@article {1195,
	title = {The quenching of CdSe quantum dots photoluminescence by gold nanoparticles in solution},
	journal = {Photochemistry and Photobiology},
	volume = {75},
	number = {6},
	year = {2002},
	note = {Nikoobakht, B Burda, C Braun, M Hun, M El-Sayed, MA},
	month = {Jun},
	pages = {591-597},
	abstract = {The photoluminescence (PL) of CdSe quantum dots (QD) in aqueous media has been studied in the presence of gold nanoparticles (NP) with different shapes. The steady state PL intensity of CdSe QD (1.5-2 nm in size) is quenched in the presence of gold NP. Picosecond bleach recovery and nanosecond time-resolved luminescence measurements show a faster bleach recovery and decrease in the lifetime of the emitting states of CdSe QD in the presence of quenchers. Surfactant-capped gold nanorods (NR) with aspect ratio of 3 and surfactant-capped and citrate-capped nanospheres (NS) of 12 nm diameter were used as quenchers in order to study the effect of shape and surface charge on the quenching rates. The Stern-Volmer kinetics model is used to examine the observed quenching behavior as a function of the quencher concentration. It was found that the quenching rate of NR is more than 1000 times stronger than that of NS with the same capping material. We also found that the quenching rate decreases as the length of the NR decreases, although the overlap between the CdSe emission and the NR absorption increases. This suggests that the quenching is a result of electron transfer rather than long-range (Forster-type) energy transfer processes. The quenching was attributed to the transfer of electron with energies below the Fermi level of gold to the trap holes of CdSe QD. The observed large difference between NR and NS quenching efficiencies was attributed to the presence of the {110} facets only in the NR, which have higher surface energy.},
	isbn = {0031-8655},
	doi = {10.1562/0031-8655(2002)075<0591:tqocqd>2.0.co;2},
	author = {Nikoobakht, Babak and Burda, Clemens and Braun, Markus and Hun, M. and El-Sayed, Mostafa A}
}
@article {1255,
	title = {Quantitative determination of the protein catalytic efficiency for the retinal excited-state decay in bacteriorhodopsin},
	journal = {Journal of Physical Chemistry B},
	volume = {102},
	number = {41},
	year = {1998},
	note = {Logunov, SL Masciangioli, TM El-Sayed, MA},
	month = {Oct},
	pages = {8109-8112},
	abstract = {It was previously found that by removing the negative charge of Asp85 in bacteriorhodopsin (bR), either by protonating it (as in deionized bR) or by mutation to Asn, the decay time of the retinal excited state increases from 0.5 ps to either 1.5 or 10 ps. The two decay components result from the presence of all-trans and 13-cis,15-syn (13-cis) retinal isomers in the modified retinal protein. To quantitatively determine the protein catalysis for the primary process in native bR, we need to determine which decay component results from the excited state of the all-trans isomer (present in the native bR). It is known that the all-trans isomer absorbs at longer wavelength than the 13-cis isomer in blue bR. In this communication, we report the results of pump-probe experiments using 100 fs laser pulses. Probing is carried out at 490 nm, where the excited state in both isomers absorbs. It is found that the ratio of the amplitudes of the two decay components in blue bR changes with variation of the excitation wavelength. The shorter-lived component is found to increase in amplitude as the excitation wavelength increases, i.e., as we excite more of the all-trans isomer. This leads to the conclusion that the short-lived component (1.5 ps) is for the decay of the all-trans excited state while the long-lived component (10 ps) is for the 13-cis retinal excited-state decay. Thus, the presence of the negative charge of Asp85 in native bR catalyzes the rate of the excited-state decay of the all-trans retinal by 300\% and that of the 13-cis isomer by >2000\%.},
	isbn = {1089-5647},
	doi = {10.1021/jp9813600},
	author = {Logunov, Stephan L. and Masciangioli, Tina M. and El-Sayed, Mostafa A}
}
