Enhanced Photoluminescence Properties Research Articles

Enhanced photoluminescence properties and stability of CsPbBr3 quantum dots borosilicate glasses modified by ZnO

Halide perovskite quantum dots (QDs) glass has attracted much attention in the field of optoelectronics, but its photoluminescence (PL) properties and water stability still need further improvement. In this work, the melt-quenching method is used to successfully precipitate CsPbBr3 QDs in borosilicate glass. By increasing the concentration of ZnO, the photoluminescence quantum yield (PLQY) of CsPbBr3 QDs glass is enhanced up to 30 times from 1.91 % to 65.87 %. The results demonstrate that the introduction of ZnO loosens the glass network structure, which contributes to the QDs to precipitate. In addition, it can be found that the PL intensity maintains 91.68 % of the initial PL intensity after 30 days of immersion, which is attributed to ZnO delays the corrosion of borosilicate glass by water. The effect of ZnO-modified borosilicate glass structure on PL and stability provides a certain reference value for further research on QDs glass, and the good PLQY and water stability make ZnO-modified CsPbBr3 QDs glass a potential material in the field of WLEDs.

The Enhanced Photoluminescence Properties of Carbon Dots Derived from Glucose: The Effect of Natural Oxidation.

The investigation of the fluorescence mechanism of carbon dots (CDs) has attracted significant attention, particularly the role of the oxygen-containing groups. Dual-CDs exhibiting blue and green emissions are synthesized from glucose via a simple ultrasonic treatment, and the oxidation degree of the CDs is softly modified through a slow natural oxidation approach, which is in stark contrast to that aggressively altering CDs' surface configurations through chemical oxidation methods. It is interesting to find that the intensity of the blue fluorescence gradually increases, eventually becoming the dominant emission after prolonging the oxidation periods, with the quantum yield (QY) of the CDs being enhanced from ~0.61% to ~4.26%. Combining the microstructure characterizations, optical measurements, and ultrafiltration experiments, we hypothesize that the blue emission could be ascribed to the surface states induced by the C-O and C=O groups, while the green luminescence may originate from the deep energy levels associated with the O-C=O groups. The distinct emission states and energy distributions could result in the blue and the green luminescence exhibiting distinct excitation and emission behaviors. Our findings could provide new insights into the fluorescence mechanism of CDs.

Microwave-Assisted Grafting of Coal onto Nitrogen-Doped Carbon Dots with a High Quantum Yield and Enhanced Photoluminescence Properties.

The fluorescent nitrogen-doped carbon dots (N-CDs) were synthesized via a facile one-pot solvothermal process using coal (Jin 15 Anthracite and Shaerhu lignite) as raw materials and dimethyl formamide (DMF) as the solvent, employing a microwave pyrolysis method. This approach demonstrates remarkable efficacy in the development of nitrogen-doped carbon dots (N-CDs) with a high quantum yield (QY). The N-CDs prepared have strong photoluminescence properties. Moreover, the obtained N-CDs emit blue PL and are easily dispersed in polymethyl methacrylate (PMMA), preserving the inherent advantages of N-CDs and the PMMA matrix. The JN-CDs exhibit a high quantum yield (QY) of 49.5% and a production yield of 25.7%, respectively. In contrast, the SN-CDs demonstrate a quantum yield of 40% and a production yield of 35.1%. It is worth noting that the production yield and quantum yield of coal-based carbon dots are inversely related indices. The lower metamorphic degree of subbituminous coal favors an enhanced product yield, while the higher metamorphic degree of anthracite promotes an improved quantum yield in the product, which may be attributed to the presence of amorphous carbon within it. Consequently, we propose and discuss potential mechanisms underlying N-CD formation.

Tuning photoluminescence properties of Au clusters by surface modification and doping: lessons from case studies of icosahedral Au13

This review article focuses on the ubiquitous icosahedral Au13 core protected by organic ligands as a benchmark and derives empirical rules for tuning and enhancing photoluminescence properties through surface modification and heterometal doping.

SNAr as a facile method to prepare polystyrene-grafted conjugated copolymers with enhanced photoluminescence properties

SNAr allows the preparation of graft copolymers in one additional step after polymerisation only, and moreover grafting with polystyrene enhances the emissive properties of the resulting graft copolymers in the solid state.

Enhancement of photoluminescence properties in Na+ doped K2BaPO4F:Sm3+ phosphors

In this paper, Sm3+-activated K2BaPO4F red phosphors were prepared by a traditional solid-state reaction method. The crystal structure and emission enhancement mechanism of the materials were systematically investigated. The photoluminescence intensity, chromaticity, lifetime, and fluorescence thermal stability were evaluated in detail. The emission intensity and quantum efficiency were significantly improved by the introduction of Na + ions. The lattice parameters of the K2BaPO4F, K2Ba0.975PO4F:0.025Sm3+, and Na-doped K2Ba0.975PO4F:0.025Sm3+ phosphors were investigated through the Rietveld refinement method. With the occupation of K+ sites by Na+ ions, the reduced volume of the unit cell increased the quantum efficiency of Sm3+ ions about 2.5 times. The present work demonstrates that the modified K2-2xNa2xBa0.975PO4F:0.025Sm3+ orange-red phosphors are expected to be used in white light-emitting diodes (w-LEDs).

Al3+ doping enhanced photoluminescence properties of Ca2InNbO6: Mn4+ far-red phosphor for plant cultivation

The study focuses on the synthesis of far-red phosphors Ca2InNbO6: xMn4+ (0 ≤ x ≤ 0.006) and Ca2InNbO6: 0.003Mn4+, yAl3+ (0 ≤ y ≤ 0.024). First-principles calculations confirmed that the indirect bandgap of Ca2InNbO6 used to be 3.522 eV. Photoluminescence spectroscopy was used to examine the luminescence characteristics and energy transfer mechanism of CINO: xMn4+ and CINO: 0.003Mn4+, yAl3+ phosphors. When Mn4+ ions undergo the 2Eg → 4A2g transition under 380 nm excitation, brilliant red light with a central wavelength of 688 nm is released. In addition, the emission intensity reaches 2.6 times that of CINO: 0.003Mn4+, when Al3+ has a 1.2% optimal doping concentration. At the same time, the thermal stability of the material is improved. The reasons for the enhanced fluorescence and thermal stability were analysed by lattice distortion and blocking of energy transfer. Additionally, the prepared red LED lamps, which shown a bright red light even after long periods of operation at high temperatures, were used for the cultivation of plant seeds, and the germination rate as well as the stems and leaves thriving growth were significantly better than the cultivation without the red LED, suggesting that Al3+ doping Ca2InNbO6: Mn4+ has potential applications in the field of plant cultivation and growth LEDs, and is a guide for ion-doped modified phosphors.

Enhancement of photoluminescence properties in Er3+-doped Gd3ScxGa5−xO12 garnet nanocrystals by Sc3+ co-doping

In this work, a series of novel garnet nanocrystals Gd3ScxGa5−xO12 (x = 0–2) doped with fixed Er3+ content were synthesized by a sol-gel combustion method. The structure, morphology, chemical composition, optical reflectance, and photoluminescence properties of the nanocrystals were investigated in detail. Following 980 nm laser excitation, steady-state and time-dependent Stokes Er3+: 4I13/2 → 4I15/2 emission spectra are investigated together with steady-state upconversion photoluminescence (UCPL) emission spectra. Although the activator content at the dodecahedral site is fixed, incorporation of Sc3+ into the octahedral site of the garnet host enhances the photoluminescence properties. The Stokes photoluminescence intensity keeps increasing with increasing Sc3+ content in the studied region. However, the intensity of UCPL is significantly increased in the Er3+-doped Gd3Sc2Ga3O12 sample. It is found that the substitution of Ga3+ by Sc3+ at the octahedral site of the studied garnet nanocrystals leads to a reduction of the maximum phonon energy and may affect the crystal field surrounding Er3+.

Design, Enhanced Photoluminescence Properties of Ti Incorporated Zr-Networked 4-[Formyl (Hydroxymethylidene)-4-Sulfanyl] Benzoic Acid Metal Organic Frameworks

Present study reports the enhanced photoluminescence properties of Ti incorporated Zr networked 4-{formyl (Hydroxymethylidine)-4-Sulfanyl] Benzoic Acid. The as-synthesized metal organic framework (MOF) was synthesized by solvothermal process and was analyzed by SEM (scanning electron microscopy), XRD (X-ray diffraction spectroscopy) and photoluminescence spectroscopy. The as-synthesized MOFs are well crystalline with average particle size of 35 to 56 nm. From XRD data X-ray diffraction patterns which illustrated the well maintained topological structure during the cation exchange process. From scanning electron microscopy study it shows irregular shape of MOFs.

Electro-optical study of thermally stable PANI/lithium doped nickel oxide composites with enhanced photoluminescence properties

PANI/Lithium doped nickel oxide nanocomposites were synthesized via in-situ chemical oxidation polymerization method. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) used to study the strucurtal confirmation of synthesized composites. FESEM images showed the fabrication of nanocomposites in porous and nanofibers form. EDS is confirming the presence of constituent elements. Thermogravimetric analysis (TGA) of fabricated materials had the excellent thermal stability extended to higher temperature after doping in host matrix. Impedance analyzer has used to examine the electrical behaviors of synthesized composites. AC conductivity of synthesized composites were enhanced as compare to pure pani. Diffuse Reflectance Spectroscopy has used to study the optical characteristics of samples. Vibrating Samples Magnetometry results of composites depicts their superparamagnetic nature. In PL investigation, photoluminescence properties of affordable electro-optical fabricated materials were found to be improved at room temperature.

Moldable Carbon Dot-Linked Elastomers for Three-Dimensional Arbitrary Fluorescent Structures

The integration of photoluminescent nanomaterials with a polymer matrix provides profitable chemical functionalities for the modern three-dimensional (3D) structure creation. Aiming at homogeneous nanomaterial generations inside moldable polymers, we report a direct carbon dot (CD) synthesis in a polydimethylsiloxane elastomer base. This approach is solvent-free without the need of dehydrating and condensation processes, enabling delicate solid 3D microstructure construction with minimal CD photoluminescence influence. The solubility of precursor species in an elastomer gel base plays the key role in generating photoluminescent nanomaterials inside a polymer matrix. This CD-linked elastomer prepared from (3-aminopropyl)trimethoxysilane (APTMS), therefore, exhibits higher fluorescence emission than that generated from the aminopropane precursor. Compared to propyltrimethoxysilane, the amino group-containing APTMS precursor provides nitrogen doping in produced CDs, accompanying an enhanced photoluminescence property. These moldable CD-linked elastomers entail a quantum yield of 7.2% and can be applied to create various structures and patterns on diverse substrates. Taking the anti-counterfeiting application as an example, the material offers the hybrid encoded information of chemical photoluminescence and physical structures to enhance the encryption level. This in situ CD generation in the polymer base approach enables arbitrary 3D structure creation with minimized fluorescence self-quenching effects.

Sterically Stabilized Carbon Dots as Solid-State Phosphors for White-Light-Emitting Diodes

Solid-state photoluminescence (PL) is highly important for practical optoelectronic applications. However, conventional carbon dots often suffer from fluorescence quenching induced by aggregation in a solid state, limiting their potential applications. In this report, sterically stabilized polymeric carbon dots (PCDs) (<2 nm) are prepared to achieve effective PL emission even in the solid-sate composite using a simple one-step hydrothermal treatment. These PCDs show unique fluorescence properties of tunable PL color change with the concentration covering the visible spectrum range from blue to orange in aqueous solution and the wavelength-dependent broad PL with maximum excitation at around 480 nm in solid-state epoxy composite. Practically applicable “single phosphor on a chip” in white-light-emitting diodes (WLEDs) application is successfully demonstrated by combining our PCDs/epoxy composite with a 460 nm blue-based LED chip, which is longer than most studies on the performance of CD-related white LEDs using UV or deep-blue LED chips as the excitation source. These results suggest that this type of PCDs may not only effectively suppress the aggregation-caused quenching effect in solid matrices but also show enhanced PL properties as a solid-state phosphor for practical white light emission applications.

Samarium-decorated ZrO2@SnO2 nanostructures, their electrical, optical and enhanced photoluminescence properties

Samarium-decorated ZrO2@SnO2 nanostructures, their electrical, optical and enhanced photoluminescence properties

Effect of ionic couple substitution on the enhanced photoluminescence properties of (BaMg)1-x(KxAl10+x)O17:Eu2+ phosphor for white LEDs application

Compared with traditional incandescent and fluorescent lamps, phosphor-converted white light-emitting diodes (LEDs) have revolutionized the lighting industry. To improve the performance of white LEDs, phosphors having excellent luminescence properties are required. BaMgAl10O17 (BAM) doped with Eu2+ is a candidate phosphor with blue emission for white LEDs. However, it has the disadvantages of low thermal stability and chromaticity coordinate deviation. Here, based on ionic couple substitution strategy, the co-substitution of Ba2+-Mg2+ in BAM: Eu2+ by K+-Al3+ until fully converted to KAl11O17:Eu2+ (KAO:Eu2+) was successfully achieved. The co-substitution leads to an improvement of luminescence thermal stability as a result of the interaction between Eu2+ ion and crystal defects. Moreover, the synthesis temperature (∼1350 °C) of KAO:Eu2+ is lower than that of BAM:Eu2+ (>1600 °C) and it exhibits better color purity than that of BAM:Eu2+ and small chromaticity coordinate deviation. A white LED device, fabricated using the KAO:Eu2+ phosphor as a blue component, exhibits better performance, and, accordingly, KAO:Eu2+ is a good blue-emitting candidate for phosphor-converted white LEDs. This study provides a practical guideline for improving the luminescence properties in the known system and developing materials with unique optical features.

A Highly Fluorescent Dinuclear Aluminium Complex with Near-Unity Quantum Yield.

The high natural abundance of aluminium makes the respective fluorophores attractive for various optical applications, but photoluminescence quantum yields above 0.7 have yet not been reported for solutions of aluminium complexes. In this contribution, a dinuclear aluminium(III) complex featuring enhanced photoluminescence properties is described. Its facile one‐pot synthesis originates from a readily available precursor and trimethyl aluminium. In solution, the complex exhibits an unprecedented photoluminescence quantum yield near unity (Φabsolute 1.0±0.1) and an excited‐state lifetime of 2.3 ns. In the solid state, J‐aggregation and aggregation‐caused quenching are noted, but still quantum yields of 0.6 are observed. Embedding the complex in electrospun non‐woven fabrics yields a highly fluorescent fleece possessing a quantum yield of 0.9±0.04.

Double Layer Growth of ZnO Nanorods by a Low Temperature Solution Method: Synthesis and Photoluminescence Properties

In the present work, double layer Zinc Oxide (ZnO) nanorods (NRs) were fabricated hydrothermally and their photoluminescence (PL) properties were investigated. Two different recipes and their combination were used to obtain double layer vertically well-aligned ZnO NRs. These recipes include polyethylenimine (PEI) and citrate as additives in the growth solution resulting long NRs with a broad defect emission and relatively short NRs with a near band-edge ultraviolet (UV) emission, respectively. Double layer growth of long-long (LL), long-short (LS) and short-short (SS) ZnO NRs were considered. Grown samples were annealed in a forming gas atmosphere for a better quality NR structure. LL ZnO NRs (long ZnO NRs grown on a long ZnO NR layer) with a 65 µm thickness showed a broad yellow-orange PL emission and no any near band-edge UV emission was observed. LS ZnO NRs representing short ZnO NRs grown on a long ZnO NR layer (LS1= 36 µm, LS2= 48 µm and LS3= 44 µm) showed an enhanced near band-edge UV emission when compared to that of the long ZnO NRs. The UV intensity was found to decrease with the increase in thickness of the NRs in LS samples. Finally, SS ZnO NR sample, (short ZnO NRs grown on a short ZnO NR layer) which has a thickness of 33 µm, displayed a stronger near band-edge UV emission with a negligible broad emission than that of as-grown SS ZnO NRs (UV peak intensity ratio 59). This study should be important for applications where longer NRs with enhanced PL properties are strictly required.

Optimising the Eu2O3 concentration and tuning the photoluminescence attributes of Eu2O3 doped borate glasses by Co–doping with silver nanoparticles

Efficacy of silver nanoparticles on photoluminescence properties on optimized Eu2O3 doped borate glasses has been studied and discussed in detail. The presence of homogeneously distributed and spherically shaped Ag nanoparticles was confirmed by electron microscopic images. With increase of AgNO3 concentration the photoluminescence intensity of Eu3+ transitions improved up to 0.6 mol% and subsequently quenched at 0.8 mol% of AgNO3. The enhancement in photoluminescence properties observed as the AgNO3 concentration raised to higher level was ascribed to local field effect and transmit of energy from Ag nanoparticles to the tri–positive europium ions. While the reduction in photoluminescence properties at higher doping level of AgNO3 was attributed to reverse transmit of energy from tri–valent europium ions to Ag nanoparticles. Other mechanisms liable for the attenuation in photoluminescence properties are also highlighted. The energy transfer from Eu3+ ions to Ag0 nanoparticles was responsible for the reduction in radiative lifetime magnitudes. The studies suggest the glass sample containing 0.6 mol% of AgNO3 (i.e. SNBEuAg0.6) beneficial for optoelectronic and photonic applications.

Synthesis and enhanced photoluminescence properties of red emitting divalent ion (Ca2+) doped Eu:Y2O3 nanophosphors for optoelectronic applications

This work presents the synthesis of Y2O3:Eu3+,xCa2+ (x = 0 mol%, 1 mol%, 3 mol%, 5 mol%, 7 mol%, 9 mol%, 11 mol%) nanophosphors with enhanced photoluminescence properties through a facile solution combustion method for optoelectronic, display, and lighting applications. The X-ray diffraction (XRD) patterns of the proposed nanophosphor reveal its structural properties and crystalline nature. The transmission electron microscope (TEM) results confirm the change in the shape of the particle and aggregation of particles after co-doping with Ca2+. Fourier transform infrared spectroscopy (FTIR) and Raman vibrations also confirm the presence of Y–O vibration and subsequently explain the crystalline nature, structural properties, and purity of the samples. All the synthesized nanophosphors samples emit intense red emission at 613 nm (5D0→7F2) under excitation with 235, 394 and 466 nm wavelengths of Eu3+ ions. The photoluminescence (PL) emission spectra excited with 235 nm illustrate the highest emission peak with two other emission peaks excited with 466 and 394 nm that is 1.4 times higher than 466 nm and 1.9 times enhanced by 394 nm wavelength, respectively. The emission intensity of Y2O3:Eu3+,xCa2+ (5 mol%) is increased 8-fold as compared to Eu:Y2O3. Doping with Ca2+ ions enhances the emission intensity of Eu:Y2O3 nanophosphors due to an increase in energy transfer in Ca2+→Eu3+ through asymmetry in the crystal field and by introduction of radiative defect centers through oxygen vacancies in the yttria matrix. It is also observed that the optical band gap and the lifetime of the 5D0 level of Eu3+ ions in Y2O3:Eu3+,xCa2+ nanophosphor sample gets changed with a doping concentration of Ca2+ ions. Nanophosphor also reveals high thermal stability and quantum yield as estimating activation energy of 0.25 eV and 81%, respectively. CIE, CCT, and color purity values (>98%) show an improved red-emitting nanophosphor in the warm region of light, which makes this material superior with a specific potential application for UV-based white LEDs with security ink, display devices, and various other optoelectronics devices.

Facile synthesis of BaMoO4 and BaMoO4/BaWO4 heterostructures with type -I band arrangement and enhanced photoluminescence properties

A series of BaMoO4 and BaMoO4/BaWO4 phosphors were successfully prepared via a polyacrylamide gel method and low temperature calcination technology. The effects of sintering temperature and mass percentage of BaMoO4/BaWO4 on the phase purity, functional group, surface morphology, charge state, photoluminescence properties and photocatalytic activity of the prepared products were studied in detail. The results indicate that the BaMoO4 phosphor is a scheelite tetragonal structure with high crystallinity. The photoluminescence spectra indicates that the phosphors have a strong blue emission peak at 440 nm with excitation wavelength of 282 nm for the BaMoO4 phosphor, and three emission peaks at 400, 440 and 460 nm with excitation wavelength of 284 nm for the BaMoO4/BaWO4 phosphors. These photoluminescence behaviors can be ascribed to the 1T2→1A1 transition, Jahn–Teller distorted tetrahedral symmetry of [MoO4]2- and surface defect. Photocatalytic experiments further confirmed that the BaMoO4/BaWO4 phosphors exhibit a high recombination rate of electron hole pairs. The result further indicates that the type-I band arrangement structure of BaMoO4/BaWO4 phosphors is beneficial to enhance the photoluminescent properties of single-phase phosphors. This study provides a novel route for preparing the type-I band arrangement structure composite phosphors with high photoluminescent properties and potential applications in light emitting devices, optoelectronic devices, laser devices and white pigments.

Enhanced photoluminescence properties of arsenic-treated diatom frustules of Cosmioneis reimeri

Enhanced photoluminescence properties of arsenic-treated diatom frustules of Cosmioneis reimeri