Addition of ferrocene derivatives to the surface of quantum-confined cadmium sulfide clusters: steady-state and time-resolved photophysical effects

Abstract

DR plots are given for three carbons of series M with increasing degree of oxidation. These results may be summarized as follows:(i) The polarity of the adsorptive prevents the filling of the micropores at low relative pressures as noted by the decrease in slope ratios from N2 to HzO.(ii) The polar moment is not the only factor to explain the deviations (relative to N2) found for SO2, CH30H, and H20 (they have very similar values); neither is the hydrogen bond by itself because is similar for water and methanol. The most important factor seem to be a low nonspecific adsorbatecarbon interaction and a high adsorptive-adsorptive interaction.(iii) The differences between C H 3 0 H and SO2 suggest that hydrogen bond causes a larger deviation than the simple polar moment interaction.(iv) Increasing degree of oxidation increases the carbon-adsorbate interaction, the adsorption mechanism approaching then that of N2, micropore filling with the adsorbate as liquid. Acknowledgment. This work was supported by CICYTThe effect of substituted ferrocene complexes on the surface of quantum-confined (Q) cadmium sulfide clusters in inverse micelles was examined by steady-state and time-resolved photoluminescence (PL) spectroscopy. Addition of (dimethylamin0)methylferrocene (DMAMF) to Q-CdS enhanced cluster PL peak areas by 120%, in contrast to the carboxylic acid derivatives ferrocenecarboxylic acid (FCA) and ferrocenedicarboxylic acid (FDCA), which quenched PL by 60% and 80%, respectively. Unsubstituted ferrocene, hydroxymethylferrocene, and ferrocenecarboxaldehyde had no effect on the PL intensity of these clusters. The induced PL changes fit a Langmuir-type adsorption isotherm from which formation constants for the Q-CdSsurface adducts were calculated. The average log Kf value calculated for DMAMF adsorption was 4.12. FCA addition gave an average log Kf of 5.17, and the average log Kf value for FDCA addition was 6.14. Binding of the amino group of DMAMF to shal!ow trap states arising from Cd2+ sites is postulated as its mechanism for PL enhancement, while the quenching mechanism for FCA and FDCA is attributed to proton transfer induced from ionization of the acids in the micelle water pools. "Competition" experiments show that quenching by the carboxylic acid derivatives can be reversed by the addition of amino-substituted ferrocene, and vice versa. The results also suggest a possible DMAMF-induced surface reconstruction. These steady-state observations are supported by measurements of the PL decay via subnanosecond timecorrelated single photon counting. Fits of the decay monitored at 620 nm to a modified stretched exponential model indicate that the average distributed decay time ( T 2 ) of nanosecond duration can be either lengthened or shortened, depending on the nature of the added ferrocene.

Quantum dots in a metallopolymer host: studies of composites of polyferrocenes and CdSe nanocrystals

“…30 The effects of different ferrocenyl derivatives on the PL of CdS nanocrystals, stabilized by inverse micelles (rather than TOPO), have also been investigated, and quenching or enhancement of the PL was observed depending on the nature of the ferrocene derivative. 28 The TOPO-capped CdSe nanocrystals used in this work were prepared by the method of Murray et al 33 The absorption feature of these nanocrystals at 530 nm in toluene solution indicates that they have a diameter of approximately 3.4 nm. 33 The PL maximum of these nanocrystals in toluene solution is centred at 545 nm.…”

“…[25][26][27] The photoluminescence of CdS nanocrystals has been shown to be either quenched or enhanced in the presence of different ferrocenyl derivatives, the enhancement occurring when a dimethylamino-substituted ferrocene was coordinated to the nanocrystal surface via amine ligation. 28 Electrochemical modification of electronic effects of metal nanoparticles by ferrocenyl-derivative capping ligands has also been demonstrated. 29 In addition, it has been shown that ferrocene and ferrocenium can exert different effects on, e.g., the luminescence of organic luminophores.…”

Dynamics of Recombination Processes in PbI2 Nanocrystals Embedded in Porous Silica Films

“…The same version of the modified KWW function was used by Chandler et al to fit PL decay data in CdS clusters, with ferrocene derivatives on their surface. 55 Beadie et al used the KWW function to fit the carrier's relaxation in CdS x Se 1-x -doped glasses, measured by a pump-probe technique. 56 The latter's model suggests that excited carriers, localized on the surface, can recombine on recombination centers, reached via continuous time random walks.…”

Photophysics and photochemistry of natural waters with emphasis on radical probe development and application

“…This system is described in detail elsewhere (19). Briefly, excitation was provided by a cavity-dumped tunable dye laser, synchronously pumped with the second harmonic of a mode-locked Nd-YAG (Coherent, Antares).…”