Tunable Photoluminescence Properties Research Articles

Optically and electrically tunable graphene quantum dot–polyaniline composite films

The tunable photoluminescence and transport properties of PANI–GQD composite can be realized by adjusting the sizes of the GQDs and the amounts of PANI.

Revealing the tunable photoluminescence properties of graphene quantum dots

Photoluminescence of graphene quantum-dot can be sensitively tuned by size, edge configurations, shape, chemical functionalities, defects, heteroatom-doping and hybridization states.

Controlled synthesis and tunable photoluminescence properties of LaOBr:Eu3+ nanostructures

Eu3+ doped lanthanum oxybromide (LaOBr) nanostructures including nanofibers, nanoribbons, and hollow nanofibers were fabricated for the first time via calcining the electrospun PVP/[La(NO3)3+Eu(NO3)3+NH4Br] composites. X-ray diffraction analysis results showed that LaOBr:Eu3+ nanostructures were tetragonal in structure with space group of P4/nmm. The morphologies and sizes of the LaOBr:Eu3+ nanostructures were studied by scanning electron microscope and transmission electron microscope. The mean diameter of the nanofibers and hollow nanofibers, and the width of nanoribbons are 118.02 ± 14.21, 115.84 ± 13.37 nm, and 1.56 ± 0.25 μm, respectively. Under the excitation of 289 nm ultraviolet light, LaOBr:Eu3+ nanostructures exhibit the red emissions of predominant peak at 618 nm, which is ascribed to the 5D0 → 7F2 transition of the Eu3+ ions. It is found that the optimum doping concentration of the Eu3+ ions in the LaOBr:Eu3+ nanofibers is 5 %. Interestingly, we found that the luminescence intensity of nanofibers is obviously greater than that of the hollow nanofibers and nanoribbons for LaOBr:Eu3+ under the same measuring conditions. Moreover, the color emissions of LaOBr:Eu3+ nanostructures can be tuned by adjusting the concentration of Eu3+ and the morphologies of nanomaterials. The obtained LaOBr:Eu3+ nanostructures may be promising nanomaterials for applications in the fields of light display systems and optoelectronic devices.

Synthesis and characterization of a novel 3D porous luminescent Ag(I) framework with a multidentate triazole ligand

By using a multidentate N-(4-(4H-1,2,4-triazol-4-yl)phenyl)formamide (L) ligand and AgClO4, a novel three-dimensional(3D) porous luminescent silver(I) complex {[Ag2(μ3-L)2]·(ClO4)2}n (1) has been isolated and characterized by single crystal diffraction analysis. The result reveals that 1 contains two kinds of distinct 1D channels with different sizes and shapes, in which free perchlorate anions are located in these 1D channels. Anion exchange experiment of 1 with NaNO3 was monitored by FT-IR, PXRD, elemental analysis and photoluminescence characterization, indicating that the porous framework of 1 can remain intact throughout the anion exchange process. 1 has green luminescence emission and can behave anion-responsive tunable photoluminescence properties. The result also reveals that the multidentate L ligand can be used for the preparation of novel functional coordination materials.

Tunable photoluminescence properties of well-aligned ZnO nanorod array by oxygen plasma post-treatment

Well-aligned ZnO nanorod arrays were prepared on Si substrates modified with ZnO seeds using a low temperature hydrothermal method. In particular, photoluminescence (PL) properties of the ZnO nanorods can be easily tuned by varying the treatment duration of O2 plasma. Penetration depth of oxygen ions near the surface is suggested to influence the effect of O2 plasma on modification of PL properties for ZnO nanorods with different sizes. O2 plasma-tuned optical quality for ZnO nanorods has been attributed to the change of depletion region width.

Mesoporous silica encapsulation of silicon nanocrystals: Synthesis, aqueous dispersibility and drug release

Silicon nanocrystals (Si-NCs) are of significant research interest because of their tunable photoluminescent properties and biological compatibility. We have encapsulated Si-NCs within a high surface area mesoporous silica shell while maintaining the NC near-IR photoluminescence. This material is a potential platform for combined biological imaging and drug delivery. Encapsulation of a single crystalline Si-NC within each nanosphere is shown using energy-filtered transmission electron microscopy. Proof-of-concept drug delivery studies show ibuprofen release from the nanospheres.

Synthesis and luminescence mechanism of multicolor-emitting g-C3N4 nanopowders by low temperature thermal condensation of melamine

Graphite like C3N4 (g-C3N4) was synthesized facilely via the low temperature thermal condensation of melamine between 300–650°C. The results showed that the products maintained as melamine when the temperature is below 300°C. With the increase of temperature, the products were transformed into carbon nitride and amorphous g-C3N4 successively. The morphology of products was changed from spherical nanoparticles of melamine into layer carbon nitride and g-C3N4 with the increase of temperature. The photoluminescence spectra showed that the carbon nitride products have continuous tunable photoluminescence properties in the visible region with increasing temperature. With the help of steady state, transient state time-resolved photoluminescence spectra and Raman microstructural characterization, a novel tunable photoluminescence mechanism was founded systematically, which is mainly related to the two dimensional π-conjugated polymeric network and the lone pair of the carbon nitride.

Nanostructures of Sr2+ doped BiFeO3 multifunctional ceramics with tunable photoluminescence and magnetic properties

Careful tuning of formation (calcination) temperature of Sr2+ doped BiFeO3 multiferroic ceramics results in tailorable particle morphologies ranging from spherical to pillar-like. Based on the minimization of Gibb’s free energy approach, the dominant homogeneous mechanism for particle growth is suggested. The chemical substitution of a trivalent ion (Bi3+) by a divalent ion (Sr2+) causes the transformation of certain fraction of Fe3+ to Fe4+ and/or the appearance of oxygen vacancies. This has been respectively proved by the analysis of XPS and refinement of neutron diffraction data. Although significant modification in the particle morphology is observed, the crystal unit cell remains rhombohedral with a R3c space group but interesting variations in physical properties are achieved. O-vacancies induced strong and sharp photoluminescence activity in the IR region, similar to ZnO, is reported for the first time. This observation opens up a new application for multiferroic ceramics. SQUID M–H data confirms the straightening of the canted spin structure of BiFeO3, which in turn results in magnetism similar to ferromagnetic materials. Findings of the magneto-dielectric effect are also discussed to claim the multiferroic nature of the sample.

Bottom-up fabrication of photoluminescent carbon dots with uniform morphology via a soft–hard template approach

A novel soft-hard template approach for preparing photoluminescent carbon dots (CDs) with tunable sizes, compositions, crystalline degrees and photoluminescence properties has been developed using four different precursors as carbon sources. The results offer a new strategy for fabrication of monodispersed CDs with well-defined morphology.

A Non-Centrosymmetric Dual-Emissive Metal–Organic Framework with Distinct Nonlinear Optical and Tunable Photoluminescence Properties

A novel dual-emissive metal–organic framework [Pb3(BPT)2(phen)2]·phen (1) has been obtained by hydrothermal reactions of biphenyl-3,4′,5-tricarboxylic acid (H3BPT), phen, and lead nitrate in aqueous solution. It consists of a main right-handed helix and three left-handed helical chains with the three left-handed helical chains sharing the same helical axis and further enwinding the main right-handed helical chain alternately. The BPT3– ligands join the 1D helical chains into 2D layers with the terminal phen liands extending upward and downward, which are further interdigitated into a 3D packing supramolecular architecture through π–π interactions between the phen molecules of neighbor layers. The second harmonic generation (SHG) measurement reveals that 1 is nonlinear optical active with SHG efficiency approximately equivalent to that of the standard potassium dihydrogen phosphate (KDP), and photoluminescent investigation displays that complex 1 exhibits distinct tunable yellow-to-violet photoluminescence...

K3[TbxEu1–xGe3O8(OH)2] (x = 1, 0.88, 0.67, 0): 2D-Layered Lanthanide Germanates with Tunable Photoluminescent Properties

A family of novel 2D-layered lanthanide germanates K(3)[Tb(x)Eu(1-x)Ge(3)O(8)(OH)(2)] (x = 1, 0.88, 0.67, 0; denoted as TbGeO-JU-87, Tb(0.88)Eu(0.12)GeO-JU-87, Tb(0.67)Eu(0.33)GeO-JU-87, and EuGeO-JU-87) were synthesized under mild hydrothermal conditions in a concentrated gel system. They are isostructural, as confirmed by the powder X-ray diffraction analysis. The single-crystal X-ray diffraction analysis of EuGeO-JU-87 reveals that it is a 2D-layered [EuGe(3)O(8)(OH)(2)](n)(3n-) anionic framework, which is built up from GeO(4)H/GeO(4) tetrahedra and EuO(6) octahedra by sharing vertex O atoms. Charge neutrality is achieved by K(+) ions located in the free void space. Interestingly, photoluminescence studies show that Tb(0.88)Eu(0.12)GeO-JU-87 and Tb(0.67)Eu(0.33)GeO-JU-87 exhibit a high Tb(3+)-to-Eu(3+) energy-transfer efficiency and the Tb(x)Eu(1-x)GeO-JU-87 system displays tunable photoluminescent properties.

Tunable photoluminescence properties of Eu(II)- and Sm(III)-coactivated Ca_9Y(PO_4)_7 and energy transfer between Eu(II) and Sm(III)

A single-phased tunable color conversion phosphor for WLED was prepared by coactivating Ca9Y(PO4)7 with Eu2+ and Sm3+ ions. The structure, UV-visible and photoluminescence spectra of the phosphor were studied as a function of annealing atmosphere and concentration ratio of Eu2+/Sm3+. The coexistence of Eu2+ and Sm3+ was achieved by annealing the phosphor in a reducing atmosphere. The as-obtained phosphors showed a blended emission of blue-green and orange-red light upon near-UV excitation. White light emission was realized by adjusting the concentration ratio. Energy transfer and dominant interaction between Eu2+ and Sm3+ was also studied.

Polymer-Chain-Induced Tunable Luminescence Properties: Amphiphilic Poly(2-oxazoline)s Possessing a N,N-Dialkylpyrene-1-carboxamide Chromophore in the Side Chain

We report a polymer-chain-induced tunable luminescence system based on a newly synthesized fluorescent polymer, N,N-dialkylpyrene-1-carboxamide-modified poly(2-methyl-2-oxazoline) (POZO-py) at various ratios of pyrene induction. Photoluminescence and thermal properties of the POZO-py were analyzed in detail. Differential scanning calorimetry (DSC) measurements revealed that the glass-transition temperature (Tg) of POZO-py was above room temperature, which implies that POZO-py is in the glassy state at room temperature. POZO-py-(0.73) (i.e., pyrene content of 0.73%, Mn = 2270, Tg = 40 °C), having the lowest pyrene induction ratio, showed higher fluorescence quantum yields in several solvents, e.g., water, or in the thin film state than did N,N-diethylpyrene-1-carboxamide (a model compound, PA), because the polymer chain prevented the molecular mobilities of the pyrene moieties. In particular, POZO-py showed strong emission (Φfl = 0.52) in glycerin, which is a highly viscous solvent. Highly modified POZO-py-(2.9) (i.e., with a pyrene content of 2.9%, Mn = 2450, Tg = 48 °C) and POZO-py-(9.1) (Mn = 2640, Tg = 57 °C) exhibited both monomer and excimer emissions. These excimers consisted of a static excimer and a dynamic excimer. These results were not obtained for the low-molecular PA. Thus, POZO can induce improved and tunable photoluminescence properties of N,N-dialkylpyrene-1-carboxamide. The synthesis and photoluminescence properties of N,N-dialkylpyrene-1-carboxamide-modified poly(2-ethyl-2-oxazoline)-gel (PEtOZO-py-gel) were also determined.

Two dual-emissive Zn(ii) coordination polymers with tunable photoluminescence properties

Two novel dual-emissive coordination polymers [Zn2(Hcpop)2(dpe)(H2O)]n·ndpe (1) and [Zn4(cpop)2(dpe)2(μ-OH)2]n·ndpe (2) (H3cpop = 4-(4-carboxyphenoxy)phthalate acid, dpe = 1,2-di(4-pyridyl)ethylene) have been designed and synthesized as promising luminescent materials, which exhibit tunable fluorescence by varying the excitation wavelength.

Controlled synthesis of Gd2(WO4)3 microstructures and their tunable photoluminescent properties after Eu3+/Tb3+ doping

We present a solution-phase synthesis to selectively produce Gd2(WO4)3 microscale belts, stars and flowers under hydrothermal conditions. Different microstructures have been controllably obtained through adjusting the reaction temperature or adding surfactants. The phases and morphologies of the products have been well characterized by XRD, SEM and TEM. Possible formation mechanisms of the different Gd2(WO4)3 microstructures were proposed based on the investigation of the growing process of these microstructures. After doping Eu3+ and Tb3+ inside these Gd2(WO4)3 microstructures, strong and multi-color emission has been realized. Notably, tunable emissions and a warm-white color have been achieved in the Eu3+ and Tb3+ co-doped microstructures. These uniform microstructures are expected to find a broad range of applications in future color displays and light-emitting devices.

Synthesis, Structure, and Thermally Stable Luminescence of Eu2+-Doped Ba2Ln(BO3)2Cl (Ln = Y, Gd and Lu) Host Compounds

A new family of chloroborate compounds, which was investigated from the viewpoint of rare earth ion activated phosphor materials, have been synthesized by a conventional high temperature solid-state reaction. The crystal structure and thermally stable luminescence of chloroborate phosphors Ba(2)Ln(BO(3))(2)Cl:Eu(2+) (Ln = Y, Gd, and Lu) have been reported in this paper. X-ray diffraction studies verify the successful isomorphic substitution for Ln(3+) sites in Ba(2)Ln(BO(3))(2)Cl by other smaller trivalent rare earth ions, such as Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb. The detailed structure information for Ba(2)Ln(BO(3))(2)Cl (Ln = Y, Gd, and Lu) by Rietveld analysis reveals that they all crystallize in a monoclinic P2(1)/m space group. These compounds display interesting and tunable photoluminescence (PL) properties after Eu(2+)-doping. Ba(2)Ln(BO(3))(2)Cl:Eu(2+) phosphors exhibit bluish-green/greenish-yellow light with peak wavelengths at 526, 548, and 511 nm under 365 UV light excitation for Ba(2)Y(BO(3))(2)Cl:Eu(2+), Ba(2)Gd(BO(3))(2)Cl:Eu(2+), and Ba(2)Lu(BO(3))(2)Cl:Eu(2+), respectively. Furthermore, they possess a high thermal quenching temperature. With the increase of temperature, the emission bands show blue shifts with broadening bandwidths and slightly decreasing emission intensities. It is expected that this series of chloroborate phosphors can be used in white-light UV-LEDs as a good wavelength-conversion phosphor.

Tunable Photoluminescence Properties of Fluorescein in a Layered Double Hydroxide Matrix by Changing the Interlayer Microenvironment

This paper reports a novel method to tune the fluorescence properties of fluorescein (FLU) in a 2D matrix of layered double hydroxide (LDH) by changing the interlayer microenvironment. FLU and surfactants with different alkyl chain lengths were cointercalated in the galleries of a Zn2Al LDH by the anion exchange method. Thin films of FLU-CnH2n+1SO3/LDH (n = 5, 6, 7, 10, and 12, respectively; n stands for the number of carbon in the alkyl chain), which possess a well c-orientation revealed by XRD and SEM, were obtained by the solvent evaporation method on Si substrates. It was found that the orientation of FLU and its anisotropy, fluorescence wavelength, fluorescence quantum yield, and lifetime correlate with the microenvironment of the LDH gallery, which can be tuned by simply changing the alkyl chain length of the surfactant. The optimal fluorescence quantum yield, anisotropy, the longest fluorescence lifetime and the strongest photostability of the FLU-CnH2n+1SO3/LDH film can be obtained with n = 7, due...

Highly Tunable Photoluminescent Properties of Amphiphilic Conjugated Block Copolymers

We report a novel class of amphiphilic conjugated block copolymers composed of poly(3-octylthiophene) and poly(ethylene oxide) (POT-b-PEO) that exhibit highly tunable photoluminescence colors spanning from blue to red. POT-b-PEO self-assembles into various well-defined core/shell-type nanostructures as a result of its amphiphilicity. The self-assembly structure can be readily controlled by altering the solvent composition or by other external stimuli. The color change was completely reversible, demonstrating that the strategy can be used to manipulate the light-emission properties of conjugated polymers in a highly controllable manner without having to synthesize entirely new sets of molecules.

ZnO cages with tunable shell thickness and photoluminescence properties

Abstract Uniform ZnO cages were fabricated via using colloidal carbon spheres as sacrificing template. ZnO precursor could be easily coated on the carbon spheres by soaking the template into Zn(CH3COO)2 aqueous solution. After calcination, the average diameter of the cages was 200 nm which experienced a large shrinkage from the initial carbon template (600 nm). The shell thickness of the cages could be manipulated from 20 nm to 40 nm by adjusting the concentration of Zn(CH3COO)2. The correlation between the shell thickness and photoluminescence (PL) performances of these cages was also investigated. Moreover, this facile method could be potentially adopted as a general way to fabricate hollow structures of other metal oxides.

CaO―La2O3―Si3N4―AlN原料系からの窒化物青色蛍光体の合成と発光特性の制御

CaO―La2O3―Si3N4―AlN原料系からの窒化物青色蛍光体の合成と発光特性の制御