Luminescent Fibers Research Articles

Electrospun Fibers Containing Emissive Hybrid Perovskite Quantum Dots.

We demonstrate a single-step fabrication process of highly stable and luminescent polymer fibers embedded with quantum dots (QDs) of the organic-inorganic hybrid perovskite (OIP) (CH3NH3PbBr3) using the electrospinning process. The fiber (∼2 μm diameter) primarily consists of poly(methyl methacrylate) dispersed with clusters of OIP quantum dots. The OIP clusters are radially distributed, normal to the fiber axis. The photoluminescence quantum yield (PLQY) is high (∼80%) and comparable to that of conventional QDs. The emission maxima are tunable by varying the concentration of OIP precursor in the electrospinning solution. Submicron emission maps show an isotropic and continuous emission along the fiber, suggesting uniform distribution of QD clusters. Temperature-dependent PL response indicates features which are a function of the particle size. For small QDs, the PLQY(T) maxima are close to the ambient temperature, whereas the PLQY(T) maxima shift sizably to T < 50 K for larger QDs. Significant waveguiding of QDs emission and amplified spontaneous emission, a prerequisite for lasing, were observed in the fiber confined OIP system at room temperature.

Stretchable and Ambient Stable Perovskite/Polymer Luminous Hybrid Nanofibers of Multicolor Fiber Mats and Their White LED Applications.

We report the fabrication and optical/mechanical properties of perovskite/thermoplastic polyurethane (TPU)-based multicolor luminescent core-shell nanofibers and their large-scale fiber mats. One-step coaxial perovskite/TPU nanofibers had a high photoluminescence quantum yield value exceeding 23.3%, surpassing that of its uniaxial counterpart, due to the homogeneous distribution of perovskite nanoparticles (NPs) by the confinement of the TPU shell. The fabricated core-shell nanofibers exhibited a high mechanical endurance owing to the well elastic properties of TPU and maintained the luminescence intensity even under a 100% stretched state after 1000 stretching-relaxing cycles. By taking advantage of the hydrophobic nature of TPU, the ambient and moisture stability of the fabricated fibers were enhanced up to 1 month. Besides, large-area stretchable nanofibers with a dimension of 15 cm × 30 cm exhibiting various visible-light emission peaks were fabricated by changing the composition of perovskite NPs. Moreover, a large-scale luminescent and stretchable fiber mat was successfully fabricated by electrospinning. Furthermore, the white-light emission from the fabricated fibers and mats was achieved by incorporating orange-light-emitting poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] into the TPU shell and coupling the turquoise blue-light-emitting perovskite NPs in the core site. Finally, the integrity of the perovskite-based TPU fibers was realized by fabricating a light-emitting diode (LED) device containing the orange-light-emitting fibers embedded in the polyfluorene emissive layer. This work demonstrated an effective way to prepare stable and stretchable luminous nanofibers and the integration of such nanofibers into LED devices, which could facilitate the future development of wearable electronic devices.

Luminescent cotton fibers coated with fluorescein dye for anti-counterfeiting applications

A simple, rapid and green method to develop fluorescent cotton yarns was established. We report the application of fluorescein (FL) into textile support by impregnation method while keeping the original cotton yarn properties for anti-counterfeiting applications. The FL-coated yarns were characterized by Scanning Electron Microscopy, reflectance and fluorescence spectroscopy. The CIE chromaticity diagram showed a yellowish green emission with a weak yellow coloration of cotton fiber. Mechanical characterization of samples shows that the application of fluorescein did not alter significantly the breaking strength and elongation at break of the fibers, even when using resins. In contrast, to resin-free impregnation process the color fastness test demonstrates that the use of resins as binder is required. The obtained results showed that cotton samples release slowly its contents and fluorescein remains more than five washing cycles.

Template-Assisted Synthesis of Luminescent Carbon Nanofibers from Beverage-Related Precursors by Microwave Heating.

Luminescent carbon nanomaterials are important materials for sensing, imaging, and display technologies. This work describes the use of microwave heating for the template-assisted preparation of luminescent carbon nanofibers (CNFs) from the reaction of a range of beverage-related precursors with the nitrogen-rich polyethyleneimine. Highly luminescent robust carbon fibers that were 10 to 30 μm in length and had a diameter of 200 nm were obtained under moderate conditions of temperature (250–260 °C) and a short reaction time (6 min). The high aspect ratio fibers showed wavelength-dependent emission that can be readily imaged using epifluorescence. The development of these multi-emissive one-dimensional (1D) carbon nanomaterials offers potential for a range of applications.

Energy transfer in and fluorescence studies of the Eu-Tb doped BPA-phen system

ABSTRACTTo enhance the red emission efficiency of Eu3+ complexes, [Eu/Tbx(BPA)3phen] (BPA = bisphenol A, phen = 1,10-phenanthroline) is designed and synthesized. The complexes are characterized fully and their luminescence properties are evaluated. Co-fluorescence is detected in the Eu/Tbx(BPA)3phen complexes, and the existence of Tb3+ enhances the luminescence intensity of the central Eu3+ because of the intramolecular energy transfer from the 5D4 level of Tb3+ to the 5D0 level of Eu3+. The luminescence intensity of europium ions at 615 nm is the highest for Eu/Tb1(BPA)3phen. To improve the thermal stabilities and mechanical properties of pure complexes, Eu/Tb1(BPA)3phen/PAN (PAN = polyacrylonitrile) is used to fabricate fibres by electrospinning. Compared with Eu/Tb1(BPA)3phen (τ = 1.1087 ms), the fibres have a longer fluorescence lifetime of 1.533 ms. The fibres also retain a high quantum yield of 47.16%. Thus, the flexible luminescent fibres have potential applications in many fields.

Energy transfer of Tb(tmhd)3 - Rhodamine B in poly(methyl methacrylate) fiber for new photonic applications

In our work we present the energy transfer phenomenon observed in poly(methyl methacrylate) co-doped by Tb(tmhd)3 and Rhodamine B. The optical properties characterization (recorded luminescence spectra and decay time measurements) indicate efficient energy transfer (up to 67%) between used complexes. Additionally, the developed matrix was used for luminescent polymeric fiber fabrication. The co-doped PMMA fiber allows significant luminescence spectrum modification by using energy transfer and optical radiation reabsorption phenomena. Presented lanthanide-organic dye co-doped poly(methyl methacrylate) fiber can be used for new photonic applications of polymeric optical fibers.

A facile method to prepare the white persistent luminescent fibers based on Sr2ZnSi2O7Eu2+, Dy3+ and fluorescence pigments

The polyacrylonitrile composite fibers with white persistent luminescence were prepared by adding different concentrations of Sr2ZnSi2O7: Eu2+, Dy3+ (SZO) and Rhodamine B fluorescent pigments (FP) into polyacrylonitrile spinning solution. Morphology, phase structure, color properties, photoluminescence properties and afterglow properties were examined. Photoluminescence test indicated that the emission spectrum of Sr2ZnSi2O7: Eu2+, Dy3+ phosphors overlapped with the excitation spectrum of fluorescent pigments in the range of 450–550 nm, which was the necessary condition for the energy transfer from the Sr2ZnSi2O7: Eu2+, Dy3+ to the Rhodamine B fluorescent pigments (FP). The phosphorescent color of the composite fibers showed that the white luminescent polyacrylonitrile fibers can be gained when weight ratios of SZO/FP ranged from 10:0.2 to 10:0.5. Decay curves suggested that the as weight ratio of SZO/FP was less than 10:0.75, the initial brightness of the composite fibers could not be significantly reduced.

Structure, thermal and luminescence properties of Eu/Tb(BA)3phen/PAN fibers fabricated by electrospinning

Novel high luminescence fibers often exhibit potential applications in the fields of color displays and sensor systems. In this study, Eu(BA)3phen and Tb(BA)3phen powders was successfully synthesized by solvothermal reactions, firstly. Then, three kinds of novel flexible Eu(BA)3phen/PAN, Tb(BA)3phen/PAN and Eu/Tb(BA)3phen/PAN (BA = benzoic acid, phen = phenanthroline, PAN = Polyacrylonitrile) fibers had been successfully prepared by electrospinning technology. The characterizations of the final products have been investigated in detail. It was found that the diameter of the as-prepared fibers were almost uniform with the fabricated complexes doping into PAN successfully. Thermogravimetric analysis indicates that the thermal stability of the pure PAN fiber could be improved by the incorporation of the complex, although only 1 wt % was added. Furthermore, in Eu/Tb(BA)3phen complex, the fluorescence intensity of Eu3+ ions was remarkably increased by adding Tb3+ ions. This is primarily due to an energy transfer from the 5D4 level of Tb (III) to the 5D0 level of Eu (III) ions, where Tb3+ acted as sensitizer. The corresponding luminescent fibers displayed the same regularity as the complexes. Moreover, with the increasing of the incorporation of complexes into PAN, the fluorescence intensities were significantly enhanced and reached its maximum value at 2.5 wt % for Eu(BA)3phen/PAN fibers and 2.0 wt% for Tb(BA)3phen/PAN fibers. The further intensity decreased with the increasing content of the complexes because of typical emission concentration quenching.

Preparation, characterization and luminescence properties of core-shell ternary terbium composites SiO2(600)@Tb(MABA-Si)•L.

Two novel core–shell structure ternary terbium composites SiO2(600)@Tb(MABA-Si)·L(L:dipy/phen) nanometre luminescence materials were prepared by ternary terbium complexes Tb(MABA-Si)·L2·(ClO4)3·2H2O shell grafted onto the surface of SiO2 microspheres. And corresponding ternary terbium complexes were synthesized using (CONH(CH2)3Si(OCH2CH3)3)2 (denoted as MABA-Si) as first ligand and L as second ligand coordinated with terbium perchlorate. The as-synthesized products were characterized by means of IR spectra, 1HNMR, element analysis, molar conductivity, SEM and TEM. It was found that the first ligand MABA-Si of terbium ternary complex hydrolysed to generate the Si–OH and the Si–OH condensate with the Si–OH on the surface of SiO2 microspheres; then ligand MABA-Si grafted onto the surface of SiO2 microspheres. The diameter of SiO2 core of SiO2(600)@Tb(MABA-Si)·L was approximately 600 nm. Interestingly, the luminescence properties demonstrate that the two core–shell structure ternary terbium composites SiO2(600)Tb(MABA-Si)·L(dipy/phen) exhibit strong emission intensities, which are 2.49 and 3.35 times higher than that of the corresponding complexes Tb(MABA-Si)·L2·(ClO4)3·2H2O, respectively. Luminescence decay curves show that core–shell structure ternary terbium composites have longer lifetime. Excellent luminescence properties enable the core–shell materials to have potential applications in medicine, industry, luminescent fibres and various biomaterials fields.

Working Conditions on the Afterglow Characteristics of Rare-earth Luminous Fibers

To test and clarify the stability of afterglow performance of luminescent fibers can accelerate the step of the commercialized application on luminescent textiles. This work investigated the possible effects of a number of working conditions on the afterglow characteristics of luminous fibers. The fibers in our studies did not show any significant change in their afterglow brightness and duration after storage for 12 months under conditions of constant temperature and humidity, after 5 hours of light exposure, or soaking in water for 4 hours. The insignificant decay appears to follow the same mechanism. Thermal perturbation seemed to cause some changes to the initial brightness and decay time with the best performance being observed at about 80°C. Moreover, contact with acid or base for 5 minutes only resulted in slight reduction of the afterglow brightness. Our studies thus indicate a high degree of stability of the afterglow performance of the luminous fibers used.

Red light emitting nano-PVP fibers that hybrid with Ag@SiO2@Eu(tta)3phen-NPs by electrostatic spinning method

This work demonstrated red light emitting nano-PVP fibers that incorporated with novel three-layer nanostructure of Ag@SiO2@Eu(tta)3phen nanoparticles (Ag@SiO2@Eu(tta)3phen-NPs), and the hybrid nano-PVP fibers were fabricated via a remarkably simple electrostatic spinning method. For Ag@SiO2@Eu(tta)3phen-NPs, the thickness of SiO2 is optimized to obtain the maximum luminescent intensity, as results, the optimized thickness of SiO2 is 20 nm. And the corresponding luminescent intensity (612 nm) of the Ag@SiO2@Eu(tta)3phen-NPs is enhanced up to 10 times compared with the pure Eu(tta)3phen complex, which indicates that with 20 nm SiO2 thickness, the localized surface plasmon resonance (LSPR) effect of Ag@SiO2 exhibits highest performance for enhancing luminescence. Moreover, the luminescent PVP fibers emit bright red light under the fluorescence microscope, which definitely confirms that the microenvironment provided by PVP polymer is absolutely suitable for the fluorescent composites.

Morphologies and Properties of PET Nano Porous Luminescence Fiber: Oil Absorption and Fluorescence-Indicating Functions.

A polyethylene terephthalate nano porous luminescence fiber (PNPLF) was prepared through electrospun technology. The SEM and TEM images show that the surfaces of the fibers are covered with pores. The diameter of the fiber is 250-500 nm, and the diameter of the pores is 20-180 nm. The water and oil contact angles of PNPLF are 135° and 27°, respectively. The oil absorption value of the as-prepared PNPLF achieves 135 g/g and has a good oil absorption function. The as-prepared PNPLF has good luminescence properties and fluorescent-indicating function. Even trace amounts of oil can also cause obvious change of fluorescence intensity of PNPLF which has a good stability from 20 °C to 70 °C. The breaking stress of yarn of PNPLF reaches 117cN. Furthermore, the good mechanical properties and thermal properties of PNPLF provide important basic conditions for their wide applications.

Water-Resistant Efficient Stretchable Perovskite-Embedded Fiber Membranes for Light-Emitting Diodes.

Cesium lead halide perovskite nanocrystals (NCs) with excellent intrinsic properties have been employed universally in optoelectronic applications but undergo hydrolysis even when exposed to atmospheric moisture. In the present study, composite CsPbX3 (X = Cl, Br, and I) perovskite NCs were encapsulated with stretchable (poly(styrene-butadiene-styrene); SBS) fibers by electrospinning to prepare water-resistant hybrid membranes as multicolor optical active layers. Brightly luminescent and color-tunable hydrophobic fiber membranes (FMs) with perovskite NCs were maintained for longer than 1 h in water. A unique remote FMs packaging approach was used in high-brightness perovskite light-emitting diodes (PeLEDs) for the first time.

Branched Aramid Nanofibers.

Interconnectivity of components in three-dimensional networks (3DNs) is essential for stress transfer in hydrogels, aerogels, and composites. Entanglement of nanoscale components in the network relies on weak short-range intermolecular interactions. The intrinsic stiffness and rod-like geometry of nanoscale components limit the cohesive energy of the physical crosslinks in 3DN materials. Nature realizes networked gels differently using components with extensive branching. Branched aramid nanofibers (BANFs) mimicking polymeric components of biological gels were synthesized to produce 3DNs with high efficiency stress transfer. Individual BANFs are flexible, with the number of branches controlled by base strength in the hydrolysis process. The extensive connectivity of the BANFs allows them to form hydro- and aerogel monoliths with an order of magnitude less solid content than rod-like nanocomponents. Branching of nanofibers also leads to improved mechanics of gels and nanocomposites.

Melt spinning fibers of Isotactic polypropylene doped with long-lifetime luminescent inorganic-organic SiO2-Eu3+ hybrid nanoparticles

Novel Stöber derived silica nanoparticles doped with europium complexes [Eu(tta)3phen]by two-step alkaline hydrolysis method have been fabricated in order to design stable luminescent hybrid nanoparticles with fine particle size. Isotactic polypropylene (iPP) was doped with long-lifetime (τ=859.2µs) luminescent nanoparticles via twin screw extrusion. The composition, structure and luminescence properties of the resulting hybrid nanoparticles were investigated in detail. STEM revealed that europium complexes were encapsulated homogenously and stably in nano silica. The luminescence measurements combined with bright red color photographs confirm the red light emission due to trivalent europium ions, while the intensity increases with the increase of corresponding doped concentrations of SiO2-Eu3+ nanoparticles in iPP hybrid materials. The melt processable luminescent optical fibers reported here is a novel application of rare earth complexes that can be used to develop new photonic and electronic materials.

Effects of photodynamic therapy for dental caries prevention on trace elements in tooth enamel

Objective To study the application of photodynamic therapy (PDT) for dental caries prevention using whole body luminescence fiber, and to investigate the effects of PDT on the content of Ca and P in rat molar enamel. Method The rat dental caries model was established by inoculating with S.mutans. Eighty male rats were randomly divided into five groups, including three experimental groups: 17 mW (8 mW/cm2) PDT (group A), 34 mW (15 mW/cm2) PDT (group B), 68 mW (30 mW/cm2) PDT (group C), a positive control group: 20 g/L NaF solution (group D), and a negative control group: 0.9% physiological saline (group E). The experimental groups were treated by 40 μg/mL hematoporphyrin monomethyl ether (HMME) and 650 nm diode laser irradiation. The experiments were conducted for 4 weeks. The contents of Ca and P in the molars of each group were measured by inductively coupled plasma emission spectrometry. Results The contents of Ca and P in group B, C and D after PDT were significantly higher than those in group A and E (all P<0.05). The contents of Ca and P in group A showed no significant difference before and after PDT, while those in groups B and C showed significant increase after PDT (all P<0.05). The increment of Ca in group A after PDT was lower than that in group D (P<0.05), while those in group B and C were significantly higher than those in group D (all P<0.05). There was no significant difference in the increment of Ca and P between group B and C after PDT. Conclusions In the range of the experimental parameters, the PDT promoted effect of tooth remineralization is better than 20 g/L NaF. The levels of Ca and P in the tooth enamel can be promoted by PDT treatment, and the contents of Ca and P are related to the pewer of PDT. The effect of low power PDT on the remineralization of enamel is not obvious. The contents of Ca and P in the tooth enamel are increased with laser power of PDT. When the laser power increased to a certain value, the change in contents of the two elements is not obvious. PDT can maintain the tooth remineralization microenvironment. Key words: Photodynamic therapy; Trace elements; Inductively coupled plasma optical emission spectrometer; Remineralization

UV radiation dosimeter with double spectral conversion

The possibility of double spectral conversion of UV radiation from the spectral range of 240–280 nm to the visible spectral region using luminescent glasses and fibers with antimony ions and molecular silver clusters is shown. Planar and fiber prototypes of UV radiation dosimeters are tested. It is shown that the sensitivities of dosimeter of the first and second types are 1400 and 360 mV/W/m2, respectively.

Luminescent properties of Tb3+-doped poly(methyl methacrylate) fiber

Lanthanide-doped polymers are very attractive, since they can be used for luminescent optical fiber fabrications. This Letter presents the terbium-ions-doped poly(methyl methacrylate) fiber fabrication and spectroscopic characterization. The measured excited state (D45) lifetime of 0.741 ms confirms that a used organometallic can be used to obtain an intense luminescence in a polymeric fiber. The luminescence spectrum shape modification versus the fiber length is also investigated.

Fabrication of circular polarized luminescent helical fibers from chiral phenanthro[9,10]imidazole derivatives

Violet fluorescent helical nanofibers with circular polarized luminescence fabricated by the self-assembly of chiral phenanthro[9,10-d]imidazole (PIM) derivatives.

Click Synthesis, Aggregation-Induced Emission and Chirality, Circularly Polarized Luminescence, and Helical Self-Assembly of a Leucine-Containing Silole.

By introducing chiral leucine pendants to silole scaffold, leucine-containing silole (Silole-Leu) is synthesized and it is endowed with not only aggregation-induced emission and circular dichroism, but excellent chiral polarized luminescence as well. Silole-Leu also has the capacity to self-assemble into nano/micro helical luminescent fibers and the dimension of the fibers can be tuned by adjusting the ratio and volume of mixed solvents for evaporation as revealed by atomic force microscope, scanning electron microscope, and fluorescence microscope. The characteristic helicity of microfibers is directly visualized for the first time by using fluorescence microscope.