Synthesis and characterisation of CdS nanoparticles in mesoporous copolymer template (original) (raw)
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Optical properties of CdS nanoparticles embedded in polymeric microspheres
Journal of Alloys and Compounds, 2010
Mesoporous microspheres of styrene-divinylbenzene (Sty-DVB) copolymer have been used as template for encapsulation of CdS nanocrystal-quantum-dots (NQDs). Raman, micro-photoluminescence and optical absorption were used to investigate the optical properties of the nanocomposites containing CdS NQDs. When a single microsphere nanocomposite is excited by a laser beam at room temperature, very strong and sharp whispering-gallery mode (WGM) is shown on the background of CdS NQD PL spectra, which confirms that coupling between the optical emission of the encapsulated NQDs and spherical cavity modes was realized. The results show that the microspheres loaded with CdS nanoparticles work as an optical microcavity allowing the observation of WGM. The lasing behavior is achieved at relatively low laser excitation intensity (∼1 mW) at room temperature. High-optical stability and low-threshold value make this optical system promising in visible microlaser applications.
Journal of Nanoparticle Research, 2013
We investigated the synthesis of CdS nanoparticles via an optimized water-in-oil microemulsion route that used the non-ionic surfactantbased system H 2 On octane -Brij30/1-octanol. For that purpose, a microemulsion that contained Cd(II) ions (le1) and another microemulsion that contained S 2ions (le2) were combined. To investigate the ways in which the non-ionic microemulsion characteristics controlled the size and emission properties of colloidal CdS quantum dots, le1 and le2 with tunable and robust similar structure were prepared. This requirement was fulfilled by matching the water emulsification failure boundary (wefb) of the two microemulsions and carrying out synthesis along this boundary. Dynamic light scattering and fluorescence probe techniques were used to investigate the size and interfacial organization of the microemulsion water droplets, and the CdS nanoparticles were characterized by UV-Vis and static fluorescence spectrometry, TEM and HRTEM. Nanoparticles of diameter 4.5-5.5 nm exhibiting enhanced band edge emission were produced by increasing the water content of the precursor microemulsions. The experimental results were combined with a Monte Carlo simulation approach to demonstrate that growth via coagulation of seed nuclei represented the driving mechanism for the CdS nanoparticle formation in the water-in-oil microemulsion.
Semiconductor Science and Technology, 2003
We report on development and characterization of Whispering Gallery Modes spherical microcavities integrated with organic dye molecules in a J-aggregate state. The microcavities are studied using microphotoluminescence spectroscopy, and fluorescence lifetime imaging confocal microscopy. Directional emission of light from the microcavity is also experimentally demonstrated and attributed to the photonic jets generated in the microsphere.
Size effects on Raman spectra of small CdSe nanoparticles in polymer films
Nanotechnology, 2008
The results of a resonant Raman scattering (RRS) study of polymer-stabilized colloidal CdSe nanoparticles (NPs) are reported. The size-selective nature of the RRS is demonstrated by analysing the NP ensembles with different average sized and size distribution d using a set of excitation wavelengths. The effect of size selection on the estimation ofd and d values from the RRS spectra is discussed, as well as some peculiarities of RRS on surface optical phonons. From the experimentally observed small variation of the I 2LO /I LO ratio for 2-5 nm NPs a minor effect ofd on the electron-phonon coupling strength in thisd range is supposed.
Nanomaterials based on CdS nanoparticles in polyethylene matrix
Inorganic Materials, 2009
The synthesis of CdS nanoparticles stabilized in the bulk of a polyethylene matrix is described. The size of synthesized nanoparticles is determined by means of transmission electron microscopy. The composition of nanoparticles is defined by X-ray phase analysis. It is shown that the variation of the process-dependent parameters during synthesis of nanoparticles in a polymer + oil solution melt results in the formation of CdS nanoparticles with average sizes of 4.9, 5.4, and 6.2 nm with a reasonably narrow size distribution and well-formed structure. The optical properties of synthesized nanomaterials are investigated. The investigation of Raman scattering reveals softening of the LO-phonon mode with decreasing CdS nanoparticle size. A broad high-energy band of photoluminescence connected with the exciton annihilation in conditions of size quantization is detected.
Optical properties of CdS micro/nanocrystalline structures prepared via a thermal evaporation method
Materials Science in Semiconductor Processing, 2014
Cadmium sulfide (CdS) micro/nanocrystalline structures were fabricated by thermal evaporation in the absence of a catalyst on ITO-coated glass and Si(100) substrates. The samples prepared at 520 1C showed two structures of CdS: nanowires (NWs) and necklace-like microstructures grown on Si(111) and ITO substrates, respectively. The crystalline structures of the grown CdS necklace-like microstructures and NWs were studied using XRD analysis. The CdS necklaces and NWs structures were formed with hexagonal (wurtzite) structure. Two emission bands (green and red) were observed in the photoluminescence spectra of the prepared samples. The green PL emission in both structures showed a strong blue-shift compared with the optical band gap of CdS. Raman spectra of the grown CdS micro/nanocrystalline structures show redshift in the fundamental (1LO) and overtone (2LO) peaks location compared with Raman bands of bulk CdS.
Synthesis of CdS nanoparticles with enhanced optical properties
Materials Characterization, 2011
Size tunability of thioglycerol capped cadmium sulphide nanoparticles has been achieved by controlling the capping reagent concentration as well as annealing temperature through chemical precipitation method. Optical and structural properties of CdS nanoparticles were studied through UV-Vis absorption, X-ray diffraction, energy dispersive X-ray, high resolution transmission electron microscopy, Raman and photoluminescence spectroscopy. Synthesis at 0.6 ml thioglycerol concentration produces stable nanoparticles of smallest size nearly 3 ± 0.5 nm having narrow size distribution, high photoluminescence intensity and lower crystallinity. Annealing improves the crystallinity and reduces the defects levels. The attachment of particles, existence of intrinsic stacking faults, extrinsic stacking faults, twin boundaries, interface dislocations as well as clear lattice fringes in high resolution transmission electron microscopy images are also discussed. a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m w w w . e l s e v i e r . c o m / l o c a t e / m a t c h a r
Facile Synthesis of Monodisperse CdS Nanocrystals via Microreaction
Nanoscale Research Letters, 2010
CdS-based nanocrystals (NCs) have attracted extensive interest due to their potential application as key luminescent materials for blue and white LEDs. In this research, the continuous synthesis of monodisperse CdS NCs was demonstrated utilizing a capillary microreactor. The enhanced heat and mass transfer in the microreactor was useful to reduce the reaction temperature and residence time to synthesize monodisperse CdS NCs. The superior stability of the microreactor and its continuous operation allowed the investigation of synthesis parameters with high efficiency. Reaction temperature was found to be a key parameter for balancing the reactivity of CdS precursors, while residence time was shown to be an important factor that governs the size and size distribution of the CdS NCs. Furthermore, variation of OA concentration was demonstrated to be a facile tuning mechanism for controlling the size of the CdS NCs. The variation of the volume percentage of OA from 10.5 to 51.2% and the variation of the residence time from 17 to 136 s facilitated the synthesis of monodisperse CdS NCs in the size range of 3.0-5.4 nm, and the NCs produced photoluminescent emissions in the range of 391-463 nm.
Self‐assembled CdSe/CdS nanorod micro‐lasers fabricated from solution by capillary jet deposition
An innovative, simple and reliable method to fabricate micro-lasers by self-assembly of rod-shaped nanocrystals is demonstrated. Dot/rod core/shell CdSe/CdS nanorods are used to form optical micro-resonators by exploiting their self-organization into well-defined coffee stain rings. The fabrication process merely consists of capillary jet deposition of a nanorod solution onto a glass substrate, and is scalable, economic, and highly reproducible. Upon optical pumping of the micro-resonators, laser emission in the red or in the blue-green spectral region is obtained, demonstrating lasing both from core and shell transitions, with low pumping thresholds. Modeling by full-wave numerical simulations according to generalized (i. e. scattering) formulation of laser theory demonstrates lasing from complex modes of the self-assembled cavity.
Cauliflower-Like CdS Microspheres Composed of Nanocrystals and Their Physicochemical Properties
2011
Cauliflower-like cadmium sulfide (CdS) microspheres composed of nanocrystals have been successfully synthesized by a hydrothermal method using poly(ethylene glycol) (PEG) as the template coordination agent and characterized by a variety of methods. Our experiments confirmed that the size of the CdS microspheres could be easily modified by controlling the chain length of PEG. Powder X-ray diffraction and Raman spectroscopy measurements revealed the cubic structure of the CdS microspheres; morphological studies performed by HR-SEM and HR-TEM methods showed the cauliflower-like structure of the synthesized CdS microspheres. Each microsphere was identified to be created by the self-assembly of CdS nanocrystals and is attributed to the oriented aggregation of the CdS nanocrystals around a polymer-Cd 2þ complex spherical framework structure. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray (EDX) analysis confirmed the stoichiometries of the CdS microspheres. Diffuse reflectance spectrum (DRS) measurements showed that increasing the PEG chain length increased the band gap value of the CdS microspheres slightly, from 1.99 to 2.06 eV. The cauliflower-like CdS microspheres could be applied to photocatalytic degradation studies.