Correlating three-dimensional morphology with function in PBDB-T:IT-M non-fullerene organic solar cells

In this work, the correlation between three‐dimensional morphology and device performance of PBDB‐T:IT‐M non‐fullerene organic solar cells is investigated. We found that a PBDB‐T‐rich top layer formed when the PBDB‐T:IT‐M film is cast on PEDOT:PSS, indicating a vertical component distribution that will hinder electron transport toward the cathode in a conventional device. This PBDB‐T‐rich top layer remained upon low‐temperature annealing at 80 °C, but disappeared when the annealing temperature is raised, resulting in an optimum annealing temperature of 160 °C for conventional devices as the removal of this polymer‐rich layer facilitates electron transport toward the top cathode layer. The PBDB‐T‐rich layer is also found in the surface region of the PBDB‐T:IT‐M film cast on a TiO2 substrate, but in this case it remained after thermal annealing at 80 or 160 °C, leading to a favorable vertical stratification for efficient charge collection in inverted devices. Although thermal annealing can enhance the crystallinity of PBDB‐T:IT‐M blend and lead to improved charge mobility, the correlation length of the PBDB‐T component increased excessively under annealing at 160 °C. Further, the packing of IT‐M clusters became loose upon high temperature annealing, an effect we believe results in more diffuse interfaces with PBDB‐T that result in reduced charge separation efficiency, consequently reducing the short‐circuit current in the inverted devices

Macrophage fumarate hydratase restrains mtRNA-mediated interferon production

Metabolic rewiring underlies the effector functions of macrophages1-3, but the mechanisms involved remain incompletely defined. Here, using unbiased metabolomics and stable isotope-assisted tracing, we show that an inflammatory aspartate-argininosuccinate shunt is induced following lipopolysaccharide stimulation. The shunt, supported by increased argininosuccinate synthase (ASS1) expression, also leads to increased cytosolic fumarate levels and fumarate-mediated protein succination. Pharmacological inhibition and genetic ablation of the tricarboxylic acid cycle enzyme fumarate hydratase (FH) further increases intracellular fumarate levels. Mitochondrial respiration is also suppressed and mitochondrial membrane potential increased. RNA sequencing and proteomics analyses demonstrate that there are strong inflammatory effects resulting from FH inhibition. Notably, acute FH inhibition suppresses interleukin-10 expression, which leads to increased tumour necrosis factor secretion, an effect recapitulated by fumarate esters. Moreover, FH inhibition, but not fumarate esters, increases interferon-β production through mechanisms that are driven by mitochondrial RNA (mtRNA) release and activation of the RNA sensors TLR7, RIG-I and MDA5. This effect is recapitulated endogenously when FH is suppressed following prolonged lipopolysaccharide stimulation. Furthermore, cells from patients with systemic lupus erythematosus also exhibit FH suppression, which indicates a potential pathogenic role for this process in human disease. We therefore identify a protective role for FH in maintaining appropriate macrophage cytokine and interferon responses

Tunable diode laser spectroscopy with wavelength modulation : calibration-free measurements of gas compositions at elevated temperatures and varying pressure

The validity of two new approaches to tunable diode laser spectroscopy (TDLS) in the near-IR, namely the residual amplitude modulation approach and the phasor decomposition method, is investigated for application in industrial process monitoring where the operating temperatures and pressures are high and subject to significant change. Both techniques allow the recovery of absolute absorption profile line shapes and are completely calibration free, making them very attractive for online deployment in stand alone instrumentation in harsh environments where the calibration factors in conventional TDLS methods are subject to significant cumulative errors and drift. Currently established TDLS techniques, and indeed conventional gas composition analysis techniques, suffer from significant limitations when applied under these conditions, and there is a clear need for the development of a suitable alternative. The primary focus in this work is the analysis of water vapor in solid oxide fuel cell diagnostics where the operating temperatures range from 700 degrees C to 950 degrees C, the gas pressures are subject to change and the recovered signal levels are low. The 1391.7 nm overtone water vapor transition is interrogated over the above temperature range of interest at concentrations of 6%-50%, while the 1650.96 nm methane transition is also analyzed over a range of gas pressures at a fixed concentration of 1%. Excellent agreement between the experimentally recovered absorption line shapes and simulations based on parameters from the HITRAN (2004) database is observed; further evidence for the efficacy of the techniques is demonstrated through the accuracy of the gas concentration measurements which were achieved by curve-fitting absorption line shape simulations to the experimental data

Calibration free gas composition measurements for industrial process control using a phasor decomposition approach to tunable diode laser spectroscopy

This paper discusses calibration free gas composition measurements for industrial process control using a phasor decomposition approach to tunable diode laser spectroscopy

Calibration free, optical measurements of gas composition for industrial process control in harsh environments

Paper describing research into calibration free and optical measurements of gas composition for industrial process control in harsh environments

Tunable diode laser spectroscopy with wavelength modulation : a calibration-free approach to the recovery of absolute gas absorption line-shapes

The principles and implementation of an alternative approach to tunable diode-laser spectroscopy with wavelength modulation are described. This new technique uses the inherent phase shift between diode-laser power modulation and frequency modulation to separate the residual amplitude modulation and the first derivative signals recovered at the fundamental modulation frequency. The technique, through analysis of the residual-amplitude-modulation signal, is absolute, yielding gas-absorption-line-shape functions, concentrations, and pressures without the need for calibration under certain defined operating conditions. It offers the simplicity of signal analysis of direct detection while providing all the advantages of phase-sensitive electronic detection. Measurements of the 1650.96-nm rotation/vibration-absorption-line-shape function for 1% and 10% methane in nitrogen at various pressures are compared to theoretical predictions derived from HITRAN data, and the excellent agreement confirms the validity of the new technique. Further measurements of concentration and pressure confirm the efficacy of the technique for determining concentration in industrial-process environments where the pressure may be unknown and changing. An analysis of signal strength demonstrates that sensitivity comparable to that of conventional approaches is achievable. The new approach is simpler and more robust in coping with unknown pressure variations and drift in instrumentation parameters (such as laser characteristics) than the conventional approach. As such, it is better suited to stand-alone instrumentation for online deployment in industrial processes and is particularly useful in high-temperature applications, where the background infrared is strong

Tunable diode laser spectroscopy for industrial process applications : system characterization in conventional and new approaches

Tunable diode laser spectroscopy (TDLS) can only be successfully implemented if a number of system characterization procedures and critical parameter measurements can be made accurately. These include: application of a wavelength/frequency scale to the signals recovered in time; measurement of the frequency dither applied to the laser; measurement of the relative phase between the laser power modulation and frequency modulation; determination of the background amplitude modulation for normalization purposes and measurement of required cross broadening coefficients for the host/target gas mixtures. Easy to implement, accurate and low-cost systems and procedures for achieving these are described and validated below. They were developed for two new approaches to TDLS measurements, viz the residual amplitude modulation (RAM) technique and the phasor decomposition (PD) method, but are equally applicable to all forms of TDLS. Following full system characterization using the new techniques, measurements of the absolute transmission function of the 1650.96 nm absorption line of methane over a wide range of concentration and pressure were made using the RAM technique. The close agreement with theoretical traces derived from HITRAN data validated the entire approach taken, including the system characterization procedures. In addition, measurements of a wide range of gas concentration and pressure were made by curve fitting theoretical traces to the measured transmission functions obtained using a variety of operating conditions. Again, the low errors confirmed the validity of the new methods and the system characterization/measurement procedures described here

Tunable diode laser spectroscopy with wavelength modulation : a phasor decomposition method for calibration-free measurements of gas concentration and pressure

method for analyzing signals in tunable diode laser spectroscopy with wavelength modulation are described. This new technique enables recovery of the isolated and normalized residual amplitude modulation (RAM) signal from measured first harmonic signals at any chosen fundamental modulation frequency. Like the previously reported RAM technique, this new approach is absolute, yielding gas absorption line shape functions, concentrations and pressures without the need for calibration, under certain defined operating conditions. It represents an advancement of the RAM technique in that it obviates the need to operate at a specific high frequency to achieve phase quadrature between the RAM and derivative signals: the signals may be recovered at their maximum levels at any frequency. Measurements of the 1650.96 nm and the 1666.2 nm rotation/vibration absorption line shape functions for 1% and 10% methane in nitrogen at various pressures are compared to theoretical predictions derived from HITRAN data. The excellent agreement confirms the validity of the new technique. Further measurements of concentration and pressure confirm the efficacy of the technique for determining concentration in industrial process environments where the pressure may be unknown and changing. With the above features this new method is particularly suited to stand alone instrumentation for on-line deployment in industrial processes where the calibration factors in the conventional approach would present significant difficulties

Diode laser spectroscopy using a calibration free phasor decomposition approach with RAM nulling

A limiting factor of tunable diode laser spectroscopy (TDLS) analysis is the large unwanted residual amplitude modulation (RAM) background present on the recovered 1st harmonic signal. A novel approach to remove the background RAM will be presented. This new technique will be used alongside the phasor decomposition method (PDM) [1], a calibration free technique for recovery of the absolute gas absorption line-shape. The RAM nulling method developed, successfully removes the background by optical cancellation. This is achieved by placing a fibre delay line, which introduces a π phase change in the modulation signal, in parallel with the gas cell line. When these lines are coupled together the background signals are at anti-phase and hence cancel each other. The main benefit being that measurement sensitivity can be increased. Results illustrating RAM nulling whilst using the PDM technique for absorption line-shape recovery will be presented. Figure 1 shows a recorded PDM measurement illustrating the difference with and without RAM Nulling

Chemical sensor networks for gas detection and environmental monitoring

This paper reviews the principles and prospects for optical fibre based measurement techniques for determining gas concentrations. Most of these exploit the precision and versatility of tuneable diode laser spectroscopy in the near infrared. We demonstrate the potential offered by large area multipoint totally passive networks and establish the performance potential which these may offer in hostile environments. These benefits include more than adequate sensitivity for most applications, automatic recalibration of both zero point and scale factor and the ability to precisely determine line shape information and in some cases perform detailed line spectrum analysis to determine concentration, pressure and temperature simultaneously. We also briefly describe the principles and application of photo acoustic spectroscopy and outline the performance improvements which tuneable diode laser systems also offer in this context. These studies have illustrated that, in appropriate niche applications, fibre based gas measurement systems offer substantial long term engineering potential