The Dynamics of Luminescence

Domestic light providing devices have always been an important component of life and continue to provide us light beyond sunset. These devices continue to be improved frequently to allow ease of use and to enhance their efficiency. The tungsten electric light bulbs are widely used, which are based on incandescence of a continuously heated tungsten element. However, their use will soon be short lived because of the increased usage of fluorescent tubes and light-emitting diode (LED) devices, which are based on luminescence emission. These emission materials that display luminescence are called phosphors, and their emission is based on electron transitions. In the following chapter, we shall look into photoluminescence from both intrinsic and extrinsic defects, covering both down- and upconversion (UP). We will look into the concept of energy transfer and persistent luminescence and lastly provide related applications of luminescence in the modern days

Graphene / TiO2 composites synthesized in one-step by laser pyrolysis for improved charge extraction in perovskite solar cells

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Structural and optical properties of sol-gel derived α-Fe2O3 nanoparticles

α-Fe2O3 nanoparticles of crystallite size between 3.9 and 9.5 nm were synthesized by a simple sol-gel method using iron (III) nitrate nonahydrate (Fe(NO3)3·9H2O) as a precursor. Polyvinyl alcohol (PVA) was added as a capping agent to avoid agglomeration of the nanoparticles. A single pure phase was obtained when the sample was annealed at 300 °C and 600 °C. The purity was further confirmed with the Fourier Transform Infrared Spectroscopy. The energy band gap of the materials was extrapolated from the Kubelka-Munk relation and it ranges between 1.8 and 2.3 eV. The Photoluminescence of the 3 samples shows a broad emission spectrum centered at about 422 nm when excited by a 336 nm lamp. The emission peaks intensities increased with an increase in the annealing temperature, accept for the 576 nm peak, which was quenched as the temperature increased from 300 °C to 600 °C. The thermoluminescence glow curves were carried out at different heating rates and the samples were exposed to different beta particle doses (82–1315 Gy). The activation energy of the trapped electrons was determined

Eco-friendly synthesized few layered graphene: main physico-chemical nanocharacterizations for optical quenching applications

The importance of green process in the synthesis of nanomaterials becomes universally known. In this study, we report on the efficiency of Aspalathus linearis's plant extract known as Rooibos tea on the synthesis of graphene via a bio-active process. Using several nanocharcterization techniques, our investigations on the main physico-chemical properties confirmed the ability of this plant extract as a reducing and capping agent on performing an effective reducing process leading to a wide and flat FLrGO sheets without folds along their length and of a mean size of 265 nm. Furthermore, this eco-friendly cost-effective process allows the control and modulation of the optical and the electrical properties of the prepared graphene. Moreover, this material was positively tested as silver NPs fluorescence quencher. Hence, Rooibos shows its ability as an effective chelating agent in the production of graphene sheets which serves electronic and optoelectronic related quenching applications