Qiuhong Cheng

Bio: Qiuhong Cheng is an academic researcher from Shandong University. The author has contributed to research in topics: Self-healing hydrogels & Supramolecular chemistry. The author has an hindex of 5, co-authored 13 publications receiving 49 citations.

A chemosensor-based chiral coassembly with switchable circularly polarized luminescence.

Abstract: Fluorescent chemosensors represent fast response to analytes with pronounced luminescent variations. They are promising as potential candidates in controlling luminescence and chiroptical activities of self-assembled chiral systems, which however have not been accomplished to date. We present a coassembled multiple component system that could respond to SO2 derivatives, giving rise to dynamic aggregation behaviors and switchable luminescence as well as circularly polarized luminescence (CPL). Cholesteryl-naphthalimide and coumarin derivatives coassemble into vesicles and nanohelices under the solvent strategy, behaving as energy transfer donor and accepter respectively. Energy transfer enables CPL transition from green to red depending on the molar fraction. After the addition of SO2 derivatives, hypochromic shifts occur to CPL due to the nucleophilic addition reaction to coumarin domain, hindering energy transfer and allow for the emergence of pristine luminescence. Here, we show a protocol to control over luminescence and chiroptical features of supramolecular chiral self-assemblies using fluorescent chemosensors. ‘Fluorescent chemisensors with fast response time and pronounced luminescence variation are important but have not been well investigated for self-assembled chiral systems. Here, the authors present a coassembled multiple component system that responds to SO2 derivatives, giving rise to dynamic aggregation behaviors and switchable luminescence as well as circularly polarized luminescence.

Fluorescent Imprintable Hydrogels via Organic/Inorganic Supramolecular Coassembly.

Abstract: Photoresponsive hydrogels with on/off luminescence show a promising application potential in writable information recording and display materials. However, it still remains a tremendous challenge to fabricate such hydrogels on account of the intrinsic fluorescence quenching effect and the lack of suitable responsive groups. Herein, we present fluorescent imprintable hydrogels constructed via organic/inorganic supramolecular coassembly. A photoisomeric cyanostilbene conjugated cationic surfactant exhibited an aggregation-induced emission behavior upon clay (laponite) complexation, along with excellent thixotropism brought by laponite. Macrocyclic cucurbituril[7] and β-cyclodextrin rings capable of forming host-guest complexes with the surfactant were utilized to give ternary hybrid hydrogels with luminescence and photoresponsive properties. On the account of trans-cis photoisomerization of the cyanostilbene unit, the fluorescence of the multicomponent hydrogels could undergo rapid quenching within a short irradiation period under UV light and be recovered when subjected to an annealing process. According to these properties, the imprinted fluorescent patterns using the hybrid hydrogels were erasable and rewritable. Thus, this research successfully integrates host-guest complexation and supramolecular coassembly into the fabrication of fluorescent imprintable hydrogels.

Aromatic vapor responsive molecular packing rearrangement in supramolecular gels

Abstract: Developing robust hydrogel materials with stimulus responsiveness to apolar organic vapors or gases is significantly challenging due to the deficient interaction between solvents and gelators, the intrinsic colloidal stability of gels toward low content solvent molecules in the gas phase and their immiscibility We herein report unprecedented aromatic vapor responsive hydrogels taking advantage of the convenient crystal transformation phenomenon of commercially available β-cyclodextrin (β-CD) One-dimensional crystallization-induced self-assembly in a dimethyl formamide (DMF)/water mixture with specific proportions allows for the formation of stable gels The hydrogel could selectively transform into crystalline precipitates upon exposure to aromatic solvent vapors The phase transition is initiated through a cage-type to a channel-type single crystal transformation with a gradual solvent etching process, in which the CH–π interaction between DMF and the benzene ring confined within β-CD dimers is regarded as the primary driving force We demonstrated that this unique gel system could act as an efficient sensor and adsorbent for hazardous aromatic vapors indoors In addition, binary organic–inorganic hydrogel composites coassembled by clay with β-CD showed haze evolution toward aromatic vapor and heating–cooling treatment, accompanied by mechanical strength enhancement dependent on the building unit proportion The present research opens an avenue to apply hydrogels in selectively sensing/adsorbing organic vapors, and would pave an alternative route for further development of responsive soft materials

Photoregulated "Breathing" Vesicle with Inversed Supramolecular Chirality.

Abstract: Though phospholipids possess chiral centers, their chiral aggregation within bilayer cell membranes has seldom been referred and recognized. Insight into the chirality at higher levels in artificial molecular bilayer assemblies such as vesicles or liposomes is important to better understand biomembrane functions. In this work, we illustrate the fabrication of chiral vesicles with photoresponsive supramolecular chirality and structural transformation property. Cholesterol was conjugated to azobenzene via different spacers, of which molecular chirality underwent transfer to supramolecular level upon aggregation in water. The resultant building block self-assembled into unilamellar vesicles that could respond to light irradiation by showing reversible extension/contraction behavior. Such "breathing" behavior was accompanied with supramolecular chirality inversion from M- to P-handedness, confirmed by the solid-state crystal structure and electronic circular dichroism spectra based on density functional theory. The vesicle membrane behaves as a matrix to accommodate guest molecules via aromatic interactions, which significantly elevated the UV light resistance with respect to the structural and supramolecular chirality transformation. This work offers an unprecedented rational control over supramolecular chirality using photoresponsiveness in vesicular membranes.

Entropically Driven Helix Formation

Abstract: The helix is a ubiquitous motif for biopolymers. We propose a heuristic, entropically based model that predicts helix formation in a system of hard spheres and semiflexible tubes. We find that the entropy of the spheres is maximized when short stretches of the tube form a helix with a geometry close to that found in natural helices. Our model could be directly tested with wormlike micelles as the tubes, and the effect could be used to self-assemble supramolecular helices.

Aggregation-Induced Emission-Active Gels: Fabrications, Functions, and Applications

Abstract: Chromophores that exhibit aggregation-induced emission (i.e., aggregation-induced emission luminogens [AIEgens]) emit intense fluorescence in their aggregated states, but show negligible emission as discrete molecular species in solution due to the changes in restriction and freedom of intramolecular motions. As solvent-swollen quasi-solids with both a compact phase and a free space, gels enable manipulation of intramolecular motions. Thus, AIE-active gels have attracted significant interest owing to their various distinctive properties and promising application potential. Herein, a comprehensive overview of AIE-active gels is provided. The fabrication strategies employed are detailed, and the applications of AIEgens are summarized. In addition, the gel functions arising from the AIE moieties are revealed, along with their structure-property relationships. Furthermore, the applications of AIE-active gels in diverse areas are illustrated. Finally, ongoing challenges and potential means to address them are discussed, along with future perspectives on AIE-active gels, with the overall aim of inspiring research on novel materials and ideas.

Correction: Fluorescent carbon dot–molecular salt hydrogels

Abstract: Correction for ‘Fluorescent carbon dot–molecular salt hydrogels’ by Angelina Cayuela et al., Chem. Sci., 2015, DOI: 10.1039/c5sc01859e.

Self-Assembly-Driven Aggregation-Induced Emission of Silver Nanoclusters for Light Conversion and Temperature Sensing

Abstract: Supramolecular self-assembly is an effective method for constructing complex ordered aggregates with specific functions by noncovalent bonding. However, silver nanoclusters (NCs) have rarely been e...

Multiple Responsive CPL Switches in an Enantiomeric Pair of Perovskite Confined in Lanthanide MOFs

Abstract: Circularly polarized luminescence (CPL) switches have attracted widespread attention due to their potential applications in advanced information technologies. However, the design and fabrication of solid‐state multiple‐responsive CPL switches remain challenging. Here, through self‐assembly of chiral metal‐organic frameworks (MOFs) and perovskite nanocrystals (NCs), a pair of crystalline enantiomeric (P)‐(+)/(M)‐(−)‐EuMOF⊃MAPbX3 (MA = CH3NH3+, X = Cl−, Br−, I−) adducts is prepared, where the achiral MAPbBr3 perovskite NCs embedded into chiral MOFs inherit the chirality of host MOFs by host‐guest EuBr and PbO coordination bonds, which is demonstrated by synchrotron‐radiation‐based X‐ray absorption spectroscopy. The chiral adducts show enhanced photoluminescence quantum yield (PLQY), good thermal stability of CPL in air, and photoswitchable CPL properties upon altering different UV irradiation. Based on two chiral emission centers and their different characteristics, reversible CPL switches are realized upon a diversity of external stimuli, for example, chemicals (water /CH3NH3Br solution) or temperatures (room temperature/high temperature). Benefiting from the extraordinary stimuli‐responsive and highly reversible switchable CPL, multiple information encryptions and decryptions integrated with CPL, together with a chiroptical logic gate are successfully designed. This work opens a new avenue to generally fabricate solid‐state CPL composite materials and develops new applications based on switchable CPL.