A Fluorescence Biosensor Based on Carbon Quantum Dots Prepared from Pomegranate Peel and T-Hg2+-T Mismatch for Hg2+ Detection.

Mercury ions (Hg2+) can cause damage to human health, and thus, the study of the detection of Hg2+ is extraordinarily important in daily life. This work reported a fluorescence biosensor for the detection of Hg2+. The key point of this strategy was that the fluorescence of carbon quantum dots made from pomegranate peel (P-CQDs) was quenched by hemin, and restored after G-quadruplex binding with hemin. The presence of Hg2+ caused thymine (T)-rich DNA fragments to form T-Hg2+-T mismatches, and this change allowed the release of G-quadruplex. G-quadruplex could change the fluorescence of hemin/P-CQDs. P-CQDs exhibited excellent properties through characterization analysis, such as transmission electron microscope, X-ray photoelectron spectroscopy and Fourier transform infrared. This proposed fluorescence detection strategy established the linear ranges of Hg2+ from 1 nM to 50 nM. In conclusion, this simple biosensor had the advantages of strong sensitivity, high selectivity, and low cost for Hg2+ detection in environmental water samples.

Self-Assembly of Amphiphilic PDI and NDI Derivatives with Opposite Thermoresponsive Fluorescent Behaviors in Aqueous Solution.

This work presents a study of the thermally induced aggregation of perylene diimide (PDI) and naphthalene diimide (NDI) derivatives modified with oligo ethylene glycol (OEG) chains in aqueous solution. Water-soluble and flexible OEG side chains were introduced into the π-core of glutamate-modified NDI and PDI structures, and the aggregation process was modulated by heating or cooling in water. Interestingly, a rare opposite temperature response of fluorescent behavior from the two amphiphilic chromophores was revealed, in which the PDI exhibited fluorescent enhancement, while fluorescent quenching upon temperature increase was observed from the NDI assembly. The mechanism of thermally induced aggregation is clearly explained by studies with various spectroscopic techniques including UV-visible, fluorescence, 1H NMR, 2D NMR spectroscopy, and SEM observation as well as control experiments operated in DMSO solution. It is found that although similar J-aggregates were formed by both amphiphilic chromophores in aqueous solution, the temperature response of the aggregates to temperature was opposite. The degree of PDI aggregation decreased, while that of NDI increased upon temperature rising. This research paves a valuable way for understanding the complicated supramolecular behaviors of amphiphilic chromophores.

Boosting the Faraday Efficiency of Electrochemical Ammonia Synthesis via the Strain Effect Induced by Interfacial Hybrid Formation between BN and Carbon Nanotubes.

The electrochemical nitrogen reduction reaction (eNRR) is a highly promising alternative to the Haber-Bosch (H-B) process, but its commercial development is limited by the high bond energy of N2 molecules and the presence of the competitive hydrogen evolution reaction (HER). Here, a metal-free composite electrocatalyst of boron nitride (h-BNNs) and carbon nanotubes (CNTs) was explored through the interfacial hybridization of h-BNNs and CNTs, which showed a highly improved eNRR Faraday efficiency (FE) of 63.9% and an NH3 yield rate of 36.5 µg h-1 mgcat.-1 at -0.691 V (vs RHE). New chemical bonds of C-B and C-N were observed, indicating a strong interaction between CNTs and h-BNNs. According to the Raman spectra and the optimized model of h-BNNs/CNTs, an obvious strain effect between h-BNNs and CNTs was supposed to play a significant role in the highly improved FE, compared with the FE of h-BNNs alone (4.7%). Density functional theory (DFT) calculations further showed that h-BNNs/CNTs had lower energy barriers in eNRR, giving them higher N2 to NH3 selectivity, while h-BNNs have lower energy barriers in the HER. This work shows the important role of the strain effect in boosting the selectivity in the eNRR process.

Heat-Set Supramolecular Hydrogelation by Regulating the Hydrophilic-Lipophilic Balance for a Tunable Circularly Polarized Luminescent Switch.

Heat-set supramolecular gels exhibited totally opposite phase behaviors of dissolution upon cooling and gelation on heating. They are commonly discovered by chance and their rational design remains a great challenge. Herein, a rational design strategy is proposed to realize heat-set supramolecular hydrogelation through regulation of the hydrophilic-lipophilic balance of the system. A newly synthesized amphiphile hydrogelator with pyrene embedded in its lipophilic terminal can self-assemble into a hydrogel through a heating and cooling cycle. However, the host-guest complex of the gelator and hydrophilic γ-cyclodextrin (γ-CyD) results in a sol at room temperature. Thus, heat-set hydrogelation is realized from the sol state in a controllable manner. Heat-set gelation mechanism is revealed by exploring critical heat-set supramolecular gelation and the related findings provide a general strategy for developing new functional molecular gels with tunable hydrophilic-lipophilic balance.

Elucidation of interactions between myofibrillar proteins and κ-carrageenan as mediated by NaCl level: Perspectives on multiple spectroscopy and molecular docking.

The present study was aimed to investigate the intermolecular interaction between myofibrillar proteins (MP) and κ-carrageenan (KC) as mediated by KC concentration (0.1, 0.2, 0.3, and 0.4 %, w/w) and NaCl levels (0.3 and 0.6 M) based on the multiple spectroscopy and molecular docking. The results showed that the incorporation of KC increased the turbidity, zeta-potential, and surface hydrophobicity of MP-KC mixed sols with a dose-dependent manner, as well as significantly decreasing the protein solubility (P < 0.05), which indicated that the interaction between KC and MP promoted the expansion of protein structure and exposed more hydrophobic groups. Fluorescence spectra result revealed that the interaction between MP and KC was a static quenching in the fluorescence quenching process, which affected the aromatic amino acids residue microenvironment of MP. Moreover, the existence of KC decreased the α-helix contents of MP (P < 0.05), contributing to the transformation from random structure to organized configuration of MP. In addition, molecular forces, the molecular docking and thermodynamic parameters indicated that hydrophobic interactions, van der Waals force, and hydrogen bonding were considered as the main interaction forces between MP and KC. Furthermore, 0.6 M NaCl level rendered higher solubility and particle size, as well as lower turbidity and the surface hydrophobicity of MP-KC mixed sols than those with 0.3 M NaCl level (P < 0.05), which promoted the unfolding of MP molecule and subsequently increased the numbers of binding sites between MP and KC, facilitating the intermolecular interactions between MP and KC in mixed sols.

Supramolecular Adhesives with Extended Tolerance to Extreme Conditions via Water-Modulated Noncovalent Interactions.

Development of supramolecular adhesives with strong tolerance to extreme conditions has emerged as an important research area. In this study, by balancing supramolecular interactions such as hydrogen bonding interactions, electrostatic interactions, π-π stacking interactions, and cation-π interactions, we designed and prepared a series of two-component supramolecular adhesives derived from small organic molecules. Highly efficient interfacial adhesion with maximum adhesion strength of ≈10.0 MPa was realized on various surfaces in air, organic solvents, or liquid nitrogen. Owing to balanced supramolecular interactions, water participation prolonged and increased the tolerance of the adhesives in extreme environments. We demonstrate that the combination of imidazole-based ionic liquids and phenols can be applied for various interfacial adhesions, thereby aiding the development of next-generation adhesives capable of adapting to various extreme conditions in a controlled manner.

Strong Dynamic Interfacial Adhesion by Polymeric Ionic Liquids under Extreme Conditions.

Interfacial adhesion under extreme conditions has attracted increasing attention owing to its potential application of stopping leakages of oil or natural gas. However, interfacial adhesion is rarely stable at ultralow temperatures and in organic solvents, necessitating the elucidation of the molecular-level processes. Herein, we used the intermolecular force-control strategy to prepare four linear polymers by tuning the proportion of hydrogen bonding and the number of electrostatic sites. The obtained polymeric ion liquids displayed strong dynamic adhesion at various interfaces. They also efficiently tolerated organic solvents and ultracold temperatures. Highly reversible rheological behaviors are observed within a thermal cycle between high and ultracold temperatures. Temperature-dependent infrared spectra and theoretical calculation reveal thermal reversibility and interfacial adhesion/debonding processes at the molecular level, respectively. This intermolecular force-control strategy may be applied to produce environmentally adaptive functional materials for real applications.

Tuning Rheological Behaviors of Supramolecular Aqueous Gels via Charge Transfer Interactions.

Rheological properties are critical for determining real applications of supramolecular gels in various fields. Correspondingly, the modulation of gel rheology will be very important for meeting real requirements. In this aspect, a few strategies were applied to tune the rheological behaviors of supramolecular gels, but some specific interactions like charge transfer (CT) interactions were less explored at the molecular level. Herein, we report a pyrene-containing derivative of diphenylalanine as a donor gelator and naphthalenediimide or 3,5-dinitrobenzene as matching acceptor molecules. It was found that the viscoelastic properties and strength of the original gel could be tuned through addition of different acceptor molecules to the original gel with changing the ratios of the selected acceptor molecules. As a result, storage modulus was continuously adjusted over a wide range from 190,000 to 50,000 Pa by CT interactions. Furthermore, the mechanism of the CT-induced change in rheological properties was understood and clarified through relevant techniques (e.g., UV-Vis, fluorescence, and FT-IR spectroscopy and TEM). The findings in this work would provide a novel strategy to modulate the rheological properties of supramolecular gels for adaption to broader fields of real applications.

Evaluation and Treatment Analysis of Air Quality Including Particulate Pollutants: A Case Study of Shandong Province, China.

At present, China's air pollution and its treatment effect are issues of general concern in the academic circles. Based on the analysis of the development stages of air pollution in China and the development history of China's air quality standards, we selected 17 cities of Shandong Province, China as the research objects. By expanding China's existing Air Quality Index System, the air quality of six major pollutants including PM2.5 and PM10 in 17 cities from February 2017 to January 2020 is comprehensively evaluated. Then, with a forecast model, the air quality of the above cities in the absence of air pollution control policies since June 2018 was simulated. The results of the error test show that the model has a maximum error of 4.67% when simulating monthly assessment scores, and the maximum mean error of the four months is 3.17%. Through the comparison between the simulation results and the real evaluation results of air quality, we found that since June 2018, the air pollution control policies of six cities have achieved more than 10% improvement, while the air quality of the other 11 cities declined. The different characteristics of pollutants and the implementation of governance policies are perhaps the main reasons for the above differences. Finally, policy recommendations for the future air pollution control in Shandong and China were provided.

Functionalized Superwettable Fabric with Switchable Wettability for Efficient Oily Wastewater Purification, in Situ Chemical Reaction System Separation, and Photocatalysis Degradation.

In view of the increasing serious water environmental and human health issues caused by oily wastewater, functional superwetting materials with controllable wettability, high durability, and scale preparation methods are highly desired for efficient oil/water separation. In this respect, a pH-responsive multifunctional fabric with switchable surface wettability, favorable mechanical durability, and self-repairing property has been developed via decorating the modified TiO2 nanoparticles of special surface compositions onto the fabric surface. By virtue of the intelligent surface wettability, the resulted superwettable fabric can be used for controllable separation of multiple oil/water mixtures, particularly the complicated oil/water/oil ternary mixtures, showing excellent separation efficiency and high filtration flux even under extreme pH conditions, which is comparable to most of the commercial and currently reported functionalized membranes. Simultaneously, the negative pressure-driven, continuous, high-speed, and highly efficient in situ purification of large volumes of oily wastewater is successfully achieved based on the resulted superwettable fabric. More importantly, with the as-prepared superwettable fabric as the filtration membrane, the continuous in situ separation of the synthetic oily product from the corresponding chemical reaction systems is well performed without interruption of the reaction, demonstrating outstanding merits of simplifying procedures, saving operation time, and increasing product yield. In addition, it is worth noting that the alkali-treated superhydrophilic fabric presents superior photocatalysis self-cleaning performance for various water-soluble organic pollutants. These unique advantages of the functionalized smart superwettable fabric ensure that it can be competent in multifarious relevant challenging settings, indicating a broad prospect for diverse practical applications, especially the oily wastewater treatment and multiple industrial operation optimizations.

Assembly of Copper Phthalocyanine on TiO2 Nanorod Arrays as Co-catalyst for Enhanced Photoelectrochemical Water Splitting.

A photoelectrochemical device was achieved by interfacial self-assembly of macrocyclic π-conjugated copper phthalocyanine (CuPc) on surface of TiO2 nanorod arrays (NRs). The photocurrent density of the elegant TiO2@CuPc NRs photoanode reaches 2.40 mA/cm2 at 1.23 V vs. RHE under the illumination of 100 mW/cm2 from AM 1.5G sun simulator, which is 2.4 times higher than that of the pure TiO2. At the same time, the photoelectrochemical device constructed through this strategy has good stability and the photocurrent density remain almost no decline after 8 h of continuous operation. The Mott-Schottky and LSV curves demonstrate that CuPc act as a co-catalyst for water oxidation and a possible mechanism is proposed for water oxidation based on careful analysis of the detailed results. The holes from VB of TiO2 photogenerated by electrons exciting are consumed by a process in which Cu2+ is oxidized to Cu3+ and Cu4+, and then oxidize water to produce oxygen. CuPc species is considered to be a fast redox mediator to reduce the activation energy of water oxidation in and effectively promote charge separation.

(R)-Binaphthyl derivatives as chiral dopants: substituent position controlled circularly polarized luminescence in liquid crystals.

A series of nonbridged axially chiral binaphthyl derivatives were synthesized and used as chiral dopants for chiral nematic liquid crystals (N*-LCs). It was found that binaphthyl derivatives substituted at 3,3' positions or 2,2' positions of binaphthyl rings could induce N*-LCs to show opposite circularly polarized luminescence (CPL) signals, despite having the same configuration. Additionally, a CPL switch could be constructed in these N*-LCs regulated by the applied electric field.

Homochiral nanotubes from heterochiral lipid mixtures: a shorter alkyl chain dominated chiral self-assembly.

It is an important topic to achieve homochirality both at a molecular and supramolecular level. While it has long been regarded that "majority rule" guides the homochiral self-assembly from an enantiomer mixture, it still remains a big challenge to manipulate the global homochirality in a complex system containing chiral species that are not enantiomers. Here, we demonstrate a new example wherein homochiral nanotubes self-assembled from a mixture of heterochiral lipids that deviated from the "majority rule". We have found that when two heterochiral lipids with mirror headgroups but a 2-methylene discrepancy in alkyl chain length are mixed, homochiral nanotubes are always formed regardless of their mixing ratio. Remarkably, the helicity of the nanotube is exclusively controlled by the molecular chirality of the lipids with shorter alkyl chains, i.e., the chiral self-assembly was dominated by the lipid with the shorter alkyl chain. MD simulation reveals that the match of both the alkyl chain length and hydrogen-bonding between two kinds of lipids plays an important role in the assembly. This work provides a new insight into the supramolecular chirality of complex systems containing multi chiral species.

Optically Active Upconverting Nanoparticles with Induced Circularly Polarized Luminescence and Enantioselectively Triggered Photopolymerization.

In this work, lanthanide-doped upconversion nanoparticles (UCNPs) showing upconverted circularly polarized luminescence were demonstrated in an organic-inorganic co-assembled system. Achiral UCNPs (NaYF4:Yb/Er or NaYF4:Yb/Tm) can be encapsulated into chiral helical nanotubes through the procedure of co-gelation. These co-gel systems display intense upconverted circularly polarized luminescence (UC-CPL) ranging from ultraviolet (UV, 300 nm) to near-infrared (NIR, 850 nm) wavelength. In addition, the UV part of UC-CPL can be used to initiate the enantioselective polymerization of diacetylene.

Long-Persistent Circularly Polarized Phosphorescence from Chiral Organic Ionic Crystals.

Long-persistent circularly polarized phosphorescence (LPCPP) is achieved for the first time in chiral organic ionic crystals at room temperature. The co-crystal composed of terephtalic acid (TPA) and chiral α-phenylethyamines (PEAs) gave rise to LPCPP with lifetimes up to 862 ms and large dissymmetric factor (glum ). The hybridization of TPA with chiral PEAs allows circular polarization of the generated long-persistent phosphorescence. The observed mirror-image twisted molecular structures in the rigid lattices were responsible for the chiroptical activation of the generated long-persistent phosphorescence.

Endowing Perovskite Nanocrystals with Circularly Polarized Luminescence.

Perovskite nanocrystals are attracting great interest due to their excellent photonic properties. Here, through a supramolecular self-assembly approach, the perovskite nanocrystals (NCs) with a novel circularly polarized luminescence (CPL) are successfully endowed. It is found that the achiral perovskite NCs can coassemble with chiral gelator in nonpolar solvents, in which the gelator molecules modify the surface of the perovskite NCs. Through such cogelation, the molecular chirality can transfer to the NCs resulting in CPL signals with a dissymmetric factor (glum ) up to 10-3 . Furthermore, depending on the molecular chirality of the gelator, the CPL sense can be selected and the mirror-imaged CPL is obtained. Such gels can be further embedded into the polymer film to facilitate flexible CPL devices. It is envisaged that this approach will afford a new insight into the designing of the functional chiroptical materials.

Solvent-Regulated Self-Assembly of an Achiral Donor-Acceptor Complex in Confined Chiral Nanotubes: Chirality Transfer, Inversion and Amplification.

A chiral gelator was designed and found to form chiral nanotwists and nanotubes in toluene and DMSO, respectively, which could serve as host chiral matrices for fabricating functional soft materials. Achiral, π-conjugated donor and acceptor guests were doped into the gel, and solvent-regulated self-assembly was observed. Although both the DMSO and toluene gels containing three components look similar as transparent gels, it was clarified microscopically that, whereas achiral dopants self-assemble in the confined nanotubes in the DMSO gel, they only dissolve in the liquid phase in the toluene gel. The existence of the achiral donor and acceptor in different phases made their properties completely different. Chirality transfer occurred from the host chiral gel matrixes to guest achiral porphyrin in DMSO. Remarkably, the addition of C60 to the porphyrin/gelator gel could invert and further amplify the induced chirality of the porphyrin due to the formation of donor-acceptor pairs. On the other hand, no chirality transfer was observed in the toluene gel. These observations clearly unveiled the selective self-assembly of different components in distinct gel phases, which could provide new insight into the design of chiroptical soft materials.

Hierarchically branched Fe2O3@TiO2 nanorod arrays for photoelectrochemical water splitting: facile synthesis and enhanced photoelectrochemical performance.

Highly photoactive and durable photoanode materials are the key to photoelectrochemical water splitting. In this paper, hierarchically branched Fe2O3@TiO2 nanorod arrays (denoted as Fe2O3@TiO2 BNRs) composed of a long Fe2O3 trunk and numerous short TiO2 nanorod branches were fabricated and used as photoanodes for water splitting. Significant improvement of photoelectrochemical water splitting performance was observed based on Fe2O3@TiO2 BNRs. The photocurrent density of Fe2O3@TiO2 BNRs reaches up to 1.3 mA cm(-2) at 1.23 V versus RHE, which is 10 times higher than that of pristine Fe2O3 nanorod arrays under the same conditions. Furthermore, an obvious cathodic shift in the onset potential of photocurrent was observed in the Fe2O3@TiO2 BNRs. More significantly, the Fe2O3@TiO2 BNRs are quite stable even after 3600 s continuous illumination, and the photocurrent density shows almost no decay. Finally, a tentative mechanism was proposed to explain the superior performance of Fe2O3@TiO2 BNRs for PEC water splitting and discussed in detail on the basis of our experimental results.

Construction of inorganic-organic 2D/2D WO3/g-C3N4 nanosheet arrays toward efficient photoelectrochemical splitting of natural seawater.

Hydrogen production from seawater and solar energy based on photoelectrochemical cells is extremely attractive due to earth-abundance of seawater and solar radiation. Herein, we report the successful fabrication of novel inorganic-organic 2D/2D WO3/g-C3N4 nanosheet arrays (WO3/g-C3N4 NSAs) grown on a FTO substrate via a facile hydrothermal growth and deposition-annealing process, and their application in natural seawater splitting. The results indicate that the WO3/g-C3N4 NSAs exhibit a photocurrent density of 0.73 mA cm(-2) at 1.23 V versus RHE under AM 1.5G (100 mW cm(-2)) illumination, which is 2-fold higher than that of WO3 NSAs. More importantly, the WO3/g-C3N4 NSA photoanode is quite stable during seawater splitting and the photocurrent density does not substantially decrease after continuous illumination for 3600 s. The remarkably enhanced performance originates primarily from the formation of the WO3/g-C3N4 heterojunction between WO3 and g-C3N4 nanosheets, which accelerates charge transfer and separation, and prolongs the lifetime of electrons as demonstrated by EIS and Mott-Schottky analyses. Finally, a possible mechanism for the improved performance was proposed and discussed.

Microstructured graphene arrays for highly sensitive flexible tactile sensors.

A highly sensitive tactile sensor is devised by applying microstructured graphene arrays as sensitive layers. The combination of graphene and anisotropic microstructures endows this sensor with an ultra-high sensitivity of -5.53 kPa(-1) , an ultra-fast response time of only 0.2 ms, as well as good reliability, rendering it promising for the application of tactile sensing in artificial skin and human-machine interface.