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KMUTNB Int J Appl Sci Technol, Vol. x, No. x, pp. x–x, (Year)
Preparation and Properties of Electrospun Fibers of Titanium Dioxide-Loaded
Polylactide/Polyvinylpyrrolidone Blends
Bunthoeun Nim, Paiboon Sreearunothai and Pakorn Opaprakasit*
School of Bio-Chemical Engineering and Technology, Sirindhorn International Institute of Technology (SIIT),
Thammasat University, Pathum Thani, Thailand
Atitsa Petchsuk
National Metal and Materials Technology Center, Thailand Science Park, Pathum Thani, Thailand
* Corresponding author. E-mail: DOI: 10.14416/j.ijast.2018.10.003
Received: 18 July 2017; Accepted: 21 August 2017; Published online: 4 October 2018
© 2019 King Mongkut’s University of Technology North Bangkok. All Rights Reserved.
Nanofibers of polylactide (PLA)/polyvinylpyrrolidone (PVP) blends loaded with titanium dioxide (TiO2)
particles have been prepared by an electrospinning technique. TiO2 particles are formed by sol-gel mechanisms
from titanium (IV) iso-propoxide (TTIP) precursor. Effect of TiO2 formation rate on properties of the fibers are
examined by adding iso-propyl alcohol (iPOH) to slow down the TiO2 precipitation process. The use of iPOH
produces fiber mats consisting of slightly bigger and smoother filaments, but smaller-sized embedded TiO2
particles. Both materials show a distinct UV absorption characteristic of TiO2 at λmax 300 nm, which can be
applied in catalytic applications. Degradation behaviors of the materials in phosphate buffer solutions have also
been investigated. The materials have high potential for use as epoxidation catalysts for conversion of vegetable
oils to polymeric building blocks and plasticizers.
Keywords: Polylactide, Polyvinylpyrrolidone, Titanium dioxide, Electrospinning, Degradation
Research Article
Selected Paper from the 6th International Thai Institute of Chemical Engineering and Applied Science Conference (ITIChE2016)
1 Introduction
Polylactide (PLA) is one of widely used biodegradable
polymers, which can be synthesized from renewable
resources. This polymer is derived from lactic acid
monomers, commonly obtained from fermentation of
agricultural products, such as corn, rice, wheat, and
cassava starch [1]. PLA is recently applied in a wide
range of applications, including packaging [2], [3],
tissue engineering [4], scaffold engineering [5], wound
dressing, drug delivery, and anti-microbial materials
[6], due to its good mechanical properties, ease of
processibility, biodegradability [7], [8], biocompatibility
[9], and high transparency [10]. Therefore, the materials
is a promising alternate to non-degradable petroleum-
based plastics to solve serious plastic waste problems.
Polymer blends and composites have attracted vast
attention from the research community and industrial
sector to further improve properties of the materials
and expand their applications [11], [12]. Various blends
and composites of PLA have been developed and used
for many specific applications. Recently, composites
of PLA with titanium dioxide (TiO2) particles were
prepared and their properties and potentials were
examined. TiO2 nanoparticles possess a unique photo-
catalytic activity that can be applied in environmental
remediation, especially degradation of organic pollutants
and bacteria with high efficiency [13]–[15].
Major advantages of using TiO2 particles include
inexpensive cost, non-toxicity, high chemical stability,
Please cite this article in press as: B. Nim, P. Sreearunothai, P. Opaprakasit, and A. Petchsuk, “Preparation
and properties of electrospun fibers of titanium dioxide-loaded polylactide/polyvinylpyrrolidone blends,”
KMUTNB Int J Appl Sci Technol, vol. x, no. x, pp. x–x, (Year).
B. Nim et al., “Preparation and Properties of Electrospun Fibers of Titanium Dioxide-Loaded Polylactide/Polyvinylpyrrolidone Blends.”
and high resistant to solvents. Various preparation
methods of TiO2 and PLA/TiO2 composites were reported,
such as in situ polymerization[16], electrospinning [6],
[17], [18], spin coating [19], [20], solution casting [9],
and a surface modified method [10]. In addition, several
PLA-based blends were used to prepare various
composites, including polyvinylpyrrolidone (PVP) [21],
polyethylene (PE) [22], polystyrene (PS) [23], and
poly(butylene succinate) (PBS) [24]. Among these,
PVP shows interesting properties, as it is water soluble,
with low toxicity and high physiological compatibility
[25]. This polymer is also considered as a conventional
polymer for safe use in pharmaceutical, cosmetic, and
food industries [26].
There are several reports of PVP carrier in an
electrospinning technique. The particles are embedded
to the polymer for various applications such as dye
degradation [15], [17], sensor [18], and bio-sensing [12].
Blends of PLA and PVP loaded with TiO2
nanoparticles (PLA/PVP/TiO2) are a promising
nanocomposite for use in improving PLAs properties
and introducing specific catalytic activities. These
composites exhibited superior properties, compared
to their neat material counterparts, such as higher
Young’s modulus, improved thermal stability, higher
photo-degradability and biodegradability, and higher
gas barrier properties [27], [28]. Nanocomposite
fibers of PLA/TiO2/PVP/ZnCl2 were fabricated by an
electrospinning technique and used in wound dressing
applications [21].
In this work, TiO2-loaded PLA/PVP nanofibers
are fabricated by an electrospinning method. The loaded
TiO2 particles are formed by sol-gel mechanisms by
employing their precursor solution mixed with the
solutions of the polymer matrix during the electrospinning
process. Effects of TiO2 particles formation rate on
properties of the fibers are examined by adding isopropyl
alcohol. Morphology and properties of the resulting
fiber mats are investigated. The materials have high
potential for use as catalytic system. Their stability and
degradability are then examined in Phosphate Buffer
Solutions (PBS), under UVA light activator [29].
2 Methodology
2.1 Materials
Polylactide 4043D (PLA) was supplied by NatureWork®.
Polyvinylpyrrolidone (PVP) K29-32 (Mw=58,000 g/mol)
and Titanium (IV) Iso-propoxide, Ti(OiPr)4 (TTIP),
precursor (98+ %) were purchased from Acros.
Chloroform RPE (>99%), N,N-dimethyl formamide
(DMF) (99.8%), and isopropyl alcohol (99.7%) (iPOH)
solvents were purchased from Carlo Erba. Sodium
dihydrogen phosphate monohydrate (NaH2PO4;H2O)
and disodium hydrogen phosphate heptahydrate
(Na2HPO4;7H2O) were supplied by Carlo Erba and
PANREAC, respectively.
2.2 Preparation of PLA/PVP blends and TiO2-loaded
PLA/PVP blends were prepared by mixing PLA (0.84 g)
with PVP at a ratio of 5:1 wt/wt, in chloroform (9 g),
and stirring until completely dissolved. The TiO2
precursor mixture was prepared from TTIP (200 μL),
mixed with DMF (3 g) and iPOH (1.5 g), followed by
adding of DI water (100 μL) drop wise. The mixture
was stirred at room temperature for 1 h. iPOH was used
to slow down the precipitation rate of TiO2 particles.
The polymer mixture was then mixed with the precursor
mixture and stirred at room temperature for 1 h to generate
suitable solutions for electrospinning. A summary of
the samples compositions and sample names is listed
in Table 1.
Table 1: Summary of sample compositions and sample
Samples PLA (g) PVP (g) TTIP (μL) iPOH (g)
P-P-T 0.84 0.168 200 0
P-P-I-T 0.84 0.168 200 1.5
2.3 Electrospinning
Fiber mats were fabricated by an electrospinning
technique. The composited mixture was placed in a
syringe (capacity of 3 mL) connected to a syringe-
stainless needle. The syringe was placed on a flow
controller (KD Scientific KD 100 Syringe Pump),
with a flow rate of 1 mL/h. The distance between the
collector and the needle tip was 15 cm. A voltage of
10 kV was applied by using a Gamma high voltage
(0–40 kV) power supply. The electrospun fibers were
gathered on an aluminum foil collector.
KMUTNB Int J Appl Sci Technol, Vol. x, No. x, pp. x–x, (Year)
2.4 Characterization
Fourier Transform Infrared (FTIR) spectroscopy,
equipped with an Attenuated Total Reflectance (ATR)
accessory (Nicolet iS5 Spectrometer), was employed
to determine functional groups and interactions of the
electrospun fiber mats. Scanning electron microscopy
(SEM-SU8030) was used to investigate size and
surface morphology of the samples. Energy-dispersive
X-ray (EDX-SU8030) was employed to observe
surface compositions of each component. A UV-Vis
spectrophotometer (Genesys 10S) was used to examine
the absorption behaviors of the fiber mats.
2.5 Degradation experiments
Degradation behaviors of the fiber mats were examined
in phosphate buffer solutions (PBS at pH 7.4) at
ambient temperature. Neat PLA, P-P-T, and P-P-I-T
fiber mats were cut into 2×2 cm2. Each specimen
was immersed into 50 mL PBS and placed at a 22 cm
distance under UVA light (UVA 15WT8 lamp). The
experiments were conducted for 6 days, in which the
specimens were removed from the solution and washed
with DI water and dried at 40°C in a vacuum oven for
overnight. FTIR and UV-Vis spectroscopy were used
to examine the chemical structures of the samples as
a function of degradation time.
3 Results and Discussion
3.1 ATR-FTIR spectroscopy
ATR-FTIR spectra of spun fiber samples of neat
PLA, P-P-T, and P-P-I-T are shown in Figure 1. Band
characteristics of PLA and PVP are observed, indicating
the presence of the 2 components on a filament’s surface.
A strong band at 1753 cm–1 is assigned to the vibration
of C=O of PLA chains, whereas that at 1659 cm–1
corresponds to the amide (N-C=O) vibrational mode.
Both P-P-T and P-P-I-T show similar FTIR spectra
pattern. This reflects that the technique may not be
able to differentiate the nature of the two samples.
Nonetheless, a broad band centered at 3400 cm–1 (O-H
stretching), observed in these 2 samples but not in
neat PLA, indicates the presence of remaining iPOH
after the TiO2 particle formation, and also bound water
molecules due to the hygroscopic nature of PVP.
3.2 Scanning electron microscopy
Figure 2 shows surface morphology of P-P-T and
P-P-I-T mats examined by SEM. Significant differences
between the 2 samples are observed. Both sample
mats show rough and irregular surface morphology,
which is different from that of neat PLA, as reported
earlier [30]. This is likely due to the interplay between
Figure 1: ATR-FTIR spectra of fiber mats: (a) Neat PLA, (b) P-P-T, and (c) P-P-I-T.
1000 1500 2000 2500 3000 3500
2994 870
Wavenumbers (cm
Band (cm
) Assignment
B. Nim et al., “Preparation and Properties of Electrospun Fibers of Titanium Dioxide-Loaded Polylactide/Polyvinylpyrrolidone Blends.”
the 2 polymeric components during electrospinning.
Nonetheless, it is clearly observed that the surface
of P-P-I-T fibers is smoother than that of P-P-T. The
fiber mats of P-P-I-T contains TiO2 beads with higher
uniformity than those of P-P-T, as the addition of iPOH
slows down the TiO2 precipitation rate. The regions of
irregular fiber (beads) shape are caused by agglomeration
of TiO2 particles present as beads embedded in
the filaments. This is confirmed by EDX results, as
illustrated in Figure 3. The Ti content in the beads
is much higher, compared to that in the regular
fiber region. The size distribution of the filaments is
compared in Figure 4. The P-P-T fibers have an
average diameter of 800 nm, slightly smaller than that
of P-P-I-T (827 nm).
3.3 UV-Vis spectroscopy
UV-Vis spectroscopy is employed to examine absorption
behaviors of the materials, as shown in Figure 5. P-P-T
and P-P-I-T fibers show a major absorption band at
λmax 214 nm. This is due to the n→π* transition of the
carbonyl groups in PLA, which is similar to that observed
in spun fibers of neat PLA. All samples also show
a broad absorption covering the full visible region,
likely due to the translucent nature of the fiber mats.
A distinct absorption band is observed at 300 nm for
P-P-T and P-P-I-T fiber mats, indicating the presence
of TiO2 particles. This enables the materials to possess
photo-catalytic activity for use in many applications,
such as epoxidation of unsaturated oils or degradation
Figure 2: SEM images of electrospun fibers (a)–(c) P-P-T and (d)–(f) P-P-I-T at 5,000×, 10,000×, and 20,000×
Figure 3: EDX spectra illustrating atomic compositions of bead defects with different sizes present in (a) P-P-T
and (b) P-P-I-T fibers.
(a) (b) (c)
(d) (e) (f)
EDS Spot 1
EDS Spot 2
0.00 1.00 2 .00 3.00 4.00 5.00
EDS Spot 1
EDS Spot 2
0.00 1.00 2.00 3.00 4.00 5.00
(a) (b)
KMUTNB Int J Appl Sci Technol, Vol. x, No. x, pp. x–x, (Year)
of contaminated water. Due to space limitations, this
will be addressed in details in a separate work.
3.4 Degradation mechanisms
Degradation behaviors of the spun fiber mats are
examined in PBS solutions by activation with UVA
light. The fiber samples were soaked in PBS at 1, 4,
and 6 days, and their FTIR and UV-Vis spectra were
recorded, as shown in Figure 6. The ATR-FTIR and
UV-Vis results show evidences of PLA degradation
as a function of time, similar to those reported in our
previous work [31]. Both P-P-T and P-P-I-T mats show
similar FTIR changes, and the latter is chosen to show
the changes. A decrease in intensity of the 1659 cm–1
band of the amide group of PVP reflects that during
the degradation, PVP present on the surface of the
filaments is released and dissolves in PBS solutions.
In addition, a weak band in the same region is observed
at 1650 cm–1, associated with carboxylate of degraded
Results from UV-Vis spectra of PBS solutions
after P-P-I-T fiber mats are soaked for 1, 4, and 6 days,
as shown in Figure 7, illustrates an absorption band of
lactate oligomers, products from the degradation of
PLA, at 202 nm. The intensity of the band increases
with the degradation time, indicating that degradation
of the PLA component takes place very early. This is
likely because of the presence of TiO2 catalytic particles
and the dissolubility of PVP from the filaments, which
in turn, exposes the PLA component to a higher degree
of hydrolysis.
4 Conclusions
Fiber mats of PLA/PVP blends loaded with TiO2
particles, i.e., P-P-T, and P-P-I-T, are successfully
fabricated by an electrospinning method. The fiber
mats absorb UV light in a region of 300 nm, which
enables their photo-catalytic activity. Preliminary
results from degradability experiments show that
degradation of the PLA component takes place very
Figure 5: UV-Vis spectra of fibers mats of: (a) neat
PLA, (b) P-P-T, and (c) P-P-I-T.
Figure 6: ATR-FTIR spectra of electrospun P-P-I-T
(10 kV) fiber soaked in PBS solution at: (a) 0, (b) 1,
(c) 4, and (d) 6 days.
Figure 7: UV-Vis spectra of P-P-I-T fiber mats as a
function of degradation time: 1, 4, and 6 days.
Figure 4: Size distribution of (a) P-P-T and (b) P-P-I-T
fiber mats.
Percentage (%)
Diameter (nm)
Average size 827 nm
Percentage (%)
Diameter (nm)
Average size 800 nm
200 300 400 500 600 700 800
Arbitrary units
Wavelength (nm)
1000 1500 2000 2500 3000 35 00
Wavenumbers (cm-1)
Wavenumber (cm
200 202 204
Arbitrary units
wavelength (nm)
(d) 6 days
(c) 4 days
(b) 1 day
(a) PBS blank
200 202 204
Arbitrary units
B. Nim et al., “Preparation and Properties of Electrospun Fibers of Titanium Dioxide-Loaded Polylactide/Polyvinylpyrrolidone Blends.”
early, due to the presence of TiO2 catalytic particles and
the dissolubility of PVP from the filaments.
The authors acknowledge financial supports from
the Thammasat University Research Fund (Theme
research) and the Center of Excellence in Materials
and Plasma Technology (M@P Tech), Thammasat
University. B.N. thanks the support from the Excellence
Foreign Scholarship (EFS) program provided by SIIT.
The authors would like to convey special appreciation
to the academic committee of The 6th International
Thai Institute of Chemical Engineering and Applied
Science Conference (ITIChE2016) for providing
the opportunity for this work to be published in this
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... Overlapped spectra were observed for PLA and biocomposite films, only differing in band intensities. In particular, a decrease in the peak appearing at 1745 cm −1 was found, which was attributed to the symmetrical stretching of PLA C=O ester groups [47], besides other characteristic PLA bands at 1451 (ν CH 3 ), 1381 (δ C-H), 1360 (δ CH 3 ), 1180 and 1080 (ν C-O), and 868 (ν C-C) cm −1 [50]. The absence of other different bands than those corresponding to PLA suggested a physical interaction between the polymer and the organic filler [47], whereas lower intensities observed for biocomposite films could be in accordance with their chemical interaction [51]. ...
... Overlapped spectra were observed for PLA and biocomposite films, only differing in band intensities. In particular, a decrease in the peak appearing at 1745 cm −1 was found, which was attributed to the symmetrical stretching of PLA C=O ester groups [47], besides other characteristic PLA bands at 1451 (ν CH3), 1381 (δ C-H), 1360 (δ CH3), 1180 and 1080 (ν C-O), and 868 (ν C-C) cm −1 [50]. The absence of other different bands than those corresponding to PLA suggested a physical interaction between the polymer and the organic filler [47], whereas lower intensities observed for biocomposite films could be in accordance with their chemical interaction [51]. ...
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Nowadays, hemp farmers are facing an urgent problem related to plant stem disposal after seed harvesting. In this work, the commonly discarded epidermis and cuticle of hemp stems were valorized, turning them towards a sustainable recycling and reuse, contributing to the circular economy concept. Cellulose deprived of amorphous regions was obtained by a green process consisting of an ethanolic ultrasound-assisted maceration followed by mild bleaching/hydrolysis. The obtained hemp cellulose was esterified with citric acid resulting in a 1.2-fold higher crystallinity index and 34 ∘C lower Tg value compared to the non-functionalized hemp cellulose. Green innovative biocomposite films were developed by embedding the modified cellulose into PLA by means of an extrusion process. The structural and morphological characterization of the obtained biocomposites highlighted the functionalization and further embedment of cellulose into the PLA matrix. Attenuated Total Reflectance–Fourier Transform Infrared spectroscopy (ATR-FTIR) results suggested physical and chemical interactions between PLA and the organic filler in the biofilms, observing a homogeneous composition by Field Emission-Scanning Electron Microscopy (FESEM). Moreover, some increase in thermal stability was found for biocomposites added with 5%wt of the hemp cellulose filler. The obtained results highlighted the feasible recovery of cellulose from hemp stem parts of disposal concern, adding value to this agro-waste, and its potential application for the development of novel biocomposite films to be used in different applications.
... The FTIR spectra of the photodegraded PLA nanocomposites were analyzed (see Figs. 12 and 13). The essential PLA signals present in all samples (see Figs. 12 and 13) are 3501 (TiO 2 -OH, hydroxy, and hydroperoxide groups), 1750 (stretching vibrations of carbonyl groups), 1450, and 1368 (CH 3 asymmetric and symmetric deformations), 1220 (C-O-C stretching), 1000, 870, 750 cm −1 , which agree with what has been observed elsewhere [10,12,[68][69][70][71][72][73][74][75]. ...
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This work presents the surface functionalization of titanium dioxide nanoparticles with 1H-1-carboxylate of isopropyl-imidazole and 3-aminopropyltrimethoxysilane. The surface and thermal properties of titanium dioxide are characterized by nuclear magnetic resonance, Fourier-transform infrared spectroscopy, zeta potential, X-ray diffraction, and differential scanning calorimetry. The functionalization mentioned above improves the dispersibility of titanium dioxide in polymeric matrices such as polylactic acid. Polylactic acid compounds are extruded with these nanoparticles; their crystallization capacity is studied by non-isothermal crystallization. The results obtained indicate the successful binding of organic structures to titanium dioxide. Likewise, the dispersion improves when the nanoparticle is silanized, reducing agglomeration when the isopropyl-imidazole 1H-1-carboxylate is bound to the organosilicon coating. DSC measurements show that isopropyl imidazole 1H-1-carboxylate adhered to the organosilicon coating exhibits excellent thermal stability up to 300 °C. Finally, the photo-degradation of the composites is studied by Fourier-transform infrared spectroscopy and atomic force microscopy, showing that the use of isopropyl-imidazole 1H-1-carboxylate inhibits the degradation of the polylactic acid composite compared to the pure polymer.
... Shown in Table 1, the highest percentage degradation, a value of 37.3%, was yielded by a catalyst load of 125 mg, a ferric nitrate value of 350 mg L -1 , and a persulfate value of 300 mg L -1 . This lines up with the favorable photocatalytic degradation of diazinon facilitated by the presence of Fe(III) resulting from a light Fenton reaction occurring in the system [13], [20]. Also, the enhanced degradation of diazinon was due to the synergistic effects of the in-situ formation of sulfate radicals (SO 4 * -) that facilitates the possible activation of C 3 N 4 . ...
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In the past years, the non-conventional treatment of pesticides in wastewater like photocatalytic degradation has been the focus of the attention of researchers to mitigate its impact on both humans and the environment. In this study, synthesized graphitic carbon nitride (g-C3N4) from urea is used in the photocatalytic degradation of diazinon as a photocatalyst with the addition of ferric nitrate (Fe3(NO3)3) and potassium persulfate (K2S2O8) to enhanced degradation. Graphitic carbon nitride was produced using direct calcination of urea at 550°C for 2 h. The physicochemical properties of the synthesized g-C3N4 were characterized using Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), and X-ray Diffractometer (XRD). The photocatalytic degradation of diazinon was conducted under a g-C3N4/Fe(III)/persulfate system using different parameters such as catalyst loading (75, 100, and 125 mg), Fe3(NO3)3 (325, 350, and 375 mg L–1), and K2S2O8 (275, 300, and 325 mg L–1) resulting to an improved photocatalytic degradation efficiency. The physicochemical results showed a synthesized g-C3N4 that exhibits properties that are following the international standards. The results of photocatalytic degradation showed the highest degradation of g-C3N4 at 37.3%, under the parametric conditions of 125 mg g-C3N4, 325 mg L–1 of Fe3(NO3)3, and 300 mg L–1 of K2S2O8. The degradation efficiency was observed to increase as the catalyst load increases, while an increase in degradation efficiency can only be observed up to a certain value using ferric nitrate and persulfate. Overall, this study provided insight on the possible use of urea, as a source of g-C3N4 and the use of g-C3N4 as a photocatalyst using visible light as a more economic approach and cost-efficient way of handling wastewater.
3D printing has been attracting attention in recent years due to its versatility in design optimization and reduced labour and production costs. It has been implemented in many major sectors such as automotive, aerospace, and healthcare. One of the most recent researches involving this technology is in the prosthetics and orthotics field. The aim of this paper is to review the recent researches on Ankle-Foot Orthosis (AFO) which uses 3D printing in its manufacturing and fabrication phase. This paper discusses the current 3D printing technologies used for AFO, the comparison between Conventional Manufacturing (CM) and Additive Manufacturing (AM) of AFO, as well as the mechanical properties of AFO prototypes built from 3D printing. Results from this review show that most current researches use Fused Deposition Modelling (FDM) or Selective Laser Sintering (SLS) for AFO manufacturing, and the materials used are mostly thermoplastics such as Nylon and Polyamide (PA). The results also show that the tensile strength and Young’s Modulus of a 3D-printed AFO could reach as high as 43 MPa and 3.9 GPa, respectively. It can be concluded that 3D printing provides wider opportunities in the development of AFO due to its versatility in optimizing complex geometries, time and weight savings, as well as its cost-effectiveness. © 2020 Academic Enhancement Department, King Mongkut's University of Technology North Bangkok. All Rights Reserved.
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Titanium dioxide/polystyrene (TiO2/PS) core–shell nanoparticles (CSNPs) reinforced linear low density polyethylene/poly (lactic acid) (LLDPE/PLA) blends were developed by means of compounding and injection moulding. TiO2/PS CSNPs were prepared by ultrasound-assisted method while PLA was prepared by polycondensation of l-lactic acid, and were added to commercial grade LLDPE. The morphological analysis, carried out by electron microscopy, revealed significant phase separation in LLDPE/PLA blends but showed improved compatibility in LLDPE/PLA (TiO2/PS) nanocomposites. The thermal behaviour of the nanocomposites, as observed from thermogravimetric analysis (TGA), was also improved as compared to its blend counterparts. The incorporation of TiO2/PS CSNPs also resulted in better mechanical properties. With the addition of 1 phr TiO2/PS CSNPs, the tensile strength and elongation of LLDPE/PLA/(TiO2/PS) nanocomposites increased significantly. The results demonstrate the effect of TiO2/PS CSNPs in providing better interfacial adhesion between LLDPE and PLA which led to significant improvement in the mechanical strength of the nanocomposites by allowing effective load transfer in the nanocomposites system. Graphical abstract
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Photodegradation of PLA/PE, PLA/PE/TiO2 nanospheres and PLA/PE/TiO2 nanotubes was obtained under simulated sunlight. The nanocomposites were analyzed by infrared spectroscopy, scanning electron microscopy and tensile-deformation measurements. TiO2 nanospheres and TiO2 nanotubes were found to present different effects on the crystallinity of PLA and a straight correlation between structural organization and photostability was observed. According to the results, TiO2 promotes the degradation of PLA and PE, affecting the organizational level of the polymers. By adding TiO2 nanoparticles to the PLA/PE films, vibration modes characteristic of degradation products were promptly observed and the lifetime of the polymer decreased when compared to the PLA/PE without TiO2 nanoparticles. Mechanical measurements showed an improvement of the mechanical properties when adding the TiO2 nanoparticles.
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Over the coming few decades bioplastic materials are expected to complement and gradually replace some of the fossil oil based materials. Multidisciplinary research efforts have generated a significant level of technical and commercial success towards these bio-based materials. However, extensive application of these bio-based plastics is still challenged by one or more of their possible inherent limitations, such as poor processability, brittleness, hydrophilicity, poor moisture and gas barrier, inferior compatibility, poor electrical, thermal and physical properties. The incorporation of additives such as plasticizers into the biopolymers is a common practice to improve these inherent limitations. Generally, plasticizers are added to both synthetic and bio-based polymeric materials to impart flexibility, improve toughness, and lower the glass transition temperature. This review introduces the most common bio-based plastics and provides an overview of recent advances in the selection and use of plasticizers, and their effect on the performance of these materials. In addition to plasticizers, we also present a perspective of other emerging techniques of improving the overall performance of bio-based plastics. Although a wide variety of bio-based plastics are under development, this review focuses on plasticizers utilized for the most extensively studied bioplastics including poly(lactic acid), polyhydroxyalkanoates, thermoplastic starch, proteinaceous plastics and cellulose acetates. The ongoing challenge and future potentials of plasticizers for bio-based plastics are also discussed.
It is challenging to integrate porous graphene foam (GF) and GF-based nanocomposites into microfluidic channels and even create microfluidic structures within these materials. This is because their irregular interior pore shape and geometry, rough exterior surface, and relatively large material thickness make it difficult to perform conventional photolithography and etching. This challenge has largely hindered the potential of using GF-based materials in microfluidics-based sensors. Here we present a simple approach to create well-defined flow-through channels within or across the GF-based materials, using a liquid-phase photopolymerization method. This method allows embedding of a nanocomposite-based scaffold of GF and titanium nitride nanofibers (GF−TiN NFs) into a channel structure, to realize flow-through microfluidic electrochemical sensors for detecting nitrate ions in agricultural soils. The unique GF−TiN nanocomposite provides high electrochemical reactivity, high electron transfer rate, improved loading capacity of receptor biomolecules, and large surface area, serving as an efficient electrochemical sensing interface with the help of immobilized specific enzyme molecules. The microfluidic sensor provides an ultralow limit-of-detection of 0.01 mg/L, a wide dynamic range from 0.01 to 442 mg/L, and a high sensitivity of 683.3 µA mg-1L cm-2 for nitrate ions in real soil solution samples. The advantageous features of GF−TiN nanocomposite, in conjunction with the in-situ integration approach, will enable a promising microfluidic sensor platform to monitor soil ions for nutrient management towards sustainable agriculture.
We report on a label-free microfluidic immunosensor with femtomolar sensitivity and high selectivity for early detection of epidermal growth factor receptor 2 (EGFR2 or ErbB2) proteins. This sensor utilizes a uniquely structured immunoelectrode made of porous hierarchical graphene foam (GF) modified with electrospun carbon-doped titanium dioxide nanofibers (nTiO2) as an electrochemical working electrode. Due to excellent biocompatibility, intrinsic surface defects, high reaction kinetics, and good stability for proteins, anatase nTiO2 are ideal for electrochemical sensor applications. The three-dimensional and porous features of GF allow nTiO2 to penetrate and attach to the surface of the GF by physical adsorption. Combining GF with functional nTiO2 yields high charge transfer resistance, large surface area, and porous access to the sensing surface by the analyte, resulting in new possibilities for the development of electrochemical immunosensors. Here, the enabling of EDC–NHS chemistry covalently immobilized the antibody of ErbB2 (anti-ErbB2) on the GF–nTiO2 composite. To obtain a compact sensor architecture, the composite working electrode was designed to hang above the gold counter electrode in a microfluidic channel. The sensor underwent differential pulse voltammetry and electrochemical impedance spectroscopy to quantify breast cancer biomarkers. The two methods had high sensitivities of 0.585 µA µM–1 cm–2 and 43.7 kΩ µM–1 cm–2 in a wide concentration range of target ErbB2 antigen from 1 × 10–15 to 0.1 × 10–6 M, and from 1 × 10–13 to 0.1 × 10–6, respectively. Utilization of the specific recognition element (i.e., anti-ErbB2) results in high specificity, even in the presence of identical members of the EGFR family of receptor tyrosine kinases, such as ErbB3 and ErbB4. Many promising applications in the field of electrochemical detection of chemical and biological species will derive from the integration of the porous GF–nTiO2 composite into microfluidic devices.
In this work, mesoporous, hollow TiO2 nanofibers were fabricated by a coaxial electrospinning technique for the photocatalytic degradation of para-nitrophenol (4-NP), a well-known model water pollutant dye. The as-synthesized hollow nanofibers were sensitized by cadmium sulphide (CdS) quantum dots (QDs) through successive ion layer adsorption and reaction (SILAR) method for different deposition cycles. The CdS QDs loaded hollow TiO2 nanofibers (TiO2/CdS) harvest catalytic spots at the QDs and TiO2 interface which helps in enhanced exciton separation. The hollow and porous TiO2/CdS photocatalyst enhances absorption of UV and visible light due to presence of CdS QDs on the nanofiber surfaces. The resultant CdS QDs synthesized hollow TiO2 nanofibers exhibit excellent photocatalytic activity as shown with the degradation of 4-NP dye in aqueous medium. The photocatalytic degradation study was probed spectrophotometrically by measuring the absorbance of the degraded 4-NP solution using a UV-Vis absorption spectrophotometer. The effect of CdS QDs deposition cycles on dye degradation performance was also studied for TiO2/CdS nanofibers. TiO2/CdS photocatalyst for 3 SILAR deposition cycles was found to be ∼3 times more efficient than hollow TiO2 nanofibers and ∼8 times effective than the solid nanofibers. These nanofibers are reusable and their nanostructures do not change after repetitive usage. Such pristine and QDs sensitized hollow TiO2 nanofibers are thus a promising platform for the development of photocatalytic wastewater treatment and other applications such as photocatalytic water splitting, sensors, Li-ion batteries, and supercapacitor electrodes.
Conference Paper
Poly (lactic acid) (PLA) blended with poly (butylene succinate) (PBS) were prepared by using twin screw extruder and injection molding machine at various contents of PBS from 0-15 wt%. The surface of titanium dioxide (TiO2) nanoparticles was treated using aminopropyl trimethoxy silane (ATS) order to disperse them into the biopolymer blends. The mechanical and thermal properties of PLA/PBS/TiO2 nanocomposites were investigated over a range of filler content 0-5 wt%. All samples with a wide range of TiO2 addition exhibit the translucency. The surface morphology showed that the addition of PBS at 10 wt% was miscible with PLA while the other contents of PBS exhibited phase separation in the blends. Additionally, a uniform dispersion of filler in the matrix existed when the nanoparticles content was less than 3 wt%. The surface treated nanoparticles played an important role in mechanical and thermal properties of the nanocomposites because of its well dispersion and strong interfacial interaction between the nanoparticles and PLA/PBS matrix.
Poly(lactic acid) (PLA) represents one of the most promising and attractive biobased polymer for the industrial development of environmentally sustainable packaging. However, oxygen and water barrier properties of PLA based films cannot compete with those of commercially available composite multilayers. To fill this gap, we used the layer-by-layer deposition technique on commercially used PLA thin films (30 pm thick) in order to increase their barrier properties to oxygen and water vapor. Nanometric films were grown by alternating branched poly(ethylene imine) (BPEI), hydrophobic fluorinated polymer (Nafion), and montmorillonite clay (MMT) layers with the aim of obtaining low gas permeability in both dry and moist conditions as well as low water vapor permeability. Two different kinds of architectures were designed and successfully prepared, based on a 4 layer repeating unit (BPEI/MMT/BPEI/Nafion), represented here as quadlayer (QL), and on a 6 layer repeating-unit ((BPEI/Nafion)(2)/BPEI/MMT), hexalayer (HL). Reduction in oxygen and water permeabilities is observed for films based on both types of repeat units. The reduction of the permeabilities increases with the number of quad and hexalayers achieving reductions in terms of oxygen permeability in both dry and humid conditions up to 98% and 97% respectively for 10 HL and QL. Furthermore, a reduction of 78% of water vapor transmission rate through the functionalized film was obtained for these films. As far as oxygen permeability is concerned, HL films are more efficient than QL films for smaller numbers of deposition units. These properties are shown to result from the complementarity between the presence of BPEI/Nafion and MMT layers.
We have fabricated partially aligned free-standing mesoporous pure anatase TiO2 nanofiber mats (TiO2-NF) for photocatalysis by electrospinning on a rotating drum collector using a blend of titanium isopropoxide (Ti(OiPr)4), with a carrier polymer, polyvinylpyrrolidone (PVP) in acetic acid and ethanol. Calcination removes PVP and generates mesoporous TiO2-NF with fiber diameters in the range of 25-75 nm by optimizing the electrospinning parameters like electric field strength, polymer concentration and flow rate of solution, etc. The band gap energy of TiO2 nanofibers form the UV-vis absorption spectra is found to increase with increase in the calcination temperature thus allowing band gap engineering for different applications. The surface morphology, phase composition, crystallinity, surface area and porosity of the TiO2-NF are also investigated. We demonstrate the efficient and reusable photocatalytic action of the partially aligned pure electrospun TiO2-NF and residual carbon containing TiO2-NF mats with an average fiber diameter ~40 nm in the photocatalytic degradation of a polycyclic aromatic hydrocarbon (PAH) dye, naphthalene. Small carbon residue (2.54%) containing TiO2-NF is found to be about twice as efficient as the pristine TiO2-NF in photodegradation of PAH dye, but the effectiveness declined at higher carbon content.