Organic open-shell materials for optoelectronic and magnetic applications

Organic open-shell materials, which are responsive to external stimuli; such as light, electronic field, magnetic field, etc., are subject to intensive studies in recent years for their potential application in the field of organic solar cells, semiconductors, supercapacitors, singletission, non-linear optical (NLO), spintronics, and magnetic materials. As the materials with an open-shell diradical (two unpaired electrons) or polyradical (multiple unpaired electrons) character have a significant promise for next-generation optoelectronics, magnetic, and spintronic devices, it is of paramount importance to design suitable materials with tunable electronic properties. Also, a proper understanding of the molecular topology with electro-magnetic properties and correlate with quantum functionalities can move forward the field of organic photovoltaics and optoelectronics. Here, we show that controlling the radical character based on the different molecular scaffolds can lead to materials from closed-shell (all electrons are paired) low-spin (singlet state) to intermediate open-shell (multi)radical state to high-spin (triplet state) ground-state in the pristine form. In this regard, several organic donoreptor (D-A) polymeric and small molecular systems are designed and characterized. We find that the diradical character is ubiquitous in the narrow bandgap organic materials. Based on this design rule, we have reported open-shell dyes for dye-sensitized solar cells (DSCs), which show significantly red-shifted absorption in the NIR than the closed-shell counterpart dyes. Our work on the alternating D-A polymers indicate stabilization of the high-spin triplet ground-state in the neutral form, not reported for D-A type polymers. A significant delocalization of the unpaired electrons provides thermodynamic stability of the polymer, which when used in supercapacitors, a best-in-class energy density, and a long cycle life are observed. Also, we find that the spin topology can be modulated by careful selection of molecular scaffold in the extended pi-conjugated D-A polymers. Furthermore, our study on D-A macrocycles indicates that the antiferromagnetic (AFM) couplings between the unpaired electrons can be tuned by thiophene pi-spacer, developing a record polyradical character in the macromolecular systems

Antibiotic-resistant Escherichia coli and Salmonella spp. associated with dairy cattle and farm environment having public health significance

Aim: The present study was carried out to determine load of total bacteria, Escherichia coli and Salmonella spp. in dairy farm and its environmental components. In addition, the antibiogram profile of the isolated bacteria having public health impact was also determined along with identification of virulence and resistance genes by polymerase chain reaction (PCR) under a one-health approach. Materials and Methods: A total of 240 samples of six types (cow dung - 15, milk - 10, milkers' hand wash - 10, soil - 10 water - 5, and vegetables - 10) were collected from four dairy farms. For enumeration, the samples were cultured onto plate count agar, eosin methylene blue, and xylose-lysine deoxycholate agar and the isolation and identification of the E. coli and Salmonella spp. were performed based on morphology, cultural, staining, and biochemical properties followed by PCR. The pathogenic strains of E. coli stx1, stx2, and rfbO157 were also identified through PCR. The isolates were subjected to antimicrobial susceptibility test against 12 commonly used antibiotics by disk diffusion method. Detection of antibiotic resistance genes ereA, tetA, tetB, and SHV were performed by PCR. Results: The mean total bacterial count, E. coli and Salmonella spp. count in the samples ranged from 4.54±0.05 to 8.65±0.06, 3.62±0.07 to 7.04±0.48, and 2.52±0.08 to 5.87±0.05 log colony-forming unit/g or ml, respectively. Out of 240 samples, 180 (75%) isolates of E. coli and 136 (56.67%) isolates of Salmonella spp. were recovered through cultural and molecular tests. Among the 180 E. coli isolates, 47 (26.11%) were found positive for the presence of all the three virulent genes, of which stx1 was the most prevalent (13.33%). Only three isolates were identified as enterohemorrhagic E. coli. Antibiotic sensitivity test revealed that both E. coli and Salmonella spp. were found highly resistant to azithromycin, tetracycline, erythromycin, oxytetracycline, and ertapenem and susceptible to gentamycin, ciprofloxacin, and imipenem. Among the four antibiotic resistance genes, the most observable was tetA (80.51-84.74%) in E. coli and Salmonella spp. and SHV genes were the lowest one (22.06-25%). Conclusion: Dairy farm and their environmental components carry antibiotic-resistant pathogenic E. coli and Salmonella spp. that are potential threat for human health which requires a one-health approach to combat the threat

Wide Potential Window Supercapacitors Using Open Shell Donor-Acceptor Conjugated Polymers With Stable N-Doped States

Supercapacitors have emerged as an important energy storage technology offering rapid power delivery, fast charging, and long cycle lifetimes. While extending the operational voltage is improving the overall energy and power densities, progress remains hindered by a lack of stable n‐type redox‐active materials. Here, a new Faradaic electrode material comprised of a narrow bandgap donor−acceptor conjugated polymer is demonstrated, which exhibits an open‐shell ground state, intrinsic electrical conductivity, and enhanced charge delocalization in the reduced state. These attributes afford very stable anodes with a coulombic efficiency of 99.6% and that retain 90% capacitance after 2000 charge–discharge cycles, exceeding other n‐dopable organic materials. Redox cycling processes are monitored in situ by optoelectronic measurements to separate chemical versus physical degradation mechanisms. Asymmetric supercapacitors fabricated using this polymer with p‐type PEDOT:PSS operate within a 3 V potential window, with a best‐in‐class energy density of 30.4 Wh kg−1 at a 1 A g−1 discharge rate, a power density of 14.4 kW kg−1 at a 10 A g−1 discharge rate, and a long cycle life critical to energy storage and management. This work demonstrates the application of a new class of stable and tunable redox‐active material for sustainable energy technologies

Wide Potential Window Supercapacitors Using Open-Shell Donor-Acceptor Conjugated Polymers with Stable N-Doped States

Supercapacitors have emerged as an important energy storage technology offering rapid power delivery, fast charging, and long cycle lifetimes. While extending the operational voltage is improving the overall energy and power densities, progress remains hindered by a lack of stable n‐type redox‐active materials. Here, a new Faradaic electrode material comprised of a narrow bandgap donor−acceptor conjugated polymer is demonstrated, which exhibits an open‐shell ground state, intrinsic electrical conductivity, and enhanced charge delocalization in the reduced state. These attributes afford very stable anodes with a coulombic efficiency of 99.6% and that retain 90% capacitance after 2000 charge–discharge cycles, exceeding other n‐dopable organic materials. Redox cycling processes are monitored in situ by optoelectronic measurements to separate chemical versus physical degradation mechanisms. Asymmetric supercapacitors fabricated using this polymer with p‐type PEDOT:PSS operate within a 3 V potential window, with a best‐in‐class energy density of 30.4 Wh kg−1 at a 1 A g−1 discharge rate, a power density of 14.4 kW kg−1 at a 10 A g−1 discharge rate, and a long cycle life critical to energy storage and management. This work demonstrates the application of a new class of stable and tunable redox‐active material for sustainable energy technologies