Solid Phosphors Research Articles

Interlaboratory Comparison on Absolute Photoluminescence Quantum Yield Measurements of Solid Light Converting Phosphors with Three Commercial Integrating Sphere Setups.

Scattering luminescent materials dispersed in liquid and solid matrices and luminescent powders are increasingly relevant for fundamental research and industry. Examples are luminescent nano- and microparticles and phosphors of different compositions in various matrices or incorporated into ceramics with applications in energy conversion, solid-state lighting, medical diagnostics, and security barcoding. The key parameter to characterize the performance of these materials is the photoluminescence/fluorescence quantum yield (Φf), i.e., the number of emitted photons per number of absorbed photons. To identify and quantify the sources of uncertainty of absolute measurements of Φf of scattering samples, the first interlaboratory comparison (ILC) of three laboratories from academia and industry was performed by following identical measurement protocols. Thereby, two types of commercial stand-alone integrating sphere setups with different illumination and detection geometries were utilized for measuring the Φf of transparent and scattering dye solutions and solid phosphors, namely, YAG:Ce optoceramics of varying surface roughness, used as converter materials for blue light emitting diodes. Special emphasis was dedicated to the influence of the measurement geometry, the optical properties of the blank utilized to determine the number of photons of the incident excitation light absorbed by the sample, and the sample-specific surface roughness. While the Φf values of the liquid samples matched between instruments, Φf measurements of the optoceramics with different blanks revealed substantial differences. The ILC results underline the importance of the measurement geometry, sample position, and blank for reliable Φf data of scattering the YAG:Ce optoceramics, with the blank's optical properties accounting for uncertainties exceeding 20%.

In situ coupling of carbon dots with zeolitic imidazolate frameworks enabling highly red emission in solid state

In this work, an extraordinary solid red emissive phosphor was prepared based on red-emitting carbon dots (R-CDs). The synthesis was conducted under an in-situ strategy, with assistance of zeolitic imidazolate frameworks. The obtained phosphor possesses a stronger red emission located at 630 nm in solid state, with CIE coordinate of (0.63, 0.35) and quantum yield of ∼ 45 %. As a consequence, not only aggregation-induced fluorescence quenching of R-CDs is avoided in solid state, but also an enhanced emission with high quantum yield is presented. Fluorescence properties were further explored in detail. The emission is found to be responsive to temperature and applied pressure. Based on the excellent emissive performance, the material has great potentials in anti-counterfeiting, latent fingerprint imaging, and temperature/pressure-sensing. This work provides a facile and promising way of preparing solid carbon-based phosphors for special applications.

Solid-State Phosphors from Coal-Derived Carbon Quantum Dots.

With unique optical and chemical properties, carbon quantum dots (CQDs) find tremendous applications in chemistry, biology, and materials science to medicine. To expand the applicability of coal-derived CQDs from the liquid to solid state, we herein report the sustainable synthesis of solid phosphors from coal-derived CQDs using poly(vinyl alcohol) (PVA) and silica (SiO2) as an organic and inorganic matrix. Two coal-derived CQDs were obtained using an eco-friendly ultrasonic-assisted wet oxidation method. The structural and chemical properties of the CQDs were extensively investigated and compared with commercial CQDs. The coal-derived CQDs exhibited blue fluorescence with 8.9 and 14.9% quantum yields. The CQDs were found to be self-co-doped with nitrogen and sulfur heteroatoms through surface and edge functional groups. Solid-state fluorescence of PVA/CQD composite films confirmed that the CQDs retained their excellent blue emission in a dry solid matrix. A facile one-pot sol-gel method was employed to fabricate SiO2/CQD phosphors with the unique fluorescence emission. Due to their special structural features, coal-derived CQDs favored the heterogeneous nucleation and rapid formation of SiO2/CQD phosphors. Further, coal-derived CQDs caused high-intensity white light emission with CIE coordinates of (0.312, 0.339) by endowing a suitable band gap structure in a SiO2/CQD solid phosphor for potential optical applications.

Synthesis of Li+ and Bi3+codoped Cs2AgInCl6 lead-free double perovskites

Cs2AgInCl6 with broadband emission has become a promising substitute for lead halide perovskite due to its unique properties. In this study, a spraying and evaporating method is developed to prepare lead-free double perovskite Cs2Ag1-xLixInCl6:Bi, involving Li+ and Bi3+ codoping, with improved photoluminescence quantum yield (PLQY) of the perovskites. The experimental results show that the PLQY of Cs2AgInCl6 increases from <1% to 36% with Li+ doping and finally reaches 76% through further Bi3+ doping. In particular, Cs2Ag0.7Li0.3InCl6:Bi yields the highest PLQY and significant stability under ultraviolet irradiation. In optoelectronic applications, white light-emitting devices are manufactured based on Cs2Ag0.7Li0.3InCl6:Bi crystals, which act as solid phosphors, and achieve excellent performance, such as Commission International de I'Eclairage color coordinates of (0.37, 0.37), a high color rendering index of 84.1, and a correlation color temperature of 4331 K. Therefore, double perovskites may find potential application in the field of light-emitting and display optoelectronic devices.

Concentration-dependent and pH response carbon dots and application in latent fingerprints recognition

Herein, red fluorescence carbon dots (R-CDs) were synthesized via solvothermal method using citric acid and urea as raw materials in DMF solvent. What is more interesting is that the synthesized CDs displayed concentration-dependent photoluminescence behavior, which can be ascribe to the fact that the intermolecular forces pulled the CDs particles closer, and the functional groups on the CDs surface combined together, thereby narrowing the energy gap, which ultimately led to the fluorescence emission peak moving to longer wavelength with the increase of concentration accompanied by a significant reduction in the fluorescent intensity. In addition, the diluted CDs displayed pH response. With the continuous increase of pH, the color of the solution changes from green to pink, and the fluorescence intensity increases significantly, which has a linear relationship in the range of pH 8–14. These characteristics are conducive to the visual detection of pH value. Moreover, in order to overcome aggregation-caused quenching (ACQ), a solid phosphor with an emission peak at 600 nm was obtained by incorporating chitosan matrix, which showed excellent performance in latent fingerprints (LFPs) detection.

High-Efficiency Continuous-Luminescence-Controllable Performance and Antithermal Quenching in Bi3+-Activated Phosphors.

Recently, Bi3+-activated phosphors have been widely researched for phosphor-converted light-emitting diode (pc-LED) applications. Herein, novel full-spectrum A3BO7:Bi3+ (A = Gd, La; B = Sb, Nb) phosphors with a luminescence-tunable performance were achieved by a chemical substitution strategy. In the La3SbO7 host material, a new luminescent center was introduced, with Gd3+ replacing La3+. The photoluminescence (PL) spectra show a large blue shift from 520 to 445 nm, thus achieving regulation from green to blue lights. Moreover, a series of solid solution-phase phosphors La3Sb1-xNbxO7:Bi3+ were prepared by replacing Sb with Nb, and a PL spectral tunability from green (520 nm) to orange-red (592 nm) was realized. Temperature-dependent PL spectra show that La3-xGdxSbO7:Bi3+ phosphors have excellent thermal stability. Upon 350 nm excitation, the PL intensity of La3-xGdxSbO7:Bi3+ phosphors at 150 °C remained at more than 93% at room temperature. With Gd3+ doping, the thermal stability gradually improved, and LaGd2SbO7:0.03Bi3+ represents splendid antithermal quenching (135.2% at 150 °C). Finally, a full-visible spectrum for pc-LED with a high color-rendering index (Ra = 94.4) was obtained. These results indicated that chemical substitution is an effective strategy to adjust the PL of Bi3+, which is of great significance in white-light illumination and accurate plant lighting.

Rational Synthesis of Solid-State Ultraviolet B Emitting Carbon Dots via Acetic Acid-Promoted Fractions of sp3 Bonding Strategy.

Carbon dots (CDs) have received tremendous attention for their excellent photoluminescence (PL) properties. However, it remains a great challenge to obtain CDs with ultraviolet (UV, 200-400nm) emission in solid state, which requires strict control of the CDs structure and overcoming the aggregation-caused quenching (ACQ). Herein, a new sp3 compartmentalization strategy is developed to meet these requirements, by employing acetic acid to promote fractions of sp3 bonding during the synthesis of CDs. It markedly decreases the size of sp2 conjugating units in the CDs, and shifts PL emission to the ultraviolet B (UVB) region (λmax = 308nm). Moreover, sp2 domains are well spatially compartmentalized by sp3 domains and the ACQ effect is minimized, enabling the high quantum yield in solid state (20.2%, λex = 265nm) with a narrow bandwidth of 24nm and environmental robustness. The solid-state UVB emissive CDs are highly desired for application in photonic devices. Hence, a demo of UVB light-emitting diodes is fabricated for plant lighting, leading to a 29% increase of ascorbic acid content in the basil. Overall, a rational and efficient way to construct solid UVB-CDs phosphors for wide applications is provided.

Defect Luminescence Based Persistent Phosphors—From Controlled Synthesis to Bioapplications

AbstractPersistent luminescence is an optical phenomenon where solid phosphors can store photoenergy in defects and release the energy by luminescence after stopping excitation. Due to the intriguing optical characteristics, the defect luminescence based persistent phosphors have attracted enormous attention in recent decades, especially in biomedical fields such as biosensing and bioimaging. Persistent luminescence nanoparticles (PLNPs) can effectively avoid the autofluorescence interference from complex samples or tissues, leading to significantly improved sensitivity in biological analysis. In this review, we summarized the methods to control the optical performance of PLNPs from the perspectives of controlled synthesis and defect regulation, and emphasized the close relationship between their optical performance and applications. We further provided a summary about a series of PLNPs nanoprobes designed by our group for biosensing and bioimaging. Our efforts, summarized in this review, will not only open a window for manipulating luminescence in PLNPs, but also further promote the application of PLNPs in biomedicine. What is the most favorite and original chemistry developed in your research group?Synthesis and bioapplications of persistent phosphors.How do you get into this specific field? Could you please share some experiences with our readers?I got into chemistry related to biomedicine during my graduate student period. The research situation of luminescent nanomaterials in China has a strong effect on me, inspiring me to pursuit new luminescent nanomaterials and their applications.We need have interest and concentrate on our research with passion. We are encouraged to work hard.What is the most important personality for scientific research?Curiosity and hard‐working.What are your hobbies? What's your favorite book(s)?Shopping and reading books. My favorite books are novels, such as “The Three‐Body Problem”.How do you keep balance between research and family?I have two boys and it takes me much time to take care of them. I need to elevate my work efficiency and work hard. I also buy household service to save time.Who influences you mostly in your life?My father. He loves reading and writing. I know one need to have passion on something under my father's influence.

Three-dimensional temperature and velocity measurements in fluids using thermographic phosphor tracer particles

Many flows of technical and scientific interest are intrinsically three-dimensional. Extracting slices using planar measurement techniques allows only a limited view into the flow physics and can introduce ambiguities while investigating the extent of 3D regions. Nowadays, thanks to tremendous progress in the field of volumetric velocimetry, full 3D-3C velocity information can be gathered using tomographic PIV or PTV hence eliminating many of these ambiguities (Discetti and Coletti, 2018; Westerweel et al., 2013). However, for scalar quantities like temperature, 3D measurements remain challenging. Previous approaches for coupled 3D thermometry and velocimetry combined astigmatism PTV with encapsulated europium chelates particles (Massing et al., 2018) or tomographic PIV with thermochromic liquid crystals particles (Schiepel et al., 2021). Here we present a new technique based on solid thermographic phosphor tracer particles, which have been extensively used for planar fluid temperature and velocity measurements (Abram et al., 2018) and are applicable in a wide range of temperatures. The particles are seeded into a gas flow where their 3D positions are retrieved by triangulation from multiple views and their temperatures are derived from two-colour luminescence ratio imaging. In the following, the experimental setup and key processing steps are described before a demonstration of the concept in a turbulent heated jet is shown.

Tailoring of White Luminescence in a NaLi3 SiO4 :Eu2+ Phosphor Containing Broad-Band Defect-Induced Charge-Transfer Emission.

Single-component materials with white-light emission are ideal for lighting applications. However, it is very challenging to achieve white luminescence in single-dopant activated solid phosphors. Herein, white NaLi3 Si1- x O4 :Eu2+ materials are designed via defect engineering and synthesized by reducing the Si content (0.15 ≤ x≤ 0.25). Stochiometric NaLi3 SiO4 :Eu2+ exhibits a narrow-band blue emission at 469nm, ascribed to the 5d → 4f transition of Eu2+ at highly symmetric cuboid Na sites, while samples with Si content reduced by 15-25% display white emission with two peaks at 472nm and 585nm. The newly appeared broadband yellow peak arises from charge-transfer transitions involving Eu2+ and nearby defects, as verified by an unusual bandwidth, a large Stokes shift, and a long decay time. A single-component white light-emitting diode device is fabricated by employing a white phosphor to demonstrate a color-rendering index of 82.9. This result provides a new design strategy for single-component white-light materials with broad-band defect-induced charge-transfer emission.

Transition Metal Ions for Solid State Lighting and Optical Thermometry

Different transition metal ions with 3d unfilled shells are used for applications in solid state lasers and phosphors. Among the whole 3d group the ions with the 3d3 configuration are of particular importance, due to their specific energy level scheme, which can lead to three kinds of photoluminescence spectra: i) sharp spin-forbidden 2E→4A2 emission; ii) broad spin-allowed 4T2→4A2 emission; iii) coexistence of both these emissions.In the present work we review recent progress in the development of crystalline materials doped with the Mn4+ and Cr3+ ions.The Mn4+ ions-doped hosts exhibit only sharp emission spectra in the range from 620 nm to ~700 nm, depending on the host [1]. The phosphors with emission between 620 nm and 650 nm (such as K2SiF6, Na2SiF6 etc) are suitable for applications in white LEDs to produce warm white light. The phosphors emitting at longer wave lengths (e.g. double perovskites Ba2LaNbO6, La2LiSbO6 etc) are used for applications in white LEDs for agriculture, to enhance plant growth [2].In addition to several examples of tuning emission peak position by chemical composition, an important issue of dependence of the emission intensity on the local symmetry will be discussed in detail.The Cr3+ ions can produce all three above-mentioned spectra, depending on the host material. For example, in ZnAl2O4 and MgAl2O4 sharp Cr3+ red 2E→4A2 emission transition is peaked at around 685 nm [3], whereas in LaSc3(BO3)4 and (Ce,Gd)Sc3(BO3)4 crystals broad infrared Cr3+ 4T2→4A2 emission band is centered at 960 nm and 1100 nm, respectively [4, 5].An interplay of the strong and weak crystal field effects can produce redistribution of relative intensities of both 2E→4A2 and 4T2→4A2 emission transitions in the Cr3+-bearing phosphors. With increased temperature, the crystal field strength is decreased and the infrared 4T2→4A2 emission gains intensity. Ratio of intensities of these two transitions can be used for non-contact temperature measurements [6, 7]. Another potential application of such systems is pressure sensing. These examples justify recently renewed interest to the Cr3+ and Mn4+ ions.

Simulation of the NaGd(MoO4)2–NaEu(MoO4)2 and Na2Gd4(MoO4)7–Na2Eu4(MoO4)7 Solid Solutions by the Interatomic Potential Method

Simulation of the solid solutions in the system of double sodium–gadolinium and sodium–europium molybdates, which are promising matrices for solid state lasers and phosphors has been carried out by the method of interatomic potentials. Two types of solid solutions have been studied, one of which contains finite components corresponding to the stoichiometric NaGd(MoO4)2–NaEu(MoO4)2 compositions with statistical distribution of cations in the crystal lattice. Another object is a cation-deficient Na2Gd4(MoO4)7–Na2Eu4(MoO4)7 system, in which we have examined the variants of statistical distribution and partial ordering of cations over structural positions. Atomistic simulation has been performed using the GULP 4.0.1 software package (General Utility Lattice Program). It is shown that when we pass from sodium-gadolinium molybdate to sodium-europium molybdate, both of stoichiometric and cation-deficient compositions, an increase in the unit cell volume is observed, while the density of the crystal, the energy of interatomic interactions in the structure, the vibrational entropy and the heat capacity decrease along with increasing europium content. The energy of interatomic interactions in the structure for cation-deficient solid solutions is less than for stoichiometric ones. Other aforementioned characteristics for cation-deficient solid solutions have greater values than for stoichiometric ones. The role of cluster europium centers in concentration quenching in NaGd(MoO4)2–NaEu(MoO4)2 solid solutions has been examined.

Моделирование твердых растворов NaGd(MoO-=SUB=-4-=/SUB=-)-=SUB=-2-=/SUB=-- NaEu(MoO-=SUB=-4-=/SUB=-)-=SUB=-2-=/SUB=- и Na-=SUB=-2-=/SUB=-Gd-=SUB=-4-=/SUB=-(MoO-=SUB=-4-=/SUB=-)-=SUB=-7-=/SUB=--Na-=SUB=-2-=/SUB=-Eu-=SUB=-4-=/SUB=-(MoO-=SUB=-4-=/SUB=-)-=SUB=-7-=/SUB=- методом межатомных потенциалов

AbstractSimulation of the solid solutions in the system of double sodium–gadolinium and sodium–europium molybdates, which are promising matrices for solid state lasers and phosphors has been carried out by the method of interatomic potentials. Two types of solid solutions have been studied, one of which contains finite components corresponding to the stoichiometric NaGd(MoO_4)_2–NaEu(MoO_4)_2 compositions with statistical distribution of cations in the crystal lattice. Another object is a cation-deficient Na_2Gd_4(MoO_4)_7–Na_2Eu_4(MoO_4)_7 system, in which we have examined the variants of statistical distribution and partial ordering of cations over structural positions. Atomistic simulation has been performed using the GULP 4.0.1 software package (General Utility Lattice Program). It is shown that when we pass from sodium-gadolinium molybdate to sodium-europium molybdate, both of stoichiometric and cation-deficient compositions, an increase in the unit cell volume is observed, while the density of the crystal, the energy of interatomic interactions in the structure, the vibrational entropy and the heat capacity decrease along with increasing europium content. The energy of interatomic interactions in the structure for cation-deficient solid solutions is less than for stoichiometric ones. Other aforementioned characteristics for cation-deficient solid solutions have greater values than for stoichiometric ones. The role of cluster europium centers in concentration quenching in NaGd(MoO_4)_2–NaEu(MoO_4)_2 solid solutions has been examined.

Silica-Coated Mn-Doped CsPb(Cl/Br)3 Inorganic Perovskite Quantum Dots: Exciton-to-Mn Energy Transfer and Blue-Excitable Solid-State Lighting

Tunability of emitting colors of perovskite quantum dots (PQDs) was generally realized via composition/size modulation. Due to their bandgap absorption and ionic crystal features, the mixing of multiple PQDs inevitably suffers from reabsorption and anion-exchange effects. Herein, we address these issues with high-content Mn2+-doped CsPbCl3 PQDs that can yield blue-excitable orange Mn2+ emission benefited from exciton-to-Mn energy transfer and Cl-to-Br anion exchange. Silica-coating was applied to improve air stability of PQDs, suppress the loss of Mn2+, and avoid anion-exchange between different PQDs. As a direct benefit of intense multicolor emissions from Mn2+-doped PQD@SiO2 solid phosphors, a prototype white light-emitting diode with excellent optical performance and superior light stability was constructed using green CsPbBr3@SiO2 and orange Mn: CsPb(Cl/Br)3@SiO2 composites as color converters, verifying their potential applications in the field of optoelectronics.

Mn2+ activated MgAlON transparent ceramic: A new green-emitting transparent ceramic phosphor for high-power white LED

A novel Mn2+ activated green-emitting MgAlON transparent ceramic phosphor was synthesized from Mg0.21Al2.57O3.80N0.20:0.03Mn2+ (MgAlON:Mn) phosphor powder by pressureless sintering combining with hot isostatic pressing. By crystalline structure refinement and cathodoluminescence (CL) characterization, it is demonstrated that Mn2+ was dissolved in the spinel lattice and occupied the tetrahedral site. The ceramic, retaining high transmittance in UV–vis region (up to 82% at 800nm) and excellent thermal-mechanical properties of MgAlON transparent ceramic-matrix, shows a strong green emission at 513nm under 445nm light excitation. Compared with its powder counterpart, the ceramic phosphor exhibits higher green color purity, higher internal quantum efficiency (47%) and lower thermal quenching. It is suggested that this novel green solid phosphor could be applied in high color rendering and high-power white light-emitting diodes when combined with a red solid phosphor and a blue LED chip.

Stress- and Temperature-Dependent Wideband Fluorescence of a Phosphor Composite for Sensing Applications

As both stress and temperature can alter the lattice of a solid phosphor in a similar way, the dopant rare-earth ion may be used as a probe for either parameter using the same sensing mechanism. Here, a wideband phosphor, YAG:Ce is used as a micro stress sensor at very low magnitudes of compressive stress. The sensing resolution can be smaller than 0.06 N/mm2 in the range of 0 ~ 1.2 N/mm2 with a sensitivity of 11 cm−1/MPa. The sensitivity is about a hundred times larger than the coefficient reported under hydrostatic pressure. The barycenter energy of the emission band of a phosphor can be used to indicate stress and/or temperature change, producing a precision beyond the spectroscopic resolution limit. The sensing functions obtained from the barycenter shift are superior to those from peak shifts. The stress/temperature dependent barycenter shift of the observed fluorescence bands of YAG:Ce were similar in magnitude. Mechanisms involving the nephelauxetic effect, crystal field effect and site symmetry of dopant ions are explored as explanations of the experimental phenomena.

Experimental Investigations for Fabrication and Comparison of Fatigue Properties of an Open Cell Porous Regular Metallic Structure and with Inner Solid Core through Rapid Manufacturing

In this study parts having Open Cell Porous Regular Interconnected Metallic Structure (OCPRIMS) of cubic unit cell and OCPRIMS with inner solid core were fabricated through developed process of Rapid Manufacturing (RM) process. Two approaches were used to fabricate inner solid core i,e one by using metallic phosphor bronze powder and other by using solid phosphor bronze rod. The specimens were fabricated in accordance with ISO 3928: 1999 and subjected to tension-tension and compressive-compressive fatigue testing. The endurance limit of OCPRIMS with solid rod cored structure was found to be on the higher side in comparison to other types of specimens. The results of Scanning Electron Microscopy (SEM) and images of fractured surfaces showed the presence of voids, shrinkage cavities and pointed edges on the designed pores. They acted as stress raisers and facilitated crack initiation and propagation in the specimens.

The structural evolution and spectral blue shift of solid solution phosphors Sr3−mCamB2O6:Eu2+

An unexpected spectral blue shift of the emission from yellow to green is observed for the solid solution phosphors Sr3−mCamB2O6:Eu2+ (m = 0–3), when larger Sr2+ ions are substituted by smaller Ca2+ ions in Sr3B2O6 lattices. The powder X-ray patterns of all the phases indicate a structural similarity to the end compounds and show a smooth variation of the structural parameters with composition in the full range. The linear structural evolution of the iso-structural Sr3−mCamB2O6 solid solutions obeying Vegard's rule has also been examined and verified by Rietveld refinement, high resolution transmission electron microscopy and Fourier transform infrared spectroscopy. The average bond lengths of the central cations to the coordinating anions and the distortion indexes of the coordination polyhedra are investigated. As a result, the symmetry of the coordination crystal field is found to be higher with increasing Ca content in the solid solutions phosphors, which should be primarily responsible for the continuous blue shift of the emission spectra of Sr2.96−mCamB2O6:0.04Eu2+ with the growth of the m value.

Understanding of nitrogen-doped carbon nanoparticles based solid phosphors for white light emitting diodes

Filter coffee powder derived nitrogen-doped carbon nanoparticles (N-CNPs) for white light emitting diodes.

Core–shell monodisperse spherical mSiO2/Gd2O3:Eu3+@mSiO2 particles as potential multifunctional theranostic agents

Core–shell nanoparticles with diameters in the range 100–500 nm have been synthesized as monodisperse spherical mesoporous (pore diameter 3 nm) silica particles with size deviation of less than 4 %, filled with gadolinium and europium oxides and coated with a mesoporous silica shell. It is shown that the melt technique developed for filling with gadolinium and europium oxides provides a nearly maximum filling of mesopores in a single-run impregnation, with gadolinium and europium uniformly distributed within the particles and forming no bulk oxides on their surface. The coating with a shell does not impair the monodispersity and causes no coagulation. The coating technique enables controlled variation of the shell thickness within the range 5–100 % relative to the core diameter. The thus produced nanoparticles are easily dispersed in water, have large specific surface area (300 m2 g−1) and pore volume (0.3 cm3 g−1), and are bright solid phosphor with superior stability in aqueous media. The core–shell structured particles can be potentially used for cancer treatment as a therapeutic agent (gadolinium neutron-capture therapy and drug delivery system) and, simultaneously, as a multimodal diagnostic tool (fluorescence and magnetic resonance imaging), thereby serving as a multifunctional theranostic agent.