state of EOGr in the PP matrix was demonstrated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). A blue shift in Raman G peak of the EOGr nanosheets was observed in the EOGr/PP composites, indicating the strong interactions between the EOGr nanosheets and the PP matrix. The onset crystallization and crystallization peak temperatures increased as the EOGr loading increases due to its good nucleating ability. An improved thermal stability of EOGr/PP composites was observed as evaluated by TGA. The EOGr/PP composites showed an insulator-to-conductor percolation transition in between that of 1 and 2 wt% EOGr content. Such strategy provides a very effective pathway to fabricate high-performance nonpolar polymer/graphene composites with excellent dispersion state of graphene.

Oxygen evolution reaction (OER) contributes to the main overpotential during water splitting. Developing efficient, nonprecious OER electrocatalysts is vital for sustainable fuels. Herein, nickel iron boride nanosheets coupled with reduced graphene oxide (rGO) has been developed as efficient OER electrocatalyst. The two-dimensional hybrid affords high surface area and abundant active sites for catalytic reaction. The rGO substrate improves the charge transfer. The ternary Ni-Fe-B supplies synergism for OER. As a result, the Ni-Fe-B/rGO exhibits excellent OER performances with low overpotential of 265 mV at 10 mA cm−2, as well as excellent catalytic stability, making it the promising candidate for OER application.

Summary Here, we sucessfully demonstrate the continuous functionalization of grain boundaries (GBs) in CH 3 NH 3 PbI 3 (MAPbI 3 ) organic-inorganic halide perovskite (OIHP) thin films with a triblock copolymer that contains rationally selected hydrophilic-hydrophobic-hydrophilic symmetric blocks. The addition of the triblock copolymer into the precursor solution assists in perovskite solution crystallization, resulting in ultrasmooth thin films with GB regions that are continuously functionalized. Tuning of the thickness of the functionalized GBs is realized, leading to MAPbI 3 OIHP thin films with simultaneously enhanced optoelectronic properties and environmental (thermal, moisture, and light) stability. The resulting perovskite solar cells show high stabilized efficiency of 19.4%, most of which is retained (92%) upon 480-hr 1-sun illumination. This approach is generic in nature, and it can be extended to a wide range of OIHPs and beyond.

Summary Significant effort is being devoted to the search for all-inorganic Pb-free halide perovskites (HPs) for photovoltaic applications. However, candidate HPs that combine all the desirable attributes — ease of synthesis, favorable bandgaps, outstanding optoelectronic properties, high stability, no toxicity — are extremely rare. Here, we demonstrate experimentally the promise of cesium titanium(IV) bromide (Cs 2 TiBr 6 ), a part of the Ti-based vacancy-ordered double-perovskite halides family, in perovskite solar cells (PSCs). We show, for the first time, that high-quality Cs 2 TiBr 6 thin films can be prepared through a facile low-temperature vapor-based method. These films exhibit a favorable bandgap of ∼1.8 eV, long and balanced carrier-diffusion lengths exceeding 100 nm, suitable energy levels, and superior intrinsic and environmental stability. The first demonstration of Cs 2 TiBr 6 thin films-based PSCs shows stable efficiency of up to 3.3%. Insights into the Cs 2 TiBr 6 film-formation mechanisms and the PSC device operation are provided, pointing to directions for improving Ti-based PSCs.

The lack of river sand is becoming increasingly serious. In this study, we consider how to use sea sand to prepare innovative construction and building materials with excellent mechanical and durability properties. Sulphate corrosion causes expansion, cracking and spalling of concrete, resulting in the reduction or even loss of concrete strength and cementation force. In this paper, artificial seawater, sea sand, industrial waste, steel fiber and polycarboxylate superplasticizer were used to prepare ultra-high-performance polymer cement mortar (SSUHPC), and the sulphate corrosion mechanism was investigated. The strength and cementation force of mortar on the SSUHPC surface decreased and flaked off with the development of sulphate erosion, and the steel fiber rusted and fell off. A 3D model was established based on X-ray computed tomography (X-CT), and the results showed that SSUHPC maintained excellent internal structural characteristics despite severe sulphate erosion on the surface. Mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were adopted to investigate the sulphate corrosion mechanism of SSUHPC. We found a transition zone within 1–5 mm of the surface of SSUHPC. The Vickers hardness of mortar in this area was increased by 5~15%, and the porosity was reduced to 3.8489%. Obvious structural damage did not occur in this area, but a high content of gypsum appeared. UHPC prepared with seawater sea sand was found to have better sulphate resistance than that prepared with freshwater river sand, which supports the development and utilization of sea sand in concrete.

Layered MoS2 has been recognized as a promising low-cost alternative to Pt-based electrocatalysts towards the hydrogen evolution reaction (HER). Intensive interest has been mainly focused on designing MoS2 nanostructures with large amounts of active edge sites and fast charge transfer. Here we report the synthesis of vanadium and nitrogen co-doped MoS2 on reduced graphene oxide with new defect sites on the basal/edge planes and expanded interlayer spacing, which shows remarkable catalytic merits with an extremely low overpotential of 68 mV at 10 mA cm−2 and a Tafel slope of 41 mV dec−1. Its performance is superior to most current MoS2 electrocatalysts. In addition to the charge transfer benefits of the RGO substrate, the vanadium and nitrogen dopants trigger defect sites on the basal/edge planes, and an optimized electronic structure and expanded interlayer distance are also responsible for the enhancement in catalysis. This contribution may offer a potential way to design advanced MoS2 catalysts by modulating the defect sites and interlayer distance for efficient electrochemical water splitting.

Solution-processed organic–inorganic halide perovskite (OIHP) thin films typically contain fine, randomly oriented grains and a high-density grain-boundary network, which are unfavorable for key film functions including charge transport and environmental stability. Here, we report a new chemical route for achieving CH3NH3PbI3 (MAPbI3) OIHP thin films comprising large, uniaxially oriented grains and an ultralow-density grain-boundary network. This route starts with a new metastable liquid-state precursor phase, MAPbI3·MACl·xCH3NH2, which converts to metastable MAPbI3·MACl and then to MAPbI3 OIHP upon stepwise release of volatile CH3NH2 and MACl. Perovskite solar cells made via this route show high power conversion efficiency of up to 19.4%, with significantly enhanced environmental stability.

The alloying behavior between FAPbI3 and CsSnI3 perovskites is studied carefully for the first time, which has led to the realization of single-phase hybrid perovskites of (FAPbI3)1−x(CsSnI3)x (0

The δ → α phase transformation is a crucial step in the solution-growth process of formamidinium-based lead triiodide (FAPbI3) hybrid organic–inorganic perovskite (HOIP) thin films for perovskite solar cells (PSCs). Because the addition of cesium (Cs) stabilizes the α phase of FAPbI3-based HOIPs, here our research focuses on FAPbI3(Cs) thin films. We show that having a large grain size in the δ-FAPbI3(Cs) non-perovskite intermediate films is essential for the growth of high-quality α-FAPbI3(Cs) HOIP thin films. Here grain coarsening and phase transformation occur simultaneously during the thermal annealing step. A large starting grain size in the δ-FAPbI3(Cs) thin films suppresses grain coarsening, precluding the formation of voids at the final α-FAPbI3(Cs)–substrate interfaces. PSCs based on the interface void-free α-FAPbI3(Cs) HOIP thin films are much more efficient and stable in the ambient atmosphere. This interesting finding inspired us to develop a simple room-temperature aging method for preparing ...

Methylamine-induced thin-film transformation at room-temperature is discovered, where a porous, rough, polycrystalline NH4PbI3 non-perovskite thin film converts stepwise into a dense, ultrasmooth, textured CH3NH3PbI3 perovskite thin film. Owing to the beneficial phase/structural development of the thin film, its photovoltaic properties undergo dramatic enhancement during this NH4PbI3-to-CH3NH3PbI3 transformation process. The chemical origins of this transformation are studied at various length scales.

Seven novel multicomponent crystals involving various substituted organic amine molecules and 6-hydroxy-2-naphthoic acid were prepared and characterized by using single crystal X-ray diffraction, infrared and thermogravimetric analyses (TGA). Crystal structures with 1,4-bis(imidazol) butane (L1) 1, 1,4-bis(imidazol-1-ylmethyl)benzene (L2) 2, 1-phenyl piperazine 3, 2-amino-4-hydroxy-6-methyl pyrimidine 4, 4,4'-bipyridine 5, 5,5'-dimethyl-2,2'-dipyridine 6, 2-amino-4,6-dimethyl pyrimidine 7 were determined. Among the seven molecular complexes, total proton transfer from 6-hydroxy-2-naphthoic acid to coformer has occurred in crystals 1–4, while the remaining were cocrystals. X-ray single-crystal structures of these complexes reveal that strong hydrogen bonding O–H···O/N–H···O/O–H···N and weak C–H···O/C–H···π/π···π intermolecular interactions direct the packing modes of molecular crystals together. The analysis of supramolecular synthons in the present structures shows that some classical supramolecular synthons like pyridine-carboxylic acid heterosynthon R 2 2 (7) and aminopyridine-carboxylic acid heterosynthon R 2 2 (8), are again observed in constructing the hydrogen-bonding networks in this paper. Besides, we noticed that water molecules act as a significant hydrogen-bonding connector in constructing supramolecular architectures of 3, 4, 6, and 7.

A methodology based on entropy-driven molecule switch signal amplification strategy has been developed for the ultrasensitive detection of DNA. The gold electrode modified with gold nanoparticles was used to immobilize capture hairpin DNA. In the presence of target DNA, the stem of hairpin DNA was opened once the hybridization reaction occurred between the capture DNA and target DNA. With the addition of the link DNA which has more complementary bases with the capture DNA, the link DNA would hybridize with the capture DNA, and the target DNA would be displaced under the entropy-driven. The released target DNA could open another hairpin DNA. Through such a cycle the target DNA could be recycled, and more hairpin DNA was opened and more link DNA would hybridize with the capture DNA. When the electrochemical nanoparticle probe which consisted of the nanoparticles, probe DNA and the electrochemical reagent was added, the link DNA would hybridize with the probe DNA. As a result, the electrochemical response can be amplified and monitored. In this work, the Salmonella typhimurium aptamer complementary DNA was chosen as a model target, and S. typhimurium was also tested by target induced strand release technology coupling the entropy-driven molecule switch signal amplified strategy. The electrochemical sensor demonstrated excellent sensing performances such as ultra low detection limit (0.3 fmol L−1 for DNA and 13 cfu mL−1 for S. typhimurium) and high specificity, indicating that it is highly promising to provide a sensitive, selective, cost-effective, and convenient approach for DNA and S. typhimurium detection.

Doping and/or alloying in the various layers in perovskite solar cells (PSCs) is playing a key role in the success of this new photovoltaic (PV) technology. Here we present a brief review of doping and alloying approaches used to enhance the efficacy of the hybrid organic–inorganic perovskite (HOIP) layer, the electron-transporting layer (ETL), the hole-transporting layer (HTL), and the electrode layers in PSCs. While the effectiveness of these approaches is beyond doubt, the fundamental understanding of doping and alloying in the majority of the cases is lacking. This presents vast research opportunities in elucidating the roles of doping and alloying, and the rational design and implementation of these approaches for enhanced PSCs performance.

We find that there exists an ion exchange phenomenon in the precursor solutions for perovskite films. Despite the different ion introduction routes, the samples fabricated from precursor solutions with same ion molar ratio finally present similar properties. This finding illuminates a wide selectivity of reactants for the preparation of perovskite films.

Methylamine-induced thin-film transformation at room-temperature is discovered, where a porous, rough, polycrystalline NH