Ultraviolet-Sensitive Photoluminescent Spray-Coated Textile

Abstract

The target of the presented research work was the development of new smart textiles with photoluminescence properties which maintain light emission for a prolonged time period, even when the illumination source is turned off. Phosphorescence has been frequently used to improve the reliability of various safety products. Thus, simple and photoluminescent and superhydrophobic smart cotton fibers were fabricated. Rare-earth-doped aluminate (REA) nanoparticles (NPs) were immobilized into room-temperature vulcanizing silicone rubber (RTV) and spray-coated onto cotton fibers. The coated fabrics were excited at 365 nm, while the emission peak was detected at 518 nm. Various concentrations of REA nanoparticles in the REANPs@RTV composite formula were used to create a homogeneous phosphorescent coating on the surface of the cellulosic fabrics. CIE (Commission Internationale de L’éclairage) lab values and emission spectra confirmed that the fabric had a white color under visible light, green color under UV rays, and greenish-yellow color in darkness. The lifetime of phosphorescence and decay time were examined. The findings also displayed an improvement in the superhydrophobic activity of the treated cellulosic fabrics as the phosphor content was increased in the REANPs@RTV composite formula. Additionally, the stiffness and air permeability of the treated cellulosic fabrics were determined in terms of comfort characteristics.

1. Introduction

Chemical agents, pressure, heat, light, magnetic and electric fields, solvent polarity and pH are all examples of external stimuli that smart fabrics can effectively identify [1,2,3,4]. Smart fabrics have been used as tools for drug release and moisturization through the human skin, detection and modification of muscle vibrations, and release substances that can regulate the body temperature. Actuation, sensing, and control units are the three main constituents to be included in the different types of smart textiles. By combining textile finishing with miniature electronic devices, smart clothing can be created, allowing digital constituents to be entrenched in the cellulosic fabrics to provide transformation, communication, and electrical conductivity [5,6,7].

Photoluminescent textile materials have been employed in a number of applications, such as photoluminescent guiding signs to evacuate buildings during power outage [8,9,10]. When exposed to an illuminating light source, phosphorescent pigments gain luminous properties in terms of their excitation and capacity to maintain light energy. Organic colorants, like porphyrins and perylenes, and inorganic colorants, like SrAl₂O₄:Eu²⁺,Dy³⁺, have been used to develop a variety of colored materials [11,12,13,14,15,16,17,18,19]. However, organic luminescent dyestuffs have a lot of drawbacks, including poor photo- and thermal properties, progressive dyestuff deterioration, increased toughness, and poor colorfastness. Most of these flaws were resolved by microencapsulation. While this technique improves the stability of photoluminescent materials, it also increases the harshness and stiffness of the treated fabric, lowering its comfortability [20,21]. Inorganic phosphors, such as SrAl₂O₄:Eu²⁺,Dy³⁺, have showed a long-persistent phosphorescence. Strontium aluminate phosphors have been used to replace sulfide phosphors for a variety of applications due to their excellent photocatalytic activity and thermal properties, exhaustion sensitivity, high quantum yield, and high durability [8]. Non-organic phosphors with extended afterglow are now used in a variety of products, including switches, ornamental items, light indications, navigation marks, and tablecloths. As primary emitters of various colors, numerous long-lasting photoluminescent pigment phosphors have indeed been designed, including CaAl₂O₄:Eu²⁺,Nd³⁺ or SrMgSi₂O₆:Eu²⁺,Dy³⁺ for blue [22], MgAl₂O₄:Mn²⁺ or SrAl₂O₄:Eu²⁺/Dy³⁺ for green [23], and CaS:Eu²⁺, Ce³⁺,Tm³⁺ for red [24]. SrAl₂O₄:Eu²⁺, Dy³⁺ has been a significant photoluminescent phosphor owing to its thermal, photo-, physical and chemical stability. Lanthanide-doped aluminates have been characterized by non-toxicity, sustainability, and non-radioactivity [25,26,27,28,29,30]. Photoluminescent pigments are made out of aggregated crystals and photonic traps. The photonic traps can be recognized by their ability to store energetic photons, whereby they often become phosphorescent once imposed to a source of light. The crystals can indeed be identified by their ability to store energetic photons and thus become phosphorescent whenever charged by a light source. As a result, even after the light supply is switched off, crystals remain stimulated and continue emitting light that is supported by photonic traps like Eu²⁺ and Dy³⁺, leading to a longer phosphorescence period. The photons of light stored in the crystals continue to be emitted until they are completely depleted [31,32,33].

Organic dyestuff-based fluorescent ribbons have been used in clothing as safety clothing, such as traffic and night work textiles. However, they have showed drawbacks, such as high stiffness, low air-permeability, poor photo- and thermal properties, low durability, and low colorfastness [34,35]. Thus, the comfort properties of warning fabrics are important parameters. The REANPs@RTV spray-coating process is a simple approach to produce smart textiles coated with luminous pigments. The production of multifunctional long-persistent afterglow cotton textiles using RTV and SrAl₂O₄:Eu²⁺,Dy³⁺ by spray-coating has not reported yet. Herein, we report the development of phosphorescent cotton clothing spray-coated with strontium aluminate as a luminous layer. The purpose of these phosphorescent textiles is to provide safety and protective textiles that are easily visible in the dark. The topographical and photoluminescence features, surface composition, and colorfastness qualities of the treated cellulosic fabrics were studied.

2. Experimental

2.1. Materials

Cotton fabric samples were kindly provided by Misr-Helwan Co. (Helwan, Egypt). Using previously described methodologies, the cotton samples were first bleached and mercerized [36]. Decoseal-2540 was purchased from ADMICO for Chemical Industries, Cairo, Egypt. Hexane was purchased from Aldrich Co. (Cairo, Egypt). Boric acid (H₃BO₃), strontium(II) carbonate (SrCO₃), europium(III) oxide (Eu₂O₃), dysprosium(III) oxide (Dy₂O₃), and aluminum(III) oxide (Al₂O₃) were bought from Sinopharm (Beijing, China). The rare-earth-doped aluminum pigment was synthesized using previously reported procedure [37], while the pigment nanoparticles were generated under the top-down method utilizing Triple Roll Mill ES80 [38].

2.2. Synthesis of REA Nanoparticles

REA nanoparticles were produced using previously described procedure [37]. Absolute ethanol was admixed with 0.2 mol of boric acid, 0.03 mol of dysprosium oxide, 0.02 mol of europium oxide, 2 mol of aluminum oxide, and 1 mol of strontium carbonate. The admixture was homogenized for 30 min under ultrasonic conditions at 35 kHz, and then dried for 24 h at 90 °C. In a planetary ball mill (TCI, Portland, OR, USA), the solid mixture was grinded for 2 h before being sintered at 1300 °C for 3 h in a reductive carbon thermosphere. The phosphor micro-sized particles were obtained by re-milling and sieving the resulting residue. The phosphor nanoparticles were formed by using the top-down process [38], wherein 10 g of phosphor powder were charged into a stainless-steel ball milling tube (20 cm) on a vibrating disc. A silicon carbide ball was exposed to collisions regularly with the phosphor-containing tube and the vibrating disc for 22 h to produce the desired REANPs.

2.3. Preparation of Functional Textiles

Different concentrations of pigment (0, 1, 2, 4, 6, 8, 10, and 12% w/w) were added to RTV (10% w/v) in hexane, which was stirred for 60 min. The sample codes, including S₀, S₁, S₂, S₄, S₆, S₈, S₁₀, and S₁₂ were used to identify the generated cotton samples at various concentrations of pigment, respectively. Each mixture was exposed to stirring for 2 h, and homogenized at 25 kHz for 30 min. The above-prepared REANPs@RTV composite formulae were then spray-coated onto bleached cotton fabrics (25 cm × 25 cm). The formed solutions were spray-coated with an automatic spray gun (Lumina STA-6R) bearing a spray nozzle (1 mm) with an orifice size of 0.1 mm. At a speed of 3 cm/s, the spraying nozzle was eventually moved above the whole cotton material. Pressurized air (250 kPa) was applied as a carrier. The spray nozzle was 25 cm away from the cotton fabric. The solutions were sprayed at a 10 mL/min flow rate. The spraying course was completed till the solution had fully absorbed by the cotton sample. The specimens were air-dried for 30 min in the fume hood.

2.4. Physical and Biological Characterization

2.4.1. Morphological Properties

The morphological characteristics were assessed by using Quanta FEG 250 scanning electron microscopy (SEM, Prague, Republic of Czech). The EDX diagrams were defined with a TEAM-EDX model. The infrared spectra were collected by using Nexus 670 Fourier transform infrared spectroscopy (FTIR, Nicolet, Rhinelander, WI, USA). The phosphor particle size was determined by the intensity-weight Gaussian distribution analytical method (Particle Sizing System, Inc., Aero Camino, CA, United States).

2.4.2. Photoluminescence Studies

The spray-coated cotton emission and excitation spectra were assessed using a JASCO FP-8300 spectrofluorometer (JASCO Co., Tokyo, Japan) well-placed to determine decay and lifetime using phosphorescence attachments. The geometrical requirements for the emission measurements were identical. For the excitation source monochromators, the light source is a 150-Watt Xenon Arc lamp with a slit bandwidth of 5 nm. The excitation spectra were obtained at the phosphorescence emission wavelength, and then the phosphorescence emission range was evaluated at the maximum excitation wavelength. Irradiation was provided by a UV lamp with a wavelength of 365 nm and a power of 6 Watt. The photostability of the coated samples was evaluated. The coated cotton was irradiated with UV light for 100 s before being retained in a dark wooden box for 60 min to induce a return to its original state. The reversible irradiation/fading process was carried out several times. The emission intensity was measured after every cycle to explore the photoluminescence reversibility and photostability of the spray-coated cotton. The ultraviolet lamp (λ = 365 nm; 6 Watt) was located 5 cm above the specimen to study the reversibility of the emission spectrum.

2.4.3. Colorimetric Properties

The colorimetric parameters were identified using UltraScan Pro (HunterLab, Reston, VA, United States). The CIE Lab colorimetric space data were utilized to evaluate the colorimetric results of cellulosic fabrics [39]. The CIE color coordinates include L* to represent lightness from 100 for white to 0 for black, a* to represent color ratio from green(+a*) to red(−a*), and b* to represent color ratio from yellow (+b*) to blue (−b*). The UV lamp was placed 5 cm above the cotton specimen for 100 s of UV irradiation. When the ultraviolet lamp was switched off, the coloration data were directly collected. The fastness of sprayed cotton was assessed using ISO-standardized procedures [40].

2.4.4. Ultraviolet Protection

The AS-NZS 4399(1996) protocol and UPF measuring system of UV-visible spectrophotometer (UVA Transmittance, AATCC 183:2010 standard protocol) were used to assess the UV shielding behavior for the cellulosic fabrics [41].

2.4.5. Hydrophobicity Screening

Using OCA-15EC (Dataphysics GmbH, Filderstadt, Germany), both the contact and slide angles were assessed. In this process, droplets (10 μL) of triple distilled water were used to establish the contact angles. In order to create a planar surface, double-sided adhesive tape was used to stabilize the cotton substrate onto glass cover slips.

2.4.6. Comfort Properties

The bending lengths of blank and sprayed cottons were assessed on Shirley Stiffness apparatus, following the ASTM D1388 standardized protocol [42]. TEXTTEST FX3300 was utilized at a gradient pressure of 100 Pa to assess the air permeability of treated and untreated cotton fabrics based on the guidelines of the ASTM D737 standard procedure [43].

2.4.7. Antimicrobial Activity

The treated cellulosic fabrics were assessed for their antimicrobial activities versus S. E. coli, S. aureus, and C. albican. The antimicrobial tests were carried out quantitatively via a standard test method based on the bacterial counting test method (AATCC 100-1999). Prior to testing, all treated cellulosic fabrics were maintained at constant temperature of 35 °C. The weighted samples were transferred to nutrient broth (1:500; 100 mL) after the incubation step, and strenuously shaken for 1 min. For all plates, a saline solution (0.9%; w/v) was prepared by dilution and added by a pipette to an agar plate containing eosin methylene blue (EMB). The bacteria were cultured for 24 h at 37 °C before the colonies were considered. The antimicrobial activity was calculated using Equation (1) to determine the bacterial reduction (%) [44].

$$\mathrm{Bacteria}\mathrm{reduction}(\%)=\frac{\left(\mathrm{B}-\mathrm{A}\right)}{\mathrm{B}}\times 100$$

(1)

In this equation, A referred to the number colonies of bacteria after being incubated with the treated cellulosic fabrics. Meanwhile, B refers to the number of bacterial colonies from the pristine fabrics.

3. Results and Discussion

3.1. Morphological Features

Figure 1 illustrates the surface morphology of pgotoluminescent cotton fabric (S₈) immobilized with SrAl₂O₄:Eu²⁺, Dy³⁺ nanoparticles. As can be proved from SEM images, the surface of the treated cellulosic fabrics becomes rough owing to the effective deposition of REANPs@RTV onto the surface of fabric using the spray-coating process. The generated nano-sized REANPs@RTV particles had a diameter of 8–19 nm. Such a pigment has the tendency to disperse evenly throughout the fabric surface, which can be ascribed to the nature of the pigment chemical interactions with the fabric surface [36].

EDX spectroscopy was utilized to investigate the chemical composition of the coated cotton.

Table 1. EDX of S₈ at three distinct sites on cotton surface.

Area	C	O	Si	Al	Sr	Eu	Dy
Region 1	49.81	30.28	12.01	4.48	2.44	0.74	0.25
Region 2	49.37	30.83	12.52	4.42	2.07	0.57	0.22
Region 3	48.97	30.65	12.59	4.04	2.97	0.83	0.31

summarizes the compositional contents (wt%) of S₈ at the three distinct areas on the sprayed cellulosic fabric. The elemental compositions selected from several scanned locations were very comparable. This demonstrates that the dispersal of SrAl₂O₄:Eu²⁺,Dy³⁺ onto cotton surface has some consistency that can be observed at low magnifications. Figure 2 displays FTIR spectra of the coated cotton samples. Cotton as a natural fiber exhibits free terminal hydroxyl groups on cellulose polymer chains, which are made up of repeated glucose units. The characteristic FTIR spectral bands of blank cotton fabric were observed at 3387 cm⁻¹ (hydroxyl stretching vibration), 2912 cm⁻¹ (aliphatic C-H stretching vibration), 1699 cm⁻¹ (moisture deformation vibration), 1314 cm⁻¹ (aliphatic C-H binding vibration), and 1025 cm⁻¹ (ether bond). After spray-coating cotton fabrics, the intensity of the hydroxyl stretching vibration was found to decrease with the increasing ratio of REANPs. This could be attributed to a coordination bond formation between the cellulose hydroxyl group and the aluminum element of REA. Other absorption bands were detected at 711, 560 and 422 cm⁻¹ due to the lattice vibrations from Al-O, Sr-O and O-Al-O, respectively [37].

3.2. Superhydrophobic Properties

The slide and contact angles of the spray-coated samples were assessed (

Table 2. Wettability time, and slide and static contact angles of pristine and treated cellulosic fabrics.

Sample	Wettability Time (min.)	Slide Angles (°)	Contact Angles (°)
S0	0	0	0
S1	45	12	132.5
S2	45	12	133.3
S4	55	11	136.9
S6	>60	10	141.2
S8	>60	9	144.8
S10	>60	8	144.2
S12	>60	8	143.6

). REANPs@RTV was sprayed onto cotton surface, resulting in a compact thin film. The REANPs@RTV composite was established for filling the holes and pores amongst the cellulosic fibers, resulting in increasing the fabric roughness. As a result, the cotton fabric becomes extremely water-repellent. The static contact angle of S₀ had not been detected because of the high wettability of the blank cotton fibers. The treated cotton fiber (S₁) exhibits a substantially better static contact angle, which recorded a contact angle equal to 132.5°. The static contacting angle increases significantly as REANPs is increased, from 132.5° for the sample with 1% of REANPs to 144.8° for the sample with 8% of REANPs. Nevertheless, as the quantity of REANPs was further increased, the static contact angle decreased significantly from 144.8° for S₈ to 143.6° for S₁₂. This could be ascribed to the total content of REANPs immobilized onto fabric surface increased, allowing for a greater roughness. Conversely, the higher total concentrations of REANPs increased their density onto the cotton surface, potentially reducing the distance between such REA particles. This could have a detrimental impact on surface roughness, resulting in lower surface roughness and, as a result, lower static contact angles. The spaces between threads were extensively occupied with REA nanoparticles, leading to reduced roughness properties. As a result, increasing the overall amount of REA nanoparticles above S₈ resulted in a reduction in surface roughness. Thus, S₈ could well be considered as the optimal total content of REANPs. The superhydrophobic effectiveness of blank and treated textiles was also evaluated using sliding angles. A wettability time of 4 s and a contact angle of 0° were reported for S₀. By increasing the amount of REA nanoparticles, the wettability period increased as the sliding angles fell, resulting in a substantially stronger hydrophobicity of sprayed cotton than S₀. The present approach can well be described as a simple and low-cost treatment method that can be used without the requirement of a complicated apparatus or extensive procedures. Furthermore, the present straightforward process can be used to make afterglow and hydrophobic textile products for a variety of protective applications, including tents and ultraviolet protective textiles. Owing to their hydrophobic nature, silicone-coated fabrics have the capacity to permeate oil whilst holding water. As a result, the current technology can be utilized to create hydrophobic fabrics with the ability to separate water and oil.

3.3. Colorimetric Measurements

Table 3. Color space values of coated cellulosic fabrics before and after 100 s of ultraviolet irradiation at various pigment concentrations.

REANPs (wt%)	L*		a*		b*		K/S
	Before	After	Before	After	Before	After	Before	After
S1	83.86	80.52	−1.25	−5.81	7.53	21.24	1.32	2.01
S2	83.49	79.40	−1.33	−6.40	8.02	19.83	1.48	2.48
S4	82.53	78.00	−1.52	−9.30	9.71	18.64	1.57	3.06
S6	81.60	75.37	−1.70	−12.53	12.60	15.36	1.75	3.55
S8	81.05	73.76	−1.80	−16.47	15.84	13.90	1.91	4.02
S10	80.74	73.57	−1.95	−17.48	15.35	13.75	2.00	4.11
S12	80.27	73.24	–2.02	–18.16	16.07	13.47	2.11	4.24

illustrate the color parameters, including L*, a*, b*, and K/S. Before spray-coating, the coated materials had a white color identical to blank cotton. When UV irradiation is absent, there was no discernible change in the values of K/S with an increasing phosphor content. The phosphorescent layer’s transparency was attributed to the low pigment concentration. Under UV exposure, a substantial growth in the K/S value was monitored. However, no substantial differences were monitored in K/S with a further increase in the pigment concentration from 8% to 12%. The UV-irradiated samples had higher K/S values than the comparable unirradiated samples. These findings revealed that the best colorimetric data were monitored at a pigment phosphor concentration of 8%. Upon excitation at 365 nm, green emission was detected at 518 nm. When pigment concentrations were increased in absence of UV radiation, all treated cotton specimens showed small variations in L*, a*, and b*, matching with the white blank cotton specimen. The –a* increased as +b* decreased under UV irradiation, resulting in a colorimetric shift from white to green.

3.4. Photoluminescence Properties

Cotton textiles are extremely pleasant fabrics that have the potential to absorb close to a third of their weight in moisture before it evaporates into the air. The spray-coating technique was used to load SrAl₂O₄:Eu²⁺,Dy³⁺ onto cotton superficies. The various concentrations of SrAl₂O₄:Eu²⁺,Dy³⁺ combined with RTV binder are the main ingredients in the spray-coating stock formula. The RTV binder behaves as an organic coat that maintains and holds the colorant phosphor onto the exterior surface of cotton fabrics via coordination binding [8].

Figure 3 displays the excitation spectrum of the of spray-coated cotton sample (S₈)_, demonstrating an excitation wavelength at 365 nm. Figure 4 shows UV-induced emission spectra of the sprayed cotton (8 wt%) after exposure to ultraviolet rays for 10 s and 100 s. It was detected that the emission intensity increases with an increase in the UV irradiation time, indicating irradiation time-dependent emission intensity. Under UV irradiation, it was observed that all spray-coated cellulosic fabrics displayed reversible phosphorescence. The phosphorescence with delayed reversibility was obtained for spray-coated cotton substrates with pigment concentration more than 1%. The ultraviolet source was shut off after 100 s of irradiation (λ = 365 nm) at ambient temperature, and phosphorescent emission was measured as a function of time.

The lifetime curves display that the treated fabric had a long period of consistent phosphorescence. Meanwhile, the pattern of afterglow for the luminescent layer on cellulosic fabrics was significant compared to the luminescent solid colorant [25]. The emission peak for the spray-coated fabric was detected at 518 nm, which would have been noticeably smaller than the emission band of the luminous SrAl₂O₄:Eu²⁺,Dy³⁺ solid-state structure. The emission spectra at different phosphor concentrations were exactly equal in the 375–700 nm spectral range. The bandwidth is regarded as vast, allowing the sample to be excited by a broad spectrum of electromagnetic radiation. The 4f⁶5D¹⟷4f⁷ transition of Eu²⁺ is the reason for the emission of REA [36]. The absence of distinctive emissions for Eu³⁺ or Dy³⁺ in the sample indicates that Eu³⁺ to Eu²⁺ conversion has occurred, and the energy absorbed by Dy³⁺ has been converted into Eu²⁺. Dy³⁺ ions were used to promote the development of hole traps; these can then be liberated after the light supply was turned off. The liberated holes were converted into Eu²⁺, which then returned to their ground state, resulting in a long-lasting light emission or afterglow [29,37].

3.5. Photostability and Durability

The major goal of the spraying method is to create a flat smooth surface whilst keeping the fabric elasticity and breathability. Shirley stiffness apparatus, that assesses the fabric stiffness, is among the technical ways for evaluating the flexibility of fabrics.

Table 4. Effect of pigment content on stiffness and gas permeability of spray-coated cotton textiles.

REANPs (wt%)	Stiffness (cm)		Gas Permeability (cm3 cm−2 s−1)
	Weft	Wrap
Blank	3.57	3.87	52.73
S1	3.86	4.46	51.52
S2	3.95	4.53	51.25
S4	4.11	4.65	50.08
S6	4.33	4.82	49.81
S8	4.49	4.98	49.64
S10	4.60	5.13	49.32
S12	4.73	5.24	48.75

shows the findings of the stiffness and air permeability testing. When the pigment concentration was raised, the coating technique had essentially little effect on the air permeability, but it did marginally increase fabric stiffness both in the warp and weft directions. The cotton substrates that had been spray-coated felt smooth to touch. The colorfastness of the coated fabric was typically acceptable to outstanding, as shown in

Table 5. Fastness of spray-coated cotton textiles.

REANPs (wt%)	Washing		Perspiration				Rubbing		Sublimation		Light
	Alt.	St.	Acid		Alkaline		Dry	Wet	180 °C	210 °C
			Alt.	St.	Alt.	St.
S1	4–5	4–5	4–5	4–5	4–5	4–5	3–4	3	4–5	4–5	6–7
S2	4–5	4–5	4–5	4–5	4–5	4–5	3–4	3	4–5	4–5	6–7
S4	4–5	4–5	4–5	4–5	4–5	4–5	3–4	3	4–5	4	6–7
S6	4–5	4–5	4	4	4–5	4–5	3	3	4–5	4	6
S8	4	4	4	4	4–5	4–5	3	3	4–5	4	6
S10	4	4	4	4	4	4	3	3	4	4	6
S12	4	4	4	4	4	4	3	3	4	4	6

Alt. = Color alteration; St. = Cotton staining.

. The emission intensity was measured to determine the fabric durability toward rubbing, sublimation, light, washing, and perspiration. The findings were very good in terms durability and photostability. A high level of resistance to sublimation (thermal stability) was observed, with no significant differences at hot-press temperatures of 180 °C or 210 °C.

3.6. Resistance to Fatigue

The reversibility was measured by reporting the emission spectra after conducting UV irradiation/darkening mutual processes as represented in Figure 5. During numerous phosphorescent cycles, the treated cotton fabrics showed exceptional fatigue resistance. The treated cottons were irradiated with UV light for 100 s before being placed in a dark box for an hour to allow light to dissipate and cottons return to their original state. Each fading and radiation exposure cycles was repeated numerous in cycles. The emission value was analyzed and compared with the values provided for the original ultraviolet exposure, implying outstanding reproducibility without fatigue.

3.7. UV-Shielding and Antimicrobial Activity

The UV-protection factor (UPF) can be used to consider the UV-shielding ability of treated cotton fabrics, as illustrated in

Table 6. Antimicrobial and UV-protection of pristine and sprayed cellulosic fabrics.

REANPs (wt%)	Bacterial Reduction %		Fungal Reduction % C. albican	UPF
	E. coli	S. aureus
S0	0.00	0.00	0.00	38
S1	36 ± 1.0	31 ± 1.4	9 ± 1.1	65
S2	40 ± 1.1	38 ± 1.7	13 ± 1.2	81
S4	43 ± 1.2	41 ± 1.7	15 ± 1.0	96
S6	47 ± 1.4	45 ± 1.5	18 ± 1.1	111
S8	55 ± 1.7	53 ± 1.0	21 ± 1.4	119
S10	57 ± 1.0	55 ± 1.1	22 ± 1.5	125
S12	57 ± 1.2	56 ± 1.1	22 ± 1.3	137

. The UPF of treated cottons were improved as the concentration of pigment was raised. The mechanism of strong pigment UV absorption property could have been the reason for the enhanced UV protection. Table 6 shows the antibacterial properties of cotton fabrics that were assessed against most of the pathogenic microorganisms by means of the plate agar count. The untreated cotton fabrics had no inhibitory impact on bacteria. Additionally, the antibacterial features of the treated cotton fabrics were found to depend mainly on pigment concentration. The antibacterial activity increased with increasing pigment concentration.

4. Conclusions

The utilization of lanthanide-doped strontium aluminate phosphor nanoparticles (8–19 nm) allowed cotton fabrics to retain their pristine comfort attributes including physical appearance, colorfastness, softness, and permeability to air while providing a long-lasting phosphorescent performance. Thus, we aimed to fabricate smart warning textile products that are effective with tunable photoluminescent capabilities and good durability using a simple spray-coating method. RTV and inorganic phosphor were used in the spray-coating formula. The hydrophobic properties increased with the increasing phosphor content. The static contact angles increased from 132.5° (1%) to 144.8° (8%). The coated fabrics displayed an emission peak at 518 nm after being excited at 365 nm. The stiffness and air-permeability of the treated cellulosic textiles did not provide a noticeable change, signifying that the flexibility and breathability of the fabric were preserved. The spray-coated cotton substrates’ outstanding reversibility, as well as photo- and thermal stability, made them intriguing for general applications like warning textiles. As a result, such techniques can be considered to inventive, facile, and substantial methods that open up new outlooks in the design of effective warning smart textiles, notably for protection and aesthetic/decorative initiatives.