82 Tekstilec, 2025, Vol. 68(1),  82–99   |   DOI: 10.14502/tekstilec.68.2024135
Brigita Tomšič, Maja Blagojevič, Nuša Klančar, Erik Makoter, Klara Močenik, Nika Pirš, Sebastijan Šmid, 
Marija Veskova, Marija Gorjanc, Mateja Kert, Barbara Simončič
University of Ljubljana, Faculty of Natural Sciences and Engineering, Aškerčeva 12, 1000 Ljubljana, Slovenia
Multifunctional  Properties of Cotton Fabric Tailored via 
Green Synthesis of TiO2/Curcumin Composite  
Večfunkcionalne lastnosti bombažne tkanine, pripravljene z 
zeleno sintezo kompozita TiO2 /kurkumin
Original scientific article/Izvirni znanstveni članek
Received/Prispelo 11–2024 • Accepted/Sprejeto 1–2025
Corresponding author/Korespondenčna avtorica:
Prof. dr. Barbara Simončič
Tel: +38513712557
E-mail: barbara.simoncic@ntf.uni-lj.si
ORCID iD: 00000-0002-6071-8829
Abstract
In this study,  a novel green process was developed to produce a multifunctional cotton (CO) fabric incorporating 
TiO2 /curcumin composites that simultaneously provides UV protection and photocatalytic performance. For 
this purpose, TiO2 was synthesised using the sol–gel process; loaded with the natural colourant curcumin as a 
visible light absorber at two temperatures, i.e., 70 and 350 °C; and applied to the CO fabric via the pad–dry–cure 
process. For comparison, TiO2 was synthesised without curcumin under the same conditions. The synthesis 
conditions at 70 °C ensured the formation of predominantly amorphous TiO2, while curcumin promoted TiO2 
crystallisation despite the low synthesis temperature. A 350 °C synthesis temperature was high enough to 
form the polymorphic TiO2 anatase phase. Although the increase in synthesis temperature and the presence 
of curcumin in the composites caused a bathochromic shift in light absorption, the photocatalytic activity of 
all samples was mainly driven by UV light. Chemically modifying the CO fabric significantly reduced the light 
transmittance of the samples, with the highest absorption of UV light obtained for the sample containing 
the TiO2 /curcumin composite synthesised at 70 °C. This sample provided excellent UV protection with a UPF 
value of 51.6. All chemically modified CO samples showed photocatalytic activity, degrading coffee stains 
and decolourising methylene blue and Rhodamine B dye solutions. The highest photocatalytic efficiency and 
reusability were obtained again for the CO sample with the TiO2 /curcumin composite synthesised at 70 °C, 
demonstrating the synergistic effect between TiO2 and curcumin in the composite prepared under these 
synthesis conditions.
Keywords: multifunctional cotton, titanium dioxide, Curcuma longa, green synthesis
Izvleček
Razvit je bil nov zelen postopek za izdelavo večfunkcionalne bombažne (CO) tkanine z vgrajenimi kompoziti 
TiO2 /kurkumin, ki hkrati zagotavlja UV-zaščito in fotokatalitsko delovanje. V ta namen je bil sintetiziran 
TiO2 s postopkom sol–gel v prisotnosti naravnega barvila kurkumina kot stabilizatorja in absorberja vidne 
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Multifunctional properties of cotton fabric tailored via green synthesis of TiO2  /curcumin composite 83
svetlobe pri dveh temperaturah, in sicer 70 in 350 °C, ter nanesen na CO-tkanino z impregnirnim postopkom. 
Za primerjavo je bil TiO2 sintetiziran pri enakih pogojih brez prisotnosti kurkumina. Pogoji sinteze pri 70 °C so 
omogočili nastanek pretežno amorfnega TiO2, je pa prisotnost kurkumina podprla kristalizacijo TiO2 kljub nizki 
temperaturi sinteze. Temperatura sinteze 350 °C je bila dovolj visoka za tvorbo TiO2 v polimorfni fazi anatasa. 
Čeprav sta zvišanje temperature sinteze in prisotnost kurkumina v kompozitih povzročila batokromni premik 
absorbirane svetlobe, je bila fotokatalitska aktivnost vseh vzorcev pogojena predvsem z UV-svetlobo. Kemijska 
modifikacija CO-tkanine je bistveno zmanjšala prepustnost svetlobe vseh vzorcev, pri čemer je bila najvišja 
absorpcija UV-svetlobe dosežena pri vzorcu, ki je vseboval kompozit TiO2/kurkumin, sintetiziran pri 70 °C. 
Ta vzorec je zagotovil odlično UV-zaščito z UZF vrednostjo 51,6. Vsi kemijsko modificirani CO-vzorci so bili 
fotokatalitsko aktivni, kar je privedlo do razgradnje madežev kave in razbarvanja raztopin barvil metilensko 
modro in Rhodamine B. Največji fotokatalitska učinkovitost in sposobnost ponovne uporabe sta bili tudi v tem 
primeru doseženi pri CO-vzorcu s kompozitom TiO2 /kurkumin, sintetiziranim pri 70 °C, kar kaže na sinergijski 
učinek med TiO2 in kurkuminom v kompozitu, pripravljenim pri teh sinteznih pogojih. 
Ključne besede: večfunkcionalni bombaž, titanov dioksid, Curcuma longa, zelena sinteza
1 Introduction
Titanium dioxide (TiO2) is a wide-band-gap semi- in the valence band. This forms electron–hole pairs 
conductor that represents one of the most versatile that can migrate to the TiO2 surface and participate 
nanomaterials (NMs) in various environmental, in redox reactions in the presence of oxygen and 
energy and biochemical fields owing to its unique water, forming highly reactive oxygen species (ROS). 
properties, including photocatalytic activity; The latter can react in subsequent reactions with 
ultraviolet (UV) light absorption; chemical, pho- various pollutants, including dye molecules in the 
tochemical and thermal stability; biocompatibility; water, and cause their degradation [5–7].
and non-toxicity [1–3]. In the field of textiles, TiO2 The photocatalytic activity of TiO2 is directly 
is an established textile finishing agent, where the influenced by various factors, including the 
application of TiO2 NMs can impart multifunctional morphology of NMs and their crystallinity and 
properties such as photocatalytic self-cleaning, modifications of the TiO2 surface and interface 
UV protection, antimicrobial activity, deodorising [8–11]. It has been reported that nanostructured 
properties, hydrophobicity, thermal stability, flame TiO2 exhibits better photocatalytic performance 
retardancy and electrical conductivity [4]. Fur- compared with bulk materials and that the most 
thermore, textiles functionalised with TiO2 can be effective photocatalytic activity can be obtained 
advantageously used for smart energy-harvesting for TiO2 NMs with polymorphic anatase crystal 
textiles and to degrade various pollutants in air or structures owing to their high surface-to-volume 
water through a photocatalytic reaction. Regarding ratio and nanoscale crystallite size. Different surface 
the latter, it has been reported that textile substrates and interfacial engineering strategies for TiO2 are 
can serve as an excellent scaffolding for TiO2 NMs to crucial for improving photocatalytic performance 
enhance their photocatalytic activity [4]. and enhancing visible light photocatalytic activity. 
The photocatalytic process in TiO2 is initiated by These mainly include multiphase heterojunctions, 
irradiation with UV light, enabling the absorption of ion doping, metal doping/loading, coupling with 
photons that excite electrons from the valence band other semiconductors and surface sensitisation 
(VB) into the conduction band (CB), leaving holes [10]. As TiO2 surface sensitisers, synthetic dyes are 
84 Tekstilec, 2025, Vol. 68(1),  82–99
usually adsorbed onto the TiO2 surface to improve presence of the natural dye curcumin as a visible light 
its absorption properties for visible light. Such pho- absorber and stabiliser and to construct a cotton/
tocatalytic systems are commonly used in dye-sen- TiO2/curcumin composite with effective multi-
sitised solar cells, with ruthenium-based dyes being functional photocatalytic performance. Co tton fabric 
the most extensively studied as sensitisers because was selected as the textile substrate because it is one 
of their high performance in improving system of the most versatile textile substrates, with a wide 
efficiency. The mechanism of photocatalytic activity range of applications. As a natural fibre with many 
for dye-sensitised TiO2 is based on the dye’s absorp- advantages – such as hydrophilicity, breathability, 
tion of visible light, promoting electron excitation flexibility, durability and biodegradability - cotton is 
from the highest occupied molecular orbital of the a very suitable textile substrate for incorporating TiO2 
dye (HOMO) to the lowest unoccupied molecular NMs to produce multifunctional composites for ap-
orbital (LUMO), followed by electron transfer from parel and technical purposes. In addition, cotton can 
the LUMO with a higher energy level to the CB of form close bonds with dye-sensitised TiO2 because of 
the TiO2 with a lower energy level. This transfer is its high functional hydroxyl group content, improving 
crucial, as it allows the oxygen reduction reaction the stability of the composite. In this experiment, 
to generate superoxide radicals, one of the most two methods were used to synthesise dye-sensitised 
important ROS, to take place on the surface of the TiO2, the first at a temperature of 350 °C, ensuring the 
TiO2 under visible light [12]. formation of the anatase crystal structure of TiO2, and 
However, synthesising heavy-metal-based dyes the second at the more sustainable low temperature 
is not in line with the principles of green chemistry of 70 °C, during which the formation of amorphous 
because of the toxicity and environmental impact TiO2 was expected. We hypothesised that curcumin 
of ruthenium [13]. Therefore, replacing rutheni- in the composite would activate the TiO2 and en-
um-based dyes in dye-sensitised TiO2 composites hance photocatalytic activity, even when synthesised 
with non-toxic alternatives is a major research at lower temperatures. For comparison, TiO2 was 
challenge. Following sustainable approaches, natural synthesised without curcumin. The effectiveness of 
dyes and pigments derived from natural sources the photocatalytic performance of cotton/TiO2/cur-
have already been used not only as stabilisers in TiO2 cumin composites compared with that of cotton/TiO2 
NM synthesis but also as visible light activators in composites was investigated by determining their UV 
the construction of dye-sensitised TiO2 [14–20]. protection properties and photocatalytic activity.
Among the natural colourants, turmeric powder 
extract, obtained from the Curcuma longa plant, has 
a long tradition in daily life, where it is used as a spice 2 Experimental
in cooking and as a natural remedy in health and skin 
care [21–25]. Turmeric powder is also often used as 2.1 Materials
a natural colourant because of its orange-coloured Chemically bleached 100 % cotton (CO) fabric in 
active ingredient, curcumin (diferuloyl methane) plain weave with a mass per unit area of 120 g/m2 
[26, 27]. Curcumin contains phenolic hydroxyl was kindly provided by Tekstina d.o.o., Ajdovščina, 
and carbonyl groups in its chemical structure that Slovenia, for this study. Titanium(IV) isopropoxide 
can form attractive hydrogen bonds with TiO2 [28], (TTIP; ≥ 97.8% concentration), isopropanol (iPrOH; 
contributing to the stability and durability of the ≥ 99% concentration) and acetic acid (AA; 99% 
composite. concentration), all products from Sigma Aldrich 
This research aims to develop a new process for (USA), were used to prepare TiO2 nanoparticles 
the green synthesis of dye-sensitised TiO2 in the (NPs). Turmeric powder (Maestro, Podravka d.d., 
Multifunctional properties of cotton fabric tailored via green synthesis of TiO2  /curcumin composite 85
Croatia) was purchased from the local supermarket. to remove all the unadsorbed curcumin. One half 
Methylene Blue (MB; Sigma Aldrich, USA) and of the sample was then dried at 70 °C for 3 hours 
Rhodamine B (RhB; Sigma Aldrich, USA) were used and labelled (T+C)70. The other half of the sample 
as dyes for monitoring the photocatalytic activity of amount was additionally calcinated at 350 °C, and 
the samples. that sample was labelled (T+C)350.
For comparison, TiO2 NPs without curcumin 
2.2 Synthesis of curcumin-sensitised TiO2 were synthesised under the same conditions at both 
The curcumin-sensitised TiO2 synthesis comprised temperatures, i.e. at 70 °C for the (T)70 sample and 
a synthesis of TiO2 NPs loaded with curcumin. To at 350 °C  for the (T)350 sample.
synthesise TiO2 NPs, a 4% solution of hydrolysed 
TTIP in isopropanol and acetic acid was prepared 2.3 Chemical modification of cotton samples
(12 g TTIP in a mixture of 168 g of iPrOH and 20 g To chemically modify the CO fabric samples, (T)70, 
of AA). The solution was prepared in a beaker and (T+C)70, (T)350 and (T+C)350 sols were prepared 
placed on a magnetic stirrer. While the solution was at 4 % concentration in distilled water and sonicated 
stirring, 200 g of distilled water was added drop by for 2 hours to obtain homogeneous dispersions. Sols 
drop. Afterwards, the sol was left stirring for the were applied to the CO samples using a pad–dry–cure 
next 15 minutes at room temperature to complete process, which included fully immersing the CO 
the TiO2 synthesis. The TiO2 NPs were then filtered samples in the sol for 1 minute (four 6 cm × 7 cm CO 
and dried at 70 °C. Turmeric extract was prepared samples for each sol), squeezing the samples with a 
in bi-distilled water at a concentration of 5 g/L. 95 ± 2% wet pick-up, drying them at 100 °C for 1 min, 
Turmeric powder was dispersed into the bi-distilled and curing them at 150 °C for 5 min. Afterwards, the 
water at room temperature. The dispersion was functionalised CO samples were rinsed with distilled 
boiled for five minutes and then left to cool down for water three times for one minute to remove unbound 
30 minutes. Afterwards, the dispersion was filtered TiO2. The synthesis processes for the (T)70, (T+C)70, 
and dried. (T)350 and (T+C)350 powder samples and their ap-
To load TiO2 NPs with curcumin, a 4 % TiO2 solu- plication to the CO fabric samples are schematically 
tion was prepared in 5 g/L of turmeric extract and presented in Figure 1. The sample codes are shown 
stirred for 12 hours in the dark at room temperature. in Table 1 according to the functionalised chemical 
The sample was then centrifuged, decanted, rinsed modification and fabrication of multifunctional 
in water three times, and centrifugated and decanted cotton samples.
Table 1: Sample codes and description of the cotton chemical modification process
Sample code Process description
CO(UN) Untreated cotton sample
CO(T)70 Cotton sample chemically modified with TiO2 dried at 70 °C
CO(T+C)70 Cotton sample chemically modified with TiO2/curcumin composite dried at 70 °C
CO(T)350 Cotton sample chemically modified with TiO2 calcinated at 350 °C
CO(T+C)350 Cotton sample chemically modified with TiO2/curcumin composite calcinated at 350 °C
86 Tekstilec, 2025, Vol. 68(1),  82–99
Figure 1: Schematic presentation of the synthesis process for TiO2 and TiO2/curcumin composites and the chem-
ical modification of CO samples
2.4 Analysis and Measurement b is the full width at half-maximum (FWHM); and q 
is the diffraction angle.
2.4.1 X-ray diffraction (XRD)
An XRD characterisation was performed for the 2.4.2 Scanning electron microscopy (SEM) and 
synthesised (T)70, (T+C)70, (T)350 and (T+C)350 energy-dispersive X-ray spectroscopy (EDX)
powders, the CO(UN), and the chemically modified SEM images of the untreated and chemically modi-
CO(T)70, CO(T+C)70, CO(T)350 and CO(T+C)350 fied CO samples were acquired using a JSM 6060 LV 
samples using a PANalyticalX’Pert PRO X-ray dif- scanning electron microscope (JEOL, Tokyo, Japan) 
fractometer (XRD) (CuK a 1 = 1.5406 Å) with a fully operated with a primary electron beam accelerated 
open X’Celerator detector (2.1225° 2q). The XRD to 10 kV. All samples were coated with a thin layer of 
pattern was measured from 10 to 90° 2q with a step gold before examination to provide conductivity and 
size of 0.034° 2q and a 100 s integration time. The improve the quality of the images.
crystallite size, D, of the powder samples was deter- EDX analysis was performed using a field 
mined from XRD spectra using the Debye–Scherrer emission scanning electron microscope, FEG-SEM 
equation [29]: Thermo Scientific Quattro S (ThermoFischer Scien-
tific, USA). Sample analysis was performed using an 
(1) Oxford Instruments Ultim Max 65 energy-dispersive 
detector (EDX) and AZtec software Ver 6.0 (Oxford 
where λ is the wavelength of X-rays equal to 0.154 nm; Instruments, USA). Samples were coated with a thin 
Multifunctional properties of cotton fabric tailored via green synthesis of TiO2  /curcumin composite 87
carbon layer before analysis to provide conductivity (T+C)70, (T)350 and (T+C)350 coatings on the CO 
and thus improve the quality of the images. samples were determined using the Tauc relation 
[30, 31]:
2.4.3 Inductively coupled plasma-mass spectrom-
etry (ICP-MS) (3)
The Ti concentrations in the CO(T)70, CO(T+C)70, where a is the energy-dependent absorption coeffi-
CO(T)350 and CO(T+C)350 samples were deter- cient, equal to 2.303 × A; h is Planck constant; n is 
mined via ICP-MS using a Perkin Elmer SCIED the frequency of the radiation; and K is a constant. 
Elan DRC spectrophotometer. A 0.5 g sample was According to Planck’s radiation law, the energy, E, of 
prepared in a Milestone microwave system via acid radiation is equal to:
decomposition with 65% HNO3 and 30% H2O2. Ti 
concentrations in studied samples were reported (4)
as the mean values of two measurements for each 
sample. Based on the measured Ti values, the TiO The values of Eg are obtained through extrapola-
2 
concentration was calculated. tion to a = 0 [31].
2.4.4 Fourier transform infrared spectroscopy 2.4.6 UV protection
(FTIR) The UV protection of the CO(UN), CO(T)70, 
The chemical compositions was analysed for the CO(T+C)70, CO(T)350 and CO(T+C)350 samples 
synthesised (T)70, (T+C)70, (T)350 and (T+C)350 was determined according to Standard EN 13758-1: 
powder samples, the untreated CO(UN), and 2001. Transmission was calculated at three different 
the chemically modified CO(T)70, CO(T+C)70, wavelength ranges, i.e., UVA from 315 to 400 nm 
CO(T)350 and CO(T+C)350 samples using an and UVB from 290 to 315 nm. The UV protection 
FTIR spectrometer, Spectrum 3 (Perkin Elmer, factor (UPF) was calculated with the following 
UK). Spectra between 4000 cm-1 and 400 cm-1 were equation [32]:
recorded with a 4 cm-1 resolution and an average of 
120 spectra per sample. (5)
2.4.5 UV–Vis spectroscopy where E(λ) represents the solar spectral irradiance; 
The transmission spectra of the CO(T)70, ε(λ) represents the relative erythemal effectiveness; 
CO(T+C)70, CO(T)350 and CO(T+C)350 samples Δ(λ) represents the wavelength interval; and T(λ) is 
were recorded in a wavelength, λ, range of 250–700 the spectral transmittance at the wavelength, λ.
nm using a Lambda 850+ UV/Vis spectrophotome-
ter (Perkin Elmer, UK). Three measurements were The UPF rating and protection categories were 
made for each sample at different warp alignment determined using UPF values with the Australian/
angles, and the average value of transmittance, T, New Zealand Standard for Sun-Protective Cloth-
at each λ was calculated. The average transmission ing—Evaluation and Classification (AS/NZS 4399, 
spectra were converted into absorption spectra 2020), where UPF values of 15 are suited to the 
using the following equation: “minimum protection” category; UPF values of 
30 are suited to the “good protection” category; 
(2) and UPF values of 50 are suited to the “excellent 
protection” category.
where A is absorbance. From the absorption spec-
tra, the optical band gap energies, Eg, of the (T)70, 
88 Tekstilec, 2025, Vol. 68(1),  82–99
2.4.7 Photocatalytic activity determined using previously prepared calibration 
The photocatalytic activity of the CO(T)70, curves. The measurements were performed using 
CO(T+C)70, CO(T)350 and CO(T+C)350 samples a Lamda 850+ UV–Vis spectrophotometer (Perkin 
was determined based on photocatalytic self-clean- Elmer, United Kingdom). The photocatalytic degra-
ing and photocatalytic dye degradation in the dation efficiency of the RhB and MB dyes was deter-
solution. To study the photocatalytic self-cleaning mined based on the dye concentration ratio, Ct/C0, 
performance, the samples were immersed in de- where Ct is the dye concentration at a given time of 
canted Turkish coffee (5 g of ground coffee/100 mL illumination, and C0 is the initial concentration of 
water) for 30 s and then air dried and illuminated the dye solution after the adsorption–desorption 
in a Xenon Alpha instrument (Atlas, USA) at 35 °C equilibrium was established [34]. The lower the Ct/C0 
and 70% humidity for 4 and 24 hours. Before and ratio, the higher the degree of dye degradation. From 
after the illumination, the colour coordinates L*, a* these results, the apparent rate constant, Kapp, of the 
and b* in the CIELAB colour space were determined photocatalytic reaction was calculated as a measure of 
for the samples using a Datacolor Spectro 1050 spec- the dyes’ photocatalytic degradation efficiency, where 
trophotometer (Datacolor, USA). Measurements pseudo-first-order kinetics was used as follow [34]:
were performed with a 9 mm aperture under D65 
illumination and an observation angle of 10°. Ten (7)
measurements were performed for each sample, and 
the colour difference,  ∆E*
ab, was calculated using the where t is the illumination time. In the case of RhB 
following equation [33]: dye solution degradation, the reusability of the CO 
samples was determined after 4 repetitive operation 
(6) cycles.
where ∆L*, ∆a* and  ∆b* are the differences between 
the lightness, green–red and blue–yellow colour 3 Results and discussion
coordinates, respectively, calculated between the 
illuminated and nonilluminated samples. 3.1 Morphological, chemical and optical 
properties
For photocatalytic dye degradation, 0.01 mM The morphological, chemical and optical properties 
MB and 0.02 mM RhB dyes were prepared in of synthesised powder particles and chemically 
distilled water. The CO samples (3.5 cm × 0.8 cm) modified CO samples were analysed using XRD, 
were immersed in the dye solution (3 ml) that the SEM, EDX, ICP-MS, FTIR and UV–Vis spectrosco-
cuvettes were previously filled with (2 parallels py. The XRD patterns of the TiO2 powder samples 
for each sample) and stabilised in the dark for 30 (Figure 2a) show that the peaks of the (T)350 and 
minutes. Two additional cuvettes with only the dye 
(T+C)350 samples were much more intense than 
solution were used as a reference (blank). Afterwards, 
the cuvettes were illuminated for a set period in a those of the (T)70 and (T+C)70 samples. Strong 
Xenotest Alpha instrument equipped with a visible diffraction 2q peaks in the (T)350 and (T+C)350 
xenon arc lamp (radiation attitude, 0.8–2.5 kVA, and samples appearing at 25.3°, 37.8°, 47.9°, 54.0°, 55.3° 
extended radiation range, 300–400 nm). After each and 62.6° are characteristic TiO2 peaks in anatase 
illumination period, the absorption spectrum of the polymorph phase and correspond to tetragonal crys-
dye solution was recorded, from which the maximal tal planes (1 0 1), (0 0 4), (2 0 0), (1 0 5), (2 1 1) and 
value of A at a suitable wavelength was determined (2 0 4), respectively [35–37]. In the case of the (T)70 
(for RhB at 552.9 nm, MB at 664.0 nm) and the powder sample, the un-sharpness and larger width 
corresponding dye concentration in solution was of the low-intensity peaks indicate that TiO2 formed 
Multifunctional properties of cotton fabric tailored via green synthesis of TiO2  /curcumin composite 89
a mostly amorphous phase during the synthesis at CO(T+C)70, CO(T)350 and CO(T+C)350 samples 
70 °C. Curcumin in the preparation of the (T+C)70 blurred the characteristic TiO2 peaks because of the 
powder sample significantly increased the intensity intensive 2q peaks at 15.0°, 16.8°, 22.7° and 34.5°, 
of the peaks in the diffractogram, suggesting that which correspond to the (1 1 0), (1 1 0), (2 0 0) and 
curcumin promotes TiO2 crystallisation even at low (4 0 0) crystallographic planes of the crystalline 
synthesis temperatures and that polymorphically structure of cellulose, respectively (Figure 2b) [38]. 
modified anatase was also partly formed in this sam- Only the TiO2 diffraction 2q peaks at 25.3° can be 
ple. Cellulose in the chemically modified CO(T)70, seen in the CO(T)350 and CO(T+C)350 samples.
Figure 2: XRD patterns of (T)70, (T+C)70, (T)350 and (T+C)350 powder samples (a) and untreated CO(UN) 
and chemically modified CO(T)70, CO(T+C)70, CO(T)350 and CO(T+C)350 samples (b)
For the (T+C)70, (T)350 and (T+C)350 powder This indicates that TiO2 sol–gel synthesis enables the 
samples, where the anatase polymorph phase was fabrication of NPs of very small sizes, around 10 nm. 
determined from the XRD patterns, the average crys- Similar results have been reported in the literature 
tallite size was calculated using the Debye–Scherrer [39]. The curcumin in the (T+C)350 sample did not 
equation and was on the nanometre scale (Table 2). significantly influence the crystallite size.
Table 2: Crystallite size of the TiO2 powder samples calculated using the Scherrer equation
Sample code 2q (°) b (rad) Crystallite size (nm) Average crystallite size (nm)
25.3 1.321 4.2
(T+C)70 5.6
47.9 1.468 7.0
25.3 0.876 12.4
(T)350 11.6
47.9 0.993 10.7
25.3 0.850 12.8
(T+C)350 12.4
47.9 0.954 11.9
Applying (T)70, (T+C)70, (T)350 and (T+C)350 synthesis enables the fabrication of very small TiO2 
to the CO samples significantly increased the rough- NPs, they agglomerated after drying. Sonicating the 
ness of the fibre surfaces. Smaller and larger TiO2 dispersions for 2 hours before applying them to the 
particle agglomerates could be seen at nano- and CO samples did not sufficiently reduce the agglomer-
micro-dimensions (Figure 3a). Although sol–gel ate size. The curcumin in the (T+C)70 and (T+C)350 
90 Tekstilec, 2025, Vol. 68(1),  82–99
samples increased the agglomeration tendency, as was present in the CO(T)350 sample, which was 
there were visible, micrometre-sized agglomerates 16000 mg/kg. This value was more than three times 
in the CO(T+C)70 and CO(T+C)350 samples. The higher than that in the CO(T)70 sample (5100 mg/
presence of TiO2 in all chemically modified samples kg), and significantly higher than in the CO(T+C)70 
was confirmed by the EDX spectra (Figure 3b) and sample (10000 mg/kg) and the CO(T+C)350 sample 
element mapping (Figure 3c). The ICP-MS results (13000 mg/kg).
(Figure 3d) show that the highest amount of TiO2 
Figure 3: SEM images (a), EDX spectra (b), element mapping images (c) and the TiO2 concentration determined 
by ICP-MS (d) of CO(T)70, CO(T+C)70, CO(T)350 and CO(T+C)350 samples
The FTIR spectra of the samples included char- stretching vibration [40, 42–44]. The same obser-
acteristic absorption bands in the 1500–850 cm-1 vation was noticed in our previous study [48]. The 
region, belonging to the cellulose fingerprint [40, TiO2 anatase absorption bands in the 400–800 cm-1 
41]. These strong vibrational cellulose bands also region characterise the stretching vibration modes of 
blurred the characteristic absorption bands of tur- different Ti–O bonds (Ti–O–Ti, Ti–O–O, O–Ti–O) 
meric in the CO(T+C)70 and CO(T+C)350 samples, (Ti–O–Ti, Ti–O–O, O–Ti–O) [45–47], and could 
appearing in the 1740–1680 cm-1 region due to C=O only be observed for the CO(T)350 sample with the 
absorption, at 1510 cm-1 due to aromatic skeletal highest TiO2 NP load (see insert in Figure 4).
stretching vibrations, and at 1030 cm-1 due to C–OH 
Multifunctional properties of cotton fabric tailored via green synthesis of TiO2  /curcumin composite 91
The presence of (T)70, (T+C)70, (T)350 and 
(T+C)350 in the CO samples significantly reduced 
the transmission of UV radiation through the CO 
fabric (Figure 5a) owing to increased UV radiation 
absorption (Figure 5b). The Tauc plots obtained from 
the absorption spectra (Figure 5c) show that TiO2 
calcination at 350 °C caused a bathochromic shift 
in the light absorption of TiO2, as expected, since 
the value of Eg decreased from 3.41 for CO(T)70 to 
3.18 for CO(T)350 (Figure 5d). The presence of cur-
cumin in the TiO2 composites also slightly decreased 
the Eg values of the CO(T+C)70 and CO(T+C)350 
samples compared with the CO(T)70 and CO(T)350 
samples. However, Eg values of 3.30 and 3.16 eV 
for the CO(T+C)70 and CO(T+C)350 samples 
correspond to the absorbance values at 376 and 393 
nm, respectively, lower than that of visible light. This 
indicates that despite the bathochromic shift in light 
Figure 4: IR ATR spectra of untreated CO(UN) sam- absorption, the photocatalytic activity of the samples 
ple and chemically modified CO(T)70, CO(T+C)70, was mainly driven by UV light.    
CO(T)350 and CO(T+C)350 samples
Figure 5: Transmission (a) and absorption (b) spectra of untreated CO(UN) and chemically modified CO(T)70, 
CO(T+C)70, CO(T)350 and CO(T+C)350 samples; Tauc plots (c) and band gap energy, Eg (d), of CO(T)70, 
CO(T+C)70, CO(T)350 and CO(T+C)350 samples
92 Tekstilec, 2025, Vol. 68(1),  82–99
3.2 Functional properties have minimal UV protection, CO(T)350 has good 
Since TiO2 has established itself as an effective UV UV protection and CO(T+C)70 has excellent UV 
absorber, the UV protection properties of the chem- protection. The results also show that increased TiO2 
ically modified CO samples were determined using concentration from 5100 mg/kg for the CO(T)70 
the transmission spectra in the 280–400 nm range sample to 16000 mg/kg for the CO(T)350 sample 
(Figure 5a). Cotton alone does not offer sufficient increased the UPF value from 22.2 to 32.1. These 
protection against UV radiation, which is reflected results were expected, as according to our previous 
in a very low UPF value (Table 3). All the chemically studies, both amorphous and crystalline TiO2 exhib-
modified CO samples retained a higher UVA and it UV protection properties that do not exceed UPF 
UVB blocking effect, increasing the UPF values. Ac- values of 35 irrespective of the application procedure 
cordingly, the CO(T)70 and CO(T+C)350 samples or concentration [48, 49].
Table 3: UVA and UVB blocking, ultraviolet protection factor (UPF) and the protection categories for the un-
treated and chemically modified cotton samples
Sample code UVA blocking (%) UVB blocking (%) UPF Protection category a)
CO(UN) 67.1 75.4 3.7 I
CO(T)70 83.0 97.2 22.2 M
CO(T+C)70 89.6 99.0 51.6 E
CO(T)350 89.5 97.6 32.1 G
CO(T+C)350 89.1 97.2 27.3 M
a) I – insufficient, M – minimum protection, G – good protection, E – excellent protection
The excellent UV protection factor of the illuminated (Figure 6a, b). The results show that the 
CO(T+C)70 sample with a significantly lower TiO2 CO(UN) sample had no self-cleaning properties, as 
amount than in the CO(T)350 sample was a sur- the colour of the coffee stain did not fade during illu-
prise, as we had found that the curcumin dye alone mination but instead became slightly darker (Figure 
at the concentration used in our experiment could 6b). The colour difference between the non-illu-
not provide UV protection for the CO sample with minated CO(T+C)70 and CO(T+C)350 samples 
a UPF of 8.75 [48]. The UV protection properties stained with coffee and the same stained samples 
of CO(T+C)70 sample were also higher than those illuminated for 4 and 24 hours was greater than that 
of the CO(T+C)350 sample, which contained TiO2 between the CO(T)70 and CO(T)350 samples, sug-
in the (T+C) composite in an even higher concen- gesting that the curcumin in the (T+C) composites 
tration. However, the absorption spectra (Figure enhanced the photocatalytic self-cleaning activity 
5b) show that the absorption in the UVB range was of the samples. When the colour coordinates of the 
significantly higher for the CO(T+C)70 sample than chemically modified samples were examined after 24 
the other samples, blocking 99.0% of UVB radiation, h of illumination, it was found that the colour of the 
giving a UPF of 51.6 (Table 3). These results indicate coffee stain became lighter, greener and bluer than 
that the synergistic effect of TiO2 and curcumin is the non-illuminated samples. A comparison of the 
undoubtedly achieved in the (T+C)70 composite, CO(T+C)70 and CO(T+C)350 samples also shows 
which is not the case for the (T+C)350 composite. that the photocatalytic self-cleaning performance 
The photocatalytic self-cleaning performance of of the CO(T+C)70 sample was much more effective 
the chemically modified CO samples degraded the than that of the CO(T+C)350 sample, with the great-
coffee stain, which faded and changed colour when est differences in the values of D  and the colour 
Multifunctional properties of cotton fabric tailored via green synthesis of TiO2  /curcumin composite 93
coordinates DL*, Da* and Db* between the non-illu- even without photocatalytically active CO samples 
minated and the coffee stained samples illuminated (blank curve in Figure 7a).
for 24 hours. When the MB dye was replaced by the RhB dye 
with significantly higher photostability (blank curve 
in Figure 7c), the photocatalytic efficiency of the 
analysed CO samples differed considerably (Figure 
7c, d). As expected, the CO(UN) sample showed 
no photocatalytic activity, but the chemically 
modified CO samples decolourised the RhB dye 
solution with the following increased photocatalytic 
efficiency: CO(T)70 < CO(T)350 < CO(T+C)350 
< CO(T+C)70. Accordingly, the curcumin in the 
TiO2 composite undoubtedly increased the rate of 
photocatalytic dye degradation. However, the rate of 
dye decolourisation in the CO(T+C)70 sample was 
significantly higher than in the CO(T+C)350 sam-
ple, which can be seen in the digital images of the 
cuvettes filled with RhB solution after 180 minutes 
of illumination (Figure 7e). This also confirms the 
findings from the literature [50] that the RhB dye 
exhibits a strong sensitivity to photocatalytic deco-
lourisation, even with visible light.
To determine the reusability of the photocatalytic 
Figure 6: Colour difference, DE*
ab , between the unil- performance, one of the most important properties 
luminated samples stained by coffee and the stained from a technological point of view, the chemically 
samples illuminated for 4 and 24 hours (a); difference modified CO samples were tested in four consecutive 
in colour coordinates, DL*, Da* and Db*, between 180-minute cycles of RhB dye solution photodegra-
the unilluminated samples stained by coffee and the dation. After each cycle, the degree of dye decolouri-
stained samples illuminated for 24 hours (b) sation was determined (Figure 7f). The results show 
that the combination of curcumin and TiO2 again 
The results for the photocatalytic degradation of improved the reusability of the tested CO samples, 
the MB and RhB dye solutions show that the pho- with the highest photostability achieved for the 
tocatalytic degradation efficiency of the investigated CO(T+C)70 sample, resulting in 98% decolourisation 
dyes was influenced not only by the chemical mod- for the RhB dye after the fourth cycle.
ification of the CO samples but also by the chemical The low photocatalytic activity of the 
structure of the dyes (Figure 7 a–e). It should be em- CO(T+C)350 sample compared with the CO(T+C)70 
phasised that higher dye degradation is associated sample was somewhat surprising, as according 
with a lower Ct/C0 ratio at a given illumination time. to the literature, nanocrystalline TiO2 has higher 
In the case of the MB dye, all tested CO samples photocatalytic activity than amorphous TiO2 [4]. 
showed very similar dye decolourisation kinetics, This phenomenon was also confirmed by the higher 
regardless of their chemical modification (Figure 7a, photocatalytic activity of the CO(T)350 samples 
b). It is also evident that the photostability of the MB compared to the CO(T)70 sample. Therefore, the 
dye is very low, as it degraded under illumination FTIR spectra of the powder samples were analysed to 
94 Tekstilec, 2025, Vol. 68(1),  82–99
Figure 7: Photocatalytic degradation of MB dye solution without and in the presence of CO samples after differ-
ent illumination times, t (a); photodegradation kinetics of MB dye solution in the presence of chemically modified 
CO samples (b); photocatalytic degradation of RhB dye solution without (blank) and in the presence of CO 
samples after a different illumination time, t (c); photodegradation kinetics of RhB dye solution in the presence 
of CO samples (d); digital images of cuvettes filled with RhB solution after 180 minutes of illumination without 
and in the presence of CO samples (e); consecutive 180 min cycles of RhB dye solution photodegradation in the 
presence of chemically modified CO samples (f)
Multifunctional properties of cotton fabric tailored via green synthesis of TiO2  /curcumin composite 95
clarify the chemical changes between the composites 4 Conclusion
(Figure 8). The results show that the (T+C)70 powder 
sample exhibited characteristic curcumin bands at To summarise, novel multifunctional hybrid CO/
1597 cm-1 and 1509 cm-1 owing to C=C stretching TiO2/curcumin composites with UV protection 
vibrations in the conjugated aromatic system of the and photocatalytic self-cleaning performance were 
curcumin and at 900 cm-1 owing to the out-of-plane successfully prepared according to the principles of 
bending vibrations of aromatic C–H bonds [42–44]. green chemistry. XRD analysis showed that the TiO2 
These bending vibrations were not clearly visible in in the powdered (T)350 and (T+C)350 samples was 
the (T+C)350 powder sample. Furthermore, an addi- present in the polymorphic anatase phase, while the 
tional band in the (T+C)350 powder sample at 1230 TiO2 in the powdered (T)70 sample was amorphous. 
cm-1—corresponding to aromatic C–H bending in Curcumin in the (T+C)70 sample significantly 
smaller aromatic fragments such as vanillin or ferulic promoted the crystallisation of TiO2, partially 
acid [51]—suggests that the curcumin was partially converting the amorphous phase into the anatase 
thermally degraded during the calcination of the phase. The crystallite size of the (T)350, (T+C)350 
composite at 350 °C, which was also accompanied by and (T+C)70 powdered samples was less than 13 
a slight lightening of the composite colour. This could nm. However, SEM analysis revealed that applying 
be why only an additive effect between curcumin all the powdered samples to the CO fabric resulted 
and TiO2 in the (T+C)350 composite was achieved, in the formation of smaller and larger agglomerates. 
in contrast to the synergistic effect of the two compo- Increasing the synthesis temperature from 70 to 350 
nents in the (T+C)70 composite. °C and introducing curcumin into the (T+C) com-
posites decreased the Eg values and consequently 
shifted the absorbance to longer wavelengths. Since 
the latter did not exceed 400 nm in any sample, it is 
reasonable to assume that all samples mainly absorb 
UV light.
The absorption in the UVA and UVB range 
showed minimal UV protection for the CO(T)70 
and CO(T+C)350 samples with UPF values of 22.2 
and 27.3, respectively; good UV protection for the 
CO(T)350 sample with a UPF value of 32.1; and 
excellent UV protection for the CO(T+C)70 sample 
with a UPF value of 51.6. Regarding the UPF val-
ues, TiO2 and curcumin had a synergistic effect in 
the CO(T+C)70 sample, as the UV-blocking effect 
was more efficient than the additive effect of the 
CO(T)70 sample and the CO sample coloured only 
with curcumin at the same concentration.
The analysis of photocatalytic self-cleaning 
performance based on the degradation rate of coffee 
stains showed that all chemically modified CO sam-
Figure 8: IR ATR spectra of the (T)70, (T+C)70, ples caused colour fading, with the highest efficiency 
(T)350 and (T+C)350 powder samples. obtained for the CO(T+C)70 sample. This showed 
the largest differences in DE* values between the 
96 Tekstilec, 2025, Vol. 68(1),  82–99
non-illuminated and the 24-hour illuminated cof- Acknowledgments
fee-stained samples. Examining the photocatalytic 
degradation of the RhB dye solutions in the presence This research was carried out within the framework 
of the chemically modified CO samples revealed that of the courses on Advanced Finishing Processes and 
the CO(T+C)70 sample was the most efficient, fol- Chemical Functionalisation of Textiles in the Master 
lowed by the CO(T+C)350 and CO(T)350 samples, Study Programme for Textile and Clothing Planning. 
and that the lowest efficiency was obtained for the The research was co-funded by the Slovenian Research 
CO(T)70 sample. This confirms that the presence and Innovation Agency (Programme P2-0213 Textiles 
of curcumin in a composite with TiO2 significantly and Ecology, Infrastructural Centre RIC UL-NTF). 
increases photocatalytic activity, which also applies The authors would like to thank prof. dr. Matej Do-
to the reusability of samples. The low photocatalytic lenec for the support in the XPS analysis and prof. dr. 
activity of the CO(T+C)350 sample compared with Aleš Nagode for the support in the EDS analysis.
the CO(T+C)70 sample was attributed to the partial 
thermal degradation of curcumin during the calci-
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