UNESCO Laboratory of Environmental Electrochemistry

Charles University in Prague

Heyrovský Institute AS CR

BORON DOPED DIAMOND FILM ELECTRODES - AN EXCELENT TOOL

FOR VOLTAMMETRIC MONITORING OF ENVIRONMENTALLY IMPORTANT

ORGANIC SUBSTANCES

Jiri Barek

UNESCO Laboratory of Environmental

Electrochemistry, Department of Analytical Chemistry, Charles University, Prague, Czech

Republic, e-mail: Barek@natur.cuni.cz

Why new electrode materials• Broader potential window• Lower noise and background current• Resistance toward passivation• Mechanical stability• Compatibility with „green analytical chemistry“

WHY BORON DOPED DIAMOND FILM ELECTRODES

• Low noise

• Broad potential windows

• Low passivation

• Mechanical and electrochemical stability

• Biocompatibility

• Comercial availability

Properties of diamondProperties of diamond

sp3 allotropic modification of carbon

Hardness

Low chemical reactivity

Insulant doping by boron

Low double layer capacity

Broad potential window

Low adsorption

Stability, biocompatibility

Properties of boron doped diamond

Boron doped diamond film electrodes

BDDFE

-2,0 -1,5 -1,0 -0,5 0,0 0,5 1,0 1,5 2,0

pH 9

pH 8

pH 7

pH 6

pH 5

pH 4

pH 3

pH 2

pH 10

pH 11

Cure

nt

E [V]

20 µApH 12

The potential window of BDD electrode, BR buffer pH 2 - 12

CVD - Chemical Vapor DepositionCVD - Chemical Vapor Deposition

Mechanism is not fully understood as yet

Radicals and other reactive species are formed in the mixture of methane and hydrogen. They diffuse to the surface of growing diamond layer. They react at the surface and deposits in the form of diamond. High hydrogen atom concentration prevents the formation of sp2 carbon species.

Boron doping from solid (boron nitride) or gaseous (boranes,B2H6) sources

CVD - Chemical Vapor Deposition

Boron doped diamond film electrode

BDDFE

Ve sse l

DFE

C o nta c tPla stic p la te

O -se a l ring

Boron doped diamond film electrode (BDDFE)

2

3

4

67

5

1

8

Legend 1. Electrode body2. Screw contact3. Screw attachment4. Small metal spring5. Brassy sheet6. DFE on Si (1,1,1)7. Silicone seal8. Access for solution

Surface of nanocrystalline diamond film electrode on Si

BDDFEGlass tube (1), copper wire (2), conductive epoxide resin

(3), non-conductive epoxide resin (4), silica wafer covered with BDDF (5), diameter of BDDFE (d, 3 mm),

surface of BDDFE (A, 7,1 mm2).

BDDFE

Lab made Commercial

Glass tube (1), copper wire (2), conductive epoxide resin (3), non-conductive epoxide

resin (4), silica wafer covered with BDDF (5)

Cyclic voltammogram of 2-nitrophenol at BDDE, BR buffer pH 3

-20

-10

0

10

-1200 -600 0 600 1200

E [V]

I [m

A]

BR buffer pH 3

red-ox

ox-red

E [mV]

2-AB (a), 3-AB (b), and 4-AB (c) DPV at BDNDFE (2-10).10-7 M

pH 7 pH 8 pH 9

DPV at BDDFE 10-5 M 1-nitropyrene 1-aminopyrene

MeOH-BR pufr pH 3 (7:3)

Regeneration

E1 = +800 mV, t1 = 0,3 s

E2 = -500 mV, t2 = 0,2 s

Pasivation1-AP (c = 1·10–4 M) MeOH-BR pufr pH 3 (7:3)

11 measurements

~ +440 mV

Potential span

0 až +1600 mV +230 až +680 mV

DPV at BDDFE of 4-NP (µM) in river water

-600 -800 -1000

-90

-120

-150

-180

I, nA

E, mV

0,0 5,0x10-6 1,0x10-5

0

-40

-80

Ip,nA

c, mol.L-1

850 900 950 1000

180

240

300

I, nA

E, mV

0,0 5,0x10-61,0x10-5

0

30

60

Ip,nA

c, mol.L-1

Reduction Oxidation

0,0 3,0x10-6 6,0x10-6 9,0x10-60

30

60

90

120

I P, n

A

c, mol dm-3

R = 0,9943

DPV 1-AP at BDDFE(0 - 10).10-6 M , MeOH-BR buffer pH 3,0 (7:3)

DPV 1-AP at BDDFE(0 - 10).10-7 M , MeOH-BR buffer pH 3,0 (7:3)

BDDFE detector TL arrangement

1‑AN a 1‑AB (5.10-6 M)DFE(a) a GCE(b)

Elektrochemical wall-jet detector with BDDFE

Counter electrode

Reference electrode

WE

rubber backing

working electrode

rubber gasket

Outlet Inlet

Reference electrode

Kel-f body, top piece

metal backing - - current collector

Kel-f body, bottom piece

screw clamp

FIA-ED or HPLC-ED TL BDDFE

BDDF microelectrodesBDDF microelectrodes

BDDF microelectrodesBDDF microelectrodes

HPLC-ED-BDDFE - 1-AP (HPLC-ED-BDDFE - 1-AP (0-10).10-7 M

MeOH:0,05M PhB pH 5,0 (80:20), E = 1000 mV, v = 1,0 ml/min

3,0x10-7 6,0x10-7 9,0x10-7 1,2x10-60,0

1,5

3,0

4,5

6,0

I P,

nA

c, mol dm-3

R = 0,9973

tR = 2,76 min

0,0 4,0x10-7 8,0x10-7 1,2x10-60,0

0,5

1,0

1,5

2,0

2,5

I P,

nA

c, mol dm-3

R = 0,9945

HPLC-ED-BDDFE - 1-HP (HPLC-ED-BDDFE - 1-HP (0-10).10-7 MMeOH:0,05M PhB pH 5,0 (80:20), E = 1000 mV, v = 0,8 ml/min

tR = 3,93 min

HPLC-ED-BDDFE 1-AP in urine after SPEHPLC-ED-BDDFE 1-AP in urine after SPE

(0 - 10).10-8 MMeOH:0,05 M PhB pH (80:20), E = 1000 mV, v =1,0 ml/min

0,0 3,0x10-8 6,0x10-8 9,0x10-8

0,7

1,4

2,1

2,8

I P,

nA

c, mol dm-3

R = 0,9881

HPLC-ED-BDDFE 1-HP in urine after SPEHPLC-ED-BDDFE 1-HP in urine after SPE

(0 - 10).10-8 MMeOH:0,05 M PhB pH (80:20), E = 1000 mV, v =0,8 ml/min

Thank you for your attention