Which fibers have dots

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Let's reshape it today. The films were cast by electrospinning the composite solution onto a 1. The clean FTO glass substrates were then coated with the hierarchically structured nanobeads composed of anatase TiO 2 nanoparticles and nanofibers enveloping CdSe QD obtained via the simultaneous electrospray and electrospinning method.

To obtain a uniform thickness over a large area, the nozzle and the substrate were placed on a motion control system regulated by a microprocessor. The working electrode was immersed into 0. To prepare the counter electrode, the FTO plates were drilled and washed first with deionized water and then 0. An aliquot of the electrolyte solution 0. The experimental details of the measurement of photovoltaic properties are described in Supplementary Note 1.

Time-resolved photoluminescence was detected using a time-correlated single-photon counting TCSPC technique to measure spontaneous photoluminescence decay. A pump pulse vertically polarized by a Glan-laser polarizer was used to irradiate the samples, and a sheet polarizer, set at an angle complementary to the magic angle Single-molecule photoluminescence was detected with a confocal microscope TEU, Nikon equipped with a sample scanning stage XE, Park Systems, Suwon, Korea at room temperature under ambient conditions.

Photoluminescence was collected using the same objective, passed through a dichroic mirror dcxru, Chroma Technology , filtered with a notch filter HNPF These data were processed using BIFL data analyzer software Scientific Software Technologies Center, Minsk, Belarus to obtain the fluorescence intensity trajectory FITs with a user-defined binning time, and the time-resolved photoluminescence decayed using photons belonging to a user-defined region in the trajectories.

Separated iQDs were imaged using a wide-field photoluminescence microscope consisting of an inverted optical microscope IX71, Olympus, Tokyo, Japan equipped with an oil immersion objective 1. The integration time per frame was 0. A pristine CdSe quantum dot solution with trioctylphosphine as a capping ligand Supplementary Note 1 and Supplementary Figure S1 and polymer composites was prepared.

Well-distributed polymer composites of QDs were prepared by screening the solvent and polymer and manipulating the polymer concentration to prevent the aggregation of QDs. PMMA was chosen as the fiber material due to its high solubility in chloroform, transparency and the ability to produce an extremely narrow diameter after electrospinning.

The sample solution was then flowed through a nozzle to which a high voltage was applied. The charged solution jet became sharply stretched and solidified during its path from the nozzle to the grounded metal plate, which served as a collector. Due to the elongational flow of the jet and the rapid solvent evaporation, QDs were expected to experience an extremely strong stretching force during the electrospinning process and to be arranged along the direction of elongation. The scanning electron microscopy image shows the morphology of nm-sized electrospun nanofibers enveloping iQDs, corresponding to the bright field confocal microscope image Figures 1a and c.

Merging with the bright-field image shows that the photoluminescence signal was evenly distributed across the nanofiber, indicating that QDs are embedded along the nanofiber without forming aggregates, which would normally appear as bright spots Supplementary Figure S5. To obtain direct information about the distribution of iQDs in the nanofiber, we captured transmission electron microscopy images of nanofiber samples Figure 2a.

One-dimensional spatial confinement of quantum dots in the nanofiber. Lower: schematic figure of iQDs in the nanofiber. Overlay of the bright field and luminescence images right. Monomeric features of isolated quantum dots iQDs in the nanofiber. A single-molecule spectroscopic study was performed, as this is the most straightforward approach to directly demonstrate the monomeric properties of iQDs.

These cumulative images show all the QDs in the fibers and indicate that among the fibers prepared with the same QD concentration, longer distances between QDs are observed in the narrower fibers, which is in a good agreement with the Monte-Carlo simulation Supplementary Figures S7 and S8 and Supplementary Note 2. As shown in Figure 3b , iQDs were also observed in the nanofiber by single-molecule confocal microscopy. The photoluminescence spectrum obtained from a single QD was similar to those of iQDs measured by ensemble measurements Figure 3c.

In addition, the photoluminescence decay curve of a single QD was very close to those obtained from ensemble measurements of iQDs Figure 3d. Accumulated images directly show the spatial distribution of quantum dots QDs in the nanofiber.

We tested the ability of these nanofiber-embedded iQDs as a new strategy for improving the performance of dye-sensitized solar cells DSCs Figure 5a. A recent study has demonstrated that the FRET concept is applicable to DSCs to fill in the absorption gaps of dye sensitizers and that this approach increases the overall light-harvesting efficiency of DSC systems, which are not able to absorb all the light.

We demonstrated that iQDs encapsulated by the nanofiber can overcome the problems described above and also can efficiently transfer energy to dye sensitizers, increasing the overall power conversion efficiency and durability of the DSC. Structure and characterization of a light-harvesting device using isolated quantum dots iQDs as an auxiliary light-harvester. A detailed schematic representation of the film morphology is presented in Supplementary Figure S9.

ZnEP1 anchored on the TiO 2 nanoparticle absorbs 3 and 2. As shown in the above spectroscopic data Figure 2c , this technique allows for the reliable isolation of QDs with a sufficient distance and effective attenuation of the energy transfer among QDs, termed self-absorption; dynamic quenching by electrolytes is also minimized because of the polymer fiber structure enveloping iQDs.

If EDs are dissolved in electrolyte solution, 8 however, energy transfer from ED to DS should be decreased by the above two interactions. Figure 5c presents the external quantum efficiency of DSCs to the photon energy with and without iQDs. DSCs without iQDs exhibited a power conversion efficiency of 5. In previous methods, EDs dissolved in electrolyte solution often suffer from several interactions, which changes their electronic character and finally causes the EDs to quench in the excited state before electron transfer can occur.

We have computationally and experimentally demonstrated that the spatial distribution of QDs can be controlled by manipulating the diameter of the nanofiber encapsulating QDs. The distance between adjacent dots tuned by the radius of the nanofiber was directly observed by single-molecule wide-field spectroscopy, and these results were in agreement with Monte-Carlo simulations. Using this reliable isolation technique, we can obtain a thick iQD nanofiber film that exhibits sufficient photoluminescence either for the ensemble spectroscopic study of iQDs or for application to light-harvesting devices.

The photoluminescence spectra as well as decay curves clearly demonstrate the absence of energy transfer from higher to lower band gap QDs. Moreover, the spectral similarity of single iQDs to ensemble spectroscopic data strongly suggests that the iQDs are monomeric, without inter-dot interactions. These characteristics are clearly distinct compared with a closely-packed film or even a solution.

We have successfully improved the performance of dye-sensitized solar cells from 5. To the best of our knowledge, this work is the first comprehensive investigation of the isolation of QDs in a thin film and light-harvesting devices with one-dimensional spatial confinement as well as their spectroscopic characterization on both the single molecule and ensemble levels.

This study provides a general strategy that could potentially be useful for the spatial control of other functional moieties in solid-state devices as well as the fundamental study of the ensemble features of monomeric functional moieties. Iengo, E. Metallacycles of porphyrins as building blocks in the construction of higher order assemblies through axial coordination of bridging ligands: solution- and solid-state characterization of molecular sandwiches and molecular wires.

Geim, A. Graphene: status and prospects. Science , — Wang, F. Gate-variable optical transitions in graphene. Koole, R. Electronic coupling and exciton energy transfer in CdTe quantum-dot molecules.

Optical, electronic, and structural properties of uncoupled and close-packed arrays of InP quantum dots. And then they were compounded with glass, no any excessive ions such as Pb and S elements for PbS QDs existed in glass matrix. This makes the resistance of QDs growth much bigger, harder to grow when influenced by external field conditions.

The research about them is the thorough currently, and they have been widely used in various applications such as subsequent biological, photoelectric fields Colvin et al. When drawing PbS QD-doped optical fiber from the preform, due to the excessive Pb and S elements in glass matrix, the secondary growth of QDs will occur via ion-migration mechanism under the driving force for the rise of temperature, so that the size of QDs is hard to control.

Therefore, confinement effect is difficult to play since QDs easily grow larger than the exciton Bohr radius. As is mentioned above, we can obtain fiber by melt-extraction method, and its advantage is easy to control the size of QD. But it is only used to prepare bare fiber. To obtain optical fiber that can be used for practical application, we must modify its fiber-drawing process, making direct access to prepare whole QD-doped glass fiber containing outer cladding layer. Based on the successful fabrication of luminescent PbS QD-doped bare fibers by melt-extraction method mentioned above, a traditional type of fiber-drawing technology - double crucible method is expected to directly fabricate optical fiber containing outer cladding layer from glass melt.

Sanghera et al. The mechanical property of glass fibers fabricated by double crucible process is better Dianov et al. These all confirmed the feasibility of double crucible technique. After drawing by double crucible process, and then heat-treatment, moderate size of QDs can be obtained in fiber by controlling the heat-treatment schedule.

By composite approach of the QDs and glass, it is also expected to prepare QD-doped glass and fiber. The QDs should be controllably synthesized firstly, and then composited with the substrate glass together through co-melting technique Chai et al. Since the resistance of QDs growth via Oswald ripening process is much bigger than the above ion-migration force of secondary growth, it is much more difficult for the secondary growth of QDs by composite approach during the fiber-drawing process.

In our previous work, we have successfully synthesized YAG nanocrystals, and making them recombined with substrate tellurate glass by novel co-melting technology. Intense 2. Those works have opened a bright future work to fabricate high-quality QDs-doped glass fibers and devices. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Arnold, G. Ion implantation effects in noncrystallization SiO2. IEEE Trans. Near-surface nucleation and crystallization of an ion-implanted lithia-alumina-silica glass. Bahnemann, D. Flash photolysis observation of the absorption spectra of trapped positive holes and electrons in colloidal TiO2.

Beenakker, C. Theory of Coulomb-blockade oscillations in the conductance of a quantum dot. B Condens. Matter 44, — Bhardwaj, A. Google Scholar. Borrelli, N. Quantum confinement of PbS microcrystals in glass. Non Cryst. Solids , 25— Bruchez, M. Semiconductor nanocrystals as fluorescent biological labels. Science , — Brus, L. Quantum crystallites and nonlinear optics. A A53, — Electron-electron and electron-hole interactions in small semiconductor crystallites: the size dependence of the lowest excited electronic state.

Carder, D. Atomic retention and near infrared photoluminescence from PbSe nanocrystals fabricated by sequential ion implantation and electron beam annealing. Methods B , — Chai, G. C , — Chao, L. Lead chalcogenide quantum dot-doped glasses for photonic devices. Glass Sci. Nanocrystal formation in glasses controlled by rare earth ions.

Photoluminescence of PbS quantum dots embedded in glasses. Solids , — Cheng, C. A multiquantum-dot-doped fiber amplifier with characteristics of broadband, flat gain, and low noise. Lightwave Technol. Experimental realization of a PbSe-quantum-dot doped fiber laser. IEEE Photon. An optical fiber glass containing PbSe quantum dots. Characteristics of bandwidth, gain and noise of a PbSe quantum dot-doped fiber amplifier. Chun, J. Ultrabroadband gain characteristics of a quantum-dot-doped fiber amplifier.

IEEE J. Colvin, V. Light-emitting diodes made from cadmium selenide nanocrystals and a semiconducting polymer.

Nature , — Derfus, A. Probing the cytotoxicity of semiconductor quantum dots. Nano Lett. Dianov, E. EerNisse, E. Compaction of ion-implanted fused silica. Efros, A. Interband absorption of light in a semiconductor sphere. Ekimov, A. Quantum size effect in semiconductor microcrystals. Solid State Commun. Fan, C. Three-dimensional photoprecipitation of oriented LiNbO 3 -like crystals in silica-based glass with femtosecond laser irradiation.

Feng, W. Chinese Phys. Grundmann, M. Ultranarrow luminescence lines from single quantum dots. Guerreiro, P. PbS quantum-dot doped grasses as saturable absorbers for mode locking of a Cr:forsterite laser.

Guo, H. PbS quantum dot fiber amplifier based on a tapered SMF fiber. Guoping, D. Broadband near-infrared luminescence and tunable optical amplification around 1. Alloys Compd. Formation, near-infrared luminescence and multi-wavelength optical amplification of PbS quantum dot-embedded silicate glasses.

Heck, M. Express 15, — Heinrichsdorff, F. Lett 71, 22— Henglein, A. Mechanism of reactions on colloidal microelectrodes and size quantization effects. Heo, J. Pbs quantum-dots in glass matrix for universal fiber-optic amplifier. Sci Mater. Hines, M. Colloidal PbS nanocrystals with size-tunable near-infrared emission: observation of post-synthesis self-narrowing of the particle size distribution. Hoogland, S. A solution-processed 1.

Express 14, — Hreibi, A. Huang, W. Tunable infrared luminescence and optical amplification in PbS doped glasses. Huang, X. Jacob, G. Jain, R. Degenerate four-wave mixing in semiconductor-doped glasses. Kellermann, G. Nucleation and growth of CdTe 1-x S x nanocrystals embedded in a borosilicate glass. Effects of sulfur content and two-step thermal annealing. Kim, S. Near-infrared fluorescent type II quantum dots for sentinel lymph node mapping. Klimov, V. Optical gain and stimulated emission in nanocrystal quantum dots.

Kolobkova, E. Fluorophosphate glasses containing PbSe quantum dots. Glass Phys. Kormann, C. Preparation and characterization of quantum-size titanium dioxide.

Kubo, R. Electronic properties of metallic fine particles. Kunets, V. CdSSe quantum dots: effect of the hydrogen RF plasma treatment on exciton luminescence. Physica E 22, — Kuntz, M. High-speed mode-locked quantum-dot lasers and optical amplifiers. Proc IEEE 95, — Lagatsky, A. Lee, J. Synthesis of ZnO nanocrystals by subsequent implantation of Zn and O species. Liu, C. Absorption and photoluminescence of PbS QDs in glasses.