Quantum-Sized Co Nanoparticles with Rich Vacancies Enabled the Uniform Deposition of Lithium Metal and Fast Polysulfide Conversion.

The notorious polysulfide shuttling and uncontrollable Li-dendrite growth are the main obstacles to the marketization of Li-S batteries. Herein, a dual-functional material consisting of vacancy-rich quantum-sized Co nanodots anchored on a mesoporous carbon layer (v-Co/meso-C) is proposed. This material exposes more active sites to improve its reaction performance and simultaneously realizes excellent lithiophilicity and sulfiphilicity characteristics in Li-S electrochemistry. As Li metal deposition hosts, v-Co/meso-C shows small nucleation overpotential, low polarization, and ultra-long cycling stability in both half and symmetric cells, as confirmed by experimental studies. On the S cathode side, experimental and theoretical calculations demonstrate that v-Co/meso-C enhances the adsorption of polysulfides and boosts their catalytic conversion rate. This, in turn, suppresses the shuttle effect of polysulfides and improves sulfur utilization efficiency. Finally, a shuttle-free and dendrite-free v-Co/meso-C@Li//v-Co/meso-C@S full cell is fabricated, exhibiting excellent rate performance (739 mAh g-1 at 5.0 C) and good cyclability (capacity decay rate is 0.033% and 0.035% per cycle at 2.0 and 5.0 C, respectively). Even a pouch cell with high sulfur loading (5.5 mg cm-2) and lean electrolyte/sulfur (4.8 µL mg-1) can still work 50 cycles with 80% capacity retention rate. This study shows far-reaching implications in the design of dendrite-free, shuttle-free Li-S batteries.

In Situ Construction of Zinc-Mediated Fe, N-Codoped Hollow Carbon Nanocages with Boosted Oxygen Reduction for Zn-Air Batteries.

The rational design of bifunctional oxygen electrocatalysts with unique morphology and luxuriant porous structure is significant but challenging for accelerating the reaction kinetics of rechargeable Zn-air batteries (ZABs). Herein, zinc-mediated Fe, N-codoped carbon nanocages (Zn-FeNCNs) are synthesized by pyrolyzing the polymerized iron-doped polydopamine on the surface of the ZIF-8 crystal polyhedron. The formation of the chelate between polydopamine and Fe serves as the covering layer to prevent the porous carbon nanocages from collapsing and boosts enough exposure and utilization of metal-based active species during carbonization. Furthermore, both the theoretical calculation and experimental results show that the strong interaction between polyhedron and polydopamine facilitates the evolution of high-activity zinc-modulated FeNx sites and electron transportation and then stimulates the excellent bifunctional catalytic activity for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). As expected, the Zn-air battery with Zn-FeNCNs as an air cathode displays a superior power density (256 mW cm-2) and a high specific capacity (813.3 mA h gZn-1), as well as long-term stability over 1000 h. Besides, when this catalyst is applied to the solid-state battery, the device exhibited outstanding mechanical stability and a high round-trip efficiency under different bending angles.

Construction of a Reversible Solid-state Fluorescence Switching Via Photochromic Diarylethene and Si-ZnO Quantum Dots.

Developing fluorescence switching as functional system is highly desirable for potential applications in the fields of light-responsive materials or devices. Attempt to construct fluorescence switching system tend to focus on the high fluorescence modulation efficiency, especially in solid state. Herein, a photo-controlled fluorescence switching system was constructed with photochromic diarylethene and trimethoxysilane modified zinc oxide quantum dots (Si-ZnO QDs) successfully. It was verified by the measurement of modulation efficiency, fatigue resistance as well as theoretical calculation. Upon irradiation with UV/Vis lights, the system exhibited excellent photochromic property and photo-controlled fluorescence switching performance. Furthermore, the excellent fluorescence switching characters could also be realized in solid state and the fluorescence modulation efficiency was determined to be 87.4%. The results will provide new strategies to the construction of reversible solid-state photo-controlled fluorescence switching for the application in the fields of optical data storage and security labels.

Preparation and Application of a Sulfur-Doped Fluorescent Carbon Dots with Aggregation-Induced Emission Character.

As a new type of zero-dimensional nanomaterial, carbon dots are widely applied in various fields. However, most of the carbon dots have aggregation fluorescence quenching properties, which limited their practical applications. In this study, a novel sulfur-doped carbon dots (S-CDs) was prepared by solvothermal method. The properties of the S-CDs in ethanol solution and in solid state were investigated respectively. The results showed that the S-CDs have an excited wavelength dependent emission of blue fluorescence in ethanol solution, and have orange fluorescence emission in solid state and composite films, indicating the prepared S-CDs has aggregation-induced emission (AIE) performance. The main reason was that the presence of S-S bonds and the intramolecular rotation of aromatic rings were limited in solid state, resulting in its emission of orange fluorescence. Furthermore, the S-CDs could be applied to identify fingerprints, anti-counterfeiting.

Two Birds with One Stone: Micro/Nanostructured SiOx Cy Composites for Stable Li-Ion and Li Metal Anodes.

Developing stable silicon-based and lithium metal anodes still faces many challenges. Designing new highly practical silicon-based anodes with low-volume expansion and high electrical conductivity, and inhibiting lithium dendrite growth are avenues for developing silicon-based and lithium metal anodes, respectively. In this study, SiOx Cy microtubes are synthesized using a chemical vapor deposition method. As Li-ion battery anodes, the as-prepared SiOx Cy not only combines the advantages of nanomaterials and the practical properties of micromaterials, but also exhibits high initial Coulombic efficiency (80.3%), low volume fluctuations (20.4%), and high cyclability (98% capacity retention after 1000 cycles). Furthermore, SiOx Cy , as a lithium deposition substrate, can effectively promote the uniform deposition of metallic lithium. As a result, low nucleation overpotential (only 6.0 mV) and high Coulombic efficiency (≈98.9% after 650 cycles, 1.0 mA cm-2 and 1.0 mAh cm-2 ) are obtained on half cells, as well as small voltage hysteresis (only 9.5 mV, at 1.0 mA cm-2 ) on symmetric cells based on SiOx Cy . Full batteries based on both SiOx Cy and SiOx Cy @Li anodes demonstrate great practicality. This work provides a new perspective for the simultaneous development of practical SiOx Cy and dendrite-free lithium metal anodes.

A photo-controlled fluorescent switching based on carbon dots and photochromic diarylethene for bioimaging.

Carbon dots (CDs) as luminescent zero-dimensional carbon nanomaterials have good aqueous dissolution, photostability, high quantum yield, and tunability of emission color. It has great application potential in many fields, including bioimaging, labeling of biological species, drug delivery, and sensing in biomedical. However, controlling the fluorescence emission of carbon dots remains a formidable challenge. Herein, we designed and exploited a photo-controlled fluorescent switching based on photochromic diarylethene (DT) and CDs for bioimaging. It could be modulated reversibly between "ON" and "OFF" under UV/vis light exposure. The fluorescent modulation efficiency was as high as 95.3%. The fluorescent switching could be used to the bioimaging in HeLa cells with low cell toxicity. Therefore, this fluorescent switching could be a promising candidate in many potential application areas, especially in bioimaging.

Single-Atom Pt Anchored on Oxygen Vacancy of Monolayer Ti3C2Tx for Superior Hydrogen Evolution.

Two-dimensional (2D) MXene-loaded single-atom (SA) catalysts have drawn increasing attention. SAs immobilized on oxygen vacancies (OV) of MXene are predicted to have excellent catalytic performance; however, they have not yet been realized experimentally. Here Pt SAs immobilized on the OV of monolayer Ti3C2Tx flakes are constructed by a rapid thermal shock technique under a H2 atmosphere. The resultant Ti3C2Tx-PtSA catalyst exhibits excellent hydrogen evolution reaction (HER) performance, including a small overpotential of 38 mV at 10 mA cm-2, a high mass activity of 23.21 A mgPt-1, and a large turnover frequency of 23.45 s-1 at an overpotential of 100 mV. Furthermore, density functional theory calculations demonstrate that anchoring the Pt SA on the OV of Ti3C2Tx helps to decrease the binding energy and the hybridization strength between H atoms and the supports, contributing to rapid hydrogen adsorption-desorption kinetics and high activity for the HER.

SiOxCy Microspheres with Homogeneous Atom Distribution for a High-Performance Li-Ion Battery.

The broad application of silicon-based materials is limited by large volume fluctuation, high preparation costs, and complicated preparation processes. Here, we synthesized SiOxCy microspheres on 3D copper foams by a simple chemical vapor deposition method using a low-cost silane coupling agent (KH560) as precursors. The SiOxCy microspheres are available with a large mass loading (>3 mg/cm2) on collectors and can be directly used as the electrode without any binders or extra conductive agents. As a result, the as-prepared SiOxCy shows a high reversible capacity of ∼1240 mAh g-1 and can be cycled more than 1900 times without decay. Ex situ characterizations show that the volume change of the microspheres is only 55% and the spherical morphology as well as the 3D structure remain intact after cycles. Full-cell electrochemical tests paired with LiFePO4 as cathodes show 87% capacity retention after 500 cycles, better than most reported results, thus showing the commercial potential of the material.

Construction of a photo-controlled fluorescent switching with diarylethene modified carbon dots.

Photo-controlled fluorescent switching is of great utility in fluorescence sensors, reversible data storage, and logic circuit, based on their modifiable emission intensity and spectra. In this work, a novel photo-controlled reversible fluorescent switching system was constructed based on photochromic diarylethene (DT) molecular modified fluorescent carbon dots (CDs). The fluorescent CDs acted as fluorescent donors and the photochromic diarylethene molecular functioned as acceptors in this fluorescent switching system. The fluorescence modulation efficiency of the fluorescent switching was determined to be 97.1%. The result was attributable to Förster resonance energy transfer between the CDs and the diarylethene molecular. The fluorescent switching could undergo 20 cycles without significant decay.

In-Situ Formed Protecting Layer from Organic/Inorganic Concrete for Dendrite-Free Lithium Metal Anodes.

In this work, a separator modified by composite material of graphite fluoride nanosheets and poly(vinylidene difluoride) (GFNs-PVDF) is fabricated to in-situ construct a protective layer on Li metal anodes. The much-improved mechanical properties of this organic/inorganic protecting layer ensure efficient restriction on the growth of Li dendrites. The LiF and graphene nanosheets generated by the reaction of GFNs with lithium metal can not only provide fast transport channels for Li ions but also protect the Li metal anode from continuous corrosion of electrolytes. In addition, GFNs' lithiophilic nature guarantees the uniform Li nucleation site and perfect contact between li metal and the protecting layer without void space, leading to a low interfacial impedance and layer-by-layer lithium deposition. Together with the scalable method and cheap raw materials, this strategy provides new insights toward practical applications of Li metal batteries.

Large-Scale Modification of Commercial Copper Foil with Lithiophilic Metal Layer for Li Metal Battery.

The application and development of lithium metal battery are severely restricted by the uncontrolled growth of lithium dendrite and poor cycle stability. Uniform lithium deposition is the core to solve these problems, but it is difficult to be achieved on commercial Cu collectors. In this work, a simple and commercially viable strategy is utilized for large-scale preparation of a modified planar Cu collector with lithiophilic Ag nanoparticles by a simple substitution reaction. As a result, the Li metal shows a cobblestone-like morphology with similar size and uniform distribution rather than Li dendrites. Interestingly, a high-quality solid electrolyte interphase layer in egg shell-like morphology with fast ion diffusion channels is formed on the interface of the collector, exhibiting good stability with long-term cycles. Moreover, at the current density of 1 mA cm-2 for 1 mAh cm-2 , the Ag modified planar Cu collector shows an ultralow nucleation overpotential (close to 0 mV) and a stable coulombic efficiency of 98.54% for more than 600 cycles as well as long lifespan beyond 900 h in a Li|Cu-Ag@Li cell, indicating the ability of this method to realize stable Li metal batteries. Finally, full cells paired with LiNi0.8 Co0.1 Mn0.1 O2 show superior rate performance and stability compared with those paired with Li foil.

A Novel Donor-Acceptor Fluorescent Sensor for Zn2+ with High Selectivity and its Application in Test Paper.

A novel donor-acceptor fluorescent sensor was designed and synthesized. The sensor exhibited high selectivity and sensitivity to Zn2+ in acetonitrile solution. When 3.0 equiv. of Zn2+ was added gradually, the emission intensity at 500 nm increased 54-fold, accompanied by the fluorescent color of the solution changed from dark to green. Job's plot and ESI-MS were carried out to verify a 1:1 stoichiometric complex was formed between the sensor and Zn2+. The limit of detection (LOD) to Zn2+ was measured to be 2.81 × 10-9 mol L-1. Moreover, the sensor not only could be used to detect Zn2+ in practical water samples with high accuracy, but also could be made into test paper for the qualitative detection for Zn2+.

A Dual-Channel Sensor for Hg(2+) Based on a Diarylethene with a Rhodamine B Unit.

A novel diarylethene derivative with a Rhodamine B unit was synthesized successfully. It displayed favorable photochromism upon irradiation with UV/vis light. Upon addition of Hg(2+), distinct changes were observed in the absorption and fluorescent spectra due to the formation of a 1:1 ligand/metal complex. As a result, the diarylethene can serve as a fluorescence / colorimetric dual-channel sensor for highly selective and sensitive recognition of Hg(2+) in acetonitrile. Moreover, a complicated logic circuit was constructed with the combinational stimuli of UV/vis, Hg(2+)/ EDTA as input signals and the fluorescence intensity at 605 nm as output signal.

Poly(butylene succinate)/cellulose composite monofilaments with microelastic response based on interfacial bonding.

Biodegradable fibers have been widely developed for advanced textile fields, but their practical applications are limited by large plastic deformation. To solve this problem, we developed a solvent-free melt spinning method to prepare poly(butylene succinate)/microcrystalline cellulose (PBS/MCC) composite monofilaments. The high modulus and rigidity of MCC limit PBS plastic deformation and the in-situ formed hydrogen bonds between MCC and amorphous PBS improved MCC dispersion and led to the formation of rigid MCC physical crosslink points. The composite monofilaments with 10-25 wt% of MCC after multi-stage and high-ratio hot stretching showed a double yielding behavior and microelastic response, indicating the permanent deformation resistance of the composite monofilaments under small deformation. Moreover, the addition of MCC improved the biodegradability of the composite monofilaments after 60 days buried in soil. Therefore, our study provides a design strategy of microelastic composite monofilaments for maintaining dimensional stability during use and accelerating degradation during waste.

Three-Dimensional Carbon Foam Modified with Mg3N2 for Ultralong Cyclability of a Dendrite-Free Li Metal Anode.

Uncontrolled growth of lithium dendrites and huge volume change during the lithium plating/stripping process as well as poor mechanical properties of the solid electrolyte interphase (SEI) are key obstacles to the development of a stable Li metal anode. Here, an ultralight Mg3N2-modified carbon foam (CF-Mg3N2) was fabricated as a collector to address these issues. The calculated results show that the CF-Mg3N2 composite is relatively stable in terms of energy. Based on the synergistic effect of the three-dimensional skeleton and the lithiophilic nature of Mg3N2, homogeneous lithium deposition/stripping was realized around the foam carbon skeleton with an extremely low nucleation overpotential (∼9.3 mV) and high retention of Coulombic efficiency (99.3%) as well as long cyclability (700 cycles and 3000 h in half and symmetrical cells, respectively). Meanwhile, Mg3N2-CF@Li//LiFePO4 full cells also showed better rate capability and more stable cycling capability than CF@Li//LiFePO4 and Li//LiFePO4 cells, exhibiting extreme practicality. Accordingly, the design concept mentioned in this work provides a far-reaching influence on the development of a stable Li metal anode.

The effect of the formyl group position upon asymmetric isomeric diarylethenes bearing a naphthalene moiety.

Three new isomeric asymmetric diarylethenes with a naphthyl moiety and a formyl group at the para, meta or ortho position of the terminal benzene ring were synthesized. Their photochromism, fluorescent-switch, and electrochemical properties were investigated. Among these diarylethenes, the one with a formyl group at the ortho position of benzene displayed the largest molar absorption coefficients and fluorescence quantum yield. The cyclization quantum yields of these compounds increased in the order of para < ortho < meta, whereas their cycloreversion quantum yields decreased in the order of meta > para > ortho. Additionally, all of these diarylethenes functioned as effective fluorescent switches in both solution and PMMA films. Cyclic voltammograms proved that the formyl group and its position could effectively modulate the electrochemical behaviors of these diarylethene derivatives.

Discovery and Structural Explorations of G-Protein Biased µ-Opioid Receptor Agonists.

Compounds that activate only the G-protein signalling pathway represent an effective strategy for making safer opioids. In the present study, we report the design, synthesis and evaluation of two classes of novel PZM21 derivatives containing the benzothiophene ring and biphenyl ring group respectively as biased µ-opioid receptor (µOR) agonists. The new compound SWG-LX-33 showed potent µOR agonist activity and produced µOR-dependent analgesia. SWG-LX-33 does not activate the ß-arrestin-2 signalling pathway in vitro even at high concentrations. Computational docking demonstrated the amino acid residue ASN150 to be critical for the weak efficacy and potency of µOR agonists in arrestin recruitment.

A novel diarylethene-based fluorescent "turn-on" sensor for the selective detection of Mg2.

A new photochromic diarylethene derivative with a 4-methylphenol unit has been designed and synthesized. It displayed distinct photochromism and fluorescent ''turn on'' features to Mg2+ in acetonitrile solution. With the addition of Mg2+, there was an obvious increase of fluorescent emission intensity at 552 nm, accompanied by a clear change of fluorescent color from dark purple to green. Meantime, the 1 : 1 stoichiometry between the derivative and Mg2+ was verified by Job's plot and HRMS. Furthermore, the sensor was successfully applied in the detection of Mg2+ in practical samples. Moreover, based on the multiple-responsive fluorescence switching behaviors, it also could be used to construct a molecular logic circuit with UV/vis lights and Mg2+/EDTA as input signals and the emission at 552 nm as the output signal.

A bifunctional sensor based on diarylethene for the colorimetric recognition of Cu2+ and fluorescence detection of Cd2.

A novel bifunctional sensor based on diarylethene with a benzyl carbazate unit was synthesized successfully. It not only served as a colorimetric sensor for the recognition of Cu2+ by showing changes in absorption spectra and solution color, but also acted as a fluorescent sensor for the detection of Cd2+ through obvious emission intensity enhancement and fluorescence color change. The sensor exhibited excellent selectivity and sensitivity towards Cu2+ and Cd2+, and the limits of detection for Cu2+ and Cd2+ were 8.36 × 10-8 mol L-1 and 1.71 × 10-7 mol L-1, respectively, which were much lower than those reported by the WHO and EPA in drinking water. Furthermore, its application in practical samples demonstrated that the sensor can be effectively applied for the detection of Cu2+ and Cd2+ in practical water samples.

Novel Diarylethene-Based Fluorescent Switching for the Detection of Al3+ and Construction of Logic Circuit.

A novel photochromic diarylethene was synthesized successfully containing a phthalazine unit. Its multistate fluorescence switching properties were investigated by stimulating with UV/vis lights and Al3+/EDTA. The synthesized diarylethene displayed excellent selectivity to Al3+ with a distinct fluorescence change, revealing that it could be used as a sensor for fluorescence identification of Al3+, and a logic circuit was constructed by utilizing this diarylethene molecular platform. Moreover, it also exhibited a high accuracy for the determination of Al3+ in practical water samples.