Chameleon Luminophore for Erasable Encrypted and Decrypted Devices: From Dual-Channel, Programmable, Smart Sensory Lanthanide Hydrogel to Logic Devices

Tailoring Nanomaterial Cross-Linkers through Lanthanide-Ligand Pairs: Guidance for Fine-Tuning the Structures and Properties of Luminescent Nanocomposite Hydrogels

Integrating luminescent nanomaterials into hydrogels provides unique optical properties and improves their mechanical features for various applications. It is challenging but highly desirable to develop a versatile luminescent nanocomposite hydrogel system with tunable structures and properties to expand the potential uses of luminescent materials. Here, multiple amine-functionalized lanthanide-containing hydroxyapatites are synthesized as tailored nanomaterial cross-linkers to interact with polydextran aldehyde through imine bonds. The microstructure, gelation time, luminescence, rheological behavior, mechanical properties, thermal stability, degradation, and swelling capability of the luminescent lanthanide-containing nanocomposite hydrogels are systematically investigated. This study reveals that the strong binding affinity between surface metal ions and capping ligands of the nanomaterial cross-linkers contributes to the densest network and the highest mechanical properties of the nanocomposite hydrogels. In addition, these nanocomposite hydrogels possess dynamic features of self-healing, shear-thinning, and injectability, improving their suitability for advanced applications. The luminescent lanthanide-containing nanocomposite lyophilized hydrogels are also demonstrated in the differentiation of volatile organic compounds. Taken together, the adjustable microstructures and characteristics of this lanthanide-containing nanocomposite hydrogel system highlight its potential for offering guidance in producing diverse luminescent materials with definable performances across various fields.

Multiple-Temperature-Responsive Double- and Triple-Network Hydrogels

Temperature-responsive hydrogels which are reversibly activated attract much attention in the field of smart materials. Herein, double- and triple-network hydrogels exhibiting dual- or triple-volume transitions upon changes of temperature are fabricated. Interestingly, the incorporation of superhydrophilic polymer network leads to a significant difference swelling or shrinkage of the multiple-network hydrogels. Applications of such hydrogels are envisioned in soft robotics or for producing programmable reactors.

4D Assembly of Time-dependent Lanthanide Supramolecular Multicolor Phosphorescence for Encryption and Visual Sensing

Supramolecular dynamic room temperature phosphorescence (RTP) is the focus of current research because of its wide application in biological imaging and information anti-counterfeiting. Herein, a time-dependent supramolecular lanthanide phosphorescent 4D assembly material with multicolor luminescence including white, which is composed of 4-(4-bromophenyl)-pyridine salt derivative (G), inorganic clay (LP)/Eu complex and pyridine dicarboxylic acid (DPA) is reported. Compared with the self-assembled nanoparticle G, the lamellar assembly G/LP showed the double emission of fluorescence at 380 nm and phosphorescence at 516 nm over time. Within 60 min, the phosphorescence lifetime and the quantum yield increases from none to 7.4 ms and 27.53% respectively, achieving the time-dependent phosphorescence emission, due to the limitation of progressive stacking of LP electrostatically driven "domino effect." Furthermore, the 4D assembly of DPA and G/LP/Eu leads to a time-resolved multicolor emission from colorless to purple to white, which is successfully applied to information multi-level logic anti-counterfeiting and efficiently antibiotic selective sensor.

Preparation of carboxymethyl chitosan-Tb3+ (CMCh-Tb3+) fluorescent probe: For high-sensitivity Cu2+ detection and mechanism study

Carboxymethyl chitosan (CMCh) is a natural polysaccharide derivative with biodegradability, rich in active amino and carboxyl groups. It can act as a ligand to coordinate with rare earth ions, transferring absorbed energy to the central ion to sensitize its luminescence. In this paper, CMCh-Tb3+ was prepared as a solid fluorescent probe by mixing CMCh solution with Tb3+. The morphology, structure and properties of CMCh-Tb3+ were characterized and analyzed by SEM, IR and XPS, and then the chemical structure of CMCh-Tb3+ was determined. CMCh-Tb3+, as a highly sensitive fluorescent sensor for detecting Cu2+, has a detection limit (LOD) of 27.14 nmol/L. Through characterization using fluorescence spectroscopy, ultraviolet absorption spectroscopy, and fluorescence lifetime, we further explored the mechanism of Cu2+ fluorescence quenching, finding that this process is primarily achieved through dynamic quenching. Additionally, we discovered that glutathione (GSH) can form a strong coordination with Cu2+, thereby inhibiting the quenching effect of Cu2+ on the emission intensity of CMCh-Tb3+ and restoring its luminescence characteristics. This finding indicates that CMCh-Tb3+ can not only serve as a fluorescence sensor for detecting Cu2+ but also as a reversible fluorescence sensor, significantly enhancing its performance in practical applications.

Lanthanide MOF-based luminescent sensor array for detection and identification of contaminants in water and biomarkers

In today's society, heavy metal ions and antibiotic contaminants have caused great harm to water systems and human health. In this study, six isostructural lanthanide metal-organic frameworks [Ln(H3imda)2(TPA)(H2O)2](Tb for CUST-881, Eu for CUST-882, Dy for CUST-883, Er for CUST-884, Nd for CUST-885, Sm for CUST-886) were constructed by selecting terephthalic acid (TPA) and 4,5-Imidazoledicarboxylic acid (H3imda) and lanthanide metal ions via solvethermal method. Among them, CUST-881 and CUST-882 can selectively detect Fe3+, Cr2O72-, CrO42, and ceftriaxone sodium (CRO) in water systems and uric acid in urine. CUST-881 shows very low detection limits for these five substances. Furthermore, Principal Component Analysis (PCA) was used to distinguish Fe3+, Cr2O72-, CrO42-, and CRO in water. To our knowledge, this is the first time that they have been able to be simultaneously distinguished. In addition, the possible sensing mechanism was studied through UV-visible spectroscopy, Infrared spectroscopy, and PXRD analysis. Furthermore, the probe also showed satisfactory repeatability and recovery when applied to UA samples that simulated urine. Based on the above results, lanthanide metal-organic frameworks have great potential for practical monitoring of contaminants in water environments.

Luminescent lanthanide-containing gelatin/polydextran/laponite nanocomposite double-network hydrogels for processing and sensing applications

Lanthanide-containing nanomaterials have gained significant popularity for their utilization in polymeric networks, enabling the creation of luminescent nanocomposites for advanced applications. In this study, we developed a new type of lanthanide-containing nanocomposite hydrogels by incorporating terbium-containing laponite (Tb3+@Lap) into the networks of polyethyleneimine-modified gelatin/polydextran aldehyde (PG/PDA) through dynamic bonds. The structures and properties of the Tb3+@Lap-containing nanocomposite double-network (ncDN) hydrogels were comprehensively investigated in comparison with the DN hydrogels with a pure polymeric network and the Lap-containing ncDN hydrogels. The PG/PDA/Tb3+@Lap ncDN hydrogels with multiple dynamic bonds (i.e., imine bonds, coordination bonds, hydrogen bonds, and electrostatic interactions) exhibited remarkable characteristics of shear-thinning and self-healing, making them suitable for the construction of hydrogel scaffolds on a macroscale using fabrication techniques such as electrospinning and 3D printing. Moreover, the PG/PDA/Tb3+@Lap ncDN hydrogels have been demonstrated to act as sensitive and selective luminescent sensors for detecting copper ions. Taken together, a versatile lanthanide-containing ncDN hydrogel platform capable of dynamic features is developed for processing and sensing applications.

Recent studies on proteins and polysaccharides-based pH-responsive fluorescent materials

Polymer-based pH-responsive fluorescent materials have the characteristics of fast response, real-time monitoring, visualisation, and easy forming. Consequently, they have attracted widespread attention in wound healing, sweat monitoring, security and anti-counterfeiting, freshness detection of aquatic products, metal-ion sensing and bioimaging. This paper analyses the preparation principles and characteristics of pH-responsive fluorescent materials based on cellulose, chitosan and proteins. It then outlines the fluorescence properties, environmental response mechanisms and applications of various luminescent materials. Next, the research indicates that amines, N-heterocyclic rings, carboxyl groups and amino plasmonic groups on the fluorescent molecule structure and polymer skeleton appear to change the degree of ionisation under acid or alkali stimulation, which affects the light absorption ability of chromophore electrons, thus producing fluorescence changes in fluorescent materials under different pH stimuli. On this basis, the challenges and growth encountered in the development of proteins and polysaccharides-based pH-responsive fluorescent materials were prospected to provide theoretical references and technical support for constructing pH-responsive fluorescent materials with high stability, high sensitivity, long-lasting pH-response and wide detection range.

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.

Molecular Visual Sensing, Boolean Logic Computing, and Data Security Using a Droplet-Based Superwetting Paradigm

Inspired by information processing and logic operations of life, many artificial biochemical systems have been designed for applications in molecular information processing. However, encoding the binary synergism between matter, energy, and information in a superwetting system remains challenging. Herein, a superwetting paradigm was proposed for multifunctional applications including molecular visual sensing and data security on a superhydrophobic surface. A Triton X-100-encapsulated gelatin (TeG) hydrogel was prepared and selectively decomposed by trypsin, releasing the surfactant to decrease the surface tension of a droplet. Integrating the droplet with the superhydrophobic surface, the superwetting behavior was utilized for visual detection and information encoding. Interestingly, the proposed TeG hydrogel can function as an artificial gelneuron for molecular-level logic computing, where the combination of matters (superhydrophobic surface, trypsin, and leupeptin) acts as inputs to interact with energy (liquid surface tension and solid surface energy) and information (binary character), resulting in superwettability transitions (droplet surface tension, contact angle, rolling angle, and bounce) as outputs. Impressively, the TeG gelneuron can be further developed as molecular-level double cryptographic steganography to encode, encrypt, and hide specific information (including the maze escape route and content of the classical literature) due to its programmability, stimuli responsive ability, and droplet concealment. This study will encourage the development of advanced molecular paradigms and their applications, such as superwetting visual sensing, molecular computing, interaction, and data security.

Thermal Enhancement of Upconversion in Lanthanide-doped Gd2Ti2O7 Crystals via Fast Evaporation in sol-gel Procedure

Thermal quenching effect caused by the increased multi-phonon assisted non-radiative relaxation possibility greatly restricts the application of luminescent materials. Herein, a modified sol-gel method where the gels are achieved by...

Fluorescence response mechanism of green synthetic carboxymethyl chitosan-Eu3+ aerogel to acidic gases

Industrial waste acidic gases are huge hazards to the environment and human health, so a material that can detect and remove them is needed. In this paper, CM chitosan-Eu³⁺ fluorescence aerogel was prepared via a green method by combining the carboxymethyl chitosan biomass polymer with Eu³⁺ ions, the structure and properties of this aerogel were characterized by SEM, TG, and stress-strain curves. The coordination of Eu³⁺ ions and carboxymethyl chitosan was analyzed with XPS and the difference in luminescence intensity of aerogel prepared at different pH values was analyzed. The monitoring of the aerogels revealed different responses to different acidic gases, and the fluorescence intensity of the aerogel showed a linear decrease with the adsorbed hydrogen chloride gas (HCl), while acetic acid gas (HAc) enhanced fluorescence. The adsorption system of the CM chitosan-Eu³⁺ aerogel was simulated using pseudo-second-order kinetics, which showed that the maximum adsorption capacity of HCl is 9.16 mmol/g. The different response mechanisms of HCl and HAc gas were analyzed with FT-IR, fluorescence lifetime imaging and Judd-Ofelt theory. This fluorescence aerogel was found to have potential applications in ensuring industrial production safety.

Modulating electron population pathways for time-dependent dynamic multicolor displays

Multicolor luminescent nanoparticles (NPs) show several potential emerging applications. In this work, we provide a new route that integrates the afterglow and upconversion (UC) that originate in a single activator to achieve color variations without the modulation of any other parameters. The Er³⁺ ions in Na₃HfF₇:Yb/Er NPs exhibit bright green afterglow upon X-ray irradiation and single-band red UC under 980 nm laser excitation, which are attributed to the significantly different electron population pathways. The UC intensity is stable and the afterglow decreases gradually over time, thus the output color is clearly changed from green to red naturally via illuminating the pre-X-ray-irradiated NPs with a 980 nm laser. Furthermore, the fine emission profiles of Er³⁺, Ho³⁺ and Tm³⁺ are achieved upon X-ray irradiation. Our results develop a new approach for time-dependent dynamic color displays and a simple route to revealing the electronic fine structures of lanthanide activators at room temperature.

Luminescent monomeric and dimeric Ru(ii) acyclic carbene complexes as selective sensors for NH3/amine vapor and humidity

A new class of luminescent bis(bipyridyl) Ru(ii) pyridyl acyclic carbene complexes with environmentally-sensitive dimerization equilibrium have been developed. Owing to the involvement of the orbitals of the diaminocarbene ligand in the emissive excited state, the phosphorescence properties of these complexes are strongly affected by H-bonding interactions with various H-bonding donor/acceptor molecules. With the remarkable differences in the emission properties of the monomer, dimer, and H-bonded amine adducts together with the change of the dimerization equilibrium, these complexes can be used as luminescent gas sensors for humidity, ammonia, and amine vapors. With the responses to amines and humidity and the corresponding change in the luminescence properties, a proof-of-principle for binary optical data storage with a reversible concealment process has been described.

Putting Ink into Polyion Micelles: Full-Color Anticounterfeiting with Water/Organic Solvent Dual Resistance

Anticounterfeiting paintings are usually with limited colors and easy blurring and need to be dispersed in an environmentally unfriendly organic solvent. We report a set of water-based polyion micellar inks to solve all these problems. Upon complexation of reversible coordination polymers formed with rare earth metal ions Eu³⁺ and Tb³⁺ and the aggregation-induced emission ligand tetraphenylethylene-L₂EO₄ with oppositely charged block polyelectrolyte P2MVP₂₉-b-PEO₂₀₅, we are able to generate polyion micelles displaying three elementary emission colors of red (R) (Φ_Eu³⁺ = 24%), green (G) (Φ_Tb³⁺ = 7%), and blue (B) (Φ_TPE = 9%). Full-spectrum emission and white light emission (0.34, 0.34) become possible by simply mixing the R, G, and B micelles at the desired fraction. Strikingly, the micellar inks remain stable even after soaking in water or organic solvents (ethyl acetate, ethanol, etc.) for 24 h. We envision that polyion micelles would open a new paradigm in the field of anticounterfeiting.

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.