Gold nanoparticles represent nanosized colloidal entities with high relevance for both basic and applied research. When gold nanoparticles are functionalized with polymer-molecule ligands, hybrid nanoparticles emerge whose interactions with the environment are controlled by the polymer coating layer: Colloidal stability and structure formation on the single particle level as well as at the supracolloidal scale can be enabled and engineered by tailoring the composition and architecture of this polymer coating. These possibilities in controlling structure formation may lead to synergistic and/or emergent functional properties of such hybrid colloidal systems. Eventually, the responsivity of the polymer coating to external triggers also enables the formation of hybrid supracolloidal systems with specific dynamic properties. This review provides an overview of fundamentals and recent developments in this vibrant domain of materials science.
- Klíčová slova
- end‐grafted polymers, gold nanoparticles, hybrid nanomaterials, nanostructure formation, responsive nanomaterials, self‐assembly, supracolloids,
- MeSH
- koloidní zlato chemie MeSH
- koloidy chemie MeSH
- kovové nanočástice * chemie MeSH
- polymery * chemie chemická syntéza MeSH
- povrchové vlastnosti MeSH
- velikost částic MeSH
- zlato * chemie MeSH
- Publikační typ
- časopisecké články MeSH
- přehledy MeSH
- Názvy látek
- koloidní zlato MeSH
- koloidy MeSH
- polymery * MeSH
- zlato * MeSH
The location of Brønsted-acid sites (bridging OH groups, b-OH) at different crystallographic positions of zeolite catalysts influences their reactivity due to varying confinement. Selecting the most stable b-OH conformers at each of the 12 T-sites (T=Si/Al) of H-MFI, a representative set of 26 conformers is obtained which includes free b-OH groups pointing into the empty pore space and b-OH groups forming H-bonds across five- or six-membered rings of TO4 tetrahedra. Chemically accurate coupled-cluster-quality calculations for periodic models show that the strength of internal H-bonds and, hence, the OH bond length vary substantially with the framework position. For 11 of the 19 H-bonded b-OH groups examined, our predictions fall into the full width at half maximum range of the experimental signals at 3250±175 cm-1 and 7.0±1.4 ppm which supports previously debated assignments of these signals to H-bonded b-OH sites.
- Klíčová slova
- Brønsted-Acid Sites, IR Spectroscopy, MFI, NMR Spectroscopy, Zeolites,
- MeSH
- katalýza MeSH
- kyseliny chemie MeSH
- magnetická rezonanční spektroskopie metody MeSH
- vodíková vazba MeSH
- zeolity * chemie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- kyseliny MeSH
- zeolity * MeSH
The P-stereogenic bis(phosphanes) 7 and 9, featuring pairs of P(Mes)-ethynyl or vinyl substituents at the dimethyl xanthene backbone show rather low barriers of stereochemical inversion at phosphorus. π-Conjugative effects are probably causing these low inversion barriers. Compound 7 reacted with B(C6 F5 )3 to form the nine-membered heterocyclic product 10, featuring a [P]-C≡C-B(C6 F5 )3 substituent. Compound 7 was converted to the bis[P(Mes)vinyl] xanthene derivative 9, which gave the zwitterionic P(H)(Mes)-CH=CH-B(C6 F5 )3 containing product 16 upon treatment with B(C6 F5 )3 . Thermally induced epimerization barriers at phosphorus of ca. 20 to 27 kcal mol-1 were calculated by DFT for the alkenyl- and alkynyl-P derived systems 6 to 9, 15 and 16 and experimentally determined for the examples 7 and 16.
- Klíčová slova
- boron, inversion, methylene phosphonium, phosphorus, stereogenic phosphorus,
- Publikační typ
- časopisecké články MeSH
