A Chemically Orthogonal Hole Transport Layer for Efficient Colloidal Quantum Dot Solar Cells

Colloidal quantum dots (CQDs) are of interest in light of their solution-processing and bandgap tuning. Advances in the performance of CQD optoelectronic devices require fine control over the properties of each layer in the device materials stack. This is particularly challenging in the present best CQD solar cells, since these employ a p-type hole-transport layer (HTL) implemented using 1,2-ethanedithiol (EDT) ligand exchange on top of the CQD active layer. It is established that the high reactivity of EDT causes a severe chemical modification to the active layer that deteriorates charge extraction. By combining elemental mapping with the spatial charge collection efficiency in CQD solar cells, the key materials interface dominating the subpar performance of prior CQD PV devices is demonstrated. This motivates to develop a chemically orthogonal HTL that consists of malonic-acid-crosslinked CQDs. The new crosslinking strategy preserves the surface chemistry of the active layer beneath, and at the same time provides the needed efficient charge extraction. The new HTL enables a 1.4× increase in charge carrier diffusion length in the active layer; and as a result leads to an improvement in power conversion efficiency to 13.0% compared to EDT standard cells (12.2%).     

Stabilizing Surface Passivation Enables Stable Operation of Colloidal Quantum Dot Photovoltaic Devices at Maximum Power Point in an Air Ambient

Colloidal quantum dots (CQDs) are promising materials for photovoltaic (PV) applications owing to their size-tunable bandgap and solution processing. However, reports on CQD PV stability have been limited so far to storage in the dark; or operation illuminated, but under an inert atmosphere. CQD PV devices that are stable under continuous operation in air have yet to be demonstrated—a limitation that is shown here to arise due to rapid oxidation of both CQDs and surface passivation. Here, a stable CQD PV device under continuous operation in air is demonstrated by introducing additional potassium iodide (KI) on the CQD surface that acts as a shielding layer and thus stands in the way of oxidation of the CQD surface. The devices (unencapsulated) retain >80% of their initial efficiency following 300 h of continuous operation in air, whereas CQD PV devices without KI lose the amount of performance within just 21 h. KI shielding also provides improved surface passivation and, as a result, a higher power conversion efficiency (PCE) of 12.6% compared with 11.4% for control devices.     

Satureja horvatii essential oil: In vitro antimicrobial and antiradical properties and in situ control of Listeria monocytogenes in pork meat

The dominant compounds in Satureja horvatii oil were p-cymene (33.14%), thymol (26.11%) and thymol methyl ether (15.08%). The minimum inhibitory concentration (MIC) varied from 0.03 to 0.57 mg/mL for bacteria, and from 0.56 to 2.23 mg/mL for yeast strains, while minimum bactericidal/yeast-cidal concentration (MBC/MYC) varied from 0.07 to 1.15 mg/mL and 1.11 to 5.57 mg/mL for bacteria and yeasts, respectively. The antiradical potential of the essential oil was evaluated using hydroxyl radical (•OH) generated in Fenton reaction. The meat preserving potential of essential oil from Satureja horvatii was investigated against L. monocytogenes. Essential oil successfully inhibited development of L. monocytogenes in pork meat. Sensorial evaluation on flavor and color of meat was performed. The color and flavor of meat treated with essential oil improved after 4 days of storage. S. horvatii essential oil can act as a potent inhibitor of food spoiling microorganisms, in meat products and also can be a useful source of natural antioxidants.     

Altered susceptibility of granary weevil Sitophilus granarius (L.) (Coleoptera: Curculionidae) populations to insecticides after selection with pirimiphos-methyl and deltamethrin

Toxicity of the contact insecticides dichlorvos, malathion, chlorpyrifos-methyl, pirimiphos-methyl, deltamethrin and cypermethrin to granary weevil Sitophilus granarius (L.) adults from five populations previously selected with deltamethrin and pirimiphos-methyl, and two populations that had no contact with pesticides over an interval of 12 generations, was investigated in the laboratory by application to filter paper. The populations originated from storage facilities situated in different parts of the former Yugoslavia.A population originating from Apatin and one from Belgrade Port were selected three times each at the LD₅₀ level with deltamethrin and pirimiphos-methyl, respectively. In separate experiments, weevils from Belgrade Port were selected once at the pirimiphos-methyl LD₇₀ level and Bijeljina and Kikinda populations both once at the deltamethrin LD₇₀ level. All selection doses were at a level obtained from determining weevil mortality after 24 h of exposure to treated filter paper.Compared with the toxicity to laboratory weevils, the weevils from Apatin after the third selection were found to be 32.1 and 51.9 times less susceptible to deltamethrin at the LD₅₀ and LD₉₅ levels, respectively, while those from Belgrade Port were 2.7 and 3.2 times less susceptible to pirimiphos-methyl. Selection of Belgrade Port weevils at the pirimiphos-methyl LD₇₀ did not significantly affect their susceptibility to that insecticide but it caused a significant decrease in deltamethrin toxicity, which is indicative of a cross-resistance between the two compounds. Selection of Bijeljina weevils caused an increased resistance to deltamethrin, while selection of Kikinda weevils had little effect on their susceptibility to dichlorvos, but it caused a significant decrease in malathion and cypermethrin toxicity, and resistance to deltamethrin markedly increased (RR=238.8 at LD₅₀ and 660.8 at LD₉₅ levels, compared with laboratory weevils). Chlorpyrifos-methyl was the most toxic insecticide to all populations, while cypermethrin was the least toxic compound.     

Decommissioned facilities for renewables harvesting—recycling and environmental issues

Clean Technologies and Environmental Policy -     

Electromyogram-Based Lip-Reading via Unobtrusive Dry Electrodes and Machine Learning Methods (Small 17/2023)

Lip-reading provides an effective speech communication interface for people with voice disorders and for intuitive human–machine interactions. Existing systems are generally challenged by bulkiness, obtrusiveness, and poor robustness against environmental interferences. The lack of a truly natural and unobtrusive system for converting lip movements to speech precludes the continuous use and wide-scale deployment of such devices. Here, the design of a hardware–software architecture to capture, analyze, and interpret lip movements associated with either normal or silent speech is presented. The system can recognize different and similar visemes. It is robust in a noisy or dark environment. Self-adhesive, skin-conformable, and semi-transparent dry electrodes are developed to track high-fidelity speech-relevant electromyogram signals without impeding daily activities. The resulting skin-like sensors can form seamless contact with the curvilinear and dynamic surfaces of the skin, which is crucial for a high signal-to-noise ratio and minimal interference. Machine learning algorithms are employed to decode electromyogram signals and convert them to spoken words. Finally, the applications of the developed lip-reading system in augmented reality and medical service are demonstrated, which illustrate the great potential in immersive interaction and healthcare applications.     

Polymer-Lipid Matrices based on Carboxymethyl Cellulose/Solagum and Liposomes for Controlled Release of Folic Acid

Liposome-encapsulated folic acid is incorporated into the films made from sodium carboxymethyl cellulose (CMC) (2 mas%) and a mixture of CMC and solagum (9:1 w/w) using the film-forming cast solution method. Histidine is used to increase solubility for folic acid in liposomes (1–5 mg mL⁻¹), and propylene glycol is used as a film plasticizer (2.6 mas%). The obtained films (50–60 µm tick) containing 3.12–20.19 mg of folic acid per gram of film are envisaged to be used as patches for transdermal delivery of folic acid. Therefore, some physical, mechanical, release and structural attributes of the films are scrutinized. Folic acid gives yellow color to the films and contributes to stronger chemical bonds which result in improved strength of the film. Liposomes prolong the release of folic acid from films to 24 h without adverse effects on mechanical properties of the films, but degrade homogeneity of the films, which can be ascribed to its agglomeration within the film matrix as revealed by atomic force microscopy. According to the release at pH 5.5, the film formulation based on a blend of CMC and solagum containing 3 mg mL⁻¹ liposome-encapsulated folic acid is recommended. Practical Application: Folic acid is effective in reducing oxidative stress levels in the skin and neutralizing the harmful free radicals and is also essential for various metabolic reactions in the body. However, the limited solubility of folic acid linked with its poor absorption in an organism, low storage stability, short half-life upon oral consumption, specific food preferences of some people, extensive liver metabolism, and pregnancy-induced vomiting point to a large potential in transdermal usage of folic acid. This has motivated us to design new multicomponent polymer-lipid systems as an alternative solution to overcome some of these drawbacks. The results obtained for these multicomponent films pointed to their potential for prolonged release of folic acid to 24 h, which can also be useful for scientists interested in encapsulating similar poorly soluble compounds in CMC patches. The finding can be also valuable information for pharmaceutical manufacturers and scientists worldwide.