Photo‐induced reduction of Noble metal ions to metal nanoparticles on tubular J‐aggregates

Abstract

Palladium and silver nanoparticles are formed on the surface of tubular J-aggregates of an amphiphilic tetrachlorobenzimidacarbocyanine dye by reduction of the respective metal cations in aqueous solution. Upon addition of the palladium complex Na 2 PdCl 4 to the aggregate solution, the absorption spectrum shows significant changes which is explained by partial destruction of the aggregates. Cryogenic transmission electron microscopy (cryo-TEM) images show that the tubular J-aggregates are randomly covered by well-separated Pd nanoparticles of approximately 1-3 nm size. Larger particles and higher particle density along the aggregates are obtained when an auxiliary reducing agent is added to the solution. The presence of the metallic particles leads to efficient fluorescence quenching giving clear evidence for super quenching. In similar experiments using AgNO 3 , silver nanoparticles are grown which are larger in size but less dense distributed along the aggregates. At least in the case of the silver particles, the spontaneous formation of metal nanoparticles is assumed to be initiated by a photo-induced electron transfer process (PET).

J‐aggregates of amphiphilic cyanine dyes: Self‐organization of artificial light harvesting complexes

“…Since in these experiments no electron donating molecules are present, some dyes at the aggregate surface must be oxidized. More details about this particle growth are found in a separate contribution by Kirstein et al in [99].…”

“…Although the details of this quenching mechanism are not understood yet, this superquenching is a clear indication of efficient energy migration in the tubular J-aggregates. More experiments on fluorescence quenching are described by the contribution of Kirstein et al in [99].…”

On the Aggregation Behaviour and Spectroscopic Properties of Alkylated and Annelated Boron‐Dipyrromethene (BODIPY) Dyes in Aqueous Solution

“…Exciton delocalization lengths of > 10 molecules as seen for cyanines are most likely not reached here. [63,64] As has been recently shown by Werz's group, chemical fixation of BODIPY units to oligomers can strongly drive J aggregate formation. [65] These authors have also observed that subtle structural modifications can have a pronounced impact on the nature of the aggregates formed.…”

Quantum Simulation of Energy Transport with Embedded Rydberg Aggregates

“…The degree of decoherence is traced back to information gained on the excitation location through the monitoring, turning the setup into an experimentally accessible model system for studying the effects of quantum measurements on the dynamics of a many-body quantum system. Introduction: Excitation transport through dipole-dipole interactions [1,2] plays a prominent role in diverse physical settings, including photosynthesis [3,4], exciton transport through quantum-dot arrays [5], and molecular aggregates [6][7][8]. Of crucial importance is the competition between the fundamentally coherent transport mechanism and the coupling to the environment, which has been under intense scrutiny in the context of photosynthesis (e.g.…”