ARTICLE

Chiral Ag23 nanocluster with open shell electronicstructure and helical face-centered cubicframeworkChao Liu1, Tao Li2, Hadi Abroshan 3, Zhimin Li1, Chen Zhang4, Hyung J. Kim 3,5, Gao Li1 & Rongchao Jin3

We report the synthesis and crystal structure of a nanocluster composed of 23 silver atoms

capped by 8 phosphine and 18 phenylethanethiolate ligands. X-ray crystallographic analysis

reveals that the kernel of the Ag nanocluster adopts a helical face-centered cubic structure

with C2 symmetry. The thiolate ligands show two binding patterns with the surface Ag atoms:

tri- and tetra-podal types. The tetra-coordination mode of thiolate has not been found in

previous Ag nanoclusters. No counter ion (e.g., Na+ and NO3−) is found in the single-crystal

and the absence of such ions is also confirmed by X-ray photoelectron spectroscopy analysis,

indicating electrical neutrality of the nanocluster. Interestingly, the nanocluster has an open

shell electronic structure (i.e., 23(Ag 5s1)–18(SR)= 5e), as confirmed by electron para-

magnetic resonance spectroscopy. Time-dependent density functional theory calculations are

performed to correlate the structure and optical absorption/emission spectra of the Ag

nanocluster.

DOI: 10.1038/s41467-018-03136-9 OPEN

1 State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, P. R. China. 2 School of PhysicalScience and Technology, ShanghaiTech University, Shanghai 201210, P. R. China. 3 Department of Chemistry, Carnegie Mellon University, Pittsburgh, PA15213, USA. 4Department of Chemistry, University of Missouri-Columbia, Columbia, MO 65211, USA. 5 School of Computational Sciences, Korea Institute forAdvanced Study, Seoul 02455, Korea. Correspondence and requests for materials should be addressed to G.L. (email: gaoli@dicp.ac.cn)or to R.J. (email: rongchao@andrew.cmu.edu)

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S ilver nanoparticles (AgNPs) constitute an important type ofnanomaterial for a variety of innovative applications1–4. Ascompared with the bulk counterpart, the nanoparticles

possess higher surface-to-volume ratios and chemical potential.These characteristics lead to unique optical, electrical, and ther-mal properties, which constitute the basis of novel applications insensing, catalysis, nanoelectronics, bio-tagging, etc5–7. The anti-bactericidal and antifungicidal activities of AgNPs have gained anincreasing interest for their applications in coatings, textiles,wound treatment, sterilization, and biomedical devices8, 9. Theuse of nano-silver reduces cytotoxicity but not antibacterial/antifungal efficacy—an attractive feature attributed to the for-mation of free radicals from the surface of the nanoparticles10.

The properties of AgNPs are strongly influenced by theirmorphology, size, shape, aggregation state, and surfaceengineering2, 11. Therefore, systematic development of AgNPs isrequired for optimization of the nanoparticles for specific appli-cations, e.g., selective destruction of cancer cells12. In this regard,significant efforts have been made to synthesize and characterizeultrasmall-sized Ag metalloid and Ag(I) nanoclusters13–24. Stu-dies have revealed important size-dependent features. Forexample, some nanoclusters with specific sizes have excellentstability and photoluminescence properties19–21. Despite the greatadvances in the synthesis, the total structure determination of Agnanoclusters still remains to be a major challenge. Thus far, only afew structures of Ag nanoclusters have been resolved by X-raycrystallography16–24.

Ultrasmall, atomically precise nanoclusters are of greatimportance in fundamental research for deep understanding ofthe chemical nature of nanomaterials1, 11. Well-defined silvernanoclusters with fully resolved crystal structures offer uniqueplatforms for accurate electronic structure calculations to shedlight on the structure–activity relationship. Such nanoclusters alsooffer insights into the origin of differences in nano- and macro-scale metal materials. For example, the plasmonic Ag nano-particles are well known to adopt a face-centered cubic (fcc)structure2. Recently, nanoclusters of Ag14(SC6H3F2)12(PPh3)8,[Ag62S12(St-Bu)32]2+, and [Ag67(SPhMe2)32(PPh3)8]3+ with fcc-type structures have also been reported16, 19, 20, and Yang et al.reported the large structures of plasmonic Ag136 and Ag374nanoclusters22.

In recent research, chiral nanostructured materials havereceived a great deal of attention owing to their applications inchemistry, pharmacology, biology, and medicine25–29. Chiralityrefers to molecules that lack an internal plane of symmetry, andhence are non-superimposable with their mirror image. Recentstudies have illustrated the potential applications offered by chiralmetal nanoparticles in biomolecular recognition as powerfulprobes for macromolecules (e.g., proteins)25. Chiral noble metalnanostructures, in particular silver and gold, exhibit characteristiclocalized surface plasmon resonance, which leads to an intenseoptical activity26, 27. Chiral metal nanoparticles can also serve as anew route to enantioselective catalysis owing to their capability ofenantioselective adsorption of chiral compounds, which is a keystep toward achieving enantiospecific catalysis, separation, andsensing28, 29. However, preparation of ultrasmall-sized chiralnanoparticles with well-defined structures is still in the early stageof scientific advancement29. This is mainly owing to difficulties inthe chemical synthesis of nanoparticles with intrinsic chiralmorphology, or reliable assembly of achiral building blocks intochiral nanostructures, which have only been observed in theatomically precise gold nanoclusters30–34.

Here, we present one-pot synthesis and crystal structuredetermination of a chiral silver nanocluster with 23 silver atomscapped by mixed organic ligands (i.e., phosphine and pheny-lethanethiolate), formulated as Ag23(PPh3)8(SC2H4Ph)18. The

structure is composed of two fcc unit cells with twist, hence,exhibiting helicity. This nanocluster also possesses an open shellelectronic structure.

ResultsSynthesis. The Ag23(PPh3)8(SC2H4Ph)18 nanocluster was syn-thesized via a facile one-pot process. In brief, AgNO3, pheny-lethanethiol, and PPh3 were dissolved in a mixed solution ofmethanol and CH2Cl2. The Ag(I) species was reduced to Agclusters using sodium borohydride. After a long “size-focusing”process at 4 °C, the initial, polydisperse silver clusters wereeventually converged to monodisperse Ag23(PPh3)8(SC2H4Ph)18.Details of the synthesis are given in the Methods. The yield of thenanoclusters is ca. 10% (Ag atom basis). Single crystals of theclusters were obtained from a mixed solution of chloroform andmethanol (3:1, v/v). The structure was solved by the X-ray crys-tallography (see details in the Supplementary Note 1 and Tables 1and 2 ).

Internal structure. The Ag23(PPh3)8(SC2H4Ph)18 nanoclusterscrystallize in the chiral monoclinic group Cc. The total structure isshown in Fig. 1. The Ag skeleton of the nanocluster is composedof 23 silver atoms (Ag23), which can be seen as two joint cells intwisted fcc packing mode (Fig. 2b, c.f. Figure 2a for ideal fccpacking). The cells are twisted relative to each other by ca. 27 ̊about the longitudinal axis of the cluster (Fig. 2b). This results inthe deformation of the supercell’s ends from a square to arhombus-like shape (Supplementary Fig. 1). The rhombuses attwo ends are not congruent; for example, their diagonals areslightly different in length (Supplementary Fig. 1). Two octahedra(Fig. 2c, highlighted in blue and red facets)—composed of11 silver atoms of face centers of the two fcc units—are twisted byca. 13° with respect to each other (Supplementary Fig. 2). TheAg−Ag interatomic distances within the nanocluster vary from2.75 to 3.50 Å. The overall Ag framework of the nanocluster

Fig. 1 Total framework of the Ag23(PPh3)8(SC2H4Ph)18 nanocluster. Colorcodes: Ag, green; S, orange; P, purple; C, gray. Hydrogen atoms are omittedfor clarity

ARTICLE NATURE COMMUNICATIONS | DOI: 10.1038/s41467-018-03136-9

2 NATURE COMMUNICATIONS | (2018) 9:744 |DOI: 10.1038/s41467-018-03136-9 |www.nature.com/naturecommunications

adopts C2 symmetry (Fig. 2d), therefore, Ag23 has a chiralstructure that originates from atomic arrangement of its metalcore rather than configurations of the protecting ligands. Of note,the C2 axis passes through the centers of the two fcc unit cells

(Fig. 2d). Eight phosphine ligands are bonded to Ag atoms at thevertices of the top and bottom of the nanocluster, with an averageAg−P distance of 2.45 Å (Fig. 2e, f, side and top views).

Crystallographic arrangement. The protecting thiolate ligandscan be grouped into two main categories according to theirbinding patterns with the surface Ag atoms: (I) tri- and (II) tetra-podal types (Supplementary Fig. 3). The first category consists ofthree non-equivalent types of thiolate ligands on the surface of thenanocluster (subcategories IA, IB, and IC). As shown in Fig. 3a, a–SRIA ligand forms three bonds with two silver atoms (located at aunit cell’s edge in the direction of the supercell’s symmetry axis)and another Ag atom (at the face center of a facet containing thisedge), with average Ag−S bond length being 2.54 Å. The twoopposite facets are ligated by eight ligands of this type (Fig. 3a andSupplementary Fig. 4). It is worth noting that the face center Agatom is shared by two –SRIA ligands facing each other.

The subcategory IB consists of four –SRIB ligands, each bindingto two neighboring silver atoms at vertices at the end of thesupercell with an average Ag−S bond length of 2.55 Å (Fig. 3b andSupplementary Fig. 5). In addition, each S atom forms a bondwith a third Ag atom, located at the center of the side facet thatcontains the two Ag atoms (Fig. 3b).

There are four thiolate ligands belonging to subcategory IC.Two of them bind to the Ag atom located at the center of thecluster’s top facet and two to Ag at the center of the bottom facet(Fig. 3c and Supplementary Fig. 6). Each of the four –SRIC ligandsalso forms bonds with two neighboring silver atoms at vertices ofthe top or bottom facet. The average Ag−S bond length of thesubcategory IC is 2.57 Å.

Finally, there are two thiolate ligands, which are located atopposite sides of the supercell, that fall into category II (Fig. 3dand Supplementary Fig. 7). The S atoms of these –SRII ligands aretetra-coordinated to silver atoms—two situated at vertices andanother two at centers of the joint unit cells. The average Ag−Sbond length is 2.64 Å. The –SRII ligands are thus shared betweentwo unit cells and can be viewed as hinges to hold the two fcc cellstogether. It is worth mentioning that the –R tails of the ligandsare perpendicular to the facets they are attached to. The tetra-podal binding mode of thiolate ligands observed in theAg23(PPh3)8(SC2H4Ph)18 cluster is a surprise. Such a coordina-tion mode has not been reported previously. Of note, the centralAg atom (only one) at the center of the nanocluster does notcoordinate to any ligand (i.e., the phosphine and thiolate).

UV-vis and photoluminescence. The optical adsorption spec-trum of the nanocluster (in CH2Cl2, 0.1 mM) shows a strong peakat 515 nm and a weak tail band at 600–700 nm (Fig. 4a); theHOMO-LOMO gap is ca. 1.4 eV (Supplementary Fig. 8). Fur-thermore, the photoluminescence of the nanocluster was studiedusing excitation wavelengths of 350, 467, and 540 nm. The resultsshow that the nanoclusters exhibit emission centered at ca. 800nm regardless of the excitation wavelength (Fig. 4b and Supple-mentary Fig. 9).

DFT simulation. Time-dependent density functional theory(TDDFT) is applied to gain insight into the correlation betweenthe nanocluster structure and its optical properties. To reduce thecomputational cost, we used Ag23(PH3)8(SCH3)18 as a model forthe nanocluster (see details in the Methods). Figure 4c shows thecomputed molecular orbitals (MOs). Of note, X-ray crystal-lographic analysis shows no counterion with the Ag nanocluster.This indicates that the number of free valance electrons of thenanocluster is odd (23–18 = 5e) and thus its electronic structurepossesses an unpaired electron. To verify this, electron

27°

C2

a b

c d

e f

Fig. 2 Anatomy of the twisted structure of Ag23(PPh3)8(SC2H4Ph)18nanocluster. a Ideal structure of 1 × 1 × 2 supercell of fcc packing mode. Theface centers and vertices of the unit cells are shown in yellow and green,respectively. b Twisted supercell observed in the Ag23 nanocluster, in whichthe two fcc unit cells are twisted by ca. 27 ̊ with respect to each other,resulting in a helical structure. c Two rhombic bipyramids within thenanocluster are highlighted by blue and red facets. d Total framework ofAg23 with C2 symmetry. e and f show the total framework of Ag23S18P8 (topand side views). Color labels: S, orange; P, purple

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paramagnetic resonance (EPR) measurements35–37 were per-formed. As shown in Supplementary Fig. 10, the EPR spectrum ofthe clusters (in CH2Cl2, at 110 K) exhibit one local maxima andone local minima, which is characteristic of a system with oneunpaired electron (s =½), with g = 1.959 and 1.955. Therefore,open shell DFT calculations were performed that could reproducethe X-ray structure reasonably (Supplementary Table 1). Both αand β orbitals are presented in Fig. 4c. The unpaired electron withthe highest energy occupies HOMO of α-MOs (shown in green).

Analysis of MOs composition indicates that the α-HOMO ismainly localized on the waist silver atoms of the nanocluster—where two unit cells adjoin together (Supplementary Fig. 11).Analysis of atomic charges according to the CHelpG scheme38

predicts that the central Ag atom carries a charge of −0.5 e,whereas all other silver atoms of the nanocluster are positivelycharged with ~0.2 e.

The optical absorption spectrum of the Ag nanocluster iscalculated using TDDFT and fitted with Lorentzian functions

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Fig. 3 Binding patterns of thiolate ligands in subcategories. For the ease of visualization, the ideal structure (without twist) of Ag23 is used, and four topvertices of the supercell are labeled by numbers

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Fig. 4 Optical properties and DFT simulation of the Ag23 nanocluster. a UV-vis absorption and b emission (λex= 540 nm and slit width= 5 nm) spectra ofAg23(PPh3)8(SC2H4Ph)18 nanoclusters in a solution of CH2Cl2. c Energy alignment of the MOs and d theoretical absorption spectrum ofAg23(PH3)8(SCH3)18

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(Fig. 4d). The theoretical spectrum of the model is in goodagreement with experimental results (Fig. 4a.d). There is anallowed electronic transition located at 829 nm, though itsintensity is considerably lower than that of the main absorptionpeak at 527 nm. The 829 nm transition is attributed to electronicexcitation of α-HOMO → α-LUMO + 2 (Fig. 4c, red arrow andlabeled as ‘a’). The main peak of the theoretical spectrum at ~527nm is assigned to α-HOMO-1 → α-LUMO and β-HOMO → β-LUMO+ 1 transitions (Fig. 4c, blue arrows and labeled as ‘b’).These results indicate that the excitation of paired electrons ismainly responsible for the main absorption band. Populationanalysis of MOs shows that the α-HOMO-1, α-LUMO, β-HOMO, and β-LUMO+ 1 are combinations of s and p atomicorbitals of Ag; therefore, the peak at ~527 nm essentially arisesfrom sp → sp transitions (Supplementary Fig. 12).

Vibrational and electronic circular dichroism. Further, thechirality of the Ag23 cluster is investigated by vibrational circulardichroism (VCD) technique. This spectroscopic technique pro-vides a tool to identify the presence of chiral components throughdetection of differences in attenuation of left- and right-circularlypolarized light39. VCD technique has already been employed tostudy the conformation of chiral thiolates on the surface of goldparticles and clusters40, 41. Figure 5 shows the experimental IRand VCD spectra of Ag23. A series of VCD peaks are observed inthe range from 1200 to 1000 cm−1, corresponding to the IR peaks.These IR peaks are assigned to the Ag–P–C and Ag–S–Cstretching modes. Other IR regions show no VCD signals,implying that the observed VCD signals are from the twistedframework of the Ag23 cluster. Although chiral HPLC isolation ofAg23 enantiomers was not successful, we have performed theo-retical simulations of the electronic circular dichroism (ECD)spectra of the Ag23 cluster. The simulated ECD of Ag23 clustersmatches well with the corresponding UV-Vis absorption bands,and the Cotton effects split the theoretical band at 527 nm intotwo bands at 465 and 570 nm (Fig. 6). Taken together, theseresults clearly show the twist-induced chirality of the Ag23 cluster.

DiscussionIn summary, we have devised a synthetic approach forAg23(PPh3)8(SC2H4Ph)18 and solved its crystal structure. Thischiral nanocluster comprises a helical fcc kernel protected byeight phosphine and 18 phenylethanethiolate ligands. Twocoordination patterns for thiolate ligands are observed: tri- andtetra-podal types. By TDDFT calculations, we have further cor-related the Ag nanocluster structure and its optical properties.

MethodsSynthesis of Ag23(SC2H4Ph)18(PPh3)8 nanoclusters. AgNO3 (22 mg, 0.13mmol) was dissolved in 1 mL methanol solution. Then, 15 µL H-SC2H4Ph thiol(0.15 mmol) and 152 mg PPh3 (0.58 mmol, dissolved in 5 mL CH2Cl2) were added.The mixed solution was stirred for 30 min at 600 rpm. A freshly prepared solutionof NaBH4 (8 mg, 0.21 mmol, dissolved in 1 mL cold water) was added drop by dropto reduce the Ag(I) species to Ag(0) nanoclusters. After reaction for 48 h, theorganic phase was thoroughly washed with ethanol to remove excess thiol, phos-phine, and salts. Then, pure Ag23(SC2H4Ph)18(PPh3)8 nanocluster was extractedwith dichloromethane. Of note, the synthetic process was carried out at 10 °Cunder air. The yield of Ag23 nanoclusters is ca. 10% (on Ag atom basis). Orangecrystals of Ag23 were obtained from the mixed solution of chloroform andmethanol (3:1, v/v).

Characterization. The UV−vis absorption spectra were recorded on a Hewlett-Packard 8543 diode array spectrophotometer. X-ray diffraction data ofAg23(SC2H4Ph)18(PPh3)8 was collected on a Bruker X8 Prospector Ultra equippedwith an Apex II CCD detector and an IµS micro-focus CuKα X-ray source (λ =1.54178 Å). Fluorescence spectra were recorded on a Fluorolog-3 spectro-fluorometer (HORIBA Jobin Yvon). The EPR experiment was performed at 100 K,and Ag23(PPh3)8(SC2H4Ph)18 nanoclusters were dissolved in CH2Cl2 solutions (2mM). The solution was introduced into a quartz tube before the EPR test. TheVCD was performed on the ChiralIR-2 × (BioTools, Inc.). The Ag23 clusters (1 mg)were mixed with 10 mg KBr, and then the mixture was pressed into a thin platebefore the test.

Computational details. DFT optimization was performed using the B3PW91hybrid density functional. The 6–31 G** basis set was employed for H, C, P, andS42–45. The LANL2DZ basis set was used for silver atoms46. TDDFT calculations ofoptical absorption spectra were performed and compared with experimental opticalspectra. All calculations were carried out with the Gaussian09 package45.

Data availability. The X-ray crystallographic coordinates for structures reported inthis work (see Supplementary Tables 2 and 3 and Note 1) have been deposited atthe Cambridge Crystallographic Data Centre (CCDC), under deposition numberCCDC-1811890. These data can be obtained free of charge from The CambridgeCrystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif.

Received: 24 November 2016 Accepted: 22 January 2018

References1. Jin, R., Zeng, C., Zhou, M. & Chen, Y. Atomically precise colloidal metal

nanoclusters and nanoparticles: fundamentals and opportunities. Chem. Rev.116, 10346–10413 (2016).

2. Jin, R. et al. Controlling anisotropic nanoparticle growth through plasmonexcitation. Nature 425, 487–490 (2003).

3. Rycenga, M. et al. Controlling the synthesis and assembly of silvernanostructures for plasmonic applications. Chem. Rev. 111, 3669–3712 (2011).

4. Diez, I. & Ras, R. H. A. Fluorescent silver nanoclusters. Nanoscale 3,1963–1970 (2011).

5. Arvizo, R. R. et al. Intrinsic therapeutic applications of noble metalnanoparticles: past, present and future. Chem. Soc. Rev. 41, 2943–2970 (2012).

1400 1200 1000 800–20

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–10

–5

0

5

10

15

20

Δε ×

10–4

VCD

Single beam/wavenumber (cm–1)

FT-IR

Fig. 5 FT-IR and VCD spectra of the Ag23 nanocluster. The IR peaks at 1179and 1159 cm−1 and 1082 and 1012 cm−1 are assigned to the Ag–S–C andAg–P–C stretching modes, respectively

400 500 600 700 800 900

Inte

nsity

Wavelength (nm)

Fig. 6 Simulated ECD spectrum of the Ag23 nanocluster. The theoreticalband at 527 nm is split into two bands at 465 and 570 nm via cotton effects

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NATURE COMMUNICATIONS | (2018) 9:744 |DOI: 10.1038/s41467-018-03136-9 |www.nature.com/naturecommunications 5

6. Zhao, J. et al. Methods for describing the electromagnetic properties of silverand gold nanoparticles. Acc. Chem. Res. 41, 1710–1720 (2008).

7. Chernousova, S. & Epple, M. Silver as antibacterial agent: Ion, nanoparticle,and metal. Angew. Chem. Int. Ed. 52, 1636–1653 (2013).

8. Obliosca, J. M., Liu, C. & Yeh, H.-C. Fluorescent silver nanoclusters as DNAprobes. Nanoscale 5, 8443–8461 (2013).

9. Choi, S., Dickson, R. M. & Yu, J. Developing luminescent silver nanodots forbiological applications. Chem. Soc. Rev. 41, 1867–1891 (2012).

10. Kim, J. S. et al. Antimicrobial effects of silver nanoparticles. Nanomed.Nanotechnol. Biol. Med. 3, 95–101 (2007).

11. Joshi, C. P., Bootharaju, M. S. & Bakr, O. M. Tuning properties in silverclusters. J. Phys. Chem. Lett. 6, 3023–3035 (2015).

12. Locatelli, E. et al. Targeted delivery of silver nanoparticles and alisertib:in vitro and in vivo synergistic effect against glioblastoma. Nanomedicine 9,839–849 (2014).

13. Rao, T. U. B., Nataraju, B. & Pradeep, T. Ag9 quantum cluster through a solid-state route. J. Am. Chem. Soc. 132, 16304–16307 (2010).

14. Bertorelle, F. et al. Synthesis, characterization and optical properties of lownuclearity liganded silver clusters: Ag31(SG)19 and Ag15(SG)11. Nanoscale 5,5637–5643 (2013).

15. Chakraborty, I. et al. The superstable 25 kDa monolayer protected silvernanoparticle: measurements and interpretation as an icosahedralAg152(SCH2CH2Ph)60 cluster. Nano Lett. 12, 5861–5866 (2012).

16. Yang, H., Wang, Y. & Zheng, N. Stabilizing subnanometer Ag(0) nanoclustersby thiolate and diphosphine ligands and their crystal structures. Nanoscale 5,2674–2677 (2013).

17. Desireddy, A. et al. Ultrastable silver nanoparticles. Nature 501, 399–402(2013).

18. Yang, H. et al. All-thiol-stabilized Ag44 and Au12Ag32 nanoparticles withsingle-crystal structures. Nat. Commun. 4, 2422 (2013).

19. Jin, S. et al. Crystal structure and optical properties of the [Ag62S12(SBut)32]2+

nanocluster with a complete face-centered cubic kernel. J. Am. Chem. Soc. 136,15559–15565 (2014).

20. Alhilaly, M. J. et al. [Ag67(SPhMe2)32(PPh3)8]:3+ Synthesis, total structure, andoptical properties of a large box-shaped silver nanocluster. J. Am. Chem. Soc.138, 14727–14732 (2016).

21. Li, G., Lei, Z. & Wang, Q.-M. Luminescent molecular Ag−S nanocluster[Ag62S13(SBut)32](BF4)4. J. Am. Chem. Soc. 132, 17678–17679 (2010).

22. Yang, H. et al. Plasmonic twinned silver nanoparticles with molecularprecision. Nat. Commun. 7, 12809 (2016).

23. Anson, C. E. et al. Synthesis and crystal structures of the ligand-stabilizedsilver chalcogenide clusters [Ag154Se77(dppxy)18],[Ag320(StBu)60S130(dppp)12], [Ag352S128(StC5H11)96], and[Ag490S188(StC5H11)114]. Angew. Chem. Int. Ed. 47, 1326–1331 (2008).

24. Dhayal, R. S. et al. [Ag21{S2P(OiPr)2}12:]+ An eight-electron superatom.Angew. Chem. Int. Ed. 54, 3702–3706 (2015).

25. Hendry, E. et al. Ultrasensitive detection and characterization of biomoleculesusing superchiral fields. Nat. Nano 5, 783–787 (2010).

26. Guerrero-Martínez, A., Grzelczak, M. & Liz-Marzán, L. M. Molecular thinkingfor nanoplasmonic design. ACS Nano 6, 3655–3662 (2012).

27. Guerrero-Martinez, A. et al. Intense optical activity from three-dimensionalchiral ordering of plasmonic nanoantennas. Angew. Chem. Int. Ed. 50,5499–5503 (2011).

28. Govorov, A. O. et al. Chiral nanoparticle assemblies: circular dichroism,plasmonic interactions, and exciton effects. J. Mater. Chem. 21, 16806–16818(2011).

29. Knoppe, S. & Bürgi, T. Chirality in thiolate-protected gold clusters. Acc. Chem.Res. 47, 1318–1326 (2014).

30. Zeng, C., Chen, Y., Kirschbaum, K., Lambright, K. J. & Jin, R. Emergence ofhierarchical structural complexities in nanoparticles and their assembly.Science 354, 1580–1584 (2016).

31. Qian, H., Eckenhoff, W. T., Zhu, Y., Pintauer, T. & Jin, R. Total structuredetermination of thiolate-protected Au38 nanoparticles. J. Am. Chem. Soc. 132,8280–8281 (2010).

32. Zeng, C. et al. Structural patterns at all scales in a nonmetallic chiralAu133(SR)52 nanoparticle. Sci. Adv. 1, e1500045 (2015).

33. Jadzinsky, P. D., Calero, G., Ackerson, C. J., Bushnell, D. A. & Kornberg, R. D.Structure of a thiol monolayer-protected gold nanoparticle at 1.1 angstromresolution. Science 318, 430–433 (2007).

34. Takano, S. & Tsukuda, T. Amplification of the optical activity of gold clustersby the proximity of BINAP. J. Phys. Chem. Lett. 7, 4509 (2016).

35. Zhu, M. et al. Reversible switching of magnetism in thiolate-protected Au25superatoms. J. Am. Chem. Soc. 131, 2490–2492 (2009).

36. Akbari-Sharbaf, A., Hesari, M., Workentin, M. S. & Fanchini, G. Electronparamagnetic resonance in positively charged Au25 molecular nanoclusters. J.Chem. Phys. 138, 024305 (2013).

37. Antonello, S., Perera, N. V., Ruzzi, M., Gascón, J. A. & Maran, F. Interplay ofcharge state, lability, and magnetism in the molecule-like Au25(SR)18 cluster. J.Am. Chem. Soc. 135, 15585–15594 (2013).

38. Breneman, C. M. & Wiberg, K. B. Determining atom-centered monopolesfrom molecular electrostatic potentials-the need for high sampling density informamide conformational-analysis. J. Comput. Chem. 11, 361–373 (1990).

39. Nafie, L. A., Keiderling, T. A. & Stephens, P. J. Vibrational circular dichroism.J. Am. Chem. Soc. 98, 2715–2723 (1976).

40. Dolamic, I., Varnholt, B. & Bürgi, T. Chirality transfer from gold nanoclusterto adsorbate evidenced by vibrational circular dichroism. Nat. Commun. 6,7117 (2015).

41. Yao, H., Nishida, N. & Kimura, K. Conformational study of chiralpenicillamine ligand on optically active silver nanoclusters with IR and VCDspectroscopy. Chem. Phys. 368, 28–37 (2010).

42. Becke, A. D. Density-functional exchange-energy approximation with correctasymptotic-behavior. Phys. Rev. A. 38, 3098–3100 (1988).

43. Becke, A. D. Density-functional thermochemistry.III. the role of exactexchange. J. Chem. Phys. 98, 5648–5652 (1993).

44. Burant, J. C., Scuseria, G. E. & Frisch, M. J. A linear scaling method forHartree-Fock exchange calculations of large molecules. J. Chem. Phys. 105,8969–8972 (1996).

45. Frisch, M. J. et al. Gaussian 09, Revision D.01. Gaussian, Inc., Wallingford CT(2009).

46. Hay, P. J. & Wadt, W. R. Abinitio effective core potentials for molecularcalculations-potentials for K to Au including the outermost core orbitals. J.Chem. Phys. 82, 299–310 (1985).

AcknowledgementsG.L. acknowledges financial support by the fund of the “Thousand Youth Talents Plan”and National Natural Science Foundation of China (No. 21601178). R.J. thanks thefinancial support from the Air Force Office of Scientific Research under AFOSR AwardNo. FA9550-15-1-9999 (FA9550-15-1-0154).

Author contributionsG.L. and R.J. designed the study. C.L. and Z.L. synthesized the samples and carried outthe testes. T.L. and C.Z. test the Ag23 structure. H.A. and H.K. performed DFT simu-lations and analyses. G.L., H.A., and R.J. wrote the manuscript. All authors discussed theresults and commented on the manuscript.

Additional informationSupplementary Information accompanies this paper at https://doi.org/10.1038/s41467-018-03136-9.

Competing interests: The authors declare no competing financial interests.

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ARTICLE NATURE COMMUNICATIONS | DOI: 10.1038/s41467-018-03136-9

6 NATURE COMMUNICATIONS | (2018) 9:744 |DOI: 10.1038/s41467-018-03136-9 |www.nature.com/naturecommunications