Enhanced photoredox chemistry in surface-modified Mg2TiO4 nano-powders with bidentate benzene derivatives

Article abstract of DOI:10.1039/c6ra16284c

Magnesium-orthotitanate (Mg₂TiO₄) nano-powder was synthesized using a Pechini-type polymerized complex route. Microstructural characterization involving transmission electron microscopy, X-ray diffraction analysis and nitrogen adsorption-desorption isotherms indicated that well-crystallized Mg₂TiO₄ nanoparticles are small in size (about 10 nm) with large specific surface area (72 m² g^-1). The surface modification of Mg₂TiO₄ nano-powders with 5-amino salicylic acid and catechol induced a significant shift of absorption to the visible spectral region due to charge transfer complex formation. It should be emphasized that tunable optical properties of Mg₂TiO₄ nano-powders have never been reported in the literature. Degradation reactions of an organic dye (crystal violet) were used to test the photocatalytic ability of pristine and surface-modified Mg₂TiO₄ nano-powders under illumination in different spectral regions. Excitation with UV light indicated, for the first time, photocatalytic ability of Mg₂TiO₄. Also, improved photocatalytic performance of surface-modified Mg₂TiO₄ nano-powders was found in comparison to unmodified ones.

Full text of DOI:10.1039/c6ra16284c

View Article Online
View Journal
RSC Advances
This article can be cited before page numbers have been issued, to do this please use: M. M. Medi, M.
Vasi, A. R. Zarubica, L. V. Trandafilovic, G. Draži, M. Dramianin and J. M. Nedeljkovi, RSC Adv., 2016, DOI:
10.1039/C6RA16284C.
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
Accepted Manuscripts are published online shortly after
acceptance, before technical editing, formatting and proof reading.
Using this free service, authors can make their results available
to the community, in citable form, before we publish the edited
article. This Accepted Manuscript will be replaced by the edited,
formatted and paginated article as soon as this is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes
to the text and/or graphics, which may alter content. The journal’s
standard Terms & Conditions and the Ethical guidelines still
apply. In no event shall the Royal Society of Chemistry be held
responsible for any errors or omissions in this Accepted Manuscript
or any consequences arising from the use of any information it
contains.
www.rsc.org/advances

Please do not adjust margins
RSC Advances
Page 1 of 8
View Article Online
DOI: 10.1039/C6RA16284C
Journal Name
ARTICLE
Enhanced photoredox chemistry in surface-modified Mg2TiO4
nano-powders with bidentate benzene derivatives
Received 00th January 20xx,
Accepted 00th January 20xx
Mina M. Medić,a Marija Vasić,b Aleksandra R. Zarubica,b Lidija V. Trandafilović,a Goran Dražić,c
Miroslav D. Dramićanin,a Jovan M. Nedeljković*a
DOI: 10.1039/x0xx00000x
Magnesium-orthotitanate (Mg2TiO4) nano-powder was synthesized using Pechini-type polymerized complex route.
Microstructural characterization involving transmission electron microscopy, X-ray diffraction analysis and nitrogen
adsorption-desorption isotherms indicated that well-crystallized Mg2TiO4 nanoparticles are small in size (about 10 nm)
with large specific surface area (72 m2/g). The surface modification of Mg2TiO4 nano-powders with 5-amino salicylic acid
and catechol induced significant shift of absorption to the visible spectral region due to charge transfer complex
formation. It should be emphasized that tunable optical properties of Mg2TiO4 nano-powders have never been reported in
the literature. Degradation reactions of organic dye (crystal violet) were used to test photocatalytic ability of pristine and
surface-modified Mg2TiO4 nano-powders under illumination in different spectral regions. Excitation with UV light
indicated, for the first time, photocatalytic ability of Mg2TiO4. Also, improved photocatalytic performance of surface-
www.rsc.org/
modified
Mg2TiO4
nano-powders
was
found
in
comparison
to
unmodified
ones.
powders prepared in the aerosol-assisted processing using
TiO2 colloids as a precursor,19, 20 TiO2 powders prepared using
sol-gel synthetic route, commercial photocatalyst Degussa P25
and commercial sodium trititanate (Na2Ti3O7) nanotubes.21, 22
Although, the main purpose of extending the absorption
spectrum of TiO2 into the red spectral region is usage of less
energetic photons to drive photo-induced reactions, there is a
lack of information concerning photocatalytic performance of
surface-modified TiO2 particles. So far, hydrogen evolution
under visible light illumination of surface-modified TiO2
nanoparticles by catechol and its derivatives has been
demonstrated,23 as well as degradation of organic dye crystal
violet using commercial Degussa P25 powder modified with
catechol.22
Introduction
Photocatalytic reactions are very important in
environmental cleanup and remediation, such as oxidation of
organic materials and reduction of heavy metal ions.1–4 The
efficient solar light utilization of oxide materials is limited by
their large band gap. For example, the most studied
photocatalyst titanium dioxide (TiO2) has the band gap of 3.2
eV, allowing only UV photons (λ<380 nm) to produce electron-
hole pairs and stimulate redox processes on the catalyst
surface. There has been tremendous interest in recent years to
improve visible light absorption of TiO2, including dye
sensitization for photoexcitation of TiO2 in the visible spectral
region via photoinduced interfacial electron transfer,5–7 and
doping with light and heavy elements to promote less
energetic excitations of electrons from mid-gap dopant levels
to conduction band of TiO2.8–10 Another emerging approach
involves a charge transfer from surface modifier into the
conduction band of nanocrystalline TiO2 particles. So far,
charge-transfer complex (CTC) formation between surface Ti
atoms and either catecholate- or salicylate-type of ligands,
accompanied with red shift of absorption onset, has been
reported for colloidal TiO2 nanoparticles,11–18 submicron TiO2
It should be emphasized that the CTC formation has never
been reported in literature for any other material except TiO2.
Also, in comparison with TiO2, photocatalytic ability of
different titanates such as: BaTiO3, SrTiO3, CoTiO3, etc., has not
been studied so extensively.24 In addition, the usage of
Mg2TiO4 for photocatalytic purposes, to the best of our
knowledge, has never been reported in literature.
Magnesium-orthotitanate (Mg2TiO4) is widely used as a
heat resistor, dielectric for microwave technology, capacitor
for temperature compensation and as refractory material.25
Mg2TiO4 has an inverse spinel structure, in which the titanium
atoms occupy octahedral sites and the magnesium atoms
occupy both tetrahedral and octahedral sites. Magnesium-
titanates are usually synthesized by high-temperature solid
state reaction at ~1400°C giving powders with relatively large,
non-uniform particles.26–29 With wet chemical methods
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 2 of 8
View Article Online
DOI: 10.1039/C6RA16284C
ARTICLE
Journal Name
reaction temperatures necessary for Mg2TiO4 formation could transformation of the mixture into a resin-like form. In order
be reduced. Up to now, Mg2TiO4 particles were successfully to obtain black, amorphous precursor mass, the resin was fired
synthesized via a sol-gel, coprecipitation, polymeric precursor at 350°C for 30 min and ground to a powder. Finally, pure
method and peroxide route.25,
30–34
So far, the Mg2TiO4 phase of Mg2TiO4 nano-powder was obtained by calcination at
particles in the nanosize domain were obtained using peroxide 600°C for 1 h, followed by natural furnace cooling to room
route (~40 nm),33 and using Pechini-type polymerized complex temperature.
route (~5 nm).34
Mg2TiO4 is a wide band gap material. Various values of the Surface modification of Mg2TiO4 powders with catechol and 5-
band gap energy, ranging from 3.7 to 4.4 eV, have been amino salicylic acid
reported in literature.35–39 Recently, Mg2TiO4 has been used as
Surface modification of Mg2TiO4 was performed by
a host for fabrication of red emitting phosphors based on the
dispersing 0.5 g of powder in 25 ml of water containing either
substitution of the lattice ions of Mg2TiO4 with rare earth40 or
55.1 mg of CAT or 76.6 mg of 5-ASA; molar ratio between
34
transition metal ions.25,
It has been shown that the
Mg2TiO4 and ligand (CAT or 5-ASA) was 6 : 1. Formation of CTC
was indicated by immediate coloration of dispersion. Mixture
was left overnight and after that surface-modified Mg2TiO4
powder was separated by centrifugation, washed several times
with water / ethanol mixture in order to remove excess
ligands, and finally dried at 40oC in the vacuum oven for 24 h.
absorption onset of Mg2TiO4 doped with Mn4+ is gradually
shifting to the visible spectral region with the increase of the
Mn4+ content.25, 34
In this study, the CTC formation between Mg2TiO4 nano-
powder and catechol (CAT) or 5-amino salicylic acid (5-ASA),
followed with extension of the absorption spectrum into
visible spectral region, was achieved. The ability of Mg2TiO4 to
form hybrids with CAT and 5-ASA showed that CTC formation
is not exclusive for TiO2, but rather general phenomenon
occurring upon proper design of material and adequate choice
of ligands. The chosen modifiers, CAT and 5-ASA, represent
typical catecholate- or salicylate-type of ligands, respectively.
The thorough microstructural characterization (X-ray
diffraction (XRD) analysis, transmission electron microscopy
(TEM) and nitrogen adsorption-desorption isotherms)
indicated that well-crystallized Mg2TiO4 powder is mesoporous
with the average particles size of about 10 nm. For the first
time, ability of pristine Mg2TiO4 nano-powders to induce
photocatalytic degradation of organic molecules was
demonstrated in test reaction with organic dye crystal violet
(CV). Also, photocatalytic ability of surface-modified Mg2TiO4
nano-powders was investigated using light sources with
different spectral profiles, and photocatalytic performance of
unmodified and surface-modified Mg2TiO4 nano-powders was
compared with commercial TiO2 photocatalyst (Degussa P25).
Characterization of Mg2TiO4 powder
X-ray diffraction (XRD) analysis of Mg2TiO4 powder was
performed using Rigaku SmartLab diffractometer. Diffraction
data were recorded in a 2θ range from 15 to 120°, counting
0.7 °/min in 0.02° steps.
The size, morphology and crystallinity of nanoparticles
were studied by high-resolution transmission electron
microscopy (HRTEM), a 200 kV Cs-probe-corrected cold-field-
emission transmission electron microscope (Jeol ARM 200 CF),
coupled with an energy-dispersive X-ray spectroscopy system
(Jeol Centurio 100 mm2). Samples were dispersed in ethanol
and placed on a copper lacy-carbon grid.
Nitrogen adsorption-desorption isotherms on Mg2TiO4
samples were determined using Sorptomatic 1990 Thermo
Finnigan automatic system at -196°C. Specific surface area of
the samples was calculated from the nitrogen adsorption-
desorption isotherms according to the Brunauer, Emmett and
Teller (BET) method.42 Pore size distribution was estimated by
applying Barret, Joyner and Halenda (BJH) method43 to the
adsorption branch of isotherm.
Optical properties of Mg2TiO4 powder, as well as surface-
modified Mg2TiO4 powders with CAT and 5-ASA were studied
in UV-Vis spectral range by using diffuse reflectance
measurements (Thermo Evolution 600 spectrophotometer
equipped with Labsphere RSA-PE-19).
Experimental
Mg2TiO4 nano-powders were synthesized using Pechini-
type polymerized complex route, described elsewhere.41
Briefly, molar ratio between precursors: titanium(IV)-
isopropoxide, magnesium(II)-nitrate, citric acid and ethylene
glycol was 1:2:5:20. In the first step, titanium(IV)-isopropoxide
(Alfa Aesar, 97%) was dissolved in ethylene glycol (Lach-Ner,
99%) under constant magnetic stirring. Then, citric acid
(Kemika, 99.5%) was added to the solutions under continuous
stirring until complete dissolution. Appropriate amount of
MgO (Alfa Aesar, 96%) was separately dissolved in hot,
concentrated nitric acid, evaporated to dryness, and added to
the titanium(IV)-isopropoxide / ethylene glycol / citric acid
mixture. After that, mixture was stirred for 1h at 60°C until it
became transparent. Further heating at 130°C (3 h) promoted
polymerization, removal of excess solvents, and subsequent
Diffuse reflectance infrared spectra of Mg2TiO4 nano-
powder, CAT and 5-ASA, as well as surface-modified Mg2TiO4
nano-powders with CAT and 5-ASA were measured using a
Thermo Nicolet 6700 FTIR spectrometer with a Collector II
Diffuse Reflectance Accessory at spectral resolution of 8 cm-1
in the region of 4000 – 400 cm-1.
Photocatalytic degradation of crystal violet
Photocatalytic ability of Mg2TiO4 powder, as well as
surface-modified Mg2TiO4 powders with CAT and 5-ASA was
studied using the organic dye crystal violet (CV) as model
system. The photocatalytic reactions were induced using UV
2 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 3 of 8
View Article Online
DOI: 10.1039/C6RA16284C
Journal Name
ARTICLE
lamps (Roth Co., 16 W, 2.5 mW/cm2) that have maxima of light
emission at 254 and 366 nm. Also, photocatalytic performance
of surface-modified Mg2TiO4 powders with CAT and 5-ASA was
studied using visible light illumination (14 W LED pseudo-white
lamp with emission from 470 to 700 nm). The rates of
photocatalytic degradation of CV were followed for different
initial concentrations in the 5.0 – 10.0 μM range. In order to
test the performance of the photocatalysts under long run
working conditions, the photocatalytic degradation of organic
dyes was studied in repeated cycles. The acidity of the
solutions was not adjusted and pH values were in the range of
6.7 – 7.0. In order to compare photocatalytic performance of
bare Mg2TiO4 powder and surface-modified Mg2TiO4 powders
with TiO2, photocatalytic experiments, under the same
experimental conditions, were performed using commercially
available Degussa P25 photocatalyst. Initial concentration of
organic dye, as well as its decrease during photodegradation
reactions were determined by measuring absorption at the
peak position of CV (λmax = 590 nm; ε590 = 8.7x104 M-1cm-1).
Fig. 2. TEM data from Mg2TiO4: (a) HRTEM image of Mg2TiO4 powder, and (c)
corresponding SAED pattern. Reconstruction of the Mg2TiO4 nanocrystals’ three-
dimensional shape from the experimental HRTEM images: (a) Experimental
HRTEM image with the labelled area used in the reconstruction. Inset is a FFT-
filtered area with nanoparticles in the [01-1] zone axis. Contours indicate a
cuboctahedron morphology. (b) Schematic drawing of a cuboctahedron in the
[01-1] orientation with labelled surface planes.
Uniform, relatively sharp rings with visible individual spots
in the selected-area electron diffraction (SAED) pattern (Fig.
2(c)) corresponded to Mg2TiO4 (Fd3-mS) spinel structure and is
characteristic of randomly oriented, roughly 10 nm sized
particles. No other crystalline phase was detected with SAED.
Examining the terminal planes of the nanoparticles, the
presence of substantial amorphous phase was not found at the
crystals. From the HRTEM images and the orientation of the
particles obtained from SAED, we were able to reconstruct
particles obtained from SAED, we were able to reconstruct
their three-dimensional shape. The Mg2TiO4 nano-particles
have an equant-to-blocky crystal habit, and some of the
studied particles were found to form cuboctahedrons (Fig.
2(b)).
Results and discussion
Microstructural characterization of Mg2TiO4 nano-powder
The XRD pattern of Mg2TiO4 powder, thermally treated at
600°C for 1 h, is shown in Fig. 1. The characteristic, intense
peaks at 18.2, 29.9, 35.2, 42.8, 56.6 and 62.1 degrees
correspond to (1 1 1), (2 2 0), (3 1 1), (4 0 0), (5 1 1) and (4 4 0)
Bragg reflection from Mg2TiO4 (ICDD 01-076-6968). It should
be mentioned that there is no indication of the presence of
any other crystalline phase. A grain size of 52 Å is determined
from the peak broadening and Scherrer’s equation.
A representative TEM image at high-magnification of
Mg2TiO4 powder is shown in Fig. 2(a). Detailed inspection of
the sample indicated that Mg2TiO4 powder consists of
nanoparticles with the average size of about 10 nm, loosely
agglomerated into micron-size particles. Thus, the grain size
given by the XRD measurements is in agreement with the size
of nanoparticles by TEM analysis of Mg2TiO4 powder.
Nitrogen adsorption-desorption isotherm of synthesized
Mg2TiO4 samples is shown in Fig. 3(a). According to the IUPAC
classification, isotherm of Mg2TiO4 powder belongs to type IV
with a hysteresis loop associated to mesoporous materials.
The shape of hysteresis loop is of type H2 which indicates a
poorly defined shape of pores. Specific surface area calculated
by BET method42 was found to be 72 m2g-1. It should be
noticed that specific surface area of synthesized Mg2TiO4
powder is higher compared to commonly used commercial
Degussa P25 TiO2 photocatalyst (50 m2g-1).44 Pore size
distribution of Mg2TiO4 powder is shown in Fig. 3(b). It is clear
that sample is mesoporous, and estimated pore radius by
applying BJH method43 to desorption branch of isotherm was
found to be in the size range 2 – 4 nm, and with bimodal pore
size distribution.
Fig. 1. XRD pattern of Mg2TiO4 powder with corresponding identification card.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 4 of 8
View Article Online
DOI: 10.1039/C6RA16284C
ARTICLE
Journal Name
Fig. 3. (a) Nitrogen adsorption-desorption isotherms of Mg2TiO4 powder, and (b) pore size distribution.
Optical properties of surface-modified Mg2TiO4 powders
powders are presented as inset to Fig. 4. In the case of
unmodified Mg2TiO4 nano-powder, steep rise of absorption
can be observed in UV spectral range bellow 350 nm (Fig. 4,
curve a), corresponding to the band gap energy of 3.55 eV.
This result is in agreement with a literature data for the band
gap energy of Mg2TiO4.39 On the other hand, significant red
shift of optical absorption can be observed for surface-
modified Mg2TiO4 powders with 5-ASA and CAT (curves b and c
in Fig. 4, respectively).Due to an increased background
absorption ranging from 400 to 800 nm, it is difficult to
determine the values for absorption onset upon surface
modification of Mg2TiO4 powders. But, the red absorption shift
due to CTC formation with either 5-ASA or CAT is roughly
estimated to be at least 1.9 eV.
When materials are nano-sized, a large fraction of the
atoms is located at the surface, and these atoms alter
materials electrochemical properties. Due to large curvature of
the nanoparticles surface atoms can be considered as defect
sites with enhanced ability to accommodate/bind solutes from
surrounding media. To test ability of Mg2TiO4 nano-powders to
form CTCs with bidentate benzene derivatives, simple
molecules 5-ASA and CAT, capable of salicylate- and
catecholate-type of bonding, respectively, were chosen.
Immediate coloration upon treatment of Mg2TiO4 nano-
powders with 5-ASA and CAT indicated red shift in the
absorption onset of surface-modified Mg2TiO4 nano-powders
compared to the unmodified ones. Kubelka–Munk
transformations of UV-Vis diffuse reflection data of
unmodified Mg2TiO4 powder and surface-modified Mg2TiO4
powder with 5-ASA and CAT are shown in Fig. 4. Also,
photographs of unmodified and surface-modified Mg2TiO4
Optical properties of these hybrids arise from the ligand-
to-metal charge transfer interaction coupled with electronic
properties of the core of Mg2TiO4 nanoparticle.
Fig. 4. Kubelka–Munk transformations of UV-Vis diffuse reflection data of unmodified Mg2TiO4 powder (a), and surface-modified Mg2TiO4 powder with 5-ASA (b) and CAT (c);
corresponding photographs are given as inset.
4 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 5 of 8
View Article Online
DOI: 10.1039/C6RA16284C
Journal Name
ARTICLE
So far, the CTC formation between surface atoms and surface-
active ligands, accompanied with red shift of the onset of
optical absorption, has been reported for the nanocrystalline
TiO2 particles45 with square-pyramidal coordination of surface
12
Ti atoms instead of octahedral.11,
Recently, it has been
shown that CTC formation takes place between commercial
TiO2 powder (Degussa P25) and bidentate benzene
derivatives.21 The surface modification of Mg2TiO4 nano-
powder with CAT and 5-ASA indicates that CTC formation is
not exclusive of TiO2, but has general character when proper
conditions are satisfied; the most important are the size of
oxide material and the choice of ligand. It should be kept in
mind that 5-ASA and CAT are representatives of two classes of
molecules that contain different functionalities, and in this
study serve to provide information whether or not two
different types of binding (salycilate- and catecholate-type)
lead to the formation of CTCs with Mg2TiO4 nano-powder. Fine
tuning of optical properties using these types of molecules by
introducing electron donating or electron withdrawing
functional groups and/or by extending aromatic ring system is
completely open for further studies.
Fig. 5. Degradation kinetic of CV over pristine Mg2TiO4 nano-powder as
a
function of initial concentration of organic dye: 5.0, 7.5 and 10.0 μM;
illumination light at 254 nm.
The attempt was made to understand the way ligands bind
to Mg2TiO4 surface using FTIR spectroscopy. The infrared
spectra of calcined Mg2TiO4 at 600°C,40 as well as free 5-
ASA46,47 and free CAT48–50 are well-known. Complete
disappearance of all vibration bands for both ligands was
observed upon their adsorption onto Mg2TiO4 powder (spectra
are not shown). It can be concluded that more sophisticated
techniques should be employed in order to understand surface
structure of these hybrids.
the best of our knowledge, so far, photocatalytic ability of
Mg2TiO4 has never been reported in the literature.
Photocatalytic performances of unmodified and surface-
modified Mg2TiO4 nano-powders with 5-ASA and CAT were
compared with the most studied TiO2 photocatalyst Degussa
P25 using two UV light sources with different spectral profiles.
Photocatalytic degradation kinetics for 7.5 μM initial
concentration of CV, obtained using UV light sources with
emission maxima at 254 and 366 nm are shown in Fig. 6 ((a)
and (b), respectively), while corresponding pseudo-first-order
rate constants are collected in Table 1. Based on the kinetic
data, some general features can be recognized. First,
degradation kinetics of CV is significantly faster over Degussa
P25 in comparison with unmodified Mg2TiO4 nano-powders
under UV light. Second, degradation rate constants of CV over
Degussa P25 and unmodified Mg2TiO4 nano-powder were
significantly reduced (almost twice) when UV light with
emission maximum at 366 nm is used for illumination instead
of UV light with emission maximum at 254 nm. These results
can be easily explained by the band gap energies of both
materials (3.2 and 3.55 eV for TiO2 and Mg2TiO4, respectively).
Third, the degradation kinetics of CV is significantly faster over
in comparison to unmodified Mg2TiO4. Fourth, only moderate
Photocatalytic performances of unmodified and surface-modified
Mg2TiO4 nano-powders
Photocatalytic ability of Mg2TiO4 nano-powders was tested
in degradation reaction of the organic dye crystal violet (CV).
The organic dye CV was chosen for this purpose because direct
photolysis does not induce its degradation. The comparison
between kinetics of photocatalytic degradation of CV for
different initial concentrations over pristine Mg2TiO4 nano-
powder is shown in Fig. 5. Complete decolorization of organic
dye with the lowest initial concentration was achieved after 24
h of exposure to light with emission maxima at 254 nm (Fig. 5,
curve I). Photocatalytic degradation of organic dyes follows
Langmuir-Hinshelwood kinetics, which for very low
concentrations of polluters simplifies to pseudo-first-order
kinetic behaviour. The decrease of rate constants (0.096, 0.062
and 0.047 h-1) was found with the increase of the initial
concentration of CV (5.0, 7.5 and 10.0 μM, respectively). To
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 5
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 6 of 8
View Article Online
DOI: 10.1039/C6RA16284C
ARTICLE
Journal Name
Fig. 6. Degradation kinetic of CV with initial concentration of 7.5 μM over pristine Mg2TiO4 nano-powder (I), surface-modified Mg2TiO4 nano-powder with CAT (II)
surface-modified Mg2TiO4 nano-powder with 5-ASA (III), and commercial TiO2 Degussa P25 powder (IV) under UV light with emission maxima at 254 nm (a) and 366
nm (b).
decrease of degradation rate constants of CV was observed for photons to drive photo-induced reactions, preliminary
both surface–modified Mg2TiO4 nano-powders when instead measurements were performed using LED pseudo-white lamp
of lamp with emission maximum at 254 nm was used lamp with emission in visible spectral range (emission range from
with emission maximum at 366 nm. This result is in agreement 470 to 600 nm). Unfortunately, the obtained results were not
with data concerning photocatalytic performance of surface- conclusive results, and we can’t claim that surface-modified
modified TiO2 capable to induce hydrogen evolution23 or to Mg2TiO4 nano-powders photocatalytically perform under
induce degradation of CV22 under visible light illumination.
In order to test the photocatalytic ability of surface-
modified Mg2TiO4, nano-powders under long run working
conditions, the degradation of CV was ascertained in repeated
cycles without the photocatalyst being subject to any cleaning
treatments. The comparison of subsequent degradation kinetic
curves for CV (results are not shown) indicated that
photocatalytic ability of surface-modified Mg2TiO4, nano-
powders is not significantly diminished under long run working
conditions. Also, spectral features of used photocatalysts were
identical to the unused ones.
visible light illumination.
Conclusions
We have demonstrated ability of Mg2TiO4 nano-powders to
form charge transfer complexes with 5-amino salicylic acid and
catechol, representatives of two classes of ligands that contain
different functionalities. For the first time, with exception of
TiO2, it has been shown that absorption spectrum of oxide
material can be extended into the red spectral region, making
Mg2TiO4 functional over a more practical range of solar
spectrum. So far, the Mg2TiO4 has never been considered as
photocatalytic material. Capability of mesoporous Mg2TiO4
Having in mind that the main purpose of extending the
absorption spectrum of Mg2TiO4 nano-powder into the more
practical visible spectral range is usage of less energetic
nano-powders
demonstrated using degradation of the organic dye crystal
violet as test reaction. Also, improved photocatalytic
to
perform
photocatalytically
was
Table 1. The pseudo-first-order rate constants (h-1) for photocatalytic degradation
reaction of 7.5 μM CV over unmodified and surface-modified Mg2TiO4 nano-powders,
as well as commercial TiO2 (Degussa P25) using light sources with emission maxima at
254 and 366 nm
a
performance of surface-modified Mg2TiO4 nano-powders with
both ligands was observed in comparison to unmodified ones.
It is clear that presented results are in embryonic stage, but,
we believe that introduction of new material whose optical
properties can be tuned by using different types of surface
active molecules opens-up possibility to extend not only
fundamental, but, also, applicable aspects of this type of
research.
k (h-1)
Photocatalyst
254 nm
0.062
0.272
0.215
0.458
366 nm
0.035
0.223
0.178
0.290
Mg2TiO4
Mg2TiO4/5-ASA
Mg2TiO4/CAT
TiO2 (Degussa P25)
6 | J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Please do not adjust margins
RSC Advances
Page 7 of 8
View Article Online
DOI: 10.1039/C6RA16284C
Journal Name
ARTICLE
26 D. M. Flot, J. T. S. Irvine, Sol. State. Ion., 2000, 135, 513–518.
27 A. K. Singh, T. D. Senguttuvan, A. M. Siddiqui, Int. J. Adv. Res.
Sci. Technol., 2013, 2, 95–97.
28 M. Isobe, Y. Ueda, J. Alloy. Compd., 2004, 383, 85–88.
29 A. K. Singh, R. Kumar, T. D. Senguttuvan, A. M. Siddiqui, AIP
Conf. Proc., 2011, 1393, 235–236.
Acknowledgements
This work was supported by the Ministry of Education,
Science and Technological Development of the Republic of
Serbia (Project 45020).
30 H. Kominami, M. Tanaka, K. Hara, Y. Nakanishi, Y. Hatanaka,
Phys. Status. Solidi. C, 2006, 3, 2758–2761.
31 M. R. S. Silva, S.C. Souza, I. M. G. Santos, M. R. Cassia-Santos,
L. E. B. Soledade, A. G. Souza, S. J. G. Lima, E. Longo, J.
Therm. Anal. Calorim., 2005, 79, 421–424.
32 M. J. Martínez-Lope, M. P. Baura-Peña, M. E. Garíca-Clavel,
Thermochim. Acta., 1992, 194, 59–65.
33 G. Pfaff, Ceram. Int., 1994, 20, 111–116.
34 M. Medić, M. Brik, G. Dražić, Ž. Antić, V. Lojpur, M. D.
Dramićanin, J. Phys. Chem. C, 2015, 119, 724–730.
Notes and references
1
2
3
4
5
6
7
M. Hoffman, S. Martin, W. Choi, D. Bahnemann, Chem. Rev.,
1995, 95, 69–96.
U. Stafford, K. A. Gray, P. V.Kamat, Heterogen. Chem. Rev.,
1996, 3, 77–104.
T. Rajh, A. E. Ostafin, O. I. Mićić, D. M. Tiede, M. C.
Thurnauer, J. Phys. Chem., 1996, 100, 4538–4545.
F. Forouzan, T. C. Richards, A. J. Bard, J. Phys. Chem., 1996,
100, 18123–18127.
I. Martini, J. Hodak, G. V. Hartland, P. V. Kamat, J. Chem.
Phys., 1997, 107, 8064–8072.
S. Y. Huang, G. Schlichthörl, A. J. Nozik, M. Grätzel, A. J.
Frank, J. Phys. Chem. B, 1997, 101, 2576–2582.
R. J. Ellingson, J. B. Asbury, S. Ferrere, H. N. Ghosh, J. R.
35 J. Stade, D. Hahn, R. Dittmann, J. Lumin., 1974,
36 H. Kominami, M. Tanaka, K. Hara, Y. Nakanishi, Y. Hatanaka,
Phys. Status. Solidi. C, 2006, , 2758–2761.
8, 308–317.
3
37 A. Golubovic, M. Radovic, J. Serb. Chem. Soc., 2011, 76
1561–1566.
,
38 Y. Qu, W. Zhou, Y. Xie, L. Jiang, J. Wang, G. Tian, Z. Ren, C.
Tian, H. Fu, Chem. Comm., 2013, 49, 8510–8512.
Sprague, T. Lian, A. J. Nozik, J. Phys. Chem. B, 1998, 102
6455–6458.
,
39 Y. D. Ho, C. H. Su, C. L. Huang, J. Am. Ceram. Soc., 2014, 97
358–360.
,
8
9
E. Barborini, A. M. Cont, I. Kholmanov, P. Piseri, A. Podesta,
P. Milani, C. Cepek, O. Sakho, R. Macovez, M. Sancrotti, Adv.
Mater., 2005, 17, 1842–1846.
M. Chiodi, C. P. Cheney, P. Vilmercati, E. Cavaliere, N.
Mannella, H. H. Weitering, L. Gavioli, J. Phys. Chem. C, 2012,
116, 311–318.
40 M. Medić, Ž. Antić, V. Đorđević, P. S. Ahrenkiel, M.
,
Marinović-Cincović, M. D. Dramićanin, J. Lumin., 2016, 170
679–685.
41 M. Kakihana, M. M. Milanova, M. Arima, T. Okubo, M.
Yashima, M. Yoshimura, J. Am. Ceram. Soc., 1996, 79, 1673–
1676.
42 S. Brunauer, P. H. Emmett, E. Teller, J. Am. Chem. Soc. 1938,
60, 309–319.
10 M. V. Dozz, E. Selli, J. Photochem. Photobiol. C, 2013, 14, 13–
28.
11 T. Rajh, J. M. Nedeljković, L. X. Chen, O. Poluektov, M. C.
Thurnauer, J. Phys. Chem. B, 1999, 103, 3515–3519.
12 L . X. Chen, T. Rajh, W. Jäger, J. Nedeljković, M. C. Thurnauer,
43 E. P. Barret, L. G. Joyner, P. P. Halenda, J. Am. Chem. Soc.,
1951, 73, 373–380.
44 C. B. Almquist, P. Biswas, J. Catal., 2002, 212, 145–156.
45 T. Rajh, N. M. Dimitrijevic, M. Bissonnette, T. Koritarov, V.
Konda, Chem. Rev., 2014, 114, 10177–10216.
46 Y. C. Panicker, H. T. Varghese, A. John, D. Philip, K. Istvan, G.
Keresztury, Spectrochim. Acta. A, 2002, 58, 281–287.
47 K. Zou, H. Zhang, X. Duan, Chem. Eng. Sci., 2007, 62, 2022–
2031.
48 P. A. Connor, K. D. Dobson, A. J. McQuillan, Langmuir., 1995,
11, 4193–4195.
49 P. Z. Araujo, C. B. Mendive, L. A. Garcia Rodenas, P. J.
Morando, A. E. Regazzoni, M. A. Blesa, D. Bahnemann,
Colloid. Surf. A, 2005, 265, 73–80.
J. Synchrotron. Rad., 1999, 6, 445–447.
13 I. A. Janković, Z. V. Šaponjić, M. I. Čomor, J. M . Nedeljković,
J. Phys. Chem. C, 2009, 113, 12645–12652.
14 I. A. Janković, Z. V. Šaponjić, E. S. Džunuzović, J. M.
Nedeljković, Nanoscale. Res. Lett., 2010,
15 T. D. Savić, I. A. Janković, Z. V. Šaponjić, M. I. Čomor, D. Ž.
Veljković, S. D. Zarić, J. M. Nedeljković, Nanoscale., 2012, 4,
1612–1619.
16 T. D. Savić, Z. V. Šaponjić, M. I. Čomor, J. M. Nedeljković, M.
D. Dramićanin, M. G. Nikolić, D. Ž. Veljković, S. D. Zarić, I. A.
Janković, Nanoscale., 2013, 5, 7601–7612.
5, 81–88.
17 T. D. Savić, M. I. Čomor, J. M. Nedeljković, D. Ž. Veljković, S.
D. Zarić, V. M. Rakić, I. A. Janković, Phys. Chem. Chem. Phys.,
2014, 16, 20796–20805.
50 P. Z. Araujo, P. J. Morando, M. A. Blesa, Langmuir., 2005, 21
3470–3474.
,
18 T. D. Savić, M. I. Čomor, N. D. Abazović, Z. V. Šaponjić, M.T.
Marinović-Cincović, D. Ž. Veljković, S. D. Zarić, I. A. Janković,
J. Alloy. Compd., 2015, 630, 226–235.
19 I. M. Dugandžić, D. J. Jovanović, L. T. Mančić, N. Zheng, S. P.
Ahrenkiel, O. B. Milošević, Z. V. Šaponjić, J. M. Nedeljković, J.
Nanopart. Res., 2012, 14, 1157–1167.
20 I. M. Dugandžić, D. J. Jovanović, L. T. Mančić, O. B. Milošević,
S. P. Ahrenkiel, Z. V. Šaponjić, J. M. Nedeljković, Mater.
Chem. Phys., 2013, 143, 233–239.
21 B. Milićević, V. Đorđević, D. Lončarević, S. P. Ahrenkiel, M. D.
Dramićanin, J. M. Nedeljković, Micropor. Mesopor. Mat.,
2015, 217, 184–189.
22 D. Jaušovec, M. Božič, J. Kovač, J. Štrancar, V. Kokol, J.
Colloid. Interf. Sci., 2015, 438, 277–290.
23 S. Higashimoto, T. Nishi, M. Yasukawa, M. Azuma, Y. Sakata,
H. Kobayashi, J. Catal., 2015, 329, 286–290.
24 P. Kanhere, Z. Chen, Molecules., 2014, 19, 19995–20022.
25 T. Ye, S. Li, X. Wu, M. Xu, X. Wei, K. Wang, H. Bao, J. Wang, J.
Chen, J. Mater. Chem. C, 2013, 1, 4327–4333.
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 7
Please do not adjust margins

RSC Advances
Page 8 of 8
View Article Online
DOI: 10.1039/C6RA16284C
28x10mm (300 x 300 DPI)