Advanced Photonic Crystals for Efficient Light-Trapping in Photocatalytic Applications

Despite advances in solar technologies, there is still a growing and urgent demand for light-harnessing materials that enable efficient utilisation of solar energy for solar-to-fuel conversion and environmental remediation applications. Existing photocatalytic technologies present inherent limitations to achieve these goals due to wide energy bandgap and poor electrochemical properties of conventional materials. A combination of fundamental and applied materials science, nanotechnology, chemistry, photonics and applied physics offers a way forward for developing new light-confining photocatalyst platforms with improved capabilities, versatilities, cost-effectiveness and sustainability to address global energy and environmental issues. This thesis presents the development of rationally engineered composite photocatalyst platforms based on nanoporous anodic alumina photonic crystals (NAA-PCs) and photoactive materials. The fabrication of these photocatalytic systems with enhanced performances is achieved through structural engineering and chemical modification of NAA-PCs. Various forms of NAA-PCs were produced by pulse-like anodisation strategies with a view to optimising optical properties to harness light–matter interactions at the nanoscale efficiently, within high-irradiance spectral regions. The essential photocatalytic properties of these PC structures, well-defined energy bandgap capable of photogeneration of charge carriers, were provided by chemical functionalisation, using photoactive layers of titanium dioxide (TiO₂) deposited onto the inner surface of NAA-PCs through sol-gel method. Photocatalytic performances of photo-active NAA-PCs as well as photocatalytic enhancements associated with distinct forms of light–matter interactions were demonstrated through photodegradation of model organics such as methylene blue, methyl orange, rhodamine B and 4-chlorophenol, under simulated solar light irradiation conditions. Photocatalytic enhancements associated with slow photons, light confinement, and plasmonic effects in noble metal nanostructures with and without NAA-PCs were also analysed. This thesis demonstrated that: (i) high-quality nanoporous anodic alumina gradient-index filters (NAA-GIFs) and hybrid NAA-PCs can be developed with tunable optical properties across the UV-visible-NIR spectrum, (ii) various forms of photo-active NAA-PCs with and without noble metal nanostructures are found to have superior performances to benchmark photocatalyst materials in many cases due to “slow photon” effect and light confinement, and (iii) 2D gold nanodot plasmonic single-lattices show outstanding performances due to efficient utilisation of solar energy at high-irradiance spectral regions and harnessing plasmonic light-matter interactions. The studies completed in this thesis advance both fundamental understanding and applied knowledge on the photocatalytic performance of chemically-modified NAA-PCs with optimised structural, optical, chemical and photocatalytic properties. These advanced materials could potentially be integrated into fully functional and marketable real-life photocatalytic devices for addressing global energy challenges and environmental pollution remediation.Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering and Advanced Materials, 202

High Affinity Maturated Human Antibodies from Naïve and Synthetic Antibody Repertoires

Recombinant human antibody technology has been the cornerstone of the uprising of biologics in the pharmaceutical industry. The introduction of various display technologies like phage, yeast, bacterial, ribosomal, mRNA, DNA display and mammalian cell surface display has allowed improved antibody generation programs. The ability to generate recombinant antibodies from available human antibody libraries by using in vitro display methods pave the way to select recombinant human antibodies against almost every antigen. The libraries are a close representation of the B-cell response elicited by the natural immune system. The introduction of various methods to fine tune the antibody affinities has made recombinant antibody technology highly sought after. The ability to engineer specific characteristics of each antibody by design is possible utilizing advanced in vitro strategies. This chapter will focus on the technologies commonly applied in antibody display technologies to engineer improved affinities

Phage Display‐Derived Antibodies: Application of Recombinant Antibodies for Diagnostics

Antibodies are produced by the human body in response towards infections as a means of protection. The in vivo production of antibodies by B-cells involves a series of intricate gene editing processes resulting in a highly diverse pool of antibodies. However, this diversity can be replicated in vitro using phage display. Phage display offers the potential to present the antibody phenotype together with the cloned genotype of the specific antibody in a single-phage particle. Antibodies are highly sought after for diagnostic applications owing to its specificity and affinity towards a target antigen. The advent of recombinant antibody (rAb) technology allows for a faster and more cost-effective solution for antibody generation. It also provides diagnostic developers with the possibility to customize the antibodies. Antibodies have been utilized successfully in various diagnostic platforms ranging from standard immunoassays to lateral-flow assays, nanoparticles, microfluidics, DNA‐integrated assays and others. The limitless application of antibodies in the field of diagnostics has made it a critical component in any diagnostic development platform. This chapter focuses on the processes involved in antibody discovery including the various forms of antibody libraries for phage display and panning processes. We also highlight some diagnostic platforms that apply recombinant antibodies

Cause-related marketing: it's influence on consumers' choice of hypermarket

Malaysia has undergone market changes which lead to transformation from small shops to larger scale shops due to the globalization. The larger scale shop such as hypermarkets will increase the supply from local suppliers if the demand of consumers toward local product is high. This indicates that cause-related marketing concept can be applied if consumers are favour to hypermarkets that intend to support local product. Therefore, this study aims to examine the factors that influence consumers’ participation intention on “support local product” CRM campaign in the Malaysia context. There were six variables included to determine their effects on participation intention in “support local product” campaign which were firm motive, perceived corporate social responsibility, offer elaboration, brand attitude, ethnocentrism and environmental concern. Multiple regression and one-way ANOVA analysis were used to carry out data analysis. The results of multiple regression analysis indicated that all the predictors have significant relationships with participation intentions except for firm motive. Based on the findings, hypermarket might choose to engage in CRM campaign that use “support local product” as a cause. By doing so, it might assist the hypermarket to differentiate themselves with other competitors in retail industry

Nanoporous Anodic Alumina Photonic Crystals for Optical Chemo- and Biosensing: Fundamentals, Advances, and Perspectives

Optical sensors are a class of devices that enable the identification and/or quantification of analyte molecules across multiple fields and disciplines such as environmental protection, medical diagnosis, security, food technology, biotechnology, and animal welfare. Nanoporous photonic crystal (PC) structures provide excellent platforms to develop such systems for a plethora of applications since these engineered materials enable precise and versatile control of light–matter interactions at the nanoscale. Nanoporous PCs provide both high sensitivity to monitor in real-time molecular binding events and a nanoporous matrix for selective immobilization of molecules of interest over increased surface areas. Nanoporous anodic alumina (NAA), a nanomaterial long envisaged as a PC, is an outstanding platform material to develop optical sensing systems in combination with multiple photonic technologies. Nanoporous anodic alumina photonic crystals (NAA-PCs) provide a versatile nanoporous structure that can be engineered in a multidimensional fashion to create unique PC sensing platforms such as Fabry–Pérot interferometers, distributed Bragg reflectors, gradient-index filters, optical microcavities, and others. The effective medium of NAA-PCs undergoes changes upon interactions with analyte molecules. These changes modify the NAA-PCs’ spectral fingerprints, which can be readily quantified to develop different sensing systems. This review introduces the fundamental development of NAA-PCs, compiling the most significant advances in the use of these optical materials for chemo- and biosensing applications, with a final prospective outlook about this exciting and dynamic field

Integrating surface plasmon resonance and slow photon effects in nanoporous anodic alumina photonic crystals for photocatalysis

This study explores the potential of gold-coated titania-functionalized nanoporous anodic alumina distributed Bragg reflectors (Au-TiO2-NAA-DBRs) as platforms to enhance photocatalytic reactions by integrating “slow photons” and surface plasmon resonance (SPR). The photocatalytic degradation rate of methylene blue – a model organic compound with a well-defined absorption band in the visible spectral region – by these composite photonic crystals (PCs) upon visible-NIR light irradiation is used as an indicator to identify coupling effects between the “slow photon” effect and SPR. Our study demonstrates that the photocatalytic enhancement in Au-TiO2-NAA-DBRs is strongly associated with “slow photon” effect, while the contribution of SPR to the overall photocatalytic enhancement is weak due to the localized generation of surface plasmons on the top surface of the composite PC structure. Photocatalytic enhancement is optimal when the characteristic photonic stopband of these PCs partially overlaps with the absorption band of methylene blue, which results in edges being positioned away from the absorption maximum of the organic dye. The overall photocatalytic degradation for methylene blue is also correlated to the type of noble metal coating and the geometric features of the PC structures. These results establish a rationale for further development of noble metal-coated NAA-based hybrid plasmonic–photonic crystal photocatalyst platforms to optimally integrate “slow photons” and SPR for enhancing the efficiency of photocatalytic reactions and other light harvesting applications.Related: [http://cer.ihtm.bg.ac.rs/handle/123456789/3007]This is peer-reviewed version of the article: Law, L. Liu, M. Markovic, A. D. Abell and A. Santos, Catalysis Science & Technology, 2019, 9, 12, 3158-3176 [https://dx.doi.org/10.1039/C9CY00627C

Non-destructive concrete strength evaluation using smart piezoelectric transducer - a comparative study, smart materials and structures

Concrete strength monitoring, providing information related to the readiness of the structure for service, is important for the safety and resource planning in the construction industry. In this paper, a semi-analytical model of surface bonded piezoelectric (lead zirconate titanate) based wave propagation (WP) technique was developed for strength evaluation of mortar with different mix, throughout the curing process. Mechanical parameters of the mortar specimen were mathematically evaluated from the surface wave (R-wave) and pressure wave (P-wave) using elastic wave equations. These parameters were then empirically correlated to the strength. The model was found to be very robust as it could be generalized to account for different water to cement (W/C) ratio. The performance of the WP technique was then compared to the electromechanical impedance technique and other conventional techniques, such as the ultrasonic pulse velocity (UPV) test and the rebound hammer test. Results showed that the WP technique performed equally well as the conventional counterparts. The proposed technique is also advantageous over embedded WP technique and the UPV test, in terms of its capability to capture two types of waves for the evaluation of dynamic modulus of elasticity and Poisson's ratio. A separate study was finally conducted to verify the applicability of this technique on heterogeneous concrete specimen. With the inherent capability of the WP technique in enabling autonomous, real-time, online and remote monitoring, it could potentially replace its conventional counterparts, in providing a more effective technique for the monitoring of concrete strength

Antioxidant and Toxicity Studies of 50% Methanolic Extract of Orthosiphon stamineus Benth

The present study evaluated the antioxidant activity and potential toxicity of 50% methanolic extract of Orthosiphon stamineus (Lamiaceae) leaves (MEOS) after acute and subchronic administration in rats. Superoxide radical scavenging, hydroxyl radical scavenging, and ferrous ion chelating methods were used to evaluate the antioxidant properties of the extract. In acute toxicity study, single dose of MEOS, 5000mg/kg, was administered to rats by oral gavage, and the treated rats were monitored for 14 days. While in the subchronic toxicity study, MEOS was administered orally, at doses of 1250, 2500, and 5000mg/kg/day for 28 days. From the results, MEOS showed good superoxide radical scavenging, hydroxyl radical scavenging, ferrous ion chelating, and antilipid peroxidation activities. There was no mortality detected or any signs of toxicity in acute and subchronic toxicity studies. Furthermore, there was no significant difference in bodyweight, relative organ weight, and haematological and biochemical parameters between bothmale and female treated rats in any doses tested.No abnormality of internal organs was observed between treatment and control groups.Theoral lethal dose determined wasmore than 5000mg/kg and the no-observed-adverse-effect level (NOAEL) of MEOS for both male and female rats is considered to be 5000mg/kg per day

Antioxidant and toxicity studies of 50% methanolic extract of Orthosiphon stamineus benth.

The present study evaluated the antioxidant activity and potential toxicity of 50% methanolic extract of Orthosiphon stamineus (Lamiaceae) leaves (MEOS) after acute and subchronic administration in rats. Superoxide radical scavenging, hydroxyl radical scavenging, and ferrous ion chelating methods were used to evaluate the antioxidant properties of the extract. In acute toxicity study, single dose of MEOS, 5000 mg/kg, was administered to rats by oral gavage, and the treated rats were monitored for 14 days. While in the subchronic toxicity study, MEOS was administered orally, at doses of 1250, 2500, and 5000 mg/kg/day for 28 days. From the results, MEOS showed good superoxide radical scavenging, hydroxyl radical scavenging, ferrous ion chelating, and antilipid peroxidation activities. There was no mortality detected or any signs of toxicity in acute and subchronic toxicity studies. Furthermore, there was no significant difference in bodyweight, relative organ weight, and haematological and biochemical parameters between both male and female treated rats in any doses tested. No abnormality of internal organs was observed between treatment and control groups. The oral lethal dose determined was more than 5000 mg/kg and the no-observed-adverse-effect level (NOAEL) of MEOS for both male and female rats is considered to be 5000 mg/kg per day