Controlled Aggregation of Functionalized Gold Nanoparticles with a Novel Conjugated Oligomer

One-Pot Synthesis of Hybrid Conjugated Oligomer-Ag Nanoparticles

Here we report one-pot, straightforward synthesis of hybrid conjugated oligomer-silver nanoparticles (AgNPs) by utilizing tertiary alkyl amine and fluorene-benzothiodiazole-containing conjugated oligomer that both acts as a reducing agent in the reduction of silver ions into metallic silver and as a matrix to accommodate the newly formed AgNPs. By tuning the reaction conditions, it is possible to control the sizes and the structural features of hybrid nanoparticles as either raspberry or core-shell type hybrid structures.

High-Stability, High-Efficiency Organic Monoliths Made of Oligomer Nanoparticles Wrapped in Organic Matrix

Oligomer nanoparticles (OL NPs) have been considered unsuitable for solid-state lighting due to their low quantum yields and low temperature stability of their emission. Here, we address these problems by forming highly emissive and stable OL NPs solids to make them applicable in lighting. For this purpose, we incorporated OL NPs into sucrose matrix and then prepared their all-organic monoliths. We show that wrapping the OL NPs in sucrose significantly increases their quantum yield up to 44%, while the efficiency of their dispersion and direct solid-film remain only at ∼6%. We further showed ∼3-fold improved temperature stability of OL NP emission within these monoliths. Our experiments revealed that a physical passivation mechanism is responsible from these improvements. As a proof-of-concept demonstration, we successfully employed these high-stability, high-efficiency monoliths as color converters on a blue LED chip. Considering the improved optical features, low cost, and simplicity of the presented methodology, we believe that this study holds great promise for a ubiquitous use of organic OL NPs in lighting and possibly in other photonic applications.

Water-Mediated Assembly of Gold Nanoparticles into Aligned One-Dimensional Superstructures

This Article shows that water in ethanol colloids of gold nanoparticles enhances the formation of linear clusters and, more important for applications in electronics, determines their assembly on surfaces. We show by dynamic light scattering that ethanol colloids contain mainly monomers and dimers and that wormlike superstructures are mostly absent, despite UV-vis evidence of aggregation. Water added to the colloid as a cosolvent was found to enhance the number of clusters as well as their average size, confirming its role in linear self-assembly, on the scale of a few particles. Water adsorbed from the atmosphere during coating was also found to be a powerful lever to tune self-assembly on surfaces. By varying the relative humidity, a sharp transition from branched to linear superstructures was observed, showing the importance of water as a cosolvent in the formation of cluster superstructures. We show that one-dimensional superstructures may form due to long-range mobility of precursor clusters on wet surfaces, allowing their rearrangement. The understanding of the phenomenon allows us to statistically align both clusters and resulting superstructures on patterned substrates, opening the way to rapid screening in molecular electronics.

A dual sensor of fluorescent and colorimetric for the rapid detection of lead

This study demonstrated a simple and reliable method to rapidly detect Pb(2+) in aqueous solution, exploiting gold nanoparticles as a lead ion probe; the results indicated that the dual channels sensor showed high selectivity and sensitivity for Pb(2+) as low as ppm levels in aqueous environment.

Enzymatic tailoring for precise control of plasmonic resonance absorbance of gold nanoparticle assemblies

We report an enzymatic method to control the plasmon resonance absorbance of gold nanoparticle (AuNP) arrays assembled on hyaluronic acids. While multiple electrostatic interactions between cysteamine on the AuNPs and the carboxylic acid residues in the whole intact hyaluronic acid induced the formation of large aggregates, precise control of the plasmon absorbance was possible by tailoring the size of the bio-polymeric templates with hyaluronidase, almost over the entire range of the resonant coupling wavelengths. It was possible to precisely tune the position of the second plasmon absorbance by manipulating the amount of the template and the enzymatic hydrolysis time. Finally, we were able to produce a chain-like array of AuNPs, which was nearly one dimensional, with a maximum shift of up to 189 nm in the plasmon absorbance at the optimal hydrolysis time of the templates. This enzymatic method can be used as a useful tool to tailor the plasmonic properties of the nanostructures required for specific applications.

Role of salt in the spontaneous assembly of charged gold nanoparticles in ethanol

This paper investigates the role of salt in the spontaneous linear assembly of charged gold nanoparticles in ethanol and attempts to clear up a misunderstanding on the role of ethanol in this process. Many prior reports have noted that the addition of ethanol to an aqueous solution of gold nanoparticles causes their aggregation into linear assemblies. It was therefore believed that ethanol plays the determining role during the assembly process. In this work, we carried out systematic studies which indicate that residual salt in conjunction with ethanol, instead of ethanol itself, induces the assembly of gold nanoparticles in ethanol. In the absence of salt, gold nanoparticles can be well dispersed in an ethanol solution. Furthermore, we find that the chainlike assemblies can disassemble upon dilution of the salt or the evaporation of ethanol if the gold nanoparticles are protected with a sufficiently strong ligand.