<?xml version="1.0" encoding="UTF-8"?><xml><records><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Jain, Prashant K</style></author><author><style face="normal" font="default" size="100%">Qian, Wei</style></author><author><style face="normal" font="default" size="100%">El-Sayed, Mostafa A</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Ultrafast cooling of photoexcited electrons in gold nanoparticle-thiolated DNA conjugates involves the dissociation of the gold-thiol bond</style></title><secondary-title><style face="normal" font="default" size="100%">Journal of the American Chemical Society</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2006</style></year><pub-dates><date><style  face="normal" font="default" size="100%">Feb</style></date></pub-dates></dates><number><style face="normal" font="default" size="100%">7</style></number><volume><style face="normal" font="default" size="100%">128</style></volume><pages><style face="normal" font="default" size="100%">2426-2433</style></pages><isbn><style face="normal" font="default" size="100%">0002-7863</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">Using UV-visible extinction spectroscopy and femtosecond pump-probe transient absorption spectroscopy, we have studied the effect of femtosecond laser heating on gold nanoparticles attached to DNA ligands via thiol groups. It is found that femtosecond pulse excitation of the DNA-modified nanoparticles at a wavelength of 400 nm leads to desorption of the thiolated DNA strands from the nanoparticle surface by the dissociation of the gold-sulfur bond. The laser-initiated gold-sulfur bond-breaking process is a new pathway for nonradiative relaxation of the optically excited electrons within the DNA-modified gold nanoparticles, as manifested by a faster decay rate of the excited electronic distribution at progressively higher laser pulse energies. The experimental results favor a bond dissociation mechanism involving the coupling between the photoexcited electrons of the nanoparticles and the gold-sulfur bond vibrations over one involving the conventional phonon-phonon thermal heating processes. The latter processes have been observed previously by our group to be effective in the selective photothermal destruction of cancer cells bound to anti-epidermal growth factor receptor-conjugated gold nanoparticles.</style></abstract><accession-num><style face="normal" font="default" size="100%">WOS:000235562900062</style></accession-num><notes><style face="normal" font="default" size="100%">Jain, PK Qian, W El-Sayed, MA</style></notes><electronic-resource-num><style face="normal" font="default" size="100%">10.1021/ja056769z</style></electronic-resource-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Jain, Prashant K</style></author><author><style face="normal" font="default" size="100%">Qian, Wei</style></author><author><style face="normal" font="default" size="100%">El-Sayed, Mostafa A</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Ultrafast electron relaxation dynamics in coupled metal nanoparticles in aggregates</style></title><secondary-title><style face="normal" font="default" size="100%">Journal of Physical Chemistry B</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2006</style></year><pub-dates><date><style  face="normal" font="default" size="100%">Jan</style></date></pub-dates></dates><number><style face="normal" font="default" size="100%">1</style></number><volume><style face="normal" font="default" size="100%">110</style></volume><pages><style face="normal" font="default" size="100%">136-142</style></pages><isbn><style face="normal" font="default" size="100%">1520-6106</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">We report the effect of aggregation in gold nanoparticles on their ultrafast electron-phonon relaxation dynamics measured by femtosecond transient absorption pump-probe spectroscopy. UV-visible extinction and transient absorption of the solution-stable aggregates of gold nanoparticles show a broad absorption in the 550-700-nm region in addition to the isolated gold nanoparticle plasmon resonance. This broad red-shifted absorption can be attributed to contributions from gold nanoparticle aggregates with different sizes and/or different fractal structures. The electron-phonon relaxation, reflected as a fast decay component of the transient bleach, is found to depend on the probe wavelength, suggesting that each wavelength interrogates one particular subset of the aggregates. As the probe wavelength is changed from 520 to 635 nm across the broad aggregate absorption, the rate of electron-phonon relaxation increases. The observed trend in the hot electron lifetimes can be explained on the basis of an increased overlap of the electron oscillation frequency with the phonon spectrum and enhanced interfacial electron scattering, with increasing extent of aggregation. The experimental results strongly suggest the presence of intercolloid electronic coupling within the nanoparticle aggregates, besides the well-known dipolar plasmon coupling.</style></abstract><accession-num><style face="normal" font="default" size="100%">WOS:000234520700028</style></accession-num><notes><style face="normal" font="default" size="100%">Jain, PK Qian, W El-Sayed, MA</style></notes><electronic-resource-num><style face="normal" font="default" size="100%">10.1021/jp055562p</style></electronic-resource-num></record><record><source-app name="Biblio" version="7.x">Drupal-Biblio</source-app><ref-type>17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">Schill, A. W.</style></author><author><style face="normal" font="default" size="100%">Gaddis, C. S.</style></author><author><style face="normal" font="default" size="100%">Qian, Wei</style></author><author><style face="normal" font="default" size="100%">El-Sayed, Mostafa A</style></author><author><style face="normal" font="default" size="100%">Cai, Y.</style></author><author><style face="normal" font="default" size="100%">Milam, V. T.</style></author><author><style face="normal" font="default" size="100%">Sandhage, K.</style></author></authors></contributors><titles><title><style face="normal" font="default" size="100%">Ultrafast electronic relaxation and charge-carrier localization in CdS/CdSe/CdS quantum-dot quantum-well heterostructures</style></title><secondary-title><style face="normal" font="default" size="100%">Nano Letters</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2006</style></year><pub-dates><date><style  face="normal" font="default" size="100%">Sep</style></date></pub-dates></dates><number><style face="normal" font="default" size="100%">9</style></number><volume><style face="normal" font="default" size="100%">6</style></volume><pages><style face="normal" font="default" size="100%">1940-1949</style></pages><isbn><style face="normal" font="default" size="100%">1530-6984</style></isbn><language><style face="normal" font="default" size="100%">eng</style></language><abstract><style face="normal" font="default" size="100%">The relaxation and localization times of excited electrons in CdS/CdSe/CdS colloidal quantum wells were measured using subpicosecond spectroscopy. HRTEM analysis and steady-state PL demonstrate a narrow size distribution of 5-6 nm epitaxial crystallites. By monitoring the rise time of the stimulated emission as a function of pump intensity, the relaxation times of the electron from the CdS core into the CdSe well are determined and assigned. Two-component rise times in the stimulated emission are attributed to intraband relaxation of carriers generated directly within the CdSe well ( fast component) and charge transfer of core-localized carriers across the CdS/CdSe interface ( slow component). This is the first reported observation of simultaneous photon absorption in the core and well of a quantum-dot heterostructure. With increasing pump intensity, the charge-transfer channel between the CdS core CdSe well contributes less to the stimulated emission signal because of filling and saturation of the CdSe well state, making the interfacial charge-transfer component less efficient. The interfacial charge-transfer time of the excited electron was determined from the slow component of the stimulated emission build-up time and is found to have a value of 1.2 ps.</style></abstract><accession-num><style face="normal" font="default" size="100%">WOS:000240465100019</style></accession-num><notes><style face="normal" font="default" size="100%">Schill, Alexander W. Gaddis, Christopher S. Qian, Wei El-Sayed, Mostafa A. Cai, Ye Milam, Valeria T. Sandhage, Kenneth</style></notes><electronic-resource-num><style face="normal" font="default" size="100%">10.1021/nl061054v</style></electronic-resource-num></record></records></xml>