Color Film Research Articles

Active Food Packaging from Alginate-Based Film Containing Onion Peel Extract (Allium cepa)

Consumers wanting safe and eco-friendly food packaging have led to better active packaging materials. Alginate is a polysaccharide extracted from seaweed and has the potential to be considered a promising material for packaging applications; however, its application is limited due to poor mechanical properties and high water vapor (WVP). The mechanical and barrier properties can be altered by adding or blending with other materials, such as the incorporation of bioactive compounds from onion peel extract (Allium Cepa). This study was designed to extract onion peel and test its antioxidant and antimicrobial activities; alginate-based film incorporated different concentrations of onion peel extract (12.5%, 25%, and 50%) (w/v) and determined its antioxidant or antimicrobial activity and physicochemical properties. Results demonstrated that the onion peel extract and alginate-based films containing onion peel extract show antioxidant activity; however, no antimicrobial activity was detected. When the concentration of onion peel extract (Allium Cepa) in alginate-based film increased, it significantly improved the alginate-based film's mechanical properties, colour, solubility, and biodegradability. However, the water vapour permeability was reduced by increasing the onion peel extract. In conclusion, adding onion peel extract improved the antioxidant activity, colour, mechanical strength, solubility, and biodegradability characteristics of alginate-based films compared to control. Hence, this film has the potential to be used as active packaging.

Efficient preparation of cellulose nanocrystals and regulation of cholesteric liquid crystals for advanced anti‐counterfeiting

AbstractCellulose nanocrystals (CNCs) can self‐assemble to form cholesteric liquid crystal, which make it one of the most promising optical materials at present. CNCs can be produced by sulfuric acid hydrolysis. It is found that hydrolysis conditions influence the existing form of reaction components and their reaction activities, which leads to different reaction routes and mechanisms under varied reaction conditions, with CNCs of varied quality produced. High‐quality CNC with more uniform particle size could be prepared at a critical acid concentration of 64 wt%, which was used to study the formation process of CNC liquid crystal and the structure regulation of cholesteric liquid crystal. By adjusting the drying temperature and adding a small molecule of water‐soluble chitosan (WSC) can well regulate cholesteric liquid crystal and change the pitch of a film, and the reflection wavelength can be redshifted, thus enriching texture patterns and creating distinctive color. Suitable addition of WSC can enhance the multi‐domain effect during liquid crystal formation process and finally creates more colorful film with fine texture. The rich and tunable liquid crystal characteristics endowed by WSC addition is irreplicable and artistic, which helps to realize the great potential application of the composite film in advanced anti‐counterfeiting.

The application of film based on gelatin/hydroxymethyl cellulose and red beetroot betalain in smart food packaging.

Edible films containing anthocyanin and betacyanin as indicators of freshness are promising systems for food smart packaging. This research aimed to develop a smart color film for food packaging using gelatin/hydroxypropylmethyl cellulose (HPMC) and red beet betalain. In this study, edible films with different ratios of gelatin to HPMC were prepared successfully, and the ratio of 3:1 was determined as optimal samples based on water vapor permeability (WVP) and mechanical properties. Betalain with different concentrations was then added to the optimal film, and the physical and mechanical properties of the resulting films were evaluated. Also, TVB-N test to assess their ability to detect beef meat and shrimp spoilage was studied. The addition of betalain improved the solubility, WVP, mechanical properties, and 2,2-diphenyl-l-picrylhydrazyl free radical scavenging activity of the film. As a final point, the incorporation of betalain into the gelatin/HPMC films can be used to indicate the freshness of food.

An intelligent myofibrillar protein film for monitoring fish freshness by recognizing differences in anthocyanin (Lycium ruthenicum)-induced color change

A novel smart film MP/BNC/ACN for real-time monitoring of fish freshness was developed using myofibrillar protein (MP) and bacterial nanocellulose (BNC) as film raw materials and anthocyanin (Lycium ruthenicum, ACN) as an indicator. Firstly, the film containing 1 % ACN (MP/BNC/ACN1) was found to have a moderate thickness (0.44 ± 0.01 mm) and superior mechanical properties (tensile strength (TS) = 8.53 ± 0.11 MPa; elongation at break (EB) = 24.85 ± 1.38 %) by determining the physical structure. The covalent, electrostatic, and hydrogen bonding interactions between anthocyanin and the film matrix were identified and confirmed by FT-IR spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM) analysis. A comprehensive evaluation concluded that MP/BNC/ACN1 exhibited excellent trimethylamine (TMA) sensitivity (total color difference (ΔE), ΔETMA0-1000 = 4.47–31.05; limit of detection (LOD), LOD = 1.03) and UV stability (ΔE96h = 4.16 ± 0.13). The performance of the films in assessing fish freshness was evaluated, principal component analysis (PCA) and hierarchical cluster analysis (HCA) revealed that MP/BNC/ACN1 (ΔE2-10d = 16.84–32.05) could clearly distinguish between fresh (0–2 d), sub-fresh (4–6 d), and spoiled (8–10 d) stages of fish, which corresponded to the film colors of red, light red, and gray-black. In conclusion, this study addresses the limitation that intelligent films cannot visually discern real-time freshness during fish storage and provides a promising approach for real-time fish freshness monitoring.

PH-responsive collagen nanocomposite films reinforced by curcumin-loaded Laponite nanoplatelets for dynamic visualization of shrimp freshness

Sustainable and intelligent packaging systems, utilizing biomass-derived matrix and bioactive indicators represent promising approaches for real-time detection and monitoring of freshness of food, as well as prolonging the shelf-life and improving the quality and safety of food products. Herein, we reported pH-responsive collagen nanocomposite films reinforced by curcumin-loaded Laponite nanoplatelets which could act as smart indicators for monitoring the freshness of shrimps. Caffeic acid, as a bio-based modifier, was covalently grafted onto the surfaces of the nanoplatelets loaded with curcumin. The collagen nanocomposite films were fabricated by the incorporation of functionalized nanoplatelets through all-aqueous casting-evaporation approach. The triple-helical structure of collagen molecules was stabilized by the functionalized nanoplatelets mainly through hydrogen bonding and electrostatic interactions with uniform distribution into the film matrix. Moreover, the resultant nanocomposite films not only demonstrated favorable hydrophobicity and water vapor barrier properties, but also exhibited effective antioxidant activity and anticipated color responsiveness to pH changes and NH3 presence. The consistent changes in color of the nanocomposite film with the shrimps following days of storage supported its feasibility and potential for monitoring the freshness of shrimps. Therefore, we envision that the developed collagen-based nanocomposite films showcase great potential in the application of sustainable and intelligent packaging system for dynamic visualization of seafood freshness.

Preparation of lanthanide aluminate‐encapsulated silica nanoparticles toward long‐persistent photoluminescent polymer paint with superhydrophobic and anticorrosion properties

AbstractSmart afterglow paints can function as energy‐saving products that are able to persist lighting in the dark. Additionally, polyurethane paints (PURPs) have shown some limitations, including weak adhesion, poor mechanical performance, poor corrosion, and low water resistance as compared with solvent‐based paints. Herein, nanoparticles of lanthanide aluminate (NLA; 16–24 nm) were mixed with polyurethane and silica to develop novel photoluminescent nanocomposite paints. A precursor of NLA‐encapsulated silica nanoparticles (NLA@Silica; 200–225 nm) can be described as a SiO2‐coated NLA pigment prepared by the heterogeneous precipitation method. Steel was coated with nanocomposite paints made of PURP, silica, and NLA. Using emission spectra and Commission Internationale de l'Eclairage (CIE) Lab coordinates, the coloring and transparency of painted films were investigated. Upon excitation at 365 nm, the UV‐irradiation of transparent painted films showed green emission at 518 nm. The hydrophobic activity and hardness properties were examined. Using electrochemical impedance spectroscopy (EIS), the anticorrosion of coatings applied to mild steel was studied. Improved anticorrosion characteristics were observed due to the fluorescence of NLA@Silica in the applied coatings. The optimal long‐lasting luminous characteristics were observed for nanocomposite films containing 12.5% of NLA@Silica.

Gamma irradiation-induced crosslinking and enhanced functionality of fish gelatin-agar edible films

Fish gelatin-agar edible films have potential for sustainable food packaging, but their limitations particularly water sensitivity require improvement. In this research, the effects of radiation from gamma rays at rates ranging from 0 to 40 kGy on the films' mechanical characteristics, microstructure, color, opacity, and water resistance were examined. Overall, gamma irradiation at doses of up to 30 kGy substantially improved the water resistance of the gelatin-agar film, as demonstrated by decreased water solubility, water absorption, and film vapor permeability. This could be due to crosslinking within the biopolymer network. However, at doses of 40 kGy, potential chain scission in the film's polymeric structure might occur, which counteracts further improvement and consequently starts degrading its water resistance. Similarly, the improvement of film's tensile strength and modulus of elasticity peaked at an optimal dose of 30 kGy, and then decreased at higher doses, while the film's elongation at break remained unaffected. FTIR and SEM analysis supported changes in functional group and structural morphology in these observations. Although irradiation caused some yellowing, an optimal dose range (at around 20–30 kGy) was identified to achieve improved functionality without degrading film integrity. These findings highlight the potential of gamma irradiation as a viable technique for modifying fish gelatin-agar films for enhanced performance in food packaging applications.

Physicochemical and Mechanical Properties of Thyme Essential Oil Containing Sodium Alginate Films

In this study, it was aimed to develop edible film from sodium alginate (%2 w/v) (SA) without additives and with three different concentrations of thyme essential oil (TEO) (0.5%, 1%, 1.5% v/v) additives with glycerol as a plasticizer using the casting technique. The physicochemical, mechanical, structural, and antioxidant properties of enriched SA films were also characterized. The highest film solubility (FS) was found as 91.78% in SA films. Mechanical properties of films were found between 50.06 MPa and 27.14 MPa for tensile strength (TS) and between 13.88% and 32.02% for elongation at break (EAB). The highest total phenolic content (TPC) and antioxidant activity was found as 382.19 mg GAE/kg and 16.20% in SA film incorporated with TEO 1.5% respectively. With the TEO added to the films, the L* value in the films increased and the film colors approached white and it is seen that the film colors approach yellow with an increase in b*.When the results of SEM analysis are evaluated it was found that SA films were more homogeneous compared to other films. In general, when the results of film analysis were evaluated, it was concluded that the addition of TEO, improves the physical and chemical properties of sodium alginate film well.

A pH-sensitive film based on chitosan/gelatin and anthocyanin from Zingiber striolatum Diels for monitoring fish freshness

As a new type of packaging method, the anthocyanin-based pH-sensitive indicator film has gained much attention owing to low cost, small size, and visually informative property. In this study, an intelligent film based on chitosan/gelatin (CG) matrix with Zingiber striolatum Diels (ZSD) anthocyanin for fish freshness monitoring was developed. The film properties, including thickness, moisture content, color, mechanical properties, UV–vis light barrier property, as well as pH and ammonia sensitivity, were evaluated. The CG-ZSD films exhibited a more compact structure when compared with the CG film. The CG-ZSD20 film showed the highest elongation at break (6.33 ± 0.62%) and lowest tensile strength (20.0 ± 0.58 MPa). FTIR spectra revealed the strong hydrogen bond interactions between ZSD and polymer matrix. Film incorporated with 15% anthocyanin extract has increased melting temperature at 118.9 °C, and a lower weight loss (13.8%) at melting temperature. In pH 1–14 buffer, the color of CG-ZSD films underwent a significant change from red to yellow-green. The CG-ZSD15 film was utilized for monitoring fish freshness and showed visible color changes from deep purple to brown. The total volatile basic nitrogen content and pH value changes of fish were closely related to the visual color changes in film. This demonstrated that the film was a highly pH-sensitive film for quantifying fish freshness in real-time.

All‐Cellulose‐Based Flexible Photonic Films

AbstractCellulose nanocrystals (CNCs) are environmentally friendly building blocks used in the preparation of chiral nematic iridescent films through evaporation‐induced self‐assembly. However, the brittleness of CNC films limits their versatility, especially in applications that require mechanical flexibility. In this study, it is innovatively engineered flexible colored CNC films entirely composed of cellulose by introducing cross‐linked chemically modified cellulose nanofibers (CNFs) as a supporting network. By reducing the surface charge content of CNFs and anchoring them in a network, the disruption to the self‐assembly process of CNCs caused by CNFs is minimized. This effectively preserves the structural colors of CNCs films. Furthermore, the CNFs network enhances the tensile strength and elongation of these all‐cellulose composite films, enabling them to be folded with excellent flexibility while still maintaining a high Young's modulus. Vibrant red, green, and blue‐colored all‐cellulose photonic films can also be achieved by simply adjusting the sonication energy input on the suspension of CNCs. The all‐cellulose‐based flexible films have the potential to be applied as an eco‐friendly and sustainable photonic material when flexibility is essential, for instance, in applications like flexible sensors, anti‐counterfeit labels, or foldable display components.

Coming Attraction: The Event of Color, Techniques of Screening and Filtering in Early “Natural” Color Film and Photography

Coming Attraction: The Event of Color, Techniques of Screening and Filtering in Early “Natural” Color Film and Photography

Influence of PEG on toughness, humidity sensitivity and structural color of cellulose nanocrystal films

Influence of PEG on toughness, humidity sensitivity and structural color of cellulose nanocrystal films

Production of biodegradable potato starch films containing Lycium barbarum polysaccharide and investigation of their physicochemical properties

Biodegradable films based on potato starch (POS) modified with Lycium barbarum polysaccharide (LBP) were prepared. The basic characteristics of the films, including thickness, opacity, swelling degree, color and water vapor permeability (WVP), were investigated. Rheometry, spectroscopy and textural analysis techniques were applied to determine the micro- and macro-physicochemical properties of the films. The inclusion of LBP in films led to a substantial reduction in thickness (from 0.16 to 0.11 mm), moisture content (from 15.16 % to 13.72 %), and WVP (from 4.03 ×10−4 to 2.69 ×10−4 g·mm·cm−2·d−1·kPa−1). The film color indices a* and b* (i.e., red and yellow) increased as the amount of added LBP was increased. No grease penetration occurred in films prepared using 0.4 or 0.6 (%, w/v) LBP, and they displayed excellent UV resistance. Incorporation of LBP significantly improved the thermal stability of potato starch films, and inhibited the swelling of film in alkaline solution. The addition of 0.4 or 0.6 (%, w/v) LBP increased the biocompatibility of films and resulted in a high tensile strength (TS) and elongation at break (EAB). Compost burial tests showed that incorporation of LBP did not disrupt the excellent degradation properties of starch films. These results prove the potential of LBP as a green modification material to improve the properties of potato starch-based films.

Biomimetic Structurally Colored Film for High‐Performance Radiative Cooling

AbstractIn recent years, passive radiative cooling has garnered considerable attention as a sustainable thermal regulation without relying on external energy sources, thus mitigating pollutants generation. However, an intrinsic limitation of these cooling systems lies in the reflective glare, often characterized by an ivory or silvery appearance. This drawback limits their practical application, especially where both functional efficiency and aesthetic appeal are pivotal. Herein, a biomimetic approach inspired by Saharan silver ants' thermoregulatory capabilities is adopted. These ants, equipped with distinctive triangular‐shaped hair, maintain body temperature lower than the ambient air. Leveraging insights from this natural model, a reusable silicon template is employed to fabricate a metasurface structural colored film with a triangular prism array structure using thermoplastic polyurethane (TPU) and the phase separation technique. The film demonstrates an average emissivity of 96% within the atmospheric window and an average solar reflectivity of 93%, leading to a maximum temperature reduction of 8.6 °C during daytime and 5.9 °C at night. Furthermore, the film displays stretchability and mechanical resilience, bolstered by the microscale prismatic structure enhancing superhydrophobicity. This work introduces a biomimetic strategy aimed at augmenting thermal emission while reconciling the challenge of achieving visual appealand high radiative cooling performance.

Study of Electrochromic Properties of PEDOT:PSS for Tunable Filter Optics with Lithium Salt Electrolyte

Nowadays, conductive polymers based on poly(3,4-ethylenedioxythiophene), poly(styrene sulfonic acid), or PEDOT:PSS, have been employed as a flexible and transparent coating in various significant electronic applications. With the demand for electrochromic properties, such as in electronic displays, further research into its electrooptic properties is required, especially the systematic understanding to obtain the optimized switching. Our research investigates the electrooptic properties of the PEDOT:PSS film, particularly the refractive index changing under various applied biases. The electrochromic device is prepared in a simple fashion, and the electroactive layer of PEDOT:PSS thickness is defined via spin-coating between two indium tin oxide (ITO) substrates. To increase the switching properties of PEDOT:PSS, lithium perchlorate (LiClO4) was prepared in acetonitrile, as the electrolyte in varied concentrations of 1.195 M, 1.5 M, and 2.0 M, respectively. A potential voltage of -4.0 V to 0.0 V is utilized to study the device's electrochromic properties with the step 5 mV/s continuously. Finally, the optical properties are characterized using the spectroscopy method based on real-time measurement of the transmission spectrum and transmission matrix calculations. The change in visible light absorption, transmission, and film color is recorded under a switching cycle that shows consistent behavior. This allows the further utilization of such a hybrid structure for possible tunable filter applications. Keywords: Electrochromic, PEDOT:PSS, Optical, Lithium salt, Electrolyte

Facile Synthesis and Photoluminescent Properties of Asymmetric Perylene Diimides Capable of Tuning Emission Colors in Polymeric Matrices.

We report the facile synthesis of asymmetric perylene diimides (asym-PDIs) using readily available reagents, demonstrating their distinct photoluminescent properties. In CHCl3, asym-PDIs exhibit higher solubility compared to traditional perylene dyes, of which solubilities can be varied by substituent selections. Among them, UV-vis absorption spectra of CPE in CHCl3 solution displayed no aggregate peaks in the ground state, maintaining high photoluminescent quantum yields. Also, CPE can be readily dispersed into poly(methyl methacrylate) PMMA (CPE-PMMA), forming thin films without aggregate formation. Importantly, the emission color of CPE-PMMA thin films significantly changes with the addition of polycyclic aromatic hydrocarbons (PAHs). These color changes should be strongly correlated with the HOMO level of the added PAHs.

The Influence of Functional Composite Coatings on the Properties of Polyester Films before and after Accelerated UV Aging.

The aim of this study was to cover biopolymeric packaging films based on PLA/PHBV blend with a functional composite coating (to retain their ecological character) and to investigate their antimicrobial properties before and after UV irradiation. As an active coating, the carrier hydroxypropyl methyl cellulose (HPMC), as well as its modified form with Achillea millefolium L., Hippophae rhamnoides L., and Hypericum L. extract (E) and a combined system based on the extracts and nano-ZnO (EZ), was used to obtain active formulations. Additionally, film surface morphology (SEM, FTIR-ATR) and color (CIELab scale) analysis of the pre- and post-UV-treatment samples were performed. The results confirmed that the E and EZ-modified films exhibited antibacterial properties, but they were not effective against phage phi6. Q-SUN irradiation led to a decrease in the activity of E coating against Staphylococcus aureus, Pseudomonas syringae, and Candida albicans. In this case, the effectiveness of EZ against C. albicans at 24 h and 72 h UV irradiation decreased. However, the irradiation boosted the antiviral effectiveness of the EZ layer. SEM micrographs of the film surface showed that UV treatment did not significantly influence the native film morphology, but it had an impact on the coated film. FTIR analysis results showed that the coatings based on HPMC altered the IR absorption of the nonpolar groups of the biopolyester material. The applied coatings only marginally affected film color changes and increased their yellowness after UV irradiation, whereas a composite layer of nano-ZnO limited these changes.

Effect of Antigonon leptopus extract in corn starch-glycerol based film as colourimetric indicator film for monitoring fish freshness

A colourimetric indicator can be used to test the freshness of fish in a rapid, straightforward and non-destructive manner. Anthocyanin, a natural dye found in Antigonon leptopus flowers, has a sensitive colour reactivity to a wide range of pH levels and can be made into colourimetric indicator films on a laboratory scale, making it a viable replacement for artificial dyes. The study's purpose was to see how the concentration of A. leptopus extract affected the colourimetric assessment of fish freshness. Ethanol was used to extract anthocyanin from A. leptopus. FTIR and pHrespond spectroscopies were used to characterise the extracts. Colourimetric indicator films were developed to assess fish freshness by incorporating A. leptopus extract into a corn starch-glycerol matrix via the solution casting method, with concentrations of 10%, 30% and 50%, respectively. The effect of A. leptopus extract on visual aspects, thickness, morphology, FTIR spectra, UV-Vis spectra and colour responses was analysed. Microbial analysis, TVB-N contents, firmness, and pH of the fish samples were analysed after storage. The colour of the original films became darker as the extracted content increased. There was no significant (p>0.05) effect of A. leptopus extract on film thickness. SEM micrographs revealed that the composite films had homogeneous and whitish granules on the surface and that increasing the A. leptopus extract concentration caused the films to become rougher. FTIR and UV-Vis spectroscopies showed successful binding between A. leptopus extracts and corn starch-glycerol film. With increasing pH, the colour change of the films exposed to pH = 3-11 solutions was no significant difference due to improper storage. An increase in the microbial population, TVB-N content and pH was observed over the storage period as a result of fish deterioration. Colour changes were also identified in the film which became darker. Overall, colourimetric indicator film with 50% A. leptopus extract was found to be the optimal formulation since it had the highest values in ∆E* during progressive spoilage of fish.

Indicator Films Containing Dendrobium Orchid Flower Extract and TiO2 Nanoparticles for Monitoring Fish Fillet Spoilage

This work aimed to study a novel pH indicator film prepared from carboxymethyl cellulose (CMC)/tapioca starch (TS) incorporating Dendrobium orchid flowers and TiO2 nanoparticles for monitoring fish fillet freshness. The films were prepared based on carboxymethyl cellulose (CMC) and tapioca starch (TS) blend (CMC/TS) incorporated with TiO2 nanoparticles and Dendrobium orchid flower (DOF) extract. The result showed that the DOF extract contained peonidin-3,5-O-diglucoside and exhibited distinguishable color changes in different pH buffers. Likewise, the CMC/TS+TiO2+DOF film’s color changed corresponding to the extract. The X-ray diffraction analysis revealed the expansion of the film’s amorphous region, due to the intermolecular interactions. Analyzing scanning electron microscope images showed the effects of TiO2 and DOF extract on the surface morphology of films. The incorporation of TiO2 and DOF extract into the film formulation improved various film properties, such as redness, opacity, tensile strength, and water solubility. For the sensitivity testing, the color of the CMC/TS+TiO2+DOF film responded to ammonia vapor more than acetic acid vapor, suitable for monitoring seafood spoilage behavior. In addition, the application of film for monitoring the freshness of fish fillets was conducted. The CMC/TS+TiO2+DOF film color changed from purple to bluish-purple corresponding to the spoilage of samples. Indicating its potential as an indicator for monitoring fish fillets' freshness.

Potato oxidized hydroxypropyl starch/pectin-based indicator film with Clitoria ternatea anthocyanin and silver nanoparticles for monitoring chilled beef freshness

Potato oxidized hydroxypropyl starch (POHS)/pectin (P) functional and smart beef freshness indicator films were prepared using butterfly pea (Clitoria ternatea) anthocyanin (BA) and silver nanoparticles (AgNPs). BA exhibited significant pH-responsive color changes. BA and AgNPs were evenly distributed within a polymer matrix to create a compatible film with POHS/P. The films containing BA and AgNPs had good UV resistance and maintained strong mechanical strength, barrier properties, and color stability. The color of the indicator film changed from purple to green when exposed to ammonia, with the 1 % POHS/P/BA/AgNPs film showing the most sensitive response. The films also demonstrated strong antibacterial and antioxidant properties. The freshness of beef was monitored using 1 % POHS/P/BA/AgNPs films and was identified as sub-fresh and spoiled on days 4 and 7, respectively. The relationship between the color change of the indicator label and the freshness of chilled beef was established: purple for fresh meat, blue for less fresh meat, and green for spoiled meat. Thus, the new POHS/P/BA/AgNPs film can serve as a smart packaging material to indicate food freshness and extend shelf life. These results suggest that POHS/P/BA/AgNPs films have significant potential as an active and smart food packaging material.