Excellent Luminescent Characteristics Research Articles

Sensitive and rapid fluorescent detection of metronidazole based on stable light-emitting vinylene-linked covalent organic framework

Development of ultra-sensitive and rapid fluorescent nanoprobe for quantitative and targeted monitoring of metronidazole is of crucial practical significance, but is of great challenge. Herein, a vinyl-linked covalent organic frameworks (sp2-BNTP-COF) was fabricated via integrating the 1,3,5-tris-(4-formylphenyl) triazine with 5,5′-bis(cyanomethyl)-2,2′-bipyridine into the skeleton. As-obtained sp2-BNTP-COF exhibited excellent luminescence characteristics with an absolute fluorescence quantum yield of 8 %. However, fluorescent emission of sp2-BNTP-COF could be sharply quenched via metronidazole based on internal filtration effect. A sensitive fluorescent strategy was built for targeted monitoring of metronidazole. Furthermore, the analysis operation could be accomplished within 20 s, which was desirable for point-of-care monitoring of metronidazole. Therefore, this work not only provides a reliable method for the sensitive, rapid, and quantitative detection of metronidazole residues based on the sp2-BNTP-COF, but also paves the way for exploring stable luminescent vinyl-linked COFs materials as promising fluorescent nanoprobes for targeted monitoring of antibiotic residues.

Study on luminescence properties and anti-counterfeiting application of Sr3Y2Ge3O12 doped Mn2+ long afterglow materials

Traditional anti-counterfeiting materials have the characteristics of static display of anti-counterfeiting patterns and are easy to be disturbed by background patterns. Consequently, the development of novel luminous materials represents an imperative objective. As a novel class of matrix material, Sr3Y2Ge3O12 has demonstrated considerable potential for application in the field of anti-counterfeiting. In this study, strontium yttrium germanate doped manganese ion long afterglow material was prepared by the high temperature solid phase method, and its afterglow performance and dynamic anti-counterfeiting application were studied. The experimental results show that the sample exhibits excellent luminescence characteristics. It is observed that the sample excited at 260 nm shows an emission band centred at 634 nm and a high-energy turning point at 578 nm. Using screen printing technology, design a variety of anti-counterfeiting labels. The prepared samples after ultraviolet excitation can maintain the pattern for a long time, and with the passage of time, the pattern shows dynamic attenuation, which is important in enhancing the anti-counterfeiting effect and improving product safety.

Sextuplet luminescence with dynamically variable color/brightness in chromium activated gallium-silicate solid solution in R3 space group

The development of dynamic multi-color luminescence is a tremendous challenge for anti-counterfeiting. Herein, we have successfully synthesized Cr3+ activated gallium-silicate base material systems as the effective luminescent materials responsive to multiple field stimulation, exhibiting sextuplet luminescence including photoluminescence, strong red persistent luminescence (PersL), photo/thermo stimulated luminescence (PSL/TSL), photo-stimulated PersL and up-conversion luminescence (UCL). The luminescence quenching temperature is also improved in Cr3+,Yb3+,Er3+ co-doping sample relatives to Cr3+ single-doping phosphor. Especially, when Er3+ and Yb3+ are co-doped into Cr3+ activated phosphor system, UV preirradiated phosphor not only demonstrates an additional UCL from Er3+ ions accompanied with red PSL from the Cr3+ under NIR laser irradiation, but also leads to a dynamic change in color/brightness under the extension of NIR laser irradiation time. The multimode luminescence mechanisms are also proposed. Based on excellent luminescence characteristics, multi-color and multi-mode anti-counterfeiting patterns have been designed, especially appearing of dynamic anti-counterfeiting on luminescent color/brightness, which provides new dimensions for anti-counterfeiting technologies.

CsPbBr3/TiO2 Z-type heterojunction for rhodamine B catalysis and efficient photodetectors

Halide perovskites have attracted widespread attention in the fields of photovoltaics, LEDs, lasers, and photocatalysis due to their unique optoelectronic properties. Here, we proposed a method to synthesize CsPbBr3/TiO2 composite material by embedding precursors into mesoporous titanium dioxide pores and inducing in-situ growth of the perovskites within the pores. Due to the encapsulation of mesoporous TiO2, CsPbBr3 maintains its excellent luminescent characteristics in water, air, and at high temperatures. Furthermore, the Z-type heterojunction structure formed between mesoporous TiO2 and internal CsPbBr3 significantly enhances the photo-generated current, and the response time has increased by 1.7 times.

Theoretical Determination of the Electronic Structures and Energy-Level Splitting for Pr3+-Doped Y2SiO5 Crystals.

Trivalent praseodymium (Pr3+)-doped yttrium silicate (Y2SiO5) crystals have been widely used in various phosphors owing to their excellent luminescence characteristics. Although a series of studies have been carried out on its application prospects, the electronic structures and energy-transfer mechanisms of Pr3+-doped Y2SiO5 (Y2SiO5:Pr) remain an exploratory topic. Herein, the crystal structure analysis by the particle swarm optimization structure search method is used to study the structural evolution of Y2SiO5:Pr. Two novel structures with local [PrO7]-11 and [PrO6]-9 [Y2SiO5:Pr (I) and Y2SiO5:Pr (II)] are successfully identified. The impurity Pr3+ ions occupy the Y3+ sites and successfully integrate into the Y2SiO5 host crystal with a Pr3+ concentration of 6.25%. The calculated electronic band structures show that the doping of Pr3+ induces a reduction in band gaps for the host Y2SiO5 crystal. The conduction bands near the Fermi level are completely composed of f states. For the atomic energies of Pr3+ in Y2SiO5, the Stark levels and transitions are properly simulated based on a new set of crystal field parameters (CFPs) at the C1 site symmetry. A satisfactory r.m.s. dev. of 15.57 cm-1 with 9 free ion parameters (plus 27 fixed CFPs as obtained from ab initio calculation) fitted to the 33 observed levels is obtained for the first time. The plentiful energy-level transition lines, from the visible light to the near-infrared region, are deciphered for Pr3+ in Y2SiO5. Blue 3P0 → 3H4 at 465 nm is calculated to be a strong emission line, and it might be an ideal channel for laser actions. These results could not only provide important insights into the rare-earth-doped crystals but also lay the foundation for future research studies of designing the new laser materials.

Luminescent/Temperature-Sensing Properties of Multifunctional Rare-Earth Upconversion Kevlar Nanofiber Composite under 1550 nm.

The unique properties of upconversion nanoparticles (UCNPs) are responsible for their diverse applications in photonic materials, medicine, analytics, and energy conversion. In this study, water-soluble rare-earth upconversion nanomaterials emitting green, yellow, and red light under 1550 nm excitation were synthesized. These nanomaterials were then integrated into water-soluble Kevlar nanofibers (KNFs) to fabricate ultra-thin composite films exhibiting favorable mechanical characteristics. The characterization of the products, along with their luminescent, mechanical, and temperature-sensing properties, was examined. The results indicate that the composite material exhibited varying colors based on the doped nanoparticles when subjected to 1550 nm excitation. The composite showed highly sensitive temperature-sensing properties, excellent luminescent characteristics, and superior mechanical strength. This study suggests that KNFs are effective carriers of UCNPs. This study offers a reference for the utilization of rare-earth upconversion in anti-counterfeiting displays, wearable health monitoring, and remote temperature sensing.

Room temperature amplified spontaneous emissions in a sub-centimeter sized CsPbBr3 bulk single crystal.

All inorganic perovskite CsPbBr3 shows great potential in laser device because of its excellent luminescence characteristics, while the room temperature amplified spontaneous emission (ASE) in a large size CsPbBr3 bulk single crystal is still quite difficult. Herein, we have obtained the room temperature ASE in a sub-centimeter size CsPbBr3 bulk single crystal pumped with the single-photon excitation. Based on the reproducible light path within the CsPbBr3 bulk single crystal, the photonic feedback between the bottom and top facets naturally enhances the population inversion, which exhibits an amplified spontaneous emission threshold of ∼320 µJ/cm2. The blue shift of the ASE peak along with the increased pumping intensity is also observed and ascribed to the reduction of the refractive index and the energy band filling effect. These findings demonstrate the sub-centimeter size CsPbBr3 bulk single crystal to be an excellent candidate as an optical gain media for crystal lasers.

Temperature-dependent steady-state and time-resolved photoluminescence spectroscopy of CsPbBr3 encapsulated with PbBrOH and PVA

In this work, photoluminescence (PL) intensity and stability of CsPbBr3/PbBrOH powders synthesized by one-pot method are enhanced through the encapsulation of poly (vinyl acetate) (PVA) in water. Understanding the function of PbBrOH and PVA matrix for photogenerated transition can be achieved through temperature-dependent steady-state and time-resolved PL. The enhanced PL quantum yield (65.9%) and longer lifetime indicate the strengthened structural stability and a significant reduction in nonradiative recombination of CsPbBr3. Negative thermal quenching can be observed and interpreted using a multilevel PL transition model. Through nanosecond time-resolved PL spectra under femtosecond laser excitation, it is revealed that the PL position shows a redshift (∼8 nm) with time delay due to the reduction of band-filling effect during the recombination of photoexcited carriers. PVA further encapsulates CsPbBr3/PbBrOH powders to form a flexible film, which exhibits excellent thermal and water stability due to the dual protective effects of PVA and PbBrOH. The experimental investigation demonstrates that CsPbBr3 encapsulated by PbBrOH and PVA possesses excellent luminescent and water-resistant characteristics, making it a new choice for practical applications in LEDs and screen printing.

Green synthesis of carbon dots from cordyceps militaris and versatile applications in alcohol detection and waterproof fluorescent ink

Carbon dots (CDs) are a class of highly efficient and low-toxicity fluorescent nanomaterials. In this study, using cordyceps militaris as a carbon source, we prepared green-emitting CDs with excellent properties, such as good photobleaching resistance, salt resistance and chemical stability, as well as high quantum yield. Further exploration of the versatile applications of G-CDs in chemical detection and information anti-counterfeiting fields revealed that G-CDs can not only be used as detection agent for analyzing alcohol content in alcoholic beverages but also serve as waterproof fluorescent ink for painting and writing due to their water-resistant property. This work is based on natural biomass as the main precursor to prepare fluorescent CDs with excellent luminescent characteristics and stable physicochemical properties. It is significant for reducing reliance on chemical reagents, lowering the cost of synthesizing CDs, and expanding the application range of CDs.

A new fluorescent probe based on metallic deep eutectic solvent for visual detection of nitrite and pH in food and water environment

Nitrite is a widely used food additive that has been shown to be carcinogenic and can cause health damage when consumed in excess. Therefore, developing a detection method is in demand. Here, we prepared a novel Fe-doped carbon dots (Fe-CDs) using metallic deep eutectic solvent (MDES) which showed high sensitivity and selectivity. Besides, it also showed excellent pH-dependent luminescence characteristics, which proved the feasibility as a pH sensor. Under the optimal conditions, the detection linear of nitrite ranged from 0.2 to 80 µM, and the detection limit was 50 nM. The recovery rate was between 98.8 % and 104.1 % in food and water samples. For pH monitoring, its fluorescence intensity was linearly correlated in the pH range from 2 to 7, accompanying a unique differential solution color change of colorless-yellow-green. Therefore, it can be used as an excellent fluorescent probe for detection of nitrite and pH in food and water environment.

Horizontal and vertical stacked Ag/MoS2 nanostructure enabled excellent carrier mobility and optoelectronic properties

Amongst 2D materials, MoS2 with highly exposed atomic edges and large specific surface area are considered potentially strong candidates for optoelectronic devices such as photogenerated electron transport layer, saturated/reverse saturated light absorber. With these prospects in mind, doped nanohybrid system was employed as a “accelerator” for problems related to conductivity and field emission. Herein, the horizontal-vertical stacked Ag/MoS2 films including horizontal nanolayer and vertical nanosheets (NSs) was firstly presented, which exhibit excellent carrier mobility and luminescence characteristics. We have confirmed that the morphology of the Ag/MoS2 NSs (including microworm-like, worm-like, and sheet-like shape), Ag content, micro strain and crystallinity can be adjusted under the different substrate temperature. Base on anisotropy bonding and ultrafast chemical conversion effect of MoS2, the cross-layer diffusion of sputtered atoms is suppressed, thereby the subsequent deposited atoms preferring to diffuse along the van der Waals gap. The efficient light-matter interaction and surface plasmon resonance (SPR) effect is introduced by the abundant exposed S-edges of horizontal-vertical stacked Ag-MoS2 nanostructure, which lead to excellent Raman signal and linear absorption characteristic. The carrier mobility and concentration of Ag/MoS2 NSs with excellent electrical behavior has reached 4480 cm2 V-1S-1 and 3.272 × 1018 cm−2, which can be regarded as the unique ohmic contact and the electron injection effect. Further, the luminescence performance (visible light region) of horizontal-vertical stacked Ag/MoS2-350 °C NSs is 2.5 times higher than that of the original MoS2 NSs, which is dominated by the hot electron injection effect. Importantly, the carrier relaxation time guided by the nonradiative recombination behavior of Ag/MoS2-350 °C NSs was not significantly changed by the incorporation of Ag nanoparticles. The above phenomenon implies that the hot electron injection effect mainly promotes the photoluminescence behavior induced by radiative recombination. The homogeneous and controllable Ag/MoS2 NSs exhibits excellent multiple optoelectronic properties, which can provide a valuable reference strategy for the application of optoelectronic nano-film materials.

Mineralogical Characteristics and Luminescent Properties of Natural Fluorite with Three Different Colors.

Fluorite is rich in mineral resources and its gorgeous colors and excellent luminescence characteristics have attracted the attention of many scholars. In this paper, the composition, structure, luminescent properties, and the potential application value of three fluorites with different colors and are systematically analyzed. The results show that REE and radioactive elements have effects on the structure, color, and luminescence of fluorite. Radioactive elements Th and U will aggravate the formation of crystal defects in fluorite. The green color is related to Ce3+ and Sm2+. Colloidal calcium and F− center are responsible for the blue-purple color of fluorite. There are many luminescent centers, such as Eu, Pr, Dy, Tb, Er, and Sm, in fluorite. The blue fluorescence is mainly caused by 4f7-4f65d1 of Eu2+. In addition, it is found that fluorite has certain temperature sensing properties in the temperature range of 303–343 K.

A multi-color persistent luminescent phosphor β-NaYF4:RE3+ (RE = Sm, Tb, Dy, Pr) for dynamic anti-counterfeiting.

Conventional luminescent materials generally exhibit uni-color and transient emission under UV excitation, which makes them mediocre in the field of anti-counterfeiting. The high-level anti-counterfeiting techniques are always becoming more complicated and in need of multi-color and persistent luminescent materials. Herein, we report a series of β-NaYF4:RE3+ (RE = Sm, Tb, Dy, Pr) persistent luminescent phosphors with multi-color emitting and ultra-long persistent luminescence under the irradiation of X-rays. The effects of doping concentrations of RE3+ on the size, morphology, radioluminescence and afterglow performance of the products are investigated in detail. Hexagonal structured rod-like β-NaYF4:Tb3+ crystals show super strong X-ray response and the afterglow signal lasts for up to seven days after X-rays are turned off. Upon X-rays irradiation, some of the F− ions are expected to escape from the crystal lattice by elastic collisions, leading to the generation of Frenkel defects: the F vacancies and interstitials , which capture electrons and release them slowly to achieve different afterglow emission times. Taking advantages of the extraordinary radioluminescence performance of the β-NaYF4:RE3+ persistent luminescent phosphors, the dynamic anti-counterfeiting patterns that containing rich time-resolved information were successfully designed.

Luminescent Zn (II) coordination polymers for highly selective detection of triethylamine, nitrobenzene and tetracycline in water systems

Two novel coordination polymers (CPs), formulated as {[Zn3(L)1.5(DMF)3]•C2H7N} n (1), and [Zn(L)0.5(bpb)0.5(H2O)2] n (2), (H4L = 1, 1′-ethylbiphenyl −3, 3′, 5, 5′- tetracarboxylic acid, bpb = 1, 4-di(pyridin-4-yl) benzene), have been acquired under hydrothermal conditions. Complexes 1 and 2 display excellent luminescence characteristics and stability in antibiotics and organic solvents. Complex 1 can detect triethylamine (TEA) and tetracycline (TET) in water by fluorescence quenching. The detection limits of 1 towards TEA and TET are 1.07 μM and 0.1 μM, respectively. Complex 2 can be used as a luminescence sensor to detect nitrobenzene (NB) and the detection limit towards NB is 0.2 μM. Moreover, complexes 1 and 2 perform excellent reproducibility, because the changes of fluorescence intensity are negligible after four cycles. The mechanism of the fluorescence quenching is discussed in detail.

Tunable Luminescence of Ce3+/Eu2+ Activated in Single-Phase Li2BaSiO4 Phosphor via Energy Transfer

A series of Ce3+,Eu2+ co-doped Li2BaSiO4 cyan-green phosphors were synthesized by a high temperature solid phase method. The crystal structure, morphology, luminescent properties and temperature characteristics of the corresponding samples were systematically studied. The main peaks of the emission spectra of Li2BaSiO4:Ce3+,Eu2+ were shifted from 400 nm to 500 nm by adjusting the Ce3+,Eu2+ co-doping concentration. And a series of phosphors with continuous changes from blue to cyan green were obtained, which effectively compensated for the gap between the white LED at 470–510 nm region. The energy transfer efficiency and mechanism of Ce3+,Eu2+ in Li2BaSiO4 were studied by fluorescence lifetime. The highest energy transfer efficiency was 46.01%, and the energy transfer mechanism was determined to be electric dipole-electric dipole transition. Finally, fabricating a white LED device which coated blue, green-yellow, red and as-prepared cyan phosphors on the surface of ultraviolet chip (350 nm), and the device exhibited excellent luminescence characteristics (Ra = 95.2, CCT = 3105 K). The results show that the Li2BaSiO4:Ce3+,Eu2+ phosphor developed can be regard as single-component tunable color luminescent materials under the excitation of near ultraviolet light.

Theoretical Understanding of Structure-Property Relationships in Luminescence of Carbon Dots.

Carbon dots (CDs) have excellent luminescence characteristics, such as good light stability, high quantum yield (QY), long phosphorescence lifetime, and a wide emission wavelength range, resulting in CDs' great success in optical applications. Understanding the structure-property relationships in CDs is essential for their use in optoelectronic applications. However, because of the complex nature of CD structures and synthesis processes, understanding the luminescence mechanism and structure-property relationships of CDs is a big challenge. This Perspective reviews the theoretical efforts toward the understanding of structure-property relationships and discusses the challenges that need to be overcome in future development of CDs.

Recent advances in upconversion nanocrystals: Expanding the kaleidoscopic toolbox for emerging applications

Lanthanide-doped upconversion nanoparticles enable anti-Stokes emission via nonlinear processes, where low-energy excitation photons in the near-infrared window can be upconverted into high-energy emission ones in the visible or ultraviolet regions. The past decade has seen great success in the high-quality synthesis of upconversion nanoparticles with controlled structure, crystalline phase, size, and shape. The unique capacity of upconversion nanocrystals to undertake near-infrared excitation, amalgamated with their excellent luminescent characteristics, such as massive anti-Stokes spectral shift, sharp emission band, multicolor emission, and long luminescence lifetime, makes these nanomaterials prime candidates for a plethora of applications. Herein, we review the field of upconversion nanoparticles from the perspectives of fundamental luminescence mechanisms, new synthetic routes, and current practical approaches to tuning emission color and enhancing upconversion efficiency. In particular, we highlight the recent advances in utilizing upconversion nanocrystals for bioimaging, therapy, biosensing, neuroscience, super-resolution imaging, photoswitching, and lasing applications. We also discuss the key challenges and issues that are critical for the further implementation of upconversion nanoparticles in diverse settings.

Luminescence dating of weathered sediments from the Paleolithic site of Fengshuzui in northern Hunan province, China

Abstract South China is an important region for the investigation of the origin of modern humans and the dispersal of Homo sapiens in Asia. However, the accurate dating of Paleolithic sites, especially for open-air sites, in the region has been difficult due to the lack of datable materials like bones that were destroyed due to intense chemical weathering. In this study, we applied optically stimulated luminescence (OSL) dating techniques to the Paleolithic site of Fengshuzui in south China, in which the deposits are intensely weathered. We first investigated the degree of chemical weathering of the deposits and the effect of weathering on dose rate, and then measured the equivalent dose of quartz extracts from five sediment samples from a ∼5 m thick archaeological section. The contents of mobile and immobile elements determined by different analysis methods show that the studied sediments are homogenous in chemical and mineral compositions. Enrichment or depletion of major and trace elements including U and Th were not detected. The sediments consist of ∼60% quartz, ∼30% illite and ∼6% feldspars, ∼3% kaolinite and ∼2% hematite. The calculated chemical weathering indices show that the sediments have been intensely weathered, and the weathering degree of the five studied samples at different depths are similar. Radioactive disequilibrium in the uranium decay series caused by weathering was not detected. All these indicate that the effect of chemical weathering on dose rate is negligible for our samples. The quartz extracts displayed excellent luminescence characteristics, and the five samples, from bottom to top, were dated to 123 ± 7, 98 ± 5, 98 ± 4, 81 ± 3, 68 ± 2 ka, respectively. The ages of the cultural layers range from 100 to 70 ka, mainly corresponding to MIS 5. This also implies that the OSL techniques can be employed to date open-air sites in south China, but the effect of weathering on dose rate should be investigated on a case by case basis.

Luminescence Property of Silicate Phosphor, Ba<sub>9</sub>Sc<sub>2</sub>Si<sub>6</sub>O<sub>24</sub>:Ce, Synthesized by Melt Quenching Technique

Well-grown Ba9Sc2Si6O24:Ce3+phosphors were synthesized by a novel melt quenching synthesis method. Sintered phosphor balls with excellent luminescent characteristics were obtained. This method is useful tool for rapid screening of phosphor materials.

Photonics of coordination complexes of dipyrrins with p- and d-block elements for application in optical devices

In the present paper spectral–luminescent, lasing, photochemical, sensory, and photosensitized characteristics of a number of Zn(II) and B(III) coordination complexes of dipyrrins with different structures are investigated. The results show that alkyl-, phenyl-, and propargylamino-derivatives of dipyrrin core in these complexes have excellent luminescent characteristics and can be used as active media for tunable liquid and solid-state lasers. Zinc (Zn-dpm2) and boron fluoride complexes of dipyrrins (BODIPYs) with halogen atoms and aza-substitution in meso-position in their ligands do not exhibit effective fluorescence, but some of them have long-lived emission due to increased nonradiative intersystem processes in an excited state proceeding by the mechanism of heavy atom and the presence of low-lying nπ- and σπ-states of different natures and multiplicities. The reason for the short-wavelength shift of the Zn-dpm2 spectra compared to the corresponding BODIPY is studied using quantum-chemical calculation. For solid samples based on halogenated complexes, a dependence of the long-lived emission intensity on the oxygen concentration in the surrounding gas mixture is established that indicates the possibility of application of these complexes for the creation of optical oxygen sensors. Moreover, results of investigations of halogen-substituted tetraphenyl-aza-BODIPY complexes as photosensitizers of singlet oxygen production are presented. Such complexes are promising for creating media for generation of singlet oxygen, which is important for photodynamic therapy and oxidation catalysis. In addition, data on the stability of these compounds in different electronic states are presented.