Fibre lasers in the mid-infrared regime are useful for a diverse range of fields, including chemical and biomedical sensing, military applications and materials processing. This Review summarizes the different rare-earth cations and host materials used in mid-infrared fibre laser technology, and discusses the future applications and challenges for the field.

Towards high-power mid-infrared emission from a fibre laser

http://users.encs.concordia.ca/~mojtaba/elec6271/Colloidal%20quantum%20dot%20solar%20cells.pdf

Colloidal quantum dot solar cells

Optical properties of pure polyvinyl alcohol (PVA) and PVA based nanocomposite films have been investigated. The nano-composite samples were prepared by the well known solution cast method. The experimental results shows that the absorption and absorption coefficient parameters are greatly affected by variation of copper oxide (CuO) nanoparticles concentration. The absorption versus wavelength for the doped samples is exponential while the absorbance of pure PVA is sharply varied with wavelength. An obvious surface plasmonic resonance peaks for the nano-composite samples were appeared. The absorption edge was greatly shifted to lower energy for the PVA doped samples. It was observed that optical band gap of pure PVA is significantly reduced upon the addition of CuO nanoparticles. The increase of refractive index with increasing CuO concentration is an evidence for the formation of new energy states and thus decreasing the energy band gap of PVA. The increase of optical dielectric constant was observed upon the addition of CuO nanoparticles. The optical dielectric loss peaks are shifted to higher wavelength with increasing the CuO concentration. The optical conductivity is increased upon the addition of CuO nanoparticles. The dispersion region in the refractive index spectra are well obeyed the single oscillator of the Wemple–Didomenico model for all the samples.

Reducing the optical band gap of polyvinyl alcohol (PVA) based nanocomposite

The effects of substrate temperature on the structural, optical, medical and electrical characteristics of Cadmium Oxide (CdO) films are investigated in the current study. Films are deposited on glass substrate at different temperatures, ranged between 450–600 oC, using Spray Pyrolysis Technique. According to X–Ray Diffraction (XRD), it is found that the films are polycrystalline and Cadmium Oxide (CdO) is of a hexagonal wurtzite structure which the preferred direction of its crystal plane is (002). The maximum optical transmittance of films is more than 85%. The size of crystallites is calculated with the maximum value in 500o C. Furthermore, Cadmium Oxide (CdO) nanoparticles were synthesized in deionized water by laser ablation of Cadmium plate. In the current paper, the effects of laser pulse energy and wavelength on the characteristics of Cadmium Oxide (CdO) nanoparticles were studied. Analyses of Transmission Electron Microscope (TEM) were confirmed that size distribution of Cadmium Oxide (CdO) nanoparticles is reduced by increase in laser pulse energy. Fluorescence spectrum of Cadmium Oxide (CdO) nanoparticles shows violet emission accompanied by blue and green band. UV emission with high intensity shows that nanostructure of Cadmium Oxide (CdO) is of a little deficiency. Also, the current study aims to study the linear and non–linear optical characteristics of Cadmium Oxide (CdO) nanoparticles and their applications. Firstly, fluorescence spectrum, as a linear characteristics of Cadmium Oxide (CdO), as well as second harmonic generation and two photons absorption, as non–linear characteristics of Cadmium Oxide (CdO), are studied. Then, some aspects of medicinal and pharmaceutical applications of Cadmium Oxide (CdO) nanoparticles for eliminating cancer cells such as the effect of Cadmium Oxide (CdO) nanoparticles on DNA of human cancer cells and the interaction of Cadmium Oxide (CdO) nanoparticles with DNA of cancer cells are originally investigated. It should be noted that the range of considered parameters are separately clarified and explained in each of related sections (Figure 1).

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Study of Composition and Morphology of Cadmium Oxide (Cdo) Nanoparticles for Eliminating Cancer Cells

Quantum dot-sensitized solar cells (QDSCs) present promising cost-effective alternatives to conventional silicon solar cells due to their distinctive properties such as simplicity in fabrication, possibility to realize light absorption in wide solar spectrum regions, and theoretical conversion efficiency up to 44%. This review highlights recent developments in critical materials including quantum dots, photoanodes, counter electrodes (CEs), and electrolytes for QDSC applications. Among them, electron recombination at the photoanode/electrolyte interface limits the evolution of high-efficiency QDSCs, therefore the optimized construction of quantum dots, the various microtopographies of wide bandgap semiconductors (TiO2, ZnO) as well as emerging CEs having good electrocatalytic activity are elaborated in this paper. We argue that these key factors can provide design guidelines for future successful applications and significantly promote the development of QDSCs. Liquid, quasi-solid-state, and solid-state electrolytes for QDSCs are summarized, aiming at enhancing the long-term stability of QDSCs. This review presented below gives a succinct summary of materials for QDSC applications, with a conclusion and future prospects section.

Recent advances in critical materials for quantum dot-sensitized solar cells: a review

Tuning photocurrent response through size control of CdTe quantum dots sensitized solar cells

The optical, thermal and electrical behavior of single-wall carbon nanotubes (SWCNTs)/poly(methyl methacrylate) (PMMA) composite are studied as a function of SWCNTs concentration. The nanocomposites were prepared in the form of films by solution casting technique. The concentrations of SWCNTs in SWCNTs/PMMA films were 0, 0.5, 1, 1.5, 2, 3.5, 5, 7.5, and 10 wt%. High-resolution transmission electron microscopy showed that SWCNTs doped in PMMA is less fragmented as compared to the powder SWCNTs. This is due to the interactions with polymers as well as the fabrication method. X-ray diffraction patterns of SWCNTs/PMMA composite films indicated that there is no covalent interaction between SWCNTs and PMMA. In addition, it demonstrates a homogeneous dispersion of SWCNTs in PMMA matrix. The optical properties of SWCNTs/PMMA films of SWCNTs concentration from 0 to 2.0 wt% have shown that the absorption intensity of the composite was enhanced ≈8.5 times as compared to the plain PMMA. Photoacoustic spectroscopy technique was used as a powerful and non-destructive tool to determine the thermal diffusivity (α), thermal effusivity (e) and thermal conductivity (k). The composites exhibited ≈160 % improvement in k at 2.0 wt%. Furthermore, the DC electrical conductivity measurements of SWCNTs/PMMA showed that the percolation threshold value was about 2.0 wt% of SWCNTs loading.

Characterization of optical, thermal and electrical properties of swcnts/pmma nanocomposite films

The concentration dependence of optical, thermophysical and electrical behavior, based on poly-methyl methacrylate filled with CdSe quantum dots (PMMA(CdSe)) have been investigated. The PMMA(CdSe) concentration was 0.001, 0.005, 0.01 and 0.05 wt.%. The composites were prepared in the form of films by the solution casting technique. The optical properties of PMMA(CdSe) films have showed that, there is a red shift of the absorption and photoluminescence (PL) after the QDs were added into PMMA. The PL peak intensity of the composite was enhanced by ≈ 2.5 times compared to the CdSe QDs. The thermal conductivity (k) was obtained by measuring the thermal diffusivity (α) and thermal effusivity (e) using the photoacoustic (PA) technique. The composites exhibit ≈ 120 % improvement in k at 0.05 wt.% . Furthermore, the dc electrical conductivity measurements of pure and doped PMMA, showed that the obtained values were enhanced about four orders of magnitude for the highest concentration compared with pure PMMA at 500 0C.

N. Al-Hosiny

Papers

Tuning photocurrent response through size control of CdTe quantum dots sensitized solar cells

Characterization of optical, thermal and electrical properties of swcnts/pmma nanocomposite films

Optical, thermophysical and electrical characterization of PMMA (CdSe QDs) composite films

The photovoltaic performance of CdS quantum dots sensitized solar cell using graphene/TiO2 working electrode

Tailoring enhanced chaos in optically injected semiconductor lasers