Sensor Innovations Based on Modified Carbon Electrodes

This thesis describes experimental work on electrochemical sensing mechanisms. Chapter 1 and Chapter 2 provide an introduction to electrochemical and surface science techniques as well as nano-carbon materials which are of interest in electroanalysis and sensing. Chapter 3 and Chapter 4 focus on electrochemical processes at liquid | liquid | electrode triple phase boundary systems. In Chapter 3 the electrochemical behaviour of CoPc (cobalt phthalocyanine) dissolved into an organic water –insoluble liquid and deposited as microdroplets on a graphite electrode is studied. Both cation and anion transfer are observed at the liquid | liquid phase boundary. Chapter 4 describes redox processes of a highly hydrophobic anthraquinone derivative where preferential transfer of protons and pH sensitivity are observed. Both systems, CoPc and anthraquinone derivative, are investigated towards CO2 sensitivity. In Chapter 3 and 4 graphite electrodes are employed, but in Chapter 5 graphitic carbon nanoaprticles are employed with a surface functionalisation to provide binding capability to DNA fragments. Layer-by-layer deposition of DNA-carbon nanoparticle composite film electrodes is demonstrated and the electrochemical properties of the films are investigated. A novel type of DNA hybridisation sensing mechanism based on a nano-gap generator – collector electrode system is proposed. Chapters 6 and 7 are dedicated to gas sensing with a novel electrochemical system based on ionomer spheres in contact to the working electrode. In Chapter 6 Dowex ionomer particles are impregnated with carbon nanoparticles which are functionalised with DOPA to provide redox activity and Faradaic current responses. The effect of ionomer type and gas composition is studied. In Chapter 7 Prussian blue nanoparticles are immobilised onto the ionomer particle surface to provide a sensing system with peroxide sensitivity. Overall, this thesis contributes to sensing of bio-molecules and of gases. By introducing new types of interfaces (triple phase boundary, ionomer contacts, carbon nanoparticle redox systems) it is shown that sensitivity and selectivity can be tailored. In future these types of sensor prototypes could be further developed for specific applications.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Tahap keyakinan diri bekas penagih dadah dalam pengawasan di Malaysia: ke arah kepulihan menyeluruh (self-esteem among former drug addicts under observation in Malaysia: towards a comprehensive recovery)

Recovering drug addict is affected by two main factors, namely internal factors (such as resilience and self-confidence) and external (support from families, employers, friends, and community). One of the internal factors that appear to influence the level of recovery of former drug addict is self-confidence. Therefore this study aims to measure the level of self-confidence among former drug addicts, also known as Orang Kena Pengawasan (OKP) who underwent rehabilitation in 6-11 months and 12-24 months. The study was conducted using cross-sectional surveys. A total of 386 former drug addicts in Peninsular Malaysia were involved in this study with 198 respondents undergoing 6-11 months rehabilitation programme and 197 were respondents who were released within 12-24 months. The data obtained were analyzed using descriptive statistics. This analysis was used to measure the level of self-confidence between respondents who underwent the 6-11 months rehabilitation programme (Group 1) and 12-24 months (Group 2). The study found that the majority of both groups showed no signiticant difference in the level of recovery from the aspect of self-confidence. The study also found the majority of respondents of both groups showed a moderate level of confidence of 58.5 percent. However, Group 1 showed a higher percentage of self-confidence (63.5%) compared to Group 2 of (53.8%). The findings have implications for the development of strategies towards a strong self-confidence among the inmates to reduce recidivism rates in Malaysia

Histological and proteome analyses of Microbacterium foliorum-mediated decrease in arsenic toxicity in Melastoma malabathricum

Arsenic (As) is an increasing threat across the globe, widely known as a non-threshold carcinogen, and it is reaching harmful values in several areas of the world. In this study, the effect of plant growth promoting bacteria (Microbacterium foliorum) on inorganic arsenic (Arsenate) phytoremediation by Melastoma malabathricum plants was investigated through histological analysis and proteome profiling of the M. malabathricum plants. Two-dimensional gel electrophoresis and transmission electron microscopy were used to conduct the proteome and histological analysis. When arsenic-treated cells were compared to untreated cells, substantial changes were found (1) severely altered the morphology of the cells, intensely disturbed; (2) the cell wall was thicker; (3) drastically changed the cytoplasm, the cells were polygonal in shape, different in size (scattered), and relatively dense. Compared to the control group, the ultra-structure of the root cells of the control group revealed intact cytoplasm, vacuole, and cell wall under exposure to As + bacteria that had a minor effect on the cell form. To further understand As + bacteria interaction, proteome profiling of the root cell was analyzed. The As-induced oxidative stress enrichment was confirmed by the up-regulation of tubulin, nucleoside diphosphate kinase, and major allergen during As + bacteria exposure It was observed that the profusion of proteins involved in defence, protein biogenesis, signaling, photosynthesis, nucleoside and energy metabolism was greater in As + bacteria as compared to the rooting out of As only. Overall, it can be obviously seen that the current study demonstrates the effectiveness of phytoremediation by M. foliorum on proteins involved and responsive pathways in dealing with As toxicity in M. malabathricum plant

Biodecolourisation of acid red 27 Dye by Citrobacter freundii A1 and Enterococcus casseliflavus C1 bacterial consortium

The feasibility of Citrobacter freundii A1 and Enterococcus casseliflavus C1 bacterial consortium under sequential facultative anaerobic-aerobic treatment for complete dye degradation using AR-27 dyes shows 98% decolourisation and 100% COD removal after 72 hours treatment. Moreover, the UV-Vis spectroscopy and Fourier Transform Infrared (FTIR) Spectroscopic analysis confirmed that the azo linkage was cleaved after the decolourisation occurred. While, the cyclic voltammetry analysis also shows that the decolourisation of AR-27 by C. Freundii A1 and E. Casseliflavus C1 was an irreversible reaction and the detection of oxidation reaction under agitation proved the presences of AR-27 degradation process. Furthermore, the HPLC analysis has confirmed the AR-27 degradation through the decrease in catechol concentration

Utilisation of raw palm oil mill effluent (POME) as a renewable substrate for fermentative H2 production: optimisation using statistical approach

ermentative H2 production was studied using raw POME as the substrate with heat-shock pre-treated POME anaerobic sludge acted as the inoculum. The effect of crucial operating variables (initial pH of medium, incubation temperature, and inoculum size) on H2 production was studied using Box−Behnken Design. A second-order polynomial regression model was generated to evaluate H2 production trend under conditions tested. The model analysis revealed the high significance of linear effects of initial pH, incubation temperature, and inoculum size (P < 0.01) towards H2 production. Similar results indicated that the interaction effect between initial pH and inoculum size, and interaction effect between incubation temperature and inoculum size were highly significant (P < 0.01). The regression model suggested that the optimum conditions were set to a pH value, incubation temperature and inoculum size of 6.4, 58.0°C and 8.0% v/v, respectively. In order to validate the optimum conditions determined by the model, heat-shock pre-treated POME anaerobic sludge was incubated with raw POME under optimum conditions. Validation experiment showed that a cumulative H2 volume of 239.0 mL was produced. Microbial community analysis of inoculum showed that mixed consortia between Clostridium sp. and other obligate anaerobic non-spore forming bacteria, mostly belonging to the Firmicutes and Bacteroidetes phyla were identified as the major H2-producers and were hugely responsible towards fermentative H2 production

Isolation and characterization of metal and antibiotic resistant psychrotrophic bacteria from refrigerated spoiled food

The aim of this study was to isolate and characterize psychrotrophic bacteria resistant to antibiotic and metals from cold samples of refrigerated spoiled food and ice. Two isolates named H and F were successfully isolated from samples incubated at 10°C and 4°C, respectively. Both isolates were able to grow at 4°C, 10°C, 20°C and 30°C and exhibited multidrug resistance to antibiotics (chloramphenicol, ampicillin, tetracycline and kanamycin). Bacteria H and F were then further tested for their resistance to metal ions such as Cd2+, Zn2+, Cr 6+ and As 3+ at concentrations ranging from 0-10 mM. The results of the test revealed that the minimum inhibitory concentration (MIC) for isolate H was determined at 2 mM for all the metal ions. By comparison, isolate F was highly resistant to Cr6+, Cd2+ and Zn2+ with MIC of 10 mM for these cations, while MIC for As3+ was 4 mM. The results of comparing 16S rRNA gens demonstrated that isolate F has 98% identity match with Bacillus sp. This strain could be used as a model microbial strain to understand the mechanisms of metal resistance and as a source of psychrotrophic enzymes with potential application for bioremediation of heavy metals in cold environment

Chapter 10 - Sustainable engineering of food waste into high-quality animal feed using a drying technology

Sustainable management through recycling of the food waste into animal feedstock is one of the promising approaches to overcome the food wastage-related issues. However, this action has been limited in some developed countries due to the lack of safety and security issues. Food waste contains high moisture content and it causes the spread-out of bacteria such as Escherichia coli, Salmonella, and sulfate reducing bacteria. The presence of these pathogens might cause food waste to be contaminated and causes infectious and pandemic diseases to human beings via animals. Thus this chapter aimed to discuss a case study where the evaluation of an effective method for food waste recycling is highlighted. As the food waste pre-drying facilities for the prerequisite animal feedstock pellets testimonial, this study ensures the end products processed inside the university (Universiti Teknologi Malaysia) are safe to be used as animal feeds by investigating the quality of end products. The observation reveals that solar drying food waste exhibits high protein and low moisture contents which the percentage is reached to 22% and 20%, respectively. Meanwhile, the oven drying method could reduce the E. coli content to only 500×103 CFU/g. Therefore, the solar drying method is the most effective to reduce high moisture content and able to achieve high protein content which is acceptable to be used as animal feeds

Hydroxycitric acid content in local exotic fruits as a potential dietary supplement for weight reduction

The content of several exotic Malaysian fruits were investigated to identify the concentration of hydroxycitric acid (HCA) in them. Among the fruits studied were Garcinia atroviridis, Canarium sp. and Averrhoa belimbi L. HCA captured high interest for its potential function as an appetite suppressor. Using FTIR, it was investigated that Garcinia atroviridis had the nearest IR profile to obtain the HCA extract. On the other hand, Averrhoa belimbi showed the worst profile and could be concluded that it doesn’t contain any HCA