Calixarene Complexation Induced Aggregation of Gold Nanoparticles

Transkriptio

1 Calixarene Complexation Induced Aggregation of Gold Nanoparticles Petri Pulkkinen, Szymon Wiktorowicz, Vladimir Aseyev, Heikki Tenhu 1

2 Problem?? 2

3 Problem cm nm 3

4 Solution: Self-Assembly 4

5 Solution: Even Better Self-Assembly 5

6 Materials Gold Nanoparticles Nanotechnological objects with fascinating properties Intermediary between molecules and bulk matter Optical, electrical and catalytical properties Properties tuneable via Quantum Size Effect: NP size and shape. Protecting agents: solubility & other surface properties Calix[4]arenes One of the smallest basket-like organic compounds that are known to exhibit complexation through the cavity Properties tuneable with upper or lower rim chemical functionalization 6

7 The Aim Synthesise and characterize a 1) calix[4]arene derivative that is able to complex organic guest molecules 2) polymeric guest molecule linker 3) calix[4]arene protected AuNPs that retain the complexation ability even when the calixarene is bound on the NP surface Perform a detailed complexation study using 1H NMR, light scattering and UV-vis spectrometry. How does the complexation link with aggregation? What changes occur in the molecules upon complexation? Can added alkanethiols fine tune the complexation? How does the complexant type affect the system? 7

8 Synthesis: The Calixarene Host To sy ls yn t he sis 8

9 Synthesis: The Complexants 9

10 Synthesis: Calixarene and Alkanethiol modified AuNPs Each type of particle purified and fractionated Brust-Schiffrin tim exc e to p han rev ent ge liga nd Low rea ctio n Fu ll Lig and Ex cha n ge followed by purification to remove reducing agents 10

11 The Nanoparticles A) C-AuNP B) C/B-AuNP C) C/D-AuNP D) TEM (C-AuNP) 11

12 Complexation Studies, NMR, Guest More Complexant Calixarene:complexant ratio C-AuNP + small organic complexant Multiplet broadening! 12

13 Complexation Studies, NMR, Host Hydroxyl (OH) substituted aromatic ring experiences a decrease in electronegativity of their environment Ether substituted (-O-) aromatic signals experience an opposite effect Evidence of induced-fit type complexation More Complexant Upon complexation, incoming positively charged pyridinium withdraws electrons from the OH substituted ring. 13

14 [Complexation Video] 14

15 Complexation Studies, NMR, Summary C) C-AuNP:Pyr-C16 Slope change indicates accessible calixarene saturation ratio by the complexant. Butanethiol has no effect on calixarene gold nanoparticle compexation ability, but dodecanethiol is detrimental to it. Multiplicity Broadening coincides with the change of slope CCR = slope change calixarene:complexant ratio 15

16 LS and UV-vis LS a) C-AuNP (2-20 nm scatterers) Negligible Aggregation b) C-AuNP + Pyr-C16 (2-200 nm scatterers) Significant Aggregation c) C-AuNP + Pyr-PEO2k-Pyr (2-100nm scatterers) Significant Aggregation UV-Vis (top to bottom) C-AuNP C-AuNP + Pyr-C16 C-AuNP + Pyr-PEO2k-Pyr Increasing red shift for the SPR band with complexant molar mass 16

17 Conclusions Synthesis objectives were reached Complexation occurs for all the samples Complexation induces particle aggregation Even in as low concentration as 0.2mg/ml Addition of long aliphatic chain alkanethiols offers a possibility of fine-tuning AuNP bound receptor sensitivity This kind of materials could be useful for selfassembly applications, where mobile species are more useful than permanently coupled ones. 17

18 Read the whole story here: RSC Adv., 2013,3, DOI: /C2RA21761A 18