Mixed self-assembled monolayers of azobenzene photoswitches with trifluoromethyl and cyano end groups

Separation of acrylonitrile-butadiene-styrene and polystyrene waste plastics after surface modification using potassium ferrate by froth flotation

This work develops a simple and practical process for separation of acrylonitrile-butadienestyrene (ABS) and polystyrene (PS) waste plastics by froth flotation after surface modification using potassium ferrate. ABS plastics containing brominated flame retardants (BFRs) can release hazardous emissions during the process of disposal. Moreover, ABS and PS are typical styrene plastics with similar properties, posing severe restrictions on their separation for recycling. Thus, potassium ferrate modification was investigated and found to decrease selectively the floatability of ABS, providing available process for separation of ABS and PS. Contact angle measurements, FT-IR, XPS and SEM characterization analysis confirmed that potassium ferrate modification can induce the desired changes in the surface properties of ABS. With consideration to separation of ABS and PS, the optimum conditions are potassium ferrate concentration 0.15 M/L, modification time 15 min, temperature 60 °C, stirring rate 200 rpm, frother concentration 14.50 mg/L and flotation time 2 min. Under optimum conditions, separation of ABS and PS with different mixing ratios was accomplished with a recovery and purity of 98.60% and 98.62% respectively. Moreover, reusing of potassium ferrate solution is feasible, further eliminating emissions and cost of this process. Consequently, surface modification using potassium ferrate can be applied for facilitating flotation separation of ABS and PS waste plastics.

Understanding the effects of packing and chemical terminations on the optical excitations of azobenzene-functionalized self-assembled monolayers

In a first-principles study based on many-body perturbation theory, we analyze the optical excitations of azobenzene-functionalized self-assembled monolayers (SAMs) with increasing packing density and different terminations, considering for comparison the corresponding gas-phase molecules and dimers. Intermolecular coupling increases with the density of the chromophores independently of the functional groups. The intense [Formula: see text] resonance that triggers photo-isomerization is present in the spectra of isolated dimers and diluted SAMs, but it is almost completely washed out in tightly packed architectures. Intermolecular coupling is partially inhibited by mixing differently functionalized azobenzene derivatives, in particular when large groups are involved. In this way, the excitation band inducing the photo-isomerization process is partially preserved and the effects of dense packing partly counterbalanced. Our results suggest that a tailored design of azobenzene-functionalized SAMs which optimizes the interplay between the packing density of the chromophores and their termination can lead to significant improvements in the photo-switching efficiency of these systems.

Surface treatment with Fenton for separation of acrylonitrile-butadiene-styrene and polyvinylchloride waste plastics by flotation

Surface treatment with Fenton was applied to flotation separation of acrylonitrile-butadienestyrene (ABS) and polyvinylchloride (PVC). After treatment, the floatability of ABS has a dramatic decrease, while the floatability of PVC is not affected. Fourier transform infrared spectroscopy (FT-IR) spectra and X-ray photoelectron spectroscopy (XPS) spectra were recorded to ascertain the mechanism of Fenton treatment. FT-IR and XPS analysis confirms that the introduction of oxygen-containing group occurs on the surface of ABS. The optimum conditions are molar ration (H₂O₂:Fe²⁺) 10000, H₂O₂ concentration 0.4M/L, pH 5.8, treatment time 2min and temperature 25°C, frother concentration 15mg/L and flotation time 3min. Particle sizes and mixing ratios were also investigated. Plastic mixtures of ABS and PVC with different particle sizes and mixing ratios can be effectively separated. The purity of ABS and PVC are up to 100% and 99.78%, respectively; the recovery of ABS and PVC are up to 99.89% and 100%, respectively. A practical, environmentally friendly and effective reagent, namely Fenton, was originally applied to surface treatment of ABS and PVC waste plastics for flotation separation of their mixtures.

Asymmetric Injection in Organic Transistors via Direct SAM Functionalization of Source and Drain Electrodes

The fabrication of organic optoelectronic devices integrating asymmetric electrodes enables optimal charge injection/extraction at each individual metal/semiconductor interface. This is key for applications in devices such as solar cells, light-emitting transistors, photodetectors, inverters, and sensors. Here, we describe a new method for the asymmetric functionalization of gold electrodes with different thiolated molecules as a viable route to obtain two electrodes with drastically different work function values. The process involves an ad hoc design of electrode geometry and the use of a polymeric mask to protect one electrode during the first functionalization step. Photoelectron yield ambient spectroscopy and X-ray photoelectron spectrometry were used to characterize the energetic properties and the composition of the asymmetrically functionalized electrodes. Finally, we used poly(3-hexylthiophene)-based organic thin-film transistors to show that the asymmetric electronic response stems from the different electronic structures of the functionalized electrodes.