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Fluorescence, the absorption and re-emission of photons with longer wavelengths, is one of those amazing phenomena of Nature. Its discovery and utilization had, and still has, a major impact on biological and biomedical research, since it enables researchers not just to visualize normal physiological processes with high temporal and spatial resolution, to detect multiple signals concomitantly, to track single molecules in vivo, to replace radioactive assays when possible, but also to shed light on many pathobiological processes underpinning disease states, which would otherwise not be possible. Compounds that exhibit fluorescence are commonly called fluorochromes or fluorophores and one of these fluorescent molecules in particular has significantly enabled life science research to gain new insights in virtually all its sub-disciplines: Green Fluorescent Protein. Because fluorescent proteins are synthesized in vivo, integration of fluorescent detection methods into the biological system via genetic techniques now became feasible. Currently fluorescent proteins are available that virtually span the whole electromagnetic spectrum. Concomitantly, fluorescence imaging techniques were developed, and often progress in one field fueled innovation in the other. Impressively, the properties of fluorescence were utilized to develop new assays and imaging modalities, ranging from energy transfer to image molecular interactions to imaging beyond the diffraction limit with super-resolution microscopy. Here, an overview is provided of recent developments in both fluorescence imaging and fluorochrome engineering, which together constitute the "fluorescence toolbox" in life science research. © 2012 by the authors. Source

Zamiri R.,University Putra Malaysia | Zamiri R.,University of Aveiro | Zakaria A.,University Putra Malaysia | Sadrolhosseini A.R.,University Putra Malaysia | And 2 more authors.
Science of Advanced Materials

Silver nanoparticles were prepared in monoolein, a glycerol derivative of oleic acid, via pulsed laser ablation of a silver plate with a Q-Switched Nd:YAG laser (1064 nm). The average size of the nanoparticles was 8.8±0.5 nm, with a narrow size distribution of 4.6 nm FWHM. No significant agglomeration or flocculation was observed after one-month storage. The observed results indicated a nonlinear dependence of the refractive index n2 on the particle volume fraction. Furthermore, the monoolein-silver nanoparticle solution showed self-defocusing behaviour, as deduced from the negative sign in n2 and spatial self-phase modulation, which depended on the volume fraction. Non-linear absorption behaviour was not observed in any of the samples analyzed. The results in this work suggest that colloidal silver nanoparticle solutions in monoolein are interesting nonlinear materials to create and control different spatial effects and that such silver-monoolein colloids might be used in a multitude of optical applications, such as spatial soliton propagation, real time holography, and liquid crystalbased applications. © 2013 by American Scientific Publishers. Source

Zheng Y.,South China Normal University | Tan C.,South China Normal University | Drummen G.P.C.,Bionanoscience and Bio Imaging Program | Wang Q.,South China Normal University
Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy

We designed a ternary europium (III) tris(2-thenoyltrifluoroacetonate) with 2-(3,4,5-trimethoxyphenyl)imidazo[4,5-f]-1,10-phenanthroline (1) ligands for the luminescent detection of various anions, such as fluoride, acetate and dihydrogen phosphate. Characterization of the sensor's photophysical properties and via NMR showed that the sensor exhibits striking emission changes to fluoride (purple), acetate (green) and dihydrogen phosphate (blue) anions, respectively. Its fluorescence lifetime was determined to be 1.10 ms for europium ions and the complex showed an overall quantum yield of 10% in DMSO. Furthermore, transparent hybrid thick films composed of the europium complex and poly-methyl methacrylate matrix were successfully prepared via copolymerization. The resulting film overall displayed intense red emissions associated with europium ions. Fluorescence microscopic evaluation showed a homogenous distribution of aggregates with average diameters of 30-50 μm throughout the film. The accordingly produced film could give rise to a luminescence change to purple in response to fluoride anions. © 2012 Elsevier B.V. All rights reserved. Source

Zamiri R.,University Putra Malaysia | Zamiri R.,University of Aveiro | Ahangar H.A.,Kharazmi University | Zakaria A.,University Putra Malaysia | And 3 more authors.
Journal of Nanoparticle Research

Goethite (α-FeOOH) nanorods were synthesized via the hydrothermal method with the assistance of coordinating ligands, i.e. ethylenediamine and thiourea. The homogeneity of the nanorod size distribution increased and the propensity to agglomerate decreased when ethylenediamine and thiourea were used in conjunction; contrary to goethite synthesis in the presence of a single ligand. The type and mode of structure-directing plays a critical role in the morphology of the final products. When using thiourea only or in combination with ethylenediamine, nanorods and nanoparticles of various morphologies were formed. Conversely, when exclusively using ethylenediamine, in addition to the nanorods, fine needles with a significantly smaller diameter were discernible. With all combinations, structurally uniform α-FeOOH nanorods were formed. This improved nanorod formation in the presence of both ligands might be attributed to a more ordered alignment and regular conformation of ethylenediamine molecules in the presence of thiourea and thus less susceptibility to thermal perturbations. Finally, higher concentrations of ligand influence the final product and increases particle aggregation. © Springer Science+Business Media 2014. Source

Amirkhanlou S.,Amirkabir University of Technology | Ketabchi M.,Amirkabir University of Technology | Parvin N.,Amirkabir University of Technology | Drummen G.P.C.,Bionanoscience and Bio Imaging Program
Metallurgical and Materials Transactions B: Process Metallurgy and Materials Processing Science

In the present work, a novel technique is introduced called continual annealing and press bonding (CAPB) for the manufacturing of a bulk aluminum matrix composite dispersed with 10 vol pct tungsten carbide particles (Al/WCp composite). The microstructural evolution and mechanical properties of the Al/WCp composite during various CAPB cycles were examined by scanning electron microscopy (SEM), wavelength dispersive X-ray spectroscopy (WDX), and tensile testing. The microstructure of the fabricated composite after fourteen cycles of CAPB showed homogenous distribution of the WC particles in the aluminum matrix and strong bonding between the various layers. According to WDX analysis, the manufactured Al/WCp composite did not evidence the presence of additional elements. The results indicated that the tensile strength of the composites increased with the number of CAPB cycles, and reached a maximum value of 140 MPa at the end of the fourteenth cycle, which was 1.6 times higher than the obtained value for annealed aluminum (raw material, 88 MPa). Even though the elongation of the Al/WCp composite was reduced during the initial cycles of CAPB process, it increased significantly during the final cycles. SEM observation of fracture surfaces showed that the rupture mode in the CAPB-processed Al/WCp composite was of the shear ductile rupture type. © 2014, The Minerals, Metals & Materials Society and ASM International. Source

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