Synthesis of dendron-protected porphyrin wires and preparation of a one-dimensional assembly of gold nanoparticles chemically linked to the pi-conjugated wires

Identification of Supramolecular Structures of Porphyrin Polymer on Single-Walled Carbon Nanotube Surface Using Microscopic Imaging Techniques

Although the supramolecular structure of porphyrin polymers on flat surfaces (i.e., mica and HOPG) has been extensively studied, the self-assembly arrays of porphyrin polymers on the SWNT (as curved nanocarbon surfaces) have yet to be fully identified and/or investigated, especially using microscopic imaging techniques, i.e., scanning tunneling microscopy (STM), atomic force microscopy (AFM), and transmission electron microscopy (TEM). This study reports the identification of the supramolecular structure of poly-[5,15-bis-(3,5-isopentoxyphenyl)-10,20-bis ethynylporphyrinato]-zinc (II) on the SWNT surface using mainly AFM and HR-TEM microscopic imaging techniques. After synthesizing around >900 mer of porphyrin polymer (via Glaser-Hay coupling); the as-prepared porphyrin polymer is then non-covalently adsorbed on SWNT surface. Afterward, the resultant porphyrin/SWNT nanocomposite is then anchored with gold nanoparticles (AuNPs), which are used as a marker, via coordination bonding to produce a porphyrin polymer/AuNPs/SWNT hybrid. The polymer, AuNPs, nanocomposite, and/or nanohybrid are characterized using 1H-NMR, mass spectrometry, UV-visible spectroscopy, AFM, as well as HR-TEM measuring techniques. The self-assembly arrays of porphyrin polymers moieties (marked with AuNPs) prefer to form a coplanar well-ordered, regular, repeated array (rather than wrapping) between neighboring molecules along the polymer chain on the tube surface. This will help with further understanding, designing, and fabricating novel supramolecular architectonics of porphyrin/SWNT-based devices.

Preparation, Functionalization, Modification, and Applications of Nanostructured Gold: A Critical Review

Gold nanoparticles (Au NPs) play a significant role in science and technology because of their unique size, shape, properties and broad range of potential applications. This review focuses on the various approaches employed for the synthesis, modification and functionalization of nanostructured Au. The potential catalytic applications and their enhancement upon modification of Au nanostructures have also been discussed in detail. The present analysis also offers brief summaries of the major Au nanomaterials synthetic procedures, such as hydrothermal, solvothermal, sol-gel, direct oxidation, chemical vapor deposition, sonochemical deposition, electrochemical deposition, microwave and laser pyrolysis. Among the various strategies used for improving the catalytic performance of nanostructured Au, the modification and functionalization of nanostructured Au produced better results. Therefore, various synthesis, modification and functionalization methods employed for better catalytic outcomes of nanostructured Au have been summarized in this review.

Functionalization of Gold Nanoparticles by Inorganic Entities

The great affinity of gold surface for numerous electron-donating groups has largely contributed to the rapid development of functionalized gold nanoparticles (Au-NPs). In the last years, a new subclass of nanocomposite has emerged, based on the association of inorganic molecular entities (IME) with Au-NPs. This highly extended and diversified subclass was promoted by the synergy between the intrinsic properties of the shell and the gold core. This review-divided into four main parts-focuses on an introductory section of the basic notions related to the stabilization of gold nanoparticles and defines in a second part the key role played by the functionalizing agent. Then, we present a wide range of inorganic molecular entities used to prepare these nanocomposites (NCs). In particular, we focus on four different types of inorganic systems, their topologies, and their current applications. Finally, the most recent applications are described before an overview of this new emerging field of research.

A 3D electropolymerized thin film based on a thiophene-functionalized Ru(ii) complex: electrochemical and photoelectrochemical insights

A 3D electropolymerized Ru(ii) complex film exhibited a rapid redox reaction and an oxygen reduction enhanced photocurrent which increased by 1.5 fold to 2.3 μA cm⁻².

Synthesis and co-assembly of gold nanoparticles functionalized by a pyrene–thiol derivative

We synthesized a series of gold nanoparticles capped with 11-(4-(pyren-1-yl)phenoxy)undecane-1-thiol and with 1-dodecanethiol. The homodispersed gold nanoparticles were fully verified and co-assembly of gold nanoparticles composited with discotic molecules were investigated.

Synthesis of a series of Zinc(II)/freebase porphyrin dimers and trimers with programmable sequences from a common key molecule

We have developed a new methodology that enables the synthesis of any sequence of metal porphyrin arrays starting from a common key molecule. Using this method, we prepared porphyrin dimers and trimers with varying component unit sequences via consecutive Suzuki coupling reactions using the same key porphyrin compound under the same reaction conditions. The key porphyrin compound was synthesized on a gram scale in one batch, and the coupling reactions afforded the desired oligomers in good yields. Thus, the prepared porphyrin arrays showed unique physical properties depending on the sequence of the central metals. The reaction is potentially applicable for the automated synthesis of porphyrin arrays.

Dumbbells, trikes and quads: organic-inorganic hybrid nanoarchitectures based on "clicked" gold nanoparticles

The controlled assembly of gold nanoparticles in terms of the spatial arrangement and number of particles is essential for many future applications like electronic devices, sensors and labeling. Here an approach is presented to build up oligomers of mono functionalized gold nanoparticles by the use of 1,3-bipolar azide alkyne cycloaddition click chemistry. The gold nanoparticles of 1.3 nm diameter are stabilized by one dendritic thioether ligand comprising an alkyne function. Together with di-, tri- and tetra-azide linker molecules the gold nanoparticle can be covalently coupled by a wet chemical protocol. The reaction is tracked with IR and UV-vis spectroscopy and the yielded organic-inorganic hybrid structures are analyzed by transmission electron microscopy. To evaluate the success of this click chemistry reaction statistical analysis of the formed oligomers is performed. The geometric and spatial arrangements of the found oligomers match perfectly the calculated values for the used linker molecules. Dimers, trimers and tetramers could be identified after the reaction with the corresponding linker molecule. The results of this model reaction suggest that the used click chemistry protocol is working well with mono functionalized gold nanoparticles.

Functionalization of bolalipid nanofibers by silicification and subsequent one-dimensional fixation of gold nanoparticles

In the present work, we describe the successful stabilization of bolalipid nanofibers by sol-gel condensation (silicification) of tetraethoxysilane (TEOS) or 3-mercaptopropyltriethoxysilane (MP-TEOS), respectively, onto the nanofibers. The conditions for an effective and reproducible silicification reaction were determined, and the silicification process was pursued by transmission electron microscopy (TEM). The resulting bolalipid-silica composite nanofibers were characterized by means of differential scanning calorimetry (DSC), TEM, (13)C, and (31)P NMR spectroscopy. Finally, the novel silicified bolalipid nanofibers were used as templates for the fixation of 5 and 2 nm AuNPs, respectively, resulting in one of the rare examples of one-dimensional AuNP arrangements in aqueous suspension.

Direct control of the spatial arrangement of gold nanoparticles in organic-inorganic hybrid superstructures

The directed assembly of gold nanoparticles is essential for their use in many kinds of applications, such as electronic devices, biological labels, and sensors. Herein an atomic alteration in the molecular structure of ligand-stabilized gold nanoparticles that can shift the interparticle distance up to 1 nm upon covalent coupling to organic-inorganic superstructures is presented. Gold nanoparticles are stabilized by two octadentate thioether ligands and have a mean diameter of 1.1 nm. The ligands contain a central rigid rod varying in length and terminally functionalized with a protected acetylene. The two peripheral functional groups on each particle enable the directed assembly of nanoparticles to dimers, trimers, and tetramers by oxidative acetylene coupling. This is a wet chemical protocol resulting in covalently bound nanoparticles. These organic-inorganic hybrid superstructures are analyzed by transmission electron microscopy, small angle X-ray scattering, and UV/vis spectroscopy. The focus of the comparison here is the subunit, which is anchoring the bridgehead, either a pyridine or benzene moiety. The pyridine-based ligands reflect the calculated length of the rigid-rod spacer in their interparticle distances in the obtained hybrid structures. This suggests a perpendicular arrangement that results from the coordination of the pyridine's lone pair to the gold surface. An atomic variation in the ligand's center leads to smaller interparticle distances in the case of hybrid structures obtained from benzene ligands. This large difference in the spatial arrangement suggests a tangential arrangement of the interparticle bridging structure in the latter case. Consequently a rather flat arrangement parallel to the particle surface must be assumed for the central benzene unit of the benzene-based ligand.

Thermoreversible covalent self-assembly of oligo(p-phenylenevinylene) bridged gold nanoparticles

Organic-inorganic hybrids have been fabricated through mild Diels-Alder cross-linking between maleimide bearing oligo(p-phenylenevinylene) (OPV) and furan functionalized gold nanoparticles with diameter smaller than 2 nm. The OPV ligands afford strong reaction ability toward furan group due to their maleimide moieties. These small gold nanoparticles form close-packed homogeneous hybrids with well-defined interfaces by incorporating OPV ligands in solutions. Covalent assembly and disassembly of gold nanoparticles can be achieved by repeated thermal stimuli on as-obtained hybrids, which can be monitored by fluorescence changes of OPVs and surface plasmon resonance absorption. Moreover, the dramatic photophysical properties and assembly behavior of these hybrids allow this procedure to be performed as a smart assay for monitoring the process of the Diels-Alder reaction.

A one-dimensional network from the self-assembly of gold nanoparticles by a necklace-like polyelectrolyte template mediated by metallic ion coordination

A new approach to one-dimensional organization of gold nanoparticles (2-4 nm) is described, using poly(4-vinylpyridine) (P4VP) molecular chain as a template with the mediation of free Cu2+ ion coordination. The assembly was conducted on freshly prepared mica surfaces and in aqueous solution, respectively. The surface assembly was characterized by tapping mode atomic force microscopy (AFM), observing the physisorbed molecules in their chain-like conformation with an average height of 0.4 nm. By the mediation of Cu2+ ions, gold nanoparticles modified by 3-mercaptopropionic acid were deposited onto the molecular chains, evidenced by a clear increase in height. Generation of the network in solution is time-dependent and pH reversible, characterized by UV-vis absorption spectra and transmission electron microscopy (TEM). No comparable network is obtained without Cu2+ ions, indicating the significance of ionic mediation. A mechanism for the self-assembly in solution is proposed, and the nature of the mediation of Cu2+ ions was identified by x-ray photoelectron spectroscopy (XPS).

Organic-inorganic nanohybrids via directly grafting gold nanoparticles onto conjugated copolymers through the Diels-Alder reaction

Nanocomposites of poly- p-phenyleneethynylene gold nanoparticles (PPE-Au) were synthesized via directly grafting maleimide functionalized gold nanoparticles (MA-Au) onto PPE chains by a mild Diels-Alder reaction. The Diels-Alder reaction between copolymers and MA-Au leads to self-assembly of the MA-Au as well as enhances electronic communication between the copolymers and inorganic particles. The as-prepared hybrid nanoassemblies show homogeneous status and well-defined interfaces, which facilitate the electronic interaction between conjugated polymers and gold nanoparticles. Moreover, dramatic photophysical properties and an influence on the assembly behavior of gold nanoparticles are also exhibited, which allows this procedure to be performed as a smart assay for monitoring the process of the Diels-Alder reaction.

Electroless gold island thin films: photoluminescence and thermal transformation to nanoparticle ensembles

Electroless gold island thin films are formed by galvanic replacement of silver reduced onto a tin-sensitized silica surface. A novel approach to create nanoparticle ensembles with tunable particle dimensions, densities, and distributions by thermal transformation of these electroless gold island thin films is presented. Deposition time is adjusted to produce monomodal ensembles of nanoparticles from 9.5 +/- 4.0 to 266 +/- 22 nm at densities from 2.6 x 1011 to 4.3 x 108 particles cm-2. Scanning electron microscopy and atomic force microscopy reveal electroless gold island film structures as well as nanoparticle dimensions, densities, and distributions obtained by watershed analysis. Transmission UV-vis spectroscopy reveals photoluminescent features that suggest ultrathin EL films may be smoother than sputtered Au films. X-ray diffraction shows Au films have predominantly (111) orientation.

Polymer-templated self-assembly of a 2-dimensional gold nanoparticle network

We here report on the formation of well-ordered 2D gold nanostructures at the air/water interface. Spreading a mixture of alkanethiol-capped gold nanoparticles (AuNPs) and an amphiphilic poly(p-phenylene) on a water surface and compressing the mixture to a surface pressure of 40 mN/m lead to the formation of a network of well-ordered gold nanostructures. The structures are transferred horizontally (Langmuir-Schäfer) onto a solid substrate and investigated with TEM, AFM, and X-ray reflectivity, showing a pattern that is repeating over several micrometers. AFM and X-ray reflectivity data at different surface pressures reveal that the polymer is lifting the AuNPs 1.5-2 nm in the vertical direction, away from the polymer layer, when the pressure is increased from 20 to 40 mN/m.