Search Results (434)

Static electricity-induced luminescence (SEL) materials exhibit luminescence in response to minute electrical charges and therefore have potential for application in self-powered charge-detection sensors that operate without an external power source. However, important aspects of their luminescence mechanism and the associated material properties remain insufficiently understood. In this study, SEL films based on SrAl₂O₄:Eu²⁺ were evaluated, and the effects of SrAl₂O₄:Eu²⁺ concentration and applied voltage on the luminescence behavior were quantitatively investigated. The results showed that the SEL intensity increased in proportion to the square of the applied voltage, while the SEL luminescence area increased monotonically with increasing voltage. These results suggest that the SEL intensity and SEL area may reflect the amount of discharge–charge from the needle electrode and the charge distribution on the film surface, respectively. In addition, increasing the SEL phosphor content enhanced the luminescence intensity, whereas no significant effect was observed on the relative change in luminescence area with applied voltage. Collectively, these findings provide fundamental insights for the design of charge-detection sensors based on SrAl₂O₄:Eu²⁺. Full article

The development of highly sensitive luminescence sensing materials has attracted much attention in recent years. In this study, a new two-dimensional porous europium metal–organic framework (EuMOF, [Eu(DHDA)₁.₅·3H₂O]_n; DHDA = 2,2-dihydroxyacetic acid) is obtained, characterized by single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), luminescence, and Fourier transform infrared spectroscopy (FT-IR). At the best excitation at 295 nm, EuMOF shows red luminescence (CIE: 0.6255, 0.3740) and has four obvious peaks at 582, 605, 641, and 689 nm, which are due to ⁵D₀ → ⁷F₁, ⁵D₀ → ⁷F₂, ⁵D₀ → ⁷F₃, and ⁵D₀ → ⁷F₄ transitions, respectively. Studies have shown that EuMOF is a stable, fast-responding, and highly sensitive luminescence sensor for isoprocarb and levofloxacin (Lvx) in aqueous solutions, apple peel and rice extract solutions, and real urine, which are closely associated with food safety and human health. The sensing behavior toward isoprocarb and Lvx may be attributed to the specific binding of the two analytes to EuMOF. The sensing of isoprocarb is a dynamic luminescence-quenching process, while that of Lvx is a dynamic luminescence-enhancing process. The limits of detection (LOD) for isoprocarb and Lvx are as low as 1.0 and 0.5 nM, respectively, which are much lower than the Chinese national standard (GB 28260-2011, 2.583 μM). EuMOF also demonstrates strong anti-interference detection of isoprocarb in apple peel and rice extract solutions, as well as Lvx in real urine, with excellent detection stability in a 0.01~9.0 nM range. The recovery rates for isoprocarb and Lvx in real samples are 99.12%~101.25%. This work provides the first bifunctional lanthanide sensor for pesticides and antibiotics. Full article

Temperature-dependent luminescence of Pr³⁺-doped materials was investigated using both conventional luminescence intensity ratio (LIR) and principal component analysis (PCA)-based thermometry. Three host matrices with distinct structural properties, LiLaP₄O₁₂, YNbO₄, and Y₂O₃, were selected to evaluate the influence of crystal structure on thermometric performance. Temperature-resolved emission spectra recorded over the 103–523 K (−170 to 250 °C) range were analyzed using both approaches, with the first principal component (PC₁) serving as a thermometric parameter in the PCA. The results show that crystal symmetry and site multiplicity strongly influence the temperature-dependent spectral evolution and, consequently, the thermometric response. LiLaP₄O₁₂ exhibits stable and well-defined spectral evolution, resulting in balanced thermometric accuracy and resolution. YNbO₄ shows enhanced sensitivity to temperature variations due to increased spectral complexity and stronger crystal-field effects, leading to improved resolution but increased calibration uncertainty. In contrast, Y₂O₃ exhibits reduced thermometric performance due to overlapping emissions from multiple crystallographically inequivalent sites with distinct thermal responses. Compared to LIR, PCA provides improved thermometric figures of merit, particularly in systems with complex and strongly overlapping emission bands, demonstrating the potential of full-spectrum analysis in luminescence thermometry. Full article

Hydrogel-based optical sensors have emerged as a versatile class of analytical materials that combine soft-matter processability, tunable network chemistry, and compatibility with luminescent, colorimetric, photonic, and hybrid transduction strategies. Progress in the field is driven not by a single sensing mechanism, but by the convergence of key advances in material functionalization, embedded selectivity, operation across diverse sample matrices, mechanical and analytical robustness, and usability beyond the laboratory. Current systems include framework-integrated, nanoparticle-doped, probe-functionalized, photonic-crystal, enzyme-immobilized, and device-coupled hydrogels, reflecting growing architectural diversity and application-oriented engineering. Selectivity has likewise advanced from basic interferent screening to recognition-specific, imprinted, and pattern-discriminative formats suited to complex environmental, food, biological, and wearable settings. Evidence of stability, reusability, and deformation tolerance further suggests that many platforms are moving beyond proof-of-concept demonstrations toward credible real-world operation. At the same time, translational priorities such as portability, smartphone readout, implantable and epidermal formats, and multifunctionality spanning antimicrobial action, adsorption, anti-counterfeiting, and device integration are becoming increasingly prominent. Together, these trends show that hydrogel-based optical sensing is maturing into a materially rich, application-responsive domain. The key challenge ahead is to unify materials design, selectivity control, durability, and deployability in standardized, reproducible, and clinically or environmentally credible sensing platforms. Full article

Temperature is a physical quantity that represents the degree of heat or cold of an object and has significant application value across various fields. Traditional contact temperature measurement technologies, such as thermocouples and infrared thermometers, suffer from limitations like poor environmental adaptability and low spatial resolution, which makes it difficult to meet the temperature measurement requirements for micro-/nano-devices and extreme environments. In recent years, non-contact optical temperature measurement technology based on the luminescence characteristics of rare earth ions has garnered widespread attention due to its high sensitivity, strong interference resistance, and good environmental adaptability. In addition to inorganic luminescent materials, lanthanide-based molecular and coordination-complex thermometers have also become an important branch of this field; however, this paper focuses on inorganic rare earth luminescence thermometry. This paper provides a systematic review of the mechanisms of temperature measurement using rare earth ion luminescence, including single-energy-level luminescence intensity measurement and luminescence intensity ratio measurement based on thermally coupled levels (TCLs) and non-thermally coupled levels (NTCLs). It analyzes the principles of various technologies, performance parameters (such as absolute sensitivity S_a, relative sensitivity S_r, and temperature resolution δT), and their application progress in fields such as biomedical imaging, high-temperature aerospace environments, and the integration of micro-/nano-devices. Special attention is paid to emerging research directions, including Stark sublevel engineering for enhanced sensitivity, negative thermal expansion (NTE) host design for anti-thermal quenching, multi-modal collaborative thermometry, and artificial intelligence (AI)-assisted material design and data processing. The article also discusses the challenges currently faced by the technology, such as high-temperature fluorescence quenching and signal interference, and looks forward to future development directions, including artificial intelligence-assisted material design and multi-modal cooperative temperature measurement, aiming to provide a reference for the research and application of rare earth luminescence temperature sensing technology. Full article

Negatively charged molecules and anions are widely present in the natural environment and can pose a threat to aquatic life, affecting their survival and reproduction. As the understanding of the hazards of negatively charged molecules and ions deepens, the need for real-time monitoring governs the development of highly sensitive and convenient sensing materials. Here, highly luminescent Zn-Cu-In-S core–shell colloidal quantum dots were grafted onto cotton fabric to produce a fluorescence cotton fabric (FCF) optical sensor demonstrating photoluminescence response to the presence of several anions in water, such as phosphate (PO₄³⁻), hydroxide (OH⁻), fluoride (F⁻), chloride (Cl⁻), or bromide (Br⁻). After contact with water solutions containing these anions, PL output from FCF remarkably decreases, with specific functional dependence on the concentration of the selected anions. The fluorescent fabric sensing material is easy to operate, achieving real-time detection of negatively charged groups and showing great potential for application in environmental monitoring. Full article

Metal–organic frameworks (MOFs) exhibit high specific surface area and porosity, which may facilitate electron transfer during electrochemical reactions. Therefore, it is clear that MOFs are promising materials for the development of electrochemical sensors. In particular, zinc (Zn) based MOFs offer several advantages such as high specific surface area, porosity, environmental friendliness and low cost. Thus, Zn-based MOF materials and their composites have been extensively utilized in the detection of various pollutants, biomolecules and food additives. The Zn-MOF-based materials have been extensively utilized in electrochemical and fluorescence sensing applications. Previously, various Zn-MOF-based sensing systems such as pristine Zn-MOF, carbon-supported Zn-MOF composites, MXene hybrids with Zn-MOF, and bimetallic/trimetallic Zn-based MOFs were explored to enhance sensing performance. Such materials exhibit remarkable analytical performance, such as a low limit of detection (LOD) (nM to pM range), wide linear response range (LR), fast response times, and high selectivity in the presence of interfering species. In electrochemical sensing, Zn-MOF-modified electrodes demonstrated improved charge-transfer kinetics and sensitivity, enabling accurate determination of the biomolecules, drugs and heavy metal ions in real samples. Similarly, Zn-MOF-based fluorescence sensors showed high luminescent properties and displayed sensitive detection of pollutants and biomolecules. Despite such promising sensing performances, some challenges, such as low stability, reproducibility and selectivity in real-time monitoring, etc., remain that need to be overcome. This review article summarizes the previously reported literature on the fabrication of Zn-MOFs, their composites and Zn-MOF-derived materials for the development of electrochemical and fluorescence sensors. We have also discussed the future directions for the rational design of the high-performance Zn-MOF-based sensing systems for environmental and biomedical applications. We believe that the present review article would be useful for the scientific community working on the fabrication of Zn-MOF-based sensors. Full article

Pr³⁺-activated phosphors are promising for non-contact optical thermometry under blue-light excitation. In tantalate hosts, Pr³⁺-Ta⁵⁺ intervalence charge transfer (IVCT) states may introduce thermally activated nonradiative pathways involving the ³P₀ and ¹D₂ levels, thus affecting their thermal quenching behavior and thermometric performance. However, the concentration- and temperature-dependent luminescence of CaTa₂O₆:Pr³⁺ remains unexplored. In this study, CaTa₂O₆:Pr³⁺ phosphors were synthesized via the solid-state reaction method, and a phosphor-in-glass (PiG) composite was fabricated by co-sintering the mixture of the phosphor and the precursor glass (PG) powder. The structural characteristics and the luminescence properties of CaTa₂O₆:Pr³⁺ phosphors under 450 nm excitation were investigated. The IVCT band was confirmed in the excitation spectrum. Optimal Pr³⁺ concentrations were 2 mol% for ³P_J and 0.7 mol% for ¹D₂ emissions. With Pr³⁺/Zr⁴⁺ or Pr³⁺/Sn⁴⁺ co-doping, the emission intensity was enhanced by 1.34 and 1.31 times, respectively. The PiG exhibited similar spectral profiles. An FIR mode based on ³P₁→³H₅/³P₀→³F₂ transitions achieved maximum relative sensitivities of 1.09% K⁻¹ for the phosphor and 1.18% K⁻¹ for the PiG at 298 K. These findings suggest that CaTa₂O₆:Pr³⁺-based materials are potential candidates for luminescence thermometry. Full article

The trace water content in industrial oil critically affects the operational stability and service life of industrial equipment and serves as a key indicator for evaluating oil quality. Therefore, the rapid, sensitive, and visual detection of trace water in oil is of great engineering significance for equipment condition monitoring and early fault warning. Existing detection methods predominantly rely on precision instruments; although they enable quantitative analysis, their operational procedures are complicated and time-consuming, which are unsuitable for on-site real-time monitoring. Consequently, there is an urgent need for a novel trace water detection sensor that offers high sensitivity, visualization, and adaptability to oil-phase environments. Herein, a coplanar electrode alternating current electroluminescent (ACEL) sensor is developed for the visual detection of trace water in oil. The ACEL sensor features a multilayer structure comprising a substrate layer, a coplanar electrode layer, and a humidity-sensitive luminescent layer. The humidity-sensitive luminescent layer consists of humidity-sensitive hydrogel and ZnS: Cu electroluminescent powder, forming a loose and porous film that enables high-sensitivity humidity sensing and simultaneously electroluminescent visual signal output. The sensing mechanism study reveals that variations in trace water content modulate the dielectric properties of the humidity-sensitive layer, which further affect the electroluminescent intensity of the ACEL sensor. In addition, the ACEL sensor enables the rapid, naked-eye recognition of humidity changes under trace water conditions without the need for precision instruments, achieving a rapid response time of 3 s and a detection limit as low as 60 ppm, all making it applicable for different types of industrial oils. Thus, this ACEL sensor features a novel detection mechanism, excellent universality, fast response, and ease of operation, offering a new visual sensing strategy for trace water detection in industrial oil and holding broad prospects for practical applications. Full article

Rare-earth elements including the fifteen lanthanides, from lanthanum (La) to lutetium (Lu), together with scandium (Sc) and yttrium (Y), can act either as matrix cations or as active luminescent centers when incorporated into host lattices. Owing to their relatively large ionic radii, high coordination numbers, and structural stability, ions such as La, Lu, Sc, Y, and gadolinium (Gd) typically serve as matrix cations in rare-earth vanadate (REVO₄)-based phosphors, while other trivalent lanthanide (Ln³⁺) ions act as active luminescent centers. These REVO₄ phosphors have proved to be good host lattices for optically active Ln³⁺ ions giving strong luminescence assigned to absorption of the vanadate (VO₄³⁻) groups, and the efficient energy transfer between host lattice and Ln³⁺ ions. The unique electronic configuration of Ln³⁺ ions, particularly their unpaired 4f electrons, makes them ideal for applications in luminescence, magnetism, electronic and magnetic relaxation, and catalysis. Due to their complementary luminescent characteristics, Ln³⁺-doped REVO₄ phosphors have attracted significant attention in recent years. Their unique optical properties make them highly valuable across a broad spectrum of applications. This paper provides a comprehensive review of the state of the art in Ln³⁺ (Eu³⁺, Sm³⁺, Tm³⁺, Er³⁺, Ho³⁺, Tb³⁺, Nd³⁺, and Yb³⁺)-doped REVO₄ (RE = Y, Gd, Lu, La) phosphors. It examines current synthesis approaches, alongside the development of advanced strategies, and explores structural characteristics, innovative designs, and luminescent behavior, including both downconversion and upconversion processes and sensing applications, of the Ln³⁺-doped REVO₄ phosphors. Full article

Luminescent organic–inorganic Cu(I) halide hybrid molecular crystals exhibit remarkable structural diversity and photophysical properties, but their application in aqueous environments is often limited by insufficient stability. Herein, we report portable and reusable photoluminescent sensors based on Cu(I)–I triethylenediamine derivatives [Cu₄I₆(pr-ted)₂] and [Cu₃I₅(bz-ted)₂] (pr-ted = 1-propyl-1,4-diazabicyclo[2.2.2]octan-1-ium; bz-ted = 1-benzyl-1,4-diazabicyclo[2.2.2]octan-1-ium). Their submicrometric particles exhibit intense UV-excited emissions and high photoluminescence quantum yields but limited water stability. To address this limitation, ultrasound sonication was employed to control particle size and produce stable suspensions that can be incorporated into polymeric matrices via 3D printing with photocurable resins or polylactic acid (PLA) films by drop-casting, yielding mechanically robust composites that retain their structural and optical properties. The devices used act as selective turn-off luminescent sensors for Fe³⁺ in aqueous media, with nanomolar detection limits (1.33–1.58 nM) below regulatory thresholds for drinking water. Moreover, [Cu₃I₅(bz-ted)₂] enables tetracycline detection in river water with a limit of detection of 0.038 nM. Mechanistic studies indicate that reversible photoinduced electron transfer is the primary quenching pathway, while composites maintain sensing performance over multiple reuse cycles. Full article

p-Nitrophenol (PNP) and bis(4-nitrophenyl) phosphate (BNPP), as typical persistent and toxic organic contaminants, present significant risks to both ecological systems and human health. Accurately quantifying these compounds using luminescent sensors remains a formidable task. In this study, we successfully synthesized a zinc-based metal–organic framework (Zn-MOF) that functions as a luminescent sensing material. The synthesized Zn-MOF demonstrates exceptional dual-response luminescent detection toward PNP and BNPP, with detection limits as low as 3.49 × 10⁻⁶ and 8.43 × 10⁻⁶ mol/L, respectively. The sensor maintains high selectivity and functionality even in the presence of various potentially interfering substances commonly found in complex environmental samples. Moreover, the material can be fabricated into a visual sensing film, greatly facilitating its application in on-site rapid detection scenarios. Overall, this work introduces a novel luminescent sensor platform that enables fast and reliable monitoring of PNP and BNPP in environmental contexts, demonstrating strong potential for integration into real-time surveillance and early warning systems. Full article

A dual-mode electrical–optical nanocomposite hydrogel is developed by integrating carboxyl-modified upconversion nanoparticles (UCNPs-COOH) and quaternized chitosan (CQAS) into a polyacrylamide (PAAm) covalent network. The hydrogel exhibits high optical transparency (>90% in the visible region), excellent mechanical properties (fracture strain of 1742%, tensile strength of 0.85 MPa, toughness of 6.57 MJ/m³), and robust adhesion to various substrates. The synergistic covalent–noncovalent hybrid network enables efficient energy dissipation, while CQAS-enhanced dispersion of UCNPs significantly improves upconversion luminescence intensity and stability, as evidenced by prolonged fluorescence lifetime from 0.564 ms to 0.691 ms at 539 nm. Leveraging distinct electrical and optical signal transduction pathways, the hydrogel functions as a highly sensitive resistive strain sensor with multistage gauge factors up to 13.85 and excellent cyclic stability over 1200 loading–unloading cycles at 100% strain for human motion monitoring. It also serves as a ratiometric optical pH sensor over a broad range (pH 1–13) based on phenolphthalein-sensitized upconversion luminescence, with excellent repeatability. By integrating real-time resistance responses with optical readouts within a single soft material, this work demonstrates a reliable dual-mode sensing strategy for simultaneous mechanical and chemical monitoring, holding promise for wearable electronics, smart healthcare, and environment-responsive sensing systems. Full article

Metal–organic frameworks (MOFs) have received significant attention as multifunctional platforms for chemical sensing due to their adjustable porosity, high specific surface area, and modular chemical architecture, which allow for customized host-guest interactions and signal transduction. This work presents a critical overview of recent advances in electrochemical and optical sensors based on MOFs for the detection of emerging contaminants, including toxic metal ions, pharmaceutical residues, and industrial pollutants in environmental and biological matrices. Special emphasis is placed on the underlying sensing mechanisms, such as redox activity, charge transfer, and luminescence modulation, as well as the main challenges related to structural stability under realistic operating conditions, including variations in pH, humidity, and temperature. Furthermore, the development of hybrid and hierarchical architecture based on MOFs is discussed as an effective strategy to improve sensitivity, selectivity, and long-term robustness. Finally, the perspective highlights how to optimize sensor performance and enable more reliable and scalable applications in monitoring emerging contaminants. Full article

Lycium barbarum L. is a widely used medicinal and edible Chinese medicinal material. However, with consumers’ heightened concern for health and food safety, pesticide residues have become one of the major challenges affecting its quality and safety. Cyhalothrin is a pyrethroid insecticide and a typical type of pesticide with excessive pesticide residues in Lycium barbarum L. Rapid detection of pesticide residues is an effective way to ensure the quality and safety of traditional Chinese medicinal materials. In this work, a molecularly imprinted polymer electrochemiluminescence (ECL) sensor based on gold nanoparticles (AuNPs)@Ru-ZIF-8 was constructed for rapid detection of cyhalothrin residues. The prepared cyhalothrin molecularly imprinted polymers (MIPs) were used as a recognition element and modified on the surface of a glassy carbon electrode (GCE) by an electrochemical polymerization method. AuNPs were utilized to promote the excitation of Ru(bpy)₃²⁺ and TPrA in the ECL system, which improved the observability of the light signal. The GCE modified with the metal–organic frameworks (MOFs) ZIF-8 was employed to increase the specific surface area and enhance the electron transfer capacity on the electrode, thereby improving the sensing sensitivity of the sensor. In addition, the luminescent reagent of Ru(bpy)₃²⁺ was introduced into the synthesis process of ZIF-8, which caused Ru(bpy)₃²⁺ to be tightly bound around it and enhanced the stability of the sensor. Under optimal conditions, the linear detection range of the sensor is 1 × 10⁻¹~1 × 10⁴ nM, with a limit of detection (LOD) of 10 pM. The accuracy of the ECL-MIP sensor has been verified through spiked recovery experiments and actual sample detection. This study has opened up a new approach to rapid detection of pesticide residues in traditional Chinese medicinal materials used for both food and medicine. Full article