Simple Disposable Odor Identification Tests for Predicting SARS-CoV-2 Positivity.

Olfactory dysfunction (OD) is a common manifestation of COVID-19 and may be useful for screening. Survey-based olfactory evaluation tends to underestimate the prevalence of OD, while psychophysical olfactory testing during a pandemic has the disadvantage of being time consuming, expensive, and requiring standardized laboratory settings. We aimed to develop a quick, simple, affordable, and reliable test to objectively assess the prevalence and diagnostic accuracy of OD in COVID-19.

Chemically transformed monolayers on acene thin films for improved metal/organic interfaces.

Anhydride terminated acene thin films were chemically transformed to thiol or carboxylic acid functionalities, groups heretofore incompatible with monolayer reactions. The molecular surface imparts large rate acceleration when imides are formed, while disfavored disulfides can be formed from the thiols. The modified surface imparts improved adhesion to top metal contacts in flexible/bendable applications.

Reaction induced morphology changes of tetracene and pentacene surfaces.

Morphology plays a critical role in determining the properties of solid-state molecular materials, yet fluctuates wildly as these materials undergo reaction. A prototypical system, a vapor-solid Diels-Alder reaction of tetracene and pentacene thin-films, is used to observe the evolution of morphology features as the reaction transitions from surface to bulk. The initial stages of reaction display little topographical change as measured by atomic force microscopy (AFM) and scanning electron microscopy (SEM), and substrates are coated with a uniform layer of product 1-2 molecules thick, as determined by energy-dispersive X-ray (EDX) spectroscopy.

Solid state and surface effects in thin-film molecular switches.

Thin-films of three dihydroindolizine molecular switches were monitored via polarization modulation infrared reflection absorption spectroscopy to quantify solid state and surface-based inhibition of switching as a function of irradiation time. In the solid state, the molecular switches diverged dramatically with flexible alkyl substituents resulting in switching rates up to three times that of switches containing rigid analogs. For thin-films, decreasing film thickness from 30 nm to approximately 4 molecules thick resulted in an increase in inhibition.

Substituent parameters impacting isomer composition and optical properties of dihydroindolizine molecular switches.

In an attempt to understand which factors influence constitutional isomer control of 6'- and 8'-substituted dihydroindolizines (DHIs), a series of asymmetric pyridines was condensed with dimethyl spiro[cycloprop[2]ene-1,9'-fluorene]-2,3-dicarboxylate. The substituents on the pyridial derivatives ranged from donating to withdrawing and demonstrated control over the isomeric ratios for all DHIs. Substituent control proved to be selective for the highly donating amino, which exclusively formed the 8' isomer.

Functionalization of organic semiconductor crystals via the Diels-Alder reaction.

A surface adlayer is generated on organic single crystals (tetracene and rubrene) using the site specific Diels-Alder reaction and a series of vapor phase dienophiles. X-ray photoelectron spectroscopy (XPS) confirms adsorption on the surfaces of tetracene and rubrene and mass spectrometry demonstrates the reaction's applicability to a range of dienophiles.

High-density amine-terminated monolayers formed on fluorinated CVD-grown graphene.

There has been considerable interest in chemically functionalizing graphene films to control their electronic properties, to enhance their binding to other molecules for sensing, and to strengthen their interfaces with matrices in a composite material. Most reports to date have largely focused on noncovalent methods or the use of graphene oxide. Here, we present a method to activate CVD-grown graphene sheets using fluorination followed by reaction with ethylenediamine (EDA) to form covalent bonds.

Assembly of nanorods into designer superstructures: the role of templating, capillary forces, adhesion, and polymer hydration.

The assembly mechanism by which hundreds of thousands of two-segment gold-polypyrrole nanorods are assembled into kinetically controlled shape-directed superstructures is examined to predict the range of nanoparticle sizes and materials that can be utilized in their formation. Four processes are responsible for assembly: templating, capillary force assembly, adhesion, and polymer hydration. It is shown that templating, where rods are prepositioned for assembly, is scale invariant and that the energy-minimized state after this step is highly disordered.

Actuation of self-assembled two-component rodlike nanostructures.

A model for predicting the effects of stimuli-induced contraction of the polypyrrole ends of two-segment gold-polypyrrole nanorods on their assembly into curved superstructures is presented. The model and experimental data presented here show that small changes (ca. 3%) in the diameter of the polypyrrole segment of each rod will induce dramatic changes (up to 20%) in the radii of the resulting superstructures, providing a convenient means for actuating their opening and closing.

Simultaneous measurements of electronic conduction and Raman response in molecular junctions.

Electronic conduction through single molecules is affected by the molecular electronic structure as well as by other information that is extremely difficult to assess, such as bonding geometry and chemical environment. The lack of an independent diagnostic technique has long hampered single-molecule conductance studies. We report simultaneous measurement of the conductance and the Raman spectra of nanoscale junctions used for single-molecule electronic experiments.

Electrochemical origin of voltage-controlled molecular conductance switching.

We have studied electron transport in bipyridyl-dinitro oligophenylene-ethynelene dithiol (BPDN) molecules both in an inert environment and in aqueous electrolyte under potential control, using scanning tunneling microscopy. Current-voltage (IV) data obtained in an inert environment were similar to previously reported results showing conductance switching near 1.6 V.

Three-terminal devices to examine single-molecule conductance switching.

We report electronic transport measurements of single-molecule transistor devices incorporating bipyridyl-dinitro oligophenylene-ethynylene dithiol (BPDN-DT), a molecule known to exhibit conductance switching in other measurement configurations. We observe hysteretic conductance switching in 8% of devices with measurable currents and find that dependence of the switching properties on gate voltage is rare when compared to other single-molecule transistor devices. This suggests that polaron formation is unlikely to be responsible for switching in these devices.

Controlling charge injection in organic field-effect transistors using self-assembled monolayers.

We have studied charge injection across the metal/organic semiconductor interface in bottom-contact poly(3-hexylthiophene) (P3HT) field-effect transistors, with Au source and drain electrodes modified by self-assembled monolayers (SAMs) prior to active polymer deposition. By using the SAM to engineer the effective Au work function, we markedly affect the charge injection process. We systematically examine the contact resistivity and intrinsic channel mobility and show that chemically increasing the injecting electrode work function significantly improves hole injection relative to untreated Au electrodes.

Neutral complexes of first row transition metals bearing unbound thiocyanates and their assembly on metallic surfaces.

A series of transition metal coordination complexes designed to assemble on gold surfaces was synthesized, their electronic structure and transitions analyzed, and their magnetic properties studied. By taking advantage of recently developed thiocyanate assembly protocols, these molecules were then assembled onto a gold surface, without the need for an inert atmosphere, to give a loosely packed monolayer. The assembled molecules exhibit properties similar to that of the bulk molecules, indicating little change in molecular structure outside of chemisorption.

Molecular engineering and measurements to test hypothesized mechanisms in single molecule conductance switching.

Six customized phenylene-ethynylene-based oligomers have been studied for their electronic properties using scanning tunneling microscopy to test hypothesized mechanisms of stochastic conductance switching. Previously suggested mechanisms include functional group reduction, functional group rotation, backbone ring rotation, neighboring molecule interactions, bond fluctuations, and hybridization changes. Here, we test these hypotheses experimentally by varying the molecular designs of the switches; the ability of the molecules to switch via each hypothetical mechanism is selectively engineered into or out of each molecule.

Kondo resonances and anomalous gate dependence in the electrical conductivity of single-molecule transistors.

We report Kondo resonances in the conduction of single-molecule transistors based on transition metal coordination complexes. We find Kondo temperatures in excess of 50 K, comparable to those in purely metallic systems. The observed gate dependence of the Kondo temperature is inconsistent with observations in semiconductor quantum dots and a simple single-dot-level model.

Inelastic electron tunneling via molecular vibrations in single-molecule transistors.

In single-molecule transistors, we observe inelastic cotunneling features that correspond energetically to vibrational excitations of the molecule, as determined by Raman and infrared spectroscopy. This is a form of inelastic electron tunneling spectroscopy of single molecules, with the transistor geometry allowing in situ tuning of the electronic states via a gate electrode. The vibrational features shift and change shape as the electronic levels are tuned near resonance, indicating significant modification of the vibrational states.

Spontaneous assembly of organic thiocyanates on gold sufaces. Alternative precursors for gold thiolate assemblies.

Thiolate self-assembly on gold has proven to be a valuable technique for assembling monolayers on a wide variety of substrates. However, the oxidative instability of the thiols, especially aromatic thiols and alpha,omega-dithiols, presents several difficulties. Shown here is that thiocyanates, easily synthesized stable thiol derivatives, can be directly assembled on gold surfaces with no auxiliary reagents required.

[Analysis of fenoterol efficacy given as an aerosol using various mouth pieces].

The effect of different mouth pieces on efficacy of fenoterol was studied in 40 patients with atopic and non-atopic bronchial asthma with reversible bronchial constriction. Four devices were studied: standard MDI unit, MDI unit with Boehringer and Astra mouth pieces, MDI unit with spacer. PEF values were registered 7 hours following inhalation.

[Gold salts in the treatment of bronchial asthma].

Gold salts are used mainly in the therapy of rheumatoid diseases. Thanks to their immunoregulative and antiinflammatory properties they may be used in treatment of chronic bronchial asthma. In order to study the efficacy of gold salts in such therapy the authors studied the effect of Solganal B (Schering) in 8 patients with chronic steroid dependent bronchial asthma.