All‐inorganic perovskites have emerged as promising photovoltaic materials due to their superior thermal stability compared to their heat‐sensitive hybrid organic–inorganic counterparts. In ...particular, CsPbI2Br shows the highest potential for developing thermally‐stable perovskite solar cells (PSCs) among all‐inorganic compositions. However, controlling the crystallinity and morphology of all‐inorganic compositions is a significant challenge. Here, a simple, thermal gradient‐ and antisolvent‐free method is reported to control the crystallization of CsPbI2Br films. Optical in situ characterization is used to investigate the dynamic film formation during spin‐coating and annealing to understand and optimize the evolving film properties. This leads to high‐quality perovskite films with micrometer‐scale grain sizes with a noteworthy performance of 17% (≈16% stabilized), fill factor (FF) of 80.5%, and open‐circuit voltage (VOC) of 1.27 V. Moreover, excellent phase and thermal stability are demonstrated even after extreme thermal stressing at 300 °C.
A spin‐forced (SF) method as a facile approach is proposed to control the crystallization kinetics of CsPbI2Br crystal growth, achieving a uniform, and high‐quality film. The perovskite film formation during spin‐coating and annealing is evaluated by optical in situ characterization. As a result, an efficiency of 17.0% with excellent thermal stability at 300 °C is achieved.
In this paper, we report a dramatic enhancement in the adsorptive removal of Congo Red (CR) dye by polyaniline-zinc titanate (PANI/ZTO) nanocomposite as compared with that when PANI or ZTO are used ...separately. The dye exhibited little adsorption in the presence of lab-synthesized pristine ZnTiO3 (ZTO) powder as adsorbent and somewhat moderate adsorption in the presence of neat polyaniline whereas excellent and much faster adsorption was exhibited in the presence of PANI/ZTO nanocomposite. The composite was prepared by carrying out the polymerization of aniline in the presence of ZTO suspensions. The composite samples were characterized using X-Ray diffraction, FT-IR Spectroscopy, Field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and Dynamic light spectroscopy, and the adsorption kinetics were studied using UV–Vis spectroscopy. The characterization data suggest that the adsorption of the CR dye gets enhanced because PANI chain molecules which are chiefly responsible for adsorption through hydrogen bonding and π–π interactions with the dye, get adsorbed/tethered on to the ZTO nanoparticles, and thereby overcome the mass transfer limitation by being better exposed to the dye molecules. The kinetics of adsorption followed the pseudo-second-order rate equation and the rate of adsorption was controlled by intra-particles diffusion. The isotherm was best described by the Langmuir model and the maximum adsorption was calculated to be 64.51 mg/g. The value of 7.80 kJ/mole obtained from the Dubinin–Radushkevich (D–R) model suggested the physisorption of CR onto PANI/ZTO nanocomposite. These results suggest that the mass of a polymeric substance, in general, can be better utilized for adsorption by suitably dispersing them over the surface of appropriate support nanoparticles.
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•A composite formed of zinc titanate (ZTO) nanoparticles and polyaniline was prepared by polymerizing aniline in presence of ZTO suspension.•Adsorption of CR dye is dramatically enhanced on the composite as compared to that on neat polymers or the nanoparticles.•The adsorption sites are present on the polymer chains.•The polymers open up by tethering on to the nanoparticles and thereby expose its adsorption sites multifold leading to enhanced adsorption.
Hexagonal phase of Zinc titanate (ZTO) powder obtained by calcining the electrospun sol in the temperature range of 700–800 °C has shown bandgap in the visible region (Perween and Ranjan, 2017) 1. ...Owing to this, ZTO can be considered as a candidate material for visible light induced photocatalysis applications, and therefore can serve as a suitable alternative for solar radiation aided treatment of environmental pollutants. Doping ZTO with a suitable dopant atom such as nitrogen can further reduce its bandgap and thereby enhance the efficacy of its catalytic response to solar light. Here we report successful incorporation of nitrogen in zinc titanate with varying fraction of nitrogen using urea as a nitrogen source. Nitrogen incorporation leads to reduction in the bandgap, and thereby improvement in its visible light induced catalytic performance of ZTO towards the degradation of phenol. Presence of nitrogen also promotes the formation of the high-temperature phase of cubic Zn2TiO4. Nitrogen incorporated ZTO (N-ZTO) nanoparticles lead to a reduction in the bandgap from 2.83 eV in un-nitrogenated samples to 2.25 eV in nitrogenated ZTO. A substitutional doping of nitrogen is confirmed by various characterization techniques such as XPS, Raman, and FT-IR which show the presence of Ti–N bonds. Nitrogen incorporation in electrospun samples yields high surface area (122 m2/g) upon calcination, generating surface states that play important role in enhancing the sensitivity to visible light in samples prepared by our technique. The rate constant (k) of the phenol degradation reaction increased to 0.02051 min−1 with N-ZTO as compared to 0.00330 min−1 obtained with ZTO.
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•Nitrogen was successfully doped using urea in hexagonal zinc titanate (ZnTiO3) nanopowder obtained by sol-electrospinning route.•Nitrogen doping led to reduction in bandgap from 2.83 eV to 2.25 eV in hexagonal zinc titanate.•Nitrogen incorporation promotes formation of high temperature phase of cubic spinel Zn2TiO4.•Nitrogen incorporation in electrospun mats yields surface states since electrospinning gives high surface area materials.•Reduced bandgap and presence of surface states enhance photocatalytic degradation of phenol under visible light.
In this work, we study and report the phase behavior of the mixture of lauric acid (LA) and stearic acid (SA) inside polyvinyl alcohol (PVA)-polydimethylsiloxane (PDMS) nanofibrous mats woven using ...the electrospinning technique. Incorporating PDMS in the fibers prevents the mechanical properties from degrading due to the eutectic melting of the fatty acid mixtures present in the mats. Based on the results from scanning electron microscopy (SEM), differential scanning calorimetry (DSC), X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), and Raman studies a phase diagram of the binary LA-SA mixture inside the PVA-PDMS nanofibrous mat environment has been constructed. The phase behavior suggests a eutectic composition in these mixtures of approximately 75 mole percent of LA, an intermediate composition between those obtained for the same mixture in a pure PVA nanofibrous environment (∼50 mole percent) and in the bulk (∼90 mole percent). We conjecture that the hydrophilicity/hydrophobicity of the surrounding fiber environment to which the fatty acid molecules are subjected influences the interactions between the fatty acid molecules and thereby their phase behavior. This work suggests that we can engineer the phase behavior of a fatty acid mixture by altering the properties of its nanoconfinement. From an application point of view, PDMS-PVA mats incorporating LA-SA can be used for fabricating sheets with the desired mechanical integrity and impregnated with phase change materials (PCMs) for thermal energy storage applications.
In this work, we study and report the phase behavior of the mixture of lauric acid (LA) and stearic acid (SA) inside polyvinyl alcohol (PVA)-polydimethylsiloxane (PDMS) nanofibrous mats woven using the electrospinning technique.
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Drilling fluids are characterized by rheological and filtration characteristics and control of these properties is critical to the success of drilling operation. Among the popular ...additives for the control of these properties, nanoparticles are emerging to be one of the best additives for drilling fluids. For water based muds, rheology and filtration loss is generally controlled by polymers and it can also be improved by addition of small amounts of nanoparticles. In this paper, we have synthesized a BiFeO3 (BFO) nanoparticle by non-aqueous wet chemical techniques and used as additive for water based mud along with bentonite and other polymeric additives. BFO nanoparticles showed good compatibility with clay resulting in improved mud properties. Interaction of nanoparticles with clay and polymers resulted in enhanced apparent viscosity (AV), plastic viscosity (PV), yield point (YP), and API fluid loss. It was found that increasing the nanoparticle concentration from zero to 0.30 w/v% resulted in 25% increase in AV, PV and YP whereas a 35% decrease in API filtrate loss was observed at 20 °C before hot rolling. Even after hot rolling at 110 °C, these properties were not degraded significantly as was the case with mud without nanoparticles. Nanoparticles combined with bentonite platelets imparted good thermal stability to the drilling fluid.
In this work, we report a facile way to fabricate composite nanofibrous mats of polyvinyl alcohol (PVA), polydimethylsiloxane (PDMS), and stearic acid (SA) by employing the electrospinning-technique, ...with PDMS fraction ranging from 40w% to nearly 80w%. The results show that for a predetermined fraction of PVA and SA, incorporation of an optimal amount of PDMS is necessary for which the mats exhibit the best mechanical behavior. Beyond this optimal PDMS fraction, the mechanical properties of the composite mats deteriorate. This result has been attributed to the ability of the SA molecules to mediate binding between the PVA and PDMS long-chain molecules via van-der-Waals bonding. The morphological, structural, mechanical, and thermal characterizations respectively using SEM, XRD, DMA/tensile test, and DSC lend support to this explanation. By this method, it is possible to control the hydrophilicity/oleophilicity of the mats, and the mats show an excellent selective permeability to oil as compared to water and successfully filter water from a water-in-oil emulsion. Incorporation of SA not only serves to aid in electrospinning of a PDMS-rich nanofibrous mat with good mechanical strength and control over hydrophilicity/oleophilicity, but also has a potential use in fabricating sheets impregnated with phase change materials for thermal energy storage.
We report on a nonoxidative topochemical route for the synthesis of a novel indate-based oxyfluoride, LaBaInO3F2, using a low-temperature reaction of Ruddlesden–Popper-type LaBaInO4 with ...polyvinylidene difluoride as a fluorinating agent. The reaction involves the replacement of oxide ions with fluoride ions as well as the insertion of fluoride ions into the interstitial sites. From the characterization via powder X-ray diffraction (PXRD) and Rietveld analysis as well as automated electron diffraction tomography (ADT), it is deduced that the fluorination results in a symmetry lowering from I4/mmm (139) to monoclinic C2/c (15) with an expansion perpendicular to the perovskite layers and a strong tilting of the octahedra in the ab plane. Disorder of the anions on the apical and interstitial sites seems to be favored. The most stable configuration for the anion ordering is estimated based on an evaluation of bond distances from the ADT measurements via bond valence sums (BVSs). The observed disordering of the anions in the oxyfluoride results in changes in the optical properties and thus shows that the topochemical anion modification can present a viable route to alter the optical properties. Partial densities of states (PDOSs) obtained from ab initio density functional theory (DFT) calculations reveal a bandgap modification upon fluoride-ion introduction which originates from the presence of the oxide anions on the interstitial sites. The photocatalytic performance of the oxide and oxyfluoride shows that both materials are photocatalytically active for hydrogen (H2) evolution.
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