Ferrocene Chalcone Enhanced Cyclotriphosphazene Photodiode Systems via Click Chemistry: Their Synthesis, Electrical, and Photophysical Properties

In this study, a new ferrocene-decorated cyclotriphosphazene compound (4) was obtained by the interaction of ferrocene chalcone with azide end groups (2) and spirophosphazene (3) bearing alkyne groups using the click method. The structures of all compounds were confirmed using Fourier transform infrared, 1H, 13C APT, and 31P NMR, and MS techniques. The optical band gaps of compounds were measured, showing values of 4.75 eV for 3, 3.53 eV for 2, and 3.46 eV for final product 4. The optical band gap of compound 4 calculated by density functional theory is 3.28 eV. The electrical properties of the compounds were investigated against the frequency. The results showed that the conduction mechanism is based on the hopping model. New types of diodes were prepared by using compounds 2 and 4. The current-voltage characteristics of the compound 4 diode showed good rectification behavior. The rectification ratio of the heterojunction diode was calculated as 629. The ideality factors were 3.35 for 2 and 7.57 for 4. The barrier heights were 0.68 and 0.92, respectively. Under sunlight (20-100 mW/cm2), both diodes exhibited photodiode properties, with compound 4 being more sensitive to light. This indicates that the diodes can be used in optoelectronic devices due to their photoconductive behavior.

Measurement of Water Uptake and States in Nafion Membranes Using Humidity-Controlled Terahertz Time-Domain Spectroscopy

Perfluorinated sulfonic acid ionomers are well known for their unique water uptake properties and chemical/mechanical stability. Understanding their performance-stability trade-offs is key to realizing membranes with optimal properties. Terahertz time-domain spectroscopy has been demonstrated to resolve water states inside industrially relevant membranes, producing qualitatively agreeable results to conventional gravimetric analysis and prior demonstrations. Using the proposed humidity-controlled terahertz time-domain spectroscopy, here we quantify this detailed water information inside commercially available Nafion membranes at various humidities for direct comparison against literature values from dynamic vapor sorption, differential scanning calorimetry, and Fourier transform infrared spectroscopy on selected samples. Using this technique therefore opens up opportunities for rapid future parameter space investigation for membrane optimization.

An adaptive absorption spectroscopy with adjustable moving window width for suppressing nonlinear effects in absorbance measurements

Absorption spectroscopy based on Lambert-Beer law has been widely used in material structure analysis, research in chemical reaction kinetics, and exploration of various physicochemical reaction mechanisms. However, serious nonlinearity between absorbance and measured concentration can occur in actual measurements. The idea of moving window is first introduced into the field of spectral nonlinearity in the paper. Combining with the characteristic absorption spectra of the substances to be measured, we propose an adaptive absorption spectroscopy (A-AS) with adjustable moving window parameters to effectively suppress the nonlinear effects in absorbance measurements. The validity of this method is verified by taking the differential optical absorption spectroscopy to detect SO₂ as an example. The 210-230 nm characteristic absorption band is traversed and divided by the moving window with adjustable parameters, and the estimated coefficient (k-value) of each band is calculated. On this basis, all k-values are initially and secondly screened to obtain the optimal k_best, and then the optimal concentration value is obtained by inversion. Compared with the broad-band method and narrow-band method, it shows excellent performance that the maximum error and standard deviation of A-AS is only 1.3% and 3.8 in the entire concentration range, suggesting good linearity and stability in both high and low concentration environments. Therefore, it is inferred that A-AS is universally adaptable and enables dynamic linear measurements over wide concentration range.

Kinetic analysis of microalgae cultivation utilizing 3D-printed real-time monitoring system reveals potential of biological CO2 conversion

The microalgae-based bioconversion process is a promising carbon utilization technology because it can upgrade CO2 into valuable substances, but a multiplex monitoring system required for process control to maximize biomass productivity has not been well established. Herein, a 3D printed real-time optical density monitoring device (RTOMD) combined platform was presented. This platform enables precise kinetics analysis by maintaining high accuracy (over 95 %) under raucous outdoor conditions. Through RTOMD-based high-frequency measurements, it was observed that maximum biomass productivity of 4.497 g L-1 d-1 was reached, which greatly exceeds the requirements for a feasible microalgae process. We discovered that the CO2 fixation efficiency could be achieved to 70.75 %, indicating the potential of a bioconversion process to realize a carbon-neutral society. Consequently, the RTOMD system can contribute to promoting microalgae cultivation as an attractive carbon mitigation technology based on an improved understanding of the photosynthetic CO2 fixation kinetics.

Study on the origin of linear deviation with the Beer-Lambert law in absorption spectroscopy by measuring sulfur dioxide

In accordance with the Beer-Lambert law, absorbance is proportional to concentration and optical path length of the absorbers in the sample, and in a linear relationship with total column concentration (product of concentration and optical path length) at a single wavelength. However, limitation of spectral resolution will result in linear deviation with the Beer-Lambert law in actual measurement. Regarding additivity of polychromatic light intensity as the theoretical basis, this paper attributed linear deviation with the Beer-Lambert law to spectral resolution, concentration and light intensity, and verified this explanation by measuring sulfur dioxide at various total column concentrations using spectrometers with different spectral resolutions in the waveband range of 216-230 nm. It was found that linear deviation with the Beer-Lambert law was in negative correlation with spectral resolution, and in positive correlation with total column concentration, and absorbance could be considered to be linear with total column concentration (below 171.4 mg/m²) of sulfur dioxide in the wavelength range of 216-230 nm. In addition, it was also proved that linear deviation increases with decreasing light intensity at a fixed sulfur dioxide column concentration.

Improved Spectrophotometric Method for Determination of High-Range Volatile Fatty Acids in Mixed Acid Fermentation of Organic Residues

Volatile fatty acids (VFAs) are the important intermediates indicating the stability and performance of fermentation process. This study developed the spectrophotometric method for determining high-range VFA concentration in mixed-acid fermentation samples. The performance was compared with the gas chromatography (GC) technique. The calibration curves of the modified method showed linearity over a wide and high concentration range of 250–5000 mg/L for individual C2–C6 VFAs in both linear and branched chains. In order to evaluate the modified method for VFA determination in complex fermentation matrices, fermentation samples produced from acidogenic fermentation of plant materials were spiked with acetic (500–1500 mg/L) and butyric acids (1000 mg/L). The accuracy and precision of the modified method for VFA determination were in the range of 94.68–106.50% and 2.35–9.26%, respectively, comparable to the GC method (94.42–99.13% and 0.17–1.93%). The developed method was applicable to measuring all C2–C6 compounds and VFA concentrations in the fermentation samples and had an acceptable accuracy and precision. The proposed method is analytically reliable and offers significant advantages in the rapid determination of VFAs in mixed acid fermentation of organic residues.

A method to determine the correct photocatalyst concentration for photooxidation reactions conducted in continuous flow reactors

When conducting a photooxidation reaction, the key question is what is the best amount of photocatalyst to be used in the reaction? This work demonstrates a fast and simple method to calculate a reliable concentration of the photocatalyst that will ensure an efficient reaction. The determination is based on shifting the calculation away from the concentration of the compound to be oxidized to utilizing the limitations on the total light dose that can be delivered to the catalyst. These limitations are defined by the photoflow setup, specifically the channel height and the emission peak of the light source. This method was tested and shown to work well for three catalysts with different absorption properties through using LEDs with emission maxima close to the absorption maximum of each catalyst.

Aggregation of slipped-cofacial phthalocyanine J-type dimers: Spectroscopic and AFM study

Direct metallation of 2-hydroxyphthalocyanine J-type slipped-cofacial dimeric ligand by Mg, Zn, Cu, Ni and Co salts has been carried out to obtain corresponding metal complexes selectively without any noticeable dissociation or polymerization of the starting ligand. Integrated analysis of aggregation properties in the synthesized series has been conducted with the involvement of AFM microscopy, UV/Vis spectroscopy and theoretical assessment. As a result, a nonlinear relationship between absorption and concentration was found, with aggregation beginning to appear at concentrations above 3.3 × 10^-5 mol L^-1 with predominant formation of trimers from the dimeric molecules in THF solutions.