Longitudinal Extension of Double π-Helix Enables Near-Infrared Amplified Dissymmetry and Chiroptical Response.

Near-infrared (NIR) circularly polarized light absorbing or emitting holds great promise for highly sensitive and precise bioimaging, biosensing, and photodetectors. Aiming at designing NIR chiral molecular systems with amplified dissymmetry and robust chiroptical response, herein, we present a series of double π-helical dimers with longitudinally extended π-entwined substructures via Ullmann or Yamamoto homocoupling reactions. Circular dichroism (CD) spectra revealed an approximate linear bathochromic shift with the rising number of naphthalene subunits, indicating a red to NIR chiroptical response. Particularly, the terrylene diimide-entwined dimers exhibited the strongest CD intensities, with the maximal |Δε| reaching up to 393 M-1 cm-1 at 666 nm for th-TDI[2]; and a record-high chiroptical response (|ΔΔε|) between the neutral and dianionic species of 520 M-1 cm-1 at 833 nm for th-TDI[2]Cl was achieved upon further reduction to its dianionic state. Time-dependent density functional theory (TDDFT) calculations suggested that the pronounced intensification of the CD spectra originated from a simultaneous enhancement of both electric (µ) and magnetic (m) transition dipole moments, ultimately leading to an overall increase in the rotatory strength (R). Notably, the circularly polarized luminescence (CPL) brightness (BCPL) reached 77 M-1 cm-1 for th-TDI[2]Cl, among the highest values reported for NIR-CPL emitters. Furthermore, all chiral dianions exhibited excellent air stability under ambient conditions with half-life times of up to 10 days in N-methylpyrrolidone (NMP), which is significant for future biological applications and chiroptic switches.

Bifunctional electrocatalytic reduction performance of nitrogen containing biomass based nanoreactors loaded with Ni nanoparticles for oxygen and carbon dioxide.

In the face of increasing energy demand, the approach of transformation that combines energy restructuring and environmental governance has become a popular research direction. As an important part of electrocatalytic reactions for gas molecules, reduction reactions of oxygen (ORR) and carbon dioxide (CO2RR) are very indispensable in the field of energy conversion and storage. However, the non-interchangeability and irreversibility of electrode materials have always been a challenge in electrocatalysis. Hereon, nickel and nitrogen decorated biomass carbon-based materials (Ni/N-BC) has been prepared by high temperature pyrolysis using agricultural waste straw as raw material. Surprisingly, it possesses abundant active sites and specific surface area as a bifunctional electrocatalyst for ORR and CO2RR. The three-dimensional porous cavity structure for the framework of biomass could not only provide a strong anchoring foundation for the active site, but also facilitate the transport and enrichment of reactants around the site. In addition, temperature modulation during the preparation process also optimizes the composition and structure of biomass carbon and nitrogen. Benefit from above structure and morphology advantages, Ni/N-BC-800 exhibits the superior electrocatalytic activity for both ORR and CO2RR simultaneously. More specifically, Ni/N-BC-800 exhibits satisfactory ORR activity in terms of initial potential and half wave potential, while also enables the production of CO under high selective. The research results provide ideas for the development and design of electrode materials and green electrocatalysts, and also expand new applications of agricultural waste in fields such as energy conversion, environmental protection, and resource utilization.

Management of Triplet States in Modified Mononuclear Ruthenium(II) Complexes for Enhanced Photocatalysis.

Controlling the interplay between relaxation and charge/energy transfer processes in the excited states of photocatalysts is crucial for the performance of artificial photosynthesis. Metal-to-ligand charge-transfer triplet states (3MLCT*) of ruthenium(II) complexes are broadly implemented for photocatalysis, but an effective means of managing the triplets for enhanced photocatalysis has been lacking. Herein, We proposed a strategy to considerably prolong the triplet excited-state lifetime by decorating a ruthenium(II) phosphine complex (RuP-1) with pendent polyaromatic hydrocarbons (PAHs). Systematic studies demonstrate that in RuP-4 decorated with anthracene, sub-picosecond electron transfer from anthracene to 3MLCT* leads to a charge-separated state that can mediate the formation of the intra-ligand triplet state (3IL) of anthracene, resulting in an exceptionally long excited-state up to several milliseconds. This triplet management strategy enables impressive photocatalytic reduction of CO2 to CO with a turnover number (TON) of 404, an optimized quantum yield of 43 % and 100 % selectivity, which is the highest reported performance for mononuclear photocatalysts without additional photosensitizers. RuP-4 also catalyzes photochemical hydrogen generation under argon. This work opens up an avenue for regulating the excited-state charge/energy flow for the development of long-lived 3IL multi-functional mononuclear photocatalysts to boost artificial photosynthesis.

Red-Light Triggered H-Abstraction Photoinitiators for the Efficient Oxygen-Independent Therapy of Hypoxic Tumors.

The clinical application of photodynamic therapy (PDT) is limited by oxygen-dependence and side effects caused by photosensitizer residues. Photoinitiators based on the H-abstraction reaction can address these challenges because they can generate alkyl radical-killing cells independently of oxygen and undergo rapid bleaching following H-abstraction. Nonetheless, the development of photoinitiators for PDT has been impeded by the absence of effective design strategies. Herein, we have developed aryl-ketone substituted cyanine (ACy-R), the first red-light triggered H-abstraction photoinitiators for hypoxic cancer therapy. These ACy-R molecules inherited the near-infrared absorption of cyanine dye, and aryl-ketone modification imparted H-abstraction capability. Experimental and quantum calculations revealed that modifying the electron-withdrawing groups of the aryl (e.g., ACy-5F) improved the contribution of the O atom to the photon excitation process promoting intersystem crossing and H-abstraction ability. Particularly, ACy-5F rapidly penetrated cells and enriched in the endoplasmic reticulum. Even under severe hypoxia, ACy-5F initiated red-light induced H-abstraction with intracellular biomolecules, inducing necroptosis and ferroptosis. Moreover, ACy-5F was degraded after H-abstraction, thus avoiding the side effects of long-term phototoxicity after therapy. This study not only provides a crucial molecular tool for hypoxic tumors therapy, but also presents a promising strategy for the development of multifunctional photosensitizers and photoinitiators.

Programmable Microfluidics Enabled by 3D Printed Bionic Janus Porous Matrics for Microfluidic Logic Chips.

Numerous structures have been functionally optimized for directional liquid transport in nature. Inspired by lush trees' xylem that enable liquid directional transportation from rhizomes to the tip of trees, a new kind of programmable microfluidic porous matrices using projection micro-stereolithography (PµSL) based 3D printing technique is fabricated. Structural matrices with internal superhydrophilicity and external hydrophobicity are assembled for ultra-fast liquid rising enabled by capillary force. Moreover, the unidirectional microfluidic performance of the bionic porous matrices can be theoretically optimized by adjusting its geometric parameters. Most significantly, the successive programmable flow of liquid in a preferred direction inside the bionic porous matrices with tailored wettability is achieved, validating by a precisely printed liquid displayer and a microfluidic logic chip. The programmable and functional microfluidic matrices promise applications of patterned liquid flow, displayer, logic chip, cell screening, gas-liquid separation, and so on.

One Fluorophore-Two Sensing Films: Hydrogen-Bond Directed Formation of a Quadruple Perylene Bisimide Stack.

Elaborately designed π-stacked molecular aggregates are significant for modulation of photophysical properties of polycyclic aromatic hydrocarbons (PAHs). Herein, a double hydrogen-bonds trussed di(pyridyl)pyrrole-perylene bisimide (HDPP-PBI) was designed and its dimerization behavior was studied. HDPP-PBI tends to form a quadruple PBI stack with a dimerization constant of ∼5.56×106  M-1 . The dimerization was ascribed to synergistic intramolecular double hydrogen-bonds formation and intermolecular π-π stacking. Addition of CF3 COOH, a hydrogen bond blocker, promotes the dimer to monomer transition. Accordingly, two distinct fluorescent films were prepared by drop-casting of the dimerized or the monomeric HDPP-PBI onto a substrate surface. Interestingly, the less-emissive PBI quadruple stack-based film showed a turn on response to acetone vapor, while the highly emissive HDPP-PBI-based film exhibited fluorescence quenching upon exposure to triethylamine vapor. We believe that the discovered synergistic effect in the PBI aggregates would enlighten the design of new PAHs aggregates with defined structures.

Selective CO2 Reduction to Ethylene Over a Wide Potential Window by Copper Nanowires with High Density of Defects.

Electrochemical reduction of CO2 to ethylene using renewable electricity is an attractive approach for sustainable carbon recycling. In situ generation of defects in catalysts is found to be a promising method to guarantee high ethylene production from CO2 with high stability. In this study, copper nanowires are prepared in situ with a high density of defects for electrocatalytic CO2 reduction. These defects effectively improve C-C coupling, thus realizing a remarkable performance toward CO2 reduction to C2 products. The obtained copper nanowires showed a high selectivity of ∼79% for C2 products and >58% for C2H4. More importantly, a significantly wide potential window of 500 mV was realized for the selective production of C2H4 with FE(C2H4) >55%. Finally, in situ Raman spectroscopy revealed that Cu0 is the real reactive site for the electrocatalytic CO2 reduction reaction.

CoMo layered double hydroxide equipped with carbon nanotubes for electrocatalytic oxygen evolution reaction.

To carry out effective resource reforming of sustainable electricity, hydrogen production by electrochemical water splitting provides an eco-friendly and economical way. Nevertheless, the oxygen evolution reaction (OER) at the anode is limited by the slow reaction process, which hinders the large-scale development and application of electrolysis technology. In this work, we present an electrocatalyst with superior OER performance, which attributed to the abundant active sites and good electronic conductivity. The two-dimensional CoMo Layered Double Hydroxide nanosheets are synthesized and deposited on conductive carbon nanotubes (CoMo LDH/CNTs), and then hybrid composites show better catalytic performance than their undecorated counterpart under identical conditions. Specifically, CoMo LDH/CNTs exhibit the low overpotential of 268 mV to obtain 10 mA cm-2and satisfactory stability (more than 40 h). We emphasize that this hybridization strategy with a conductive supporting framework could design more abundant and low-cost OER electrocatalysts to minimize electrical energy consumption, thereby achieving efficient conversion between energy sources.

Through-Space Charge Transfer: A New Way to Develop a High-Performance Fluorescence Sensing Film towards Opto-Electronically Inert Alkanes.

New strategies are in high demand for fast, sensitive, selective, on-site and real-time detection of the important but challenging alkane vapors owing to their opto-electronic inertness. Herein, we report, for the first time, a high-performance fluorescent film sensor (FFS) for the alkanes with a rationally designed through-space charge transfer (TSCT) molecule as the sensing fluorophore. Steady-state fluorescence, femto-second transient absorption spectroscopy and theoretical studies revealed continuous TSCT dynamics in the excited U-shaped molecule with increasing medium polarity. Furthermore, the interlocked, face-to-face alignment between the donor and acceptor favors mass transport of the analyte molecules in the film state. As anticipated, the compound-based FFS showed an experimental detection limit of ≈10 ppm for n-pentane, less than 5 s for a full detection, negligible interference and super-stability, revealing the effectiveness of the design strategy. Notably, the sensor is small (≈3.7 cm3 ), power-saving, and workable at room temperature.

High-Performance NMHC Detection Enabled by a Perylene Bisimide-Cored Metallacycle Complex-Based Fluorescent Film Sensor.

Non-methane hydrocarbons (NMHCs) can serve as precursors of ozone and photochemical smog, and hence their highly efficient detection is of great importance for air quality monitoring. Here, we synthesized a new fluorescent perylene bisimide (PBI)-cored metallacycle complex through coordination-driven self-assembly and used it for the production of a fluorescent film sensor. The unique rectangular structure of the developed fluorophore endows the sensor with enhanced sensing performance and discriminability to n-alkanes (C5-10). Specifically, the experimental detection limits for n-pentane, n-hexane, and n-decane are 39, 7, and 1.4 mg/m3, respectively, and the corresponding linear ranges are from 39 to 2546, 7 to 1745, and 1.4 to 85 mg/m3, respectively. Moreover, the sensing is fully reversible. In tandem with a gas chromatographic separation system, the film sensor showed comparable detection ability for the n-alkanes with a commercial flame ionization detector (FID), while the film sensor needs no hydrogen; it occupies a much smaller size (30 × 30 × 44 mm3) and consumes less energy (0.215 W). Further studies demonstrated that the developed sensor can be used for on-site and real-time quantification of NHMCs, laying the foundation for developing into a portable detector.

Perylene Bisimide-Cored Supramolecular Coordination Complexes: Interplay between Ensembles, Excited State Processes, and Aggregation Behaviors.

Manipulating the optical properties of fluorescent species is challenging owing to complicated and tedious synthetic works. Herein, the photophysical properties of perylene bisimide (PBI) were effectively tuned by varying the geometrical arrangement of PBI moieties within supramolecular coordination complexes (SCCs), where a PBI-based dicycle (2) and a trigonal prism (3) were generated via using a typical 90° Pt(II) reagent, cis-(PEt3 )2 Pt(OTf)2 -based coordination-driven self-assembly approach. The ligand, an ortho-tetrapyridiyl-PBI (1), exhibits a moderate fluorescence quantum yield (∼13 %) and efficient inter-system crossing (ISC). 2, however, is much more emissive with a fluorescence quantum yield of ∼41 %, and the relevant ISC process is significantly hindered. The fluorescence quantum yield of 3 is merely ∼6 % due to the observed symmetry-breaking charge separation (SB-CS), which turns to triplet state upon charge recombination. Interestingly, 3 could be fully transformed into 2 by simply adding a suitable amount of a 90° Pt(II)-based neutral triangle. Moreover, 2 tends to form discrete dimers both in crystal and solution states, but 3 does not show the property. Therefore, controlling geometrical arrangement of fluorophores through coordination-driven self-assembly could be taken as another effective way to tune their excited state relaxation pathways and construct high-performance optical molecular materials, which generally have to be prepared via organic synthesis.

High performance benzene vapor sensor based on three-dimensional photonic crystals of zeolitic imidazolate framework-8@graphene quantum dots.

Superior sensitive, selective, and repeatable real-time detection of low concentrations of benzene vapor is vitally important for environmental protection and human health. A benzene vapor sensor using three-dimensional photonic crystals (3-D PCs) based on zeolitic imidazolate framework-8@graphene quantum dots (ZIF-8@GQDs) was proposed. The 3-D PCs were acquired by centrifuging ZIF-8@GQDs pseudo-solutions, which were prepared via hydrothermal methods. The application of the ZIF-8@GQDs 3-D PCs sensor for optical benzene vapor detection via the strong π-π stacking interactions and large specific surface area and abundant open-framework structure of the ZIF-8@GQDs was investigated. The ZIF-8@GQDs 3-D PCs sensor exhibits a more sensitive response to benzene vapor compared with the ZIF-8 3-D PCs sensor. The relationship between the wavelength shift and the benzene vapor concentration was demonstrated to be linear. Additionally, the ZIF-8@GQDs 3-D PCs sensor presents a fast optical response and recovery times of 1 s and 7 s for 200 ppm benzene vapor detection, the benzene vapor detection limit can reach 1 ppm, and the deviation of the reflected wavelength varied within 2 nm after 10 cycles. Moreover, the fabricated ZIF-8@GQDs 3-D PCs sensor exhibited reliability and exceptional thermal and long-time storage stability, demonstrating great potential for practical benzene vapor sensing applications.

NiFe Layered Double Hydroxide/FeOOH Heterostructure Nanosheets as an Efficient and Durable Bifunctional Electrocatalyst for Overall Seawater Splitting.

Electrolysis of seawater can not only desalinate seawater but also produce high-purity hydrogen. Nevertheless, the presence of chloride ions in seawater will cause electrode corrosion and also undergo a chlorine oxidation reaction (ClOR) that competes with the oxygen evolution reaction (OER). Therefore, highly efficient and long-term stable electrocatalysts are needed in this field. In this work, an advanced bifunctional electrocatalyst based on NiFe layered double hydroxide (LDH)/FeOOH heterostructure nanosheets (NiFe LDH/FeOOH) was synthesized on nickel-iron foam (INF) via a simple electrodeposition method. The NiFe LDH/FeOOH electrode demonstrates excellent electrocatalytic activity and stability, which results from the strong interaction between FeOOH and NiFe LDH. Furthermore, ex situ X-ray photoelectron spectroscopy (XPS) and in situ Raman spectroscopy revealed the catalytic process and also demonstrated that the NiFe LDH/FeOOH heterostructure could facilitate the formation of active NiOOH species in the reaction. The obtained NiFe LDH/FeOOH catalyst displays low overpotentials of 181.8 mV at 10 mA·cm-2 for hydrogen evolution reaction (HER) and 286.2 mV at 100 mA·cm-2 for OER in the 1.0 M KOH + 0.5 M NaCl electrolyte. Furthermore, it also exhibits a low voltage of 1.55 V to achieve the current density of 10 mA·cm-2 and works steadily for 105 h at 100 mA·cm-2 for overall alkaline simulated seawater splitting. This work will afford a valid strategy for designing a non-noble metal catalyst for seawater splitting.

Self-Assembled Perylene Bisimide-Cored Trigonal Prism as an Electron-Deficient Host for C60 and C70 Driven by "Like Dissolves Like".

Poor processability of fullerenes is a major remaining drawback for them to be studied monomolecularly and to find real-life applications. One of the strategies to tackle this problem is to encapsulate them within a host, which is however quite often, accompanied by significant alteration of their physical/chemical properties as encountered in chemical modification. To minimize the effect, an electron-deficient entities-based, dissolvable, and fluorescence active supramolecular host was designed and constructed via coordination-driven self-assembly of o-tetrapyridyl perylene bisimide (PBI) with cis-(PEt3)2Pt(OTf)2. The trigonal prism 1 possesses a trigonal-prismatic inner cavity with 14.7 Šas the diameter of its inscribed circle. Host-guest chemistry investigations revealed that both C60 and C70 could be quantitatively encapsulated by the host in a 1:1 ratio. Further studies demonstrated that the produced host-guest complex 1⊃C70 is significantly more stable than 1⊃C60, allowing complete transformation of the latter to the former and separation of C70 from its mixture with C60. The fullerenes in the inclusion state could rotate freely within the cavity. Electrochemistry and spectroscopy studies disclosed that the encapsulation of the guests shows little effect upon the reduction of the host and its fluorescence properties. Thus, "like dissolves like" is believed to be the main driving force for the formation of the host-guest complexes. Moreover, the host and host-guest complexes can be fabricated into monomolecular membranes using the conventional Langmuir-Blodgett technique. We propose that these unique host-guest complexes could be used as model ensembles for further studies of the physical/chemical properties of fullerenes in both single molecular and 2D membrane states. In addition, their reversible four-electron reduction property may allow them to find applications in photo/electrocatalysis, organic electronics, etc.

Manganese-Modulated Cobalt-Based Layered Double Hydroxide Grown on Nickel Foam with 1D-2D-3D Heterostructure for Highly Efficient Oxygen Evolution Reaction and Urea Oxidation Reaction.

Hydrogen production by energy-efficient water electrolysis is a green avenue for the development of contemporary society. However, the oxygen evolution reaction (OER) and the urea oxidation reaction (UOR) occurring at the anode are impeded by the sluggish reaction kinetics during the water-splitting process. Consequently, it is promising to develop bifunctional anodic electrocatalysts consisting of nonprecious metals. Herein, a bifunctional CoMn layered double hydroxide (LDH) was grown on nickel foam (NF) with a 1D-2D-3D hierarchical structure for efficient OER and UOR performance in alkaline solution. Owing to the significant synergistic effect of Mn doping and heterostructure engineering, the obtained Co1 Mn1 LDH/NF exhibits satisfactory OER activity with a low potential of 1.515 V to attain 10 mA cm-2 . Besides, the potential of the Co1 Mn1 LDH/NF catalyst for UOR at the same current density is only 1.326 V, which is much lower than those of its counterparts and most reported electrocatalysts. An urea electrolytic cell with a Co1 Mn1 LDH/NF anode and a Pt-C/NF cathode was established, and a low cell voltage of 1.354 V at 10 mA cm-2 was acquired. The optimized strategy may result in promising candidates for developing a new generation of bifunctional electrocatalysts for clean energy production.

Coordination-Driven Self-Assembled Metallacycles Incorporating Pyrene: Fluorescence Mutability, Tunability, and Aromatic Amine Sensing.

Constructing polycyclic aromatics-based, highly emissive fluorophores with good solubility and tunable aggregated structures and properties is of great importance for film fabrication, solution processing, and relevant functionality studies. Herein, we describe a general strategy to endow conventional organic fluorophores with enhanced solubility and modulated fluorescent properties via their incorporation into coordination-driven self-assembled metallacycles. A widely used fluorophore, pyrene, was decorated with two pyridyl groups to yield functionalized pyrene 4. Mixing 4 with three aromatic dicarboxylates with different lengths and a 90° Pt(II) metal acceptor in a 2:2:4 stoichiometric ratio resulted in the formation of three metallacycles, 1, 2, and 3. The metallacycles display good solubility in polar organic solvents, highly aggregation-dependent fluorescence, and size-dependent emissions at higher concentrations. Moreover, metallacycle 2-based, silica-gel-supported film as fabricated not only is more emissive than the ligand 4-based one but also displays much improved sensing properties for amines in the vapor state, as demonstrated by significantly increased response speed and decreased recovery time. The enhanced solubility, unique fluorescence behavior, and multi-factor modulation character show that coordination-driven self-assembly can be utilized for the development of new fluorophores through simple modification of conventional fluorophores. The fluorophores synthesized this way possess not only complex topological structures but also good modularity and tunability in fluorescence behavior, which are important for grafting multi-stage energy-transfer systems necessary for the development of high-performance sensing materials.

Marriage of Aggregation-Induced Emission and Intramolecular Charge Transfer toward High Performance Film-Based Sensing of Phenolic Compounds in the Air.

Film-based fluorescence sensing is recognized as one of the most optimized techniques for trace analysis of chemicals in the air after the invention of ion mobility spectrometry. The performance of the technique is highly dependent on the design of the film. This paper reports a new fluorescent film which shows unprecedented and discriminative sensing performance to the presence of phenol, o-cresol, m-cresol, and p-cresol in the air with an ultralow detection limit as low as 0.4, 0.3, 10, and 0.8 ppt, respectively. The film was designed via combination of the advantages of aggregation-induced emission (AIE) and those of intramolecular charge transfer (ICT), where the former provides the opportunity to avoid the widely encountered aggregation-caused quenching (ACQ) effect and the latter allows sensitive sensing of the microenvironment change of the film. The biggest challenge of the design is to find a fluorophore possessing both AIE and ICT effects. Fortunately, a newly synthesized biphenyl derivative of o-carborane capped with azetidine moiety (BZPCarb) shows the properties as expected. Importantly, the fluorophore is photochemically stable, a prerequirement for multiple uses of a film device. In addition, the nonplanar structure of the fluorophore is also favorable for film sensing as it could form porous films owing to screening of dense stacking of the molecules. It is the merits that make BZPCarb-based film show outstanding sensing and discriminative performances. Based on the fluorophore and the design, a conceptual high-performance fluorescent vapor sensor for phenolic compounds was developed.

Interaction between Cd and Zn on Metal Accumulation, Translocation and Mineral Nutrition in Tall Fescue (Festuca arundinacea).

Tall fescue (Festuca arundinacea), an accumulator that is able to accumulate and excrete cadmium (Cd), has attracted much attention for its possible use in phytoremediation of heavy metal contaminated soils. In the present study, the interaction between Cd and Zn, and their uptake, translocation and accumulation under external Cd and Zn treatment in tall fescue were investigated. The concentrations of K, Ca, Mg in xylem sap under Cd and Zn treatment were measured to determine the level of mineral nutrients and their relationship with Cd alleviation. The result showed that Cd and Zn antagonized each other in the roots, while Cd antagonized Zn and Zn synergized Cd in the shoots of tall fescue. Compared with Cd only treatment, the concentrations of Ca, Mg and K in xylem sap increased after the addition of Zn, and they increased the most in the guttation. This result indicated that the addition of Zn facilitates the level of mineral elements to alleviate Cd toxicity, which might be used to improve the phytoremediation efficiency of Cd contaminated soils by tall fescue.

Dynamic Chemistry-Based Sensing: A Molecular System for Detection of Saccharide, Formaldehyde, and the Silver Ion.

Development of artificial complex molecular systems is of great importance in understanding complexity in natural processes and for achieving new functionalities. One of the strategies is to create them via optimized utilization of noncovalent interactions and dynamic covalent bonds. We report here on a new complex molecular system, which was constructed by integrating the multiple interactions containing a dynamic covalent interaction between 1,2-diol and boronic acid, a coordination interaction between the silver ion and pyridyl, and an easy accessible reaction between secondary amine and formaldehyde. By employing the three dynamic interactions, a pyrene (Py) labeled fluorophore, PPB, was designed and synthesized. The compound reacts with fructose (F), a monosaccharide, in aqueous phase and produces a fluorescent adduct, PPB-F, which can be further used as a sensing platform for formaldehyde (FA) and the silver ion. The respective dynamic interactions are accompanied with color changes due to the reversible switching between Py-monomer emission and excimer emission. The respective experimental detection limits (DLs) for the three analytes are much lower than 0.2 mM, 0.1 mM, and 2.5 µM, respectively. The presence of relevant compounds or ions shows little effect upon the sensing. No doubt, the results as presented show that the integration of supramolecular interactions including dynamic covalent bonds can be employed as a general strategy to develop new functional molecular systems or materials.

Differential effects of citric acid on cadmium uptake and accumulation between tall fescue and Kentucky bluegrass.

Organic acids play an important role in cadmium availability, uptake, translocation, and detoxification. A sand culture experiment was designed to investigate the effects of citric acid on Cd uptake, translocation, and accumulation in tall fescue and Kentucky bluegrass. The results showed that two grass species presented different Cd chemical forms, organic acid components and amount in roots. The dormant Cd accumulated in roots of tall fescue was the pectate- and protein- integrated form, which contributed by 84.85%. However, in Kentucky bluegrass, the pectate- and protein- integrated Cd was only contributed by 35.78%, and the higher proportion of Cd form was the water soluble Cd-organic acid complexes. In tall fescue, citric acid dramatically enhanced 2.8 fold of Cd uptake, 3 fold of root Cd accumulation, and 2.3 fold of shoot Cd accumulation. In Kentucky bluegrass, citric acid promoted Cd accumulation in roots, but significantly decreased Cd accumulation in shoots. These results suggested that the enhancements of citric acid on Cd uptake, translocation, and accumulation in tall fescue was associated with its promotion of organic acids and the water soluble Cd-organic acid complexes in roots.