Metal-Organic Framework (MOF)-Based Materials: Aerosol Synthesis and Photocatalytic Applications

Metal-organic frameworks (MOFs) have been attracting great attention in the past several decades mainly because of their amazing properties, including tunable surface chemistry, flexible structure, large surface area, and huge porosity. Endorsed by those merits, MOFs have been applied in a wide range of applications, such as catalysis, gas separation, drug delivery, and sensing. Typically, MOFs are synthesized via the hydrothermal method, which, however, is difficult to scale up and requires long reaction durations (e.g., from hours to days). To achieve the full potentials of MOFs, the exploration of a novel strategy is necessary for the facile and fast synthesis of MOFs. Here in this dissertation, the aerosol route was presented as a facile route to synthesize MOFs and MOF-based composites. The aerosol route not only enabled fast crystallization of MOFs (i.e., within seconds), but also allowed continuous tuning of MOF’s properties by simply adjusting the operating parameters (e.g., temperature, pressure, and precursor conditions). To map out the formation mechanism of MOFs inside the microdroplets, systematic experimental and simulation work were carried out, which demonstrated that the fast heat and mass transfer during the aerosol route played a vital role in the rapid synthesis of MOFs. Beyond the synthesis of MOFs, the photocatalytic applications of MOF-based materials for energy and environmental sustainability were also studied in detail. More specifically, several efficient MOF-based composite photocatalysts were designed, including HKUST-1/TiO2, HKUST-1/TiO2/Cu2O, ZIF-8/ZnO, and MIL-100(Fe)/TiO2. The composite photocatalysts exhibited remarkable efficiencies towards either CO2 photoreduction or water remediation. In-depth exploration of the photocatalytic mechanism was carried out with the aid of several advanced techniques, such as in situ diffuse reflectance infrared Fourier spectroscopy (DRIFTS), photoluminescence spectroscopy, grazing-incidence wide-angle X-ray scattering, and ultrafast transient absorption spectroscopy. Meanwhile, the density functional theory (DFT) calculation was also applied to provide further mechanistic insights. The results demonstrated that MOFs acted as excellent co-catalysts, which not only facilitated molecule adsorption and activation, but also promoted the separation of the photo-induced charge carriers, leading to increased charge carrier densities in the photocatalytic systems for significantly enhanced efficiencies. The work from this dissertation is expected to broaden the synthesis strategies for the synthesis of MOF-based materials and advance the fundamental understanding of MOFs’ roles in photocatalytic applications, which should have a great impact on the rational design of MOF-based composite photocatalysts for energy and environmental sustainability

LASER SHOCK IMPRINTING OF METALLIC NANOSTRUCTURES AND SHOCK PROCESSING OF LOW-DIMENSIONAL MATERIALS

Laser shock imprinting (LSI) is proposed and developed as a novel ultrafast room-temperature top-down technique for fabricating and tuning of plasmonic nanostructures, and processing of one-dimensional semiconductor nanowires and two-dimensional crystals. The technique utilizes a shock pressure generated by laser ablation of sacrificial materials. Compared with conventional technologies, LSI features ambient condition, good scalability, low cost and high efficiency

Plasma Nanoscience: from Nano-Solids in Plasmas to Nano-Plasmas in Solids

The unique plasma-specific features and physical phenomena in the organization of nanoscale solid-state systems in a broad range of elemental composition, structure, and dimensionality are critically reviewed. These effects lead to the possibility to localize and control energy and matter at nanoscales and to produce self-organized nano-solids with highly unusual and superior properties. A unifying conceptual framework based on the control of production, transport, and self-organization of precursor species is introduced and a variety of plasma-specific non-equilibrium and kinetics-driven phenomena across the many temporal and spatial scales is explained. When the plasma is localized to micrometer and nanometer dimensions, new emergent phenomena arise. The examples range from semiconducting quantum dots and nanowires, chirality control of single-walled carbon nanotubes, ultra-fine manipulation of graphenes, nano-diamond, and organic matter, to nano-plasma effects and nano-plasmas of different states of matter.Comment: This is an essential interdisciplinary reference which can be used by both advanced and early career researchers as well as in undergraduate teaching and postgraduate research trainin

The Spectroscopic Characterization Of Newly Developed Emissive Materials And The Effects Of Environment On Their Photophysical Properties

The development of new materials capable of efficient charge transfer and energy storage has become increasingly important in many areas of modern chemical research. This is especially true for the development of emissive optoelectronic devices and in the field of solar to electric energy conversion. The characterization of the photophysical properties of new molecular systems for these applications has become critical in the design and development of these materials. Many molecular building blocks have been developed and understanding the properties of these molecules at a fundamental level is essential for their successful implementation and future engineering. This dissertation focuses on the characterization of some of these newly-developed molecular systems. The spectroscopic studies focus on the characterization of newly-developed molecules based on perylene and indolizine derivatives for solar to electric energy conversion, thienopyrazine derivatives for near infrared (NIR) emissive applications, an SCS pincer complex for blue emissive materials and a fluorescent probe for medical applications. The effects of noncovalent interactions are also investigated on these systems and a benchmark biological molecule trimethylamine N-oxide (TMAO)

Low-cost, bottom-up fabrication of large-scale single-molecule nanoarrays by DNA origami placement

Large-scale nanoarrays of single biomolecules enable high-throughput assays while unmasking the underlying heterogeneity within ensemble populations. Until recently, creating such grids which combine the unique advantages of microarrays and single-molecule experiments (SMEs) has been particularly challenging due to the mismatch between the size of these molecules and the resolution of top-down fabrication techniques. DNA Origami Placement (DOP) combines two powerful techniques to address this issue: (i) DNA origami, which provides a 100-nm self-assembled template for single-molecule organization with 5 nm resolution, and (ii) top-down lithography, which patterns these DNA nanostructures, transforming them into functional nanodevices via large-scale integration with arbitrary substrates. Presently, this technique relies on state-of-the-art infrastructure and highly-trained personnel, making it prohibitively expensive for researchers. Here, we introduce a bench-top technique to create meso-to-macro-scale DNA origami nanoarrays using self-assembled colloidal nanoparticles, thereby circumventing the need for top-down fabrication. We report a maximum yield of 74%, two-fold higher than the statistical limit of 37% imposed on non-specific molecular loading alternatives. Furthermore, we provide a proof-of-principle for the ability of this nanoarray platform to transform traditionally low-throughput, stochastic, single-molecule assays into high-throughput, deterministic ones, without compromising data quality. Our approach has the potential to democratize single-molecule nanoarrays and demonstrates their utility as a tool for biophysical assays and diagnostics