PubMed İndeksli Yayınlar Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/397

Browse

Now showing 1 - 3 of 3

Citation - WoS: 13
Citation - Scopus: 14
TD-DFTB Study of Optical Properties of Silver Nanoparticle Homodimers and Heterodimers
(Amer Inst Physics, 2020) Liu, Zhen; Alkan, Fahri; Aikens, Christine M.; 01. Abdullah Gül University
The absorption spectra for face-centered cubic nanoparticle dimers at various interparticle distances are investigated using time-dependent density functional tight binding. Both homodimers and heterodimers are investigated in this work. By studying nanoparticles at various interparticle distances and analyzing their vertical excitations, we found that as the interparticle distance decreases, a red shift arises from contributions of the transition dipole moment that are aligned along the z-axis with nondegenerate features; blue shifts occur for peaks that originate from transition dipole moment components in the x and y directions with double degeneracy. When the nanoparticles are similar in size, the features in the absorption spectra become more sensitive to the interparticle distances. The best-fit curves from vertical excitation energy in the form of AR(-b) for Delta E-redshift/Delta E-blueshift vs R are determined. In this way, we determined trends for absorption peak shifts and how these depend on the interparticle distance.
Citation - WoS: 63
Citation - Scopus: 61
An Ultrastable 155-Nuclei Silver Nanocluster Protected by Thiacalix[4]Arene and Cyclohexanethiol for Photothermal Conversion
(Wiley-VCH Verlag GmbH, 2022) Wang, Zhi; Alkan, Fahri; Aikens, Christine M.; Kurmoo, Mohamedally; Zhang, Zhen-Yi; Song, Ke-Peng; Sun, Di; 01. Abdullah Gül University
Thiacalix[4]arenes have emerged as a family of macrocyclic ligands to protect metal nanoparticles, but it remains a great challenge to solve the mystery of their structures at the atomic level, especially for those larger than 2 nm. Here, we report the largest known mixed-valence silver nanocluster [Ag-155(CyS)(40)(TC4A)(5)Cl-2] (Ag155) protected by deprotonated cyclohexanethiol (CySH) and macrocyclic ligand p-tert-butylthiacalix[4]arene (H(4)TC4A). Its single-crystal structure consists of a metallic core of four concentric shells, Ag-13@Ag-42@Ag-30@Ag-70, lined with a organic skin of 40CyS(-) and 5TC4A(4-) and 2Cl(-). Ag155 manifests an unusual pseudo-5-fold symmetry dictated by the intrinsic metal atom packing and the regioselective distribution of mixed protective ligands. This work not only reveals a macrocyclic ligand effect on the formation of a large silver nanocluster, but also provides a new structural archetype for comprehensively perceiving their interface and metal kernel structures.
Citation - WoS: 14
Citation - Scopus: 12
Understanding Plasmon Coupling in Nanoparticle Dimers Using Molecular Orbitals and Configuration Interaction
(Royal Soc Chemistry, 2019) Alkan, Fahri; Aikens, Christine M.; 01. Abdullah Gül University
We perform a theoretical investigation of the electronic structure and optical properties of atomic nanowire and nanorod dimers using DFT and TDDFT. In both systems at separation distances larger than 0.75 nm, optical spectra show a single feature that resembles the bonding dipole plasmon (BDP) mode. A configuration interaction (CI) analysis shows that the BDP mode arises from constructive coupling of transitions, whereas the destructive coupling does not produce significant oscillator strength for such separation distances. At shorter separation distances, both constructive and destructive coupling produce oscillator strength due to wave-function overlap, which results in multiple features in the calculated spectra. Our analysis shows that a charge-transfer plasmon (CTP) mode arises from destructive coupling of transitions, whereas the BDP results from constructive coupling of the same transitions at shorter separation distances. Furthermore, the coupling elements between these transitions are shown to depend heavily on the amount of exact Hartree-Fock exchange (HFX) in the functional, which affects the splitting of CTP and BDP modes. With 50% HFX or more, the CTP and BDP modes mainly merge into a single feature in the spectra. These findings suggest that the effects of exact exchange must be assessed during the prediction of CTP modes in plasmonic systems.

Browse

Browsing PubMed İndeksli Yayınlar Koleksiyonu by Author "Aikens, Christine M."