Homo polypeptide can guide the self-assembly of nanoparticles

Nanoparticles – polymer composite materials are often capable of binding to both the advantages with excellent optical, electrical, magnetic, has great potential application in the memory, and the sensor field of microelectronics. Nanoparticle – Polymer materials meet, the structure of the polymer matrix material often affects the performance, even imparting new functions, for example in response to stimulation of the response and the like or a hand. Previously, only the guide block copolymer as a matrix polymer nanoparticles in an ordered arrangement in the composite material. Although the block copolymer is a good polymer matrix composite material, still have three limitations: First, the layered assembly structure has some limitations for a volume fraction of two blocks, typically 40-60% ; second, difficult to precisely control the position of the nanoparticle in the composite material; a third, for the experimental conditions of concentration, temperature, solvent and the like has a strong dependence. Recently, University of Toulouse, France, Simon Tricard Task Force and Colin Bonduelle Task Force United in \”Nature Communication \”in a speech entitled\” bidimensional lamellar assembly by coordination of peptidic homopolymers to platinum nanoparticles \”research papers, we reported the use of homo polypeptide guide platinum nanoparticles to achieve a self-assembled two-dimensional layered structure. In the article, the authors chose five different degree of polymerization of poly (γ-benzyl-L-glutamate) (PBLG) as a model system because PBLG α helix can be formed in a rigid bar-like organic solvent. Of an ultra-small platinum nanoparticles (about 1.2 nm) as the research object, because of its size and a repeating unit rather homopolymeric polypeptides. We investigated the influence of the proportion of homo polypeptide PBLG platinum nanoparticles on the assembly behavior systematically. Transmission color electron microscope (TEM) FIG displayed (figure 1), the equivalent ratio (the number of platinum atoms and a monomer ratio) of 0.5 and 1.0 when the depth of platinum nanoparticles can be formed with the alternately layered PBLG ordered self-assembled, dark areas comprising platinum nanoparticles, lightRegion free of platinum nanoparticles. When the equivalent ratio of excessively high or low are unable to form a more ordered periodic structures. A three-dimensional reconstructed image (Figure 1 below) shows platinum nanoparticles uniformly distributed within the region of the layered structure within the look, no aggregation occurs, X-ray small angle scattering (the SAXS) experiments corroborated the average distance from about platinum nanoparticles 2.5 nm.

Figure 1 (a) of PBLG platinum nanoparticle layer forming a two-dimensional periodic structure; a three-dimensional reconstruction of the two directions (the lower) shows FIG platinum nanoparticles PBLG polymer matrix distribution.

In order to study the mechanism of PBLG platinum nanoparticles, the authors used a solid-state 13C nuclear magnetic resonance magic angle (13C-MAS-SSNMR) were observed before and after assembly PBLG with platinum nanoparticles. Chemical shifts alkynyl groups PBLG end of 72ppm and 80ppm, two peaks in the signal after mixing with the platinum nanoparticles have disappeared, the complexation between the surface of the platinum nanoparticles and alkynyl groups. To further confirm this mechanism, the authors synthesized alkynylzinc no homopolymerization polypeptide PBLG-H. After mixing PBLG-H platinum nanoparticles, the assembly of the ordered structure compared to PBLG markedly reduced, dispersibility of the platinum nano particles is significantly decreased (FIG. 2). X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) shows the effect of platinum nano-particles and the bit PBLG terminal alkyne and an amide bond with both.

FIG. 2, (left) end groups form a relatively ordered assembly structure is an alkynyl group can be guided PBLG platinum nanoparticles. Structure (right) end groups formed is PBLG-H and alkyl ordered platinum nanoparticles poor.

Next, the synthesis of PBLG five different degrees of polymerization, the degree of polymerization for influencing PBLG study of the assembled structure. PBLG five kinds of different degree of polymerization are the degree of polymerization (DP) PBLG1 18 a, DP = PBLG2 69 a, DP = PBLG3 120 a, DP = PBLG4 217, and the DP = PBLG5 481. PBLG1 too low due to the polymerization can not effectively guide assembly platinum nano particles. From discovery to the assembly structure PBLG5 PBLG2 platinum particles cm, a width of the periodic structure of the polymerization degree of the layered assembly of linear correlation appears(image 3). Analysis showed, α helix with a length corresponding to the width of the assembled structure PBLG light zone is formed equivalent. Assembled structure corresponding to the dark areas are only one-sixth group PBLG-scale random coil form, it is probably because α helix PBLG is destroyed in the dark areas, there has been under the effect of nanoparticles 6-7 fold times.

FIG. 3, a-e distribution PBLG1, PBLG2, PBLG3, PBLG4, PBLG5 five kinds of molecular weight to the results with Pt nanoparticles. f, summarizes the periodic structure of the assembled width of the effect of different degrees of polymerization PBLG.

summary, articles using the homopolymeric polypeptide PBLG platinum nanoparticles led to achieve the orderly assembly of the two-dimensional layered structure. Homo polypeptide to the guide assembly material as the polymer matrix nanoparticles nanoparticles is based block copolymer – polymer composites good supplement. The article realized two breakthroughs: First, the guide realized homo polypeptide anisotropic metal nanoparticles form a layered assembly; the second, the polypeptide can be homopolymerized by simply to regulate the degree of polymerization Periodic implemented width of the assembled structure polymer nanoparticles 10 nm to 100 nm.