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Electrochemical oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA) is a highly promising strategy for producing biomass-based valuable chemicals. Exploration of robust and cost-effective electrocatalysts for HMF oxidation is of significant importance. Here, we proposed a facile and controllable strategy for the preparation of carbon-based heterostructures by direct pyrolysis of rationally designed precursor deep eutectic solvents. The as-prepared Co9S8–Ni3S2@N,S,O-tri-doped carbon (NSOC) heterostructures exhibit an excellent HMF electrooxidation performance with a conversion of nearly 100%, a Faraday efficiency of 98.6% and a selectivity of 98.8% owing to the unique hollow structure and ternary heterogeneous interface. X-ray photoelectron spectroscopy analysis and theoretical calculations confirm the electron transfer from Ni3S2 to NSOC and Co9S8 at the heterogeneous interfaces, where hole accumulation on Ni3S2 is beneficial for optimizing the HMF electrooxidation reaction (HMF EOR). [ABSTRACT FROM AUTHOR]

A van der Waals (vdW) magnetic tunnel junction (MTJ) comprising different two-dimensional (2D) layered materials can be used in the field of spintronics owing to its significant tunneling magnetoresistance (TMR) and spin filtering effect (SFE). In light of the elemental compatibility with the existing Si/Ge based electronic components, we designed silicane and germanane based vdW-MTJs that comprise an insulator barrier sandwiched between two half-metallic Li-adsorbed chromium triiodide (Li0.5CrI3) electrodes. We investigated the magnetic anisotropy energy (MAE), SFE and TMR of these junctions by using the density functional theory combined with the non-equilibrium Green's function method. Large MAEs of up to 10 meV per unit cell and high Curie temperatures of up to 130 K were observed for Li0.5CrI3‖Si/Ge‖Li0.5CrI3 tunnel junctions, demonstrating their robust magnetic ability against thermal fluctuations. It was observed that these two MTJs not only exhibit high TMR ratios (over 2000%) but also possess a perfect SFE (almost 100%). Moreover, an obvious negative differential resistance was observed in our systems. The transport phenomena were explained using the spin-dependent transmission coefficients at different voltages. Our results suggest that the vdW MTJs formed by the silicane/germanane barrier and Li0.5CrI3 electrodes hold promising potential for future spintronic applications, such as in read heads and spin valves. [ABSTRACT FROM AUTHOR]

A near-infrared reactive cyanine platform (probe A) was prepared by condensation of 9-chloro-1,2,3,4-tetrahydro-10-methyl-acridinium iodide with Fisher's aldehyde. A near-infrared fluorescent probe (probe B) was prepared by modifying a reactive chlorine atom of probe A with tert-butyl(2-aminoethyl)carbamate through a substitution reaction. The deprotection of the Boc group of probe B was achieved under an acidic condition, affording an amine-functionalized cyanine dye (probe C). A near-infrared ratiometric fluorescent probe (probe D) for mitochondrial pH detection was synthesized by conjugating a FRET coumarin donor to a FRET cyanine acceptor (probe C) through an amide bond connection. Probe A shows low fluorescence of 2% due to an electron-withdrawing chlorine atom, while probes B–D display high fluorescence quantum yields of 60%, 32%, and 35% in aqueous solutions containing 10% ethanol, respectively. Probes B–D show strong fluorescence with push–pull molecular structures in neutral and basic pH conditions. However, protonation of the probe's second amine at the 9-position under acidic condition disrupts the push–pull feature of the probes, resulting in fluorescence quenching of the new cyanine fluorophores. The probes can selectively stain mitochondria, while probe D was employed to detect pH changes in HeLa cells and Drosophila melanogaster first-instar larvae. [ABSTRACT FROM AUTHOR]

A near-infrared fluorescent probe (AH+) has been prepared by incorporating an oxazolidine switch into a near-infrared hemicyanine dye. The probe shows fast and sensitive responses to pH from an oxazolidine switch to the hemicyanine dye upon pH decreases from 10.0 to 5.0. The probe shows good photostability, low cytotoxicity, and reversible fluorescence responses to pH changes with a pKa value of 7.6. It has been successfully used to determine pH changes in mitochondria. [ABSTRACT FROM AUTHOR]

Two ratiometric near-infrared fluorescent probes have been developed to selectively detect mitochondrial pH changes based on highly efficient through-bond energy transfer (TBET) from cyanine donors to near-infrared hemicyanine acceptors. The probes consist of identical cyanine donors connected to different hemicyanine acceptors with a spirolactam ring structure linked via a biphenyl linkage. At neutral or basic pH, the probes display only fluorescence of the cyanine donors when they are excited at 520 nm. However, acidic pH conditions trigger spirolactam ring opening, leading to increased π-conjugation of the hemicyanine acceptors, resulting in new near-infrared fluorescence peaks at 740 nm and 780 nm for probes A and B, respectively. This results in ratiometric fluorescence responses of the probes to pH changes indicated by decreases of the donor fluorescence and increases of the acceptor fluorescence under donor excitation at 520 nm due to a highly efficient TBET from the donors to the acceptors. The probes only show cyanine donor fluorescence in alkaline-pH mitochondria. However, the probes show moderate fluorescence decreases of the cyanine donor and considerable fluorescence increases of hemicyanine acceptors during the mitophagy process induced by nutrient starvation or under drug treatment. The probes display rapid, selective, and sensitive responses to pH changes over metal ions, good membrane penetration, good photostability, large pseudo-Stokes shifts, low cytotoxicity, mitochondria-targeting, and mitophagy-tracking capabilities. [ABSTRACT FROM AUTHOR]

The development of effective solvents for lignin is of high importance. Herein, two types of novel deep eutectic solvents (DESs) were designed employing lactic acid and N-methylthiourea as hydrogen bond donors and four different quaternary ammonium salts as hydrogen bond acceptors. The designed DESs could efficiently dissolve different types of lignin, including dealkaline lignin (DAL), enzymatic hydrolysis lignin (EHL), sodium lignosulfonate (SL), and organosolv lignin (OL). The investigation of the mechanism revealed that the functional groups in the DESs significantly affected their ability to dissolve lignin, and a positive correlation was found between the solubility of lignin and the subtraction value of α and β (Kamlet–Taft empirical parameters) for the dissolution of EHL, DAL and OL. Additionally, the unique dissolution behaviour of SL was due to its salt-like structure. [ABSTRACT FROM AUTHOR]

Three near-infrared ratiometric fluorescent probes (A–C) based on TBET and FRET near-infrared rhodamine acceptors with different pKa values were designed and synthesized to achieve sensitive ratiometric visualization of pH variations in lysosomes in visible and near-infrared channels. Tetraphenylethene (TPE) was bonded to near-infrared rhodamine dyes through short electrical π-conjugation linkers to prevent an aggregation-caused quenching (ACQ) effect and allow highly efficient energy transfer of up to 98.9% from TPE donors to rhodamine acceptors. Probes A–C respond to pH variation from 7.4 to 3.0 in both buffer solutions and live cells with significant decreases of donor fluorescence and concomitant extraordinary increases of rhodamine acceptor fluorescence because of highly efficient energy transfer. In addition, probe C is capable of determining pH fluctuations in live cells treated with chloroquine. The probes show good photostability, excellent cell membrane permeability, high selectivity to pH, and two well-resolved emission peaks to ensure accurately comparative and quantitative analyses of intracellular pH changes. [ABSTRACT FROM AUTHOR]

New near-infrared rhodamine dyes with large Stokes shifts were developed and applied for sensitive detection of cellular pH changes and fluctuations by incorporating an additional amine group with fused rings into the rhodamine dyes to enhance the electron donating ability of amine groups and improve the spectroscopic properties of the dyes. [ABSTRACT FROM AUTHOR]

Novel stimuli-responsive microscale materials capable of undergoing diverse out-of-plane helical motions (e.g., bending, twisting and coiling) when exposed to electron irradiation are reported. The macroscopic morphological changes of microribbons induced by electrons arise from the combination of diagonal in-plane, non-bonded distortion relative to the long axis of the microribbon and vertical non-bonded distortion. [ABSTRACT FROM AUTHOR]

Highly fluorescent and photoconductive nanoribbons assembled from an asymmetric perylene diimide (PDI) were used as a dual-mode sensor for sensitive and selective discrimination of two classes of organic amines in the vapor phase, i.e., alkyl amines and aromatic amines. [ABSTRACT FROM AUTHOR]

Highly fluorescent bilayer nanotubes with a right- or left-handed helical sense were assembled from a chiral asymmetric perylene diimide for the first time, which constitute a new family member of self-assembled organic nanotubes. [ABSTRACT FROM AUTHOR]

Different from the conventional piezochromic materials with a mono-redshift of single emission, our well-designed molecule demonstrates a sensitive turn-on and color-tunable piezochromic luminescence in response to the hydrostatic pressure. The molecule PXZ-W-SOF possesses dual-emission and pressure-induced bidirectional shifting characteristics. On the basis of in-depth experimental studies, on one hand, it is confirmed that the origin of the dual-emission behavior is the intramolecular charge transfer, namely thermally activated delayed fluorescence (TADF), and the intermolecular excimer; on the other hand, the emission of the excimer exhibits three-step variations with increasing pressure, which is mainly attributed to the molecular structure and its crystal packing state. The remarkable color change of PXZ-W-SOF from sky-blue to green to deep-blue during the whole process of boosting and releasing pressure is a result of intramolecular and intermolecular energy-transfer interactions. The PXZ-W-SOF molecular model is an extremely rare example of highly sensitive fluorescence tuning driven by TADF and excimer conversion under mechanical stimulation, thus providing a novel mechanism for the field of piezochromism. The unique molecular design also offers a new idea for rare deep-blue and ultraviolet TADF materials., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

In the pursuit of designing van der Waals magnetic tunneling junctions (vdW-MTJs) with two-dimensional (2D) intrinsic magnets, as well as to quantitatively reveal the microscopic nature governing the vertical tunneling pathways beyond the phenomenological descriptions on CrI 3 -based vdW-MTJs, we investigate the structural configuration, electronic structure and spin-polarized quantum transport of graphene|2 monolayer(2ML)-CrI 3 |graphene heterostructure with Ag(111) layers as the electrode, using density functional theory (DFT) and its combination of non-equilibrium Green's function (DFT-NEGF) methods. The in-plane lattice of CrI 3 layers is found to be stretched when placed on the graphene (Gr) layer, and the layer-stacking does not show any site selectivity. The charge transfer between CrI 3 and Gr layers make the CrI 3 layer lightly electron-doped, and the Gr layer hole-doped. Excitingly, the inter-layer hybridization between graphene and CrI 3 layers render the CrI 3 layer metallic in the majority spin channel, giving rise to an insulator-to-half-metal transition. Due to the metallic/insulator characteristics of the spin-majority/minority channel of the 2ML-CrI 3 barrier in vdW-MTJs, Gr|2ML-CrI 3 |Gr heterostructures exhibit an almost perfect spin filtering effect (SFE) near the zero bias in parallel magnetization, a giant tunneling magnetoresistance (TMR) ratio up to 2 × 10 4 %, and remarkable negative differential resistance (NDR). Our results not only give an explanation for the observed giant TMR in CrI 3 -based MTJs but also show the direct implications of 2D magnets in vdW-heterostructures., Competing Interests: All authors declare that they have no conflicts of interest., (This journal is © The Royal Society of Chemistry.)

Three near-infrared ratiometric fluorescent probes ( A-C ) based on TBET and FRET near-infrared rhodamine acceptors with different p K a values were designed and synthesized to achieve sensitive ratiometric visualization of pH variations in lysosomes in visible and near-infrared channels. Tetraphenylethene (TPE) was bonded to near-infrared rhodamine dyes through short electrical π -conjugation linkers to prevent an aggregation-caused quenching (ACQ) effect and allow highly efficient energy transfer of up to 98.9% from TPE donors to rhodamine acceptors. Probes A-C respond to pH variation from 7.4 to 3.0 in both buffer solutions and live cells with significant decreases of donor fluorescence and concomitant extraordinary increases of rhodamine acceptor fluorescence because of highly efficient energy transfer. In addition, probe C is capable of determining pH fluctuations in live cells treated with chloroquine. The probes show good photostability, excellent cell membrane permeability, high selectivity to pH, and two well-resolved emission peaks to ensure accurately comparative and quantitative analyses of intracellular pH changes., Competing Interests: Conflicts of interest There are no conflicts to declare.

Highly fluorescent bilayer nanocoils assembled from an asymmetric perylene diimide molecule exhibit unprecedented sensitivity to trace amines, that is, three orders of magnitude greater than our previously reported solid nanofibers. The coiled nanostructure design for new sensing materials offers a novel option for optimizing the sensitivities of fluorescence sensors based on organic nanomaterials.