Study of Doping Phenomena in Functional Materials

The disruptive technologies that are currently emerging across the semi-conductor and electronics industries demand the need for a continual focus on decreasing the size of integrated circuits and renewable energy technology devices. To support this demand requires comprehensive research into understanding the functional properties of materials at an atomic level across a three-dimensional space. These functional properties of materials originate from atomic level properties such as structural, optical and electronic properties, all of which can be modified to optimise the functionality of a material. This is the reason why these atomic level properties were comprehensively studied and reported in this thesis. The introduction of atomic level impurities, via the phenomena of doping, has helped to modify the structural, optical and electronic properties of the materials investigated in this thesis. An insight into the effect and potential that high temperature solid-state doping can bring towards improving the functional properties of three materials namely titania-rutile (single crystal substrates), titanates (powders) and Magnesium Silicon Nitrides MgSiN2 (powders), were gained from the experiments and results reported in this thesis. NB: titanates studied include sodium and potassium hexatitanates, sodium trititanate and caesium titanate. Chapters 3-8 of this thesis were written with a specific focus on the spatial arrangement of dopant atoms (such as B, C, S and N) introduced into photocatalytic titania-rutile and the associated influence it has on bonding, diffusion behaviours as well as structural and electronic properties. The insight gained about these properties of titania-rutile are essential when working on an industrial scale to optimise the performance of renewable energy devices, or to at least match with that of fossil fuels. The choice of anionic dopant introduced into the titania-rutile can help to vary the structural or electronic properties in titania-rutile. Additionally, the unit cell structure that determines the surface and bulk structure of the titania-rutile single crystal substrate that was chosen was observed to also help modify the structural or electronic properties. While the carbon, sulphur and nitrogen anions were predominantly incorporated as surface dopants in titania-rutile, this was not the case with boron anions, which also showed results that were dependent on the orientation of the titania-rutile. Boron incorporation in (110)-titania-rutile led to the formation of a TiBO3 surface layer, approximately 120 nm thick as per XPS data. This TiBO3 layer, as per XRD data, is epitaxially arranged on the rutile (110) surface along the (108), (118) and (018) planes. While this layer was also seen on the rutile (100) surface, no XRD evidence of TiBO3 was found with the rutile (001) surface. As well as observing a shift in the XPS valence band onset, the emergence of new states and O2p orbital mixing was also observed upon anion incorporation into rutile. This study, reporting the structural and electronic effects observed as a result of doping, will be crucial when working with photocatalysts that are widely studied for the water splitting process, used to produce hydrogen, which is a ‘clean’ energy fuel. The main insight gained from chapter 9 is about making use of the structure of titanate materials (e.g. in open layered and tunnelled titanates) as a scaffold, to control the spatial distribution of any given dopant. This is particularly relevant when the material being investigated is in its powdered form, with no well-defined surface or a bulk. Chapter 9 was written with a specific focus on the effect of doping temperature on the location of the incorporated nitrogen dopant (aka. structural properties), electronic and optical properties in the open layered and tunnelled titanates. While these relationships are widely reported in the literature already, the challenge that this study addresses are about carrying out nitrogen doping at three different temperatures in the same system to ensure the same ammonia flow rate, which is a parameter that is often very challenging to reproduce. This ensures reproducibility of results and therefore reliability in the conclusions. Also, this study is also more comprehensive than that reported in literature the and discusses samples that are fully characterised. The preferential incorporation of nitrogen into the Ti-O-Ti bonds than the Na-O-Ti bonds was observed in the tunnelled titanates, Na2Ti6O13 and K2Ti6O13, and (not in the open layered titanates Na2Ti3O7 and Cs0.68Ti1.825O4), is potentially what led to the creation of Ti3+ defects as observed in their optical absorption spectrum. The resulting Ti 3d and N 1s states observed in the XPS valence band spectrum is potentially what caused the observed band gap narrowing. The modification of the electronic, optical and structural properties of the titanates using nitrogen doping can be used to optimise the functionality of titanates e.g. when it is used as photocatalysts or as battery materials. The main insight gained from chapter 10 is about exploring the alternative material that can replace the expensive aluminium nitride, which is known to be a promising substrate material with ideal thermal conductivity and minimal dissipation of heat. This was done by studying the change in structural properties including associated unit cell volume. The effect of the addition of varying amounts of aluminium as a dopant into the MgSiN2 structure, helped to find that the phase transformation from MgSiN2 to AlN-wurtzite structure is observed between 30% and 50% aluminium dopant introduction, as per XPS and XRD. While the doubling of the magnesium reactant mass led to a single phase MgSiN2, it can potentially affect particle size properties, as hinted by the XRD peak broadening observed. Increasing the aluminium content to above 50% led to unit cell volume contraction as Al3+ ions are smaller than the lattice Mg2+ ions they are substituting. These findings can help gain an understanding of the fundamental chemistry underpinning the development of cheaper, alternative materials for any applications

Seasonal Variations of Iron levels in the Meenachil river, Kottayam, Kerala, South India.

Water with high iron content leads to discoloration of garments and sanitary items and gives a bitter astringent flavour. Issues with taste and smell can result from filamentous organisms that feed on iron compounds. Iron in little quantities is necessary for nourishment, but overdose may cause severe health issues. The Meenachil River, alternatively referred to as Kavanar or Valanjar, is a watercourse coursing through Kerala, India. Renowned for its perilous characteristics, including sudden floods, powerful undercurrents, and the transport of timber and debris from the mountains, it poses significant challenges to navigation. Flowing through the core of Kerala\u27s Kottayam district, this river spans approximately 78 kilometers and originates in the Western Ghats, serving as a vital geographical feature in the southern Indian state.Water samples from 15 locations along the Meenachil River in Kottayam, Kerala, were taken over three seasons: pre-monsoon, monsoon, and post-monsoon, to monitor the level of iron. Many individuals use water from the Meenachil river for drinking and agricultural activities. The greatest iron content of 1056.15 µg/L was recorded at station MS 15 (Illikkal) in the downstream layer during the monsoon season. Station. MS 2 (Adivarum) reported the lowest concentration of iron at 11.63 µg/L during the pre-monsoon season. Iron levels exhibit a seasonal fluctuation at all locations, peaking during the monsoon. Iron levels are often higher at downstream sites than at upstream and middle stream stations. Water quality management is crucial in the research region. It is imperative to formulate proficient management approaches to alleviate iron contamination and uphold the ecological balance of river ecosystems

STATUS OF LEPIDOPTERAN DIVERSITY AT ASOKAPURAM LOCALITY, ALUVA, KERALA, SOUTH INDIA

The insect order Lepidoptera comprises both butterflies and moths. There are over 180,000 Lepidoptera species described, divided into 126 families and 46 superfamilies. 10% of the total number of living creatures described. It is one of the most common and well-known insect orders on the planet. Butterflies are an important category of insects that can function as sensors of environmental change. Butterflies are insects from the order Lepidoptera's macrolepidopteran clade Rhopalocera. Except for Antarctica, there are around 18,500 species of butterflies. Moths are a paraphyletic group of insects that contain all non-butterfly members of the order Lepidoptera, with moths constituting the great bulk of the order. Moths are expected to number over 160,000 species. The majority of moth species are nocturnal, however there are crepuscular and diurnal species as well. Asokapuram is a tiny hamlet located east of Aluva. The current analysis was carried out to identify the Lepidopterans in the area for 6 in diverse habitats surrounding the area. During the inquiry, a total of 46 lepidopterans were noted, 27 of which were recognised, 13 of which were various species of butterflies and the remaining 14 were different species of moths

Preliminary Studies on the Spider Fauna in the Residential Area of Palakkad, North Kerala, India

Spiders are the largest order of arachnids and rank seventh in the total species diversity among all other organisms. The spider diversity of Kottayi Panchayath, Palakkad district of Northern Kerala, was studied for a period of four months (November 2021–February 2022). The exploration yielded 43 species of spiders under 38 genera belonging to 14 families. Salticidae was the most abundant family with 12 species, followed by Araneidae with 8 species. The least abundant families observed during the study period were Clubionidae, Corinnidae, Philodromidae, Sparassidae, Scytodidae, and Hersiliidae, with 1 species. Based on their foraging behaviour in the field, six feeding guilds (Functional groups) of spiders were identified: scattered line weavers, orb weavers, foliage hunters, ground runners, stalkers, and ambushers. The most dominant guild was the orb web weavers, constituting 35% of the total species. Out of 43 species, 24 were wandering spiders, and 19 were web-builder spiders. Spiders foraging strategies involve alert attacks and behavioural responses through the perception of habitat vibration, while others prefer dead prey

Role of omega-3 fatty acids and digoxin in cardiovascular diseases – A comprehensive review

Digoxin and omega-3 fatty acids are two different agents that have been studied for their potential roles in managing cardiovascular diseases. Cardiovascular diseases (CVDs) continue to be a global health concern, with their prevention and management being of paramount importance. Omega-3 fatty acids, including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), have garnered substantial attention for their potential therapeutic role in mitigating CVD risk factors and improving cardiovascular health. This comprehensive review aims to summarize the current state of knowledge regarding the impact of omega-3 fatty acids on cardiovascular diseases. The review encompasses a wide range of studies, including epidemiological investigations, and experimental research, to provide a holistic understanding of the mechanisms through which omega-3 fatty acids influence CVD. Key areas of focus include their effects on lipid profiles, inflammation, endothelial function, blood pressure regulation, and arrhythmia prevention. Additionally, their potential roles in secondary prevention, such as reducing the risk of recurrent myocardial infarction and sudden cardiac death, are explored. The review also discusses the challenges and controversies surrounding omega-3 supplementation, including dosing, sources, and patient selection. Furthermore, it addresses emerging areas of research, such as the interplay between omega-3 fatty acids and gut microbiota, genetics, and personalized medicine. This comprehensive review underscores the multifaceted role of omega-3 fatty acids in cardiovascular diseases. While evidence suggests their potential benefits, further research is needed to refine recommendations and identify optimal strategies for integrating omega-3 fatty acids into cardiovascular disease prevention and management. Understanding the complexities of omega-3's effects on CVD will contribute to more effective and personalized approaches to improve cardiovascular healt

Inference on P(Y<X) Based on Record Values for Generalized Pareto Distribution

In this article, the estimation of [Formula: see text] is considered when [Formula: see text] and [Formula: see text] are two independent generalized Pareto distributions. The maximum likelihood estimators and Bayes estimators of [Formula: see text] are obtained based on record values. The Asymptotic distributions are also obtained together with the corresponding confidence interval of [Formula: see text]. AMS 2000 subject classification: 90B25 </jats:p

Inference on P(Y < X) Based on Ranked Set Sample for Generalized Pareto Distribution

In this paper, the problem of estimation of R = P(Y &lt; X) based on ranked set sampling, when (X,Y) follows generalised Pareto distribution (GPD) is considered. The maximum likelihood (ML) estimators and Bayes estimators of R are obtained. A Monte Carlo simulation is also performed to study the behaviour of different estimators