Anthocyanins of Delonix Regia Floral Petals: A Novel Approach on Fluorescence Enhancement, Forster Resonance Energy Transfer Mechanism and Photostability Studies for Optoelectronic Applications

In this work, we focused on extracting the anthocyanin dye in acetone, butanol, ethanol, and water solvents from Delonix regia flowers by a simple maceration extraction process. The identification of functional group analysis, vibrational studies, energy transfer mechanisms, optoelectronic properties, photostability studies, FRET-assisted potential light emissions and photometric properties of the anthocyanin dyes are successively investigated. FTIR spectroscopy and vibrational studies have confirmed the existence of polyphenolic groups in 2-phenyl chromenylium (anthocyanin) dyes. The optoelectronic results show the least direct bandgap (2.04 eV), indirect bandgap (1.55 eV), Urbach energy (0.380 eV), high refractive index (1.20), dielectric constant (2.794), and high optical conductivity (1.954 × 103 S/m) for the anthocyanin dye extracted found in water solvent. The photoluminescence properties such as Stoke's shift, high quantum yield, and lifetime results show that anthocyanin dyes are promising candidates for red-LEDs and optical materials. The absorption and emission spectra of the anthocyanin dyes follow the mirror image rule and the Franck-Condon factor exists between vibrational energy levels corresponding to all the electronic transitions. The excellent correspondence between the absorption and emission spectra reinforces that the anthocyanins are efficient (46%) FRET probes. Further, photometric properties such as CIE, CRI, CCT and colour purity results of anthocyanins in all studied solvents revealed that this material exhibits orange to red shades (x = 0.48 → 0.54 and y = 0.36 →0.45) and is well suitable for have great potential in the manufacturing of Organic-LEDs and other optoelectronic device applications.

A supramolecular assembly-based strategy towards the generation and amplification of photon up-conversion and circularly polarized luminescence

For the molecular properties in which energy transfer/migration is determinantal, such as triplet-triplet annihilation-based photon up-conversion (TTAUC), the overall performance is largely affected by the intermolecular distance and relative molecular orientations. In such scenarios, tools that may steer the intermolecular interactions and provide control over molecular organisation in the bulk, become most valuable. Often these non-covalent interactions, found predominantly in supramolecular assemblies, enable pre-programming of the molecular network in the assembled structures. In other words, by employing supramolecular chemistry principles, an arrangement where molecular units are arranged in a desired fashion, very much like a Lego toy, could be achieved. This leads to enhanced energy transfer from one molecule to other. In recent past, chiral luminescent systems have attracted huge attention for producing circularly polarized luminescence (CPL). In such systems, chirality is a necessary requirement. Chirality induction/transfer through supramolecular interactions has been known for a long time. It was realized recently that it may help in the generation and amplification of CPL signals as well. In this review article we have discussed the applicability of self-/co-assembly processes for achieving maximum TTA-UC and CPL in various molecular systems.

A polyacrylamide gel containing an engineered hexameric hemoprotein as a cross-linking unit toward redox-responsive materials

Hydrogels containing synthetic polymers and supramolecular cross-linking units are expected to exhibit unique functions and properties. The heme-heme pocket interaction in hemeproteins may be useful for development of a cross-linking unit because heme binding depends on the redox states of the iron center. In this work, hexameric tyrosine-coordinated hemoprotein (HTHP) is employed as a cross-linking unit in a polyacrylamide gel to create redox-responsive hydrogels. First, redox-dependent stability of the heme-heme pocket interaction in HTHP was evaluated, and it was found that the heme affinity dramatically decreases in the Fe(ii) state. Second, the polymerization of acrylamide and engineered HTHP possessing acryloyl group-tethering heme moieties provided a polyacrylamide gel containing HTHP as a cross-linking unit. A reduction-triggered gel-sol transition in the presence of apomyoglobin was observed. Furthermore, the mechanical properties of the gels containing the engineered HTHP and methylene bisacrylamide were evaluated by a tensile test, and the Young's modulus value was determined to be 14 kPa, which is higher than that of the control gel containing only methylene bisacrylamide (8.5 kPa). Compression tests of the gels revealed redox-responsive mechanical behavior, resulting in a decrease in the compressive modulus upon the addition of a reductant. This behavior is qualitatively consistent with the redox-responsive heme binding of HTHP in a solution state. This finding is expected to contribute to the development of redox-responsive materials for biomedical and biological applications.

Efficient manipulation of Förster resonance energy transfer through host-guest interaction enables tunable white-light emission and devices in heterotopic bisnanohoops

In this study, we synthesized and reported the heterotopic bisnanohoops P5-[8,10]CPPs containing cycloparaphenylenes (CPPs) and a pillar[5]arene unit, which act not only as energy donors but also as a host for binding energy acceptors. We demonstrated that a series of elegant FRET systems could be constructed successfully through self-assembly between donors P5-[8,10]CPPs and acceptors with different emissions via host-guest interaction. These FRET systems further allow us to finely adjust the donors P5-[8,10]CPPs and acceptors (BODIPY-Br and Rh-Br) for achieving multiple color-tunable emissions, particularly white-light emission. More importantly, these host-guest complexes were successfully utilized in the fabrication of white-light fluorescent films and further integrated with a 365 nm LED lamp to create white LED devices. The findings highlight a new application of carbon nanorings in white-light emission materials, beyond the common recognition of π-conjugated molecules.

Macrocycle Self-Assembly Hydrogel for High-Efficient Oil-Water Separation

Supramolecular hydrogels involved macrocycles have been explored widely in recent years, but it remains challenging to develop hydrogel based on solitary macrocycle with super gelation capability. Here, the construction of lantern[33 ]arene-based hydrogel with low critical gelation concentration (0.05 wt%), which can be used for efficient oil-water separation, is reported. The lantern[33 ]arenes self-assemble into hydrogen-bonded organic nanoribbons, which intertwine into entangled fibers to form hydrogel. This hydrogel which exhibits reversible pH-responsiveness characteristics can be coated on stainless-steel mesh by in situ sol-gel transformation. The resultant mesh exhibits excellent oil-water separation efficiency (>99%) and flux (>6 × 104 L m-2 h-1 ). This lantern[33 ]arene-based hydrogel not only sheds additional light on the gelation mechanisms for supramolecular hydrogels, but also extends the application of macrocycle-based hydrogels as functional interfacial materials.

Recent advances in the development of europium(III) and terbium(III)-based luminescent supramolecular metallogels

In the recent past, special attention has been paid to the development of metallogels as novel luminescent materials from rationally designed gelators with lanthanide ions, especially europium (Eu(III)) and terbium (Tb(III)) metal ions. Lanthanide (Ln(III)) based metallogels possess various useful properties with an extensive range of applications in the field of advanced materials, and electronic and bio-technologies. Lanthanide ions in coordination with appropriate sensitizer ligands can reproduce metal-based optical, redox, and electronic properties in soft gel materials. The optical properties of the luminescent Ln(III) based metallogels can be tuned over the complete visible spectrum (400-750 nm) including the generation of white light by mixing both Eu(III) and Tb(III) with the ligand in various stoichiometric ratios. Additionally, the dynamic nature of the lanthanide-ligand (Ln-N) coordination bond allows the Ln(III) based metallogels to respond to various external stimuli. Luminescent self-healing supramolecular gels using organic ligands as 'hosts' and Ln(III) ions as 'guests' are also a current topic of research interest. In this review, we discuss and summarize some selected recent examples of newly developed luminescent Eu(III) and Tb(III) based supramolecular metallogels with potential applications in the fields of optoelectronic devices, stimuli responsiveness, self-healing, luminescent films, and sensors.

Fluorescent Mechanism and Optical Switching of Fluorophore-Free Organogel

Fluorophore is essential to enable the fluorescence and optical switching in most of polymer gels. Herein, a novel concept is proposed to develop a fluorophore-free organogel that is capable of generation of blue fluorescence at transparent state, while it proceeds with optical switching from blue to purple upon phase transition into non-transparent state in water. Ammonium persulphate (APS) is utilized to initiate co-crosslinking of hydrophilic acrylamide (AM) and hydrophobic 2,2,3,4,4,4-hexafluorobutyl acrylate (HFBA) in dimethyl sulphoxide (DMSO) to give organogel of AM@HFBA at 80 °C. APS decomposes to generate not only radicals, but also ammonium bisulfate (ABS) during heating, in which the elements of ABS produce blue fluorescence (λ = 440 nm), excited by UV light (λ = 365 nm). After the phase transition into non-transparent state, light-reflection behavior at the phase-transitioned surface triggers the optical switching of the organogel from blue to purple under UV light. The optical switching is patternable and reversible, which enables the applications of organogel of AM@HFBA for information encoding/encryption and optical-switchable soft actuators. This method is universal to achieve fluorescence and optical switching for free radical polymerization-based gel systems as long as they are initiated by APS in DMSO.

Quinoxaline-probe embedded injectable fluorogenic hydrogels: Comparative detection of mesitylene in guar gum and i-carrageenan hydrogels

The innovation of novel chemosensor probes for the recognition of trace volatile organic compounds is critical due to their hazardous effect on the environment and human health. A nitro-group integrated quinoxaline probe with a profound discriminative fluorescence 'turn-on' response to mesitylene was fabricated into guar gum and i-carrageenan, two biopolymer-based hydrogel matrices, to develop compact, portable fluorogenic hydrogel sensors and assess their fluorescence properties. A comparative characterization-based analysis of native, probe-associated, and probe-analyte-associated hydrogels, (comprising of FT-IR, XRD, TGA) was investigated to ascertain the overall compatibility of the hydrogel-based sensors for use as a smart rapid detection tool. Dynamic rheological measurements also validated the mechanical stability and robustness of the developed hydrogel matrices. Fluorescence spectroscopic investigations yielded promising results of 0.15 ppm limit of detection (LOD) in guar gum and 0.29 ppm LOD in i-carrageenan hydrogels respectively. FESEM and Fluorescence microscopy studies represented the morphological variations of the hydrogel sensors on interaction with mesitylene. The practical feasibility of the chemosensor in hydrogel form for mesitylene detection in the vapor phase was also explored. Probe-embedded hydrogels with injectable property was shown, depicting its use as security ink for information encryption functions. This approach of incorporating chemosensors into biobased hydrogel networks has the potential to broaden its opportunities in the field of chemical, biomedical, and environmental sensing sectors.

Full-Color-Tunable Nanohydrogels as High-Stability Intracellular Nanothermometers

Full-color-tunable hydrogels with ultrahigh stability can be used in various fields, including intracellular temperature sensing. However, constructing full-color-tunable organic nanohydrogels with excellent biocompatibility and stability for intracellular temperature sensing remains a great challenge. Here, we report a full-color-tunable nanohydrogel with ultrahigh stability as an intracellular nanothermometer. Three types of temperature-sensitive polymers with red, green, and blue fluorescence were synthesized. Through easy mixing of these three polymers with regulation of the mass ratio, these polymers can be encoded to full-color-tunable fluorescent nanohydrogels, including nanohydrogels with white-light emission (NWLEs), with sizes of about 200 nm in aqueous media. Further study suggested that the as-obtained NWLEs exhibited good performance in intracellular temperature sensing because of their ultrahigh stability on their fluorescence properties and morphologies.

Multiple Effects of an Anionic Cyclodextrin Macrocycle on the Reversible Isomerization of a Photoactive Guest Dye

Understanding and controlling the reversible isomerization of photoactive molecules in order to obtain a tunable optical response is desirable for many photofunctional applications. This study describes the interesting effects of an anionic cyclodextrin host (sulfated-βCD, SCD) on the photoisomerization and protonation equilibrium of an important hemicyanine dye (trans-4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide, DSP). The SCD host assists in unlocking the photoisomerization potential of DSP by promoting protonation of the dye. It also assists in stabilizing the cis isomer of the protonated dye, thereby significantly delaying the reverse cis to trans isomerization of DSPH⁺. Furthermore, the interplay of both hydrophobic and electrostatic interactions in the complex formation of SCD with DSPH⁺ makes the reverse cis to trans isomerization of DSPH⁺ amenable to influence by the added salt. The stimuli-responsive reversible isomerization of SCD-DSPH⁺ is an interesting case from the perspective of chemical sensing or light operated functional materials with host-guest systems.

Recent Progress in Smart Polymeric Gel-Based Information Storage for Anti-Counterfeiting

Information security protection has a tremendous impact on human life, social stability and national security, leading to the rapid development of anti-counterfeiting materials and related techniques. However, the traditional stored information on hard or dry media is often static and lacks functions, which makes it challenging to deal with increasing and powerful counterfeiting technologies. Modified intelligent polymeric gels exhibit color changes and shape morphing under external stimuli, which give them great potential for applications in information storage. This paper provides an overview of the latest progress in polymeric gel-based information storage materials in relation to counterfeiting. Following a brief introduction of anti-counterfeiting materials, the preparation methods for intelligent gels with adjustable colors (e.g., chemical colors and physical colors) and various encryption/decryption modes involving dimensions and diverse colors are outlined. Finally, the challenges and prospects for information storage and anti-counterfeiting based on smart gels are discussed.

Superhydrophobic cotton fabric membrane prepared by fluoropolymers and modified nano-SiO2 used for oil/water separation

At present, the preparation methods of oil–water separation membranes include chemical vapor deposition, electrospinning, atom transfer radical polymerization, etc. Basically, they all have issues of low recycling rate and incontinuous use. In this paper, the epoxy polymer P(GMA-r-MMA) obtained by traditional radical polymerization of glycidyl methacrylate (GMA) monomer and methacrylic acid (MMA) monomer, and pentafluoropropionic acid (PFPA) is used to modify polymer P(GMA-r-MMA) to obtain fluorine-containing epoxy polymer P(GMA-r-MMA)-g-PFPA. Secondly, fluorine-containing epoxy polymer P(GMA-r-MMA)-g-PFPA and amino-modified nano SiO₂ is blended, and the cotton fabric is dip-coated to obtain a superhydrophobic surface, thereby preparing an oil–water separation membrane. By controlling the solution concentration, dipping time, drying time and other conditions, the superhydrophobic performance of the separation membrane was characterized, and the best construction conditions for the superhydrophobic surface were obtained: 0.3 mg mL⁻¹ polymer concentration, immersion time 6 h, drying temperature 120°, and drying time 4 h, and the maximum water contact angle can reach to 150° ± 2°. Finally, the cotton fabric was modified under the best dipping conditions, and used as an oil–water separation membrane to study the oil–water separation performance of n-hexane, n-octane, kerosene, chloroform and water mixtures in batch operation and continuous operation. In batch operations, the separation efficiency can reach 99% and can achieve 5 consecutive high-efficiency separations without intermittent drying. In continuous flow operation, oil–water separation can last for more than 12 hours and the separation efficiency can reach 98%. It also has stable oil–water separation performance for oil–water emulsion.

Cotton modified with polymer P(GMA-r-MMA)-g-PFPA and modified silica can obtain super-hydrophobic surfaces, and can be used as oil–water separation membrane for hexane, octane, kerosene, chloroform and water mixtures in batch and continuous operation.

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

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.

Cyclodextrin-Cross-Linked Hydrogels for Adsorption and Photodegradation of Cationic Dyes in Aqueous Solution

Possessing three-dimensional porous structures and tunable mechanical strengths, cyclodextrin-containing polymeric hydrogels are one of the most promising water-based adsorbent materials due to their easy availability, simple chemical modification and environmental friendliness. In this work, two kinds of hydrogels were prepared via the copolymerization with acrylic acid and vinyl-derivatized β-cyclodextrins in water. These two gels have showed good adsorption performance towards cationic dyes through the noncovalent interactions with their anionic backbones and porous network. Meanwhile, pseudo-second-order model was selected to clarify the adsorption kinetics process. Moreover, nano-scaled TiO₂ was doped into these resultant cyclodextrins-based hydrogels to achieve efficient degradation of dyes upon light irradiation. The obtained TiO₂ -loaded hydrogels could exhibit improved adsorption performance and make the adsorbed dyes photo-degraded with the decolorization rates above 95%. It can be envisioned that such cyclodextrin-based soft materials may find applications in dye clearance and water treatment.

Polysaccharide-Based Supramolecular Hydrogel for Efficiently Treating Bacterial Infection and Enhancing Wound Healing

Nowadays, the rapid emergence of antibiotic-resistant pathogens has become a serious threat to human health. As an effective antimicrobial therapy, supramolecular materials show unprecedented advantages because of their flexible and adjustable interactions with biological molecules. Supramolecular hydrogels are now widely applied in biomedical fields because of their outstanding biocompatibility, high water content, easy preparation, and unique functions. Herein, we conveniently prepared a stable supramolecular hydrogel by simply mixing β-cyclodextrin-modified chitosan (CS-CD) with AgNO₃ in a basic environment. The obtained supramolecular hydrogel, which is positively charged and possesses numerous β-cyclodextrin cavities, could efficiently load anionic drug diclofenac sodium (DS) through the electrostatic interaction and host-guest inclusion. Significantly, the biological experiments demonstrated that this supramolecular hydrogel exhibited a high antibacterial effect and good ability of promoting wound healing owing to the cooperative contribution of CS, Ag⁺, and DS.

Aqueous Systems with Tunable Fluorescence Including White-Light Emission for Anti-Counterfeiting Fluorescent Inks and Hydrogels

White-light-emitting materials have attracted wide interest for potential applications in information displays and lighting. To date, the majority of reported white-light-emitting materials have been multicomponent systems that are typically processed with organic solvents. These features are associated with complex processing, poor white-light quality, and environmental pollution. Herein, a white-light-emitting aqueous system is realized by encapsulating a fluorophore, which has a vibration-induced emission effect, in Pluronic F127 micelles. Tunable multicolor fluorescence is achieved by changing the temperature, and the use of organic solvents is effectively avoided. Through this process, white-light emission with Commission Internationale de l'Eclairage coordinates of (0.3351, 0.3326) is obtained, which is very close to pure white light, and its color rendering index is as high as 89. The fluorescence color tunability of this system could be performed in a wide temperature range, rendering it a potential material in optical thermometry. Besides, the aqueous system also allows for the application of the material as a fluorescent ink and white-light-emitting hydrogels. Information could be embedded in paper-based materials and hydrogels through the fluorescence quenching effect of iron ions (Fe³⁺) on the fluorophore. Fluorescence could then be recovered upon removal of Fe³⁺ by adenosine 5'-triphosphate. Thus, fluorescent patterning and triple-mode anti-counterfeiting could be expected due to the temperature-sensitive emission, fluorescence quenching, and recovering properties.

Engineering luminescent pectin-based hydrogel for highly efficient multiple sensing

Luminescent hydrogels with sensing capabilities have attracted much interest in recent years, especially those responsive to stimuli, making such materials potential for various applications. Pectin is a high-molecular-weight carbohydrate polymer that has the ability to form hydrogel upon heating or mixing with divalent cations. However, intrinsic pectin gels are weak and lack of functionalities. In this study, lanthanide ions and silk fibroin derived carbon dots were incorporated into Pectin/PVA hydrogel (PPH) to form luminescent tough hydrogels. The luminescence of the hydrogel can be tuned by adjusting the ratio of blue emission carbon dots to Eu³⁺ ions (red emission) and Tb³⁺ ions (green emission). Such incorporation of emitters only slightly changed the mechanical properties of the tough hydrogel. Notably, the luminescent Pectin/PVA hydrogel (LPPH) showed chromic response to external stimuli, like pH and metal ions. By measuring the ratio of luminescent intensity at 473 nm and 617 nm (I₄₇₃/I₆₁₇), the pH response can be quantified in high sensitivity. In addition, the specific detection of Cu²⁺ and Fe³⁺ ions using the fabricated hydrogel were demonstrated, the mechanism was also proposed. The different chromic responses to Fe²⁺ and Fe³⁺ endow the luminescent tough Pectin/PVA hydrogel potential for multiple sensing applications.

Facile construction of a double network cross-linked luminescent supramolecular elastomer by hydrosilylation and pillar[5]arene host-guest recognition

Reticulated copolymer host pillar[5]arene cross-linked with poly(dimethylsiloxane) (PDMS) was synthesized for the facile construction of a double network cross-linked elastomer upon noncovalently cross-linking with tetraphenyethylene (TPE)-based tetratopic guests through host-guest interactions. The obtained sample strips had better mechanical properties and luminescence capabilities.

Highly efficient full-color and white circularly polarized luminescent nanoassemblies and their performance in light emitting devices

Chiral nanomaterials with circularly polarized luminescence (CPL) have attracted increasing attention as they show improved luminous efficiency and high contrast images in optical displays. Herein, nanotwisted fibers with bright full-color CPL are developed through the co-assembly of chiral phenylalanine derived gelators and achiral aromatic molecules. The synergic effect of π-π stacking and hydrogen bonding interactions between the chiral and achiral building blocks results in long-range ordered self-assembly, enabling the chirality of the gelators to be better transmitted to the achiral aromatic molecules. Highly ordered co-assemblies lead to the formation of supramolecular gels with high glum values which range up to 10-3. Moreover, nanoassemblies with white CPL are obtained by tuning the ratio of colorful achiral aromatic molecules in the gels. These nanotwisted gels show diverse colors or even white circularly polarized light when coated on UV chips, which enable their future application in the construction of low-cost and flexible light-emitting devices such as circularly polarized organic light-emitting diodes (CPOLEDs).

Injectable supramolecular nanohydrogel from a micellar self-assembling calix[4]arene derivative and curcumin for a sustained drug release

In the search for soft and smart materials for nanomedicine, which is a present challenge, supramolecular nanohydrogels built on self-assembling low-molecular-weight building blocks attract interest for their structural, mechanical and functional properties. Herein, we describe a supramolecular nanohydrogel formed by a biofriendly micellar self-assembling choline-calix[4]arene derivative in the presence of curcumin, a natural and multitarget pharmacologically relevant drug. Morphology and mechanical properties of the nanohydrogel were investigated, and theoretical simulation performed to model the nanohydrogel structure. The self-healing and injectable nanohydrogel easily formed in PBS medium at physiologic pH, without using additives and organic solvents. The micellar nanohydrogel protected curcumin from rapid chemical and photochemical degradation, and slowly dissolved in curcumin-loaded micelles sustaining the drug release in a low rate. The nanohydrogel which combines the mechanical properties of a hydrogel and the benefits of a nanoscale micelle in drug delivery, appears a promising novel material for drug delivery.

Two-Dimensional Conductive Metal-Organic Frameworks Based on Truxene

Two dimensional conductive metal-organic frameworks (2D cMOFs) have been widely applied as electrocatalysts, electronic devices, and sensors. In addition, their intrinsic electronic properties could be efficiently tuned via varying the conjugated linkers. Herein, we report a novel 2D cMOF based on complexation of 2,3,7,8,12,13-hexahydroxyl truxene and copper ions via the energy economical interfacial reaction. This 2D cMOF was obtained as a brilliant black powder and showed a bulk electrical conductivity of 3.5 × 10^-3 S cm^-1 at 30 °C. Additionally, the cMOF-modified glassy carbon electrode could act as an electrochemical sensor for sensing paraquat with a limit of detection at 4.1 × 10^-8 M (S/N = 3). The accession of truxene-Cu to the cMOF family would shed new light on the impact of the organic conjugated linker and broaden the scope of cMOFs' applications.

Solvent-controlled assembly of pillar[5]arene-based supramolecular networks via π–π interactions for white light modulation

A supramolecular network based on pyrene-containing pillar[5]arene and a red emissive Eu(iii) complex was constructed, whose assembly and emission can be controlled by solvent polarity, eventually achieving white light emission.

Chirality on dendrimers: “roll booster” of the molecule-level self-sorting assembly in two-component supramolecular gel system

Chirality-induced recognition-promoted thermodynamic phase separation and different rate-kinetically controlled assembly helps molecule-level self-sorting emerge in a dendritic multicomponent gel.

Terpyridine-functionalized chemically cross-linked polyacrylamide hydrogel for white emission and multistimuli-responsive behaviour

A highly efficient and multifunctional white-emitting hydrogel was fabricated using a facile copolymerization process by introducing a hydrophilic terpyridine-based chromophore into a polyacrylamide network.

Pillar[5]arene-based supramolecular AIE hydrogel with white light emission for ultrasensitive detection and effective separation of multianalytes

A novel pillar[5]arene-based supramolecular AIE hydrogel (PDG) with white light emission was constructed. The PDG could be used for ultrasensitive detection and effective separation of multianalytes, and as fluorescent display materials.

Multicolor luminescent supramolecular hydrogels based on cucurbit[8]uril and OPV derivative

Supramolecular hydrogels have received considerable attention because of their various fascinating applications. Herein, an alkyl chain-modified oligo(p-phenylenevinylene) (Py-OPV) derivative was synthesized. When assembled with cucurbit[7]uril, its fluorescence intensity was enhanced without any change in color. However, the molecules underwent J-type dimerization when encased in the cavity of cucurbit[8]uril, which possessed different emission properties based on the monomer. By simply changing the concentration of cucurbit[8]uril, the fluorescence properties of the assemblies were easily altered. In addition, luminescent supramolecular hydrogels were constructed with Py-OPV and cucurbit[8]uril based on the photopolymerization of acrylamide. By embedding the assembly in the polymer to confine it, hydrogels emitting various tones of blue light were easily constructed. The preparation method of such luminescent hydrogels provides a new reference method for the construction of specific luminescent materials.

Mutualistic benefit in the self-sorted co-aggregates of peri-naphthoindigo and a 4-amino-1,8-naphthalimide derivative

Photoluminescence enhancement for all the members of a self-sorted co-aggregate was observed for the first time by successfully amalgamating AIEE and social self-sorting. Intermolecular H-bonding and π-π stacking were utilised to prepare several co-aggregates of peri-naphthoindigo (PNI) and a 4-amino-1,8-naphthalimide derivative dye, NH₂-NMI. In the heteromeric aggregates, photoluminescence intensities were increased by 28% for the imide and more than 400% for PNI. Due to spectral overlap between the emission of the imide and the absorption of PNI, energy transfer took place from the former to the latter. The heteromeric aggregates are dual emissive and the relative intensities of the emissions can easily be tuned by varying the stoichiometry of the dyes.

Multistimuli-Responsive and Photocontrolled Supramolecular Luminescent Gels Constructed by Anthracene-Bridged Bis(dibenzo-24-crown-8) with Secondary Ammonium Salt Polymer

A novel multistimuli-responsive and photcontrolled supramolecular luminescent gel is fabricated from anthracene-bridged bis(dibenzo-24-crown-8) (1) and secondary ammonium salt-functionalized graft polymer (3). X-ray crystallographic analysis reveals that the dibenzo-24-crown-8 (DB24C8) ring is located at the opposite site of 1, which will greatly hinder the mutual intermolecular π-π stacking between anthracene groups. By taking advantage of the controllable binding of 1 with 3, the unique gel-sol transition could occur under different temperatures, pH, and competitive guest bindings. Benefiting from the photo-oxygenation of anthracene, the luminescence behavior of the supramolecular gel could be switched off and on under UV light (365 nm) and heating treatment, which provides a new approach for constructing photocontrolled supramolecular luminescent gel.

Supramolecular hydrogel with tunable multi-color and white-light fluorescence from sulfato-β-cyclodextrin and aminoclay

A multi-color-tunable supramolecular hydrogel is constructed from aminoclay (AC), sulfato-β-cyclodextrin (SCD), and 4-methyl-styrylpyridinium (SP), in which the SCD⊃SP complex emits monomer fluorescence, and AC provides a restricted environment for excimer emission. The emission color of the supramolecular hydrogel can be tuned from yellow → white → blue by adjusting the SCD/SP molar ratio.

Photo-responsive cyclodextrin/anthracene/Eu3+ supramolecular assembly for a tunable photochromic multicolor cell label and fluorescent ink

A photo-responsive supramolecular assembly was successfully constructed through the stoichiometric 2 : 1 non-covalent association of two 4-(anthracen-2-yl)pyridine-2,6-dicarboxylic acid (1) units in one γ-cyclodextrin (γ-CD) cavity, followed by the subsequent coordination polymerization of the γ-CD·1 2 (1 2 = two 1) inclusion complex with Eu(iii). Interestingly, owing to the photodimerization behavior of anthracene units and the excellent luminescence properties of Eu(iii), the Eu3+⊂γ-CD·1 2 system showed multicolor fluorescence emission from cyan to red by irradiation for 0-16 minutes. Moreover, white light emission with CIE coordinates (0.32 and 0.36) was achieved at 4 min. Importantly, white light-containing multicolor emission could be obtained in water, solid films and living cells. Especially, the Eu3+⊂γ-CD·1 2 system could tag living cells with marvelous white fluorescence and display no obvious cytotoxicity. Thus, this supramolecular assembly offers a new pathway in the fields of tunable photochromic fluorescent ink and cell labelling.

White-light emission from a structurally simple hydrazone

Two hydrazones featuring a unique excitation wavelength-dependent dual fluorescence emission have been developed.

Construction and efficient dye adsorption of supramolecular hydrogels by cyclodextrin pseudorotaxane and clay

Supramolecular hydrogels, which are usually used to develop excellent smart soft materials, are widely applied in miscellaneous fields due to their inherent reversible properties, unique functions and mechanical properties. Compared with covalently linked hydrogels, supramolecular hydrogels have advantages of easy preparation, stimulus responsiveness and good biocompatibility. Herein, after threading amino-modified β-cyclodextrins onto poly(propyleneglycol)bis(2-amionopropylether) (PPG-NH2) chains, the resultant pseudorotaxanes non-covalently interacted with a clay nanosheet (CNS) matrix to construct supramolecular hydrogels bearing negative charges, and the mechanical properties of these hydrogels were positively correlated with the number of amino groups on the pseudorotaxane. Significantly, these hydrogels presented good adsorption properties for cationic dyes. The adsorption capacity (Qe) of the hydrogels towards rhodamine B (RhB), crystal violet (CV), and methylene blue (MB) could reach 181-228 mg g-1, and most of the dyes were adsorbed within 5 min. Thus, these hydrogels may have potential applications in the field of waste water treatment.

Single Chromophore-Based White-Light-Emitting Hydrogel with Tunable Fluorescence and Patternability

Bioluminescence is widespread in nature such as the jellyfish, which inspires scientists to design polymer hydrogels with tunable fluorescence. However, it remains a big challenge to develop white-light-emitting hydrogels with local tunability of the fluorescent behavior. Herein, we report a white fluorescent hydrogel prepared by one-pot micellar copolymerization of hydrophilic acrylamide and hydrophobic single donor-acceptor chromophore monomer, in which the unimer and the dimer of the chromophore coexist and generate high- and low-energy emission, respectively, under excitation. The fluorescent behavior of the hydrogel can be well tuned by phototreatment or heat treatment that induces unimer-to-dimer transformation of the chromophore and thus variation of the fluorescent color from blue to white and then to yellow. The fluorescence can also be reversibly switched off by forming terpyridine-Cu²⁺ chelate complexes and recovered by using chelating agent to extract the Cu²⁺ ions out of the gel matrix. These properties afford patterning the fluorescent hydrogel, which is transparent under daylight yet shows the pattern under ultraviolet light. These patterned fluorescent hydrogels should find applications in protected message display for improved information security.

Dynamic hydrogels mediated by macrocyclic host-guest interactions

Hydrogels have attracted increasing research interest in recent years due to their dynamic properties and potential applications in biomaterials. Concurrently, macrocycle-based host-guest interactions have played an important role in the development of supramolecular chemistry. Recently, research towards dynamic hydrogels mediated by various macrocyclic host-guest interactions has been gradually disclosed. In this review, we will outline the burgeoning progress in the development of functional hydrogels mediated by various host molecules, such as cyclodextrins, cucurbit[n]urils, calix[n]arenes, pillar[n]arenes, and other macrocycles. Smart hydrogels with outstanding properties, like biocompatibility, toughness, and self-healing, are mainly focused. We believe that this review will highlight the potential of dynamic hydrogels mediated by macrocycle-based host-guest interactions.

Bistable [2]rotaxane encoding an orthogonally tunable fluorescent molecular system including white-light emission

By combining a rotaxane-type molecular switch and traditional fluorescent switch, an orthogonally tunable fluorescent molecular system was constructed, which can generate multicolor fluorescence including white light.

Hyperbranched poly(ether amine) nanomicelles as nanoreactors for the unexpected ultrafast photolysis of fluorescein dyes

hPEA nanomicelles can encapsulate fluorescein dyes as a nanoreactor, leading to the fast photobleaching of dyes.

Macrocycle crosslinked mesoporous polymers for ultrafast separation of organic dyes

Mesoporous polymers were synthesized by interfacial polymerization of macrocycles (sulfonatocalix[4]arenes and pillar[5]arenes) and terephthaloyl chloride.

Tunable photo-luminescence behaviors of macrocycle-containing polymer networks in the solid-state

Two porous polymers were synthesized from tetraphenylethylene (TPE) crosslinked β-cyclodextrins (β-CD) and sulfonatocalix[4]arene (SC4A).