Figure Captions

Fig.S1. (A) Schematic Representation of graphene and characterization using (B) TEM, (C) UV, (D) FTIR and (E) Raman spectroscopy.

Fig.S2. Isotopic pattern of peak at m/z 472 and 488 (Monoisotopic mass), inset represent the simulated pattern of the two peaks, respectively.

Fig. S3 . GALDI response to various metal ions ( A) and in presence of Hg2+(B). Metals: T were mixed in molar ratio 1:2.

m/z Assignments

23 Na+

39 K+

126 [T+H]+

149 [T+Na]+

165 [T+K]+

472 [Hg(T)2(H2O)+H]+

488 [Hg(T)2(H2O)2+H]+

Table S1: Peaks assignments of GALDI-MS

290 300 310 320 330 340 3500

2

4

6

8A

bsor

ptio

n

Wavelength, nm

Graphene

1.Oxidation (H2SO4, KMnO4, H2O2)

2.Reduction (NH2NH2)

Fig.S1

A

B C

D E

1000 1500 2000 2500 3000

150

200

250

300

350

400

Inte

nsi

ty a

.u.

Raman shift,cm-1

Fig.S2

Molecular formula:

C10H14HgN4O5

Molecular weight:

470.841

Monoisotopic mass:

472.067

Number lines: 90

Molecular formula:

C10H16HgN4O6

Molecular weight:

488.85682

Monoisotopic mass:

490.0776

Number lines: 95

450 455 460 465 470 475 480 485 490 495 500

0

10000

20000

30000

40000

Inte

nsity

m/z

1

2

1

2

790 795 800 805 810 815 820 825 830 835 840 845 8500

1000

2000

3000

Inten

sity

m/z

Fig.S3

Th

ym

ine

(1)

Hg2+

(2)

1+

2+

Cd

2+

1+

2+

Cu

2+

1+

2+

Ni2

+

1+

2+

Zn

2+

1+

2+

Fe2

+

1+

2+

Fe3

+

0.0

0.2

0.4

0.6

0.8

1.0

Rel

ati

ve

MA

LD

I In

ten

sity

(m

/z 4

88)

Thymine Hg2+ Cd2+ Cu2+ Ni2+ Zn2+ Fe2+ Fe3+ --

0.0

0.2

0.4

0.6

0.8

1.0

Rel

ati

ve

MA

LD

I In

ten

sity

Fig.S4 A

B