SYNTHESIS OF FLUORESCENT METAL HALIDE PEROVSKITE NANOMATERIALS AND THEIR NANOCOMPOSITES FOR THE INVESTIGATION OF MORPHOLOGICAL AND PHOTOPHYSICAL PROPERTIES

Abstract

The thesis, titled "SYNTHESIS OF FLUORESCENT METAL HALIDE PEROVSKITE NANOMATERIALS AND THEIR NANOCOMPOSITES FOR THE INVESTIGATION OF MORPHOLOGICAL AND PHOTOPHYSICAL PROPERTIES" has been structured into six chapters. Chapter 1 This chapter provided a short and systematic overview of metal lead halide-based perovskite nanocrystals (PNCs) and their applications in different optical devices. Afterwards, addressing viable and appropriate synthetic approaches for perovskite nanomaterial synthesis. The HOIP nanoparticles exhibit charge transfer capabilities with a variety of acceptor molecules, including organic and inorganic compounds, as well as the materials' capacity to sense biological molecules. Chapter 2 In this chapter, we synthesized cesium lead halide perovskite nanomaterial (CsPbBr3) using ligand-assisted reprecipitation (LARP) procedures and characterized it using UV, PL, TCSPC, FTIR, XRD, SEM, TEM, and XPS. We employed these materials for charge transfer applications with two distinct organic acceptor molecules, anthraquinone (AQ) and tetracyanoquinodimethane (TCNQ). A novel approach for charge separation is a hybrid combination of organic acceptors such as AQ and TCNQ with CsPbX3 (X=Cl, Br, I) perovskite nanomaterials at the interface. The surface of the perovskite nanomaterial is crucial in electron-hole charge separation. The interaction between this redox pair is controlled by the surface of the perovskite nanomaterial. Only such molecules have higher charge separation, which allows them to interact more efficiently with the excited state of perovskite nanocrystals (PNCs), but relatively few organic compounds have these redox capabilities.Chapter 3 Bright luminescence hybrid halide perovskites nanocrystals (PNCs) as a novel fluorophore class have not been broadly explored in biological sensing. In this chapter, we synthesized highly fluorescent CsPbBr3 PNCs through the LARP method, using oleic acid and oleyl amine as a capping ligand. Morphological and optical properties of as-synthesized PNCs were studied using TEM, XRD, UV-Vis, and emission spectroscopic analysis. Oleic acid and oleyl amine-capped perovskite nanocrystals are employed for sensitive and selective detection of bilirubin (BR). A panel of characterizations (time-correlated single-photon count spectroscopy and photoluminescence) was carried out to investigate the detailed sensing study of PNCs-BR composite for quenching the PL emission of CsPbBr3 with bilirubin. It has been noticed that the synthesized nanoparticles are highly capable of detecting bilirubin and thus act as a biological material sensor.Chapter Lead halide perovskites have garnered significant attention in the field of optoelectronics due to their high efficiency in applications such as photovoltaics and light-emitting devices. CsPbBr3, an all-inorganic perovskite, is particularly notable for its increased stability. In this study, we introduced CT-DNA during the synthesis process, resulting in the transformation of traditional cubic CsPbBr3 nanoparticles into hexagonal CsPbBr3 perovskite nanoparticles. In addition to exploring morphological evolution, we investigated charge transfer dynamics in CsPbBr3@CT-DNA, where CT-DNA acts as a hole-transporting material. To analyze the charge transfer dynamics, we conducted various characterizations, and to examine the morphological changes, scanning electron microscope (SEM) and transmission electron microscope (TEM) analyses were performed.Chapter 5 In this chapter, we employed a mechanochemical grinding approach to synthesize CsPbBr3 perovskite nanocrystals (PNCs), utilizing various aliphatic and aromatic capping ligands. The utilization of CsPbBr3 halide perovskite in electronic devices and artificial photosynthesis has been gaining prominence. However, there is a need for greener and more durable synthesis methodologies, especially considering their application in humid conditions. Currently, there are multiple approaches for producing cesium lead halide perovskite nanocrystals, including solid-phase synthesis through grinding and milling. This investigation presents a straightforward mechanochemical method for producing CsPbBr3 perovskite nanocrystals with optimization of crystal size and shape. Through mechanochemical grinding, the authors successfully synthesized CsPbBr3 perovskite nanocrystals at ambient temperature by mixing different carboxylic acids and amines, such as oleic acid, phenylacetic acid, mesityl acetic acid, benzylamine, and oleyl amine.In this chapter, we synthesized hydrophobically capped formamidinium lead bromide (FAPbBr3) perovskite nanocrystals (PNCs) and their nanocomposites with graphitic carbon nitride (g-C3N4).The FAPbBr3 PNCs exhibited bright green emissions in solution states. Photoluminescence (PL) spectral studies and Time-Correlated Single Photon Count (TCSPC) measurements were conducted to assess the interfacial hole transfer phenomenon. Both the absolute photoluminescence quantum yield (PLQY) and decay lifetime values decreased with the introduction of graphitic carbon nitride (g-C3N4), attributed to the migration of the hole from the ground state of PNC to g-C3N4. The quenching of emission was accompanied by a change in lifetime value, indicating the static nature of quenching. Moreover, the PL quenching phenomenon was also analyzed through electrochemical studies. The decoration of FAPbBr3 perovskite NCs onto g-C3N4 was examined through TEM images. The change in the oxidation state of nanocomposites, such as FAPbBr3@g-C3N4 compared to Pristine-FAPbBr3, evidenced the modified chemical environment of FAPbBr3.