Viologen based electroactive polymers and composites for durable electrochromic systems

Electrochromism, the phenomenon of reversible color change induced by a small electric charge, forms the basis for operation of several devices including mirrors, displays and smart windows. Although, the history of electrochromism dates back to the 19th century, only the last quarter of the 20th century has its considerable scientific and technological impact. The commercial applications of electrochromics (ECs) are rather limited, besides top selling EC anti-glare mirrors by Gentex Corporation and airplane windows by Boeing, which made a huge commercial success and exposed the potential of EC materials for future glass industry. It is evident from their patents that viologens (salts of 4,4ʹ-bipyridilium) were the major active EC component for most of these marketed devices, signifying the motivation of this thesis focusing on EC viologens. Among the family of electrochromes, viologens have been utilized in electrochromic devices (ECDs) for a while, due to its intensely colored radical cation formation induced by applying a small cathodic potential. Viologens can be synthesized as oligomer or in the polymeric form or as functionality to conjugated polymers. In this thesis, polyviologens (PVs) were synthesized starting from cyanopyridinium (CNP) based monomer precursors. Reductive coupling of cross-connected cyano groups yields viologen and polyviologen under successive electropolymerization using for example the cyclic voltammetry (CV) technique. For further development, a polyviologen-graphene composite system was fabricated, focusing at the stability of the PV electrochrome without sacrificing its excellent EC properties. High electrical conductivity, high surface area offered by graphene sheets together with its non-covalent interactions and synergism with PV significantly improved the electrochrome durability in the composite matrix. The work thereby continued in developing a CNP functionalized thiophene derivative and its copolymer for possible utilization of viologen in the copolymer blend. Furthermore, the viologen functionalized thiophene derivative was synthesized and electropolymerized in order to explore enhancement in the EC contrast and overall EC performance. The findings suggest that such electroactive viologen/polyviologen systems and their nanostructured composite films as well as viologen functionalized conjugated polymers, can be potentially applied as an active EC material in future ECDs aiming at durable device performances.Elektrokromismi on ilmiö, jossa pienellä sähköisellä varauksella saadaan aikaan palautuva värinmuutos. Monien laitteiden, kuten peilien, näyttöjen tai älykkäiden ikkunoiden, toiminta perustuu tähän ilmiöön. Historiallisesti elektrokromismi on tunnettu 19. vuosisadalta asti, mutta vasta 20. vuosisadan viimeinen neljännes on osoittanut ilmiön huomattavan tieteellisen ja teknologisen merkityksen. Näiden elektrokromismiin perustuvien tekniikoiden kaupallinen hyödyntäminen on vielä melko vähäistä. Tähän asti myydyimpiä tuotteita ovat olleet häikäisysuojatut peilit (Gentex Corporation) ja lentokoneen ikkunat (Boeing), jotka olivat valtavia kaupallisia menestyksiä osoittaen tekniikan mahdollisuudet tulevaisuuden lasiteollisuudessa. Patenteista selviää, että viologeenit (4,4ʹ-bipyridiniumin suolat) ovat yleisimpiä aktiivisia komponentteja useimmissa markkinoilla olevissa sovelluksissa, minkä perusteella tässä väitöskirjassa keskitytään viologeeneihin. Erilaisista sähköväriaineista viologeenejä on käytetty elektrokromisissa laitteissa jo jonkin aikaa johtuen niiden voimakkaan värisestä radikaalikationista, joka saadaan syntymään pienellä katodisella jännitteellä.Viologeenejä voidaan syntetisoida oligomeerinä tai polymeerinä, sekä toiminnallisena ryhmänä osana konjugoitua polymeeriä. Tässä väitöskirjassa polyviologeenit syntetisoitiin käyttämällä lähtöaineena syanopyridinium-pohjaista monomeeriä. Ristiinkytkettyjen syanoryhmien pelkistävä kytkeytyminen tuottaa viologeeniä ja polyviologeeniä peräkkäisissä sähköpolymerisaatioreaktioissa, mikä voidaan toteuttaa käyttämällä menetelmänä esimerkiksi syklistä voltammetriaa. Systeemiä kehitettiin edelleen siten, että polyviologeenistä ja rafeenista valmistettiin komposiitti, jossa parannettiin polyviologeenin stabiilisuutta, menettämättä sen erinomaisia elektrokromisia ominaisuuksia. Grafeenilevyjen hyvä sähköinen johtavuus ja suuri pinta-ala yhdistettynä ei-kovalenttisiin vuorovaikutuksiin ja synergiaetuihin PV:n kanssa paransi huomattavasti komposiittimatriisin elektrokromista kestävyyttä. Työtä jatkettiin kehittämällä CNP:llä funktionalisoitu tiofeenijohdos ja vastaava polymeeri, mikä mahdollisti viologeenin hyödyntämisen kopolymeeriseoksessa. Lisäksi syntetisoitiin ja sähköpolymeroitiin viologeenillä funktionalisoitu tiofeenijohdos, jonka avulla tutkittiin elektrokromisen kontrastin ja kokonaissuorituskyvyn parantumista. Havainnot osoittavat, että sähköisesti aktiivisia viologeeni/polyviologeenisysteemejä ja niistä valmistettuja nanorakenteisia komposiittikalvoja, sekä myös viologeenillä funktionalisoituja konjugoituja polymeerejä on mahdollista hyödyntää aktiivisena elektrokromisena materiaalina tulevissa suorituskyvyltään kestävissä elektrokromisissa laitteissa.Siirretty Doriast

Exploring amide linkage in a polyviologen derivative towards simultaneous voltammetric determination of Pb(II), Cu(II) and Hg(II) ions

In this study, we report reductive electrosynthesis of a polyviologen derivative bearing amide linkage in its side chain, derived from a cyanopyridinium based monomer with amide functionality. The as grown film was characterized by cyclic voltammetry which displays a well-defined and reversible two step redox response characteristic of viologen. FTIR analysis show evidence of amide linkage and successful reduction of cyanopyridinium moieties to polyviologen. In situ multi ESR/UV-Vis-NIR spectroelectrochemistry show a single line in ESR signal, thereby suggesting polarons as the only charge carrier involved during charging/discharging process. Furthermore, a characteristic UV&ndash;Vis absorption spectra confirms viologen formation. Finally, the polyviologen film is subjected to simultaneous voltammetric determination of heavy metal ions, Pb(II), Cu(II) and Hg(II). The amide linkage in the polyviologen derivative is supposedly complexing these divalent metal ions, enabling their sensitive and simultaneous determination with low detection limits.</div

Assessing geographical and economic inequalities in caesarean section rates between the districts of Bihar, India: a secondary analysis of the National Family Health Survey

Background In Bihar, one of the most populous and poorest states in India, caesarean sections have increased over the last decade. However, an aggregated caesarean section rate at the state level may conceal inequities at the district level. Objectives The primary aim of this study was to analyse the inequalities in the geographical and socioeconomic distribution of caesarean sections between the districts of Bihar. The secondary aim was to compare the contribution of free-for-service government-funded public facilities and fee-for-service private facilities to the caesarean section rate. Setting Bihar, with a population in the 2011 census of approximately 104 million people, has a low GDP per capita (US$610), compared with other Indian states. The state has the highest crude birth rate (26.1 per 1000 population) in India, with one baby born every two seconds. Bihar is divided into 38 administrative districts, 101 subdivisions and 534 blocks. Each district has a district (Sadar) hospital, and six districts also have one or more medical college hospitals. Methods This retrospective secondary data analysis was based on open-source national datasets from the 2015 and 2019 National Family Health Surveys, with respective sample sizes of 45 812 and 42 843 women aged 15–49 years. Participants Secondary data analysis of pregnant women delivering in public and private institutions. Results The caesarean section rate increased from 6.2% in 2015 to 9.7% in 2019 in Bihar. Districts with a lower proportion of poor population had higher caesarean section rates (R2=0.45) among all institutional births, with 10.3% in private and 2.9% in public facilities. Access to private caesarean sections decreased (R2=0.46) for districts with poorer populations. Conclusion Marked inequalities exist in access to caesarean sections. The public sector needs to be strengthened to improve access to obstetric services for those who need it most

An epidemiological study to assess the awareness of hepatitis B infection in the dental students, college staff, practitioners, and auxiliary staff in city of Maharashtra

Introduction: Hepatitis B is a major health problem worldwide and more serious in India. Hepatitis B virus has only human reservoir, and it is easily transmitted to one another. In the field of dentistry, it involves with saliva and blood, and it also involves many accidental injuries. Dentist with their associates are more prone to get infected. Aim: To assess the level of understanding and awareness about hepatitis B infection among the dental undergraduate and postgraduate students, institutional staff of a reputed dental college, dental practitioners, dental auxiliary, and paramedics of a city in Maharashtra. Materials and Methods: A cross-sectional survey was carried out in 350 subjects using a self-administered pretested questionnaire containing 15 questions on awareness about prevention and transmission, vaccination status of hepatitis B, awareness of postexposure prophylaxis (PEP), and complications associated with hepatitis B. Descriptive analysis was carried out and was presented as a percentage. Results: The response rate was 100% (n = 350). Majority of the undergraduate and postgraduate students, college staff, and dental practitioners were aware of hepatitis B infection, its vaccination, and its importance but knowledge and awareness regarding the incubation period, PEP, and complications associated were less. Dental auxiliary staff has the minimal knowledge and awareness about hepatitis B infection. Conclusion: Overall good knowledge and awareness are observed among the undergraduate and postgraduate students, college staff, and in the dental practitioners. The auxiliary and paramedical staffs are minimally aware

Evaluation of the posterior superior alveolar artery using cone beam computed tomography

BACKGROUND: Maxillary posterior tooth region is an important area with respect to periapical surgery, implant placement, and sinus lifts. Posterior superior alveolar artery (PSAA) is located on the lateral wall of maxillary sinus and may become injured during such surgical procedures. Therefore, knowledge of the subject is essential to a clinician. The goal was to determine the anatomical relationship of posterior superior alveolar artery to the floor of maxillary sinus and alveolar crest. In our study we attempted to present the locations and course of posterior superior alveolar artery (PSAA) using cone beam computed tomography (CBCT) imaging. MATERIAL AND METHODS: CBCT scans of 50 patients (30 males, 20 females) who had undergone computed tomography imaging were analyzed. We assessed the visibility and location of vascular canal/notch of posterior superior alveolar artery on cross sectional images and measured the distances from lower margin to the floor of maxillary sinus and alveolar crest in the 1st molar and 2nd molar regions. Unpaired t-test was carried out in the analysis to determine the level of significance. RESULTS: Maxillary PSAA was visualized in 36 patients (70%). Mean diameter of the vessel was 0.63 mm. Mean distance between PSAA and alveolar crest was the shortest in the 2nd molar region. The mean distance between PSAA and floor of maxillary sinus was 9.96 mm. CONCLUSIONS: Periapical surgeries, implants and maxillary sinus lift are performed on routine basis. PSAA is an important structure in the posterior maxillary region; the clinician should be aware of its location and course. CBCT is an excellent tool to localize the PSAA because of it provides finer details at low exposure and less radiation. It should be recommended in clinical practices

Ecological distribution conflicts (EDCs) over mineral extraction in India: An overview

Mineral extraction is growing worldwide, generating serious social and environmental impacts, and in the process, sparking significant resistance. The present article provides the first overview of non-fuel mining conflicts in India. The analysis is based on 100 cases of conflicts that occurred between 1992 and 2014, which constitutes the most exhaustive database compiled to date. In each case, location, mineral extracted, actors involved, cited causes of protest, conflict duration and outcomes were recorded. We found that the commodity responsible for the most conflicts is sand, the extraction of which is widespread and often carried out illegally by small-scale actors near rivers. Resistance against metallic ore mining, in contrast, typically pits local populations against larger corporations. Most resistance movements are composed of subaltern rural and/or indigenous populations; very few national and international NGOs were found to be involved in local movements. The causes of such conflicts have largely been ecological and responsible for an undermining of local livelihoods. Mineral extraction is expected to increase in India over the next decade, and with it, the number of associated conflicts