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The product selectivity of the CO2 reduction reaction occurring on transition metal-doped ZnS monolayers was theoretically studied.

This work presents a simple hydrothermal synthesis of nitrogen-doped carbon dots (N-CDs), fabrication of microfluidic paper-based analytical device (μPAD), and their joint application for colorimetric determination of total cholesterol (TC) in human blood. The N-CDs were characterized by various techniques including transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and X-ray powder diffraction (XRD), and the optical and electronic properties of computational models were studied using the time-dependent density functional theory (TD-DFT). The characterization results confirmed the successful doping of nitrogen on the surface of carbon dots. The N-CDs exhibited high affinity toward 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)-diammonium salt (ABTS) with the Michaelis-Menten constant (KM) of 0.018 mM in a test for their peroxidase-like activity. Particularly, since hydrogen peroxide (H2O2) is the oxidative product of cholesterol in the presence of cholesterol oxidase, a sensitive and selective method of cholesterol detection was developed. Overall, the obtained results from TD-DFT confirm the strong adsorption of H2O2 on the graphitic N positions of the N-CDs. The laminated three-dimensional (3D)-μPAD featuring a 6 mm circular detection zone was fabricated using a simple wax screen printing technique. Classification of TC according to the clinically relevant criteria (healthy, 6.2 mM) could be determined by the naked eye within 10 min by simple comparison using a color chart. Overall, the proposed colorimetric device serves as a low-cost, rapid, simple, sensitive, and selective alternative for TC detection in whole blood samples that is friendly to unskilled end users.

The development of fast and non-invasive techniques to detect SARS-CoV-2 virus at the early stage of the infection would be highly desirable to control the COVID-19 outbreak. Metal-organic frameworks (MOFs) are porous materials with uniform porous structures and tunable pore surfaces, which would be essential for the selective sensing of the specific COVID-19 biomarkers. However, the use of MOFs materials to detect COVID-19 biomarkers has not been demonstrated so far. In this work, for the first time, we employed the density functional theory calculations to investigate the specific interactions of MOFs and the targeted biomarkers, in which the interactions were confirmed by experiment. The five dominant COVID-19 biomarkers and common exhaled gases are comparatively studied by exposing them to MOFs, namely MIL-100(Al) and MIL-100(Fe). The adsorption mechanism, binding site, adsorption energy, recovery time, charge transfer, sensing response, and electronic structures are systematically investigated. We found that MIL-100(Fe) has a higher sensing performance than MIL-100(Al) in terms of sensitivity and selectivity. MIL-100(Fe) shows sensitive to COVID-19 biomarkers, namely 2-methylpent-2-enal and 2,4-octadiene with high sensing responses as 7.44 x 10

The adsorption properties of the hydrogen atom on our newly designed materials were investigated using density functional theory (DFT) calculations, focusing on the role of dopants in modulating the binding properties of the metal. We proposed decorating Ti4 on pristine, B- and N-doped graphene surfaces for preparing a large-capacity hydrogen-storage device. Computational results indicate that the doping of B on graphene enhances the interaction between the metal cluster and the supporting substrate with a very strong binding energy of −6.45 eV, which is the strongest interaction among our proposed catalysts. This binding energy prevents the aggregation and formation of Ti–metal clusters. Dissociative chemisorption of the first H2 molecule occurs on all materials. Metal hydrides preferentially exhibit strong hybridization between the H-1s and Ti-3d orbitals. Furthermore, Ti4 decorated B-graphene is the most effective, with a high capacity of hydrogen adsorption which could be released under practical conditions. We confirmed that eight H2 molecules could stably adsorb on Ti4/BGr with six reversible hydrogen adsorptions. Our proposed B-doped graphene-based material, Ti4/BGr, offers high cluster-stability on the substrate with high-capacity hydrogen storage compared to various other surfaces in the previous work. Therefore, Ti4 decorated B-graphene is a promising candidate material for use as a reversible hydrogen storage material.

A single palladium (Pd) atom embedded in a high curvature defective carbon nanocone (Pd/dCNC) is investigated for formic acid (FA) decompositions using DFT calculations. We used Pd/dCNC as the catalyst for either trans-FA or cis-FA decomposition. FA is stably adsorbed on Pd/dCNC with very high adsorption energy compared to the Pd/dG surface. For the reaction mechanisms, the preferable FA dehydrogenation mechanisms proceed via the formate pathway, with a rate-determining step of only 0.50 eV (trans-FA) and 0.54 eV (cis-FA), which are less than that on active Pd (111) catalysts. The rate of hydrogen (H2) production is dependent on the FA concentration. The active neighboring C atom plays a significant role in facilitating FA dehydrogenation into H2. The side reaction producing CO and H2O via the formyl or carboxyl pathway cannot occur on Pd/dCNC due to a high energy-barrier and low production rate obtained by microkinetic simulations. Thus, our proposed catalysts effectively provide excellent activity and selectivity for FA dehydrogenation into H2.

A number of groups have invested considerable time synthesizing double-decker silsesquioxane (DD SQ) copolymers; however, to our knowledge, no one has sought to explore through-chain electronic com...

In this work, we investigate the catalytic role of platinum-decorated defective CNC (Pt/dCNC) in CO2 hydrogenation to formic acid (FA) by a density functional theory (DFT) approach. The reaction follows the equation CO2(g) + H2(g) → HCOOH(g). Combining highly reactive Pt atoms with defective CNC provides Pt/dCNC, a reactive monodispersed atomic catalyst for CO2 hydrogenation. We propose our new mechanism of CO2 hydrogenation over the Pt/dCNC catalyst involving a H2 dissociation and H spillover sequence that is energetically favorable. The rate-determining step is formic acid desorption that requires an energy barrier of 1.11 eV. Furthermore, our findings show that the rate of FA production is dependent on H2 concentration. Altogether, the theoretical results support the concept of the spillover mechanism, playing a key role in promoting CO2 hydrogenation via a formate intermediate. These results improve our understanding of the mechanism involving H2 dissociation with the H spillover process and the catal...

A coordination complex, lithium hepta(i-butyl)silsesquioxane trisilanolate (1; Li-T7), a stable intermediate in silsesquioxane (SQ) syntheses, was successfully isolated in 65% yield and found to be...

Bromination and iodination of title double decker (DD) phenylsilsesquioxane macromonomers occurs at ortho and para positions, respectively, as in PhT8,10,12 cages. Heck cross-coupling with 4-Me/CNs...

Macromonomers [RPhSiO1.5]8,10,12 and [RCH═CHSiO1.5]8,10,12, where R is a conjugated group, have previously been shown to offer photophysical properties wherein excitation promotes an electron from ...

The adsorption properties of the hydrogen atom on our newly designed materials were investigated using density functional theory (DFT) calculations, focusing on the role of dopants in modulating the binding properties of the metal. We proposed decorating Ti

Multiple studies have explored using cage silsesquioxanes (SQs) as backbone elements in hybrid polymers motivated by their well-defined structures, physical and mechanical properties. As part of this general exploration, we reported unexpected photophysical properties of copolymers derived from divinyl double decker (DD) SQs, [vinyl(Me)Si(O 0.5 ) 2 ][PhSiO 1.5 ] 8 [(O 0.5 ) 2 Si(Me)vinyl] (vinylDDvinyl). These copolymers exhibit strong emission red-shifts from model compounds and implying unconventional conjugation, despite vinyl(Me)Si(O-) 2 siloxane bridges. In an effort to identify minimum SQ structures that do/do not offer extended conjugation; we explored Heck catalyzed co-polymerization of vinyl-ladder(LL)-vinyl compounds, vinyl(Me/Ph)Si(O 0.5 ) 2 [PhSiO 1.5 ] 4 (O 0.5 ) 2 Si(Me/Ph)vinyl, with Br-Ar-Br where Br-Ar-Br = 1,4-dibromobenzene, 4,4'-dibromo-1,1'-biphenyl, 4,4''-dibromo- p -terphenyl, 4,4'-dibromo- trans -stilbene, 2,7-dibromo-9,9-dimethyl-9H-fluorene, 2,5-dibromothiophene, 5,5'-dibromo-2,2'-bithiophene and 2,5-dibromo-thieno[3,2- b ]thiophene. Most surprising, the resulting oligomers show 30-60 nm emission red-shifts beyond those seen with vinylDDvinyl analogs despite lacking a true cage . Further evidence for unconventional conjugation includes apparent integer charge transfer (ICT) between LL-co-thiophene, bithiophene and thienothiophene with 10 mol% F 4 TCNQ, suggesting potential as p-type doped organic/inorganic semiconductors. Brominating DD/LL-co-phenyl polymer vinyl groups eliminates emission red-shifts. Zn debromination thereafter restores vinyl groups and emission red-shifts but brominated phenyls remain providing potential access to families of "hairy" conjugated SQ polymers.

In this work, we investigated the mechanism of CO2 hydrogenation over the Pt-doped boron nitride nanosheets (Pt-BNNSs) by using the density functional theory (DFT). It is found that a Pt adatom can be effectively stabilized in boron vacancy site (Pt-BV). Our investigation shows that the reaction mechanisms of CO2 hydrogenation over Pt-BV can be found in three possible reaction pathways: (i) co-adsorption, (ii) H2 dissociation, and (iii) co-adsorption together with H2 dissociation pathways. The co-adsorption together with H2 dissociation provides the most favorable pathway among of these three proposed mechanisms. The important finding of our study is that the presence of CO2 in step of hydrogen dissociation plays an important role in producing the FA on the Pt-BV catalyst. Moreover, we found that the hydrogenation of CO2 via carboxylate (COOH) has the rate-determining step of 0.63 eV in the step of hydrogen dissociation. In addition, the microkinetic modelling suggests that the COOH route is found to be more energetically and kinetically feasible rather than that it is formate route (HCOO) with the reaction temperature at 350 K and pressure of 5 bar. Our calculation results provide an important information for developing Pt-BV catalysts and might shed light on experimental design the novel Pt-BV catalyst for the CO2 hydrogenation and the conversion of greenhouse gases into value-added products.

We investigated H-spillover mechanisms on Pt atoms decorating defective carbon nanocones (Pt/dCNC) using the multicomponent B3LYP (MC_B3LYP) method, which can take account of the nuclear quantum effect (NQE) of light nuclei. MC_B3LYP shows reduced relative energies for all stationary-point structures and lower energy barriers to H-spillover reactions. Interestingly, MC_B3LYP calculations reveal that the activation energy for H2 dissociation completely vanishes indicating that H2 molecules dissociate readily on Pt/dCNC. Our crucial finding is that the different metal (Pt and Pd) on dCNC surface has affected the thermodynamic favorability of the hydrogen dissociation process, on Pt/dCNC is facile and highly exothermic, while on Pd/dCNC is dramatically endothermic. Furthermore, comparison of combined dissociation-spillover mechanism on Pt decorated on carbon nanocone (Pt/dCNC) and Pt decorated on graphene (Pt/dG) catalysts have been focused to explain the curvature effect which can facilitate the hydrogen spillover process and provide a highly exothermic reaction, which is more thermodynamically favorable than that of a metal-graphene surface. Our new understanding of this reaction mechanism and the influence of NQEs on electronic properties will be useful for the future development of the spillover mechanism as well as the synthesis of high-performance Pt/dCNC for H2 energy applications.

Phytochemical examination on the different extracts of leaves and twigs of Holoptelea integrifolia (H. integrifolia) were carried out with varied polar organic solvents. The chemical constituents of crude extracts were separated and isolated by using chromatography technique and characterized by using spectroscopies of 1H, 13C and 2D NMR. Two known compounds, the stigmasterol (1) and octamethylcyclohexane-1,4-dione (2), and one new compound, di-myo-inositol (3) were isolated and characterized. Chemical constituent 2 and 3 has been reported for the first time in H. integrifolia; in addition, constituent 3 was new phytochemical finding.