Excited-State Behaviors of M₁Au₂₄(SR)₁₈ Nanoclusters: The Number of Valence Electrons Matters

Abstract

Doping is a quite useful strategy for probing the structure and properties of metal nanoclusters, but the effect of doping on the photodynamical properties is still not fully understood. Here, we reveal that the number of valence electrons plays a major role in determining the photodynamics of M 1 Au 24 (SR) 18 nanoclusters. By carrying out temperature-dependent optical absorption, it is found that Cd doping enhances electron−phonon coupling while Hg doping does not significantly alter the coupling. Moreover, the relaxation dynamics of [M 1 Au 24 (SR) 18 ] 0 (M = Hg/Cd) nanoclusters show similar features to that of the negatively charged Au 25 nanocluster. Specifically, the 8-electron M 1 Au 24 (M = Cd/Hg) nanoclusters show a long excited-state lifetime (50−200 ns) and a weak picosecond relaxation, similar to the case of the anionic [Au 25 ] − nanocluster. On the other hand, the non-8-electron MAu 24 (M = Pd/Pt) nanoclusters show much more significant picosecond relaxation and thus much shorter excited-state lifetimes, which resembles the case of neutral [Au 25 ] 0 . The picosecond relaxation in all six cases can be explained by core−shell charge transfer or relaxation to the surface trap state. These results are of great importance for fundamental understanding of the interplay between the valence electrons and the optical properties of metal nanoclusters.

Metal Doping of Au25(SR)18– Clusters: Insights and Hindsights

“…Modification of the metal composition has been studied for several clusters, but most research has focused on Au25(SR)18, which is an atomically precise cluster that has been long considered a convenient benchmark system for understanding properties and devising applications of gold nanoclusters. 10,11 Controlled doping of Au25(SR)18 − has been carried out with the noble metals platinum [12][13][14][15][16] and palladium, 14,[16][17][18][19] and less noble metals, such as cadmium [20][21][22] and mercury, 15,[20][21][22][23] also because of the ease by which monodoping could be achieved with these metals as opposed to, say, copper and silver. 9 Mass spectrometry and single crystal X-ray crystallography were extensively employed to interpret the doping results and, particularly, assign the specific locations where these single foreign-metal atoms go.…”

Atomically Precise Bimetallic Nanoclusters as Photosensitizers in Photoelectrochemical Cells

“…In these demonstrations, one of the most important roles of the NCs is acting as a photosensitizer to extend the photoresponse of the semiconductor (i.e., TiO 2 ) from the UV to the Vis‐IR region . Advanced techniques such as time‐resolved optical spectrometry have been used to study the excited states of NCs . Several NCs (i.e., Au 25 and Ag 44 ) are reported to possess long‐lived excited states, which could favor the electron injection from the excited state of NCs to the conduction band of the semiconductor .…”

“…[24][25][26][27][28] Advanced techniquess uch as time-resolved opticals pectrometry have been used to studyt he excited states of NCs. [29][30][31][32][33][34][35][36][37][38][39] Several NCs (i.e., Au 25 and Ag 44 )a re reportedt op ossess long-livede xcited states, which could favor the electroni njection from the excited state of NCs to the conduction band of the semiconductor. [29][30][31] However,i ti ss till unclear whether there are other important factors that affect the overall efficiency of the system.…”

Deepening the Understanding of Thiolate-Protected Metal Clusters Using High-Performance Liquid Chromatography

“…To confirm this, we extracted the ion intensities of Au 25¹x Ag x (SC 4 H 9 ) 18 (x = 04) from the time-dependent mass spectrum (Figure 14(a)). As shown in Figure 14 (Figure 16(a)) 148,286,507,568,603,706,721,767,768,791,795,813,826 and co-reduction method (Figure 16(b)). 43,58,174,219,222,241,262,300,305,311,346,356,431,536,587,601,614 In this study, we found that the isomer distribution also depends on the standing time in solution.…”