Hydrothermal synthesis, characterization and enhanced photocatalytic activity and toxicity studies of a rhombohedral Fe2O3 nanomaterial

Article abstract of DOI:10.1039/c9ra04978a

The present investigation focuses on the synthesis of metal oxide nanoparticles (MONPs) via a facile hydrothermal route. The material has been characterized by using X-ray diffractometry (XRD), X-ray fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), high resolution transmission electron microscopy (HR-TEM), energy dispersive spectroscopy (EDS), photoluminescence (PL), atomic force microscopy (AFM) and Brunauer-Emmett-Teller (BET) techniques. However, the application of Fe₂O₃ metal oxide nanoparticles (MONPs) tied with their inimitable chemical and physical nature is thought to emphasize their exploitable medical and biological applications nowadays. Rhodamine-B (RB) was used for photocatalytic degradation studies by using rhombohedral Fe₂O₃, afterwards the material was recycled and utilized for toxicity assessments. Undeniably, a meticulous assessment is needed of the factors that influence the biocompatibility and is essential for the safe and sustainable development of the emerging chemically synthesized metal oxide nanoparticle (MONPs). The toxicity assessment of Fe₂O₃ is necessary to know the bioaccumulation and local or systemic toxicity associated to them. The aim of the present study is to investigate the effects of Fe₂O₃ and its histological alterations of the heart tissue of albino Wistar rat. The synthesized materials high dose was found to be highly stable and we found more toxicity against the skin melanoma cells (B16-F10), human embryonic kidney (HEK), 293 cells depending on dose. Finally, Escherichia coli, (MTCC 7410) bacterial cell wall damage studies were also conducted to provide a clear determination of rhombohedral nanomaterial behaviour. The fusion of these biocompatibility investigations paves a way for further applications in utilization of these materials in future eco-friendly applications.

Full text of DOI:10.1039/c9ra04978a

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Hydrothermal synthesis, characterization and
enhanced photocatalytic activity and toxicity
Cite this: RSC Adv., 2019, 9, 25158
studies of a rhombohedral Fe2O3 nanomaterial†
a
Mavinakere Ramesh Abhilash,
Akshatha Gangadhar,ab Jagadish Krishnegowda,ab
c
ab
*
Mahendra Chikkamadaiah and Shivanna Srikantaswamy
The present investigation focuses on the synthesis of metal oxide nanoparticles (MONPs) via a facile
hydrothermal route. The material has been characterized by using X-ray diffractometry (XRD), X-ray
fluorescence (XRF), Fourier-transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), high
resolution transmission electron microscopy (HR-TEM), energy dispersive spectroscopy (EDS),
photoluminescence (PL), atomic force microscopy (AFM) and Brunauer–Emmett–Teller (BET)
techniques. However, the application of Fe2O3 metal oxide nanoparticles (MONPs) tied with their
inimitable chemical and physical nature is thought to emphasize their exploitable medical and biological
applications nowadays. Rhodamine-B (RB) was used for photocatalytic degradation studies by using
rhombohedral Fe2O3, afterwards the material was recycled and utilized for toxicity assessments.
Undeniably, a meticulous assessment is needed of the factors that influence the biocompatibility and is
essential for the safe and sustainable development of the emerging chemically synthesized metal oxide
nanoparticle (MONPs). The toxicity assessment of Fe2O3 is necessary to know the bioaccumulation and
local or systemic toxicity associated to them. The aim of the present study is to investigate the effects of
Fe2O3 and its histological alterations of the heart tissue of albino Wistar rat. The synthesized materials
high dose was found to be highly stable and we found more toxicity against the skin melanoma cells
(B16-F10), human embryonic kidney (HEK), 293 cells depending on dose. Finally, Escherichia coli, (MTCC
7410) bacterial cell wall damage studies were also conducted to provide a clear determination of
rhombohedral nanomaterial behaviour. The fusion of these biocompatibility investigations paves a way
for further applications in utilization of these materials in future eco-friendly applications.
Received 1st July 2019
Accepted 2nd August 2019
DOI: 10.1039/c9ra04978a
rsc.li/rsc-advances
applications of Fe2O3 metal oxide nanoparticle (MONPs) are
wider than others due to biocompatibility nature, high stability
1 Introduction
and ease of use and have a more applications in drug
delivery.10,11 Metal oxide photocatalysis is an enthralling appli-
cation tool for solar energy conversion and dye degradation due
to its prominent nature.12 Because of widespread application of
these particles in various industries human exposition to them
increased, so investigation of this nanoparticle role in cell
growth and survival has more importance.13 Iron oxide is the
most stable under ambient conditions to perform various
applications with environment friendly label with a band gap of
2.1 eV with tuneable nature,14–16 there are many methods used
for the synthesis of Fe2O3 metal oxide nanoparticle (MONPs)
like sol–gel method,17 hydrothermal and solvothermal
synthesis,14 thermal breakdown,18 and sonochemical
synthesis,19 have been used for synthesis of Fe2O3 with different
morphologies and concerned nanostructures. Human skin,
heart, lungs and digestive system are the most common entry
routes for nanoparticles and its pathogenicity.20 The airborne
nanoparticles have high mobility and can be inhaled into the
respiratory system easily.21 One of the most common damaging
There is a growing interest about the strong associations
between exposure to nanoparticles and adverse health effects in
humans.1 For this strong reason, environmental contamination
by nanoparticles is attracting considerable and increasing
global concern.2–5 The behaviour and toxicity of particles mainly
comes from studies on orally administrated MONPs.6,7 (MONPs)
may differ in reactivity and solubility and may interact with all
kinds of endogenous proteins, lipids, polysaccharides and cells
and series of tests were anticipated for systematic evaluation of
the toxicity of (MONPs) used in drug delivery systems.8,9 Medical
aDepartment of Studies in Environmental Science, University of Mysore,
Manasagangotri, Mysore 570006, India. E-mail: srikantas@hotmail.com; abhilash@
envsci.uni-mysore.ac.in
bCentre for Materials Science and Technology, Vijnana Bhavan, University of Mysore,
Manasagangotri, Mysore 570006, India
cDepartment of Studies in Botany, University of Mysore, Manasagangotri, Mysore
570006, India
† Electronic supplementary information (ESI) available. See DOI:
10.1039/c9ra04978a
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effects of nanoparticles are rise of reactive oxygen species (ROS)
that refer to oxidative stress in human and animal tissues. It's
conrmed that almost all of the studied nanoparticle produce
reactive oxygen species and it is the main mechanism for
nanoparticle toxicity that can lead to inammation and
apoptosis.22 The unique properties and interactions between
nanomaterials with biological system are essential.23,24 Cell line
toxicity of human cell lines by using several synthesized metal
oxides are more attractive in understanding the relationship
between nanoparticle–cell interaction as well as in biocompat-
ibility studies.25,26 Furthermore, biocompatibility must be con-
ducted with particular focus on the environment in which the
nanomaterial will be placed in.27 Size, shape, and morphology
of nanoparticles, play a vital role in mammalian cell culture
medium and the nanoparticle are much more toxic than the
hydrothermally synthesized nanocomposite semiconductor.28
The drug delivery, evaluation of metal oxide nanomaterial
biocompatibility is essential to secure drug release with low
cytotoxicity.29,30 The biocompatibility evaluation of structured
nanoparticles for drug delivery applications has been expanded
from being primarily investigated in a laboratory setting to
being applied in the multi-billion-dollar pharmaceutical
industry.31–34 The rhombohedral Fe2O3 (MONPs) are effectively
utilized for degradation of rhodamine-B (RB-B) degradation
process nanomaterial was successfully recycled and utilized for
toxicity assessment potentials. Aer the degradation studies, it
is a researcher duty to assess the toxicity of material before
releasing to environmental systems, in the point of view, we
have successfully conducted the in vivo consequences of oral
administration and histological characterization of the heart
tissues due to Fe2O3 (MONPs) has not been documented and
identied before and attempt has been made to characterize the
possible histological alterations in the heart tissues aer oral
administration of (MONPs). Additionally, we have focused on
exploiting and utilizing Fe2O3 for biocompatibility studies of
heart tissue of albino Wistar rat and melanoma cells (B16-F10),
human embryonic kidney (HEK), 293 cells, and Escherichia coli,
(MTCC 7410) bacterial cell wall damage studies were conducted
to synthesized material action (Fig. 1).
Fig. 1 Hydrothermal growth of rhombohedral Fe2O3 degradation and
recyclability studies.
microwave unit at 60 ꢀC and material is ready for
characterization.
2.2. Photocatalytic experiments of degradation of dyes
The photocatalytic behaviour of the synthesized rhombohedral
Fe2O3 were evaluated by the degradation of rhodamine-B (RB)
dyes with slight modication to increase the photocatalytic
activity. The experiment performed and the catalytic reading
taken with the help of Heber-immersion type photoreactor.35 In
this experiment a specically weighted amount of photo-
catalysts was systematically added in the ask with adjusting
pH with NaOH and HCl in the similar type of ask at pH 2 to 7.
The ask was sited under Heber-immersion type photoreactor,
by steady shaking by magnetic stirrer. The experimental trials
were performed with an initial rhodamine-B (RB-B) concentra-
2 Experimental
2.1. Hydrothermal preparation of Fe2O3
The rhombohedral Fe2O3 were synthesized by microwave
assisted hydrothermal method with slight modication in our
earlier report,25 to get the perfect rhombohedral geometry, in
the point of assessment of toxicity in various biological experi-
ments. FeCl3 and NaOH, Ammonia (Sigma Aldrich, India)
tion of 9 mM, catalyst concentration of 0.75 g Lꢁ1
.
2.3. Animal and treatment studies
10.14 g (37.5 mol) FeCl3$6H2O and 7.45 g (37.5 mmol) FeCl2- An adult male Wistar rats (weight nearly about 130–160 g) were
$4H2O were dissolved into 25 ml of H2O. 25 ml of 30% liquid systematically used for the study. The animals were kept in inox
ammonia was slowly added to the salt solution under stirring steel cages and maintained in a 22 ꢂ 2 ꢀC, 50–80% relative
condition at 1000 rpm for 5 minutes, aer 20 ml of combination humidity area with 12 hour light/dark pulse. The rats were
was put into a Teon-lined stainless Morey autoclave, and the maintained on a commercial pellet diet and allowed to access
autoclave be heated to 180 ꢀC in an oven and maintained at 10 deionized water and libitum. All animals were cared for
hour reaction time. Autoclave was naturally cooled to room according to the standards of the Guide for the Care and Use of
temperature; the end products were dried under conventional Laboratory Animals. Body weight, water intake, and dietary
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consumption were monitored daily. Aer one-week acclima- a Thermo Scientic Nicolet, 6700 Analytical FT-IR spectrome-
tion, the rats were randomly divided into two groups: a control ters. Zeta potential measurements of the attenuate dispersions
group (n ¼ 10), a Fe2O3 (MONPs) treated group (n ¼ 10). Oral (0.1 mg mLꢁ1) of the nanocomposites were conducted using
administrations of Fe2O3 nanoparticle were given at dose of a Brookhaven Nano-Brook Omni Instrument at 25 ꢀC. The
20 mg kgꢁ1 respectively,36,37 the control rat treated with physi- particle size distribution (PDS) nanocomposite was monitored
ological saline. Aer 3, 6, 12, 24 and 36 hours treated animals by using Microtrac (USA) particle size analyser. The analyser
were sacriced by cervical dislocation. From each animal's provides the size measurement, which conrms the particle size
heart tissue was studied, the rat tissue was preserved in Bouin's distribution. The measurement of the specic surface area of
xative and tissues blocks were embedded with paraffin and materials by using Brunauer–Emmett–Teller (BET), BEL:2
sliced into 5 mm thick section, then stained using haematoxylin SORP, Japan and atomic force microscopy (AFM), APE Research,
and eosin.38
AFM, 100, ITALY used to determine the resolution on the order
of fractions of a nanometre of a synthesized material. The
photoluminescence results were taken from photo-
luminescence spectrometer, FLS-1000, the identication of
rhodamine-B (RB) degradation intermediate products were
measured by a liquid chromatography-mass spectrometer (LC-
MS) model, (Waters-USA, Synapt G-2 HDMS). Microscopic
with camera Olympus, (USA, 2000) used to take the photograph
of HEK, 293 control and effected cell lines. The responding data
replicates (three) were analysed for every attempt and for every
analysis of discrepancy (ANOVA) using SPSS-Inc. 22.0. Trivial
effects of treatments were resolved by F values (p # 0.05).
2.4. Determination of anti-bacterial activity and live and
dead cell analysis
The Fe2O3 for bacterial screening along with the control by disc
diffusion method,39,40 Escherichia coli, (MTCC 7410) bacteria.
Hydrothermally synthesized Fe2O3and control were prepared in
sterile distilled water (stock solution) over a range of different
concentrations in 100 mg mlꢁ1. The analysis was performed to
distinguish dead and viable bacterial cells upon treatment with
Fe2O with minor modications.
2.5. B16-F10 cell culture and treatment and normal cell line
toxicity testing using HEK-293
3 Results and discussions
3.1. Characterization results of synthesized rhombohedral
The B16-F10 cell culture dose-dependent response curve was
plotted using propagation and MTT [(2-(3,5-diphenyltetrazol-2-
ium-2-yl)-4,5-dimethyl-1,3-thiazole bromide)] assay, aer 72
hours of exposure was determined according to,41,42 HEK-293
(human embryonic kidney), cell lines were gotten from the
American Type Culture Collection (ACC), USA. The method-
ology involved in HEK-293 cell line IC50 assessment, parallelly
the test Fe2O3 nanomaterial inhibits the 50% of the prolifer-
ating the normal cells as per above environmental conditions
for 48 hours.43,44 This procedure is non-hazardous, uses a ther-
mally stable reagent and shows good correlation with constant
proportion.45 The experiments were performed in triplicate and
three independent repetitions.
Fe2O3 nanomaterial
The X-ray uorescence is recorded with ne focus X-ray tube,
MO target of multi-layer monochromator of 17.5 keV.46 The XRF
spectra of Fe2O3 clearly indicate that the presence of Fe3+. XRF
pattern of Fe2O3 nanomaterial are shown in Fig. 2. The
diffraction peaks in 6.2 to 7.2 keV and the concentration of the
compound of Fe-KA is 153 256.1 cps are perfectly aligned to the
rhombohedral phase in Fe2O3.
In Fig. 3, shows XRD patterns of the samples obtained at
180 ꢀC in 10 hour hydrothermal reaction. According to the
gure, it clearly shows that, the position of the diffraction peaks
is in a good argument with those of rhombohedral Fe2O3
2.6. Characterizations and measurements
The structure and composition of Fe2O3 (MONPs) were char-
acterized by a various tools; Brunauer–Emmett–Teller (BET)
specic surface area, pore volume, and pore size distribution of
the samples were determined by N2 sorption at 77 K using
a Micromeritics ASAP-2020, Ultima-III Series, RIGAKU, TSX
System, Japan, was used to assess the crystallinity with wide-
angle X-ray diffraction (XRD) patterns, high resolution trans-
mission electron microscopic (HR-TEM) images of Fe2O3
(MONPs) was captured using Jeol/JEM 2100, LaB6, 80–2000 mm
with 200 kV acceleration voltages. The tissue section examined
with the help of Carl Zeiss, Axio image A2M, advanced polar-
izing microscope, USA. The Energy Dispersive Spectroscopy
(EDS) analysis was carried out using HITACHI (Noran System 7,
USA) system attached to the Zeiss Supra 55VP, FE-SEM is an
extremely soaring resolution eld emission scanning electron
microscope for the detection of composite nanoparticles.
Fourier-transformed infrared (FT-IR) spectra were obtained on Fig. 2 X-ray fluorescence spectra of Fe2O3 metal oxide nanoparticle.
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Fig. 3 X-ray diffraction profile of synthesized Fe2O3 nanoparticle.
Fig. 4 HR-TEM images of Fe2O3 nanoparticles, (a) rhombohedral
Fe2O3, (b) SAED of Fe2O3 material (c) and (d) nanomaterial selected
area of electron diffraction (SAED) pattern and magnified area of
region.
(JCPDS no. 33-0664).47,48 There is no other crystalline and
impurities, those results clear indication of purity of the
nanomaterial. However, the diffraction peaks have shown
a clear geometric shape in the point of utilization in various
applications. The mean crystallite sizes of Fe2O3 from the XRD
data effectively by using Debye–Scherer formula. The mean
crystallite sizes of rhombohedral Fe2O3 is 10 nm, An HR-TEM
and EDX result gives a clear justication to this argument.
The properties of Nano-structured materials habitually
depend on their morphology and size. Table S1 in ESI† shows
FT-IR spectrums of Fe2O3 nanoparticles in the range 400–
4000 cmꢁ1, nanoparticles show the spectral absorption in 3420,
3192, 1603, 1388, 1114, and 454 cmꢁ1. The absorption peaks at
3420 and 1603 cmꢁ1 can be assigned to the stretching vibration
and bending vibration of OH groups of H2O.49 The bands at
1114 and 454 cmꢁ1 can be attributed to the Fe–O stretching
vibration modes in Fe2O3. This FTIR results indicate the
formation of Fe2O3 in the present outcome, which are reliably
matched with XRD patterns. It is evident that, the FTIR peaks of
Fe2O3 nanoparticles have higher frequency to compare with
already reported morphologies.50,51
are the good proof for compact arrangement of the
nanoparticles.
Energy dispersive spectroscopy (EDS) analysis conrmed the
phase transparency of the Fe2O3 as shown in Fig. 5. The char-
acteristic peaks of Fe and O appear in the spectrum of Fe2O3 and
conrming its successive formation and purity (Table S1 and
Fig. S7 in ESI†). The peak of (C) carbon seems due to the carbon
tape used sample container in the energy dispersive unit. The
particles histogram using DLS of Fe2O3, distribution of particle
sizes when immersed in the solvent have a range from 10–
20 nm. Zeta potential measurement is the reliable method for
assessing material interaction with other biological system. The
particles examined presently possessed a zeta potential for
Fe2O3 as – 13.9 mV (Fig. S6 and S7 in ESI†), indicating safe to
environmental as well as biological utilization.
The surface area is an important tool to determine the bio-
logical adoptability of nanoparticles and nanomaterial with
a high surface area is easily attracting the biological material at
High resolution-TEM of synthesized rhombohedral shaped
Fe2O3 nanoparticles was shown in Fig. 4; from the images it
evidently showed that, the high-quality geometry, in addition,
the material results in the formation of mesopores between the
particles (Fig. S6 in ESI†), which clearly conrmed by BET
surface area and pore volume measurements. The size of both
the individual nanoparticles was between 10 to 20 nm which are
in concordant with the results of XRD, DLS and also FT-IR, and
those results are in a good argument with Debye–Scherer
formula in the above stated results. It was also observed that,
the d-spacing measurements of twin domains were measured to
˚
˚
be approximately 0.2 A to 0.4 A nm and corresponding to (110)
to (220) planes of Fe2O3, respectively, the interplanar spacing of
ꢃ0.25 nm agrees well with the spacing between (110) planes of
rhombohedral iron oxide crystals (0.25 nm) and SAED patterns
Fig. 5 The energy dispersive spectrum elemental composition of
Fe2O3.
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the faster rate due to his inert nature. The superior specic
surface area provides more surface-active sites and well-
organized transport lanes to reactant molecules and products
in environment as well in biological systems. BET surface area
as a function of pore volume and the size of the synthesized
samples present in similar (type-II).10,52,53 The BET surface areas
reading of Fe2O3 is 5.676 m2 gꢁ1 (Fig. 6 and Table S2 in ESI†).
According to the hysteresis loop in the relative pressure region
approximately 0.4–0.9, the nitrogen adsorption/desorption
isotherms showed that the Fe2O3 exhibited a similar (type-IV)
curve and it is in nanoporous structure, with an increase in
the surface area and decrease in the pore size, as well as the
large total pore volume, of Fe2O3 is expected to have a high
biological hold up.
UV-Vis diffuse reectance spectra (DRS) and band-gap
energy of Fe2O3 are shown in Fig. 7. DRS were used to
investigate the light-harvesting nature of the Fe2O3 photo-
catalyst, but in this study we are effectively adopting to
determine the material environment for biological suscepti-
bility. Conduction-band minimum (CBM) and valence-band
maximum (VBM) is play a vital understanding to mecha-
nism absorption on biological materials. To investigate the
CBM and VBM of the Fe2O3. UV-DRS spectra were used to
record the spectrum. The associated band-gap values were
calculated using the equation in ref. 54. Which are consistent
with the similar results obtained from the related work.55,56
Evidently calculated band-gaps of rhombohedral Fe2O3 were
found to be 1.96, this reading is important, because of
nanomaterial can be photo excited to generate more elec-
tron–hole pair under visible-light irradiation, it's results have
higher catalytic performance. This mechanism leads to more
impact on natal material effect (Table S3 in ESI†).
Fig. 7 The Fe2O3 band-gap calculation by using Tauc plot.
similar systems, correlations and many more multifaceted
trends and also act as starting place for photoluminescence in
catalytic and also many body systems.
The atomic force microscopy (AFM) image shows synthe-
sized material in a high quality, it is essential to execute
corrections of the sample slope and background.59,60 Apropos
the instabilities occurred during scanning, especially in the
ranges under 4 mm, the AFM used to assess the particle size and
morphology and thus to explain the colour difference. The iron
oxide nanoparticles with the size of 10–20 nm and with the
morphology corresponding to very thin rhombohedral
geometric structures, particles of metal oxide nanomaterials
prepared by hydrothermal route method, just the different
values of vertical dimensions, which are accountable for
dissimilar colour excellence, cannot be effortlessly found by
using other techniques together with HR-TEM.
PL spectra of Fe2O3 are evidently shown in Fig. 8. The PL
emission is light source emission from any form of matter aer
the absorption of photons. The peaks are observed at 416 nm
and 440 nm. In general photoluminescence positive energy can
be viewed as an indication of electron populated an exited state
associated with transition energy.56–58 The true atoms are the
Surface roughness (Ra) value, the Ra value indicates average
of a set of individual measurements of a surface's peaks or
valleys. The Ra value for rhombohedral Fe2O3 was 27.2 nm that
shows the evenness of nanomaterial (Fig. 9). Due to rough
surface texture of synthesized nanoparticle, there was well
Fig. 6 The BET N2 absorption/desorption graph of rhombohedral
Fe2O3.
Fig. 8 Photoluminescence (PL) spectra Fe2O3.
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Fig. 10 Photocatalytic degradation kinetics of rhodamine-B (RB-B)
using various photocatalysts.
Fig. 9 Atomic force microscopy (AFM) for the characterization of
Fe2O3 rhombohedral nanomaterial.
The photodegradation intermediates in the reaction process
were help to predict the actual reaction process.65,66 The tiny
molecules during mineralization process are responsible for
CO2 and H2O, the COD and TOC (Table S4 in ESI†), results
evident to photodegradation process (Fig. 11). The two spirited
actions have occurred at the same time during the photoreac-
tion: N-deethylation and destruction of dye chromophore
structure,67 The negative correlation was observed in COD and
TOC in respective time consider for the study of degradation
(Fig. S9 and S10 in ESI†). Interpermeates of photocatalytic
degradation of rhodamine-B (RB) were performed using LC-MS
and results were hypothesized in ESI (Table S7 in ESI†).
The recovery of a photocatalytic nanomaterial is the most
important for eco-friendly utilization of product.68,69 In order to
examine the constancy and stability of the Fe2O3 nanomaterial
is essential aer the photodegradation of rhodamine-B (RB-B).
The photodegradation proportion of ve consecutive cycles is
76.23%, 73.78%, 72.56%, 71.09% and 71.43%, respectively, and
showed in Fig. 12.
absorption in heart muscles caused inammation like
increased neutrophil count was observed in this study.
In the photocatalytic activity of nanomaterials effect of pH
play a vital role.61 The forethought of rhodamine-B (RB-B)
(Fig. S9 in ESI†) and catalyst dosage were xed at 9 mM
rhodamine-B (RB-B) and 0.75 g Lꢁ1 (rhombohedral Fe2O3),
respectively. The outcome of pH on the photodegradation of
rhodamine-B (RB-B) is revealed in Fig. S2 in ESI†. pH zero-point
charge (zpc), the external play an important role in dye degra-
dation and mineralization studies.62,63 The zpc values of rhom-
bohedral Fe2O3 is 7.4 respectively, this clearly below pH the
surface of material is positively charge and dye was simulta-
neously degraded and nontoxic small molecular intermediates
was obtained (Table S7 in ESI†).
The photocatalytic activity of ZnO, TiO2 and Cu2O for clear
determination synthesized nanomaterial behaviour. This
research conrmed that 82.14% of rhodamine-B (RB-B) was
besmirched by the Fe2O3 nanomaterials at 120 minutes of
irradiation time in Heber-immersion type photoreactor. The
degradation percentages of commercially available ZnO, TiO2,
and Cu2O are 59.61%, 69.87%, and 70.56%, respectively. The
solar induced photocatalytic activity of rhombohedral Fe2O3
(97.42%) is advanced when compared to the standards in Fig. S3
in ESI†.
The Langmuir–Hinshelwood model.12,64 was efficiently used
to gure out the degradation kinetics of rhombohedral Fe2O3
photodegradation. Fig. 10 explains the apparent logarithmic
plot of rhodamine-B (RB-B) concentration as a utility of irradi-
ation time. The pseudo-rst-order rate kinetics explains Fe2O3 is
2.65 ꢄ 10ꢁ2 sꢁ1 is appreciably higher than of TiO2 (5.12 ꢄ 10ꢁ3
sꢁ1) and CuO2 (7.38 ꢄ 10ꢁ3 sꢁ1). For this reason, the activity of
the Fe2O3 rhombohedral material is about 2.7 percent superior
than that of other examined material and the ZnO (2.01 ꢄ 10ꢁ3
Sꢁ1) shows the triing photocatalytic activity to compare to
other efficient materials in various studies so far.
Fig. 11 Chemical oxygen demand (COD) and total organic carbon
(TOC) readings.
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The rhombohedral Fe2O3 nanomaterial exhibits an average allowing dye molecules to move from solitary explication to the
of 73.18% of solar driven activity aer ve successive cycles. In material interface and to subsequently carbon dioxide (CO2),
addition, there is slight change observed in the XRD pattern of water (H2O) and other small molecular intermediates are the by-
Fe2O3, due to absorption of small molecular intermediates products of redox reactions as clearly showed in Fig. 14.
organic material present in dye (Fig. 13), aer ve cycles.
The systematic hydrogen production by photo-induced water
break-down was more captivating and give a suitable solution
for energy conversion and conversional problems.65,70 H2
generation methods and photocatalytic water excruciating
using visible light spectrum with low cost and more sustain-
ability features in the photo reaction system are more popular.
This radical piercing process makes a crucial role in the
degradation of dyes rhodamine-B (RB-B) concentration. In our
experiment, we are proposed the photo-reaction efficiency of
the adsorption of untreated organic dye on the by rhombohe-
dral Fe2O3 and the progression of splitting photo-twisted elec-
tron–hole pairs. The holes can either react through
rhombohedral pore surface, and form hydroxyl to hydroxy
radicals. Consequently, the degradation was occurred to
3.2. Biological toxicity results of synthesized rhombohedral
Fe2O3 nanomaterial
The epidemiological studies have clearly recommended
that, health effects of nano and micro particles dependent
one and each other.71,72 An earlier toxicity studies showed
that nanoparticle was made specic acute effects while
micro particles induced chronic effects.73–75 In this study,
our study explains the environmental and health concern by
using biological specimens mimic oral exposure. We found
that structured Fe2O3 nanoparticles entered the body via
oral administration; they became systemically and cause
toxic effects in cardiovascular system. These actions were
measured to be the essential mechanisms of organ damage.
The metal oxide nanoparticles (MONPs), due to his high
calibre in their size, they are probably transported from the
oral way into body circulation, and reach cardiovascular
system and made remarkable hazard. Metal oxide nano-
particles (MONP's) by products from industrial as well as
biomedical output will in aquatic systems. However, some
studies have shown that the solubility of metal oxide
nanoparticles in biological liquids is in addition one of the
factor that, determines legatee velocity of penetration into
blood streams,76 especially Fe2O3 nanoparticles has been
shown to dissolve in normal environment and easily get in
to living systems.77–79 Simultaneously, musculus skin
Fig. 12 Rhombohedral Fe2O3 catalyst recycling performance cycles.
Fig. 14 Probable photocatalytic dye degradation mechanism via
visible light irradiation.
Fig. 13 XRD pattern rhombohedral Fe2O3 nanoparticle.
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melanoma cells (B16-F10), human embryonic kidney (HEK),
293 cells, and Escherichia coli, (MTCC 7410) bacterial cell
wall impairment also carryout (Fig. 15).
The result of anti-bacterial activity showed that, there exists
a signicant zone of inhibition against test pathogens, many
studies have proved that the photo-generated holes and $OH are
the main oxidative agents for Escherichia coli suppression. It
should be noted that, the test samples, due to its large surface
area Fe2O3 nanoparticle, Escherichia coli, (MTCC 7410) were
used for study with different concentrations of material were
added to the disc plate containing a nutrient agar media (NA),
yields the maximum inhibition zones 20.60 ꢂ 0.24 at 1.0 mg,
followed by 0.6 mg is 18.35 ꢂ 0.08, and 0.3 mg was 15.81 ꢂ 0.15
(Table S5 in ESI†), respectively (Fig. 16). We did not observe any
zone of inhibition in SDW (Sterile Distilled Water) diffused
discs against test pathogens. This revise clearly suggests that,
Fe2O3 material inhibit the E. Coli (MTCC 7410) bacterial path-
ogens by rupturing the outer and inner wall of the cell which
leads to toxic and damage the cell membrane. The uorescent
microscopic images (Fig. 17) are agreed the clear evident of
bacterial death.
Fig. 16 Anti-bacterial activity of Escherichia coli, (MTCC 7410) treated
against different concentration of rhombohedral Fe2O3 material via,
disc diffusion method, [C] sterile distilled water.
In Fig. 18a, normal rat demonstrating normal heart muscle,
the rhombohedral Fe2O3 treated rat received 20 mg kgꢁ1 of
10 nm particles for 0 to 6 hours (Fig. 18b and c) demonstrating
benign normal looking heart muscle with normal muscle
direction and fascicles with no pathological effects. The metal
oxide nanoparticles (MONP's) for 6 to 12 hours (Fig. 18d and e),
demonstrating spread in the extravasations of red blood cells,
Fig. 17 Scanning Electron Microscopic (SEM) images of (a) E. coli, (Live
cells) untreated with Fe2O3, (b) E. coli, (Dead cells) treated with Fe2O3,
(c) and (d) selected live and dead cell representative fluorescent
microscopic images (40ꢄ), Fe2O3 in general both the series, green
dots represent live bacterial cells and yellow/orange dots represent
dead cells. (e) E. coli, cell wall loss by Fe2O3, (f) graphical representation
of cell wall damage.
Fig. 15 Toxicity assessments using rhombohedral Fe2O3.
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vesicles, and become incapable of reaching the cytosol system.
The prociency mainly depends on nanomaterial size, shape,
physical, chemical and its dispersive nature. Finally, the
hydrothermally synthesized rhombohedral metal oxides can be
used effectively at a very low concentration against different
types of cell lines for the drug delivery procedures and also,
pharmaceutical applications. The efficient permeability effects
(EPR) of nanoparticle play an vital role with a solution for
frequent toxicity assessment strategies through cell line, the
targeting efficiency via a wide spectrum of nanomaterial based
on various engineering methodologies,80–83 up till now, ample of
immunotherapy strategies against cell line toxicity have
undergone extensive development and clinical testing, from.84,85
HEK-293 cells have been extensively utilized in biological
research for many years, for the reason of consistent develop-
ment and penchant. The therapeutic effect of human embry-
onic kidney (HEK), 293 cell line efficacies by rhombohedral
Fe2O3 in vivo toxicity effect were inoculated in the right ank of
mice and applied treatments 7 days later. The cell line volume
was recorded in the following two systematic weeks. Fe2O3
exhibited the most excellent on cell line growth with was
compared with free drugs loaded vessel systematically
(Fig. 19a). Obviously, there is effect in the photograph of the
normal cell line, the staining pictures of cell line sections from
each cluster were dependable with the results like incompact
cells, shrunk nuclei and damaged morphology were observed in
both (Fig. 19b and c), which reected more advanced cell
apoptosis was induced by Fe2O3, aer systemic administration.
We deem the conception of this toxicity combined approach
could also be applicable for other proper anti-cancer drugs and
immune-stimulating agents to rescue the liposomes in future.
Fig. 18 Histopathology alterations of heart tissue from rats exposed to
Fe2O3 nanoparticles for 3 days (magnification ¼ 0.2–0.5 mm). The rats
were sacrificed at 3, 6, 12, 24 and 36 hours after the final administra-
tion. (a) No inflammation in control group, (b) Fe2O3 treated rats at 3
hours with no toxic effects observed in cardiac tissue, (c) Fe2O3 treated
rats at 6 hours with minimal inflammation were observed, (d) Fe2O3
treated rats at 12 hours with mild neutrophilic infiltration on cardiac
muscle due to the time interval, (e) and (f) Fe2O3 treated rats at 24 and
36 hours shows a maximum neutrophilic infiltration was observed.
packed dilated blood vessels, prominent focus of tiny lympho-
cytic inltrate associated with focus of muscle hyalinosis,
troubled muscle fascicles and scattered red blood cells. In the
view of 24 to 36 hours (Fig. 18f), demonstrating dense prom-
inent focuses of inammatory cells inltrate of minute
lymphocytes and few plasma cells and prominent congested
dilated, blood vessels and few scattered extravasation red blood
cells. Histological studies induced in the heart tissue exposure
could be an indication of congested cardiovascular system with
extravasations, red blood cells and vessels, heart muscle hyali-
nises, troubled muscle fascicles, inammatory cells inltrate by
small lymphocytes and plasma cells, due to higher dose Fe2O3
toxicity. The nano residue accumulated heart muscle leads to
metabolic and structural changes. The increased neutrophil
counts have been indicated in the red coloured square boxes in
the respective images.
The projecting anti-proliferative outcome of functionalized
Fe2O3 on HEK-293 as exposed by its IC50 built on XTT assay was
instigate to be 202.14 ꢂ 0.14 equated with the standard drug
cisplatin >500 (Table S6 and Fig. S8 in ESI†). Consequently, the
hydrothermally synthesized material is the promising aspirant
for hopeful drug to anti-cancer with its toxicity. However, the
synthesis methodology gives a nontoxic nature to rhombohe-
dral Fe2O3. The plasma semi-penetrable membrane allows
freely dissemination of tiny and non-polar molecules available
in the synthesized material were uptake the endocytosis. Most
of chemically worked Fe2O3 are easily taken up by the cells
Fig. 19 Cell line toxicity testing (selected images) of rhombohedral
Fe2O3 using human embryonic kidney (HEK), 293 cells, (a) and (d)
control cell line, (b) and (e) human embryonic kidney (HEK), 293 cells,
treated 300 mg mlꢁ1 of nanomaterial showed in-site box and (c) and (f)
accumulated material were observed in 500 mg mlꢁ1 treated with
through endocytic mechanisms, and persist in endosome respective cell line. The red colour boxes in the (d) and (c) shows the
nanoparticle deposition and cell damage.
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Conflicts of interest
The authors declare no competing nancial interest.
Acknowledgements
Abhilash M. R., DST – INSPIRE (SRF), would like to acknowledge
funding support from Science and Technology, Govt. of India
(Grant No. IF160104).
Notes and references
Fig. 20 Toxicity testing of the Fe2O3 material using melanoma cells
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