Metal–organic frameworks (MOFs) with high surface area, tunable porosity, and diverse structures are promising platforms for chemiresistors; however, they often exhibit low sensitivity, poor ...selectivity, and irreversibility in gas sensing, hindering their practical applications. Herein, we report that hybrids of Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) nanoflakes and Fe2O3 nanoparticles exhibit highly sensitive, selective, and reversible detection of NO2 at 20 °C. The key parameters to determine their response, selectivity, and recovery are discussed in terms of the size of the Cu3(HHTP)2 nanoflakes, the interaction between the MOFs and NO2, and an increase in the concentration and lifetime of holes facilitated by visible-light photoactivation and charge-separating energy band alignment of the hybrids. These photoactivated MOF–oxide hybrids suggest a new strategy for designing high-performance MOF-based gas sensors.
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In manufacturing C−N bond‐containing compounds, it is an important challenge to alternate the conventional methodologies that utilize reactive substrates, toxic reagents, and organic solvents. In ...this study, we developed an electrochemical method to synthesize a C−N bond‐containing molecule avoiding the use of cyanides and amines by harnessing nitrate (NO3−) as a nitrogen source in an aqueous electrolyte. In addition, we utilized oxalic acid as a carbon source, which can be obtained from electrochemical conversion of CO2. Thus, our approach can provide a route for the utilization of anthropogenic CO2 and nitrate wastes, which cause serious environmental problems including global warming and eutrophication. Interestingly, the coreduction of oxalic acid and nitrate generated reactive intermediates, which led to C−N bond formation followed by further reduction to an amino acid, namely, glycine. By carefully controlling this multireduction process with a fabricated Cu–Hg electrode, we demonstrated the efficient production of glycine with a faradaic efficiency (F.E.) of up to 43.1 % at −1.4 V vs. Ag/AgCl (current density≈90 mA cm−2).
By electrochemical method, stable oxalic acid and nitrate substrates were coupled into an amino acid, glycine. Insertion of electrons resulted in their conversion into nucleophile and electrophile, respectively, which led to C=N bond formation between them, as well as the conversion of the reversible C=N double bond to a stable C−N single bond.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Glucose homeostasis is controlled by the islets of Langerhans which are equipped with
α
-cells increasing the blood glucose level,
β
-cells decreasing it, and
δ
-cells the precise role of which still ...needs identifying. Although intercellular communications between these endocrine cells have recently been observed, their roles in glucose homeostasis have not been clearly understood. In this study, we construct a mathematical model for an islet consisting of two-state
α
-,
β
-, and
δ
-cells, and analyze effects of known chemical interactions between them with emphasis on the combined effects of those interactions. In particular, such features as paracrine signals of neighboring cells and cell-to-cell variations in response to external glucose concentrations as well as glucose dynamics, depending on insulin and glucagon hormone, are considered explicitly. Our model predicts three possible benefits of the cell-to-cell interactions: First, the asymmetric interaction between
α
- and
β
-cells contributes to the dynamic stability while the perturbed glucose level recovers to the normal level. Second, the inhibitory interactions of
δ
-cells for glucagon and insulin secretion prevent the wasteful co-secretion of them at the normal glucose level. Finally, the glucose dose–responses of insulin secretion is modified to become more pronounced at high glucose levels due to the inhibition by
δ
-cells. It is thus concluded that the intercellular communications in islets of Langerhans should contribute to the effective control of glucose homeostasis.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The incorporation of small amounts of 3,5-diaminobenzoic acid (DABA) comonomer (usually 5–20 mol %) into an ortho-hydroxypolyimide (HPI) precursor constitutes a new methodology to easily improve the ...gas transport performance of thermally rearranged (TR) polymer membranes. Thermogravimetric analysis (TGA) profiles of HPI with DABA copolyimides (HPID) suggests that there is an overlap between the temperature ranges of two processes: the degradation of DABA carboxyl groups and the actual thermal rearrangement process. During thermal treatment at 450 °C, carboxyl pendant groups in DABA degrade while a more rigid biphenyl cross-linked structure is formed either following or at the same time as the rearrangement of imide to benzoxazole. Mixed-gas CO2/CH4 (1:1) experiments proved this new series of cross-linked TR poly(benzoxazole-co-imide) (XTR-PBOI) membranes as superior materials for CO2/CH4 separation applications, with enhanced permeability and selectivity, as well as high resistance to plasticization up to 40 bar.
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Electro-oxidation of neutral substrates to produce cationic species, such as protons or metal cations to serve as Bronsted acids or Lewis acids, can potentially be coupled with the CO2 reduction ...reaction at the cathode. In particular, coupling the electrochemical CO2 reduction reaction with the anodic generation of a Lewis acid can be a new approach to synthesizing new products from CO2 while avoiding a high proton environment. In this study, we explored the coupling of the anodic Lewis acid generation by the dissolution of a titanium anode and the cathodic production of formate from CO2 in a methanol electrolyte. As a result, we observed methyl formate as a CO2 conversion product with the highest faradaic efficiency of 69% under ambient conditions. Interestingly, methyl formate was observed only when NaBF4 was used in an undivided electrochemical cell, whereas only formic acid/formate was produced when sodium salts of other anion counterparts were utilized. We have shown that the anodic generation of Ti4+ cations surrounded by less coordinating anions led to fluoride abstraction from BF4 – anions. This resulted in BF3, the active Lewis acid in the esterification reaction of formate and methanol, producing methyl formate.
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The article
Heterojunction between bimetallic metal-organic framework and TiO
2
: Band-structure engineering for effective photoelectrochemical water splitting
, written by Ji Won Yoon et al., was ...erroneously originally published electronically on the publisher’s internet portal (currently SpringerLink) on 17 May 2022 with the Acknowledgements.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Bimetallic Fe/Ni-based metal-organic frameworks (MOFs) with different Fe/Ni ratios were coated on TiO
2
nanorods (NRs), and the performances of the heterojunction photoanodes in photoelectrochemical ...water splitting were investigated. The bandgaps and band positions of the MOFs could be modulated by changing the ratio of the Fe and Ni components. An ideal band alignment was achieved between the TiO
2
NRs and bimetallic MOFs with an optimum ratio of Fe/Ni = 0.25/0.75, which allowed efficient light absorption and charge separation. The coating of NH
2
−MIL(Fe)−88 layer on the TiO
2
NRs decreased the photocurrent density by 33%. In comparison, TiO
2
/NH
2
−MIL(Ni)−88 showed a modest improvement in photocurrent density (0.85 mA·cm
−2
at 1.23 V vs. a reversible hydrogen electrode (RHE)). When bimetallic NH
2
−MIL(Fe
0.25
Ni
0.75
)−88 was coated on the TiO
2
NRs, the photocurrent density reached 1.56 mA·cm
−2
, which was an efficiency enhancement of 3.2 times. The mechanism underlying high photoelectrochemical performance was investigated.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Thermally rearranged polybenzoxazoles (TR-PBO) are some of the most promising materials for gas separation because of their microporous and bimodal cavities that offer high gas transport performance. ...However, the brittleness of fully converted TR-PBO membranes has impeded their widespread industrial implementation. In this study, we prepared novel, thermally rearranged poly(benzoxazole-co-imide) membranes (TR-PBOI) with improved mechanical strength and good gas separation performance. These membranes are based on two commercially available TR-able diamines and two non-TR-able diamines with various compositions and different polymer rigidities. TR-PBOI membranes with the appropriate ratio of PBO and PI displayed a high fractional free volume and therefore exceptional gas separation properties (CO2 permeability over 300 barrer and CO2/N2 ideal selectivity above 20); both these values were higher than those of the corresponding original TR-PBO membranes. Furthermore, a substantial improvement in the mechanical properties of TR-PBOI membranes relative to their TR-PBO counterparts was observed.
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