Thermosensitive poly(N‐isopropylacrylamide) (PNIPAm)‐coated gold nanoparticles (AuNPs) were prepared by self‐assembly of the azobenzene‐terminated PNIPAm on the surface of the α‐cyclodextrin (α‐CD)‐capped AuNPs via the host–guest molecular recognition between α‐CD and azobenzene. Reversible attachment–detachment of azobenzene‐terminated PNIPAm on the surface of α‐CD‐capped AuNPs was achieved when subjected to visible and UV light irradiation alternately, which endowed thermosensitive AuNPs with tunable smart properties.
Summary: A well‐dispersed gold nanoparticle/poly(N‐isopropylacrylamide) (PNIPAm) hydrogel nanocomposite with thermoswitchable electrical properties is prepared by the copolymerization of functional Au nanoparticles with N‐isopropylacrylamide. It is found that the electrical conductivity of the nanocomposite changes by two orders of magnitude at moderate temperature (Ttran) upon temperature stimuli. The change of electrical properties is reversible during a heating and cooling cycle.
Schematic illustration of the mechanism of the thermo‐switchable electronic properties of the Au nanoparticle/PNIPAm composite. 相似文献
An organosilane with an alkyne group at the non‐condensable end, [(2‐propynylcarbamate)propyl]triethoxysilane, has been synthesized. Condensation of this organosilane with tetraethoxysilane can be achieved by a co‐condensation strategy to produce silica nanoparticles with surface alkyne functionality. The size and uniformity of size distribution of the silica nanoparticles are influenced by varying the concentration of the added organosilane. The alkyne‐functionalized silica nanoparticles are coupled directly with azide‐modified polymers by ‘click chemistry’ to yield organic–inorganic hybrid nanomaterials.
We have discovered a novel method to prepare a protein‐based hydrogel, that is, a ‘three‐dimensional nanostructured protein hydrogel’ (3D NPH), which is composed of loosely inter‐connected protein–polymer hybrid nanoparticles. The 3D NPH can be easily prepared by spotting a protein/polymer mixture on a substrate. Surprisingly, gold nanoparticles carrying protein molecules easily diffuse into the 3D NPH through pores and spaces. We have shown that the protein chip made by our 3D NPH method has tremendously improved sensitivity in detecting protein–protein interactions compared with that by direct protein immobilization methods.
Monolithic materials were prepared via electron‐beam curing from ethyl methacrylate, trimethylolpropane triacrylate, and norborn‐5‐ene‐2‐ylmethyl acrylate. Reaction of the norborn‐2‐ene groups with either RuCl2(PCy3)2(CHPh) ( 1 ) or RuCl2(PCy3)(1,3‐dimesityl‐4,5‐dihydroimidazol‐2‐inylidene)(CHPh) ( 2 ) resulted in the surface attachment of the initiators. The extent of initiator immobilization was found to be substantially higher for 1 than for 2 . Reaction of the surface immobilized initiators with various monomers resulted in the desired surface modification of EB‐derived monoliths. The amounts of grafted monomer were determined by elemental analysis and ICP‐OES.
Gold nanoparticles with hydrophobic polystyrene (PS) and hydrophilic poly[poly(ethylene glycol) methyl ether methacrylate] (PPEGMA) mixed polymer brushes are prepared. Different morphologies of the nanoparticles can be observed in chloroform (a common solvent for both of the polymers) and water (a precipitant for PS and a good solvent for PPEGMA). The nanoparticles can be used as surfactants in Pickering suspension polymerization. Upon addition of nanoparticles to a mixture of oil and water, the nanoparticles locate at the interface and the size of the oil droplets gets smaller. After polymerization of styrene oil droplets PS colloid particles with gold nanoparticles on the surface can be obtained.
A dextran‐based dual‐sensitive polymer is employed to endow gold nanoparticles with stability and pH‐ and temperature‐sensitivity. The dual‐sensitive polymer is prepared by RAFT polymerization of N‐isopropylacrylamide from trithiocarbonate groups linked to dextran and succinoylation of dextran after polymerization. The functionalized nanoparticles show excellent stability under various conditions and can be stored in powder‐form. UV and DLS measurements confirm that the temperature‐induced optical changes and aggregation behaviors of the particles are strongly dependent on pH.
Poly(dimethylsiloxane) copolymers were synthesized directly from AA/BB monomers employing a CuAAC reaction (click chemistry) in a polyaddition approach. Using organic dialkynes and oligo(siloxane)s end‐functionalized with azide moieties it was possible to obtain siloxane‐based copolymers with TPE properties by click chemistry for the first time. As seen from DSC experiments, properties were strongly dependent on the incorporated organic comonomer.
Summary: We report a new method for the preparation of polyaniline nanoballs by using HAuCl4 as an oxidizing agent. During the reaction, aniline is oxidized and forms polyaniline whilst the hydrogen tetrachloroaurate is reduced and forms gold nanoparticles. These gold nanoparticles are found to decorate the nanoballs.
The resultant precipitate and corresponding TEM image of the gold‐nanoparticle covered polyaniline nanoball. 相似文献
Dendrimer‐protected gold nanoparticles have been facilely obtained by heating an aqueous solution containing third‐generation poly(propyleneimine) dendrimers and HAuCl4 without the additional step of introducing other reducing agents. Transmission electron microscopy (TEM) and UV‐vis data indicate the size, the nucleation, and growth kinetics of gold nanoparticles thus formed, which can be tuned by changing the initial molar ratio of dendrimer to gold.
The formation of dendrimer–gold nanoparticles by the heat treatment of an aqueous solution containing third‐generation poly(propyleneimine) dendrimers and HAuCl4. 相似文献
A “click” polymerization of dialkynes that contain an ester linkages and diazides to has been performed to synthesize various polyesters, termed “click polyesters” with a high of 1.0 × 104 to 7.0 × 104 in an excellent yield. This polymerization accompanied a formation of 1,4‐disubstituted triazoles in the polyester main chain by a CuI catalyst. The triazole ring formation in the polyester main chain leads to improved thermal properties and enhancement of the even–odd effect of methylene chain length of the produced click polyesters. This report is the first report of the application of click chemistry to synthesize a series of polyesters under mild conditions.
The preparation of metal nanoparticles generally requires the use of mostly toxic reducing agents according to state‐of‐the‐art procedures. Here, we report that polysorbate 80, a polymeric nonionic surfactant, when reacted with a gold salt in water at room temperature, yields well‐dispersed gold nanoparticles. Furthermore, we could control the particle size by simply altering concentration or temperature. The synthetic procedure presented here is easy, inexpensive, straightforward, and user‐friendly.
Nanofiber scaffolds of collagen have been fabricated via electrospinning using benign solvent systems as a replacement for 1,1,1,3,3,3 hexafluoro‐2‐propanol. Simple binary mixtures of phosphate‐buffered saline and ethanol have been found to be highly effective for electrospinning. FTIR spectra suggest that the triple helical structure of collagen was conserved after dissolution and electrospinning. Crosslinking of the electrospun collagen scaffolds was achieved with standard methods.
Highly dispersed ZnO nanoparticles with variable particle sizes were successfully prepared within an amphiphilic hyperbranched polyetherpolyol matrix via decomposition of an organometallic precursor in the presence of air leading to stable nanocomposites. The high degree of stabilization during and after the synthesis by the polymer permits control over the nanoparticle size and therefore, due to the quantum‐size‐effect, the particle properties. Furthermore, these polymer‐inorganic nanocomposites can easily be dispersed in apolar solvents to yield highly transparent, stable solutions.
New multifunctional copoly(2‐oxazoline) nanoparticles were prepared for cell studies. The polymer contains double‐bond side chains as potential reaction sites for “thio”‐click reactions as well as a fluorescein label covalently bound to the polymer backbone. Using the nanoprecipitation technique, spherical nanoparticles of 200–800 nm were obtained. Confocal laser scanning microscopy measurements revealed the cellular uptake of the nanoparticles.
Summary: This paper demonstrates a new, reliable, and simple method for fabricating micropatterned nanoparticle arrays that can serve as templates for the surface‐initiated polymerization of polymer brushes. As a proof of concept, we micropatterned gold nanoparticles (Au‐NPs, ≈10 nm) onto glass, silicon, polystyrene, and gold surfaces by a simple three‐step process: (1) microcontact printing of soluble polymer, (2) incubation with a solution of Au‐NPs, and (3) lift‐off of the template in a mixture of ethanol and deionized water. 40 µm wide features were successfully fabricated without any significant defects or nonspecific adsorption on the background. To demonstrate the utility of these Au‐NP templates, we subsequently polymerized N‐isopropylacrylamide by surface‐initiated polymerization, using a surface‐bound initiator.
Synthesis of PNIPAAm brushes from micropatterned Au‐NP. 相似文献
We have created a new functional biosensor coating composed of polyelectrolyte multilayers containing gold nanoparticles. This gold‐hybridized polyelectrolyte multilayer film possesses a stable nanoporous structure under physiological conditions. Antibody molecules were successfully conjugated onto the gold nanoparticles within the film. This functional coating successfully extinguished false signals from non‐specific binding of proteins and cells and also provided highly enhanced detection sensitivity. Furthermore, the drastic differences in protein and cellular adhesion properties between a chip coated with the nanoporous PEM film and a bare chip demonstrate that morphological control of biological interactions on chip surfaces is possible.
