Kinetic-Control of Block Copolymer Micelles for Tunable Nanomaterials Towards Energy Devices

Nano-scale inorganic porous materials are crucial for numerous applications ranging from electronics to energy conversion. The ability to control the morphology and the key architectural parameters of nanomaterials largely determines the transport characteristics and performance of such devices. But, there is very little understanding and development to tune these key architectural parameters such as inorganic wall-thickness and pore diameter. Even though there are numerous examples available on the fabrication of porous nanomaterials via block copolymer co-assembly, there is limited understanding on independent control over key architectural parameters. Because of that the major focus of this thesis is to explore and develop tunable nanomaterials with block copolymer micelles that could use to fabricate nano-optimize energy storage devices with high energy and fast rate capabilities. Towards this end, tunability of the key architectural parameters was studied and processing guidelines and solution conditions that enable nanostructures with tunable wall-thickness and pore diameters are presented. First, a new block copolymer poly (ethylene oxide-b-hexyl acrylate) (PEO-b-PHA) structure directing agent (SDA) was synthesized and used to demonstrate the tunability of the inorganic wall-thickness. Specifically, the use of a polymer with a high Flory-Huggins effective interaction parameter, χ, and appropriate solution conditions lead to the kinetic entrapment of micelles to produce persistent micelles which were used as templates to fabricate tunable isomorphic architectures. The use of different inorganic loadings with persistent micelles resulted in different wall-thicknesses with constant pore size. The processing guidelines for persistent micellar templating (PMT) were elaborated using mesoporous Nb2O5 that was thermally stable at 600 oC giving access to crystalline materials. Overall, this method provides a simple and a predictable path to produce porous nanomaterials with tunable wall thickness. Second, these kinetically entrapped block copolymer micelles resulted from a single block copolymer were re-arranged into different micelle sizes to achieve a range of pore dimeters. This target is particularly challenging since the rate of single-chain exchange and micelle fusion/fission reactions are hindered by the large thermodynamic barrier for rearrangement in these kinetically trapped micelle systems. The rate of the chain exchange reactions in block copolymer micelles will increase due to the production of solution-air interface as reported in literature. Here, we used ultrasonic cavitation for rapid interface production that accelerates micelle growth by an order of magnitude over agitation via vortexing. This extremely simple but powerful modification can be used as an unique handle to tune the pore diameter of nanomaterials by achieve a range of micelle sizes from a single block copolymer. Third, the PMT derived macroporous isomorphic architectures of Nb2O5 were used to show the potential application in understanding the operative mechanism of energy storage at different length scale. This sort of model systems could use to systematically investigate the optimal length scale of ion and electron diffusion to produce nano-optimize porous electrode systems. In this study T-Nb2O5 was selected as the electrode material due to its well-known pseudocapacitive behavior which has ability to combine both high energy densities and high-power densities into one materials. The overall goal of this thesis is to contribute towards the assembling the nano-porous electrodes into most effective architecture to achieve next generation high energy and power density devices. Therefore, this work demonstrated that the careful tuning of the block copolymer micelles in solution paves a simple and versatile path to obtain tunable nanomaterials which could be highly useful in nanotechnologies such as advanced energy conversion and storage devices

Transforming the Pandemic into a gateway for zeroing waste-related emissions at the University of Colombo, Sri Lanka

The University of Colombo (UoC) has turned the Covid-19 pandemic into a win-win situation by adopting new measures to overcome limitations the pandemic has brought in while improving its overall waste management. It has incorporated a paperless system by conducting academic work online, including applying for new courses, distributing e-learning material and submitting assignments. Every lecture, meeting, and function has been held virtually, eliminating food, paper, plastic and decoration waste. Students now study from home and employees have been reporting to work according to rosters, reducing food and office waste generation significantly. The employees now adhere to the pre- and newly included post-pandemic environmental guidelines, litterless lunches, and have been provided with shuttle services for safer commuting, leading to lower greenhouse gas emissions. Identifying the potential environmental damage through improper disposal, using reusable masks is being promoted through regular online awareness programmes; eco-friendly sanitizers are used instead of liquid soap, which consumes water and generates wastewater. Although the amount of waste generated during the pandemic is low, the UoC-owned Waste Storage Center continues to function with waste segregation and recycling, and the composting facility is currently expanding its production. The waste reduction has also caused lowered waste-related greenhouse gas emissions.Keyword: Waste Management, Paperless System, Guidelines, Waste Storage Center, Segregation and Recyclin

Threshold Rainfall Ranges for Landslide Occurrence in Matara District and Findings of a Social Survey on Emergency Preparedness

Matara district has faced several devastating landslide events within past few decades. Impacts of those landslide events would have been reduced if the threats had been identified early enough and the early warnings were disseminated at the right time. The objectives of this research were (a) to identify the effects of antecedent rainfall on the probability of landslide occurrence and (b) to analyse the knowledge of the community on landslide response, preparedness and landslide warning signs in general. During this study the major landslide events occurred in 2003 and 2017 were studied for the rainfall impact. The landslide locations were collected and the rainfall relevant to each and every landslide location was extracted by using a GIS-based interpolation method. Simultaneously a social survey was conducted to achieve the second objective described above. Starting from the daily rainfall of two days prior to landslide event (i.e. Day 3) till the daily rainfall of landslide day (Day 1), there was an identifiable pattern. There is more than 90 percent chance for a landslide to occur, when the rainfall of the day of the landslide event is close to 300 mm (in our case 290 mm) or above with a rainfall of ~80 mm or above on the previous day (Day 2). The majority of the events (over 94 percent) had a daily rainfall of ~80 mm or above on Day 3. The cumulative rainfall of the landslide day up to three days prior to the landslide event shows a significant pattern (Day 1-Day 4). There is more than 94% chance for a landslide to occur when the total rainfall received on Day 1 and Day 2 exceeds 375 mm. Overall, when there is a rainfall event of ~80 mm or over, people need to be warned/cautions about a potential landslide within the next three days, if the rainfall continues to be high. Social survey shows that during 2017 event/s people were more prepared for landslides compared to 2003, but still there are many steps to be taken in terms of response, preparedness and early warnings.Keywords: Landslides, Rainfall pattern, Early warnings, Community preparednes

Ordered Mesoporous to Macroporous Oxides with Tunable Isomorphic Architectures: Solution Criteria for Persistent Micelle Templates

Porous and nanoscale architectures of inorganic materials have become crucial for a range of energy and catalysis applications, where the ability to control the morphology largely determines the transport characteristics and device performance. Despite the availability of a range of block copolymer self-assembly methods, the conditions for tuning the key architectural features such as the inorganic wall-thickness have remained elusive. Toward this end, we have developed solution processing guidelines that enable isomorphic nanostructures with tunable wall-thickness. A new poly(ethylene oxide-b-hexyl acrylate) (PEO-b-PHA) structure-directing agent (SDA) was used to demonstrate the key solution design criteria. Specifically, the use of a polymer with a high Flory-Huggins effective interaction parameter, χ, and appropriate solution conditions leads to the kinetic entrapment of persistent micelle templates (PMT) for tunable isomorphic architectures. Solubility parameters are used to predict conditions for maintaining persistent micelle sizes despite changing equilibrium conditions. Here, the use of different inorganic loadings controls the inorganic wall-thickness with constant pore size. This versatile method enabled a record 55 nm oxide wall-thickness from micelle coassembly as well as the seamless transition from mesoporous materials to macroporous materials by varying the polymer molar mass and solution conditions. The processing guidelines are generalizable and were elaborated with three inorganic systems, including Nb2O5, WO3, and SiO2, that were thermally stable to 600 °C for access to crystalline materials

Topographical Effects on Soil Carbon in a High Grown Tea Plantation of Nawalapitiya

Soil organic carbon (SOC) storage is an important component of global carbon cycle and climate change mitigation. SOC storage depends on climate, topography and soil properties. The main objective of this research was to quantify average soil SOC content across the toposequence of a selected mountain terrain. The secondary objective was to compare the impact of microclimatic variables and slope angle on soil organic carbon content. It was hypothesized that mountainous locations with an overall high percent slope have lower SOC than the mountainous locations with lower percent slope.In this study, four slope positions across the toposequence of two tea fields (Field A and Field B) within Queensberry tea estate, Nawalapitiya were sampled for soil analyses. Measurements on micrometeorological variables (soil and air temperature, relative humidity, wind velocity, light intensity), litter and soil cores were taken in the field, and soil parameters including soil moisture, pH, texture and SOC stocks were analyzed in the laboratory.The overall average soil organic carbon stock in the studied soils was 159.85 t/ha .The overall percent slope of field A (25 percent) was higher than that of field B (21 percent). A significant difference in soil carbon stock could be seen among the slope positions considered across the toposequence of each field (P<0.0005). Percent soil moisture (P<0.0005; adjusted R²=61.60%) and sampling fields (which differed in overall slope angle; P<0.005; adjusted R²=26.48%) have a notable effect on SOC stock while litter depth (F=2.68; P>0.05) have no significant effect on SOC stock. The SOC stock was higher at the field B (172.16 t/ha) which had the lower percent slope while SOC stock was lower at the field A (147.52t/ha) which had the higher percent slope. Therefor our hypothesis that mountainous locations with high percent slope would have lower SOC than the mountainous locations with lower percent slope was supported.Overall, the SOC stocks were significantly different with regard to the differences in slope angle (as found for the two fields) and the slope position across the toposequence (as observed within each field) in the medium-gradient tea plantation considered in the current study. Among the microclimatic variables, only the moisture had a significant influence on the SOC stock.Keywords: SOC stock, Slope position, Slope angle, Percent soil moisture, Medium-gradient tea plantatio

OFF-GRID, COMMUNITY-BASED DENDROTHERMAl POWER GENERATION A ViABLE OPTION FOR CLEAN DEVELOPMENT MECHANISM

Sri Lanka has taken various measures to implement Ole United Nations Framework Conventionon Climate Change within the country. Clean development mechanism (CDM) provides aframework for participation of developing countries in mitigating climatic effects. In CDM, adeveloped country will implement and finance a project that reduces or mitigates greenhouse gas(carbon dioxide) emissions in a developing country, for which the developed country partywould get Certified Emission Reductions (CERs), certifying the emissions reduced from theCDM project. Such a CDM project would help the developing country in achieving itssustainable development goals, and the country can a lso profit by selling any carbon avoided bythe CDM project to the developed country partyIn Sri Lanka, power sector is a potential sector for CDM, due to high carbon emissionsassociated with thermal power generation. Since Sri Lanka has almost reached its maximumhydropower potential, the country needs to consider having more thermal and renewable energyoptions in the power sector. One potential, relatively cheap renewable option is dendrothermalpower generation. Power generation using biomass collected from energy plantations could beconsidered as a suitable renewable option, especially in remote areas, where power supply fromthe national grid is not easy. Such energy plantations can be successfully grown and maintainedby the communities in rural Sri Lanka, and it has a high potential as a means of povertyeradication and employment generation in those areas. Energy plantations also improve soilquality and nutrient cycling within the ecosystem.Dendrothermal power generation is considered carbon neutral, as carbon emitted during powergeneration is absorbed by the energy plantations in photosynthesis. If a certain percentage of theplanned thermal power (coal) generation in future e-m be replaced with dendrothermal powergeneration, the country can profit by selling the avoided carbon in shifting to dendrothermalpower. Therefore dendrothermal power generation satisfies the criteria relevant to CDM. Thisstudy economically analyses the feasibility of havir ..g off-grid dendrothermal power generationas a potential CDM option, while evaluating socio-economic and other benefits associated withit.The study showed that the unit cost of dendrothermal power generation (US cts. 4.68) is slightlyhigher than that of coal (US cts. 4.34), but the country can significantly profit if the avoidedcarbon is sold at a reasonable price. Hence the study clearly shows that dendrothermal powergeneration is a viable option for CDM.

Nanostructure Dependence of T‐Nb₂O₅ Intercalation Pseudocapacitance Probed Using Tunable Isomorphic Architectures

Intercalation pseudocapacitance has emerged as a promising energy storage mechanism that combines the energy density of intercalation materials with the power density of capacitors. Niobium pentoxide was the first material described as exhibiting intercalation pseudocapacitance. The electrochemical kinetics for charging/discharging this material are surface‐limited for a wide range of conditions despite intercalation via diffusion. Investigations of niobium pentoxide nanostructures are diverse and numerous; however, none have yet compared performance while adjusting a single architectural parameter at a time. Such a comparative approach reduces the reliance on models and the associated assumptions when seeking nanostructure–property relationships. Here, a tailored isomorphic series of niobium pentoxide nanostructures with constant pore size and precision tailored wall thickness is examined. The sweep rate at which niobium pentoxide transitions from being surface‐limited to being diffusion‐limited is shown to depend sensitively upon the nanoscale dimensions of the niobium pentoxide architecture. Subsequent experiments probing the independent effects of electrolyte concentration and film thickness unambiguously identify solid‐state lithium diffusion as the dominant diffusion constraint even in samples with just 48.5–67.0 nm thick walls. The resulting architectural dependencies from this type of investigation are critical to enable energy‐dense nanostructures that are tailored to deliver a specific power density

Lignin Biopolymers in the Age of Controlled Polymerization

Polymers made from natural biomass are gaining interest due to the rising environmental concerns and depletion of petrochemical resources. Lignin isolated from lignocellulosic biomass is the second most abundant natural polymer next to cellulose. The paper pulp process produces industrial lignin as a byproduct that is mostly used for energy and has less significant utility in materials applications. High abundance, rich chemical functionalities, CO2 neutrality, reinforcing properties, antioxidant and UV blocking abilities, as well as environmental friendliness, make lignin an interesting substrate for materials and chemical development. However, poor processability, low reactivity, and intrinsic structural heterogeneity limit lignins′ polymeric applications in high-performance advanced materials. With the advent of controlled polymerization methods such as ATRP, RAFT, and ADMET, there has been a great interest in academia and industry to make value-added polymeric materials from lignin. This review focuses on recent investigations that utilize controlled polymerization methods to generate novel lignin-based polymeric materials. Polymers developed from lignin-based monomers, various polymer grafting technologies, copolymer properties, and their applications are discussed

New distributional record of Cylindera (Oligoma) paradoxa (W. Horn, 1892) (Coleoptera: Cicindelidae) in Ratnapura District, Sri Lanka

Since the 19th century, Cylindera (Oligoma) paradoxa (W. Horn, 1892) has been recorded from only 10 locations in Sri Lanka, with only 2 of those recorded in the past 30 years. We recently found this species in the Keeragala estate (Ratnapura District) during field surveys. Our new record fills a gap in the knowledge of this species’ distribution in Sri Lanka

Incorporation of crop phenology in Simple Biosphere Model (SiBcrop) to improve land-atmosphere carbon exchanges from croplands

Croplands are man-made ecosystems that have high net primary productivity during the growing season of crops, thus impacting carbon and other exchanges with the atmosphere. These exchanges play a major role in nutrient cycling and climate change related issues. An accurate representation of crop phenology and physiology is important in land-atmosphere carbon models being used to predict these exchanges. To better estimate time-varying exchanges of carbon, water, and energy of croplands using the Simple Biosphere (SiB) model, we developed crop-specific phenology models and coupled them to SiB. The coupled SiB-phenology model (SiBcrop) replaces remotely-sensed NDVI information, on which SiB originally relied for deriving Leaf Area Index (LAI) and the fraction of Photosynthetically Active Radiation (fPAR) for estimating carbon dynamics. The use of the new phenology scheme within SiB substantially improved the prediction of LAI and carbon fluxes for maize, soybean, and wheat crops, as compared with the observed data at several AmeriFlux eddy covariance flux tower sites in the US mid continent region. SiBcrop better predicted the onset and end of the growing season, harvest, interannual variability associated with crop rotation, day time carbon uptake (especially for maize) and day to day variability in carbon exchange. Biomass predicted by SiBcrop had good agreement with the observed biomass at field sites. In the future, we will predict fine resolution regional scale carbon and other exchanges by coupling SiBcrop with RAMS (the Regional Atmospheric Modeling System)