- Title
- Development of novel mesoporous carbon nitride nanohybrids for antibacterial and sensing applications
- Creator
- John Britto, Jolitta Sheri
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2025
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Pathogens, including bacteria, fungi and viruses, cause infections in humans and are major concerns for public health. Gram-positive and gram-negative pathogenic bacteria can cause urinary diseases and further cause severe infections in the throat, lungs, and skin, thereby causing pain, fever and swelling in the affected body parts. To protect humans against such infections and their transmission, antibacterial agents are employed. It is often challenging to inhibit the growth of drug-resistant bacteria. While nanomaterials (such as metal and metal oxide nanoparticles) have been demonstrated to be a good candidate for anti-bacterial activities owing to high surface area and adequate physical and chemical properties, carbon-based nanomaterials, in particular, can be implemented for preventing antibiotic-resistant bacteria. Moreover, these nanomaterials are widely used in biosensing applications such as glutathione and glucose sensing. While glutathione is primarily responsible for increasing cell proliferation, its excess amount can lead to melanoma and liver cancer. On the other hand, routine glucose testing is needed for diabetic patients. Thus, early detection of glutathione and glucose can help diagnose early-stage disease and eventually reduce mortality rate. Carbon-based nanomaterials can be adequately engineered by surface functional groups, defects, loading, and hybridization to have desirable physical and chemical properties that are useful for enhanced interactions between them and bacterial pathogens. While the high aspect ratio (specific surface area to volume ratio) of nanomaterials provides their efficient adsorption on the bacterial cells followed by disruption of their intra-cellular components, rendering them excellent anti-bacterial agents. In addition, these advanced materials enhance the sensitivity and selectivity of the sensing process which make them more attractive for the commercialisation of these technologies. Cost-effective and scalable production of graphitic carbon nitride (g-C3N4) crystallographic frameworks from commonly available precursors, visible range band gap ~2.7 eV, renders them lucrative for antibacterial activity than other carbon allotropes such as graphene. Designer materials engineering by defects/loading/surface functionalities to the crystalline framework having vacancies/vacancy clusters render g-C3N4 useful for a light-assisted antibacterial activity which restricts their application in indoor surface disinfection. The increased surface area brought by mesoporosity and improved electrostatics at a higher N/C ratio can, in principle, help in antibacterial activity. It is believed that ordered mesoporous carbon nitride (MCN) synthesized by employing a hard templating strategy with the help of inorganic porous templates such as SBA-15 template, will have excellent antibacterial activity compared to bulk g-C3N4 for both gram-positive and gram-negative bacteria. The large surface area of the CN framework and pore volume provide more access to surface functionalities (organic and inorganic molecules) and therefore are supposed to enhance their antibacterial activity as well as their sensing performances. It is also believed that the number of active sites or bandgaps of these unique materials could be tuned with the simple adjustment of the nitrogen contents in the CN framework as it offers unique molecular structure and could enhance the antibacterial activity. As a result, my Ph. D. project aims to develop nitrogen-rich mesoporous carbon nitrides (mC3N5, and mC3N6) in their pristine forms as well as those incorporated by copper atoms for antibacterial activity, as well as bio-molecular (glucose and glutathione) sensing. Therefore, mesoporous carbon nitrides were obtained from nitrogen-rich precursors, namely 3-amino-1,2,4 triazole and aminoguanidine hydrochloride using hard templating strategy involving mesoporous SBA-15 as the template. The mesoporous carbon nitride materials loaded with the copper (Cu) metal within the mesoporous framework were tested for their antibacterial activity and sensing applications. The crystalline order, textural properties and physicochemical properties (such as morphology, functional group, chemical bonding nature, and optical absorption) of the synthesized materials were analyzed by using diverse microscopic and spectroscopic techniques, X-ray diffractometer and surface area measurements. Mesoporosity and metal incorporation are supposed to increase the antibacterial and sensing (glucose and glutathione) performances. The present research findings have been included in this thesis as chapters. The first chapter introduces infectious diseases and early biomolecule detection which explains the importance of antibacterial activity and glutathione and glucose sensing. The advantages of surface coating and early detection are vividly illustrated in this chapter, providing brief knowledge about the mechanisms of antibacterial activity and sensing performances. In addition, this chapter explores different carbon-based nanomaterials and existing methods used to analyze antibacterial activity and biomolecular detection. Finally, this chapter highlights the attributes of carbon nitride materials qualifying them as an effective antibacterial agent and nano mediator used for biomolecule detection. The second chapter is a comprehensive study of multifunctional carbon nanomaterial-based biosensors for cancer detection. The review highlights the importance of carbon-based nanomaterials for biosensing applications towards cancer diagnosis. Therefore, carbon-based biosensors are more selective and recognize cancer biomarkers quickly. Carbon allotropes (such as graphene as well as carbon dots (CDs)) and graphitic carbon nitrides (g-C3N4) are the materials employed for the highly sensitive detection of biomarkers. It also provides an insight into the various classes of biosensors and their main recognition elements, leading to very low detection limits, which is a major principle for detecting cancer biomarkers. Moreover, this chapter provides the limitations and prospects to overcome their challenges in high sensitivity as well as selectivity for cancer biomarkers detections. In the third chapter, mesoporous C3N5 was synthesized with the help of hard silica template SBA-15. The copper metal-incorporated mesoporous C3N5 framework was synthesized and explored for antibacterial efficiency. The synthesized materials were further analyzed for their physico-chemical properties using various analytical techniques. While XRD was used to verify the mesoporous texture mimicking the hard template, FTIR and NEXAFS were conducted to study surface functional groups attached to CN framework. The morphology of the synthesized mC3N5 was analyzed by HR-TEM and SEM microscopies. The mesoporous pure C3N5 and copper loaded C3N5 (xCu-C3N5) were synthesized and explored for antibacterial activity, which was examined by qualitative and quantitative methods. Moreover, toxicity studies were performed on both bacteria which established ROS-mediated cell death. Due to this, xCu-mC3N5 showed a higher antibacterial activity in gram-positive Bacillus subtilis than in E. coli which is gram-negative. In comparison to mesoporous C3N5, 1.50Cu-mC3N5 revealed much more effective antibacterial activities against both gram-positive and negative bacteria. The fourth chapter explores the mesoporous carbon nitride (mC3N6) and copper-loaded mesoporous carbon nitride (xCu-mC3N6) nano morphologies by utilizing a hard templating strategy involving SBA-15 as a hard template. The physico-chemical characterizations were performed on synthesized mC3N6 and xCu-mC3N6 materials. In addition, nitrogen adsorption and desorption isotherms were utilized to establish their textural properties. ICP-MS analysis was performed to measure the presence of copper metal contents in the C3N6 framework. The structural morphologies of the synthesized materials were analyzed by using HR-TEM and SEM microscopies. The mC3N6 and xCu-mC3N6 materials were then exposed to gram-positive and gram-negative bacteria. Detailed studies on anti-bacterial activity were performed for these materials including changes in the bacterial morphology through SEM imaging. xCu-mC3N5 samples were found to exhibit an excellent antibacterial behavior against gram-positive bacteria as compared to gram-negative bacteria. Interestingly, 1.50 Cu-mC3N6 was observed to perform antibacterial activity higher than its mesoporous counterpart. In the fifth chapter, the mesoporous C3N6 and xCu-mC3N6 materials were synthesized and characterized through various analytical methods to confirm the crystallinity, surface area and porous morphology. The synthesized materials were subjected to analysis of peroxidase-like activity for further detection of glutathione and glucose molecules. The 1.00Cu-mC3N6 material was found to have excellent peroxidase activity which influences the detection of glutathione and glucose molecules with high sensitivity and selectivity. The low detection limit (LOD) was observed to be 0.54 PPM for glutathione molecules, whereas it was found to be 0.29 mM for glucose. Therefore, 1.00Cu-mC3N6 material bestows excellent opportunity to be employed as active material especially for an early-stage disease diagnosis, desirable for preventing the mortality rate. In the sixth chapter, the importance of mesoporous C3N6 and copper-loaded C3N6 has been summarized for antibacterial and sensing applications. The chapter further deals with the limitations of existing materials systems. The low surface area of existing materials is held responsible for marginal antibacterial and biomolecule sensing performances. This chapter briefly explains the aim of the project and the advantages of the mesoporous materials utilized in antibacterial and biosensing applications. Enhancing nitrogen/carbon ratio in the CN framework can in principle make them desirable materials for such applications. Indeed, nitrogen-rich mesoporous C3N6 and Cu-C3N6 exhibited superior antibacterial activity and glucose sensing performances.
- Subject
- mesoporous; carbon nitride; metal-loaded; anti-bacterial; bBiosensing
- Identifier
- http://hdl.handle.net/1959.13/1519693
- Identifier
- uon:57415
- Rights
- Copyright 2025 Jolitta Sheri John Britto
- Language
- eng
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