Droplet Microfluidics-Assisted Fabrication of Shape Controllable Iron-Alginate Microgels with Fluorescent Property.

Droplet-based microfluidics-assisted fabrication of alginate microgels has extensive applications in biomaterials, biomedicines, and related fields. This approach is typically achieved by crosslinking droplets of an aqueous solution of sodium alginate with various divalent and trivalent ions, such as Ca2+, Ba2+, Sr2+, etc. Despite the exceptional features exhibited by bulk alginate hydrogels when using iron ions as the crosslinking reagent, including stimulus responsiveness and complex chemistry, no attention has been given to studying the fabrication of Fe-alginate microgels through droplet microfluidics. In this work, a facile method is presented for fabricating Fe-alginate microgels using single emulsion droplets as templates and an off-chip crosslinking technique to solidify the droplets. The morphologies of the resulting microgels can be systematically adjusted by manipulating different parameters such as viscosities and ionic strength of the collecting solutions. It should be noted that these resulting microgels undergo a color change from light brown to dark brown due to presumed self-oxidation of iron ions within their skeleton structure. Furthermore, these Fe-alginate microgels are functionalized by decorating them with a positively charged linear polymer via electrostatic interactions to impart them with stable fluorescent property. These functionalized Fe-alginate microgels may find potential applications in drug delivery carriers and biomimetic structures.

Injectable Thermosensitive Iodine-Loaded Starch-g-poly(N-isopropylacrylamide) Hydrogel for Cancer Photothermal Therapy and Anti-Infection.

Although photothermal therapy (PTT) can effectively eliminate tumors, the normal tissues near tumors are inevitably damaged by heat and infected by bacteria, which greatly limits the therapeutic effect. In this work, an injectable thermosensitive hydrogel based on iodine-loaded starch-g-poly(N-isopropylacrylamide) (PNSI) is developed to overcome this problem. FTIR, 1 H NMR, and UV-vis spectra confirm the graft copolymerization of poly(N-isopropylacrylamide) with starch and the formation of "iodine-starch" complex. Transmission electron microscope images show PNSI polymer self-assembles into regular spherical nanogel with a size of ≈50 nm. The concentrated nanogel dispersion is a sol at room temperature and transforms to hydrogel at body temperature. Under NIR laser irradiation for 10 min, the ΔT of the nanogel dispersion approachs about 20 °C with excellent thermal stability and high cytotoxicity due to the photothermal effect of the "iodine-starch" complex. After intratumor injection, this injectable hydrogel efficiently inhibites the tumor growth under 808 nm laser irradiation. Furthermore, it can also suppress Staphylococcus aureus infection in the wound post-PTT due to the release of iodine, which promotes wound healing. Therefore, this injectable thermosensitive "iodine-starch" composite hydrogel with advantages of good biocompatible and easy preparation possesses potential application for tumor photothermal therapy and antibacterial infection.

Reversible Redox Switching of Concurrent Luminescence and Visual Color Change Based on Lanthanide Metallogel.

The development of reversible redox supramolecular gels capable of concurrent luminescence switch and visible color change with the facile redox process has always been an intriguing challenge. A redox-responsive supramolecular lanthanide metallogel with strong luminescence and yellow color is obtained via coordination interaction between 3,5-dinitrosalicylic acid (DNSA) and europium (Eu3+). Upon the addition of TiO2 to the prepared gel (DNSA/Eu3+ gel), the oxidation process of the gel (DNSA/Eu3+/TiO2 gel) can be easily achieved by UV irradiation. The DNSA/Eu3+/TiO2 gel exhibits a concurrent reversible "on-off" luminescence and color change in response to redox stimuli. The DNSA/Eu3+/TiO2 gel shows a concurrent quench of luminescence and a color change from yellow to red when the gel was stimulated by the reductant. Upon UV irradiation, the luminescence and color of the reduced DNSA/Eu3+/TiO2 gel restored to its initial state due to the strong oxidation ability of hydroxyl radicals derived from photocatalytic oxidation of TiO2. The results of UV-vis and mass spectroscopy indicated that the reversible redox responsiveness of DNSA/Eu3+/TiO2 gel depends on the reversible oxidation-reduction reactions of DNSA. Moreover, DNSA/Eu3+/TiO2 gel remains stable because the morphology of the gel had no change during the redox process. Exemplarily, the application of DNSA/Eu3+/TiO2 gels to achieve luminescent patterning was investigated. The results demonstrated that the prepared metallogel has potential applications in the fields of writable materials, anticounterfeiting, sensors, and others.

One-step preparation of nano-in-micro poly(vinyl alcohol) embolic microspheres and used for dual-modal T1/T2-weighted magnetic resonance imaging.

It is crucial to develop dual or multi-modal self-imaging embolic microspheres to evaluate the effects of transcatheter arterial embolization therapy of tumor. However, the preparation of such hybrid microspheres always involved in multiple steps or complicated conditions. Here, poly(vinyl alcohol) (PVA) hybrid microspheres with dual-modal T1/T2-weighted magnetic resonance imaging (MRI) have been prepared based on microfluidic technique in one step. Gd2O3 and Fe3O4 nanoparticles with a size of ~5 nm act as T1- and T2-weighted MRI contrast agents, respectively, which are simultaneously in-situ synthesized in the PVA matrix via the reaction of metal ions and alkali with PVA chains as a soft template. Meanwhile, these metallic-oxide nanoparticles act as cross-linker to gelatinize the PVA droplets to obtain nano-in-micro PVA microspheres in one step. This procedure is simple, economic and feasible. The obtained nano-in-micro PVA microspheres show good magnetothermal effect, enhanced T1- and T2-weighted MRI and embolization effect.

In situ pore-forming alginate hydrogel beads loaded with in situ formed nano-silver and their catalytic activity.

An aqueous mixture of sodium carbonate (Na2CO3) and sodium alginate (Na-ALG) was added dropwise into an aqueous solution of Ca(NO3)2, leading to the formation of calcium alginate (Ca-ALG) hydrogel beads. Meanwhile Na2CO3 as a pore-forming precursor was transformed in situ into CaCO3 nanoparticles (CaCO3 NPs). SEM images show that CaCO3 NPs aggregates with a size of ∼10 µm were uniformly distributed in the Ca-ALG hydrogel beads. After subsequent erosion using acetic acid, Ca-ALG hydrogel beads with a uniform microporous structure were obtained. The porosity and specific surface area of such in situ pore-formed hydrogel beads are 16 and 14 times higher than those of the beads prepared in the absence of Na2CO3. Additionally, their porous structure can be modulated by varying the amount of Na2CO3. The obtained porous Ca-ALG hydrogel beads were further immersed into an aqueous solution of AgNO3. Under UV irradiation, the Ag(+) ions adsorbed in the Ca-ALG were in situ reduced to Ag nanoparticles (Ag NPs). SEM and TEM images show that Ag NPs with a size of ∼10 nm were uniformly distributed in the matrix of the hydrogel beads. The loading amount of Ag in the beads can also be modulated by varying the amount of Na2CO3. Furthermore, the resultant Ca-ALG beads loaded with Ag NPs (Ag/Ca-ALG) were used as catalysts. Their catalytic activity was evaluated by using the reduction reaction of 4-nitrophenol as a model reaction. The rate constant of the reaction in the presence of dry porous Ag/Ca-ALG beads was found to be 36 times higher than that in the presence of beads prepared in the absence of Na2CO3. Such a high catalytic efficiency can be attributed to their porous structure and consequent high Ag-loading capacity.

Ion-unquenchable and thermally "on-off" reversible room temperature phosphorescence of 3-bromoquinoline induced by supramolecular gels.

Ion-unquenchable and thermally on-off reversible room temperature phosphorescence (RTP) can be induced by entrapping 3-bromoquinoline (3-BrQ) into supramolecular gels formed by the self-assembly of a sorbitol derivative (DBS). In comparison with conventional substrates inducing RTP, the gel state 3-BrQ/DBS can produce strong RTP due to the efficient restriction of the vibration of 3-BrQ. Notably, the rather inconvenient deoxygenation is no longer necessary in the preparation of 3-BrQ/DBS gels. The produced RTP was found to be very fast to reach stable, not depending on the standing time. As a reference, in the liquid state of 3-BrQ/sodium deoxycholate (NaDC), stable RTP can be observed after standing for 5 h. The investigation of RTP quenching indicates that the mechanism of RTP induced by DBS gels mainly involves the microenvironment in which 3-BrQ is located. 3-BrQ was entrapped in the hydrophobic 3D network structure of DBS gels, thereby restricting the motion and collision of 3-BrQ and avoiding RTP quenching and additionally quenching by ions. Furthermore, the RTP of 3-BrQ/DBS gels show an excellent "on-off" effect at 10 or 80 °C. This indicates that the solid DBS gel is beneficial for the preparation of RTP sensor devices.

X-ray visible and uniform alginate microspheres loaded with in situ synthesized BaSO4 nanoparticles for in vivo transcatheter arterial embolization.

The lack of noninvasive tracking and mapping the fate of embolic agents has restricted the development and further applications of the transcatheter arterial embolization (TAE) therapy. In this work, inherent radiopaque embolic material, barium alginate (ALG) microspheres loaded with in situ synthesized BaSO4 (denoted as BaSO4/ALG microspheres), have been synthesized by a one-step droplet microfluidic technique. One of the advantages of our microfluidic approach is that radiopaque BaSO4 is in the form of nanoparticles and well dispersed inside ALG microspheres, thereby greatly enhancing the imaging quality. The crystal structure of in situ synthesized BaSO4 nanoparticles in ALG microspheres is confirmed by X-ray diffraction analysis. Results of in vitro and in vivo assays from digital subtraction angiography and computed tomography scans demonstrate that BaSO4/ALG microspheres possess excellent visibility under X-ray. Histopathological analysis verifies that the embolic efficacy of BaSO4/ALG microspheres is similar to that of commercially available alginate microsphere embolic agents. Furthermore, the visibility of radiopaque BaSO4/ALG microspheres under X-ray promises the direct detection of the embolic efficiency and position of embolic microspheres after embolism, which offers great promises in direct real-time in vivo investigations for TAE.

Multifunctional photonic microobjects with asymmetric response in radial direction and their anticounterfeiting performance.

There are few explorations that have integrated multiple properties into photonic microobjects in a facile and controlled manner. In this work, we present a straightforward method to integrate different functions into individual photonic microobject. Droplet-based microfluidics was used to produce uniform droplets of an aqueous dispersion of monodispersed SiO2 nanoparticles (NPs). The droplets evolved into opal-structured photonic microballs upon complete evaporation of water. After infiltration of an aqueous solution of acrylamide (AAm) and acrylic acid (AAc) monomers into the interstices among SiO2 NPs, opal-structured SiO2 NPs/pAAm-co-AAc hydrogel composite photonic microballs were obtained upon UV irradiation. Afterwards, a wet etching process was introduced to etch the microballs in a controlled manner, yielding individual photonic microball composed of an SiO2 NPs/pAAm-co-AAc composite opal core and a neat pAAm-co-AAc shell. The pendant carboxylic acid groups in the skeleton of the hydrogel matrix were further utilized to react with positively charged compounds, such as Ruthenium compound containing fluorescent polymers. The resulting photonic microobjects eventually featured with localized stimulus-responsive properties and multiple colors under different modes. The multifunctional photonic microobjects were discovered to have fivefold of anticounterfeiting properties when used as building blocks for anticounterfeiting structures and may have other potential applications.

New features of edge-selectively hydroxylated graphene nanosheets as NIR-II photothermal agent and sonothermal agent for tumor therapy.

Second near-infrared (NIR-II) laser-mediated photothermal therapy and sonothermal therapy using low-intensity focused ultrasound exposure for tumors have attracted increasing attention owing to their ability to penetrate deep tissues and provide noninvasive ablation with high therapeutic efficacy. However, their applications were limited by the shortness of optimal NIR-II photothermal agents and sonothermal agents. In this study, we discovered that the edge-selectively hydroxylated graphene nanosheets (EHG NSs) with excellent water dispersibility and an "intact conjugated plane" were not only an outstanding NIR-II photothermal agent but also an effective sonothermal agent for tumor therapy. EHG NSs were incorporated into an injectable adhesive thermosensitive hydrogel with a characteristic sol-gel phase transition behavior. EHG NSs endowed the injectable hydrogel with an exceptional photothermal effect under the laser irradiation (1064 nm, 1.0 W cm-2) as well as an effective sonothermal effect under ultrasonic exposure (3.0 MHz, 2.1 W cm-2), effectively killing tumor cells in vitro and inhibiting tumor growth after intratumoral injection. Especially, the NIR-II photothermal therapy based on the hybrid hydrogel completely ablated the primary tumors and effectively activated systemic anti-tumor immune responses benefiting from the protein adsorption capacity of the injectable hydrogel, significantly inhibiting the growth of the distal tumors. Collectively, EHG nanosheets loaded in the injectable hydrogel will be a promising "all-rounder" for noninvasive deep penetrating thermotherapy and a potent platform that integrates various therapies.

Janus photonic crystal microspheres: centrifugation-assisted generation and reversible optical property.

A new strategy to prepare core/shell Janus photonic crystal (PC) microspheres with reversible optical spectrum property is demonstrated. The microfluidic technique was employed to generate the uniform core/shell PC microspheres containing nanogels aqueous suspension. Under centrifugal force, the nanogel particles homogeneously dispersed in the core of microspheres would aggregate in the half of the microspheres, leading to Janus PC microspheres with varied reflection spectra at the different side of the spheres. More interestingly, such Janus structure of PC microspheres and their reflection spectrum were significantly reversible when the centrifugation was employed and removed alternatively. In addition, due to the soft and thermal-responsive nature of the building blocks (e.g., nanogels), Janus structures and optical properties of the PC microspheres are highly influenced by the temperature, centrifugal speed, and time, providing the other parameters on the manipulation of properties of the PC microspheres. This strategy provides a new concept for the preparation of Janus PC microspheres with tunable structures and optical properties, which will find potential applications in the field of sensors, optical devices, barcodes, etc.

Sulfate-reducing bacteria loaded in hydrogel as a long-lasting H2S factory for tumor therapy.

The continuous supply of hydrogen sulfide (H2S) gas at high concentrations to tumors is considered a promising and safe strategy for tumor therapy. However, the absence of a durable and cost-effective H2S-producing donor hampers its extensive application. Sulfate-reducing bacteria (SRB) can serve as an excellent H2S factory due to their ability to metabolize sulfate into H2S. Herein, a novel injectable chondroitin sulfate (ChS) hydrogel loaded with SRB (SRB@ChS Gel) is proposed to sustainably produce H2S in tumor tissues to overcome the limitations of current H2S gas therapy. In vitro, the ChS Gel not only supports the growth of encapsulated SRB, but also supplies a sulfate source to the SRB to produce high concentrations of H2S for at least 7 days, resulting in mitochondrial damage and immunogenic cell death. Once injected into tumor tissue, the SRB@ChS Gel can constantly produce H2S for >5 days, significantly inhibiting tumor growth. Furthermore, such treatment activates systemic anti-tumor immune responses, suppresses the growth of distant and recurrent tumors, as well as lung metastases, meanwhile with negligible side effects. Therefore, the injectable SRB@ChS Gel, as a safe and long-term, self-sustained H2S-generating factory, provides a promising strategy for anti-tumor therapy.

Microfluidic fabrication and thermoreversible response of core/shell photonic crystalline microspheres based on deformable nanogels.

Soft photonic crystals (PC) are more appealing due to the responsiveness of the building blocking-deformable nanoparticles to the external stimuli. In this report, we demonstrate, for the first time, the generation of soft core/shell PC microspheres through a combination of a microfluidic technique, encapsulation of well-ordered temperature responsive polymer nanogels suspension, and photopolymerization of a transparent shell resin. This strategy not only ensures the monodispersity of core/shell PC microspheres, but also precisely controls their size, shell thickness, and optical properties by simply adjusting the flow rate ratio and mass fraction of the nanogels. More interestingly, the intensity of the reflection spectra of the crystalline nanogel arrays in the core can be modulated reversibly by controlling the shell thickness or the temperature. As a result of their symmetric structure, the resulting PC microspheres exhibited excellent structural colors and photonic band gaps for normal incident light independent of the position on the spherical surface. Multifunctional PC microspheres can also be generated by simply dispersing functional species together with the nanogels. This core/shell PC microsphere with tunable shell thickness and reversible thermoresponse could be significant for potential applications in the fields of chemical/biological sensors, display, encoding, and optical switching.

Naked-eye sensing and target-guiding treatment of bacterial infection using pH-tunable multicolor luminescent lanthanide-based hydrogel.

In this work, a pH-tunable multicolor luminescent lanthanide-based hydrogel (CS/DEX/CP) was prepared based on lanthanide coordination polymer (CP), dextran aldehyde (DEX) and chitosan (CS). The CP was obtained by the self-assembly of guanosine acid (GMP), ciprofloxacin (CIP), Eu3+, and Tb3+. As-prepared CS/DEX/CP hydrogel could emit blue, green, and red luminescence of CIP, Tb3+, and Eu3+, respectively. It was also found that the luminescence of CS/DEX/CP hydrogel exhibited visual color change in the pH range of 5.5 to 8. Such pH-sensitive hydrogel was multicolor-responsive to protons produced by bacterial growth, therefore, it could provide early warning of bacterial infection by naked-eye. In addition, the increased acidity resulted in not only the degradation of acid-labile Schiff base linkages between DEX and CS, but also the fracture of coordination between CIP and lanthanide ions. As a result, the released CIP and CS showed significantly antibacterial activity against both S. aureus and E. coli.

Cascade Reaction of "Mn2+ -Catechol" Triggered by H2 O2 to Integrate Firm Tumor Vessel Embolization and Hypoxic Response Relief.

Transcatheter arterial embolization (TAE) therapy requires firm and long-term vessel embolization without recanalization. However, firm embolization usually leads to unanticipated hypoxic response which promotes tumor recurrence and metastasis. Herein, an injectable thermosensitive hydrogel containing catechol groups and Mn2+ (PNDM) has been developed to enhance embolization and inhibit hypoxic response utilizing augmented H2 O2 after TAE. This novel embolic agent converts H2 O2 into hydroxyl radicals via Mn2+ -dependent Fenton-like reaction, which are subsequently scavenged through a "catechol-quinone" transition to suppress hypoxic responses. Quinone structure can not only make hydrogel internal structure more compact, but also enhance hydrogel adhesion to vessel wall. In vivo experiments confirm that the rabbit renal artery can be firmly embolized for 84 days. Studies in liver VX2 tumor-bearing rabbits demonstrate that the PNDM-based TAE can promote tumor necrosis, inhibit angiogenesis and tumor metastasis, and greatly prolong rabbit survival. This strategy opens new sights in the TAE therapy for liver cancer.

Carboxymethyl chitosan‒promoted luminescence of lanthanide metallogel and its application in assay of multiple metal ions.

In this work, the luminescence of lanthanide supramolecular metallogel formed by the self-assembly of 5,5',5″-(1,3,5-triazine-2,4,6-triyl)tris(azanediyl)triisophthalate (H6L) and Tb3+ was efficiently promoted by carboxymethyl chitosan (CMCS). The total quantum yield of the resultant metallogel (denoted as H6L/Tb3+/CMCS gel) was 9 times higher than the gel without CMCS. The average lifetime of H6L/Tb3+/CMCS gel increased from 0.51 ms to 1.20 ms. More importantly, the aqueous dispersion of H6L/Tb3+/CMCS xerogels showed a stable and pH-dependent luminescence. Based on the selective affinity of CMCS to different metal ions as well as with the aid of principal component analysis, H6L/Tb3+ /CMCS can be used as a sensor array to distinguish 11 metal ions (P < 0.05). This work provides a new strategy for the design and development of bio-based functional luminescent lanthanide supramolecular metallogels.

Luminescence sensitization of terbium-loaded supramolecular gels by hydroxybenzoic acids and used for salicylates sensing.

The luminescent terbium (Tb3+)-loaded supramolecular gels were facilely prepared through the self-assembly of Fmoc-diphenylalanine (FmocPhePhe) at room temperature. Hydroxybenzoic acid (HA, the isomers are denoted as 2-HA, 3-HA, and 4-HA depending upon the positions of hydroxyl groups) was used as a sensitizer to Tb3+. The luminescence sensitization of Tb3+ in the gels was realized by the coordination with hydroxybenzoic acids. The spectra of luminescence, UV-vis, FT-IR, and 1H NMR verified that this sensitization was attributed to the energy transfer from hydroxybenzoic acids to Tb3+. The results of XRD, SEM, and phase transfer temperature further indicated that the initial molecule arrangement of the gels was significantly changed by 2-HA, resulting in more ordered and more compact morphology of the gels. 2-HA exhibited more effective sensitization to Tb3+ in the gels than 3-HA and 4-HA. It was also found that 2-HA did not affect the self-assembly of FmocPhePhe. Due to the effective fluorescence sensitization by 2-HA, the as-prepared gels can be used for salicylic acid sensing with 6.8 µM of the detection limit. This strategy has been successfully used for the detection of salicylates in pharmaceuticals and cosmetics.

Injectable zwitterionic thermosensitive hydrogels with low-protein adsorption and combined effect of photothermal-chemotherapy.

Injectable hydrogels have been developed as biomedical materials in various fields but the biofouling on their surface limits applications in vivo. In this work, a zwitterionic structure was introduced into an injectable hydrogel based on thermosensitive nanogels to overcome the foreign body reaction. The hydrodynamic diameter of the resultant poly(N-isopropylacrylamide-co-sulfobetaine methacrylate) (PNS) nanogels was ca. 105 nm. The aqueous dispersion with a high content of PNS nanogels showed a flowable sol state at room temperature, and turned into a hydrogel in situ at ∼36 °C due to the thermosensitivity of the PNS nanogels. In particular, the resulting hydrogel exhibited lower biofouling both in vitro and in vivo in comparison with similar hydrogels without a zwitterionic structure. Polydopamine nanoparticles (PDA NPs) as a photothermal agent and an anti-tumour drug could be easily co-loaded in the injectable hydrogel. Under near-infrared (NIR) irradiation for 10 min, the temperature of the PNS system containing PDA NPs could reach ca. 38 °C. The drug release from the in situ-forming hydrogel could be accelerated by NIR laser irradiation, and showed a sustainable release behavior and adjustability. The results of intratumoral injection of the as-prepared injectable hydrogel containing PDA NPs and an anti-tumour drug showed significant anticancer effects combining photothermal therapy and local chemotherapy. This constructed injectable zwitterionic thermosensitive hydrogel is easy to use with the advantage of low-fouling and may become a promising platform for various biomedical applications.

Osmosis manipulable morphology and photonic property of microcapsules with colloidal nano-in-micro structure.

Full visible spectrum photonic droplets and consequent microcapsules with nano-in-micro structure were prepared through microfluidic technique. Photo-curable resin and suspension of monodispersed soft nanogels were used as shell and core of the microcapsules, respectively. Upon UV irradiation, the droplets can be subsequently transformed into photonic microcapsules with an ultrathin polymeric shell. The shell thickness of the photonic microcapsules was found to be approximately 700 nm. Due to the ultrathin shell and soft core, the photonic microcapsules with nano-in-micro structure display dramatic changes both in shapes and photonic property under the impact of osmosis effect or temperature stimulus. Typically, the shell and core parts of nano-in-micro structure could respectively undergo a size expansion/even rupture and a size decrease/buckling under hypotonic and hypertonic condition. Correspondingly, the peak value of the reflection spectra of the microcapsules showed a redshift and blue shift, respectively. The mechanism to the structure and optical properties variation involves the osmotic pressure induced the volume-fraction change of the nanogel-based photonic dispersion and the shell buckling of the core/shell microcapsules.

Multi-Responsive Lanthanide-Based Hydrogel with Encryption, Naked Eye Sensing, Shape Memory, Self-Healing, and Antibacterial Activity.

In this work, we reported a multi-responsive luminescent hydrogel with properties of encryption, naked eye sensing of glucose, shape memory, self-healing, and antibacterial activity. The hydrogel (GA/CCS/DNSA/Eu3+) was obtained by mixing phenylboronic acid-modified gelatin (GA-DBA), catechol-modified carboxymethyl chitosan (CCS-PCA), 3,5-dinitrosalicylic acid (DNSA), and Eu3+ ions through a facile heating-cooling process. The resultant hydrogel exhibits reversible luminescence and color and phase changes in response to temperature, acid/base, salt, and redox stimuli. Based on the multiple responsiveness, information encryption and decryption, naked eye sensing of glucose, remarkable shape memory, and enhanced mechanical properties of the as-prepared hydrogel were realized. In addition, the self-healing capacity was also achieved due to the dynamic bonds in GA/CCS/DNSA/Eu3+ hydrogels. Specifically, the GA/CCS/DNSA/Eu3+ hydrogels possess antibacterial activity owing to the bacteriostasis of the CCS-PCA and DNSA/Eu3+ complex. Thus, GA/CCS/DNSA/Eu3+ hydrogels have potential applications in the fields of anticounterfeiting, wearable devices, biomedicine, sensing, etc.

A heat-set lanthanide metallogel capable of emitting stable luminescence under thermal, mechanical and water stimuli.

Preparing luminescence-stable lanthanide materials in a facile manner has always been an intriguing challenge. Herein we report an easy approach to the preparation of a heat-set lanthanide-based metallogel (H6L/Tb gel) with stable luminescence from 5,5',5''-(1,3,5-triazine-2,4,6-triyl)tris(azanediyl) triisophthalate (H6L) as a Tb3+ coordinating ligand. The heat-set H6L/Tb gel exhibits luminescence that mostly retains its intensity in the 0-90 °C temperature range and under mechanical stimulus. In addition, the H6L/Tb xerogel is also luminescent in aqueous solution. UV-vis and FT-IR spectroscopy and XRD studies reveal that the stable luminescence of the H6L/Tb gel depends on heat-set-induced strong hydrogen bonding, π-π stacking, and metal-ligand interactions. This study provides a heat-set approach to the preparation of luminescence-stable metallogel materials, such metallogels are potentially useful in anti-counterfeiting and sensing fields, among others.