1

Supporting Information

Preparation of gas phase naked silver cluster cations outside a mass spectrometer from ligand protected clusters in solution

Madhuri Jash,a Arthur C. Reber,b Atanu Ghosh,a Depanjan Sarkar,a Mohammad Bodiuzzaman,a Pallab Basuri,a Ananya Baksi,a Shiv N. Khanna,*b and Thalappil Pradeep*a aDST Unit of Nanoscience (DST UNS) and Thematic Unit of Excellence (TUE), Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India bDepartment of Physics, Virginia Commonwealth University, Richmond, Virginia 23284, United States *To whom correspondence should be addressed. E-mail: pradeep@iitm.ac.in; snkhanna@vcu.edu Table of Contents

Name Description Page No. S1 Photograph of the instrumental set-up 3 S2 Characterization of [Ag18H16(TPP)10]2+ cluster 4 S3 Characterization of [Ag18D16(TPP)10]2+ cluster 5 S4 Comparison between the experimental and the

calculated spectra 6

S5 Full range ESI mass spectra of [Ag18H16(TPP)10]2+

cluster during heating 7

S6 Formation of Ag17+ from both Ag17H14

+ and Ag17D14+ 8

S7 Comparision of ESI mass spectra of [Ag18H16(TPP)10]2+ cluster during heating at different

capillary and tube lens voltage

9

S8 Full range ESI mass spectra of [Ag18H16(TPP)10]2+

cluster during heating at higher capillary and tube lens voltage

10

S9 Ion chronograms of selected ions 11 S10 MS2 for Ag17

+, Ag17H14+ and Ag18H+ ions 12

S11 Thermal dissociation of thiolate protected cluster with same experimental conditions

13

S12 Effect of distance between the heating tube and the ESI source

14

S13 Photograph of the instrumental set-up and diagram used for ion/molecule reactions

15

S14 Comparison of oxygen addition reaction of naked clusters with CD3OD as solvent

16

S15 Comparison of oxygen addition reaction of naked clusters created from [Ag18H16(TPP)10]2+ and

[Ag18D16(TPP)10]2+

17

S16 Comparison of reactivity between Ag17+ and Ag18H+

ions with oxygen 18

S17 MS2 of Ag17O+, Ag17O2+, Ag17O3

+ and Ag17O4+ ions

19

S18 Comparison of MS2 results of Ag17(H2O)2O2+ and

Ag17H4O4+ ions

20

Electronic Supplementary Material (ESI) for Nanoscale.This journal is © The Royal Society of Chemistry 2018

2

S19 TEM images of [Ag18H16(TPP)10]2+ cluster and the electrosprayed products collected

21

S20 The calculated structures of Ag15+, Ag17

+, Ag18+, and

Ag18H+ ions 22

S21 Isomers of Ag18H+ and their energies 23 S22 Experimental and calculated masses measured with

the LTQ 24

S23 Experimental and calculated masses measured using the G2-Si

25

3

Supporting information 1 Photograph of the instrumental set-up:

S1: Photograph of the instrumental set-up used for the creation of naked cluster ions.

Separating distance

Heating tube

Inlet of LTQ

Separating distance

N2 Gas

4

Supporting information 2 Characterization of [Ag18H16(TPP)10]2+ cluster:

Fig. S2 (A) UV-vis absorption spectrum of [Ag18H16(TPP)10]2+ cluster in MeOH showing characteristic absorption features. (B) ESI mass spectrum of the cluster in positive mode (using the G2-Si) is showing a sharp peak at m/z 2290 which is assigned as [Ag18H16(TPP)10]2+. Other small peaks separated by m/z 131 are due to PPh3 loss which are shown by asterisks. (C) Peak at m/z 2290 is expanded, which is matching well with the calculated isotope pattern of [Ag18H16(TPP)10]2+.

2285 2290 2295m/z

2000 3000 4000 5000m/z

400 600 800 10000.0

0.2

0.4

0.6

0.8

1.0

Abso

rban

ce

Wavelength (nm)

(A) (B)

(C)

[Ag18H16(TPP)10]2+

5

Supporting information 3 Characterization of [Ag18D16(TPP)10]2+ cluster:

Fig. S3 ESI mass spectra of [Ag18H16(TPP)10]2+ and [Ag18D16(TPP)10]2+ cluster ions (using the G2-Si). The mass shift is due to the exchange of hydride ions with deuteride ions. In [Ag18D16(TPP)10]2+, 100% exchange of hydrogen with deuterium was not there due to the presence of non-deutereted solvents in the synthesis.

2280 2290 2300 2310m/z

[Ag18H16(TPP)10]2+ [Ag18D16(TPP)10]2+

6

Supporting information 4 Comparison between the experimental and the calculated spectra:

Fig. S4 Experimental mass spectra of Ag17H14

+, Ag17+, Ag18H13

+ and Ag18H+ ions match well with the calculated isotopic patterns.

1920 1930 1940 1950 1960 1970m/z

1930 1940 1950 1960 1970m/z

1820 1830 1840 1850 1860m/z

1820 1830 1840 1850 1860 m/z

1820 1830 1840 1850 1860 m/z

Ag17+

Ag17H14+Ag17

+

Ag17H14+

Ag18H+

Ag18H13+

Ag18H+

Ag18H13+

ExperimentalCalculated

7

Supporting information 5 Full range ESI mass spectra of [Ag18H16(TPP)10]2+ cluster during heating:

Fig. S5 Full range ESI mass spectra of [Ag18H16(TPP)10]2+ cluster with varying the heating tube temperature from 250 ̊C to 350 ̊C at CV and TV of 45 V and 100 V, respectively. At 250 ̊C, Ag17H14

+ and Ag18H13

+ were detected and at 300 ̊C, Ag17+ and Ag18H+ were seen along with their hydride clusters.

Finally, at 350 ̊C only Ag17+ and Ag18H+ were seen without mass selection. At lower mass region, there

were oxidation peaks of [Ag(TPP)]+, [Ag(TPP)2]+ and TPP+.

1200 1400 1600 1800 2000m/z

400 800 1200 1600 2000m/z

[Ag(TPP)OH2]+

350 ̊C

300 ̊C

250 ̊C

[Ag(TPP)2]+

[Ag(TPP)2O]+[Ag(TPP)O2]+

Ag17H14+

Ag18H13+

Ag18H+

Ag17+

[Ag11H6(TPP)]+

Fragments andunidentifiedspecies

x104

Capillary voltage = +45 VTube lens voltage = +100 V

[TPPO(H3O)]+

8

Supporting information 6 Formation of Ag17

+ from both Ag17H14+ and Ag17D14

+:

Fig. S6 ESI mass spectra of Ag17H14

+ and Ag17D14+ starting from [Ag18H16(TPP)10]2+ and

[Ag18D16(TPP)10]2+, respectively. In the spectrum of Ag17D14+, the peaks shown by asterisks (35%) are

arising due to the presence of hydrogen, which are coming due to the partial isotope exchange (principally due to Ag17D13H+), due to the presence of non-deuterated solvents. Ag17H14

+ and Ag17D14+

are both converted to Ag17+ at 350 ̊C.

1835 1840 1845 1850 1855 1860 1865m/z

1820 1830 1840 1850 m/z

1850 1855 1860 1865 1870m/z

Ag17H14+ Ag17D14

+

Ag17+

9

Supporting information 7 Comparision of ESI mass spectra of [Ag18H16(TPP)10]2+ cluster during heating at different capillary and tube lens voltage:

Fig. S7 ESI mass spectra of [Ag18H16(TPP)10]2+ cluster with varying the heating tube temperature at CV and TV of 45 V and 100 V (left) and 140 V and 240 V (right). These two sets of CV and TV give different results at different temperatures of heating tube which is mainly due to the in-source fragmentation at higher CV and TV. Finally at 350 ̊C, at CV and TV of 45 V and 100 V, only Ag17

+ and Ag18H+ were seen without mass selection, whereas at CV and TV of 140 V and 240 V, naked clusters along with smaller core sizes appear due to fragmentation. The weak features shown by pink triangles are due to [Agx(TPP)y]+ clusters. Note the difference in intensities of odd and even numbered clusters.

1200 1400 1600 1800 2000m/z

1200 1400 1600 1800 2000m/z

Ag17+

Ag16+

Ag15+

Ag14+

Ag13+

Ag12+

Ag11+

Ag17H14+

Ag17H14+

Ag17+

Ag18H+

Ag18H13+

Ag18H+

250 ̊C

room temp

350 ̊C

250 ̊C

room temp

350 ̊C

Capillary voltage = +45 VTube lens voltage = +100 V

Capillary voltage = +140 VTube lens voltage = +240 V

10

Supporting information 8 Full range ESI mass spectra of [Ag18H16(TPP)10]2+ cluster during heating at higher capillary and tube lens voltage:

Fig. S8 Full range ESI mass spectra of [Ag18H16(TPP)10]2+ cluster with varying heating tube temperature from room temperature to 350 ̊C at CV and TV of 140 V and 240V. At room temperature, Ag17H14

+ was detected along with some low mass region peaks. At 250 ̊C, Ag11+, Ag13

+, Ag15+, Ag16

+, Ag17

+ and Ag18H+ were seen. Finally at 350 ̊C, all the naked clusters of silver along with Ag17+ and

Ag18H+ were detected.

[Ag(TPP)OH2]+

1000 1200 1400 1600 1800 2000m/z

400 800 1200 1600 2000m/z

250 ̊C

room temp

350 ̊C

x102

Ag17+

Ag16+

Ag15+

Ag14+

Ag13+

Ag12+

Ag11+

Ag18H+

Ag17H14+

[PPh2 - 2H]+

Capillary voltage = +140 VTube lens voltage = +240 V

[TPP]+

[(TPP)O2]+

[Ag(TPP)2]+

11

Supporting information 9 Ion chronograms of selected ions:

Fig. S9 Ion chronograms of selected ions during the formation of naked clusters. At time zero the temperature was 250 ̊C and there were only existence of Ag17H14

+ and Ag18H13+. Then slowly

temperature was raised to 350 ̊C over a few minutes, which results the appearance of Ag17+ and Ag18H+.

0 1 2 3 4 5 6

time (min)

Re

lativ

e Ab

unda

nce

Ag17H14+

Ag18H13+

Ag18H+

Ag17+

12

Supporting information 10 MS2 for Ag17

+, Ag17H14+ and Ag18H+ ions:

Fig. S10 MS2 for (A) Ag17

+, (B) Ag17H14+, (C) Ag18H+ ions and the isolation widths are m/z 10, 10 and

8, respectively centered at the middle of the isotopic clusters. The collision energies used for the Ag17+,

Ag17H14+ and Ag18H+ ions are 37, 17 and 24 in instrumental units, respectively. Due to higher collision

energy, Ag17+ breaks into smaller sized naked clusters whereas the hydrides of silver ions give back the

metallic core, Ag17+. RA refers to relative abundance.

1000 1200 1400 1600 1800 20000

50

100

RA

m/z

1000 1200 1400 1600 1800 20000

50

100

RA

m/z

1500 1600 1700 1800 1900 20000

50

100

RAm/z

Ag17+

Ag16+

Ag15+

Ag17H14+

Ag17+

Ag18H+

Ag17+

(A) (B)

(C)

Ag17H14+Ag17

+

Ag18H+

13

Supporting information 11 Thermal dissociation of thiolate protected cluster with the same experimental conditions:

Fig. S11 ESI mass spectra of [Ag25(DMBT)18]3- cluster at different temperatures (same conditions like before) after electrospraying the cluster solution. The thermal dissociation results in [AgmLn]-1 but not the naked cluster. Note that these clusters are thiolate protected, for them the mass spectra show intense features till the mass limit of the instrument (m/z 4000).

1000 1500 2000 2500 3000 3500 4000m/z

200 ̊C

230 ̊C

250 ̊C

280 ̊C

300 ̊C

Incr

easi

ng te

mpe

ratu

re

Ag5L6-1

Ag19L12-1

Ag2L7-1

AgLAgL

AgLAgL

Ag2L7-1

Ag5L6-1

14

Supporting information 12 Effect of distance between the heating tube and the ESI source:

Fig. S12 ESI mass spectra of Ag17+ with varying distances (ΔY) between the heating tube and ESI

source keeping the constant 5 mm distance between the heating tube and inlet. Here, with increasing ΔY, H2O and O2 addition peaks of Ag17

+ appear along with the Ag17H14+ peak. At last, only Ag17H14

+ peak appears due to the decreasing temperature, as more air flows through the heating tube.

1800 1825 1850 1875 1900 1925 1950 1975 2000m/z

Ag17+ Ag17H14

+

ΔY = 10 mm

ΔY = 5 mm

ΔY = 0 mm

Ag17(H2O)2O2+

Ag18H+

HV MS

N2

ΔΔY 5 mm

Ag17(H2O)O+ Ag17(O2)3+

15

Supporting information 13 Photograph of the instrumental set-up and diagram used for ion/molecule reactions: (A)

(B)

S13: (A) Photograph and (B) schematic diagram of the instrumental set-up used for ion/molecule reactions of naked cluster ions with oxygen.

Heating tube

Inlet of LTQN2 Gas

O2 Gas

HV MS

N2

Δ

O2

16

Supporting information 14 Comparison of oxygen addition reaction of naked clusters with CD3OD as solvent:

Fig. S14 ESI mass spectra of Ag17

+ and Ag18H+ ion clusters after reaction with oxygen (O2) gas in presence of CD3OD and CH3OH as the two different solvents. There were no shifts for the Ag17H4Ox

+ and Ag18H3Oy

+ peaks in the case of deuterated and non-deuterated methanol as the solvents.

1800 1850 1900 1950 2000m/z

Ag17H4Ox+

1 2 3 4Ag17+

Ag18H3Oy+

1 2 3Ag18H+

Reaction with O2 with CD3OD as the solvent

Reaction with O2 with CH3OH as the solvent

17

Supporting information 15 Comparison of oxygen addition reaction of naked clusters created from [Ag18H16(TPP)10]2+ and [Ag18D16(TPP)10]2+:

Fig. S15 (A) ESI mass spectra of Ag17+, Ag18H+ (green) and Ag17

+ and Ag18D+ (red) after reaction with oxygen (O2) gas. (B) Magnified view of the isotopic separation of Ag18H3Oy

+, generated from both Ag18H+ (green) and Ag18D+ (red). Top and bottom spectra in each case were generated from [Ag18D16(TPP)10]2+ and [Ag18H16(TPP)10]2+, respectively. MS/MS of oxygen added peaks of Ag18H/D+

could not be performed due to poor intensity.

1940 1960 1980 2000m/z

Ag18H3Oy+

1 2 3Ag18D+

Ag18H+

(B)

1840 1880 1920 1960 2000m/z

Ag17H4Ox+

1 2 3 4

Ag17+

Ag18H3Oy+

1 2 3

Ag18D+

Ag18H+

(A)

Ag17+

18

Supporting information 16 Comparison of reactivity between Ag17

+ and Ag18H+ ions with oxygen:

Fig. S16 Relative intensities of Ag17

+ and Ag18H+ as function of oxygen flow rate which shows the faster reactivity of Ag17

+ with oxygen compared to the Ag18H+.

5 6 7 8 9 10

Ag17+

Ag18H+

Rela

tive

Inte

nsity

Flow rate (L/min)

19

Supporting information 17 MS2 of Ag17H4O+, Ag17H4O2

+, Ag17H4O3+ and Ag17H4O4

+ ions:

Fig. S17 MS2 of (A) Ag17H4O+, (B) Ag17H4O2

+, (C) Ag17H4O3+ and (D) Ag17H4O4

+ and the isolation widths are m/z 5, 4.5, 4 and 3, respectively centered at the middle of the isotopic clusters. The collision energies used for Ag17H4O+, Ag17H4O2

+, Ag17H4O3+ and Ag17H4O4

+ are 28, 50, 28 and 50 in instrumental units, respectively. For all these cases, due to collisional activation, there is oxygen detachment which results in the parent Ag17

+ cluster. RA refers to relative abundance.

1000 1200 1400 1600 1800 20000

50

100RA

m/z1000 1200 1400 1600 1800 20000

50

100

RA

m/z

1000 1200 1400 1600 1800 20000

50

100

RAm/z

1000 1200 1400 1600 1800 20000

50

100

RA

m/z

Ag17+

Ag17H4O+

Ag17H4O2+

Ag17+

Ag17+

Ag17O2+

Ag17H4O3+ Ag17

+

Ag17O2+

Ag17H4O4+

(A) (B)

(C) (D)

Ag17H4O2+Ag17H4O+

Ag17H4O3+ Ag17H4O4

+

20

Supporting information 18 Comparison of MS2 results of Ag17(H2O)2O2

+ and Ag17H4O4+ ions:

Fig. S18 MS2 spectra of (A) Ag17(H2O)2O2

+ and (B) Ag17H4O4+ at the collision energy of 50 in

instrumental units. The isolation widths were m/z 5 and 3, respectively centered at the middle of the isotopic clusters. RA refers to relative abundance.

1000 1200 1400 1600 1800 20000

50

100

RAm/z

Ag17+

Ag17O2+

Ag17H4O4+

Ag17H4O4+

1000 1200 1400 1600 1800 20000

50

100

RA

m/z

Ag17(H2O)2O2+

Ag17O2+

Ag17+

Ag17(H2O)2O2+

Ag15+

Ag14+

(A) (B)

21

Supporting information 19 TEM images of [Ag18H16(TPP)10]2+ cluster and the electrosprayed products collected:

Fig. 19 (A) TEM image of [Ag18H16(TPP)10]2+ cluster before electrospray. Particle distribution shows an average size of 1.68 ± 0.19 nm for the nanoclusters. Lattice spacing of 0.24 nm of d(111) of plane of silver is marked in the inset. (B) EDS spectrum of cluster confirms the composition. (C) TEM image of the collected electrosprayed product of [Ag18H16(TPP)10]2+ cluster at the heating tube temperature of 350 ̊C. In inset, lattice spacing of 0.24 nm is marked which confirmed the d(111) plane of silver. (D) EDS spectrum of the collected product at heating tube temperature of 350 ̊C. The products of electrospray were collected using a set-up as shown below.

1.2 1.4 1.6 1.8 2.0 2.20

10

20

30

40

50

60

Particle size (nm)

Coun

t

keV keV

(A)

(B)

(C)

(D)

Heating tube

Collected in a round bottom flask

22

Supporting information 20 The calculated structures of Ag15

+, Ag17+, Ag18

+, and Ag18H+ ions:

Fig. S20 The structure and HOMO- LUMO gaps of Ag15

+, Ag17+, Ag18

+ and Ag18H+. Ag15+ was found

to be resistant to O2 etching due to very high HOMO-LUMO gap.

Ag17+

H-L Gap = 0.52 eV0 μb

Ag15+ Ag18

+ Ag18H+

H-L Gap = 0.16 eV1 μb

H-L Gap = 0.99 eV0 μb

H-L Gap = 1.25 eV0 μb

23

Supporting information 21 Isomers of Ag18H+ and their energies:

Fig. S21 The structures, relative energies and HOMO-LUMO gaps of the lowest energy isomers for Ag18H+.

Ag18H+

ΔE= 0.00 eVH-L Gap = 0.99 eV

ΔE= 0.05 eVH-L Gap = 0.83 eV

ΔE= 0.12 eVH-L Gap = 0.94 eV

ΔE= 0.13 eVH-L Gap = 0.70 eV

ΔE= 0.13 eVH-L Gap = 1.10 eV

ΔE= 0.14 eVH-L Gap = 0.85 eV

ΔE= 0.17 eVH-L Gap = 0.80 eV

ΔE= 0.17 eVH-L Gap = 0.70 eV

24

Table S22 Experimental and calculated masses measured with the LTQ: The most abundant peak of the isotopic cluster is used to define the m/z value.

*Peak is seen with two hydrogens losses.

Experimental m/z

Calculated m/z

Assignment [Agm(PPh3)n(PPh2)oHpOq(H2O)r]z+

Ag (m)

PPh3 (n)

PPh2 (o)

H (p)

O (q)

H2O (r)

Charge (z)

183.00 182.95 1* 1 262.17 262.09 1 1 294.08 294.08 1 2 1 297.17 297.10 1 1 1 1 1 386.83 387.01 1 1 2 1 1 400.83 400.99 1 1 2 1 631.17 631.09 1 2 1 647.17 647.08 1 2 1 1 1185.92 1185.95 11 1 1294.75 1294.86 12 1 1401.67 1401.76 13 1 1454.08 1454.09 11 1 6 1 1510.50 1510.67 14 1 1521.67 1521.75 14 10 1 1617.42 1617.57 15 1 1726.33 1726.48 16 1 1737.58 1737.56 16 11 1 1833.42 1833.38 17 1 1847.50 1847.49 17 14 1 1853.42 1853.41 17 4 1 1 1867.33 1867.39 17 1 1 1 1869.42 1869.40 17 4 2 1 1885.33 1885.40 17 4 3 1 1901.33 1901.39 17 2 2 1 1901.42 1901.39 17 4 4 1 1929.33 1929.35 17 6 1 1943.42 1943.30 18 1 1 1955.50 1955.39 18 13 1 1961.25 1961.31 18 3 1 1 1977.33 1977.30 18 3 2 1 1993.33 1993.30 18 3 3 1

25

Table S23 Experimental and calculated masses measured using the G2-Si: The most abundant peak of the isotopic cluster is used to define the m/z value.

Experimental m/z

Calculated m/z

Assignment [Agm(PPh3)nHo]z+

Ag (m)

PPh3 (n)

H (o)

Charge (z)

2290.1587 2290.2152 18 10 16 2

2159.3291 2159.6199 18 9 16 2

2028.3219 2028.5740 18 8 16 2

1897.3425 1897.5281 18 7 16 2

1765.8406 1765.9827 18 6 16 2