Reactive precursor particles as synthetic platform for the generation of functional nanoparticles, nanogels, and microgels

Precise control of the chemical functionality of polymer nanoparticles is a key requirement in tailoring their (dynamic) colloidal properties toward advanced applications. However, current synthetic techniques are still limited in the versatility of chemical design and preparation of such functional colloidal nanomaterials. Two major challenges remain: First, various particle preparation methods are restricted in their functional group tolerance, thus hindering certain combinations of polymer backbones with specific functional groups. Second, the preparation of particles with different functionalities requires the synthesis of different particle batches. But this often results in a simultaneous variation of colloidal features. As a result, the accurate determination of important structure–property relations is still hindered. To address these restrictions, postmodification of preformed reactive particles is gaining more attention. This technique has evolved from polymer synthesis, where postpolymerization functionalization enables the introduction of a plethora of functional groups without changing the degree of polymerization and the molecular weight distribution. Similarly, modifying precursor particles enables the introduction of functional groups into particles while reducing variations in colloidal features, e.g., particle size and size distribution. This powerful synthetic method complements established procedures for functionalization of particle surfaces, thereby enabling the facile preparation of (multi‐)functional particle libraries, which will allow precise investigations of structure–property relations

Candida antarctica lipase-catalyzed synthesis and characterization of novel acrylic teroligomers

The synthesis of three novel low molecular weight acrylic terpolymers, containing at random sequences of ethyl acrylate, acrylic acid and N-(2-hydroxyethyl)acrylamide, catalyzed by Candida antarctica lipase was successfully conducted in organic media. For the first time, these products have been enzymatically synthesized using ethyl acrylate as the only monomer starting material and taking advantage of a triple activity displayed by the lipase. In the presence of ethanolamine, the enzyme not only catalyzes the chain polymerization of ethyl acrylate but also the aminolysis and hydrolysis of the pendant ester groups affording the terpolymers. The products were characterized by 1H and 13C NMR and UV-MALDI-TOF-MS.Fil: Baldessari, Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; ArgentinaFil: Fatema, M. Kaniz. Ehime University; JapónFil: Nonami, Hiroshi. Ehime University; JapónFil: Erra Balsells, Rosa. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Centro de Investigaciones en Hidratos de Carbono. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Centro de Investigaciones en Hidratos de Carbono; ArgentinaFil: Rustoy, Eduardo Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Unidad de Microanálisis y Métodos Físicos en Química Orgánica. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Unidad de Microanálisis y Métodos Físicos en Química Orgánica; Argentin

Transient optical studies of photoinduced charge transfer in semiconductor quantum dot solar cells

Semiconductor quantum dots (also referred to as 'nanocrystals‘) are well suited as light-harvesting agents in solar cells because they are robust, have tuneable effective band gaps, and are easy to process. The research presented in this thesis is targeted towards the study of excitonic solar cells employing semiconductor nanocrystals as a light harvesting component. Gaining control of the interfacial charge transfer processes in operation in these devices forms a crucial part of any attempt to optimise their performance. In particular, the use of transient spectroscopic techniques reveals how efficient and long-lived charge separation can be achieved in these solar cell architectures. The primary focus of this research is to investigate the parameters influencing charge transfer in dye-sensitised solar cells (DSSCs) using colloidal quantum dots as light-absorbers. One aim is to study the impact of varying the thermodynamic driving forces provided for interfacial electron transfer on the yield of both the electron injection and hole regeneration reactions occurring within the DSSC; this can be achieved by varying the energetics of each component of the system (metal oxide, quantum dot and hole conductor) in turn. In addition, the interfacial morphology can be modulated by changing the passivating ligands present at the QD surface, and by modifying the structure of the redox mediator (or hole conductor). In doing so, we also attempt to improve our understanding of how charge carrier trapping in quantum dots impacts upon solar cell performance. Furthermore, new strategies towards solar cell design are presented, which show great potential as a result of their favourable photophysical properties. One of these approaches (presented in the final chapter) is to effect the in situ growth of CdS nanocrystals in a conducting polymer, a method which circumvents many of the processing issues associated with the use of nanocrystals in polymer blend solar cell architectures. It is hoped that the work presented in this thesis is used to develop design rules for the construction of semiconductor nanocrystal-based excitonic solar cells. By identifying which key parameters control the rates and yields of electron transfer at the nanocrystal interface, improvements in device efficiency can be realised. It is believed that these studies fill an important gap in our current understanding, and highlight some of the potential benefits and shortcomings of using semiconductor nanocrystals in cheap, solution-processed solar cells

Protein-based materials, toward a new level of structural control

Through billions of years of evolution nature has created and refined structural proteins for a wide variety of specific purposes. Amino acid sequences and their associated folding patterns combine to create elastic, rigid or tough materials. In many respects, nature’s intricately designed products provide challenging examples for materials scientists, but translation of natural structural concepts into bio-inspired materials requires a level of control of macromolecular architecture far higher than that afforded by conventional polymerization processes. An increasingly important approach to this problem has been to use biological systems for production of materials. Through protein engineering, artificial genes can be developed that encode protein-based materials with desired features. Structural elements found in nature, such as β-sheets and α-helices, can be combined with great flexibility, and can be outfitted with functional elements such as cell binding sites or enzymatic domains. The possibility of incorporating non-natural amino acids increases the versatility of protein engineering still further. It is expected that such methods will have large impact in the field of materials science, and especially in biomedical materials science, in the future

Poly(bromoethyl acrylate) : a reactive precursor for the synthesis of functional RAFT materials

Postpolymerization modification has become a powerful tool to create a diversity of functional materials. However, simple nucleophilic substitution reactions on halogenated monomers remains relatively unexplored. Here we report the synthesis of poly(bromoethyl acrylate) (pBEA) by reversible addition–fragmentation chain transfer (RAFT) polymerization to generate a highly reactive polymer precursor for postpolymerization nucleophilic substitution. RAFT polymerization of BEA generated well-defined homopolymers and block copolymers over a range of molecular weights. The alkylbromine-containing homopolymer and block copolymer precursors were readily substituted by a range of nucleophiles in good to excellent conversion under mild and efficient reaction conditions without the need of additional catalysts. The broad range of nucleophilic species that are compatible with this postmodification strategy enables facile synthesis of complex functionalities, from permanently charged polyanions to hydrophobic polythioethers to glycopolymers

Multicomponent Reaction Based Synthesis of 1-Tetrazolylimidazo[1,5- a]pyridines

A series of unprecedented tetrazole-linked imidazo[1,5- a]pyridines are synthesized from simple and readily available building blocks. The reaction sequence involves an azido-Ugi-deprotection reaction followed by an acetic anhydride-mediated N-acylation-cyclization process to afford the target heterocycle. Furthermore, the scope of the methodology was extended to diverse R3-substitutions by employing commercial anhydrides, acid chlorides, and acids as an acyl component. The scope for the postmodification reactions are explored and the usefulness of the synthesis is exemplified by an improved three-step synthesis of a guanylate cyclase stimulator

Triggering white-light emission in a 2D imine covalent organic framework through lanthanide augmentation

Recently, covalent organic frameworks (COFs) have emerged as an interesting class of porous materials, featuring tunable porosity and fluorescence properties based on reticular construction principles. Some COFs display highly emissive monocolored luminescence, but attaining white-light emission from COFs is difficult as it must account for a wide wavelength range. White-light emission is highly desired for solid-state lighting applications, and obtaining it usually demands the combination of red-, green-, and blue-light components. Hence, to achieve the targeted white-light emission, we report for the first time grafting of lanthanides (Eu3+/Tb3+) on a two-dimensional imine COF (TTA-DFP-COF). We studied the luminescence properties of the hybrid materials prepared by anchoring Eu3+ (red light) and Tb3+ (green light) beta-diketonate complexes onto the TTA-DFP-COF. Reticular construction is exploited to design strong coordination of Eu3+ and Tb3+ ions into nitrogen-rich pockets of the imine COF. Mixed Eu3+/Tb3+ materials are then prepared to incorporate red and green components along with the inherent blue light from the organic moieties of the COF to produce white-light emission. We show that COFs have the potential for hosting Eu3+ and Tb3+ complexes, which can be tuned to obtain desired excitations for applications in the field of optoelectronics, microscopy, optical sensing, and bioassay

Metal-organic frameworks as selective or chiral oxidation catalysts

Since the discovery of Metal Organic Frameworks (MOFs) in the early 1990s, the amount of new structures has grown exponentially. A MOF typically consists of inorganic nodes that are connected by organic linkers to form crystalline, highly porous structures. MOFs have attracted a lot of attention lately, as the versatile design of such materials holds promises of interesting applications in various fields. In this review, we will focus on the use of MOFs as heterogeneous oxidation catalysts. MOFs are very promising candidates to replace homogeneous catalysts by sustainable and stable heterogeneous catalysts. The catalytic active function can be either the active metal sites of the MOF itself or can be introduced as an extra functionality in the linker, a dopant or a "ship-in-a-bottle" complex. As the pore size, pore shape, and functionality of MOFs can be designed in numerous ways, shape selectivity, and even chiral selectivity can be created. In this article, we will present an overview on the state of the art of the use of MOFs as a heterogeneous catalyst in liquid phase oxidation reactions