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.

1. Extraction of curcumin
<ol>
	<li>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.</li>
	<li>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.</li>
	<li>Sonicate the tube for 30 min at normal sonic mode and high intensity setting for extraction.</li>
	<li>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.</li>
	<li>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.</li>
</ol>
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.
<ol>
	<li>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.</li>
	<li>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.</li>
	<li>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.</li>
	<li>On the software, click Measure &#62; Advanced to set the file name. After naming the sample, click on Basic tab and measure the IR transmittance of dried extract.</li>
	<li>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.</li>
	<li>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.</li>
</ol>
3. UV-visible measurement of C. longa extract
NOTE: The UV-visible spectrophotometer was operated following standard procedures found in the user manual.
<ol>
	<li>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.</li>
	<li>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.</li>
	<li>Prepare 25 mL dilutions of C. longa extract ranging from 1:1000 to 1:100 with 1:100 increments using ethanol as a solvent.</li>
	<li>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.</li>
	<li>Measure absorbance of the extract as described below.
	<ol>
		<li>Clean the cuvette with ethanol and repeat the measurements for the other dilutions.</li>
		<li>To ensure the accuracy of absorption, rinse the cuvettes thoroughly with the diluted extract before transferring the test solution.</li>
	</ol>
	</li>
	<li>Repeat steps 3.4-3.5.2 for other concentrations.</li>
</ol>
4. Photoluminescence measurement of C. longa extract
NOTE: The operation of the fluorescence spectrometer followed standard procedures found in the user manual.
<ol>
	<li>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.</li>
	<li>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.</li>
	<li>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.</li>
	<li>Measure the emission of the extract using a 365 nm excitation source. Set the emission range from 380 nm to 625 nm.</li>
	<li>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.</li>
	<li>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.</li>
	<li>Measure the emission-excitation matrix of C. longa extract as described below.
	<ol>
		<li>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.</li>
		<li>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.</li>
	</ol>
	</li>
</ol>
5. Photoluminescence measurement of chitosan
<ol>
	<li>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.</li>
	<li>Measure the emission-excitation matrix of Chitosan as described below.
	<ol>
		<li>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 
		&#8203;Excitation range: 385-450 nm</li>
	</ol>
	</li>
	<li>Measure the IR spectra of fabrics as described below.
	<ol>
		<li>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.</li>
		<li>Measure the IR transmittance of the fabrics. Repeat the measurement on other fabrics.</li>
	</ol>
	</li>
</ol>
6. Dyeing of fabrics
<ol>
	<li>Weigh the fabrics to determine the amount of dye and chitosan finishing to be used.</li>
	<li>Prepare C. longa extract solutions at dilutions 1:1, 1:10, 1:50, 1:100, 1:500, and 1:1000 using 99% ethanol.</li>
	<li>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.</li>
	<li>Hang the fabrics to dry. Rinse the fabrics with tap water and hang to dry.</li>
	<li>Carry out fabric finishing as described below.
	<ol>
		<li>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.</li>
		<li>Hang the fabrics to dry. Rinse the fabrics with tap water and hang to dry.</li>
	</ol>
	</li>
</ol>
7. Photoluminescence measurements of dyed fabrics
<ol>
	<li>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.</li>
	<li>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.</li>
	<li>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.</li>
	<li>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.</li>
	<li>Repeat measurement step 7.1 to 7.4 for other types of sample fabrics and with different concentrations.</li>
	<li>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.</li>
	<li>Collect the spectrochemical data for interpretation.</li>
</ol>
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.
<ol>
	<li>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.</li>
	<li>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.</li>
	<li>Utilize the built-in imaging software to insert a scale bar and capture the image.</li>
	<li>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.</li>
	<li>Turn OFF the white light source and switch on the 365 nm light source. Capture an image using the same imaging parameters.</li>
	<li>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.</li>
</ol>

Use of Chitosan to Enhance Photoluminescence of Curcumin for Textile Authentication

The authors have nothing to disclose.

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 differe...

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&#160;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&#160;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&#160;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.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>(Curcumin) C. longa, spray dried&#160;</td>
			<td>N/A</td>
			<td>N/A</td>
			<td>Naturally Sourced</td>
		</tr>
		<tr>
			<td>100 mL Graduated Cylinder</td>
			<td>n/a</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>10 mL Serological Pipette</td>
			<td>n/a</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>200 mL Beaker</td>
			<td>n/a</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>365 nm UV Light</td>
			<td>AloneFire</td>
			<td></td>
			<td>SV004 LG</td>
		</tr>
		<tr>
			<td>50 mL Centeifuge Tube</td>
			<td>n/a</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>AATCC Multitester Fabric</td>
			<td>Testfabrics, Inc.</td>
			<td>401002</td>
			<td>AATCC Multifiber test fabric # 1 precut pieces of 2 X 2 inches, Heat Sealed</td>
		</tr>
		<tr>
			<td>Analytical Balance</td>
			<td>Satorius</td>
			<td></td>
			<td>BSA 224S-CW</td>
		</tr>
		<tr>
			<td>Aspirator</td>
			<td>n/a</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>ATR- FTIR</td>
			<td>Bruker</td>
			<td></td>
			<td>Bruker Tensor II</td>
		</tr>
		<tr>
			<td>Centrifuge</td>
			<td>Hermle Labortechnik GmbH</td>
			<td></td>
			<td>Z 206 A</td>
		</tr>
		<tr>
			<td>Chitosan</td>
			<td>Tokyo Chemical Industries</td>
			<td>9012-76-4</td>
			<td></td>
		</tr>
		<tr>
			<td>Digital&#160; Camera</td>
			<td>ToupTek</td>
			<td></td>
			<td>XCAM1080PHB</td>
		</tr>
		<tr>
			<td>Drying Rack</td>
			<td>n/a</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Chem-Supply</td>
			<td>64-17-5</td>
			<td>Undenatured, 99.9% purity</td>
		</tr>
		<tr>
			<td>Glacial Acetic Acid</td>
			<td>RCI-Labscan</td>
			<td>64-19-7</td>
			<td>AR Grade, 99.8% purity</td>
		</tr>
		<tr>
			<td>Glass Slide</td>
			<td>n/a</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Iron Clamp</td>
			<td>n/a</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Iron Stand</td>
			<td>n/a</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Magnetic Stirrer</td>
			<td>Corning</td>
			<td></td>
			<td>PC-620D</td>
		</tr>
		<tr>
			<td>Pasteur Pipette</td>
			<td>n/a</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Propan-2-ol</td>
			<td>RCI-Labscan</td>
			<td>67-63-0</td>
			<td>AR Grade, 99.8% purity</td>
		</tr>
		<tr>
			<td>Sonicator</td>
			<td>Jeio Tech Inc.</td>
			<td></td>
			<td>UCS-20</td>
		</tr>
		<tr>
			<td>Spectrofluorometer&#160;</td>
			<td>Horiba (Jovin Yvon)</td>
			<td></td>
			<td>Horiba Fluoromax Plus</td>
		</tr>
		<tr>
			<td>Stirring Bar</td>
			<td>n/a</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>UV-Vis Spectrophotometer</td>
			<td>Agilent</td>
			<td></td>
			<td>Cary UV 100</td>
		</tr>
		<tr>
			<td>Wash bottle</td>
			<td>n/a</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Zoom Stereo Microscope</td>
			<td>Olympus</td>
			<td></td>
			<td>SZ61</td>
		</tr>
	</tbody>
</table>

enhanced photoluminescence of curcuma longa extracts via chitosan-mediated energy transfer for textile authentication applications

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.

Author Spotlight: Eco-friendly Photoluminescent Textile Authentication with Curcumin

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

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) ...

Watch this Scientific Journal Video about Enhanced Photoluminescence of Curcuma longa Extracts via Chitosan-Mediated Energy Transfer for Textile Authentication Applications at JoVE.com

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.

Dyes for security markings play a pivotal role in safeguarding the integrity of products across various fields, such as textiles, pharmaceuticals, food, ...

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1.0K Views.  Smart Colorants R&D Program, Philippine Textile Research Institute. 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. 