Design of a scalable AuNP catalyst system for plasmon-driven photocatalysis

Article abstract of DOI:10.1039/c8ra03661f

In this work we present a simple, fast and cost-efficient synthesis of a metal nanoparticle catalyst on a glass support for plasmon driven heterogeneous photocatalysis. It is based on efficient mixing of metal salts as particle precursors with porous glass as the supporting material in a mixer ball mill, and the subsequent realization of a complete catalyst system by laser sintering the obtained powder on a glass plate as the support. By this, we could obtain catalyst systems with a high particle proportion and an even spatial particle distribution in a rapid process, which could be applied to various kinds of metal salt resulting in plasmon active metal nanoparticles. Furthermore, the catalyst production process presented here is easily scalable to any size of area that is to be coated. Finally, we demonstrate the catalytic performance of our catalysts by a model reaction of ethanol degradation in a self-designed lab-scale reactor.

Full text of DOI:10.1039/c8ra03661f

RSC Advances
View Article Online
View Journal | View Issue
PAPER
Design of a scalable AuNP catalyst system for
plasmon-driven photocatalysis†
Cite this: RSC Adv., 2018, 8, 30289
Heike Lisa Kerstin Stephanie Stolle, *ab Frank Garwe, Robert Muller,
a
a
¨
c
d
d
a
Thomas Krech, Bastian Oberleiter, Thomas Rainer, Wolfgang Fritzsche
b
and Achim Stolle
In this work we present a simple, fast and cost-efficient synthesis of a metal nanoparticle catalyst on a glass
support for plasmon driven heterogeneous photocatalysis. It is based on efficient mixing of metal salts as
particle precursors with porous glass as the supporting material in a mixer ball mill, and the subsequent
realization of a complete catalyst system by laser sintering the obtained powder on a glass plate as the
support. By this, we could obtain catalyst systems with a high particle proportion and an even spatial
particle distribution in a rapid process, which could be applied to various kinds of metal salt resulting in
plasmon active metal nanoparticles. Furthermore, the catalyst production process presented here is
easily scalable to any size of area that is to be coated. Finally, we demonstrate the catalytic performance
of our catalysts by a model reaction of ethanol degradation in a self-designed lab-scale reactor.
Received 28th April 2018
Accepted 10th August 2018
DOI: 10.1039/c8ra03661f
rsc.li/rsc-advances
restoring force of the positively charged nuclei, can be excited
by wavelengths resonant to this movement, resulting in
1
. Introduction
Plasmon active noble metal nanoparticles like silver, gold, a simultaneous oscillation of electrons (plasmon resonance).
platinum or palladium nd applications in many elds of The wavelength of light necessary to initiate this process is
1
–3
research, e.g. in bioanalytical sensing,
surface enhanced different for each metal but also varies with shape and particle
4,5
6–11
34–36
Raman spectroscopy (SERS) and in catalysis.
The synthesis size of the same metal.
By this effect, a strongly enhanced
of such particles is possible, in different shapes and sizes, using electric eld is formed in the direct environment of a particle.
noble metal salts. Like this, gold nanoparticles have been This eld enhancement can be around six times higher than the
1
2–15
37
synthesized, e.g. as colloidal, quasi-spherical particles,
eld intensity of irradiating photons for gold nanospheres and
3
35
16–18
19,20
21
nanorods,
nanocubes
and nanostars. For silver nano- even up to 10 times higher in the cases of other shapes. The
particles, plenty of different shapes are also available, for oscillation can be kept up for times in the fs and ps regions for
2
2,23
24,25
26–28
instance spheres,
nanocubes
and prisms.
However, electron–electron and electron–phonon relaxation, respec-
36,38
platinum has mainly been synthesized in non-specic struc- tively.
tures or as platinum cubes, which is similar for palladium resonant light irradiated can be scattered, which is particularly
nanoparticle synthesis.
What makes these particles so interesting for applications is carriers of energetic charge in the case of smaller particles.
the so called localized surface plasmon resonance (LSPR) effect Energetic charge carriers can either relax and form heat at the
Decay is possible in different processes. Thus, the
29
30
31–33
35
the case for larger particles above 100 nm, or it can form
10
34
they show, which is characteristic of such particles. In this nanoparticle surface, heating up components in their close
effect, the valence electrons in the metal, which – under the environment (plasmonic heating), or they can result in elec-
10,38
inuence of light – are constantly oscillating against the tron–hole-pairs,
meaning electrons can be donated to
surrounding molecules or taken from them, with both of these
11,35,39
initiating their degradation process.
a
Leibniz Institute of Photonic Technology (IPHT), Department of Nanobiophotonics,
The abundance of possible mechanisms of converting light
energy makes metal nanoparticles a desirable material for
photocatalysts. Photocatalysts in general are becoming more
popular, because classical catalysts which are activated with
thermal energy require a high energy input, and in order to
maintain the temperature for the highest turn-over a constant
Albert-Einstein-Straße 9, D-07745 Jena, Germany. E-mail: Lisa.Stolle@leibniz-ipht.de
b
Institute of Technical and Environmental Chemistry, Faculty of Chemistry and Earth
39
Sciences, Friedrich-Schiller-University Jena, Philosophenweg 7A, D-07743 Jena,
Germany
c
JENOPTIK Automatisierungstechnik GmbH, Konrad-Zuse-Straße 9, D-07745 Jena,
Germany
d
HEGLA boraident GmbH & Co. KG, K ¨o thener Straße 33a, D-06118 Halle/Saale, energy input is required. In the case of photocatalysis, this is
Germany
not necessary, because in the best cases sunlight, which is
abundantly available and makes any other energy sources
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/c8ra03661f
1
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 30289–30297 | 30289

View Article Online
RSC Advances
Paper
34
redundant, can be used to drive reactions. Due to this, the a similar system for gas phase conversion of CO
2
to hydrocar-
catalysis becomes easily switchable by having a light on when bons over TiO , AuNP/TiO or pure AuNP catalysts on a glass
2
2
energy is required to activate the catalyst, and having the light support, where gold was introduced by electron beam
59
off when it is not. Gold nanoparticles are especially in demand evaporation.
for implementation as catalysts, as these particles exhibit a rich The preparation of plasmon-based catalyst systems
variety of shapes covering the absorption of almost the entire described so far in the literature is usually based on several
35,40
39
spectrum of visible light,
and are also very stable.
working steps, consuming time and also resources, especially
Regarding plasmon catalysis, this makes gold a very interesting regarding the metal precursor salts. Usually the systems
catalyst material exploiting the energy of the VIS area of (sun) described are laid out for classical packed bed reactors and
34
light. But combining gold catalysts with particles of other are difficult to scale-up or scale-down for smaller reactor
41,42
43–46
47
metals like silver,
palladium
or platinum and semi- systems. In the present paper, we introduce a new method to
conductors like TiO (ref. 48–50) is also possible. Such combi- design a complete catalyst system consisting of plasmon
2
nations open up new possibilities for plasmon catalysis, as active nanoparticles on a glass support. In the process, we
41,42
these allow the tuning of the irradiation wavelength needed.
were able to obtain integrated AuNP catalysts. Therefore, the
The synthesis of metal nanoparticles of different metals and methodology is very easy and fast to carry out, is cost-efficient
in different shapes is nowadays state of the art, as described regarding the metal precursors used, and is scalable to
here. Bottom-up techniques range from classical wet-chemical different sizes of supporting glass plates. This catalyst is
1
2–19,21–27,29–33
20,28
synthesis
to microuidic
and photochemical intended for use in packed bed reactors with bypass ow,
5
1
syntheses using metal salts as precursor materials, and to allowing thorough irradiation of the catalyst in comparison to
electrochemical synthesis approaches utilizing metal plates as classical packed bed reactors. In total, only two steps are
52
electrodes. Classical top-down methods include lithographic necessary for the catalyst production: the rst being the
approaches and laser ablation, where a metal plate in water is grinding of the metal precursor material HAuCl with porous
treated with a laser, resulting in monometallic particles, but glass, and the second being the laser sintering of the obtained
4
53
54
55
the production of alloys or bimetallic particles is also metal precursor/glass mixture on the desired glass plate
possible. Problems regarding these techniques are, however, support, resulting in spherical metal nanoparticles. The
the low yields of particles as catalysts and the production costs, process was preliminarily tested for small object slides
making them inappropriate for catalyst production and their (coated area 60 ꢀ 20 mm), but could be also demonstrated on
5
6
upscaling.
glass plates of 100 ꢀ 100 mm. Finally, the catalytic perfor-
Another obstacle is making the particles usable for their mance of the realized catalyst systems was evaluated by
application as catalysts. Here, more preparation steps are oen degradation experiments of ethanol in a self-designed testing
required. In (quasi-)homogeneous catalysis, this problem is plant and a bypass-ow photoreactor.
quite simple to overcome because the particles of the material
to be used can stay in the solution where they were synthesized.
Aerwards, the reactants are added (as solution) and the cata-
2
. Experimental section
lytic reaction is initiated by light of the required wavelength.
This was done, for example, by utilizing Ag and Au nanospheres
and AgAu-nanorings in solution to oxidize and degrade meth-
2.1 Chemicals and materials
Ethanol and HAuCl -trihydrate (49.5% Au content) were ob-
4
41
tained commercially from Alfa Aesar, Karlsruhe, Germany and
were used without further purication. Porous glass with
different pore sizes was delivered by HEGLA boraident (Halle/
Saale, Germany). Glass samples with initial pore sizes of 1–
ylene blue. The case of heterogeneous catalysis (which repre-
sents the majority of catalytic applications) is not that simple, as
the metal nanoparticles need to be immobilized on a support-
ing material. Here, mostly particles of different materials are
used as a support and are coated with the plasmon active
nanoparticles, and are utilized to feed packed bed reac-
2
2
nm, 50 and 100 nm were delivered in larger pieces, whereas
00 and 370 nm glass samples were obtained preground. As
6
,10,57,58
a support material for the coating, Schott BOROFLOAT® plates
with a size of 150 ꢀ 150 ꢀ 1 mm obtained from HEGLA bor-
aident (Halle/Saale, Germany) were used.
tors.
materials, as shown in the studies from Mukherjee et al.
describing the dissociation of H mediated by plasmon heating
of supported AuNPs prepared in a 3-step process.
et al. present the oxidation of CO at AuNPs on SiO , activated by
-mercaptopropyltrimethoxysilane prior to loading with AuNPs
by thermal reduction of a HAuCl solution in the presence of For the mixing of the particle precursor, 1 g of porous glass was
This involves the use of TiO or SiO as supportive
2 2
2
10,57
Rombi
2
4
2.2 Mixing of HAuCl with porous glass
3
4
58
citrate. Studies from Christopher et al. demonstrated the use put into a 35 mL ZrO -milling beaker and 20 mg of HAuCl was
2
4
of a-Al O particles as a support for AgNPs for plasmon cata- added, in order to obtain in total a 1 wt% distribution of metal
2
3
6
lyzed oxidation reactions. In other systems, like the micro- to glass. Through two slots for milling beakers, the second
uidic reaction chamber reported by Adleman et al. used for the milling beaker was lled only with porous glass for comparison

plasmon-assisted catalysis of ethanol and water in the liquid of the resulting powders. Then, 25 g of 5 mm ZrO milling balls
2
phase, a catalyst system consisting of gold nanoparticles spin- was added to each beaker and the grinding process was carried
8
coated onto a glass object slide was used. Hou et al. describe out at 30 Hz for 60 min with a mixer ball mill Retsch 400M.
30290 | RSC Adv., 2018, 8, 30289–30297
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
.3 Characterization of ground mixtures
RSC Advances
2
The pressure of the gas mixture is controlled by a pressure
gauge (Keller LEO 2) before and aer passing the reactor.
Plasmonic catalysis is initiated by irradiation with a Xe arc lamp
The grinding mixtures were evaluated by particle size distribu-
tion measurements (PSD-measurements by dynamic light
scattering, DLS) with a Fritsch Analysette 22 with a wet disper-
sion unit. Each measurement was carried out with ultrasound.
Measurements for the analysis of BET surface areas and total
pore volumes were done with a Quantachrome Autosorb iQ3
system. All ten samples (79.5–110.0 mg) were degassed for 1.2 h
(
LSB530A, obtained from LOT-QuantumDesign GmbH) with
a spectral range of 200–900 nm in a LOT Oriel LSH201 housing
and control unit. The reaction is monitored with the help of an
Agilent gas chromatograph 7890B equipped with a ame ioni-
zation detector (FID) and a thermal conductivity detector (TCD).
A PoraPLOT Q (25 m, 320 mm, 10 mm) was used as the column.
The GC was calibrated with different amounts of ethanol in the
gas phase and the ethanol concentration was calculated from
the peak areas of ethanol. For calculations, a saturated vapor
pressure of ethanol at 273.15 K of 1568 Pa (Dortmund Database,
DDBST) was used. The measured pressure in the testing plant
was 102 000 Pa before and aer the reactor chamber. The
ꢁ
at temperatures up to 150 C before nitrogen adsorption
measurements were carried out at 77.35 K. For all of the
samples, complete adsorption/desorption isotherms were
measured. SEM imaging was carried out with a eld emission
scanning electron microscope, FE-SEM JSM 6300F, JEOL, in BSE
contrast aer sputtering the samples with graphite. Light
microscopy was done with a Zeiss Axio Imager.A1m with Axio
Cam MRc5 device.
retention time of CO
2
was veried by the injection of pure CO
2
.
The calculations of percentual ethanol degradation/CO
2
increase are based on the average peak areas measured without
light (except outliers) and the respective value measured aer
the light was switched on. Here, a range of strong ethanol
degradation was measured before reaching steady-state condi-
tions. For comparison, the average value of the latter was used.
2
.4 Laser sintering of obtained mixtures on supporting glass
plates
The comminuted mixtures were dispersed in ethanol and
homogenized in an ultrasonic bath. Aerwards, the mixture was
applied homogeneously onto a 76 ꢀ 26 mm object slide in an
area of 60 ꢀ 20 mm, and onto 150 ꢀ 150 mm oat glass plates
in a square of 100 ꢀ 100 mm in the middle of the plates and the
ethanol was evaporated under IR radiation. Then, the material
3
. Results and discussion
3.1 Analysis of grinding mixtures
was laser sintered with a CO -laser under mild conditions in The mixtures obtained from the grinding process – without and
2
a cross-hatch, so that the glass/metal precursor mixture was just with HAuCl – are displayed in Fig. 1, le. A change in color can be
4
ꢂ1
supercially sintered. The laser feed rate was 40 mm s and the seen for the sample containing the gold precursor, exhibiting
line distance was 150 mm. The laser power was 0.85 W.
a purple to violet color. This color points to an initial formation of
UV/VIS measurements of the catalysts on supports were particles already in the grinding step, as mixtures containing only
conducted using an Ulbricht sphere with a Perkin Elmer the precursors are expected to be yellow arising from the colour of
Lambda 900 UV/VIS/NIR Spectrometer. XRD measurements HAuCl . SEM images (Fig. 1, right) conrm this assumption, but
4
were made with an X’PERT MPD Pro (PANalytical) system using also show that this happens only occasionally and most of the
Cu K-alpha-radiation (l ¼ 0.154 nm). The crystallite size L was material is still present as the glass/metal salt bulk. Data for
calculated according to the Scherrer equation. Raman particle size analyses and nitrogen adsorption measurements of
measurements were carried out using a confocal WITec Raman the porous glasses with and without addition of HAuCl can be
4
Microscope alpha300 R setup with a water immersion objective found in the ESI (Tables S1 and S2† respectively).
from Nikon with 10ꢀ magnication and a numerical aperture
(
NA) of 0.25. The excitation wavelength was 785 nm by a cw
3
.2 Analysis of complete catalyst plates
diode laser from Toptica Photonics. Grating was set to 300
grooves per mm and the integration times were 2 s for the pure
sample before and aer catalysis, and 5 s for the sample with
ethanol.
The formation of metal nanoparticles through laser irradiation
without reducing agents present was demonstrated in the
literature for AuNPs from HAuCl in solution. However, for the
4
60
utilized glass support, tests needed to be done in order to
evaluate whether it is possible to obtain a stable and regular
coating with nanoparticles through laser impact on mixtures of
2.5 Catalytic tests
4
Catalytic tests were carried out in a self-constructed testing glass powder and HAuCl . Therefore, pretests on object slides
plant made of Swagelok® stainless-steel tubes, a temperature- were done in areas of 20 ꢀ 60 mm. The obtained coated glasses
controlled glass saturator and a self-designed bypass-ow- exhibit a strong red to deep wine red colour comparable to the
photoreactor. The glass saturator with ethanol was tempered powder obtained by grinding, indicating the formation of gold
to 273 K by an IKA RC2 Basic thermostat in order to evaporate nanoparticles. Also, it can be seen in both cases that the coating
the alcohol as the component to be degraded. A mass ow is regular, which indicates a uniform coating with the nano-
controller for nitrogen (Brooks GF series) with a control unit particles (Fig. 2).
ꢂ1
(
Brooks 0254) was set to 30 mL min , directing the vaporized
The localization of the catalyst particles on the glass surface
ethanol towards the reactor. Before reaching the reactor, is crucial for catalytic applications, in order to enable light
ꢂ1
another mass ow controller for air was set to 300 mL min
.
activation and to be accessible for the reactants in order to
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 30289–30297 | 30291

View Article Online
RSC Advances
Paper
Fig. 1 Left: Photo of samples ground with no metal salt (white powder), and with HAuCl
4
(purple powder). Right: The SEM images of the samples
4
with HAuCl /glass after grinding show a few gold nanoparticles in the bulk (bright structures).
4
Fig. 2 Gold particles laser sintered on the object slides (left image; from left to right: HAuCl with 1–2, 50, 100, 200 and 370 nm porous glass). A
light microscopy close up view with 5ꢀ magnification of the coating structure with gold nanoparticles (right image). Here, the course of the laser
is visible in the red sintered grids with particles and the white non-sintered spaces containing no particles.
induce catalysis of chosen contaminants. SEM images from the peak at 522 nm is typical for 30 nm gold spheres, and at 528 for
61
surface of a slide coated with gold (Fig. 3, le) and the fracture particles with a size of 42 nm. Thus, the Ulbricht sphere
plane of such an object slide (Fig. 3, right) show evidence that measurements support the size found in the SEM images, but
gold nanoparticles of around 30 nm in size are present on the also clarify that the particles must be placed at the glass surface.
surface (visible as bright spherical spots), but are also found
Simulations using Mie-theory revealed a red-shi of the
melted into the glass or in second order pores of sizes up to 3 absorption band of gold nanoparticles from air (520 nm) to
mm (which were apparently formed by the melting of the glass water (545 nm) and to the glass environment (565 nm; Fig. 5).
during the laser sintering process).
When comparing these results with the Ulbricht sphere
Transmission measurements of the different sample object measurements (absorption maxima at 522 and 528 nm; Fig. 4)
slides in an Ulbricht-sphere (Fig. 4) revealed a transmission and knowing that the approximate size of the particles is
minimum (absorption maximum) of 522 nm for the gold around 30 nm, it can be concluded that the obtained particles
samples with porous glass of 1–2, 50, 100 and 200 nm, and of are located on the surface, exposed to air and therefore able to
528 for the sample with 370 nm porous glass. An absorption be activated by light and reachable by contaminant molecules.
Fig. 3 SEM images of gold nanoparticles on a laser sintered glass substrate (top view, left image) and a fracture plane image of an object slide
right image) with gold nanoparticles in pores (blue circle) and on the surface (green circle).
(
30292 | RSC Adv., 2018, 8, 30289–30297
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
RSC Advances
Fig. 4 UV/VIS transmission spectra of AuNP catalysts on different
porous glasses (pore sizes are given on each curve).
Fig. 6 An XRD diffractogram of AuNPs on a layer of porous (200 nm
pore size) glass.
as it was for the object slides with the same glass/metal
precursor mixture in the pretests. This should result in repro-
ducible products. Indeed, we could also see a uniform, brightly
red coloured coating of gold nanoparticles for such a large area.
In total, six plates with a pure gold coating and two with
a bimetallic coating were obtained by this process (Fig. 7). This
technique also allows estimation of the amount of metal
precursor utilized, and therefore the catalyst mass per plate
(Table 1). The plates are denoted regarding the pore size of the
glass used in the grinding process.
Besides the scalability of the process, the costs of the
precursor for the nanoparticles can also be considered as
favorable, as they range from 0.15 V in the case of the 200 nm
porous glass plate B to 0.76 V for the 1–2 nm porous glass with
AuNPs. Through adding more metal precursor to the glass/
metal salt mixture, an increase in the number of catalyst
particles on the support could be achieved easily, however this
consequently results in higher metal salt costs.
Fig. 5 Results from Mie-calculations for the absorption wavelengths
of 80 nm AuNPs in different surrounding media (air, water and glass).
This is also in good agreement with the literature, where similar
shiing effects of gold nanoparticles (20 nm size) embedded in
glass could be obtained by calculations.
62
3.3 Application of catalyst system in heterogeneous catalysis
Besides these UV/VIS measurements using the Ulbricht The obtained catalysts are intended to be used for plasmon
sphere, XRD was utilized to study the particle size using the driven heterogeneous catalysis for waste gas cleaning by
Scherrer equation (Fig. 6, Table S3 ESI†). For the measured degradation of relevant contaminants. In the following experi-
sample containing gold particles with 200 nm porous glass, the ments, the catalytic performance of the constantly irradiated
positions of the (111), (200), (220) and (311) features of mono- catalysts was validated using ethanol as a model contaminant in
crystalline gold nanoparticles are at positions of 2Q ¼ 38.2, the gas phase. In order to investigate the catalytic effect of the
63,64
44.4, 64.6 and 77.6, which is consistent with the literature.
produced catalyst system, tests were carried out in a self-
The calculated crystallite size L resulted in a value of 30 nm for constructed laboratory testing plant (Fig. 8).
this sample, supporting the previous results from Ulbricht-
sphere measurements and from SEM imaging.
The model contaminant ethanol was placed in a glass satu-
rator and vaporized at 273 K, and was carried into the testing
The scaling-up of the production process was demonstrated plant by nitrogen in order to inhibit reactions before passing
by coating of carrier plates matching the test reactor. These the catalyst. Therefore, oxidant air is mixed with the nitrogen/
plates are of a 150 ꢀ 150 mm size with an area of 100 ꢀ 100 mm ethanol gas ow shortly before the reactor. The results of the
in the center of the plate to be coated with the catalytic active degradation tests with the 200 nm catalyst plate B are displayed
material. The coating process was therefore carried out exactly in Fig. 9.
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 30289–30297 | 30293

View Article Online
RSC Advances
Paper
Fig. 7 Catalyst plates with a 150 ꢀ 150 mm size and a coated area of 100 ꢀ 100 mm each. A ¼ 1–2 nm, B ¼ 50 nm, C ¼ 100 nm, D ¼ 200 nm
plate, A, E ¼ 200 nm plate and B, F ¼ 370 nm porous glass.
2
Table 1 Gold precursor costs referring to the mass of each layer of a 100 mm area (HAuCl
October 2016) and the final gold content in the layer
4
-trihydrate, 49.5% Au, 1 g ¼ 85.4 V at Alfa Aesar,
a
Pore size of
glass [nm]
Amount of glass/metal
precursor per layer [mg]
Au content per
layer [as mg HAuCl
Au content in
layer [as mg Au]
4
Costs of HAuCl per
layer [V]
b
4
]
1
5
1
2
3
–2
0
00
00
70
439
288
214
299/87
159
8.91
5.99
4.02
6.07/1.76
3.14
4.41
2.97
1.99
3.00/0.87
1.55
0.76
0.51
0.34
0.52/0.15
0.27
c
a
b
The Au content of the laser-sintered layers relates to the gold content of the glass/metal precursor and its amount used for laser sintering.
Applied amount of the glass/metal precursor for laser sintering. For the samples with glass of 200 nm initial porosity, two plates were
c
obtained (displayed in Fig. 7D and E).
The ethanol peak area measured without light is stable, with the air ow measured by TCD (Fig. 9 top, circles in the blue
the exception of a few outliers (Fig. 9 top, crosses in the blue area). When the light is switched on, a rapid decrease in the
area). The same applies to the peak areas of CO
2
coming from ethanol concentration can be seen along with an increase in
Fig. 8 Setup of the laboratory testing plant.
30294 | RSC Adv., 2018, 8, 30289–30297
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
RSC Advances
Regarding the stability of the catalyst plate, it remained
stable during the entire catalytic process for 720 min and no
change of colour, loss of material, or adsorption of contami-
nants could be detected. Concerning the last point mentioning
adsorption of the model contaminant ethanol on the catalyst,
Raman studies were carried out with the used catalyst plate
before and aer catalysis and with ethanol in order to verify its
Raman shi (Fig. S2, ESI†). The measured peak position of
65,66
ethanol is in good agreement with the literature
and it could
be conrmed that no ethanol was adsorbed onto the catalyst
plate, guaranteeing still accessible gold nanoparticles aer the
catalytic process.
4. Conclusion
In the present studies we could demonstrate an elegant, easy
and inexpensive way to design a heterogeneous catalyst system
on a glass support with different support sizes. The technique
requires only two steps; the production of glass/metal precursor
powders in a mixer ball mill, and the laser sintering of this
material on the glass support with the desired size. Here, we
could show that it is possible to obtain catalysts on supports
with sizes of 20 ꢀ 60 to 100 ꢀ 100 mm with AuNPs as plasmon
catalytic active particles. Through the grinding and laser sin-
tering processes, the porosity of the glasses mixed with the
metal precursors is not preserved, but metal nanoparticles were
formed. The sizes of these particles were usually around 30 nm.
Thus, it seems to be unimportant whether the utilized glass
shows any porosity or which size the pores are, so any kind of
glass seems applicable. A very important aspect of this to
question is if the formed gold nanoparticles are also located on
the glass surface. This could be conrmed, which enables the
established catalyst systems to be used for catalytic
applications.
Fig. 9 Result of the degradation tests with ethanol at a flow rate of 30
mL min for ethanol/nitrogen and 300 mL min for air at a 273 K
ꢂ1
ꢂ1
saturator temperature regarding evolution of ethanol/CO
2
peak areas
formation
(
top) and the percentage of ethanol degradation/CO
bottom).
2
(
CO , indicating ethanol degradation (Fig. 9 top, crosses and
2
circles in the red area, and see also Fig. S1 ESI†). However, aer
around 50 min, the ethanol peak area increases again until it
reaches steady state. In parallel, the CO peak area decreases,
2
and then reaches a plateau (Fig. 9 top, crosses and circles in the
grey area). This behaviour could be due to desorption processes
of ethanol from the catalyst. As the conditioning and
measurements of the initial ethanol concentration without light
are carried out by bypass ow through the reactor with the
catalyst inside, a certain amount of ethanol could adsorb onto
the catalyst surface. When the light is switched on, only the
ethanol arriving in the gas ow is degraded, until the catalyst is
heated up to the extent that the adsorbed ethanol is also
released. This might happen either through the thermal energy
coming from the utilized light source or through plasmon
heating. The outer temperature at the reactor window was
A key issue regarding the utilization of noble metal catalysts
is the costs of such systems, especially for the cost-intensive
metal salts used as particle precursors. Calculating the costs
of our method, we could obtain prices ranging from a few cents
2
up to 0.76 V for HAuCl per 100 cm catalyst area, which is
4
a rather inexpensive approach.
Finally, catalytic tests analyzing the degradation of ethanol
showed that a decrease in ethanol concentration of up to 30% is
possible with the catalyst system displayed. Parallel to the
2
ethanol degradation, CO formation could be measured as the
ꢁ
around 45 C. Later, the catalyst reaches equilibrium of
resulting degradation product. It turned out, however, that the
catalyst requires a certain warm-up time to reach equilibrium of
the ethanol adsorption/desorption and degradation, which
occurs due to thermal energy input or plasmon heating. This
leads to a lowered but stable ethanol degradation of around 5%
adsorption/desorption and degradation, and a stable ethanol
peak area is measured lying beyond the initial ethanol
concentration.
Looking at the degradation of ethanol and the CO
tion by percent (Fig. 9, bottom), an ethanol degradation of up to
0% was achieved along with a CO increase of around 5%.
2
forma-
2
and a CO formation of 2%.
3
2
In conclusion, a novel approach for the fabrication of
a heterogeneous plasmon-driven photocatalyst system is intro-
duced, based on the laser-assisted sintering of a mixture of
ground glass with a metal salt precursor on a glass substrate.
The fabrication process is demonstrated, and the resulting
catalyst areas are characterized as well as successfully tested
using ethanol degradation as a model reaction. The procedure
Aer reaching equilibrium, the ethanol degradation was at
values of around 5% and the CO was around 2%. Along with
2
the degradation rates, it was possible to evaluate the weight
hourly space velocity (WHSV) as a catalytic key gure describing
the reactor system (Table S4, ESI†). In our case, the WHSV could
ꢂ1
be calculated as 5.94 h
.
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 30289–30297 | 30295

View Article Online
RSC Advances
Paper
is easily scalable to larger areas and is quite cost-efficient, rep- 14 M. Brust, M. Walker, D. Bethell, D. J. Schiffrin and
resenting a promising novel approach for heterogeneous
photocatalysis.
R. Whyman, J. Chem. Soc., Chem. Commun., 1994, 801–802.
15 N. G. Bast u´ s, J. Comenge and V. Puntes, Langmuir, 2011, 27,
1
1098–11105.
6 N. R. Jana, L. Gearheart and C. J. Murphy, J. Phys. Chem. B,
001, 105, 4065–4067.
17 B. Nikoobakht and M. A. El-Sayed, Chem. Mater., 2003, 15,
957–1962.
1
Conflicts of interest
2
There are no conicts to declare.
1
1
8 J. P ´e rez-Juste, I. Pastoriza-Santos, L. M. Liz-Marz ´a n and
P. Mulvaney, Coord. Chem. Rev., 2005, 249, 1870–1901.
Acknowledgements
This work was carried out within the project #6 of pades 19 H.-L. Wu, C.-H. Kuo and M. H. Huang, Langmuir, 2010, 26,
Wachstumskern Th u¨ ringen (FKZ 03WKCN06). We thank pades
12307–12313.
Partikeldesign Th u¨ ringen and the BMBF (German Federal 20 M. Thiele, J. Z. E. Soh, A. Knauer, D. Malsch, O. Stranik,
Ministry of Education and Research) for funding this project.
Also we cordially thank Torsten Langer from JENOPTIK
R. M u¨ ller, A. Cs ´a ki, T. Henkel, J. M. K ¨o hler and
W. Fritzsche, Chem. Eng. J., 2016, 288, 432–440.
Automatisierungstechnik GmbH (Jena) and Robert Bischoff 21 P. S. Kumar, I. Pastoriza-Santos, B. Rodr ´ı guez-Gonz ´a lez,
from HEGLA boraident (Halle/Saale). We would also like to
express many thanks to Beate F ¨a hndrich from the Institute of
F. J. Garc ´ı a de Abajo and L. M. Liz-Marz ´a n,
Nanotechnology, 2008, 19, 015606.
Technical Chemistry and Environmental Chemistry, Friedrich- 22 A. Pyatenko, M. Yamaguchi and M. Suzuki, J. Phys. Chem. C,
Schiller-University Jena for BET measurements and Andrea 2007, 111, 7910–7917.
Dellith (Leibniz-Institute of Photonic Technology Jena) for SEM 23 Y. Wan, Z. Guo, X. Jiang, K. Fang, X. Lu, Y. Zhang and N. Gu,
imaging, Christa Schmidt (Leibniz-Institute of Photonic Tech- J. Colloid Interface Sci., 2013, 394, 263–268.
nology Jena) for XRD measurements and Dr Clara Stiebing and 24 Y. Sun and Y. Xia, Science, 2002, 298, 2176–2179.
Dr Jan R u¨ ger (Leibniz-Institute of Photonic Technology Jena) for 25 D. Yu and V. W.-W. Yam, J. Am. Chem. Soc., 2004, 126, 13200–
Raman measurements. We express our special thanks to the
13201.
Open Access Fund of the Leibniz Association for the funding of 26 I. Pastoriza-Santos and L. M. Liz-Marz ´a n, Nano Lett., 2002, 2,
the publication of this article.
903–905.
27 D. Aherne, D. M. Ledwith, M. Gara and J. M. Kelly, Adv. Funct.
Mater., 2008, 18, 2005–2016.
References
2
8 A. Knauer, A. Cs ´a ki, F. M ¨o ller, C. H u¨ hn, W. Fritzsche and
J. M. K ¨o hler, J. Phys. Chem. C, 2012, 116, 9251–9258.
29 T. Teranishi, M. Miyake and M. Hosoe, Adv. Mater., 1997, 9,
65–67.
30 T. S. Ahmadi, Z. L. Wang, A. Henglein and M. A. El-Sayed,
Chem. Mater., 1996, 8, 1161–1163.
31 J. Turkevich and G. Kim, Science, 1970, 169, 873–879.
1
2
3
4
5
6
7
8
9
A. Cs ´a ki, M. Thiele, J. Jatschka, A. Dathe, D. Zopf, O. Stranik
and W. Fritzsche, Eng. Life Sci., 2015, 15, 266–275.
K. A. Willets and R. P. V. Duyne, Annu. Rev. Phys. Chem., 2007,
5
8, 267–297.
S. Szunerits and R. Boukherroub, Chem. Commun., 2012, 48,
999–9010.
8
A. Campion and P. Kambhampati, Chem. Soc. Rev., 1998, 27, 32 T. Teranishi and M. Miyake, Chem. Mater., 1998, 10, 594–
41–250. 600.
K. Kneipp, H. Kneipp, I. Itzkan, R. R. Dasari and M. S. Feld, 33 W. Niu, Z.-Y. Li, L. Shi, X. Liu, H. Li, S. Han, J. Chen and
Chem. Rev., 1999, 99, 2957–2976. G. Xu, Cryst. Growth Des., 2008, 8, 4440–4444.
P. Christopher, H. Xin and S. Linic, Nat. Chem., 2011, 3, 467– 34 S. Sarina, E. R. Waclawik and H. Zhu, Green Chem., 2013, 15,
72.
1814–1833.
R. Narayanan and M. A. El-Sayed, J. Phys. Chem. B, 2005, 109, 35 S. Linic, P. Christopher and D. B. Ingram, Nat. Mater., 2011,
2663–12676.
10, 911–921.
J. R. Adleman, D. A. Boyd, D. G. Goodwin and D. Psaltis, Nano 36 C. Burda, X. Chen, R. Narayanan and M. A. El-Sayed, Chem.
Lett., 2009, 9, 4417–4423. Rev., 2005, 105, 1025–1102.
B. Dong, Y. Fang, X. Chen, H. Xu and M. Sun, Langmuir, 2011, 37 J. Li, E. Saydanzad and U. Thumm, Phys. Rev. A, 2016, 94,
7, 10677–10682. 051401.
0 S. Mukherjee, F. Libisch, N. Large, O. Neumann, L. V. Brown, 38 M. Bernardi, J. Mustafa, J. B. Neaton and S. G. Louie, Nat.
2
4
1
2
1
J. Cheng, J. B. Lassiter, E. A. Carter, P. Nordlander and
N. J. Halas, Nano Lett., 2013, 13, 240–247.
1 G. L. Hallett-Tapley, M. J. Silvero, M. Gonz ´a lez-B ´e jar,
Commun., 2015, 6, 7044.
39 M. Gonzalez-Bejar, K. Peters, G. L. Hallett-Tapley, M. Grenier
and J. C. Scaiano, Chem. Commun., 2013, 49, 1732–1734.
1
M. Grenier, J. C. Netto-Ferreira and J. C. Scaiano, J. Phys. 40 S. Eustis and M. A. El-Sayed, Chem. Soc. Rev., 2006, 35, 209–
Chem. C, 2011, 115, 10784–10790. 217.
2 J. Turkevich, P. C. Stevenson and J. Hillier, Discuss. Faraday 41 T. S. Rodrigues, A. G. M. da Silva, A. B. L. de Moura,
1
1
Soc., 1951, 11, 55–75.
I. G. Freitas and P. H. C. Camargo, RSC Adv., 2016, 6,
62286–62290.
3 G. Frens, Nature (London), Phys. Sci., 1973, 241, 20–22.
30296 | RSC Adv., 2018, 8, 30289–30297
This journal is © The Royal Society of Chemistry 2018

View Article Online
Paper
RSC Advances
4
4
4
2 H. Wu, P. Wang, H. He and Y. Jin, Nano Res., 2012, 5, 135– 55 R. Intartaglia, G. Das, K. Bagga, A. Gopalakrishnan,
1
44.
3 Z. Zheng, T. Tachikawa and T. Majima, J. Am. Chem. Soc.,
015, 137, 948–957.
A. Genovese, M. Povia, E. Di Fabrizio, R. Cingolani,
A. Diaspro and F. Brandi, Phys. Chem. Chem. Phys., 2013,
15, 3075–3082.
2
4 F. Wang, C. Li, H. Chen, R. Jiang, L.-D. Sun, Q. Li, J. Wang, 56 J. Zhang, M. Chaker and D. Ma, J. Colloid Interface Sci., 2017,
J. C. Yu and C.-H. Yan, J. Am. Chem. Soc., 2013, 135, 5588–
601.
5 X. Huang, Y. Li, Y. Chen, H. Zhou, X. Duan and Y. Huang,
489, 138–149.
5
57 S. Mukherjee, L. Zhou, A. M. Goodman, N. Large, C. Ayala-
Orozco, Y. Zhang, P. Nordlander and N. J. Halas, J. Am.
Chem. Soc., 2014, 136, 64–67.
4
4
4
Angew. Chem., 2013, 125, 6179–6183.
6 P. Wang, B. Huang, Y. Dai and M.-H. Whangbo, Phys. Chem. 58 E. Rombi, M. G. Cutrufello, R. Monaci, C. Cannas,
Chem. Phys., 2012, 14, 9813–9825.
D. Gazzoli, B. Onida, M. Pavani and I. Ferino, J. Mol. Catal.
A: Chem., 2015, 404–405, 83–91.
7 Z. Zheng, T. Tachikawa and T. Majima, J. Am. Chem. Soc.,
2
014, 136, 6870–6873.
59 W. Hou, W. H. Hung, P. Pavaskar, A. Goeppert, M. Aykol and
S. B. Cronin, ACS Catal., 2011, 1, 929–936.
4
4
8 C. Wang and D. Astruc, Chem. Soc. Rev., 2014, 43, 7188–7216.
9 S. A. Ansari, M. M. Khan, M. O. Ansari and M. H. Cho, New J. 60 T. Nakamura, J. Mater. Res., 2008, 23, 968–974.
Chem., 2015, 39, 4708–4715.
61 W. Haiss, N. T. Thanh, J. Aveyard and D. G. Fernig, Anal.
Chem., 2007, 79, 4215–4221.
62 V. A. G. Rivera, F. A. Ferri and E. Marega Jr, in Plasmonics –
Principles and Applications, ed. K. Y. Kim, InTech, Rijeka,
2012, ch. 11, DOI: 10.5772/50753.
5
5
5
5
5
0 N. Pugazhenthiran, S. Murugesan, P. Sathishkumar and
S. Anandan, Chem. Eng. J., 2014, 241, 401–409.
1 F. Kim, J. H. Song and P. Yang, J. Am. Chem. Soc., 2002, 124,
14316–14317.
2 Y.-Y. Yu, S.-S. Chang, C.-L. Lee and C. R. C. Wang, J. Phys. 63 S. Krishnamurthy, A. Esterle, N. C. Sharma and S. V. Sahi,
Chem. B, 1997, 101, 6661–6664. Nanoscale Res. Lett., 2014, 9, 627.
3 V. Amendola, S. Polizzi and M. Meneghetti, J. Phys. Chem. B, 64 M. M. H. Khalil, E. H. Ismail and F. El-Magdoub, Arabian J.
006, 110, 7232–7237. Chem., 2012, 5, 431–437.
4 J. Zhang, D. N. Oko, S. Garbarino, R. Imbeault, M. Chaker, 65 B. N. Khlebtsov, Z. Liu, J. Ye and N. G. Khlebtsov, J. Quant.
2
A. C. Tavares, D. Guay and D. Ma, J. Phys. Chem. C, 2012,
16, 13413–13420.
Spectrosc. Radiat. Transfer, 2015, 167, 64–75.
66 Q. Wang, Z. Li, Z. Ma and L. Liang, Sens. Actuators, B, 2014,
1
202, 426–432.
This journal is © The Royal Society of Chemistry 2018
RSC Adv., 2018, 8, 30289–30297 | 30297