Magic-functional polymer chain end, for the accurate preparation of <2 nm arrays of nanoclusters
nanoclusters (nanoclusters) is less than a diameter of less than 300 atoms consisting of 2 nm submicroscopic aggregates. Because the particles exhibit molecular orbital having a high surface area / volume ratio of a discrete, catalytic, optical, and magnetic fields typically exhibit superior performance. Although by controlling the nucleation and growth process, the preparation of the bulk liquid phase reactor and nano synthesis method may be used precise number of atoms nanoclusters prepared, however so far, sub-nanometer diameter less than 2 nm cluster arrays the preparation method has not yet been reported. Precise control cluster sub-nanometer particle size and composition, and other related properties of nanomaterials will open a new road in the field of optical sensing and biomedical imaging. To this end, researchers have attempted to use poly (ethylene oxide) -b- poly (2-vinylpyridine) (PEO-b-P2VP) nano-reactor, the diameter prepared by a method of reducing the volume or the metal loading of the reactor less than 2 nm for the sub-nanometer particle clusters. However, when the volume is very small nano-reactor, since the unevenness in the metal precursor PEO-b-P2VP dispersion, such that a change between the content of the metal precursor each reactor is very large, resulting in distribution of the particles prepared is uneven. To solve the above problem, recently, Northwestern University Prof. Chad A. Mirkin were designed and synthesized a novel porphyrin PEO terminated by fixing the metal atoms per polymer chain quantity, and uniform distribution of the ultrafine nanoparticles prepared. Experimental results show that the processing means of dip pen nanolithography etching techniques (DPN), to Pt 2+ loaded polymer \”ink\”, the system can control the volume of the nano-reactor lowest up to 10 -24 L ; nano such small size reactor may be converted by thermal annealing to 1 ~ 5 nm size of the Pt nanoparticles ; in addition, Cu , after the mixture of polymers and Pt were supported Ni as \”ink\”, may be prepared binary and ternary alloys of ultrafine particles. Using porphyrins terminated PEO preparation of this strategy nanoarray to obtain novel nanostructures site-specific manner to open up a new way. The research results, entitled \”Chain-End Functionalized Polymers for the Controlled Synthesis of Sub-2 nm Particles \”published in the\” Journal of American Chemical Society \”a (DOI: https://dx.doi.org/ 10.1021 / jacs.0c02244). <img class=\"aligncenter size-full wp-image-2767 j-lazy\" src=\"https://oss.yantuo.com.cn/wp-content/uploads/2020/04/2020041708234886.png\" alt=\"神奇链端功能化聚合物，用于精准制备
1. synthesis MTPP-PEO5k functionalized polymer
triphenylphosphonium 5,10,15 20- (4-carboxymethyl benzene yl) porphyrin and porphyrin coupling reaction of methoxy polyethylene oxide amines (PEO5k, Mn = 5000) amidation hexafluorophosphate Azar ammonium benzotriazole tetramethyluronium (HATU) -mediated terminated PEO, i.e. TPP-PEO5k. for Cu 2+ , Ni 2+ , Co 2+ or Zn 2+ load polymer, TPP-PEO5k may be immersed in the corresponding metal acetates, and the mixture obtained was stirred at 80 deg.] C; and the need for more severe loading conditions of metal ions (e.g. Pt 2+ It requires 190 deg.] C), the metal ion may be previously loaded into the porphyrin ring, and then amidation reaction PEO5k. TOFMS and UV analysis showed that TPP-PEO5k functional polymerization method can be successfully prepared various metal loading , i.e. MTPP-PEO5k
2. preparation and characterization of sub-nano-cluster arrays
using a DPN technique PtTPP-PEO5k silicon polymer may be printed on-chip, after thermal annealing the metal loaded polymer may be converted into a uniform size matrix Pt nanoclustersColumn (Figure 2A and B). At the same time the metal functionalized polymer supported nanoparticle size can be precisely controlled, positive correlation between the size of the resulting nanoparticles and polymer nanoparticles reactor. 2C, when the diameter of the polymer nano-reactor dropped from 65 nm to 25 nm, the average diameter of the nanoparticles dropped from 5.2 nm to 1.3 nm, and the resulting nano-sized particles are in the size range of theory.
3. Preparation of binary and ternary alloys ultrafine particles
In order to verify the feasibility of the process for preparing ultrafine particles of alloy, of equal amounts of CuTPP-PEO5k (or NiTPP-PEO5k) PtTPP-PEO5k added to the polymer mixture in order to \”ink\” attempts to prepare nanoparticles. EDS confirmed that this method was successfully synthesized and PtCu PtNi binary alloy nanoparticles (Fig. 3B and C). Further, the authors PtTPP-PEO5k, CuTPP-PEO5k, NiTPP-PEO5k to 2: 1: 1 molar ratio were mixed, may be prepared PtCuNi ternary alloy nanoparticles obtained, shown in Figure 3D.
The first study reported an array of sub-nano-clusters is less than 2 nm in diameter were prepared in a functional polymer supported as a single metal nano-reactor. Since the PEO porphyrin-terminated, can maintain a certain stoichiometry between metal atoms on a polymer, such that the polymer nano-specific manner, reactor size can be synthesized and site-controlled ultra-small size sub-nanometer cluster array. This work has shown that polymeric nanoparticles universally reactor suitable for preparingNanoparticles, and because of the extensive synthetic polymers, but also for the preparation of different nanoparticles, a novel idea. The full text link: https: //pubs.acs.org/doi/abs/10.1021/jacs.0c02244