Genetic Exponentially Fitted Method for Solving Multi-dimensional Drift-diffusion Equations

A general approach was proposed in this article to develop high-order exponentially fitted basis functions for finite element approximations of multi-dimensional drift-diffusion equations for modeling biomolecular electrodiffusion processes. Such methods are highly desirable for achieving numerical stability and efficiency. We found that by utilizing the one-one correspondence between continuous piecewise polynomial space of degree $k+1$ and the divergence-free vector space of degree $k$, one can construct high-order 2-D exponentially fitted basis functions that are strictly interpolative at a selected node set but are discontinuous on edges in general, spanning nonconforming finite element spaces. First order convergence was proved for the methods constructed from divergence-free Raviart-Thomas space $RT_0^0$ at two different node set

Retail Clerks International Protective Association, Local 872 (1936)

Improved methods for quickly identifying neutral organic compounds and differentiation of analytes with similar chemical structures are widely needed. We report a new approach to effectively “fingerprint” neutral organic molecules by using ¹⁹F NMR and molecular containers. The encapsulation of analytes induces characteristic up- or downfield shifts of ¹⁹F resonances that can be used as multidimensional parameters to fingerprint each analyte. The strategy can be achieved either with an array of fluorinated receptors or by incorporating multiple nonequivalent fluorine atoms in a single receptor. Spatial proximity of the analyte to the ¹⁹F is important to induce the most pronounced NMR shifts and is crucial in the differentiation of analytes with similar structures. This new scheme allows for the precise and simultaneous identification of multiple analytes in a complex mixture

An Organocobalt–Carbon Nanotube Chemiresistive Carbon Monoxide Detector

A chemiresistive detector for carbon monoxide was created from single-walled carbon nanotubes (SWCNTs) by noncovalent modification with diiodo(η⁵:η¹-1-[2-(N,N-dimethylamino)ethyl]-2,3,4,5-tetramethylcyclopentadienyl)-cobalt(III) ([Cp[superscript ∧]CoI₂]), an organocobalt complex with an intramolecular amino ligand coordinated to the metal center that is displaced upon CO binding. The unbound amino group can subsequently be transduced chemiresistively by the SWCNT network. The resulting device was shown to have a ppm-level limit of detection and unprecedented selectivity for CO gas among CNT-based chemiresistors. This work, the first molecular-level mechanistic elucidation for a CNT-based chemiresistive detector for CO, demonstrates the efficacy of using an analyte’s reactivity to produce another chemical moiety that is readily transduced as a strategy for the rational design of chemiresistive CNT-based detectors.National Science Foundation (U.S.) (DMR-1410718)National Science Foundation (U.S.) (1122374

Distinct Interfacial Fluorescence in Oil-in-Water Emulsions via Exciton Migration of Conjugated Polymers

Commercial dyes are extensively utilized to stain specific phases for the visualization applications in emulsions and bioimaging. In general, dyes emit only one specific fluorescence signal and thus, in order to stain various phases and/or interfaces, one needs to incorporate multiple dyes and carefully consider their compatibility to avoid undesirable interactions with each other and with the components in the system. Herein, surfactant‐type, perylene‐endcapped fluorescent conjugated polymers that exhibit two different emissions are reported, which are cyan in water and red at oil–water interfaces. The interfacially distinct red emission results from enhanced exciton migration from the higher‐bandgap polymer backbone to the lower‐bandgap perylene endgroup. The confocal microscopy images exhibit the localized red emission exclusively from the circumference of oil droplets. This exciton migration and dual fluorescence of the polymers in different physical environments can provide a new concept of visualization methods in many amphiphilic colloidal systems and bioimaging.National Science Foundation (U.S.) (National Science Foundation DMR‐1410718

Synthesis of 3,4-Bis(benzylidene)cyclobutenes

The syntheses of several derivatives of 3,4-bis(benzylidene)cyclobutene are reported. Previously unknown 1,2-dibromo-3,4-bis(benzylidene)cyclobutene was obtained through in situ generation of 1,6-diphenyl-3,4-dibromo-1,2,4,5-tetraene followed by electrocyclic ring closure. Ensuing reduction and metal-catalyzed cross-coupling provided additional derivatives. The effects of ring strain on the geometry and electronics of these derivatives were examined by X-ray crystallography and ¹H NMR spectroscopy, respectively.National Science Foundation (U.S.)United States. Army Research OfficeMassachusetts Institute of Technology. Institute for Soldier Nanotechnologie

Single-Walled Carbon Nanotube–Metalloporphyrin Chemiresistive Gas Sensor Arrays for Volatile Organic Compounds

National Science Foundation (U.S.) (DMR-1410718)National Science Foundation (U.S.) (1122374)Massachusetts Institute of Technology. Institute for Soldier NanotechnologiesUnited States. Defense Advanced Research Projects Agency (W911NF-14-1-0087

The Synthesis of Azaperylene-9,10-dicarboximides

The syntheses of two azaperylene 9,10-dicarboximides are presented. 1-Aza- and 1,6-diazaperylene 9,10-dicarboximides containing a 2,6-diisopropylphenyl substituent at the N-imide position were synthesized in two steps starting from naphthalene and isoquinoline derivatives

High internal free volume compositions for low-k dielectric and other applications

The present invention provides materials, devices, and methods involving new heterocyclic, shape-persistent monomeric units with internal free volume. In some cases, materials the present invention may comprise monomers, oligomers, or polymers that incorporate a heterocyclic, shape-persistent iptycene. The present invention may provide materials having low dielectric constants and improved stability at high operating temperatures due to the electron-poor character of materials. In addition, compositions of the invention may be easily synthesized and readily modified to suit a particular application

Chemiresistive Sensor Arrays from Conductive 2D Metal–Organic Frameworks

Applications of porous metal–organic frameworks (MOFs) in electronic devices are rare, owing in large part to a lack of MOFs that display electrical conductivity. Here, we describe the use of conductive two-dimensional (2D) MOFs as a new class of materials for chemiresistive sensing of volatile organic compounds (VOCs). We demonstrate that a family of structurally analogous 2D MOFs can be used to construct a cross-reactive sensor array that allows for clear discrimination between different categories of VOCs. Experimental data show that multiple sensing mechanisms are operative with high degrees of orthogonality, establishing that the 2D MOFs used here are mechanistically unique and offer advantages relative to other known chemiresistor materials.Camille & Henry Dreyfus Foundation. Postdoctoral Program in Environmental ChemistrAlfred P. Sloan FoundationResearch Corporation for Science Advancement3M CompanyNational Science Foundation (U.S.). Graduate Research Fellowship Program (Grant 1122374)Massachusetts Institute of Technology. Institute for Soldier Nanotechnologie

Redox Switchable Thianthrene Cavitands

A redox activated vase-to-kite conformational change is reported for a new resorcinarene-based cavitand appended with four quinoxaline-fused thianthrene units. In its neutral state, the thianthrene-containing cavitand was shown by 1H NMR to adopt a closed vase conformation. Upon oxidation the electrostatic repulsion among the thianthrene radical cations promotes a kite conformation in the thianthrene-containing cavitand. The addition of acid produced a shoulder feature below 300 nm in the cavitand’s UV-Vis spectrum that we have assigned to the vase-to-kite conformation change. UV-Vis spectroelectrochemical studies of the cavitand revealed a development of a similar shoulder peak consistent with the oxidation-induced vase-to-kite conformation change. To support that the shoulder peak is diagnostic for a vase-to-kite conformation change, a model molecule constituting a single quinoxaline wall of the cavitand was synthesized and studied. As expected UV-Vis spectroelectrochemical studies of the cavitand arm did not display a shoulder peak below 300 nm. The oxidation-induced vase-to-kite conformation is further confirmed by the distinctive upfield shift in 1H chemical shift of the methine signal. Key words: redox active, thianthrene, resorcinarene cavitands, electrochemical switching, conformation changeNational Science Foundation (U.S.). Center for Energy Efficient Electronics Science (Award ECCS0939514)Singapore. Agency for Science, Technology and Research (Graduate Scholarship