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Overall urea–water electrolysis has the potential to be employed in the purification of urea-containing wastewater and the production of hydrogen. However, the lack of cost-effective catalysts currently presents a significant obstacle to the further development of this technology. Through a simple template-directed selenium reaction in a novel type of highly active solution, an interface engineering strategy was designed to synthesize hollow CuSe nanocubes as an efficient bifunctional catalyst. The unique hollow CuSe nanocubes exhibit significant catalytic efficiency because of their larger electrolyte contact area and faster ion transport. In 1 M KOH with a 0.5 M urea electrolyte, CuSe/NF required an overpotential of 199 mV for HER and a potential of 1.38 V for UOR to achieve a current density of 10 mA cm−2. It can work stably for 24 h without significant degradation of activity at 10 mA cm−2, showing excellent durability and excellent stability. For overall urea–water electrolysis, it exhibits a remarkable activity with a low cell voltage of 1.61 V at 10 mA cm−2. Consequently, the design strategy of this unique hollow-structured CuSe provides a new insight to improve electrocatalytic performance and stability. [ABSTRACT FROM AUTHOR]

Monitoring of reactive oxygen species (ROS), such as O2˙−, etc., in organisms is of great significance, not only for their essential role in biological processes, but their excessive production may also result in many diseases. Flavin (FL) is a fluorophore that naturally exists in flavoenzymes, and its fluorescent emission (FE) becomes negligible when reduced. This enables the application of FL derivatives as fluorescent sensors for ROS. We presented a theoretical investigation to address the impact of amino substitution on the photophysical properties of aminoflavins (AmFLs). Resulting from the interplay of electronic and positional effects, amination at C8 enhances the electronic coupling between the ground state and the first singlet excited state by enlarging the adiabatic energy change of the electronic transitions and the emission transition dipole moments, weakens the vibronic coupling by decreasing the contribution of isoalloxazine to the frontier molecular orbitals, redshifts the absorption band, and enhances the fluorescent emission drastically in 8AmFL. The theoretically estimated fluorescent emission intensity of 8AmFL is ∼40 times that of FL, suggesting its potential application as a fluorescent sensor. [ABSTRACT FROM AUTHOR]

Considering the difficulty in recovering powder materials and the low photocatalytic efficiency, we have developed a series of Fe-MOFs (MIL-53(Fe), NH2-MIL-53(Fe), MIL-101(Fe), NH2-MIL-101(Fe) and MIL-100(Fe)) on pure iron mesh. In this study, the growth of Fe@MILs on the iron mesh was confirmed through SEM, XRD, and FT-IR characterizations. Among the photocatalytic experiments, Fe@NH2-MIL-53(Fe) and Fe@NH2-MIL-101(Fe), which are amine-functionalized, showed improved photocatalytic activity. This improvement is believed to be due to the combination of NH2 functionality and electron transfer to the Fe–O cluster centre, resulting in dual excitation pathways. Furthermore, Fe@MIL-100(Fe) showed the highest performance for the removal of Cr(VI), with over 92% of Cr(VI) being removed in the fifth photocatalytic cycle. The mechanism indicated the close connection between the compact structure of Fe-MOFs and effective electron migration. Additionally, sacrificial reagent experiments identified two important species for Cr(VI) reduction: electrons (e−) and superoxide radicals (˙O2−). The photocatalytic recovery tests showed a 97% recovery rate of Cr(VI). This work offers a novel solution for the treatment of water sources contaminated with Cr(VI). [ABSTRACT FROM AUTHOR]

Photooxidative coupling of benzylic amines using naturally abundant O2 as an oxidant under visible light irradiation is an alternative green approach to synthesis imines and is of both fundamental and practical significance. We investigated the photophysical properties of flavin (FL) that is a naturally available sensitizer and its derivatives, i.e. 9-bromoflavin (MB-FL), 7,8-dibromoflavin (DB-FL) and 10-phenylflavin (Ph-FL), as well as the performance of these FL-based sensitizers (FLPSs) in the photooxidative coupling of benzylic amines to imines combining experimental and theoretical efforts. We showed that chemical functionalization with Br and phenyl effectively improves the photophysical properties of these FLPSs, in terms of absorption in the visible light range, singlet oxygen quantum yields, triplet lifetime, etc. Apart from nearly quantitative selectivity for the production of imines, the performance of DB-FL is superior to those of other FLPSs, and it is among the best photocatalysts for imine synthesis. Specifically, 0.5 mol% DB-FL is capable of converting 91% of 0.2 mmol benzylamine and more than 80% of 0.2 mmol fluorobenzylic amine derivatives into their corresponding imines in 5 h batch runs. Mechanistic investigation finely explained the observed photophysical properties of FLPSs and highlighted the dominant role of electron transfer in FLPS sensitized coupling of benzylic amines to imines. This work not only helps to understand the pathways for photocatalysis with FLPSs but also paves the way for the design of novel and efficient PSs to promote organic synthesis. [ABSTRACT FROM AUTHOR]

The commercialization of lithium–sulfur batteries is facing great challenges, such as the "shuttle effect" and the poor conductivity of sulfur and Li2S2/Li2S, so it is extremely important to design new separator-modified materials with fast charge transfer capability and effective immobilization of polysulfides (LiPSs) to facilitate their conversion to address these challenges. In this paper, we propose a simple way to synthesize NiCo2O4 nanospheres containing oxygen vacancies (OV-NiCo2O4 NSs) and thus modify the separator. The synthesized OV-NiCo2O4 NSs accelerated the conversion of LiPSs through strong chemical interactions. In addition, the introduction of oxygen vacancies provided more active sites for LiPSs, which improved the electron conduction rate and accelerated the ion transport. Based on the above advantages, the battery with an OV-NiCo2O4 modified separator showed excellent electrochemical performance (the initial capacity of the battery was 801 mA h g−1 at 0.5 C, the specific capacity of discharge was maintained at 695 mA h g−1 after 500 cycles, and the capacity retention rate was as high as 87%). [ABSTRACT FROM AUTHOR]

To overcome the sluggish kinetics for catalytic hydrolysis of ammonium borane (AB) to generate hydrogen, it is crucially important to design advanced catalysts with tertiary pore structures and substantial surface-exposed active sites. In this study, we report an architecture engineering strategy to construct nitrogen-rich porous carbon nanosheets with hollow worm-like nanowires (h-NCNWs) using low-cost/non-toxic and easily available graphitic carbon nitride as a self-sacrificing template and nitrogen source. The obtained h-NCNWs enable the uniform deposition of ultrafine Rh nanoparticles (Rh/h-NCNWs). The resultant Rh/h-NCNW catalyst exhibits an excellent hydrogen production performance for AB hydrolysis without any alkali promoters. Specifically, the Rh/h-NCNW catalyst with a low Rh loading of 2.12 wt% delivers much higher catalytic activity with a turnover frequency of 1234 min−1. The hollow worm-like nanowires created in Rh/h-NCNWs can provide diverse flexible channels to facilitate the exposure of copious surface-active sites and mass transport for AB hydrolysis, thereby promoting hydrogen evolution rates. This study provides an efficient strategy to engineer the architecture of the catalyst support for upgrading Rh metal-catalyzed hydrogen evolution from AB hydrolysis. [ABSTRACT FROM AUTHOR]

The efficient and selective photocatalytic conversion of chemicals with visible light and naturally abundant resources has long been desired, but this requires finely designed sensitizers that are capable of converting light into chemical energy for the required energy/electron transfer, bond formation and scission, etc. Inspired by flavin (FL) based enzymes that are capable of initiating many redox reactions in biological systems in visible light, FL and naphthalimide chromophores were fused together as a heavy-atom-free triplet photosensitizer (NI-FL). It is expected that the extended conjugation within NI-FL may benefit absorption in the visible light range, promoting the intersystem crossing to triplet excited states for efficient chemoselective conversions. The absorption and emission maximum of NI-FL are redshifted by ∼40 nm and the absorption is more than doubled (1.53 × 104 M−1 cm−1 at 484 nm) with respect to FL (7.5 × 103 M−1 cm−1 at 439 nm), and a long-lived triplet excited state of intramolecular electron transfer nature was captured (τT = 45.3 μs). The performances of FL and NI-FL in the photooxidation of sulfides in air were also examined. Apart from nearly quantitative selectivity for sulfoxide, NI-FL demonstrates a 0.5–5 fold enhanced performance with respect to FL and the conversion proceeds through radical intermediates formed by electron transfer at excited states with substrates. Mechanistic investigation satisfactorily explained the observed photophysical properties and the dominant role of radical intermediates in the NI-FL catalyzed photooxidation. The findings may help to understand photooxidation sensitized by FL derivatives and benefit the design of novel efficient photosensitizers. [ABSTRACT FROM AUTHOR]

Five novel lanthanide-substituted polyoxomolybdates (NH4)5Na3H2[{Ln(H2O)7}2{Mo5O15(1,4-O3PCH2C6H4CH2PO3)}4]·nH2O [Ln = Tb3+ (1), Ho3+ (2), Er3+ (3), Tm3+ (4), Yb3+ (5); n = 33, 32, 41, 30, 47] have been prepared in a conventional aqueous solution reaction of ammonium molybdate with Ln3+ ions and p-xylyenediphosphonic acid. Crystal structure analyses reveal that 1–5 are isomorphic. The prominent architecture characteristic is that their structural units consist of a tetrameric cyclic-shaped [{Mo5O15(1,4-O3PCH2C6H4CH2PO3)}4]16− segment stabilized by two [Ln(H2O)7]3+ cations, which are connected to propagate one-dimensional chain by Ln3+ ions. As is known, compounds 1–5 stand for the first Ln-substituted aromatic-bisphosphonate-functionalized polyoxomolybdates. The solid-state photoluminescence measurement of 1 has been performed at ambient temperature, and it displayed the characteristic emissions of Tb ions based on its 4f–4f transitions. In addition, the magnetic properties of 1–5 compounds show that they all exhibit anti-ferromagnetic interactions. [ABSTRACT FROM AUTHOR]

Cesium lead halide perovskite nanocrystals (NCs) have compelling photoelectric properties while their poor stability severely impedes their practical applications. Herein, we demonstrate novel CsPbBr3–CsPbBr3 homostructured NCs induced by a thioacetamide-oleylamine (TAA-OAm) ligand system via a facile room temperature re-precipitation method. The TAA-OAm ligand system could form long-chain N-substituted thioamides and short-chain S2− ligands, resulting in two different growth rates of CsPbBr3 NCs and finally forming CsPbBr3–CsPbBr3 homostructured NCs. The performed structural and compositional characterizations corroborate the existence of CsPbBr3–CsPbBr3 homostructured NCs. The obtained CsPbBr3–CsPbBr3 homostructures exhibit green emission of 510 nm and superior stability at room temperature in air. Our study provides a new approach to improve the stability of halide perovskite NCs, which may pave the way for future optoelectronic applications. [ABSTRACT FROM AUTHOR]

Magnesium (Mg) and iron (Fe) are almost immiscible under ambient conditions; this makes Mg an unusual candidate to be considered as a main light element in the earth's core; on the other hand, recent studies have shown that a significant amount of Mg can be dissolved in Fe to form Fe–Mg compounds under high pressure as high pressure can sufficiently improve the solubility of Mg in Fe. However, the formation mechanism and structures of the Fe–Mg compounds are still unknown to date. Herein, we proposed a series of unexpected Fe–Mg compounds (FeMg4, FeMg3, FeMg2, Fe2Mg3, FeMg and Fe2Mg) using the CALYPSO structure search method in conjunction with first-principles calculations. The results show that valence electrons of the Mg atoms transfer to the Fe atoms under high pressure, leading to the formation of these Fe–Mg compounds. This study represents a significant step forward in the understanding of binary Fe–Mg compounds. [ABSTRACT FROM AUTHOR]

We proposed a novel noninvasive method for glucose detection using a photoacoustic (PA) technique utilizing both the peak-to-peak value and peak arrival time delay information. Without increasing apparatus and system complexity, we demonstrated the accuracy enhancement of 29.5% and 33.63% for high (0–7 g dL−1) and low (0–350 mg dL−1) concentration of glucose solution, compared to conventional amplitude-based prediction. [ABSTRACT FROM AUTHOR]

In this work, we designed a simple and sensitive fluorescence probe for sequential detection of lysozyme and trypsin. Firstly, l-cysteine was chosen as a stabilizer to obtain l-cysteine-capped CdTe QDs. Lysozyme with positive charges can interact with l-cysteine capped CdTe quantum dots (QDs) via the special assembly between lysozyme and l-cysteine, resulting in the quenching of the fluorescence of CdTe QDs. Lysozyme can be hydrolyzed into small fragments in the presence of trypsin, and the interaction between l-cysteine-capped CdTe QDs and lysozyme would be inhibited, which could be used for trypsin quantification. There was a linear relationship between the fluorescence intensity of CdTe QDs and the lysozyme concentration in the range of 75–1000 ng mL−1 and another linear relationship between the fluorescence intensity of CdTe QDs and the logarithm of the trypsin concentration in the range of 10–500 ng mL−1. The detection limits were 28.33 ng mL−1 for lysozyme and 8.35 ng mL−1 for trypsin, respectively. The established method showed a good selectivity for lysozyme and trypsin detection. [ABSTRACT FROM AUTHOR]

We have developed a simple and efficient fluorescence detection system for lysozyme utilizing I–III–VI type Cu–In–S ternary quantum dots (CuInS2 QDs) as the probe. Water-soluble near-infrared CuInS2 QDs capped with 3-mercaptopropionic acid were directly synthesized by using a hydrothermal method. Poly(dimethyl diallyl ammonium chloride), as a cationic polyelectrolyte, could bind to 3-mercaptopropionic acid-capped CuInS2 QDs via electrostatic interactions that would lead to fluorescence quenching of CuInS2 QDs. And the addition of a lysozyme aptamer could effectively turn on the quenched fluorescence due to the stronger interaction between the cationic polyelectrolyte and negatively charged aptamer. The addition of lysozyme would result in fluorescence quenching of CuInS2 QDs again due to the specific binding between lysozyme and the lysozyme aptamer. Therefore, this label-free fluorescence system could be applied to selectively detect lysozyme. [ABSTRACT FROM AUTHOR]

Cubic silver cages were prepared on monolithic activated carbon (MAC) pre-absorbed with Cl−, SO42−, or PO43− anions. Silver insoluble salts served as templates for the morphosynthesis of silver cages. The silver ions were reduced by reductive functional groups on MAC micropores through a galvanic cell reaction mechanism. [ABSTRACT FROM AUTHOR]

A novel, rapid and highly sensitive fluorescence turn-on assay for the detection of biothiols (glutathione, and l-cysteine), histidine and threonine was developed. Water-soluble CuInS2 ternary quantum dots (QDs) capped by mercaptopropionic acid (MPA) were directly synthesized in aqueous solution, and then functionalized using tyrosine molecules to form tyrosine-functionalized CuInS2 QDs (T-CuInS2 QDs). The fluorescence of T-CuInS2 QDs would decrease in the presence of Cu2+ due to the coordination effect of phenolic hydroxyls of the tyrosine molecules. Subsequently, the addition of biothiols (glutathione and l-cysteine), histidine or threonine could turn on the fluorescence of the T-CuInS2 QDs–Cu2+ system due to their strong affinity for Cu2+. The proposed method was simple in design and fast in operation, and it was applied for the detection of glutathione, l-cysteine, histidine, and threonine in human serum samples with satisfactory results. [ABSTRACT FROM AUTHOR]

A novel sensing strategy for sequence-specific recognition of Staphylococcus aureus (S. aureus) DNA was designed based on the DNA hybridization between dye-labeled single-stranded DNA (ssDNA) and the complementary target DNA. Graphene oxide (GO) can adsorb FITC-labeled probes and quench the fluorescence efficiently via Förster resonance energy transfer (FRET). However, the formation of double-stranded DNA (dsDNA) will alter the conformation of ssDNA and disturb the interaction between GO and ssDNA. Thus the dsDNA–GO mixture exhibits a stronger fluorescence emission than that of the ssDNA–GO mixture, and the relative fluorescence intensity ΔI/I0 (ΔI = Ia−Iq) is related to the concentration of ssDNA (S. aureus DNA). Here we illustrate a “post-mixing” strategy in which the fluorescent dye-labeled DNA was allowed to hybridize with S. aureus DNA prior to the addition of GO. In this experiment, the competition between ssDNA–GO adsorption and the dsDNA formation was avoided and the incubation time was shortened to 20 min. Under the optimum conditions, the relative fluorescence intensity ΔI/I0 was proportional to the concentration of S. aureus DNA in the range 0.0125–3.125 nmol L−1, with a detection limit of 0.00625 nmol L−1 and good sequence selectivity. [ABSTRACT FROM AUTHOR]

We demonstrate here a seed-directed synthesis (SDS) of Beta, Levyne, and Heulandite zeolites in the absence of organotemplates, where the seeds drive crystallization of the zeolites. Compared with conventional Beta synthesized in the presence of organic templates, Beta-SDS exhibits large textural parameters, stable Al species, and unprecedentedly high density of active sites, resulting in superior catalytic activity and selectivity for valuable products in catalysis. [ABSTRACT FROM AUTHOR]