Multimodal Luminescence Research Articles

A dynamic three-path authenticating model for anti-counterfeiting in a single host of CaAl2Si2O8

Luminescent materials are one of the most fascinating candidates for the field of data communication and information security because of their special optical characteristics. Unfortunately, unimodal output of luminescent performance reaches unsatisfied security of anti-counterfeiting. Hence, achieving multicolor, multitemporal, and multimodal luminescence performance simultaneously is still a fascinating target, especially in a single host. Here, multi-model optical output is realized for the multiple emission centers of CaAl2Si2O8 doped with Eu3+/Eu2+ ions. Moreover, a successive defect structure is constructed via the introduction of Nd3+ ions, which enables the thermo-/photon- responded luminescence properties. Herein, an efficient three-path authenticating model that performs a dynamic multiple color response and stimulated-sources dependent emission is accomplished in the CaAl2Si2O8 host matrix. The explored multichannel approach offers a unique insight for designing advanced anti-counterfeiting technology.

Afterglow Carbon Dots: From Fundamentals to Applications.

The ability of carbon dots (CDs) to emit afterglow emission in addition to fluorescence in response to UV-to-visible excitation allows them to be a new class of luminescent materials. When compared with traditional organic or inorganic afterglow materials, CDs have a set of advantages, including small size, ease of synthesis, and absence of highly toxic metal ions. In addition, high dependence of their afterglow color output on temperature, excitation wavelength, and aggregation degrees adds remarkable flexibility in the creation of multimode luminescence of CDs without the need for changing their intrinsic attributes. These characteristics make CDs particularly attractive in the fields of sensing, anticounterfeiting, and data encryption. In this review, we first describe the general attributes of afterglow CDs and their fundamental afterglow mechanism. We then highlight recent strategic advances in the generation or activation of the afterglow luminescence of CDs. Considerable emphasis is placed on the summarization of their emergent afterglow properties in response to external stimulation. We further highlight the emerging applications of afterglow CDs on the basis of their unique optical features and present the key challenges needed to be addressed before the realization of their full practical utility.

The integration of diverse fluorescence performances of Sr2−xSnO4:xSm3+ ceramics with an infinite luminescence modulation ratio

Reversible luminescence modification has received considerable interest due to its potential applications in optical storage technology and high-sensitivity optical switches. However, there is no any report that multi-mode luminescence modification behavior can be achieved in one material so far. In this study, a novel multifunctional luminescence phosphor Sr2−xSnO4:xSm3+ has been developed. Photoluminescence, photoluminescence modulation associated with the photochromism reaction, photo-stimulated luminescence, thermoluminescence are realized in one single ceramic material Sr2−xSnO4:xSm3+. The optimized photoluminescence modulation ratio based on the photochromism reaction reaches 72.2%. Based on the photo-stimulated luminescence, the photoluminescence modulation ratio reaches an infinite value ∞, which provides a different approach for optical storage and can avoid the bit error in information storage. In addition, the mechanisms of photoluminescence modulation, photo-stimulated luminescence, thermoluminescence are analyzed. The diverse luminescence properties in Sr2−xSnO4:xSm3+ are tightly related to the formed defects induced by Sm3+ doping. The high integration level for fluorescence performances can widen the application of activator-doped oxides.

Creating dual-mode luminescence in piezoelectric calcium niobates through lanthanide-doped for anti-counterfeiting and temperature sensing

Lanthanide-doped luminescent materials have been widely used in the field of information security and optical sensing, owing to their unique optical properties. However, conventional luminescent materials usually exhibit unicolor and single-peak emission, which leads to a decrease in the application efficiency of anti-counterfeiting and optical temperature sensing. In this work, we have successfully developed a series of novel multi-mode stimulation luminescent materials in the Ca2Nb2O7 system via the solid phase reaction. This luminescent material is synthesized by doping dual lanthanide ions to realize adjustable multi-mode luminescence, which simultaneously create luminescent centers and carrier traps in the host lattice. The multi-colored emission can be realized under different excitation wavelengths. Meanwhile, it has a combination of fluorescent phenomenon by upconversion, down-shifting and thermal stimulation. In addition, the fluorescence intensity ratio of lanthanide ions shows significant temperature dependence, and the maximum Sr is 0.0072 K−1 at 293 K. Hence, we have fabricated a novel material that can be used for multi-mode anti-counterfeiting and optical temperature sensing.

Multimode luminescence thermometry based on emission and excitation spectra

Luminescence thermometers are widely known to provide contactless and noninvasive temperature sensing when traditional thermometers are useless. Their operation principle is based on the monitoring of the chosen temperature dependent luminescence parameter. The vast majority of known luminescence thermometers use one parameter to define temperature, while multimode sensors, which could broaden the working range and improve thermometric characteristics, are still rare. We report on YVO4:Er3+ 0.1 at.% sample as a thermal sensor in 299–466 K range with multiple sensing techniques utilized luminescence intensity ratio, spectral line position and bandwidth. These temperature dependent parameters were obtained from both emission and excitation spectra. The relative thermal sensitivity was varied from 0.34 to 2.61% K−1 at room temperature depending on the chosen luminescence parameter. All studied sensing methods provide sub-degree temperature resolution.

Multimodal Luminescent Yb3+ /Er3+ /Bi3+ -Doped Perovskite Single Crystals for X-ray Detection and Anti-Counterfeiting.

Anti-counterfeiting techniques have become a global topic since they is correlated to the information and data safety, in which multimodal luminescence is one of the most desirable candidates for practical applications. However, it is a long-standing challenge to actualize robust multimodal luminescence with high thermal stability and humid resistance. Conventionally, the multimodal luminescence is usually achieved by the combination of upconversion and downshifting luminescence, which only responds to the electromagnetic waves in a limited range. Herein, the Yb3+ /Er3+ /Bi3+ co-doped Cs2 Ag0.6 Na0.4 InCl6 perovskite material is reported as an efficient multimodal luminescence material. Beyond the excitation of ultraviolet light and near-infrared laser (980nm), this work extends multimodal luminescence to the excitation of X-ray. Besides the flexible excitation sources, this material also shows the exceptional luminescence performance, in which the X-ray detection limit reaches the level of nGy s-1 , indicating a great potential for further application as a colorless pigment in the anti-counterfeiting field. More importantly, the obtained double perovskite features high stability against both humidity and temperature up to 400°C. This integrated multifunctional luminescent material provides a new directional solution for the development of multifunctional optical materials and devices.

Dual-mode luminescence tuning of Er[formula omitted] doped Zinc Sulfide piezoelectric microcrystals for multi-dimensional anti-counterfeiting and temperature sensing

In this study, a multi-color and multi-mode luminescence material has been developed for anti-counterfeiting and temperature sensing. The rare earth ions Er3+ are selected as the luminescent center to be doped in the piezoelectric material ZnS. The prepared samples can generate multi-color (orange–yellow–green) and multi-mode (upconversion/down-shifting/energy transfer) emission through the energy transitions of lanthanide ions in the ZnS host. When the excitation wavelength or the temperature is selected to be different, the luminous color is obviously different due to different mode emission. Therefore, multiple anti-counterfeiting of a single compound can be realized, the security degree of the anti-counterfeiting can be improved and overcome the defect of the general fluorescent material in a single light-emitting mode. The work will establish experimental basis for the design and development of a new high-integration functional luminescence material, and is expected to use the developed materials in the fields of optical anti-counterfeiting and information encryption.

Multistimuli‐Responsive Display Materials to Encrypt Differentiated Information in Bright and Dark Fields

AbstractVisually readable codes play a crucial role in anticounterfeiting measures. However, current coding approaches do not enable time‐dependent codes to be visually read, adjusted, and differentiated in bright and dark fields. Here, using a combined strategy of piezoelectric lattice selection, oxygen vacancy engineering, and activator doping, a lanthanide ion‐doped titanate is developed that integrates mechano‐, thermo‐, and photo‐responsive color change (>18 h for bright field), persistent luminescence (>6 h for dark field), and stimulus‐triggered multimodal luminescence. The feasibility of optical encoding, visual displaying, and stimulus‐responsive encrypting of time‐dependent, dual‐field information by using the developed material is demonstrated. In particular, the differentiated display of dual‐field modes is achieved by combining mechanostimulated abolition of only the persistent luminescence and thermo‐ and photostimulated reversal of both the color change and persistent luminescence. The results provide new insights for designing advanced materials and encryption technologies for photonic displays, information security, and intelligent anticounterfeiting.

Achieving Thermo-Mechano-Opto-Responsive Bitemporal Colorful Luminescence via Multiplexing of Dual Lanthanides in Piezoelectric Particles and its Multidimensional Anticounterfeiting.

Optical characteristics of luminescent materials, including emission color (wavelength), lifetime, and excitation mode, play crucial roles in data communication and information security. Conventional luminescent materials generally display unicolor, unitemporal, and unimodal (occasionally bimodal) emission, resulting in low-level readout and decoding. The development of multicolor, multitemporal, and multimodal luminescence in a single material has long been considered to be a significant challenge. In this study, for the first time, the superior integration of colorful (red-orange-yellow-green), bitemporal (fluorescent and delayed), and four-modal (thermo-/mechano-motivated and upconverted/downshifted) emissions in a particular piezoelectric particle via optical multiplexing of dual-lanthanide dopants is demonstrated. The as-prepared versatile NaNbO3 :Pr3+ ,Er3+ luminescent microparticles shown are particularly suitable for embedding into polymer films to achieve waterproof, flexible/wearable and highly stretchable features, and synchronously to provide multidimensional codes that can be visually read-out using simple and commonly available tools (including the LED of a smartphone, pen writing, cooling-heating stimuli, and ultraviolet/near-infrared lamps). These findings offer unique insight for designing highly integrated stimuli-responsive luminophors and smart devices toward a wide variety of applications, particularly advanced anticounterfeiting technology.

Spectrally resolved two-photon absorption properties and switching of the multi-modal luminescence of NaYF4:Yb,Er/CdSe hybrid nanostructures

The combination of NaYF4:Yb,Er NPs and CdSe QDs into NaYF4:Yb,Er/CdSe HNSs allowed lanthanide-based up-conversion and two-photon absorption to be merged in a single HNS for security applications.

Multimodal luminescence properties of surface-treated ZnSe quantum dots by Eu

ZnSe:Eu quantum dots (QDs) were synthesized using the heating-up method by adding a Eu precursor in Zn and Se precursors. The optical property was investigated based on the change in the multimodal emission caused by increasing the amount of the Eu precursor. The emission wavelength of ZnSe QDs increased from 398nm to 405nm when the reaction was carried out for 30–300s. The broad spectrum was attributed to the 4F65D1→4F7 transition when the Eu2+ emission was increased from 450 to 550nm. Eu3+ shows characteristic red emission peaks at 579, 592, 615, 651, and 700nm owing to the electronic transition of 5D0→7Fj (j=0, 1, 2, 3, 4). The expected structure of the ZnSe:Eu QDs was verified by XRD, TEM, and XPS. Compared to the diffraction peaks of pristine ZnSe, the corresponding peaks for the ZnSe:Eu QDs are shifted, by about 0.43°, to larger angles, because the ionic radius of Eu3+ (0.95Å) is larger than that of Zn2+ (0.74Å). They also have Eu2+O and Eu3+O dangling bonds on the surface of Eu3+-doped ZnSe QDs, with an average size of about 3.15nm. These semiconductor QDs with rare earth elements are promising candidates to fabricate light-converting materials.

Emission in Gd6O5F8:Yb3+,Er3+ micro-particles for multimodal luminescence and temperature sensing upon 980 nm excitation.

Mono-dispersed Gd6O5F8:Yb3+/Er3+ micro-particles with different doping concentrations (Er3+: 0.1-1%) were synthesized by a facile hydrothermal route. The emission spectra, luminescent dynamic power-dependence and temperature sensing of up-conversion photoluminescence were investigated in detail. Under 980 nm excitation, the as-prepared samples exhibit intense red up-conversion and NIR emissions, which are influenced by the doping concentrations of Er3+ within Gd6O5F8. With increasing concentrations of Er3+ ions, the visible up-conversion emissions first increase and then decrease, but NIR down-conversion emissions display a distinct trend, in which one peak at 1010 nm is highly suppressed and another at 1530 nm is increased quickly. Furthermore, the 980 nm excited optical temperature sensing property of the synthesized sample is realized over a wide temperature range by monitoring the intensity of up-conversion luminescence. The study provides a novel strategy based on lanthanide oxy-fluoride micro-particles for multifunctional displays, lighting and temperature sensing in a single system.

Multi-modal luminescence properties of RE3+ (Tm3+, Yb3+) and Bi3+ activated GdNbO4 phosphors—upconversion, downshifting and quantum cutting for spectral conversion

This work investigates the promising multi-modal luminescence (upconversion (UC), downshifting (DS) and quantum cutting (QC)) properties of RE3+ (Tm3+, Yb3+) and Bi3+ activated GdNbO4 phosphors synthesized using the well-known solid state reaction method. Structural characterization using x-ray diffraction measurements confirms the formation of the pure phase of the GdNbO4 host with no impurities. The optical band gap (Eg) of GdNbO4 (with and without RE3+ ions) calculated from UV–Vis–near-infrared (NIR) measurements was found to be the same ~4.44 eV which indicates that GdNbO4 is a wide band gap material. Further, Bi3+ doping presents an interesting Eg tuning of the GdNbO4 phosphor, i.e. Eg increases up to 5.38 eV. In terms of luminescence, this material produces intense blue and NIR emission via multi-modal optical processes. On NIR excitation (λexc = 980 nm), Gd0.94Tm0.01Yb0.05NbO4 produces intense upconverted blue and NIR and relatively weak red emission. In addition to the UC process, Gd0.94Tm0.01Yb0.05NbO4 also exhibits pump power dependent variation in fluorescence intensity ratio for I472/I477 showing the applicability of this material as an optical heater. On UV excitation (λexc = 265 nm), Gd0.99Tm0.01NbO4 produces intense DS blue emission due to the Tm3+ ion, overlapped with the emission of the (NbO4)3− ion through strong energy transfer (ET) from (NbO4)3− to Tm3+ ions. Interestingly, NIR QC has also been successfully observed in Gd0.9Yb0.1NbO4, Gd0.89Bi0.01Yb0.1NbO4 and Gd0.79Tm0.01Yb0.2NbO4 phosphors through cooperative ET from the (NbO4)3− group to the Yb3+ ion, Bi(6s)–Nb(4d) to the Yb3+ ion and the Tm3+ ion to the Yb3+ ion, respectively. The mechanisms involved in these processes are explained in detail in this work. The QC efficiency in this work has been found to be ~177%. Thus, the multi-modal luminescence (UC, DS and QC) property of this material makes it a promising candidate for display devices, spectral converters for enhancing the efficiency of silicon solar cells, etc.

New perspective in garnet phosphor: low temperature synthesis, nanostructures, and observation of multimodal luminescence.

Herein, we report a new concept for garnet materials in terms of the synthesis of nanocrystalline structure at low temperatures and its multimodal luminescence processes. Terbium- and ytterbium-ion-codoped yttrium gallium garnet nanophosphors have been synthesized via solution combustion technique; nearly pure phase nanophosphor samples were obtained. The synthesized nanophosphor shows efficient multimodal upconversion (UC), downshifting (DS), and quantum cutting (QC)/downconversion (DC) luminescence, which is a new paradigm in garnet material. The garnet nanophosphor shows strong green emission through DS and UC processes both. Furthermore, cooperative energy transfer (CET) has been described in detail, and a possible mechanism for the QC process is also proposed. A UV/blue photon absorbed by Tb(3+) ion splits into two near-infrared photons (wavelength range 900-1040 nm), emitted by a Yb(3+) ion pair, with an efficiency of more than 100%. The Yb(3+) concentration dependent ET from Tb(3+) to Yb(3+) has been verified using time domain analysis. An ET efficiency as high as 28% and a corresponding QC efficiency of about 128% (for 15 mol % of Yb(3+) concentration) have been attained. Such a multimode emitting nanophosphor could be very useful in display devices and for enhancing the conversion efficiency of next generation solar cells via spectral modification etc.