The synthesis, light-harvesting, and photocatalysis of naphthylporphyrin-functionalized platinum nanocomposites

Article abstract of DOI:10.1016/j.dyepig.2009.12.004

A tetraphenylporphyrin bearing four naphthalene donor moieties (5,10,15,20-tetrakis(4-(naphthalen-1-ylmethoxy)phenyl)porphyrin were synthesized and characterized using ¹H NMR, FTIR, UV-vis, FL, TEM, and XRD. Substituting the naphthalene groups

Full text of DOI:10.1016/j.dyepig.2009.12.004

Dyes and Pigments 86 (2010) 81e86
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
The synthesis, light-harvesting, and photocatalysis of
naphthylporphyrin-functionalized platinum nanocomposites
,
b,
Mingshan Zhu a, Ming Han a, Yukou Du a, Ping Yang a , Xiaomei Wang
*
*
a College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China
b College of Chemistry and Bioengineering, Suzhou University of Science and Technology, Suzhou 215011, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A tetraphenylporphyrin bearing four naphthalene donor moieties (5,10,15,20-tetrakis(4-(naphthalen-1-
ylmethoxy)phenyl)porphyrin were synthesized and characterized using 1H NMR, FTIR, UVevis, FL, TEM,
and XRD. Substituting the naphthalene groups onto the porphyrin ring led the molecule to absorb over
a broader range (200e700 nm) and to undergo efficient intramolecular energy transfer from the
naphthalene to the porphyrin ring. FTIR, XRD and TEM analyses indicated that within a functionalized
platinum nanocomposite comprising the porphyrin, the photoreceptive dye forms a shell containing
a nanosize Pt core (w2.8 nm). The photocatalytic activity of the Pt nanocomposite towards water
reduction to hydrogen was >twice that of a Pt-naphthalene-free porphyrin system. The turnover
Received 28 September 2009
Received in revised form
3 December 2009
Accepted 6 December 2009
Available online 16 December 2009
Keywords:
Naphthylporphyrin
Pt nanocomposites
Fluorescence
numbers (TONPt and TONdye) and quantum yields of hydrogen ðFH Þ were 72, 7200 and 3.0%, respectively,
2
calculated on the basis of the total amount of H2 evolved after 12 h irradiation.
Light-harvesting
Photocatalysis
Hydrogen
Ó 2009 Elsevier Ltd. All rights reserved.
1. Introduction
Naphthalene is a bulky electron-rich unit, and when substituted in
the meso-position of a porphyrin ring, it can help achieve photo-
Porphyrin research can be traced back to Fischer's pioneering
synthesis of hemin in the 1920s [1]. One of the most interesting
features of porphyrins is that their properties can be finely tuned by
substitution of peripheral functional groups [2e4]. Owing to their
intriguing optoelectronic and photochemical properties, there has
been long-standing interest in using porphyrins as photosensitizers
to mimic natural photosynthesis [5e9]. However, improving the
efficiency of energy and/or charge transfer between an excited
photosensitizer and an electronic relay remains a challenge. Okura
and coworkers investigated the properties of some covalently
linked viologen porphyrins and showed that the photoexcited
porphyrin could reduce the viologen and the reduction potential of
the viologen was sufficiently negative to reduce water into
hydrogen [10e13]. As the photosensitizer and the electron relay
were in the same molecule, the covalently linked systems appeared
to display higher energy transfer efficiency than that of traditional
four-component systems used for solar energy conversion. Fused-
ring aromatic compounds including naphthalene derivatives are
often used to synthesize naphthalene-linked porphyrins [14e17].
induced electron or energy transfer between the porphyrin and
chromophores [15].
In a traditional four-component system for solar energy transfer,
noble metal (e.g., Pt) nanoparticles are usually used as catalysts for
hydrogen evolution [18,19]. A stabilizing agent is necessary to
provide stable nanoparticles in solution [20]. Polymers, den-
drimers, and even some organic dyes can be used as stabilizers to
prevent metal nanoparticles from agglomerating [21e24]. Recently,
Kamat and coworkers reported that noble metal nanoparticles
functionalized by dye molecules showed high electron-transfer
efficiency between the photosensitizer and the metal nanoparticles
[24,25]. The electron density of the metal nanoparticles altered
greatly as a result of energy transfer from the excited dye molecules
to the metal surfaces. Kamat's findings motivated our current study
into the potential application of dye-functionalized Pt nano-
composites in photosynthesis. This paper discusses the preparation
and photocatalysis of naphthylporphyrin-functionalized Pt nano-
composites. Our results show that naphthylporphyrin is dominated
by broad absorptions in the region of 200e700 nm and the efficient
intramolecular energy transfer occurs from the naphthalene
substitutes to the porphyrin ring of the molecule. Moreover, the
photocatalytic activity of Pt-naphthylporphyrin was much higher
than that of Pt-naphthalene-free porphyrin under the same reac-
tion conditions.
* Corresponding authors. Tel.: þ86 512 65880361; fax: þ86 512 65880089.
E-mail addresses: pyang@suda.edu.cn (P. Yang), xmwangsuda@yahoo.com.cn
(X. Wang).
0143-7208/$ e see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2009.12.004

82
M. Zhu et al. / Dyes and Pigments 86 (2010) 81e86
2. Experimental
2.2. Characterization of porphyrin-functionalized
platinum nanocomposites
2.1. Chemicals and synthesis
UVevis absorption spectra of the porphyrin derivatives and the
Pt colloidal solutions were recorded on a TU1810 SPC spectropho-
tometer, while fluorescence spectra of the samples were taken on
an Edinburgh FLS920 fluorospectrophotometer. A Philips diffrac-
All chemical reagents were purchased from Acros and were used
without further purification.
2.1.1. Synthesis of 5,10,15,20-tetrakis(4-(hydroxyl)phenyl)
porphyrin (TPPH)
tometer with Ni-filtered Cu Ka radiation was used to obtain X-ray
diffraction (XRD) patterns of the samples. Transmission electron
microscopy (TEM) studies were conducted on a TECNAI-G20 elec-
tron microscope operating at an accelerating voltage of 200 kV. The
samples for TEM analysis were prepared by dropping about 3 mm3
of the dilute colloidal solution onto a carbon-covered copper grid
and letting the solution air dry at room temperature.
The photoelectrochemical experiments were carried out in
a three-electrode system devised of an indium tin oxide (ITO) glass
covered with porphyrin-functionalized platinum nanocomposites,
a platinum wire, and a saturated calomel electrode (SCE). The ITO
covered with the platinum nanocomposites acted as the working
electrode, the platinumwire as the counter electrode, and the SCE as
the reference electrode. The electrodes were immersed in a DMF
solution containing 0.1 mol dmꢀ3 LiClO4. The working electrode was
irradiated with a GY-10 xenon lamp (150 W) during the measure-
ment. Photocurrentetime (Iet) characteristics were recorded with
a CHI 660B potentiostat/galvanostat electrochemical analyzer.
5,10,15,20-tetrakis(4-(hydroxyl)phenyl)porphyrin was synthe-
sized and purified according to the method reported in the litera-
ture [26], and characterized using 1H NMR and FTIR. 1H NMR
(d6-DMSO; 400 MHz) dH: ꢀ2.88 (s, 2H, NH), 7.21e7.26 (d, 8H,
phenyl), 7.98e8.05 (d, 8H, phenyl), 8.88 (s, 8H, pyrrole),10.07 (s, 4H,
hydroxy). FTIR (KBr), nmax/(cmꢀ1): 3444 (NeH), 1606, 1508 1471
(C]C, C]N), 1170 (]CeOH), 968 (NeH), 800.
2.1.2. Synthesis of 5,10,15,20-tetrakis(4-(naphthalen-1-ylmethoxy)
phenyl)porphyrin (TPPNA)
The synthesis of TPPNA using the Williamson method is shown
in Fig. 1. TPPH (0.1 mmol) and anhydrous potassium carbonate
(1 mmol) were mixed with 25 cm3 DMF in a 50 cm3 three-necked
round-bottom flask using a magnetic stir bar. Upon dissolution of
the solids, 0.8 mmol 1-bromomethyl naphthalene (1-BrMN) and
0.2 mmol KI were added and the ensuing mixture was heated to
363 K and maintained at this temperature under nitrogen for 10 h.
After the reaction was complete, the mixture underwent rotary
evaporation, and the contents were added dropwise into ice-water.
The resulting dark red solids were collected by centrifugal separa-
tion and then washed thoroughly with water and ethanol, respec-
tively. The product was purified by silica-gel column
chromatography using a petroleum ether/ethyl acetate (1.5:1 v/v)
mixture as the eluent; the yield was 24%. The product was char-
acterized by 1H NMR and FTIR. 1H NMR (CDCl3; 400 MHz) dH: ꢀ2.88
(s, 2H, NH), 4.9 (s, 8H, eOCH2e), 7.2e8.4 (m, 44H, naphthyl,
phenyl), 8.89 (s, 8H, pyrrole). FTIR (KBr), nmax/(cmꢀ1): 3036 (NeH),
2962 (]CeOeCH3), 1664, 1598, 1506, 1469 (C]C, C]N), 1236
(CeOeC), 1062 (CeOeC), 968 (NeH), 794.
2.3. Photocatalytic reaction
The photocatalytic reaction was carried out in a 50 cm3 quartz
flask equipped with a flat optical entry window. In the flask, 38 cm3
distilled water, 2 cm3 EDTA (0.1 mmol) and 10 cm3 porphyrin-
functionalized Pt colloidal solution (Pt w2.32 ꢁ 10ꢀ3 mmol) were
added. The system was deaerated by bubbling nitrogen into the
solution for 30 min before the reaction. The solution was stirred
continuously and irradiated by a GY-10 xenon lamp (150 W) at
298 K. The gases produced were analyzed with an online gas
chromatograph (GC102AT) equipped with a TCD detector.
3. Results and discussion
2.1.3. Preparation of porphyrin-functionalized
platinum nanocomposites
3.1. UVevis and fluorescence spectra
TPPNA functionalized platinum nanocomposites were prepared
using the ethanol reduction method [27]. In a typical experiment,
7.7 ꢁ 10ꢀ3 mmol of H2PtCl6 and 7.7 ꢁ 10ꢀ5 mmol TPPNA were
mixed with 30 cm3 aqueous ethanol solution (Vwater:Vethanol ¼ 1:1)
at pH 9e10. The solution was heated under reflux for 2 h, resulting
in a dark brown platinum colloidal solution. The ratio of metal:
TPPNA was varied from 50 to 200, the samples being labeled as Pt-
TPPNA-x, where x designated the molar ratio of platinum to TPPNA
in the sample. For comparison, hydroxylporphyrin-functionalized
Pt nanocomposites (Pt-TPPH) were also synthesized by the same
method.
Fig. 2 presents the UVevis spectra of porphyrin derivatives and
porphyrin-functionalized platinum nanocomposites. The bands of
the porphyrins are from the electronic transitions from the ground
state (S0) to the two lowest singlet excited states S1 (Q state) and S2
(Soret state). The spectrum of TPPH (spectrum a) has a strong
absorption peak centered at 421 nm and four other peaks centered
at 517, 554, 592, and 649 nm. The peak at 421 nm is the Soret band
arising from the a1u
ð
p
Þ ꢀ e*gð
Þ transition, and the other four
p
absorption peaks are attributed to the Q bands of the a2u
ð
p
Þ ꢀ e*gð
Þ
p
transition [28]. The spectrum clearly identifies the porphyrinic
ΟΗ
Br
O
CH
OH
propionic acid/ethanoic acid
nitrobenzene,reflux
4
NH
N
4
4
OH
HO
N
H
N HN
K2CO3,KI/DMF
OH
TPPH
TPPNA
Fig. 1. The procedure used to prepare TPPNA.

M. Zhu et al. / Dyes and Pigments 86 (2010) 81e86
83
2000
2.5
2.0
1.5
1.0
0.5
0.0
Pt-TPPNA
a
b
Soret
0.8
0.6
0.4
0.2
0.0
1500
1000
200
300
400
500
600
700
λ / nm
a b
500
Qx(0,1)
Qy(0,0)
Qy(0,1)
500
c
d
Qx(0,0)
c
0
300
400
600
700
500
550
600
650
700
750
Wavelength / nm
Wavelength / nm
Fig. 2. UVevis spectra of TPPH (a), TPPNA (b), and 1-BrMN (c) in 5 ꢁ 10ꢀ3 mmol dmꢀ3
CH2Cl2. The inset shows the UVevis spectrum of Pt-TPPNA.
Fig. 3. Fluorescence spectra of TPPNA (a), TPPH (b), Pt-TPPH-100 (c), and Pt-TPPNA-
100 (d) in 5 ꢁ 10ꢀ3 mmol dmꢀ3 ethanol excited at 421 nm at room temperature.
chromophore of TPPH. The absorption spectrum of TPPNA (spec-
trum b) closely matches the superposition of the spectra of the
separate components of 1-BrMN (spectrum c) and TPPH. UVevis
spectrum of Pt-TPPNA shows features from both TPPNA and the
metallic nanoparticle. As seen in the inset in Fig. 2, the metallic
nanoparticle is characterized by a broad absorption at wavelengths
>300 nm and an absorption peak at ca. 220 nm. The photophysical
parameters of all the samples are summarized in entries 2e7 in
Table 1.
The fluorescence spectra of TPPH and TPPNA at 421 nm excita-
tion show the emission signature of the porphyrin unit at 657 nm
(Fig. 3, spectra a and b). The spectral shapes and band maxima of
the peaks in the TPPNA spectrum are similar to the peaks in the
TPPH spectrum. In the spectra of Pt-TPPH-100 and Pt-TPPNA-100 at
421 nm excitation, the intensity of the porphyrin peak at 657 nm is
much smaller than those in the TPPH and TPPNA spectra (Fig. 3,
spectra c and d). The fluorescence data and quantum yields of the
samples are summarized in entries 8e9 in Table 1. The quantum
absorbed by the organic molecules is quickly transferred to the Pt
core of the nanocomposites.
Upon irradiation at 283 nm, in the fluorescence spectrum of
TPPNA, there is a peak at 657 nm from the relaxation of porphyrin
(Fig. 4, spectrum a) while TPPH did not fluoresce at all at the same
excitation wavelength (Fig. 4, spectrum b). Moreover, the fluores-
cence spectrum of 1-BrMN at 283 nm excitation has an emission
peak centered at 386 nm that overlaps significantly with the Soret
band of the porphyrin ring and fulfills the first condition for energy
transfer (Fig. 4, inset) [31,32]. In order to investigate whether it is an
intramolecular or an intermolecular energy transfer, the fluores-
cence spectrum of the mixture of TPPH and 1-BrMN with similar
stoichiometry of TPPNA was measured (see Fig. 5). The fluorescence
spectrum of the mixture at 283 nm excitation shows the emission
signature of 1-BrMN at w340 nm, however, there is no an apparent
emission at w650 nm. These facts confirm that it is mainly an
intramolecular energy transfer from the naphthalene donor to the
porphyrin acceptor.
yield (F) was calculated by the following equation [29]:
The energy transfer efficiency can be estimated by the following
formula [33].
Fsample
FTPPH Asample
ATPPH
Fsample
¼
FTPPH
$
$
(1)
where Fsample and FTPPH are the measured fluorescence integral
areas of the sample and TPPH, respectively; Asample and ATPPH are
the absorbances of the sample and TPPH, respectively; and Fsample
and FTPPH are the quantum yields of the sample and TPPH,
respectively, at the same excitation wavelength. FTPPH is 0.14 as
reported in the literature [30]. The quantum yield of TPPNA (0.15) at
421 nm is almost equal to that of TPPH (0.14) at the same excitation
wavelength, suggesting that TPPNA and TPPH have long-lived
charge-separated states. The low quantum yields of Pt-TPPH-100
(0.06) and Pt-TPPNA-100 (0.04) confirm that most of the energy
2000
8000
0.8
0.6
0.4
0.2
0.0
7000
6000
5000
4000
3000
2000
1000
0
1500
1000
500
0
a
b
300
400
500
600
λ / nm
700
800
Table 1
The data of absorption and emission spectra of samples.
Sample
Absorption/nm
Emission/nm
p
e
p
Scoret Qy0e1 Qy0e0 Qx0e1 Qx0e0 Ex ¼ 421 nm
F
400
500
600
Wavelength / nm
700
800
1-BrMN
TPPH
TPPNA
Pt-TPPH
292
/
w285 421
420
517
517
518
525
554
554
570
561
592
592
649
649
667
655
657 716
656 716
657
0.14
0.15
0.06
0.04
Fig. 4. Fluorescence spectra of TPPNA (a) and TPPH (b) in 5 ꢁ 10ꢀ3 mmol dmꢀ3 ethanol
excited at 283 nm at room temperature. The inset shows the fluorescence spectrum of
1-BrMN excited at 283 nm and the absorption spectrum of TPPNA.
/
435
436
Pt-TPPNA 285
656

84
M. Zhu et al. / Dyes and Pigments 86 (2010) 81e86
3000
2500
2000
1500
1000
500
-60
ex: 283 nm
ex: 421 nm
-80
a
b
-100
-120
-140
-160
-180
-200
-220
Light
off
Light
on
c
0
500
600
700
800
0
40
80
120
160
200
240
280
320
360
Time / s
Wavelength / nm
Fig. 5. Fluorescence spectra of the mixture of 1-BrMN (2 ꢁ 10ꢀ2 mmol dmꢀ3) and
TPPH (5 ꢁ 10ꢀ3 mmol dmꢀ3) in ethanol excited at 283 nm and 421 nm at room
temperature, respectively.
Fig. 6. Photocurrent responses of ITO (a), ITO/Pt-TPPH-100 (b), and ITO/Pt-TPPNA-100
(c) to UVevis irradiation in 30 cm3 DMF containing 0.1 mol dmꢀ3 LiClO4 recorded at
0.05 V. The illumination from a 150 W xenon lamp was interrupted every 20 s.
attributed to the transfer of charge carriers by the photoexcited dye
molecules. TPPNA has a higher photocurrent than TPPH due to
TPPNA's greater absorption of light.
Ad$Ida
FET ¼ 1 ꢀ
(2)
A
da$Id
where Ada and Ad are the absorbances of TPPNA and 1-BrMN,
respectively; and Ida and Id are the emission intensities of TPPNA
and 1-BrMN, respectively. From the fluorescence spectrum of
TPPNA at 283 nm excitation, we calculated using Eq. (2) that the
efficiency of energy transfer from naphthalene donor moiety to
porphyrin acceptor moiety in TPPNA was ca. 95%.
3.3. Characterization of dye-functionalized
platinum nanocomposites
Fig. 7 presents TEM images of Pt nanocomposites. The average
sizes of the Pt nanoparticles were 2.8 ꢂ 0.3 nm and 3.0 ꢂ 0.4 nm for
Pt-TPPNA-100 and Pt-TPPH-100, respectively. The colloidal solu-
tions of Pt-TPPNA and Pt-TPPH were stable without signs of
precipitation at room temperature for more than 6 months. As seen
in Fig. 8, the Pt nanocomposites had XRD peaks at 39.7, 46.2, 67.5,
and 81.2ꢃ, corresponding to the (111), (200), (220), and (311)
crystalline planes of the face-centered cubic metallic platinum,
respectively [36]. The broadening of the diffraction peaks indicates
that the sizes of the Pt particles were in the nanometer range. The
FTIR spectra shown in the inset of Fig. 8 demonstrate that there is
a ca. 50 cmꢀ1 difference between the C]N band of Pt-TPPNA at
w1417 cmꢀ1 and the C]N band of TPPNA at w1469 cmꢀ1. The
3.2. Photoelectrochemical properties
Fig. 6 shows the currentetime (Iet) curves of the ITO electrode
covered with the Pt nanocomposite (Pt-TPPH or Pt-TPPNA). The
illumination was periodically interrupted to obtain the light current
and dark current densities [34,35]. The photocurrent of the bare ITO
electrode was negligible (jph w0.6
m
A cmꢀ2); however, under
similar illumination conditions, when the electrode was covered
with Pt-TPPH and Pt-TPPNA, photocurrents reached 37.1 and
57.4 m
A cmꢀ2, respectively. This enhancement in photocurrent is
Fig. 7. TEM images of Pt-TPPNA-100 (a) and Pt-TPPH-100 (b).

M. Zhu et al. / Dyes and Pigments 86 (2010) 81e86
85
Table 2
a--TPPNA
b--Pt-TPPNA
Turnover numbers and quantum yields of hydrogen of Pt-TPPH-100 and Pt-
TPPNA-100.
b
a
(111)
Compound
TONPt after 12 h
TONdye after 12 h
FH =mol$einsteinꢀ1
2
Pt-TPPH
Pt-TPPNA
33
72
3300
7200
1.38%
3.02%
(200)
2000
1800
1600
1400
1200
1000
800
wavenumber / cm-1
The quantum yield of hydrogen ðFH Þ is defined by the following
2
b
a
(220)
equation [37]:
(311)
2$nH
2
FH
¼
(4)
2
I0$t
where I0 is the number of photons per unit area and unit time,
which was measured by chemical actinometry using K3[Fe(C2O4)3]
[38]. I0 was found to be 2.84 ꢁ 10ꢀ7 einstein sꢀ1
.
40
50
60
70
80
The total amount of H2 evolved from the Pt-TPPNA system after
(°)
2θ /
12 h irradiation (185.5
mmol) is much higher than that from the Pt-
TPPH system (84.8 mol), as seen in Fig. 9. As TPPNA is composed of
m
Fig. 8. XRD patterns of Pt-TPPNA-100 (a) and Pt-TPPH-100 (b). The inset shows FTIR
a porphyrin ring linked to four naphthalene moieties via ether
bridges, upon irradiation by UVevis light, the photoexcited naph-
thalene substitutes transfer the absorbed energy to the porphyrin
ring in TPPNA. Thus, the higher H2 production by Pt-TPPNA can be
attributed to the broader light absorption of TPPNA and the effi-
cient energy transfer from the naphthalene substitutes to the
porphyrin ring in TPPNA, as well as from the photoexcited TPPNA to
the platinum nanocore of the nanocomposite. From the results of
this study, we suggest the following mechanism to explain the
photocatalytic process: (1) electrons are transferred from the
photoexcited porphyrin molecule to the Pt nanoparticle [24]; (2)
water is reduced, producing H2 on the Pt nanocomposites; (3) the
photosensitizer is regenerated using EDTA as a sacrificial electron
donor. Fig. 10 shows the influence of the composition of Pt-TPPNA
on the amount of H2 evolved. The optimized molar ratio of the
platinum to the dye is 100; this ratio leads to the greatest
production of H2 in a given period of time. If the molar ratio of the
metal to TPPNA is higher than 100, the amount of light absorbed by
the system is significantly reduced because there are not enough
sensitizer molecules; if the ratio is lower than 100, an over-
abundance of sensitizer molecules in the system shortens the
distance between the dye molecules, resulting in intermolecular
energy transfer and a decrease in photocatalytic efficiency.
spectra of TPPNA and Pt-TPPNA.
significant peak shift towards lower energy for Pt-TPPNA is
evidence of the interaction between the Pt nanocomposite and the
nitrogen atoms of the porphyrin ring. Therefore, the structure of
the nanocomposites can be described as a photoreceptive dye shell
enveloping the Pt nanocore. Because the organic photosensitizing
moiety of the nanoparticle is in direct contact with the metallic
core, increasing the efficiency of energy transfer between the two
will significantly enhance the photocatalytic abilities of these dye-
functionalized metallic nanocomposites.
3.4. Photoinduced hydrogen evolution
The photocatalytic results of Pt-TPPH and Pt-TPPNA are shown
in Fig. 9 and summarized in Table 2. The turnover number (TON) is
defined as the moles of H2 evolved per mole of Pt or photosensitizer
after experiencing irradiation over a certain time period:
nH
2
À
Á
TON ¼
(3)
nPt or ndye
200
200
180
160
140
120
100
80
Pt-TPPNA-50
Pt-TPPNA-100
Pt-TPPNA-200
180
160
140
120
100
80
Pt-TPPH-100
Pt-TPPNA-100
60
60
40
40
20
20
0
0
0
2
4
6
8
10
12
0
2
4
6
8
10
12
Time / h
Time / h
Fig. 9. The amount of H2 evolved as a function of irradiation time using Pt-TPPH-100 and
Fig. 10. The amount of H2 evolved as a function of irradiation time using Pt-TPPNA
with various Pt:TPPNA molar ratios as photocatalysts. Reaction conditions:
[Pt] ¼ 4.64 ꢁ 10ꢀ2 mmol dmꢀ3, [EDTA] ¼ 2 mmol dmꢀ3, T ¼ 298 K.
Pt-TPPNA-100 as photocatalysts. Reaction conditions: [Pt] ¼ 4.64 ꢁ 10ꢀ2 mmol dmꢀ3
,
[EDTA] ¼ 2 mmol dmꢀ3, T ¼ 298 K.

86
M. Zhu et al. / Dyes and Pigments 86 (2010) 81e86
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c
(18):4556e62.
Novel naphthylporphyrin-functionalized platinum nano-
composites were synthesized and used successfully as the pho-
tocatalysts for hydrogen evolution without an electron relay.
The photophysical studies of naphthylporphyrin reported here
demonstrate efficient energy transfer from naphthalene to
porphyrin. Using Pt-TPPNA-100 as the photocatalyst, the total
amount of H2 produced and the apparent quantum efficiency were
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tion for 12 h. The photocatalytic activity of Pt-TPPNA was more
than two times that of Pt-naphthalene-free porphyrin under the
same reaction conditions. This study shows that the photocatalytic
activity of a Pt-porphyrin system can be significantly improved by
choosing proper peripheral functional groups of porphyrin with
a high light-harvesting capability.
[22] Dai J, Du Y, Wang F, Yang P. PtCo/Au nanocomposite: synthesis, characteriza-
tion, and magnetic properties. Physica E: Low-dimensional Systems and
Nanostructures 2007;39(2):271e6.
Acknowledgements
[23] Zhang W, Li L, Du Y, Wang X, Yang P. Gold/platinum bimetallic core/shell
nanoparticles stabilized by a Fréchet-type dendrimer: preparation and cata-
lytic hydrogenations of phenylaldehydes and nitrobenzenes. Catalysis Letters
2009;127(3):429e36.
[24] Kamat PV. Photophysical, photochemical and photocatalytic aspects of metal
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Accounts of Chemical Research 2003;36(12):888e98.
The authors gratefully appreciate the financial support of the
National Natural Science Foundation of China (20673075 and
50673070) and Ministry of Education of China, Science and Tech-
nology Research Key Project (204053).
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