ZINC OXIDE-BASED THIN FILM ELECTRONICS

Ph.DDOCTOR OF PHILOSOPH

Effects of elevated temperature on the tropical soil bacterial diversity

Bacteria are important biological components of soil that play pivotal roles in improving soil quality and maintaining a balanced ecosystem. However, global climate change may have severe impacts on biodiversity and ecosystems including species loss and extinction of plants and animals, including microbes. Thus, it is crucial to determine how elevated temperature may alter soil bacterial diversity and composition. In this study, an in vitro simulated temperature rise experiment was carried out on soils from three sampling sites, referring to S1, S2, and S3 around Sabah, Malaysia. Soils were incubated at 25 °C (control) and 27 °C (simulated warming) with constant parameters in a growth chamber up to 16 months. Total DNA was extracted from microbes in the soil and used for PCR amplification targeting the V3-V4 region of the 16S rRNA gene. These amplicons were sequenced using the MiSeq platform (Illumina, USA). Raw DNA sequences were trimmed, merged, and aligned against the 16S rRNA sequences in the NCBI 16S database. The results showed that the analyzed soils were mainly dominated by Proteobacteria, Actinobacteria, Acidobacteria, and Verrucomicrobia. After 16 months of simulated warming, a net decrease of Proteobacteria, Acidobacteria, and Planctomycetes, and an increase of Actinobacteria and Chloroflexi were observed for all three soil samples, indicating that these phyla were highly affected by a temperature rise. At the genus level, Gaiella and Nocardioides exhibited a net increase while Bradyrhizobium, Mycobacterium, Tepidisphaera, and Paludibaculum demonstrated net decrease after 16 months of simulated warming. Knowledge on the changes of soil bacterial diversity patterns as a result of temperature elevation will contribute to select the best intervention strategy to overcome global warming issue in the future

Tropical soil bacterial diversity in Sabah, Malaysia

Bacteria are an essential biological component of soil function that plays fundamental roles in biogeochemical cycling, soil quality improvement, habitat-shaping, and ecosystem conservation. It is therefore important to have a good record of soil bacteria in the tropics in order to monitor future changes that may occur due to global warming and other factors. However, extremely limited data are available on the diversity of bacteria in soils in some tropical Borneo regions such as Sabah, Malaysia. This research, therefore, was undertaken to determine the bacterial diversity of soils from various locations in Sabah, Malaysia. Ten soil samples (n=10) were collected around Sabah. 16S rDNA of bacterial DNA extracted from soils were amplified and analysed using the Denaturing Gradient Gel Electrophoresis (DGGE). A total of 100 dominant and well-defined DNA fragments observed in the DGGE gel were extracted, sequenced, and aligned. The results indicated that 93 different bacterial operational taxonomic units (OTUs) representing bacteria from 8 different phyla were present. The most abundant phyla in the analysed Sabah soils were Proteobacteria followed by Acidobacteria, Firmicutes, Actinobacteria, Planctomycetes, Verrucomicrobia, Chloroflexi, and Bacteroidetes. The examined soils of Sabah and Peninsular Malaysia had similar dominant phyla in general, except that the most dominant phylum in Peninsular Malaysia soils is the Acidobacteria instead of Proteobacteria. These baseline data generated from this work are important and can be used to track bacterial diversity shifts due to soil or environmental changes in the future

Sb₂Te₃–Bi₂Te₃ Direct Photo–Thermoelectric Mid‐Infrared Detection

A compact and responsive thermoelectric photodetector is introduced for the mid‐infrared. By resonantly coupling mid‐infrared light to a Sb2Te3‐Bi2Te3 thermoelectric junction, a thermocouple is formed that is directly heated by narrow‐band mid‐infrared radiation. Near‐perfect absorption is achieved at this hot junction through the resonantly enhanced coupling of light to free‐electrons in the Bi2Te3 and Sb2Te3 materials. The fabricated devices operate at 3.6 µm and demonstrate a responsivity of 10.2 V W−1, a specific detectivity of 4.6 × 106 cm Hz1/2 W−1, and a bandwidth in the order of 1 kHz. The optimal detection wavelength can be spectrally tuned by changing the resonant cavity dimensions. This work shows a path toward miniaturized mid‐infrared detectors and spectrometers with high sensitivity, responsivity, and bandwidth. Importantly, the device presented here is ideal for industrial production, which it is hoped will provide wider access to mid‐infrared technologies for chemical sensing, medicine, and security

Progress in thermochemical co-processing of biomass and sludge for sustainable energy, value-added products and circular economy

To achieve the main goal of net zero carbon emission, the shift from conventional fossil-based energy/products to renewable and low carbon-based energy/products is necessary. Biomass has been perceived as a carbon–neutral source from which energy and value-added products can be derived, while sludge is a slurry waste that inherently contains high amount of minerals and organic matters. Hence, thermochemical co-processing of biomass wastes and sludge could create positive synergistic effects, resulting in enhanced performance of the process (higher conversion or yield) and improved qualities or characteristics of the products as compared to that of mono-processing. This review presents the current progress and development for various thermochemical techniques of biomass-sludge co-conversion to energy and high-value products, and the potential applications of these products from circular economy’s point of view. Also, these technologies are discussed from economic and environmental standpoints, and the outlook towards technology maturation and successful commercialization is laid out

香港居家安老面對的挑戰 : 服務提供者及使用者之經驗

隨著人口老化，居家安老成為香港社會重大的挑戰。政府多年來提倡「居家安老為本，院舍照顧為後援」的政策方針，透過加強社區照顧服務，以減少院舍入住率。然而，政策需要由家居環境、以至社區支援互相配合，創造可供市民居家安老的先天條件方能成事。本研究旨在探討香港推行居家安老時所面對的困難與挑戰。研究團隊訪問了30名60歲或以上、曾經或正在使用長者服務的使用者和19名從事長者社區照顧及支援服務行業的服務提供者，從不同的角度探討長者居家安老的狀況和社區照顧及支援服務的成效。 研究團隊綜合了長者居家安老的狀況，提出了幾方面的改進建議。在家居環境和社區設施方面，建議 (1) 政府應主動協助長者改善「居住環境」和安裝「緊急呼叫系統」，並(2) 建設合適長者的公共交通工具和道路設施和交通配套。在醫療層面方面，建議 (3) 資助有緊急需要的長者使用私營醫療服務、(4) 擴展醫療券計劃至購買坊間藥物和 (5) 改善普通科門診醫療預約系統和公開長者預約專籌的數量及其使用狀況。在長者社區照顧及支援服務方面，建議 (6) 檢視社區照顧服務券的宣傳和使用狀況、(7) 對長者家庭進行家訪，及早識別有需要個案和 (8) 檢視未來各區長者比例，規劃長者設施服務。 研究團隊分析了社福機構人員在提供長者服務過程中所遇到的困難後，提出了四方面的建議，分別爲 (1) 改進安老服務人員資歷架構和服務外包、(2) 簡化並加強服務資訊的宣傳、(3) 優化一站式服務平台及個案管理和 (4) 制訂長遠的安老政策方向

A review on potential of green solvents in hydrothermal liquefaction (HTL) of lignin

One of the greatest challenges in biorefinery is to reduce biomass’ recalcitrance and enable valorization of lignin into higher value compounds. Likewise, green solvents and hydrothermal liquefaction (HTL) with feasible economic viability, functionality, and environmental sustainability have been widely introduced in extraction and conversion of lignin. This review starts with the underscore of disadvantages and limitations of conventional pretreatment approaches and role of green solvents in lignin extraction. Subsequently, the effect of process parameters along with the reaction mechanisms and kinetics on conversion of lignin through HTL were comprehensively reviewed. The limitations of green solvents in extraction and HTL of lignin from biomass were discussed based on the current advancements of the field and future research scopes were also proposed. More details info on HTL of biomass derived lignin which avoid the energy-intensive drying procedures are crucial for the accelerated development and deployment of the advanced lignin biorefinery

Hydrogen sulfide (H2S) conversion to hydrogen (H2) and value-added chemicals : Progress, challenges and outlook

Hydrogen sulfide (H2S) is a toxic gas released from natural occurrences (such as volcanoes, hot springs, municipal waste decomposition) and human economic activities (such as natural gas treatment and biogas production). Even at very low concentrations, H2S can cause adverse health impacts and fatality. As such, the containment and proper management of H2S is of paramount importance. The recovered H2S can then be transformed into hydrogen (H2) and various value-added products as a major step towards sustainability and circular economy. In this review, the state-of-the-art technologies for H2S conversion and utilization are reviewed and discussed. Claus process is an industrially established and matured technology used in converting H2S to sulfur and sulfuric acid. However, the process is energy intensive and emits CO2 and SO2. This calls for more sustainable and energy-efficient H2S conversion technologies. In particular, recent technologies for H2S conversion via thermal, biological, plasma (thermal and non-thermal), electrochemical and photocatalytic routes, are critically reviewed with respect to their strengths and limitations. Besides, the potential of diversified value-added products derived from H2S, such as H2, syngas, carbon disulfide (CS2), ammonium sulphate ((NH4)2SO4), ammonium thiosulfate ((NH4)2S2O3), methyl mercaptan (CH3SH) and ethylene (C2H4) are elucidated in detail with respect to the technology readiness level, market demand of products, technical requirements and environmental impacts. Lastly, the technological gaps and way forward for each technology are also outlined