The first linear silver supercluster based on icosahedral Ag13 units has been constructed via bridging of dpa ligands: Ag61(dpa)27(SbF6)4 (Hdpa = dipyridylamine) (Ag 61 ). Single-crystal X-ray ...diffraction reveals that this rod-shaped cluster consists of four vertex-sharing Ag13 icosahedra in a linear arrangement. This Ag 61 cluster represents the longest one-dimensional metal nanocluster with a resolved structure. Unprecedented electron coupling develops between their constituent Ag13 units. Theoretical studies disclose that the stabilities of the two superclusters are dictated by a strong interaction between the Ag13 units as well as the ligand effect of the dpa–Ag motifs. The quantum size effect accounts for the significant enhancement of the metal-related absorptions and the red shift at the near-infrared region as the length of the cluster increases. This work sheds light on the evolution of one-dimensional materials and an understanding of the electronic communication between the constituent clusters.
Carbon dots (CDs) are photoluminescent nanomaterials with wide-ranging applications. Despite their photoactivity, it remains unknown whether CDs degrade under illumination and whether such ...photodegradation poses any cytotoxic effects. Here, we show laboratory-synthesized CDs irradiated with light degrade into molecules that are toxic to both normal (HEK-293) and cancerous (HeLa and HepG2) human cells. Eight days of irradiation photolyzes 28.6-59.8% of the CDs to <3 kilo Dalton molecules, 1431 of which are detected by high-throughput, non-target high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. Molecular network and community analysis further reveal 499 cytotoxicity-related molecules, 212 of which contain polyethylene glycol, glucose, or benzene-related structures. Photo-induced production of hydroxyl and alkyl radicals play important roles in CD degradation as affected by temperature, pH, light intensity and wavelength. Commercial CDs show similar photodegraded products and cytotoxicity profiles, demonstrating that photodegradation-induced cytotoxicity is likely common to CDs regardless of their chemical composition. Our results highlight the importance of light in cytocompatibility studies of CDs.
The “complexity = action” duality states that the quantum complexity is equal to the action of the stationary AdS black hole within the Wheeler–DeWitt patch at late time approximation. We compute the ...action growth rates of the neutral and charged black holes in massive gravity and the neutral, charged and Kerr–Newman black holes in
f
(
R
) gravity to test this conjecture. Besides, we investigate the effects of the massive graviton terms, higher derivative terms and the topology of the black hole horizon on the complexity growth rate.
Shadow of a charged black hole with scalar hair Guo, Wen-Di; Wei, Shao-Wen; Liu, Yu-Xiao
European physical journal. C, Particles and fields,
03/2023, Letnik:
83, Številka:
3
Journal Article
Recenzirano
Odprti dostop
Seeking singularity free solutions are important for further understanding black holes in quantum level. Recently, a five-dimensional singularity free black hole/topological star was constructed (Bah ...and Heidmann in Phys Rev Lett 126:151101, 2021). Through the Kaluza–Klein reduction, an effective four-dimensional static spherically symmetric charged black hole with scalar hair can be obtained. In this paper, we study shadow of this charged black hole with scalar hair in terms of four kinds of observers, i.e., static observers, surrounding observers, freely falling observers, and escaping observers in four-dimensional spacetime. For a spherically symmetric black hole, the shadow is circular for any observer, but the shadow size depends on the motion status of the observer. On the other hand, the effect of plasma is also investigated by a simple model. The radius of the photon sphere depends on the plasma model. Most importantly, we find that the shadow sizes do not monotonically decrease with
r
in some cases.
Surface organic ligands are critical in determining the formation and properties of atomically precise metal nanoclusters. In contrast to the conventionally used thiolate, phosphine and alkynyl ...ligands, the amine ligand dipyridylamine is applied here as a protecting agent in the synthesis of atomically precise metal nanoclusters. We report two homoleptic amido-protected Ag nanoclusters as examples of all-nitrogen-donor-protected metal nanoclusters: Ag
(dpa)
SbF
(Ag
) and Ag
(dpa)
(SbF
)
(Ag
) (dpa = dipyridylamido). Single crystal X-ray structural analysis reveals that both clusters consist of a centered-icosahedron Ag
core wrapped by 12 dpa ligands. The flexible arrangement of the N donors in dpa facilitates the solvent-triggered reversible interconversion between Ag
and Ag
due to their very different solubility. The successful use of dpa in the synthesis of well-defined silver nanoclusters may motivate more studies on metal nanoclusters protected by amido type ligands.
Silver nanoclusters containing Ag0 atoms protected by amino acids were synthesized and characterized. Chiral superatomic silver nanoclusters Ag47L12(C≡CtBu)16BF4 (L=l‐/d‐valine or l‐/d‐isoleucine) ...have been prepared by reducing AgC≡CtBu and amino acids (AAs) with NaBH4. Single crystal X‐ray diffraction revealed that these clusters have T symmetry, and the Ag47 metal kernel can be viewed as a tetracapped truncated tetrahedron (Ag17) surrounded with six W‐shaped Ag5 units. The clusters are homochiral as evidenced by CD measurements. As for the strong CD signals, large contributions are found from the occupied Ag s,p states (superatomic D states) near the Fermi level. Electron counting revealed that these clusters are 18‐electron systems, suggesting they are superatomic clusters. The superatomic nature with a 1S21P61D10 configuration was supported by DFT calculations. This work paves the way of taking AAs as facile chiral induction agents for the synthesis of metal nanoclusters.
Amino acids protected silver nanoclusters with Ag0 atoms Ag47L12(C≡CtBu)16BF4 (L=l‐/d‐ valine or l‐/d‐ isoleucine) have been synthesized for the first time. The Ag47 kernel consists of a tetracapped truncated tetrahedron (Ag17) and six W‐shaped Ag5 units. They are superatoms with 1S21P61D10 configuration as revealed by DFT calculations. This work offers a facile method to obtain chiral nanoclusters by incorporating amino acids.
Surface organic ligands are critical in dictating the structures and properties of atomically precise metal nanoclusters. In contrast to the conventionally used thiolate, phosphine and alkynyl ...ligands, nitrogen donor ligands have not been used in the protection for well‐defined metal nanoclusters until recently. This review focuses on recent developments in atomically precise metal nanoclusters stabilized by different types of nitrogen donor ligands, in which the synthesis, total structure determination and various properties are covered. We hope that this review will provide insights into the rational design of N donor‐protected metal nanoclusters in terms of structural and functional modulation.
Beyond the conventional thiolate, phosphine and alkynyl ligands, nitrogen donor ligands have recently emerged as protecting agents for well‐defined metal nanoclusters. Given the terminal coordination preference of the negatively charged amido and amidinate ligands with multidentate donors, interesting structural and functional features are observed for metal nanoclusters protected by these types of N donor ligands.
In this paper, we study the structure and gravitational resonances of thick branes generated by a mimetic scalar field in
f
(
R
) gravity. We obtain several typical thick brane solutions for
f
(
R
)
...=
R
+
α
R
2
. To study their stability, we analyze the tensor perturbation of the metric. It is shown that any thick brane model with
d
f
/
d
R
>
0
is stable and the graviton zero mode can be localized on the brane for each solution, which indicates that the four-dimensional Newtonian gravity can be restored. The effect of the parameter
α
on the gravitational resonances is studied. As a brane splits into multi sub-branes, the effective potential of the tensor perturbation will have an abundant inner structure with multi-wells, and this will lead to new phenomena of the gravitational resonances.
We report the synthesis and crystal structure determination of two novel chiral gold nanoclusters. By utilizing BINAP, we isolate atomically precise intrinsically chiral Au nanoclusters ...Au9(R-/S-BINAP)4(CF3COO)3 and Au10(R-/S-BINAP)4(p-CF3C6H4CC)(CF3COO)3 in high yield with one-pot synthesis. Au 9 has C 2 geometry, while Au 10 is C 1 symmetric. Interestingly, reversible interconversion between Au 9 and Au 10 can be realized by the addition or removal of a RCCAu component. The transformation from Au 9 to Au 10 leads to significant enhancement of CD signals. The maximum anisotropy factor in the visible region of Au10(BINAP)4(p-CF3C6H4CC)3+ is the hitherto largest (up to 6.6 × 10–3) among gold nanoclusters, which is approximately twice of that of Au9(BINAP)43+. This work demonstrates that the chiroptical activity of gold nanoclusters can be modulated by structural control through the introduction of second ligands.
Gravitational resonances on f(T)-branes Tan, Qin; Guo, Wen-Di; Zhang, Yu-Peng ...
European physical journal. C, Particles and fields,
04/2021, Letnik:
81, Številka:
4
Journal Article
Recenzirano
Odprti dostop
In this work, we investigate the gravitational resonances in various
f
(
T
)-brane models with the warp factor
e
A
(
y
)
=
tanh
(
k
(
y
+
b
)
)
-
tanh
(
k
(
y
-
b
)
)
, where
f
(
T
) is an arbitrary ...function of the torsion scalar
T
. For three kinds of
f
(
T
), we give the solutions to the system. Besides, we consider the tensor perturbation of the vielbein and obtain the effective potentials by the Kaluza–Klein (KK) decomposition. Then we analyze what kind of effective potential can produce the gravitational resonances. The effects of different parameters on the gravitational resonances are analyzed. The lifetimes of the resonances could be long enough as regards the age of our universe in some ranges of the parameters. This indicates that the gravitational resonances might be considered as one of the candidates for dark matter. Combining the current experimental observations, we constrain the parameters for these brane models.
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