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

Several Curcuma researchers focus on medical and cosmetic applications. Very few have delved into its photoluminescent properties. In this study, we demonstrate a facile, cost-effective, and eco-friendly approach to enhance the photoluminescent emission of Curcuma dyes, geared towards the development of covert markings for textile application.

Current developments revolve around the preparation of diverse luminescent materials, such as inorganic quantum dots, carbon dots, perovskites, and synthetic organic dyes. Recent technological advances in the development of photoluminescent materials usually centralized along its industrial applications, such as LEDs. What's interesting is that these same photoluminescent materials, from organic pigments to inorganic phosphorus and quantum dots, are also feasible precursors for anti-counterfeiting applications when given the proper experimental design.

The primary challenge in our experiment is ensuring the quality of the result we collected. We've optimized the experiment procedures to not only maintain data accuracy, but also to do so efficiently, enabling simple replications for fellow researchers interested in textiles and photoluminescence. To bind Curcuma into textiles, traditional metallic mordants, like iron, aluminum, and copper are used.

However, metals in post-dyeing waste water effluence may pose environmental risk. This study utilizes chitosan, a byproduct from crabs and shrimps, as alternative mordant for securing curcumin into the fabric, providing excellent colorfastness properties. To begin FTIR characterization of Curcuma longa extract, first, clean the ATR crystal with two propanol, then, use the measure option on the instrument and click on the basic tab.

With a Pasteur pipette, apply 0.3 milliliters of crude Curcuma longa extract onto the ATR crystal. Now, click on measure, followed by advanced and set the file name, then press the basic tab and measure the IR transmittance of the dried extract. To perform UV visible measurement of the extract, first, keep the spectrophotometer on for 15 to 30 minutes, then fill the reference cell with ethanol.

Next, click on the setup option and the carry tab to set the measurement parameters. Set the scan time to 0.1 seconds, data interval to one nanometer, and the scan rate of 600 nanometers per minute. Then, set the wavelength range from 200 nanometers to 700 nanometers.

Prepare 25 milliliters to dilution of Curcuma longa extract in increments of one to 100 with ethanol as the solvent. After transferring 3.5 milliliters of the diluted extract into a quart cuvette, measure its absorbance. After the first measurement, clean the cuvette with ethanol.

Thoroughly rinse the cuvettes with the diluted extract, then fill it with the test solution to ensure the accuracy of absorption measurements. FTIR analysis of the extract showed significant peaks at various lengths, corresponding to its functional groups. UV analysis showed a broad absorption spectrum, ranging from 350 to 500 nanometers.

The positive correlation between the absorbence and the concentration showed good linearity. To begin, warm up a fluorescent spectrophotometer for 15 to 30 minutes before measurement, then click on measure and set the integration time to 0.1 seconds, increments to one nanometer, slit width to one nanometers, and the signal formula to S1c/R1c. Next, use a Pasteur pipette to carefully transfer 3.5 milliliters of a diluted Curcuma longa extract into a quartz cuvette.

Measure the emission spectra with a 365 nanometer excitation source and set the emission range from 380 nanometers to 625 nanometers. Measure the excitation spectrum of the sample with the wavelength of highest emission. Set the lower limit for the excitation range at 330 nanometers and the upper limit set to the monitored emission wavelength minus 15 nanometers.

Remeasure the emission spectrum of the sample with the highest excitation wavelength. Set the emission range starting at the excitation wavelength plus 15 nanometers up to 625 nanometers. Next, set the excitation range fixed between 330 and 435 nanometers and the emission between 450 and 650 nanometers for all dilutions of Curcuma longa extract.

Then, clean the cuvette with ethanol and measure the emissions of the remaining dilutions. To measure the emission excitation matrix of chitosin, set the slit width to one nanometer and the integration time to 0.1 seconds. The emission ranges from 300 to 370 nanometers and the excitation range from 385 to 450 nanometers.

Then, transfer the chitosin solution to a washed cuvette and place it in the spectrophotometer to measure its emission excitation matrix. Place a multitester fabric over the ATR crystal of the FTIR instrument, then measure the IR transmittance of the fabric. To perform fluorescent analysis of the chitosin-dyed fabric, place the fabric in the sample holder of the instrument.

Fix the fabric position in the middle of the window with glass slides. Now, set the integration time to 0.1 seconds, increments to one nanometer, slit width to 0.6 nanometers, and signal formula to S1c/R1c, then set the emission range between 380 to 635 nanometers and measure the fluorescence at 365 nanometers. Use the wavelength of highest excitation as determined by the photoluminescence analysis to measure the emission spectrum of the sample.

Add 15 nanometers to the excitation wavelength and set it as the lower limit for the emission range. Set the upper limit to 625 nanometers. Lastly, measure the emission spectra of one to 50 diluted chitosin-finished Curcuma longa-dyed fabrics at 365 nanometers.

To perform morphological analysis of fabrics, first, mount a handheld UV source of 365 nanometers on an iron stand. Point it towards a stereo microscope. Next, place the fabric on the stage and open the white light source.

Set the zoom to the lowest magnification to locate the target imaging area. Increase the magnification to four times and refine the image focus with the fine adjustment knob. With the built-in imaging software, insert a scale bar and capture the image.

To ensure uniform imaging, set the exposure compensation to 100, the exposure time to 100 milliseconds, and the gain to 20. Then, adjust the hue values of red to 27, green to 32, blue to 23. Lastly, adjust the sharpness to 75, denoise to 35, saturation to 50, gamma to six, and contrast to 50.

Switch on the ultraviolet lamp after turning off the white light source. Now, capture the image with the same imaging parameters for all fabrics. UV analysis of the multitest fabrics showed the successful deposition of the curcuminoid solution at different concentrations.

The photoluminescent emission spectra of curcuminoid chitosin-dyed fabrics showed enhanced optical properties.