Effects of stress, defects, and layer composition on the development of corrosion features on protected silver mirrors.

The long-term environmental durability of protected silver mirror coatings is influenced by numerous factors. Here, accelerated environmental exposure testing of model silver mirror coatings illuminated the effects of stress, defects, and layer composition on the extent and mechanisms of corrosion and degradation. Experiments to reduce stress in the highest-stress layers of the mirror coatings revealed that, while stress may affect the extent of corrosion, coating defects and the composition of the mirror layers have the largest influence on corrosion feature development and growth.

Paper-based microfluidic devices for glucose assays employing a metal-organic framework (MOF).

This paper describes the development of two microfluidic paper-based analytical devices (µPADs), one well-based and the other based on a lateral flow assay (LFA) configuration, to detect glucose via a colorimetric assay using the solid metal-organic framework (MOF) Zr-PCN-222(Fe), to encapsulate glucose oxidase (GOx). The well-based platform consisted of laminate sheets and multiple layers of wax-printed chromatography paper. Solutions of KI and glucose placed into the well flowed through the device and reacted with the GOx@MOF species sandwiched between the paper layers realizing a yellow-brown color. The LFA platform consisted of chromatography paper between parafilm and polyvinyl acetate (PVA) layers. GOx@MOFs spotted on the paper subjected to solutions of KI and glucose yielded a brown color. The devices were then dried, scanned, and analyzed yielding a correlation between average inverse yellow intensity and glucose concentrations. The development of these devices employing MOFs as biomimetic catalysts should further expand the applications of microfluidic technologies for sensors a variety of analytes.

Chemistry of Singlet Oxygen with a Cadmium-Sulfur Cluster: Physical Quenching versus Photooxidation.

We investigated the chemistry of singlet oxygen with a cadmium-sulfur cluster, (Me4N)2[Cd4(SPh)10]. This cluster was used as a model for cadmium-sulfur nanoparticles. Such nanoparticles are often used in conjunction with photosensitizers (for singlet oxygen generation or dye-sensitized solar cells), and hence, it is important to determine if cadmium-sulfur moieties physically quench and/or chemically react with singlet oxygen. We found that (Me4N)2[Cd4(SPh)10] is indeed a very strong quencher of singlet oxygen with total rate constants for 1O2 removal of (5.8 ± 1.3) × 108 M-1 s-1 in acetonitrile and (1.2 ± 0.5) × 108 M-1 s-1 in CD3OD. Physical quenching predominates, but chemical reaction leading to decomposition of the cluster and formation of sulfinate is also significant, with a rate constant of (4.1 ± 0.6) × 106 M-1 s-1 in methanol. Commercially available cadmium-sulfur quantum dots ("lumidots") show similar singlet oxygen quenching rate constants, based on the molar concentration of the quantum dots.