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The development of metal-free and recyclable catalysts for significant yet challenging transformations of naturally abundant feedstocks has long been sought after. In this work, we contribute a general strategy of combining the rationally designed crystalline covalent organic framework (COF) with a newly developed chiral frustrated Lewis pair (CFLP) to afford chiral frustrated Lewis pair framework (CFLPF), which can efficiently promote the asymmetric olefin hydrogenation in a heterogeneous manner, outperforming the homogeneous CFLP counterpart. Notably, the metal-free CFLPF exhibits superior activity/enantioselectivity in addition to excellent stability/recyclability. A series of in situ spectroscopic studies, kinetic isotope effect measurements, and density-functional theory computational calculations were also performed to gain an insightful understanding of the superior asymmetric hydrogenation catalysis performances of CFLPF. Our work not only increases the versatility of catalysts for asymmetric catalysis but also broadens the reactivity of porous organic materials with the addition of frustrated Lewis pair (FLP) chemistry, thereby suggesting a new approach for practical and substantial transformations through the advancement of novel catalysts from both concept and design perspectives.
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Developing efficient and robust electrode materials for electrochemical sensors is critical for real-time analysis. In this paper, a hierarchical holmium vanadate/phosphorus-doped graphitic carbon nitride (HoVO4/P-CN) nanocomposite is synthesized and used as an electrode material for electrochemical detection of hydrogen peroxide (H2O2). The HoVO4/P-CN nanocomposite exhibits superior electrocatalytic activity at a peak potential of -0.412 V toward H2O2 reduction in alkaline electrolytes while compared with other reported electrocatalysts. The HoVO4/P-CN electrochemical platform operated under the optimized conditions shows excellent analytical performance for H2O2 detection with a linear concentration range of 0.009-77.4 µM, a high sensitivity of 0.72 µA µM-1 cm-2, and a low detection limit of 3.0 nΜ. Furthermore, the HoVO4/P-CN-modified electrode exhibits high selectivity, remarkable stability, good repeatability, and satisfactory reproducibility in detecting H2O2. Its superior performance can be attributed to a large specific surface area, high conductivity, more active surface sites, unique structure, and synergistic action of HoVO4 and P-CN to benefit enhanced electrochemical activity. The proposed HoVO4/P-CN electrochemical platform is effectively applied to ascertain the quantity of H2O2 in food and biological samples. This work outlines a promising and effectual strategy for the sensitive electrochemical detection of H2O2 in real-world samples.
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Graphene oxide-based composite membranes have received enormous attention for highly efficient water desalination. Herein, we prepare arginine/graphene oxide (Arg/GO) composite membranes by surface functionalizing GO nanosheets with arginine amino acid. Arginine has a unique combination of hydroxyl and amino functional groups that cross-link GO nanosheets through hydrogen bonding and electrostatic interactions. The as-prepared Arg@GO composite membranes with different thicknesses are used to separate the salt and dye molecules. The 900-nm-thick Arg@GO composite membrane shows high rejection of 98% for NaCl and 99.8% for MgCl2, Ni(NO3)2, and Pb(NO3)2 with good water permeance. Such a membrane also shows a high separation efficiency (100%) for methylene blue, rhodamine B, and Evans blue dyes. At the same time, the ultrathin Arg@GO composite membrane (220 ± 10 nm) exhibits high water permeance of up to 2100 ± 10 L m-2 h-1 bar-1. Furthermore, the 900-nm-thick Arg@GO composite membrane is stable in an aqueous environment for 40 days with significantly less swelling. Therefore, these membranes can be utilized in future desalination and separation applications.
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Textile and pharmaceutical effluents contain significant amounts of dyes and antibiotics, which pose a serious threat to the ecosystem when discharged directly. Therefore, they should be treated by facile treatment techniques using low-cost materials. Layered double hydroxide (LDH) and its hybrids have emerged as robust and economic adsorbents for water treatment. Herein, magnesium/aluminum LDH and its starch-based composite were synthesized by a co-precipitation technique. The physicochemical features of the developed adsorbents were thoroughly characterized using various analytical tools. The developed materials were tested for the eradication of methylene blue (MB) and amoxicillin (AMX) in batch mode adsorption by varying operating conditions. Adsorption performance depends on the solution's pH. Under optimum adsorption conditions of pH 11, adsorbent dosage of 50 mg/L, and treatment time of 120 min, starch-impregnated MgAl-LDH exhibited maximum MB and AMX adsorption capacities of 114.94 and 48.08 mg/g, respectively. The adsorption mechanism states that hydrogen bonds and weak van der Waals forces are responsible for the removal of pollutants by the developed materials. Moreover, equilibrium and kinetic studies revealed that the removal of dye and antibiotic followed the Freundlich and Langmuir models with the pseudo-second-order reaction kinetics, respectively. The spent adsorbents were regenerated using 0.1 M HCl (for MB) and methanol (for AMX) eluent, and reusability studies ensured that the developed adsorbents retained their performance for up to four consecutive adsorption/desorption cycles. MgAl-LDH and its starch-based hybrid could thus be used to effectively remove organic contaminants from wastewater streams on a commercial scale.
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Azul de Metileno , Poluentes Químicos da Água , Cinética , Azul de Metileno/química , Adsorção , Amoxicilina , Ecossistema , Poluentes Químicos da Água/química , Hidróxidos/química , Corantes , Antibacterianos , Concentração de Íons de HidrogênioRESUMO
Correction for 'A first-principles study of the stability, electronic structure, and optical properties of halide double perovskite Rb2Sn1-xTexI6 for solar cell applications' by Muhammad Faizan et al., Phys. Chem. Chem. Phys., 2021, 23, 4646-4657, DOI: 10.1039/D0CP05827K.
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Owing to their emerging role in solar cell technology, lead halide perovskites have aroused significant research interest in the recent past. However, due to its obvious toxicity, looking for a potential alternative to lead is becoming one of the most important pursuits in present times. We present our work based on density functional theory (DFT) investigating lead free defect perovskites (Rb2Sn1-xTexI6 (0 ≤x≤ 1)). In particular, we explore the crystal structure, thermodynamic stability, electronic structure, and optical properties of Rb2Sn1-xTexI6 (0 ≤x≤ 1) as a function of increasing Te concentration. Our results show that the Sn-Te alloyed perovskites exhibit considerable stability, a suitable band gap, small effective mass, and excellent light absorption. Especially, Rb2Sn0.75Te0.25I6 and Rb2Sn0.50Te0.50I6 have a direct band gap of 1.35 and 1.44 eV, respectively, which is highly favorable for use in a single-junction photovoltaic cell. We hope that our work will arouse the interest of experimental as well as theoretical scientists for synthesizing new materials and/or exploring the Sn-Te mix as a potential substitute for lead in photovoltaic materials.
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The design and synthesis of polyhedra using coordination-driven self-assembly has been an intriguing research area for synthetic chemists. Metal-organic polyhedra are a class of intricate molecular architectures that have garnered significant attention in the literature due to their diverse structures and potential applications. Hereby, we report Cu-MOP, a bifunctional metal-organic cuboctahedra built using 2,6-dimethylpyridine-3,5-dicarboxylic acid and copper acetate at room temperature. The presence of both Lewis basic pyridine groups and Lewis acidic copper sites imparts catalytic activity to Cu-MOP for the tandem one-pot deacetalization-Knoevenagel/Henry reactions. The effect of solvent system and time duration on the yields of the reactions was studied, and the results illustrate the promising potential of these metal-organic cuboctahedra, also known as nanoballs for applications in catalysis.
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Greenly synthesized nanoparticles have garnered attention due to their low environmental footprint, but impurities limit their applications. A novel semi-organic method for synthesizing silver nanoparticles (AgNPs) using bio-based chelating fuels (Beta vulgaris subsp., Spinacia oleracea, and Ipomoea batatas) reduces the undesirable impurities. The study also showcases the impact of bio-based chelating fuel on various characteristics of AgNPs in comparison to synthetic chelating fuel. The antimicrobial efficacy of the synthesized AgNPs in conjunction with honey was also assessed against E. coli. The XRD analysis showed cubic structure of AgNPs. The FESEM and TEM analysis showed that the well-connected spherical-shaped AgNPs (â¼3-120 nm diameter) while EDS confirmed the presence of Ag in all samples. The TEM analysis also revealed layers of carbonates in AgNPs synthesized using bio-based chelating fuels. XPS investigation confirmed the absence of any prominent impurities in prepared samples and AgNPs have not experienced oxidation on their surface. However, notable surface charging effects due to the uneven conductivity of the particles were observed. The broth dilution method showed that all mixtures containing AgNPs in combination with honey exhibited a significant bacterial growth reduction over a period of 120 h. The highest growth reduction of â¼75 % is obtained for the mixture having AgNPs (Ipomoea batatas) while the least growth reduction of â¼51 % is obtained for the mixture having AgNPs (Beta vulgaris subsp.). The findings affirm that AgNPs can be successfully synthesized using bio-based chelating fuels with negligible ecological consequences and devoid of contaminants. Moreover, the synthesized AgNPs can be employed in conjunction with honey for antibacterial purposes.
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Various strategies have been adapted to fabricate stable organic-inorganic hybrid perovskite (PVT) solar cells (PSCs). The triple-cation (CH3NH3+ (MA+), CH3(NH2)2+ (FA+), and Cs+) along with dual-anion (I- and Br-)-based PVT (TC-PVT) layer offers better stability than single cation-based PVTs. The deprivation of the PVT absorber is also influenced by the interface of the absorber with the charge transport layer (electron transport layer (ETL) and hole transport layer (HTL)). Here, the degradation of the TC-PVT coated on Al-doped zinc oxide (AZO) as well as FTO/AZO/TC-PVT/HTL structured PSC was examined for various Al to Zn molar ratio (RAl/Zn) of AZO. The PL decay study of FTO/AZO/TC-PVT revealed that the lowest degradation in the power (35.38%) was observed for the AZO with RAl/Zn of 5%. Furthermore, the PV cell parameters of the PSCs were analytically determined to explore the losses in the PSCs during degradation. The shunt resistance reduction was maximum (50.32%) for RAl/Zn = 10%, whereas, minimum shunt loss (7.33%) for RAl/Zn of 2%. The highest loss due to series resistance was observed for RAl/Zn of 0%. The changes in diode ideality factor (n) and reverse saturation current density (J0) were the smallest for RAl/Znof 10%.
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COVID-19 is a pandemic disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This virus is mainly spread by droplets, respiratory secretions, and direct contact. Caused by the huge spread of the COVID-19 epidemic, research is focused on the study of biosensors as it presents a rapid solution for reducing incidents and fatality rates. In this paper, a microchip flow confinement method for the rapid transport of small sample volumes to sensor surfaces is optimized in terms of the confinement coefficient ß, the position of the confinement flow X, and its inclination α relative to the main channel. A numerical simulation based on two-dimensional Navier-Stokes equations has been used. Taguchi's L9(33) orthogonal array was adopted to design the numerical assays taking into account the confining flow parameters (α, ß, and X) on the response time of microfluidic biosensors. Analyzing the signal-to-noise ratio allowed us to determine the most effective combinations of control parameters for reducing the response time. The contribution of the control factors to the detection time was determined via analysis of variance (ANOVA). Numerical predictive models using multiple linear regression (MLR) and an artificial neural network (ANN) were developed to accurately predict microfluidic biosensor response time. This study concludes that the best combination of control factors is α 3 ß 3 X 2 that corresponds to α = 90 ∘ , ß = 25 and X = 40 µm. Analysis of variance (ANOVA) shows that the position of the confinement channel (62% contribution) is the factor most responsible for the reduction in response time. Based on the correlation coefficient (R 2), and value adjustment factor (VAF), the ANN model performed better than the MLR model in terms of prediction accuracy.
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Hybrid hydrogels based on n-isopropylacrylamide, zwitterionic comonomer, and graphene oxide were synthesized to study their physical and mechanical properties. The compositional variation largely influenced the swelling characteristics of the hybrid hydrogels compared to mechanical properties, i.e., elongation and compression. Additionally, Rheometric swelling measurements on the swollen hydrogels were performed until they reached equilibrium showed a very low phase angle δ indicating strong covalent network, which intrun increases with increasing content of zwitterions and GO. Swelling kinetics were studied and found to follow Fickian dynamics, albeit zwitterion-containing gels showed a peculiar 2-step swelling pattern. Interestingly, differences in the swelling mechanism are also clear for the hydrogels with 2D GO (Graphene oxide) nano-fillers from its 1D nano-filler CNTs (Carbon nanotubes). In elongation, the samples break in a brittle fashion at Hencky strains εmax around 0.4-0.65 with the maximum stress being observed for samples with high Zw-content and 0.2% GO, which can be explained by the stress-rising properties of sharp edges of GO. In contrast, the data in compression profits from higher GO-contents as crack growth is less important in this deformation mode. This work will contribute to future composite gel applications.
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Grafite , Nanotubos de Carbono , Água , HidrogéisRESUMO
Vanadium oxide (V2O5) and carbon spheres (Cs)-doped NiO2 nanostructures (NSs) were prepared using the co-precipitation approach. Several spectroscopic and microscopic techniques, including X-ray diffraction (XRD), UV-vis, FTIR, TEM, and HR-TEM investigations, were used to describe the as-synthesized NSs. The XRD pattern exhibited the hexagonal structure, and the crystallite size of pristine and doped NSs was calculated as 29.3, 32.8, 25.79, and 45.19 nm, respectively. The control sample (NiO2) showed maximum absorption at 330 nm, and upon doping, a redshift was observed, leading to decreased band gap energy from 3.75 to 3.59 eV. TEM of NiO2 shows agglomerated nonuniform nanorods exhibited with various nanoparticles without a specific orientation; a higher agglomeration was observed upon doping. The (4 wt %) V2O5/Cs-doped NiO2 NSs served as superior catalysts with a 94.21% MB reduction in acidic media. The significant antibacterial efficacy was estimated against Escherichia coli by measuring the zone of inhibition (3.75 mm). Besides their bactericidal analysis, V2O5/Cs-doped NiO2 was shown to have a binding score of 6.37 for dihydrofolate reductase and a binding score of 4.31 for dihydropteroate synthase in an in silico docking study of E. coli.
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In the present study, single phase nickel based disulphide (NiS2) and diselenide (NiSe2) nanostructures were prepared hydrothermally in a short time span (4 h) under subcritical temperature (160 °C). The nanostructures grow in cubic crystal phases. Average crystallite sizes and intrinsic microstrains were determined using Williamson-Hall (W-H) plot analysis. Hollow NiS2 nanospheres and bipyramidal NiSe2 nanostructures are reported that are suitable for surface related applications. Thermal gravimetric analysis (TGA) indicated high stability of the nanostructures at elevated temperatures. Optical studies indicated visible light activeness of the nanostructures exhibiting sharp band edges. The nanostructures are mesoporous in nature with NiS2 and NiSe2 having respectively a large specific surface area of 310 m2/g and 177 m2/g. A primarily work done to determine the electrochemical nature of the nanostructures showed the materials are pseudo-capacitive in nature with specific capacitances of 1022 F/g and 480 F/g respectively for NiS2 and NiSe2. The photo-catalytic activity of the nanostructures was explored against a colourless pollutant; phenol. The nanostructures degraded most of the phenol (>90 %) under visible light illumination and the reusability experiments performed determined industrial value of the photocatalysts.
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Cationic dyes present in industrial effluents significantly reduce the effectiveness of remediation operations. Considering the terrible impact of these pollutants on environment and biodiversity, investigating strategies to remove potentially harmful compounds from water is becoming an increasingly intriguing issue. In this work, we employed a simple hydrothermal technique to synthesize Fe-doped CdO (2, 4, and 6 wt %) nanostructures and assessed their efficacy in degrading methylene blue (MB) dye and inhibiting the growth of Staphylococcus aureus and Escherichia coli, respectively. Structural, morphological, and optical characterization of produced nanomaterials was also performed using X-ray diffraction, TEM, and UV absorption spectra. The photocatalytic decomposition of MB was significantly enhanced (58.8%) by using Fe (6 wt %)-doped CdO catalysts for 80 min under irradiation. In addition, 2.05-5.05 mm inhibitory zones were seen against Gram-positive bacteria (S. aureus), whereas the range for Gram-negative bacteria (E. coli) was 1.65-2.75 mm. These nanostructures were shown to be very effective inhibitors of beta-lactamase, d-alanine-d-alanine ligase B, and fatty acid synthase inhibitor by in silico molecular docking investigations.
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Semiconductor materials show a restricted degradation response to organic pollutants due to limited photocatalytic activity under visible light. Therefore, researchers have devoted much attention to novel and effective nanocomposite materials. For the first time, herein, a novel nano-sized semiconductor calcium ferrite modified by carbon quantum dots (CaFe2O4/CQDs) photocatalyst is fabricated via simple hydrothermal treatment for the degradation of aromatic dye using a visible light source. The crystalline nature, structure, morphology, and optical parameters of each of the synthesized materials were investigated using X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and UV-visible spectroscopy. The nanocomposite exhibits excellent photocatalytic performance (90% degradation) against Congo red (CR) dye. In addition, a mechanism for CaFe2O4/CQDs improving photocatalytic performance has been proposed. The CQDs in the CaFe2O4/CQD nanocomposite are considered to act as an electron pool and transporter, as well as a strong energy transfer material, during photocatalysis. CaFe2O4/CQDs appear to be a promising and cost-effective nanocomposite for dye-contaminated water purification, according to the findings of this study.
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Hydrogen heralded as a promising renewable and environmentally friendly energy carrier, carries inherent risks owing to its highly flammable nature. A mere 4 % concentration of hydrogen in the air can trigger an explosion. To counteract this peril, a composite material comprising PbOX -ZnO (2 : 1) was synthesized, characterized, and subsequently employed to fabricate a hydrogen sensing device. Various analytical tools were used to characterize as-deposited materials, including X-ray diffraction, Scanning electron microscopy /Energy Dispersive X-ray Spectroscopy, Transmission electron microscopy UV-Vis Reflectance Spectroscopy and Fourier-transform infrared spectroscopy. The device exhibited favorable properties, such as good selectivity, stability, and a low detection limit for hydrogen. At ambient room temperature, the device demonstrated a sensing signal reaching 468.7, with a response time (T90) of 155 seconds and a recovery time (Tr90) of 69 seconds when exposed to a hydrogen concentration of 5â ppm. This performance underscores the device's rapid and effective response to hydrogen exposure. Moreover, the PbOX-ZnO (2 : 1) composite-based device exhibited a detection limit of 2.4â ppm, functioning accurately within a linear range spanning from 5â ppm to 50â ppm. This capability confirms its precision in accurately detecting hydrogen concentrations within this designated range.
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Contaminants removal is usually becoming an exciting subject of research from water considering their environmental and ecological effects. This work provides pathways to remove organic pollutants from water via nanomaterials and is used as an antibiotic against bacteria like Escherichia coli (E. coli). In this study, molybdenum trioxide (MoO3) and yttrium (Y) doped (2 and 4%) MoO3 nanorods were synthesized by co-precipitation method. Advanced characterization techniques have been introduced to study textural structures, morphological developments, and optical characteristics of produced products. X-ray diffraction studied multiple crystalline structures of prepared samples as hexagonal, orthorhombic, and monoclinic of pure MoO3 with decrease in crystallinity and crystallite size upon Y doping. UV-visible spectroscopy unveiled a redshift (bathochromic effect) in absorption pattern attributed to band gap energy (Eg) decreases. Photoluminescence spectra examined the recombination rate of electrons (e-) and holes (h+) as charge carriers. A sufficient catalytic activity (CA) was observed against methylene blue (MB) dye in an acidic medium (99.74%) and efficient bactericidal action was studied against (E. coli) with zone of inhibition (5.20 mm) for 4% Y-doped MoO3. In addition, in silico docking demonstrated potential inhibitory effect of produced nanomaterials on FabH and FabI enzymes of fatty acid biosynthesis.
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Escherichia coli , Nanotubos , Simulação de Acoplamento Molecular , Antibacterianos/farmacologiaRESUMO
For polymer solar cells (PSCs), the mixture of polymer donors and small-molecule acceptors (SMAs) is fine-tuned to realize a favorable kinetically trapped morphology and thus a commercially viable device efficiency. However, the thermodynamic relaxation of the mixed domains within the blend raises concerns related to the long-term operational stability of the devices, especially in the record-holding Y-series SMAs. Here, a new class of dimeric Y6-based SMAs tethered with differential flexible spacers is reported to regulate their aggregation and relaxation behavior. In their polymer blends with PM6, it is found that they favor an improved structural order relative to that of Y6 counterpart. Most importantly, the tethered SMAs show large glass transition temperatures to suppress the thermodynamic relaxation in mixed domains. For the high-performing dimeric blend, an unprecedented open circuit voltage of 0.87 V is realized with a conversion efficiency of 17.85%, while those of regular Y6-base devices only reach 0.84 V and 16.93%, respectively. Most importantly, the dimer-based device possesses substantially reduced burn-in efficiency loss, retaining more than 80% of the initial efficiency after operating at the maximum power point under continuous illumination for 700 h. The tethering approach provides a new direction to develop PSCs with high efficiency and excellent operating stability.
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Electrode materials with high fast charging and high capacity are urgently required for the realization of sodium-ion batteries (SIBs). In this work, zinc ferrite (ZnFe2O4) nanospheres have been prepared by the simple hydrothermal route and the structural analysis of ZnFe2O4 was evaluated by using X-ray diffraction. The morphology and microstructural characterizations are obtained using scanning electron microscopy and transmission electron microscopy. The results indicate that a single phase material was obtained with uniform sphere-like morphology and high crystallinity. The Brunauer-Emmett-Teller method was employed to determine the specific surface area of the ZnFe2O4 nanospheres which has been calculated to be 32 m2 g-1. The electrochemical results indicate that the composite possesses high sodium storage capability (478 mA h g-1), and good cycling stability (284 mA h g-1 at 100th cycle) and rate capability (78 mA h g-1 at 2 A g-1). The high sodium storage performance of the ZnFe2O4 electrode is ascribed to the mesoporous nature of the ZnFe2O4 nanospheres. Further, sodium kinetics and the reaction mechanism in ZnFe2O4 nanospheres have been elucidated using electrochemical impedance spectroscopy, galvanostatic intermittent titration technique, ex situ TEM, and XAS. The acquired results indicate sluggish kinetics, reversibility of the material, and the stable structure of ZnFe2O4. Therefore, such a structure can be considered to be an attractive contender as a low cost anode for SIBs.
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Unlike the previous several investigations on planar donor-π-acceptor chromophores, the present investigation highlights the importance of twisted molecular configurations to effectively tune the optical and nonlinear optical (NLO) response properties. A variety of substitutions are made to design several twisted molecular compounds (1-7). These compounds are designed using pyrenyl and naphthalimide moieties, which are twisted with each other in their molecular configurations. The calculated versus experimental highest intensity absorption energy peaks (3.482 V. 3.444 eV) and experimental ionization potentials (6.07 V. 5.93 eV) of parent compound 1 reproduced reasonably well at M06/6-311G∗∗ methodology. The twisted chromophores show significantly larger amplitudes of third-order NLO polarizabilities (<γ>), which are found to be as large as 778.31 × 10-36 esu for compound 7 at the M06/6-311G∗∗ methodology. The <γ> amplitudes were also compared with planar donor-π-acceptor prototype para-nitroaniline (p-NA) molecule to provide the semi-quantitative assessment. For instance, the <γ> amplitudes of all compounds are about â¼7-â¼39 times bigger from the amplitude of p-NA at the same computational level. The origin of larger amplitudes has been traced though three-level model using the TD-DFT results. The larger oscillator strengths, lower transitions energies and larger change between the electronic dipole moment between the ground and the excited states. We believe the present study will not only put these compounds under the spotlight of material science but also provide structure-property relationships in designed compounds.