Search Results (209)

Precise remote temperature sensing at the micro- and nanoscale is a growing necessity in modern science and technology. We report a series of luminescent tris-acetylacetonate lanthanide complexes, Ln(acac)₃(H₂O)₂ (Ln = Eu (1Eu), Tb (1Tb), Yb (1Yb)); acac⁻ = acetylacetonate), operating as self-referenced thermometers in the 290–350 K range, both in the solid state and when embedded in hybrid nanoparticles. Among the investigated systems, the Eu³⁺ complex exhibits excellent lifetime-based thermometric performance, achieving a maximum relative sensitivity (S_rmax) of 2.9%·K⁻¹ at 340 K with a temperature uncertainty (δT) as low as 0.02 K and an average temperature uncertainty ($\overline{\delta T}$) of 0.5 K, placing it among the most effective ratiometric lanthanide-based luminescent thermometers reported to date. The Yb³⁺ analog enables intensity-based thermometry in the near-infrared domain with a good sensitivity S_rmax = 0.5%·K⁻¹ at 293 K, δT = 0.5 K at 303 K, and $\overline{\delta T}$ = 1.6 K. These molecular thermometers were further incorporated into the shell of Prussian Blue@SiO₂ core–shell nanoparticles. Among the resulting hybrids, PB@SiO₂-acac/(1Tb/1Eu) (with a Tb/Eu ratio of 2/8) stood out by enabling ratiometric temperature sensing based on the Eu³⁺⁵D₀ → ⁷F₂ lifetime, with satisfactory parameters (S_rmax = 0.9%·K⁻¹, δT = 0.21 K at 303 K, and $\overline{\delta T}$ = 1.1 K). These results highlight the potential of simple coordination complexes and their nanohybrids for advanced luminescent thermometry applications. Full article

Near-infrared (NIR) photoelectric synaptic devices show great potential in studying NIR artificial visual systems integrating excellent optical characteristics and bionic synaptic plasticity. However, NIR synapses based on transition metal dichalcogenides (TMDCs) suffer from low stability and poor environmental performance. Thus, an environmentally friendly NIR synapse was fabricated based on lanthanide-doped upconversion nanoparticles (UCNPs) and two-dimensional (2D) WSe₂ via solution spin coating technology. Biological synaptic functions were simulated successfully through 975 nm laser regulation, including paired-pulse facilitation (PPF), spike rate-dependent plasticity, and spike timing-dependent plasticity. Handwritten digital images were also recognized by an artificial neural network based on device characteristics with a high accuracy of 97.24%. In addition, human and animal identification in foggy and low-visibility surroundings was proposed by the synaptic response of the device combined with an NIR laser and visible simulation. These findings might provide promising strategies for developing a 24/7 visual response of humanoid robots. Full article

A tetraerbium cluster containing soft-base dianionic 4,8-difluorobenzo [1,2-d:5,4-d′]bisthiazole-2,6-dithiol (H₂L) ligands, μ-OH, and coordinated 1,2-dimethoxyethane (DME) of the general formula {Er₄(μ-L)₄(μ-OH)₄(DME)₄} (1) was synthesized using a one-pot method. X-ray analysis revealed that 1 is an asymmetrical tetramer in which there are four μ₂-bridging bisthiazole ligands and four μ₂-bridging hydroxide anions per four erbium ions. The molecule of 1 has inherent chirality, and the geometry of intramolecular F…F short contacts implies the formation of a classical halogen bond. Upon excitation by a 375 nm diode laser, compound 1 shows the moderate metal-centered emission of Er³⁺ ions that peaked at 1530 nm. Full article

An extensive experimental study of trivalent iron (Fe³⁺) ions in orthorhombic lithium gallate nanocrystals was undertaken. Various spectroscopic methods, such as Raman spectroscopy, extended X-ray absorption fine structure, the Mössbauer effect, electron paramagnetic resonance, photoluminescence, thermoluminescence, and cathodoluminescence were used to investigate the synthesized phosphor. This study revealed the existence of multiple Fe³⁺ sites, out of which the tetrahedral sites are preferentially occupied. Extensive optical studies showed that the Fe³⁺ doped lithium gallate phosphor is a promising candidate for various luminescence and thermoluminescence-related applications in the near-infrared regime. Full article

Coupling organic light-harvesting materials with lead halide perovskite quantum dots (LHP QDs) is an attractive approach that could provide great potential in optoelectronic applications owing to the diversity of organic materials available and the intriguing optical and electronic properties of LHP QDs. Here, we demonstrate energy collection by CsPbI₃ QDs from a near-infrared (NIR) light-harvesting upconversion system. The upconversion system consists of Pd-tetrakis-5,10,15,20-(p-methoxycarbonylphenyl)-tetraanthraporphyrin (PdTAP) as the sensitizer to harvest NIR photons and rubrene as the annihilator to generate upconverted photons via triplet fusion. Steady-state and time-resolved photoluminescence spectra reveal that CsPbI₃ QDs are energized via radiative energy transfer from the singlet excited rubrene with photophysics fidelity of respective components. In addition, a volumetric display demo incorporating CsPbI₃ QDs as light emitters employing triplet fusion upconversion was developed, showing bright luminescent images from CsPbI₃ QDs. These results present the feasibility of integrating organic light-harvesting systems and perovskite QDs, enabling diverse light harvesting and activation of perovskite materials for optoelectronic applications. Full article

The development of efficient scintillators emitting in the red and/or infrared spectral range represents an important scientific challenge, as such materials could find numerous practical applications. This work studies newly grown CsI:Yb,Sm and CsI:Eu,Sm single crystals demonstrating red and infrared luminescence. We measured luminescence spectra in the visible and near-IR range, excitation spectra across visible, UV, VUV, and X-ray ranges, Raman spectra, and thermoluminescence spectra. The results show that divalent europium and ytterbium ions can efficiently transfer excitation to samarium ions. The light output of the obtained crystals under X-ray excitation was roughly estimated from the X-ray luminescence spectra, with expected values of 37,000 photons/MeV for CsI:Yb,Sm and 40,000 photons/MeV for CsI:Eu,Sm. Full article

Bi-doped glasses and fibers have been widely applied in solid-state and fiber lasers. However, the mechanism underlying near-infrared (NIR) luminescence remains unclear, and Bi-related luminescence centers (BLCs) are prone to alteration during fiber fabrication, making it challenging to achieve high-performance Bi-doped glass fibers. In this work, Bi-, Bi-Al-, and Bi-Ge-doped silica glasses were investigated to elucidate the origin of NIR luminescence. Two broad NIR fluorescence bands were observed in silica glasses, originating from distinct BLCs. The longer-wavelength fluorescence band at 1423 nm, demonstrating sensitivity to Bi doping concentration and homogeneity, is attributed to Bi clusters (aggregates of Bi⁺ ions), whereas the shorter-wavelength emission, independent of Bi concentration, originates from isolated Bi⁺ ions. A vacuum-assisted melting-in-tube method with a single-step heating process was employed to fabricate Bi-doped silica-based glasses and fibers. The fluorescence bands of the fibers remained consistent with those of the precursor glasses, indicating no new BLCs were formed during fiber fabrication. The modulation of fluorescence bands was primarily governed by Bi cluster formation. Suppressing Bi clustering through co-doping with Al/Ge or optimizing fabrication conditions offers an effective route to tailor the fluorescence properties of Bi-doped glasses and fibers. Full article

Thiol–epoxy photopolymerization offers exceptional advantages for high-performance protective coatings, yet efficiently curing thick formulations remains a significant challenge due to the limited penetration depth of conventional UV light. Herein, we report a novel near-infrared (NIR) light-activated photopolymerization system for deep-curing applications, strategically integrating upconversion nanoparticles (UCNPs) as NIR-to-UV converters, isopropylthioxanthone (ITX) as a photosensitizer, and a liquid N-phenylglycine-based photobase generator (NPG-TBD) with enhanced resin solubility. Upon 980 nm NIR irradiation, photogenerated TBD efficiently catalyzes thiol–epoxy polymerization through an anionic mechanism, enabling uniform network formation with epoxy and thiol functional group conversions greater than 90% throughout samples exceeding 2.5 cm in thickness. The resulting coatings exhibit excellent mechanical properties including 3H pencil hardness, strong adhesion (0 grade), and good flexibility (2 mm), significantly outperforming conventional UV systems limited to approximately 1.5 mm. Additionally, the cured materials demonstrate multifunctional characteristics including distinctive upconversion luminescence and dual-responsive shape memory behavior. This approach addresses critical limitations in deep-photocuring technology while offering significant potential for applications in protective coatings for marine infrastructure, chemical storage facilities, and smart materials requiring both substantial barrier properties and programmable responsiveness. Full article

In this study, Zn-doped Ga₂O₃ polycrystalline samples were prepared by solid-phase sintering, and the effects of Zn doping on the optical properties of Ga₂O₃ were investigated. It is found that the introduced Zn ions disrupted the Ga-O bonds and formed Zn_Ga, altering the Ga-O vibration modes and causing a blue shift in the related Raman mode. From near-infrared to visible light-range was a transparent region for Zn-doped Ga₂O₃. The fundamental optical bandgap underwent a decrease with increasing Zn doping content, primarily due to the p-d orbital hybridization of the O 2p and Zn 3d orbitals causing an upward shift valence band maximum and band renormalization effect-induced band-tails. The recombination of electrons at donor levels (V_O) and holes at acceptor levels (V_Ga or V_O-V_Ga) gave rise to blue-green luminescence. Zn doping increased the concentration oxygen vacancies (V_O), resulting in significant blue-green luminescence enhancement in Zn-doped Ga₂O₃. Additionally, Zn doping resulted in a noticeable reduction in the red luminescence of Ga₂O₃, which may be attributed to Zn doping suppressing nitrogen incorporation from the air during high-temperature preparation processes. Full article

Phosphorescent Pt(II) complexes have garnered significant attention as key components in luminescence-based systems due to their highly efficient emission properties. A notable characteristic of these complexes is their ability to form excimers through strong molecular stacking in concentrated solutions or solid film states. This aggregation-driven emission, primarily arising from metal–metal to ligand charge transfer (MMLCT), is influenced by overlapping d-orbitals oriented perpendicular to the square planar structure of the Pt(II) complexes. Although this property hinders the development of pure blue-emitting Pt(II) complexes, it facilitates the design of materials that emit red- and near-infrared (NIR) light. By employing advanced molecular design techniques, dinuclear Pt(II) complexes have been optimized to significantly enhance red and NIR emissions through the modulation of Pt-Pt interactions and adjustments in ligand electron densities. This review elucidates how the control of Pt-Pt distances and strategic ligand modifications can directly influence the emission spectra toward red and NIR regions. A comparative analysis of recent studies underscores the novelty and effectiveness of double-decker-type dinuclear Pt(II) complexes in achieving efficient emission characteristics in the long-wavelength range. These insights may guide the design of molecular structures for next-generation organometallic phosphorescent materials. Full article

The optical properties of Mn⁵⁺ ions, which are responsible for the intense green–turquoise–blue coloration of Mn⁵⁺-based pigments and the near-infrared emission of phosphors, are the focus of this article. Mn⁵⁺ ions enter crystalline matrices in four-fold coordinated positions and can maintain their 5+ valence state when crystalline hosts meet the conditions described in this work. Mn⁵⁺ ions have [Ar]3d² electronic configuration and always experience a strong crystal field due to a high electric charge; therefore, their lower electronic states have the ³A₂ < ¹E < ¹A₁ < ³T₂ < ³T₁ progression in energy. We present the properties of several Mn⁵⁺-based pigments and discuss the electronic transitions responsible for their coloration. Specifically, we show that the color is determined by the spin-allowed ³A₂ → ³T₁(³F) absorption, which extends across the orange–red–deep red spectral region and is strongly influenced by crystal field strength. The narrow-band emission Mn⁵⁺-activated near-infrared phosphors arise from the spin-forbidden ¹E → ³A₂ transition, whose energy is independent of the crystal field strength and determined by the nephelauxetic effect. We demonstrate the linear relationship between ¹E state energy and the nephelauxetic parameter β₁ using Racah parameter literature data for Mn⁵⁺ phosphors. Lastly, we address the recent applications of these Mn⁵⁺ phosphors in luminescence thermometry. Full article

Ciprofloxacin (CIP), a widely used broad-spectrum antibiotic, poses a serious threat to human health and environmental safety due to its residues. The complementary monomers molecularly imprinted electrochemiluminescence sensor (MIECLS) based on a polyvinylpyrrolidone-functionalized copper nanowires (CuNWs@PVP) luminescent probe was constructed for the ultra-sensitive detection of CIP. CuNWs with low cost and high conductivity exhibited near-infrared electrochemiluminescence (NIR ECL) properties, yet their self-aggregation and oxidation led to a weakened emission phenomenon. PVP with solvent affinity and large skeleton was in situ attached to CuNWs surface to avoid CuNWs sedimentation and aggregation, and self-enhanced ECL signals were achieved. The bifunctional monomers molecularly imprinted polymer (MIP) possessed complementary active centers that increased their affinity with CIP, enhancing the accurate and sensitive detection of the target substances. The linear range of CIP using MIECLS was 5.00 × 10⁻⁹–5.00 × 10⁻⁵ mol L⁻¹ with a low limit of detection (LOD) of 2.59 × 10⁻⁹ mol L⁻¹, while the recovery rates of CIP in the spiking recovery experiment were 84.39% to 92.48%. The combination of bifunctional monomer MIP and NIR copper-based nano-luminescent probe provides a new method for the detection of CIP in food. Full article

Near-infrared persistent luminescence (PersL) nanoparticles (NPs) have great potential in biomedical applications due to their ability to continuously emit tissue-penetrating light. Despite numerous reports on the distribution, biological safety and other consequences of PersL NPs in vitro and in vivo, there has been a lack of studies on the optical properties of these NPs in the physiological environment. In light of this, we investigated the effects of short-term immersion of the prominent Cr³⁺-doped ZnGa₂O₄ (CZGO) NPs in a simulated physiological environment for up to 48 h. This paper reports the changes in the structural and optical properties of CZGO NPs after their immersion in a phosphate-buffered saline (PBS) solution for pre-determined time intervals. Interestingly, the luminescence intensity and lifetime noticeably improved upon exposure to the PBS media, which is unusual among existing nanomaterials explored as bioimaging probes. After 48 h of immersion in the PBS solution, the CZGO NPs were approximately twice as bright as the non-immersed sample. X-ray spectroscopic techniques revealed the formation of ZnO, which results in an improvement in observed luminescence. Full article

Atomically precise noble metal nanoclusters protected by ligands are broadly discussed in the literature as a promising new class of materials with many interesting properties. Of those, the most prominent is the characteristic luminescence in the visible and near-infrared light. Within the plethora of conjugates of metal nanoclusters to various protective ligands, protein-enveloped systems present several unique features arising from an interplay of the nanocluster photophysics and the protein chemistry along its macromolecular dynamics. The specific properties of protein–metal nanocluster conjugates underlie various applications of these systems, especially in bioimaging. This review, in contrast to many already published, focuses on protein-protected gold nanoclusters (AuNCs) from the standpoint of the proteinaceous shell which plays a crucial role in the biocompatibility, solubility, and excellent in-solution stability of such nanohybrid complexes. Factors such as the protein’s size, structural rigidity, amino acid composition, electric charge, and the electron donor properties of composite amino acids are discussed. Full article

The use of biomass feedstocks for producing high-value-added chemicals is gaining significant attention in the academic community. In this study, near-infrared carbon dots (NIR-CDs) with antimicrobial and bioimaging functions were prepared from Epigynum auritum branches and leaves using a novel green synthesis approach. The spectral properties of the synthesized NIR-CDs were characterized by ultraviolet–visible (UV-Vis) absorption and fluorescence spectroscopy. The crystal structures of the NIR-CDs were further characterized by high-resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), and X-ray diffraction (XRD). The NIR-CDs exhibited minimal toxicity, excellent biocompatibility, and high penetrability in both in vivo and in vitro environments, making them ideal luminescent probes for bioimaging applications. Moreover, the antimicrobial activity of NIR-CDs was tested against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), showing significant bacterial growth inhibition. The antimicrobial effect is likely attributed to the NIR-CDs disrupting the cell membrane integrity, leading to the leakage of the intracellular contents. Therefore, NIR-CDs hold promise as fluorescent bioimaging probes and antimicrobial agents. Full article