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Perovskite solar cells (PSCs) expressed great potentials for offering a feasible alternative to conventional photovoltaic technologies. 2D/3D hybrid PSCs, where a 2D capping layer is used over the 3D film to avoid the instability issues associated with perovskite film, have been reported with improved stabilities and high power conversion efficiencies (PCE). However, the profound analysis of the PSCs with prolonged operational lifetime still needs to be described further. Heading towards efficient and long-life PSCs, in-depth insight into the complicated degradation processes and charge dynamics occurring at PSCs' interfaces is vital. In particular, the Au/HTM/perovskite interface got a substantial consideration due to the quest for better charge transfer; and this interface is debatably the trickiest to explain and analyze. In this study, multiple characterization techniques were put together to understand thoroughly the processes that occur at the Au/HTM/perovskite interface. Inquest analysis using current–voltage (I–V), electric field induced second harmonic generation (EFISHG), and impedance spectroscopy (IS) was performed. These techniques showed that the degradation at the Au/HTM/perovskite interface significantly contribute to the increase of charge accumulation and change in impedance value of the PSCs, hence resulting in efficiency fading. The 3D and 2D/3D hybrid cells, with PCEs of 18.87% and 20.21%, respectively, were used in this study, and the analysis was performed over the aging time of 5000 h. Our findings propose that the Au/HTM/perovskite interface engineering is exclusively essential for attaining a reliable performance of the PSCs and provides a new perspective towards the stability enhancement for the perovskite-based future emerging photovoltaic technology. [ABSTRACT FROM AUTHOR]

Multi walled carbon nanotubes (MWCNTs) were decorated by activated carbon nanoparticles of resorcinol-formaldehyde aerogels. Carbon nanospheres and MWCNTs were mixed by equal mass ratios for different durations. The products were characterized by Raman spectroscopy, thermal gravimetric analysis, nanoscanning electron microscopy, transmission electron microscopy and x-ray diffraction. The results indicated that a significant decoration with carbon nanoparticles occurred onto the MWCNTs. [ABSTRACT FROM AUTHOR]

In this study, a zeolitic imidazolate framework-8 (ZIF-8) and its copper-doped variants (Cu-doped ZIF-8) were synthesized using a rapid microwave technique. The products were characterized by XRD, NanoSEM, FTIR, Raman spectra, TGA, XPS, and EDX. The gas adsorption properties of samples were performed using C3 and C4 hydrocarbons including propane, propylene, isobutane, and n-butane gases at 25 °C. Both equilibrium adsorption and kinetics were studied. It was found that ZIF-8 and Cu-doped ZIF-8 samples open their nanogates (i.e., six-membered rings) at some threshold pressures when adsorbing different gases, which it is denotes later as the gate-opening pressure (p0). The p0 value for each ZIF toward each gas was evaluated by fitting equilibrium adsorption data against a modified version of the Langmuir adsorption isotherm model. It was observed that the value of p0 differs significantly for each gas utilized, and with different extents for ZIF samples. The overall mass transfer coefficient values of adsorption process were estimated. Therefore, it is possible that the distinct values of p0 afford a unique chance to separate and purify these gases at mass production, and the best-studied adsorbent to for this purpose was Cu30%/ZIF-8. [ABSTRACT FROM AUTHOR]

Synthesis of ZIF with zinc, cobalt, or copper was carried out by microwaves. The effect of metal center on morphologies and pores of products was studied. Nitrogen adsorption/desorption onto ZIFs was examined by density functional theory. The micro, meso, and macropores of ZIF-8, Zn/Co-ZIF-8, and Cu/ZIF-8 ranged 99.814–99.969%, 0.055–0%, and 0.031–0.130%, respectively. Average pore sizes of ZIF-8, Zn/Co-ZIF-8, and Cu/ZIF-8 are 1.291, 1.194, and 1.164 nm, respectively. Monolayer saturation limits of nitrogen onto ZIF-8, Zn/Co-ZIF-8, and Cu/ZIF-8 were 21.152, 18.943, and 17.784 mmol/g, respectively. Further, the results included densities, total surface areas, total pore volumes, and average particle sizes of ZIF-8, Zn/Co-ZIF-8, and Cu/ZIF-8. [ABSTRACT FROM AUTHOR]

The current study provides an insight into the thermal stability of perovskite solar cells (PSCs) and the factors causing their degradation. To this end, a systematic stability study was carried out on n-i-p type perovskite solar cells involving mesoporous TiO2 layer. The samples were subjected to varying moisture and thermal conditions under light soaking while being exposed to long-term indoor (5000 h) and outdoor (75 h) harsh environmental conditions (i.e. 30%-80% RH and 40 °C-70 °C). To identify performance and morphological changes of PSCs after exposure to thermal stress, advanced characterization techniques including impedance spectroscopy, scanning electron microscopy and glow discharge optical emission spectrometry along with I-V characteristics were used. The un-encapsulated samples exposed to high thermal stress (40-70 °C) show degradation in their efficiency more than 40% within the 75 h of thermal stress. In contrast, the samples that were kept at room temperature were found to be very stable over 5000 h. [ABSTRACT FROM AUTHOR]

Resorcinol-formaldehyde xerogel was prepared, carbonized and activated in specific conditions to form resorcinol-formaldehyde activated carbon xerogel (RF-ACX) that was to produce microporous nanoparticles. RF-ACX was used in the adsorption of CO, CH, and N gases. Adsorption/desorption isotherms of CO, CH, and N gases onto RF-ACX adsorbent were measured gravimetrically by a magnetic suspension microbalance at five different temperatures (20, 30, 40, 50 and 60 °C) in the pressure range of 0-1 MPa. All adsorption/desorption isotherms were found to be favorable and well correlated with dual site Langmuir's model. The adsorption capacities of the three adsorbates increased with increasing pressure or with decreasing temperature. Nonetheless, the corresponding increase of CO adsorption capacity was much higher than those of CH and N. The fitting parameters deduced from dual site Langmuir's model were used to provide approximate predictions of the adsorption equilibria and selectivities of the corresponding binary mixtures (CO/CH, CH/N and CO/N), which relate to separation processes of high influence to various energy and environmental applications. [ABSTRACT FROM AUTHOR]

The world is faced with intrinsic environmental issues. Among these issues, the minimization of greenhouse gas emission to acceptable levels presents a high priority. This study seeks to help to reduce the greenhouse effect in sustainable manner. A resorcinol-formaldehyde xerogel was synthesized at specific conditions and used to prepare an activated carbon xerogel (RF-ACX). RF-ACX exhibited micropores in range of 1.2-1.4 nm, a surface area of 496 m/g and a cumulative pore volume of 0.81 cm/g. Scanning electron microscopy showed that it is made of microspherical particles with an almost uniform particle size of 1.3 ± 0.2 μm. Equilibrium and kinetic studies for the adsorption of CO, CH and N on RF-ACX were conducted at five temperatures (293, 303, 313, 323, and 333 K) and pressures of up to 1 MPa. The adsorption capacity on RF-ACX was highest for CO, followed by CH and then N. Isosteric heats of adsorption and adsorption rates were investigated. The measured adsorption equilibria were fitted with the extended multisite Langmuir adsorption model and further used to predict adsorption equilibria of their corresponding binary systems. [ABSTRACT FROM AUTHOR]

Osmotic shock in a vesicle or cell is the stress build-up and subsequent rupture of the phospholipid membrane that occurs when a relatively high concentration of salt is unable to cross the membrane and instead an inflow of water alleviates the salt concentration gradient. This is a well-known failure mechanism for cells and vesicles (for example, hypotonic shock) and metal alloys (for example, hydrogen embrittlement). We propose the concept of collective osmotic shock, whereby a coordinated explosive fracture resulting from multiplexing the singular effects of osmotic shock at discrete sites within an ordered material results in regular bicontinuous structures. The concept is demonstrated here using self-assembled block copolymer micelles, yet it is applicable to organized heterogeneous materials where a minority component can be selectively degraded and solvated whilst ensconced in a matrix capable of plastic deformation. We discuss the application of these self-supported, perforated multilayer materials in photonics, nanofiltration and optoelectronics. [ABSTRACT FROM AUTHOR]

Xerogels were prepared by the sol-gel polymerization of resorcinol with formaldehyde at different conditions. The effects of different synthesis factors (namely, resorcinol-to-formaldehyde ratio, resorcinol-to-water ratio, resorcinol-to-catalyst ratio, and initial solution pH) on the surface areas, pore volumes, pore size distributions, and adsorption capacity of liquid nitrogen were studied. Factorial design was also used to investigate the relative significance of these factors on the resulting xerogels properties, and the possible interactions between them. The mean effects of the most significant factors and factor interactions on determining the pore structures and adsorption capacities were evaluated. The synthesized xerogels were characterized by Fourier transmission infrared spectroscopy, thermal gravimetric analysis, scanning electron microscopy, and surface area analyzer. The results showed that surface areas, pore size distributions, and nitrogen adsorption capacity are dependent completely on the recipes used to prepare the xerogels. Pore structure results put xerogel samples as candidates for adsorption technology, ultra-filtration, and nano-filtration fields based on pore sizes and pore volume scales. [ABSTRACT FROM AUTHOR]

High-performance membranes are attractive for molecular-level separations in industrial-scale chemical, energy and environmental processes. The next-generation membranes for these processes are based on molecular sieving materials to simultaneously achieve high throughput and selectivity. Membranes made from polymeric molecular sieves such as polymers of intrinsic microporosity (pore size<2?nm) are especially interesting in being solution processable and highly permeable but currently have modest selectivity. Here we report photo-oxidative surface modification of membranes made of a polymer of intrinsic microporosity. The ultraviolet light field, localized to a near-surface domain, induces reactive ozone that collapses the microporous polymer framework. The rapid, near-surface densification results in asymmetric membranes with a superior selectivity in gas separation while maintaining an apparent permeability that is two orders of magnitude greater than commercially available polymeric membranes. The oxidative chain scission induced by ultraviolet irradiation also indicates the potential application of the polymer in photolithography technology. [ABSTRACT FROM AUTHOR]

Since the early spring of 2020, the coronavirus pandemic (COVID-19) outbreak has hindered traditional face-to-face teaching and hands-on, traditional delivery of laboratory courses, forcing universities to migrate from the traditional way of teaching to a remote online approach. Although few studies addressed the pandemic's impact on educational outcomes, no studies are found to investigate the impact of the remote online teaching approach on laboratory courses. This paper highlights the impact of the online teaching approach, coupled with flipped learning pedagogy, as a substitute for traditional laboratories. The course learning outcomes and assessment tools are analyzed and discussed for 46 students enrolled in the Unit Operations Laboratory course in the chemical engineering program at Qatar University. Results show that the course learning outcomes are achieved effectively using the hybrid online-flipped learning pedagogy, which can be considered for computerized traditional laboratories as a moderation solution to alleviate pandemic COVID-19 confinement on learning outcome. This methodology can also be sustained in the future to facilitate the teaching of such lab courses, even in normal conditions, to optimize the resources and avail the delivery of such courses to a larger audience who may have various obstacles to attending traditional lab courses., Competing Interests: Conflict of interestThe authors declare that they have no conflict of interest.Informed consentThe authors consent not to have any conflicts of interest, no experiments were done on humans or animals, and all ethical standards were met therein in accordance with Qatar University policies and regulations., (© The Author(s) 2021.)