25 research outputs found
Efficient Er/OâDoped Silicon LightâEmitting Diodes at Communication Wavelength by Deep Cooling
A silicon light source at the communication wavelength is the bottleneck for developing monolithically integrated silicon photonics. Doping silicon with erbium and oxygen ions is considered one of the most promising approaches to produce silicon light sources. However, this method suffers from a high concentration of defects in the form of nonradiative recombination centers at the interface between the crystalline silicon and large Er2O3/ErSi1.7 precipitates during the standard rapid thermal treatment. Here, a deep cooling process is applied to suppress the growth of these precipitates by flushing the highâtemperature Er/Oâdoped silicon substrates with helium gas cooled in liquid nitrogen. The resultant lightâemitting efficiency at room temperature is enhanced by two orders of magnitude in comparison with that of the sample treated via standard rapid thermal annealing. The deepâcoolingâprocessed Si samples are further processed into lightâemitting diodes. Bright electroluminescence with a main spectral peak at 1536Â nm is also observed from the siliconâbased diodes with the external quantum efficiency reaching â0.8% at room temperature. Based on these results, the development of electrically driven silicon optical amplifiers or even lasers at communication wavelengths is promising for monolithically integrated silicon photonics.A deep cooling technique is developed for silicon light sources by suppressing the growth of Er/Oârelated precipitates. The resultant nearâinfrared emission shows efficiency enhancement by two orders of magnitude. Bright electroluminescence with a main spectral peak at 1536Â nm is also observed. The external quantum efficiency can reach 0.8% at room temperature.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/162702/3/adom202000720.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/162702/2/adom202000720-sup-0001-SuppMat.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/162702/1/adom202000720_am.pd
Influence of ammonium polyphosphate on flame-retardant behavior and smoke suppression property of EVA/magnesium hydroxide composites
Assembly of polyoxometalate-templated metal-organic framework with effective peroxidase-like catalytic activity
Boosting the High Working Voltage of an Aqueous Symmetric Supercapacitor by a Phosphotungstic Acid-Based Coordination Polymer Coating with Polypyrrole
The low working voltage limits the energy density and
feasibility
of practical applications of aqueous supercapacitors (SCs) to some
extent. Herein, new CuPW12@PPy (n, n = 1, 2, 3) nanocomposites were designed and fabricated
by involving the hydrothermal synthesis of crystalline H4[Cu2(bix)4][PW12O40]2·8H2O (CuPW12) and subsequently
pyrrole in situ oxidation polymerization on the CuPW12 surface.
These were then used as electrode materials to widen the working voltage
of SC. As expected, CuPW12@PPy (n, n = 1, 2, 3) can operate stably within â0.6 to 1.0
V while inhibiting the hydrogen evolution reaction, which exhibits
higher specific capacitance in 2 M H3PO4. Specifically,
CuPW12@PPy (2) shows a 711.2 F gâ1 specific
capacitance at 1.5 A gâ1, attributed to the high
ion/electron transportation and their synergy from the conductive
PPy covering the CuPW12 surfaces. Finally, the assembled
symmetric SC cell can operate at 1.6 V and deliver a 43.67 Wh kgâ1 energy density and 1280 W kgâ1 power
density at 1.0 A gâ1 and a 91.3% capacitance retention
at 5 A gâ1 after 10,000 cycles
Isomeric organic ligand dominating polyoxometalate-based hybrid compounds: synthesis and as electrocatalysts and pH-sensitive probes
Isomeric organic ligand dominating polyoxometalate-based hybrid compounds: synthesis and as electrocatalysts and pH-sensitive probes
<p>By introducing isomeric organic ligands into polyoxometalate (POM) systems, two new POM-based hybrid compounds, [Cu<sub>6</sub>(<i>m</i>-pyttz)<sub>2</sub>(H<sub>2</sub>O)][HPMo<sub>12</sub>O<sub>40</sub>] (<b>1</b>) and [Ag<sub>3</sub>(<i>p</i>-H<sub>2</sub>pyttz)(<i>p</i>-Hpyttz)Cl][H<sub>2</sub>PMo<sub>12</sub>O<sub>40</sub>]·6H<sub>2</sub>O (<b>2</b>) (<i>m</i>-/<i>p</i>-H<sub>2</sub>pyttz = 3-(pyrid-3/4-yl)-5(1H-1,2,4-triazol-3-yl)-1,2,4-triazolyl), have been hydrothermally synthesized and characterized. Single-crystal structural analysis shows the <i>m</i>-pyttz ligands link Cu<sup>I</sup> ions to generate a two-dimensional layer with hanger-like rhombus, which is pillared by the PMo<sub>12</sub> anions in <b>1</b>. Compound <b>2</b> exhibits a three-dimensional supramolecular framework, in which PMo<sub>12</sub> anions are building blocks facilitating the extension of the whole structure. The influence of the coordination modes of <i>m</i>-/<i>p</i>-H<sub>2</sub>pyttz on the structures is discussed in detail. Furthermore, electrochemical properties of <b>1</b> and <b>2</b> have been studied and they display excellent electrocatalytic activities toward the reduction of nitrite and hydrogen peroxide and pH-dependent electrochemical behaviors.</p
Synthesis and polypyrrole-loading study of antifungal medicine fluconazole functionalized Keggin polyoxotungstates
<p>To rich the coordination polymer and polyoxometalate (POM) chemistry, two new hybrid compounds based on Keggin POMs with antifungal medicine fluconazole (Hfkz = [1-(2,4-difluorophenyl)-1,1-bis [(1H-1,2,4-triazol-1-yl)-methyl]methanol]), [Ag<sub>4</sub>(Hfkz)<sub>2</sub>][PW<sub>12</sub>O<sub>40</sub>] (AgFkzPW<sub>12</sub>) and [Ag<sub>4</sub>(Hfkz)<sub>2</sub>][SiW<sub>12</sub>O<sub>40</sub>] (AgFkzSiW<sub>12</sub>), have been successfully synthesized and structurally characterized. Moreover, to improve the photogenerated electron-hole pair separation properties, the surface of hybrid compounds was loaded by polypyrrole (PPy) through a chemical oxidation polymerization process <i>in situ</i> fabricating hybrid nanocomposites AgFkzPW<sub>12</sub>@PPy and AgFkzSiW<sub>12</sub>@PPy. As a result, the Hfkz molecules were successfully grafted onto the surface of the Keggin polyoxoanions, and their nanocomposites exhibit better photocatalytic activity than the respective matrix compounds under the irradiation of visible light.</p