Nickel electrodeposition on copper substrate for cyclotron production of 64Cu

Article abstract of DOI:10.1134/S1066362209060125

Natural nickel electrodeposition on a copper substrate with a gold layer was studied with the aim of production of ⁶⁴Cu radionuclide. The electrodeposition experiments were carried out in acid plating baths. The operating parameters such as pH,

Full text of DOI:10.1134/S1066362209060125

ISSN 1066-3622, Radiochemistry, 2009, Vol. 51, No. 6, pp. 628–632. © Pleiades Publishing, Inc., 2009.
Published in Russian in Radiokhimiya, 2009, Vol. 51, No. 6, pp. 546–550.
Nickel Electrodeposition on Copper Substrate
for Cyclotron Production of 64Cu1
M. Sadeghi, M. Amiri, Z. Gholamzadeh, and P. Rowshanfarzad
Agricultural, Medical, and Industrial Research School, P.O. Box 31485-498, Karaj, Iran;
e-mail: msadeghi@nrcam.org
Received February 11, 2009
Abstract—Natural nickel electrodeposition on a copper substrate with a gold layer was studied with the aim of
production of 64Cu radionuclide. The electrodeposition experiments were carried out in acid plating baths. The
operating parameters such as pH, temperature, and current density were optimized. The current efficiency was
measured at different current densities. The optimum conditions of the nickel electrodeposition are as follows:
5.7 g 1–1 nickel, pH 3–4, dc current density 85.54 mA cm–2, and 55°C, with 97% current efficiency. SEM pho-
tomicrographs demonstrated fine-grained structure of the deposit obtained from the optimum bath. A 46-μm
high-quality layer was deposited on a gold layer of the copper substrate.
Key words: nickel, electrodeposition, copper-64 production
PACS numbers: 81.15.Pq
DOI: 10.1134/S1066362209060125
The 64Cu decay parameters (t1/2 = 12.7 h, Eβ+
0.66 MeV, Eβ– = 0.58 MeV, Iβ+ = 17.8%, Iβ– = 38.4%,
EC = 43.8% [1, 2]) show some potential for endoradio-
=
plating on the gold layer of a copper substrate was
studied.
I
The nickel electrodeposition is commonly carried
therapy applications in addition to its usefulness as a
PET radiotracer [3]. It can become an effective radio-
therapy agent for cancer treatment. Copper-64 is
widely labeled as DTPA-peptide, DOTA-peptide, or
monoclonal antibody in colon cancer studies. Cop-
per-64 labeled antibodies have shown promising results as
radioimmunotherapy (RIT) agents [1]. Research has
also shown that 64Cu-PTSM is a potential agent for
tumor blood-flow quantification and hypoxia [4].
To produce 64Cu, several nuclear processes were
considered; 64Ni(p, n)64Cu and 68Zn(p, αn)64Cu reac-
tions were found to be most suitable [5, 6], partly be-
cause they could be used at a medium- to low-energy
cyclotrons. The Agricultural, Medical, and Industrial
Research School employs a Cyclone-30 cyclotron
(IBA, Belgium). Consequently, targetry for the second
reaction was considered in this study. Solid targets of
these accelerators are made of pure copper substrates
with target materials, such as nickel, electrodeposited
on them. Gold layer is insoluble in most of acids;
therefore, a gold layer electrodeposited on a copper
substrate can decrease chemical impurities in dissolved
target material solution. In this work, nickel electro-
out using Watts and sulfamate baths. The Watts bath
consists of nickel chloride, boric acid, and nickel sul-
famate. Nickel chloride levels the deposit surface;
however, its large amount increases the internal stress
of the electrodeposit. Boric acid fixes the bath acidity.
However, its large amounts produce thrush electrode-
posits at high current density, and small amounts of the
acid cause the deposit to crack or burn; hence, the bo-
ric acid amount in the bath should be optimized. The
sulfamate baths have the same Watts bath composi-
tions but with different amounts of the components.
These baths have high throwing power and assure ex-
cellent deposits. Temperature is a very important pa-
rameter of the baths. Correct control of the bath tem-
perature can lead to 95–100% current efficiency.
EXPERIMENTAL
Materials. The electrolysis solution was prepared
from 6 g of NiSO4 and 0.5 g of NiCl2 in 450 ml of de-
ionized water. The electrolysis was performed with
direct current. Before plating nickel, to ensure good
adhesion, the gold plate was cleaned with sandpaper of
(1000) grade and then rinsed with deionized water.
1 The test was submitted by the authors in English.
628

NICKEL ELECTRODEPOSITION ON COPPER SUBSTRATE
629
Nonreactive plating vessels are hollow Perspex cyl-
inders (diameter 6 cm, height 20 cm) fitted with an
axial Pt anode wire mounted at the bottom by means of
a tube-end fitting with perforated septum. Four sym-
metrical windows (22.36 or 11.69 cm2) on the vertical
side wall allow positioning of up to four copper cath-
odes (target substrates). Each slot is sealed by an
O-ring fitted window. The slot geometrical shape de-
termines the actual target electrodeposition area. The
liquid-tight sealing of the windows is provided by
stainless steel mechanical pestles mounted on a PVC
ring surrounding the plating vessel and by pressing of
the copper substrate against the O-ring seal. An exter-
nal PVC ring is fitted with four supporting pins to hold
a motor–stirrer combination in position. The stirrer is a
hollow perforated POM cylinder mounted on the axis
of a dc motor and surrounding the platinum anode. The
stirrer rotation speed is set at 600 rpm. Its rotating di-
rection is reversed after each 8 s to improve the deposit
homogeneity. To keep the desired temperature at a pre-
set level, a heater [a series of six isolated 1 Ω/1 W re-
sistors, through which an appropriate direct current is
forced (1.1 A at 40°C, up to 1.8 A at 60°C)] is circu-
larly mounted at the bottom of the vessel. An insulated
sensor, introduced through the stirrer support-plate,
monitors the plating bath bulk temperature. As elec-
trolysis to depletion requires prolonged (up to 24 h)
plating, evaporation of the plating solution occurs. To
maintain a constant liquid volume, 450 ml, a conduc-
tivity glass/graphite sensor monitors the solution level
and actuates a peristaltic pump at the required rate,
supplying distilled water to compensate evaporation
loss.
nickel crystal lattice and/or for their presence in the
carrier/nickel layer interface. In both cases, irradiation
will cause loss of the target material, peeling off, and a
decrease in the 64Cu yield.
Calculations of required deposit thickness. To
take full benefit of the excitation function and to avoid
formation of radionuclidic impurities, the proton en-
trance energy should be 15 MeV [9, 10]. The physical
thickness of the nickel layer is chosen in such a way
that for a given beam/target angle geometry the parti-
cle exit energy should be 3 MeV. According to SRIM
code (The Stopping and Range of Ions in Matter); the
thickness should be 428.15 µm for 90° geometry [11].
To minimize the thickness of the nickel layer, 6° ge-
ometry is preferred, in which case a 43-µm layer is
recommended.
Nickel targets are prepared by dc-CCE (constant
current electrolysis) with deposition of the metal from
acid plating solutions.
Pretreatment of Cu subtsrate. Application of a
voltage before pouring the solution leads to poor adhe-
sion of the nickel deposit. Blistering, cracking, gas
pits, peeling off, and poor adhesion may also be due to
hydrogen evolution in ways not yet identified. Plating
on a dietary or greasy surface inevitably leads to blis-
tering or peeling of. Cathodic cleaning in either acid or
alkaline solutions provides large quantities of hydro-
gen for absorption [14]. In all experiments, the
substrate surface was cleaned with sandpaper of
(1000) grade and immersed in a 2 M nitric acid bath.
Then the surface was washed with water, and oil
contaminations were removed by a mixture of alkali
cleaning powders. Finally the surface was washed with
acetone.
Natural nickel sulfamate was purchased from Fluka
to carry out the initial experiments. The freshly pre-
pared solution of nickel sulfamate was introduced into
the plating vessel. This refined procedure is a result of
several repeated experiments in which the bath acidity,
temperature, and electroplating current were varied.
Influence of current density. Too large amounts
of nickel in the bath cause reduction of deposit adhe-
sion at a low current density, and insufficient amounts
of nickel cause a burn-up of the deposit at a high cur-
rent density. Thus, the optimal current density is com-
pletely determined by the nickel content in the bath.
The morphology of all the electrodeposited Ni tar-
get layers was examined by scanning electron micros-
copy (SEM) using a Jeol model JSM 6400 device at an
accelerating voltage of 20 kV.
According to some publications [12, 13] concerning
concentrations of nickel salts, a bath with 6 g of NiSO4
and 0.5 g of NiCl2 was prepared. Low cathode effi-
ciency was observed at low temperature, high pH, and
high metal content [14]. Too low current density leads
to poor quality of the deposit, whereas too high current
density reduces the overvoltage of hydrogen and de-
creases the quality of the deposit and the current effi-
The thermal shock tests involved heating of the tar-
get to 500°C (the temperature that the nickel layer can
experience during high-current irradiation) for 1 h,
followed by submersion of the hot target in cold water
(15°C). The thermal shock test is a measure for the
incorporation of plating bath compounds into the
RADIOCHEMISTRY Vol. 51 No. 6 2009

630
SADEGHI et al.
ciency [15]. Hence an optimal range of current density
and bath acidity was investigated.
were carried out at a higher temperature (35°C) under
equal other conditions. We found that the current effi-
ciency increased to ~50% but deposit adhesion left
much to be desired (see table).
Influence of pH. Adjusting the bath acidity is im-
portant, ensuring the process efficiency and good
physical properties of the coating. Too low acidity re-
sults in blistering or peeling. Too high bath acidity
causes the electroplating current efficiency to decrease.
After preparing the nickel bath for studying the effects
of solution acidity on the electroplating quality, the
acidity was varied from 1 to 4.
The experiments were repeated using the bath tem-
perature of 45°C. In these experiments, the quality of
the deposit was improved and current efficiency in-
creased too. Still the current efficiency was less than
50% (see table). When nickel was electrodeposited at a
higher bath temperature, 55°C, both the current density
and adhesion were improved compared to the previous
experiments except that at 45°C. The maximum thick-
ness of 22.92 μm was achieved using 2900 mA cur-
rent, 248.07 mA cm–2; however, its adhesion was weak
and the deposit easily rolled under thermal shock (see
table). Repetition of electroplating at 60°C temperature
showed that the current efficiency increased by a factor
of almost 2 compared to the previous experiments in
the current density range 34.21–85.54 mA cm–2, but
the deposit quality was not improved significantly. At
this temperature, the maximum current efficiency was
62% at 85.54 mA cm–2 current density, and the maxi-
mum thickness was 20.9 mm at a current density of
171.08 mA cm–2 (see table).
Influence of temperature. Increasing the tempera-
ture of the solution increases the mobility of the ions
and reduces the viscosity of the solvent. As a result, it
reduces the concentration polarization and thus en-
hances the quality of the deposit (weaker tendency to
dendrite formation) and the current efficiency [15].
The influence of temperature on the deposit quality
was examined in the range from 24 to 60°C.
Target quality control. The quality of the electro-
plated nickel targets is evaluated taking into account
the homogeneity, morphology, visual appearance of
the nickel layer, and thermal shock test. The homoge-
neity of the nickel layer is important as it may seri-
64
ously affect the Cu production rate. This was deter-
Thus, electroplating of nickel at pH < 1 in the tem-
perature range 24–60°C does not ensure the current
efficiency exceeding 62%. Therefore, the next experi-
ments were carried out at a lower bath acidity: pH 2–3
and 3–4. When nickel electrodeposition was performed
at pH 2–3, the current efficiency was improved consid-
erably compared to pH 0–1, except the experiment at
room temperature. The maximum nickel thickness
achieved in these experiments was 43.5 μm (current
density 248.07 mA cm–2, bath temperature 45°C); nev-
ertheless, 0.45 mg of nickel was removed after clean-
ing. The best morphology was observed for a deposit
of thickness 13.99 μm electroplated at a current den-
sity of 85.54 mA cm–2 with 80.88% current efficiency
(see table).
mined by measuring the thickness of several parts of
the layer with a micrometer and calculating the stan-
dard deviation of the data.
RESULTS AND DISCUSSION
The first experiments were performed at pH 0–1 at
room temperature. The results of these experiments
indicate that higher current efficiency is obtained with
an increase in the current density. The maximum thick-
ness of the deposits obtained was about 10 μm at
2000 mA current. On increasing the current over
2000 mA, a deposit with poor adhesion was obtained
(see table).
Experiments at pH increased to 3–4 were per-
formed in the temperature range 24–60°C. The data
obtained show that this increase does not allow
the current efficiency to be increased over 90% at
a current of 600 mA in all the experiments except
that at room temperature. The thickness of the opti-
mum deposit was 16.78 μm at a current density of
85.54 mA cm–2 and current efficiency of 97% (see
table).
The deposits were weighed immediately after plat-
ing, and then they were cleaned with a print-board
eraser to remove weakly adhering grains from the de-
posit surfaces. The deposits were reweighed, and their
weights before and after cleaning were compared.
Large differences between them indicate that the de-
posit was poor-grained. At pH 0–1 the difference was
insignificant, but the current efficiency was very poor.
Temperature could be one of the factors affecting the
current efficiency; therefore, subsequent experiments
After the electrodeposition completion, the feeble
RADIOCHEMISTRY Vol. 51 No. 6 2009

NICKEL ELECTRODEPOSITION ON COPPER SUBSTRATE
631
Influence of conditions on the efficiency of Ni deposition (6 g of NiSO4, 0.5 g of NiCl2 in solution, 55°C, 10 min)a
pH 0–1
Wc
pH 2–3
Wc
pH 3–4
Wc
J
W0
dc
CE
J
W0
dc
CE
J
W0
dc
CE
24°C
24°C
24°C
13.1133
13.4789
13.5299
13.2559
13.3183
13.6519
14.0246
14.7917
14.8063
13.2462
14.5490
14.4281
8.55 13.6549 13.6554 0.05
2.70
8.55
13.1193 0.57 33.33
8.55
14.8088 1.64 95.00
14.8739 6.50 93.00
13.3416 9.10 88.33
14.7129 15.75 91.05
14.8450 40.07 115.80
35°С
14.6161 1.61 93.34
14.4161 6.05 87.09
12.9484 10.98 95.00
14.3495 16.76 96.88
13.9147 32.69 94.50
45°С
16.0646 0.59 31.32
12.0709 6.50 93.80
12.7230 10.60 98.98
15.5390 16.60 96.00
14.1625 31.93 92.30
55°С
14.0126 1.48 86.11
14.8423 6.07 87.77
12.9062 10.03 93.79
14.1603 16.78 97.00
15.0193 32.44 93.77
17.10 13.2009 13.2047 0.36 10.50 17.10
34.21 13.4219 13.4303 0.80 11.66 34.21
51.32 12.8661 12.8763 1.26 12.28 51.32
68.43 13.6291 13.6558 2.56 18.34 68.43
85.54 12.7751 12.8022 2.60 15.05 85.54
128.31 13.8628 13.9240 5.88 22.66 171.08
171.08 12.7190 12.8237 10.06 29.08
13.4947 1.51 43.88 34.21
13.5695 3.80 55.00 51.32
13.3334 7.40 71.75 85.54
13.4087 8.68 62.77 171.08
13.7722 11.56 66.83
14.5993
14.3534
12.8458
14.1751
13.5745
14.2230 19.06 55.11
35°С
8.55
51.32
85.54
13.4080
13.7614
13.4668
14.4667
13.5390
248.07 12.7262 12.8073 7.79 15.53
8.55
51.32
13.4089 0.09
5.00
35°С
13.8063 4.31 62.36 171.08
13.7546
13.5479 7.80
0.75
248.07
8.55
34.21
51.32
85.54
171.08
248.07
13.7564 0.17 10.00 85.54
13.9166 0.96 12.88 171.08
14.2701 1.82 17.59 248.07
14.3555 9.77 56.50
14.1032 15.13 49.22
14.0353 19.73 39.31 17.10
13.9066
14.2511
14.2538
13.9457
13.8301
14.6092 13.69 79.16
13.7982 24.90 72.00
45°С
14.0584
14.0033
12.6116
15.3662
13.8302
8.55
51.32
12.9799 12.9845
12.6666 12.6846
13.1651 13.2035
13.5353 13.7342
13.2438 13.3412
8.55
0.44 25.56 85.54
1.73 50.00 171.08
3.69 53.00 248.07
9.50 91.57
45°С
34.21
15.5778
13.6179
14.1412
13.4567
14.1675
14.2539
13.8357
13.8588
13.8039
8.55
17.10
34.21
51.32
68.43
85.54
128.31
171.08
248.07
15.5780 0.19
13.6215 0.34 10.00 68.43
1.66 51.32
13.9971
14.7791
12.8049
13.9857
14.6817
14.1079 14.5828
60°С
14.0012
14.0756
13.1319
13.9044
14.1972
9.36 63.67
8.55
13.4548
14.1018
13.6104
55°С
14.1613 1.93 35.82 85.54 13.3092
13.4907 3.26 31.48 128.31 13.8167
14.2242 5.44 39.37 248.07 13.1578
14.3248 6.81 39.38
13.99 80.88 34.21
27.40 79.19 51.32
43.50 86.70 85.54
171.08
14.6338
13.5080
13.9710
13.7500
14.3463
13.9484 10.83 41.74
14.0056 14.10 40.77 51.32
14.0146 20.25 40.36 85.54
8.55
14.6455 1.12 65.00 248.07
13.5934 8.20 79.07
14.1044 12.89 74.11
14.0527 29.09 84.08 34.21
14.7507 38.86 77.47 51.32
60°С
14.4284 0.36 21.11 171.08
13.5897 7.20 70.27 248.07
14.5700 11.67 67.50
14.8916 28.89 83.50
15.0625 40.55 80.83
45.64 90.97
8.55
14.0124 1.07 62.22
14.1385 6.04 87.50
13.2353 9.90 95.74
14.0743 16.33 94.38
14.5057 29.65 85.69
55°С
171.08
248.07
9.44
13.2550
13.5578
13.9556
14.5172
14.2170
13.7451
8.55
34.21
51.32
85.54
171.08
248.07
13.2567 0.16
13.5715 1.21 19.02
13.9853 2.85 27.50
14.5750 5.55 32.11 34.21
14.3639 14.11 40.80 51.32
13.9843 22.99 45.82 85.54
85.54
14.2446
13.5138
14.4485
14.5910
14.6406
8.55
14.1058 14.5914
46.67 93.02
60°С
171.08
14.2670
14.4276
14.3281
14.0287
14.3333
8.55
51.32
85.54
171.08
248.07
14.2692 0.21
8.18
14.4572 2.84 41.11
14.3840 5.37 52.17
14.1954 10.83 62.61
14.5509 20.90 60.44
(J) Current density, mA cm–2; (W0) initial substrate weight, g; (Wc) weight of substrate with coating after cleaning, g; (dc) coating
thickness, μm; (CE) current efficiency %.
a
mation nor peeling off was observed during a thermal
shock treatment.
Ni of the deposit was easily removed by simply rub-
bing the surface layer with a print-board eraser. The
feeble nickel was not observed under the optimum
conditions of the electrodeposition. Neither crater for-
The quality of the layers was evaluated by SEM.
The size and shape of the Ni particles and the extent of
RADIOCHEMISTRY Vol. 51 No. 6 2009

632
SADEGHI et al.
(a)
in the bath. The layer thickness is governed by
the amount of Ni in the plating bath. As the deposits
stand the thermal shock test, beam currents exceeding
200 μA can be applied.
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their mutual overlap were analyzed. The smaller, more
spherical, and more overlapping nuclei were consid-
ered to be an evidence of the good plating quality.
SEM photomicrographs showed that the targets elec-
troplated at a current density of 85.54 mA cm–2 and
55°C had a good adhesion between the deposit and
backing. The granulometry of the target electroplated
at pH 3–4 acidity seems to be more desirable com-
pared to electroplating at pH 0–1 (Fig. 1).
Thus, 64Cu can be produced by nickel electrode-
position on a gold layer from a nickel sulfamate solu-
tion. The electrodeposition experiments were contin-
ued for depletion of natNi (current efficiency η > 98%)
with 46 µm and optimum amount of nickel (5.7 g l–1)
RADIOCHEMISTRY Vol. 51 No. 6 2009