University of Waterloo

About: University of Waterloo is a education organization based out in Waterloo, Ontario, Canada. It is known for research contribution in the topics: Population & Context (language use). The organization has 36093 authors who have published 93906 publications receiving 2948139 citations. The organization is also known as: UW & uwaterloo.

Understanding the Nature of Absorption/Adsorption in Nanoporous Polysulfide Sorbents for the Li–S Battery

Abstract: The possibility of achieving high-energy, long-life storage batteries has tremendous scientific and technological significance. A prime example is the Li–S cell, which can offer a 3–5-fold increase in energy density compared with conventional Li-ion cells, at lower cost. Despite significant recent advances, there are challenges to its wide-scale implementation. Upon sulfur reduction, intermediate soluble lithium polysulfides readily diffuse into the electrolyte, causing capacity fading and poor Coulombic efficiency in the cell. Herein, we increase the capacity retention and cycle life of the Li–S cell through the use of nanocrystalline and mesoporous titania additives as polysulfide reservoirs and examine the role of surface adsorption vs pore absorption. We find that the soluble lithium polysulfides are preferentially absorbed within the pores of the nanoporous titania at intermediate discharge/charge. This provides the major factor in stabilizing capacity although surface binding (adsorption) also plays...

Controlling the Spontaneous Emission of a Superconducting Transmon Qubit

Abstract: We present a detailed characterization of coherence in seven transmon qubits in a circuit QED architecture. We find that spontaneous emission rates are strongly influenced by far off-resonant modes of the cavity and can be understood within a semiclassical circuit model. A careful analysis of the spontaneous qubit decay into a microwave transmission-line cavity can accurately predict the qubit lifetimes over 2 orders of magnitude in time and more than an octave in frequency. Coherence times T1 and T_{2};{*} of more than a microsecond are reproducibly demonstrated.

Instantaneous and Quantitative Functionalization of Gold Nanoparticles with Thiolated DNA Using a pH-Assisted and Surfactant-Free Route

Abstract: The attachment of thiolated DNA to gold nanoparticles (AuNPs) has enabled many landmark works in nanobiotechnology. This conjugate chemistry is typically performed using a salt-aging protocol where, in the presence of an excess amount of DNA, NaCl is gradually added to increase DNA loading over 1–2 days. To functionalize large AuNPs, surfactants need to be used, which may generate difficulties for downstream biological applications. We report herein a novel method using a pH 3.0 citrate buffer to complete the attachment process in a few minutes. More importantly, it allows for quantitative DNA adsorption, eliminating the need to quantify the number of adsorbed DNA and allowing the adsorption of multiple DNAs with different sequences at predetermined ratios. The method has been tested for various DNAs over a wide range of AuNP sizes. Our work suggests a synergistic effect between pH and salt in DNA attachment and reveals the fundamental kinetics of AuNP aggregation versus DNA adsorption, providing a novel ...

Non‐Aqueous and Hybrid Li‐O2 Batteries

Abstract: With the increasing importance of electrified transport, the need for high energy density storage is also increasing. Possible candidates include Li-O2 batteries, which are the subject of rapidly increasing focus worldwide despite being in their infancy of understanding. This excitement owes to the high energy density of Li-O2 (up to 2-3 kWh kg−1), theoretically much higher compared to that of other rechargeable systems, and the open “semi-fuel” cell battery configuration that uses oxygen as the positive electrode material. To bring Li-O2 batteries closer to reality as viable energy storage devices, and to attain suitable power delivery, understanding of the underlying chemistry is essential. Several concepts have been proposed in the last year to account for the function and target future design of Li-O2 batteries and these are reviewed. An overview is given of the efforts to understand oxygen reduction/evolution and capacity limitations in these systems, and of electrode and electrolyte materials that are suitable for non-aqueous and hybrid (nonaqueous/aqueous) cells.