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. 2026 May 23;32(33):e71162. doi: 10.1002/chem.71162

Polylactic Acid‐Based Biodegradable Room‐Temperature Phosphorescent Materials: A Review

Nianshuang Zhang 1, Yujing Qin 1, Haoyi Ma 1, Jinbin Liu 1, Minghui Lu 1, Shanfeng Xue 1, Qikun Sun 1,✉, Wenjun Yang 1,✉
PMCID: PMC13532166  PMID: 42175790

ABSTRACT

Polylactic acid (PLA) is an ideal matrix for constructing pure organic room‐temperature phosphorescence (RTP) materials due to its renewability, biodegradability, and excellent biocompatibility. This study investigates the preparation, luminescence mechanisms, and application potential of PLA‐based RTP materials. By evaluating both chemical grafting and physical doping strategies, we highlight the distinct advantages of PLA‐based systems. Our findings demonstrate that the unique properties of the PLA matrix are pivotal in activating and enhancing RTP performance. These materials hold significant promise for bioimaging, information encryption, and 3D printing, effectively overcoming the degradation of RTP properties typically encountered in photocuring processes. Finally, we discuss the future prospects for PLA‐based room‐temperature phosphorescent materials.

Keywords: 3D printing, anti‐counterfeiting, organic room temperature phosphorescence, photoactive printing process, polylactic acid

This review highlights PLA as an ideal biodegradable matrix for room‐temperature phosphorescence due to its rigidity. Chemical grafting and physical doping enable efficient RTP by suppressing non‐radiative decay. Potential applications include bioimaging, encryption, and 3D printing. Future work targets near‐infrared RTP and 4D‐printed smart devices.

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1. Introduction

Room‐temperature phosphorescence (RTP) refers to the radiative decay phenomenon where a material, upon excitation, undergoes intersystem crossing (ISC) from a singlet excited state to a triplet excited state, followed by photon emission at ambient temperatures. Compared to traditional fluorescent materials, RTP materials offer distinct advantages, including long emission lifetimes, large Stokes shifts, and tunable luminescence colors. Consequently, they have demonstrated vast potential in organic light‐emitting diodes (OLEDs), sensors, information encryption, anti‐counterfeiting, and biomedicine [1, 2, 3, 4, 5]. Recently, pure organic RTP materials have emerged as a research hotspot due to their structural flexibility, low cost, and superior biocompatibility. Various strategies have been developed to prolong phosphorescence lifetimes, including host–guest doping [6, 7, 8], crystal engineering [9, 10], H‐aggregation [11, 12, 13], metal‐organic and supramolecular frameworks [14, 15], self‐assembly [16], as well as the use of luminescent polymers [17, 18, 19, 20] and carbon dots [21, 22, 23].

The systematic study of triplet exciton behavior in small‐molecule phosphorescent probes within a polystyrene matrix was first conducted by Burkhart et al. Their work demonstrated that the activation energies for triplet exciton trapping and detrapping are primarily dictated by the chemical structure of the dopant rather than the polymer matrix [24]. Subsequently, the Forrest group proved that phosphorescent materials could simultaneously harvest both singlet and triplet excitons, achieving a theoretical internal quantum efficiency (IQE) of 100%. This breakthrough surpassed the 25% efficiency limit of fluorescent materials and provided the fundamental impetus for the development of phosphorescent‐doped systems [25]. As research progressed, Zhang et al. systematically reviewed the intrinsic mechanisms of doping strategies, including the suppression of non‐radiative transitions by rigid matrices and the modulation of ISC by guest molecules, thereby establishing robust structure–property relationships [26]. Incorporating pure organic molecules into polymer matrices to construct RTP materials has since become a prominent research focus. For instance, Chi's team successfully developed materials with a phosphorescence lifetime of up to 2.32 s by doping indole‐based carbazole molecules with intramolecular charge transfer (ICT) characteristics into polyvinyl alcohol (PVA); notably, these molecules exhibit no phosphorescence in their crystalline state at room temperature [27]. Similarly, Li's group prepared phosphorescent thin films by doping planar phthalimide molecules with ICT features into polyacrylates [28]. Furthermore, Yang et al. synthesized a triplet‐generating molecule (DIA) containing two rotatable benzene rings. When doped into PMMA films, DIA exhibited ultralong green and blue RTP signals with lifetimes of 2146 and 2656 ms, respectively, highlighting the critical role of “pre‐locking” internal rotation units in enhancing RTP performance [29]. This team also extended this doping strategy to matrices such as acrylonitrile butadiene styrene(ABS), methyl methacrylate butadiene styrene(MBS), and styrene–isoprene–styrene(SIS), effectively prolonging the RTP lifetimes [30].

As a polyester derived from renewable resources such as corn starch, PLA possesses excellent biocompatibility, low toxicity, biodegradability, and commercial availability. Furthermore, its rigid polymer chain structure effectively restricts the molecular motion of doped luminophores, thereby suppressing non‐radiative energy loss and promoting the generation and enhancement of RTP. Recently, PLA‐doped systems have emerged as a focal point in the research of pure organic RTP materials, with their application potential in fields such as bioimaging garnering widespread attention [31, 32, 33, 34]. This review elucidates the design strategies for PLA‐based RTP materials from the perspectives of chemical grafting and physical doping, summarizes the underlying luminescence mechanisms for achieving RTP within a PLA matrix, and concludes with a forward‐looking perspective on the future development of these materials.

2. Design Strategies for PLA‐Based RTP Materials: Chemical Grafting Versus Physical Doping

To impart PLA with superior RTP properties, researchers have developed various design strategies, which can be broadly classified into two categories: chemical grafting (copolymerization) and physical doping. The central objective of both approaches is to leverage the rigid backbone and internal functional group network of the PLA to construct a highly restricted microenvironment for phosphorescent chromophores. This architecture effectively suppresses the non‐radiative decay of triplet excitons and provides a robust barrier against oxygen‐induced quenching.

2.1. Chemical Grafting and Copolymerization Systems

The chemical grafting strategy involves the direct covalent attachment of luminophores with phosphorescence potential onto the backbone or terminal groups of PLA (Figure 1). A significant advantage of this approach is its ability to fundamentally circumvent common issues associated with physical doping, such as phase separation and aggregation‐caused quenching (ACQ) resulting from the aggregation of guest molecules. Consequently, this strategy provides a more stable, uniform, and rigid confinement environment for the luminescent centers [35, 36, 37, 38, 39, 40, 41, 42].

FIGURE 1.

FIGURE 1

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Grafting phosphorescent small molecules onto PLA via covalent bonding and their lifetime of phosphorescence.

As early as 2007, the Fraser group conducted pioneering work by initiating the ring‐opening polymerization (ROP) of lactide to synthesize end‐functionalized, single‐component luminescent polymers, designated as BF2dbmPLA [43, 44, 45, 46]. The abundant carbonyl and hydroxyl groups within the PLA chains induce strong intra‐ and intermolecular hydrogen bonding, which rigidly anchors the luminophores. This configuration enables the material to exhibit green RTP lasting several seconds in the solid state (Figure 2a). In the phosphorescence spectrum, a shoulder peak at 450 nm aligns with the fluorescence characteristics. Given that this peak disappears at 77 K due to insufficient activation energy, it is confirmed to originate from thermally activated delayed fluorescence (TADF) caused by the reverse intersystem crossing (RISC) from the triplet to the singlet state. Furthermore, the long‐lived phosphorescence of BF2dbmPLA makes it an ideal candidate for highly sensitive oxygen sensors based on the quenching effect (Figure 2b,c). Subsequently, the team systematically investigated the synergistic regulation of RTP performance by heavy‐atom substitution and polymer molecular weight [47]. Their findings revealed that introducing heavy halogen atoms (e.g., Br, I) onto the luminophore significantly enhances spin‐orbit coupling (SOC) and promotes the ISC process, thereby increasing phosphorescence intensity [48, 49, 50, 51], albeit at the cost of shortened phosphorescence lifetimes (Figure 2d). Additionally, the polymer chain length (molecular weight) plays a decisive role: increasing the molecular weight of PLA broadens the energy gap between the singlet and triplet states (ΔEST ). Although this leads to a reduced ISC rate, it effectively prolongs the RTP lifetime [52, 53] (Figure 2e).

FIGURE 2.

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(a) Polymer synthesis and boron initiator and polymer luminescence (λ ex) 365 nm; room temperature in air unless indicated) [45]. (b) Normalized emission spectra for a BF2dbmPLA thin film. (c) Lifetime Stern–Volmer plot for a BF2dbmPLA film showing oxygen quenching of room temperature phosphorescence. Copyright 2007, American Chemical Society. (d) Phosphorescence of high MW BF2dbmPLA polymer films. (e) Influence of the halide substituent on the photostability of BF2dbmPLA spin‐cast films. Total intensity versus UV exposure time (λ ex = 369 nm; normalized to initial intensity) [46]. Copyright 2015, American Chemical Society.

Zhang et al. confirmed through both experimental studies and theoretical calculations that PLA materials featuring this donor–acceptor (D–A) geometric configuration (Figure 3a) not only achieve a high absolute quantum yield of 39.4% but also exhibit rare dual‐emission characteristics, including fluorescence–phosphorescence or dual phosphorescence [54]. To further overcome the spin‐forbidden limitations inherent in pure organic molecules, researchers have proposed incorporating ICT states into PLA copolymerization systems. Inspired by charge transfer (CT) state‐induced RTP, Zhang et al. constructed D–A structures by introducing carbazole (electron donor) into systems such as naphthalimide (NI) [55, 56, 57, 58]. By covalently anchoring these structures into PLA, polymers with long‐lived RTP were synthesized. This design ingeniously integrates n–π and π−π transition networks [59, 60, 61]. The electron‐donating effect of the carbazole moiety facilitates charge transfer and significantly narrows the ΔEST , thereby markedly enhancing the ISC efficiency.

FIGURE 3.

FIGURE 3

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(a) Macromolecular acceptor–donor–PLA structure (top) and design concept of highly efficient purely organic RTP materials (bottom) [53]. (b) Preparation of PLA‐Lig, photoactivated RTP properties of PLA‐Lig, phosphorescence spectra of PLA‐Lig upon UV irradiation (black line) and phosphorescence spectra of PLA‐Lig activated by UV irradiation in an ambient environment for 10 min (red line), 30 min (blue line), 60 min (green line), and 120 min (purple line), RTP lifetime of PLA‐Lig upon UV irradiation and after switching off the UV light source [62].

Driven by the trend toward full material sustainability, the integration of natural biomass macromolecules with PLA has emerged as a burgeoning research hotspot [62, 63]. Chen et al. utilized abundant natural lignin as a macromolecular initiator for the in situ ring‐opening polymerization of lactide, developing a fully renewable RTP material (PLA‐Lig) (Figure 3b). Upon continuous UV irradiation, the triplet excitons of lignin facilitate the conversion of triplet oxygen within the system into singlet oxygen, thereby triggering a photo‐activated RTP effect. After the UV source is removed, the emission intensity of the activated RTP in PLA‐Lig gradually diminishes at ambient temperature, becoming nearly undetectable after 2 h. Notably, a brief 20‐s UV exposure causes the phosphorescence lifetime to leap from 3.0 to 221.1 ms. Furthermore, when the material is re‐exposed to air for several hours after ceasing irradiation, the phosphorescence is quenched again due to oxygen re‐infiltration, enabling a reversible optical switching function. This “activation–quenching” cycle can be repeated seven times without significant optical fatigue, and the RTP lifetime remains stable even after storage at room temperature for one month. These findings underscore the pivotal role of covalent bonding between lignin and PLA in RTP emission and confirm that covalent grafting, π–π interactions, and oxygen consumption/diffusion are the key factors modulating its RTP performance [64].

2.2. Physical Doping Systems

Compared to chemical grafting, physical doping methods—such as solution casting and melt blending—are regarded as the most versatile and commercially viable routes for constructing polymer‐based RTP materials due to their operational simplicity, low cost, and scalability. In these physical doping systems, guest phosphorescent molecules are dispersed within the PLA matrix through non‐covalent interactions.

As an aliphatic polyester containing a high density of ester groups (─COO─), PLA is inherently an excellent hydrogen‐bond acceptor. When guest phosphors (e.g., aromatic compounds bearing ─NH or ─OH groups) are incorporated into the PLA matrix, they readily form a dense hydrogen‐bonded cross‐linking network with the carbonyl groups of PLA [65]. This hydrogen‐bond‐driven complexation, synergized with the glassy rigid backbone of PLA at room temperature, stringently restricts the translational, rotational, and vibrational motions of the guest molecules. Consequently, this effectively suppresses the non‐radiative deactivation pathways of triplet excitons (Figure 4a). Through this mechanism, even the simple small‐molecule dopants can exhibit intense, visible, long‐lived afterglow within the PLA matrix.

FIGURE 4.

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(a) Schematic of the mechanism of ultralong RTP in doped PLA films. (b) Schematic illustration of design strategy and the structure of doped systems. (c) The PL Photographs of doped PLAs before and after turning off UV light (365 nm), and the samples are prepared by 3D printing. (d) The steady‐state photoluminescence and phosphorescence spectra of eight PLA‐based RTP films; CZ@PLA: 𝜆 ex = 300 nm; PCz@PLA, DCz, ECz, BCz, OCz: 𝜆 ex = 320 nm; FCz, PyCz: 𝜆ex = 365 nm; delayed time: 0.1 s. (e) The time‐resolved RTP decay curves of eight PLA‐based RTP films under 365 nm UV excitation. (f) The structures of Phosphorescent dopants and the schematic diagram of the mechanism that realizes ultralong RTP in PLA [67]. Copyright 2025 Wiley‐VCH GmbH.

The convenience of physical doping is further demonstrated by its seamless integration with nanoengineering techniques, which expands the biomedical applications of PLA‐based RTP materials. Using a microemulsion method, Zhang et al. co‐dissolved an organic phosphor (TpPBr) with PLA and, with the assistance of a PVA surfactant, successfully fabricated TpPBr/PLA@PVA polymer nanoparticles with an average size of approximately 200 nm [66]. Owing to the exceptionally rigid confinement provided by the PLA matrix, these nanoparticles exhibit a phosphorescence lifetime of up to 118 ms and excellent photo‐activation properties, even at an ultra‐low dopant concentration (less than 2%). Benefiting from the superior biocompatibility and low toxicity of PLA, these low‐dye‐loading nano‐RTP materials achieved an exceptionally high signal‐to‐background ratio (SBR) of 2061 in in vivo bioimaging, demonstrating remarkable potential for time‐resolved imaging (Figure 5b).

FIGURE 5.

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(a) Enantiomeric forms of lactic acid and PLA cycle in nature [70]. Copyright 2022, The Author(s), under exclusive license to Springer‐Verlag GmbH Germany, part of Springer Nature. (b) Schematic illustration of the fabrication process for UV light‐activated, persistent room‐temperature phosphorescent polymeric nanoparticles designed for bioimaging [65]. Copyright 2025, American Chemical Society. (c) Schematic illustration of the emitter doping into the film for photo‐activated UOP [71]. (d) A series of BF2bdks derivatives containing naphthyl and phenyl groups grafted with PLA, and their photophysical properties in air and nitrogen [72].

Yang et al. achieved full‐color tunable RTP emission (440–628 nm) within a PLA matrix by systematically modulating the π‐conjugated systems of aryl‐fused carbazoles to tune their triplet energy levels (Figure 4b,d). Utilizing a physical doping strategy (Figure 4a,b,f), the synthesized planar rigid molecules were uniformly dispersed into the PLA matrix via solution blending and thermoplastic processing. Notably, the DCz@PLA material exhibited extraordinary luminescence performance, with a phosphorescence lifetime of 3.84 s and an afterglow visible to the naked eye for up to 48 s (Figure 4c,e). This is primarily attributed to the synergistic inhibition of non‐radiative decay by the rigid polymer network of PLA and the strong hydrogen‐bonding interactions between its carbonyl groups (─C═O) and the guest amine groups (─NH). Furthermore, the enhanced SOC from the nitrogen atoms in the guest, along with the optimized ΔEST , significantly improved the ISC efficiency, thereby further prolonging the RTP lifetime. Because physical doping preserves the polymer backbone and the inherent thermoplasticity of PLA, these materials can be processed into standard filaments for fused deposition modeling (FDM) 3D printing and recycling. This approach effectively circumvents the degradation of RTP properties typically associated with photocuring‐based 3D printing, laying a foundation for the personalized fabrication and commercial application of ultralong phosphorescent materials [67].

In summary, whether through chemical grafting with precise molecular control or physical doping relying on strong hydrogen‐bonding networks and rigid microenvironments, PLA has proven to be an exceptional host for achieving pure organic, long‐lived RTP.

3. Core Mechanisms of RTP in PLA‐Based Doping Systems

PLA is a linear aliphatic thermoplastic polyester derived from lactic acid (LA). Due to the presence of asymmetric carbon atoms in its molecular structure, lactic acid exists as two enantiomers: L‐lactic acid (L‐LA) and D‐lactic acid (D‐LA). The specific ratio of L‐LA to D‐LA significantly dictates the thermal and mechanical properties of the resulting PLA [68, 69, 70]. The core advantages of PLA lie in its environmental sustainability and biocompatibility; it is synthesized from renewable resources such as corn and wheat, remains biodegradable, and poses no environmental pollution (Figure 5a).

The capability of PLA‐doped systems to achieve efficient RTP is fundamentally rooted in the “rigid confinement” effect exerted by the PLA matrix on the luminophores. Meanwhile, its inherent biocompatibility ensures the viability of these materials for practical applications. The underlying mechanisms can be categorized into the following three aspects:

3.1. Suppression of Non‐Radiative Decay by the Rigid Matrix

The vibration and rotation of luminophores are the primary contributors to non‐radiative decay. The rigid polymer chain structure of PLA creates a stable spatial network that anchors doped organic phosphors within its matrix. This architecture effectively restricts both intramolecular vibrations and intermolecular collisions of the luminophores, thereby minimizing the non‐radiative dissipation of triplet excitons and promoting their radiative transition to achieve RTP emission. Experimental evidence shows that organic phosphors (e.g., TpPBr) combined with a PVA matrix exhibit no discernible phosphorescence; in contrast, when TpPBr is doped into a PLA matrix, significant and persistent RTP is observed (Figure 5b). This comparative result underscores the critical role of the PLA matrix in activating and sustaining RTP [65].

Huang et al. proposed a facile strategy to gradually consume oxygen through UV irradiation and radical coupling, thereby prolonging the photo‐activated phosphorescence lifetime and shortening the activation time. When organic phosphine ligands are incorporated into poly (methyl methacrylate) (PMMA), polylactic acid (PLA), or poly (vinyl acetate) (PVAc), the resulting polymer films exhibit slow photo‐activation and short initial phosphorescence lifetimes. Energy transfer effectively prevents the conversion of neutral molecules into photo‐generated radical pairs. Through this process, the phosphorescence lifetimes of the polymer films were extended from 0.08 to 360 ms [71] (Figure 5c). Furthermore, Fraser et al. synthesized a series of BF2bdks derivatives containing naphthyl and phenyl groups and systematically investigated their photophysical properties in both dichloromethane and PLA. By modulating the polymer molecular weight, dye attachment sites, and the spatial arrangement of heavy bromine atoms, they achieved precise control over the optical properties of the dye–PLA composites. Notably, they successfully developed heavy‐atom‐free systems with extended phosphorescence lifetimes, providing a critical foundation for lifetime‐based oxygen sensing technologies [72] (Figure 5d).

3.2. Molecular Confinement and Crystallization Suppression

Thermoplastic processing plays a decisive role in reshaping polymer morphology and enhancing RTP performance. Yang et al. noted that during conventional solution casting, slow solvent evaporation allows polymer chains sufficient time to rearrange and form spherulites, resulting in a semi‐crystalline state. This dense crystalline lattice tends to exclude bulky dopant molecules, hindering their uniform dispersion at the molecular level. Moreover, the casting process often introduces micropores and residual solvents, which provide pathways for oxygen permeation and non‐radiative transitions [73]. To address this, they proposed employing shear forces during thermoplastic processing to disrupt crystalline domains, thereby enhancing RTP. Subsequently, the team discovered that when using a PLA matrix, strong shear not only promotes the molecular‐level dispersion of guest molecules and eliminates residual solvents but, more importantly, transforms PLA into a dense amorphous state by disrupting crystallinity. In this amorphous phase, increased interchain cohesive forces strictly compress and confine the phosphors within a dense network, significantly boosting both RTP lifetime and intensity (Figure 6a). Conversely, uniaxial stretching of these amorphous PLA films induces cold crystallization, which disrupts the original amorphous rigid confinement and leads to the significant quenching of phosphorescence. This mechanism has been successfully applied to the visual monitoring of mechanical stress [67].

FIGURE 6.

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(a) Spectra, infrared spectra, and XRD patterns of DCZ in PLA [67]. Copyright 2025 Wiley‐VCH GmbH. (b) Chemical structures of NDI‐ or dibromo‐NDI‐bisfunctionalized linear polyesters. (c) UV–vis absorption spectra of bisfunctionalized NDI polyester (P1−P6) in dilute CH2Cl2 solutions at 298 K and steady‐steady photoluminescence emission (PL) and delayed emission (DL) spectra at 77 K (λ ex = 385 nm) [74]. Copyright 2022 Wiley‐VCH GmbH.

Zhang et al. covalently linked naphthalenediimide (NDI) to PLA chains, thereby disrupting the inherent crystallization tendency of NDI molecules and maintaining their molecular‐level dispersion within the polymer matrix. This configuration facilitates the formation of microscopic ground‐state aggregates, whose triplet emission energy levels are lower than those of isolated phosphors. They employed dihydroxy‐functionalized NDI to initiate the ring‐opening polymerization of L‐lactide (LA) and ε‐caprolactone (CL), yielding the linear polymers NDI‐PLA2 and NDI‐PCL2. Through the rational design of substituent combinations, this system simultaneously achieves broadband visible‐light absorption and near‐infrared RTP with millisecond‐scale lifetimes. For naphthalenediimide (NDI) phosphors, which are prone to aggregation, the “site‐isolation‐by‐polymerization” strategy facilitates the formation of diverse microscopic ground‐state aggregates. The triplet emission energy of these aggregates is lower than that of individual phosphors, which effectively suppresses the ACQ typically observed in bulk materials. This methodology demonstrates significant potential for expansion to other molecular RTP systems [74] (Figure 6b).

4. Applications of PLA‐Based RTP Materials

4.1. Bioimaging

In recent years, significant progress has been made in the development of biodegradable and biocompatible materials for biomedical and related applications [75, 76, 77]. Bioimaging requires materials with good biocompatibility, low toxicity, high signal‐to‐noise ratio, and deep tissue penetration capability. As a biodegradable material with excellent biocompatibility, PLA can be combined with RTP‐emitting units to effectively avoid background fluorescence interference and improve imaging quality, while also being degradable in vivo, thereby reducing biotoxicity.

The BF2dbmPLA nanoparticles prepared by Zhang et al. exhibit high biocompatibility; due to the extreme sensitivity of their phosphorescence to oxygen, they enable the precise contrast imaging of hypoxic tumor tissues [46]. Furthermore, Zhang et al. discovered that by substituting the polyester matrix (e.g., PLLA or PCL) or modulating its molecular weight, the luminescence efficiency and stability of red‐light chromophores (TDPP) can be significantly tuned [78], allowing for the customization of high‐performance cellular imaging contrast agents (Figure 7a). Utilizing a BCz‐loaded silicon‐based composite system (HPPs), Huang et al. achieved afterglow imaging in nude mice with a signal‐to‐background ratio (SBR) as high as 31 (Figure 7b). This “long‐afterglow” characteristic effectively eliminates interference from biological background autofluorescence [79]. Additionally, the Fraser group first reported the dual‐emission properties (fluorescence and phosphorescence) of BF2dbmPLA nanoparticles, which are suitable for ratiometric oxygen sensing [19]. In addition, their synthesized nanoparticles (<100 nm) were successfully internalized by T41 mouse mammary tumor cells, enabling high‐resolution cellular imaging via fluorescence microscopy [80] (Figure 7c).

FIGURE 7.

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(a) Schematic procedures for 4T1 Cell imaging [78]. Copyright 2024, American Chemical Society. (b) Bioimaging performance of BCz‐loaded HPPs within a physiological environment [79]. Copyright 2020 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim. (c) Fluorescence and bright‐field microscopy image overlay shows CHO cells after one hour of incubation with filtered BF2dbmPLA nanoparticle suspension (pre‐filtration concentration: 405 µg/mL), along with images of perinuclear localization of fluorescent nanoparticles within individual cells [80]. Copyright 2008, American Chemical Society.

4.2. Information Encryption and Security Authentication

Owing to their long‐lived emission, RTP materials offer unique advantages in the field of information encryption. By integrating phosphorescent materials with varying excitation conditions, lifetimes, and emission colors, high‐security information encryption and anti‐counterfeiting can be achieved. The excellent processability of PLA‐based RTP materials allows them to be fabricated into various forms, such as films and inks (Figure 8a), making them highly suitable for printing and security labeling applications [81].

FIGURE 8.

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(a) Data encryption by non‐emissive polymer inks [81]. Copyright 2023 Wiley‐VCH GmbH. (b) The preparation process of CDs‐PLA film, schematic diagram of the photoactive printing process, and phosphorescence photos of CDs‐PLA film after photoactive printing [82]. Copyright 2024 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies. (c) Color change of a hydrogel pattern (NdCD6) printed on a paper surface under daylight and UV light, and a hydrogel cast film under UV light [83]. Copyright 2024 Society of Plastics Engineers.

For instance, Zeng et al. developed CDs–PLA composite films [82] featuring dynamic photo‐activated phosphorescence. Under UV irradiation, these films exhibit a yellow‐to‐green dynamic afterglow that fades naturally, enabling their use in erasable optical printing and information encryption (Figure 8b). Furthermore, Khalaf et al. synthesized a self‐healing NdCD@PLA hydrogel ink [83] that emits blue phosphorescence under UV excitation. This ink can be stamped into diverse patterns and exhibits outstanding photostability and durability, rendering it ideal for high‐level security authentication (e.g., in banknotes, passports, and identity cards). Notably, the self‐healing capability of the ink further extends its service life by mitigating the impact of physical damage (Figure 8c).

4.3. Additive Manufacturing

PLA‐based RTP materials possess distinctive advantages, including environmental biodegradability, excellent processability, and unique phosphorescent effects. These attributes align perfectly with the “eco‐friendly and innovative” development trends in modern art and design, showing significant application potential in niche fields such as decorative design, cultural and creative products, and interactive art installations. In 2025, based on the “assembly‐induced emission” strategy, Yang et al. fabricated high‐performance, processable PLA‐based RTP composites using PLA as a green matrix and phosphorescent small molecules as guest materials. These materials exhibit both stimulus‐responsive properties and full‐color tunability. By utilizing 3D printing, a series of cultural and creative artworks were produced [67], which display uniform and soft multi‐colored long‐lived afterglow lasting for 10–15 s under UV excitation (Figure 9). This work provides critical technical support for the application of PLA‐based RTP materials in high‐end artistic design.

FIGURE 9.

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(a) Fine structures 3D printed at a base speed of 200 mm s−1 using a 0.4 mm extrusion head. (b) Various handicrafts printed with PLA material [67]. Copyright 2025 Wiley‐VCH GmbH.

4.4. Future Challenges and Perspectives

Despite significant progress, PLA‐based RTP materials still face several formidable challenges. Constrained by the “energy gap law,” long‐wavelength phosphorescence remains highly susceptible to quenching. Future endeavors should focus on integrating sophisticated molecular engineering—such as the design of D‐A architectures—with the multi‐confinement strategies inherent to the PLA matrix to develop high‐efficiency NIR‐RTP materials for deep‐tissue bioimaging. Furthermore, by leveraging the intrinsic shape‐memory effect of PLA, researchers can develop 4D‐printed structures with dual‐responsiveness in both morphology and luminescence [84]. Conduct in‐depth research into the interaction mechanisms between the rigid PLA matrix network and dopants [85], and clarify the effects of hydrogen bonding, molecular confinement, and crystallinity on RTP performance; achieve precise control over phosphorescence intensity, lifetime, and emission color by adjusting the PLA molecular weight, the π‐system of the dopant, and the substitution position of heavy atoms, thereby developing an environmentally friendly RTP system free of heavy atoms and featuring a long lifetime. Such advancements are expected to bring revolutionary changes to the fields of soft robotics and adaptive optical devices.

5. Conclusion

PLA, a renewable, biodegradable, and biocompatible thermoplastic polyester, serves as an ideal matrix for developing RTP materials. This review systematically summarizes the design strategies, underlying mechanisms, and practical applications of PLA‐based RTP systems, with a particular focus on two methodologies: chemical grafting and physical doping. Chemical grafting covalently attaches phosphorescent chromophores to the PLA backbone to suppress phase separation and ACQ. In contrast, physical doping offers a facile and cost‐effective approach, leveraging dense hydrogen‐bonding networks between the PLA matrix and guest luminophores to achieve efficient RTP emission. The activation and enhancement of RTP in these systems stem from the synergistic effects of three factors: the rigid confinement of triplet excitons provided by the PLA matrix to minimize non‐radiative deactivation, the modulation of molecular confinement and crystallization through thermoplastic processing, and specific intermolecular interactions. These factors collectively enhance ISC efficiency and minimize energy loss. While such materials show great promise in bioimaging, information encryption, and 3D printing—specifically in overcoming performance degradation during light‐curing processes—challenges remain. In particular, the “energy gap law” continues to hinder the development of quenching‐resistant, long‐wavelength phosphorescence. Future advancements will necessitate the integration of molecular engineering with multi‐level confinement strategies to expand the application frontiers of these materials.

Conflicts of Interest

The authors declare no conflicts of interest.

Acknowledgments

This work was supported by the Fundamental Research Funds for National Natural Science Foundation of China (No. 52273183), Natural Science Foundation of Shandong Province (No. ZR2020QE083), Taishan Scholar Constructive Engineering Foundation of Shandong Province of China (No. tsqn202211164), the Foundation of Key Laboratory of Rubber‐Plastics (No. KF2025014), Ministry of Education/Shandong Province Key Laboratory of High Performance Rubber Materials and Engineering, Qingdao University of Science & Technology.

Biographies

Qikun Sun received the Ph.D. degree from Qingdao University of Science and Technology in 2019. After graduation, he went to the Ulsan National Institute of Science and Technology for postdoctoral research in the Department of Chemistry. In 2021, he joined the College of Polymer Science and Engineering at Qingdao University of Science and Technology. His current research interests lie in the preparation and application exploration of multi‐stimulus responsive organic molecules/polymers for optoelectronic materials, mainly focusing on the areas of force‐induced/photoluminescent materials, and organic room temperature phosphorescent materials.

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Wenjun Yang received the Ph.D. degree from Jilin University in 1997. In 2002, he served as a Research Professor in the Department of Chemistry at Korea University in Korea, and since 2007, he has been a Professor in the School of Polymer Science and Engineering at Qingdao University of Science and Technology. Currently, he is mainly engaged in the research areas of functional organic polymer design and synthesis; organic optoelectronic materials and devices.

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Contributor Information

Qikun Sun, Email: qksun@qust.edu.cn.

Wenjun Yang, Email: ywjph2004@qust.edu.cn.

Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request

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Associated Data

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Data Availability Statement

The data that support the findings of this study are available from the corresponding author upon reasonable request

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