Showing papers by "Chenjie Zeng published in 2019"
TL;DR: Unraveling the grand evolution from nonscalable to scalable optical properties and their mechanisms will greatly deepen scientific understanding of the nature of quantum-sized gold NCs and will also provide implications for plasmonic NPs.
Abstract: The evolution of the optical properties of gold nanoclusters (NCs) versus size is of great importance because it not only reveals the nature of quantum confinement in NCs, but also helps to understand how the molecular-like Au NCs transit to plasmonic nanoparticles. While some work has been done in studying the optical properties of NCs of certain individual sizes, the global picture remains unclear, such as the detailed relationship between size/structure and properties. Here, we investigate the grand evolution of the optical properties by comparing the steady-state absorption, bandgap, transient absorption, as well as carrier dynamics of a series of thiolate-protected gold NCs ranging from tens to hundreds of gold atoms. We find that, on the basis of their optical behaviors, gold NCs can be classified into three groups: (i) ultrasmall NCs (ca. 100 Au atoms) exhibit optical properties solely dependent on size, and the structure effect fades out. Unraveling the grand evolution from nonscalable to scalable optical properties and their mechanisms will greatly deepen scientific understanding of the nature of quantum-sized gold NCs and will also provide implications for plasmonic NPs.
91 citations
TL;DR: This work exploits accessible InCl3- and pnictogen chloride-oleylamine as precursors to synthesize III-V QDs and achieves size and stoichiometry-tunable, binary InAs and InSb as well as ternary alloy InAs1-xSbx QDs.
Abstract: The synthesis of colloidal III–V quantum dots (QDs), particularly of the arsenides and antimonides, has been limited by the lack of stable and available group V precursors. In this work, we exploit...
34 citations
TL;DR: Overall, this work provides some benchmarking features for organic dye molecules, organometallic complexes, metal nanoclusters, and plasmonic nanoparticles, as well as small organic molecules.
Abstract: Recent advances in the determination of crystal structures and studies of optical properties of gold nanoclusters in the size range from tens to hundreds of gold atoms have started to reveal the grand evolution from gold complexes to nanoclusters and further to plasmonic nanoparticles. However, a detailed comparison of their photophysical properties is still lacking. Here, we compared the excited state behaviors of gold complexes, nanolcusters, and plasmonic nanoparticles, as well as small organic molecules by choosing four typical examples including the Au10 complex, Au25 nanocluster (1 nm metal core), 13 diameter Au nanoparticles, and Rhodamine B. To compare their photophysical behaviors, we performed steady-state absorption, photoluminescence, and femtosecond transient absorption spectroscopic measurements. It was found that gold nanoclusters behave somewhat like small molecules, showing both rapid internal conversion (<1 ps) and long-lived excited state lifetime (about 100 ns). Unlike the nanocluster form in which metal–metal transitions dominate, gold complexes showed significant charge transfer between metal atoms and surface ligands. Plasmonic gold nanoparticles, on the other hand, had electrons being heated and cooled (~100 ps time scale) after photo-excitation, and the relaxation was dominated by electron–electron scattering, electron–phonon coupling, and energy dissipation. In both nanoclusters and plasmonic nanoparticles, one can observe coherent oscillations of the metal core, but with different fundamental origins. Overall, this work provides some benchmarking features for organic dye molecules, organometallic complexes, metal nanoclusters, and plasmonic nanoparticles.
32 citations
TL;DR: The [Au133(SR)52]q nanocluster is discovered to possess one spin per particle when q = 0, but no unpaired electron whenq = +1.
Abstract: The transition from the discrete, excitonic state to the continuous, metallic state in thiolate-protected gold nanoclusters is of fundamental interest and has attracted significant efforts in recent research. Compared with optical and electronic transition behavior, the transition in magnetism from the atomic gold paramagnetism (Au 6s1) to the band behavior is less studied. In this work, the magnetic properties of 1.7 nm [Au133(TBBT)52]0 nanoclusters (where TBBT = 4-tert-butylbenzenethiolate) with 81 nominal “valence electrons” are investigated by electron paramagnetic resonance (EPR) spectroscopy. Quantitative EPR analysis shows that each cluster possesses one unpaired electron (spin), indicating that the electrons fill into discrete orbitals instead of a continuous band, for that one electron in the band would give a much smaller magnetic moment. Therefore, [Au133(TBBT)52]0 possesses a nonmetallic electronic structure. Furthermore, we demonstrate that the unpaired spin can be removed by oxidizing [Au133(TBBT)52]0 to [Au133(TBBT)52]+ and the nanocluster transforms from paramagnetism to diamagnetism accordingly. The UV-vis absorption spectra remain the same in the process of single-electron loss or addition. Nuclear magnetic resonance (NMR) is applied to probe the charge and magnetic states of Au133(TBBT)52, and the chemical shifts of 52 surface TBBT ligands are found to be affected by the spin in the gold core. The NMR spectrum of Au133(TBBT)52 shows a 13-fold splitting with 4-fold degeneracy of 52 TBBT ligands, which are correlated to the quasi-D2 symmetry of the ligand shell. Overall, this work provides important insights into the electronic structure of Au133(TBBT)52 by combining EPR, optical and NMR studies, which will pave the way for further understanding of the transition behavior in metal nanoclusters.
30 citations