Solution-processed n-type organic field-effect transistors (OFETs) are essential elements for developing large-area, low-cost, and all organic logic/complementary circuits. Nonetheless, the development of air-stable n-type organic semiconductors (OSCs) lags behind their p-type counterparts. The trapping of electrons at the semiconductor-dielectric interface leads to a lower performance and operational stability. Herein, we report printed small-molecule n-type OFETs based on a blend with a binder polymer, which enhances the device stability due to the improvement of the semiconductor-dielectric interface quality and a self-encapsulation. Both combined effects prevent the fast deterioration of the OSC. Additionally, a complementary metal-oxide semiconductor-like inverter is fabricated depositing p-type and n-type OSCs simultaneously.

Chemical kinetic experiments to determine rate laws are common in high school and college chemistry courses. For reactions involving a color change, rate laws can be determined experimentally using spectrophotometric or colorimetric equipment though this equipment can be cost prohibitive. Previous work demonstrated that inexpensive handheld camera devices can be used to quantify the concentration of a colored analyte in solution. This paper extends this approach to the kinetic study of the color fading of crystal violet upon reaction with sodium hydroxide. The results demonstrate accurate determination of the reaction order, with respect to crystal violet, using a method accessible in many high school and college laboratories. M ost high school and college students have some practical knowledge about speeds of reactions before taking a chemistry course. For example, students understand that foods cook faster at higher temperature. This knowledge is supported and extended by the study of chemical kinetics. While studying kinetics, students learn that rate laws for chemical reactions can only be determined experimentally. Experiments suitable for exploration of kinetic concepts are essential for building connections to the curriculum. Rate laws can be determined by measuring initial rates or monitoring concentration over time.Monitoring changes in concentration of a colored analyte in solution can be accomplished through spectrophotometry or colorimetry. Traditional equipment used for these measurements can cost hundreds to thousands of dollars per instrument; many high schools do not have the financial means to purchase such instrumentation. Recently, Kehoe and Penn published a method for performing quantitative colorimetry using handheld camera devices. 1 Their work demonstrated suitable precision and accuracy; thus, quantitative colorimetry can be performed even in the absence of traditional equipment.Crystal violet, an intensely violet-colored triphenylmethane dye, reacts with hydroxide ions in aqueous solution to form a colorless compound (Scheme 1). For years, this reaction has been successfully used as a lab exercise for the experimental determination of a rate law. 2,3 A large excess of sodium hydroxide relative to crystal violet is used, which means that the reaction's rate depends only on the concentration of crystal violet. Analytical spectrophotometry or colorimetry is performed at specified time intervals. Students monitor the concentration of crystal violet, which fades over time, by Scheme 1. Reaction Scheme between Crystal Violet and Hydroxide Ions a a Structures (a) and (b) are two resonance structures of crystal violet before the reaction, and structure (c) is the colorless product of the reaction.Laboratory Experiment pubs.acs.org/jchemeduc

Spectrophotometry and colorimetry experiments are common in high school and college chemistry courses, and nanotechnology is increasingly common in every day products and new devices. Previous work has demonstrated that handheld camera devices can be used to quantify the concentration of a colored analyte in solution in place of traditional spectrophotometric or colorimetric equipment. This paper extends this approach to quantifying the concentration of gold nanoparticles in a colloidal gold "dietary supplement". With the addition of free Google applications, the investigation provides a feasible, sophisticated lab experience and introduction to nanotechnology.

The lack of long-term stability in thin films of organic semiconductors can often be caused by the low structural stability of metastable phases that are frequently formed upon deposition on a substrate surface. Here, thin films of 2,7-dioctyloxy[1]benzothieno[3,2-b]benzothiophene (C 8 O-BTBT-OC 8) and blends of this material with polystyrene by solution shearing are fabricated. Both types of films exhibit the metastable surface-induced herringbone phase (SIP) in all the tested coating conditions. The blended films reveal a higher device performance with a field-effect mobility close to 1 cm 2 V −1 s −1 , a threshold voltage close to 0 V, and an on/off current ratio above 10 7. In situ lattice phonon Raman microscopy is used to study the stability of the SIP polymorph. It is found that films based on only C 8 O-BTBT-OC 8 slowly evolve to the Bulk cofacial phase, significantly impacting device electrical performance. In contrast, the blended films stabilize the SIP phase, leading to devices that maintain a high performance over 1.5 years. This work demonstrates that blending small-molecule organic semiconductors with insulating binding polymers can trap metastable polymorphs, which can lead to devices with both improved performance and long-term stability.

A compact and planar donor-acceptor molecule 1 comprising tetrathiafulvalene (TTF) and benzothiadiazole (BTD) has been synthesised and experimentally characterised by structural, optical and electrochemical methods. Solution processed and thermally evaporated thin films of 1 have also been explored as active material in organic field-effect transistors (OFETs). For these devices, a hole field-effect mobility of FE = (1.3 ± 0.5) ×10-3 cm 2 /Vs and of FE = (2.7 ± 0.4) ×10 -3 cm 2 /Vs could be determined for the solution processed and thermally evaporated thin films, respectively. An intense intramolecular charge-transfer (ICT) transition around 495 nm dominates the optical absorption spectrum of the neutral dyad, which also shows a weak emission from its ICT state. The iodine induced oxidation of 1 leads to a partially oxidised crystalline charge-transfer (CT) salt {(1) 2 I 3 }, and eventually also to a fully oxidized compound {1I 3 } ½I 2 .Single crystals of the former CT compound, exhibiting a highly symmetrical crystal structure, reveal a fairly good room temperature electrical conductivity of the order of 2 S cm -1 . The one-dimensional spin system bears compactly bonded BTD acceptors (spatial localisation of LUMO) along its ridge.

A novel sensing scheme is exemplified through the detection of ricin B-chain (RBC) in water and liquid food matrices: surface-enhanced Raman spectroscopy (SERS) coupled with an N-acetyl-galactosamine glycopolymer capture layer. The sensing scheme’s detection limit was well below that of the predicted oral exposure limit. Theoretical predictions of the normal Raman spectrum of the glycomonomer give insight into polymer–RBC intermolecular interactions.

Microfluidic sensing platforms facilitate parallel, low sample volume detection using various optical signal transduction mechanisms. Herein, we introduce a simple mixing microfluidic device, enabling serial dilution of introduced analyte solution that terminates in five discrete sensing elements. We demonstrate the utility of this device with on-chip fluorescence and surface-enhanced Raman scattering (SERS) detection of analytes, and we demonstrate device use both when combined with a traditional inflexible SERS substrate and with SERS-active nanoparticles that are directly incorporated into microfluidic channels to create a flexible SERS platform. The results indicate, with varying sensitivities, that either flexible or inflexible devices can be easily used to create a calibration curve and perform a limit of detection study with a single experiment.

Surface-based sensors that rely on diffusion for transport of target molecules to the sensor surface can lead to long and sometimes impractical detection time for low analyte concentrations. Here we describe a new method for rapid in situ SERS detection of ultralow subpicomolar concentration of the analyte molecules. The method is based upon a dynamic dielectrophoresis-enabled assembly of metal nanoparticles in the form of pearl chains with nanometer-sized gaps. We demonstrate in situ SERS measurement of benzenethiol in less than 2 min without the requirement of long incubation times. This approach is then extended to detect the biological analyte, adenine, at femtomolar concentrations in a short time from a 2 μL sample droplet.