Triethylamine: a versatile ligand to control the properties of nanomaterials
Creators: name: Singh, Mandeep
Publisher: name: RMIT University
Year: 2024
Subjects: classificationCode: 310607
subject: Nanobiotechnology
classificationCode: 401807
subject: Nanomaterials

description: Triethylamine (TEA) acts as an outstanding hydrolysing agent along with certain shape-directing properties for nanomaterial synthesis. The use of TEA in this thesis for nanomaterial synthesis offers new potential in controllably tuning the underlying synthesis reaction pathways to obtain nanomaterials of different compositions and morphologies. Firstly, TEA was found to be quite effective for nanoparticle synthesis concerning the low cost of material production through high yields, the requirement of less-intensive purification steps, and facile long-term storage offered by high ambient stability of materials prepared using TEA. These characteristics are other difficult to control and therefore restricts the applications of nanomaterials at the industrial scale. This low molecular weight organic tertiary amine has certain unique characteristics that allow it to perform in diverse ways, as illustrated throughout this thesis; these include amphiphilicity (ability to dissolve both in aqueous and organic solvents), high basicity (similar to that of ammonia), and newly discovered shape-directing ability. As such, this thesis reports the development of a range of nanomaterials by establishing new synthesis protocols, while keeping TEA as the central theme as one of the reagents employed during proposed methodologies and reactions. Chapter 1 provides a state-of-the-art of the prior literature in the field, and a diverse range of instrumental techniques employed to characterize the nanomaterials prepared using TEA thoroughly are captured in Chapter 2. Chapter 3 then discusses the experimental outcomes of this thesis and is sub-divided into multiple sub-chapters, each covering a specific nanomaterial employing TEA in different ways. Chapter 3a first demonstrates the ability of the TEA to directly synthesise iron oxide (γFe2O3) nanoparticles both in aqueous and organic solvents. Secondly, it is demonstrated how TEA can be used as a dynamic amphiphilic molecule for the phase transfer of the organic ligand-stabilised iron oxide particles from an organic to an aqueous phase. The magnetic hyperthermia properties of these materials were evaluated, and the role of Brownian relaxation in magnetic hyperthermia was highlighted. Chapter 3b demonstrates the importance of TEA in obtaining highly oxygen-deficient and photostable copper oxide (Cu2O) nanoparticles. It is well known that Cu(I) is highly unstable in water and is prone to oxidation to Cu(II), which makes the aqueous synthesis of Cu2O challenging. This works shows that TEA can act as a coordinating ligand to form a Cu(I)TEA complex, which on water-mediated hydrolysis produces Cu2O particles. The application of these mateials for enhanced visible light photocatalytic activity is demonstrated by establishing the importance of oxygen vacancies in photo-induced catalytic reactions. Chapter 3c demonstrates that gadolinium-based one-dimensional (1D) nanorods of Gd(OH)3 and Gd2O3 can be realised using TEA as a dynamic molecule. These Gd-based nanomaterials showed inherent enzyme-mimic peroxidase-like NanoZyme activity. Such Gd-based nanorods were exploited for the first time as colourimetric sensors for rapid detection of cysteine, a biologically important molecule. In Chapter 3d, I demonstrate that TEA can be used to obtain layered tin monoxide (SnO) microspheres which can then act as a starting material to obtain high-quality 2D SnO nanosheets. In the context of the importance of this process, it may be appreciated that over the last decade, a new dimension of the material aspect, i.e. two-dimensional (2D) research has emerged where nanomaterials have shown remarkable distinctive or enhanced properties in comparison to the other dimensional materials. Although much progress has been made to explore such 2D materials using the top down approach but rather limited efforts have been made to obtain such materials using bottom up approach. This chapter fills this gap by preparing 2D SnO using a bottom-up approach. Further, we explored detailed optical characteristics of the bulk SnO w.r.t to 2D thin SnO, and our findings revealed an unprecedented opening of the bandgap from ~2.7 eV (bulk) to 4.1 eV (monolayers) due to strong quantum confinement. These 2D SnO sheets were utilized for photodetector applications.<br>