Enhanced Photoluminescence of <em>Curcuma longa</em> Extracts via Chitosan-Mediated Energy Transfer for Textile Authentication Applications

Gabriel Nicolo A. De Guzman; Jeff Ryan S. Magalong; Jose Paolo O. Bantang; Julius L. Lean&#771;o, Jr.

doi:10.3791/66035

JoVE Journal > Chemistry

Química

Enhanced Photoluminescence of Curcuma longa Extracts via Chitosan-Mediated Energy Transfer for Textile Authentication Applications

Published: December 22, 2023

doi:

10.3791/66035

Gabriel Nicolo A. De Guzman¹, Jeff Ryan S. Magalong¹, Jose Paolo O. Bantang¹, Julius L. Leaño, Jr.¹

¹Department of Science and Technology,Smart Colorants R&D Program, Philippine Textile Research Institute

Summary

Photoluminescence is one of the most effective authentication mechanisms being used today. Utilizing and enhancing naturally sourced materials with inherent photoluminescent properties and incorporating them into fabric substrates can lead to development of green, sustainable, and functional textiles for smart applications.

Abstract

Dyes for security markings play a pivotal role in safeguarding the integrity of products across various fields, such as textiles, pharmaceuticals, food, and manufacturing among others. However, most commercial dyes used as security markings are costly and may contain toxic and harmful substances that pose a risk to human health. Curcumin, a natural phenolic compound found in turmeric, possesses distinct photoluminescent properties alongside its vibrant yellow color, making it a potential candidate material for authentication applications. This study demonstrates a cost-effective and eco-friendly approach to develop enhanced photoluminescent emissions from curcumin dyes for textile authentication. Curcumin was extracted from C. longa using sonication-assisted-solvent extraction method. The extract was dip-coated and dyed into the textile substrates. Chitosan was introduced as a post-mordanting agent to stabilize the curcumin and as a co-sensitizer. Co-sensitization of curcumin with chitosan triggers energy transfer to enhance its luminescent intensity. The UV-visible absorption peak at 424 nm is associated with the characteristic absorption of curcumin. The photoluminescence measurements showed a broad emission peaking at 545 nm with significant enhancement attributed to the energy transfer induced by chitosan, thus showing great potential as a naturally derived photoluminescent dye for authentication applications.

Introduction

Counterfeiting is considered a scourge in widespread industries across the globe. The rapid surge of counterfeit products in the market causes economic havoc, which impedes the livelihood of the primary inventor¹^,²^,³^,⁴^,⁵^,⁶. This was brought to the fore in 2020⁷ on the ongoing concern of emerging counterfeit products as evidenced by the increasing trend of publications consisting of the keyword anticounterfeiting or counterfeiting in their titles. A significant increase can be observed in counterfeit-related publications since last reported in 2019, suggesting that considerable efforts are being made to combat the production and distribution of fraudulent goods. On the other hand, it can also be quite alarming, given that it signifies the progression of the counterfeiting industry, which is expected to persist if not addressed effectively. The textile industry is not insulated from this problem, as the presence of counterfeit textile products has severely impacted the livelihood of genuine sellers, manufacturers and weavers, among others³^,⁸. For instance, the textile industry in West Africa was long considered one of the leading export markets in the world. However, it was reported⁹ that approximately 85% of the market share is held by smuggled textiles that infringe upon West African textile trademarks. The effects of counterfeiting have also been reported in other continents like Asia, America, and Europe, indicating that this crisis has reached an uncontrollable level and poses a significant threat to the already struggling textile industry²^,³^,⁴^,¹⁰^,¹¹^,¹².

With the rapid advancements of science, technology, and innovation, researchers took upon the role of developing functional materials for the purpose of anti-counterfeiting applications. The use of covert technology is one of the most common and effective approaches to counteract the production of fraudulent goods. It involves utilizing photoluminescent materials as security dyes that exhibit a specific light emission when irradiated by different wavelengths¹³^,¹⁴. However, some photoluminescent dyes available in the market may impose toxicity at high concentrations, thereby posing threats to human health and the environment¹⁵^,¹⁶.

Turmeric (Curcuma longa) is an essential plant used in myriad applications such as paints, flavoring agents, medicine, cosmetics, and fabric dyes¹⁷. Present in the rhizomes are naturally occurring phenolic chemical compounds called curcuminoids. These curcuminoids include curcumin, demethoxycurcumin, and bisdemethoxycurcumin, among which curcumin is the main constituent responsible for the vibrant yellow to orange coloration and the properties of turmeric¹⁸. Curcumin, otherwise known as 1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione¹⁹^,²⁰ with an empirical formula of C₂₁H₂₀O₆, has attracted a significant amount of attention in the biomedical and pharmaceutical fields due to its antiseptic, anti-inflammatory, anti-bacterial, and antioxidant properties¹⁷^,¹⁸^,²¹^,²²^,²³. Interestingly, curcumin also possesses spectral and photochemical characteristics. Particularly noteworthy is its intense photoluminescent properties when subjected to ultraviolet (UV) excitations which have been explored only by a few studies¹⁹^,²⁴^,²⁵. Given these characteristics, in tandem with its hydrophobic nature and non-toxic properties, curcumin emerges as an ideal colorant for authentication markings.

The extraction of curcumin from turmeric was first reported in the early 1800s. Over the past centuries, numerous extraction methodologies and techniques have been devised and improved to achieve higher yield²⁶^,²⁷^,²⁸^,²⁹^,³⁰^,³¹^,³²^,³³. Conventional solvent extraction is a widely used approach as it employs organic solvents such as ethanol, methanol, acetone, and hexane among others, to isolate curcumin from turmeric³⁴^,³⁵. This method has evolved through modifications, coupled with more advanced techniques such as microwave-assisted extraction (MAE)¹⁸^,³⁶^,³⁷, Soxhlet extraction³⁸^,³⁹, enzyme-assisted extraction (EAE)³⁹^,⁴⁰, and ultrasonic extraction³⁶, among others to increase the yield. Generally, the solvent extraction method has been applied for natural dye extraction due to its versatility, low energy requirement, and cost-effectiveness making it ideal for scalable industries such as textiles.

Curcumin has been integrated as natural dyes for textiles due to its distinct yellow hue. However, the poor adsorption of natural dyes unto textile fibers pose as a challenge that hinders its commercial viability⁴¹. Mordants, such as metals, polysaccharides, and other organic compounds, serve as common binders to strengthen the affinity of natural dyes unto the fabric. Chitosan, a polysaccharide derived from crustaceans, has been widely utilized as an alternative mordanting agent due to its abundance in nature, biocompatibility, and wash durability⁴². This study reports a facile and straight forward approach in preparing curcumin-based authentication marking. Crude curcumin extracts were obtained via sonication-assisted solvent extraction method. The photoluminescent properties of the extracted curcumin were comprehensively investigated on textile substrates and further enhanced with the introduction of chitosan as a mordanting agent. This demonstrates the significant potential as a naturally derived photoluminescent dye for authentication applications.

Protocol

1. Extraction of curcumin

Weigh 3 g of C. longa powder in a 50 mL centrifuge tube.
NOTE: A 50 mL centrifuge tube was used to ease the centrifugation process and process the extraction on a single container.
Add 38 mL of ethanol (AR, 99%) to the centrifuge tube. Shake the tube gently to ensure thorough mixing of ethanol with the C. longa powder.
Sonicate the tube for 30 min at normal sonic mode and high intensity setting for extraction.
To separate the solid materials, centrifuge the tube at 4430 x g for 10 min. Before using the centrifuge, open the tube and close it again to depressurize and prevent leakage.
Decant to collect the supernatant and store it in dry, ambient conditions. The supernatant contains curcumin extract in ethanol solvent. It is important to keep the container closed to prevent solvent leakage.

2. Fourier transform infrared ( FTIR) characterization of C. longa extract

NOTE: Attenuated total reflectance- Fourier transform infrared (ATR-FTIR) spectrophotometer was operated following standard procedures found in the user manual.

Before measuring the IR spectra, the measurement parameters must be set. Use the Measure option, click on the Advanced tab and set the parameters for the sample and background scan time to 40 scans, scan resolution to 4 cm¹, and the range from 4000 – 400 cm^-1.
Clean the ATR crystal with Propan-2-ol (99.8%). After cleaning, switch to Basic.
NOTE: Background scans are necessary to eliminate environmental interference, ensuring that the IR spectra exclusively represent the sample being analyzed. Background measurements are only performed before starting the operation of the instrument. Cleaning the ATR crystal should always take place before every new measurement.
Use a Pasteur pipette to apply 0.3 mL of crude C. longa extract into the ATR crystal and let it dry for 3 to 5 min to remove the interference of ethanol.As the ethanol dries, the extract consequently accumulates to the crystal which reduces the transmittance reading.
On the software, click Measure > Advanced to set the file name. After naming the sample, click on Basic tab and measure the IR transmittance of dried extract.
Repeat steps 2.3 and 2.4 up to 3x or until the resolution of the spectra improves.
NOTE: An improved resolution is determined by a decrease in transmittance in the spectrum.
After completing the reading, clean the ATR crystal using 99% ethanol and lint-free wipes. Subsequently, clean the ATR sample stage using Propan-2-ol.

3. UV-visible measurement of C. longa extract

NOTE: The UV-visible spectrophotometer was operated following standard procedures found in the user manual.

Before measuring the samples, allow the instrument to warm up for 15 to 30 min. This will stabilize the light source and detector, thereby ensuring reproducible readings. Fill the reference cell with ethanol.
Before measuring the absorption spectra, set the measurement parameters. Use the Setup option, click the Cary tab, and set the scan time to 0.1 s, data interval to 1 nm, and scan rate to 600 nm/min. Finally, set the range from 200 nm to 700 nm.
Prepare 25 mL dilutions of C. longa extract ranging from 1:1000 to 1:100 with 1:100 increments using ethanol as a solvent.
Transfer approximately 3.5 mL of diluted C. longa into a quartz cuvette using a Pasteur pipette. For easier cleaning after each sample measurement, begin with 1:1000 dilution and work up to 1:100.
Measure absorbance of the extract as described below.
1. Clean the cuvette with ethanol and repeat the measurements for the other dilutions.
2. To ensure the accuracy of absorption, rinse the cuvettes thoroughly with the diluted extract before transferring the test solution.
Repeat steps 3.4-3.5.2 for other concentrations.

4. Photoluminescence measurement of C. longa extract

NOTE: The operation of the fluorescence spectrometer followed standard procedures found in the user manual.

Before measuring the samples, allow the instrument to warm up for 15 to 30 min. This will stabilize the light source and detector, thereby ensuring the reproducibility of each measurement.
Before measuring the fluorescent spectra, first set the measurement parameters. Click the Measure button and set the integration time to 0.1 s, increments to 1 nm, and slit width to 1 nm. The measurement range may vary depending on the excitation or emission source.
Using a Pasteur pipette, carefully transfer around 3.5 mL of diluted C. longa in the quartz cuvette. To facilitate easier cleaning after sample measurement, start the measurement from 1:1000 up to 1:100.
Measure the emission of the extract using a 365 nm excitation source. Set the emission range from 380 nm to 625 nm.
Using the wavelength with the highest emission from step 4.4, measure the excitation spectrum of the sample. Set the lower limit for the excitation range to 330 nm and calculate the upper limit using the monitored emission wavelength minus 15 nm. The allowance of 15 nm ensures that no first-order scattering will be observed on the spectra.
Using the wavelength with the highest excitation from step 4.5, measure the emission spectrum of the sample again. Calculate the lower limit for emission range using the excitation wavelength plus 15 nm. Set the upper limit to 625 nm.
Measure the emission-excitation matrix of C. longa extract as described below.
1. For consistency, set the measuring range for excitation from 330-435 nm and the emission to 450-650 nm. Maintain these parameters for all concentrations.
2. Clean the cuvette with ethanol and repeat the measurements for other dilutions. To ensure the accuracy of fluorescence measurements, rinse the cuvettes with the diluted extract before transferring the test solution.

5. Photoluminescence measurement of chitosan

Prepare 300 mL of 1% w/v solution of Chitosan. Mix 3 g of chitosan to 1% v/v acetic acid (99.8%) solution until it reaches 300 mL. Stir the solution for 24 h or until it homogenizes.
Measure the emission-excitation matrix of Chitosan as described below.
1. Use the following measuring parameters for chitosan:
  Slit width: 1 nm (both emission and excitation)
  Integration time: 0.1 s
  Emission range: 300-370 nm
  Excitation range: 385-450 nm
Measure the IR spectra of fabrics as described below.
1. Place the multi-tester fabric (Fabric #1) above the ATR crystal. The multi-tester fabric contains six types of fabric shown in Figure 1A. When measuring using ATR-FTIR, make sure the whole ATR crystal is covered with the sample. The fabric should make full contact with the ATR crystal by pulling the lever of the sample presser. This will decrease the transmittance it collects.
2. Measure the IR transmittance of the fabrics. Repeat the measurement on other fabrics.

6. Dyeing of fabrics

Weigh the fabrics to determine the amount of dye and chitosan finishing to be used.
Prepare C. longa extract solutions at dilutions 1:1, 1:10, 1:50, 1:100, 1:500, and 1:1000 using 99% ethanol.
Dye the fabrics with diluted C. longa extract at a 1:25 material-liquor ratio for 1 h by soaking the fabric in the solutions.
Hang the fabrics to dry. Rinse the fabrics with tap water and hang to dry.
Carry out fabric finishing as described below.
1. Soak the dyed fabrics with 1% w/v Chitosan solution at a 1:40 material to liquor ratio for 1 h by soaking the fabric in the solution.
2. Hang the fabrics to dry. Rinse the fabrics with tap water and hang to dry.

7. Photoluminescence measurements of dyed fabrics

Place the fabric in the sample holder. When using AATCC multi-tester fabrics, ensure that the tested fabric is placed in the middle of the window and no other fabrics are within the measurement area. To fix the position of fabrics, use glass slides as support. An example of the positioning of fabric is shown in Figure 1.
For measurement of fabric photoluminescence, set the integration time to 0.1 s, increments to 1 nm, and slit width to 0.6 nm. Measure the fluorescence of dyed fabrics at 365 nm excitation. Similar to measuring solutions, set the emission range to 380-625 nm.
Using the wavelength with the highest emission from step 5.3, measure the excitation spectrum of the sample. Set the lower limit for the excitation range to 330 nm and calculate the upper limit for the excitation range using the monitored emission wavelength minus 15 nm. The allowance of 15 nm ensures that no first-order scattering will be observed on the spectra.
Using the wavelength with the highest excitation from step 7.3, measure the emission spectrum of the sample. Calculate the lower limit for emission range using the excitation wavelength plus 15 nm. Set the upper limit to 625 nm.
Repeat measurement step 7.1 to 7.4 for other types of sample fabrics and with different concentrations.
Measure the emission spectra of 1:50 diluted Chitosan-finished C. longa extract-dyed fabrics using 365 nm excitation wavelength.
NOTE: The fabrics dyed with 1:50 dilution are used for the analysis of the effects of Chitosan finishing as it shows the highest photoluminescence. Similar to step 4.4, set the emission range from 380-625 nm.
Collect the spectrochemical data for interpretation.

8. Morphological analysis of fabrics

NOTE: Morphological analysis of fabrics involves two types of lighting: white light and 365 nm UV light. The choice of light source can reveal how the dye and finishing adhere to the fabric.

Since the microscope lacks a UV light source, use a handheld 365 nm UV light source. Fix the light source securely to maintain a consistent position without affecting the imaging process. Use a clamp attached to an iron stand to mount the 365 nm UV light, pointing it toward the stereo zoom microscope stage.
Place the fabric on the stage and open the white light source. Use the coarse adjustment knob to set the zoom to its lowest magnification and locate the target imaging area. Gradually increase the magnification up to 4x and refine it using the fine adjustment knob.
Utilize the built-in imaging software to insert a scale bar and capture the image.
To ensure consistent imaging, configure the exposure parameters with the following values: set exposure compensation to 100, exposure time to 100 ms, and gain to 20. Additionally, adjust the hue values to red: 27, green: 32, and blue: 23. Other specified parameters requiring adjustment include sharpness: 75, denoise: 35, saturation: 50, gamma: 6, and contrast: 50.
Turn OFF the white light source and switch on the 365 nm light source. Capture an image using the same imaging parameters.
Repeat steps 8.3 to 8.6 for all types of fabrics and conditions (blank, dyed, finishing only, dyed and finished) until images of all the fabrics are captured. In total, there should be 48 images of fabrics.

Representative Results

FTIR analyses of fibers determine the chemical structure of each fiber represented in the multi-tester fabrics #1. FTIR spectroscopy was utilized in order to characterize the functional groups present in each component of the multi-test fabrics. As shown in Supplementary Figure 1, the distinction occurs due to the presence of N-H functional groups, which leads to the fabric being subcategorized into nitrogenous (Supplementary Figure 1A) and cellulosic (Supplementary Figure 1B). Protein-based fibers (such as worsted wool and silk) and synthetic polyamide fall under the nitrogenous fabrics in correspondence to the presence of amide functional groups (-CONH-) in their chemical structure. Similarly, the spun viscose, bleached cotton, and filament acetate follow a cellulosic chain structure. As shown in Supplementary Table 1, fabrics made from worsted wool, spun silk, and spun polyamide contain similar characteristic peaks indicating the presence of amides. On the other hand, fabrics made from spun viscose, bleached cotton, and filament acetate show characteristic peaks of cellulose fibers. The peak at 1732 cm^-1 of filament acetate corresponds to the presence of an ester group in the fabric, which bleached cotton and spun viscose do not have⁴³.

The verification of the extract was evaluated using FTIR (Figure 2) and UV-visible (Figure 3) spectroscopy to confirm the presence of curcumin. Significant peaks at 3352 cm^-1, 3015 cm^-1, 2922 cm^-1, 1705 cm^-1, 1624 cm^-1, and 1512 cm^-1, and 1271 cm^-1 reflect the presence of functional groups characteristic of the target molecule. These results match well with an earlier reported FTIR spectra of pure curcumin⁴⁴, which suggests that the collected extract contains curcuminoids (Supplementary Table 2). The highly conjugated nature of curcumin (Figure 2B,C) gives off a broad absorption spectrum ranging from 350 – 500 nm as presented in Figure 3A. All dilutions follow the broad band profile with a characteristic peak at 424 nm which may be attributed to the π to π* electron excitation of curcumin⁴⁵. The positive correlation between the absorbance and the concentration (Figure 3B) showed good linearity (R²= 0.99376) which is a typical outcome corresponding to the increasing presence of absorption centers with respect to increasing concentrations of curcuminoid solution¹⁹^,⁴⁶. However, the limitations of the spectrometer were observed beyond the 1:300 dilution ratio as the absorption begins to saturate.

Following the verification of the extracted curcuminoid solution, its viability as an authentication dye was evaluated through its deposition into textile substrates. The extracted curcuminoid solutions were deposited onto the multi-test fabrics #1 composed of worsted wool, spun silk, spun polyamide (nylon 6,6), spun viscose, bleached cotton, and filament acetate to evaluate the compatibility of the dyes with natural and synthetic fabrics. As shown in Figure 4, the successful deposition of the curcuminoid solution was observed at different concentrations as evidenced by the photoluminescent emissions produced when illuminated with ultraviolet (UV) light excitation even after several washes of the dyed textiles.

Photoluminescence (PL) measurements were performed to assess the optical properties of the dyed textiles and characterize the interactions of the curcuminoid solution with textile substrates. Shown in Supplementary Figure 2 are the PL measurements of curcuminoid dyed cellulosic fabrics composed of bleached cotton (Supplementary Figure 2A–C), spun viscose (Supplementary Figure 2D– F), and filament acetate (Supplementary Figure 2G–I). Alternatively, the PL measurements of curcuminoid dyed nitrogenous fabrics composed of worsted wool (Supplementary Figure 3A–C), spun silk (Supplementary Figure 3D–F), and spun polyamide (Supplementary Figure 3G–I) can be found in Supplementary Figure 3. The left panel corresponds to the PL excitation while the middle and right panel corresponds to the normalized and relative PL emission, respectively. The PL excitation spectra of the cellulosic fabrics follow a broad band excitation covering 350 – 500 nm. The concentration dependent excitations of the curcuminoid solution become visible as evidenced by the characteristic red-shift on the normalized PL spectra at increasing concentrations, signifying the color-tunability of curcuminoid dyes. The performance of varying curcuminoid concentrations on each substrate was also evaluated in terms of relative PL intensity. The PL curcumin covers a broad emission ranging from 450 – 600 nm. With increasing concentrations of the curcuminoid solutions, all of the dyed fabric samples (Supplementary Figure 2 and Supplementary Figure 3, right panel) exhibited an expected increasing trend up to the optimal concentrations, followed by a decreasing trend ascribed to concentration dependent quenching. The optimized concentration was found to vary across different substrates with 1:100 and 1:50 yielding the most favorable results. This variation suggests the unique interaction of the curcuminoid solution within different substrates.

It is important to note that the emission and excitation spectra of the diluted extract were measured with a slit width of 1 nm and an integration time of 0.1 s. The data collected were initially processed through a correction parameter within the instrument to neglect background noise from the readings. The emission and excitation range are set considering the excitation source and monitored emission wavelength to prevent detection of the first order and second order Rayleigh scattering. Detection of scattering not only affects the quality of the spectrum but also potentially decreases the lifespan of the detector.

Similar standard procedures were implemented with the measurements of the emission and excitation spectra of the fabrics. Alternatively, a slit width of 0.6 nm and an integration time of 0.1 s was utilized as the intensity of the fluorescence reached beyond the limitations of the instrument when the extracts were deposited onto the substrate. The emission and excitation range were once again set considering the excitation source and monitored emission wavelength to prevent detection of first order and second order Rayleigh scattering.

Figure 1: Mounting procedure of fabrics into the sample holder. (A) The fabric composition, (B) alignment of fabric to the window, (C) application of glass slides as support, and (D) mounting of the holder into the spectrofluorometer. The mounting procedure utilizes the solid sample holder of the spectrometer and demonstrates its proper alignment with the spectrometer. Please click here to view a larger version of this figure.

Figure 2: Images of dyed and finished multi-tester fabrics #1 under white and 365 nm light. The images show the effect of dye concentrations with respect to each partition of the multi-tester fabric. Please click here to view a larger version of this figure.

Figure 3: Structural characterization of the extracted curcumin. (A) FTIR spectra of curcumin. Chemical structure of tautometric variations of curcumin (B) diketo form, and (C) keto-enol form. The functional groups of curcumin are highlighted with different colors which can be visualized and attributed to the tautometric variations. Please click here to view a larger version of this figure.

Figure 4: UV-visible spectra of curcumin solutions. (A) Absorbance spectra of the curcuminoid solutions with varying concentrations. (B) Linear correlation of the absorbance with respect to concentration. The UV-Vis spectra show the characteristic absorption peak of curcumin even at low concentrations. Please click here to view a larger version of this figure.

Figure 5: Excitation-emission matrix of (A) curcuminoid and (B) chitosan solutions. The excitation – emission matrix shows a 3-dimensional perspective of the photoluminescent properties exhibited by the sample. The EM wavelength in the X-axis stands for the emission wavelength while the EX wavelength in the Y-axis stands for the excitation wavelength. Please click here to view a larger version of this figure.

Figure 6: Photoluminescent emission of curcuminoid-chitosan dyed nitrogenous (top panel) fabrics composed of (A) worsted wool, (B) spun silk, (C) spun polyamide, and cellulosic (bottom panel) fabrics composed of (D) bleached cotton, (E) filament acetate, and (F) spun viscose under 365 nm excitation. The spectra show the enhanced optical properties of the nitrogenous fabrics with the incorporation of chitosan into the system. Please click here to view a larger version of this figure.

Supplementary Figure 1: FTIR spectra and chemical structure of multi-test fabrics. (A) Nitrogenous fabrics. (B) Cellulosic fabrics. The fabrics are subcategorized into nitrogenous and cellulosic as determined by the presence of N-H functional groups on half of the fabric types. Please click here to download this File.

Supplementary Figure 2: Photoluminescent excitation (left) and emission (middle– normalized intensity; right – relative intensity) of curcuminoid dyed cellulosic fabrics composed of (A-C) bleached cotton, (D-F) spun viscose, and (G-I) filament acetate. The spectra show the concentration dependence of curcumin with respect to the optical properties of the cellulosic fabrics. Please click here to download this File.

Supplementary Figure 3: Photoluminescent excitation (left) and emission (middle – normalized intensity; right – relative intensity) of curcuminoid dyed nitrogenous fabrics composed of (A-C) worsted wool, (D-F) spun silk, and (G-I) spun polyamide. The spectra show the concentration dependence of curcumin with respect to the optical properties of the nitrogenous fabrics. Please click here to download this File.

Supplementary Figure 4: Surface morphology of Blank multi-tester fabric under 365 nm and white light. This multi-tester fabric serves as the reference with no dye treatment. Please click here to download this File.

Supplementary Figure 5: Surface morphology of multi-tester fabric treated with chitosan under 365 nm and white light. The addition of chitosan on the fabrics shows minimal to zero change upon visual inspection of the surface of the samples. Please click here to download this File.

Supplementary Figure 6: Surface morphology of curcuminoid dyed multi-tester fabric under 365 nm and white light. The incorporation of curcuminoid dyes show immediate changes in coloration and good distribution across the surface of the sample when visualized under white and 365 nm light. Please click here to download this File.

Supplementary Figure 7: Surface morphology of curcuminoid-chitosan dyed multi-tester fabric under 365 nm and white light. The addition of chitosan to the curcuminoid dyes shows similar coloration and distribution with respect to the curcuminoid dyed fabric under white and 365 nm light. Please click here to download this File.

Table 1: Comparative analysis of different extraction methods for separating curcumin from turmeric. The table shows the different methodologies of curcumin extraction as reported in previous literature. Please click here to download this Table.

Supplementary Table 1: Observed FTIR frequencies of the multi-test fabrics. The units within the table correspond to the profile of the peaks (w = weak; m = medium; s = sharp peak). The data was verified with values obtained by Vahur et al.⁴³. Similar results were obtained in the two studies. Please click here to download this File.

Supplementary Table 2: Observed FTIR frequencies of the extracted curcumin. The units within the table correspond to the profile of the peaks (w = weak; m = medium; s = sharp peak). Please click here to download this File.

Discussion

Textile finishing is a common practice within the industry in order to incorporate additional functional properties onto the fabrics, making them more suitable for specific applications⁴⁵^,⁴⁷^,⁴⁸. In this study, the extracted curcumin was utilized as a natural dye to serve as authentication mechanisms for textile applications. The protocols give emphasis not only to the extraction of curcumin from turmeric, but also to the different advantages of using these methods for textile applications.

Given that the textile industry is considered as one of the highest polluting sectors, it has become vital for the industry to adopt more sustainable practices⁴⁹. Table 1 shows the comparison of different extraction methods in the past two decades. As seen, the sonication-assisted solvent extraction method offers a simple yet effective approach for extraction of curcumin. It is green and sustainable as it offers several advantages such as shorter extraction times, reduced solvent consumption, and increased extraction efficiency. Although the purity of the extract may be of importance to other studies such as the isolation of specific curcuminoids for biological applications²⁸, the application of natural dyes does not require such high purity so long as the output color or emission are as per the requirement of the consumer. After the extraction procedure, the supernatant was utilized as dyes and applied onto the fibers to serve as authentication markings. The inherent photoluminescent properties of curcumin exhibit a bright green to orange emission showcasing its potential in covert security. However, the poor affinity of natural dyes with textile fibers has become a challenge in terms of maintaining the optical properties of curcumin upon deposition to textile substrates⁴¹. Considering that supplementary treatments can alter the photoluminescent properties brought about by the deposited curcumin, it is essential to test the optical performance of the security markings after the textile finishing process. Among the various finishing procedures being implemented in the industry, anti-microbial finishing holds notable significance as it gives the capability to inhibit microbial growth within the fabrics⁴². Taking this into consideration, chitosan (Chi) was utilized for the finishing process for its biocompatible and antimicrobial properties⁵⁰. It is also worth noting that chitosan also exhibits inherent luminescent properties. Figure 5 presents the excitation – emission matrix of curcumin (Figure 5A) and chitosan (Figure 5B) solutions. The characteristic emission spectrum of chitosan was observed to overlap with the excitation of curcumin. This spectral overlap gives rise to enabling potential energy transfer pathways from chitosan to the curcumin molecules within close proximity⁵¹. Previous reports have already established the photoluminescent enhancement through polysaccharide-aided interaction of curcumin-protein complexes⁵²^,⁵³. Wang et al.⁵¹ emphasized that the curcumin-bovin serum albumin-Chitosan (C-BSA) ternary complex exhibits higher PL emission intensities than a C-BSA binary system. The enhanced PL emission can be associated to a shortened distance between curcumin and bovine serum albumin upon addition of chitosan, leading to efficient energy transfer within the ternary complex. A similar phenomenon was observed in this work. Figure 6A–C show the enhanced PL spectra of the curcumin-dyed nitrogenous fabrics with chitosan. Despite this, it was noted that no significant enhancements were observed for the cellulosic fabrics (Figure 5D–F) suggesting a preferential interaction with nitrogenous fabrics. This signifies that enhanced PL interactions can also be attained within solid-state systems such as protein and polyamide-based textile substrates. Nevertheless, this further emphasizes the unexplored realm in terms of curcumin research, allowing avenues for future investigations on this versatile compound.

Congruent with other studies, this work also possesses a few limitations which may be used as grounds for future research and development. The dye used in the fabric comes from a natural source and is extracted using the proposed technique, which involves the use of ethanol for both extraction and dyeing processes. Ethanol is an effective solvent for extracting curcumin; however, it's worth considering that other solvents may also be viable, potentially affecting the quantity of extracted dye compounds, impurities, and their interactions with the fabric. Future studies could explore the use of different solvents in the extraction and dyeing steps. Given the time constraints and limited availability of testing facilities, we have not included any electron microscopy results. However, we have included stereo zoom microscopy images (Supplementary Figure 4, Supplementary Figure 5, Supplementary Figure 6, Supplementary Figure 7) of the tested fabrics with and without dyes as an alternative. Though electron microscopy would be recommended if the dyes being implemented have nanoparticle finishings.

Furthermore, the methods for extraction and dyeing were simplified for practical purposes. The extracted solution was not purified, as the dyeing process can still proceed even if the solution contains impurities. It's important to note that the impact of these impurities on the fabric and mordant interactions was not investigated in this study.

Lastly, this research primarily focuses on analyzing the photoluminescence enhancement of various fabrics dyed with curcumin and mordanted with chitosan. While optical properties received significant attention, physical tests such as durability and colorfastness were not conducted. This presents an opportunity for future researchers to explore further the material's potential for authentication purposes in textiles.

For other researchers who are interested in replicating this work, it must be noted that certain parameters reported may not correspond to the target result. This may be due to the presence of human error, random error, and the environmental conditions around the experimental setup. Therefore, following troubleshooting guidelines should remedy the problem.

In summary, this study lays the foundation of a comprehensive approach for curcumin as an alternative and robust authentication platform, providing extraction and analysis methods that could find applications across diverse fields including textile, authentication, and functional nanomaterials. The insights from this study provide a robust framework for future investigations and innovation in curcumin-related applications. The verification process, combining FTIR and UV-Vis spectroscopy, establishes a reliable means of confirming the presence of curcumin. The successful deposition of curcumin onto various fabric substrates, evidenced by their sustained photoluminescent emissions, hold significant implications for the development of effective and reliable authentication solutions, thereby enabling exciting possibilities in anti-counterfeiting and security marking. The comprehensive PL measurements performed on curcumin-dyed textiles provide a comprehensive understanding of how curcumin interacts with different textile substrates. This analytical approach not only sheds light on the optical properties of curcumin but also unveils the unique substrate-specific behaviors that guide tailored applications and optimal deployment strategies. Moreover, the investigation of chitosan not only for antimicrobial finishing, but as a mediating agent for enhanced luminescence unveils tremendous possibilities for novel applications within the fields of photonics and biomedicine. With these multifaceted approaches, this study re-ignites the interest towards natural pigments research, propelling further investigations towards technical and functional applications.

Declarações

The authors have nothing to disclose.

Acknowledgements

This work is supported by the Department of Science and Technology – Philippine Textile Research Institute under the DOST Grants-in-Aid (DOST-GIA) Project entitled Covert Technology Towards Sustainability and Protection of the Philippine Textile Sectors under the Digitalization of the Philippine Handloom Weaving Industry Program.

Materials

(Curcumin) C. longa, spray dried	N/A	N/A	Naturally Sourced
100 mL Graduated Cylinder	n/a
10 mL Serological Pipette	n/a
200 mL Beaker	n/a
365 nm UV Light	AloneFire		SV004 LG
50 mL Centeifuge Tube	n/a
AATCC Multitester Fabric	Testfabrics, Inc.	401002	AATCC Multifiber test fabric # 1 precut pieces of 2 X 2 inches, Heat Sealed
Analytical Balance	Satorius		BSA 224S-CW
Aspirator	n/a
ATR- FTIR	Bruker		Bruker Tensor II
Centrifuge	Hermle Labortechnik GmbH		Z 206 A
Chitosan	Tokyo Chemical Industries	9012-76-4
Digital Camera	ToupTek		XCAM1080PHB
Drying Rack	n/a
Ethanol	Chem-Supply	64-17-5	Undenatured, 99.9% purity
Glacial Acetic Acid	RCI-Labscan	64-19-7	AR Grade, 99.8% purity
Glass Slide	n/a
Iron Clamp	n/a
Iron Stand	n/a
Magnetic Stirrer	Corning		PC-620D
Pasteur Pipette	n/a
Propan-2-ol	RCI-Labscan	67-63-0	AR Grade, 99.8% purity
Sonicator	Jeio Tech Inc.		UCS-20
Spectrofluorometer	Horiba (Jovin Yvon)		Horiba Fluoromax Plus
Stirring Bar	n/a
UV-Vis Spectrophotometer	Agilent		Cary UV 100
Wash bottle	n/a
Zoom Stereo Microscope	Olympus		SZ61

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De Guzman, G. N. A., Magalong, J. R. S., Bantang, J. P. O., Leaño, Jr., J. L. Enhanced Photoluminescence of Curcuma longa Extracts via Chitosan-Mediated Energy Transfer for Textile Authentication Applications. J. Vis. Exp. (202), e66035, doi:10.3791/66035 (2023).