Search for: All records

Hypervalent iodine compounds are a widely used class of metal-free oxidants that find application in organic synthesis. Due to the homology between the reactivity of hypervalent iodine and many transition metals ¾ oxidative addition, ligand exchange, and reductive elimination can be facile for both ¾ hypervalent iodine species find application in a variety of synthetically important organic transformations. Major limitations of these reagents include the frequent need for (super)stoichiometric loading and the intrinsically poor atom economy that results from the generation of stoichiometric quantities of iodoarene byproducts. In addition, hypervalent iodine reagents are often synthesized using metal-based terminal oxidants, which compound the resulting waste stream. Recently, substantial progress has been made to address these limitations. Here, we discuss progress towards sustainable synthetic methods for the preparation of hypervalent iodine compounds and application of those methods in the context of hypervalent iodine catalysis. The discussion is organized according to the active oxygen content, and thus atom economy, of the terminal oxidant employed. Hypervalent iodine electrochemistry and the development of recyclable iodoarenes are also discussed. 

Diatoms are a group of single-celled photosynthetic algae that use biochemical pathways to bio-mineralize and self-assemble three-dimensional photonic crystals with unique photonic and micro- & nano-fluidic properties. In recent years, diatom biosilica has been used in surface-enhanced Raman scattering (SERS) based optofluidic sensors for detection of a variety of chemical and biological molecules. In this paper, we present a study to develop a microfluidic pumping system using super-hydrophilic diatom thin films. The desire to develop such a system stems from the requirement to create a low-cost, self-powered microfluidic pumping system that can sustain a continuous flow over an extended period of time. The diatom biosilica acts not only as the driving force behind the flow, but also serves as ultra-sensitive SERS substrates that allows for trace detection of various molecules. Liquid is drawn from a reservoir to the tip of a 150μm inner diameter capillary tube positioned directly over the diatom film. A thin and long horizontal reservoir is used to prevent flooding on the diatom film when the liquid is initially drawn to the diatom film through a capillary tube from the reservoir. The connection of the meniscus from the capillary to the film was maintained from a horizontal reservoir for a recorded time of 20 hours and 32 minutes before the partially filled reservoir emptied. Flow rates of 0.38, 0.22 and 0.16µL/min were achieved for square biosilica thin films of 49mm2, 25mm2, and 9mm2 at a temperature of 63̊F and 45% relative humidity respectively. A temperature-controlled system was introduced for the 49mm2 substrate and flow rates of 0.60, 0.82, 0.93, and 1.15µL/min were observed at 72, 77, 86, and 95̊F at 21% relative humidity respectively. More testing and analysis will be performed to test the operation limits of the proposed self-powered microfluidic system. 

Tissue biopsy evaluation in the clinic is in need of quantitative disease markers for diagnosis and, most importantly, prognosis. Among the new technologies, quantitative phase imaging (QPI) has demonstrated promise for histopathology because it reveals intrinsic tissue nanoarchitecture through the refractive index. However, a vast majority of past QPI investigations have relied on imaging unstained tissues, which disrupts the established specimen processing. Here we present color spatial light interference microscopy (cSLIM) as a new whole-slide imaging modality that performs interferometric imaging on stained tissue, with a color detector array. As a result, cSLIM yields in a single scan both the intrinsic tissue phase map and the standard color bright-field image, familiar to the pathologist. Our results on 196 breast cancer patients indicate that cSLIM can provide stain-independent prognostic information from the alignment of collagen fibers in the tumor microenvironment. The effects of staining on the tissue phase maps were corrected by a mathematical normalization. These characteristics are likely to reduce barriers to clinical translation for the new cSLIM technology.