Luminescent magnetic nanoparticles encapsulated in MOFs for highly selective and sensitive detection of ClO-/SCN- and anti-counterfeiting

Encapsulating Fe3O4 Nanoparticles and Carbon Dots in a Metal-Organic Framework for Magnetic Fluorescent Taggants

Magnetic fluorescent composite nanomaterials have broad application prospects in the fields of biological imaging, anticounterfeiting identification, suspicious object tracking, and identification of latent fingerprints in forensic medicine. For an effective taggant, a clearly visible identifying mark is necessary to enable observers to capture labeling information quickly and accurately, even from a distance. The preparation method of magnetic fluorescent composite materials is complicated and usually needs different surface modification and assembly processes. The limited loading capacity of fluorescent materials also limits the fluorescence properties of the composite, so it is difficult to produce obvious fluorescence as a taggant to meet the requirements of visible labeling. In this study, a core-shell structure of a magnetic fluorescent composite was prepared by using the metal-organic framework ZIF-8 as the host of fluorescent materials and an encapsulation shell coated on the Fe3O4 nanoparticles. The porous ZIF-8 is beneficial for increasing the loading capacity of fluorescent materials to ensure the fluorescence performance of the composite materials. Further modification of the composite surface prevented the desorption of fluorescent materials from the pores of ZIF-8, enabling the samples to maintain good fluorescence properties even after multiple washing cycles. The preparation method is simple, rapid, and cost-effective, and the prepared magnetic fluorescent composite nanomaterial has high magnetic separation performance and fluorescence performance, making it a promising material for identification, marking, and tracking.

Selective detection of food contaminants using engineered gallium-organic frameworks with MD and metadynamics simulations

The exclusion mechanism of food contaminants such as bisphenol A (BPA), Flavonoids (FLA), and Goitrin (GOI) onto the novel gallium-metal organic framework (MOF) and functionalized MOF with oxalamide group (MOF-OX) is evaluated by utilizing molecular dynamics (MD) and Metadynamics simulations. The atoms in molecules (AIM) analysis detected different types of atomic interactions between contaminant molecules and substrates. To assess this procedure, a range of descriptors including interaction energies, root mean square displacement, radial distribution function (RDF), density, hydrogen bond count (HB), and contact numbers are examined across the simulation trajectories. The most important elements in the stability of the systems under examination are found to be stacking π-π and HB interactions. It was confirmed by a significant value of total interaction energy for BPA/MOF-OX (- 338.21 kJ mol-1) and BPA/MOF (- 389.95 kJ mol-1) complexes. Evaluation of interaction energies reveals that L-J interaction plays an essential role in the adsorption of food contaminants on the substrates. The free energy values for the stability systems of BPA/MOF and BPA/MOF-OX complexes at their global minima reached about BPA/MOF = - 254.29 kJ mol-1 and BPA/MOF-OX = - 187.62 kJ mol-1, respectively. Nevertheless, this work provides a new strategy for the preparation of a new hierarchical tree-dimensional of the Ga-MOF hybrid material for the adsorption and exclusion of food contaminates and their effect on human health.

The Application of Metal-Organic Frameworks in Water Treatment and Their Large-Scale Preparation: A Review

Over the last few decades, there has been a growing discourse surrounding environmental and health issues stemming from drinking water and the discharge of effluents into the environment. The rapid advancement of various sewage treatment methodologies has prompted a thorough exploration of promising materials to capitalize on their benefits. Metal-organic frameworks (MOFs), as porous materials, have garnered considerable attention from researchers in recent years. These materials boast exceptional properties: unparalleled porosity, expansive specific surface areas, unique electronic characteristics including semi-conductivity, and a versatile affinity for organic molecules. These attributes have fueled a spike in research activity. This paper reviews the current MOF-based wastewater removal technologies, including separation, catalysis, and related pollutant monitoring methods, and briefly introduces the basic mechanism of some methods. The scale production problems faced by MOF in water treatment applications are evaluated, and two pioneering methods for MOF mass production are highlighted. In closing, we propose targeted recommendations and future perspectives to navigate the challenges of MOF implementation in water purification, enhancing the efficiency of material synthesis for environmental stewardship.

Efficient Multi-stimulus-Responsive Luminescent Eu(III)-Modified HOFs Materials: Detecting Thiram and Caffeic Acid and Constructing a Flexible Substrate Anti-counterfeiting Platform

The powerful capability of multi-stimulus-responsive luminescent hydrogen-bonded organic frameworks (HOFs) to respond to external chemical or physical stimuli in various manners makes them appealing in the luminescence anti-counterfeiting field. Herein, a novel Eu3+-functionalized HOF (Eu@GC-2) that combines the emission of HOFs with the characteristic emission of Eu3+ ions has been successfully synthesized, which can generate various fluorescence at different excitation wavelengths. Eu@GC-2 has enormous potential as a raw material for a paper-based sensor that is designed for detecting the pesticides thiram and caffeic acid in crops with favorable selectivity, anti-interference, and high efficiency. Based on the above excellent properties, Ln3+-functionalized HOFs (Ln@GC-2) were then employed to produce four luminescent anti-counterfeiting inks. With the incorporation of back-propagation neural network and Gray code conversion functions, a multi-stimulus-responsive luminescent anti-counterfeiting platform, coregulated by the excitation light and the chemical reagent, has been constructed. This approach can not only achieve multiple encryptions and fast information identification but also enhance the code-breaking complexity, making it an efficient strategy for information encryption and decryption.

Resonance-Based Sensing of Magnetic Nanoparticles Using Microfluidic Devices with Ferromagnetic Antidot Nanostructures

We demonstrated resonance-based detection of magnetic nanoparticles employing novel designs based upon planar (on-chip) microresonators that may serve as alternatives to conventional magnetoresistive magnetic nanoparticle detectors. We detected 130 nm sized magnetic nanoparticle clusters immobilized on sensor surfaces after flowing through PDMS microfluidic channels molded using a 3D printed mold. Two detection schemes were investigated: (i) indirect detection incorporating ferromagnetic antidot nanostructures within microresonators, and (ii) direct detection of nanoparticles without an antidot lattice. Using scheme (i), magnetic nanoparticles noticeably downshifted the resonance fields of an antidot nanostructure by up to 207 G. In a similar antidot device in which nanoparticles were introduced via droplets rather than a microfluidic channel, the largest shift was only 44 G with a sensitivity of 7.57 G/ng. This indicated that introduction of the nanoparticles via microfluidics results in stronger responses from the ferromagnetic resonances. The results for both devices demonstrated that ferromagnetic antidot nanostructures incorporated within planar microresonators can detect nanoparticles captured from dispersions. Using detection scheme (ii), without the antidot array, we observed a strong resonance within the nanoparticles. The resonance's strength suggests that direct detection is more sensitive to magnetic nanoparticles than indirect detection using a nanostructure, in addition to being much simpler.

Au@Ag Nanopencil with Au Tip and Au@Ag Rod: Multimodality Plasmonic Nanoprobe based on Asymmetric Etching for the Detection of SCN- and ClO. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023;19:e2302302. [PMID: 37211700 DOI: 10.1002/smll.202302302]

In this paper, Au@Ag nanopencil is designed as a multimodality plasmonic nanoprobe based on asymmetric etching for the detection of SCN- and ClO- . Au@Ag nanopencil with Au tip and Au@Ag rod is prepared by asymmetric tailoring of uniformly grown silver-covered gold nanopyramids under the combined effect of partial galvanic replacement and redox reaction. By asymmetric etching in different systems, Au@Ag nanopencil exhibits diversified changes in the plasmonic absorption band: O2 •- facilitated by SCN- etches Au@Ag rod from the end to the tip, causing a blue shift of the localized surface plasmon resonance (LSPR) peak as the aspect ratio decreases; while the ClO- can retain Au@Ag shell and etch Ag within rod from the tip to the end, causing a redshift of the LSPR peak as the coupling resonance weakens. Based on peak shifts in different directions, a multimodality detection of SCN- and ClO- has been established. The results demonstrate the detection limits of SCN- and ClO- are 160 and 6.7 nm, and the linear ranges are 1-600 µm and 0.05-13 µm, respectively. The finely designed Au@Ag nanopencil not only broadens the horizon of designing heterogeneous structures, but also enriches the strategy of constructing multimodality sensing platform.

Reticular Chemistry for Optical Sensing of Anions

In the last few decades, reticular chemistry has grown significantly as a field of porous crystalline molecular materials. Scientists have attempted to create the ideal platform for analyzing distinct anions based on optical sensing techniques (chromogenic and fluorogenic) by assembling different metal-containing units with suitable organic linking molecules and different organic molecules to produce crystalline porous materials. This study presents novel platforms for anion recognition based on reticular chemistry with high selectivity, sensitivity, electronic tunability, structural recognition, strong emission, and thermal and chemical stability. The key materials for reticular chemistry, Metal-Organic Frameworks (MOFs), Zeolitic Imidazolate Frameworks (ZIFs), and Covalent-Organic Frameworks (COFs), and the pre- and post-synthetic modification of the linkers and the metal oxide clusters for the selective detection of the anions, have been discussed. The mechanisms involved in sensing are also discussed.

Dye-based dual-emission Eu-MOF synthesized by Post-modification for the sensitive ratio fluorescence visualization sensing of ClO. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2023;285:121863. [PMID: 36126623 DOI: 10.1016/j.saa.2022.121863]

As we all know, excessive hypochlorite will be transformed into highly toxic substances, while insufficient hypochlorite can not completely kill bacteria and viruses in water. Therefore, it is desirable to develop a new analytical method to detect ClO^- in environmental water. Here, a novel and simple fluorescence sensor was constructed for monitoring ClO^- by an effective strategy. An Acriflavine@lanthanide metal-organic framework (Acr@Eu(BTEC)) was designed by covalently integrating amino-rich dye (Acr) and carboxyl-rich Eu(BTEC) via post-synthesis method. The created fluorescence sensor has two emission centers originating from Acr and Eu(BTEC), respectively. In the presence of ClO^-, the strong green fluorescence derived from Acr was significantly quenched, while the invariant red emission from Eu³⁺ acted as the reference signal. Thus, Acr@Eu(BTEC) with two emissions was developed as a ratiometric fluorescence sensor for highly sensitive and selective detection of ClO^-. The limit of detection (LOD) was as low as 10.75 nM. Moreover, visual detection of ClO^- by the naked eyes is feasible with obvious fluorescent color changes from green to orange and then red. This method shows excellent performance in practical application, which suggests that it has great potential in water quality monitoring.

Recent progress on porous MOFs for process-efficient hydrocarbon separation, luminescent sensing, and information encryption

Metal-organic frameworks (MOFs), as an emerging class of porous materials, excel in designability, regulatability, and modifiability in terms of their composition, topology, pore size, and surface chemistry, thus affording a huge potential for addressing environment and energy-related challenges. In particular, MOFs can be applied as porous adsorbents for the purification of industrially important hydrocarbons through certain process-efficient separation schemes based on selectivity-reversed adsorption and multicomponent separation. Moreover, the vast combination possibilities and controllable and engineerable luminescent units of MOFs make them a versatile platform to develop functionally tailored materials for luminescent sensing and optical data encryption. In this feature article, we summarize the recent progress in the use of porous MOFs for the separation and purification of acetylene (C₂H₂) and ethylene (C₂H₄) based on selectivity-reversed adsorption and multicomponent separation strategies. Moreover, we highlight the advances over the past three years in the field of MOF-based luminescent materials for thermometry, turn-on sensing, and information encryption.

Research progress of smart response composite hydrogels based on nanocellulose

In recent years, smart-responsive nanocellulose composite hydrogels have attracted extensive attention due to their unique porous substrate, hydrophilic properties, biocompatibility and stimulus responsiveness. At present, the research on smart response nanocellulose composite hydrogel mainly focuses on the selection of composite materials and the construction of internal chemical bonds. The common composite materials and connection methods used for preparation of smart response nanocellulose composite hydrogels are compared according to the different types of response sources such as temperature, pH and so on. The response mechanisms and the application prospects of different response types of nanocellulose composite hydrogels are summarized, and the transformation of internal ions, functional groups and chemical bonds, as well as the changes in mechanical properties such as modulus and strength are discussed. Finally, the shortcomings and application prospects of nanocellulose smart response composite hydrogels are summarized and prospected.

Metal–organic frameworks (MOFs) as fluorescence sensors: principles, development and prospects

This review classifies the latest developments of MOF-based fluorescence sensors according to the analytes, and discusses the challenges faced by MOF-based fluorescence sensors and promotes some directions for future research.

Recent advances in luminescent metal-organic frameworks and their photonic applications

In recent years, metal-organic frameworks (MOFs) have been attracting ever more interest owing to their fascinating structures and widespread applications. Among the optoelectronic materials, luminescent MOFs (LMOFs) have become one of the most attractive candidates in the fields of optics and photonics thanks to the unique characteristics of their frameworks. Luminescence from MOFs can originate from either the frameworks, mainly including organic linkers and metal ions, or the encapsulated guests, such as dyes, perovskites, and carbon dots. Here, we systematically review the recent progress in LMOFs, with an emphasis on the relationships between their structures and emission behaviour. On this basis, we comprehensively discuss the research progress and applications of multicolour emission from homogeneous and heterogeneous structures, host-guest hybrid lasers, and pure MOF lasers based on optically excited LMOFs in the field of micro/nanophotonics. We also highlight recent developments in other types of luminescence, such as electroluminescence and chemiluminescence, from LMOFs. Future perspectives and challenges for LMOFs are provided to give an outlook of this emerging field. We anticipate that this article will promote the development of MOF-based functional materials with desired performance towards robust optoelectronic applications.

The untapped potential of magnetic nanoparticles for forensic investigations: A comprehensive review

With a growing interest in precise and sensitive diagnosis for criminal investigations, nanoparticles (NPs) have intrigued scientific minds working in the field of forensic science due to their exceptional properties. Magnetic nanoparticles (MNPs) have emerged as a powerful tool for improving forensic analysis due to their super magnetic behavior combined with smaller dimensions. MNP-based applications can benefit criminologists to solve criminal mysteries with greater precision and pace. This review highlights the different types of MNP-based applications and their developmental and implicational aspects of forensic science. It also renders insight into the future prospects of a splendid blend of nanotechnology and forensic science, leading to a better scientific analysis.

Encapsulation of Luminescent Guests to Construct Luminescent Metal-Organic Frameworks for Chemical Sensing

Metal-organic frameworks (MOFs), which are a class of coordination polymers constructed by metal ions or clusters with organic ligands, have emerged as exciting inorganic-organic hybrid materials with the superiorities of inherent crystallinity, adjustable pore size, clear structure, and high degree of functionalization. The MOFs have attracted much attention to develop good luminescent functional materials due to their inherent luminescent centers of both inorganic and organic photonic units. Furthermore, the pores within MOFs can also be used to encapsulate a large number of luminescent guest species, which provides a broader luminescent property for MOF materials. MOFs possess the incomparable multifunctional advantages of inorganic and organic luminescent materials. A large number of luminescent MOFs (LMOFs) have been synthesized for applications in sensing, white-light-emitting diodes (LED), photocatalysis, biomedicine, etc. This paper reviews the encapsulation of various luminescent guests such as lanthanide ions, dyes, quantum dots, and luminescent complexes in metal-organic frameworks to construct luminous sensors with single- or double-emission centers, as well as the research progress of these sensors in chemical sensing. Finally, the challenges in these fields were outlined and the prospects for future development were put forward.

An advanced color tunable persistent luminescent NaCa2GeO4F:Tb3+ phosphor for multicolor anti-counterfeiting

Luminescent materials play an important role in anticounterfeiting applications due to their superior properties of visual convenience and high concealment. However, traditional luminescent materials usually exhibit monochromatic emission and are easily counterfeited. Therefore, in this work, we report a multicolor long persistent luminescence (PersL) material, NaCa2GeO4F:Tb3+ (abbreviated as NCGOF:Tb3+), where the color of PersL can be tuned from blue to cyan and bright green by changing the concentration of Tb3+, and the afterglow (concentration) can last for 5.62 h (0.1%), 8.52 h (0.4%) and 7.14 h (0.8%) at the corresponding concentrations of Tb3+, respectively. Investigation revealed that the multicolor PersL is essentially associated with the opportune traps and cross-relaxation effect of Tb3+ in NCGOF. Based on the unique features of PersL, anticounterfeiting devices have been fabricated, and the results indicate that their multicolor features can be easily detected using a portable ultraviolet lamp, and that they are impossible to counterfeit using any substitute so far, meaning that they provide a high level of security for use in practical applications.

Shape-Controlled and Well-Arrayed Heterogeneous Nanostructures via Melting Point Modulation at the Nanoscale

A novel method for fabricating shape-controlled and well-arrayed heterogeneous nanostructures by altering the melting point of the metal thin film at the nanoscale is proposed. Silver nanofilms (AgNFs) are transformed into silver nanoislands (AgNIs), silver nanoparticles (AgNPs), and silver nanogaps (AgNGs) that are well-ordered and repositioned inside the gold nanoholes (AuNHs) depending on the diameter of the AuNHs, the thickness of the AgNF, and the heating temperature (120-200 °C). This method demonstrates the ability to fabricate uniform, stable, and unique structures with a fast, simple, and mass-producible process. For demonstrating the diverse applicability of the developed structures, high-density AgNGs inside the AuNHs are utilized as surface-enhanced Raman spectroscopy (SERS) substrates. These AgNGs-based SERS substrates exhibit a performance enhancement, which is 1.06 × 10⁶ times greater than that of a metal film, with a relative standard deviation of 19.8%. The developed AgNP/AgNI structures are also used as nonreproducible anti-counterfeiting signs, and the anti-counterfeiting/readout system is demonstrated via image processing. Therefore, our method could play a vital role in the nanofabrication of high-demand nanostructures.

Luminescence modulation, near white light emission, selective luminescence sensing, and anticounterfeiting via a series of Ln-MOFs with a π-conjugated and uncoordinated lewis basic triazolyl ligand

A series of Ln-MOFs with π-conjugated and uncoordinated lewis basic triazolyl ligand have luminescence modulation, near white light emission, selective luminescence sensing, and anticounterfeiting.

Energy Manipulation in Lanthanide-Doped Core-Shell Nanoparticles for Tunable Dual-Mode Luminescence toward Advanced Anti-Counterfeiting

Developing advanced luminescent materials and techniques is of significant importance for anti-counterfeiting applications, and remains a huge challenge. In this work, a new and efficient approach for achieving efficient dual-mode luminescence with tunable color outputs via Gd³⁺ -mediated interfacial energy transfer, Ce³⁺ -assisted cross-relaxation, and core-shell nanostructuring strategy is reported. The introduction of Ce³⁺ into the inner core not only serves the regulation of upconversion emission, but also facilitates the ultraviolet photon harvesting and subsequent energy transfer to downshifting (DS) activators in the outer shell layer. Furthermore, the construction of the core@shell nanoarchitecture enables the spatial separation of upconverting activators and DS centers, which greatly suppresses their adverse cross-relaxation processes. Consequently, efficient and multicolor-tunable dual-mode emissions can be simultaneously observed in the pre-designed NaGdF₄ :Yb/Ho/Ce@NaYF₄ :X (X = Eu, Tb, Sm, Dy) core-shell nanostructures under 254 nm ultraviolet light and 980 nm laser excitation. The proof-of-concept experiment demonstrates that 2D-encoded patterns based on dual-mode emitting nanomaterials are very promising for anti-counterfeiting applications. It is believed that this preliminary study will advance the development of the fluorescent materials for potential applications in anti-counterfeiting and optical multiplexing.

Highly sensitive and selective colorimetric sensor for thiocyanate based on electrochemical oxidation-assisted complexation reaction with Gold nanostars etching

In this work, we developed an electrochemical oxidation-assisted complexation strategy for highly sensitive and selective detection of thiocyanate (SCN^-). Gold nanostars (AuNSs) with uniform and sharp tips were first prepared, and we found they can be quickly etched to gold nanoparticles (AuNPs) under electrochemical oxidation with the existence of halide and halogen-like ions. Through introducing SCN^--selective molecule: zinc phthalocyanine (ZnPc), the fabricated ZnPc-AuNSs/ITO electrode can rapidly and selectively response to SCN^- under electrochemical oxidation, manifesting as a noticeable change in color from navy blue to red. Thus SCN^- concentration can be easily reflected. The wide wavelength tuning range of AuNSs to AuNPs make the ZnPc-AuNSs/ITO sensor obtain a much wider detection range for SCN^- (10 nM to 80 mM) than most other reported studies. In addition, the detection limit is as low as 3 nM. It renders the sensor to be easily used in much diluted matrixes, which can further lower the interference. We further applied the colorimetric sensor to SCN^- detection in wastewater and milk, excellent performance was obtained. The proposed electrochemical oxidation-assisted complexation strategy will have good promise in developing colorimetric sensors with high selectivity and wide detection range, and will display more useful application in environmental monitoring.

Bioinspired Superhydrophobic Thermochromic Films with Robust Healability

Thermochromic films with intriguing functionalities have great potential in soft actuators, heat storage devices, and interactive interface sensors. Inspired by the unique features of bird feathers (such as Nicobar pigeon, Anna hummingbird, mandarin duck, etc.), a superhydrophobic thermochromic film (STF) with robust healability is proposed for the first time through sandwiching an electric heater between a top thermochromic layer and a bottom poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) substrate. The STF exhibits fast and reversible color conversions of blue-pink-yellow under a low input power and has a superhydrophobic property with a contact angle of 155°. Furthermore, owing to the strong dynamic dipole-dipole interactions between the polar CF₃ groups of flexible PVDF-HFP chains, the STF possesses a robust healing capability of structure and conductivity. By means of the temperature difference generated by the objects contacting (finger, iron, and water) as a stimulus, the STFs achieve tactile imaging and writing record with advantages of transient display, automatic erasure, and excellent reusability. Additionally, the STF-based anti-counterfeiting security labels with superhydrophobicity and three-state color switching simultaneously realize facile distinguishment and difficult forgery. The findings conceivably stand out as a new methodology to fabricate functional thermochromic materials for innovative applications.

Zeolitic imidazolate frameworks for use in electrochemical and optical chemical sensing and biosensing: a review

This review (with 145 refs.) summarizes the progress that has been made in the use of zeolitic imidazolate frameworks in chemical sensing and biosensing. Zeolitic imidazolate frameworks (ZIFs) are a type of porous material with zeolite topological structure that combine the advantages of zeolite and traditional metal-organic frameworks. Owing to the structural flexibility of ZIFs, their pore sizes and surface functionalization can be reasonably designed. Following an introduction into the field of metal-organic frameworks and the zeolitic imidazolate framework (ZIF) subclass, a first large section covers the various kinds and properties of ZIFs. The next large section covers electrochemical sensors and assays (with subsections on methods for gases, electrochemiluminescence, electrochemical biomolecules). This is followed by main sections on ZIF-based colorimetric and luminescent sensors, with subsections on sensors for metal ions and anions, for gases, and for organic biomolecules. The last section covers SERS-based assays. Several tables are presented that give an overview on the wealth of methods and materials. A concluding section summarizes the current status, addresses current challenges, and gives an outlook on potential future trends. Graphical abstract In recent years, ZIFs and their composites have been widely used as probes in chemical sensing, and these probes have shown great advantages over other materials. This review describes the current progress on ZIFs toward electrochemical, luminescence, colorimetric, and SERS-based sensing applications, highlighting the different strategies for designing ZIFs and their composites and potential challenges in this field.

Sonochemical Synthesis of Carbon Dots/Lanthanoid MOFs Hybrids for White Light-Emitting Diodes with High Color Rendering

Although lanthanoid metal-organic frameworks (Ln-MOFs) have been widely developed for white light-emitting diodes (WLEDs), the color rendering index (CRI) values are still lower than 80. To overcome this limitation, a series of CDs/Ln-MOFs hybrids, namely, CDs-2@Ln-MOF, CDs-3@Ln-MOF, and CDs-4@Ln-MOF containing blue-emitting CDs and yellow-emitting bimetallic [(Eu_1.22Tb_0.78(1,4-phda)₃(H₂O)](H₂O)₂ were prepared via sonication at room temperature to restrict the self-quenching of CDs in composite materials. The as-synthesized composite materials were investigated by Fourier transform infrared, powder X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and photoluminescence. The luminescent color of the materials can be adjusted by varying the amount of CDs and excitation wavelengths. The resulting CDs-3@Ln-MOF achieved excellent CRI up to 93 with the ideal Commission International ed'Eclairage coordinate (0.334, 0.334) and appropriate correlated color temperature (CCT) (5443 K). In addition, the tunable multicolored luminescence based on single and bimetallic Eu_xTb_2-x(1,4-phda)₃(H₂O)](H₂O)₂, x = 0, 0.73, 1.22, 1.57, 1.94, and 2, were applied as the luminescent security inks for anti-counterfeiting application through encoding/decoding and rewritable data.

A smart nanoprobe based on a gadolinium complex encapsulated by ZIF-8 with enhanced room temperature phosphorescence for synchronous oxygen sensing and photodynamic therapy

The phosphorescence lifetime approach based on the room temperature phosphorescence (RTP) property has received considerable attention in recent years due to its excellent performance in the precise measurement of oxygen. Herein, a smart nanoprobe, Gd[PC]@ZIF-8, was designed and assembled by homogenously encapsulating a rare-earth complex phosphor Gd[(Pyr)₄cyclen] (Pyr = pyrenol) into a zeolitic imidazolate framework (ZIF-8). Because of the restriction of the metal-organic framework (MOF) matrix and host-guest interactions, the nanoprobe Gd[PC]@ZIF-8 exhibited highly enhanced RTP properties, including intensity, quantum yield, and elongated decay lifetime. It displayed an outstanding linear relationship between the phosphorescence decay lifetime, intensity and oxygen concentration, which can be applied in the field of oxygen sensing. Moreover, the complex Gd[(Pyr)₄cyclen] in the nanoprobe Gd[PC]@ZIF-8 served as a favorable photosensitizer that resulted in the simultaneous conversion of sufficient oxygen molecules into single state oxygen (¹O₂) under irradiation during the phosphorescence quenching process, which is conducive to photodynamic therapy (PDT). Thus, the design of the smart nanoprobe Gd[PC]@ZIF-8 in this study provides an ingenious strategy of utilizing a MOF as a matrix to enhance the RTP properties of phosphors for synchronous oxygen sensing and PDT.

Advanced Dynamic Photoluminescent Material for Dynamic Anticounterfeiting and Encryption

Anticounterfeiting is a vitally important issue in modern society. At present, the most commonly used luminescent anticounterfeiting technique is based on static photoluminescence (PL), which is easily counterfeited by certain substitutes. In this work, we report for the first time a dynamic PL material, Na₂CaGe₂O₆:Tb³⁺. Irradiated by a portable ultraviolet (254 nm) lamp, the PL color of the material due to Tb³⁺ changes from the initial red to yellow and, finally, green. The investigation reveals that the dynamic PL is due to the presence of appropriate traps and the cross-relaxation effect of Tb³⁺ in Na₂CaGe₂O₆. By employing this unique dynamic PL material, high-level dynamic luminescent anticounterfeiting and encryption devices can be fabricated. The dynamic PL features of the devices are easily detected using a cheap portable lamp, and at present, it is impossible for the features to be faked by any substitutes. In a virtual military scenario, the results demonstrate that the encryption device is safe and that a spy will be detected. Accordingly, this dynamic PL material could inspire more ingenious security designs.

Naked-Eye Heterogeneous Sensing of Fluoride Ions by Co-Polymeric Nanosponge Systems Comprising Aromatic-Imide-Functionalized Nanocellulose and Branched Polyethyleneimine

Heterogeneous colorimetric sensors for fluoride ions were obtained by cross-linking TEMPO-oxidized cellulose nanofibers (TOCNF) with chemically modified branched polyethyleneimine 25 kDa (bPEI). Functionalization of bPEI primary amino groups with aromatic anhydrides led to the formation of the corresponding mono- and bis-imides on the grafted polymers (f-bPEI). A microwave-assisted procedure allowed the optimization of the synthetic protocol by reducing reaction time from 17 h to 30 minutes. Hydrogels obtained by mixing different ratios of TOCNF, bPEI and f-bPEI were lyophilized and thermally treated at about 100 °C to promote the formation of amide bonds between the amino groups of poly-cationic polymers and the carboxylic groups of cellulose nanofibers. This approach generated a series of cellulose nanosponges S1-S3 which were characterized by FT-IR and by solid state ¹³ C CPMAS NMR. These sponge materials can act as colorimetric sensors for the selective naked-eye recognition of fluoride ions over chloride, phosphate and acetate ions at concentrations of up to 0.05 M in DMSO. Moreover, when the sponges were functionalized with perylene tetracarboxylic diimide, successful naked-eye detection was achieved with only 0.02 % w/w of chromophore units per gram of material.

Rapid and visual detection for hypochlorite of an AIE enhanced fluorescence probe

In this paper, a new 'turn-on' fluorescence probe for the rapid, sensitive, and visual detection of hypochlorite is reported. The push-pull type trianiline-tricyanofuran-based fluorescent probe was prepared using a condensation reaction between tricyanofuran and the thiophene-trianiline derivative that had high quantum yields and showed aggregation-induced emission enhanced properties. Upon exposure to hypochlorite, prominent fluorescence enhancement of the probe was observed via the release of the fluorophore from the probe. The probe showed a ratiometric absorption change at 315 nm and 575 nm. Importantly, the probe showed an excellent detection limit for hypochlorite at 1.2 × 10^-7  M in solution and it was successfully applied for monitoring hypochlorite in waste water by test strip. This work reports a new fluorescence analytical sensing method for hypochlorite that has potential practical value in environmental monitoring and biological discrimination.

Tetracycline Generated Red Luminescence Based on a Novel Lanthanide Functionalized Layered Double Hydroxide Nanoplatform

Considerable interest in using lanthanide complexes in optics have been well-known persisted for a long time. But such molecular-based edifices have been excluded from practical application because of their poor thermal or photo stabilities. Here a novel europium embedded layered double hydroxide (Mg-Al LDH-Eu) has been established and such an inorganic-organic framework demonstrates improved thermal performance due to hydrolysis and poly condensation of the trimethoxysilyl-unit. In addition, the incorporation of a functional building block such as ethylenediamine triacetic acid can significantly minimize the negative effects of hydroxyl groups. In the presence of tetracycline (Tc), the nanoprobe exhibits an "off-on" change in aqueous solution, and the red luminescence can be excited in the visible light range (405 nm). It provides a very sensitive signal response to Tc with an excellent linear relation in the range of 0.1 μM to 5.0 μM, and the detection limit of this probe is measured to be 7.6 nM. This nanoplatform exhibits low cytotoxicity during in vitro experiments and can be employed for the detection of tetracycline in 293T cells.

Tuning the net topology of a ternary Ag(i)-1,2,4,5-tetra(4-pyridyl)benzene-carboxylate framework: structures and photoluminescence

Changing of auxiliary ligands leads to the formation of 1D–3D coordination structures and the use of dye molecules provides a way to promote the luminescence properties of MOFs.

Three layer-structured cadmium coordination polymers based on flexible 5-(4-pyridyl)-methoxylisophthalic acid: rapid synthesis and luminescence sensing

Three layered Cd-CPs, synthesized by a MW-assisted solvothermal method within two or three minutes, serve as fluorescent sensors for Fe³⁺ ions.

Facile preparation of N-doped graphene quantum dots as quick-dry fluorescent ink for anti-counterfeiting

N-GQDs are synthesized using a simple and fast one-step protocol and applied for preparing quick-dry fluorescent ink for both writing and printing.