Production of photochromic nanocomposite film via spray-coating of rare-earth strontium aluminate for anti-counterfeit applications

Recent advances in photoresponsive printing inks for security encoding applications

Counterfeiting of banknotes, important documents, and branded goods continues to be a major worldwide problem for governments, businesses, and consumers. This problem has serious financial, security, and health implications. Due to their stability for printing on various substrates, the photochromic anticounterfeiting inks have received important interest. There have been various photochromic agents, such as polymer nanoparticles, quantum and carbon dots, and organic and inorganic fluorophores and luminophores, which have been broadly used for antiforging applications. In comparison to organic agents, inorganic photochromic materials have better stability under reversible/long-term light illumination. Recently, the remarkable optical characteristics and chemical stability of photoluminescent and photochromic agents have led to their extensive usage anticounterfeiting products. There have been also several strategies to tackle the rising problem of counterfeiting. Both of solvent-based and water-based inks have been developed for security encoding purposes. Additionally, the printing methods, including screen printing, labeling, stamping, inkjet printing, and handwriting, that have been used to apply anticounterfeiting inks onto various surfaces are discussed. The limitations of photoluminescent and photochromic agents and the potential for their future preparation to combat counterfeiting were discussed. This review would benefit academic researchers and industrial developers who are interested in the area of security printing.

Investigation of silicon doped carbon dots/Carboxymethyl cellulose gel platform with tunable afterglow and dynamic multistage anticounterfeiting

The remarkable optical properties of carbon dots, particularly their tunable room-temperature phosphorescence, have garnered significant interest. However, challenges such as aggregation propensity and complex phosphorescence control via energy level manipulation during synthesis persist. Addressing these issues, we present a facile gel platform for tunable afterglow materials. This involves chemically cross-linking biomass-derived silicon-doped carbon dots with carboxymethylcellulose and incorporating non-precious metal salts (BaCl2, CaCl2, MgCl2, ZnCl2, ZnBr2, ZnSO4) to enhance phosphorescence. Metal salts boost intersystem crossing via spin-orbit coupling, elevating triplet state transitions and activating phosphorescence. Chemical bonding and salt-induced coordination/electrostatic interactions establish confinement effects, suppressing non-radiative transitions. Diverse salt-gel interactions yield gels with tunable phosphorescence lifetimes (9.48 ms to 32.13-492.39 ms), corresponding to afterglow durations ranging from 3.20 to 11.86 s. With its broad tunability and high recognition, this gel material exhibits promising potential for dynamic multilevel anti-counterfeiting applications.

Silicon-Doped Carbon Dots Crosslinked Carboxymethyl Cellulose Gel: Detection and Adsorption of Fe3

The excessive emission of iron will pollute the environment and harm human health, so the fluorescence detection and adsorption of Fe3+ are of great significance. In the field of water treatment, cellulose-based gels have attracted wide attention due to their excellent properties and environmental friendliness. If carbon dots are used as a crosslinking agent to form a gel with cellulose, it can not only improve mechanical properties but also show good biocompatibility, reactivity, and fluorescence properties. In this study, silicon-doped carbon dots/carboxymethyl cellulose gel (DCG) was successfully prepared by chemically crosslinking biomass-derived silicon-doped carbon dots with carboxymethyl cellulose. The abundant crosslinking points endow the gel with excellent mechanical properties, with a compressive strength reaching 294 kPa. In the experiment on adsorbing Fe3+, the theoretical adsorption capacity reached 125.30 mg/g. The introduction of silicon-doped carbon dots confers the gel with excellent fluorescence properties and a good selective response to Fe3+. It exhibits a good linear relationship within the concentration range of 0-100 mg/L, with a detection limit of 0.6595 mg/L. DCG appears to be a good application prospect in the adsorption and detection of Fe3+.

Preparation of high-strength photochromic alginate fibers based on the study of flame-retardant properties

Color-changing fibers have attracted much attention for their wide applications in camouflage, security warnings, and anti-counterfeiting. The inorganic color-changing material tungsten trioxide (WO3) has been widely investigated for its good stability, controllability, and ease of synthesis. In this study, photochromic alginate fibers (WO3@Ca-Alg) were prepared by incorporating UV-responsive hybrid tungsten trioxide nanoparticles in the fiber production process. The prepared photochromic alginate fibers changed from white to dark blue after 30 min of UV irradiation and returned to their original color after 64 h. It can be seen that WO3@Ca-Alg has the advantage of long color duration. The strength of this fiber reached 2.61 cN/dtex and the limiting oxygen index (LOI) was 40.9 %, which indicates that the fiber exhibited mechanical resistance and flame-retardant properties. After the cross-linking of WO3@Ca-Alg by sodium tetraborate, a new core-shell structure was generated, which was able to encapsulate tungsten trioxide in it, thus reducing the amount of tungsten trioxide loss, and its salt and washing resistance was greatly improved. This photochromic alginate fiber can be mass produced and spun into yarn.

Transparent regenerated cellulose film containing azobenzene group with reversible stimulus discoloration property

The cellulose film, exhibiting color alterations in response to external stimuli, presents itself as a promising functional material. In this study, a universal dissolution-regeneration technique was employed to manufacture a transparent, regenerated cellulose film, characterized by its reversible multi-stimulus discoloration property. This functional cellulose film, endowed with both photochromic and acid-chromic attributes, was synthesized through the introduction of a cellulose-grafted azobenzene derivative into the cellulose solution. The hue of a cellulose film irradiated with ultraviolet light could be inverted upon exposure to visible light or heat. Furthermore, when subject to heating, irradiation, or immersion in an acidic medium, this functional film demonstrated pronounced transparency. The acid-chromic behavior of the film was readily discernible when exposed to highly concentrated acidic aqueous solutions. Both the photochromic and acid-chromic phenomena were discernable to the unaided eye. After ten cycles, no fading of the reversible discoloration properties of the material occurred. This transparent regenerated cellulose film stands as a viable candidate for applications in optical data storage, intelligent switches, and sensors, owing to its capacity for reversible stimulus-triggered discoloration.

Dual-mode security authentication of SrAl2 O4 :Eu,Dy phosphor encapsulated in electrospun cellulose acetate nanofibrous films

Photochromic inks have been an attractive authentication strategy to improve the anti-counterfeiting efficiency of commercial products. However, recent reports have shown significant disadvantages with photochromic inks, including poor durability and high cost. In this context, we developed novel photochromic nanofibres for advanced anti-counterfeiting applications. Lanthanide-doped strontium aluminate (LdSA) nanoparticles (NPs) were prepared and immobilized into electrospun cellulose acetate nanofibres (CANF). Authentication materials immobilized with inorganic photochromic agents can warranty durability and photostability. Therefore, the ultraviolet-stimulated photochromism of LdSA-encapsulated cellulose acetate nanofibres (LdSA@CANF) demonstrated high reversibility and photostability. A broad range of cellulose acetate nanofibres with unique emission characteristics was developed when applying different ratios of LdSA NPs. LdSA@CANF appeared colourless under visible daylight, whereas a green emission was monitored under ultraviolet-light illumination. The shape and chemical content of the photochromic fibrous films were examined using various analytical techniques. The mechanical characteristics of LdSA@CANF-coated paper were investigated. The emission wavelength was detected at 514 nm to designate green colour, whereas the excitation wavelength was detected at 369 nm to indicate transparency. The prepared cellulose acetate nanofibrous film can be described as an efficient strategy for the anti-counterfeiting of commercialized items.

Development of Photoluminescent and Photochromic Polyester Nanocomposite Reinforced with Electrospun Glass Nanofibers

A polyester resin was strengthened with electrospun glass nanofibers to create long-lasting photochromic and photoluminescent products, such as smart windows and concrete, as well as anti-counterfeiting patterns. A transparent glass@polyester (GLS@PET) sheet was created by physically immobilizing lanthanide-doped aluminate (LA) nanoparticles (NPs). The spectral analysis using the CIE Lab and luminescence revealed that the transparent GLS@PET samples turned green under ultraviolet light and greenish-yellow in the dark. The detected photochromism can be quickly reversed in the photoluminescent GLS@PET hybrids at low concentrations of LANPs. Conversely, the GLS@PET substrates with the highest phosphor concentrations exhibited sustained luminosity with slow reversibility. Transmission electron microscopic analysis (TEM) and scanning electron microscopy (SEM) were utilized to examine the morphological features of lanthanide-doped aluminate nanoparticles (LANPs) and glass nanofibers to display diameters of 7-15 nm and 90-140 nm, respectively. SEM, energy-dispersive X-ray spectroscopy (EDXA), and X-ray fluorescence (XRF) were used to analyze the luminous GLS@PET substrates for their morphology and elemental composition. The glass nanofibers were reinforced into the polyester resin as a roughening agent to improve its mechanical properties. Scratch resistance was found to be significantly increased in the created photoluminescent GLS@PET substrates when compared with the LANPs-free substrate. When excited at 368 nm, the observed photoluminescence spectra showed an emission peak at 518 nm. The results demonstrated improved hydrophobicity and UV blocking properties in the luminescent colorless GLS@PET hybrids.

Development of Thermochromic Ink Using the Anthocyanidin-Based Red-Cabbage Extract for Anticounterfeiting Applications

Temperature-driven colorful switching inks have been an interesting security encoding method to improve the anticounterfeiting properties of commercially available merchandise. Recently, thermochromic inks have faced many disadvantages, such as low efficiency, high cost, and low durability. In the current study, we developed self-healable ink from poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPSA) integrated with the anthocyanidin(ACY)-based red-cabbage extract in the presence of ferrous sulfate for authentication purposes. Self-healable inks have been able to guarantee durability and thermal stability. Environmentally friendly, ACY-based chromophore was extracted from Brassica oleracea L. var. Capitata (red-cabbage) to serve as a spectroscopic probe immobilized into PAMPSA. The prepared self-healable nanocomposite ink (PAMPSA-ACY) displayed temperature-induced chromism with high reversibility and thermal stability. Different self-healable nanocomposite inks of thermochromic features were prepared employing different ratios of the ACY-based red-cabbage extract. As described by Commission Internationale de L'éclairage Lab coordinates, homogeneous films were stamped on the paper surface to show a purple color (631 nm) able to switch color into red (458 nm) with the increase in temperature from 25 to 65 °C, respectively. Transmission electron microscopy, infrared spectra (FT-IR), energy-dispersive X-ray, and scanning electron microscopy were utilized to inspect the morphological behavior and chemical compositions of thermochromic prints. Both mechanical and rheological properties of ink-printed paper substrates and ink solution were also investigated. Both of antimicrobial activity and cytotoxicity study of the nanocomposite ink (PAMPSA-ACY) were also evaluated. Various industries can take the advantage of the current ink as a competent approach for anticounterfeiting purposes.

Preparation of photoluminescent nanocomposite ink for detection and mapping of fingermarks

Simple and efficient detection and mapping method based on a strong turn-on fluorescent pigment was developed for fingerprint analysis. We present a phosphor powder characterized by strong emission which is useful to achieve better fingerprint detection on multicolored or photoluminescent surfaces, such as currency notes characterized by optically changeable inks and highly fluorescent positions, because it offers better contrast and reduce the difficulty of background interference. Novel photochromic ink was prepared to establish a fingerprinted colorless film onto cellulose documents with green emission for anticounterfeiting applications as illustrated by photoluminescence spectra. Inorganic/organic nanoscale composite ink was prepared from rare-earth doped aluminate phosphor nanoparticles (PNPs; 27-49 nm) dispersed in a polyacrylic acid binding agent. PNPs were dispersed efficiently in polyacrylic acid to generate a colorless mark. The produced photochromic inks were spray-coated onto off-white paper sheets enclosing invisible fingermarks, and then exposed to thermofixation. Photochromic film was detected on paper surface presenting a transparent appearance under visible daylight and switchable to green under UV light. The CIE Lab parameters and photoluminescence spectra were studied under visible light and ultraviolet irradiation. The fingerprinted sheets showed fluorescence band at 517 nm upon excitation at 366 nm, showing a bathochromic shift and reversible photochromism without fatigue. The morphologies of pigment phosphor particles and fingerprinted sheets were inspected. The rheological properties of ink and mechanical behavior of the fingerprinted paper samples were explored. HIGHLIGHTS: Novel smart ink with alkaline-earth aluminate and polyacrylic acid was developed. Dual-mode fluorescent photochromism was presented for latent fingerprint analysis. Off-white fingerprinted films under daylight showed color change to green under UV. Fluorescence band monitored at 517 nm upon excitation at 366 nm. Fluorescent fingermark on paper sheets demonstrated good photostability.

Solution blowing spinning of polylactate/polyvinyl alcohol/ZnO nanocomposite toward green and sustainable preparation of wound dressing nanofibrous films

The outstanding biodegradability, biocompatibility, affordability, and renewability of polylactic acid have made it a prominent biomaterial. Herein, an innovative, easy, and eco-friendly technique is used to prepare sodium polylactate (SP)-based nanofibers. Solution blowing spinning (SBS) was used to create fibrous mats of SP and polyvinyl alcohol (PVA). SBS's SP nanfibers were crosslinked using an aqueous solution of calcium chloride to produce moisture-resistant calcium polylactate nanofibrous spun mats. Both of UV-visible absorption spectra and transmission electron microscopy were utilized to study the produced zinc oxide (ZnO) nanoparticles (NPs) to indicate a diameter of around 15-23 nm with a high intensity absorption intensity at 370 nm. New polylactate copolymer was synthesized and characterized by infrared and NMR spectroscopic techniques. In order to prepare SP/PVA/ZnO nanocomposite nanofibers, various ZnO ratios were used. The morphologies of the composite nanofibers were investigated by infrared spectroscopy (FTIR), energy-dispersive X-ray analyzer, and scanning electron microscopy. The cytotoxicity tests of the prepared mat were studied by conducting experiments with L-929 cells at various time intervals. The prepared composite SP/PVA/ZnO nanofibers were subjected to cytotoxicity tests to determine their cytocompatibility. Results showed that those with ZnO concentrations between 0.5% and 2% were found to be less harmful than those with higher concentrations. A variety of bacterial species, including Bacillus pumilus and Staphylococcus aureus, as well as Klebseilla pneumoniae and Escherichia coli, were used to test the antibacterial properties of SP/PVA/ZnO spun mats. The ZnO NPs integrated in the SP/PVA fibrous mats were responsible for their antibacterial properties. After finding the appropriate concentration of ZnO that is least harmful while yet giving a satisfactory antibacterial activity, this biomaterial might be perfect for wound dressing applications. HIGHLIGHTS: New eco-friendly biodegradable sodium polylactate (SP) copolymer was synthesized. Zinc oxide nanoparticles (ZnO NPs) with a diameter of 15-23 nm were prepared. High antibacterial SP/PVA/ZnO fibers were prepared by solution blowing spinning. SP/PVA/ZnO nanofibers (180-220 nm) with various ratios of ZnO were presented. Cytotoxicity results showed that the cell viability decreases with increasing ZnO.

Preparation of photoluminescent and anticorrosive epoxy paints immobilized with nanoscale graphene from sugarcane bagasse agricultural waste

Sugarcane bagasse agricultural waste has been one of the most common solid pollutants worldwide. Thus, introducing a simple method to convert sugarcane bagasse into value-added materials has been highly significant. Herein, we develop a simple and green strategy to reprocess sugarcane bagasse as a starting material for the preparation of graphene oxide nanosheets toward the preparation of novel photoluminescent, hydrophobic, and anticorrosive epoxy nanocomposite coatings integrated with lanthanide-doped aluminate nanoparticles. Environmentally friendly graphene oxide (GO) nanostructures were provided by a single-step preparation procedure from sugarcane bagasse (SCB) agricultural waste using ferrocene-based oxidation under muffled conditions. The oxidized SCB nanostructures were applied as a drier, anticorrosion, and crosslinking agent for epoxy coatings. Different concentrations of pigment phosphor were applied onto the epoxy coating. The generated epoxy-graphene-aluminate (EGA) paints were then coated onto mild steel. The hydrophobic properties and hardness as well as resistance to scratch of the EGA paints were examined. The transparency and colorimetric screening of the EGA nanocomposite paints were determined by the absorption spectral analysis and CIE Lab parameters. The luminescent translucent paints demonstrated a bright green emission at 520 nm when excited at 372 nm. The anticorrosion properties of the painted steel submerged in NaCl_(aq) were inspected by the electrochemical impedance spectral (EIS) method. The EGA paints with phosphor (11% w/w) exhibited the most distinct anti-corrosion properties and long-persistent luminescence. The produced paints displayed high durability and photostability.

Optical properties of novel luminescent nacre-like epoxy/graphene nanocomposite coating integrated with lanthanide-activated aluminate nanoparticles

Nacre structure has aragonite polygonal tablets, tessellated to generate separate layers, and exhibits adjacent layers and tablets within a layer bonded by a biopolymer. Herein, we report the development of nacre-like organic/inorganic hybrid nanocomposite coating consisting of epoxy tablets as well as rare-earth activated aluminate and graphene oxide tablet/tablet interfaces. The lanthanide-activated aluminate was prepared by the high temperature solid-state approach followed by the top-down technology to provide the phosphor nanoparticles (PNPs). Graphene oxide nanosheets were prepared from graphite. The prepared epoxy/graphene/phosphor nanocomposites were applied onto mild steel. Covalent bonds were formed between epoxy polymer chains resin and graphene oxide nanosheets. Those interface interactions results in tough surface, high tensile strength, and excellent durability. The usage of phosphor in the nanoparticle form guaranteed no agglomerations were produced throughout the hardening procedure by allowing better distribution of PNPs in the nacre-like matrix. The generated nacre-like substrates displayed reversible fluorescence. The excitation of the white colored nacre-like coats at 367 nm results in a green emission band at 518 nm as designated by CIE Lab and photoluminescence spectra. Various analysis methods were utilized to inspect the surface structure and elemental composition of the nacre-like coats. An improved hydrophobicity and mechanical characteristics were detected with increasing the phosphor concentration. Due to the astonishing characteristics of the prepared nacre-like composite paint, both ceramics and metals can benefit from the current simple strategy.

Photoluminescent and photochromic smart window from recycled polyester reinforced with cellulose nanocrystals

Smart windows with long-persistent phosphorescence, UV protection, high transparency, and high rigidity were developed by easily immobilizing varying ratios of lanthanide-activated aluminate phosphor nanoscale particles within a composite of recycled polyester/cellulose nanocrystals (RPET/CNC). Cellulose nanocrystals were prepared from rice straw waste. Cellulose nanocrystals were used at low concentration as both crosslinker and drier to improve both transparency and hardness. The phosphor nanoscale particles must be distributed into the recycled polyester/cellulose nanocrystals composite bulk without agglomeration in order to produce transparent RPET/CNC substrates. Photoluminescence characteristics were also studied by using spectroscopic profiles of excitation/emission and decay/lifetime. The hardness efficiency was also examined. This transparent recycled polyester waste/cellulose nanocrystals nanocomposite smart window has been shown to change color under UV light to strong green and to greenish-yellow when it is dark, as proved by CIE Lab color parameters. It was found that the afterglow RPET/CNC smart window had phosphorescence intensities of 428, 493 and 523 nm upon excitation at 368 nm. There were evidences of improved UV shielding, photostability, and hydrophobic activity. In the presence of low phosphor ratio, the luminescent RPET/CNC substrates showed quick and reversible fluorescent photochromic activity when exposed to UV radiation.

Color-switchable and photoluminescent poly (vinyl chloride) for multifunctional smart applications

Recycled poly (vinyl chloride) (PVC) waste was used to prepare transparent material with long-lasting phosphorescence, photochromic activity, hydrophobicity, strong optical transmission, ultraviolet (UV) protection, and stiffness. Lanthanide-activated aluminate (LaA) microparticles were prepared via the high temperature solid state procedure, which were subjected to the top-down grinding technology to afford LaA nanoparticles (LaAN). Laminated poly (vinyl chloride) bottles were shredded into a transparent plastic matrix, which was combined with LaAN and drop-casted to produce smart materials for a variety of applications. Smart window and photochromic film for smart packaging can be made from recycled poly (vinyl chloride) waste by immobilizing it with various ratios of LaAN. Long-lasting phosphorescent translucent poly (vinyl chloride) smart window and films need LaAN to be evenly dispersed in PVC without clumping. Different analytical methods were employed to assess the materials' morphological structure and chemical composition. Photoluminescence and decay spectra were all employed to investigate the luminescence characteristics. In addition, the mechanical performance was studied. According to CIE Lab (Commission Internationale de L'éclairage) color measurements, this transparent PVC smart material becomes a bright green under UV rays and turns a greenish-yellow in the dark. The PVC luminescence was observed to exhibit an apparent emission bands at 429 and 513 nm when excited at 367 nm. Improvements have been monitored in the UV shielding and hydrophobicity with increasing the phosphor concentration. LaAN-immobilized PVC exhibited reversible photochromism. The present approach can be applied for a variety of applications, such as anticounterfeiting films for smart packaging, smart window, and warning lightening marks.

Development of functional glow-in-the-dark photoluminescence linen fabrics with ultraviolet sensing and shielding

Linen fibres were coated with a glow-in-the-dark photoluminescence, flame-retarding, and hydrophobic smart nanocomposite using the pad-dry-curing process. Ecologically friendly ammonium polyphosphate and lanthanide-activated strontium aluminium oxide (LSAO) nanoparticles were immobilized into linen fabric using eco-friendly room-temperature-vulcanizing silicone rubber. Different analytical techniques were used to examine the morphological characteristics and elemental compositions of LSAO nanoparticles and treated linen textiles. The self-extinguishing properties of the treated linen textiles were tested for their fire resistance. After 24 washing cycles, the coated linen samples retained their flame-retarding properties. The treated linen's superhydrophobicity rose in direct proportion to the LSAO concentration. After being excited at 365 nm, the colourless luminescent film that was coated on linen surface gave out an emission wavelength of 519 nm. The photoluminescent linen was monitored to create a range of different colours, including off-white in daytime light and green under ultraviolet (UV) light radiation, according to the Commission Internationale de l'éclairage laboratory colorimetric coordinates and photoluminescence spectra. Emission, excitation, and lifetime spectral analysis of the treated linen revealed persistent phosphorescence. For mechanical and comfort evaluation, the coated linen textiles' bending length and air permeability were assessed. Good UV light shielding and enhanced antibacterial activity were detected in the treated linens.

Development of photoluminescent artificial nacre-like nanocomposite from polyester resin and graphene oxide

Long-lasting phosphorescent nacre-like material was simply prepared from a nanocomposite of inorganic and organic materials. Low molecular weight unsaturated polyester (PET), graphene oxide (GO), and nanoparticles of rare-earth activated aluminate pigment were used in the preparation process of an organic/inorganic hybrid nanocomposite. Using methylethylketone peroxide (MEKP) as a hardener, we were able to develop a fluid solution that hardens within minutes at room temperature. Covalent and hydrogen bonds were introduced between the polyester resin and graphene oxide nanosheets. The interface interactions of those bonds resulted in toughness, excellent tensile strength, and high durability. The produced nacre substrates demonstrated long-persistent and reversible luminescence. The excitation of the produced nacre substrates at 365 nm resulted in a 524 nm emission. After being exposed to UV light, the photoluminescent nacre substrates became green. The increased superhydrophobic activity of the produced nacre substrates was achieved without affecting their physico-mechanical properties.

Optical Detection of Acetone Using "Turn-Off" Fluorescent Rice Straw Based Cellulose Carbon Dots Imprinted onto Paper Dipstick for Diabetes Monitoring

Persistent bad breath has been reported as a sign of serious diabetes health conditions. If an individual's breath has a strong odor of acetone, it may indicate high levels of ketones in the blood owing to diabetic ketoacidosis. Thus, acetone gas in the breath of patients with diabetes can be detected using the current easy-to-use fluorescent test dipstick. In another vein, rice straw waste is the most well-known solid pollutant worldwide. Thus, finding a simple technique to change rice straw into a valuable material is highly important. A straightforward and environmentally friendly approach for reprocessing rice straw as a starting material for the creation of fluorescent nitrogen-doped carbon dots (NCDs) has been established. The preparation process of NCDs was carried out via one-pot hydrothermal carbonization using NH₄OH as a passivation substance. A testing strip was developed on the basis of cellulose CD nanoparticles (NPs) immobilized onto cellulose paper assay. The NCDs demonstrated a quantum yield of 23.76%. A fluorescence wavelength was detected at 443 nm upon applying an excitation wavelength of 354 nm. NCDs demonstrated remarkable selectivity for acetone gas as their fluorescence was definitely exposed to quenching by acetone as a consequence of the inner filter effect. A linear correlation was observed across the concentration range of 0.5-150 mM. To detect and measure acetone gas, the present cellulose paper strip has a "switch off" fluorescent signal. A readout limit was accomplished for an aqueous solution of acetone as low as 0.5 mM under ambient conditions. The chromogenic fluorescence of the cellulose assay responsiveness depends on the fluorescence quenching characteristic of the cellulose carbon dots in acetone. A thin fluorescent cellulose carbon dot layer was deposited onto the surface of cellulose strips by a simple impregnation process. CDs were made using NP morphology and analyzed using infrared spectroscopy and transmission electron microscopy. The carbon dot distribution on the paper strip was evaluated by scanning electron microscope and energy-dispersive X-ray analysis. The absorption and fluorescence spectral analyses were investigated. The paper sheets' mechanical qualities were also examined.

Simple preparation of novel photochromic polyvinyl alcohol/carboxymethyl cellulose security barcode incorporated with lanthanide-doped aluminate for anticounterfeiting applications

Forgery and low-quality products pose a danger to the society. Therefore, there are increasing demands for the production of easy to recognize and difficult to copy anti-counterfeiting materials. Products with smart photochromic and fluorescent properties can change color and emission spectra responding to a light source. In this context, we devised a straightforward preparation of luminescent polyvinyl alcohol/carboxymethyl cellulose (PVA/CMC) nanocomposite to function as a transparent labeling film. The lanthanide-doped aluminate (LdA) was prepared in the nanoparticle form to indicate diameters of 35-115 nm. Different ratios of the lanthanide-doped aluminate (LdA) were physically dispersed in the PVA/CMC nanocomposite label film to provide photochromic, ultraviolet protection, antimicrobial activity and hydrophobic properties. Fluorescence peaks were detected at 365 and 519 nm to indicate a color change to green. As a result of increasing the phosphor ratio, improved superhydrophobic activity was achieved as the contact angle increased from 126.1° to 146.0° without affecting the film original physical and mechanical properties. Both UV protection and antibacterial activity were also investigated. The films showed quick and reversible photochromic response without fatigue. The current strategy reported the development of photochromic smart label that is transparent, cost-effective and flexible. As a result, numerous anticounterfeiting products can benefit from the current label for a better market. LdA-loaded PVA/CMC films demonstrated antibacterial activity between poor, good, very good and outstanding as the percentage of LdA in the film matrix increased. The current film can be applied as a transparent photochromic security barcode for anticounterfeiting applications and smart packaging.

Effect of Compatibilizer on the Persistent Luminescence of Polypropylene/Strontium Aluminate Composites

There is a demand for long afterglow composites due to their potential applications in nighttime signal boards, sensors, and biomedical areas. In this study, Polypropylene (PP)/strontium aluminate-based composites [SrAl2O4:Eu2+/Dy3+ (SAO1) and Sr4Al14O25: Eu+2, Dy+3 (SAO2)] with maleic anhydride grafted PP compatibilizer (PRIEX) were prepared, and their auto-glowing properties were examined. After UV excitation at 320 nm, the PP/5PRIEX/SAO1 composites showed green emission at 520 nm, and blue emission was observed for PP/5PRIEX/SAO2 around 495 nm. The intensity of phosphorescence emission and phosphorescence decay was found to be proportional to the filler content (SAO1 and SAO2). The FTIR analysis excluded the copolymerization reaction between the SAO1 and SAO2 fillers and the PP matrix during the high-temperature melt mixing process. The SAO1 and SAO2 fillers decreased the overall crystallinity of the composites without affecting the Tm and Tc (melting and crystallization temperature) values. The thermal stability of the composites was slightly improved with the SAO1 and SAO2 fillers, as seen from the TGA curve. Due to the plasticizing effect of the compatibilizer and the agglomeration of the SAO1 and SAO2 fillers, the tensile modulus, tensile strength, and storage modulus of the composites was found to be decreased with an increase in the SAO1 and SAO2 content. The decreasing effect was more pronounced, especially with the bulk-sized SAO2 filler.

Simple Preparation of Photoluminescent and Color-Tunable Polyester Resin Blended with Alkaline-Earth-Activated Aluminate Nanoparticles

A simple inorganic/organic nanocomposite was used to generate long-lasting phosphorescent pebbles for easy commercial manufacturing of smart products. An organic/inorganic nanocomposite was made from low-molecular-weight unsaturated polyester and rare-earth-activated strontium aluminum oxide nanoparticles doped with europium and dysprosium. The polyester resin was mixed with phosphorescent strontium aluminate oxide nanoparticles and methylethyl ketone peroxide as a cross-linking agent to create a viscous mixture that can be hardened in a few minutes at room temperature. Before adding the hardener catalyst, the phosphorescent strontium aluminate nanoparticles were dispersed throughout the polyester resin in a homogeneous manner to ensure that the pigment did not accumulate. Long-lasting, reversible luminescence was shown by the photoluminescent substrates. The emission was reported at 515 nm upon exciting the pebble at 365 nm. In normal visible light, both blank and luminescent pebbles had a translucent appearance. As a result of UV irradiation, the photoluminescent pebbles produced an intense green color. The three-dimensional CIE Lab (International Commission on Illumination) color coordinates and luminescence spectra were used to investigate the color changing characteristics. Photophysical characteristics, including excitation, emission, and lifetime, were also investigated. Scanning electron microscopy, wavelength-dispersive X-ray fluorescence spectroscopy, and energy-dispersive X-ray analysis were employed to report the surface morphologies and elemental content. Without impairing the pebbles' original physico-mechanical characteristics, the pebbles showed improved superhydrophobic activity. The current simple colorless long-lasting phosphorescent nanocomposite can be applied to a variety of surfaces, like ceramics, glassware, tiles, and metals.

Development of silica-coated rare-earth doped strontium aluminate toward superhydrophobic, anti-corrosive and long-persistent photoluminescent epoxy coating

Long-persistent phosphorescent smart paints have the ability to continue glowing in the dark for a prolonged time period to function as energy-saving products. Herein, new epoxy/silica nanocomposite paints were prepared with different concentrations of lanthanide-doped aluminate nanoparticles (LAN; SrAl₂ O₄ : Eu²⁺ , Dy³⁺ ). The LAN pigment was firstly coated with SiO₂ utilizing the heterogeneous precipitation technique to provide LAN-encapsulated between SiO₂ nanoparticles (LAN@SiO₂ ). The epoxy/silica/lanthanide-doped aluminate nanoparticles (ESLAN) nanocomposite paints were coated on steel. The prepared ESLAN paints were studied by transmission electron microscope (TEM), infrared spectra (FTIR), scanning electron microscope (SEM), X-ray fluorescence analysis (XRF), and energy-dispersive X-ray spectra (EDS). The transparency and coloration properties of the nanocomposite coated films were explored by CIE Lab parameters and photoluminescence spectra. The ultraviolet-induced luminescence properties of the transparent coated films demonstrated greenish phosphorescence at 518 nm upon excitation at 368 nm. Both hardness and hydrophobic activities were investigated. The anticorrosion activity of the nanocomposite films coated onto mild steel substrates immersed in NaCl_(aq) (3.5%) was studied by the electrochemical impedance spectral (EIS) analysis. The silica-containing coatings were monitored to exhibit anticorrosion properties. Additionally, the nanocomposite films with LAN@SiO₂ (25%) exhibited the optimized long-lasting luminescence properties in the dark for 90 minutes. The nanocomposite films showed highly reversible and durable long-lived phosphorescence.