Design, Synthesis and Study of Redox and Optoelectronic Properties of Aromatic Oxidants and Polycyclic Aromatic Hydrocarbons

Organic materials play a significant role for the next generation photovoltaic devices that convert solar energy into usable forms of energy. In this regard, polycyclic aromatic hydrocarbons (PAHs) are fundamental tools in the developing area of molecular electronics and photovoltaics as they show excellent optical/electronic properties and are well-suited for applications in such developing areas as flexible display devices, field effect transistors and solar cell panels. Design and synthesis of novel materials for photovoltaics applications would require the proper understanding the mechanism of charge transport and identification of the structural features necessary in a particular molecular wire or PAH. To understand the charge transport mechanism and the hole delocalization one needs to generate the cation radical of a given electron donor in solution by using robust aromatic oxidants. Among these oxidants, magic blue has been widely used as an aromatic oxidant for the one electron oxidation due to its commercial availability and a reasonable oxidizing power. However, a modest stability of the magic blue salt leads to a slow decomposition to produce unknown impurities, which have been named “blues brothers”. Importantly, these impurities produce a noticeable band in the near-IR region—that is the same region where one usually expects to see an intervalence band of the cation radical with extensive hole delocalization. In this work a rational approach to synthesis of novel analogue of the magic blue that does not undergo degradation has been demonstrated. Furthermore, in the course of the rational design of novel molecular wires with enhanced redox and optical properties, one usually considers various geometrical factors in order to control the mechanism of charge delocalization. For example, a relatively small interplanar dihedral angle between adjacent units in poly-p-phenylene wire leads to a significant interchromophoric electronic coupling and thereby to extensive hole delocalization. However, it remains unclear how change in the interplanar angle would impact the redox and optical properties of the wire as well the mechanism of the hole delocalization in its cation radical. Accordingly, in this work it has been described the syntheses and study of the electrochemical and optoelectronic properties of a number of different series of biaryls connected by different numbers of methylene group to vary the dihedral angle in order to probe the mechanism and extent of hole delocalization in biaryls. Although significant progress has been made in understanding the charge transport mechanisms in various polycyclic aromatic hydrocarbons (PAHs), the usefulness of such materials in functional devices remains limited; hence design and synthesis of new PAHs to better understand the charge transport mechanisms remains an active area of research. An oxidative cyclodehydrogenation strategy was used for synthesizing a highly soluble, fluorene based larger derivative of hexa-peri-hexabenzocoronene (FHBC), where twelve carbon-carbon bonds are formed in a single step. Deployment of fluorenes at the periphery of the HBC core not only imparts solubility to the structure, but also allows the new PAHs to be functionalized further to make bigger PAHs to tune its desirable electronic properties

Future importance of healthy oceans: Ecosystem functions and biodiversity, marine pollution, carbon sequestration, ecosystem goods and services

The paper provides a review the current status of ecosystem and resource extraction to provide a series of thoughts related to the future challenges in maintaining the health of the Marine and coastal ecosystems at the Bay of Bengal. The chapter highlighted the challenges current efforts and future interventions necessary to keep the Bay of Bengal large marine ecosystem healthy. They are mainly linked to climate change, environmental pollution from different sources, biodiversity conservation, sediment movement. marine spatial planning and adoption of protected area concept to design marine reserve, fish sanctuary and ecological critical areas in the coastal zone were highlighted. The importance and means of monitoring of the marine and coastal ecosystem at the Bay of Bengal required local and international collaboration in order to ensure adoption and management of an objective monitoring syste

Development of a hot water treatment plant suitable for banana

Banana is a year round fruit in Bangladesh.  After harvesting, banana is attacked by postharvest disease caused by some fungi.  The quality and quantity losses of banana occur due to disease attacks and lack of proper postharvest handling.  Fungus can be destroyed or made inactive by chemical or heat treatment.  Most of the chemicals are hazardous to human health.  Heat treatment technology is simple and is a non-chemical method to kill or inactivate pest and to control fungus.  A hot water treatment plant was designed and developed with local materials for treating banana fruits.  Overall dimensions of the hot water treatment plant were 1600 mm×926 mm×1566 mm and operated by an electrical motor of 0.38 kW.  Water was heated by the six electric immersion heaters of 2,000 W of each.  The capacity of the plant was 350 kg h-1.  The price of the hot-water treatment plant was Taka 1,00,000 (US$1300) and treatment cost was Taka 0.55 kg-1 ($0.007).  The effective combinations of temperatures and exposure periods of BARI Kola 1 and Sabri Kola were found to be 55°C for 5 min.  When the banana fruits were treated with hot water, the shelf-life of the fruits was found to increase by 30% and the postharvest loss reduced by 70% over those of untreated bananas.  The break-even point of the plant was 70 h yr-1.  Banana fruits treated by the plant can be profitable to traders when the annual use of the plant exceeds 70 h.  Payback period of the plant was estimated to be 26 d.  Therefore, there is a good opportunity of farmers and traders to increase income and generate employment using the hot water treatment plant.   Keywords: Hot-water treatment plant, banana, temperature, exposure period, break-even point and payback perio

Spreading Electron Density Thin: Increasing the Chromophore Size in Polyaromatic Wires Decreases Interchromophoric Electronic Coupling

The development of novel polychromophoric materials using extended polycyclic aromatic hydrocarbons as a single large chromophore holds promise for long-range charge-transfer applications in photovoltaic devices and molecular electronics. However, it is not well-understood how the interchromophoric electronic coupling varies with the chromophore size in linearly connected molecular wires. Here, we show with the aid of electrochemistry, electronic spectroscopy, density functional theory calculations, and theoretical modeling that as the number of aromatic moieties in a single chromophore increases, the interchromophoric electronic coupling decreases and may reach negligible values if the chromophore is sufficiently large. The origin of this initially surprising result becomes clear when one considers this problem with the aid of Hückel molecular orbital theory, as at the polymeric limit energies of the molecular orbitals cluster to form bands and thus the energy spacing between orbitals, and thereby the electronic coupling must decrease with the chromophore expansion

Role of bronchoalveolar lavage in the diagnosis of lung cancer

Background: Early diagnosis of lung cancer plays a vital role in reducing the lung cancer death rate. Different modalities can be applied e.g. radiology, bronchoscopy, bronchoalveolar lavage (BAL), and fine needle aspiration cytology. Cytological diagnostic techniques are safer, economical, and provide quick results. The aim of the study was to find out diagnostic yields of bronchoalveolar lavage in diagnosing lung cancer, and to determine the sensitivity, and specificity of BAL fluid cytology considering the bronchial biopsy as the gold standard.Methods: This cross-sectional study was carried out in the Department of Respiratory Medicine, Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka during the period from November 2018 to March 2020 with a total of 38 participants.Results: 33 (86.84%) patients were male, and 5 (13.16%) were female; the mean age was 58.29±13.11 years. In clinical presentations, cough was present in all 100% of the patients, and some more frequent presentations were shortness of breath in 26 (68.4%), hemoptysis in 24 (63.15%), and chest pain in 21 (55.26%). Majority of the patients (78.95%) were smokers. Considering histopathological findings, maximum patients had squamous cell carcinoma 13 (38.23%), then adenocarcinoma 11 (32.35%), small cell carcinoma 5 (14.70%), large cell carcinoma 3 (8.82%), and poorly differentiated non-small cell carcinoma 2 (5.88%). The sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy of BAL were 70.59%, 100%, 100%, 28.57%, and 73.68% respectively.Conclusions: BAL fluid cytology is a useful tool for the diagnosis of lung cancer. It has good sensitivity, and specificity, and shows nearly identical information as biopsy

Regeneration potential of seedling explants of chilli (Capsicum annuum)

A study was conducted with hypocotyl, cotyledon and shoot tip of chilli as explants for regeneration on MS medium supplemented with different concentrations and combinations of auxins and cytokinins. Regeneration potential was determined by two ways. One is regeneration of shoot via callus formation from hypocotyls and cotyledon explants; another was direct shoot regeneration from shoot tip explant. The highest callus was induced from hypocotyl in a combination of BAP (5.0 mgL-1) with NAA (0.1 mgL-1) and cotyledon in a combination of BAP (5.0 mgL-1) with IAA ((1.0 mgL-1). The callus induction as well as shoot initiation was higher in hypocotyls than cotyledon. Shoot tips regenerated into plantlets directly with sporadic small callus at the base. Shoot elongation was accelerated by using additional supplementation of GA3 and AgNO3. Regenerated shoots rooted best on the MS medium supplemented with 0.1 mg L-1 NAA + 0.05 mg L-1 IBA

Future importance of healthy oceans: Ecosystem functions and biodiversity, marine pollution, carbon sequestration, ecosystem goods and services

The paper provides a review the current status of ecosystem and resource extraction to provide a series of thoughts related to the future challenges in maintaining the health of the Marine and coastal ecosystems at the Bay of Bengal. The chapter highlighted the challenges current efforts and future interventions necessary to keep the Bay of Bengal large marine ecosystem healthy. They are mainly linked to climate change, environmental pollution from different sources, biodiversity conservation, sediment movement. marine spatial planning and adoption of protected area concept to design marine reserve, fish sanctuary and ecological critical areas in the coastal zone were highlighted. The importance and means of monitoring of the marine and coastal ecosystem at the Bay of Bengal required local and international collaboration in order to ensure adoption and management of an objective monitoring syste