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Scheme 1. Illustration of the supramolecular self-assembly process (a)-(b), the preparation of Au nanodots based on supramolecular self-assembly (b)-(d) and the phase transfer of Au nanodots from the oil phase to the water phase (d)-(e).
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A new strategy for preparing luminescent and intelligent gold nanodots based on supramolecular self-assembly is described in this paper. The supramolecular self-assembly was initiated through electrostatic interactions and ion pairing between palmitic acid and hyperbranched poly(ethylenimine). The resulting structures not only have the dynamic reve...
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... pH response of Au nanodots is proved by the phase transfer of Au nanodots from the chloroform phase into the water phase. The photoluminescence photographs under 365 nm are shown in figure 1. After dialysis and rotary evaporation, Au nanodots can be redispersed in chloroform solution containing palmitic acid in the form of Au-HPEI/PA nanocomposites. ...Citations
... Nanocrystal (NC) synthesis and NC encapsulation have been important applications of dendritic polymers over the years [24][25][26]. Until now, dendritic poly(amidoamine)s (PAMAM) [27][28][29][30][31][32], poly(ethylenimine)s (PEI) [20,[33][34][35][36][37][38], poly(propylenimine)s (PPI) [39], polyglycerols (PG) [40], poly(amine ester)s (PAE) [41] and their derivatives have often been used as stabilizers for NC synthesis. By preparing or encapsulating nanocrystals (NCs) within dendritic polymers, the properties and HPAMAM (from Supplementary Materials Figure S2, M w = 3.8 × 10 3 , PDI = 1.27) was gained [33]. Worthy of mention was that an oil pump was used for the reaction at 120 and 140 • C to get a high vacuum degree and high molecular weight of HPAMAM. 1 0.1501 g HPAMAM was dissolved with 50 mL anhydrous ethanol in a 150 mL flask. ...
A new strategy for nanocrystal encapsulation, release and application based on pH-sensitive covalent dynamic hyperbranched polymers is described. The covalent dynamic hyperbranched polymers, with multi-arm hydrophobic chains and a hydrophilic hyperbranched poly(amidoamine) (HPAMAM) core connected with pH-sensitive imine bonds (HPAMAM–DA), could encapsulate CdTe quantum dots (QDs) and Au nanoparticles (NPs). Benefiting from its pH response property, CdTe QDs and Au NPs encapsulated by HPAMAM–DA could be released to aqueous phase after imine hydrolysis. The released CdTe/HPAMAM and Au/HPAMAM nanocomposites exhibited excellent biological imaging behavior and high catalytic activities on p-nitrophenol hydrogenation, respectively.
... NP synthesis is one of the most important applications of hyperbranched polymers in recent years. With a three-dimensional globular architecture, numerous cavities, and plenty of peripheral functional groups [34][35][36], hyperbranched polymers are regarded as ideal stabilizers and nanoreactors/templates to prepare size-controlled semiconductors [37][38][39][40][41], metal nanoparticles (NPs) [42][43][44][45][46][47], metal nanodots [48,49], and metal oxide nanocrystals [25,26,50,51], etc. Until now, various hyperbranched polymers, not only the conventional covalent hyperbranched polymers but also supramolecular multiarm hyperbranched polymers [41,52] have been reported to prepare nanocrystals. ...
With a hyperbranched poly(amidoamine) core and many water-soluble poly(ethylene glycol) monomethyl ether arms connected by pH-sensitive acylhydrazone bonds, multiarm hyperbranched polymer was used as nanoreactor and reductant to prepare metal nanoparticles endowed with intelligence and biocompatibility. The multiarm hyperbranched polymer encapsulated nanoparticles (NPs) showed excellent catalytic activity for hydrogenation, thus an excellent catalyst system for hydrogenation was established. The rate constants could reach as high as 3.48 L·s−1·m−2, which can be attributed to the lack of surface passivation afforded by the multiarm hyperbranched polymer.
A very simple and effective approach of fabricating Au-reduced graphene oxide (Au-RGO) nanocomposite is herein reported. The nanocomposite was synthesized through a one-pot in situ reduction of graphene oxide (GO) and HAuCl4 under ultraviolet (UV) irradiation without using any additional chemical reducing agents, capping agents, stabilizer or surfactant. The surface characterization with various techniques such as UV–vis spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and transmission electron microscopy (TEM) showed that GO was effectively reduced and Au nanoparticles with a uniform size were well dispersed on the surface of RGO. This UV light assisted synthesis of Au-RGO nanocomposite is expected to be a universal and clean approach for the formation of various RGO-based nanocomposites. Significantly, the as-prepared nanocomposite possessed high activity in the redox behavior of As (III). Based on the Au-RGO nanocomposite modified electrode, a simple, sensitivity and selective sensing platform for the detection of As (III) was developed. Under optimum conditions, a detection range of 0.3–20 ppb and a low detection limit of 0.1 ppb were obtained, which is found to be well below the World Health Organization (WHO) guidelines of 10 ppb.
Sub-nanometer-sized metal clusters, having dimensions between metal atoms and nanoparticles, have attracted tremendous attention in the recent past due to their unique physical and chemical properties. As properties of such materials depend strongly on size, development of synthetic routes that allows precise tuning of the cluster cores with high monodispersity and purity is an area of intense research. Such materials are also interesting owing to their wide variety of applications. Novel sensing strategies based on these materials are emerging. Owing to their extremely small size, low toxicity, and biocompatibility, they are widely studied for biomedical applications. Primary focus of this review is to provide an account of the recent advances in their applications in areas such as environment, energy, and biology. With further experimental and theoretical advances aimed at understanding their novel properties and solving challenges in their synthesis, an almost unlimited field of applications can be foreseen.
In this paper, Au nanoparticles (AuNPs) have been homogeneously deposited on citrate-functionalized graphene nanosheets (Cit-GNs) by a simple one-pot reducing method. The morphology and composition of the thus-prepared AuNPs/Cit-GNs were characterized by transmission electron microscopy (TEM), high resolution TEM, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The results showed that the AuNPs with a uniform size are well dispersed on the surface of the Cit-GNs. Significantly, the as-prepared AuNPs/Cit-GNs possess intrinsic peroxidase-like activity, which can catalyze the oxidation of the peroxidase substrate 3,3,5,5-tetramethylbenzidine (TMB) by hydrogen peroxide (H2O2) to develop a blue color in aqueous solution. The catalysis was in accordance with Michaelis-Menten kinetics and the AuNPs/Cit-GNs showed a strong affinity for both H2O2 and TMB. Moreover, by comparing with Cit-AuNPs, AuNPs/GNs and AuNPs/PVP-GNs, the AuNPs/Cit-GNs composite exhibits a higher catalytic ability with a lower Michaelis constant (Km) value, suggesting that the GNs with a large surface area and the citrate ions with more carboxyl groups around the AuNPs can greatly enhance the peroxidase-like activity of AuNPs/Cit-GNs. Taking the advantages of the high catalytic activity, the good stability and the low cost, the novel AuNPs/Cit-GNs represent a promising candidate as an enzyme mimic and may find a wide range of new applications in biochemistry and biotechnology.
Hyperbranched poly(amidoamine)s with methyl ester terminals (HPAMAM-COOCH3) were used as nanoreactors and reductants to prepare gold or silver nanoparticles (Au NPs or Ag NPs). HPAMAM-COOCH3 could bind AuCl4− (or Ag+) and then reduce AuCl4− (or Ag+) into Au NPs (or Ag NPs) through their internal amines, while the external methyl ester groups prevented the aggregation of polymers. The formation of Au NPs or Ag NPs was verified using transmission electron microscopy (TEM), ultraviolet-visible spectroscopy (UV-Vis), X-Ray powder diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA), confirming the formation of Au NPs or Ag NPs with small particle size and low size distribution.POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers
