Color Centers Formation in Lithium Fluoride Nanocubes Doped with Different Elements

Nanocrystalline cubes of pure and doped LiF material were fabricated. They were doped with Cu, Ag, Dy, Tb, and Eu and studied for their PL properties. Shape of the obtained nanocubes was found to be modified by introducing dopants into the host of LiF. The crystallinity was also decreased by increasing the concentration of these dopants (i.e., Eu and Tb). These impurities could induce exothermic peaks at around 250°C in the measured DSC curves. Moreover, incorporating such impurities into the host of LiF was found to enhance intensity of the broad band at 370–550 nm that was observed in the pure one. Extra sharp emissions were also observed in Eu and Tb doped samples. These results showed that the active color centers created in pure LiF nanocubes can be enriched/enhanced by these impurities, mainly Eu and Tb. This implies that these nanocubes might be useful in the development of optical devices and advanced color center laser

Data Fitting to Study Ablated Hard Dental Tissues by Nanosecond Laser Irradiation.

Laser ablation of dental hard tissues is one of the most important laser applications in dentistry. Many works have reported the interaction of laser radiations with tooth material to optimize laser parameters such as wavelength, energy density, etc. This work has focused on determining the relationship between energy density and ablation thresholds using pulsed, 5 nanosecond, neodymium-doped yttrium aluminum garnet; Nd:Y3Al5O12 (Nd:YAG) laser at 1064 nanometer. For enamel and dentin tissues, the ablations have been performed using laser-induced breakdown spectroscopy (LIBS) technique. The ablation thresholds and relationship between energy densities and peak areas of calcium lines, which appeared in LIBS, were determined using data fitting. Furthermore, the morphological changes were studied using Scanning Electron Microscope (SEM). Moreover, the chemical stability of the tooth material after ablation has been studied using Energy-Dispersive X-Ray Spectroscopy (EDX). The differences between carbon atomic % of non-irradiated and irradiated samples were tested using statistical t-test. Results revealed that the best fitting between energy densities and peak areas of calcium lines were exponential and linear for enamel and dentin, respectively. In addition, the ablation threshold of Nd:YAG lasers in enamel was higher than that of dentin. The morphology of the surrounded ablated region of enamel showed thermal damages. For enamel, the EDX quantitative analysis showed that the atomic % of carbon increased significantly when laser energy density increased

Ionic Liquid-Sulfolane Composite Electrolytes for High-Performance and Stable Dye-Sensitized Solar Cells

Ionic liquid electrolytes are prepared using sulfolane as a plasticizer for eutectic melts to realize highly stable and efficiently performing dye-sensitized solar cells (DSCs) in hot climate conditions. Variations in the viscosity of the formulations with sulfolane content are measured and performance in DSCs is investigated using the ruthenium dye C106 as a sensitizer. A power conversion efficiency (PCE) of 8.2% is achieved under standard reporting conditions. Apart from lowering the viscosity, the addition of sulfolane induces a negative shift of the TiO2 conduction band edge. Strikingly the device performance increases to 8.4% at 50 degrees C due to higher short circuit photocurrent and fill factor, over-compensating the loss in open circuit voltage with increasing temperature. The PCE increases also upon decreasing the light intensity of the solar simulator, reaching up to 9% at 50 mW cm(-2). Devices based on these new electrolyte formulations show excellent stability during light soaking for 2320 h under full sunlight at 60 degrees C and also during a 1065 h long heat stress at 80 degrees C in the dark. A detailed investigation provides important information about the factors affecting the principal photovoltaic parameters during the aging process and the first results from a series of outdoor measurements are reported

Outdoor Performance and Stability under Elevated Temperatures and Long-Term Light Soaking of Triple-Layer Mesoporous Perovskite Photovoltaics

Lack of proven stability has become a major obstacle on the path of metal halide perovskite solar cells (PSCs), in particular methylammonium lead triiodide (MAPbI(3)), towards commercial viability. This correlates with the intrinsic affinity of MAPbI(3) towards moisture and ambient air in particular, leading to its degradation in ambient conditions. We performed extensive stability tests to prove the durability of hole-conductor-free PSCs based on a triple-layer architecture employing carbon as a back contact, including outdoor tests in the hot desert climate and indoor long-term light soaking as well as heat exposure during 3months at 80-85 degrees C. These results show no evidence for device degradation under the test conditions, confirming that the triple-layer device architecture provides a promising path towards realizing efficient and stable perovskite photovoltaics

Molecular gelation of ionic liquid-sulfolane mixtures, a solid electrolyte for high performance dye-sensitized solar cells

Cyclohexanecarboxylic acid-[4-(3-tetradecylureido)phenyl]amide is an efficient gelator to solidify ionic liquid electrolytes. In this paper we apply this low molecular weight gelator to solidify the newly prepared sulfolane based ionic liquid electrolyte. This solid electrolyte is successfully applied as an electrolyte for dye sensitized solar cells. This solid electrolyte is thermo-reversible, upon heating it will become a liquid and at room temperature it will solidify, facilitating the cell filling by the electrolyte. Applying this solid electrolyte we obtained 7.8% power conversion efficiency under simulated AM 1.5 full sunlight intensity. The devices with liquid and solid electrolytes were analysed by electrochemical impedance spectroscopy to explain the differences in the photovoltaic performance. These cells were also measured under outdoor conditions at Jeddah, Saudi Arabia to explore the feasibility of practical applications of this electrolyte

LIBS spectra of enamel and dentin laser ablation.

<p> The intensity in arbitrary units (a.u.) of calcium lines in the LIBS spectra of enamel and dentin Nd:YAG laser ablation.</p

SEM images.

<p>Enamel surface after ablation with Nd:YAG laser at energy density of 17.2 J/cm² and 100 shots.</p

Elements atomic % for non-irradiated and irradiated enamel tissue at energy densities of 5.6, 11.2, and 17.2 J/cm².

<p>Elements atomic % for non-irradiated and irradiated enamel tissue at energy densities of 5.6, 11.2, and 17.2 J/cm².</p

The relation between the peak areas of calcium lines and energy densities.

<p>(a) calcium line peak area versus energy density for enamel (b) calcium line peak area versus energy density for dentin.</p