Recent developments in the synthesis of regioregular thiophene-based conjugated polymers for electronic and optoelectronic applications using nickel and palladium-based catalytic systems

Thiophene-based conjugated polymers hold an irreplaceable position among the continuously growing plethora of conjugated polymers due to their exceptional optical and conductive properties, which has made them a centre of attention for the past few decades and many researchers have contributed tremendously by designing novel strategies to reach more efficient materials for electronic applications. This review aims to highlight the recent (2012–2019) findings in design and synthesis of novel thiophene-based conjugated polymers for optical and electronic devices using organometallic polycondensation strategies. Nickel- and palladium-based protocols are the main focus of this account. Among them nickel-catalyzed Kumada catalyst-transfer polycondensation, nickel-catalyzed deprotonative cross-coupling polycondensation, palladium-catalyzed Suzuki–Miyaura and Migita–Kosugi–Stille couplings are the most popular strategies known so far for the synthesis of functionalized regioregular polythiophenes exhibiting fascinating properties such as electronic, optoelectronic, chemosensitivity, liquid crystallinity and high conductivity. This account also presents a brief overview of direct arylation polymerization (DArP) protocol that has shown a great potential to lessen the drawbacks of conventional polymerization techniques. DArP is a cost-effective and green method as it circumvents the need for the synthesis of arylene diboronic acid/diboronic ester and distannyl arylenes using toxic precursors. DArP also puts off the need to preactivate the C–H bonds, hence, presenting a facile route to synthesize polymers with controlled molecular weight, low polydispersity index, high regioregularity and tunable optoelectronic properties using palladium-based catalytic systems.

Thiophene-based conjugated polymers are important conjugated polymers due to their exceptional optical and conductive properties, over the past few decades many researchers have designed novel strategies to reach more efficient materials for electronic applications.     

Size-dependent magnetic and magnetothermal properties of gadolinium silicide nanoparticles

Gadolinium silicide (Gd₅Si₄) nanoparticles are an interesting class of materials due to their high magnetization, low Curie temperature, low toxicity in biological environments and their multifunctional properties. We report the magnetic and magnetothermal properties of gadolinium silicide (Gd₅Si₄) nanoparticles prepared by surfactant-assisted ball milling of arc melted bulk ingots of the compound. Using different milling times and speeds, a wide range of crystallite sizes (13–43 nm) could be produced and a reduction in Curie temperature (T_C) from 340 K to 317 K was achieved, making these nanoparticles suitable for self-controlled magnetic hyperthermia applications. The magnetothermal effect was measured in applied AC magnetic fields of amplitude 164–239 Oe and frequencies 163–519 kHz. All particles showed magnetic heating with a strong dependence of the specific absorption rate (SAR) on the average crystallite size. The highest SAR of 3.7 W g⁻¹ was measured for 43 nm sized nanoparticles of Gd₅Si₄. The high SAR and low T_C, (within the therapeutic range for magnetothermal therapy) makes the Gd₅Si₄ behave like self-regulating heat switches that would be suitable for self-controlled magnetic hyperthermia applications after biocompatibility and cytotoxicity tests.

Gadolinium silicide (Gd₅Si₄) nanoparticles prepared by surfactant-assisted ball milling exhibit a size-dependent reduction in magnetic ordering temperature and a high magnetothermal effect making them suitable for magnetic hyperthermia applications.     

Molecularly imprinted polymeric coatings for sensitive and selective gravimetric detection of artemether

Monitoring antimalarial drugs is necessary for clinical assays, human health, and routine quality control practices in pharmaceutical industries. Herein, we present the development of sensor coatings based on molecularly imprinted polymers (MIPs) combined with quartz crystal microbalance (QCM) for sensitive and selective gravimetric detection of an antimalarial drug: artemether. The MIP coatings are synthesized by using artemether as the template in a poly(methacrylic acid-co-ethylene glycol dimethacrylate) matrix. Artemether-MIP and the non-imprinted polymer (NIP) control or reference layers are deposited on 10 MHz dual-electrode QCM by spin coating (187 ± 9 nm layer thickness after optimization). The coatings are characterized by FTIR spectroscopy and atomic force microscopy that reveal marked differences among the MIP and NIP. The MIP-QCM sensor exhibits high sensitivity (0.51 Hz ppm⁻¹) with sub-10 ppm detection and quantification limits. The MIP-QCM sensor also exhibits a 6-fold higher sensitivity compared to the NIP-QCM, and a dynamic working range of 30–100 ppm. The response time of MIP-QCM devices for a single cycle of analyte adsorption, signal saturation, and MIP regeneration is less than 2.5 min. The sensor also demonstrates selectivity factors of artemether-MIP of 2.2 and 4.1 compared to artemisinin and lumefantrine, respectively. Reversibility tests reveal less than 5% variation in sensor responses over three cycles of measurements at each tested concentration. The MIP-QCM showed lower detection limits than conventional HPLC-UV, and faster response time compared to HPLC-UV and liquid chromatography-mass spectrometry (LC-MS).

Chemical structures of the antimalarial drugs: artemisinin, artemether (a methyl ether derivative of artemisinin), and lumefantrine.     

Behavioral problems among children living in orphanage facilities of Karachi,Pakistan: comparison of children in an SOS Village with those in conventional orphanages

Purpose  

This study compared the behavioral problems of children living in an SOS Village, which attempts to provide a family setup for its children, with those living in conventional orphanages.     

The economic burden of blindness in Pakistan: A socio-economic and policy imperative for poverty reduction strategies

State and nonstate health programs in developing countries are often influenced by priorities that are defined in the Millennium Development Goals (MDGs). In the wake of recessionary pressures, policy makers in the health sector are often seen to divert significant budgets to some specific health programs and make only token allocations for other health problems that are important but do not fall under the traditional MDG box of health priorities. This paper illustrates the economic argument for investment in one such program: The eye health program and employs a country case study of Pakistan to demonstrate that there are significant economic gains that are being foregone by not addressing the needs of the blind in poverty reduction strategies. By applying appropriate growth and discounting factors and using the average wage rate, the paper estimates the total productivity gains that are realizable over a period of 10 years if the blind population in Pakistan is rehabilitated and their carers released to participate in the mainstream economic activity. Our findings indicate that significant productivity gains accumulated over 10 years, range from Rs. 61 billion (US$ 709 million) to Rs. 421 billion (US$ 4.9 billion) depending upon whether the entire blind population or only those affected by a specific cause are rehabilitated. The per annum productivity gains of rehabilitating the entire blind population represents 0.74% of the current gross domestic product of Pakistan, which is higher than the total public spending on health. In order to reap these benefits, the subsequent absorption of the rehabilitated blind and their carers into mainstream economic activity is as important as their effective rehabilitation.     

What to listen for in the consultation. Breast cancer patients’ own focus on talking about acceptance-based psychological coping predicts decreased psychological distress and depression

Objective

To analyze whether qualitative themes in breast cancer patients’ self-presentations predicted symptoms of psychological distress and depression in order to improve the consultation process.

Methods

Ninety-seven breast cancer patients gave unstructured, 10-min self-presentations at their first consultation in a clinical registered trial (CRT identifier: NCT00990977). Self-presentations were categorized thematically and the most prevalent themes investigated as predictors for scores on the symptom check-list 90-revised (SCL-90-R) and the center for epidemiological studies depression scale (CES-D).

Results

Among the qualitative themes, only the percentage of words spent on talking about ‘Acceptance-based psychological coping’ was related to symptoms. In regression models controlling for age, education and time since diagnosis, a stronger focus on acceptance-based coping predicted less psychological distress and depression, respectively. A cross-validation including only the first few minutes of speech per patient confirmed these results and supported their practical utility in health consultations.

Conclusion

Patients’ focus on acceptance-based coping significantly predicted decreased psychological distress and depression, respectively. No other qualitative themes predicted symptoms. Doctor–patient studies may benefit from combined qualitative–quantitative methods.

Practice implications

While quantitative symptom assessment is important for a consultation, health care providers may improve their understanding of patients by attending to patients’ presentations of acceptance-based psychological coping.     

The Escherichia coli multidrug transporter MdfA catalyzes both electrogenic and electroneutral transport reactions

The resistance of cells to many drugs simultaneously (multidrug resistance) often involves the expression of membrane transporters (Mdrs); each recognizes and expels a broad spectrum of chemically unrelated drugs from the cell. The Escherichia coli Mdr transporter MdfA is able to transport differentially charged substrates in exchange for protons. This includes neutral compounds, namely chloramphenicol and thiamphenicol, and lipophilic cations such as tetraphenylphosphonium and ethidium. Here we show that the chloramphenicol and thiamphenicol transport reactions are electrogenic, whereas the transport of several monovalent cationic substrates is electroneutral. Therefore, unlike with positively charged substrates, the transmembrane electrical potential (negative inside) constitutes a major part of the driving force for the transport of electroneutral substrates by MdfA. These results demonstrate an unprecedented ability of a single secondary transporter to catalyze discrete transport reactions that differ in their electrogenicity and are governed by different components of the proton motive force.