Double hydrophilic Block Copolymer-Templated Nanoparticle and Energy Application

Department of Energy EngineeringThis thesis describes a variety of utilization of double hydrophilic block copolymer (DHBC), in the synthesis of NP (NP) and its broad applications. Double hydrophilic block copolymer can be induced to form a micellar structure through electrostatic or coordinative interaction with metal precursor in aqueous solution. These interactions can then lead to the synthesis of metal or metal oxide NP with the treatment of proper reductant. Poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA) copolymer used in this thesis consists of both water-soluble, and chemically distinct blocks. These different functionalities in each block are effectively utilized to synthesize NP with a controlled size and shape, further influencing the properties of resulting NP. Au NPs can be prepared by interaction between metal precursor and carboxylate groups in PAA block through coordinative bonding. It is found that the size of Au NPs is independent of the molecular weight of PAA, while the micellar structure with metal precursor is mainly induced by PAA block. This result indicates the density of DHBC in a single NP decreases when the molecular weight of PAA block increases. This polymeric density difference of each NP shows the different stability in a harsh condition. We have also demonstrated that additional Ag shell structure on Au NPs could be synthesized by utilizing the PEO block on the surface of Au NP template by DHBC, resulting in Au-Ag core-shell nanostructure. Interestingly, we found the changes in configuration of core-shell NP as well as the tunable thickness of Ag shell could be attributed to PEO chains, leading to the transition of intrinsic plasmonic absorption band in a wide spectrum. This phenomenon allows the integration of NPs into optoelectronic devices with enhanced properties. Considering a wide range of tunability and functionalities of DHBCs, we anticipate that the DHBCs can offer a novel synthetic approaches for nanomaterials and allow the NPs to be applicable into various applications including biological and energy fields.ope

Versatile double hydrophilic block copolymer: dual role as synthetic nanoreactor and ionic and electronic conduction layer for ruthenium oxide nanoparticle supercapacitors

The facile synthetic approach to ruthenium oxide nanoparticles using double hydrophilic block copolymers (DHBCs) and their application toward the supercapacitor are presented. Nanostructured hydrous ruthenium oxide (RuO2) nanoparticles are synthesized using a double hydrophilic block copolymer of poly(ethylene oxide)-block-poly(acrylic acid) (PEO-b-PAA) as a template, forming a micelle upon addition of the ruthenium precursor, which then transformed into RuO2 nanoparticles of controlled dimension with reducing agents. The synthesized hydrous RuO2 center dot xH(2)O nanoparticles are very stable for several months without any noticeable aggregates. Furthermore, we have demonstrated their utility in application as supercapacitors. Through annealing at 400 degrees C, we found that the crystallinity of RuO2 nanoparticles increases considerably with a simultaneous transformation of the surrounding double hydrophilic block copolymer into ionic and electronic conducting buffer layers atop RuO2 nanoparticles, which contribute to the significant enhancement of the overall specific capacitance from 106 to 962 F g(-1) at 10 mV s(-1). The RuO2 nanoparticles annealed at 400 degrees C also exhibit a superior retention of capacitance over 1000 cycles at very high charge-discharge rates at 20 A g(-1). We envision that the double hydrophilic block copolymer will provide a facile and general tool in creating functional nanostructures with controlled dimensions that are useful for various applications.close9

Mussel-inspired green synthesis of silver nanoparticles on graphene oxide nanosheets for enhanced catalytic applications

We report a facile green approach to the synthesis of silver nanoparticles (Ag NPs) on the surface of graphene oxide nanosheets functionalized with mussel-inspired dopamine (GO-Dopa) without additional reductants or stabilizers at room temperature. The resulting hybrid Ag/GO-Dopa exhibits good dispersity and excellent catalytic activity in the reduction of nitroarenes.close191

Plasmonic Transition via Interparticle Coupling of Au@Ag Core-Shell Nanostructures Sheathed in Double Hydrophilic Block Copolymer. for High-Performance Polymer Solar Cell

We herein report a facile synthetic method for the preparation of gold-core, silver-shell nanopartides (Au@Ag NPs) with tunable surface plasmon resonance (SPR) using the double hydrophilic block copolymer (DHBC), poly(ethylene oxide)block-poly(acrylic acid) (PEO-b-PAA), as a template (Au@Ag@DHBC NPs), and the utilization of their unique optical properties in polymer solar cells (PSCs). It is demonstrated that two different functionalities of DHBC facilitate the formation of the respective Au-core and Ag-shell NPs. Interestingly, the isolated core shell NPs in solution are found to be transformed into coupled NPs that ultimately exhibit the transition of intrinsic plasmonic properties to a wide range in the visible spectrum. Furthermore, plasmonic Au@Ag@DHBC NPs are effectively integrated into the active layer of PSCs, which remarkably enhance the power conversion efficiency (PCE) up to 9.0% (16% enhancement) because of the strong plasmonic effect of the coupled NPs and the thin polymeric layer surrounding the NPs. This study suggests the widespread potential application of DHBCs as a template for the synthesis of novel core shell nanostructures. We anticipate that this approach will provide new means for creating a variety of plasmonic nanomaterials in various fields of optoelectronic devicesclose0

Hybrid gold nanoparticle-reduced graphene oxide nanosheets as active catalysts for highly efficient reduction of nitroarenes

We demonstrate a simple, one-step synthesis of hybrid gold nanoparticle-graphene oxide nanosheets (Au-GO) through electrostatic self-assembly. This method affords a facile means of controlling the effective concentration of the active Au nanoparticles on the graphene sheets, but also offers the necessary stability of the resulting Au-GO nanostructure for catalytic transformation. Furthermore, this hybrid Au-GO is successfully employed in the catalytic reduction of a series of nitroarenes with high catalytic activity. Through careful investigation of the catalyst, we find the synergistic catalytic effect of Au nanoparticles and GO, further highlighting the significance of hybrid Au-GO nanostructure. Considering the wide potential applications of a two-dimensional graphene sheet as a host material for a variety of nanoparticles, the approach developed here may lead to new possibilities for the fabrication of hybrid nanoparticle-graphene nanosheet structures endowed with multiple functionalities.close513

Highly stable Au nanoparticles with double hydrophilic block copolymer templates: correlation between structure and stability

We herein report a facile synthetic method for preparing gold nanoparticles (Au NPs) with superior colloidal stability using a series of double hydrophilic block copolymers (DHBC), poly(ethylene oxide)block-poly(acrylic acid) (PEO-b-PAA), as a template (Au@DHBC NPs). Due to the presence of a well-defined polymeric shell around the Au NPs, this DHBC-based synthetic method provides superior stability when compared to conventional citrate-based synthesis. We have investigated NP performance by systematically varying the molecular weight of the interacting PAA block from 5000 g mol(-1) to 27 000 g mol(-1). Interestingly, the size of the Au NPs did not significantly depend on the molecular weight of the PAA block and the density of DHBC present around a single NP decreased upon an increase in the molecular weight of the PAA block. Cyanide etching of Au@DHBC NPs further confirmed the presence of DHBC with different densities around the NPs, resulting in tunable stability. Considering the structural variability of DHBCs, it is expected that the approach presented in this study will offer a new means for creating Au NPs with enhanced colloidal stability for potential biological and biomedical applications

Carbon-based layer-by-layer nanostructures: from films to hollow capsules

Over the past years, the layer-by-layer (LbL) assembly has been widely developed as one of the most powerful techniques to prepare multifunctional films with desired functions, structures and morphologies because of its versatility in the process steps in both material and substrate choices. Among various functional nanoscale objects, carbon-based nanomaterials, such as carbon nanotubes and graphene sheets, are promising candidates for emerging science and technology with their unique physical, chemical, and mechanical properties. In particular, carbon-based functional multilayer coatings based on the LbL assembly are currently being actively pursued as conducting electrodes, batteries, solar cells, supercapacitors, fuel cells and sensor applications. In this article, we give an overview on the use of carbon materials in nanostructured films and capsules prepared by the LbL assembly with the aim of unraveling the unique features and their applications of carbon multilayers prepared by the LbL assembly.close282

Thermoresponsive graphene nanosheets by functionalization with polymer brushes

We report the preparation of thermoresponsive graphene nanosheets functionalized by the polymer brushes. This approach involves the direct growth of thermoresponsive polymer brushes from functional graphene sheets (FGSs) by chemical modification with initiators followed by extension with poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) through surface-initiated atom transfer radical polymerization. The highly controllable polymerization method affords the hybrid FGS-PDMAEMA with tailorable length of PDMAEMA brushes possessing the average molecular weight (M n) ranging from 7.4 ?? 10 3 to 6.0 ?? 10 4 with low molecular weight distributions (M w/M n = 1.09-1.22). The resulting FGS-PDMAEMA was carefully characterized with a number of techniques, including elemental analysis, thermogravimetric analysis, differential scanning calorimetry, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy, all supporting the successful integration of polymer brushes onto the surface of FGS. Most importantly, we accomplished the reversible phase transfer of this hybrid FGS-PDMAEMA between aqueous and organic phases via temperature control by taking advantage of the thermoresponsive nature of PDMAEMA brushes. Moreover, the composite film prepared by depositing the suspensions of FGS-PDMAEMA demonstrated the facile control over the wettability upon temperature changes. This tailored control over dispersion in water, selective solubilization between aqueous and organic solvents, and wettability control upon temperature variation have a significant impact on the ability to improve properties of hybrid graphene-based materials. Because of the highly versatile and tunable properties of surface-initiated atom transfer polymerization, we anticipate that the general concept presented here offers a unique potential platform for integrating responsive polymers for graphene nanosheets for advanced electronic, energy, and sensor applications.close1