Persistent Luminescence Properties Research Articles

Dual co-doping strategy for prolonged luminescence in laser-sintered BaAl2O4:Eu2+, RE3+ ceramics

This work reports on the influence of co-doping on the luminescence and persistent luminescence properties of BaAl2O4 (BaO·Al2O3) laser-sintered ceramics. The samples were doped with Eu and doubly co-doped with different rare earths (Dy, Er, Nd, Pr, and Tm) followed by laser-sintering without an atmospheric control, at a power density of 1.6 W/mm2. All sintered ceramics contained the hexagonal BaAl2O4 phase and had a homogeneous microstructure. A photoluminescence emission band centered at 495 nm was observed, which was due to the 4f65 d1 → 4f7 Eu2+ transition in the BaAl2O4 matrix. The persistent luminescence emission was monitored for 15 min after charging at 345 nm for 3 min. The combination of Nd and Dy co-doping led to substantial improvements in decay time and persistent luminescence intensity compared to individual co-doping. These results suggested that the two co-dopants interacted by modifying the trap configurations in the BaAl2O4 matrix.

Chromium-doped zinc gallate: Impact of Sn4+ co-doping on the persistent luminescence properties at the nanoscale applied to bio-imaging

Persistent luminescence (PersL) nanoparticles emit a signal that lasts long after the excitation has ended, enabling highly sensitive bioimaging without background noise. By using UV light as the excitation source prior to injection, a strong PersL signal can be detected in vivo before disappearing within a few hours. For long-term imaging, we have shown in the past that visible LED can be used to re-excite ZnGa1.995Cr0.005O4 (ZGO:Cr3+) nanoparticles in vivo, producing a signal intensity that is, however, much lower compared to the signal obtained after the UV pre-excitation method. This lower signal intensity of the nanoprobe when using a visible LED may prevent its detection in some cases. Herein, we report an improvement in visible LED excitation efficiency using PersL Zn1.33Ga1.335Cr0.005Sn0.33O4 (ZGSO:Cr3+) nanoparticles. We fully compared ZGSO:Cr3+ and the original ZGO:Cr nanoparticles in terms of structure, optical properties and bio-imaging potential. Co-doping with tin strongly increases persistent luminescence, even at the nanoscale. In vivo imaging results showed that ZGSO:Cr3+ exhibited an approximately 3-fold signal enhancement over ZGO:Cr3+ using UV pre-excitation. More interestingly, when using LED excitation, the signal intensity of ZGSO: Cr3+ is more than 10 times higher than that of ZGO:Cr3+, making ZGSO nanoparticles much easier to detect. ZGSO:Cr nanoparticles can be surface-modified with PEG to produce nanoprobes with much longer residence time in blood. This unique comparison between the two compositions makes ZGSO:Cr3+ a more effective imaging diagnostic probe than the original ZGO:Cr3+ nanoparticles, opening up new applications for in vivo diagnostics.

Pr3+-Doped Lithium Niobate and Sodium Niobate with Persistent Luminescence and Mechano-Luminescence Properties

In this research, a comprehensive series of Pr3+-doped lithium niobate and sodium niobate materials were obtained at different temperatures via solid-state sintering, and their structures and properties were compared. NaNbO3: 0.75% Pr3+ phosphors were synthesized by sintering at 1150 °C for 2 h and emitted red persistent luminescence for more than 1200 s, peaking at 612 nm under UV excitation, which was a typical long persistent luminescence phenomenon. Furthermore, the sample glowed when pressurized, and a red bright luminescence which lasted for several seconds was visible to the naked eye. This was a typical mechanical luminescence phenomenon of samples under mechanical stress, directly converting mechanical energy into light energy. It was determined that NaNbO3:Pr3+ and LiNbO3:Pr3+ both possess multimode luminescence. Owing to their red long persistent luminescence (LPL) and mechano-luminescence (ML) properties, Pr3+ phosphors can be employed in fields, such as display technologies, stress sensing, structural damage detection, and other complex applications.

Chemical tuning of photo- and persistent luminescence of Cr3+-activated β-Ga2O3 by alloying with Al2O3 and In2O3

An effect of alloying of the monoclinic β-Ga2O3 with Al2O3 and In2O3 on the photoluminescent, thermoluminescent and persistent luminescent properties of Cr3+ ions has been comprehensively investigated. For this purpose, various series of Cr3+ and Ca2+ co-doped microcrystalline phosphors were synthesized by the solution combustion method, including pseudobinary compounds like (Ga-Al)2O3 with up to 20 % Al and (Ga-In)2O3 with up to 50 % In as well as pseudoternary compounds (Ga-Al-In)2O3 with balanced proportion of Al, Ga and In. The phase composition and crystal structure of the obtained materials were examined by X-ray powder diffraction technique. Detailed luminescence studies were conducted for the (Ga-Al)2O3 and (Ga-In)2O3 compounds which exhibited a single-phase monoclinic structure. Low-temperature and time-resolved photoluminescence investigations of the Cr-doped pseudobinary compounds unveiled several types of Cr3+ centres, attributed to the Al-, Ga- and In-centred octahedra in the studied alloys. The obtained results underscore the benefit of bandgap engineering through alteration in the host lattice chemical composition for efficient tuning of the thermoluminescent and persistent luminescent properties of the near-infrared-emitting β-Ga2O3:Cr based phosphors. Furthermore, it was demonstrated that modification of the chemical composition of the host lattice also adjusts the thermometric performance of the studied phosphors. Indeed, the specific sensitivity of the β-Ga2O3:Cr3+ decay time luminescence thermometer showed nearly twofold enhancement when the host lattice was alloyed with 30 % of In2O3.

Trap engineering in LiInSi2O6:Cr,Pr by excess cristobalite silica for X-ray activated near-infrared persistent luminescence imaging in vivo

Chromium-doped persistent luminescence nanoparticles (PLNPs) have promising biomedical applications in X-ray charged near-infrared (NIR) luminous imaging. The persistent luminescence (PersL) property was usually adjusted by co-doping with other ions. Impurity phases were thought to be adverse to the PersL. In this study, a composite material, LiInSi2O6:Cr,Pr·2SiO2 (LICP-S), was synthesized with a PersL peak at 800 nm after being charged by 1 Gy X-ray while LiInSi2O6:Cr (LIC) and LiInSi2O6:Cr,Pr (LICP) possessed no or very weak PersL. Distinctively, excess metastable cristobalite silica was found essential for the much more intense PersL of LICP-S than LICP and LIC. Thermostimulated luminescence spectra studies indicated that cristobalite adjusted the Pr-related traps from deep traps to shallow ones, which facilitated the room temperature PersL. The low dose X-ray charged PersL of LICP-S was applied to demonstrate the luminous labeling of a medical silicone prosthesis that was supposed to be imbedded in body for years via X-ray activated PersL imaging in vitro and in vivo. This work not only provides a kind of PLNPs with 800 nm emission suitable for low dose X-ray activation, but also an unusual strategy for trap engineering in PersL materials by designing multi-phase composites.

Study on preparation, optical properties and mechanism of Zn2SnO4:Cr3+ with high NIR luminescence intensity

In this work, Zn2SnO4:xCr3+ with high near-infrared luminescence intensity (broad emission centered at 800 nm and sharp emission at 703 nm) were successfully prepared by high temperature solid state method. Measurements indicated that the samples exhibited obvious photoluminescence as well as persistent luminescence properties. The results of X-ray diffraction indicated that high temperature facilitated the entry of Cr3+ into the Zn2SnO4 crystal lattice and formed replacement doping and promoted the luminescence efficiency of the samples. And, under the condition of 1450 °C and 0.002 at% Cr3+ concentration, sample with optimum NIR fluorescence properties was prepared. In the high-temperature sintering process, many defects of Zn2SnO4 were generated, which effectively promoted the formation of vacancies. The energy levels of these lattice defects (trap energy levels) facilitated the sub-stable trapping of electrons and produce afterglow properties. Analysis of luminescence mechanism reveals that the broad emission band centered at 800 nm and the sharp emission peak at 703 nm were derived from the energy level transitions of 4T2(4F)→4A2 and 2E→4A2 of Cr3+, respectively. Though, the long afterglow luminescence duration of Zn2SnO4:Cr3+ needs to be further improved compared with gallate-based NIR phosphors, Zn2SnO4:Cr3+ do have a promising application in bio-imaging due to its special NIR emission range.

Persistent luminescence of commercial TLD-100 dosimeter: Using shallow traps for radiation dosimetry

This work reports the persistent luminescence (PersL) properties of the commercial LiF:Mg,Ti (TLD-100) dosimeter and its performance in dosimetry applications. The thermoluminescence (TL) glow curve of the TLD-100 exhibits a peak at 96 °C that rapidly vanishes at room temperature, enabling the PersL phenomenon. The TLD-100 was exposed to beta particle irradiation within in the range of 0.22–32 Gy. The resulting PersL intensity was measured and found to increase as the irradiation dose increased. Notably, there was no saturation of the PersL intensity within this dose range with linear dependence from 0.55 to up 32 Gy. The TLD-100 showed good repeatability with a deviation of 0.1% after seven irradiation-readout cycles for twenty irradiations. The calculated lower detection limit was 2 mGy. Our results indicate that the TLD-100 can be used as a PersL and TL dosimeter for dosimetry applications, with the advantages of fast post-irradiation measurements.

Exploring the luminescence of tin‐incorporated nickel‐sensitized lithium gallate short‐wave‐infrared phosphors

AbstractA series of Ni2+‐sensitized LiGa5O8 nanocrystals doped with varying amounts of Sn4+ were synthesized via a high‐temperature solid‐state method. X‐ray diffraction and scanning electron microscopy were employed to investigate the microstructure of the LiGa5O8 host, and optical spectroscopy was used to examine the effects of Sn4+ addition on the emission spectra and persistent luminescence (PersL) properties, which indicated a homogeneous distribution of the constituent elements in the phosphor. The Sn4+ incorporation led to an approximately sixfold enhancement of photoluminescence intensity at room temperature and decrease in the energy transition of Ni2+(3T2(3F)→3A2(3F)), which resulted in ∼65 nm bathochromic shift in the photoluminescence emission maxima. However, the addition of Sn4+ dopant led to a decrease in the quantum yield of luminescence compared to that of the original phosphor. Temperature‐dependent thermoluminescence measurements revealed that doping of LiGa5O8 with Sn4+ interfered with the Ni2+ trap centers. Moreover, Ni2+‐sensitized Sn4+‐doped LiGa5O8 nanocrystals exhibited an afterglow effect that persisted for up to 300 s.

Color-tunable persistent luminescence phosphor for multimode dynamic anti-counterfeiting

Using a solid-state approach, the persistent luminescence property in sodium yttrium silicate which was single-doped or co-doped by europium or cerium was studied. The orthorhombic structure with the space group P212121 could be indexed to all samples, according to X-ray powder diffraction. The luminescence characteristics of these phosphors, including photoluminescence, luminescence degradation, and temperature-dependent emission, were systematically investigated. Under UV (∼365 nm) irradiation, blue/green emissions with broad bands peaking at 450/510 nm attributed to the characteristic 5d→4f/4f65d→4f7 transitions of Ce3+/Eu2+ could be observed in Na3LuSi3O9:Ce3+ and Na3LuSi3O9:Eu2+, respectively. Moreover, blue and green persistent luminescence was also observed in Ce3+ or Eu2+ single-doped samples. Thermoluminescence curve of Na3LuSi3O9:Eu2+, Ce3+ reveals that Na3LuSi3O9:Ce3+ and Na3LuSi3O9:Eu2+ have similar trap distribution. Tunable persistent luminescence can be realized via ratio control of Ce3+ and Eu2+. A possible afterglow mechanism was presented and discussed. The prepared materials have the potential of multimode dynamic luminescence, because they are highly sensitive to the composition, the excitation wavelength, and the detecting time. The outstanding abilities of Na3LuSi3O9:Ce3+, Eu2+ demonstrate the practical capability of this material for fingerprint identification and anti-counterfeiting.

Optical Bioimaging and Therapy

Optical Bioimaging and Therapy

Polychromatic long persistent luminescence of CaAlSiN3:Ln (Ln=Eu, Ce, Dy, Pr, Tb, Gd, Sm, Tm, Nd) phosphors prepared by combustion synthesis

Although the phosphors based on CaAlSiN3 (e.g. CaAlSiN3:Eu2+, CaAlSiN3:Ce3+) have been extensively studied in phosphor-converted white light emitting diodes (w-LEDs) due to its outstanding luminescent properties, there have been rare literatures on the persistent luminescence of CaAlSiN3 except for the red afterglow emission of CaAlSiN3:Eu2+. In our work, a series of CaAlSiN3:Ln (Ln=Eu, Ce, Dy, Pr, Tb, Gd, Sm, Tm, Nd) phosphors have been successfully prepared by combustion synthesis and their polychromatic visible afterglow emissions were observed. The long persistent luminescent properties of the phosphors were studied systematically, among which, CaAlSiN3:Eu2+ and CaAlSiN3:Ce3+ show the best red and yellow long persistent luminescence with persistent time of 4980 s and 4860 s at the 0.32 mcd/m2 threshold value, respectively, and other phosphors show relatively weak persistent luminescence performance with other afterglow emission colors. Moreover, Eu2+, Ce3+ co-doped CaAlSiN3 were synthesized to enhance the red long persistent luminescence performance, whose persistent time has reached 6300 s due to a more appropriate trap depth distribution of 0.83–0.9 eV compared with Eu2+ and Ce3+ singly doped CaAlSiN3. We believe that this work is of significance for extending the studies of CaAlSiN3 system to a host material for polychromatic long persistent luminescence.

A series of zinc coordination compounds showing persistent luminescence and reversible photochromic properties via charge transfer

Long persistent luminescence materials have wide application prospects in the fields of optical communication, sensors, and anticounterfeiting. Recently, some researchers have proved the feasibility of charge transfer effect in the construction of visible light excited room temperature phosphorescence (RTP) materials. However, materials with electronic effects require elaborate design to exhibit long-lived phosphorescence. Herein, a series of coordination compounds based on viologen ligand HL⋅Cl (4-carboxybenzyl)-4,4′-bipyridinium chloride) and Zn2+ with benzoic acid derivatives (o-, m-, p-phthalic acid) were reported. They exhibit not only reversible photochromic properties, but also long-lived persistent phosphorescence. Three complexes possess different structures through different auxiliary ligands with different optical physical properties. Complex 1 exhibits dynamic phosphorescence emission at low temperatures. Interestingly, we synthesized the first viologen complex (complex 2) with excitation wavelength dependent fluorescence, and the emission color gradually changed from blue to red with the increase of excitation wavelength. In addition, the applications of three complexes in data encryption and anticounterfeiting are further demonstrated. This work not only presents coordination compounds with dynamic afterglow materials, excitation wavelength- and time-dependent emission properties, but also provides a new strategy for the charge transfer effect in visible light-excited RTP materials.

A new insight into the mechanism of persistent luminescence phosphors SrS: Eu2+, Pr3+

The red persistent luminescence phosphors SrS: , (x = 0∼0.001, y = 0∼0.003) were synthesized by the solid-state reaction method in a weak reducing atmosphere of active carbon. The synthetic parameters, photoluminescence characteristics, and dynamic properties of thermoluminescence of the phosphors were studied systematically. According to the results of photoluminescence spectra of SrS: , , the energy level scheme of the phosphors was confirmed quantitatively. Based on the studies of the scanning electron microscope (SEM), UV-Visible absorbance spectra, afterglow decay curves, thermoluminescence(TL) spectra, and X-ray photoelectron spectroscopy (XPS) spectra, we found that the SrS: , (SSEP) phosphor presented the best persistent luminescence property, which mainly resulted from its outstanding absorbance characteristic, deeper depth of () defects, and fewer defect concentration belonging to the higher-order kinetics. Those comprehensive results deduced that a complex defect ()- should present in the Eu2+ doping phosphors, and the Pr3+ doping will produce defects, which can suppress the formation of () defects and increase their energy depth.

Persistent Luminescence Zn2GeO4:Mn2+ Nanoparticles Functionalized with Polyacrylic Acid: One-Pot Synthesis and Biosensing Applications.

Zinc germanate doped with Mn2+ (Zn2GeO4:Mn2+) is known to be a persistent luminescence green phosphor with potential applications in biosensing and bioimaging. Such applications demand nanoparticulated phosphors with a uniform shape and size, good dispersibility in aqueous media, high chemical stability, and surface-functionalization. These characteristics could be major bottlenecks and hence limit their practical applications. This work describes a one-pot, microwave-assisted hydrothermal method to synthesize highly uniform Zn2GeO4:Mn2+ nanoparticles (NPs) using polyacrylic acid (PAA) as an additive. A thorough characterization of the NPs showed that the PAA molecules were essential to realizing uniform NPs as they were responsible for the ordered aggregation of their building blocks. In addition, PAA remained attached to the NPs surface, which conferred high colloidal stability to the NPs through electrostatic and steric interactions, and provided carboxylate groups that can act as anchor sites for the eventual conjugation of biomolecules to the surface. In addition, it was demonstrated that the as-synthesized NPs were chemically stable for, at least, 1 week in phosphate buffer saline (pH range = 6.0-7.4). The luminescence properties of Zn2GeO4 NPs doped with different contents of Mn2+ (0.25-3.00 mol %) were evaluated to find the optimum doping level for the highest photoluminescence (2.50% Mn) and the longest persistent luminescence (0.50% Mn). The NPs with the best persistent luminescence properties were photostable for at least 1 week. Finally, taking advantage of such properties and the presence of surface carboxylate groups, the Zn2GeO4:0.50%Mn2+ sample was successfully used to develop a persistent luminescence-based sandwich immunoassay for the autofluorescence-free detection of interleukin-6 in undiluted human serum and undiluted human plasma samples. This study demonstrates that our persistent Mn-doped Zn2GeO4 nanophosphors are ideal candidates for biosensing applications.

Highly transparent Ce3+,Cr3+ co-doped GYAGG single crystals with enhanced persistent luminescence

Despite significant interest in persistent luminescence materials, the focus of all recent works remains on the exploitation of materials in powder form. Here, a new point of view based on persistent luminescence in single crystals is presented. The garnet crystals [(Gd0.67Y0.33)3-xCex)](Al2-yCry)Ga3O12 and [(Gd0.33Y0.67)3-xCex](Al2-yCry)Ga3O12 (GYAGG) codoped with Ce3+ and different concentrations of Cr3+ have been elaborated and their persistent luminescence properties are fully characterized within this work. The persistent luminescence of Ce3+, Cr3+-codoped GYAGG single crystals is optimized due to their high optical quality, very good crystallinity and a volume effect where the whole material can be excited and charged by the excitation light. Furthermore, thanks to their transparency, robustness and homogeneity; in-depth optical spectroscopy characterization is possible, shedding light on the mechanism responsible for the afterglow.

Photochromism and Long Persistent Luminescence in Pr3+‐Doped Garnet Transparent Ceramic via UV or Blue Light Up‐Conversion Charging

AbstractMultifunctional phosphors with photochromism and persistent luminescent (PersL) properties have attracted increasing interest owing to the capability of absorbing the photon energy and trapping the generated carriers via defects. However, the opacity of materials compromises the enhancement of photochromism and PersL properties; besides, the need of high energy excitation light source limits their applicability. To bridge these obstacles, Pr3+‐doped Y3Al2Ga3O12 transparent ceramic with in‐line transmittance over 80% at 1,800 nm is reported, which exhibits strong red PersL after several minutes UV light or blue light up‐conversion charging. The luminance duration time can reach >7 h at 0.32 mcd m−2 threshold value after UV light charging. Interestingly, the phosphor also displays photochromic properties with robust fatigue resistance, i.e., the color changes from light green to red by UV/blue light illumination and is bleached at 300 °C. The nature of trap centers, trapping and detrapping processes is explored based on thermoluminescence and electron spin resonance. Finally, the mechanism of photochromism and PersL is discussed by using vacuum referred binding energy diagram. This work opens new avenues for future research on multifunctional materials and brings potential applications in optical information encryption media and optical sensors.

Broadband and Multimode Near‐Infrared Emitter Based on Cr3+‐Activated Stannate for Multifunctional Applications

AbstractBroadband near‐infrared (NIR) phosphors have recently received considerable attention in spectroscopy technology fields, but designing inexpensive, emission peaks centered above 800 nm, and multimodal broadband NIR luminescence material still remains a great challenge. Here, by selecting stannate compound Mg2SnO4 (MSO) as the host, a kind of broadband NIR phosphor MSO:Cr3+ with multimode luminescence properties is reported. The designed material exhibits an emission peaking at 800 nm and a full‐width at half maximum of 180 nm (≈2730 cm−1). The site occupation of Cr3+ in MSO is unraveled by density functional theory calculation. The constructed NIR light‐emitting device based on MSO:Cr3+ displays a high NIR output power of 187.19 mW@100 mA and remarkable photoelectric efficiency of 13.67%, and its multifunctional applications in information encryption, non‐destructive detection, and so on are also demonstrated. Additionally, through defect site reconstruction, MSO:Cr3+ presents superior broadband NIR persistent luminescence (PersL) properties with PersL duration time longer than 50 h. This work provides a feasible strategy to develop intelligent optical material integrated with multimodal luminescence through low‐cost stannate compounds as the host toward versatile applications such as non‐destructive detection and bioimaging.

Persistent Luminescence Induced by Upconversion: An Alternative Approach for Rechargeable Bio‐Emitters

AbstractThe charging of persistent luminescence using an infrared laser as a power source and an upconversion process is a recently proposed trend in the field of persistent luminescence that allows expansion of the potential applications for these materials. In bioimaging at nanoscale, it allows for increased rechargeability capacity, as the excitation wavelength is fully inside the biological window. In this work, a novel approach is proposed to this phenomenon using energy transfer on associated materials. For this purpose, β‐NaGd0.8Yb0.17Er0.03F4 nanoparticles, known for their efficient upconversion, and Zn1.33Ga1.335Sn0.33Cr0.005O4 nanoparticles, known for their persistent luminescence properties, have been synthesized and associated through a dry impregnation method. The obtained hybrid material is found to present persistent luminescence at 700 nm after charging with a 980 nm laser. A mechanism is proposed to explain this energy transfer process and the capabilities of the hybrid material as rechargeable persistent nanoprobe for in vivo applications are shown.

Recent Progress in Inorganic Afterglow Materials: Mechanisms, Persistent Luminescent Properties, Modulating Methods, and Bioimaging Applications

AbstractPersistent luminescence (PL) is a distinctive optical phenomenon with long‐lasting afterglow emissions after the cessation of excitation, thus emerging huge prospects in the applications of anti‐counterfeiting, information or data storage, photocatalysis, sensing, and bioimaging. In this regard, it is of great importance to optimize the PL performance. Recently, no comprehensive literature review on inorganic persistent phosphors is reported to aid researchers in focusing on the systematic adjustment of afterglow properties based on reported progress made in recent ten years. Accordingly, the motivation of this work is to review the inorganic persistent phosphors that are of interest for the dopant and host selection criteria, the afterglow intensity, and multi‐color modulating methods, from the perspectives of composition optimization, defect engineering, and coordination environment of hosts. Then, X‐ray, light emitting diode (LED), ultraviolet (UV), and near‐infrared (NIR) excited PL imaging and multimodal imaging of persistent phosphors are introduced. Finally, the summary, challenge, outlook, and future development direction in this field are provided. With the profound influence of the afterglow materials, it is believed that this review will be a guideline for the design, synthesis, and optical performance optimization of persistent materials in the future.

Mesoporous polyacrylic acid/calcium phosphate coated persistent luminescence nanoparticles for improved afterglow bioimaging and chemotherapy of bacterial infection.

Coating mesoporous drug carriers on the surface of persistent luminescence nanoparticles (PLNPs) not only allows continuous luminous imaging without spontaneous fluorescence interference, but also provides drug release guidance. However, in most cases, the encapsulation of the drug-loaded shells significantly reduces the luminescence of PLNPs, which is unfavorable for bioimaging. In addition, conventional drug-loaded shells alone, such as silica shells, have difficulty in achieving responsive fast drug release. Herein, we report the fabrication of mesoporous polyacrylic acid (PAA)/calcium phosphate (CaP) shell-coated PLNPs (PLNPs@PAA/CaP) for improved afterglow bioimaging and drug delivery. The encapsulation of the PAA/CaP shell effectively prolonged the decay time and enhanced the sustained luminescence of PLNPs by about three times due to the passivation of the surface defects of PLNPs by the shell, and the energy transfer between the shell and PLNPs. Meanwhile, the mesoporous structure and negative charge of the PAA/CaP shells enabled the prepared PLNPs@PAA/CaP to carry the positively charged drug doxycycline hydrochloride efficiently. Under the acidic conditions of bacterial infection, the degradation of PAA/CaP shells and the ionization of PAA enabled fast drug release for effective killing of bacteria at the infection site. The excellent persistent luminescence properties, outstanding biocompatibility, and rapid responsive release feature make the prepared PLNPs@PAA/CaP a promising nanoplatform for diagnostic and therapeutic applications.