Self-Assembled Monolayers for Improved Charge Injection of Silver Back Electrodes in Inverted Organic Electronic Devices.

Self-assembled monolayers (SAMs) formed from thiol compounds bound to Ag and Au electrodes have been used as an important strategy in improving the stability and efficiency of optoelectronic devices. Thiol compounds provide only one binding site with the metal electrode which limits their influence. Dithiolane/dithiol compounds can provide multiple binding sites and could be useful in enhancing the performance of the device. In this study, inverted organic semiconducting hole-only devices were fabricated by using Ag back electrodes in conjunction with SAMs formed from disulfide lipoic acid-based compounds and were compared to a long aliphatic chain thiol. The binding and the electronic properties as well as electrical characteristics of the SAMs on silver were studied to look at the influence of their structure on charge injection in the organic semiconductor devices. It was found that the SAMs formed with (±)-α-lipoic acid, isolipoic acid, and (±)-4-phenylbutyl 5-(1,2-dithiolan-3-yl) pentanoate significantly improved the charge injection by either changing the work function of the Ag or altering the physical interaction between the polymer and the metal surface. This study may lead to an understanding of how the nature of the functional groups of the SAM and the number of bonds formed between each SAM molecule and the metal electrode influence the contact resistance and the performance of organic semiconductor devices.

Optical Biosensors for Virus Detection: Prospects for SARS-CoV-2/COVID-19.

The recent pandemic of the novel coronavirus disease 2019 (COVID-19) has caused huge worldwide disruption due to the lack of available testing locations and equipment. The use of optical techniques for viral detection has flourished in the past 15 years, providing more reliable, inexpensive, and accurate detection methods. In the current minireview, optical phenomena including fluorescence, surface plasmons, surface-enhanced Raman scattering (SERS), and colorimetry are discussed in the context of detecting virus pathogens. The sensitivity of a viral detection method can be dramatically improved by using materials that exhibit surface plasmons or SERS, but often this requires advanced instrumentation for detection. Although fluorescence and colorimetry lack high sensitivity, they show promise as point-of-care diagnostics because of their relatively less complicated instrumentation, ease of use, lower costs, and the fact that they do not require nucleic acid amplification. The advantages and disadvantages of each optical detection method are presented, and prospects for applying optical biosensors in COVID-19 detection are discussed.

Identification of the local electrical properties of crystalline and amorphous domains in electrochemically doped conjugated polymer thin films.

Doped polymer thin films have several applications in electronic, optoelectronic and thermoelectric devices. Often the electrical properties of doped conjugated polymer thin films are affected by their local physical and mechanical characteristics. However, investigations into the effects of doping on local domain properties have not been carried out. Here, we study the physical, mechanical and optical properties of electrochemically doped P3HT thin films at the nanoscale and establish a relation between doping level and the physical properties of P3HT thin films. Bulk crystallinity of both pristine and doped P3HT thin films, characterized using grazing incidence X-ray diffraction, shows a clear loss in crystallinity upon doping. Nanoscale crystalline and amorphous domains in the films are visualized by multimode atomic force microscopy (AFM). It is apparent that the crystalline domains are most affected by doping and have a higher degree of doping compared to amorphous domains. This results in crystalline domains exhibiting superior electrical conductivity at a local level. These results are further supported by Raman mapping and elemental analysis of doped films. A direct relation is established between the physical, mechanical and electrical properties of doped P3HT thin films based on the AFM data. The findings demonstrate that higher dopant concentrations are found in crystalline domains compared to amorphous domains, which has not been shown before to the best of our knowledge. This study can be used to optimize the electronic properties of doped P3HT thin films for use in electronic and optoelectronic device applications.

A versatile LC-MS/MS approach for comprehensive, quantitative analysis of central metabolic pathways.

Liquid chromatography-mass spectrometry (LC-MS/MS) based approaches are widely used for the identification and quantitation of specific metabolites, and are a preferred approach towards analyzing cellular metabolism. Most methods developed come with specific requirements such as unique columns, ion-pairing reagents and pH conditions, and typically allow measurements in a specific pathway alone. Here, we present a single column-based set of methods for simultaneous coverage of multiple pathways, primarily focusing on central carbon, amino acid, and nucleotide metabolism. We further demonstrate the use of this method for quantitative, stable isotope-based metabolic flux experiments, expanding its use beyond steady-state level measurements of metabolites. The expected kinetics of label accumulation pertinent to the pathway under study are presented with some examples. The methods discussed here are broadly applicable, minimize the need for multiple chromatographic resolution methods, and highlight how simple labeling experiments can be valuable in facilitating a comprehensive understanding of the metabolic state of cells.